JP2006156212A - Semiconductor electrode and photoelectric conversion element using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which is superior in photoelectric conversion characteristics. <P>SOLUTION: This is a semiconductor electrode which is composed of a substrate having conductivity on the surface, of a semiconductor layer covered on its conductive surface, and of one or more kinds of adsorbed sensitizing dyes for forming a molecular aggregate on the surface of its semiconductor layer, and which is a compound in which this sensitizing dye is shown by a general formula (1). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion element using a dye molecular aggregate as a photoelectric conversion material.

Global warming due to the increase in CO ₂ due to the use of fossil fuels such as coal and oil, and the increase in energy demand accompanying population growth, and the depletion of fossil fuels that will occur in the near future are recognized as problems related to the existence of humankind Yes. This is why the use of clean and infinite sunlight has been actively studied in recent years. Inorganic solar cells using single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, indium copper selenide, and the like are in practical use.

  However, these inorganic solar cells require high-purity materials, have a drawback that the purification process is complicated, and the cost is high. In addition, there are many demands for weight reduction, and there are many fatal points such as a long payback, and there has been a problem in the spread.

  On the other hand, many solar cells using organic materials have been proposed. A Schottky photoelectric conversion element that joins a p-type organic semiconductor and a metal having a small work function, a heterojunction photoelectric conversion element that joins a p-type organic semiconductor and an n-type inorganic semiconductor, or a p-type organic semiconductor and an electron-accepting organic compound Organic semiconductors to be used are synthetic dyes and pigments such as chlorophyll and perylene, conductive polymer materials such as polyacetylene, or composite materials thereof. A thin film battery is formed by vacuum deposition, casting, dipping, or the like. Although these organic materials have advantages such as low cost and easy area enlargement, the conversion efficiency is often as low as 1% or less, and the durability is poor.

  Under such circumstances, it can be said that the solution-based solar cell reported by Dr. Gretzel has high efficiency and has come one step closer to practical use (for example, see Non-Patent Document 1). The battery proposed in this document is a wet solar cell called a Gretzel type solar cell, which uses a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. A cheap oxide semiconductor such as titanium oxide can be used for the working electrode, it is inexpensive because it does not need to be purified with high purity, and the available light extends to a wide visible light range, and sunlight with a large amount of visible light components. Can be converted into electricity effectively.

  On the other hand, there are many issues to be solved for practical use. One of them is the use of ruthenium complexes as sensitizing dyes. Ruthenium is a rare metal and has resource problems. In addition, the development of inexpensive organic dyes is essential for practical use. As sensitizing dyes, 9-phenylxanthene, cyanine dyes, merocyanine dyes and the like have been proposed (see, for example, Patent Documents 1 to 3). However, these dyes have a low sensitization effect because they have a weak adsorption power to titanium oxide or an inappropriate excitation energy level, and there is a problem in stability over time.

In addition, it is known from Dr. Gretzel that a ruthenium-containing dye, which is famous as an N3 dye, has a high conversion efficiency when adsorbed in a single layer using a spacer compound such as a bile acid derivative. This single molecule adsorbent of dye is advantageous because of its high efficiency, but it is expensive for the above reasons and has a problem in durability because it is easily desorbed by moisture due to single molecule adsorption. In terms of durability, polymer dyes and dye aggregates are advantageous, but intermolecular interactions such as electron transfer occur after light absorption, and sensitization efficiency is inferior to that of monomolecular substances.
Japanese Patent Laid-Open No. 10-92477 Japanese Patent Laid-Open No. 10-189065 JP 2002-334729 A Nature, 353,737 (1991)

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

  The inventors of the present invention diligently studied to achieve the object, combining a sensitizing dye capable of forming at least one molecular assembly with a photoelectric conversion material, and forming a J aggregate of the dye on a porous semiconductor thin film such as titanium oxide. By using the compound represented by the general formula (1) as a sensitizing dye that forms a multilayer adsorbing structure and a molecular assembly, a highly sensitive and stable photoelectric conversion element was obtained.

