EP1859494A1 - Photoactive component with organic layers - Google Patents

Abstract

The invention relates to a photoactive component comprising organic layers, in particular, solar cells, comprising a layer which comprises an electrode and a counter-electrode in addition to a sequence of organic layers which is arranged between the electrode and the counter-electrode. Photoactive areas are formed in two adjacent layers, that is, an electron harvesting layer (EHL - “Electron Harvesting Layer” ) and an electron separating layer (ESL - “Electron Separating Layer” ) in one of the sequences of organic layers. The electron harvesting layer (EHL) is a mixed layer which contains an organic material (A) and at least one additional organic material (B), wherein: (i) the lowest singlet-excitation state for electrons (S1A ) of the organic material (A) is energetically higher than the lowest singlet-excitation state for electrons (S1B ) of the additional organic material (B), (ii) the additional organic material (B) is formed by means of converting an ISC- mechanism (ISC - “Inter-System-Crossing” ) of singlet electrons on triplet electrons having a quantum yield of at least approximately 20 %, preferably, at least approximately 50 % and (iii) the lowest triplet excitation state for electrons (T1B) of the additional organic material (B) is energetically higher that the lowest triplet-excitation state for electrons (T1A ) of the organic material (A); and in the region of the defining surface, a triplet electron of the organic material (A) is formed in free charge carrier pairs of separating donor-acceptor hetero transitions between the electron harvesting layer (EHL) and the electron separating layer (ESL).

Description

 Photoactive component with organic layers

The invention relates to a photoactive component having organic layers, in particular a solar cell, having a layer arrangement which has an electrode and a counterelectrode as well as a series of organic layers which is arranged between the electrode and the counterelectrode.

Background of the invention

Since the demonstration of the first organic solar cell with a percentage efficiency by Tang et al. In 1986 (CW Tang et al., Appl. Phys. Lett 48, 183 (1986)), organic materials are extensively studied for various electronic and optoelectronic devices. Organic solar cells consist of a series of thin layers, which typically have a thickness of between 1 μm and 1 μm, of organic materials which are preferably vapor-deposited in vacuo or applied from a solution. The electrical contacting is usually carried out by metal layers and / or transparent conductive oxides (TCOs).

The advantage of such organic-based devices over conventional inorganic-based devices, such as semiconductors such as silicon, gallium arsenide, are the sometimes extremely high optical absorption coefficients of up to ² × ^{10 5} cm ^-1 , so that there is the possibility of using low material and energy required to produce very thin solar cells. Further technological aspects are the low costs, the possibility of producing flexible large-area components on plastic films, and the almost unlimited possibilities of variation in organic chemistry.

A solar cell converts light energy into electrical energy. In contrast to inorganic solar cells, solar cells do not directly generate free charge carriers by light, but excitons are first formed, ie, electrically neutral excitation states, namely bound electron-hole pairs. These excitons can only be separated by very high electric fields or at suitable interfaces. In organic solar cells sufficiently high fields are not available, so that all promising concepts for organic solar cells on the exciton separation at photoakti- Interfaces are based (organic donor-acceptor interface - CW Tang, Appl. Phys. Lett, 48 (2), 183-185 (1986)) or interface to an inorganic semiconductor (see B. O'Regan et al. Nature 353, 737 (1991)). This requires that excitons generated in the bulk of the organic material can diffuse to this photoactive interface.

The low-recombination diffusion of excitons to the active interface thus plays a critical role in organic solar cells. In order to make a contribution to the photocurrent, therefore, in a good organic solar cell, the exciton diffusion length must be at least of the order of the typical penetration depth of the light, so that the greater part of the light can be used. Structurally and with regard to chemical purity, perfect organic crystals or thin films definitely fulfill this criterion. For large-scale applications, however, the use of monocrystalline organic materials is not possible and the production of multiple layers with sufficient structural perfection is still very difficult.

Instead of increasing the exciton diffusion length, one can also reduce the mean distance to the nearest interface. The document WO 00/33396 proposes the formation of a so-called interpenetrating network: A layer contains a colloidally dissolved substance which is distributed so as to form a network through which charge carriers can flow (percolation mechanism). The task of light absorption takes over in such a network either only one of the components or both.

The advantage of such a mixed layer is that the generated excitons only have to travel a very short distance until they reach a domain boundary where they are separated. The removal of the electrons and the holes takes place separately in the dissolved substance or in the remaining layer. Since the materials in the mixed layer are in contact with each other everywhere, it is crucial in this concept that the separate charges have a long service life on the respective material and that from each location closed percolation paths for both types of charge carriers are present for the respective contact. Efficiencies of 2.5% were achieved with this approach (CJ Brabec et al., Advanced Functional Materials 11, 15 (2001)). Further known approaches for realizing or improving the properties of organic solar cells are listed below:

- One contact metal has a large and the other a small work function, so that a Schottky barrier is formed with the organic layer (US 4,127,738). The active layer consists of an organic semiconductor in a gel or binder (US 3,844,843, US 3,900,945, US 4,175,981 and US 4,175,982).

- Preparation of a transport layer containing small particles with a size of about 0.01 to 50 microns, which take over the charge carrier transport (US 5,965,063).

A layer contains two or more types of organic pigments which have different spectral characteristics (JP 04024970).

- One layer contains a pigment that generates the charge carriers, and in addition a material that carries away the charge carriers (JP 07142751).

Polymer-based solar cells containing carbon particles as electron acceptors (US Pat. No. 5,986,206) Doping of the above-mentioned mixing systems to improve the transport properties in multilayer solar cells (see DE 102 09 789)

Arrangement of individual solar cells one above the other, so that a so-called tandem cell is formed (US 4,461,922, US 6,198,091, US 6,198,092).

- Tandem cells can be further improved by using p-i-n structures with doped transport layers large band gap (DE 103 13 232).

The document US Pat. No. 5,093,698 discloses the doping of organic materials. By adding an acceptor-like or a donor-like dopant, the equilibrium charge carrier concentration in the layer is increased and the conductivity is increased. According to the document US 5,093,698, the doped layers are used as injection layers at the interface with the contact or electrode materials in electroluminescent devices. Similar doping approaches are analogously useful for solar cells.

Despite the advantages of interpenetrating networks described above, a critical issue is that closed transport paths must be present in the mixed layer for both electrons and holes to their respective contacts. As well as the each material fill only a portion of the mixed layer, the transport properties for the charge carriers deteriorate significantly compared to the pure layers.

