JP5310230B2 - Organic photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic photoelectric conversion element having high photoelectric conversion efficiency. <P>SOLUTION: In the organic thin-film photoelectric conversion element, including a positive electrode having at least a transparent conductive layer, a photoelectric conversion layer, and a negative electrode on a transparent substrate, the photoelectric conversion layer contains a fluorinated acrylic compound. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an organic photoelectric conversion element, and particularly relates to an organic photoelectric conversion element having excellent photoelectric conversion efficiency.

  Organic thin-film solar cells composed of organic photoelectric conversion elements are attracting attention as solar cells suitable for mass production because they can be formed by a coating method, and are actively studied in many research institutions. Organic thin-film solar cells have improved charge separation efficiency, which has been a problem, by a so-called bulk heterojunction structure in which an electron donor material and an electron acceptor material are mixed (see, for example, Patent Document 1).

  In recent years, the photoelectric conversion efficiency has improved to the 5-6% range, and it can be said that this is a field in which research for practical use has become more active. However, in organic photoelectric conversion elements for practical use in the future, development of organic photoelectric conversion elements that generate power with higher efficiency is desired.

  As described above, although the charge separation efficiency is improved by using the bulk heterojunction structure, it is actually necessary to reduce the film thickness because the charge mobility of organic materials is small. is there. When the film thickness of the photoelectric conversion layer is reduced, the distance between the electrodes is shortened, so that leakage due to a short circuit is likely to occur, and reverse charge transport is likely to occur.

  So far, in the layer design of organic photoelectric conversion elements, it is easy to selectively pass electrons between the second electrode, which is generally a cathode made of metal, and the active layer, which is to be a photoelectric conversion layer. It is known that the photoelectric conversion efficiency is improved by introducing the hole block layer (see, for example, Patent Documents 2 and 3), but the hole block has an improvement effect, but the photoelectric conversion efficiency is still not improved. It was not enough.

  In addition, a fullerene derivative in which a substituent having a low surface energy is fluorinated is mixed and applied to a photoelectric conversion layer for forming a bulk heterojunction structure (see, for example, Non-Patent Document 1), whereby photoelectric conversion with a cathode is performed. Although a proposal has been made to form a passivation layer at the interface between the layers and suppress charge recombination at the interface between the electrode and the organic semiconductor, it has not been sufficient.

  On the other hand, proposals to improve the light ingress and output of organic electronic devices by providing a low refractive index organic buffer layer using a fluorinated compound between a transparent electrode and a photoelectric conversion layer containing an organic semiconductor (for example, However, this is different from the effect and configuration of the present invention.

  In the present invention, an effective passivation layer for preventing charge recombination can be formed at the interface between the cathode and the photoelectric conversion layer, and the photoelectric conversion efficiency can be improved.

US Pat. No. 5,331,183 JP 2004-319705 A JP 2007-273939 A Special table 2007-536718 gazette

Adv. Mater. , 2008, 20, 1-6

  An object of the present invention is to provide an organic photoelectric conversion element having high photoelectric conversion efficiency.

  The above object of the present invention can be achieved by the following configuration.

1. In a bulk heterojunction type organic thin film photoelectric conversion element having at least a transparent conductive layer on a transparent substrate, a photoelectric conversion layer, and a cathode, the photoelectric conversion layer contains a fluorine-containing acrylic compound ,
The ratio of fluorine atom to carbon atom in the molecule of the fluorine-containing acrylic compound (F / C) is 0.15 to 1.0,
The organic photoelectric conversion element, wherein the photoelectric conversion layer is formed by a coating method .

  By this invention, the organic photoelectric conversion element which has high photoelectric conversion efficiency was able to be provided.