  The molecular aggregate of the dye of the present invention refers to what is called a J aggregate. Among organic dyes that can form aggregates, photographic sensitizing dyes called cyanine dyes are well known and well studied. Many dyes have a special molecular skeleton and molecular structure, but even a molecular skeleton that does not usually form an aggregate can be easily obtained by introducing a substituent such as a long-chain alkyl group at an appropriate position by a similar method of LB film formation. Can form J aggregates. In addition to cyanine dyes, merocyanine dyes and troponone dyes “Chem. Lett., 175 (1988)” are also known to have compounds that form aggregates. Formation of lower aggregates of dyes other than J aggregates, that is, dimers, trimers, etc., causes desensitization when used in solar cells as well as sensitization of photographs. For spectral sensitization and J-aggregates of silver halide photography, see THJames: THE THEORY OF THE PHOTOGRAPHIC PROCESS 4th (1977) Macmillan Publishing Co. Inc., Japan Photographic Society: Basics of Revised Photo Engineering (1979) Corona, etc. For more information on the formation and electron transfer of molecular aggregates, the Chemical Society of Japan: Chemistry Review No. 33 “New Developments in Organic Photochemistry” (1982) Academic Publishing Center, Chemistry Review No. 40 “Molecular Assemblies” (1983).

(In General Formula (1), R ₁ represents an alkyl group, an aralkyl group, an alkenyl group, an aryl group, or a heterocyclic ring, and may have a substituent. R ₂ is a linkage that forms a cyclic structure with a nitrogen atom. In addition, R ₁ and R ₂ , R ₁ and a nitrogen atom may be combined with a benzene ring to form a ring, and R ₃ represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom. R ₄ represents a direct bond, a divalent linking group, an aryl group, or a heterocyclic ring, and the carbon-carbon double bond may be either E-type or Z-type. R ₅ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and may have a substituent, R ₆ may be an ionic bond or a covalent bond, in addition to a hydrogen atom and an alkyl group , May have an onium salt structure and may have a substituent. .)

  By using a semiconductor electrode using a dye that forms the molecular assembly used in the present invention, a solar cell having high and stable photoelectric conversion performance can be obtained.