If interpenetrating networks are to be dispensed with, the critical parameter for organic solar cells is the diffusion length for excitons L _D , which can be calculated from the lifetime of the excitons τ and the diffusion constant D corresponding to L _D = ^ DT. For singlet excitons, the diffusion length is usually very low, for example 3 to 10 nm, because of its short lifetime of about 0.1 to 10 ns (see M. Hoffmann et al., J. of Fluorescence, 5 (2), 217 (1995) or P. Peumans et al., J. Appl. Phys., 93, 3693 (2003)). For triplet excitons, the diffusion length can be significantly greater since these lifetimes are several orders of magnitude longer, from about 1 μs to about 10 ms (see C. Adachi et al., Appl. Phys. Lett. 79, 2082, (2001). )) exhibit.

Upon excitation with light, singlet excitons are first generated because the photons of the light have no spin and the overall spin is preserved during the excitation process. In special classes of materials, but especially in phosphorescent complexes of heavy metals such as Ir or Pt, singlet excitons are rapidly and efficiently converted into triplet excitons. This mechanism is called inter-system crossing (ISC).

The document DE 103 13 232 describes an organic solar cell in which materials with increased ISC probability are used as a component of an organic heterojunction. Other solar cells (see P. Peumans et al., Appl. Phys. Lett., 79 (1), 126 (2001).) Are based in part on the fact that excitations in fullerene C _{60 are} most likely to be included in the triplet Pass state and there have high diffusion lengths of about 40 nm (P. Peumans et al., J. Appl. Phys., 93, 3693 (2003)).

However, the direct use of such materials with increased IS C probability as a component of an organic heterojunction presents several problems. Both typical phosphorescent metal complexes and fullerene C ₆₀ have very low absorption coefficients in the region of the lowest excitation energy. For the phosphorescent metal complexes, this is because the lowest excited state in an excitation of an electron from the metal into the organic ligand exists (MLCT - "metal to ligand charge transfer") and such transitions due to the small spatial overlap of the participating orbitals have low oscillator strengths, as is shown by way of example from Fig.l. 1 shows the chemical structure of a typical iridium complex as well as a graphic representation of a phosphorescence emission in the red spectral region and an absorption spectrum of a 20nm thick layer on quartz glass The low-energy absorption band around 550 nm is very weak.

For fullerene C ₆ o, the optical excitation of the lowest excited state is symmetry-forbidden. Efficient absorption thus only takes place for higher excited states. The excitation energy then relaxes very quickly into the lowest state, which means a loss of energy for the solar cell.

Materials that favor the mechanism of inter-system crossing, for example because of heavy metals, therefore inevitably have lower triplet life, for example, only lμs for Ir (ppy) ₃ (see C. Adachi et al., Appl Lett., 77 (6), 904-906 (2000)). This value can still decrease by several orders of magnitude due to non-radiative recombination channels in aggregates (see MA Baldo et al., Appl. Phys. Lett., 75 (1), 4-6 (1999)), since the recombination is again an Inter - includes system crossing. This has a negative effect on the diffusion length of the triplet excitons: Accordingly, diffusion lengths for triplet excitons of up to 140 nm were reported for the non-phosphorescent material Alq ₃ (MA Baldo et al., Phys. Rev. B 60, 14422 (FIG. 1999)). Similarly high values are not known for phosphorescent systems.

Object of the invention

The object of the invention is to provide a photoactive device with organic layers, in which the efficiency of the energy conversion is improved. Summary of the invention

This object is achieved according to the invention by a photoactive component according to independent claim 1. Advantageous embodiments of the invention are the subject of dependent subclaims.

The invention includes the idea of providing a photoactive component having organic layers, in particular a solar cell, with a layer arrangement which has an electrode and a counter electrode and a series of organic layers which is arranged between the electrode and the counter electrode, wherein:

two adjacent layers are formed in a photoactive region comprised of the sequence of organic layers, namely an exciton-collecting layer the exciton-collecting layer (EHL) and an exciton-separating layer (ESL) ); the exciton-collecting layer (EHL) is a mixed layer containing an organic material (A) and at least one further organic material (B), in which:

a lowest singlet excitation state for excitons (Sf) of the organic material (A) is higher in energy than a lowest singlet excited state for excitons (Sf) of the further organic material (B), - the further organic material (B) by means of an ISC Mechanism (ISC, inter-

System crossing ") singlet excitons are formed in triplet excitons with a quantum yield of at least about 20%, preferably at least about 50%, and

a lowest triplet excitation state for excitons (Tf) of the further organic material (B) is energetically higher than a lowest triplet excited state for

Excitons (T _λ ^Λ ) of the organic material (A); and

in the region of an interface between the exciton-collecting layer (EHL) and the exciton-separating layer (ESL), a triplet exciton of the organic material (A) is formed in donor-acceptor heterojunction separating free carrier pairs.

The exciton-collecting layer (EHL), in which triplet excitons are formed due to light absorption, is obtained as a mixture of an organic material A and at least one further organic material B formed. After excitation of a singlet exciton on the organic material A, the excitation energy is transferred to the further organic material B, which requires that its lowest singlet excited state Sf is lower in energy than the lowest singlet excited state Sf of the organic material A. The further organic material B is chosen so that the inter-system crossing is favored, so that on the further organic material B singlet excitons are converted with a probability of at least 50% in triplet excitons on the other organic material B. Then a back transfer of the triplet excitons from the further organic material B to the organic material A takes place, which requires that the lowest triplet excited state T * on the organic material A is lower in energy than the lowest triplet excited state T _X ^B the other organic material B.

In this way, long-lived triplet excitons are generated on the organic material A with high quantum yield, which diffuse to an interface to the exciton-separating layer (ESL), the interface between the exciton-collecting layer (EHL) and the exciton-separating layer (FIG. ESL) is designed so that the long-lived triplet excitons from the exciton-collecting layer (EHL) are separated into a charge carrier on the exciton-collecting layer (EHL) and an inversely charged charge carrier on the exciton-separating layer (ESL).

Thus, the photoactive interface may be formed to form either holes in the exciton-collecting layer (EHL) and electrons in the exciton-separating layer (ESL) or vice versa. The charge carriers formed in this way in the exciton-collecting layer (EHL) are referred to below as "photogenerated charge carriers." The transport of the photogenerated charge carriers may take place within the exciton-collecting layer, preferably on the organic material A or on the further organic material B. If, in an advantageous embodiment of the invention, the photogenerated charge carriers are transported on the organic material A or in the same way on the organic material A and the further organic material B, then the further organic material B is neither required for charge carrier transport nor for exciton transport, which is imperative below with reference to the embodiment 4 is explained in more detail. It is therefore sufficient for a very low concentration of the other organic material B, which must meet only the condition that a large part of the singlet excitation states on the organic material A must reach an area with the other organic material B during their life, in order to triplet Excitons to be converted. This means that a mean distance of the molecules or clusters of the further organic material B in the organic material A must be less than the diffusion length of the singlet excitons in the organic material A, which is typically about 3 to 20 nm.

