JP2002246626A - Method of manufacturing photoelectric transducer, and photoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye-sensitized photoelectric transducer which is excellent in the conversion efficiency and in durability against long-time light irradiation, and a method of manufacturing the same. SOLUTION: This method of manufacturing the photoelectric transducer is to manufacture a photoelectric transducer comprising a layer of semiconductor fine grains to which a dye having a carboxyl group is adsorbed and an electrically conductive supporting body, wherein the semiconductor fine grains are treated with an esterificating reagent. By this method, the photoelectric transducer is manufactured. The photoelectric transducer is used to constitute a photovoltaic cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a photoelectric conversion element, and more particularly, to a method for producing a photoelectric conversion element using semiconductor fine particles sensitized with a dye, a photoelectric conversion element produced by the method, and this photoelectric conversion element. The present invention relates to a photovoltaic cell using an element.

[0002]

2. Description of the Related Art Photoelectric conversion elements are used in various optical sensors, copying machines, photovoltaic devices and the like. Various types of photoelectric conversion elements have been put into practical use, such as those using metals, those using semiconductors, those using organic pigments and dyes, and those combining these.

U.S. Pat.Nos. 4,492,721, 4,684,537 and 5,084
365, 5350644, 5463057, 5525440 and WO
No. 98/50393, JP-A-7-249790 and JP-A-10-504521 disclose a photoelectric conversion element using semiconductor fine particles sensitized by a dye (hereinafter referred to as dye-sensitized photoelectric conversion). (Abbreviated as element), and materials and manufacturing techniques for producing the element. An advantage of this method is that an inexpensive oxide semiconductor such as titanium dioxide can be used without being purified to a high degree of purity, so that a relatively inexpensive photoelectric conversion element can be provided. However, such a photoelectric conversion element does not always have a sufficiently high conversion efficiency,
In addition, a decrease in conversion efficiency after long-time light irradiation was also observed,
It has been desired to further improve the conversion efficiency and durability.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dye-sensitized photoelectric conversion element which is excellent in conversion efficiency and durability when irradiated with light for a long time, and a method for producing the same.

[0005]

Means for Solving the Problems As a result of intensive studies in view of the above objects, the present inventor has found that the objects of the present invention can be achieved by the following constitutions.

(1) A method for producing a photoelectric conversion element having a layer of semiconductor fine particles having a dye having a carboxyl group adsorbed thereon and a conductive support, wherein the semiconductor fine particles are treated with an esterification reactant. How to create a conversion element. (2) The method for producing a photoelectric conversion element according to (1), wherein the esterification reactant is a carbodiimide. (3) The method for producing a photoelectric conversion element according to (1) or (2), wherein the semiconductor fine particles are treated using a solution containing an esterification reactant. (4) In the method for producing a photoelectric conversion element according to any one of (1) to (3), after adsorbing a dye to the semiconductor fine particles,
A method for producing a photoelectric conversion element, wherein the method is performed with an esterification reagent. (5) In the method for producing a photoelectric conversion element according to any one of (1) to (3), at the same time that the dye is adsorbed on the semiconductor fine particles, the photoelectric conversion element is treated with an esterification reagent. How to create (6) The method for producing a photoelectric conversion element according to any one of (1) to (5), wherein the dye is a metal complex dye. (7) A photoelectric conversion element prepared by the method according to any one of (1) to (6). (8) A photovoltaic cell using the photoelectric conversion element according to (7).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The photoelectric conversion element of the present invention has a photosensitive layer on a conductive support, and the photosensitive layer is composed of semiconductor fine particles to which a dye having a carboxyl group is adsorbed. In the method of the present invention, the photoelectric conversion element having high conversion efficiency is obtained by treating the semiconductor fine particles with at least one esterification reactant. The photoelectric conversion element of the present invention has a small decrease in conversion efficiency after being exposed to sunlight for a long time and has excellent durability. Hereinafter, the esterification reactant used in the present invention, a treatment method using the same, and the photoelectric conversion element and the photovoltaic cell of the present invention will be described in detail.

[I] Esterification Reagent The esterification reagent used in the present invention is used when an ester is synthesized from a compound having at least one hydroxy group and a compound having at least one carboxyl group. It means a compound that can promote the esterification reaction by being added. Here, the “carboxyl group” may be in a state where a proton is dissociated, or may form a salt.

Examples of preferred esterification reagents include "Experimental Chemistry Course" (4th edition, edited by The Chemical Society of Japan, published by Maruzen Co., Ltd., 1992), vol. 22, p. 43, 1.2. Reactants and the like described in Section 2 "Synthesis of Esters from Carboxylic Acids and Carboxylic Acid Derivatives" include "reactants for activating carboxylic acids or salts thereof" and "reactants for activating alcohols". Is more preferred. Specific examples of the reagents include those described in the above-mentioned "Experimental Chemistry Course", Vol. 22, pp. 45-46, such as carbodiimides (such as dicyclohexylcarbodiimide (DCC) and diisopropylcarbodiimide), pyridinium salts, benzoxazole salts, and benzoxazole. Thiazole salt, Wiltzmeier reagent, chlorosulfonyl isocyanate, 1,1'-carbonyldiimidazole,
Acid anhydrides (trifluoroacetic anhydride and the like), halocarbonates (ethyl chlorocarbonate and the like), acid halide agents (thionyl chloride, oxalyl chloride and the like), diethyl azodicarboxylate and the like can be mentioned. Specific examples of the compound include sulfonyl halides (methanesulfonyl chloride, trifluoromethanesulfonyl chloride, paratoluenesulfonyl chloride, etc.), phosphines (triphenylphosphine, etc.), halogenating agents (thionyl chloride, phosphorus pentachloride, etc.), acyls Agents (such as trifluoroacetic acid chloride). The esterification reagent is particularly preferably a "reactant for activating a carboxylic acid or a salt thereof", and most preferably carbodiimides.

[0010] The esterification reactants may be used alone or in combination. Hereinafter, specific examples of the esterification reactant preferably used in the present invention are shown,
The present invention is not limited to them.

[0011]

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[0012]

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[II] Treatment Method Using Esterification Reactant The term “treatment” in the present invention means an operation of bringing semiconductor fine particles into contact with the esterification reactant for a certain period of time. It does not matter whether or not is adsorbed. Further, the esterification reactant may be decomposed after the contact. Here, “contact for a certain time” means 0.1 seconds or more, preferably 1 second to 72 hours, more preferably
For at least 10 seconds and up to 24 hours, at least one molecule of the esterification reactant is
Means to collide.

When treating with an esterification reactant,
Preferably, an acid (such as p-toluenesulfonic acid) or a base (such as pyridines) acts, and more preferably, a base (such as pyridines) acts. In particular, when carbodiimides are used as the esterification reactant, pyridines are preferably used, and N, N-dimethylaminopyridine or t-butylpyridine is more preferably used.

The treatment may be performed in any state in the process of producing the photoelectric conversion element, but it is preferable to perform the treatment after forming the semiconductor fine particle film. The esterification reactant is preferably used after being dissolved or dispersed in a solvent. However, when the reactant itself is a liquid, it may be used without a solvent. Less than,
A solution in which the esterification reagent is dissolved in a solvent is referred to as a processing solution, and a dispersion in which the esterification reagent is dispersed in the solvent is referred to as a processing dispersion. The treatment is more preferably performed using a treatment solution, and the solvent used for the treatment solution is preferably an organic solvent.

When an organic solvent is used, it can be appropriately selected according to the solubility of the esterification reactant. For example, nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amide (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), Carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.),
These mixed solvents can be used. Of these, nitriles and amides are particularly preferred solvents.

