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WO2014025435A2 - Dipyrrin based materials for photovoltaics, compounds capable of undergoing symmetry breaking intramolecular charge transfer in a polarizing medium and organic photovoltaic devices comprising the same - Google Patents

Dipyrrin based materials for photovoltaics, compounds capable of undergoing symmetry breaking intramolecular charge transfer in a polarizing medium and organic photovoltaic devices comprising the same Download PDF

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Publication number
WO2014025435A2
WO2014025435A2 PCT/US2013/041079 US2013041079W WO2014025435A2 WO 2014025435 A2 WO2014025435 A2 WO 2014025435A2 US 2013041079 W US2013041079 W US 2013041079W WO 2014025435 A2 WO2014025435 A2 WO 2014025435A2
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WIPO (PCT)
Prior art keywords
group
chosen
optionally substituted
donor
compound
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PCT/US2013/041079
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French (fr)
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WO2014025435A9 (en
WO2014025435A3 (en
Inventor
Stephen R. Forrest
Mark E. Thompson
John J. Chen
Jonathan R. Sommer
Peter I. Djurovich
Kathryn R. ALLEN
Original Assignee
Forrest Stephen R
Thompson Mark E
Chen John J
Sommer Jonathan R
Djurovich Peter I
Allen Kathryn R
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Priority claimed from US13/564,953 external-priority patent/US20150303377A1/en
Application filed by Forrest Stephen R, Thompson Mark E, Chen John J, Sommer Jonathan R, Djurovich Peter I, Allen Kathryn R filed Critical Forrest Stephen R
Priority to CN201380031559.4A priority Critical patent/CN105409020A/en
Priority to JP2015512780A priority patent/JP6339561B2/en
Priority to EP13802466.6A priority patent/EP2850670A2/en
Priority to AU2013300142A priority patent/AU2013300142A1/en
Priority to KR20147034571A priority patent/KR20150020297A/en
Priority to CA2873468A priority patent/CA2873468A1/en
Publication of WO2014025435A2 publication Critical patent/WO2014025435A2/en
Publication of WO2014025435A9 publication Critical patent/WO2014025435A9/en
Publication of WO2014025435A3 publication Critical patent/WO2014025435A3/en
Priority to IL235713A priority patent/IL235713A0/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
    • C07F5/02—Boron compounds
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/321—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3]
    • H10K85/322—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3] comprising boron
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/361—Polynuclear complexes, i.e. complexes comprising two or more metal centers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
    • H10K30/30—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/20—Carbon compounds, e.g. carbon nanotubes or fullerenes
    • H10K85/211—Fullerenes, e.g. C60
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/549—Organic PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present disclosure generally relates to organic photosensitive optoelectronic devices comprising at least one boron dipyrrin compound.
  • the present disclosure relates to methods of making organic photosensitive optoelectronic devices comprising at least one boron dipyrrin compound.
  • the present disclosure also generally relates to chromophoric compounds, including boron dipyrrin compounds, that combine strong absorption of light at visible to near infrared wavelengths with the ability to undergo symmetry- breaking intramolecular charge transfer (ICT), and their use for the generation of free carriers in organic photovoltaic cells (OPVs) and electric-field-stabilized geminate polaron pairs.
  • ICT intramolecular charge transfer
  • OOVs organic photovoltaic cells
  • the present disclosure also relates to the synthesis of such compounds, methods of manufacture, and applications in photovoltaic systems and organic lasers.
  • Optoelectronic devices rely on the optical and electronic properties of materials to either produce or detect electromagnetic radiation electronically, or to generate electricity from ambient electromagnetic radiation.
  • Photosensitive optoelectronic devices convert electromagnetic radiation into electricity.
  • Solar cells also called photovoltaic (PV) devices
  • PV devices which may generate electrical energy from light sources other than sunlight, can be used to drive power consuming loads to provide, for example, lighting, heating, or to power electronic circuitry or devices such as calculators, radios, computers or remote monitoring or communications equipment.
  • power generation applications also often involve the charging of batteries or other energy storage devices so that operation may continue when direct illumination from the sun or other light sources is not available, or to balance the power output of the PV device with a specific application's requirements.
  • the term "resistive load” refers to any power consuming or storing circuit, device, equipment or system.
  • Another type of photosensitive optoelectronic device is a
  • photoconductor cell In this function, signal detection circuitry monitors the resistance of the device to detect changes due to the absorption of light.
  • signal detection circuitry monitors the resistance of the device to detect changes due to the absorption of light.
  • a photodetector In operation a photodetector is used in conjunction with a current detecting circuit which measures the current generated when the photodetector is exposed to electromagnetic radiation and may have an applied bias voltage.
  • a detecting circuit as described herein is capable of providing a bias voltage to a photodetector and measuring the electronic response of the photodetector to electromagnetic radiation.
  • These three classes of photosensitive optoelectronic devices may be characterized according to whether a rectifying junction as defined below is present, and also according to whether the device is operated with an external applied voltage, also known as a bias or bias voltage.
  • a photoconductor cell does not have a rectifying junction and is normally operated with a bias.
  • a PV device has at least one rectifying junction and is operated with no bias.
  • a photodetector has at least one rectifying junction and is usually but not always operated with a bias.
  • a photovoltaic cell provides power to a circuit, device or equipment, but does not provide a signal or current to control detection circuitry, or the output of information from the detection circuitry.
  • photoconductor provides a signal or current to control detection circuitry, or the output of information from the detection circuitry but does not provide power to the circuitry, device or equipment.
  • photosensitive optoelectronic devices have been constructed of a number of inorganic semiconductors, e.g., crystalline, polycrystalline and amorphous silicon, gallium arsenide, cadmium telluride and others.
  • semiconductor denotes materials which can conduct electricity when charge carriers are induced by thermal or electromagnetic excitation.
  • photoconductive generally relates to the process in which electromagnetic radiant energy is absorbed and thereby converted to excitation energy of electric charge carriers so that the carriers can conduct, i.e., transport, electric charge in a material.
  • photoconductor and photoconductive material are used herein to refer to semiconductor materials which are chosen for their property of absorbing electromagnetic radiation to generate electric charge carriers.
  • PV devices may be characterized by the efficiency with which they can convert incident solar power to useful electric power.
  • Devices utilizing crystalline or amorphous silicon dominate commercial applications, and some have achieved efficiencies of 23% or greater.
  • efficient crystalline-based devices, especially of large surface area are difficult and expensive to produce due to the problems inherent in producing large crystals without significant efficiency-degrading defects.
  • high efficiency amorphous silicon devices still suffer from problems with stability.
  • Present commercially available amorphous silicon cells have stabilized efficiencies between 4 and 8%.
  • PV devices may be optimized for maximum electrical power generation under standard illumination conditions (i.e., Standard Test Conditions which are 1000 W/m 2 , AM1 .5 spectral illumination), for the maximum product of photocurrent times photovoltage.
  • standard illumination conditions i.e., Standard Test Conditions which are 1000 W/m 2 , AM1 .5 spectral illumination
  • the power conversion efficiency of such a cell under standard illumination conditions depends on the following three parameters: (1 ) the current under zero bias, i.e., the short-circuit current c, in Amperes; (2) the photovoltage under open circuit conditions, i.e., the open circuit voltage Voc, in Volts; and (3) the fill factor, ff.
  • PV devices produce a photo-generated current when they are connected across a load and are irradiated by light.
  • a PV device When irradiated under infinite load, a PV device generates its maximum possible voltage, V open-circuit, or Voc- When irradiated with its electrical contacts shorted, a PV device generates its maximum possible current, I short-circuit, or Isc- When actually used to generate power, a PV device is connected to a finite resistive load and the power output is given by the product of the current and voltage, I *V.
  • the maximum total power generated by a PV device is inherently incapable of exceeding the product l S c x V 0 c- When the load value is optimized for maximum power extraction, the current and voltage have the values Lax and V max , respectively.
  • a figure of merit for PV devices is the fill factor, ff defined as:
  • ff ⁇ lmax V max ⁇ / ⁇ l SC Voc ⁇ (1 )
  • ff is always less than 1 , as Isc and Voc are never obtained simultaneously in actual use. Nonetheless, as ff approaches 1 , the device has less series or internal resistance and thus delivers a greater percentage of the product of Isc and V 0 c to the load under optimal conditions.
  • the power efficiency of the device, ⁇ ⁇ may be calculated by:
  • n-type denotes that the majority carrier type is the electron. This could be viewed as the material having many electrons in relatively free energy states.
  • p-type denotes that the majority carrier type is the hole. Such material has many holes in relatively free energy states.
  • the type of the background, i.e., not photo-generated, majority carrier concentration depends primarily on unintentional doping by defects or impurities.
  • the type and concentration of impurities determine the value of the Fermi energy, or level, within the gap between the conduction band minimum and valance band maximum energies.
  • the Fermi energy characterizes the statistical occupation of molecular quantum energy states denoted by the value of energy for which the probability of occupation is equal to 1 ⁇ 2.
  • a Fermi energy near the conduction band minimum energy indicates that electrons are the predominant carrier.
  • a Fermi energy near the valence band maximum energy indicates that holes are the predominant carrier. Accordingly, the Fermi energy is a primary
  • rectifying denotes, inter alia, that an interface has an asymmetric conduction characteristic, i.e., the interface supports electronic charge transport preferably in one direction. Rectification is associated normally with a built- in electric field which occurs at the junction between appropriately selected materials.
  • the terms “donor” and “acceptor” refer to the relative positions of the HOMO and LUMO energy levels of two contacting but different organic materials. This is in contrast to the use of these terms in the inorganic context, where “donor” and “acceptor” may refer to types of dopants that may be used to create inorganic n- and p- types layers, respectively.
  • donor and “acceptor” may refer to types of dopants that may be used to create inorganic n- and p- types layers, respectively.
  • the LUMO energy level of one material in contact with another is lower, then that material is an acceptor. Otherwise it is a donor. It is energetically favorable, in the absence of an external bias, for electrons at a donor-acceptor junction to move into the acceptor material, and for holes to move into the donor material.
  • a significant property in organic semiconductors is carrier mobility. Mobility measures the ease with which a charge carrier can move through a conducting material in response to an electric field.
  • a layer including a material that conducts preferentially by electrons due to a high electron mobility may be referred to as an electron transport layer, or ETL.
  • a layer including a material that conducts preferentially by holes due to a high hole mobility may be referred to as a hole transport layer, or HTL.
  • an acceptor material is an ETL and a donor material is a HTL.
  • heterojunction is believed to be important to the operation of organic PV devices due to the fundamental nature of the photogeneration process in organic materials.
  • Upon optical excitation of an organic material localized Frenkel or charge-transfer excitons are generated.
  • the bound excitons must be dissociated into their constituent electrons and holes.
  • Such a process can be induced by the built-in electric field, but the efficiency at the electric fields typically found in organic devices (F ⁇ 10 6 V/cm) is low.
  • the most efficient exciton dissociation in organic materials occurs at a donor-acceptor (D-A) interface.
  • D-A donor-acceptor
  • the donor material with a low ionization potential forms a heteroj unction with an acceptor material with a high electron affinity.
  • the dissociation of the exciton can become energetically favorable at such an interface, leading to a free electron polaron in the acceptor material and a free hole polaron in the donor material.
  • Organic PV cells have many potential advantages when compared to traditional silicon-based devices.
  • Organic PV cells are light weight, economical in materials use, and can be deposited on low cost substrates, such as flexible plastic foils.
  • organic PV devices typically have relatively low external quantum efficiency (electromagnetic radiation to electricity conversion efficiency), being on the order of 1 % or less. This is, in part, thought to be due to the second order nature of the intrinsic photoconductive process. That is, carrier generation requires exciton generation, diffusion and ionization or collection. There is an efficiency ⁇ associated with each of these processes.
  • the diffusion length (I_D) of an exciton is typically much less (I_D ⁇ 50 ⁇ ) than the optical absorption length (-500 ⁇ ), requiring a tradeoff between using a thick, and therefore resistive, cell with multiple or highly folded interfaces, or a thin cell with a low optical absorption efficiency.
  • polymer organic PVs While favorable absorption and charge mobility characteristics make polymer organic PVs among the most highly efficient organic PV devices, polymer organic PVs may have several drawbacks. For example, polymers can be harder to synthesize, less predictable in terms of morphology, and not sublimable. Thus, there is a continuing need to develop new classes of compounds for photovoltaic applications.
  • BODIPY 4,4-difluoro-4-bora-3a,4a-diaza-s- indacene
  • R 1 is chosen from an optionally substituted monocyclic group, an optionally substituted C6- 24 multicyclic group, and an optionally substituted meso-linked BODIPY, or R 1 and R 2 and R 7 taken together with any intervening atoms comprise a substituted BODIPY, wherein R 1 is meso-linked and R 2 and R 7 are beta-linked;
  • R 2 is chosen from hydrogen, an alkyl group, and a cyano group, or R 2 and R 3 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group, or R 2 and R 1 and R 7 taken together with any intervening atoms comprise a substituted BODIPY, wherein R 1 is meso-linked and R 2 and R 7 are beta-linked;
  • R 3 is chosen from hydrogen, an alkyl group, and a cyano group, or R 3 and R 2 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group, or R 3 and R 4 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group;
  • R 4 is chosen from hydrogen, an alkyl group, and a cyano group, or R 4 and R 3 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group;
  • R 5 is chosen from hydrogen, an alkyl group, and a cyano group, or R 5 and R 6 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group;
  • R 6 is chosen from hydrogen, an alkyl group, and a cyano group, or R 6 and R 5 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group, or R 6 and R 7 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group; and
  • R 7 is chosen from hydrogen, an alkyl group, and a cyano group, or R 7 and R 6 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C 6 -2 4 multicyclic group, or R 7 and R 1 and R 2 taken together with any intervening atoms comprise a substituted BODIPY, wherein R 1 is meso-linked and R 2 and R 7 are beta-linked;
  • R 1 is chosen from optionally substituted benzene and optionally substituted fused benzene.
  • R 2 and R 7 are both chosen from hydrogen, an alkyl group, and a cyano group.
  • R 5 and R 4 are both chosen from hydrogen, an alkyl group, and a cyano group.
  • R 3 and R 6 are both chosen from hydrogen, an alkyl group, and a cyano group.
  • R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 are all chosen from hydrogen, an alkyl group, and a cyano group.
  • the present disclosure also provides methods for making the photosensitive optoelectronic devices of the present disclosure.
  • the method comprises depositing a photoactive region over a substrate, wherein the photoactive region comprises at least one compound of formula (I).
  • the photoactive region comprises a donor material and an acceptor material, wherein at least one of the donor and acceptor materials comprise at least one compound of formula (I).
  • candidate molecules must combine strong absorption of light at visible wavelengths with an ability to undergo symmetry-breaking ICT. There are few dimeric molecules that meet these criteria. To date, the best studied system of this sort is 9,9'-bianthryl. However, 9,9'-bianthryl predominantly absorbs ultraviolet light.
  • an organic photosensitive optoelectronic device comprising at least one higher order compound, such as dyads, triads and tetrads, that are capable of undergoing symmetry-breaking intramolecular charge transfer in a polarizing medium.
  • the intramolecular charge transfer occurs at a polarizing donor/acceptor interface.
  • the higher order compounds disclosed herein exhibit a high absorptivity of light in the visible and near infrared spectrum.
  • "high absorptivity of light” includes absorptivity of > 10 4 M “1 cm “1 at one or more visible to near infrared wavelengths ranging from 350 to 1500 nm.
  • the higher order compound forms at least one donor and/or acceptor region in a donor-acceptor heterojunction.
  • the donor-acceptor heterojunction absorbs photons to form excitons.
  • the device is an organic device, such as an organic photodetector, an organic solar cell, or an organic laser.
  • the photosensitive optoelectronic device comprising a higher order compound.
  • the device may be an organic photodetector, in another an organic solar cell.
  • Figure 1 depicts a scheme for synthesizing BenzoBODIPY.
  • Figure 2 depicts a scheme for synthesizing IndoBODIPY.
  • Figure 3 depicts a scheme for synthesizing CyanoBODIPY.
  • Figure 4 provides Nuclear Magnetic Resonance (NMR) data for BenzoBODIPY.
  • Figure 5 provides NMR data for IndoBODIPY.
  • Figure 6 provides NMR data for CyanoBODIPY.
  • Figure 7(a) shows absorption spectra for synthesized BenzoBODIPY in its solution and solid states.
  • Figure 7(c) shows excitation and emission spectra for BenzoBODIPY in its solution and solid states.
  • Figure 8(a) shows solution absorption and emission spectra for CyanoBODIPY.
  • Figure 8(b) shows film excitation, emission, and absorption spectra for CyanoBODIPY.
  • Figures 9(a), 9(b), and 9(c) show PV performance data of an organic PV using CuPc as the donor material and of organic PVs using BenzoBODIPY as the donor material at various thicknesses.
  • Fig. 9(a) shows current- voltage curves
  • Fig. 9(b) shows external quantum efficiencies (EQEs)
  • Fig. 9(c) shows dark current curves.
  • Figures 10(a) and 10(b) show additional PV performance data of organic PVs using BenzoBODIPY as the donor material at various thicknesses.
  • Fig. 10(a) shows current-voltage curves
  • Fig. 10(b) shows EQEs.
  • Figures 11 (a) and 11 (b) show PV performance data of organic PVs that were thermally annealed after deposition of the donor layer but prior to deposition of the acceptor material and that used BenzoBODIPY as the donor material at various thicknesses.
  • Fig. 1 1 (a) shows current-voltage curves
  • Fig. 11 (b) shows EQEs.
  • Figure 11 (c) shows absorption spectra for non-treated and thermally treated organic PVs.
  • Figures 12(a) and 12(b) show PV performance data of organic PVs that were thermally annealed after deposition of the donor and acceptor layers and that used BenzoBODIPY as the donor material at various thicknesses.
  • Fig. 12(a) shows current-voltage curves
  • Fig. 12(b) shows EQEs.
  • Figures 13(a) and 13(b) show PV performance data of an organic PV device using CuPc and C 6 o as donor and acceptor materials, respectively, and of an organic PV device using CuPc as the donor material and a 1 :1 ratio of
  • CyanoBODIPY and C60 as acceptor materials.
  • One CyanoBODIPY device was thermally annealed after deposition of the acceptor layer.
  • Fig. 13(a) shows current- voltage curves and Fig. 13(b) shows EQEs.
  • Figure 14 is a schematic representation of symmetry-breaking ICT to facilitate charge separation at a polarizing donor/acceptor interface.
  • Figure 15 shows examples of dyes that can be coupled into dimers, trimers, etc. for symmetry breaking ICT.
  • Figure 16 shows examples of dipyrrin chromophores synthesized for symmetry breaking ICT.
  • Figure 17 shows the synthetic scheme and displacement ellipsoid of BODIPY dyad 23 of Figure 16.
  • Figure 18 shows a synthetic scheme for BODIPY dyad 26.
  • Figure 19 represents the normalized absorption and emission spectra of dyad 23 and the absorption spectra of 3,5-Me 2 BODIPY-Ph in CH 2 CI 2 .
  • Figure 20 shows the cyclic voltammetry of dyad 23 in CH 2 CI 2 .
  • Figures 21 (a) and 21 (b) represent the ultrafast transient absorption spectra of dyad 23 after excitation at 508 nm, and time domain slices of transient absorptions at 507 and 550 nm with predicted traces based on kinetic parameters.
  • Figure 22 shows the transient absorption of dyad 23 in toluene.
  • Figure 23 shows the absorption spectra of dyad 26 in CH 2 CI 2 and emission spectra of 26 in solvents of varying polarity.
  • Figure 24 shows the normalized emission decays of dyad 26 in cyclohexane (564 nm) and CH 2 CI 2 (651 nm) following excitation at 405 nm.
  • Figure 25 represents the transient absorption of dyad 26 in CH 2 CI 2 .
  • Figure 26 represents the generation of stabilized intramolecular polaron pairs in the presence of an electric field.
  • Figure 27(a), 27(b), and 27(c) represent methods for structuring symmetry-breaking ICT dyads, triads, and tetrads ((a), (b) and (c) respectively) where R represents the linking molecule between the dyes.
  • Figure 28 represents methods for connecting two dyes to facilitate symmetry-breaking ICT.
  • Figure 29 shows the transient absorption of dyad 23 in acetonitrile with all transient spectral features completely relaxed within ca. 150 ps.
  • Figure 30 represents time domain slices of transient absorption of dyad 23 in toluene.
  • Figure 31 shows the normalized emission decay of dyad 23 in toluene (535 nm) following excitation at 435 nm.
  • Figure 32 represent time domain slices of transient absorptions at 475 and 575 nm with predicted traces based on kinetic parameters.
  • Figure 33 shows the X-ray structure of dyad 23.
  • Figure 34(a) shows device structures of organic PVs using compound 31 of Figure 16;
  • Figure 34(b) shows current-voltage characteristics of the organic PVs under AM1 .5G illumination;
  • Figure 34(c) shows EQEs.
  • Figure 35 shows a non-limiting example of a lamellar device structure of an organic PV using at least one compound of formula (I) as a donor material.
  • the organic photosensitive optoelectronic device is a solar cell. In other embodiments, the organic photosensitive optoelectronic device is a photodetector. In some embodiments, the organic photosensitive optoelectronic device is a photosensor. In other embodiments, the organic photosensitive optoelectronic device is a
  • the at least one compound of formula (I) exhibits an absorptivity of light greater than 10 4 M "1 cm “1 at one or more wavelengths ranging from 450 to 900 nm. In some embodiments, the at least one compound of formula (I) exhibits an absorptivity of light greater than 10 5 M "1 cm “1 at one or more wavelengths ranging from 450 to 900 nm.