If, in other expedient embodiments of the invention, the photogenerated charge carriers in the exciton-collecting layer (EHL) are preferably transported on the further organic material B, which is explained in more detail below with reference to the first to third exemplary embodiments, the concentration of the further organic material B in the organic material A are above a percolation limit to provide closed transport paths for charge carriers available. The concentration is advantageously greater than about 15%, preferably greater than about 30%.

In contrast to the proposal in the document DE 103 13 232 is not exploited in the device according to the invention, the diffusion of triplet excitons on the material with increased IS C probability, but the other organic material B with an efficient inter-system crossing mechanism serves as a type of "catalyst" to generate long lived triplet excitons in the host material, organic material A.

The layer arrangement according to the invention can be used in different embodiments of the invention in solar cells with a MiM, a pin, a mip or a min structure, the following abbreviations apply: M - metal, p - p-doped organic or inorganic Semiconductor, n-n-doped organic or inorganic semiconductor and i-intrinsically conductive system of organic layers (see, for example, J. Drechsel et al., Org. Electron., 5 (4), 175 (2004), Maennig et al., Appl. Phys. A 79, 1-14 (2004)). A preferred embodiment of the invention provides for the use of the layer arrangement according to the invention in a tandem cell, as described as such by Peumans et al. (See P. Peumans et al., J. Appl. Phys., 93 (7), 3693-3723 (2003), US 4,4619,22, US 6,198,091 or US 6,198,092). The use in tandem cells of two or more stacked MiM, pin, Mip or Min diodes can also be provided (compare DE 10 2004 014046 A1, J. Drechsel et al., Thin Solid Films, 451452, 515-517 (2004)).

As exciton separating layer ESL, a layer can be selected which serves exclusively for exciton separation and for charge carrier transport, as provided below in Exemplary Embodiment 1. However, it can also be a layer which, moreover, absorbs light and is suitable for converting the resulting states of excitation in the volume or at one of their interfaces into free pairs of charge carriers. For example, the exciton-separating layer may comprise a photoactive volume heterojunction, as provided below in Exemplary Embodiment 5 (see G. Yu et al., Science, 270 (5243), 1789 (1995), WO 00/33396), or it may be a layer that allows diffusion of singlet or triplet excitons to the interface to the exciton-collecting layer, which is provided in Embodiment 4 below.

Further advantageous embodiments of the invention will become apparent from the dependent claims.

An expedient development of the invention provides that for one or more organic materials (Ci; i> 1), from which the excitons separating layer (ESL) is formed, and for the organic material (A) and the at least one further organic material (B), from which the exciton-collecting layer (EHL) is formed, the following applies:

- for at least one of the organic materials (Ci) lies a highest occupied orbital

(HOMO) is higher in energy than a respective highest occupied orbital (HOMO) of the organic material (A) and of the at least one other organic material (B); and - A respective lowest unoccupied orbital (LUMO) is energetically higher for all organic materials (Ci) than a respective lowest unoccupied orbital (LUMO) of the organic material (A) or at least one other organic material (B).

In a preferred embodiment of the invention can be provided that for one or more organic materials Ci (i> 1), from which the excitons separating layer (ESL) is formed, and for the organic material (A) and the at least one further organic Material (B) from which the exciton-collecting layer (EHL) is formed is:

for at least one of the organic materials (Ci), a lowest unoccupied orbital (LUMO) is lower in energy than a respective lowest unoccupied orbital (LUMO) of the organic material (A) and the at least one further organic material (B) and

- A respective highest occupied orbital (HOMO) is energetically lower for all organic materials (Ci) than a respective highest occupied orbital (HOMO) of the organic material (A) or of the at least one further organic material (B).

An expedient embodiment of the invention may provide that a mass fraction of the organic material (A) in the excitonic layer (EHL) collecting layer is greater than about 30%, preferably greater than about 60%, and more preferably greater than about 90%.

In an advantageous embodiment, it is provided that the lowest unoccupied orbital (LUMO) of the organic material (A) is lower in energy or at most about O.leV higher than the lowest unoccupied orbital (LUMO) of the at least one other organic material (B).

A preferred development of the invention provides that the highest occupied orbital (HOMO) of the organic material (A) is higher in energy or at most about O.leV lower than the highest occupied orbital (HOMO) of the at least one further organic material (B).

A preferred embodiment of the invention provides that both a mass fraction of the organic material (A) and a mass fraction of the further organic material (B) in the excitonic layer (EHL) collecting layer is greater than about 15%, preferably greater than about 30%.

In an expedient embodiment of the invention, it may be provided that a lowest unoccupied orbital (LUMO) of the organic material (B) is lower in energy or at most approximately O.leV higher than the lowest unoccupied orbital (LUMO) of the organic material (A). ,

An advantageous embodiment of the invention provides that a highest occupied orbital (HOMO) of the at least one further organic material (B) is higher in energy or at most about O.leV lower than the highest occupied orbital (HOMO) of the organic material (A ).

A preferred embodiment of the invention provides that a triplet transport layer (TTL) of one or more organic materials is arranged between the exciton-collecting layer (EHL) and the exciton-separating layer (ESL), the energy of a lowest Triplet excited state of the triplet transport layer is less than or equal to the energy of the lowest triplet excited state of the organic material (A) in the excitonic convergent layer (EHL).

A preferred embodiment of the invention provides that a highest occupied orbital (HOMO) of the triplet transport layer (TTL) is energetically equal to or lower than the respective highest occupied orbital (HOMO) of the organic material (A) or of the at least one further organic material in the excitonic layer (EHL) which forms as a mixed layer.

In an expedient embodiment of the invention it can be provided that a lowest unoccupied orbital (LUMO) of the triplet transport layer (TTL) is energetically equal to or higher than the lowest unoccupied orbital (LUMO) of the organic Material (A) or the at least one other organic material in the running as a mixed layer excitons layer (EHL). An advantageous embodiment of the invention provides that in the at least one further organic material (B), an energy difference between the lowest singlet excitation state for excitons (S ₁ ⁵ ) and the lowest triplet excited state for

Excitons (Tf) less than about 0.5eV, preferably less than about 0.3eV.

A preferred development of the invention provides that the at least one further organic material (B) is from one of the following material classes:

Fullerenes or carbon nanotubes, in particular C ₆₀ , C ₇₀ or C ₈₄ and their derivatives; - Metal-organic compounds, in particular those whose lowest excited state at least partially an excitation of an electron from the metal to the ligand (MLCT - "metal-to-ligand charge transfer") or ligand to metal (LMCT - "ligand-to-metal charge transfer "); and

Phosphorescent materials having a phosphorescence quantum yield greater than about 0.1%, preferably greater than about 1% in dilute solution.