The order of the step of adsorbing the dye on the semiconductor fine particle film and the step of treating with the esterification reagent in the process of producing the photoelectric conversion element is as follows. Hereinafter, referred to as a post-treatment method), a method of simultaneously performing the adsorption of the dye and the treatment with the esterification reagent (hereinafter, referred to as a simultaneous treatment method), and a method of performing the adsorption of the dye after the treatment with the esterification reagent ( Hereinafter, it is referred to as a pretreatment method), but a posttreatment method or a simultaneous treatment method is preferable. Some of these three types of processing methods may be combined for continuous processing. For example, a two-step processing of post-processing semiconductor particles that have been simultaneously processed may be mentioned as a preferable method. When the treatment is performed continuously in this manner, the esterification reactants used for each treatment may be the same or different.

As a method of processing using a processing solution or a processing dispersion (hereinafter, both liquids are collectively referred to as a processing liquid),
A method of immersing the semiconductor fine particle film in the treatment liquid (hereinafter referred to as an immersion treatment method) is preferably exemplified. In the case of the post-treatment method and the pre-treatment method, a method of spraying the treatment liquid in a spray form for a predetermined time (hereinafter, referred to as a spray method) can also be applied. When performing the immersion treatment method, the temperature of the treatment liquid and the time taken for the treatment may be arbitrarily set, but at a temperature of 20 ° C to 80 ° C, 30 ° C.
It is preferable to carry out the immersion treatment for seconds to 24 hours. After the immersion treatment, it is preferable to wash with a solvent. The solvent used for washing is preferably the same as the solvent used for the treatment liquid, or a polar solvent such as nitriles and amides.

The dye is adsorbed on the semiconductor fine particle film by dipping a conductive support having a well-dried semiconductor fine particle layer in a dye solution or by applying a dye solution to the semiconductor fine particle layer. it can. In the former case, the immersion method,
Dip method, roller method, air knife method and the like can be used. In the case of the immersion method, the dye may be adsorbed at room temperature or may be heated and refluxed as described in JP-A-7-249790. Examples of the latter coating method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. Alternatively, a dye may be applied in the form of an image by an inkjet method or the like, and the image itself may be used as a photoelectric conversion element. In the case of the simultaneous treatment method, the adsorption can be carried out by a similar method using a treatment liquid containing both the esterification reactant and the dye.

The unadsorbed dye is preferably removed by washing immediately after the adsorption. The washing is preferably performed using a wet washing tank with a polar solvent such as acetonitrile, an organic solvent such as an alcohol solvent, or the like.

The total amount of the dye adsorbed is preferably 0.01 to 100 mmol per unit area (1 m ² ) of the porous semiconductor electrode substrate. The amount of the dye adsorbed on the semiconductor fine particles is preferably in the range of 0.01 to 1 mmol, more preferably 0.05 to 0.5 mmol, per 1 g of the semiconductor fine particles. With such an amount of dye adsorbed, a sufficient sensitizing effect in the semiconductor can be obtained. On the other hand, if the amount of the dye is too small, the sensitizing effect becomes insufficient, and if the amount of the dye is too large, the dye not adhering to the semiconductor floats and causes a reduction in the sensitizing effect. In order to increase the amount of the dye adsorbed, it is preferable to perform a heat treatment before the adsorption. After the heat treatment, the temperature of the semiconductor electrode substrate is maintained at 60 to 150
It is preferable to carry out the dye adsorption operation quickly at a temperature of between ° C.

The above-mentioned treating solution is added to the esterification reactant,
If necessary, other substances may be contained as additives. For example, in order to reduce the interaction such as aggregation between the dyes, a colorless compound having surface active properties may be added to the treatment liquid and co-adsorbed to the semiconductor fine particles. Examples of such colorless compounds include steroid compounds having a carboxyl group (such as chenodeoxycholic acid) and the following sulfonates. Further, an ultraviolet absorber, a surfactant and the like may be added to the treatment liquid.

[0023]

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It is preferred that a base is present in the treatment solution used for the post-treatment or the pre-treatment. Examples of the base include:
Pyridines (4-methylpyridine, 4-t-butylpyridine,
4-methoxypyridine, etc.), imidazoles (imidazole, N-methylimidazole, etc.), 1,8-diazabicycloundecene, tertiary amines (triethylamine, diethylisopropylamine, 1,4-diazabicyclooctane, etc.)
And the like. Among them, pyridines are particularly preferred.

When the simultaneous treatment is carried out, the amount of the esterification reactant to be added is preferably 0.01 to 100 times the mol of the dye,
The molar ratio is more preferably 0.1 to 10 times, and particularly preferably 1 to 5 times. The concentration of the pre-treatment or post-treatment is preferably 1 × 10 ^{−6 to 2} mol / l, more preferably 1 × 10 ^{−6 to 2} mol / l.
× 10 ^{-5 to} 5 × 10 ^-1 mol / l.

[III] Photoelectric conversion element The photoelectric conversion element of the present invention preferably comprises a conductive layer 10, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, as shown in FIG.
The counter electrode conductive layer 40 is laminated in this order, and the photosensitive layer 20 is composed of semiconductor fine particles 21 sensitized by the dye 22 and the charge transport material 23 penetrating into the gaps between the semiconductor fine particles 21. The charge transport material 23 is the same as the material used for the charge transport layer 30. Also, in order to impart strength to the photoelectric conversion element, a conductive layer
A substrate 50 may be provided as a base for the conductive layer 10 and / or the counter electrode 40. In the present invention, the conductive layer 10 and the optional substrate 50
The layer made of is referred to as a “conductive support”, and the layer formed of the counter electrode conductive layer 40 and an optional substrate 50 is referred to as a “counter electrode”. Note that the conductive layer 10, the counter electrode conductive layer 40, and the substrate 50 in FIG. 1 may be a transparent conductive layer 10a, a transparent counter electrode conductive layer 40a, and a transparent substrate 50a, respectively. A photovoltaic cell is made for the purpose of generating electrical work by connecting this photoelectric conversion element to an external load (power generation), and an optical sensor is made for the purpose of sensing optical information. Of the photovoltaic cells, a case where the charge transport material 23 is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and a case where the main purpose is power generation by sunlight is called a solar cell.

In the photoelectric conversion device of the present invention shown in FIG. 1, when the semiconductor fine particles are n-type, the light incident on the photosensitive layer 20 containing the semiconductor fine particles 21 sensitized by the dye 22 excites the dye 22 and the like. Then, the high-energy electrons in the excited dye 22 and the like are transferred to the conduction band of the semiconductor fine particles 21 and further reach the conductive layer 10 by diffusion. At this time, molecules such as the dye 22 are oxidized. In the photovoltaic cell, the electrons in the conductive layer 10 return to an oxidized substance such as the dye 22 through the counter electrode conductive layer 40 and the charge transport layer 30 while working in an external circuit, and the dye 22 is regenerated. The photosensitive layer 20 functions as a negative electrode (photo anode), and the counter electrode conductive layer 40 functions as a positive electrode. Boundary of each layer (for example, boundary between conductive layer 10 and photosensitive layer 20, photosensitive layer 20 and charge transport layer
30; boundary between charge transport layer 30 and counter electrode conductive layer 40)
Then, the constituent components of each layer may be mutually diffused and mixed. Hereinafter, each layer will be described in detail.

(A) Conductive Support The conductive support comprises (1) a single layer of a conductive layer or (2) two layers of a conductive layer and a substrate. In the case of (1), a material that maintains sufficient strength and sealing properties as a conductive layer, for example, a metal material (platinum, gold, silver, copper, zinc, titanium, aluminum,
Alloys containing these, etc.) can be used. In the case of (2), a substrate having a conductive layer containing a conductive agent on the photosensitive layer side can be used. Preferred conductive agents include metals (platinum, gold, silver, copper, zinc, titanium, aluminum, indium, alloys containing them, etc.), carbon, and conductive metal oxides (indium-tin composite oxide, tin oxide and fluorine Or those doped with antimony). The thickness of the conductive layer is preferably about 0.02 to 10 μm.

The lower the surface resistance of the conductive support, the better. The preferred range of the surface resistance is 50 Ω / □ or less, more preferably 20 Ω / □ or less.

