JP2007227146A - Photoelectric conversion material, semiconductor electrode, and photoelectric conversion element using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element having high conversion efficiency and high age-based characteristics. <P>SOLUTION: A compound represented by formula (I) is used as a photoelectric conversion material. A semiconductor electrode and the photoelectric conversion element use the photoelectric conversion material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element.

Global warming caused by CO ₂ concentration increases caused by the use of large amounts of fossil fuels, further increase in energy demand associated with population growth have been recognized as problems associated to the fate of mankind. 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 in that conversion efficiency is low at 1% or less, and durability is poor.

  Under such circumstances, a solar cell exhibiting good characteristics has been reported by Dr. Gretzell of Switzerland (for example, Patent Document 1). 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 it is not necessary to purify an inexpensive oxide semiconductor such as titanium oxide to high purity, and therefore, it is inexpensive and more usable light extends over a wide visible light region, so that a solar with a large amount of visible light components is used. It is that light 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. In order to solve these problems, a merocyanine-based organic dye using an indoline skeleton mimetic has been proposed (for example, Non-Patent Document 1). Furthermore, an organic dye having a pyran skeleton has been proposed (for example, Patent Document 2). However, none of the organic dyes has been put into practical use due to problems of conversion efficiency and aging characteristics.
US Pat. No. 4,927,721 Japanese Patent Laid-Open No. 2005-32475 Journal of the American Chemical Society, 2004, (126), 12218-12219.

  The subject of this invention is providing the photoelectric conversion element excellent in conversion efficiency and a time-dependent characteristic.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors were able to achieve the goal by using the compound represented by the general formula [I] as a photoelectric conversion material.

  The photoelectric conversion material means all members constituting an element that converts light into electric energy, such as a material constituting a conductive support, a material constituting a semiconductor electrode, an electrolyte, and a material constituting a counter electrode. To do. By adsorbing and supporting a dye that absorbs light in the visible region on a semiconductor electrode that does not have photoelectric conversion capability in the visible region, the photoelectric conversion capability of the semiconductor electrode can be expanded to the visible region. The dye used in is called a sensitizing dye. The dye described in claim 2 of the present invention acts as this sensitizing dye.

In the general formula [I], R ₁ represents an alkyl group, an aralkyl group, an alkenyl group, an aryl group, a phenyl group, or a heterocyclic ring, and may have a substituent. R ₂ is a hydrogen atom, a lower alkyl group or a lower alkoxy group, and R ₃ is a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a phenyl group, a lower alkyl group or a styryl optionally substituted with a lower alkoxy group. R ₂ and R ₃ may be bonded to each other to form a 5-membered or 6-membered ring together with the carbon atom of the pyran ring to which they are bonded. R ₄ and R ₅ represent an alkylene residue which is linked together to form a 5-membered ring or a 6-membered ring. R ₆ is a substituent of an oxygen atom, and the bond type may be an ionic bond or a covalent bond, and represents a hydrogen atom, an alkyl group, or a quaternary ammonium salt. In the case of a quaternary ammonium salt, it may have an alkyl substituent on the nitrogen atom. L is a hydrogen atom or an electron-withdrawing group, and n is an integer of 1 or more.

  By using the compound of the general formula [I] used in the present invention as a dye, it is possible to obtain a photoelectric conversion element that exhibits excellent conversion efficiency and excellent time-lapse characteristics.

  The compound represented by the general formula [I] includes a polymethine or merocyanine dye having a specific 4H-pyran skeleton and an indoline skeleton mimetic.

In the general formula [I], R ₁ represents an alkyl group such as a methyl group, an ethyl group, an isopropyl group, an n-hexyl group, a 2-ethylhexyl group or a dodecyl group, an aralkyl group such as a benzyl group or a 1-naphthylmethyl group, vinyl Group, an alkenyl group such as a cyclohexenyl group, an aryl group such as a phenyl group and a naphthyl group, and a heterocyclic residue such as a furyl group, a thienyl group and an indolyl group. The R ₁ group may have a substituent. Specific examples of the substituent include the same alkyl group as R ₁ , an alkoxy group such as a methoxy group, an ethoxy group, and an n-hexyloxy group, methylthio Groups, alkylthio groups such as n-hexylthio group, aryloxy groups such as phenoxy group and 1-naphthyloxy group, arylthio groups such as phenylthio group, halogen atoms such as chlorine and bromine, diamino such as dimethylamino group and diphenylamino group substituted amino group, the same aryl group as R _1, the same heterocycle with R _1, carboxyl group, carboxyalkyl carboxyalkyl group such as methyl group, sulfonyl propylsulfonyl alkyl groups such as groups, phosphate groups, hydroxamic acid And an electron-withdrawing group such as a cyano group, a nitro group, and a trifluoromethyl group. As specific examples of R ₁ , the following substituents are used.