A preferred embodiment of the invention provides that the metal-organic compound comprises a heavy metal having an atomic number of greater than 21, preferably greater than 39.

In an expedient embodiment of the invention, it can be provided that the organometallic compound comprises a metal from the following group of metals: Ru, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ti, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Er, Tm, Yb or Lu, preferably Ru, Rh, Re, Os, Ir or Pt.

An advantageous embodiment of the invention provides that the organic material (A) in the excitonic convergent layer (EHL) is an oligothiophene derivative, a perylene derivative, in particular a derivative of perylenetetracarboxylic dianhydride, perylenetetracarboxylic diimide or perylenetetracarboxylic bisimidazole, or a phthalocyanine , A preferred embodiment of the invention provides that the exciton-separating layer (ESL) is formed as a light-absorbing and singlet and / or triplet excited states generating layer, wherein generated singlet and / or triplet excitation states to the interface between the excitons collecting Layer (EHL) and the exciton separating layer (ESL) diffuse and can be converted there into pairs of charge carriers.

A preferred embodiment of the invention provides that the exciton-separating layer (ESL) is a mixed layer containing a plurality of organic materials, in which: a lowest singlet excitation state for excitons of one of the plurality of organic materials is higher than a lowest singlet excited state for excitons Excitons of another of the several organic materials;

- The further organic material is formed so that it is formed with a quantum yield of at least 20%, preferably at least 50% by means of an ISC mechanism (ISC -, Intersystem Crossing ") singlet excitons in triplet excitons transforming;

a lowest triplet excited state for excitons of the further organic material is higher in energy than a lowest triplet excited state for excitons of the one organic material.

In an expedient embodiment of the invention, provision may be made for a photoactive volume-donor-acceptor heterojunction to be formed in the excitonic separating layer (ESL) in the form of a mixed layer by means of the one organic material and the at least one further organic material.

An advantageous embodiment of the invention provides that an interface of the exciton-collecting layer (EHL), which faces away from the interface with the exciton-separating layer (ESL) / triplet transport layer (TTL), has a triplet block layer (TBL ) is energetically higher in the energetically lowest-energy triplet excitation states than low-energy triplet excitation states in the exciton-collecting layer (EHL). A preferred development of the invention provides that the contact and / or the mating contact are semitransparent or transparent.

A preferred embodiment of the invention provides that a p-doped layer is arranged between the contact and the photoactive region (M-i-p component).

In an expedient embodiment of the invention, it can be provided that an n-doped layer is arranged between the mating contact and the photoactive region (M-i-n device or n-i-p device).

An advantageous embodiment of the invention provides that one or more layers in the organic region by means of thermal evaporation in a high vacuum or evaporation of organic materials in an inert carrier gas, which transports the organic materials to a substrate ("Organic Vapor Phase Deposition '') deposited are.

A preferred embodiment of the invention provides that one or more layers are deposited in the organic region from a liquid solution, in particular by spin coating, knife coating or printing.

A preferred embodiment of the invention provides that the excitons collecting layer (EHL) has a thickness between about 5nm and about 200nm.

In an advantageous embodiment of the invention can be provided that the excitons collecting layer (EHL), the exciton separating layer (ESL) and / or the triplet transport layer (TTL) from a donor-acceptor donor oligomer or a Acceptor-donor-acceptor oligomer are formed.

Preferred embodiments of the invention

The invention is explained below with reference to embodiments with reference to figures of a drawing. Hereby show: 1 shows the chemical structure of a typical iridium complex and a graphic representation of a phosphorescence emission in the red spectral region and an absorption spectrum of a 20 nm thick layer on quartz glass; Fig. 2 shows the structural formula of DCV3T; Fig. 3 shows the chemical structure of MeOTPD (above, MeO denotes a methoxy group) and 4P-TPD (below);

4 shows a schematic representation with energy levels for explaining the mode of operation of a photoactive component according to a first exemplary embodiment with an exciton-collecting layer of a mixture of DCV3T and C ₆₀ and an exciton-separating layer of MeOTPD;

Figure 5 is a graphical representation of absorption and Photolumineszenzmesswerten a function of the wavelength for a DCVIT-Emzelschicht having a thickness of 20 nm, a DCV3T. C ₆₀ mixed layer with a thickness ratio of 20 nm: 27 nm, and a C ₆₀ -Einzelschicht having a thickness from 27nm; 6 is a graph showing a change in transmittance at a measurement temperature of 1OK for a DCV3T layer having a thickness of 20 nm (circles) and a DCV3T. C ₆₀ mixed layer with a thickness ratio of 20 nm: 27 nm (squares) after excitation with a . Ar (+) - laser at 514 nm with a power density 30mW / cm ^"2; Figure 7 is a current-voltage characteristic under illumination with simulated sunlight intensity of 127 W / cm ² and without illumination for a photoactive component according to a second exemplary embodiment with a 30 nm-thick mixed layer of DCV3T and C ₆₀ (1: 2) collecting as exciton layer and tetramethoxy-tetraphenyl benzidine (MeOTPD) as exciton separating layer; Figure 8 is a graph showing the wavelength dependence of external quantum efficiency (EQE - "external quantum efficiency. "), which is shown by a solid line, a photoactive device with the layer sequence ITO / C ₆₀ / DCV3T / MeOTPD / p-doped MeO TPD / Gold and dashed line the course of the absorption coefficient of DCV3T and as dotted lines the sorption coefficient of C ₆₀ ; 9 shows a schematic representation with energy levels for explaining the mode of operation of a photoactive component according to a sixth exemplary embodiment; and

Fig. 10 Structural formulas for a class of compounds that can be used as organic material A in an exciton-collecting layer, with a radical R

May be hydrogen, an alkyl group or a cyano group and the group X in the oligothiophene chain may be one of the groups a) to d) or another homo- or heterocyclic compound having a conjugated π-electron system.

In the following, with reference to FIGS. 2 to 10, various exemplary embodiments for a photoactive component with organic layers will be described, which can be implemented in particular as a solar cell.

