JP2002261310A - Manufacturing method for titanium oxide fine particles, photoelectric conversion element and photocell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of titanium oxide fine particles which are suitable for a photoelectric conversion element and to provide a dye sensitized photoelectric conversion element of superior conversion efficiency and a photocell. SOLUTION: This manufacturing method of the titanium oxide fine particles is provided with the process of heating titanium oxide sol which is in the presence of a specified urea compound, and the method is used for the photoelectric conversion element and the photocell.

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 fine titanium oxide particles, and more particularly, to a method for producing fine titanium oxide particles preferably used in a photoelectric conversion element using semiconductor fine particles sensitized with a dye. Furthermore, the present invention relates to a photoelectric conversion element and a photovoltaic cell using the titanium oxide fine particles obtained by the above production method.

[0002]

2. Description of the Related Art Photoelectric conversion elements are used in various optical sensors, copying machines, and photovoltaic devices. 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.

[0003] US Patent Nos. 4,927,721 and 46,845
No. 37, No. 5084365, No. 5350644, No. 5463057, No. 5525440, International Publication WO
Nos. 98/50393 and JP-A-7-249.
No. 790, Japanese Patent Publication No. 10-504521,
A photoelectric conversion element using semiconductor fine particles sensitized by a dye (hereinafter abbreviated as a dye-sensitized photoelectric conversion element), or a material and a manufacturing technique for manufacturing the same are disclosed. The advantage of this method is that an inexpensive photoelectric conversion element can be provided because titanium oxide fine particles can be used. Usually, a sol-gel method is preferably used for the production of titanium oxide fine particles. The sol-gel method is a method for synthesizing fine particles widely known in the art, and is described in detail in, for example, Burnside et al., Chemistry of Materials, Vol. 10, No. 9, pp. 2419-2425. An example of applying titanium oxide fine particles produced by the sol-gel method to a dye-sensitized photoelectric conversion device is described in Journal of American Ceramic Society, Vol. 80, No. 12, pages 3157-3171 reported by Barbe et al. (1997). However, such a photoelectric conversion element does not always have high conversion efficiency for all the created elements,
Further improvement in conversion efficiency has been desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing fine titanium oxide particles which, when used in a dye-sensitized photoelectric conversion element, improves the conversion efficiency of the element. It is another object of the present invention to provide a dye-sensitized photoelectric conversion element having improved conversion efficiency using the titanium oxide fine particles and a photovoltaic cell using the same.

[0005]

According to the present invention, a method for producing titanium oxide fine particles having the following constitution, a photoelectric conversion element and a photovoltaic cell are provided, and the above object of the present invention is achieved. 1. A method for producing titanium oxide fine particles, comprising a step of heating a titanium oxide sol or a titanium oxide precursor in the presence of a urea compound represented by the following general formula (1).

[0006]

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In the formula, R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a primary amino group, an alkylamino group or a dialkylamino group. Represent. Where R ₁ , R ₂ , R ₃ , and R
₄ may combine with each other to form a ring. 2. _{3. The} method for producing titanium oxide fine particles according to the above item 2, wherein both R ₃ and R ₄ in the general formula (1) are hydrogen atoms. 3. 3. The method for producing titanium oxide fine particles according to the above 1 or 2, wherein the molecular weight of the urea compound is 200 or less. 4. (1) the urea compound is water-soluble;
4. The method for producing fine titanium oxide particles according to any one of claims 1 to 3. 5. The heating step is performed at 150 ° C. to 30 ° C. using a pressure vessel.
The method for producing titanium oxide fine particles according to any one of the above items 1 to 4, which is performed at a temperature of 0 ° C. 6. The method for producing titanium oxide fine particles according to any one of the above 1 to 5, wherein the titanium oxide sol is obtained by hydrolyzing a titanium oxide precursor or a complex thereof. 7. 7. The method for producing titanium oxide fine particles according to the above item 6, wherein the titanium oxide precursor is a compound selected from a titanium halide and an orthotitanate. 8. A photoelectric conversion element having at least a layer of a semiconductor fine particle film to which a dye is adsorbed and a conductive support, wherein the titanium oxide fine particles produced by any one of the above methods 1 to 7 are used for the semiconductor fine particle layer. A photoelectric conversion element characterized in that: 9. 9. The photoelectric conversion element as described in 8 above, wherein the average particle diameter of the titanium oxide fine particles is 5 to 50 nm. 10. The average particle diameter is 100 to 400 in the layer of the semiconductor fine particle film.
10. The photoelectric conversion element as described in 9 above, wherein fine particles of titanium oxide having a diameter of 10 nm are used in combination. 11. The photoelectric conversion element according to any one of the above items 8 to 10, wherein a ruthenium complex dye is used as the dye. 12. A photovoltaic cell using the photoelectric conversion element according to any one of the above items 8 to 11.

[0008]

Embodiments of the present invention will be described below in detail. [1] Production method of titanium oxide fine particles The production method of titanium oxide in the present invention is basically a method based on a sol-gel method. The sol-gel method includes the steps of hydrolysis of a titanium oxide precursor, heat treatment in a pressure vessel, and post-treatment. The present invention is characterized in that the urea compound represented by the general formula (1) is added in the hydrolysis step or the heat treatment step in a pressure vessel.

In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom; an alkyl group, preferably an alkyl group having 1 to 6 carbon atoms, for example, methyl, ethyl, An alkenyl group, preferably an alkenyl group having 2 to 6 carbon atoms such as vinyl and allyl; an aryl group, preferably an aryl group having 6 to 10 carbon atoms such as phenyl; a primary amino group; an alkylamino group And preferably an alkylamino group having 1 to 6 carbon atoms such as methylamino and ethylamino; or a dialkylamino group, preferably a dialkylamino group having 2 to 6 carbon atoms such as dimethylamino and diethylamino. R ₁ , R ₂ , R ₃ and R ₄ are each linked to form 5
A 6-membered ring may be formed. These groups may further have a substituent.