R ₂ and R ₃ will be described. Examples of the lower alkyl group include linear or branched alkyl groups having 1 to 6 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, an n-pentyl group, an isopentyl group, a neo-pentyl group, and a hexyl group. . Examples of the lower alkoxy group include linear or branched alkoxy groups having 1 to 6 carbon atoms. Specific examples include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, and an n-butoxy group. , Isobutoxy group, sec-butoxy group, tert-butoxy group, n-pentyloxy group, isopentyloxy group, hexyloxy group and the like.

The substituents R ₂ and R ₃ may be bonded to each other to form a cyclohesan ring, a benzene ring or a 1,3-dioxolane ring together with the carbon atoms of the pyran ring to which they are bonded.

  Specific examples of the electron-withdrawing group of the substituent L include a cyano group, a halogen atom such as chlorine, a trifluoromethyl group, a nitro group, a phenyl group, an alkoxycarboxyl group, a carboxyl group and its ester group, and a benzoyloxy group. It is done. Among these, a cyano group excluding a nitro group, a trifluoromethyl group, a trifluoromethoxycarbonyl group, a trifluoroethoxycarbonyl group, a benzoyloxy group, and the like are preferable. N in the general formula [I] is a positive integer, preferably an integer of 1 to 3.

R ₄ and R ₅ represent an alkylene residue which is linked together to form a 5-membered ring or a 6-membered ring. Specific examples of R ₆ include a hydrogen atom, an alkyl group such as a methyl group and an ethyl group, and a quaternary ammonium salt such as an ammonium ion, a tetraethylammonium ion, and a tetrabutylammonium ion.

  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 compound represented by the general formula [I] includes, for example, two intermediate raw materials (aldehyde compound and active methyl compound), alcohol such as ethanol and isopropyl alcohol, acetic acid and ester thereof, aromatic hydrocarbon such as toluene, dioxane and the like. It can be obtained by being dispersed or dissolved in a solvent such as cyclic ether and reacting with stirring in a temperature range of room temperature to about 150 ° C. using a basic compound such as piperidine, ammonium acetate, sodium hydroxide and the like as a catalyst. In the synthesis, it is important to change the raw material concentration, the type of solvent, the type of catalyst, the reaction temperature, etc., depending on the difference in solubility of the raw material in the solvent. In particular, the reaction with a homogeneous solvent is important from the viewpoint of promoting the reaction.

  The synthesis process of the compound represented by the general formula [I] will be specifically described. In addition, all the substituents in the following reaction formula apply to general formula [I].

Synthesis process 1
A 2-methyl-γ-pyrone derivative (a) and an active methylene derivative (b) are dissolved in a solvent, a catalyst is added, and the mixture is heated to obtain a compound (c).

Synthesis process 2
Compound (d) is dissolved in dimethylformamide, and a mixed solution of phosphorus oxychloride / dimethylformamide is added to obtain compound (e) containing an aldehyde group at the para position of the nitrogen atom. (Vilsmeier reaction)

Synthesis process 3
The obtained compound (c) and compound (e) are dissolved in a solvent, a catalyst is further mixed, and the mixture is heated and stirred.

  The target compound is taken out from the reaction solution obtained in the synthesis step 3 and used in the present invention after recrystallization, column purification, and the like. The obtained compound is adsorbed to the semiconductor layer by its carboxylic acid, and when it is irradiated with light in the intrinsic absorption band of the compound, charge separation is performed and electrons are injected into the semiconductor layer (photosensitization).

  The photoelectric conversion element of the present invention comprises a substrate having conductivity on the surface, a semiconductor layer sensitized by a dye placed on the conductive surface, a charge transfer layer, and a counter electrode. 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 substrate having conductivity on the surface, a substrate having conductivity on the support itself such as metal, or a glass or plastic support having a conductive layer containing a conductive agent on the surface can be used. 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 substrate having conductivity on the surface preferably has a transparency that transmits 10% or more of light, 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 lowering the resistance of the surface conductive layer in the transparent substrate having conductivity on the surface, 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 installed on the transparent conductive support 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 substrate having conductivity on the surface.

  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.