It is sectional drawing of the bulk hetero junction type organic photoelectric conversion element of this invention. 1 is a cross-sectional view of a bulk heterojunction type organic photoelectric conversion element having a three-layered photoelectric conversion layer according to the present invention.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of earnest studies on the problem of improving the efficiency of the organic photoelectric conversion element, the present inventor obtained photoelectric conversion in an organic photoelectric conversion element having at least a transparent conductive layer on a transparent substrate, a photoelectric conversion layer, and a cathode. It has been found that an organic photoelectric conversion element having high photoelectric conversion efficiency can be produced by an organic photoelectric conversion element characterized by containing a fluorine-containing acrylic compound in the layer, and the present invention has been achieved.

  The present inventors presume the reason why the object effect of the present invention is obtained by adopting the configuration defined in the present invention as follows.

  In the organic photoelectric conversion element of the present invention, when a photoelectric conversion layer made of a p-type semiconductor material or an n-type semiconductor material is provided on an anode such as ITO (Indium Tin Oxide) as a transparent electrode, By adding the fluorine-containing acrylic compound of the present invention to the coating solution for forming the conversion layer, the fluorine-containing acrylic compound is locally oriented at the interface of the photoelectric conversion layer in the process in which the coating solution is formed by the coating process. By doing so, a so-called passivation layer formed of a fluorine-containing acrylic compound is formed between the photoelectric conversion layer and the cathode, and charge recombination between the photoelectric conversion layer and the electrode is suppressed, and the photoelectric conversion efficiency is improved. It is considered a thing.

(Organic photoelectric conversion element)
FIG. 1 is a cross-sectional view showing a bulk heterojunction organic photoelectric conversion element. In FIG. 1, a bulk heterojunction organic photoelectric conversion element 10 has an anode 12, a hole transport layer 15, a photoelectric conversion layer 14, an electron transport layer 16, and a cathode 13 sequentially stacked on one surface of a substrate 11. .

  The substrate 11 is a member that holds the anode 12, the photoelectric conversion layer 14, and the cathode 13 that are sequentially stacked. In the present embodiment, since light photoelectrically converted enters from the substrate 11 side, the substrate 11 can transmit the light subjected to photoelectric conversion, that is, transparent to the wavelength of the light to be photoelectrically converted. It is an important member. As the substrate 11, for example, a glass substrate or a resin substrate is used. The substrate 11 is not essential. For example, the bulk heterojunction type organic photoelectric conversion element 10 may be configured by forming the anode 12 and the cathode 13 on both surfaces of the photoelectric conversion layer 14.

  The photoelectric conversion layer 14 is a layer that converts light energy into electric energy, and includes a photoelectric conversion layer in which a p-type semiconductor material and an n-type semiconductor material are uniformly mixed. The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.

  In FIG. 1, light incident from the anode 12 through the substrate 11 is absorbed by the electron acceptor or electron donor in the photoelectric conversion layer 14, electrons move from the electron donor to the electron acceptor, and holes and An electron pair (charge separation state) is formed. Due to the internal electric field, for example, when the work functions of the anode 12 and the cathode 13 are different, due to the potential difference between the anode 12 and the cathode 13, electrons pass between the electron acceptors and holes pass between the electron donors. Each is carried to a different electrode and the photocurrent is detected. For example, when the work function of the anode 12 is larger than that of the cathode 13, electrons are transported to the anode 12 and holes are transported to the cathode 13. If the magnitude of the work function is reversed, electrons and holes are transported in the opposite direction. In addition, the transport direction of electrons and holes can be controlled by applying a potential between the anode 12 and the cathode 13.

  Although not shown in FIG. 1, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.

  As a more preferable configuration, the photoelectric conversion layer 14 has a so-called p-i-n three-layer configuration (FIG. 2). A normal photoelectric conversion layer is a single i layer in which a p-type semiconductor material and an n-type semiconductor layer are mixed. By sandwiching a p-layer composed of a single p-type semiconductor material and an n-layer composed of a single n-type semiconductor material, The rectifying property of holes and electrons is further increased, loss due to recombination of holes and electrons separated by charge is reduced, and higher photoelectric conversion efficiency can be obtained.