  • the term "monocyclic” refers to a carbocyclic or heterocyclic group comprising only a single ring.
  • multicyclic refers to a carbocyclic or heterocyclic group comprising at least two rings. Some or all of the rings in the “multicyclic” group can be peri-fused, ortho-fused and/or bridged.
  • alkyl refers to a straight-chain or branched saturated hydrocarbyl group.
  • aryl refers to an aromatic hydrocarbyl group.
  • the “aryl” group is monocyclic or multicyclic.
  • heteroaryl refers to an aryl group having at least one N, O, or S ring atom, with C atom(s) as the remaining ring atom(s).
  • substituted means that the chemical group has at least one hydrogen atom replaced by a substituent.
  • the at least one compound of formula (I) is chosen from
  • R is chosen from an optionally substituted monocyclic group and an optionally substituted C6- 24 multicyclic group.
  • the optionally substituted monocyclic or multicyclic group of R is an aryl or a heteroaryl group.
  • R is chosen from
  • R' is chosen from H, alkyl, and aryl or heteroaryl groups.
  • the at least one compound of formula (I) does not include
  • the device comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises at least one compound of formula (I).
  • the at least one donor material comprises at least one compound of formula (I).
  • the at least one acceptor material comprises at least one compound of formula (I).
  • both the donor and acceptor materials comprise at least one compound of formula (I), wherein the at least one compound of formula (I) that comprises the donor material is different from the at least one compound of formula (I) that comprises the acceptor material.
  • the use of the BODIPY compounds disclosed herein as a donor and/or acceptor material depends upon the relationship of the HOMO and LUMO levels between two BODIPY compounds or between the BODIPY compound and a second organic semiconducting material used to complete a donor-acceptor pair.
  • the at least one donor material comprises at least one compound of formula (I), and the at least one acceptor material comprises a fullerene or a derivative thereof.
  • the at least one acceptor material comprises at least one of C 6 o, C 7 o and phenyl-C 7 i-butyric-acid-methyl ester (PCBM).
  • the at least one acceptor material comprises at least one compound of formula (I), and the at least one donor material comprises copper phthalocyanine (CuPc).
  • the at least one acceptor material comprises at least one compound of formula (I) and a second organic semiconducting material.
  • the second organic semiconducting material comprises Cm-
  • the at least one donor material and the at least one acceptor material form a donor-acceptor heterojunction.
  • the donor-acceptor heteroj unction may be planar or non-planar.
  • the donor and acceptor materials may form at least one of a mixed heterojunction, planar heterojunction, bulk heterojunction, and hybrid planar-mixed heterojunction.
  • the at least one donor material and the at least one acceptor material form a lamellar structure, wherein the at least one donor material comprises at least one compound of formula (I) and has a thickness ranging from about 1 - 150 nm, or about 10 - 150 nm, or about 10 - 100 nm, or about 20 - 80 nm.
  • a non-limiting example of a device comprising at least one donor material and at least one acceptor material forming a lamellar structure, wherein the at least one donor material comprises at least one compound of formula (I), is shown in Figure 35.
  • the organic photosensitive optoelectronic device of the present disclosure may further comprise two electrodes comprising an anode and a cathode.
  • a photoactive region can be located between the anode and the cathode, wherein the photoactive region comprises at least one compound of formula (I).
  • the photoactive region comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises the at least one compound of formula (I).
  • the donor and acceptor materials may form a donor-acceptor heterojunction as described herein.
  • the stacked device may comprise a plurality of photosensitive optoelectronic subcells, wherein at least one subcell comprises two electrodes comprising an anode and a cathode in superposed relation, and a photoactive region between the two electrodes, wherein the photoactive region comprises at least one compound of formula (I).
  • the photoactive region comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises at least one compound of formula (I).
  • the donor and acceptor materials may form a donor-acceptor heterojunction as described herein.
  • the donor and acceptor materials may form a lamellar structure as described herein.
  • optoelectronic device typically includes a complete set of electrodes, i.e., positive and negative. In some stacked configurations, it is possible for adjacent subcells to utilize common, i.e., shared, electrode, charge transfer region or charge
  • subcell is disclosed herein to encompass the subunit construction regardless of whether each subunit has its own distinct electrodes or shares electrodes or charge transfer regions with adjacent subunits.
  • the subcells may be electrically connected either in parallel or in series.
  • the organic photosensitive optoelectronic devices of the present disclosure may also comprise one or more blocking layers, such as exciton blocking layers (EBLs), between the two electrodes.
  • one or more blocking layers are located between the photoactive region and the anode, between the photoactive region and the cathode, or both. Examples of blocking layers are described in U.S. Patent Publication Nos. 2012/0235125 and 201 1/0012091 and in U.S. Patent Nos. 7,230,269 and 6,451 ,415, which are incorporated herein by reference for their disclosure of blocking layers.
  • the organic photosensitive devices of the present disclosure may be structured in various configurations with varying material combinations. Examples of device configurations and materials are described in U.S. Patent Application No. 13/666,664, U.S. Patent Publication Nos. 2012/0235125 and 2010/0102304, and U.S. Patent Nos. 6,657,378; 6,580,027, and 6,352,777, which are incorporated herein by reference for their disclosure of organic photosensitive optoelectronic device structures, particularly photovoltaic structures, and materials.
  • the method comprises depositing a photoactive region over a substrate, wherein the photoactive region comprises at least one compound of formula (I).
  • the photoactive region comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises at least one compound of formula (I).
  • the at least one donor material comprises the at least one compound of formula (I).
  • the at least one acceptor material comprises the at least one compound of formula (I).
  • both the donor and acceptor materials comprise at least one compound of formula (I), wherein the at least one compound of formula (I) that comprises the donor material is different from the at least one compound of formula (I) that comprises the acceptor material.
  • the deposition of the photoactive region comprises depositing at least one compound of formula (I) over the substrate.
  • the deposition of the photoactive region comprises codepositing an organic semiconducting material and at least one compound of formula (I) over the substrate.
  • the deposition of the photoactive region may form at least one of a donor-acceptor mixed heterojunction, planar heterojunction, bulk heterojunction, and hybrid planar-mixed heterojunction.
  • the deposition of the photoactive region forms a lamellar device structure.
  • the deposition of the photoactive region comprises depositing at least one donor material over a substrate, thermally annealing the substrate and the at least one donor material, and depositing at least one acceptor material over the at least one donor material.
  • the at least one donor material comprises at least one compound of formula (I).
  • the at least one donor material comprises at least one compound of formula (I)
  • the at least one acceptor material comprises Cm- In other embodiments, the at least one acceptor material comprises at least one compound of formula (I).
  • the deposition of the photoactive region comprises depositing at least one donor material over a substrate, depositing at least one acceptor material over the at least one donor material, and thermally annealing the substrate, the at least one donor material, and the at least one acceptor material.
  • the at least one donor material comprises at least one compound of formula (I).
  • the at least one donor material comprises at least one compound of formula (I)
  • the at least one acceptor material comprises Cm-
  • the at least one acceptor material comprises at least one compound of formula (I).
  • the at least one acceptor material comprises at least one compound of formula (I), and the at least one donor material comprises CuPc.
  • annealing is performed between 90 °C and 150 °C from 0 to 30 minutes. Suitable times and temperatures for annealing may be chosen based on the particular materials used.
  • Organic layers may be deposited using methods known in the art.
  • One advantage of the BODIPY dyes disclosed herein is that they are solution- processable and sublimable.
  • the at least one compound of formula (I) is deposited over a substrate using a technique chosen from spin casting and vapor deposition.
  • Another aspect of the present disclosure relates to compounds that exhibit the light absorption and symmetry breaking properties required for applications in OPVs. By extension, these compounds of the present disclosure mimic features seen in the photosynthetic reaction center.
  • Compounds that exhibit the light absorption and symmetry breaking properties required for applications in OPVs include, for example, higher order compounds, such as symmetrical dyads, triads, tetrads, etc. These compounds may populate intramolecular charge-transfer states in a polarizing medium by symmetry breaking, but cannot do so in the absence of a polarizing medium because of their symmetry.
  • the higher order compounds may have at least C 2 symmetry and should have a luminescent lifetime of at least 1 ps to allow charge transfer to take place prior to other radiative or non-radiative decay processes.
  • the higher order compounds may comprise, for example, dye compounds chosen from perylenes, malachites, xanthenes, cyanines, bipyridines, dipyrrins, coumarins, acridines, phthalocyanines, subphthalocyanines, porphyrins, and acenes. These dyes may be substituted with alkyl, H, electron donating or electron withdrawing groups at any position other than the linking site to control the physical and electronic properties of the dye.
  • the relevant physical properties include solubility as well as sublimation and melting temperatures.
  • the relevant electronic properties include the absorption and emission energies, as well as the oxidation and reduction potentials.
  • the higher order compounds are chosen from the following dipyrrin chromophores:
  • Another embodiment of the present disclosure provides for symmetry- breaking ICT compounds and their use as chromophores for the generation of electric-field-stabilized geminate polaron pairs. These polaron pairs collapse in the absence of an electric field, generating a high concentration of excitons and may be useful for the construction of organic lasers. In this process a large electric field is applied to drive the charge separation of excitons formed on light absorption and stabilize the geminate polaron pairs toward recombination. This was accomplished with a lightly doped matrix, where the dopant absorbs light and acts as one of the polarons (cation or anion), with the other polaron on the matrix material.
  • BODIPY dyads and related compounds described herein have donor and acceptor present in the same molecule (though in the absence of an electric field there is no driving force for excited-state charge separation), such that charge separation to form the geminate pairs can be efficiently achieved within the chromophore itself.
  • This allows the chromophore to be doped into nonconductive host materials, preventing carrier leakage.
  • the inherent C2 symmetry of the substituted porphryins ensure that nearly every molecule is present in an orientation that will promote charge separation (Figure 26).
  • An orientation that cannot be efficiently coupled with the electric field is one in which the plane of the dyad is perpendicular to the applied electric field. By using a randomly doped film, only a low percentage of the dopant is present in the nonproductive orientation.
  • the constituent higher order dye compounds must exhibit high absorptivity ( ⁇ > 10 "4 M "1 cm “1 ) of light at some visible to near infrared wavelengths (350-1500 nm), for example, dyads of xanthenes dyes (e.g., fluorescein, eosins, and rhoadmines), coumarins, acridines, phthalocyanines, subphthalocyanines, porphyrins, acenes such as tetracene or pentacene, perylenes, malachites, cyanines, bipyridines, and dipyrrins, among others.
  • xanthenes dyes e.g., fluorescein, eosins, and rhoadmines
  • coumarins e.g., acridines, phthalocyanines, subphthalocyanines, porphyrins, acenes such as tetracene or pentacen
  • the higher order dye compounds may exhibit high absorptivity of light at some visible to near infrared wavelengths between 350 to 950 nm.
  • the higher order dye compounds may exhibit high absorptivity of light at some visible to near infrared wavelengths between 350 nm to at least 1200 nm.
  • the higher order dye compounds may exhibit high absorptivity of light at some visible to near infrared wavelengths between 350 nm to at least 1500 nm.
  • the dyad (or triad, tetrad, etc.) must also possess an intramolecular charge-transfer (ICT) state that is energetically accessible from the photogenerated Si state in a polarizing medium. It is known that the energy of an ICT state can be approximated as:
  • E(ICT) IP(D) - EA(A) +C + ⁇ 80 ⁇ ⁇ (1)
  • IP(D) is the ionization potential of the donor
  • EA(A) is the electron affinity of the acceptor
  • C is the Coulombic stabilization of a neighboring cation and anion in the system
  • ⁇ 80 ⁇ ⁇ is the stabilization of the ion pair by a surrounding polar environment (due to solvent or otherwise).
  • the donor and acceptor are the same moiety, so a crude approximation of the energy of a symmetry-breaking ICT state can come from the energy required to pass one electron through the potential difference between the one-electron oxidation and reduction events, as determined by cyclic voltammetry or other electrochemical method. Since C and ⁇ 80 ⁇ ⁇ only serve to stabilize the ICT state, this method will always lead to an overestimate of the energy. Thus, for example, if the difference in oxidation and reduction events for a dye is 2.50 V, then the energy of an ICT state for a dyad constructed from that dye will be less than 2.50 eV.
  • dimers (and higher order structures) of dyes with a first singlet excited state (S-i) energy greater than E / cr- 0.260 eV may be able to undergo symmetry-breaking intramolecular charge transfer at a polarizing donor/acceptor interface to facilitate charge separation in photovoltaics.
  • S-i first singlet excited state
  • E,cr as determined by this method minus 10kT
  • the absorption profiles of the chromophores in Figure 16 are generally similar to the monomer units of their respective dyes, indicating minimal excitonic coupling between the two (or three or more) dye units on the chromophore molecule. They are also generally invariant across different solvent polarities, since accessing any ICT state should first excite directly to the Si state.
  • the absorption of the chromophores from Figure 16 are listed in Table 2 for different solvents.
  • the dyes In order to undergo such symmetry-breaking charge transfer, the dyes must be able to communicate electronically (though there need not be any ground- state interaction). Thus, the manner in which they are connected is important.
  • Three examples are illustrated in Figure 27 for bringing two, three, or four dyes together.
  • the two constituent dyes may be connected directly or through a linker that places them in linear or cofacial arrangements (Figure 28).
  • the linker must have higher energy optical transitions than the dyes to prevent direct energy transfer from the dye to the linker.
  • Numerous linkers can be utilized, including saturated and unsaturated hydrocarbon linkers, with the most important requirement being that the linker must have ground state oxidation and reduction potentials, such that the linker is neither reduced nor oxidized by the photoexcited dye.
  • Figure 27(a) contemplates a wide range of effectively divalent linkers.
  • the linker could be a single atom, as illustrated for the Zinc based materials in compounds 31-34 of Figure 16.
  • This divalent group can also be a disubstituted arene, as illustrated in compounds 23-25 or a single bond as illustrated in
  • Figure 27(b) illustrates three dyes disposed around a linker. This effectively trivalent linkage is demonstrated for 1 ,3,5-benzene in compound 30 of Figure 16. This linkage could also be a trivalent metal atom such as Al or Ga, or a transition metal. These complexes are analogous to compounds 31-34 of Figure 16, except the central metal atom would be surrounded by three bidentate ligands.
  • One of skill in the art can envision a range of similar trivalent linkers using trivalent atoms or effective trivalent linkers constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkenyl, a heterocycle, or organosilane moiety.
  • Figure 27(c) illustrates four dyes bound to a central linker.
  • This linkage could be a tetravalent metal atom such as Ti, Zr or Hf.
  • These complexes are analogous to compounds 31-34 of Figure 16, except the central metal atom would be surrounded by four bidentate ligands.
  • One of skill in the art can envision a range of similar tetravalent linkers using trivalent atoms or effective tetravalent linkers constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkenyl, a heterocycle, or organosilane moiety.
  • a number of other geometries can be envisioned for higher-order structures, with the requirement that they be symmetric or pseudosymmetric in the ground state so that there is no driving force for ICT in the absence of a polarizing medium. Moreover, any interaction of the two molecules in the ground or excited state should not lead to the formation of an excited state lower in energy than the ICT, such as a triplet or excimeric excited state. These alternate excited states can exist, but they must be higher in energy than the ICT.
  • the symmetry-breaking charge transfer compounds has at least C 2 symmetry, and this symmetry is maintained upon linkage in the dyad, triad, tetrad, etc..
  • the symmetry can be maintained by having the atom linking the dye to the linker lying on the C 2 axis, as in cynines, malachites, xanthenes and perylenes.
  • the dye can be bound in such a way that the C 2 symmetry is retained in the bound structure— no atom bonded to the linkage center is on the C 2 axis.
  • one aspect of the disclosure provides for the synthesis and unusual symmetry- breaking ICT properties of symmetrical BODIPY dyads, wherein the units are connected through the meso position either indirectly by an intervening phenylene or directly through a C-C bond. Further investigation found the directly linked dyad to have excited-state properties that mimic behavior found in 9,9'-bianthryl.
  • Phenylene-bridged BODIPY dyad 23 of Figure 16 was initially targeted due to its structural semblance to BODIPY-porphyrin hybrids.
  • Dyad 23 was prepared by acid-catalyzed condensation of
  • Dyad 26 was prepared in low yield ( ⁇ 3%) from 1 ,1 ,2,2-tetrakis(5-methyl-1 H-pyrrol-2yl)ethene, which in turn was synthesized by a McMurry reaction, using standard oxidation and difluoroborylation conditions (Eq I). Although X-ray quality single crystals of dyad 26 have not been obtained, structure minimization using DFT (B3LYP/63lg*) methods indicated that the planar BODIPY units of dyad 26 have local geometries similar to those of dyad 23, and are canted at a dihedral angle of 71 ° with respect to each other.
  • dyad 26 represents the first example of a dyad that combines symmetry- breaking formation of an emissive ICT state with intense absorption in the visible region of the spectrum. While porphyrins are in many respects related to dipyrrins, the meso-linked porphyrin analogues of dyad 26 do not undergo symmetry-breaking ICT because formation of such an excited state is endothermic with respect to the Si state. BODIPY dyads directly linked at the a- or ⁇ positions also do not exhibit this sort of emissive behavior. However, Benniston et al.
  • BODIPY dyads 23 and 26 lead to formation of ICT states in polar media by solvent-induced symmetry breaking. The further presence of strong absorption at visible wavelengths enables these molecules to mimic features seen in the photosynthetic reaction center. Model systems that possess both these characteristics are rare. Differing degrees of rotational freedom in the dyads significantly alter the behavior of the ICT state. Whereas dyad 23 undergoes rapid non-radiative decay to the ground state, the more hindered dyad 26 has a long-lived ICT state with moderate-to-high fluorescence quantum efficiency.
  • Femtosecond transient absorption measurements were performed using a Tksapphire regenerative amplifier (Coherent Legend, 3.5 mJ, 35 fs, 1 kHz repetition rate). Approximately 10% of the amplifier output was used to pump a type II OPA (Spectra Physics OPA-80OC) resulting in the generation of excitation pulses centered at 508 nm with 1 1 .5 nm of bandwidth. At the sample position, the pump was lightly focused to a spot size of 0.29 mm (FWHM) using a 50 cm CaF 2 lens. Probe pulses were generated by focusing a small amount of the amplifier output into a rotating CaF 2 plate, yielding a supercontinuum spanning the range of 320-950 nm. A pair of off-axis aluminum parabolic mirrors collimated the supercontinuum probe and focused it into the sample.
  • the measured transient spectra indicate that in dyad 23, the initially excited population evolves over time to form an ICT state that non-radiatively returns to the ground state while in dyad 26 the ICT state persists for nanosecond or longer time scales.
  • the transient spectra can be described using a three-state model governed by a series of sequential first order rate processes:
  • Csi ⁇ and Cicr(t) denote their time-dependent populations of the Si and ICT states of a given dyad
  • ⁇ $ ⁇ ( ⁇ ) and ⁇ / ⁇ ) represent the time-independent characteristic transient absorption spectrum that results from the population of either state.
  • the present disclosure provides for an organic photosensitive optoelectronic device comprising: at least one compound chosen from a higher order structure, wherein said compound's absorptivity of light at some visible wavelength is about > 10 4 M "1 cm "1 , and wherein said compound is capable of undergoing symmetry-breaking intramolecular charge transfer in the excited state.
  • the organic photosensitive devices disclosed herein can be, for example, an organic
  • the at least one compound is chosen from dyads of xanthenes dyes, coumarins, acridines, phthalocyanines,
  • the compound is chosen from even higher order structures such as triads and tetrads.
  • the intramolecular charge transfer occurs in a polarizing medium.
  • the intramolecular charge transfer in the excited state is energetically accessible from a photogenerated Si state in a polarizing medium.
  • the dyads may be connected either directly or through a linker (such as saturated or unsaturated linear or branched hydrocarbons, or aromatic rings, e.g., phenylene, or constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkynyl, alkenyl, a heterocycle, a diazo or organosilane moiety), such that the dyads are arranged in linear or cofacial fashion.
  • a linker such as saturated or unsaturated linear or branched hydrocarbons, or aromatic rings, e.g., phenylene, or constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkynyl, alkenyl, a heterocycle, a diazo or organosilane moiety
  • the higher order compound is 1 ,4-Bis(4,4- difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl)benzene or a salt or hydrate thereof.
  • the higher order compound is Bis(4,4- difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl), or a salt or hydrate thereof.
  • a further embodiment is directed to a process for preparing 1 ,4- Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl)benzene, or a salt or hydrate thereof, comprising treating a mixture comprising terephthalaldehyde and 2-methylpyrrole with a halogenated carboxylic acid, an oxidizing agent, and Lewis acid to form 1 ,4-Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8- yl)benzene.
  • the halogenated carboxylic acid can be trifluoroacetic acid
  • the oxidant can be DDQ
  • the Lewis acid can be boron trifluoride diethyl etherate.