When light is irradiated from the conductive support side, the conductive support is preferably substantially transparent.
The term “substantially transparent” means that the region is in the visible to near infrared region (400 to 120).
0 nm) means that the transmittance is 10% or more in part or all of the light, preferably 50% or more, and 80% or more.
The above is more preferable. In particular, it is preferable that the transmittance in a wavelength region where the photosensitive layer has sensitivity is high.

As the transparent conductive support, it is preferable to form a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic by coating or vapor deposition. Preferred as the transparent conductive layer is tin dioxide or indium-tin oxide (ITO) doped with fluorine or antimony. Transparent substrates include soda glass, which is advantageous in terms of cost and strength, and glass substrates such as non-alkali glass that is not affected by alkali elution.
A transparent polymer film can be used. Transparent polymer film materials include triacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS),
Polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PE
S), polyimide (PI), polyetherimide (PEI),
There are cyclic polyolefin, brominated phenoxy resin and the like. To secure a sufficient transparency, the coating amount of the conductive metal oxide support 1 m ² per glass or plastic
It is preferably 0.01 to 100 g.

It is preferable to use a metal lead for the purpose of lowering the resistance of the transparent conductive support. The material of the metal lead is preferably a metal such as platinum, gold, nickel, titanium, aluminum, copper, and silver. Metal leads are installed on a transparent substrate by vapor deposition, sputtering, etc., and conductive tin oxide, ITO
It is preferable to provide a transparent conductive layer made of a film or the like. The decrease in the amount of incident light due to the installation of the metal leads is preferably within 10%, more preferably 1 to 5%.

(B) Photosensitive Layer In the photosensitive layer, the semiconductor acts as a photoreceptor, absorbs light and separates electric charges to generate electrons and holes. In a dye-sensitized semiconductor, light absorption and the resulting generation of electrons and holes mainly occur in the dye, and semiconductor fine particles have a role of receiving and transmitting the electrons (or holes). The semiconductor used in the present invention is preferably an n-type semiconductor in which a conductor electron becomes a carrier under photoexcitation and gives an anode current.

(1) Semiconductors Semiconductors include simple semiconductors such as silicon and germanium, group III-V compound semiconductors, metal chalcogenides (oxides, sulfides, selenides, composites thereof, etc.), and perovskite structures. (Such as strontium titanate, calcium titanate, sodium titanate, barium titanate, and potassium niobate) can be used.

Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium,
Hafnium, strontium, indium, cerium,
Examples include oxides of yttrium, lanthanum, vanadium, niobium or tantalum, sulfides of cadmium, zinc, lead, silver, antimony or bismuth, selenides of cadmium or lead, tellurides of cadmium, and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, selenides of gallium-arsenic or copper-indium, and sulfides of copper-indium. Further, M _x O _y S _z or M _1x M _2y O _z (M, M ₁ and M ₂ are metal elements, O is oxygen, x, y and z are the number of combinations whose valence is neutral) Compounds such as are also preferably used.

Preferred examples of the semiconductor used in the present invention are Si, TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, Z
nS, PbS, Bi ₂ S ₃ , CdSe, CdTe, SrTiO ₃ , GaP, InP, GaA
s, CuInS ₂ , CuInSe _{2 and the} like, more preferably TiO ₂ , Zn
_{O, SnO 2, Fe 2 O} 3, WO 3, Nb 2 O 5, CdS, PbS, CdSe, SrTi
O ₃ , InP, GaAs, CuInS ₂ or CuInSe ₂ , particularly preferably TiO ₂ or Nb ₂ O ₅ , most preferably TiO ₂ . TiO ₂ containing 70% or more of anatase crystal among TiO ₂
Is preferred, and TiO ₂ of 100% anatase type crystal is particularly preferred. It is also effective to dope a metal for the purpose of improving electron conductivity in these semiconductors. The metal to be doped is preferably a divalent or trivalent metal. It is also effective to dope the semiconductor with a monovalent metal for the purpose of preventing a reverse current from flowing from the semiconductor to the charge transport layer.

The semiconductor used in the present invention may be a single crystal or polycrystal. However, from the viewpoints of production cost, securing of raw materials, energy payback time, etc., polycrystal is preferable, and a porous film composed of semiconductor fine particles is particularly preferable. In addition, a part of the amorphous portion may be included.

The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably from 5 to 200 nm, and from 8 to 200 nm. 100 nm is more preferred. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 30 μm. Two or more types of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 25 nm or less, more preferably 10 nm or less.
For the purpose of improving the light capture rate by scattering incident light, it is also preferable to mix semiconductor particles having a large particle diameter, for example, about 100 to 300 nm.

Two or more kinds of different kinds of semiconductor fine particles may be mixed and used. When two or more kinds of semiconductor fine particles are used in combination, one of them is preferably TiO ₂ , ZnO, Nb ₂ O ₅ or SrTiO ₃ . The other is preferably SnO ₂ , Fe ₂ O ₃ or WO ₃ . More preferred combinations include combinations of ZnO and SnO ₂ , ZnO and WO ₃ , ZnO and SnO ₂ and WO _{3, and the} like. When two or more kinds of semiconductor fine particles are used as a mixture, the respective particle diameters may be different. In particular, a combination in which TiO ₂ , ZnO, Nb ₂ O ₅ or SrTiO ₃ has a large particle diameter and SnO ₂ , Fe ₂ O ₃ or WO ₃ is small is preferable. Preferably, particles having a large particle diameter are 100 nm or more, and particles having a small particle diameter are 15 nm or less.

As methods for producing semiconductor fine particles, Sakuhana Shizuo's "Sol-Gel Method Science" Agne Shofusha (1998), Technical Information Association "Sol-Gel Method for Thin Film Coating" (1995 ) And Tadao Sugimoto's "Synthesis of Monodisperse Particles and Control of Size and Morphology by New Synthetic Gel-Sol Method", Materia, Vol. 35, No. 9, 1012-1018.
The gel-sol method described on page (1996) is preferred. Also
A method developed by Degussa to produce an oxide by high-temperature hydrolysis of a chloride in an oxyhydrogen salt can also be preferably used.

When the semiconductor fine particles are titanium oxide, any of the above-mentioned sol-gel method, gel-sol method, and high-temperature hydrolysis method in chloride oxyhydrogen salt are preferred. Applied Technology "Gihodo Publishing (1997)
The sulfuric acid method or chlorine method described in (1) can also be used. Further, as a sol-gel method, Barbe et al.
American Ceramic Society, Vol. 80, No. 12
No., pages 3157-3171 (1997) and Burnside
La no Chemistry of Materials, Vol. 10, No. 9
Pp. 2419-2425 are also preferred.

(2) Semiconductor fine particle layer In order to coat the semiconductor fine particles on the conductive support, in addition to the method of coating a dispersion or colloid solution of the semiconductor fine particles on the conductive support, the above-mentioned sol-gel is used. A method can also be used. In consideration of mass production of photoelectric conversion elements, physical properties of semiconductor fine particle liquid, flexibility of a conductive support, and the like, a wet film forming method is relatively advantageous. Typical examples of the wet film forming method include a coating method, a printing method, an electrolytic deposition method, and an electrodeposition method. In addition, a method of oxidizing a metal, a method of depositing a metal solution in a liquid phase by ligand exchange or the like (LPD method), a method of vapor deposition by sputtering or the like, a CVD method, or a metal that thermally decomposes on a heated substrate An SPD method in which an oxide precursor is sprayed to form a metal oxide can also be used.

In addition to the above-mentioned sol-gel method, a method of preparing a dispersion of semiconductor fine particles, a method of grinding in a mortar, a method of dispersing while pulverizing with a mill, and a method of synthesizing a semiconductor in a solvent when synthesizing a semiconductor. And then use as it is as fine particles.