Examples of the substituent include a halogen atom, an alkyl group (including a cycloalkyl group and a bicycloalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, and a heterocyclic group. , Cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy, amino group (anilino group Acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl and arylsulfonylamino group, mercapto group, alkylthio group, arylthio , A heterocyclic thio group, a sulfamoyl group, a sulfo group, an alkyl or arylsulfinyl group, alkyl or arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group,
Examples include carbamoyl, aryl and heterocyclic azo groups, imide groups, phosphino groups, phosphinyl groups, phosphinyloxy groups, phosphinylamino groups, and silyl groups.

The urea compound represented by the general formula (1) is desired to be water-soluble. Therefore, the molecular weight of the urea compound is preferably 200 or less. It is also preferable that the terminal is unsubstituted, that is, both R3 and R4 in the general formula (1) are hydrogen atoms. Further, a substituent for increasing water solubility (for example, a carboxyl group and a salt thereof,
It is also preferable to have a sulfo group and a salt thereof, a hydroxyl group, an amino group, etc.). The preferable range of the solubility of the urea compound in water is 0.1 g or more, preferably 1 g or more per 100 g of water. Preferred specific examples of the urea compound represented by the general formula (1) are shown below, but the present invention is not limited thereto.

[0012]

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[0013]

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In the present invention, the urea compound may be present in the heating step, and the urea compound may be added in any of the hydrolysis step and the heating step in a pressure vessel. In any case, the amount of the urea compound added was 100 water in the reaction solution.
The amount is preferably 0.1 to 20 g, more preferably 1 to 10 g, based on g.

Next, a method for producing titanium oxide fine particles will be described in detail. [Hydrolysis of Titanium Oxide Precursor] Titanium oxide precursor is one that produces titanium oxide by hydrolysis, for example, titanium halide (titanium trichloride, titanium tetrachloride, etc.),
Orthotitanate (eg, methyl orthotitanate, ethyl orthotitanate, isopropyl orthotitanate, butyl orthotitanate) and the like. Of these, orthotitanate is preferred. Prior to hydrolysis, these precursors are converted to various ligands (eg, acetylacetone, aminoethanol, diethanolamine, triethanolamine, ethylenediamine, other amines, pyridinecarboxylic acid, tartaric acid, oxalic acid, lactic acid, glycolic acid, other Hydroxycarboxylic acid, etc.)
A precursor complex may be formed and the complex used for hydrolysis.

The above-mentioned precursor or its complex is heated and hydrolyzed in water. The heating temperature is usually 40 ° C ~ 100
° C, preferably from 60 ° C to 90 ° C. The heating time is generally 1 to 20 hours, preferably 2 to 10 hours. At the time of hydrolysis, an additive for promoting or suppressing the reaction may be added. Examples of such additives include acetic acid, sulfuric acid, nitric acid, ammonia, tetraalkylammonium hydroxide, the aforementioned ligands and the like.
By this step, a sol-like titanium oxide ultrafine particle dispersion is usually obtained.

[Heat treatment in pressure vessel] The titanium oxide sol obtained in the hydrolysis step is placed in a pressure vessel (for example, a titanium autoclave, a stainless steel autoclave, etc.).
To 100 ° C to 400 ° C, preferably 150 ° C to 30 ° C.
Heat to 0 ° C. The autoclave is preferably equipped with a stirrer. The heating time is 1 to 60 hours, preferably 5 to 30 hours. By this step, a dispersion of titanium oxide is obtained. The heating temperature, the particle size of titanium oxide
The average particle size is usually 5 to 50 nm, depending on the heating time, the type and amount of the additive. The titanium oxide usually precipitates when the dispersion is allowed to stand.

In the present invention, in this heat treatment step,
It is essential that the urea compound represented by the general formula (1) be present. Due to the presence of the urea compound, the sol-like ultrafine titanium oxide particles generated in the hydrolysis step grow into porous titanium oxide fine particles. Since the titanium oxide fine particles are porous, when they are used for a photoelectric conversion element, the amount of dye carried increases and the photoelectric conversion characteristics are improved. From such a viewpoint, the amount of the urea compound present in the heating step is, as in the case of the addition amount, 0.1 to 100 g of water.
It is preferably 20 g, more preferably 1 to 10 g.
g.

[Post-treatment] The titanium oxide dispersion obtained in the heating step is concentrated or solvent-replaced by post-treatment.
Finally, a dry powder, an aqueous dispersion, an aqueous dispersion paste, an organic solvent dispersion, or an organic solvent dispersion paste is prepared depending on the purpose of use. Examples of the method of concentration include a method by standing or centrifugation followed by decantation, a method of distilling water under reduced pressure, and the like. The method of solvent replacement is generally a method of repeating centrifugation, decantation, and addition of a solvent. Examples of the thickener for obtaining the paste include various polymers (for example, polystyrene sulfonate, polyacrylic acid and its salts, polyethylene oxide, polypropylene oxide, polyacrylamide, etc.), polysaccharides, gelatin, various low-molecular thickeners. Agents (citronellol, nerol, terpineol, etc.) are preferred. The content of titanium oxide in the aqueous dispersion, the aqueous dispersion paste, the organic solvent dispersion, and the organic solvent dispersion paste is preferably 1 to 40%, and
-30% is more preferable.

