JP2006244753A - Photoelectric conversion material, semiconductor electrode, and photoelectric conversion device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion device which is excellent in a property of photoelectric conversion by using a specific compound. <P>SOLUTION: A colorant represented by Formula [1] is used as a photoelectric conversion material. In the formula: R<SB>1</SB>represents an alkyl group, an aralkyl group, an alkenyl group, an alkoxy group, an aryl group or a heterocycle; R<SB>2</SB>and R<SB>3</SB>of an alkylene residue group formed with 5 to 6 rings by linking of R<SB>2</SB>and R<SB>3</SB>; R<SB>4</SB>is an H (hydrogen atom), an alkyl group, an alkoxy group, an aryl group, a heterocycle or a halogen atom; R<SB>5</SB>and R<SB>6</SB>are an H (hydrogen atom), an alkyl group, an aryl group, a halogen atom or a cyano group; R<SB>7</SB>is an H (hydrogen atom), an alkyl group or an aryl group; X is an SO<SB>2</SB>and SO; R<SB>8</SB>is an alkyl group, a fluoroalkyl group, an aralkyl group or an aryl group; and l is 0 or 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion element.

Global warming due to the increase in CO ₂ concentration caused by the use of a large amount of fossil fuel, and the increase in energy demand accompanying population increase are recognized as problems related to the existence of human beings. For this reason, in recent years, the use of sunlight that is infinite and does not generate harmful substances has been energetically studied. What is currently put into practical use as sunlight, which is a clean energy source, includes residential single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide.

  However, these inorganic solar cells also have drawbacks. For example, a silicon system is required to have a very high purity. Naturally, the purification process is complicated, the number of processes is large, and the manufacturing cost is high. In addition, there is a demand for weight reduction and the like, and in particular, it is disadvantageous in that payback to the user is long, and there is a problem in the spread.

  On the other hand, many solar cells using organic materials have been proposed. As an organic solar cell, a Schottky photoelectric conversion element that joins a p-type organic semiconductor and a metal having a low work function, a p-type organic semiconductor and an n-type inorganic semiconductor, or a p-type organic semiconductor and an electron-accepting organic compound are joined. There are heterojunction photoelectric conversion elements and the like, and organic semiconductors used are synthetic dyes and pigments such as chlorophyll and perylene, conductive polymer materials such as polyacetylene, or composite materials thereof. These are thinned by a vacuum deposition method, a casting method, a dipping method, or the like to form a battery material. Although organic materials have advantages such as low cost and easy area enlargement, there are many problems that the conversion efficiency is as low as 1% or less and the durability is poor.

  Under such circumstances, a solar cell exhibiting good characteristics has been reported by Dr. Gretzell of Switzerland (see Non-Patent Document 1). This document also discloses materials and manufacturing techniques necessary for battery fabrication. The proposed battery is called a dye-sensitized solar cell or a Gretzel solar cell, and is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. The advantage of this method is that an inexpensive oxide semiconductor such as titanium oxide does not need to be purified to a high purity, and is therefore inexpensive. Furthermore, since a sensitizing dye having a wide absorption in the visible light region can be used, sunlight in the visible region can be effectively converted into electricity.

On the other hand, ruthenium complexes with limited resources are used, so when this solar cell is put to practical use, the supply of ruthenium complexes is in danger. Moreover, since this ruthenium complex is expensive, this problem can be solved if it can be changed to an inexpensive organic dye. Merocyanine dyes, cyanine dyes, and 9-phenylxanthene dyes have been reported as dyes for this battery (see, for example, Patent Documents 1 to 3). However, these dyes have low adsorption to titanium oxide and have not yet achieved a high sensitizing effect, and also have problems with stability over time.
JP 11-238905 A JP 2001-76773 A Japanese Patent Laid-Open No. 10-92477 Nature, 353, 737 (1991)

  An object of the present invention is to provide a high-performance photoelectric conversion element.