As the dispersion medium, water and various organic solvents (eg, methanol, ethanol, isopropyl alcohol, citronellol, terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.) can be used. At the time of dispersion, a polymer such as polyethylene glycol, hydroxyethylcellulose, carboxymethylcellulose, a surfactant, an acid, a chelating agent and the like may be used as a dispersion aid, if necessary. By changing the molecular weight of the polyethylene glycol, the viscosity of the dispersion can be adjusted, and a semiconductor layer that is hard to peel off can be formed, and the porosity of the semiconductor layer can be controlled. Therefore, it is preferable to add polyethylene glycol.

The application method includes a roller method and a dip method as an application system, an air knife method, a blade method, and the like as a metering system.
No. 589, the wire bar method disclosed in U.S. Pat.
The slide hopper method, extrusion method, curtain method and the like described in JP-A Nos. 94, 2761419, 2761791 and the like are preferable. As a general-purpose machine, a spin method or a spray method is also preferable. As the wet printing method, intaglio printing, rubber printing, screen printing and the like are preferable, including three major printing methods of letterpress, offset and gravure. A film forming method may be selected from these methods according to the liquid viscosity and the wet thickness.

The layer of semiconductor fine particles is not limited to a single layer, but a multi-layer coating of a dispersion of semiconductor fine particles having different particle diameters, or a coating layer containing semiconductor fine particles of different types (or different binders and additives) may be formed in multiple layers. It can also be applied. Multilayer coating is effective even when the film thickness is insufficient by one coating.

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) increases, the amount of dye carried per unit projected area increases, so that the light capture rate increases, but the diffusion distance of generated electrons increases. Therefore, the loss due to charge recombination also increases. Therefore, the preferred thickness of the semiconductor fine particle layer is
It is 0.1-100 μm. When used for a photovoltaic cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, more preferably 2 to 25 μm. The coating amount per support 1 m ² of the semiconductor fine particles 0.
5 to 100 g is preferable, and 3 to 50 g is more preferable.

After coating the semiconductor fine particles on the conductive support, the semiconductor fine particles are brought into electronic contact with each other,
Heat treatment is preferably performed to improve the strength of the coating film and the adhesion to the support. A preferred heating temperature range is from 40 ° C to 700 ° C, more preferably from 100 ° C to 600 ° C. The heating time is about 10 minutes to 10 hours. When a support having a low melting point and softening point such as a polymer film is used, high-temperature treatment is not preferable because it causes deterioration of the support. From the viewpoint of cost, the temperature is preferably as low as possible (for example, 50 ° C. to 350 ° C.). Low temperature can be achieved by heat treatment in the presence of small semiconductor particles of 5 nm or less, mineral acids, and metal oxide precursors.
Further, the irradiation can be performed by irradiation of ultraviolet rays, infrared rays, microwaves, or the like, or by applying an electric field or ultrasonic waves. At the same time, for the purpose of removing unnecessary organic substances and the like, it is preferable to use a combination of heating, decompression, oxygen plasma treatment, pure water cleaning, solvent cleaning, gas cleaning and the like in addition to the above irradiation and application, as appropriate.

After the heat treatment, a chemical plating treatment using, for example, an aqueous solution of titanium tetrachloride is carried out for the purpose of increasing the surface area of the semiconductor fine particles, increasing the purity in the vicinity of the semiconductor fine particles, and increasing the efficiency of electron injection from the dye into the semiconductor fine particles. Electrochemical plating using an aqueous solution of titanium trichloride may be performed. In order to prevent a reverse current from flowing from the semiconductor fine particles to the charge transport layer, it is also effective to adsorb an organic substance having low electron conductivity other than the dye on the particle surface. The organic substance to be adsorbed preferably has a hydrophobic group.

The semiconductor fine particle layer preferably has a large surface area so that many dyes can be adsorbed. The surface area in a state where the layer of the semiconductor fine particles is applied on the support is preferably 10 times or more, and more preferably 100 times or more with respect to the projected area. The upper limit is not particularly limited, but is usually about 1000 times.

(3) Dye The dye used in the photosensitive layer may be used alone or in combination of two or more. At least one dye has a carboxyl group. Here, the “carboxyl group” may be in a state where a proton is dissociated, or may form a salt. The dye used in the present invention has an absorption in the visible region or the near infrared region, and can be arbitrarily used as long as it is a compound capable of sensitizing a semiconductor, and a metal complex dye, a methine dye, a porphyrin dye, or a phthalocyanine dye is used. Preferably, metal complex dyes are more preferred. In order to widen the wavelength range of photoelectric conversion as much as possible and to increase the conversion efficiency, it is preferable to use two or more dyes in combination or in combination. In this case, the pigments to be used or mixed and the ratio thereof can be selected so as to match the wavelength range and the intensity distribution of the target light source.

Such a dye is formed by a suitable interlocking group having an adsorption ability to the surface of the semiconductor fine particles.
It is preferable to have Preferred linking groups include
-COOH group, -OH group, -SO ₃ H group, -P (O) (OH) 2 group and -OP (O) (O
H) acidic group such as a ₂ groups, as well as oxime, dioxime,
Π-conducting chelating groups such as hydroxyquinoline, salicylates and α-keto enolates. Among them, a —COOH group, a —P (O) (OH) ₂ group and a —OP (O) (OH) ₂ group are particularly preferable. These groups may form a salt with an alkali metal or the like, or may form an intramolecular salt.
In the case of a polymethine dye, if the methine chain contains an acidic group as in the case of forming a squarylium ring or a croconium ring, this portion may be used as a bonding group.

Hereinafter, preferred sensitizing dyes for use in the photosensitive layer will be specifically described. (a) Metal complex dye When the dye is a metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye or a ruthenium complex dye is preferable, and a ruthenium complex dye is particularly preferable. Ruthenium complex dyes include, for example, U.S. Pat.
4537, 5084365, 5350644, 5463057, 5
525440, JP-A-7-249790, JP-T10-504512, WO9
8/50393 and JP-A-2000-26487.

The ruthenium complex dye used in the present invention is preferably represented by the following general formula (I): (A ₁ ) _p Ru (Ba) (Bb) (Bc) (I) In the general formula (I), A ₁ represents a mono- or bidentate ligand, preferably Cl, SCN, H ₂ O, Br,
It is a ligand selected from the group consisting of I, CN, NCO, SeCN, β-diketone derivative, oxalic acid derivative and dithiocarbamic acid derivative. p is an integer of 0 to 3. Ba, Bb and Bc each independently represent an organic ligand represented by any of the following formulas B-1 to B-10.

[0055]

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In the formulas B-1 to B-10, R ₁₁ represents a hydrogen atom or a substituent. Examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and a carbon atom. 7 atoms
~ 12 substituted or unsubstituted aralkyl groups, having 6 to 6 carbon atoms
Examples include 12 substituted or unsubstituted aryl groups, the aforementioned acidic groups (these acidic groups may form a salt), and chelating groups. Here, the alkyl part of the alkyl group and the aralkyl group may be linear or branched, and the aryl part of the aryl group and the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). Ba, Bb and Bc may be the same or different, and may be any one or two.

Preferred specific examples of the metal complex dye are shown below, but the present invention is not limited thereto.

[0058]

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[0059]

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(B) Methine Dye Preferred methine dyes for use in the present invention are polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes. Examples of the polymethine dye preferably used in the present invention, JP-A-11-35836, JP-A-11-35836
-67285, JP-A-11-86916, JP-A-11-97725, JP-A-11-158395, JP-A-11-163378, JP-A-11-214730
No., JP-A-11-214731, JP-A-11-238905, JP-A-2000
-26487, European Patents 892411, 911841, and 991092
And the dyes described in each of the specifications. Specific examples of preferred methine dyes are shown below.