  • An additional embodiment is directed to a process for preparing Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl), or a salt or hydrate thereof, comprising treating a mixture comprising a first Lewis acid and a transition metal with a mixture comprising bis(5-methyl-1 H-pyrrol-2-yl)methanone to form 1 , 1 ,2,2-tetrakis(5-methyl-1 H-pyrrol-2-yl)ethene; and treating a mixture comprising 1 ,1 ,2,2-tetrakis(5-methyl-1 H-pyrrol-2-yl)ethene and a base with an oxidant and second Lewis acid to form Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a- diaza-s-indacene-8-yl).
  • the first Lewis acid can be TiCI4, the transition metal can be zinc, the base can be triethylamine, the oxidant can be DDQ, and the second Lewis acid can be boron trifluoride diethyl etherate.
  • the present disclosure also provides for methods of making an organic photosensitive device comprising an organic photosensitive optoelectronic device, wherein said organic photosensitive optoelectronic device comprises: at least one compound chosen from a dyad or higher order structure, wherein said compounds absorptivity of light at some visible wavelength is about > 10 4 M "1 cm "1 , and wherein said compound is capable of undergoing symmetry-breaking
  • BenzoBODIPY was prepared in two steps from the corresponding pyrrole and aldehyde followed by retro-Diels-Alder deprotection.
  • the required pyrrole was prepared via Barton-Zard synthesis from the necessary precursors with yields generally >80 %.
  • the pyrrole carboxylate ester was converted to the methyl pyrrole moiety using lithium aluminum hydride and used without further purification due to its sensitivity to air.
  • a yield of about 40 % was obtained for the masked BenzoBODIPY.
  • the masked BenzoBODIPY was quantitatively converted to BenzoBODIPY. The materials were then recrystallized into copper-colored crystals and sublimed.
  • IndoBODIPY was prepared by first isolating its corresponding diindolyl-methane precursor. The precursor was isolated using known literature techniques. The boron complex was prepared using conditions identical to those of BenzoBODIPY, though only a yield of 7 % was achieved. The materials were recrystallized to give a purple solid.
  • CyanoBODIPY was prepared using the synthetic scheme shown in Figure 3.
  • Example 2 Optical Properties of BenzoBODIPY, IndoBODIPY, and CvanoBODIPY
  • IndoBODIPY broadened significantly, deviating from the narrow bandwidth that is usually observed for this class of materials as exhibited by BenzoBODIPY in Figure 7(a).
  • Figure 7 also shows that the film excitation of BenzoBODIPY was much wider and more red shifted than the solution absorption due to strong intermolecular interactions. A larger Stokes shift was also observed when comparing solution and solid-state.
  • Photovoltaic devices using BenzoBODIPY as a donor material and a device using CuPc as a donor material were fabricated on ITO-glass substrates cleaned with Tergitol, alcohols, acetone, followed by UV-ozone treatment.
  • Cm MRR Limited
  • BCP 2,9-dimethyl-4,7-diphenyl-1 ,10-phenanthroline
  • BenzoBODIPY were purified by sublimation prior to use.
  • Aluminum Alfa Aesar
  • All devices were fabricated as lamellar devices in a vacuum deposition chamber with a fixed deposition rate for each layer.
  • Three BenzoBODIPY devices were fabricated each with a different donor layer thickness— 10 nm, 20 nm, and 30 nm.
  • Device performance (Current- Voltage curve and external quantum efficiency (EQE)) was measured under simulated AM 1 .5G solar illumination (Oriel Instruments) using a Keithley 2420 3A Source Meter. The device structures and performance of each device are summarized below and in Figure 9.
  • CuPc Device Glass/ITO/CuPc(40 nm)/C 60 (40 nm)/BCP(10nm)/AI
  • BenzoBODIPY Device Glass/ITO/BDPY(30-10 nm)/C 60 (40 nm)/BCP(10 nm)/AI.
  • CyanoBODIPY purified by sublimation was used in preparing the devices.
  • the devices were prepared and tested under the conditions described above in Example 3.
  • Unannealed and annealed CyanoBODIPY devices employed copper phthalocyanine (CuPc) as an electron donor material and a 1 : 1 ratio codeposited layer of CyanoBODIPY and Cm as an electron acceptor.
  • the annealed device the device was heated at 1 10 °C under nitrogen for 10 minutes after deposition of the acceptor layer.
  • the device structures are summarized as follows:
  • 2-M ethyl pyrrole was obtained by a Wolff-Kishner reduction of pyrrole- 2-carboxaldehyde as previously described.
  • 1 -Methyl-4,7-dihydro-2/-/-4,7- ethanoisoindole was prepared by lithium aluminum hydride reduction of the corresponding ester according to literature procedure. All other reagents were purchased from commercial vendors and used without further purification. All air- sensitive manipulations were performed using standard Schlenk techniques as needed, following the procedures indicated below for each preparation. NMR spectra were recorded at ambient temperature on Varian Mercury 400 MHz and 600 MHz spectrometers. 1 H chemical shifts were referenced to residual solvent.
  • UV-vis spectra were recorded on a Hewlett-Packard 4853 diode array spectrophotometer. Steady-state emission experiments were performed using a Photon Technology International QuantaMaster Model C-60SE spectrofluorimeter. Fluorescence lifetime measurements were performed by a time-correlated single-photon counting method using an IBH Fluorocube lifetime instrument by equipped with a 405 nm or 435 nm LED excitation source. Quantum efficiency measurements were carried out using a Hamamatsu C9920 system equipped with a xenon lamp, calibrated integrating sphere and model C10027 photonic multichannel analyzer.
  • Phenylene Bridged Dyad 23 Terephthalaldehyde (762 mg, 5.68 mmol) and 2-methylpyrrole (2.03 g, 23.3 mmol) were dissolved in dry, degassed CH 2 CI 2 (40 mL) under N 2 . The resulting solution was further degassed for 10 min, and trifluoroacetic acid (64 ⁇ _, 0.84 mmol) was added in two portions, causing the solution to darken immediately, and the reaction was allowed to proceed with stirring for 2 h. DDQ (2.58 g, 1 1 .4 mmol) was added in one portion, causing an immediate color change to dark red-orange, and the resulting mixture was stirred for 13 h.
  • N,N- Diisopropylethylamine (8.0 mL, 46 mmol) was added at once, causing a color change to dark brown, and stirring was continued for 15 min.
  • Boron trifluoride diethyl etherate (8.0 mL, 64 mmol) was added slowly over the course of 1 min, causing the mixture to warm slightly. After 45 min, the mixture was quenched with NaHC0 3 (5% aq, 200 mL) and stirred vigorously for 2 h. Organics were removed and washed with Na 2 S0 3 (10% aq, 2 100 mL), HCI (5% aq, 1 ⁇ 100 mL), and brine (2 100 mL).
  • Phenylene Bridged Dyad 24 Terephthalaldehyde (1 g, 7.55 mmol) and 2,4-dimethylpyrrole (2.98 g, 31 .3 mmol) were dissolved in dry, degassed CH 2 CI 2 (30 mL) under N 2 . The resulting solution was further degassed for 10 min, and trifluoroacetic acid (1 drop) was added and the reaction was allowed to proceed with stirring for 5 h. DDQ (3.38 g, 14.9 mmol) was added in one portion, and the resulting mixture was stirred overnight.
  • Phenylene Bridged Dyad 25 Terephthalaldehyde (1 g, 7.46 mmol) and 2,4-dimethyl-3-ethylpyrrole (3.67 g, 29.8 mmol) were dissolved in dry, degassed CH 2 CI 2 (40 mL) under N 2 . The resulting solution was further degassed for 10 min, and trifluoroacetic acid (1 drop) was added and the reaction was allowed to proceed with stirring for 2 h. DDQ (3.39 g, 14.9 mmol) was added in one portion, causing an immediate color change to dark red-orange, and the resulting mixture was stirred for 13 h.
  • Example 6 General Reaction Scheme for Directly Linked Dyads 26, 27, 28, and 29 of Figure 16.
  • ⁇ /,/V-Diisopropylethylamine (8.58 mL, 49.3 mmol) was added at room temperature, causing a color change to clear orange, and stirring was continued for 30 min followed by dropwise addition of BF 3 »OEt 2 (6.18 mL, 49.3 mmol). During addition of BF 3 »OEt 2 the color changed to dark red.
  • ⁇ /,/V-Diisopropylethylamine (0.10 mL, 0.58 mmol) was added in one portion, followed after 15 min by dropwise addition of BF 3 »OEt 2 (0.07 mL, 0.6 mmol).
  • the reaction was left stirring for 15 min and then was quenched with saturated Na 2 S 2 0 3 (25 mL), washed with saturated NaHC0 3 (2 ⁇ 50 mL) and the organic layer was removed.
  • Step 1 1 .1 .2.2-tetrakis(5-methyl-IH-pyrrol-2-yl)ethene.
  • Titanium tetrachloride (87 uL, 0.80 mmol) was added dropwise to a solution of dry THF (15 mL) at 0 °C under nitrogen. The solution was stirred for 10 min, after which a suspension of zinc powder (98 mg, 1 .5 mmol) in 3 mL of dry THF was added via cannula. The resulting blue slurry was heated at reflux for 3 h and cooled to room temperature. Dry pyridine (55 uL, 0.68 mmol) was added and the solution set to reflux for 30 min.
  • Step 2 Bis(4,4-ditluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl). 1 , 1 ,2,2- tetrakis(5-methyl-1 H-pyrrol-2-yl)ethene (90 mg, 0.26 mmol) was dissolved in dry, degassed CH 2 CI 2 (15 mL) under N 2 . The solution was degassed for an additional 5 min, and Et 3 N (0.29 mL, 2.0 mmol) added by syringe. The resulting solution was stirred for 30 min at room temperature and DDQ (68 mg, 0.30 mmol) added.
  • Triad 30. 1 ,3,5-Benzenetricarbonyl trichloride (1 g, 3.76 mmol) was dissolved in dry dichloromethane (80 ml) under N 2 .
  • 2,4-Dimethyl-3-ethylpyrrole (2.78 g, 22.6 mmol) was added and the flask was fitted with a condenser and refluxed overnight.
  • ⁇ /Jv-Diisopropylethylamine (7.85 ml, 45.12 mmol) was added at reflux. After 15 minutes, the mixture was cooled to room temperature and boron trifluoride etherate (5.66 mL, 45.12 mmol) was added in one portion.
  • Example 8 General Reaction Scheme for Zinc Compounds 31 -34 of Figure 16.
  • Zinc Compound 31 5-Mesityldipyrromethane (2 g, 7.57 mmol) was dissolved in 200 ml of freshly distilled THF under Nitrogen. 2,3-Dichloro-5,6- dicyano-1 ,4-benzoquinone (DDQ) (1 .72 g, 7.57 mmol) in 15 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 5 ml of Triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure.
  • DDQ 2,3-Dichloro-5,6- dicyano-1 ,4-benzoquinone
  • the product mixture was dissolved in 200 ml of dichloromethane, and was washed with saturated NaHC0 3 solution in water (150 ml, 3 times) and brine (150 ml, 1 time). The solution was then dried over anhydrous Na 2 S0 4 and filtered. This solution of 5-mesityldipyrromethene was used without further purification.
  • the obtained solid was passed through short neutral alumina plug using hexanes/dichloromethane (50/50) mixture as eluent, the portion in orange color was collected. Solvent was then removed under reduced pressure to obtain 1 g of orange solid (14% yield).
  • the obtained 10 was further purified by gradient sublimation under ultra high vacuum (10 " 5 torr) at 180°C - 140°C - 100°C gradient temperature zones.
  • 1 H NMR 400 MHz, CDCI 3
  • Zinc Compound 32 A mixture of mesitaldehyde (4.6 g, 30.9 mmol) and 2-methylpyrrole (5 g, 61 .7 mmol) was dissolved in 200 ml dichloromethane in a 500-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. Then 5 drops of trifluoroacetic acid (TFA) was added to the reaction mixture, the solution turned to dark red color. Reaction mixture was stirred under nitrogen for 6 hours until the starting materials were completely consumed. The reaction was quenched with 3 ml of triethylamine.
  • TFA trifluoroacetic acid
  • Reaction mixture was then washed with saturated Na 2 CC>3 solution in water (100 ml, 3 times) and brine (100, 1 time). Solution was dried over anhydrous Na 2 S0 4 . Solvent was then removed under reduced pressure to obtain the viscous pale yellow liquid (it turns to solid upon standing at room temperature).
  • This product was dissolved in 250 ml of freshly distilled THF under Nitrogen. 2,3-Dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ) (7.02 g, 30.9 mmol) in 35 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour.
  • DDQ 2,3-Dichloro-5,6-dicyano-1 ,4-benzoquinone
  • Zinc Compound 33 A mixture of mesitaldehyde (5 g, 33.5 mmol) and 2,4dimethylpyrrole (6.4 g, 67 mmol) was dissolved in 250 ml dichloromethane in a 500-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. Then 5 drops of trifluoroaceticacid (TFA) was added to the reaction mixture, the solution turned to dark red color. Reaction mixture was stirred under Nitrogen for 7 hours until the starting materials were completely consumed. The reaction was quenched with 3 ml of triethylamine.
  • TFA trifluoroaceticacid
  • Reaction mixture was then washed with saturated Na 2 CC>3 solution in water (100 ml, 3 times) and brine (100, 1 time). Solution was dried over anhydrous Na 2 S0 4 . Solvent was then removed under reduced pressure to obtain the viscous pale yellow liquid (it turns to solid upon standing at room temperature).
  • the crude product obtained was dissolved in 250 ml of freshly distilled THF under nitrogen.
  • DDQ (7.61 g, 30.9 mmol) in 40 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 10 ml of Triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure.
  • the product mixture was dissolved in 500 ml of dichloromethane, and was washed with saturated NaHCC solution in water (250 ml, 3 times) and brine (250 ml, 1 time). The solution was then dried over anhydrous Na 2 S0 4 and filtered. This solution of 1 ,3, 7,9-tetramethyl-5-Mesityldipyrromethene was used without further purification.
  • reaction mixture was filter using filter paper. Solvent was then removed under reduced pressure. The obtained solid was passed through short neutral alumina plug using hexanes/dichloromethane (70/30) mixture as eluent, the portion in orange-red color was collected. Solvent was then removed under reduced pressure to obtain 3.0 g of orange-red solid (13 % total yield).
  • the obtained 33 was further purified by gradient sublimation under ultra high vacuum (10 "5 torr) at 230°C - 160°C - 120°C gradient temperature zones.
  • Zinc Compound 34 2,8diethyl1 ,3,7,9-tetramethyl-5- Mesityldipyrromethane.
  • a mixture of mesitylaldehyde (2 g, 13.4 mmol) and 3- ethyl2,4dimethylpyrrole (3.3 g, 26.8 mmol) was dissolved in 150 ml dichloromethane in a 500-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. Then 3 drops of trifluoroaceticacid (TFA) was added to the reaction mixture, the solution turned to dark red color. Reaction mixture was stirred under Nitrogen for 7 hours until the starting materials were completely consumed.
  • TFA trifluoroaceticacid
  • reaction was quenched with 3 ml of triethylamine. Reaction mixture was then washed with saturated Na 2 CC>3 solution in water (100 ml, 3 times) and brine (100, 1 time). Solution was dried over anhydrous Na 2 S0 4 . Solvent was then removed under reduced pressure. This product was dissolved in 150 ml of freshly distilled THF under nitrogen. DDQ (3.3 g, 13.4 mmol) in 15 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 10 ml of Triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure.
  • the obtained 34 was further purified by gradient sublimation under ultra high vacuum (10 "5 torr) at 240°C - 160°C - 120°C gradient temperature zones.
  • Example 9 An Organic Photosensitive Optoelectronic Device Using
  • OPVs using compound 31 of Figure 16 as a donor material and fullerene Cm as an acceptor material have been fabricated using vacuum deposition technique on glass coated with Indium doped Tin Oxide (ITO) substrate.
  • ITO Indium doped Tin Oxide
  • the OPV device with Mo03 as hole conducting/electron blocking layer was also fabricated.
  • the device structures and characteristics are shown in the table below and in Figure 34. Both devices have significant photocurrents (3.06 and 3.49 mA/cm2).
  • External Quantum Efficiency measurements (Figure 34(c)) confirm the contribution of compound 31 to the photocurrent (up to 30% EQE at 500 nm).
  • the Mo03 hole conducting/electron blocking layer increases the open circuit voltage (VOC) from 0.60 to 0.82 V, while the short circuit current (JSC) and the fill factor (FF) decreases slightly compared to the device without Mo03. Thus, both devices (D1 and D2) have comparable power conversion efficiency (0.9%).
  • VOC open circuit voltage
  • JSC short circuit current
  • FF fill factor
  • D1 ITO/Mo03 (8 nm)/31 (10 nm)/C60 (40 nm)/BCP (10 nm)/AI
  • D2 ITO/31 (10 nm)/C60 (40 nm)/BCP (10 nm) /AI.

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Abstract

The present disclosure generally relates to organic photosensitive optoelectronic devices comprising at least one boron dipyrrin compound. In addition, the present disclosure relates to methods of making organic photosensitive optoelectronic devices comprising at least one boron dipyrrin compound. The present disclosure also generally relates to chromophoric compounds that combine strong absorption of light at visible wavelengths with the ability to undergo symmetry-breaking intramolecular charge transfer (ICT), and their use for the generation of free carriers in organic photovoltaic cells (OPVs) and electric-field-stabilized geminate polaron pairs. The present disclosure also relates to the synthesis of such compounds, methods of manufacture, and applications in photovoltaic systems and organic lasers.

Description

DIPYRRIN BASED MATERIALS FOR PHOTOVOLTAICS,
COMPOUNDS CAPABLE OF UNDERGOING SYMMETRY BREAKING INTRAMOLECULAR CHARGE TRANSFER IN A POLARIZING MEDIUM AND ORGANIC PHOTOVOLTAIC DEVICES COMPRISING THE SAME
Cross-Reference to Related Application
[001 ] This application claims the benefit of priority to U.S. Provisional Patent Application No. 61/647,360 filed on May 15, 2012, and is a continuation-in- part of, and claims the benefit of priority to, U.S. Patent Application No. 13/564,953 filed on August 2, 2012. The contents of these two applications are incorporated herein by reference.
Statement Regarding Federally Sponsored Research
[002] This invention was made with U.S. Government support under Contract No. DE-SC0001013 awarded by the Department of Energy. The
government has certain rights to this invention. Joint Research Agreement
[003] The subject matter of this application was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university- corporation research agreement: University of Southern California, University of Michigan, and Global Photonic Energy Corporation. The agreement was in effect on and before the date the subject matter of this application was made, and such was made as a result of activities undertaken within the scope of the agreement.
[004] The present disclosure generally relates to organic photosensitive optoelectronic devices comprising at least one boron dipyrrin compound. In addition, the present disclosure relates to methods of making organic photosensitive optoelectronic devices comprising at least one boron dipyrrin compound.
[005] The present disclosure also generally relates to chromophoric compounds, including boron dipyrrin compounds, that combine strong absorption of light at visible to near infrared wavelengths with the ability to undergo symmetry- breaking intramolecular charge transfer (ICT), and their use for the generation of free carriers in organic photovoltaic cells (OPVs) and electric-field-stabilized geminate polaron pairs. The present disclosure also relates to the synthesis of such compounds, methods of manufacture, and applications in photovoltaic systems and organic lasers.
[006] Optoelectronic devices rely on the optical and electronic properties of materials to either produce or detect electromagnetic radiation electronically, or to generate electricity from ambient electromagnetic radiation.
[007] Photosensitive optoelectronic devices convert electromagnetic radiation into electricity. Solar cells, also called photovoltaic (PV) devices, are a type of photosensitive optoelectronic device that is specifically used to generate electrical power. PV devices, which may generate electrical energy from light sources other than sunlight, can be used to drive power consuming loads to provide, for example, lighting, heating, or to power electronic circuitry or devices such as calculators, radios, computers or remote monitoring or communications equipment. These power generation applications also often involve the charging of batteries or other energy storage devices so that operation may continue when direct illumination from the sun or other light sources is not available, or to balance the power output of the PV device with a specific application's requirements. As used herein the term "resistive load" refers to any power consuming or storing circuit, device, equipment or system.
[008] Another type of photosensitive optoelectronic device is a
photoconductor cell. In this function, signal detection circuitry monitors the resistance of the device to detect changes due to the absorption of light. [009] Another type of photosensitive optoelectronic device is a
photodetector. In operation a photodetector is used in conjunction with a current detecting circuit which measures the current generated when the photodetector is exposed to electromagnetic radiation and may have an applied bias voltage. A detecting circuit as described herein is capable of providing a bias voltage to a photodetector and measuring the electronic response of the photodetector to electromagnetic radiation.
[010] These three classes of photosensitive optoelectronic devices may be characterized according to whether a rectifying junction as defined below is present, and also according to whether the device is operated with an external applied voltage, also known as a bias or bias voltage. A photoconductor cell does not have a rectifying junction and is normally operated with a bias. A PV device has at least one rectifying junction and is operated with no bias. A photodetector has at least one rectifying junction and is usually but not always operated with a bias. As a general rule, a photovoltaic cell provides power to a circuit, device or equipment, but does not provide a signal or current to control detection circuitry, or the output of information from the detection circuitry. In contrast, a photodetector or
photoconductor provides a signal or current to control detection circuitry, or the output of information from the detection circuitry but does not provide power to the circuitry, device or equipment.