[2] Photoelectric Conversion Element Next, the photoelectric conversion element, which is a use of the titanium oxide produced by the method of the present invention, will be described in detail. The photoelectric conversion element of the present invention has at least a layer of a semiconductor fine particle film to which a dye is adsorbed and a conductive support, and the titanium oxide fine particles produced by the method of the present invention are used for the semiconductor fine particle film layer. Preferably, the photoelectric conversion element of the present invention is characterized in that, as shown in FIG. 1, the conductive layer 10, the undercoat layer 60, the photosensitive layer 20, the charge transport layer 30, the counter electrode conductive layer 40 are laminated in this order, Titanium oxide fine particles sensitized to the photosensitive layer 20 by a dye 22
21 and a charge transport material 23 that has penetrated into the voids between the titanium oxide fine particles 21. Here, the photosensitive layer 20 corresponds to a layer of a semiconductor fine particle film (hereinafter also referred to as a “semiconductor fine particle layer”), and the titanium oxide fine particles manufactured by the method of the present invention are used for all or a part of the titanium oxide fine particles 21. . The charge transport material 23 is composed of the same components as the materials used for the charge transport layer 30. Further, in order to impart strength to the photoelectric conversion element, a substrate 50 is used as a base of the conductive layer 10 and / or the counter electrode conductive layer 40.
May be provided. Hereinafter, in the present invention, a layer composed of the conductive layer 10 and the optional substrate 50 is referred to as a “conductive support”, and a layer composed of the counter electrode conductive layer 40 and the optional substrate 50 is referred to as a “counter electrode”.
Call. In the present invention, the photosensitive layer 20 is composed of a plurality of layers having different light scattering properties. Incidentally, the conductive layer 10 in FIG. 1,
The counter electrode conductive layer 40 and the substrate 50 may be the transparent conductive layer 10a, the transparent counter electrode conductive layer 40a, and the 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.

(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. A substrate is not necessarily required if a conductive layer that maintains sufficient strength and sealing properties is used.

In the case of (1), a conductive layer having sufficient strength such as metal and having conductivity is 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 are metals (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, or conductive metal oxides (indium-tin composite oxide, tin oxide doped with fluorine, etc.). Is mentioned. 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. A preferred range of the surface resistance is 100 Ω / □ or less, more preferably 40 Ω / □ or less. The lower limit of the surface resistance is not particularly limited, but is usually about 0.1Ω / □.

When light is irradiated from the conductive support side, the conductive support is preferably substantially transparent.
Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more, and particularly preferably 70% or more.

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. Of these, conductive glass in which a conductive layer made of tin dioxide doped with fluorine is deposited on a transparent substrate made of low-cost soda-lime float glass is preferable. For a low-cost and flexible photoelectric conversion element or solar cell, a transparent polymer film provided with a conductive layer is preferably used. Transparent polymer film materials include tetraacetyl cellulose (TAC),
Polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polysterene (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES) , Polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like. To ensure sufficient transparency,
The coating amount of the conductive metal oxide is preferably a support 1 m ² per 0.01~100g of glass or plastic.

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 aluminum, copper, silver, gold, platinum, and nickel, and particularly preferably aluminum and silver. Metal leads are installed on a transparent substrate by evaporation, sputtering, etc.
It is preferable to provide a transparent conductive layer made of tin oxide doped with fluorine or an ITO film thereon. It is also preferable to provide a metal lead on the transparent conductive layer after providing the transparent conductive layer on the transparent substrate. The decrease in the amount of incident light due to the installation of metal leads is preferably within 10%, more preferably 1 to 5%.
And

(B) Photosensitive Layer In the present invention, the semiconductor fine particle layer before dye adsorption is called a semiconductor fine particle layer, and the semiconductor fine particle layer after dye adsorption is called a photosensitive layer. In the light conversion element of the present invention, the titanium oxide fine particles produced by the method of the present invention are used for all or a part of the titanium oxide fine particles constituting the semiconductor fine particle layer. (1) Photosensitive Layer In the photosensitive layer, the titanium oxide fine particles act as a so-called photoreceptor, absorb light to separate charges, and generate electrons and holes. In the dye-sensitized semiconductor fine particles, light absorption and the resulting generation of electrons and holes mainly occur in the dye, and the titanium oxide fine particles have a role of receiving and transmitting the electrons. Titanium oxide is an n-type semiconductor that gives an anodic current by conducting electrons as carriers under photoexcitation.

According to the study of the present inventors, the titanium oxide fine particles (average particle diameter of 5 to 50 n) produced by the method of the present invention are shown.
m) and titanium oxide particles (large particles) having a particle size of 100 to 400 nm were used as a mixture, which revealed that the conversion efficiency was high. Therefore, it is preferable that the titanium oxide used has such a configuration. The ratio of the titanium oxide fine particles produced by the method of the present invention to the total titanium oxide particles is 30 to 30%.
95% is preferable, and 60 to 90% is more preferable.

(2) Semiconductor Fine Particle Layer In order to coat semiconductor fine particles (titanium oxide particles) on a conductive support, a wet film forming method is relatively advantageous. As a wet film forming method, a coating method and a printing method are typical.
As a method for preparing a dispersion of semiconductor fine particles, in addition to the above-described method, there is a method in which powder is ground in a mortar, or a method in which powder is dispersed while being ground using a mill.

Examples of the dispersion medium include water and various organic solvents (eg, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). At the time of dispersion, if necessary, a polymer such as polyethylene glycol, a surfactant, an acid, a chelating agent, or the like may be used as a dispersion aid. By changing the molecular weight of polyethylene glycol, it is possible to form a film that does not easily peel off or to adjust the viscosity of the dispersion liquid. Therefore, it is preferable to add polyethylene glycol.