[0061]

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[0062]

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(C) Charge Transport Layer The charge transport layer is a layer containing a charge transport material having a function of replenishing an oxidized dye with electrons. The charge transporting material used in the present invention may be (i) a charge transporting material involving ions, or (ii) a charge transporting material involving carrier movement in a solid. (i) Charge transport materials involving ions include a molten salt electrolyte composition, a solution in which redox couple ions are dissolved (electrolyte solution), and a so-called gel electrolyte composition in which a redox couple solution is impregnated in a polymer matrix gel. ,
A solid electrolyte composition and the like can be mentioned, and (ii) a charge transporting material related to carrier transfer in a solid include an electron transporting material and a hole (hole) transporting material. These charge transport materials can be used in combination.

(1) Molten Salt Electrolyte Composition The molten salt electrolyte is preferably used as a charge transport material from the viewpoint of achieving both photoelectric conversion efficiency and durability. The molten salt electrolyte is a liquid at room temperature or an electrolyte having a low melting point, for example, WO95 / 18456, JP-A-8-259543,
Examples include pyridinium salts, imidazolium salts, and triazolium salts described in Electrochemistry, Vol. 65, No. 11, p. 923 (1997). Melting point of molten salt is 100 ℃
It is preferably the following, and particularly preferably a liquid at around room temperature.

In the present invention, the following general formulas (Ya), (Yb) and
The molten salt represented by any of (Yc) can be preferably used.

[0066]

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Q _y1 in the general formula (Ya) represents an atomic group which forms a 5- or 6-membered aromatic cation together with a nitrogen atom. Q
_y1 is preferably constituted by an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom and a sulfur atom. The 5-membered ring formed by Q _y1 is an oxazole ring, a thiazole ring, an imidazole ring, a pyrazole ring, an isoxazole ring, a thiadiazole ring, an oxadiazole ring,
It is preferably a triazole ring, an indole ring or a pyrrole ring, more preferably an oxazole ring, a thiazole ring or an imidazole ring, and particularly preferably an oxazole ring or an imidazole ring. The 6-membered ring formed by Q _y1 is a pyridine ring, a pyrimidine ring, a pyridazine ring,
It is preferably a pyrazine ring or a triazine ring, and particularly preferably a pyridine ring.

A _y1 in the general formula (Yb) represents a nitrogen atom or a phosphorus atom.

R _{y1 to} R in the general formulas (Ya), (Yb) and (Yc)
_y11 is each independently a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, and may be linear, branched, or cyclic; for example, a methyl group , Ethyl group, propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group,
t-octyl group, decyl group, dodecyl group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, etc., or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms) ,
It may be linear or branched and represents, for example, a vinyl group, an allyl group, etc.). R _{y1 to} R _y11 are each independently preferably an alkyl group having 2 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms, and particularly preferably an alkyl group having 2 to 6 carbon atoms.

Two or more of R _{y2 to} R _{y5 in} the general formula (Yb) may be linked to each other to form a non-aromatic ring containing A _y1, and R _y6 to R _y6 in the general formula (Yc) Two or more of R _y11 may be linked to each other to form a ring.

The above Q _y1 and R _{y1 to} R _y11 may have a substituent. Preferred examples of the substituent include a halogen atom (F, Cl, Br, I, etc.), a cyano group, an alkoxy group (a methoxy group, an ethoxy group, a methoxyethoxy group, a methoxyethoxyethoxy group, etc.), an aryloxy group (a phenoxy group) ), Alkylthio group (methylthio group, ethylthio group, etc.), alkoxycarbonyl group (ethoxycarbonyl group, etc.), carbonate group (ethoxycarbonyloxy group, etc.), acyl group (acetyl group, propionyl group, benzoyl group, etc.), sulfonyl Group (methanesulfonyl group, benzenesulfonyl group, etc.), acyloxy group (acetoxy group, benzoyloxy group, etc.), sulfonyloxy group (methanesulfonyloxy group, toluenesulfonyloxy group, etc.), phosphonyl group (diethylphosphonyl group, etc.), Amide group (acetylamino group, benzoy Amino group), carbamoyl group (N, N-dimethylcarbamoyl group, etc.), alkyl group (methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, 2-carboxyethyl group, benzyl group, etc.) , Aryl group (phenyl group, toluyl group, etc.), heterocyclic group (pyridyl group, imidazolyl group,
Furanyl group), alkenyl group (vinyl group, 1-propenyl group, etc.), silyl group, silyloxy group and the like.

[0072] formula (Ya), molten salt represented by any of (Yb) and (Yc) may form a multimer through one of Q _y1 and R _{y 1} to R _y11 .

[0073] In the general formula (Ya), (Yb) and (Yc), X ^- represents an anion. X ^- Preferred examples halide ion ^{(I -, Cl -, Br} - , _{^{etc.), SCN -, BF 4 -}} , PF 6 -, ClO 4 -,
_{(CF 3 SO 2) 2 N} -, (CF 3 CF 2 SO 2) 2 N -, CH 3 SO 3 -, CF 3 SO 3 -, CF 3
COO ⁻ , Ph ₄ B ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , and the like. X ^- is SC
_{^{N -, CF 3 SO 3 -}} , CF 3 COO -, (CF 3 SO 2) 2 N - or BF ₄ ^- and more preferable.

Specific examples of the molten salt preferably used in the present invention are shown below, but the present invention is not limited to these.

[0075]

[Formula 10]

[0076]

[Formula 11]

[0077]

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[0078]

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[0079]

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[0080]

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The molten salt may be used alone or as a mixture of two or more. In addition, other iodine salts such as LiI and CF ₃ CO
An alkali metal salt such as OLi, CF ₃ COONa, LiSCN, or NaSCN can be used in combination. The addition amount of the alkali metal salt is preferably 0.02 to 2% by mass relative to the whole composition,
1 to 1% by mass is more preferred.

The molten salt electrolyte is preferably in a molten state at room temperature, and it is preferable not to use a solvent in a composition containing the same. Although the solvent described below may be added, the content of the molten salt is preferably at least 50% by mass, particularly preferably at least 90% by mass, based on the whole composition.
Further, it is preferable that 50% by mass or more of the salt contained in the composition is an iodine salt.

It is preferable to add iodine to the molten salt electrolyte composition. In this case, the content of iodine is preferably 0.1 to 20% by mass relative to the whole composition, and 0.5 to 5% by mass.
More preferably, it is mass%.

(2) Electrolyte The electrolyte is preferably composed of an electrolyte, a solvent and an additive. The electrolyte contains I ₂ and iodide (Li
I, NaI, KI, CsI, metal iodide such as CaI _2, tetraalkylammonium iodide, a combination of pyridinium iodide, quaternary ammonium compounds such as imidazolium iodide iodine salt, etc.), Br ₂ and a bromide (LiBr, N
ABR, KBr, CsBr, CaBr _2, etc. metal bromides, tetraalkylammonium bromide, in addition to the combination of a quaternary ammonium compound bromine salt, etc.), such as pyridinium bromide, ferrocyanide - ferricyanide or ferrocene - ferricinium ion Metal complexes such as sodium sulfide, sulfur compounds such as alkyl thiol-alkyl disulfide, viologen dyes, hydroquinone-quinone, and the like. I ₂ and LiI or pyridinium iodide Among these, an electrolyte that combines a quaternary ammonium compound iodine salt such as imidazolium iodide. The above-mentioned electrolytes may be used as a mixture.

The electrolyte concentration in the electrolyte is preferably 0.1 to 1
0M, more preferably 0.2-4M. When iodine is added to the electrolytic solution, the preferable concentration of iodine is 0.01 to 0.5M.

The solvent used in the electrolytic solution may be a compound that can exhibit excellent ionic conductivity by lowering the viscosity and improving the ion mobility or increasing the dielectric constant and improving the effective carrier concentration. desirable. As such a solvent, ethylene carbonate, carbonate compounds such as propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, dioxane, ether compounds such as diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether,
Chain ethers such as polyethylene glycol dialkyl ether and polypropylene glycol dialkyl ether, alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether and polypropylene glycol monoalkyl ether, ethylene glycol , Propylene glycol, polyethylene glycol, polypropylene glycol, polyhydric alcohols such as glycerin, acetonitrile, glutarodinitrile, methoxyacetonitrile,
Examples thereof include nitrile compounds such as propionitrile and benzonitrile, aprotic polar substances such as dimethyl sulfoxide and sulfolane, water, and the like, and these can be used as a mixture.