[01 1 ] Traditionally, photosensitive optoelectronic devices have been constructed of a number of inorganic semiconductors, e.g., crystalline, polycrystalline and amorphous silicon, gallium arsenide, cadmium telluride and others. Herein the term "semiconductor" denotes materials which can conduct electricity when charge carriers are induced by thermal or electromagnetic excitation. The term "photoconductive" generally relates to the process in which electromagnetic radiant energy is absorbed and thereby converted to excitation energy of electric charge carriers so that the carriers can conduct, i.e., transport, electric charge in a material. The terms "photoconductor" and "photoconductive material" are used herein to refer to semiconductor materials which are chosen for their property of absorbing electromagnetic radiation to generate electric charge carriers.
[012] PV devices may be characterized by the efficiency with which they can convert incident solar power to useful electric power. Devices utilizing crystalline or amorphous silicon dominate commercial applications, and some have achieved efficiencies of 23% or greater. However, efficient crystalline-based devices, especially of large surface area, are difficult and expensive to produce due to the problems inherent in producing large crystals without significant efficiency-degrading defects. On the other hand, high efficiency amorphous silicon devices still suffer from problems with stability. Present commercially available amorphous silicon cells have stabilized efficiencies between 4 and 8%.
[013] PV devices may be optimized for maximum electrical power generation under standard illumination conditions (i.e., Standard Test Conditions which are 1000 W/m2, AM1 .5 spectral illumination), for the maximum product of photocurrent times photovoltage. The power conversion efficiency of such a cell under standard illumination conditions depends on the following three parameters: (1 ) the current under zero bias, i.e., the short-circuit current c, in Amperes; (2) the photovoltage under open circuit conditions, i.e., the open circuit voltage Voc, in Volts; and (3) the fill factor, ff.
[014] PV devices produce a photo-generated current when they are connected across a load and are irradiated by light. When irradiated under infinite load, a PV device generates its maximum possible voltage, V open-circuit, or Voc- When irradiated with its electrical contacts shorted, a PV device generates its maximum possible current, I short-circuit, or Isc- When actually used to generate power, a PV device is connected to a finite resistive load and the power output is given by the product of the current and voltage, I *V. The maximum total power generated by a PV device is inherently incapable of exceeding the product lSc x V0c- When the load value is optimized for maximum power extraction, the current and voltage have the values Lax and Vmax, respectively.
[01 5] A figure of merit for PV devices is the fill factor, ff defined as:
ff = { lmax Vmax }/{ lSC Voc } (1 ) where ff is always less than 1 , as Isc and Voc are never obtained simultaneously in actual use. Nonetheless, as ff approaches 1 , the device has less series or internal resistance and thus delivers a greater percentage of the product of Isc and V0c to the load under optimal conditions. Where Pinc is the power incident on a device, the power efficiency of the device, ηΡ, may be calculated by:
Figure imgf000007_0001
[01 6] To produce internally generated electric fields that occupy a substantial volume of the semiconductor, the usual method is to juxtapose two layers of material with appropriately selected conductive properties, especially with respect to their distribution of molecular quantum energy states. The interface of these two materials is called a photovoltaic junction. In traditional semiconductor theory, materials for forming PV junctions have been denoted as generally being of either n- or p-type. Here n-type denotes that the majority carrier type is the electron. This could be viewed as the material having many electrons in relatively free energy states. The p-type denotes that the majority carrier type is the hole. Such material has many holes in relatively free energy states. The type of the background, i.e., not photo-generated, majority carrier concentration depends primarily on unintentional doping by defects or impurities. The type and concentration of impurities determine the value of the Fermi energy, or level, within the gap between the conduction band minimum and valance band maximum energies. The Fermi energy characterizes the statistical occupation of molecular quantum energy states denoted by the value of energy for which the probability of occupation is equal to ½. A Fermi energy near the conduction band minimum energy indicates that electrons are the predominant carrier. A Fermi energy near the valence band maximum energy indicates that holes are the predominant carrier. Accordingly, the Fermi energy is a primary
characterizing property of traditional semiconductors and the prototypical PV junction has traditionally been the p-n interface.
[017] The term "rectifying" denotes, inter alia, that an interface has an asymmetric conduction characteristic, i.e., the interface supports electronic charge transport preferably in one direction. Rectification is associated normally with a built- in electric field which occurs at the junction between appropriately selected materials.
[018] In the context of organic materials, the terms "donor" and "acceptor" refer to the relative positions of the HOMO and LUMO energy levels of two contacting but different organic materials. This is in contrast to the use of these terms in the inorganic context, where "donor" and "acceptor" may refer to types of dopants that may be used to create inorganic n- and p- types layers, respectively. In the organic context, if the LUMO energy level of one material in contact with another is lower, then that material is an acceptor. Otherwise it is a donor. It is energetically favorable, in the absence of an external bias, for electrons at a donor-acceptor junction to move into the acceptor material, and for holes to move into the donor material.
[019] A significant property in organic semiconductors is carrier mobility. Mobility measures the ease with which a charge carrier can move through a conducting material in response to an electric field. In the context of organic photosensitive devices, a layer including a material that conducts preferentially by electrons due to a high electron mobility may be referred to as an electron transport layer, or ETL. A layer including a material that conducts preferentially by holes due to a high hole mobility may be referred to as a hole transport layer, or HTL. In one embodiment, an acceptor material is an ETL and a donor material is a HTL.
[020] Conventional inorganic semiconductor PV cells employ a p-n junction to establish an internal field. Early organic thin film cell, such as reported by Tang, Appl. Phys Lett. 48, 183 (1986), contain a heterojunction analogous to that employed in a conventional inorganic PV cell. However, it is now recognized that in addition to the establishment of a p-n type junction, the energy level offset of the heterojunction also plays an important role. The energy level offset at the organic D-A
heterojunction is believed to be important to the operation of organic PV devices due to the fundamental nature of the photogeneration process in organic materials. Upon optical excitation of an organic material, localized Frenkel or charge-transfer excitons are generated. For electrical detection or current generation to occur, the bound excitons must be dissociated into their constituent electrons and holes. Such a process can be induced by the built-in electric field, but the efficiency at the electric fields typically found in organic devices (F ~ 106 V/cm) is low. The most efficient exciton dissociation in organic materials occurs at a donor-acceptor (D-A) interface. At such an interface, the donor material with a low ionization potential forms a heteroj unction with an acceptor material with a high electron affinity. Depending on the alignment of the energy levels of the donor and acceptor materials, the dissociation of the exciton can become energetically favorable at such an interface, leading to a free electron polaron in the acceptor material and a free hole polaron in the donor material.
[021 ] Organic PV cells have many potential advantages when compared to traditional silicon-based devices. Organic PV cells are light weight, economical in materials use, and can be deposited on low cost substrates, such as flexible plastic foils. However, organic PV devices typically have relatively low external quantum efficiency (electromagnetic radiation to electricity conversion efficiency), being on the order of 1 % or less. This is, in part, thought to be due to the second order nature of the intrinsic photoconductive process. That is, carrier generation requires exciton generation, diffusion and ionization or collection. There is an efficiency η associated with each of these processes. Subscripts may be used as follows: P for power efficiency, EXT for external quantum efficiency, A for photon absorption exciton generation, ED for diffusion, CC for collection, and INT for internal quantum efficiency. Using this notation: ηρ ~ ηΕΧτ = ηΑ * ηΕϋ * r\cc
r\EXT = r\A * ηΐΝΤ
[022] The diffusion length (I_D) of an exciton is typically much less (I_D ~ 50Δ) than the optical absorption length (-500Δ), requiring a tradeoff between using a thick, and therefore resistive, cell with multiple or highly folded interfaces, or a thin cell with a low optical absorption efficiency. [023] While favorable absorption and charge mobility characteristics make polymer organic PVs among the most highly efficient organic PV devices, polymer organic PVs may have several drawbacks. For example, polymers can be harder to synthesize, less predictable in terms of morphology, and not sublimable. Thus, there is a continuing need to develop new classes of compounds for photovoltaic applications.
[024] Disclosed herein is a new class of 4,4-difluoro-4-bora-3a,4a-diaza-s- indacene (BODIPY) dyes for use in organic optoelectronic devices, particularly PVs. Thus, the present disclosure provides an organic photosensitive optoelectronic device comprising at least one compound of formula (I):
Figure imgf000011_0001
(I)
wherein: R1 is chosen from an optionally substituted monocyclic group, an optionally substituted C6-24 multicyclic group, and an optionally substituted meso-linked BODIPY, or R1 and R2 and R7 taken together with any intervening atoms comprise a substituted BODIPY, wherein R1 is meso-linked and R2 and R7 are beta-linked;
R2 is chosen from hydrogen, an alkyl group, and a cyano group, or R2 and R3 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R2 and R1 and R7 taken together with any intervening atoms comprise a substituted BODIPY, wherein R1 is meso-linked and R2 and R7 are beta-linked; R3 is chosen from hydrogen, an alkyl group, and a cyano group, or R3 and R2 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R3 and R4 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group;
R4 is chosen from hydrogen, an alkyl group, and a cyano group, or R4 and R3 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group;
R5 is chosen from hydrogen, an alkyl group, and a cyano group, or R5 and R6 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group;
R6 is chosen from hydrogen, an alkyl group, and a cyano group, or R6 and R5 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R6 and R7 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group; and
R7 is chosen from hydrogen, an alkyl group, and a cyano group, or R7 and R6 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R7 and R1 and R2 taken together with any intervening atoms comprise a substituted BODIPY, wherein R1 is meso-linked and R2 and R7 are beta-linked;
and wherein the optionally substituted monocyclic and multicyclic groups are chosen from aryl and heteroaryl groups.
[025] In some embodiments, R1 is chosen from optionally substituted benzene and optionally substituted fused benzene.
[026] In some embodiments, R2 and R3 taken together with any intervening atoms, and R6 and R7 taken together with any intervening atoms, both comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, wherein the optionally substituted monocyclic and multicyclic groups are chosen from aryl and heteroaryl groups.
[027] In some embodiments, R3 and R4 taken together with any intervening atoms, and R5 and R6 taken together with any intervening atoms, both comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, wherein the optionally substituted monocyclic and multicyclic groups are chosen from aryl and heteroaryl groups.
[028] In some embodiments, R2 and R7 are both chosen from hydrogen, an alkyl group, and a cyano group.
[029] In some embodiments, R5 and R4 are both chosen from hydrogen, an alkyl group, and a cyano group.
[030] In some embodiments, R3 and R6 are both chosen from hydrogen, an alkyl group, and a cyano group.
[031 ] In some embodiments, R2, R3, R4, R5, R6, and R7 are all chosen from hydrogen, an alkyl group, and a cyano group.
[032] The present disclosure also provides methods for making the photosensitive optoelectronic devices of the present disclosure. In some embodiments, the method comprises depositing a photoactive region over a substrate, wherein the photoactive region comprises at least one compound of formula (I). In some embodiments, the photoactive region comprises a donor material and an acceptor material, wherein at least one of the donor and acceptor materials comprise at least one compound of formula (I).
[033] In addition, photoinduced electron transfer reactions are important for energy storage processes in both biological and photovoltaic systems. Interfacial charge separation is a step in the generation of free carriers in OPVs. In the photosynthetic reaction center, electron transfer from the "special pair" is preceded by ultrafast formation of an intradimer charge-transfer state via symmetry breaking. In principle, the same sort of symmetry-breaking strategy could be used to facilitate the generation of free carriers in OPVs, but has not been utilized due to several important limitations. First, in order to form an intramolecular charge-transfer (ICT) state akin to the intradimer Charge Transfer (CT) state in Photosystem II, there must be a driving force for the formation of a CT state. Second, candidate molecules must combine strong absorption of light at visible wavelengths with an ability to undergo symmetry-breaking ICT. There are few dimeric molecules that meet these criteria. To date, the best studied system of this sort is 9,9'-bianthryl. However, 9,9'-bianthryl predominantly absorbs ultraviolet light.
[034] As previously described in the literature, involvement of symmetry- breaking CT states can facilitate charge separation with minimal energy loss and slow recombination. This is likely the reason why the photosynthetic reaction center initiates its electron-transfer cascade with the fast (picosecond) formation of an intradimer CT state. Thus, a minimal-energy-loss mechanism could be useful for maximizing open-circuit voltage in OPVs. However, due to the low diffusivity of CT excitons in neat films, the use of standard donor/acceptor compounds in thin film photovoltaics has proven to be less desirable.
[035] Therefore, there is also a present need to develop compounds having accessible symmetry-breaking ICT states, since such states generally only form in polarizing environments. The archetypical example of such a molecule is 9,9'- bianthryl, which forms a normal singlet excited state (S-i ) in nonpolar solvents but undergoes ultrafast solvent-induced ICT in more polar environments.
[036] Without wishing to be bound by theory, it is believed that molecules that undergo symmetry-breaking ICT in polar environments will allow excitation energy to move quickly and over long distances through the bulk material in neat films by Forster energy transfer processes before internal conversion to an ICT state by symmetry breaking at the polarizing donor/acceptor interface (Figure 14).
[037] Therefore, there is also disclosed an organic photosensitive optoelectronic device comprising at least one higher order compound, such as dyads, triads and tetrads, that are capable of undergoing symmetry-breaking intramolecular charge transfer in a polarizing medium. In one embodiment, the intramolecular charge transfer occurs at a polarizing donor/acceptor interface.
[038] The higher order compounds disclosed herein exhibit a high absorptivity of light in the visible and near infrared spectrum. In at least one embodiment, "high absorptivity of light" includes absorptivity of > 104 M"1 cm"1 at one or more visible to near infrared wavelengths ranging from 350 to 1500 nm.
[039] In some embodiments, the higher order compound forms at least one donor and/or acceptor region in a donor-acceptor heterojunction. In some embodiments, the donor-acceptor heterojunction absorbs photons to form excitons. [040] In some embodiments, the device is an organic device, such as an organic photodetector, an organic solar cell, or an organic laser.
[041 ] There are also disclosed methods of making an organic
photosensitive optoelectronic device comprising a higher order compound. In one embodiment, the device may be an organic photodetector, in another an organic solar cell.
[042] The foregoing and other features of the present disclosure will be more readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the attached drawings. It will be noted that, for convenience, all illustrations of devices show the height dimension exaggerated in relation to the width.
[043] Figure 1 depicts a scheme for synthesizing BenzoBODIPY.
[044] Figure 2 depicts a scheme for synthesizing IndoBODIPY.
[045] Figure 3 depicts a scheme for synthesizing CyanoBODIPY.
[046] Figure 4 provides Nuclear Magnetic Resonance (NMR) data for BenzoBODIPY.
[047] Figure 5 provides NMR data for IndoBODIPY.
[048] Figure 6 provides NMR data for CyanoBODIPY.
[049] Figure 7(a) shows absorption spectra for synthesized BenzoBODIPY in its solution and solid states.
[050] Figure 7(b) shows an absorption spectrum for synthesized
IndoBODIPY in its solution state.
[051 ] Figure 7(c) shows excitation and emission spectra for BenzoBODIPY in its solution and solid states. [052] Figure 8(a) shows solution absorption and emission spectra for CyanoBODIPY.
[053] Figure 8(b) shows film excitation, emission, and absorption spectra for CyanoBODIPY.
[054] Figures 9(a), 9(b), and 9(c) show PV performance data of an organic PV using CuPc as the donor material and of organic PVs using BenzoBODIPY as the donor material at various thicknesses. In particular, Fig. 9(a) shows current- voltage curves, Fig. 9(b) shows external quantum efficiencies (EQEs), and Fig. 9(c) shows dark current curves.
[055] Figures 10(a) and 10(b) show additional PV performance data of organic PVs using BenzoBODIPY as the donor material at various thicknesses. In particular, Fig. 10(a) shows current-voltage curves, and Fig. 10(b) shows EQEs.
[056] Figures 11 (a) and 11 (b) show PV performance data of organic PVs that were thermally annealed after deposition of the donor layer but prior to deposition of the acceptor material and that used BenzoBODIPY as the donor material at various thicknesses. In particular, Fig. 1 1 (a) shows current-voltage curves, and Fig. 11 (b) shows EQEs.
[057] Figure 11 (c) shows absorption spectra for non-treated and thermally treated organic PVs.
[058] Figures 12(a) and 12(b) show PV performance data of organic PVs that were thermally annealed after deposition of the donor and acceptor layers and that used BenzoBODIPY as the donor material at various thicknesses. In particular, Fig. 12(a) shows current-voltage curves, and Fig. 12(b) shows EQEs.
[059] Figures 13(a) and 13(b) show PV performance data of an organic PV device using CuPc and C6o as donor and acceptor materials, respectively, and of an organic PV device using CuPc as the donor material and a 1 :1 ratio of
CyanoBODIPY and C60 as acceptor materials. One CyanoBODIPY device was thermally annealed after deposition of the acceptor layer. Fig. 13(a) shows current- voltage curves and Fig. 13(b) shows EQEs.
[060] Figure 14 is a schematic representation of symmetry-breaking ICT to facilitate charge separation at a polarizing donor/acceptor interface.
[061 ] Figure 15 shows examples of dyes that can be coupled into dimers, trimers, etc. for symmetry breaking ICT.
[062] Figure 16 shows examples of dipyrrin chromophores synthesized for symmetry breaking ICT.
[063] Figure 17 shows the synthetic scheme and displacement ellipsoid of BODIPY dyad 23 of Figure 16.
[064] Figure 18 shows a synthetic scheme for BODIPY dyad 26.
[065] Figure 19 represents the normalized absorption and emission spectra of dyad 23 and the absorption spectra of 3,5-Me2BODIPY-Ph in CH2CI2.
[066] Figure 20 shows the cyclic voltammetry of dyad 23 in CH2CI2.
[067] Figures 21 (a) and 21 (b) represent the ultrafast transient absorption spectra of dyad 23 after excitation at 508 nm, and time domain slices of transient absorptions at 507 and 550 nm with predicted traces based on kinetic parameters.
[068] Figure 22 shows the transient absorption of dyad 23 in toluene.
[069] Figure 23 shows the absorption spectra of dyad 26 in CH2CI2 and emission spectra of 26 in solvents of varying polarity.
[070] Figure 24 shows the normalized emission decays of dyad 26 in cyclohexane (564 nm) and CH2CI2 (651 nm) following excitation at 405 nm.
[071 ] Figure 25 represents the transient absorption of dyad 26 in CH2CI2. [072] Figure 26 represents the generation of stabilized intramolecular polaron pairs in the presence of an electric field.
[073] Figure 27(a), 27(b), and 27(c) represent methods for structuring symmetry-breaking ICT dyads, triads, and tetrads ((a), (b) and (c) respectively) where R represents the linking molecule between the dyes.
[074] Figure 28 represents methods for connecting two dyes to facilitate symmetry-breaking ICT.
[075] Figure 29 shows the transient absorption of dyad 23 in acetonitrile with all transient spectral features completely relaxed within ca. 150 ps.
[076] Figure 30 represents time domain slices of transient absorption of dyad 23 in toluene.
[077] Figure 31 shows the normalized emission decay of dyad 23 in toluene (535 nm) following excitation at 435 nm.
[078] Figure 32 represent time domain slices of transient absorptions at 475 and 575 nm with predicted traces based on kinetic parameters.
[079] Figure 33 shows the X-ray structure of dyad 23.
[080] Figure 34(a) shows device structures of organic PVs using compound 31 of Figure 16; Figure 34(b) shows current-voltage characteristics of the organic PVs under AM1 .5G illumination; and Figure 34(c) shows EQEs.
[081 ] Figure 35 shows a non-limiting example of a lamellar device structure of an organic PV using at least one compound of formula (I) as a donor material.
[082] The compounds described herein have application in organic photosensitive optoelectronic devices. In some embodiments, the organic photosensitive optoelectronic device is a solar cell. In other embodiments, the organic photosensitive optoelectronic device is a photodetector. In some embodiments, the organic photosensitive optoelectronic device is a photosensor. In other embodiments, the organic photosensitive optoelectronic device is a
photoconductor.
[083] In some embodiments, the at least one compound of formula (I) exhibits an absorptivity of light greater than 104 M"1 cm"1 at one or more wavelengths ranging from 450 to 900 nm. In some embodiments, the at least one compound of formula (I) exhibits an absorptivity of light greater than 105 M"1 cm"1 at one or more wavelengths ranging from 450 to 900 nm.
[084] As used herein, the term "monocyclic" refers to a carbocyclic or heterocyclic group comprising only a single ring.
[085] As used herein, the term "multicyclic" refers to a carbocyclic or heterocyclic group comprising at least two rings. Some or all of the rings in the "multicyclic" group can be peri-fused, ortho-fused and/or bridged.
[086] As used herein, the term "alkyl" refers to a straight-chain or branched saturated hydrocarbyl group.
[087] As used herein, the term "aryl" refers to an aromatic hydrocarbyl group. The "aryl" group is monocyclic or multicyclic.
[088] As used herein, the term "heteroaryl" refers to an aryl group having at least one N, O, or S ring atom, with C atom(s) as the remaining ring atom(s).
[089] As used herein, the term "substituted" means that the chemical group has at least one hydrogen atom replaced by a substituent.
[090] In some embodiments, the at least one compound of formula (I) is chosen from
Figure imgf000021_0001

Figure imgf000022_0001
Figure imgf000022_0002
wherein R is chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group. In some embodiments, the optionally substituted monocyclic or multicyclic group of R is an aryl or a heteroaryl group. In some embodiments, R is chosen from
Figure imgf000022_0003
Figure imgf000022_0004
Figure imgf000023_0001
wherein R' is chosen from H, alkyl, and aryl or heteroaryl groups.