The compound represented by the general formula (1) used in the present invention will be described in more detail. Specific examples of R ₁ of the compound represented by the general formula (1) include alkyl groups such as methyl group, ethyl group and isopropyl group, aralkyl groups such as benzyl group and 1-naphthylmethyl group, vinyl group, Examples thereof include alkenyl groups such as cyclohexenyl group, aryl groups such as phenyl group and naphthyl group, and heterocycles such as furyl group, thienyl group and indolyl group. The R ₁ group may have a substituent. Specific examples of the substituent include alkoxy groups such as the above-described alkyl group, methoxy group, ethoxy group, n-hexyloxy group, 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 , The above aryl group, the above-mentioned heterocycle, carboxyl group, carboxyalkyl group such as carboxymethyl group, sulfonylalkyl group such as sulfonylpropyl group, acidic group such as phosphoric acid group, hydroxamic acid group, cyano group, nitro group And an electron withdrawing group such as a trifluoromethyl group. R ₂ is a linking group that forms a cyclic structure together with the nitrogen atom, and R ₁ and R ₂ , or R ₁ and the nitrogen atom may form a cyclic structure. Specific examples thereof are shown in (2) to (29). Can be mentioned. R ₃ represents a hydrogen atom, the above alkyl group, the above alkoxy group, or the above halogen atom, and may have a substituent. Specific examples of the substituent include the above-described alkyl groups, methoxy groups, ethoxy groups, alkoxy groups such as n-hexyloxy groups, alkylthio groups such as methylthio groups and n-hexylthio groups, phenoxy groups, and 1-naphthyloxy groups. Aryloxy groups such as phenylthio groups, halogenthio groups such as chlorine and bromine, disubstituted amino groups such as dimethylamino groups and diphenylamino groups, the above aryl groups, the above heterocycles, carboxyl groups, and carbodimethyls. Examples thereof include carboxyalkyl groups such as sulfonyl groups, sulfonylalkyl groups such as sulfonylpropyl groups, acidic groups such as phosphoric acid groups and hydroxamic acids, and electron withdrawing groups such as cyano groups, nitro groups, and trifluoromethyl groups. The acidic group may be in the form of a quaternary ammonium salt, metal salt, ester or amide. Specific examples of R ₄ include a direct bond or alkylene group such as methylene group, 1,2-ethylene group, alkenylene group such as 1,2-vinylene group, 1,4-phenylene group, 1,4-naphthylene group, and the like. And a divalent linking group having one or more heterocycles such as an arylene group and a 2,5-thienylene group. R ₅ represents a hydrogen atom, the above alkyl group, the above alkoxy group, or the above halogen atom, and may have a substituent. Specific examples of the substituent include the above-described alkyl groups, methoxy groups, ethoxy groups, alkoxy groups such as n-hexyloxy groups, alkylthio groups such as methylthio groups and n-hexylthio groups, phenoxy groups, and 1-naphthyloxy groups. Aryloxy groups such as phenylthio groups, halogenthio groups such as chlorine and bromine, disubstituted amino groups such as dimethylamino groups and diphenylamino groups, the above aryl groups, the above heterocycles, carboxyl groups, and carbodimethyls. Examples thereof include carboxyalkyl groups such as sulfonyl groups, sulfonylalkyl groups such as sulfonylpropyl groups, acidic groups such as phosphoric acid groups and hydroxamic acids, and electron withdrawing groups such as cyano groups, nitro groups, and trifluoromethyl groups. The acidic group may be in the form of a quaternary ammonium salt, metal salt, ester or amide. Specific examples of R ₅ include a hydrogen atom, the above alkyl group, the above alkoxy group, the above alkylthio group, the above aryl group, and the above heterocycle, and may have a substituent. . Specific examples of the substituent include the above-described alkyl groups, methoxy groups, ethoxy groups, alkoxy groups such as n-hexyloxy groups, alkylthio groups such as methylthio groups and n-hexylthio groups, phenoxy groups, and 1-naphthyloxy groups. Aryloxy groups such as phenylthio groups, halogenthio groups such as chlorine and bromine, disubstituted amino groups such as dimethylamino groups and diphenylamino groups, the above aryl groups, the above heterocycles, carboxyl groups, and carbodimethyls. Examples thereof include carboxyalkyl groups such as sulfonyl groups, sulfonylalkyl groups such as sulfonylpropyl groups, acidic groups such as phosphoric acid groups and hydroxamic acids, and electron withdrawing groups such as cyano groups, nitro groups, and trifluoromethyl groups. The acidic group may be in the form of a quaternary ammonium salt, metal salt, ester or amide. Most preferred as a specific example of R ₆ is a hydrogen bond. Other preferred structures include alkyl groups such as methyl groups, aryl groups such as phenyl groups, and alkyl groups such as benzyl groups as covalent substituents.

  Specific examples of dyes that form J aggregates that can be used in the present invention will be given below, but the invention is of course not limited thereto, and it is effective if J aggregates can be formed.

  The photoelectric conversion element of the present invention comprises a conductive support, a semiconductor layer sensitized by a dye placed on the conductive support, a charge transfer layer, and a counter electrode. The photosensitive 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 photosensitive layer of the conductive support, the boundary between the photosensitive 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.

  A metal lead wire may be used for the purpose of reducing the resistance of the transparent conductive substrate. Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. A metal lead wire is installed on a transparent substrate by vapor deposition, sputtering, pressure bonding, or the like, and a method of providing ITO or FTO thereon or a metal lead wire on a 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 may 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 with the support, 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. The age of the heat treatment and the heating temperature are 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. The press treatment is preferably 100 kg / cm ² or more, more preferably 1000 kg / 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.

  The pigment | dye used for the photoelectric conversion element of this invention is restricted to what can form J aggregate as shown in the specific example. The formation of the J aggregate can be easily discerned by observing a long wavelength shift of 40 to 100 nm as compared to the absorption maximum of the dye solution.

  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. However, the immersion method using a solution is the best method for reliably achieving the adsorption equilibrium of the dye.