The application method includes a roller method and a dipping method as an application system, an air knife method and a blade method as a metering system, and a method in which the application and the metering can be the same part.
-4589, the wire bar method, US Patent 268
The slide hopper method, extrusion method, curtain method, and the like described in Nos. 1294, 2761419, and 2761791 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. From these, a preferable film forming method is selected according to the liquid viscosity and the wet thickness.

The viscosity of the dispersion of semiconductor fine particles greatly depends on the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as a surfactant and a binder. For a high viscosity liquid (for example, 0.01 to 500 Poise), an extrusion method, a casting method, a screen printing method, or the like is preferable. For a low-viscosity liquid (for example, 0.1 Poise or less), a slide hopper method, a wire bar method, or a spin method is preferable, and a uniform film can be formed. If a certain amount of coating is used, application by the extrusion method is possible even in the case of a low-viscosity liquid. As described above, a wet film forming method may be appropriately selected according to the viscosity of the coating solution, the coating amount, the support, the coating speed, and the like.

In the case of multi-layer coating, multi-layer coating may be applied simultaneously, or several to ten and several times may be successively applied. Furthermore, a screen printing method can also be preferably used in the case of successive coating.

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) becomes larger, 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 solar cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, more preferably 2 to 25 μm. The total coating amount of the semiconductor fine particles support 1 m ² per
0.5 to 100 g is preferred, and 5 to 50 g is more preferred.

After applying 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 40 ° C to 700 ° C, more preferably 100 ° C to 600 ° C.
It is. The heating time is about 10 minutes to 10 hours. When a support having a low melting point or softening point such as a polymer film is used, high-temperature treatment is not preferable because it causes deterioration of the support. It is preferable that the temperature be as low as possible from the viewpoint of cost. The lowering of the temperature can be attained by the above-mentioned combined use of small semiconductor particles of 5 nm or less, heat treatment in the presence of a mineral acid, and the like. Coating and heat treatment may be sequentially repeated in order to obtain a photosensitive layer having a multilayer structure.

For the purpose of increasing the surface area of the semiconductor fine particles after the heat treatment, 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, for example, chemical plating using an aqueous titanium tetrachloride solution or titanium plating Electrochemical plating using an aqueous solution of titanium chloride may be performed.

The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. Therefore, the surface area in a state where the layer of semiconductor fine particles is coated on the support is preferably 10 times or more the projected area,
Further, it is preferably 100 times or more. The upper limit is not particularly limited, but is usually about 1000 times.

(3) Dye The sensitizing dye used in the photosensitive layer may be any compound that has absorption in the visible or near infrared region and can sensitize a semiconductor. Dyes, porphyrin dyes or phthalocyanine dyes are preferred. Further, two or more dyes can be used in combination or mixed in order to widen the wavelength range of photoelectric conversion as much as possible and to increase the conversion efficiency. 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 particularly preferable that the particle size range used as in the present invention is large because the particles are equally adsorbed on the respective surfaces. Preferred linking groups include COOH
Groups, OH groups, SO3H groups, acidic groups such as -P (O) (OH) ₂ or -OP (O) (OH) ₂ groups, or oximes, dioximes, hydroxyquinolines, salicylates or α-ketoenolates Chelating groups having an appropriate π conductivity. Among them, COOH group (carboxyl group), -P (O) (OH) ₂ groups
(Phosphonyl group) or —OP (O) (OH) ₂ group (phosphoryl group) is particularly preferred. 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) Organic 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.
684537, 5084365, 5350644, 5463057,
No. 5525440, JP-A-7-249790, JP-T10-504512,
Complex dyes described in International Publication WO98 / 50393, JP-A-2000-26487 and the like can be mentioned.

The ruthenium complex dye which can be preferably used in the present invention is represented by the following general formula (I): (A ₁ ) pRu (Ba) (Bb) (Bc) (I) preferable. In the general formula (I), A ₁ is 1
Or a bidentate ligand, Cl, SCN, H ₂ O, Br, I, C
Preferred are ligands selected from the group consisting of N, NCO and SeCN, and derivatives of β-diketones, oxalic acid and dithiocarbamic acid. p is an integer of 0 to 3. Ba,
Bb and Bc are each independently the following formulas B-1 to B-10:

[0043]

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(Provided that 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, a substituted or unsubstituted alkyl group having 7 to 12 carbon atoms, Examples include an unsubstituted aralkyl group, a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, or the above-mentioned acidic group (these acidic groups may form a salt) or a chelating group. The alkyl portion of the group and the aralkyl group may be linear or branched,
The aryl group and the aryl moiety of the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). ) Represents an organic ligand selected from the compounds represented by The organic ligands Ba, Bb and Bc may be the same or different, and the number of organic ligands may be any of 1 to 3.

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

[0046]

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[0047]

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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 are described in JP-A-11-35836, JP-A-11-67285, JP-A-11-86916, JP-A-11-97725, and JP-A-11-158395.
JP-A-11-163378, JP-A-11-214
No. 730, JP-A-11-214731, JP-A-11-
No. 238905, JP-A-2000-26487, European Patent Nos. 892411, 911841 and 9910
No. 92, each of which is described in the specification. Specific examples of preferred methine dyes are shown below.

[0049]

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[0050]

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(4) Adsorption of Dye on Semiconductor Fine Particles The dye is adsorbed on the semiconductor fine particles by dipping a conductive support having a well-dried semiconductor fine particle layer in a dye solution or by dissolving the dye solution in a semiconductor solution. A method of applying to the fine particle layer can be used. In the former case, a dipping method, a dipping method, a roller method, an air knife method, or 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. Preferred solvents for dissolving the dye include, for example, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated Hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methyl Pyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.),
Examples include carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) and mixed solvents thereof. .