  As a method for forming a semiconductor layer on a substrate having conductivity on the surface, there are a method of applying a dispersion or colloidal solution of semiconductor fine particles 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 subjected to a heat treatment for the purpose of improving the electronic contact between the particles after being coated on a substrate having conductivity on the surface. 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, if the temperature is raised too much, the specific surface area of titanium oxide decreases, so the heating temperature is preferably 40 to 700 ° C, and 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 semiconductor electrode and photoelectric conversion element of the present invention use a compound represented by the general formula [I] as a dye. Moreover, you may use these together.

  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.

  As the charge transport layer according to the present invention, an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a polymer matrix is impregnated with a liquid in which the redox couple is dissolved in an organic solvent, a molten salt containing the redox couple, A solid electrolyte, an inorganic hole transport material, 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 are metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide, and quaternary compounds such as tetraalkylammonium iodide, pyridinium iodide, and imidazolium iodide. Iodine salt of ammonium compound-iodine combination, metal bromide-bromine combination such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, quaternary ammonium such as tetraalkylammonium bromide, pyridinium bromide Bromine-bromine combinations of 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.

  When an inorganic hole transport material 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.

  It is also possible to use an organic charge transport material instead of the electrolyte. For example, oxadiazoles shown in Japanese Patent Publication No. 34-5466 etc., triphenylmethanes shown in Japanese Patent Publication No. 45-555 etc., and Japanese Patent Publication No. 52-4188. Pyrazolines, hydrazones disclosed in JP-B-55-42380, oxadiazoles disclosed in JP-A-56-123544, etc., disclosed in JP-A-54-58445 Tetraarylbenzidines, and stilbenes disclosed in JP-A-58-65440 or JP-A-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.

  Further, a conductive polymer can be used as the organic charge transport material. Polyaniline and derivatives thereof, polypyrrole and derivatives thereof, polythiophene and derivatives thereof, and the like can be used. In particular, polythiophene is an excellent conductive polymer having a high hole transporting ability. In particular, since the alkyl substituted at the 3-position is soluble in organic solvents such as toluene, chloroform, tetrahydrofuran, etc., it is easy to handle and has excellent film-forming properties. It is a substance. In addition, polythiophene into which a sensitive group such as a long-chain alkyl is introduced using 3-thiophene methanol, 3-thiophene ethanol, or 3-thiophene aldehyde having a reactive functional group at the 3-position as a starting material can also be used.

  Specific examples of polythiophene derivatives having an alkyl substituent at the 3-position include poly (3-butylthiophene-2,5-diyl), poly (3-hexylthiophene-2,5-diyl) (hereinafter abbreviated as P3HT), Poly (3-octylthiophene-2,5-diyl), poly (3-decylthiophene-2,5-diyl), poly (3-dodecylthiophene-2,5-diyl), poly (3-cyclohexyl-4- Methylthiophene-2,5-diyl), poly (3-cyclohexylthiophene-2,5-diyl), poly (3-phenylthiophene-2,5-diyl) and the like.

  Furthermore, for the purpose of improving the charge transport efficiency in the charge transport layer, a certain kind of electron withdrawing compound can be added to the charge transport layer. Examples of the electron-withdrawing compound include quinones such as 2,3-dichloro-1,4-naphthoquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-chloroanthraquinone, and phenanthrenequinone, 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. Furthermore, trace amounts of iodine can also be used.

  When forming a charge transport layer using a charge transport material, 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 transport layer. One is a method in which a counter electrode is first pasted on a semiconductor layer carrying a sensitizing dye, and a liquid charge transport layer is sandwiched between the two, and the other is on a semiconductor layer carrying a sensitizing dye. This is a method of directly providing a charge transport layer. In the latter case, a counter electrode is newly provided on the charge transport layer.

  In the former case, examples of the method for sandwiching the charge transport 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 transport 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 electrolytic solution, the organic charge transport material solution and gel electrolyte can be applied in the same manner as the semiconductor layer and pigment application, as well as the immersion method, roller method, dipping method, air knife method, extrusion method, slide Examples thereof include a hopper method, a wire bar method, a spin method, a spray method, a casting method, and various printing methods.

  The counter electrode can be used on a support having a conductive layer in the same manner as the substrate having conductivity on the surface, 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 substrate and the counter electrode on the surface holding the semiconductor layer must be substantially transparent. In the photoelectric conversion element of the present invention, a method is preferred in which the conductive substrate is transparent on the surface holding the semiconductor fine particle layer, and sunlight is incident from the conductive substrate side holding the semiconductor layer. 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 transport layer and when applied on the semiconductor layer. In any case, the counter electrode material can be appropriately formed on the charge transport layer or the semiconductor 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 transport layer. When the charge transport layer is solid, the counter electrode can be formed directly on the charge transport 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.