  In the case of dye adsorption, a condensing agent may be used in combination. The condensing agent may be either a catalyst that physically or chemically binds the dye to the inorganic surface or a substance that reacts stoichiometrically. Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

  Solvents that dissolve or disperse the dye are alcohol solvents such as water, methanol, ethanol, and isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and nitriles such as acetonitrile and 3-methoxypropionitrile. Solvents, ester solvents such as ethyl formate, ethyl acetate, or n-butyl acetate, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethyl Amide solvents such as acetamide or N-methyl-2-pyrrolidone, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chloroben , O-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or halogenated hydrocarbon solvents such as 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, Examples include hydrocarbon solvents such as methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene, and these are used alone or as a mixture of two or more. be able to.

  The temperature at which these are used and the dye is adsorbed is preferably -50 ° C or higher and 200 ° C or lower. At this time, the dye solution may be stirred. 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 still more preferably 1 minute or more and 150 hours or less.

  In the present invention, the steroidal compound represented by the general formula (2) may be used in combination when adsorbing the dye. This steroid derivative, particularly a cholic acid derivative, is preferred, but it has also been found that the addition promotes the formation of J aggregates. Specific examples of the steroidal compound include those shown in (B-1) to (B-10). The addition amount of the steroidal compound is preferably 0.01 to 1000 parts by mass, and more preferably 0.1 to 100 parts by mass with respect to 1 part by mass of the pigment.

(In the general formula (2), R ₇ represents an alkyl group that substitutes an acidic group. R ₈ represents a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocycle, an acyl group, an acyloxy group, An oxycarbonyl group, an oxo group, an acidic group, which may have a substituent, n represents an integer of 1 to 13. When n is 2 or more, R ₈ may be the same or different. In addition, the steroid ring may contain a double bond.)

  The charge transfer layer of the photoelectric conversion element of the present invention contains an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a liquid in which a redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, and a redox couple Molten salts, solid electrolytes, organic hole transport materials, and 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, 3-methoxypropionitrile and benzonitrile, and 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, the counter electrode is newly added thereafter.

  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.

  As the counter electrode, a support having a conductive layer can be used in the same manner as the conductive support described above, but the support is not necessarily required in a configuration in which the strength and the sealing performance are sufficiently maintained. 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 and the counter electrode must be substantially transparent. In the photoelectric conversion element of this invention, the electroconductive support body is transparent and the method of making sunlight inject from a support body 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.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples. In addition, all the parts and percentages in the examples are based on mass.

Synthesis Example Synthesis of Exemplified Compound (A-40) Compound (C-1) (1.0 g), cyanoacetic acid (0.40 g), and ammonium acetate (0.13 g) were dissolved in 4.7 g of acetic acid at 120 ° C. Heat stirring. After 30 minutes, solidify as soon as heating is stopped. After cooling to room temperature, water (50 ml) was added and stirred, and the crystals were collected by filtration. The crystals were transferred to a beaker and washed twice with water (100 ml) and then twice with 2-propanol (50 ml) to obtain Exemplified Compound (A-40). Melting point: 226-229 ° C. (decomposition). Maximum absorption wavelength (λmax) 428 nm. Maximum molar absorption coefficient (εmax) 5.1 × 10 ⁴ mol · cm

  2 hours of 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 5 μm, dried at room temperature, and then baked at 100 ° C. for 1 hour and further at 500 ° C. for 1 hour to produce a titanium oxide film.

   The dye represented by the exemplary compound (A-40) was dissolved in a mixed solution of t-butanol / acetonitrile (1/1) to prepare a dye solution having a concentration of 0.5 mM. The visible-ultraviolet absorption spectrum of this dye solution is shown in FIG. In this dye solution, the previously produced semiconductor electrode was immersed at room temperature for 15 hours for adsorption treatment. The visible-ultraviolet absorption spectrum of this semiconductor electrode is shown in FIG. From FIG. 1, the maximum absorption wavelength in the solution of this dye is 428 nm, whereas the maximum absorption wavelength of the dye adsorbed on the titanium oxide thin film shown in FIG. 2 is increased to 492 nm, and the dye is a titanium oxide thin film. It is suggested that J aggregates are formed above.