[091 ] In certain embodiments, the at least one compound of formula (I) does not include
Figure imgf000023_0002
[092] In some embodiments of the photosensitive optoelectronic device of the present disclosure, the device comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises at least one compound of formula (I). In some embodiments, the at least one donor material comprises at least one compound of formula (I). In some embodiments, the at least one acceptor material comprises at least one compound of formula (I). In some embodiments, both the donor and acceptor materials comprise at least one compound of formula (I), wherein the at least one compound of formula (I) that comprises the donor material is different from the at least one compound of formula (I) that comprises the acceptor material. As one of ordinary skill in the art would appreciate, the use of the BODIPY compounds disclosed herein as a donor and/or acceptor material depends upon the relationship of the HOMO and LUMO levels between two BODIPY compounds or between the BODIPY compound and a second organic semiconducting material used to complete a donor-acceptor pair.
[093] In some embodiments, the at least one donor material comprises at least one compound of formula (I), and the at least one acceptor material comprises a fullerene or a derivative thereof. In certain embodiments, the at least one acceptor material comprises at least one of C6o, C7o and phenyl-C7i-butyric-acid-methyl ester (PCBM).
[094] In some embodiments, the at least one acceptor material comprises at least one compound of formula (I), and the at least one donor material comprises copper phthalocyanine (CuPc).
[095] In some embodiments, the at least one acceptor material comprises at least one compound of formula (I) and a second organic semiconducting material. In certain embodiments, the second organic semiconducting material comprises Cm-
[096] In some embodiments, the at least one donor material and the at least one acceptor material form a donor-acceptor heterojunction. The donor-acceptor heteroj unction may be planar or non-planar. For example, the donor and acceptor materials may form at least one of a mixed heterojunction, planar heterojunction, bulk heterojunction, and hybrid planar-mixed heterojunction.
[097] In some embodiments, the at least one donor material and the at least one acceptor material form a lamellar structure, wherein the at least one donor material comprises at least one compound of formula (I) and has a thickness ranging from about 1 - 150 nm, or about 10 - 150 nm, or about 10 - 100 nm, or about 20 - 80 nm. A non-limiting example of a device comprising at least one donor material and at least one acceptor material forming a lamellar structure, wherein the at least one donor material comprises at least one compound of formula (I), is shown in Figure 35.
[098] The organic photosensitive optoelectronic device of the present disclosure may further comprise two electrodes comprising an anode and a cathode. A photoactive region can be located between the anode and the cathode, wherein the photoactive region comprises at least one compound of formula (I). In some embodiments, the photoactive region comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises the at least one compound of formula (I). The donor and acceptor materials may form a donor-acceptor heterojunction as described herein.
[099] Stacked organic photosensitive optoelectronic devices are further contemplated herein. The stacked device according to the present disclosure may comprise a plurality of photosensitive optoelectronic subcells, wherein at least one subcell comprises two electrodes comprising an anode and a cathode in superposed relation, and a photoactive region between the two electrodes, wherein the photoactive region comprises at least one compound of formula (I). In some embodiments, the photoactive region comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises at least one compound of formula (I). The donor and acceptor materials may form a donor-acceptor heterojunction as described herein. The donor and acceptor materials may form a lamellar structure as described herein.
[0100] When a subcell is used individually as a photosensitive
optoelectronic device, it typically includes a complete set of electrodes, i.e., positive and negative. In some stacked configurations, it is possible for adjacent subcells to utilize common, i.e., shared, electrode, charge transfer region or charge
recombination zone. In other cases, adjacent subcells do not share common electrodes or charge transfer regions. The term "subcell" is disclosed herein to encompass the subunit construction regardless of whether each subunit has its own distinct electrodes or shares electrodes or charge transfer regions with adjacent subunits. The subcells may be electrically connected either in parallel or in series.
[0101 ] The organic photosensitive optoelectronic devices of the present disclosure may also comprise one or more blocking layers, such as exciton blocking layers (EBLs), between the two electrodes. In some embodiments, one or more blocking layers are located between the photoactive region and the anode, between the photoactive region and the cathode, or both. Examples of blocking layers are described in U.S. Patent Publication Nos. 2012/0235125 and 201 1/0012091 and in U.S. Patent Nos. 7,230,269 and 6,451 ,415, which are incorporated herein by reference for their disclosure of blocking layers.
[0102] The organic photosensitive devices of the present disclosure may be structured in various configurations with varying material combinations. Examples of device configurations and materials are described in U.S. Patent Application No. 13/666,664, U.S. Patent Publication Nos. 2012/0235125 and 2010/0102304, and U.S. Patent Nos. 6,657,378; 6,580,027, and 6,352,777, which are incorporated herein by reference for their disclosure of organic photosensitive optoelectronic device structures, particularly photovoltaic structures, and materials.
[0103] Methods for making the photosensitive optoelectronic devices of the present disclosure are also disclosed herein. In some embodiments, the method comprises depositing a photoactive region over a substrate, wherein the photoactive region comprises at least one compound of formula (I). In some embodiments, the photoactive region comprises at least one donor material and at least one acceptor material, wherein at least one of the donor and acceptor materials comprises at least one compound of formula (I). In some embodiments, the at least one donor material comprises the at least one compound of formula (I). In some embodiments, the at least one acceptor material comprises the at least one compound of formula (I). In some embodiments, both the donor and acceptor materials comprise at least one compound of formula (I), wherein the at least one compound of formula (I) that comprises the donor material is different from the at least one compound of formula (I) that comprises the acceptor material.
[0104] In some embodiments, the deposition of the photoactive region comprises depositing at least one compound of formula (I) over the substrate. In some embodiments, the deposition of the photoactive region comprises codepositing an organic semiconducting material and at least one compound of formula (I) over the substrate. The deposition of the photoactive region may form at least one of a donor-acceptor mixed heterojunction, planar heterojunction, bulk heterojunction, and hybrid planar-mixed heterojunction. In some embodiments, the deposition of the photoactive region forms a lamellar device structure. [0105] In some embodiments, the deposition of the photoactive region comprises depositing at least one donor material over a substrate, thermally annealing the substrate and the at least one donor material, and depositing at least one acceptor material over the at least one donor material. In some embodiments, the at least one donor material comprises at least one compound of formula (I). In some embodiments, the at least one donor material comprises at least one compound of formula (I), and the at least one acceptor material comprises Cm- In other embodiments, the at least one acceptor material comprises at least one compound of formula (I).
[0106] In some embodiments, the deposition of the photoactive region comprises depositing at least one donor material over a substrate, depositing at least one acceptor material over the at least one donor material, and thermally annealing the substrate, the at least one donor material, and the at least one acceptor material. In some embodiments, the at least one donor material comprises at least one compound of formula (I). In some embodiments, the at least one donor material comprises at least one compound of formula (I), and the at least one acceptor material comprises Cm- In other embodiments, the at least one acceptor material comprises at least one compound of formula (I). In some embodiments, the at least one acceptor material comprises at least one compound of formula (I), and the at least one donor material comprises CuPc.
[0107] In some embodiments, annealing is performed between 90 °C and 150 °C from 0 to 30 minutes. Suitable times and temperatures for annealing may be chosen based on the particular materials used.
[0108] Organic layers may be deposited using methods known in the art. One advantage of the BODIPY dyes disclosed herein is that they are solution- processable and sublimable. Thus, in some embodiments, the at least one compound of formula (I) is deposited over a substrate using a technique chosen from spin casting and vapor deposition.
[0109] Another aspect of the present disclosure relates to compounds that exhibit the light absorption and symmetry breaking properties required for applications in OPVs. By extension, these compounds of the present disclosure mimic features seen in the photosynthetic reaction center.
[01 10] Compounds that exhibit the light absorption and symmetry breaking properties required for applications in OPVs include, for example, higher order compounds, such as symmetrical dyads, triads, tetrads, etc. These compounds may populate intramolecular charge-transfer states in a polarizing medium by symmetry breaking, but cannot do so in the absence of a polarizing medium because of their symmetry. The higher order compounds may have at least C2 symmetry and should have a luminescent lifetime of at least 1 ps to allow charge transfer to take place prior to other radiative or non-radiative decay processes.
[01 1 1 ] In one embodiment, the higher order compounds may comprise, for example, dye compounds chosen from perylenes, malachites, xanthenes, cyanines, bipyridines, dipyrrins, coumarins, acridines, phthalocyanines, subphthalocyanines, porphyrins, and acenes. These dyes may be substituted with alkyl, H, electron donating or electron withdrawing groups at any position other than the linking site to control the physical and electronic properties of the dye. The relevant physical properties include solubility as well as sublimation and melting temperatures. The relevant electronic properties include the absorption and emission energies, as well as the oxidation and reduction potentials. [01 12] In another embodiment, the higher order compounds are chosen from the following dipyrrin chromophores:
Figure imgf000030_0001
[01 13] Another embodiment of the present disclosure provides for symmetry- breaking ICT compounds and their use as chromophores for the generation of electric-field-stabilized geminate polaron pairs. These polaron pairs collapse in the absence of an electric field, generating a high concentration of excitons and may be useful for the construction of organic lasers. In this process a large electric field is applied to drive the charge separation of excitons formed on light absorption and stabilize the geminate polaron pairs toward recombination. This was accomplished with a lightly doped matrix, where the dopant absorbs light and acts as one of the polarons (cation or anion), with the other polaron on the matrix material. The
BODIPY dyads and related compounds described herein have donor and acceptor present in the same molecule (though in the absence of an electric field there is no driving force for excited-state charge separation), such that charge separation to form the geminate pairs can be efficiently achieved within the chromophore itself. This allows the chromophore to be doped into nonconductive host materials, preventing carrier leakage. The inherent C2 symmetry of the substituted porphryins ensure that nearly every molecule is present in an orientation that will promote charge separation (Figure 26). An orientation that cannot be efficiently coupled with the electric field is one in which the plane of the dyad is perpendicular to the applied electric field. By using a randomly doped film, only a low percentage of the dopant is present in the nonproductive orientation.
[01 14] In order to prove useful in solar cell applications, the constituent higher order dye compounds must exhibit high absorptivity (ε > 10"4 M"1 cm"1) of light at some visible to near infrared wavelengths (350-1500 nm), for example, dyads of xanthenes dyes (e.g., fluorescein, eosins, and rhoadmines), coumarins, acridines, phthalocyanines, subphthalocyanines, porphyrins, acenes such as tetracene or pentacene, perylenes, malachites, cyanines, bipyridines, and dipyrrins, among others. In some solar cell applications, for example, single cell solar cells, the higher order dye compounds may exhibit high absorptivity of light at some visible to near infrared wavelengths between 350 to 950 nm. In other solar cell applications, for example, tandem solar cells, the higher order dye compounds may exhibit high absorptivity of light at some visible to near infrared wavelengths between 350 nm to at least 1200 nm. In an organic photodetector, the higher order dye compounds may exhibit high absorptivity of light at some visible to near infrared wavelengths between 350 nm to at least 1500 nm.
[01 1 5] The dyad (or triad, tetrad, etc.) must also possess an intramolecular charge-transfer (ICT) state that is energetically accessible from the photogenerated Si state in a polarizing medium. It is known that the energy of an ICT state can be approximated as:
E(ICT) = IP(D) - EA(A) +C +ΔΕ80ιν (1)
where IP(D) is the ionization potential of the donor, EA(A) is the electron affinity of the acceptor, C is the Coulombic stabilization of a neighboring cation and anion in the system, and ΔΕ80ιν is the stabilization of the ion pair by a surrounding polar environment (due to solvent or otherwise).
[01 1 6] For the molecules proposed, the donor and acceptor are the same moiety, so a crude approximation of the energy of a symmetry-breaking ICT state can come from the energy required to pass one electron through the potential difference between the one-electron oxidation and reduction events, as determined by cyclic voltammetry or other electrochemical method. Since C and ΔΕ80ιν only serve to stabilize the ICT state, this method will always lead to an overestimate of the energy. Thus, for example, if the difference in oxidation and reduction events for a dye is 2.50 V, then the energy of an ICT state for a dyad constructed from that dye will be less than 2.50 eV. To a first approximation, dimers (and higher order structures) of dyes with a first singlet excited state (S-i) energy greater than E/cr- 0.260 eV (i.e., E,cr as determined by this method minus 10kT) may be able to undergo symmetry-breaking intramolecular charge transfer at a polarizing donor/acceptor interface to facilitate charge separation in photovoltaics. The oxidation and reduction potentials and E0o energies for some of the compounds in Figure 16 are listed in Table 1 .
Figure imgf000033_0001
Table 1 . Oxidation and reduction potentials of molecules from Figure 16 in CH2CI2.
[01 1 7] The absorption profiles of the chromophores in Figure 16 are generally similar to the monomer units of their respective dyes, indicating minimal excitonic coupling between the two (or three or more) dye units on the chromophore molecule. They are also generally invariant across different solvent polarities, since accessing any ICT state should first excite directly to the Si state. The absorption of the chromophores from Figure 16 are listed in Table 2 for different solvents.
ET (30) (kcal
Solvent mol V 23 24 25 26 27 28 29 30 31 32 33 34
Cyclohexane 30.9 513 NM 525 523 NM 540 NM 537 484 493 489 506
Toluene 33.9 515 501 526 526 516 542 550 537 486 495 491 508
Dichloromethane 40.7 513 500 525 530 515 541 550 538 485 493 488 506
Acetonitrile 45.6 508 495 520 526 516 538 545 531 481 490 NM NM
Figure imgf000034_0001
16. Solvent polarity index, No emission was observed in these solvents. NM - No measurement taken in this solvent.
[01 1 8] The fluorescence for each chromophore (Table 3) can be altered based on the solvent environment, as the increasing solvent polarity should stabilize access to the CT state and decrease the energy of that CT state. Thus, a red shift of any emissive CT state should be seen in the fluorescence spectra and is noted for directly linked dyads 26, 27, 28 and 29. Chromophores 31 -34 illustrate separate CT bands that grow in as solvent polarity increases at longer wavelength. However, the rest of the chromophores seem to possess non-emissive CT states. Evidence for these CT states is seen when measuring the photoluminescent quantum yield (Table 3), which decreases for all candidates as solvent polarity increases. The decrease in quantum yield indicates there is some state that is increasingly non-emissive as solvent polarity increases. PL uantum ield
Figure imgf000035_0001
Table 3. Photoluminescence quantum yields in varying solvents of compounds from Figure 16. aSolvent polarity index, bNo emission was observed in these solvents NM - no
measurement taken.
[01 19] Support for the formation of an ICT state in polar solvents was provided by femtosecond transient absorption measurements (Table 4). Excitation at a BODIPY wavelength (-500 nm) in acetonitrile populates the Si state, as reflected by the appearance of a stimulated emission band from 525-600 nm for the BODIPY chromophores. Over the course of 10 ps, this band disappears concomitant with the rise of a weak induced absorption band peaked at -545 nm that matches absorption spectra reported for the BODIPY radical anion. A global fit to the data yields a rate formation of this ICT state (kcr 1)- Subsequently, all transient spectral features decay with a rate constant given as krec '1. The evidence of the CT state decreases as solvent polarity decreases from acetonitrile to dichloromethane to toluene and the recombination increases (becomes faster) correspondingly. We also note that as sterics increase (i.e. from 1 to 4), /ccf 1 increases (becomes faster) and krec '1 decreases (becomes slower). TOLUENE DICHLO OMETHANE ACETONITRILE
Molecule k k 1 Molecule k k 1 Molecule k k 1
23 NA NA 1 18 ps 1.6 ns 23 4.8 ps 34 ps
24 NA NA 2 136 ps 3.2 ns 24 53.0 ps 196 ps
25 NA NA 3 165 ps 2.5 ns 25 74.0 ps 288 ps
26 4.5 ps NA 4 0.49 ps 6.7 ns 26 0.17 ps 650 ps
27 2.35 ps 14.5 ps 5 1.34 ps 10.3 ns 27 0.32 ps 1.93 ns
28 1.7 ps 6.1 ns 6 0.78 ps 16.8 ns 28 0.21 ps 1.8 ns
31 9.0 ps NA 10 5.7 ps NA 31 3.5 ps NA
32 5.7 ps NA 11 NA NA 32 1.1 ps NA
33 2.6 ps NA 12 NA NA 33 1 ps NA
Table 4. Rates of charge transfer (ke 1) and charge recombination (krec"1) for the compounds in Figure 16 in various solvents as calculated using femtosecond transient absorption spectroscopy. NA - No measurement was taken because of instrument limitation or lack of CT formation.
[0120] In order to undergo such symmetry-breaking charge transfer, the dyes must be able to communicate electronically (though there need not be any ground- state interaction). Thus, the manner in which they are connected is important. There are a number of possible ways to link the dyes together to allow for symmetry breaking ICT to take place. Three examples are illustrated in Figure 27 for bringing two, three, or four dyes together. For dyad-type structures, the two constituent dyes may be connected directly or through a linker that places them in linear or cofacial arrangements (Figure 28). The linker must have higher energy optical transitions than the dyes to prevent direct energy transfer from the dye to the linker. Numerous linkers can be utilized, including saturated and unsaturated hydrocarbon linkers, with the most important requirement being that the linker must have ground state oxidation and reduction potentials, such that the linker is neither reduced nor oxidized by the photoexcited dye.
[0121 ] Figure 27(a) contemplates a wide range of effectively divalent linkers. The linker could be a single atom, as illustrated for the Zinc based materials in compounds 31-34 of Figure 16. This divalent group can also be a disubstituted arene, as illustrated in compounds 23-25 or a single bond as illustrated in
compounds 26-29. One of skill in the art can envision a range of similar divalent linkers using other divalent atoms or effective divalent linkers constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkynyl, alkenyl, a single bond (R is a single bond), a heterocycle, a diazo or organosilane moiety. A tetravalent atom may also be used to link dyads, if the linker makes two covalent bonds to each dye. Such a connection with a carbon or silicon atom is termed a spiro connection and leads to a rigorous orthogonal of the two molecules bridged by the spiro C or Si.
[0122] Figure 27(b) illustrates three dyes disposed around a linker. This effectively trivalent linkage is demonstrated for 1 ,3,5-benzene in compound 30 of Figure 16. This linkage could also be a trivalent metal atom such as Al or Ga, or a transition metal. These complexes are analogous to compounds 31-34 of Figure 16, except the central metal atom would be surrounded by three bidentate ligands. One of skill in the art can envision a range of similar trivalent linkers using trivalent atoms or effective trivalent linkers constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkenyl, a heterocycle, or organosilane moiety.
[0123] Figure 27(c) illustrates four dyes bound to a central linker. This linkage could be a tetravalent metal atom such as Ti, Zr or Hf. These complexes are analogous to compounds 31-34 of Figure 16, except the central metal atom would be surrounded by four bidentate ligands. One of skill in the art can envision a range of similar tetravalent linkers using trivalent atoms or effective tetravalent linkers constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkenyl, a heterocycle, or organosilane moiety. A number of other geometries can be envisioned for higher-order structures, with the requirement that they be symmetric or pseudosymmetric in the ground state so that there is no driving force for ICT in the absence of a polarizing medium. Moreover, any interaction of the two molecules in the ground or excited state should not lead to the formation of an excited state lower in energy than the ICT, such as a triplet or excimeric excited state. These alternate excited states can exist, but they must be higher in energy than the ICT.
[0124] In one embodiment, the symmetry-breaking charge transfer compounds has at least C2 symmetry, and this symmetry is maintained upon linkage in the dyad, triad, tetrad, etc.. The symmetry can be maintained by having the atom linking the dye to the linker lying on the C2 axis, as in cynines, malachites, xanthenes and perylenes. Alternatively, the dye can be bound in such a way that the C2 symmetry is retained in the bound structure— no atom bonded to the linkage center is on the C2 axis.
[0125] To continue studies on charge and energy transfer reactions in BODIPY-porphyrin hybrids, one aspect of the disclosure provides for the synthesis and unusual symmetry- breaking ICT properties of symmetrical BODIPY dyads, wherein the units are connected through the meso position either indirectly by an intervening phenylene or directly through a C-C bond. Further investigation found the directly linked dyad to have excited-state properties that mimic behavior found in 9,9'-bianthryl.
[0126] Phenylene-bridged BODIPY dyad 23 of Figure 16 was initially targeted due to its structural semblance to BODIPY-porphyrin hybrids.
[0127] Dyad 23 was prepared by acid-catalyzed condensation of
terephthalaldehyde and 2-methylpyrrole, followed by oxidation with DDQ and difluoroborylation in the presence of Λ/JV-diisopropylethylamine and boron trifluoride diethyl etherate. Analysis of dyad 23 by single-crystal x-ray diffraction reveals two coplanar BODIPY units rendered identical by a crystallographic center of symmetry (Figure 33). The phenylene bridge is canted at an angle of 47° relative to the BODIPY planes, suggesting minimal steric encumbrance to partial rotation of the BODIPY units with respect to the linker. Thus, electronic superexchange, which requires interaction of the BODIPY and phenylene n-orbitals, should be possible across the phenylene bridge.