Production of titanium oxide dispersion Titanium oxide P25 3.0g made by Degussa
Ishihara Sangyo acicular titanium oxide FTL-300 1.0g
Acetylacetone 0.2g
0.2 g of polyoxyethylene (10) octylphenyl ether
7.8g of ethanol
7.8 g of isopropanol
Zirconia beads 2mm diameter 60g
Was placed in a 100 ml polypropylene container and dispersed in a paint shaker for 30 hours.

Fabrication of Semiconductor Electrode Titanium oxide dispersion prepared was diluted with ethanol / isopropanol, and nitric acid was further added dropwise to give a predetermined viscosity and applied onto the FTO transparent electrode. The coating film was baked at 450 ° C. for 2 hours to obtain a porous titanium oxide film having a thickness of 2 μm and a thickness of 0.8 μm. On the other hand, the organic dye (Dye_1) is dissolved in a mixed solution of acetonitrile and tert-butanol (volume ratio 1: 1) so as to have a concentration of about 0.2 mmol / liter, and the titanium oxide porous film is immersed for 24 hours. Thus, two types of porous semiconductor electrodes having different thicknesses were produced.

Preparation of electrolyte solution for dye-sensitized solar cell 3-methoxypropionitrile 20 ml
Lithium iodide 0.34g
Iodine 0.25g
1-propyl-3-methylimidazolium iodine salt 2.5g
tert-Butylpyridine 1.3g
The above was mixed to prepare an electrolyte solution for a dye-sensitized solar cell.

A 2 μm thick porous semiconductor electrode was attached with a platinum electrode facing through a 15 μm spacer, and the prepared electrolyte was injected to prepare a dye-sensitized solar cell. This battery was irradiated with simulated sunlight AM1.5 (irradiation intensity: 100 mW / cm ² ) generated from a solar simulator (YSS-40S, manufactured by Yamashita Denso Co., Ltd.), and an electrochemical measurement device (SI-1280B, solar Output characteristics were measured using TRON Co., Ltd. Furthermore, the output characteristics after continuing to irradiate the artificial sunlight for 3 hours were also measured, and the results are shown in Table 1.

  A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the organic dye (Dye_2) was used, and the results are also shown in Table 1.

(Comparative Example 1)
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the organic dye (Dye_10) was used, and the results are also shown in Table 1.

(Comparative Example 2)
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the organic dye (Dye_11) was used, and the results are also shown in Table 1.

  A 0.8 μm thick porous semiconductor electrode produced in Example 1 was spin-coated with a toluene solution having a P3HT concentration of 1.5%, and gold was further deposited as a counter electrode, whereby an all-solid dye-sensitized solar cell was obtained. Produced. The output characteristics under simulated sunlight were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
An all-solid dye-sensitized solar cell was produced in the same manner as in Example 3 except that the organic dye (Dye_10) was used, and the results are shown in Table 1.

  It was confirmed that the compound of the present invention has excellent photoelectric conversion efficiency.

  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 comprising a compound represented by the general formula [I].

(In the general formula [I], R ₁ represents an alkyl group, an aralkyl group, an alkenyl group, an aryl group, a phenyl group, or a heterocyclic ring, and may have a substituent. R ₂ represents a hydrogen atom or a lower alkyl group. Or a lower alkoxy group, R ₃ is a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a phenyl group, a lower alkyl group or a styryl group optionally substituted with a lower alkoxy group, and R ₂ and R _{3 May} combine with each other to form a 5-membered or 6-membered ring with the carbon atoms of the pyran ring to which they are bonded, and R ₄ and R ₅ are linked together to form a 5-membered or 6-membered ring. .R ₆ showing the alkylene residue is a substituent of an oxygen atom, bound form may be a covalent bond in an ionic bond, a hydrogen atom, an alkyl group or a quaternary ammonium salt, For quaternary ammonium salts may have an alkyl substituent on the nitrogen atom .L is a hydrogen atom or an electron-withdrawing group, n represents an integer of 1 or more.)   In a semiconductor electrode comprising a substrate having conductivity on the surface, a semiconductor layer coated on the conductive surface, and a dye adsorbed on the surface of the semiconductor layer, the compound represented by the above general formula [I] is used as the dye. A semiconductor electrode characterized by being used.   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.