  As a result of intensive studies to achieve the above object, the present inventors were able to achieve the goal by using at least one dye represented by the general formula [I] as a photoelectric conversion material.

In the general formula [I], R ₁ represents an alkyl group, an aralkyl group, an alkenyl group, an alkoxy group, an aryl group, or a heterocyclic ring, which may further have a substituent. R ₂ and R ₃ are alkylene residues which are linked together to form a 5-membered or 6-membered ring, and R ₄ is a substituent on the aromatic ring, which is a hydrogen atom, alkyl group, alkoxy group, aryl A group, a heterocycle, or a halogen atom, which may further have a substituent; R ₅ and R _{6 each} represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, or a cyano group. R ₇ represents a hydrogen atom, an alkyl group, or an aryl group. X represents a functional group represented by the following general formula [II] or general formula [III]. R ₈ represents an alkyl group, a fluoroalkyl group, an aralkyl group, or an aryl group, which may further have a substituent. l represents 0 or 1;

  By using the compound of the general formula [I] used in the present invention, a photoelectric conversion element exhibiting excellent conversion efficiency can be obtained.

Specific examples of R ₁ include alkyl groups such as a methyl group, ethyl group, and isopropyl group, aralkyl groups such as a benzyl group and 1-naphthylmethyl group, and alkenyl groups such as a vinyl group, a diphenylvinyl group, and a cyclohexenyl group. And aryl groups such as phenyl group and 1-naphthyl group, and heterocycles such as furyl group, thienyl group and indolyl group. R ₁ may further have a substituent. Specific examples of the substituent include an alkoxy group such as an alkyl group, a methoxy group, an ethoxy group, and an n-hexyloxy group, a methylthio group, n- Alkylthio groups such as hexylthio group, aryloxy groups such as phenoxy group, 1-naphthyloxy group, arylthio groups such as phenylthio group, halogen atoms such as chlorine and bromine, disubstituted amino groups such as dimethylamino group and diphenylamino group, Aryl groups, heterocycles, carboxyl groups such as carboxyl groups and carboxymethyl groups, sulfonylalkyl groups such as sulfonylpropyl groups, acidic groups such as phosphate groups and hydroxamic acid groups, cyano groups, nitro groups, trifluoromethyl groups, etc. The electron withdrawing group can be mentioned. The acidic group may be in the form of a quaternary ammonium salt, a metal salt, or an ester or amide.

R ₂ and R ₃ represent an alkylene residue which is linked together to form a 5-membered or 6-membered ring.

Specific examples of R ₄ include a hydrogen atom, an alkyl group such as a methyl group, an ethyl group and a cyclohexyl group, an alkoxy group such as a methoxy group and an ethoxy group, an aryl group such as a phenyl group, a biphenyl group and a 1-naphthyl group, Heterocycles such as a furyl group, a thienyl group, an indolyl group, or a halogen atom, which may further have a substituent. Specific examples of the substituent include an alkylthio group, an aryloxy group, an arylthio group, a halogen atom, a disubstituted amino group, an aryl group, and a heterocyclic ring.

R ₅ and R _{6 each} represents a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, or a cyclohexyl group, an aryl group such as a phenyl group, a biphenyl group, or a 1-naphthyl group, a halogen atom, or a cyano group.

Specific examples of R ₇ include a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, and an isopropyl group, and an aryl group such as a phenyl group and a 1-naphthyl group.

Specific examples of R ₈ include alkyl groups such as methyl group, ethyl group, and cyclohexyl group, fluoroalkyl groups such as trifluoromethyl group and pentafluoroethyl group, aralkyl groups such as benzyl group and phenethyl group, or phenyl group, Examples include aryl groups such as a biphenyl group and a 1-naphthyl group. Further, as substituents of these functional groups, alkyl groups such as methyl group, ethyl group, cyclohexyl group, alkoxy groups such as methoxy group, ethoxy group, n-hexyloxy group, methylthio group, n-hexylthio group, etc. Of arylthio groups such as alkylthio groups, phenoxy groups and 1-naphthyloxy groups, arylthio groups such as phenylthio groups, halogen atoms such as chlorine and bromine, and electron-withdrawing properties such as cyano groups, nitro groups and trifluoromethyl groups The group can be mentioned.