In the various embodiments of the component, a layer arrangement is provided, which has an electrode and a counterelectrode and a sequence of organic layers which is arranged between the electrode and the counterelectrode. Two adjoining layers are formed in a photoactive region encompassed by the sequence of organic layers, namely an exciton-collecting layer (EHL) and an exciton-separating layer (ESL). The exciton-collecting layer (EHL) is a mixed layer containing an organic material A and another organic material B. In the mixed layer, a lowest singlet excited state for excitons (Sf) of the organic material (A) is higher in energy than a lowest singlet. Excitation state for excitons (Sf) of the further organic material B. The further organic material B converts with high quantum yield of at least about 20%, preferably of at least about 50%, singlet excitons by means of an ISC mechanism (ISC). Furthermore, the mixed layer is designed so that a lowest triplet excitation state for excitons (Tf) of the further organic material B is higher in energy than a lowest triplet excitation state for excitons (T _X ^Λ ) of the organic material A, so that the triplet exciton formed on the material B with high probability on the Ma terial A is transferred. By means of an interface between the exciton-collecting layer (EHL) and the exciton-separating layer (ESL) a donor-acceptor heterojunction is formed, which triplet excitons of the organic material A can separate into free charge carrier pairs.

First embodiment

In a first embodiment, the following layer sequence is provided: ITO / DCV3T * C ₆₀ / MeOTPD / p-doped MeOTPD / gold. Here, ITO refers to a transparent base contact of indium tin oxide and C ₆₀ the Buckminster fullerene.

The structure of the other materials is shown in FIGS. 2 and 3. Fig. 2 shows the structural formula of DCV3T. The radical R is a hydrogen atom in DCV3T but may also be a cyano group in derivatives (TCV3T, see T. M. Pappenfus et al., Org. Lett, 5 (9), 1535-1538 (2003)) or an alkyl radical. Figure 3 shows the chemical structure of MeoTPD (top of Figure 3, MeO denotes a methoxy group) and 4P-TPD (bottom of Figure 3).

The p-doping is carried out, for example, by means of mixed evaporation with perfluorinated tetracyano-quinodimethane (F ₄ -TCNQ). In this first exemplary embodiment, the exciton-collecting layer consists of DCV3T (organic material A) and C ₆₀ (further organic material B) and the exciton-separating layer of MeOTPD.

4 shows a schematic illustration for explaining the mode of operation of a component according to the first exemplary embodiment with an exciton-collecting layer of a mixture of DCV3T and C ₆₀ and an exciton-separating layer of MeOTPD. The following subprocesses are shown: (0) excitation of a singlet exciton on DCV3T by light absorption;

(1) transfer of singlet excited state from DCV3T to C _60;

(2) inter-system crossing to C _60;

(3) transfer of triplet excited state from C ₆₀ to DCV3T;

(4) diffusion of the triplet excited state on DCV3T to the interface between the exciton-collecting layer and the exciton-separating layer;

(5) separation of the triplet excited state into an electron in the exciton-collecting layer, namely on the lowest unoccupied orbital (LUMO) of C ₆₀ , and a hole in the exciton-separating layer, namely on the highest occupied orbital (HOMO) of MeOTPD.

Singlet excitons are first generated on DCV3T by light absorption. The excitation energy is transferred very quickly to C ₆₀ . Evidence for this is that pure layers of DCV3T show efficient fluorescence with a mean decay time of about 200ps. This fluorescence is reduced to below 1% of the original intensity by admixture with C ₆₀ , which is shown in FIG. As a result, an erase process on the time scale of less than 1ps occurs.

It is known that singlet excitons on C _{60 are} highly likely to be converted to triplet excitons, and according to Peumans (see P. Peumans et al., J. Appl. Phys., 93, 3693 (2003)) η _ISC = 96% at room temperature. The triplet excitons are transferred back to DCV3T in a next step. This is evident when comparing the photoinduced absorption of a pure DCV3T layer with the mixed layer of DCV3T and _C6 o, as shown in Fig. 6. In both cases, after pulsed excitation, an additional "photoinduced" absorption with the same spectrum occurs, which is due to the excitation of triplet excitons to higher states, but the measurement signal is amplified by a factor of three, due to the admixture of C ₆₀ shows that the triplet excited state population is increased to DCV3T due to the mechanism described above.

The thus formed triplet excitons on DCV3T can now diffuse to the interface with Me-OTPD and there are separated into free holes on MeOTPD and free electrons on C ₆₀ . In the chosen embodiment, the lowest unoccupied orbital (LUMO) of the further organic material, C ₆₀ , is lower than the lowest unoccupied orbital (LUMO) of the organic material A, namely DCV3T, so that the charge transport of electrons on the further organic material B takes place. This results in the requirement that the additional organic material B must be present in sufficient concentration to provide closed percolation paths available. Second exemplary embodiment

In a second embodiment, the following layer sequence for the photoactive component is provided: ITO / C ₆₀ / DCV 3 T * C ₆₀ / MeOTPD / p-doped MeOTPD / gold.

In contrast to the first exemplary embodiment, an additional pure C ₆₀ layer is arranged here as a triplet blocking layer (TBL) between the exciton-collecting layer and the ITO electrode Exemplary Embodiment The triplet block layer performs the function of preventing triplet excitons diffusing toward the ITO electrode from being quenched there, instead the triplet excitons are reflected at C ₆₀ and have another chance to cross the interface 7 shows a current-voltage characteristic under illumination with simulated sunlight of intensity 127 m W / cm ² and without illumination for a component according to the second exemplary embodiment with a 30 nm thick mixed layer of DCV3T and C. ₆₀ (1: 2) as exciton-collecting layer and tetramethoxy-tetraphenyl-benzidine (MeOTPD) as Exz itonen separating layer. The layer sequence is given in detail in FIG. 7, where p-MeOTPD and p-ZnPc are p-doped layers of MeOTPD / zinc phthalocyanine with F ₄ -TCNQ as acceptor dopants.

Third embodiment

In a third embodiment, the following layer sequence is provided for the photoactive component: ITO / C ₆₀ / DCV 3 T * C ₆₀ / DCV 3 T / MeOTPD / p-doped MeOTPD / gold.

Compared to the second embodiment, an additional triplet transport layer (TTL) of DCV3T (excitatory ion organic material A) is placed between the exciton-collecting layer and the exciton-separating layer Excitons collecting layer must here additionally diffuse through the DCV3T layer until it at the Interface to the exciton-separating layer can be separated in holes on MeOTPD and electrons on DCV3T.

The transfer of triplet excitons from C ₆₀ to DCV3T and the diffusion of the transferred triplet excitons to DCV3T proves that the C _60- originated signal is in the external quantum efficiency of a solar cell with the ITO / C ₆₀ / DCV3T layer sequence / MeOTPD / p-doped MeOTPD / gold (see Fig. 8). In addition, in the third embodiment, the diffusion of singlet excitons on DCV3T to the exciton-separating layer is utilized to the charge carrier generation.