[0128] Absorption spectra of dyad 23 in solvents of varying polarity are nearly identical to the model compound 3,5Me2BODIPY-Ph, indicating minimal ground-state interaction or excitonic coupling between the chromophores of dyad 23 (Figure 19). Emission spectra of dyad 23 display small Stokes shifts that are nearly invariant in all 60 solvents. However, the photoluminescence quantum efficiencies (QE) are less than 0.1 and drop precipitously in the most polar solvents (Table 5). In contrast, the QE of 3,5Me2BODIPY-Ph is 0.29 in cyclohexane, and declines to 0.17 in acetonitrile. The sharp decrease in the QE of dyad 23 indicates the possible formation of a non-emissive charge-transfer state that entails some degree of symmetry breaking since the BODIPY units are identical to the linker.
Table 5
Figure imgf000039_0001
2-Methyltetrahydrofuran 36.5 51 1 540 0.046
Chloroform 39.1 515 538 0.097
Dichloromethane 40.7 513 538 0.069
Acetone 42.2 509 534 <0.001
N,N-Dimethylformaide 43.2 512 536 O.001
Acetonitrile 45.6 508 531 O.001 aSolvent polarity index
[0129] The potential for dyad 23 to undergo symmetry-breaking ICT was examined by electrochemistry. Cyclic voltammetry of dyad 23 revealed a reversible reduction (Ei/2 = -1 .37 V) and an irreversible oxidation (EPA = 940 mV, both versus Fc/Fc+). The difference between oxidation and reduction values (2.31 V) indicates that the Si state of dyad 23 (E0o = 2.38 eV in cyclohexane) should be energetic enough to undergo ICT, as previously discussed by Zander and Rettig.
[0130] Support for the formation of an ICT state in polar solvents was provided by femtosecond transient absorption measurements (Figure 21 ). Excitation of dyad 23 at 508 nm in acetonitrile populates the Si state, as reflected by the appearance of a stimulated emission band from 525-600 nm that matches the Si emission line shape. Over the course of 10 ps, this band disappears concomitant with the rise of a weak induced absorption band peaked at 545 nm that matches absorption spectra reported for the BODIPY radical anion. A global fit to the data (Figure 21 (b)) yields a rate of 4.8 ps for the formation of this ICT state.
Subsequently, all transient spectral features decay with a rate constant of 34 ps, indicating a fast non-radiative return to the So state, consistent with asymmetric dyads incorporating a BODIPY acceptor. On other hand, excitation of dyad 23 in toluene leads to formation of an Si state that decays at a rate consistent with the lifetime determined from emission studies (τ = 850 ps).
[0131 ] The importance of twisting and other structural changes of ICT excited states in donor/acceptor molecules has been extensively explored.
Additionally, rotation of meso-aryl substituents relative to BODIPY chromophores has previously been invoked as a major pathway for non-radiative deactivation. In the present case, facile rotation of the phenylene bridge in dyad 23 is also what likely allows the ICT state to undergo ultrafast direct surface crossing to the ground state. Thus, these studies were extended using dyad 26 of Figure 16, with the two BODIPY units linked directly at the meso position by a C-C bond, for which rotational freedom should be significantly restricted. Dyad 26 was prepared in low yield (<3%) from 1 ,1 ,2,2-tetrakis(5-methyl-1 H-pyrrol-2yl)ethene, which in turn was synthesized by a McMurry reaction, using standard oxidation and difluoroborylation conditions (Eq I). Although X-ray quality single crystals of dyad 26 have not been obtained, structure minimization using DFT (B3LYP/63lg*) methods indicated that the planar BODIPY units of dyad 26 have local geometries similar to those of dyad 23, and are canted at a dihedral angle of 71 ° with respect to each other.
[0132] Absorption spectra of dyad 26 are nearly invariant across several solvents and are similar to that of dyad 23 and other BODIPY chromophores. Slight splitting of the primary (So→Si) absorption band at 530 nm indicates a modest degree of exciton coupling between the BODIPY units. Fluorescence spectra, on the other hand, were dramatically affected by solvent. A small Stokes shift and high quantum efficiency were observed in cyclohexane. A progressive red-shift in the emission wavelength was observed with increasing solvent polarity, with concomitant broadening and decrease in QE (Figure 23 and Table 6). The spectra indicated that dyad 26 has a nonpolar ground state and a significantly higher dipole moment in the excited state, even though the two constituent chromophores are identical. Similar behavior was observed for the 9,9'-bianthryl molecule.
Table 6
Solvent ET(30)a (kcal mol"1) λmax,abλmax, λ™χ,^λ™χ, em Φ
em S(nm) s(nm)
Cyclohexane 30.9 523 564 0.78
Toluene 33.9 526 574 0.62
2-Methyltetrahydrofuran 36.5 524 620 0.18
Chloroform 39.1 526 585 0.35
Dichloromethane 40.7 530 651 0.087
Acetone 42.2 528 -b ~b
N,N-Dimethylformaide 43.2 530 -b -b
Acetonitrile 45.6 526 -b -b aSolvent polarity index;
bNo emission observed
[0133] Dyad 26 exhibited a simple first-order luminescence decay in cyclohexane (τ = 9.3 ns), whereas biexponential decay was observed in dichloromethane, comprised of a fast component (<200 ps) accompanied by a longer-lived (ca 7 ns) decay. (Figure 24) The non-radiative decay rate of dyad 26 (k, = 1 .4 X 108 S"1) in CH2CI2 is more than two orders of magnitude slower than that of dyad 23 in acetonitrile. These results indicate that a local Si state formed upon photoexcitation of dyad 26 undergoes ultrafast transformation to an emissive ICT state by solvent-induced symmetry breaking in polar solvents.
[0134] Femtosecond transient absorption spectroscopy in CH2CI2 was used to further illuminate the charge-transfer behavior of dyad 26 in polar media. The Si state observed upon excitation at 508 nm quickly evolves (kic"1 = 570 ± 80 fs) to produce an excited state that absorbs at 580 nm, consistent with the formation of a BODIPY radical anion (Figure 25). In contrast to the ICT state observed in dyad 23 however, the spectral features associated with the ICT state in dyad 26 show only minimal change in amplitude over the course of 1 ns, indicating that this state has a lifetime comparable to that of the emissive state. [0135] Although several biacenes display similar luminescent properties, to the best of our knowledge dyad 26 represents the first example of a dyad that combines symmetry- breaking formation of an emissive ICT state with intense absorption in the visible region of the spectrum. While porphyrins are in many respects related to dipyrrins, the meso-linked porphyrin analogues of dyad 26 do not undergo symmetry-breaking ICT because formation of such an excited state is endothermic with respect to the Si state. BODIPY dyads directly linked at the a- or β positions also do not exhibit this sort of emissive behavior. However, Benniston et al. have reported a hybrid of dyad 26 and 9,9'-bianthryl, a meso-linked 9-anthracenyl- BODIPY compound, that readily forms an emissive ICT state in polar solvents, akin to an exciplex.
[0136] These directly linked dyads serve as a visible-light-absorbing analogue of 9,9'-bianthryl.
[0137] BODIPY dyads 23 and 26 lead to formation of ICT states in polar media by solvent-induced symmetry breaking. The further presence of strong absorption at visible wavelengths enables these molecules to mimic features seen in the photosynthetic reaction center. Model systems that possess both these characteristics are rare. Differing degrees of rotational freedom in the dyads significantly alter the behavior of the ICT state. Whereas dyad 23 undergoes rapid non-radiative decay to the ground state, the more hindered dyad 26 has a long-lived ICT state with moderate-to-high fluorescence quantum efficiency.
[0138] Femtosecond transient absorption measurements were performed using a Tksapphire regenerative amplifier (Coherent Legend, 3.5 mJ, 35 fs, 1 kHz repetition rate). Approximately 10% of the amplifier output was used to pump a type II OPA (Spectra Physics OPA-80OC) resulting in the generation of excitation pulses centered at 508 nm with 1 1 .5 nm of bandwidth. At the sample position, the pump was lightly focused to a spot size of 0.29 mm (FWHM) using a 50 cm CaF2 lens. Probe pulses were generated by focusing a small amount of the amplifier output into a rotating CaF2 plate, yielding a supercontinuum spanning the range of 320-950 nm. A pair of off-axis aluminum parabolic mirrors collimated the supercontinuum probe and focused it into the sample.
[0139] Samples consisting of either dyad 23 or 26 dissolved in the appropriate solvent were held in a 1 cm path length quartz cuvette and had a peak optical density between 0.13 and 0.18. Data were collected for perpendicularly oriented pump and probe. This allowed for the suppression of scatter originating from the pump beam by passing the probe through an analyzing polarizer after the sample. A spectrograph (Oriel MS127I) was used to disperse the supercontinuum probe onto a 256 pixel silicon diode array (Hamamatsu) that enabled multiplex detection of the transmitted probe as a function of wavelength. An optical chopper was used to block every other pump pulse, allowing for differential detection of the pump-induced changes in the probe. The data in the main text represent the average probe transmission change measured for 1500 on/off pump pulse pairs.
[0140] At early time delays, a strong non-resonant signal from the sample cell and solvent is observed, but relaxes within 300 fs. Careful measurement of this non- resonant signal enabled its partial subtraction from the transient data. The non- resonant solvent response also provided a measure of the temporal dispersion of the supercontinuum probe resulting from propagation through the CaF2 plate and sample. The presented data have been corrected to account for this dispersion.
[0141 ] Transient experiments were carried out using a pump fluence of 265 uJ/cm2. Based on the cross sections of dyads 23 and 26, at this fluence we expect less than one excitation per dyad molecule. Transient experiments carried out at a fluence of 135 uJ/cm2 scaled linearly with those measured at higher fluence and yielded similar fit time constants, suggesting that annihilation processes do not contribute to the signal.
[0142] The measured transient spectra indicate that in dyad 23, the initially excited population evolves over time to form an ICT state that non-radiatively returns to the ground state while in dyad 26 the ICT state persists for nanosecond or longer time scales. To obtain rates for the formation of the ICT state in either dyad as well as for the non-radiative repopulation of the ground state in dyad 23, it is assumed that the transient spectra can be described using a three-state model governed by a series of sequential first order rate processes:
SI K1CT > ICT K„ > S^ (S 1 ) where kicr and knr denote the rates for the formation of the ICT state and non- radiative return to the ground state, respectively. On the basis of Eq S1 we can linearly decompose the transient spectra of either dyad, S(A,t), as:
S(A,t) = csl(t)asl(A) + cICT(t)aICT(A). (S2)
Here, Csi ^ and Cicr(t) denote their time-dependent populations of the Si and ICT states of a given dyad, while σ$ί(λ) and σ/οτ{λ) represent the time-independent characteristic transient absorption spectrum that results from the population of either state. These basis spectra contain both positive features due to excited state absorption and negative going peaks due to a combination of stimulated emission and ground state depopulation (bleaching).
[0143] The time dependent behavior of Csi(t) and Cicr(t) is given by the solution to the set of coupled differential equations implied by Eq. S1 : dcsl(t)
Figure imgf000046_0001
where lo is the initial population placed in the SI state by the excitation pulse. To model the behavior of dyad 23 in acetonitrile, both /c,cr and /cnr were determined through a least squares minimization routine. Since transient spectra of 26 in dichloromethane showed minimal signatures of non-radiative relaxation to the ground state over the course of the experimental time window (1 ns), / was constrained to match the non-radiative decay rate of 26 determined by luminescence measurements (1 .4 x 108 S"1).
[0144] The fits that result from the global analysis model appear alongside the experimental transients plotted in Figure 21 (b) and Figure 32. Overall, the agreement between the experimental data and our model is quite good. Regarding dyad 23, Figure 21 (b) shows that the disclosed model reproduces the growth of the induced absorption at 550 nm resulting from formation of the ICT state (1/kicr =4.8 ps). This feature subsequently decays at a rate that matches the recovery of the ground state bleach at 507 om (1/knr =34 ps), indicating that decay of the ICT state results in refilling of the ground state. In contrast, the ICT state of dyad 26 develops nearly an order of magnitude faster than that of dyad 23 (1/kicr = 570 fs) as evidenced by the rapid formation of an induced absorption band at 575 nm (Figure 32), but shows no indication of ground state reformation over the experimental time window (1 ns).
[0145] Crystal Data and Structure Refinement for Dyad 23
Empirical formula C28H24B2F4N4
Formula weight 514.13
Temperature 123(2) K Wavelength 0.71073 A
Crystal System Orthorhombic
Space group Pbca
Unite cell dimensions a = 12.808(3) A a= 90°.
b = 12.205(2) A β= 90°.
c = 15.019(3) A γ= 90°.
Volume 2347.8(8) A3
Z 4
Density (calculated) 1.455 Mg/m3
Absorption coefficient 0.108 mm"1
F(000) 1064
Crystal Size 0.10 x 0.09 x 0.07 mm3
Theta range for data collection 2.67 to 27.55°.
Index ranges -16<=h<=16, -10<=k<=15, -19<=l<=18
Reflections collected 13598
Independent reflections 2688 [R(int)=0.1065]
Completeness to theta = 25.00° 100.0%
Absorption correction Semi-empirical from equivalents
Max. and min. transmission 0.7456 and 0.5788
Refinement method Full-matrix least-squares on F2
Data / restraints / parameters 2688 / 0 / 174
Goodness-of-fit on F2 1.119
Final R indices [l>2sigma(l)] R1 = 0.0571 , wR2 = 0.0838
R indices (all data) R1 = 0.1215, wR2 = 0.0926
Largest diff. peak and hole 0.285 and -0.209 e.A3
[0146] The combination of strong visible-light absorption and excited-state ICT make dyads 23 and 26, as well as their analogues, promising candidates for applications such as those described above, where organic materials with accessible ICT states efficiently move singlet excitation energy to a D/A interface before undergoing intramolecular charge transfer to maximize the rate of forward electron transfer while minimizing the reverse interfacial recombination process.
[0147] The present disclosure provides for an organic photosensitive optoelectronic device comprising: at least one compound chosen from a higher order structure, wherein said compound's absorptivity of light at some visible wavelength is about > 104 M"1 cm"1 , and wherein said compound is capable of undergoing symmetry-breaking intramolecular charge transfer in the excited state. The organic photosensitive devices disclosed herein can be, for example, an organic
photodetector, or an organic solar cell.
[0148] In some embodiments, the at least one compound is chosen from dyads of xanthenes dyes, coumarins, acridines, phthalocyanines,
subphthalocyanines, porphyrins, acenes, perylenes, malachites, cyanines, bipyridines, and dipyrrins. In other embodiments, the compound is chosen from even higher order structures such as triads and tetrads.
[0149] In some embodiments, the intramolecular charge transfer occurs in a polarizing medium.
[0150] In some embodiments, the intramolecular charge transfer in the excited state is energetically accessible from a photogenerated Si state in a polarizing medium.
[0151 ] In some embodiments, the dyads may be connected either directly or through a linker (such as saturated or unsaturated linear or branched hydrocarbons, or aromatic rings, e.g., phenylene, or constructed from aryl, fused aryl, such as naphthyl, anthryl, etc., alkyl, alkynyl, alkenyl, a heterocycle, a diazo or organosilane moiety), such that the dyads are arranged in linear or cofacial fashion. [0152] In some embodiments, the higher order compound is 1 ,4-Bis(4,4- difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl)benzene or a salt or hydrate thereof. In other embodiments, the higher order compound is Bis(4,4- difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl), or a salt or hydrate thereof.
[0153] A further embodiment is directed to a process for preparing 1 ,4- Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl)benzene, or a salt or hydrate thereof, comprising treating a mixture comprising terephthalaldehyde and 2-methylpyrrole with a halogenated carboxylic acid, an oxidizing agent, and Lewis acid to form 1 ,4-Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8- yl)benzene. In further embodiments, the halogenated carboxylic acid can be trifluoroacetic acid, the oxidant can be DDQ and the Lewis acid can be boron trifluoride diethyl etherate.
[0154] An additional embodiment is directed to a process for preparing Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl), or a salt or hydrate thereof, comprising treating a mixture comprising a first Lewis acid and a transition metal with a mixture comprising bis(5-methyl-1 H-pyrrol-2-yl)methanone to form 1 , 1 ,2,2-tetrakis(5-methyl-1 H-pyrrol-2-yl)ethene; and treating a mixture comprising 1 ,1 ,2,2-tetrakis(5-methyl-1 H-pyrrol-2-yl)ethene and a base with an oxidant and second Lewis acid to form Bis(4,4-difluoro-3,5-dimethyl-4-bora-3a,4a- diaza-s-indacene-8-yl). In further embodiments, the first Lewis acid can be TiCI4, the transition metal can be zinc, the base can be triethylamine, the oxidant can be DDQ, and the second Lewis acid can be boron trifluoride diethyl etherate.
[0155] The present disclosure also provides for methods of making an organic photosensitive device comprising an organic photosensitive optoelectronic device, wherein said organic photosensitive optoelectronic device comprises: at least one compound chosen from a dyad or higher order structure, wherein said compounds absorptivity of light at some visible wavelength is about > 104 M"1 cm"1 , and wherein said compound is capable of undergoing symmetry-breaking
intramolecular charge transfer in the excited state.
Examples
Example 1 : Synthesis of BenzoBODIPY, IndoBODIPY, and CvanoBODIPY
[0156] As shown in Figure 1 , BenzoBODIPY was prepared in two steps from the corresponding pyrrole and aldehyde followed by retro-Diels-Alder deprotection. The required pyrrole was prepared via Barton-Zard synthesis from the necessary precursors with yields generally >80 %. The pyrrole carboxylate ester was converted to the methyl pyrrole moiety using lithium aluminum hydride and used without further purification due to its sensitivity to air. Under known conditions for BODIPY synthesis using Hunig's base and BF3»Et20, a yield of about 40 % was obtained for the masked BenzoBODIPY. Upon heating, the masked BenzoBODIPY was quantitatively converted to BenzoBODIPY. The materials were then recrystallized into copper-colored crystals and sublimed.
[0157] As shown in Figure 2, IndoBODIPY was prepared by first isolating its corresponding diindolyl-methane precursor. The precursor was isolated using known literature techniques. The boron complex was prepared using conditions identical to those of BenzoBODIPY, though only a yield of 7 % was achieved. The materials were recrystallized to give a purple solid.
[0158] CyanoBODIPY was prepared using the synthetic scheme shown in Figure 3. Example 2: Optical Properties of BenzoBODIPY, IndoBODIPY, and CvanoBODIPY
[0159] The absorption maxima of the BODIPY dyes disclosed herein, for example BenzoBODIPY and IndoBODIPY, were red-shifted when compared to an unsubstituted BODIPY core. A typical BODIPY core has a solution absorption maximum of -510 nm, but, as shown in Figures 7(a) and 7(b), the solution absorption maxima of BenzoBODIPY and IndoBODIPY were at 604 nm and 559 nm, respectively. Furthermore, Figure 7(b) shows that the solution absorption of
IndoBODIPY broadened significantly, deviating from the narrow bandwidth that is usually observed for this class of materials as exhibited by BenzoBODIPY in Figure 7(a). Figure 7 also shows that the film excitation of BenzoBODIPY was much wider and more red shifted than the solution absorption due to strong intermolecular interactions. A larger Stokes shift was also observed when comparing solution and solid-state.
[0160] The CyanoBODIPY exhibited a sharp maximum around ~ 500 nm, as shown in Figure 8(a). Due to the CyanoBODIPY's smaller π-system than the
BenzoBODIPY, a smaller degree of peak broadening and red-shift were observed for thin-film properties, as shown in Figure 8(b).
[0161 ] Molar absorptivity was measured in a glass cuvette in
dichloromethane. A value of 3.03 x 105 M"1 cm"1 was measured for BenzoBODIPY, and a value of 1 .46 x 105 M"1 cm"1 was measured for CyanoBODIPY.
Example 3: Photovoltaic Devices Using BenzoBODIPY
[0162] Photovoltaic devices using BenzoBODIPY as a donor material and a device using CuPc as a donor material were fabricated on ITO-glass substrates cleaned with Tergitol, alcohols, acetone, followed by UV-ozone treatment. Cm (MTR Limited), 2,9-dimethyl-4,7-diphenyl-1 ,10-phenanthroline (BCP) (Aldrich), and
BenzoBODIPY were purified by sublimation prior to use. Aluminum (Alfa Aesar) was used for metal cathode deposition. All devices were fabricated as lamellar devices in a vacuum deposition chamber with a fixed deposition rate for each layer. Three BenzoBODIPY devices were fabricated each with a different donor layer thickness— 10 nm, 20 nm, and 30 nm. Device performance (Current- Voltage curve and external quantum efficiency (EQE)) was measured under simulated AM 1 .5G solar illumination (Oriel Instruments) using a Keithley 2420 3A Source Meter. The device structures and performance of each device are summarized below and in Figure 9.
CuPc Device: Glass/ITO/CuPc(40 nm)/C60(40 nm)/BCP(10nm)/AI
BenzoBODIPY Device: Glass/ITO/BDPY(30-10 nm)/C60(40 nm)/BCP(10 nm)/AI.
[0163] The Current-Voltage curves are shown in Figure 9(a). The external quantum efficiencies (EQEs) are plotted in Figure 9(b). The dark current curves are shown in Figure 9(c). The performance data is recorded in Table 7. As shown in Table 7, device performance was dependent on the thickness of the donor layer. These experiments led to an optimal thickness around 20 nm, at which the device demonstrated the highest short-circuit current of 12.4 mA/cm2. Although increasing the thickness generally increases the open-circuit voltage, the Voc averaged out at around 730 mV for the two thicker devices. The 10 nm device may have had aggregates of donor materials, forming islands on the surface and leaving direct Οεο and ITO contact. Lack of complete coverage on the surface may have led to a drop in potential and charge generation. With a fill factor of 0.53, the highest performing device achieved a power conversion efficiency (PCE) of 4.17 %.