(Fluorine-containing acrylic compound)
The fluorine-containing acrylic compound according to the present invention is an oligomer or polymer having a fluorine-containing acrylic ester or a fluorine-containing methacrylic ester as a monomer. These oligomers and polymers may be homopolymerized or copolymerized.

  As a monomer of fluorine-containing acrylic acid ester or fluorine-containing methacrylic acid ester, 1H, 1H, 3H-tetrafluoropropyl (meth) acrylate, 1H, 1H, 5H-octafluoropentyl (meth) acrylate, 1H, 1H , 7H-dodecafluoroheptyl (meth) acrylate, 1H, 1H, 9H-hexadecafluorononyl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3- Pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ethyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) acrylate, 2-par Fluorodecylethyl (meth) acrylate, -Perfluorobutyl-2-hydroxypropyl (meth) acrylate, 3-perfluorohexyl-2-hydroxypropyl (meth) acrylate, 3-perfluorooctyl-2-hydroxypropyl (meth) acrylate, 2- (perfluoro- 3-methylbutyl) ethyl (meth) acrylate, 2- (perfluoro-5-methylhexyl) ethyl (meth) acrylate, 2- (perfluoro-7-methyloctyl) ethyl (meth) acrylate, 3- (perfluoro- 3-methylbutyl-2-hydroxypropyl (meth) acrylate, 3- (perfluoro-5-methylhexyl) -2-hydroxypropyl (meth) acrylate, 3- (perfluoro-7-methyloctyl) -2-hydroxypropyl (Meth) acrylate, 1 -1- (trifluoromethyl) trifluoroethyl (meth) acrylate, 1H, 1H, 3H-hexafluorobutyl (meth) acrylate, trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, perfluorooctylethyl acrylate, 2- (per Fluorobutyl) ethyl-α-fluoroacrylate.

  The fluorine-containing acrylic compound according to the present invention may be a copolymer of a fluorine-containing monomer such as a fluorine-containing acrylic ester and a monomer not containing fluorine.

  Further, the copolymerizable vinyl monomer may be any monomer having a vinyl group, and specifically, alkyl methacrylates such as methyl methacrylate and butyl methacrylate, methyl acrylate, and ethyl acrylate. Examples thereof include alkyl acrylates and styrenes such as styrene and α-methylstyrene, and these can be used alone or in combination.

  The fluorine-containing acrylic compound according to the present invention may be used by adding to a coating solution for forming a photoelectric conversion layer, or a coating solution containing the compound of the present invention may be coated on the photoelectric conversion layer. When adding to the coating liquid which forms a photoelectric converting layer, it is preferable to use the addition amount in the range of 0.01-2.0 mg / ml.

  The fluorine-containing acrylic compound preferably has a fluorine atom to carbon atom ratio (F / C) of 0.15 to 1.0 in order to obtain the effects of the present invention. When F / C is 1.0 or more, after applying the coating liquid containing the fluorine-containing acrylic compound according to the present invention, when a functional layer is formed on the upper layer, the photoelectric conversion element without coating failure such as repellency Can be formed.

(P-type semiconductor material)
Examples of the p-type semiconductor material used in the photoelectric conversion layer according to the present invention include various condensed polycyclic aromatic low-molecular compounds and conjugated polymers / oligomers.

  Examples of the condensed polycyclic aromatic low molecular weight compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, thacumanthracene, bisanthene, zeslene. , Heptazethrene, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, etc., porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene ( BEDTTTTF) -perchloric acid complexes, and derivatives and precursors thereof.

  Examples of the derivative having the above condensed polycycle include International Publication No. 03/16599, International Publication No. 03/28125, US Pat. No. 6,690,029, Japanese Patent Application Laid-Open No. 2004-107216. A pentacene derivative having a substituent described in JP-A No. 2003-136964, a pentacene precursor described in US Patent Application Publication No. 2003/136964, and the like; Amer. Chem. Soc. , Vol. 127. No. 14.4986, J. MoI. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. 9, acene-based compounds substituted with a trialkylsilylethynyl group described in 2706 and the like.