Also, J. Am. Ceram. Soc., 80 (12) 3157
-3171 (1997), it is preferable to add a basic compound such as tert-butylpyridine, 2-picoline or 2,6-lutidine to the above-mentioned molten salt electrolyte or electrolytic solution. The preferred concentration range when adding a basic compound is
0.05-2M.

(3) Gel Electrolyte Composition In the present invention, the above-mentioned molten salt electrolyte composition and electrolytic solution are prepared by a method such as addition of a polymer, addition of an oil gelling agent, polymerization containing a polyfunctional monomer, and crosslinking reaction of a polymer. It can be used after gelation (solidification). When gelling by adding a polymer, use the “Polymer Electrolyte Re
The compounds described in views-1 and 2 ″ (co-edited by JR MacCallum and CA Vincent, ELSEVIER APPLIED SCIENCE) can be used, but polyacrylonitrile and polyvinylidene fluoride are particularly preferably used. In the case of chemical conversion, refer to Industrial Science Magazine (J. Chem. Soc. Japan, Ind. Chem. Sec.), 46, 779.
(1943), J. Am. Chem. Soc., 111, 5542 (1989), J. Ch.
em. Soc., Chem. Commun., 1993, 390, Angew. Chem. I
Ent., 35, 1949 (1996), Chem. Lett., 1996,
885, and J. Chem. Soc., Chem. Commun., 1997, 545.
Can be used. Preferred compounds are compounds having an amide structure in the molecular structure. An example in which the electrolyte is gelled is described in JP-A-11-185863, and an example in which the molten salt electrolyte is gelled is described in JP-A-2000-58140, and these can be applied to the present invention.

When the polymer is gelled by a crosslinking reaction, it is desirable to use a polymer having a crosslinkable reactive group and a crosslinking agent together. In this case, a preferable crosslinkable reactive group is an amino group, a nitrogen-containing heterocycle (a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, a triazole ring, a morpholine ring, a piperidine ring, a piperazine ring, and the like). The agent is a bifunctional or higher functional reagent capable of electrophilic reaction with a nitrogen atom (alkyl halides, aralkyl halides, sulfonic esters, acid anhydrides, acid chlorides, isocyanate compounds, α, β- Saturated sulfonyl compounds, α, β-unsaturated carbonyl compounds, α, β-unsaturated nitrile compounds, etc.), and the crosslinking technique described in JP-A-2000-17076 and JP-A-2000-86724 can also be applied.

(4) Hole Transport Material In the present invention, a solid hole transport material that is organic or inorganic or a combination of both can be used instead of an ion-conductive electrolyte such as a molten salt.

(A) Organic hole transporting material As the organic hole transporting material applicable to the present invention, J. Hag
en, et al., Synthetic Metal, 89, 215-220 (1997), N
ature, Vol.395, 8 Oct., p583-585 (1998) and WO97 / 10
617, JP-A-59-194393, JP-A-5-234681, U.S. Pat.No. 4,923,774, JP-A-4-308688, U.S. Pat.
No. 25, JP-A-3-269084, JP-A-4-129271, JP-A-4-
No. 175395, JP-A-4-264189, JP-A-4-290851, JP-A-4-364153, JP-A-5-25473, JP-A-5-239455,
JP-A-5-320634, JP-A-6-1972, JP-A-7-138562
No. JP-A-7-252474, aromatic amines shown in JP-A-11-144773 and the like, JP-A-11-149821, JP-A-11-14
The triphenylene derivatives described in No. 8067, JP-A-11-176489 and the like can be preferably used. Also, Adv.Ma
ter., 9, No. 7, p557 (1997), Angew. Chem. Int. Ed.
Engl., 34, No. 3, p303-307 (1995), JACS, Vol. 120, N
o.4, p664-672 (1998), etc., an oligothiophene compound, K. Murakoshi, et al., Chem. Lett. p471
(1997), "Handbook of Organic
Conductive Molecules and Polymers, Vol. 1,2,3,4 ”
(NALWA, published by WILEY) Polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly (p-phenylenevinylene) and its derivatives, polythienylenevinylene and its derivatives, polythiophene and its derivatives And conductive polymers such as polyaniline and its derivatives, and polytoluidine and its derivatives.

Nature, Vol. 395, 8 Oc
t., p583-585 (1998) to add a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate to control the dopant level, A salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added to perform potential control (compensation of the space charge layer) on the surface of the semiconductor material.

(B) Inorganic hole transport material As the inorganic hole transport material, a p-type inorganic compound semiconductor is used.
Can be. P-type inorganic compound semiconductor for this purpose
Preferably has a band gap of 2 eV or more,
More preferably, it is 2.5 eV or more. Also, p-type mineralization
Ionization potential of compound semiconductor reduces holes in dye
The ionization potential of the dye adsorption electrode
It is necessary to be smaller. P depending on the dye used
Potential of ionization type inorganic compound semiconductor
Although the range varies, it is generally between 4.5 eV and 5.5 eV.
And more preferably between 4.7 eV and 5.3 eV.
Is preferred. Preferred p-type inorganic compound semiconductors are monovalent
A compound semiconductor containing copper, and a compound semiconductor containing monovalent copper.
Examples of conductors are CuI, CuSCN, CuInSe_Two, Cu (In, Ga) S
e _Two, CuGaSe_Two, Cu_TwoO, CuS, CuGaS_Two, CuInS_Two, CuAlSe_Twoetc
Is mentioned. Among them, CuI and CuSCN are preferable, and CuI and CuSCN are preferable.
I is most preferred. Other p-type inorganic compound semiconductors
GaP, NiO, CoO, FeO, Bi_TwoO_Three, MoO_Two, Cr_TwoO_ThreeUse
Can be.

(5) Formation of the charge transport layer The charge transport layer can be formed in two ways. One is a method in which a counter electrode is first stuck on the photosensitive layer, and a liquid charge transport layer is sandwiched in the gap. The other is a method in which a charge transport layer is provided directly on the photosensitive layer, and a counter electrode is subsequently provided.

In the former method, as a method for sandwiching the charge transport layer, a normal pressure process utilizing a capillary phenomenon by immersion or the like, or a vacuum process of replacing the gas phase in the gap with a liquid phase at a pressure lower than normal pressure is used. Available.

In the case of the latter method, the wet charge transport layer is provided with a counter electrode in an undried state to take measures to prevent liquid leakage at the edge. Further, in the case of a gel electrolyte, there is a method of applying it by a wet method and solidifying it by a method such as polymerization. In that case, a counter electrode can be provided after drying and fixing. As a method for applying a wet organic hole transport material or a gel electrolyte in addition to the electrolytic solution, a method similar to the method for applying the semiconductor fine particle layer or the dye described above can be used.

In the case of a solid electrolyte or a solid hole transport material, the charge transport layer can be formed by a dry film forming process such as a vacuum evaporation method or a CVD method, and then a counter electrode can be provided. The organic hole transporting material can be introduced into the electrode by a method such as a vacuum evaporation method, a casting method, a coating method, a spin coating method, a dipping method, an electrolytic polymerization method, and a photoelectrolytic polymerization method. In the case of an inorganic solid compound, it can be introduced into the electrode by a method such as a casting method, a coating method, a spin coating method, a dipping method, an electrolytic deposition method, and an electroless plating method.

(D) Counter electrode Like the above-mentioned conductive support, the counter electrode may have a single-layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate. Examples of the conductive material used for the counter electrode conductive layer include metals (platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, and conductive metal oxides (indium-tin composite oxide, fluorine-doped tin oxide, etc.). Is mentioned. Among them, platinum, gold,
Silver, copper, aluminum and magnesium can be preferably used. The support substrate used for the counter electrode is preferably a glass substrate or a plastic substrate, and the above conductive material is applied or vapor-deposited on the substrate. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. The lower the surface resistance of the counter electrode conductive layer, the better. The preferred range of the surface resistance is 50 Ω / □ or less, more preferably 20 Ω / □.
/ □ or less.