8 shows a graph of the wavelength dependence of the external quantum efficiency (EQE), which is shown by a solid line 80, of a photoactive component with the layer sequence ITO / C ₆₀ / DCV3T / Me-OTPD / p- The absorption coefficient of C ₆₀ is shown with the aid of a dotted line 82. The outer quantum efficiency has a peak at a wavelength of 450 nm, which is due to the absorption coefficient of DCV3T Absorption of the C _{60 is} due.

The device according to the third embodiment has the further advantage over the devices according to the first and the second embodiment in that the LUMO of the additional pure DCV3T layer is higher than the LUMO of C ₆₀ . Thus, charge carrier pairs having a larger free energy are formed at the exciton-separating layer interface, and the device achieves a higher photo-voltage.

Fourth embodiment

In a fourth embodiment, the following layer sequence for the photoactive component is provided: ITO / C ₆₀ / DCV 3 T * C ₆₀ / ZnPc / p-doped MeOTPD / gold.

In contrast to the second exemplary embodiment, zinc phthalocyanine (ZnPc) is used as exciton-separating layer, which has a strong absorption in the visible spectral range. The excitons photogenerated in ZnPc can be used for excitons Diffuse layer and there are separated into free electrons on C ₆₀ and free holes on ZnPc, so that here also the excitons collecting layer makes a contribution to the photocurrent generation.

Fifth embodiment

In a fifth embodiment, the following layer sequence is provided for the photoactive device: ITO / C ₆₀ / C ₆₀ DCV3T * / 4P-TPD * C ₆₀ (1: 3) / MeOTPD / p-doped MeOTPD / gold.

A mixed layer of 4P-TPD (see Fig. 3) and C ₆ o is provided as an exciton-separating layer. The operation of the device according to the fifth embodiment corresponds to that of the device according to the second embodiment.

In addition, 4P-TPD and C ₆₀ in the exciton-separating layer form a volume heterojunction, which in its entire volume can convert excitons formed on either material into charge-carrier pairs, holes on 4P-TPD and electrons on C ₆₀ . Thus, here the excitons separating layer contributes in addition to the photocurrent generation. Alternatively, in this embodiment, the material 4P-TPD may be replaced by other hole transport materials with greater absorbency, for example, a phthalocyanine or an oligothiophene derivative.

Sixth embodiment

In a fifth embodiment, the following layer sequence for the photoactive component is provided: ITO / TCV3T * C ₆₀ / MeOTPD / p-doped MeOTPD / gold.

The operation of the device according to the sixth embodiment corresponds to that of the device according to the first embodiment, with the difference that the charge separation at the exciton separating layer for generation of electrons on TCV3T, which is the organic material A of the excitons Layer, and holes on MeOTPD results because here the organic material A has a deeper LUMO as the other organic material B, namely C ₆₀ . Here, therefore, the transport of triplet excitons and of charge carriers, namely electrons on the organic material A, takes place, while the further organic material B serves exclusively to support the ISC. Consequently, the additional organic material B need not provide closed percolation paths in the exciton-collecting layer, and a concentration between about 0.1 and 10% is sufficient. This is an advantage for the photocurrent generation because the organic material A typically has the stronger absorption.

9 shows a schematic representation of the mode of operation of a photoactive component according to the sixth exemplary embodiment. The following sub-processes are shown:

(0) excitation of a singlet exciton on TCV3T by light absorption;

(1) transfer of the singlet excited state from TCV3T to C _60;

(2) inter-system crossing to C _60; (3) transfer of triplet excited state from C ₆ o to TCV3T;

(4) diffusion of the triplet excited state on TCV3T to the interface between the exciton-collecting layer and the exciton-separating layer;

(5) Separation of the triplet excited state into an electron in the exciton-collecting layer, namely, on the LUMO of TCV3T, and a hole in the excitons separating, namely, the highest occupied orbital (HOMO) of MeOTPD.

In photoactive devices having a layer sequence according to one of the above embodiments, as the organic material A in the exciton-collecting layer, alternatively, a thiophene derivative having a structural formula of Fig. 10 or a perylene derivative can be used. Figure 10 shows structural formulas for a class of compounds that can be used as organic material A in the exciton-collecting layer. Here, the radical R may be hydrogen, an alkyl radical or a cyano group. The group X in the oligothiophene chain may be one of the groups a) to d) or another homo- or heterocyclic compound having a conjugated π-electron system. For the organic material A in the exciton-collecting layer as well as for the materials of the TTL and the exciton-separating layer, a donor-acceptor-donor-oligomer or an acceptor-donor-acceptor-oligomer as described in the simultaneously filed PCT- Registration with the title "Organic Photoactive Device", the contents of which are incorporated herein by reference, or other donor-acceptor cooligomers.

In the above embodiments, besides the light absorption and the exciton transport, the exciton-collecting layer has the function of transporting photogenerated electrons. It therefore preferably has an electron mobility of at least 5.times.10.sup.- ⁷ cm.sup.-3, but the component can also be designed vice versa so that photogenerated holes are transported in the exciton-collecting layer.For this, materials which have an organic material A in the exciton-collecting layer can also be used 10 with suitably chosen radical R, which is preferably hydrogen or an alkyl radical but not electron-withdrawing groups such as CN A suitable material is, for example, DCV5T, a compound where R = H, n = 0, m = 0 and k = 5.

As a further organic material B, a heavy metal complex can be used, for example a platinum complex (PtK) or an iridium complex (IrK) with a phosphorescence in the infrared spectral range. This results in the following layer sequence for a further exemplary embodiment: ITO / C ₆₀ / DCV5T * IrK / p-doped MeOTPD / gold. Here, the exciton-collecting layer is formed by means of a mixture of DCV5T and IrK, and C ₆₀ forms the exciton-separating layer. Depending on the energetic position of the HO-MO of IrK, hole transport in the mixed layer of IrK with DCV5T predominantly occurs on DCV5T, if the highest occupied orbital (HOMO) of IrK lies deeper than the highest occupied orbital (HOMO) of DCV5T, or predominantly on IrK takes place if the highest occupied orbital (HOMO) of IrK is higher than the highest occupied orbital (HOMO) of DCV5T. In the former case, a very low concentration of IrK in DCV5T of about 0.1 to about 10%, analogous to the considerations on the concentration of C ₆₀ in TCV3T in the sixth embodiment is sufficient. In the latter case, IrK must be present in the mixed layer in sufficient concentration, namely at least 15%, preferably at least 30%, so that efficient hole transport to IrK can take place. An advantageous embodiment is still present if the highest occupied orbital (HOMO) of IrK is higher by a maximum of O.leV than the highest occupied orbital (HOMO) of DCV5T, so that IrK forms a shallow trap for holes in DCV5T. Since the holes can be easily released from the traps by thermal energy, the hole transport can take place on DCV5T, and here too a very low concentration of IrK in DCV5T between about 0.1 and about 10% is sufficient.