  As the conjugated polymer, for example, a polythiophene such as poly-3-hexylthiophene (P3HT) and an oligomer thereof, or a technical group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Polythiophene, Nature Material, (2006) vol. 5, p328, polythiophene-thienothiophene copolymer, polythiophene-diketopyrrolopyrrole copolymer described in WO08 / 664, Adv. Mater. , 2007, p4160, a polythiophene-thiazolothiazole copolymer, Nature Mat. , Vol. 6 (2007), p497 described in PCPDTBT, etc., polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, Examples thereof include polymer materials such as σ-conjugated polymers such as polysilane and polygermane.

  In addition, oligomer materials instead of polymer materials include thiophene hexamer α-seccithiophene, α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis ( 3-Butoxypropyl) -α-sexithiophene and the like can be suitably used.

  Among these compounds, compounds that are highly soluble in an organic solvent to the extent that a solution process can be performed, can form a crystalline thin film after drying, and can achieve high mobility are preferable.

  In addition, when the electron transport layer is formed on the photoelectric conversion layer by coating, there is a problem that the electron transport layer solution dissolves the photoelectric conversion layer, so a material that can be insolubilized after being applied by a solution process is used. Also good.

  Examples of such materials include materials that can be insolubilized by polymerizing the coating film after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Or a soluble substituent reacts and insolubilizes by applying energy such as heat as described in U.S. Patent Application Publication No. 2003/136964 and JP-A-2008-16834 (pigment). Material).

(N-type semiconductor material)
The n-type semiconductor material used for the photoelectric conversion layer according to the present invention is not particularly limited. For example, fullerene, octaazaporphyrin, and the like, p-type semiconductor perfluoro products (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalene, and the like. Examples thereof include aromatic carboxylic acid anhydrides such as tetracarboxylic acid anhydride, naphthalene tetracarboxylic acid diimide, perylene tetracarboxylic acid anhydride, and perylene tetracarboxylic acid diimide, and polymer compounds containing the imidized product thereof as a skeleton.

  However, fullerene derivatives that can perform charge separation efficiently with various p-type semiconductor materials at high speed (˜50 fs) are preferable. Fullerene derivatives include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), etc. Partially by hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group, silyl group, etc. Examples thereof include substituted fullerene derivatives.

  Among them, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6,6] -phenyl C61- Butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n-hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, US Pat. No. 7,329,709, etc. It is preferable to use a fullerene derivative having a substituent and having improved solubility, such as fullerene having a cyclic ether group such as a calligraphy.

(Functional layer)
The organic photoelectric conversion element of the present invention has a hole transport layer between the photoelectric conversion layer and the anode, and it is possible to take out charges generated in the photoelectric conversion layer more efficiently. It is preferable.

  Examples of the material constituting these layers include, as the hole transport layer, PEDOT such as StarkVutec, trade name BaytronP, polyaniline and its doped material, cyan described in WO06 / 19270, etc. A compound or the like can be used.

  Note that the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the photoelectric conversion layer has a rectifying effect that prevents electrons generated in the photoelectric conversion layer from flowing to the anode side. It has an electronic block function. Such a hole transport layer is also called an electron block layer, and it is preferable to use a hole transport layer having such a function.

  As such a material, a triarylamine compound described in JP-A-5-271166 or a metal oxide such as molybdenum oxide, nickel oxide, or tungsten oxide can be used.

  Moreover, the layer which consists of a p-type semiconductor material single-piece | unit used for the photoelectric converting layer can also be used. The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method. Forming a coating film in the lower layer before forming the photoelectric conversion layer is preferable because it has the effect of leveling the coating surface and reduces the influence of leakage and the like.