Since the light may be irradiated from one or both of the conductive support and the counter electrode, in order for the light to reach the photosensitive layer, at least one of the conductive support and the counter electrode is substantially transparent. I just need. From the viewpoint of improving the power generation efficiency, it is preferable that the conductive support is transparent and light is incident from the conductive support side. In this case, the counter electrode preferably has a property of reflecting light. As such a counter electrode, glass or plastic on which a metal or a conductive oxide is deposited,
Alternatively, a metal thin film can be used.

The counter electrode is formed by applying a conductive agent directly on the charge transport layer,
Plating or vapor deposition (PVD, CVD) may be performed, or a conductive layer side of a substrate having a conductive layer may be attached. Further, as in the case of the conductive support, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode, particularly when the counter electrode is transparent. In addition, the preferable material and the installation method of the metal lead, the decrease of the incident light amount by the installation of the metal lead, and the like are the same as those of the conductive support.

(E) Other layers In order to prevent a short circuit between the counter electrode and the conductive support, a dense semiconductor thin film layer is previously coated as an undercoat layer between the conductive support and the photosensitive layer. Is preferred. The method of preventing a short circuit by using the undercoat layer is particularly effective when an electron transporting material or a hole transporting material is used for the charge transporting layer. Undercoat layer is preferably _{TiO 2, SnO 2, Fe 2} O 3, WO 3, ZnO or Nb ₂
Consist O _5, more preferably consists of TiO _2. The undercoat layer can be applied by, for example, a spray pyrolysis method described in Electrochim. Acta, 40, 643-652 (1995), a sputtering method, or the like. The preferred thickness of the undercoat layer is 5 to 1000 nm, more preferably 10 to 500 nm.

A functional layer such as a protective layer or an anti-reflection layer may be provided on the outer surface of one or both of the conductive support serving as an electrode and the counter electrode, between the conductive layer and the substrate, or in the middle of the substrate. Good. For forming these functional layers, a coating method, a vapor deposition method, a sticking method, or the like can be used depending on the material.

(F) Specific Example of Internal Structure of Photoelectric Conversion Element As described above, the internal structure of the photoelectric conversion element can take various forms according to the purpose. When roughly divided into two, a structure in which light can enter from both sides and a structure in which light can be entered only from one side are possible. 2 to 9 exemplify an internal structure of a photoelectric conversion element which can be preferably applied to the present invention.

The structure shown in FIG. 2 has a structure in which the photosensitive layer 20 and the charge transport layer 30 are interposed between the transparent conductive layer 10a and the transparent counter electrode conductive layer 40a. Has become. In the structure shown in FIG. 3, a metal lead 11 is partially provided on a transparent substrate 50a, a transparent conductive layer 10a is provided thereon, and an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are sequentially formed. Is provided, and further, a support substrate 50 is arranged,
Light is incident from the conductive layer side. The structure shown in FIG. 4 has the conductive layer 10 on the support substrate 50 and the undercoat layer 60.
A transparent substrate 50a provided with a charge transport layer 30 and a transparent counter electrode conductive layer 40a further provided with a metal lead 11 in a part thereof is disposed with the metal lead 11 side inside. , A structure in which light enters from the counter electrode side. The structure shown in FIG. 5 has a structure in which a metal lead 11 is partially provided on a transparent substrate 50a, and a transparent conductive layer 10a (or 40a) is further provided. An undercoat layer 60, a photosensitive layer 20, and a charge transport layer 30 are provided between a pair. And light enters from both sides. The structure shown in FIG. 6 includes a transparent conductive layer 10a, an undercoat layer 60,
The photosensitive layer 20, the charge transport layer 30, and the counter electrode conductive layer 40 are provided, and the support substrate 50 is disposed thereon. In this structure, light is incident from the conductive layer side. The structure shown in FIG.
Having the conductive layer 10 thereon, providing the photosensitive layer 20 via the undercoat layer 60, further providing the charge transport layer 30 and the transparent counter electrode conductive layer 40a,
A transparent substrate 50a is disposed thereon, and has a structure in which light is incident from the counter electrode side. The structure shown in FIG. 8 has a transparent conductive layer 10a on a transparent substrate 50a, a photosensitive layer 20 provided with an undercoat layer 60 therebetween, and further includes a charge transport layer 30 and a transparent counter electrode conductive layer 40.
a, on which a transparent substrate 50a is arranged,
Light is incident from both sides. In the structure shown in FIG. 9, the conductive layer 10 is provided on the support substrate 50, the photosensitive layer 20 is provided through the undercoat layer 60, and the solid charge transport layer 30 is further provided.
A part thereof has a counter electrode conductive layer 40 or a metal lead 11, and has a structure in which light is incident from the counter electrode side.

[IV] Photovoltaic cell The photovoltaic cell of the present invention causes the above-mentioned photoelectric conversion element to work with an external load. Among photovoltaic cells, a case where the charge transport material is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and a case where the main purpose is power generation by sunlight is called a solar cell.

The side surface of the photovoltaic cell is preferably sealed with a polymer, an adhesive or the like in order to prevent deterioration of components and volatilization of the contents. The external circuit itself connected to the conductive support and the counter electrode via the lead may be a known one.

When the photoelectric conversion device of the present invention is applied to a solar cell, the structure inside the cell is basically the same as the above-described structure of the photoelectric conversion device. Further, the dye-sensitized solar cell using the photoelectric conversion element of the present invention can have a module structure basically similar to a conventional solar cell module. The solar cell module generally has a structure in which cells are formed on a supporting substrate such as a metal and a ceramic, and the cells are covered with a filling resin or a protective glass or the like, and light is taken in from the opposite side of the supporting substrate. It is also possible to adopt a structure in which a transparent material such as tempered glass is used for the support substrate, a cell is formed thereon, and light is taken in from the transparent support substrate side. Specifically, module structures called super straight type, substrate type, potting type,
A substrate-integrated module structure and the like used in an amorphous silicon solar cell and the like are known, and the module structure of the dye-sensitized solar cell of the present invention can be appropriately selected depending on the purpose of use, the place of use, and the environment. Specifically, see JP-A-2000-2
It is preferable to adopt the structure and embodiment described in 68892.

[0108]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Embodiment 1 1. Preparation of Coating Solution Containing Titanium Dioxide Particles Except that the autoclave temperature was set to 230 ° C., the titanium dioxide concentration was reduced by the same method as described in Barbe et al., Journal of American Ceramic Society, Vol. 80, p. 3157. An 11% by mass dispersion of titanium dioxide was obtained.
The average size of the obtained titanium dioxide particles was about 10 nm. To this dispersion, 20% by mass of polyethylene glycol (molecular weight: 20,000, manufactured by Wako Pure Chemical Industries) based on titanium dioxide was added and mixed to obtain a coating solution.

[0110] 2. Preparation of titanium dioxide electrode adsorbing dye (1) Preparation of comparison electrode Transparent conductive glass coated with fluorine-doped tin oxide (Nippon Sheet Glass, surface resistance: about 10Ω / cm ² )
On the conductive surface side, apply the above coating solution with a doctor blade to 120 μm
And dried at 25 ° C. for 30 minutes, and then fired at 450 ° C. for 30 minutes using an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific). The applied amount of titanium dioxide was 18 g / m ² , and the thickness of the applied layer was 12 μm. After the completion of the calcination, the mixture was cooled, and the ruthenium complex dye cis- (dithiocyanate) -N, N'-bis (2,
It was immersed in an adsorbent of 2'-bipyridyl-4,4'-dicarboxylic acid) ruthenium (II) complex (R-1) for 16 hours. The adsorption temperature is 25 ° C, the solvent of the adsorption solution is a 1: 1 (volume ratio) mixture of ethanol and acetonitrile, and the dye concentration is 3 ×
It was 10 ^-4 mol / l. The titanium dioxide electrode on which the dye was dyed was sequentially washed with ethanol and acetonitrile to prepare a comparative electrode T-1.