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 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, to avoid water adsorbing on the surface of the semiconductor fine particles,
It is preferable to carry out the dye adsorption operation quickly at a temperature of the semiconductor electrode substrate of 60 to 150 ° C. without returning to normal temperature. Also,
For the purpose of reducing the interaction such as aggregation between the dyes, a colorless compound may be added to the dyes and co-adsorbed to the semiconductor fine particles. Compounds effective for this purpose are compounds having surface active properties and structures, and include, for example, steroid compounds having a carboxyl group (for example, chenodeoxycholic acid) and sulfonates such as those described below.

[0053]

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The unadsorbed dye is preferably removed by washing immediately after the adsorption. It is preferable to perform washing with a polar solvent such as acetonitrile and an organic solvent such as an alcohol solvent using a wet washing tank. After the dye is adsorbed, the surface of the semiconductor fine particles may be treated with an amine or a quaternary salt. Preferred amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like, and preferred quaternary salts include tetrobutylammonium iodide and tetrahexylammonium iodide. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.

(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. Examples of typical charge transport materials that can be used in the present invention include (i)
As an ion transport material, a solution (electrolyte solution) in which redox couple ions are dissolved, a so-called gel electrolyte in which a redox couple solution is impregnated in a gel of a polymer matrix, a molten salt electrolyte containing redox counter ions, and a solid Electrolytes are mentioned, and a composition containing these electrolytes (electrolyte composition) can be used for the charge transport layer. In addition to the charge transporting material involving ions, an electron transporting material or a hole (hole) transporting material may be used as (ii) a charge transporting material involving carrier movement in a solid. These charge transport materials can be used in combination.

(1) Molten Salt Electrolyte Molten salt electrolyte is particularly preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. A molten salt electrolyte is a liquid at room temperature or an electrolyte having a low melting point, such as WO
95/18456, JP-A-8-259543, Electrochemistry, Volume 65, 11
No., p.923 (1997), etc., and known electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts. A molten salt that becomes liquid at a temperature of 100 ° C. or lower, particularly around room temperature, is preferred.

The molten salt which can be preferably used includes those represented by any of the following formulas (Ya), (Yb) and (Yc).

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In the general formula (Ya), Q _y1 is 5 together with a nitrogen atom.
Or an atomic group capable of forming a 6-membered aromatic cation. Q _y1 is preferably composed of one or more atoms selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom and a sulfur atom. 5 formed by Qy1
The membered ring is preferably an oxazole ring, a thiazole ring, an imidazole ring, a pyrazole ring, an isoxazole ring, a thiadiazole ring, an oxadiazole ring, a triazole ring, an indole ring or a pyrrole ring, and is preferably an oxazole ring, a thiazole ring or an imidazole ring. Is more preferable, and an oxazole ring or an imidazole ring is particularly preferable. The 6-membered ring formed by Q _y1 is preferably a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring or a triazine ring, and more preferably a pyridine ring.

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

R in the general formulas (Ya), (Yb) and (Yc)
_{y1 to Ry6} each independently represent a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, which may be linear or branched, or cyclic; For example, 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, A cyclohexyl group, a cyclopentyl group or the like) or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, which may be linear or branched; for example, a vinyl group,
Allyl group), more preferably 2 to 18 carbon atoms
Or an alkenyl group having 2 to 18 carbon atoms, particularly preferably an alkyl group having 2 to 6 carbon atoms.

Further, two or more of R _{y1 to} R _{y4 in} the general formula (Yb) may be linked to each other to form a non-aromatic ring containing A _y1, and R in the general formula (Yc) Two or more of _{y1 to Ry6} may be connected to each other to form a ring structure.

Q in the general formulas (Ya), (Yb) and (Yc)
_y1 and R _y1 to R _y6 may have a substituent, examples of preferred substituents, a halogen atom (F, Cl, Br, I
), Cyano group, alkoxy group (methoxy group, ethoxy group, methoxyethoxy group, methoxyethoxyethoxy group, etc.), aryloxy group (phenoxy group, etc.), alkylthio group (methylthio group, ethylthio group, etc.), alkoxycarbonyl group (ethoxy, etc.) Carbonyl 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, benzoyl group) Oxy group, etc.), sulfonyloxy group (methanesulfonyloxy group, toluenesulfonyloxy group, etc.), phosphonyl group (diethylphosphonyl group, etc.), amide group (acetylamino group, benzoylamino group, etc.), carbamoyl group (N, N -
Dimethylcarbamoyl group), 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) etc),
Examples include an alkenyl group (vinyl group, 1-propenyl group, etc.), a silyl group, a silyloxy group, and the like.

According to the general formula (Y-a), (Y-b) or (Y-c)
The compound represented by_y1Or R_y1~ R _y6Multimer through
May be formed.

These molten salts may be used alone or
The iodine anion may be used in combination with a molten salt obtained by replacing the iodine anion with another anion. As the anion to replace the iodine anion,
Halide ions (Cl ^-, Br ^{-, _{etc.), SCN -, BF 4 -}} , P
_{^{F 6 -, ClO 4 -,}} (CF 3 SO 2) 2 N -, (CF 3 CF 2 SO 2) 2 N -, CH 3 SO 3 -,
Preferred examples include CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , Ph ₄ B ⁻ , (CF ₃ SO ₂ ) ₃ C ^{− and the} like, and SCN ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , (CF ₃ SO ₂ ) ₂ N
^- or BF ₄ ^- and more preferable. Further, other iodine salts such as LiI and alkali metal salts such as CF ₃ COOLi, CF ₃ COONa, LiSCN and NaSCN can also be added. The addition amount of the alkali metal salt is preferably about 0.02 to 2% by mass,
0.1 to 1% by mass is more preferable.