  In the organic photoelectric conversion element of the present invention, by forming an electron transport layer between the photoelectric conversion layer and the cathode, it becomes possible to more efficiently take out the charges generated in the photoelectric conversion layer. It is preferable to have a layer.

  In addition, as the electron transport layer, octaazaporphyrin, a p-type semiconductor perfluoro product (perfluoropentacene, perfluorophthalocyanine, etc.) can be used. Similarly, the p-type semiconductor material used for the photoelectric conversion layer The electron transport layer having a HOMO level deeper than the HOMO level is provided with a hole blocking function having a rectifying effect so that holes generated in the photoelectric conversion layer do not flow to the cathode side.

  Such an electron transport layer is also called a hole blocking layer, and it is preferable to use an electron transport layer having such a function. Examples of such materials include phenanthrene compounds such as bathocuproine, n-type semiconductor materials such as naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, and titanium oxide. N-type inorganic oxides such as zinc oxide and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride can be used.

  Moreover, the layer which consists of a n-type semiconductor material single-piece | unit used for the photoelectric converting layer can also be used. The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method.

  For the purpose of improving energy conversion efficiency and device life, it is possible to have various intermediate layers in the device. Examples of the intermediate layer include a hole block layer, an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer.

(Transparent electrode (anode))
The transparent electrode according to the present invention is not particularly limited to the cathode and the anode, and can be selected depending on the element configuration, but preferably the transparent electrode is used as the anode. For example, when used as an anode, it is preferably an electrode that transmits light of 380 to 800 nm. As the material, for example, transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ and ZnO, metal thin films such as gold, silver and platinum, metal nanowires and carbon nanotubes can be used.

  Also selected from the group consisting of derivatives of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene and polynaphthalene. Conductive polymers can also be used. A plurality of these conductive compounds can be combined to form a transparent electrode.

(Counter electrode (cathode))
The counter electrode may be a single layer of a conductive material, but in addition to a conductive material, a resin that holds these may be used in combination. As the conductive material of the counter electrode, a material having a small work function (4 eV or less) metal, alloy, electrically conductive compound and a mixture thereof is used.

Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like.

Among these, from the viewpoint of electron extraction performance and durability against oxidation, etc., a mixture of these metals and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, magnesium / Aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.

  The counter electrode can be produced by forming a thin film from these electrode materials by a method such as vapor deposition or sputtering. The film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

  If a metal material is used as the conductive material of the counter electrode, the light that has come to the counter electrode side is reflected and reflected to the anode side, and this light can be reused and absorbed again by the photoelectric conversion layer, resulting in higher photoelectric conversion efficiency. Improved and preferable.

  The counter electrode may be a metal (eg, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon nanoparticle, nanowire, or nanostructure. A dispersion is preferable because a transparent and highly conductive counter electrode can be formed by a coating method.

  Moreover, when making the counter electrode side light-transmitting, for example, after forming a conductive material suitable for the counter electrode such as aluminum and aluminum alloy, silver and silver compound in a thin film thickness of about 1 to 20 nm, By providing a film of the conductive light transmissive material mentioned in the description of the transparent electrode, a light transmissive counter electrode can be obtained.

(substrate)
When light that is photoelectrically converted enters from the substrate side, the substrate is preferably a member that can transmit the light that is photoelectrically converted, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted.

  As the substrate, for example, a glass substrate, a resin substrate and the like are preferably mentioned, but it is desirable to use a transparent resin film from the viewpoint of light weight and flexibility. There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things.

  For example, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, polyolefin resins such as cyclic olefin resin Film, vinyl resin film such as polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, A polyamide resin film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more at ~800nm), can be preferably applied to a transparent resin film according to the present invention.

  Among them, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film. More preferred are a stretched polyethylene terephthalate film and a biaxially stretched polyethylene naphthalate film.

  The transparent substrate used in the present invention can be subjected to a surface treatment or an easy adhesion layer in order to ensure the wettability and adhesiveness of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

  Further, for the purpose of suppressing the permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate, or a hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred. Good.