  Next, specific examples of the compound of the general formula [I] according to the present invention will be given, but the present invention is not limited thereto.

  The photoelectric conversion element of the present invention includes a semiconductor electrode, a charge transfer layer, and a counter electrode. In addition, the semiconductor electrode is composed of a conductive support and a semiconductor layer sensitized by a pigment placed thereon. The semiconductor layer may be a single layer structure or a stacked structure, and is designed according to the purpose. In addition, at the boundary of this element such as the boundary between the conductive layer and the semiconductor layer of the conductive support, the boundary between the semiconductor layer and the moving layer, the constituent components of each layer may be diffused or mixed with each other.

  As the conductive support, there can be used a support made of glass or plastic having a conductive layer containing a conductive agent on its surface, such as a metal having a conductive property in itself. In the latter case, the conductive agent is a metal oxide such as platinum, gold, silver, copper, aluminum or the like, carbon or indium-tin composite oxide (hereinafter abbreviated as “ITO”), fluorine-doped tin oxide or the like. (Hereinafter abbreviated as “FTO”) and the like. The conductive support preferably has a transparency that transmits light of 10% or more, and more preferably transmits 50% or more. Among these, conductive glass in which a conductive layer made of ITO or FTO is deposited on glass is particularly preferable.

  For the purpose of reducing the resistance of the transparent conductive support, a metal lead wire may be used. Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. The metal lead wire is placed on the transparent conductive material by vapor deposition, sputtering, pressure bonding, or the like, and a method of providing ITO or FTO thereon, or a metal lead wire is placed on the transparent conductive layer.

  As the semiconductor, a single semiconductor such as silicon or germanium, a compound semiconductor typified by a metal chalcogenide, a compound having a perovskite structure, or the like can be used. Metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, or tantalum oxide, cadmium, zinc, lead, silver, antimony, bismuth. Sulfide, cadmium, lead selenide, cadmium telluride and the like. Other compound semiconductors are preferably phosphides such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide, and the like. As the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.

  The semiconductor used in the present invention may be single crystal or polycrystalline. As the conversion efficiency, a single crystal is preferable, but a polycrystal is preferable in terms of manufacturing cost, securing raw materials, and the like, and the particle size of the semiconductor is preferably 2 nm or more and 1 μm or less.

  Examples of a method for forming a semiconductor layer on a conductive support include a method in which a dispersion or colloidal solution of semiconductor fine particles is applied on a conductive support, a sol-gel method, and the like. The dispersion can be prepared by the above-mentioned sol-gel method, a method of mechanically pulverizing with a mortar, etc., a method of dispersing while pulverizing using a mill, or a fine particle in a solvent when synthesizing a semiconductor. And a method of using it as it is.

  In the case of a dispersion prepared by mechanical pulverization or pulverization using a mill, it is formed by dispersing at least semiconductor fine particles alone or a mixture of semiconductor fine particles and a resin in water or an organic solvent. Resins used include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid esters, methacrylic acid esters, silicone resins, phenoxy resins, polysulfone resins, polyvinyl butyral resins, polyvinyl formal resins, polyester resins. , Cellulose ester resin, cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin, polyimide resin and the like.

  Solvents for dispersing the semiconductor fine particles include alcohol solvents such as water, methanol, ethanol, and isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethyl formate, ethyl acetate, and n-butyl acetate. Ester solvents, diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or ether solvents such as dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or amide solvents such as N-methyl-2-pyrrolidone , Dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodine Halogenated hydrocarbon solvents such as debenzene or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, Examples thereof include hydrocarbon solvents such as m-xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

  Examples of a method for applying the obtained dispersion include a roller method, a dip method, an air knife method, a blade method, a wire bar, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method.