Figure imgf000053_0001
[0164] An additional study was performed using device structures identical to the previous example, except that the thickness of the BenzoBODiPY donor layer was further varied (40, 70, 100, and 130 nm). Current-voltage curves are shown in Figure 10(a). The EQEs are shown in Figure 10(b). The performance of each device is summarized in Table 8 below. The highest performing device achieved a PCE of 5.68 %. Increasing the donor layer initially improved device performance, but performance dropped between 70 nm and 100 nm BenzoBODiPY thickness. The decrease in performance for thicker devices was mainly due to the overall drop in photoresponse across all wavelengths, hence lower Jsc was observed.
Table 8, Photovoltaic Data for BenzoBODiPY Devices
Figure imgf000053_0002
[0165] Further data was generated at certain BenzoBODiPY thicknesses (20, 25, 30, 35 nm) using the device structures above, except that the devices were thermally annealed prior to deposition of the Cm layer. The glass substrate, ITO and BenzoBODiPY layers were heated. The thermal treatment was performed under nitrogen at 100 °C for 15 minutes. Current-voltage curves are shown in Figure 1 1 (a). The EQEs are shown in Figure 1 1 (b). The performance of each device is summarized in Table 9 below. Device performances for all thicknesses were significantly worse than standard devices. The J-V curves were S-shaped, suggesting energetic barriers that may have resulted from trap-states generated from increased crystalline boundaries of the donor material. Compared to unannealed films, the film annealed prior to Ceo deposition exhibited a red shift in absorption, as shown in Figure 1 1 (c), suggesting an increase in crystallinity from a higher degree of π-π interaction between crystalline domains. No beneficial effect was observed for thermally annealing the devices before the deposition of Ceo- Even though the EQE showed similar photoresponse from different thicknesses, all parameters suffered from the pre-C6o thermal treatment with lower currents, voltages, and fill factors. The decrease in power conversion efficiency may have been due to the crystallinity of the donor layer after thermal annealing.
Table S, Photovoltaic Data for BerczoBODIPY Devices
Thermally Treated Before Deposition of Acceptor Layer
Figure imgf000054_0001
[0166] Additional data was generated at certain BenzoBODIPY thicknesses (40, 70, 100, 130 nm) using the device structures above, except that the devices were thermally annealed post deposition of the C6o layer. Current-voltage curves are shown in Figure 12(a). The EQEs are shown in Figure 12(b). The performance of each device is summarized in Table 10 below. Thermal treatment post deposition of Ceo showed improvements in Jsc, with a slight drop in Voc and fill factor. Performance similar to unannealed devices was obtained.
Table 10, Photovoltaic Data for BenzoBODIPY Devices
Thermally Treated After Deposition of Acceptor Layer
Figure imgf000055_0001
Example 4: Photovoltaic Devices Using CyanoBODIPY
[0167] CyanoBODIPY purified by sublimation was used in preparing the devices. The devices were prepared and tested under the conditions described above in Example 3. Unannealed and annealed CyanoBODIPY devices employed copper phthalocyanine (CuPc) as an electron donor material and a 1 : 1 ratio codeposited layer of CyanoBODIPY and Cm as an electron acceptor. A control device using CuPc and C6o as donor and acceptor layers, respectively, was also fabricated. For the annealed device, the device was heated at 1 10 °C under nitrogen for 10 minutes after deposition of the acceptor layer. The device structures are summarized as follows:
CyanoBODIPY Device:
Glass/ITO/CuPc(40 nm)/CyanoBDPY:C60 1 :1 (40 nm)/BCP(10 nm)/AI
CuPc Device:
Glass/ITO/CuPc(40 nm)/C60(40 nm)/BCP(10 nm)/AI.
[0168] Current-voltage curves for the devices are shown in Figure 13(a). The EQEs are shown in Figure 13(b). The performance of each device is
summarized in Table 1 1 below. The devices performed at about 50% PCE of analogous CuPc/C6o devices. The fill factor is similar, presumably due to similar donor-acceptor interfaces as with CuPc/C6o devices. All other parameters were lower with respect to the control device. The open-circuit voltage was a few hundred millivolt lower and the short-circuit current was about half of the control device. The drop in PCE is predominantly due to the loss in photoresponse from CuPc. The loss in Ceo absorption around 420 nm was roughly compensated by the CyanoBODIPY absorption at 520 nm. However, there was about a 50% loss in the region where CuPc absorbs, which was similarly reflected in the PCE. Thermal treatment for the CyanoBODIPY devices showed no beneficial effects on the performance.
Table 11. Photovoltaic Data for CyanoBODIPY Devices
Figure imgf000056_0001
Examples 5-9
General Considerations
[0169] 2-M ethyl pyrrole was obtained by a Wolff-Kishner reduction of pyrrole- 2-carboxaldehyde as previously described. 1 -Methyl-4,7-dihydro-2/-/-4,7- ethanoisoindole was prepared by lithium aluminum hydride reduction of the corresponding ester according to literature procedure. All other reagents were purchased from commercial vendors and used without further purification. All air- sensitive manipulations were performed using standard Schlenk techniques as needed, following the procedures indicated below for each preparation. NMR spectra were recorded at ambient temperature on Varian Mercury 400 MHz and 600 MHz spectrometers. 1 H chemical shifts were referenced to residual solvent. UV-vis spectra were recorded on a Hewlett-Packard 4853 diode array spectrophotometer. Steady-state emission experiments were performed using a Photon Technology International QuantaMaster Model C-60SE spectrofluorimeter. Fluorescence lifetime measurements were performed by a time-correlated single-photon counting method using an IBH Fluorocube lifetime instrument by equipped with a 405 nm or 435 nm LED excitation source. Quantum efficiency measurements were carried out using a Hamamatsu C9920 system equipped with a xenon lamp, calibrated integrating sphere and model C10027 photonic multichannel analyzer.
Example 5: General Reaction Scheme for Phenylene Bridged Dyads 23, 24 and 25 of Figure 16
Figure imgf000057_0001
[0170] Phenylene Bridged Dyad 23. Terephthalaldehyde (762 mg, 5.68 mmol) and 2-methylpyrrole (2.03 g, 23.3 mmol) were dissolved in dry, degassed CH2CI2 (40 mL) under N2. The resulting solution was further degassed for 10 min, and trifluoroacetic acid (64 μΙ_, 0.84 mmol) was added in two portions, causing the solution to darken immediately, and the reaction was allowed to proceed with stirring for 2 h. DDQ (2.58 g, 1 1 .4 mmol) was added in one portion, causing an immediate color change to dark red-orange, and the resulting mixture was stirred for 13 h. N,N- Diisopropylethylamine (8.0 mL, 46 mmol) was added at once, causing a color change to dark brown, and stirring was continued for 15 min. Boron trifluoride diethyl etherate (8.0 mL, 64 mmol) was added slowly over the course of 1 min, causing the mixture to warm slightly. After 45 min, the mixture was quenched with NaHC03 (5% aq, 200 mL) and stirred vigorously for 2 h. Organics were removed and washed with Na2S03 (10% aq, 2 100 mL), HCI (5% aq, 1 χ 100 mL), and brine (2 100 mL). The organics were removed and dried with MgS04, filtered, and concentrated to a dark solid, which was purified by column chromatography (Si02 gel, CHCI3 eluent, Rf = 0.5) to afford dyad 23 as a pure red-orange solid (200 mg, 7%). UV-vis (CH2CI2) Amax: 350, 513. 1 H NMR (CDCI3): δ 7.62 (s, 4H, phenylene Ar-H), 6.76 (d, JHH = 4.4 Hz, 4H, BODIPY Ar-H), 6.31 (d, 3JHH = 4.4 Hz, 4H, BODIPY Ar-H), 2.68 (s, 12H, -CH3). 13C NMR (CDCI3): δ 158.38, 141 .14, 135.94, 134.47, 130.41 , 130.32, 1 19.91 , 15.13. MALDI, mlz for C28H2 B2F4N4 calcd 514.21 (100%), 513.22 (51 %), 515.22 (33%); found 512.83 (100%), 51 1 .83 (51 %), 513.82 (45%).
[0171 ] Phenylene Bridged Dyad 24. Terephthalaldehyde (1 g, 7.55 mmol) and 2,4-dimethylpyrrole (2.98 g, 31 .3 mmol) were dissolved in dry, degassed CH2CI2 (30 mL) under N2. The resulting solution was further degassed for 10 min, and trifluoroacetic acid (1 drop) was added and the reaction was allowed to proceed with stirring for 5 h. DDQ (3.38 g, 14.9 mmol) was added in one portion, and the resulting mixture was stirred overnight. Λ/,/V-Diisopropylethylamine (10.4 mL, 59.6 mmol) was added at once, and stirring was continued for 15 min. Boron trifluoride diethyl etherate (7.5 mL, 59.6 mmol) was added. After 45 min, the mixture was quenched with NaHC03 (5% aq, 200 mL) and stirred vigorously for 2 h. Organics were removed and washed with Na2S03 (10% aq, 2 100 mL), HCI (5% aq, 1 * 100 mL), and brine (2 χ 100 mL). The organics were removed and dried with MgS04, filtered, and concentrated to a dark solid, which was purified by column chromatography (Si02 gel, CH2CI2 eluent) to afford dyad 24 as a pure red-orange solid (427 mg, 10%). 1H NMR (CDCI3): δ 7.52 (s, 4H, phenylene Ar-H), 6.01 (s, 4H, BODIPY Ar-H), 2.57 (s, 12H, -CH3), 1 .53 (s, 12H, -CH3).
[0172] Phenylene Bridged Dyad 25. Terephthalaldehyde (1 g, 7.46 mmol) and 2,4-dimethyl-3-ethylpyrrole (3.67 g, 29.8 mmol) were dissolved in dry, degassed CH2CI2 (40 mL) under N2. The resulting solution was further degassed for 10 min, and trifluoroacetic acid (1 drop) was added and the reaction was allowed to proceed with stirring for 2 h. DDQ (3.39 g, 14.9 mmol) was added in one portion, causing an immediate color change to dark red-orange, and the resulting mixture was stirred for 13 h. Λ/,/V-Diisopropylethylamine (10.4 mL, 59.7 mmol) was added at once, causing a color change to dark brown, and stirring was continued for 15 min. Boron trifluoride diethyl etherate (7.5 mL, 59.7 mmol) was added slowly over the course of 1 min, causing the mixture to warm slightly. After 45 min, the mixture was quenched with NaHC03 (5% aq, 200 mL) and stirred vigorously for 2 h. Organics were removed and washed with Na2S03 (10% aq, 2 100 mL), HCI (5% aq, 1 χ 100 mL), and brine (2 100 mL). The organics were removed and dried with MgS04, filtered, and concentrated to a dark solid, which was purified by column chromatography (Si02 gel, CHCI3 eluent) to afford dyad 25 as a pure red-orange solid (254 mg, 5%). 1H NMR (CDCI3): δ 7.51 (s, 4H, phenylene Ar-H), 2.55 (s, 12H, -CH3), 2.32 (q, 8H, - CH2), 1 .47 (s, 12H), 1 .00 (t, 12H).
Example 6: General Reaction Scheme for Directly Linked Dyads 26, 27, 28, and 29 of Figure 16.
Figure imgf000059_0001
[0173] Directly Linked Dyad 26. 2-Methylpyrrole (2.01 g, 24.8 mmol) was dissolved in dry, degassed CH2CI2 (20 mL) in an oven-dried three-necked flask that had been purged with N2. The solution was cooled to 0 °C and acetoxyacetyl chloride (2.02 g, 14.8 mmol) was added in one portion in the dark and the reaction was allowed to proceed with stirring for 1 h, during which time the color turned dark red. Λ/,/V-Diisopropylethylamine (8.58 mL, 49.3 mmol) was added at room temperature, causing a color change to clear orange, and stirring was continued for 30 min followed by dropwise addition of BF3»OEt2 (6.18 mL, 49.3 mmol). During addition of BF3»OEt2 the color changed to dark red. The reaction was left stirring for 30 min and then was concentrated and purified by flash chromatography (Si02 gel, 25 % CH2CI2/hexanes, Rf = 0.14) to yield 8-acetoxymethyl-4,4-difluoro-3,5-dimethyl- 4-boro-3a,4a-diaza-s-indacene as a gold-pink solid (235 mg, 1 1 %). 1H NMR
(CDCI3, 600 MHz): δ 7.18 (d, 3JHH = 4.2 Hz, 2H, BODIPY Ar-H), 6.30 (d,
3JHH = 4.2 Hz, 2H, BODIPY Ar-H), 5.22 (s, 2H, -CH2), 2.62 (s, 6H, -CH3), 2.09 (s, 3H, -COCH3). 13C NMR (CDCI3, 600 MHz): δ 170.20, 158.96, 134.60, 133.97, 127.98, 1 19.84, 59.1 1 , 20.85, 14.98. HRMS for Ci4Hi6BN202F2 (MH+) calcd
293.1267, found 293.1261 . 8-Acetoxymethyl-4,4-difluoro-3,5-dimethyl-4-boro-3a,4a- diaza-s-indacene (350 mg, 1 .20 mmol) was dissolved in acetone (60 mL) and a solution of 4 M HCI (36 mL) was added. A condenser was fitted to the flask and the reaction was heated to 40 °C until the solution turned green and the TLC showed no starting material. The crude mixture was diluted with CH2CI2, washed with water (2 x 75 mL), saturated NaHCC>3 (2 χ 75 mL) and the organic layer was removed, dried over MgS04, filtered, concentrated and purified by flash chromatography (Si02 gel, CH2CI2, Rf = 0.16) to afford 8-hydroxymethyl-4,4-difluoro-3,5-dimethyl-4-boro- 3a,4a-diaza-s-indacene as a red-gold solid (210 mg, 71 %). 1H NMR (CDCI3, 600 MHz): δ 7.23 (d, 3JHH = 4.2 Hz, 2H, BODIPY Ar-H), 6.97 (s, 1 H, -OH), 6.27 (d, 3JHH = 4.2 Hz, 2H, BODIPY Ar-H), 4.79 (s, 2H, -CH2), 2.60 (s, 6H, -CH3). 13C NMR (CDCI3, 600 MHz) δ 158.41 , 139.17, 133.97, 127.59, 1 19.53, 59.45, 14.93. HRMS for Ci2H14BN2OF2 (MH+) calcd 251 .1 162, found 251 .1 167. 8-hydroxymethyl-4,4- difluoro-3,5-dimethyl-4-boro-3a,4a-diaza-s-indacene (200 mg, 0.8 mmol) was dissolved in dry, degassed CH2CI2 (15 mL) and was cannulated into a solution of Dess-Martin periodinane (509 mg, 1.20 mmol) in dry, degassed CH2CI2 (15 mL) at 0 °C. The solution was allowed to warm to room temperature and left stirring for 1 h. When the TLC showed no starting material the reaction was quenched with saturated Na2S2O3 (50 mL), washed with saturated NaHC03 (2 χ 50 mL) and water (2 x 50 mL). The organic layer was removed, dried over MgS04, filtered and concentrated, then purified by passing through a plug of S1O2 gel with CH2CI2 ( f = 0.38). 8-Formylmethyl-4,4-difluoro-3,5-dimethyl-4-boro-3a,4a-diaza-s-indacene was collected as a dark purple solid (164 mg, 83%). 1 H NMR (CDCI3, 600 MHz): δ 10.33 (s, 1 H, -CHO), 7.51 (d, 3JHH = 4.2 Hz, 2H, BODIPY Ar-H), 6.40 (d,
3JHH = 4.2 Hz, 2H, BODIPY Ar-H), 2.65 (s, 6H, -CH3). 13C NMR (CDCI3, 600 MHz) δ 188.75, 161.39, 134.87, 129.74, 125.87, 121.86, 15.33. HRMS for C12H 12BN2OF2 (MH+) calcd 249.1005, found 249.1008. 8-Formyl-4,4-difluoro-3,5-dimethyl-4-boro- 3a,4a-diaza-s-indacene (36 mg, 0.15 mmol) was dissolved in dry, degassed CH2CI2 (10 mL) and 2-methylpyrrole (24 mg, 0.29 mmol) was added. The reaction was monitored by TLC until no starting material remained. DDQ (33 mg, 0.15 mmol) was added in one portion and the reaction was monitored by TLC until the condensation product was consumed. Λ/,/V-Diisopropylethylamine (0.10 mL, 0.58 mmol) was added in one portion, followed after 15 min by dropwise addition of BF3»OEt2 (0.07 mL, 0.6 mmol). The reaction was left stirring for 15 min and then was quenched with saturated Na2S203 (25 mL), washed with saturated NaHC03 (2 χ 50 mL) and the organic layer was removed. The crude mixture was dried over MgS0 , filtered and passed through a plug of Si02 gel using CH2CI2 (Rf = 0.33) to recover a dark pink-green solid (25 mg, 38 %). UV-vis (CH2CI2) Amax: 334, 530. 1H NMR (CDCI3, 400 MHz): δ 6.84 (d, 3JHH = 4.4 Hz, 4H, BODIPY Ar-H), 6.23 (d, 3JHH = 4.4 Hz, 4H, BODIPY Ar-H), 2.65 (s, 12H, -CH3). 13C NMR (CDCI3, 600 MHz) 8 159.55, 135.04, 131 .87, 130.06, 120.13, 15.06. HRMS for C22H2i B2N4F4 (MH+) calcd 439.1883, found 439.1893.
Directly Linked Dyad 26 (Alternate Synthetic Scheme).
Figure imgf000062_0001
[0174] Step 1 : 1 .1 .2.2-tetrakis(5-methyl-IH-pyrrol-2-yl)ethene. Titanium tetrachloride (87 uL, 0.80 mmol) was added dropwise to a solution of dry THF (15 mL) at 0 °C under nitrogen. The solution was stirred for 10 min, after which a suspension of zinc powder (98 mg, 1 .5 mmol) in 3 mL of dry THF was added via cannula. The resulting blue slurry was heated at reflux for 3 h and cooled to room temperature. Dry pyridine (55 uL, 0.68 mmol) was added and the solution set to reflux for 30 min. After cooling to room temperature, bis(5-methyl-1 H-pyrrol-2- yl)methanone in 3 mL of dry THF was added via cannula, and the solution refluxed for 3 h. The reaction was cooled to room temperature and poured into 100 mL of K2CC>3 solution (10% aq), which was then stirred vigorously for 10 min. Organics were removed by extraction into dichloromethane, and washed with water (2 x 50 mL) and brine (1 x 50 mL), and dried over MgS04. Solvent was removed, and the crude product used without further purification. MALDI, m/z for C22H24N4 calcd 344.20, found 344.41 .
Step 2: Bis(4,4-ditluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene-8-yl). 1 , 1 ,2,2- tetrakis(5-methyl-1 H-pyrrol-2-yl)ethene (90 mg, 0.26 mmol) was dissolved in dry, degassed CH2CI2 (15 mL) under N2. The solution was degassed for an additional 5 min, and Et3N (0.29 mL, 2.0 mmol) added by syringe. The resulting solution was stirred for 30 min at room temperature and DDQ (68 mg, 0.30 mmol) added. The solution was allowed to stir for an additional 30 min, after which boron trifluoride diethyl etherate (0.331 mL, 2.62 mmol) was added slowly. After 2 h, the mixture was quenched with saturated NaHCOs and stirred overnight. The organics were removed and washed with Na2S03 (10% aq, 3 x 25 mL), water (2 x 25 mL), and brine (2 x 25 mL). The organics were dried over MgS04, filtered, and concentrated to a dark red oil, which was purified by column chromatography (Si02 gel, 1 :1 CH2CI2:hexanes, Rr = 0.35) to afford dyad 26 as a pink solid (3 mg, 3%). A small quantity of green reflective crystals was obtained by slow evaporation from a CHCI3 solution of 26 at room temperature. These were used for photophysical analysis, but were too thin for X-ray diffraction studies. UV-vis (CH2CI2) max: 334,530. IH NMR (CDCI3): δ 6.84 (d, 3JHH = 4.2 Hz, 4H, ΒΟΌ\ ΡΎ Ar-H), 6.23 (d, 3JHH = 4.2 Hz, 4H, ΒΟΌ\ ΡΎ Ar-H), 2.65 (s, 12H, -CH3). MALDI, m/z for C22H20B2F4N4 calcd 438.18 (100%),437.18 (49%), 439.18 (25%); found 437.94 (100%), 438.96 (61 %), 437.01 (45%).
[0175] Directly Linked Dyad 27. 8-Formyl-4,4-difluoro-1 ,3,5,7-tetramethyl-4- boro-3a,4a-diaza-s-indacene was synthesized similarly to 8-formyl-4,4-difluoro-3,5- dimethyl-4-boro-3a,4a-diaza-s-indacene. 8-Formyl-4,4-difluoro-1 ,3,5,7-tetramethyl-4- boro-3a,4a-diaza-s-indacene (97 mg, 0.35 mmol) was dissolved in dry, degassed CH2CI2 (30 mL) and 2,4-dimethylpyrrole (70 mg, 0.74 mmol) was added. The reaction was monitored by TLC until no starting material remained. DDQ (80 mg, 0.35 mmol) was added in one portion and the reaction was monitored by TLC until the condensation product was consumed. Λ/,/V-Diisopropylethylamine (0.25 mL, 14 mmol) was added in one portion, followed after 15 min by dropwise addition of BF3»OEt2 (0.18 mL, 14 mmol). The reaction was left stirring for 15 min and then was quenched with saturated Na2S203 (25 mL), washed with saturated NaHC03 (2 χ 50 mL) and the organic layer was removed. The crude mixture was dried over MgS0 , filtered and passed through a plug of Si02 gel using CH2CI2 to recover a dark pink-green solid (25 mg, 38 %). 1 H NMR (CDCI3): δ 6.02 (s, 4H, BODIPY Ar-H), 2.56 (s, 12H, -CH3), 1 .89 (s, 12H, -CH3).