(Film formation)
Examples of methods for forming a photoelectric conversion layer, a transport layer, and an electrode in which an electron acceptor and an electron donor are mixed include a vapor deposition method, a coating method (including a casting method and a spin coating method), and the like. Among these, as a formation method of a photoelectric converting layer, a vapor deposition method, the apply | coating method (a casting method, a spin coat method is included), etc. can be illustrated. Among these, the coating method is preferable in order to increase the area of the interface where charges and electrons are separated from each other as described above and to produce a device having high photoelectric conversion efficiency. Also, the coating method is excellent in production speed.

  Although there is no restriction | limiting in the coating method used in this case, For example, a spin coat method, the cast method from a solution, a dip coat method, a blade coat method, a wire bar coat method, a gravure coat method, a spray coat method etc. are mentioned. Furthermore, patterning can also be performed by a printing method such as an inkjet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, a flexographic printing method, or the like.

  After coating, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and improvement of mobility and absorption longwave due to crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, a part of the particles is microscopically aggregated or crystallized and the photoelectric conversion layer can have an appropriate phase separation structure. As a result, the carrier mobility of the photoelectric conversion layer is improved and high efficiency can be obtained.

  The photoelectric conversion layer may be composed of a single layer in which an electron acceptor and an electron donor are uniformly mixed, or may be composed of a plurality of layers in which the mixing ratio of the electron acceptor and the electron donor is changed. Good. In this case, it can be formed by using a material that can be insolubilized after coating as described above.

(Patterning)
There is no restriction | limiting in particular in the method and process of patterning the electrode concerning this invention, a photoelectric converting layer, a positive hole transport layer, an electron carrying layer, etc., A well-known method can be applied suitably.

  If it is a soluble material such as a photoelectric conversion layer and a transport layer, only unnecessary portions may be wiped after the entire surface of die coating, dip coating, etc., or patterning is directly performed at the time of coating using a method such as an ink jet method or screen printing. May be.

  In the case of an insoluble material such as an electrode material, the electrode can be patterned by a known method such as mask evaporation at the time of vacuum deposition or etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Organic photoelectric conversion element STC-1 >>
ITO was vapor-deposited with an average film thickness of 150 nm on a PEN film having a barrier layer (total light transmittance of 90%) to produce an anode TC-1.

  On the anode TC-1, a conductive polymer PEDOT / PSS (poly (3,4-ethylenedithiophene) -poly (stylensulfonate)) (Baytron P4083, manufactured by HC Starck) has a dry film thickness of 30 nm. After spin coating as described above, it was dried by heating at 140 ° C. in the air for 10 minutes.

  After this, the substrate was brought into the glove box and worked under a nitrogen atmosphere. First, the substrate was heat-treated at 140 ° C. for 3 minutes in a nitrogen atmosphere.

Next, P3HT (manufactured by Plextronics: regioregular poly-3-hexylthiophene) (Mw = 52000, high-molecular p-type semiconductor material) and PCBM (Mw = 911, low-molecular n-type semiconductor) are used as the coating liquid for the photoelectric conversion layer. material) (Frontier carbon: 6,6-phenyl _{-C 61} - butyric acid methyl ester) and to be 3.0 wt% 1: mixed solution was prepared in 1, thickness 150nm while filtered through a filter Then, coating was performed using a spin coater, and the film was allowed to stand at room temperature to form a photoelectric conversion layer.

  On the photoelectric conversion layer, a solution in which Ti-isopropoxide is dissolved in ethanol so as to have a concentration of 0.05 mol / L is prepared, masked, and then applied so as to have a film thickness of 20 nm. The electron transport layer was formed by leaving it in controlled nitrogen.

Next, the anode on which the series of photoelectric conversion layers and the electron transport layer were formed was placed in a vacuum deposition apparatus. After depressurizing the inside of the vacuum deposition apparatus to 10 ⁻³ Pa or less, Al was deposited by 80 nm to obtain an organic photoelectric conversion element STC-1 having a size of 2 mm square.