  Furthermore, the semiconductor layer may be a single layer or multiple layers. In the case of multiple layers, a dispersion of semiconductor fine particles having different particle diameters can be applied in multiple layers, or different types of semiconductors, and application layers having different compositions of resins and additives can be applied in multiple layers. In addition, when the film thickness is insufficient with a single coating, the multilayer coating is an effective means.

  In general, as the thickness of the semiconductor layer increases, the amount of supported dye increases per unit projected area and the light capture rate increases. However, the diffusion distance of the generated electrons also increases, and the recombination of charges also increases. End up. Therefore, the film thickness of the semiconductor layer is preferably 0.1 to 100 μm, and more preferably 1 to 30 μm.

The semiconductor fine particles need not be heat-treated after being coated on the conductive support, but from the viewpoint of improving the electronic contact between the particles and the strength of the coating film and the adhesion to the support, Is preferable. Furthermore, microwave irradiation, press treatment, or electron beam irradiation may be performed, and these treatments may be performed alone or in combination of two or more. In the heat treatment, the heating temperature is preferably 40 to 700 ° C, more preferably 80 to 600 ° C. The heating time is preferably 5 minutes to 50 hours, and more preferably 10 minutes to 20 hours. The microwave irradiation may be performed from the semiconductor layer forming side of the semiconductor electrode or from the back side. Although there is no restriction | limiting in particular in irradiation time, It is preferable to carry out within 1 hour. Pressing treatment is preferably 100 kgf / cm ² or more, more preferably 1000 kgf / cm ^2. There is no particular limitation on the pressing time, but it is preferably performed within 1 hour.

  The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For this reason, it is preferable that the surface area in the state which coated the semiconductor layer on the support body is 10 times or more with respect to a projection area, and it is more preferable that it is 100 times or more.

  As the dye in the photoelectric conversion element of the present invention, the dye represented by the general formula [I] is used as a photoelectric conversion material.

  As a method of adsorbing the dye to the semiconductor layer, a method of immersing a working electrode containing semiconductor fine particles in a dye solution or a dye dispersion, or a method of applying a dye solution or a dispersion to the semiconductor layer and adsorbing it is used. Can do. In the former case, dipping method, dipping method, roller method, air knife method, etc. can be used, and in the latter case, wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray method, etc. Can be used.

  When adsorbing the dye, a condensing agent may be used in combination. The condensing agent may be either one that has a catalytic action that is supposed to physically or chemically bind the dye to the inorganic surface, or one that acts stoichiometrically to favorably shift the chemical equilibrium. Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

  Solvents for dissolving or dispersing the dye are water, methanol, ethanol, alcohol solvents such as isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or n-butyl acetate. Ester solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, nitrile solvents such as acetonitrile, propionitrile, N, N-dimethylformamide, N, N-dimethylacetamide, or Amide solvents such as N-methyl-2-pyrrolidone, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-di Halogenated hydrocarbon solvents such as lolobenzene, fluorobenzene, bromobenzene, iodobenzene, or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene , Hydrocarbon solvents such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, or cumene, and these can be used alone or as a mixture of two or more.

  The temperature at which these are used and the dye is adsorbed is preferably -50 ° C or higher and 200 ° C or lower. Further, this adsorption may be performed while stirring. Examples of the stirring method include, but are not limited to, a stirrer, a ball mill, a paint conditioner, a sand mill, an attritor, a disperser, and ultrasonic dispersion. The time required for adsorption is preferably 5 seconds or more and 1000 hours or less, more preferably 10 seconds or more and 500 hours or less, and further preferably 1 minute or more and 150 hours.

  In the present invention, a steroidal compound may be used in combination when adsorbing the dye represented by the general formula [I].

  Specific examples of the steroid compound include those shown in (B-1) to (B-10). 0.01-1000 mass parts is preferable with respect to 1 mass part of pigment | dyes, and, as for the quantity of a steroid type compound, 0.1-100 mass parts is more preferable.