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

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The above molten salt electrolyte is preferably in a molten state at room temperature, and it is more preferable not to use a solvent. 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 entire electrolyte composition. Further, it is preferable that 50% by mass or more of the salt is an iodine salt.

It is preferable to add iodine to the above-mentioned electrolyte composition. In this case, the content of iodine is preferably 0.1 to 20% by mass based on the whole electrolyte composition, and 0.5 to 20% by mass.
More preferably, it is 5% by mass.

(2) Electrolyte When an electrolyte is used for the charge transport layer, the electrolyte is an electrolyte,
It is preferable to be composed of a solvent and an additive. Book
The electrolyte of the invention is I_TwoAnd iodide combinations (iodide
Include LiI, NaI, KI, CsI, CaI_TwoSuch
Metal iodide or tetraalkyl ammonium
Iodide, pyridinium iodide, imidazolium
Iodine salts of quaternary ammonium compounds such as iodide
Etc.), Br _TwoAnd bromide (the bromide is L
iBr, NaBr, KBr, CsBr, CaBr_TwoSuch
Metal bromide or tetraalkylammonium
Quaternary ammonium such as romide and pyridinium bromide
Bromide salts), ferrocyanate salts
Ferricyanate and ferrocene-ferricinium ions
Which metal complex, sodium polysulfide, alkyl thiol
-Sulfur compounds such as alkyl disulfide, viologen
Dyes, hydroquinone-quinone and the like can be used.
You. Among them, I2 and LiI and pyridinium iodide
And quaternary ammonium such as imidazolium iodide
An electrolyte combining a compound iodine salt is preferred. Above
The used electrolytes may be used as a mixture.

The preferred electrolyte concentration is 0.1 M or more and 10 M or less, more preferably 0.2 M or more and 4 M or less. When iodine is added to the electrolytic solution, a preferable concentration of iodine is 0.01 M or more and 0.5 M or less.

The solvent used for the electrolyte may be a compound having a low viscosity to improve ionic mobility, or a compound having a high dielectric constant and an effective carrier concentration to exhibit excellent ionic conductivity. desirable. Examples of such a solvent include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, and polyethylene. Chain ethers such as 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,
Polyhydric alcohols such as polypropylene glycol and glycerin, acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, nitrile compounds such as benzonitrile, dimethyl sulfoxide, aprotic polar substances such as sulfolane, water and the like, Can also be used as a mixture.

Further, according to the present invention, J. Am. Ceram. Soc.,
80 tert- as described in (12) 3157-3171 (1997)
It is preferable to add a basic compound such as butylpyridine, 2-picoline or 2,6-lutidine to the above-mentioned molten salt electrolyte or electrolytic solution. A preferred concentration range when a basic compound is added is 0.05M or more and 2M or less.

(3) Gel Electrolyte In the present invention, the above-mentioned molten salt electrolyte or the electrolytic solution is gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including a polyfunctional monomer, and crosslinking reaction of the polymer. (Solidification). When gelling by adding a polymer, use the “Polymer Electrolyte Re
Compounds described in "vi ews-1 and 2" (co-edited by JR MacCallum and CA Vincent, ELSEVIER APPLIED SCIENCE) can be used, and particularly, polyacrylonitrile and polyvinylidene fluoride can be preferably used. In the case of gelation by addition, use the industrial science magazine (J. Chem Soc. Japan, Ind. Chem. Sec.),
46,779 (1943), J. Am. Chem. Soc., 111,5542 (1989),
J. Chem. Soc., Chem. Com mun., 1993, 390, Angew. C
hem. Int. Ed. Engl., 35, 1949 (1996), Chem. Lett., 1
996, 885, J. Chm. Soc., Chem. Commun., 1997, 545, and preferred compounds are compounds having an amide structure in the molecular structure. An example in which the electrolytic solution is gelled is disclosed in JP-A-11-185683.
Japanese Patent Laid-Open Publication No. 2000-2000 discloses an example in which a molten salt electrolyte is gelled.
-58140, and can be applied to the present invention.

When the electrolyte is gelled by a crosslinking reaction of the polymer, it is desirable to use a polymer having a crosslinkable reactive group and a crosslinking agent together. In this case, preferred crosslinkable reactive groups are an amino group, a nitrogen-containing heterocyclic ring (for example, 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), Preferred crosslinking agents are bifunctional or higher functional reagents capable of electrophilic reaction with a nitrogen atom (for example, alkyl halides, aralkyl halides, sulfonic esters, acid anhydrides, acid chlorides, isocyanate compounds, α , Β-unsaturated sulfonyl group-containing compounds, α, β-unsaturated carbonyl group-containing compounds, α, β-unsaturated nitrile group-containing compounds, etc.).
The crosslinking technique described in JP-A-00-86724 can also be applied.