Figure 5 shows absorbance and photoluminescence readings versus wavelength. For a DCV3T single layer with a thickness of 20 nm, the absorption curve 10 and the course of the photoluminescence 11 are shown as dashed lines. For a DCV3T: C ₆ o mixed layer formed by means of mixed evaporation with a thickness ratio of 20 nm: 27 nm, the absorption curve 20 and the course of the photoluminescence 21 are shown as dash-dot lines. Furthermore, the solid line shows the absorption curve 30 and the course of the photoluminescence 31 for a C ₆₀ single layer with a thickness of 27 nm.

The luminescence of the single layer of DCV3T at an excitation wavelength of 530 nm is quenched by the presence of C ₆₀ in the DCV 3 T: C ₆₀ mixed layer. Residual luminescence of the mixed layer at an excitation wavelength of 530 nm, which is represented by a factor of 100, results from the weak fluorescence of C ₆₀ , which results from a comparison with the measured values for Cgo single-layer multiplied by a factor of 400. at an excitation wavelength of 512nm. The occurrence of the C ₆₀ fluorescence even when excited by DCV3T the transfer of the singlet excitation energy from DCV3T to C ₆₀ shows.

Fig. 6 shows the results of a measurement of the so-called "photo-induced absorption" at a measuring temperature of 1OK for a DCV3T layer having a thickness of 20 nm (circles) and for a DCV3T: C ₆₀ mixed layer with a thickness ratio of 20 nm: 27 nm (squares after excitation with an Ar (+) laser at 514 nm with a power density of 30 mW / cm ² . In "Photoinduced Absorption" measurements, a sample is subjected to periodically modulated illumination, in this case realized by an Ar ion laser, which is directed through a rotating chopper wheel onto the sample, so that this "pump beam" results in a periodic scan varied excitation of the sample and thus to a corresponding oscillating population density of excitation states (excitons). At the same time, a measuring beam of constant intensity is directed onto the sample and the transmission is measured by means of a photodetector beyond the sample. Since excited molecules have a different absorption spectrum than molecules in the ground state, now also the transmission probability of the measuring beam oscillates with the oscillation of the excitation density. Even if this change in transmission ΔT is only in the region of about 10.sup.- ^{4 of} the total transmission T, the relevant signal at the chopper frequency can be filtered out by lock-in technology .Figure 6 shows the transmission change normalized to the transmission (.DELTA.T / T The modulation of the wavelength of the measuring beam was realized by combining a halogen lamp with a grating monochromator.

For positive values of a transmission change below a wavelength of 660 nm, the ground state bleaching is recognizable The negative transmission change, namely additional absorption of the layer after the excitation, in a broad spectral range around 820 nm, becomes a triplet The excitation state τ of the triplet excitation state is determined to be T = 25 μs (from variation of the modulation frequency).

In the mixed layer, the spectral shape of the photoinduced absorption does not change compared to the pure DCV3T layer; Similarly, the lifetime of the observed excitation is unchanged. However, the measured signal is larger by a factor of 3 compared to the single layer. The magnitude of the observed signal is largely determined by the product of lifetime and population of the state for small frequencies (ω τ "1) (see, for example, Dellepiane et al., Phys. Rev. B, 48, 7850 (1993); Epshtein et al, Phys. Rev. B, 63, 125206 (2001)). Thus, with unchanged lifetimes, the observed behavior suggests an increased population of the triplet state on DCV3T mediated by C ₆₀ according to the mechanism depicted in FIG. 4.

The features of the invention disclosed in the above description, the claims and the drawings may be significant both individually and in any combination for the realization of the invention in its various embodiments.