  After adsorbing the dye, or after co-adsorbing the dye and the steroidal compound, basic compounds such as t-butylpyridine, 2-picoline, 2,6-lutidine, or phosphoric acid, phosphate ester, alkyl phosphoric acid Further, it may be dipped in an organic solvent containing an acidic compound such as acetic acid or propionic acid.

  As the charge transfer layer of the present invention, an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a liquid in which the redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, a molten salt containing the redox couple, a solid An electrolyte, an organic hole transport material, or the like can be used.

  The electrolytic solution used in the present invention is preferably composed of an electrolyte, a solvent, and an additive. Preferred electrolytes include metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, calcium iodide, tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, and the like. Iodine salts of quaternary ammonium compounds-iodine combinations, metal bromides such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide-bromine combinations, quaternary compounds such as tetraalkylammonium bromide, pyridinium bromide Bromine-bromine combinations of ammonium compounds, metal complexes such as ferrocyanate-ferricyanate, ferrocene-ferricinium ion, sulfur compounds such as sodium polysulfide, alkylthiol-alkyldisulfide, viologen Dye, hydroquinone - quinones, and the like. The above-mentioned electrolytes may be a single combination or a mixture. Further, a molten salt in a molten state at room temperature can also be used as the electrolyte. When this molten salt is used, it is not necessary to use a solvent.

  The electrolyte concentration in the electrolytic solution is preferably 0.05 to 20M, and more preferably 0.1 to 15M. Solvents used for the electrolyte include carbonate solvents such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether solvents such as dioxane, diethyl ether and ethylene glycol dialkyl ether, methanol, ethanol Alcohol solvents such as polypropylene glycol monoalkyl ether, nitrile solvents such as acetonitrile and benzonitrile, aprotic polar solvents such as dimethyl sulfoxide and sulfolane are preferred. Further, basic compounds such as t-butylpyridine, 2-picoline, and 2,6-lutidine may be used in combination.

  In the present invention, the electrolyte can be gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. Preferable polymers in the case of gelation by polymer addition include polyacrylonitrile, polyvinylidene fluoride and the like. Preferred gelling agents for gelation by adding an oil gelling agent include dibenzylden-D-sorbitol, cholesterol derivatives, amino acid derivatives, trans- (1R, 2R) -1,2-cyclohexanediamine alkylamide derivatives, alkylureas Derivatives, N-octyl-D-gluconamide benzoate, double-headed amino acid derivatives, quaternary ammonium derivatives and the like can be mentioned.

  Preferred monomers for polymerization with a polyfunctional monomer include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, and the like. be able to. Furthermore, esters and amides derived from acrylic acid such as acrylamide and methyl acrylate and α-alkyl acrylic acid, esters derived from maleic acid and fumaric acid such as dimethyl maleate and diethyl fumarate, butadiene, cyclohexane and the like. Dienes such as pentadiene, aromatic vinyl compounds such as styrene, p-chlorostyrene and sodium styrene sulfonate, vinyl esters, acrylonitrile, methacrylonitrile, vinyl compounds having a nitrogen-containing heterocyclic ring, vinyl having a quaternary ammonium salt A monofunctional monomer such as a compound, N-vinylformamide, vinylsulfonic acid, vinylidene fluoride, vinyl alkyl ethers, N-phenylmaleimide may be contained. 0.5-70 mass% is preferable and the polyfunctional monomer which occupies for the monomer whole quantity has more preferable 1.0-50 mass%.

  The above-mentioned monomers can be polymerized by radical polymerization. The monomer for gel electrolyte that can be used in the present invention can be radically polymerized by heating, light, electron beam or electrochemical. The polymerization initiator used when the crosslinked polymer is formed by heating is 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2. Azo initiators such as 2,2′-azobis (2-methylpropionate) and peroxide initiators such as benzoyl peroxide are preferable. The addition amount of these polymerization initiators is preferably 0.01 to 20% by mass and more preferably 0.1 to 10% by mass with respect to the total amount of monomers.