(2) Preparation of Post-Treatment Electrode The electrode T-1 prepared as in the above (1) was mixed with the post-treatment liquids A-1 to A-3 containing the esterification reagent shown in Table 1 below. 1.
After immersion for 5 hours, washing with acetonitrile, and drying in a dark place under a nitrogen stream, post-treatment electrodes TA-1 to TA-3 were respectively formed. The concentration of the esterification reactant in the processing solution was 0.01 mol /
l, The solvent was unified to acetonitrile, and t-butylpyridine was added as an additive. Further, a comparison electrode TAH-1 using the post-treatment solution AH-1 containing only t-butylpyridine and no esterification reactant was similarly prepared.

[0112]

[Table 1]

(3) Preparation of Simultaneous Treatment Electrode The above-described electrode T-1 was prepared except that the esterification reagents shown in Table 2 below were added to the dye adsorbing solution to obtain simultaneous treatment solutions D-1 to D-7. Simultaneously processed electrodes TD-1 to TD-7 were prepared in the same manner as the preparation method. The concentration of the dye in the adsorption solution was 3 × 10 ⁻⁴ mol / l,
The concentration of the esterification reagent was 3 × 10 ⁻⁴ mol / l, the solvent was standardized to acetonitrile, and dimethylaminopyridine or t-butylpyridine (3 × 10 ⁻⁴ mol / l) was added as an appropriate additive. Also contains only the same concentration of t-butylpyridine,
An electrode TDH-1 for comparison using the treatment solution DH-1 containing no esterification reactant was similarly prepared.

[0114]

[Table 2]

(4) Preparation of Pretreated Electrode A coating solution was applied to a transparent conductive glass in the same manner as in the method of preparing the electrode T-1, dried, fired, and cooled. Pretreatment liquid B- containing esterification reagent
1 for 1.5 hours at 40 ° C., washed with acetonitrile, dried under a stream of nitrogen, and further heated for 30 seconds on a hot plate at 120 ° C., followed by the ruthenium dye R- The pretreatment electrode TB-1 was prepared by performing the adsorption of 1. The concentration of the esterification reactant in the pretreatment solution was 0.01%.
mol / l, and acetonitrile was used as a solvent.

[0116]

[Table 3]

3. Preparation of Photoelectric Conversion Element Each electrode (2 cm × 2 cm) obtained as described above was overlaid with platinum-evaporated glass of the same size. Next, an electrolytic solution (0.65 mol /
l, 1-ethyl-3-methylimidazolium (Y6-1), 0.05mo
acetonitrile solution containing 1 / l of iodine) and introduced into the electrode, and the photoelectric conversion elements C-1, C-2 and C-6 for comparison shown in Table 4 below, and the photoelectric conversion of the present invention. Element C-3
To C-5 and C-7 to C-14 were obtained. “TBP” in Table 4 is t
-Butylpyridine, "DMAP" represents dimethylaminopyridine. According to the present embodiment, the conductive glass 1 (having the conductive agent layer 3 on the glass 2), the TiO ₂ layer 4 having the dye adsorbed thereon, the electrolytic solution 5, the platinum layer 6 and the glass 7 shown in FIG. A stacked photoelectric conversion element was created.

4. Measurement of Photoelectric Conversion Efficiency Simulated sunlight was generated by passing 500 W xenon lamp (Ushio) light through a spectral filter (Oriel AM1.5). The intensity of this light was 100 mW / cm ² in the vertical plane. A silver paste was applied to the end of the conductive glass of each photoelectric conversion element obtained as described above to form a negative electrode, and this negative electrode and platinum-deposited glass (positive electrode) were connected to a current / voltage measuring device (Keithley SMU238 type). . The current-voltage characteristics were measured while simulating sunlight vertically, and the conversion efficiency was determined.
Table 4 shows the conversion efficiency of each photoelectric conversion element. Table 4 also shows the results of similarly measuring the conversion efficiency after the simulated sunlight was irradiated for 1000 hours.

[0119]

[Table 4]

Table 4 shows that the photoelectric conversion elements of the present invention treated with the esterification reagent had higher conversions than the untreated comparative photoelectric conversion elements C-1, C-2 and C-6. It turns out that it shows efficiency. Further, it was also found that the treatment with the esterification reactant can suppress a decrease in conversion efficiency after long-time light irradiation. Furthermore, photoelectric conversion elements C-3, C
-4, C-7 and C-8 show higher conversion efficiency than other devices,
In addition, it is understood that carbodiimides are preferably used as the esterification reactant because of excellent durability.

Example 2 Ruthenium complex dye R-1 was used in place of ruthenium complex dye R-1
Comparative electrodes T-2 to T-4 were prepared in the same manner as in the method of preparing comparative electrode T-1, except that merocyanine dye M-3 or squarylium dye M-6 was used. However, the concentration of each dye in the adsorbent was 1 × 10 ⁻⁴ mol / l.
Further, except that the electrodes T-2 to T-4 were used in place of the electrode T-1, the post-processing electrodes TA-4 to TA-6 were respectively formed in the same manner as in the method of preparing the post-processing electrode TA-2. Created. Using the obtained comparative electrodes T-2 to T-4 and the post-treatment electrodes TA-4 to TA-6, the photoelectric conversion elements C-15 to
C-17 and the photoelectric conversion elements C-18 to C-20 of the present invention were obtained. Table 5 shows the results of measuring the conversion efficiency of each photoelectric conversion element in the same manner as in Example 1 above. Table 5 shows that the conversion efficiency and durability of the device can be improved by treating with an esterification reactant as in Example 1. Note that “TB” in Table 5
"P" represents t-butylpyridine.

[0122]

[Table 5]

[0123]

As described in detail above, by treating semiconductor fine particles with an esterification reactant, a dye-sensitized photoelectric conversion element having improved conversion efficiency and excellent durability as compared with the prior art can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 2 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 3 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 4 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 5 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 6 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 7 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 8 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 9 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 10 is a partial cross-sectional view illustrating a structure of a photoelectric conversion element prepared in an example.

[Explanation of symbols]

10 conductive layer 10a transparent conductive layer 11 metal lead 20 photosensitive layer 21 fine semiconductor particles 22 dye 23 charge transport material 30 charge transfer layer 40: Counter-electrode conductive layer 40a: Transparent counter-electrode conductive layer 50: Substrate 50a: Transparent substrate 60: Undercoat layer 1: Conductive glass 2: Glass 3: Conductive agent Layer 4: TiO ₂ layer 5: Electrolyte 6: Platinum layer 7: Glass

Claims (8)

[Claims] 1. A method for producing a photoelectric conversion element having a layer of semiconductor fine particles having a dye having a carboxyl group adsorbed thereon and a conductive support, wherein the semiconductor fine particles are treated with an esterification reactant. How to create a conversion element. 2. The method for producing a photoelectric conversion element according to claim 1, wherein the esterification reactant is a carbodiimide. 3. The method for producing a photoelectric conversion element according to claim 1, wherein the semiconductor fine particles are treated using a solution containing the esterification reactant. 4. The method for producing a photoelectric conversion element according to claim 1, wherein a dye is adsorbed on the semiconductor fine particles, and then the semiconductor fine particles are treated with the esterification reactant. How to make a device. 5. The method for producing a photoelectric conversion element according to claim 1, wherein a treatment is performed with the esterification reactant at the same time as the dye is adsorbed on the semiconductor fine particles. How to create a conversion element. 6. The method for producing a photoelectric conversion element according to claim 1, wherein the dye is a metal complex dye. 7. A photoelectric conversion element produced by the method according to claim 1. 8. A photovoltaic cell using the photoelectric conversion element according to claim 7.