[0176] Directly Linked Dyad 28. 8-Formyl-4,4-difluoro-1 ,3,5,7-tetramethyl- 2,6-diethyl-4-boro-3a,4a-diaza-s-indacene was synthesized similarly to 8-formyl-4,4- difluoro-1 ,3,5,7-tetramethyl-4-boro-3a,4a-diaza-s-indacene. 8-Formyl-4,4-difluoro- 1 ,3,5,7-tetramethyl-2,6-diethyl-4-boro-3a,4a-diaza-s-indacene (208 mg, 0.63 mmol) was dissolved in dry, degassed CH2CI2 (20 mL) and 2,4-dimethyl-3-ethylpyrrole (154 mg, 0.91 mmol) was added. The reaction was monitored by TLC until no starting material remained. DDQ (142 mg, 0.63 mmol) was added in one portion and the reaction was monitored by TLC until the condensation product was consumed. Λ/,/V-Diisopropylethylamine (0.44 mL, 2.5 mmol) was added in one portion, followed after 15 min by dropwise addition of BF3»OEt2 (0.32 mL, 2.5 mmol). The reaction was left stirring for 15 min and then was quenched with saturated Na2S203 (25 mL), washed with saturated NaHC03 (2 χ 50 mL) and the organic layer was removed. The crude mixture was dried over MgS04, filtered and passed through a plug of Si02 gel using CH2CI2 to recover a dark pink-green solid (42 mg, 1 1 %). 1 H NMR (CDCI3): 2.55 (s, 12H, -CH3), 2.32 (q, 8H, -CH2), 1 .81 (s, 12H, -CH3), 0.96 (t, 12H, -CH3). MALDI, m/z for C22H20B2F4N4 calcd 606.37 found 605.74.
[0177] Directly Linked Dyad 29. 8-Formyl-4,4-difluoro-3,5-dimethyl-4-boro- 3a,4a-diaza-1 ,2,6,7-ethanoisoindole was synthesized similarly to 8-formyl-4,4- difluoro-1 ,3,5,7-tetramethyl-4-boro-3a,4a-diaza-s-indacene. 8-Formyl-4,4-difluoro- 3, 5-dimethyl-4-boro-3a,4a-diaza-1 ,2,6,7-ethanoisoindole (37 mg, 0.10 mmol) was dissolved in dry, degassed CH2CI2 (10 ml.) and 1 -methyl-4,7-dihydro-2H-4,7- ethanoisoindole (32 mg, 0.20 mmol) was added. The reaction was monitored by TLC until no starting material remained. DDQ (22 mg, 0.10 mmol) was added in one portion and the reaction was monitored by TLC until the condensation product was consumed. Λ/,/V-Diisopropylethylamine (0.07 mL, 0.04 mmol) was added in one portion, followed after 15 min by dropwise addition of BF3»OEt2 (0.05 mL,
0.04 mmol). The reaction was left stirring for 15 min and then was quenched with saturated Na2S203 (25 mL), washed with saturated NaHC03 (2 χ 50 mL) and the organic layer was removed. The crude mixture was dried over MgS04, filtered and passed through a plug of Si02 gel using CH2CI2 to recover a dark pink-green solid (5 mg, 0.7%). 1 H NMR (CDCI3): δ 6.32 (m, 4H, alkene -CH), 6.01 -5.91 (m, 4H, alkene -CH), 3.80 (m, 4H, bridgehead -CH), 3.59-3.48 (m, 4H, bridgehead -CH), 2.58 (multiple s, 12H, -CH3), 1 .25 (m, 16H, bridghead -CH2).
Example 7: General Reaction Scheme for Triad 30 of Figure 16.
Figure imgf000065_0001
[0178] Triad 30. 1 ,3,5-Benzenetricarbonyl trichloride (1 g, 3.76 mmol) was dissolved in dry dichloromethane (80 ml) under N2. 2,4-Dimethyl-3-ethylpyrrole (2.78 g, 22.6 mmol) was added and the flask was fitted with a condenser and refluxed overnight. Λ/Jv-Diisopropylethylamine (7.85 ml, 45.12 mmol) was added at reflux. After 15 minutes, the mixture was cooled to room temperature and boron trifluoride etherate (5.66 mL, 45.12 mmol) was added in one portion. After one hour, the reaction was quenched with saturated Na2S2O3 (50 ml_), washed with saturated NaHC03 (2 x 50 ml.) and water (2 χ 50 mL). The organic layer was removed, dried over MgS04, filtered and concentrated. The product was purified by flash
chromatography (Si02 gel, CH2CI2) to give the product in trace amounts. 1 H NMR (CDCI3): δ 7.73 (s, 1 H, Ar-H), 2.55 (s, 18H, BODIPY -CH3), 2.31 (q, 12H, BODIPY - CH2), 1 .69 (s, 18H, BODIPY -CH3), 1 .01 (t, 18H, -CH3).
Example 8: General Reaction Scheme for Zinc Compounds 31 -34 of Figure 16.
Figure imgf000066_0001
[0179] Zinc Compound 31. 5-Mesityldipyrromethane (2 g, 7.57 mmol) was dissolved in 200 ml of freshly distilled THF under Nitrogen. 2,3-Dichloro-5,6- dicyano-1 ,4-benzoquinone (DDQ) (1 .72 g, 7.57 mmol) in 15 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 5 ml of Triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure. The product mixture was dissolved in 200 ml of dichloromethane, and was washed with saturated NaHC03 solution in water (150 ml, 3 times) and brine (150 ml, 1 time). The solution was then dried over anhydrous Na2S04 and filtered. This solution of 5-mesityldipyrromethene was used without further purification. Zinc acetate dihydrate (Zn(OAc)2*2H20) (10 g, 45.5 mmol) in 50 ml of methanol was added to the solution of 5-mesityldipyrromethene in dichloromethane and stirred overnight. After that, reaction mixture was filter using filter paper. Solvent was then removed under reduced pressure. The obtained solid was passed through short neutral alumina plug using hexanes/dichloromethane (50/50) mixture as eluent, the portion in orange color was collected. Solvent was then removed under reduced pressure to obtain 1 g of orange solid (14% yield). The obtained 10 was further purified by gradient sublimation under ultra high vacuum (10" 5 torr) at 180°C - 140°C - 100°C gradient temperature zones. 1H NMR (400 MHz, CDCI3) δ ppm 7.027.01 (m, 12H), 6.22-6.21 (m, 8H), 2.02 (s, 24H), 1 .55 (s, 6H).
[0180] Zinc Compound 32. A mixture of mesitaldehyde (4.6 g, 30.9 mmol) and 2-methylpyrrole (5 g, 61 .7 mmol) was dissolved in 200 ml dichloromethane in a 500-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. Then 5 drops of trifluoroacetic acid (TFA) was added to the reaction mixture, the solution turned to dark red color. Reaction mixture was stirred under nitrogen for 6 hours until the starting materials were completely consumed. The reaction was quenched with 3 ml of triethylamine. Reaction mixture was then washed with saturated Na2CC>3 solution in water (100 ml, 3 times) and brine (100, 1 time). Solution was dried over anhydrous Na2S04. Solvent was then removed under reduced pressure to obtain the viscous pale yellow liquid (it turns to solid upon standing at room temperature). This product was dissolved in 250 ml of freshly distilled THF under Nitrogen. 2,3-Dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ) (7.02 g, 30.9 mmol) in 35 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 10 ml of triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure. The product mixture was dissolved in 500 ml of dichloromethane, and was washed with saturated NaHCC>3 solution in water (250 ml, 3 times) and brine (250 ml, 1 time). The solution was then dried over anhydrous Na2S04 and filtered. Zinc acetate dihydrate (Zn(OAc)2 »2H20) (20 g, 91 mmol) in 100 ml of methanol was added to the solution in dichloromethane and stirred overnight. After that, reaction mixture was filter using filter paper. Solvent was then removed under reduced pressure. The obtained solid was passed through short neutral alumina plug using
hexanes/dichloromethane (70/30) mixture as eluent, the portion in orange-red color was collected. Solvent was then removed under reduced pressure to obtain 2.5 g of dark green solid (12.3 % total yield). The obtained 32 was further purified by gradient sublimation under ultra high vacuum (10"5 torr) at 220°C - 160°C - 120°C gradient temperature zones. 1 H NMR (400 MHz, CDCI3): δ ppm 6.92 (s, 4H), 6.46- 6.43 (m, J = 4.25 Hz, 4H), 6.13 (d, J = 3.94 Hz, 4H), 2.37 (s, 6H), 2.14 (s, 12H), 2.1 1 ( s, 12H).
[0181 ] Zinc Compound 33. A mixture of mesitaldehyde (5 g, 33.5 mmol) and 2,4dimethylpyrrole (6.4 g, 67 mmol) was dissolved in 250 ml dichloromethane in a 500-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. Then 5 drops of trifluoroaceticacid (TFA) was added to the reaction mixture, the solution turned to dark red color. Reaction mixture was stirred under Nitrogen for 7 hours until the starting materials were completely consumed. The reaction was quenched with 3 ml of triethylamine. Reaction mixture was then washed with saturated Na2CC>3 solution in water (100 ml, 3 times) and brine (100, 1 time). Solution was dried over anhydrous Na2S04. Solvent was then removed under reduced pressure to obtain the viscous pale yellow liquid (it turns to solid upon standing at room temperature). The crude product obtained was dissolved in 250 ml of freshly distilled THF under nitrogen. DDQ (7.61 g, 30.9 mmol) in 40 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 10 ml of Triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure. The product mixture was dissolved in 500 ml of dichloromethane, and was washed with saturated NaHCC solution in water (250 ml, 3 times) and brine (250 ml, 1 time). The solution was then dried over anhydrous Na2S04 and filtered. This solution of 1 ,3, 7,9-tetramethyl-5-Mesityldipyrromethene was used without further purification. Zinc acetate dihydrate (Zn(OAc)2*2H2C)) (20 g, 91 mmol) in 100 ml of methanol was added to the solution of 1 ,3,7,9-tetramethyl-5- Mesityldipyrromethene in dichloromethane and stirred overnight. After that, reaction mixture was filter using filter paper. Solvent was then removed under reduced pressure. The obtained solid was passed through short neutral alumina plug using hexanes/dichloromethane (70/30) mixture as eluent, the portion in orange-red color was collected. Solvent was then removed under reduced pressure to obtain 3.0 g of orange-red solid (13 % total yield). The obtained 33 was further purified by gradient sublimation under ultra high vacuum (10"5 torr) at 230°C - 160°C - 120°C gradient temperature zones. 1 H NMR (500 MHz, CDCI3): δ ppm 6.93 (s, 4H), 5.91 (s 4H), 2.35 (s, 6H), 2.12 (s, 12H), 2.04 (s, 12H), 1 .31 (s, 12H). 13C NMR (500 MHz, CDCI3): δ ppm 155.90, 143.63, 143.15, 137.35, 136.22, 135.57, 134.54, 128.73, 1 19.56, 21 .21 , 19.26, 16.12, 14.83. HRMS: calcd for C44H5i N4Zn (MH+): 699.3400, found: 699.3407. C, H, N elemental analysis for C44H5i N4Zn: calcd (%) C (75.47), H (7.20), N (8.00); found (%) C (75.84), H (7.27), N (8.06).
[0182] Zinc Compound 34. 2,8diethyl1 ,3,7,9-tetramethyl-5- Mesityldipyrromethane. A mixture of mesitylaldehyde (2 g, 13.4 mmol) and 3- ethyl2,4dimethylpyrrole (3.3 g, 26.8 mmol) was dissolved in 150 ml dichloromethane in a 500-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. Then 3 drops of trifluoroaceticacid (TFA) was added to the reaction mixture, the solution turned to dark red color. Reaction mixture was stirred under Nitrogen for 7 hours until the starting materials were completely consumed. The reaction was quenched with 3 ml of triethylamine. Reaction mixture was then washed with saturated Na2CC>3 solution in water (100 ml, 3 times) and brine (100, 1 time). Solution was dried over anhydrous Na2S04. Solvent was then removed under reduced pressure. This product was dissolved in 150 ml of freshly distilled THF under nitrogen. DDQ (3.3 g, 13.4 mmol) in 15 ml of freshly distilled THF was added slowly to the solution. Reaction mixture turned to dark red color. Reaction mixture was stirred under nitrogen for 1 hour. The reaction was quenched by adding 10 ml of Triethylamine, stirred for another 5 min. Solvent was then removed under reduced pressure. The product mixture was dissolved in 300 ml of dichloromethane, and was washed with saturated NaHC03 solution in water (150 ml, 3 times) and brine (150 ml, 1 time). The solution was then dried over anhydrous Na2S04 and filtered and was used without further purification. Zinc acetate dihydrate
(Zn(OAc)2 »2H20) (8 g, 36.4 mmol) in 50 ml of methanol was added to the solution of 2,8-diethyl-1 ,3,7,9-tetramethyl-5-mesityldipyrromethene in dichloromethane and stirred overnight. After that, reaction mixture was filter using filter paper. Solvent was then removed under reduced pressure. The obtained solid was passed through short neutral alumina plug using hexanes/dichloromethane (70/20) mixture as eluent, the portion in red color was collected. Solvent was then removed under reduced pressure to obtain 0.8 g of orange-red solid (7.7 % total yield). The obtained 34 was further purified by gradient sublimation under ultra high vacuum (10"5 torr) at 240°C - 160°C - 120°C gradient temperature zones. 1H NMR (500 MHz, CDCI3): δ ppm 6.92 (s, 4H), 2.36 (s, 6H), 2.25 (q, J = 7.40 Hz, 8H), 2.1 1 (s, 12H), 1 .97 (s, 12H), 1 .19 (s, 12H), 0.91 (t, J = 7.49 Hz, 12H). 13C NMR (500 MHz, CDCI3): δ ppm 154.68, 142.03, 137.19, 137.10, 137.03, 136.00, 134.17, 130.66, 128.55, 21 .24, 19.47, 17.92, 15.25, 14.35, 1 1 .75. HSMS: calculated for C52H67N4Zn (MH+) 81 1 .4652, found 81 1 .4658. CNH analysis for C52H66N4Zn: calculated (%) C (76.87), H (8.19), N (6.90); found C (76.98), H (8.35), N (6.97).
Example 9: An Organic Photosensitive Optoelectronic Device Using
Compound 31 of Figure 16.
[0183] OPVs using compound 31 of Figure 16 as a donor material and fullerene Cm as an acceptor material have been fabricated using vacuum deposition technique on glass coated with Indium doped Tin Oxide (ITO) substrate. The OPV device with Mo03 as hole conducting/electron blocking layer was also fabricated. The device structures and characteristics are shown in the table below and in Figure 34. Both devices have significant photocurrents (3.06 and 3.49 mA/cm2). External Quantum Efficiency measurements (Figure 34(c)) confirm the contribution of compound 31 to the photocurrent (up to 30% EQE at 500 nm). The Mo03 hole conducting/electron blocking layer increases the open circuit voltage (VOC) from 0.60 to 0.82 V, while the short circuit current (JSC) and the fill factor (FF) decreases slightly compared to the device without Mo03. Thus, both devices (D1 and D2) have comparable power conversion efficiency (0.9%). One of ordinary skill in the art would understand that the OPVs of Example 9 represent only one illustration of the present disclosure and that OPV device performance can be improved by methods known in the art.
Figure imgf000071_0001
Device performance characteristics under AM1 .5G illumination. D1 : ITO/Mo03 (8 nm)/31 (10 nm)/C60 (40 nm)/BCP (10 nm)/AI, and D2: ITO/31 (10 nm)/C60 (40 nm)/BCP (10 nm) /AI. [0184] Specific examples of the disclosure are illustrated and/or described herein. However, it will be appreciated that modifications and variations of the disclosure are covered by the above teachings and within the purview of the appended claims without departing from the spirit and scope of the disclosure.

Claims

WHAT IS CLAIMED IS:
1 . An organic photosensitive optoelectronic device comprising at least one compound of formula (I):
Figure imgf000073_0001
(I)
wherein:
R1 is chosen from an optionally substituted monocyclic group, an optionally substituted C6-24 multicyclic group, and an optionally substituted meso-linked
BODIPY, or R1 and R2 and R7 taken together with any intervening atoms comprise a substituted BODIPY, wherein R1 is meso-linked and R2 and R7 are beta-linked;
R2 is chosen from hydrogen, an alkyl group, and a cyano group, or R2 and R3 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R2 and R1 and R7 taken together with any intervening atoms comprise a substituted BODIPY, wherein R1 is meso-linked and R2 and R7 are beta-linked;
R3 is chosen from hydrogen, an alkyl group, and a cyano group, or R3 and R2 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R3 and R4 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group;
R4 is chosen from hydrogen, an alkyl group, and a cyano group, or R4 and R3 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group;
R5 is chosen from hydrogen, an alkyl group, and a cyano group, or R5 and R6 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group;
R6 is chosen from hydrogen, an alkyl group, and a cyano group, or R6 and R5 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R6 and R7 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group; and
R7 is chosen from hydrogen, an alkyl group, and a cyano group, or R7 and R6 taken together with any intervening atoms comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group, or R7 and R1 and R2 taken together with any intervening atoms comprise a substituted BODIPY, wherein R1 is meso-linked and R2 and R7 are beta-linked; and wherein the optionally substituted monocyclic and multicyclic groups are chosen from aryl and heteroaryl groups.
2. The device of claim 1 , wherein R1 is chosen from optionally substituted benzene and optionally substituted fused benzene.
3. The device of claim 1 , wherein R2 and R3 taken together with any intervening atoms, and R6 and R7 taken together with any intervening atoms, both comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group.
4. The device of claim 1 , wherein R3 and R4 taken together with any intervening atoms, and R5 and R6 taken together with any intervening atoms, both comprise a group chosen from an optionally substituted monocyclic group and an optionally substituted C6-24 multicyclic group.
5. The device of claim 1 , wherein R2 and R7 are both chosen from hydrogen, an alkyl group, and a cyano group.
6. The device of claim 1 , wherein R5 and R4 are both chosen from hydrogen, an alkyl group, and a cyano group.
7. The device of claim 1 , wherein R3 and R6 are both chosen from hydrogen, an alkyl group, and a cyano group.
8. The device of claim 1 , wherein R2, R3, R4, R5, R6, and R7 are all chosen from hydrogen, an alkyl group, and a cyano group.
9. The device of claim 1 , wherein the at least one compound of formula (I) is chosen from
Figure imgf000076_0001
Figure imgf000076_0002
6
Figure imgf000076_0003
10 11 12
Figure imgf000076_0004
Figure imgf000077_0001
16 17 18 19
Figure imgf000077_0002
wherein R is chosen from an optionally substituted monocyclic aryl or heteroaryl group and an optionally substituted C6-24 multicyclic aryl or heteroaryl group.
10. The device of claim 9, wherein R is chosen from
Figure imgf000077_0003
Figure imgf000077_0004
Figure imgf000078_0001
wherein R' is chosen from H, alkyl, and aryl or heteroaryl groups.
1 1 . The device of claim 9, further comprising at least one donor material and at least one acceptor material, wherein one of the donor and acceptor materials comprises the at least one compound of formula (I).
12. The device of claim 1 , further comprising at least one donor material and at least one acceptor material, wherein one of the donor and acceptor materials comprises the at least one compound of formula (I).
13. The device of claim 12, wherein the at least one donor material comprises the at least one compound of formula (I).
14. The device of claim 13, wherein the at least one acceptor material comprises C6o-
15. The device of claim 12, wherein the at least one acceptor material comprises the at least one compound of formula (I).
16. The device of claim 15, wherein the at least one donor material comprises CuPc.
17. The device of claim 12, wherein the at least one donor material comprises the at least one compound of formula (I), and the at least one acceptor material comprises another compound of formula (I).
18. The device of claim 12, wherein the at least one donor material and the at least one acceptor material form a donor-acceptor heterojunction.
19. The device of claim 13, wherein the at least one donor material and the at least one acceptor material form a lamellar structure, and wherein the at least one donor layer has a thickness ranging from about 1 nm to about 150 nm.
20. The device of claim 19, wherein the thickness of the at least one donor layer ranges from about 20 nm to about 80 nm.
21 . The device of claim 1 , wherein the device is an organic solar cell.
22. A method of making an organic photosensitive optoelectronic device of claim 1 , comprising depositing a photoactive region over a substrate, wherein the photoactive region comprises at least one compound of formula (I).
23. The method of claim 22, wherein the photoactive region comprises at least one donor material and at least one acceptor material, wherein one of the donor and acceptor materials comprises the at least one compound of formula (I).
24. The method of claim 22, wherein the deposition of the photoactive region comprises depositing the at least one compound of formula (I) over a substrate using a technique chosen from spin casting and vapor deposition.
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