  When the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a reactive group necessary for the crosslinking reaction and a crosslinking agent in combination. Preferable examples of the crosslinkable reactive group include nitrogen-containing heterocycles such as pyridine, imidazole, thiazole, oxazole, triazole, morpholine, piperidine, piperazine, etc. Preferred crosslinking agents include alkyl halides, halogens Bifunctional or higher functional reagents capable of electrophilic reaction with nitrogen atoms such as aralkyl fluoride, sulfonic acid ester, acid anhydride, acid chloride, and isocyanate can be exemplified.

  When an inorganic solid compound is used instead of the electrolyte, copper iodide, copper thiocyanide, or the like can be introduced into the electrode by a casting method, a coating method, a spin coating method, a dipping method, electrolytic plating, or the like.

  In the present invention, an organic charge transport material can be used instead of the electrolyte. Charge transport materials include hole transport materials and electron transport materials. Examples of the former include, for example, oxadiazoles disclosed in Japanese Patent Publication No. 34-5466, triphenylmethanes disclosed in Japanese Patent Publication No. 45-555, and Japanese Patent Publication No. 52-4188. Pyrazolines shown in the above, hydrazones shown in JP-B-55-42380, oxadiazoles shown in JP-A-56-123544, etc., JP-A-54-58445 And tetrasylbenzidines disclosed in JP-A No. 58-65440, and stilbenes disclosed in JP-A No. 60-98437. Among them, examples of the charge transport material used in the present invention are shown in JP-A-60-24553, JP-A-2-96767, JP-A-2-183260, and JP-A-2-226160. Particularly preferred are the hydrazones described, and the stilbenes shown in JP-A-2-51162 and JP-A-3-75660. Moreover, these can be used individually or in mixture of 2 or more types.

  On the other hand, examples of the electron transport material include chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 1,3,7-trinitrodibenzothiophene, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, etc. . These electron transport materials can be used alone or as a mixture of two or more.

  Further, as a sensitizer that further increases the sensitizing effect, a certain kind of electron-withdrawing compound can be added. Examples of the electron-withdrawing compound include 2,3-dichloro-1,4-naphthoquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-chloroanthraquinone, phenanthrenequinone and other quinones, 4-nitro Aldehydes such as benzaldehyde, ketones such as 9-benzoylanthracene, indandione, 3,5-dinitrobenzophenone, or 3,3 ', 5,5'-tetranitrobenzophenone, phthalic anhydride, 4-chloronaphthalic anhydride Acid anhydrides such as terephthalalmalononitrile, 9-anthrylmethylidenemalononitrile, 4-nitrobenzalmalononitrile, or cyano compounds such as 4- (p-nitrobenzoyloxy) benzalmalononitrile, 3-benzalphthalide , 3- (α-cyano- - Nitorobenzaru) phthalide, or 3- (alpha-cyano -p- Nitorobenzaru) -4,5,6,7 can be mentioned phthalides such as tetrachloro phthalide like.

  When forming a charge transfer layer using these charge transport materials, a resin may be used in combination. When resin is used in combination, polystyrene resin, polyvinyl acetal resin, polysulfone resin, polycarbonate resin, polyester resin, polyphenylene oxide resin, polyarylate resin, acrylic resin, methacrylic resin, phenoxy resin and the like can be mentioned. Among these, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, and polyarylate resin are preferable. These resins may be used alone or as a copolymer in combination of two or more.

  There are two main methods for forming the charge transfer layer. One is a method in which a counter electrode is first pasted on a semiconductor fine particle-containing layer carrying a sensitizing dye, and a liquid charge transfer layer is sandwiched between the opposite electrodes, and the other is a method in which a charge is directly applied on the semiconductor fine particle-containing layer. This is a method of providing a moving layer. In the latter case, a counter electrode is newly provided on the charge transfer layer.