An electrolytic solution was injected into a gap in which a semiconductor electrode adsorbing a dye and a counter electrode were arranged to face each other, to produce a photoelectric conversion element using the semiconductor electrode as a working electrode. The counter electrode is a platinum film formed on a titanium plate by sputtering, and the electrolyte solution is 0.1M lithium iodide, 0.05M iodine, 1,2-dimethyl-3-n-propylimidazolium iodide,. A 5M 3-methoxyacetonitrile solution was used. This photoelectric conversion element was irradiated with artificial sunlight (AM1.5, irradiation intensity 100 mW / cm ² ) from a solar simulator light source from the working electrode side. As a result, the open circuit voltage was 0.64 V, the short-circuit current density was 11.4 mA / cm ² , the shape factor was 0.63, and the conversion efficiency was 4.59%.

(Comparative Example 1)
Eosin Y was dissolved in a mixed solution of t-butanol / acetonitrile (1/1) to prepare a dye solution having a concentration of 0.5 mM. The UV absorption spectrum of this dye solution is shown in FIG. In this dye solution, the previously produced semiconductor electrode was immersed at room temperature for 15 hours for adsorption treatment. The UV absorption spectrum of this semiconductor electrode is shown in FIG. From FIG. 3, the maximum absorption wavelength of this dye in the solution was 538 nm, whereas the maximum absorption wavelength of the dye adsorbed on the titanium oxide thin film shown in FIG. 4 was 539 nm, and no change in the spectrum was observed. This suggests that the dye is adsorbed monomolecularly on the titanium oxide thin film.

The photoelectric conversion element was produced by immersing the electrolyte solution used in Example 1 between the previously produced semiconductor electrode and the counter electrode. The characteristics of the obtained photoelectric conversion element were evaluated in the same manner as in Example 1. As a result, the open circuit voltage was 0.55 V, the short-circuit current density was 3.1 mA / cm ² , the form factor was 0.57, and the conversion efficiency was 0.97%.

  As is clear from the above, according to the present invention, a photoelectric conversion element having good conversion efficiency can be provided.

  As an application example of the present invention, a dye-sensitized solar cell excellent in photoelectric conversion efficiency can be mentioned.

The UV absorption spectrum in the solution of a pigment | dye (A-40). The UV absorption spectrum when adsorb | sucking on the titanium oxide thin film of a pigment | dye (A-40). UV absorption spectrum of eosin Y in solution. UV absorption spectrum when adsorbed on a titanium oxide thin film of eosin Y.

Claims (5)

In a semiconductor electrode formed by adsorbing at least one or more sensitizing dyes that form a molecular assembly on the surface of a semiconductor layer coated on the conductive surface, a semiconductor layer coated on the conductive surface, and a surface of the semiconductor layer, A semiconductor electrode, wherein the sensitizing dye is a compound represented by the general formula (1).

(In General Formula (1), R ₁ represents an alkyl group, an aralkyl group, an alkenyl group, an aryl group, or a heterocyclic ring, and may have a substituent. R ₂ is a linkage that forms a cyclic structure with a nitrogen atom. In addition, R ₁ and R ₂ , R ₁ and a nitrogen atom may be combined with a benzene ring to form a ring, and R ₃ represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom. R ₄ represents a direct bond, a divalent linking group, an aryl group, or a heterocyclic ring, and the carbon-carbon double bond may be either E-type or Z-type. R ₅ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and may have a substituent, R ₆ may be an ionic bond or a covalent bond, in addition to a hydrogen atom and an alkyl group , May have an onium salt structure and may have a substituent. .)   2. The semiconductor electrode according to claim 1, wherein the semiconductor electrode is formed by adsorbing at least one steroid compound. The semiconductor electrode according to claim 2, wherein the steroid compound is a compound represented by the general formula (2).

(In the general formula (2), R ₇ represents an alkyl group that substitutes an acidic group. R ₈ represents a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocycle, an acyl group, an acyloxy group, An oxycarbonyl group, an oxo group, an acidic group, which may have a substituent, n represents an integer of 1 to 13. When n is 2 or more, R ₈ may be the same or different. In addition, the steroid ring may contain a double bond.)   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, 4. The semiconductor electrode according to claim 3, comprising at least one metal chalcogenide selected from gallium, chromium, cobalt, and nickel.   A photoelectric conversion element using the semiconductor electrode according to claim 1.

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