(4) Hole transporting material In the present invention, an organic or inorganic or a solid hole transporting material combining the both can be used in place of the ion conductive electrolyte such as a molten salt. (A) Organic hole transport material As the organic hole transport material applicable to the present invention, J. Hage
n et al., Synthetic Metal 89 (1997) 215-220, Nature, V
ol. 395, 8 Oct. 1998, p583-585 and WO97 / 10617, JP-A-59-194393, JP-A-5-234681, U.S. Patent No. 4,923,774, JP-A-4-308688. Gazette, U.S. Pat.No. 4,764,625, JP-A-3-269084, JP-A-4-1
No. 29271, JP-A-4-175395, JP-A-4-26418
No. 9, 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, JP-A-7-138562, JP-A-7-252474, JP-A-11
-144773, etc., aromatic amines disclosed in
JP 1-149821, JP-A-11-148067, JP-A-11-17
The triphenylene derivatives described in JP-A-6489 can be preferably used. Adv. Mater. 1997, 9, N0.
7, p557, Angew. Chem. Int. Ed. Engl. 1995, 34, No. 3,
Oligothiophene compounds described in p303-307, JACS, Vol120, N0.4, 1998, p664-672 and the like, K. Murakoshi et al.
al.,; Polypyrrole described in Chem. Lett. 1997, p471,
“Handbook of Organic Conductive Molecules and Pol
Polymers and derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylenevinylene) and derivatives thereof, and polymers described in Ymers Vol. 1,2,3,4 ”(by NALWA, published by WILEY) Conductive polymers such as thienylenevinylene and its derivatives, polythiophene and its derivatives, polyaniline and its derivatives, and polytoluidine and its derivatives can be preferably used.

For hole transporting materials, see Nature, Vol.
395, 8 Oct. 1998, p583-585, in order to control the dopant level.
A compound such as Li [(CF3SO2) 2N] for adding a compound containing a cation radical such as bromophenyl) aminium hexachloroantimonate or for controlling the potential of the oxide semiconductor surface (compensating the space charge layer). Salt may be added.

(B) Inorganic hole transport material As the inorganic hole transport material, a p-type inorganic compound semiconductor can be used. The p-type inorganic compound semiconductor for this purpose preferably has a band gap of 2 eV or more,
Further, it is preferably 2.5 eV or more. Further, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye adsorption electrode from the condition that the holes of the dye can be reduced. Although the preferred range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 eV or more and 5.5 eV or less, and more preferably 4.7 eV or more and 5.3 eV or less. Preferred p-type inorganic compound semiconductors are compound semiconductors containing monovalent copper, and examples of compound semiconductors containing monovalent copper include CuI, CuSCN, CuInSe ₂ , Cu (In, Ga)
Se ₂ , CuGaSe ₂ , Cu ₂ O, CuS, CuGaS ₂ , CuInS ₂ , CuAlSe _{2 and the} like. Among them, CuI and CuSCN are preferable, and CuI is most preferable. Other p-type inorganic compound semiconductors include GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O ₃
Etc. can be used.

(5) Formation of Charge Transport Layer There are two methods for forming the charge transport layer. 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 case, as a method for sandwiching the charge transport layer, a normal pressure process utilizing a capillary phenomenon by immersion or the like,
Alternatively, a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used.

In the latter case, the wet type charge transport layer is provided with a counter electrode in an undried state to take measures to prevent liquid leakage at the edge portion. 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 transporting material, the charge transporting layer may be formed by a dry film forming process such as a vacuum evaporation method or a CVD method, and then a counter electrode may be provided. The organic hole transporting material can be introduced into the inside of 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.
Even 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. As a conductive material used for the counter electrode conductive layer, metal (for example, platinum, gold, silver, copper, aluminum, magnesium, indium, or the like), carbon, or conductive metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, Etc.). Among them, platinum, gold, silver, copper, aluminum and magnesium can be preferably used as the counter electrode layer. An example of a preferable support substrate for the counter electrode is glass or plastic, to which the above-described conductive agent is applied or vapor-deposited. 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 layer, the better. The preferred range of the surface resistance is 50 Ω / □ or less, and more preferably 20 Ω / □ or less.

Since light may be emitted from one or both of the conductive support and the counter electrode, at least one of the conductive support and the counter electrode must be substantially transparent in order for the light to reach the photosensitive layer. I just want it. From the viewpoint of improving power generation efficiency,
It is preferable that the conductive support is made 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, or a metal thin film can be used.

For the counter electrode, a conductive material may be applied directly on the charge transport layer, plated or vapor-deposited (PVD, CVD), or the conductive layer side of the substrate having the conductive layer may be attached. Further, similarly to 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, a preferable material and a setting method of the metal lead,
The decrease in the amount of incident light due to the installation of the metal leads is the same as in the case 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 may be previously coated between the conductive support and the photosensitive layer as an undercoat layer. It is particularly effective when an electron transporting material or a hole transporting material is used for the charge transporting layer. TiO ₂ , SnO ₂ , Fe ₂ O ₃ , W
O ₃ , ZnO, and Nb ₂ O ₅ are more preferable, and TiO ₂ is more preferable.
The undercoat layer is, for example, Electrochim. Acta 40, 643-652 (19
In addition to the spray pyrolysis method described in 95), it can be applied by 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 antireflection 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.