  In the former case, examples of the method for sandwiching the charge transfer layer include a normal pressure process using a capillary phenomenon due to immersion and a vacuum process in which the gas phase is replaced with a liquid phase at a pressure lower than normal pressure. In the latter case, in the wet charge transfer layer, it is necessary to provide a counter electrode without being dried to prevent liquid leakage at the edge portion. In the case of a gel electrolyte, there is a method in which it is applied in a wet manner and solidified by a method such as polymerization. In that case, you may provide a counter electrode after drying and fixing. In addition to the electrolyte solution, the organic charge transport material solution and the gel electrolyte can be applied in the same manner as the semiconductor fine particle-containing layer and the dye, as in the immersion method, roller method, dipping method, air knife method, and extrusion method. , Slide hopper method, wire bar method, spin method, spray method, casting method, various printing methods, and the like.

  The counter electrode can be used on a support having a conductive layer in the same manner as the conductive support described above, but the support is not necessarily required when the conductive layer itself has sufficient strength and sealing properties. Specific examples of the material used for the counter electrode include metals such as platinum, gold, silver, copper, aluminum, rhodium and indium, carbon compounds, and conductive metal oxides such as ITO and FTO. There is no particular limitation on the thickness of the counter electrode.

  In order for light to reach the photosensitive layer, at least one of the conductive support holding the semiconductor fine particle layer and the counter electrode must be substantially transparent. In the photoelectric conversion element of the present invention, a method in which the conductive support holding the semiconductor fine particle layer is transparent and sunlight is incident from the conductive support side is preferable. In this case, a material that reflects light is preferably used for the counter electrode, and a metal, glass, plastic, or metal thin film on which a conductive oxide is deposited is preferable.

  As described above, there are two types of coating of the counter electrode: when applied on the charge transfer layer and when applied on the semiconductor fine particle layer. In any case, the counter electrode material can be appropriately formed on the charge transfer layer or the semiconductor fine particle-containing layer by a technique such as coating, laminating, vapor deposition, or bonding depending on the type of the counter electrode material or the type of the charge transfer layer. When the charge transfer layer is solid, the counter electrode can be formed directly on the charge transfer layer by a technique such as coating, vapor deposition, or CVD.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to these at all.

Example 1
Titanium oxide (P-25 manufactured by Nippon Aerosil Co., Ltd.), 0.2 g of acetylacetone, and 0.3 g of surfactant (Triton X-100 manufactured by Aldrich) together with 6.5 g of water in a paint conditioner (manufactured by Red Devil) for 6 hours Dispersion treatment was performed. Further, 0.2 g of concentrated nitric acid, 0.4 ml of ethanol, and 1.2 g of polyethylene glycol (# 20,000) were added to 4.0 g of this dispersion to prepare a paste. This paste was applied onto an FTO glass substrate so as to have a film thickness of 12 μm, dried at room temperature, and then fired at 100 ° C. for 1 hour and further at 550 ° C. for 1 hour.

  The dye represented by the exemplary compound (A-2) was dissolved in a mixed solution of t-butanol / acetonitrile (1/1) to prepare a dye solution having a concentration of 0.3 mM. In this dye solution, the previously produced semiconductor electrode was immersed at room temperature for 15 hours for adsorption treatment. The electrolyte is a lithium iodide 0.1M, iodine 0.05M, 1,2-dimethyl-3-n-propylimidazolium iodide 0.5M 3-methoxyacetonitrile solution, and the counter electrode is sputtered with platinum on a titanium plate. We used what we did.

An electrolytic solution was immersed between both electrodes to produce a photoelectric conversion element. Here, pseudo-sunlight generated from a solar simulator (AM1.5G, irradiation intensity 100 mW / cm ² ) is irradiated as a light source from the working electrode side, and evaluation is performed using an electrochemical measurement apparatus (SI-1280B) manufactured by Solartron. Went. As a result, the open circuit voltage was 0.63 V, the short-circuit current density was 15.5 mA / cm ² , the shape factor was 0.58, and the conversion efficiency was 5.66%.

(Examples 2 to 6)
A device was prepared and evaluated in the same manner as in Example 1 except that the exemplified compound (A-2) was changed to the exemplified compounds shown in Table 1. The results are shown in Table 1.