  The obtained organic photoelectric conversion element STC-1 is a flexible sealing made of polyethylene terephthalate as a base material, except for the end portion, so that an external extraction terminal of the anode and the cathode can be formed, with an adhesive applied around the cathode. After pasting the members, the adhesive was cured by heat treatment.

<< Organic photoelectric conversion element STC-2 >>
In the organic photoelectric conversion element STC-1, 3.0% by mass of P3HT (manufactured by Plextronics: regioregular poly-3-hexylthiophene) (Mw = 52000, polymer p-type semiconductor material) as a coating solution for the photoelectric conversion layer. , PCBM (Mw = 911, low molecular n-type semiconductor material) (Frontier carbon: 6,6-phenyl _{-C 61} - butyric acid methyl ester) and 3.0 wt%, F-Ac1 (poly (perfluorooctyl) Organic photoelectric conversion element STC-2 was produced in the same manner except that a liquid prepared by mixing ethyl acrylate and weight average molecular weight Mw: about 5000) at 0.5 mg / ml was prepared and used.

<< Organic photoelectric conversion element STC-3-6 >>
Organic photoelectric conversion elements STC-3 to 6 were produced in the same manner except that the organic photoelectric conversion element STC-2 was changed to a fluorine-containing compound as shown in Table 1 instead of F-Ac1. The fluorine-containing acrylic compounds in Table 1 are as follows. Each weight average molecular weight Mw is about 5000.

F-Ac2: poly (perfluorobutyl) ethyl methacrylate F-Ac3: (perfluorooctyl) ethyl acrylate / methyl methacrylate copolymer (copolymer ratio 30:70)
F-Ac4: (perfluorobutyl) ethyl methacrylate / methyl methacrylate copolymer (copolymer ratio 15:85)
F-Ac5: (perfluorobutyl) ethyl methacrylate / methyl methacrylate copolymer (copolymer ratio 5:95).

[Evaluation of organic photoelectric conversion elements]
<< Photoelectric conversion efficiency >>
An organic photoelectric conversion element sealed with a glass sealing cap and a UV curable resin is irradiated with light from a solar simulator (AM1.5G) at an intensity of 100 mW / cm ² to obtain voltage-current characteristics. The photoelectric conversion efficiency was determined by measurement. That is, for each organic photoelectric conversion element, current-voltage characteristics were measured at room temperature using an IV tester, and short circuit current density (Jsc), open circuit voltage (Voc), and form factor (FF) were measured. The photoelectric conversion efficiency (η (%)) was determined from these. In addition, the photoelectric conversion efficiency ((eta) (%)) of the solar cell was computed based on the following formula (A).

η = 100 × (Voc × Jsc × FF) / P (A)
Here, P is the incident light intensity [mW / cm ² ], Voc is the open circuit voltage [V], Jsc is the short-circuit current density [mA · cm ⁻² ], F.R. F. Indicates a form factor.

  From Table 1, it can be seen that the organic photoelectric conversion element of the present invention has improved short-circuit current density and shape factor, and has high photoelectric conversion efficiency.

DESCRIPTION OF SYMBOLS 10 Bulk heterojunction type organic photoelectric conversion element 11 Substrate 12 Anode 13 Cathode 14 Photoelectric conversion layer 14p p layer 14i i layer 14n n layer 15 Hole transport layer 16 Electron transport layer

Claims (1)

In a bulk heterojunction type organic thin film photoelectric conversion element having at least a transparent conductive layer on a transparent substrate, a photoelectric conversion layer, and a cathode, the photoelectric conversion layer contains a fluorine-containing acrylic compound ,
The ratio of fluorine atom to carbon atom in the molecule of the fluorine-containing acrylic compound (F / C) is 0.15 to 1.0,
The organic photoelectric conversion element, wherein the photoelectric conversion layer is formed by a coating method .

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