Claims

claims 1. A photoactive component having organic layers, in particular a solar cell, having a layer arrangement which has an electrode and a counterelectrode and a sequence of organic layers which is arranged between the electrode and the counterelectrode, wherein: two adjacent layers are formed in a photoactive region encompassed by the sequence of organic layers, namely an exciton-collecting layer, the exciton-collecting layer (EHL) and an exciton-separating layer (ESL, Jilectron Separating Layer) ); the exciton-collecting layer (EHL) is a mixed layer containing an organic material (A) and at least one further organic material (B), in which: a lowest singlet excitation state for excitons (Sf) of the organic material (A) is higher in energy than a lowest singlet excitation state for excitons (Sf) of the further organic material (B), - The further organic material (B) by means of an ISC mechanism (ISC, Jn- System-Crossing ") singlet excitons in triplet excitons with a quantum yield of at least about 20%, preferably converted by at least about 50% and - a lowest triplet excitation state for excitons (T ₁ ⁶⁾ of the further organic material (B) lies energetically higher than a lowest triplet excitation state for excitons (T _λ ^a) of the organic material (a); and in the region of an interface between the exciton-collecting layer (EHL) and the exciton-separating layer (ESL), a triplet exciton of the organic material (A) is formed in donor-acceptor heterojunction separating free carrier pairs. 2. Component according to claim 1, characterized g ek ennzei chn et that for one or more organic materials (Ci; i> 1), from which the excitons separating layer (ESL) is formed, and for the organic material (A) and the at least one further organic material (B) from which the exciton-collecting layer (EHL) is formed is: for at least one of the organic materials (Ci), a highest occupied orbital (HOMO) is higher in energy than a respective highest occupied orbital (HOMO) of the organic material (A) and of the at least one further organic material (B); and - a respective lowest unoccupied orbital (LUMO) is energetically higher for all organic materials (Ci) than a respective lowest unoccupied orbital (LUMO) of the organic material (A) or of the at least one further organic material (B). 3. The component according to claim 1 or 2, characterized ek enn zei ch net, that for one or more organic materials Ci (i> 1), from which the excitons separating layer (ESL) is formed, and for the organic material (A ) and the at least one further organic material (B) from which the exciton-collecting layer (EHL) is formed, applies: - for at least one of the organic materials (Ci), a lowest unoccupied orbital (LUMO) is lower in energy than a respective lowest one unoccupied orbital (LUMO) of the organic material (A) and the at least one other organic material (B) and - A respective highest occupied orbital (HOMO) is energetically lower for all organic matter (Ci) than a respective highest occupied orbital (HOMO) of the organic material (A) or of the at least one further organic material (B). 4. The component according to claim 1, characterized in that a mass fraction of the organic material (A) in the as Mixed layer excitement collecting layer (EHL) is greater than about 30%, preferably greater than about 60%, and more preferably greater than about 90%. 5. The component according to claim 4, as far as dependent on claim 1 or 2, characterized ek e n ez ei chn et, that lowest unoccupied orbital (LUMO) of the organic material (A) energetically lower or at most about O.leV is higher than the lowest unoccupied orbital (LUMO) of the at least one other organic material (B). 6. Component according to claim 4, as far back to spoke 1 or 3, characterized in that highest occupied orbital (HOMO) of the organic material (A) energetically higher or at most about O.leV lower than the highest occupied orbital (HOMO) of the at least one further organic material (B). 7. Device according to at least one of the preceding claims, characterized in that both a mass fraction of the organic material (A) and a mass fraction of the further organic material (B) in the running as a mixed layer excitons collecting layer (EHL) greater than about 15% , preferably greater than about 30%. 8th component according to claim 7, as far back to Speech 1 or 2, characterized in that a lowest unoccupied orbital (LUMO) of the organic material (B) energetically lower or at most about O.leV is higher than the lowest unoccupied orbital (LUMO) of the organic material (A). 9. The component according to claim 7, as far back to spoke 1 or 3, characterized in that a highest occupied orbital (HOMO) of the at least one other organic material (B) energetically higher or at most about O.leV lower than the highest occupied orbital (HOMO) of the organic material (A). 10. The component according to at least one of the preceding claims, characterized in that between the exciton-collecting layer (EHL) and the exciton-separating layer (ESL) a triplet transport layer (TTL) of one or more organic materials is arranged, wherein the Energy of a lowest triplet excited state of the triplet transport layer is less than or equal to the energy of the lowest triplet excited state of the organic material (A) in the excitonic ion collecting layer (EHL). 11. The element according to claim 10, characterized in that a highest occupied orbital (HOMO) of the triplet transport layer (TTL) is energetically equal to or lower than the respective highest occupied orbital (s) ( HOMO) of the organic material (A) or of the at least one further organic material in the layer formed as a mixed layer excitons (EHL). 12. The component according to claim 10, characterized in that a lowest unoccupied orbital (LUMO) of the triplet transport layer (TTL) is energetically equal to or higher than the lowest unoccupied (n ) Orbital (LUMO) of the organic material (A) or of the at least one other organic material in the layer forming excitons (EHL) as a mixed layer. 13. The component according to claim 1, characterized in that at least one further organic material (B) has an energy difference between the lowest singlet excitation state for excitons (Sf) and the lowest triplet excited state for excitons (T ₁ ³ ) is less than about 0.5eV, preferably less than about 0.3eV. 14. The component according to claim 1, characterized in that the at least one further organic material (B) is from one of the following material classes: Fullerenes or carbon nanotubes, in particular C ₆₀ , C ₇₀ or C ₈₄ and their derivatives; - Metal-organic compounds, in particular those whose lowest excited state at least partially an excitation of an electron from the metal to the ligand (MLCT - "metal-to-ligand charge transfer") or ligand to metal (LMCT - "Hgand-to-metal charge transfer "); and - phosphorescent materials having a phosphorescence quantum yield of greater than about 0.1%, preferably greater than about 1% in dilute solution. 15. Component according to claim 14, characterized in that the organometallic compound comprises a heavy metal having an atomic number greater than 21, preferably greater than 39. 16. The component according to claim 15, characterized gekennt ei chn et, that the organometallic compound comprises a metal from the following group of metals: Ru, Pd, Ag, Cd, In, Sn, Ta, W ₃ Re, Os, Ir, Pt, Au, Hg, Ti, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Er, Tm, Yb or Lu, preferably Ru, Rh, Re, Os, Ir or Pt. 17. Component according to claim 1, characterized in that the organic material (A) in the excitonic layer (EHL) collecting layer is an oligothiophene derivative, a perylene derivative, in particular a derivative of perylenetetracarboxylic dianhydride , Perylenetetracarboxylic diimide or perylenetetracarboxylic bisimidazole, or a phthalocyanine. 18. Component according to claim 1, characterized in that the exciton-separating layer (ESL) is formed as a light-absorbing and singlet and / or triplet excited state generating layer, wherein generated singlet and / or triplet Excitation states can diffuse to the interface between the exciton-collecting layer (EHL) and the exciton-separating layer (ESL) and can be converted there into charge-carrier pairs. 19. Component according to claim 1, characterized in that the exciton-separating layer (ESL) is a mixed layer comprising a plurality of organic materials, in which: a lowest singlet excitation state for excitons of one of the plurality of organic materials is higher in energy than a lowest singlet excitation state for excitons of another of the plurality of organic materials; - The further organic material is formed so that it with a quantum yield of at least 20%, preferably at least 50% by means of an ISC mechanism (ISC, Younger System Crossing) Converting singlet excitons into triplet excitons; a lowest triplet excitation state for excitons of the further organic material is higher in energy than a lowest triplet excited state for excitons of an organic material. 20. The component according to claim 19, characterized e e e e e e chn et chn et, that in the running as a mixed layer excitons separating layer (ESL) by means of an organic Material and the at least one further organic material, a photoactive volume donor-acceptor heterojunction is formed. 21. The component according to claim 1, characterized in that an interface of the exciton-collecting layer (EHL) which faces away from the interface with the exciton-separating layer (ESL) / the triplet transport layer (TTL) , is a triplet block layer (TBL), in which energetically low-energy triplet excitation states are energetically higher than low-energy triplet excitation states in the exciton-collecting layer (EHL). 22. The component according to at least one of the preceding claims, characterized in that the contact and / or the mating contact are semitransparent or transparent. 23. The component according to claim 1, characterized in that a p-doped layer is arranged between the contact and the photoactive region (M-i-p component). 24. The component according to claim 1, wherein an n-doped layer is arranged between the mating contact and the photoactive region (M-i-n device or n-i-p device). 25. The component according to claim 1, wherein one or more layers in the organic region are thermally evaporated in a high vacuum or organic materials are vaporized into an inert carrier gas which transports the organic materials to a substrate (Organic Vapor Phase deposition ") are deposited. 26. The component according to at least one of the preceding claims, characterized in that one or more layers are deposited in the organic region of a liquid solution, in particular by spin coating, knife coating or printing. 27. The component according to at least one of the preceding claims, characterized in that the excitons collecting layer (EHL) has a thickness between about 5nm and about 200nm. 28. Component according to at least one of the preceding claims, characterized in that the excitons collecting layer (EHL), the exciton separating layer (ESL) and / or the triplet transport layer (TTL) from a donor-acceptor donor Oligomer or an acceptor donor acceptor oligomer. 29. Arrangement with at least two components according to at least one of the preceding claims, characterized in that the at least two components are stacked on each other.