(Example 7)
The pigment | dye shown by exemplary compound (A-2) was melt | dissolved in the mixed solution of t-butanol / acetonitrile (1/1), and the pigment | dye solution of a density | concentration of 0.3 mM was produced. The steroid compound (B-1) was dissolved in this dye solution at a concentration of 0.6 mM. Subsequently, the semiconductor electrode produced in Example 1 was immersed in this dye solution at room temperature for 15 hours to perform an adsorption treatment. The electrolyte is a lithium iodide 0.1M, iodine 0.05M, 1,2-dimethyl-3-n-propylimidazolium iodide 0.5M 3-methoxyacetonitrile solution, and the counter electrode is sputtered with platinum on a titanium plate. We used what we did.

An electrolytic solution was immersed between both electrodes to produce a photoelectric conversion element. Here, pseudo-sunlight generated from a solar simulator (AM1.5G, irradiation intensity 100 mW / cm ² ) is irradiated as a light source from the working electrode side, and evaluation is performed using an electrochemical measurement apparatus (SI-1280B) manufactured by Solartron. Went. As a result, the open circuit voltage was 0.65 V, the short-circuit current density was 15.7 mA / cm ² , the shape factor was 0.60, and the conversion efficiency was 6.12%.

(Examples 8 to 12)
A device was prepared and evaluated in the same manner as in Example 7 except that the exemplary compound (A-2) was changed to the exemplary compound shown in Table 2 and the steroid compound (B-1) was changed to the exemplary compound shown in Table 2. did. The results are shown in Table 2.

(Comparative Example 1)
A device was prepared and evaluated in the same manner as in Example 1 except that the exemplified compound (A-2) was changed to the compound shown in (C-1). As a result, the open circuit voltage was 0.55 V, the short-circuit current density was 5.8 mA / cm ² , the shape factor was 0.51, and the conversion efficiency was 1.63%, which were low values compared to the dye of the present invention.

(Comparative Example 2)
A device was prepared and evaluated in the same manner as in Example 7 except that the exemplified compound (A-2) was changed to the compound shown in (C-2). As a result, the open circuit voltage was 0.53 V, the short-circuit current density was 6.0 mA / cm ² , the shape factor was 0.52, and the conversion efficiency was 1.65%, which were low values compared to the dye of the present invention.

  Examples of utilization of the present invention include photosensors that are sensitive to light of a specific wavelength, in addition to photoelectric conversion elements such as solar cells.

Claims (4)

A photoelectric conversion material characterized by using a compound of general formula [I].

(In the general formula [I], R ₁ represents an alkyl group, an aralkyl group, an alkenyl group, an alkoxy group, an aryl group, or a heterocyclic ring, which may further have a substituent. R ₂ , R ₃ Represents an alkylene residue which is linked together to form a 5-membered ring or a 6-membered ring, and R ₄ is a substituent on the aromatic ring, which is a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic ring, Or a halogen atom, which may further have a substituent, R ₅ and R _{6 each} represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, or a cyano group, and R ₇ represents a hydrogen atom; X represents a functional group represented by the following general formula [II] or general formula [III], and R ₈ represents an alkyl group, a fluoroalkyl group, an aralkyl group, or an aryl group. ,That Good .l may have a further substituent represents 0 or 1.)

  A compound represented by the above general formula [I] as a dye in a semiconductor electrode comprising a support having conductivity on the surface, a semiconductor layer coated on the conductive surface, and a dye adsorbed on the surface of the semiconductor layer A semiconductor electrode characterized by containing at least one or more.   The semiconductor is titanium, tin, zinc, iron, copper, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, tantalum, cadmium, lead, silver, antimony, bismuth, molybdenum, aluminum, 3. The semiconductor electrode according to claim 2, comprising at least one metal chalcogenide selected from gallium, chromium, cobalt, and nickel.   A photoelectric conversion element using the semiconductor electrode according to claim 2.