FIG. 2 shows the transparent conductive layer 10 a and the transparent counter electrode conductive layer 4.
The photosensitive layer 20 and the charge transport layer 30 are interposed between the photosensitive layer 20 and the light transport layer 0a, and have a structure in which light enters from both sides.
FIG. 3 shows that a metal lead 11 is partially provided on a transparent substrate 50a, a transparent conductive layer 10a is further provided, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are provided in this order, and further supported. The substrate 50 is arranged, and has a structure in which light is incident from the conductive layer side. FIG. 4 shows that the conductive layer 10 is further provided on the supporting substrate 50, the photosensitive layer 20 is provided via the undercoat layer 60, the charge transport layer 30 and the transparent counter electrode conductive layer 40a are provided, and the metal leads 11 are partially provided. Is disposed with the metal lead 11 side inside, and has a structure in which light is incident from the counter electrode side. FIG. 5 shows 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.
And a charge transport layer 30 interposed therebetween, and has a structure in which light enters from both sides. FIG. 6 is a diagram in which a transparent conductive layer 10a, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are provided on a transparent substrate 50a, and a support substrate 50 is disposed thereon. This is a structure where light enters. FIG.
Has a conductive layer 10 on a supporting substrate 50, a photosensitive layer 20 is provided via an undercoat layer 60, a charge transport layer 30 and a transparent counter electrode conductive layer 40a are further provided, and a transparent substrate 50a is disposed thereon. This is a structure in which light is incident from the counter electrode side. FIG.
On the transparent substrate 50a, a transparent conductive layer 10a is provided, a photosensitive layer 20 is provided via an undercoat layer 60, a charge transport layer 30 and a transparent counter electrode conductive layer 40a are further provided, and the transparent substrate 50a is disposed thereon. There is a structure in which light enters from both sides. FIG. 9 shows that a conductive layer 10 is provided on a support substrate 50, a photosensitive layer 20 is provided via an undercoat layer 60, a solid charge transport layer 30 is further provided, and a partial counter electrode conductive layer 40 or a metal lead 11 is provided thereon. And has a structure in which light is incident from the counter electrode side.

[2] Photocell The photocell of the present invention has the above-mentioned photoelectric conversion element processed by 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. It is preferable that the side surface of the photovoltaic cell is 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 a 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 structure of the above-described photoelectric conversion device. Further, the dye-sensitized solar cell of the present invention can have a module structure basically similar to that of 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, a superstrate type, a substrate type, a module structure called a potting type, a substrate-integrated module structure used in an amorphous silicon solar cell and the like are known, and the dye-sensitized solar cell of the present invention is also used. These module structures can be appropriately selected depending on the use location and environment. Specifically, it is preferable to adopt the structure and embodiment described in JP-A-2000-268892.

[0096]

The present invention will be specifically described below with reference to examples. Example 1 (1) Preparation of Comparative Titanium Oxide Particle Dispersion To a liquid obtained by mixing 360 g of water and 12 g of acetic acid was added 62 g of tetraisopropyl orthotitanate (manufactured by Wako Pure Chemical Industries) at 25.degree. Add 6 ml of concentrated nitric acid and add 80
Stirred at 4 ° C. for 4 hours. Transfer 50 ml of the obtained titanium oxide sol to a stainless steel autoclave,
Stirred at 40 ° C. for 16 hours. The obtained titanium oxide dispersion was centrifuged at 15,000 rpm for 30 minutes. The supernatant was removed by decantation, and 0.3 g of polyethylene glycol (molecular weight: 20,000, manufactured by Wako Pure Chemical Industries) and 11 g of water were added and dissolved. Further, 1 g of ethanol and 0.4 ml of concentrated nitric acid were added to obtain a titanium oxide dispersion (A) for comparison. The content of titanium oxide in (A) was 15%, and the average particle size determined by X-ray diffraction was 16 nm.

(2) Preparation of Titanium Oxide Dispersion of the Present Invention First, a titanium oxide dispersion B-1 was prepared in the same manner as in the above (1) except that a urea compound was added to 360 g of water as shown in Table 1. ~ B-5 was prepared. Titanium oxide content,
The particle size was the same as the comparative dispersion.

(3) Preparation of Titanium Oxide Dispersion of the Present Invention Containing Large Particles The titanium oxide dispersion prepared by the same method as in the above B-1 to B-5 was anatase-type TiO ₂ (Kanto Chemical Co., Ltd.) B:
0.4 g of an average particle diameter of 100 nm to 300 nm), 2.5 ml of water, and 0.06 g of polyethylene glycol (molecular weight: 20,000, manufactured by Wako Pure Chemical Industries) were added. This liquid was stirred at 45 ° C. for 3 hours and mixed well to obtain coating liquids C-1 to C-5. C-
The mixing ratio of the titanium oxide particles of the present invention and titanium oxide particles C in 1 to C-5 is 5: 1 by weight.

[0099]

[Table 1]

2. Preparation of dye-adsorbed titanium oxide electrode Transparent conductive glass coated with fluorine-doped tin oxide (Nippon Sheet Glass, surface resistance is about 10Ω / cm ² )
Were prepared, and the coating solution (A), B-1 to 5, and C-1 to 5 obtained above were applied to the conductive surface side thereof using a doctor blade. After drying at 25 ° C for 30 minutes, an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific)
At 450 ° C. for 30 minutes. The amount of application per unit area was calculated from the weight change before and after application and firing. After baking, it was immersed in an adsorption solution containing 0.3 mmol / l of the following dye (A) for 16 hours. The adsorption temperature is 25 ° C., and the solvent of the adsorption solution is a 1: 1: 2 (volume ratio) mixture of ethanol, t-butanol, and acetonitrile. The titanium oxide electrode on which the dye had been dyed was sequentially washed with ethanol and acetonitrile.

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The amount of the dye carried at this time was measured.
8 × 10 ⁻⁵ mo for a titanium oxide electrode composed of the coating solution (A)
l / cm ² , while the titanium oxide electrode composed of the coating solution (B-1) showed an increase in the amount of dye carried, which was 1.1 × 10 ⁻⁴ mol / cm ² .

3. Preparation of Photoelectric Conversion Element The dye-sensitized titanium oxide electrode substrate (2 cm × 2 cm) prepared as described above was overlaid with platinum-evaporated glass of the same size (see FIG. 1). Next, an electrolytic solution (1,3-dimethylimidazolium iodide 0.65 mol / l, iodine 0.05
Mol / liter, acetonitrile solution of t-butylpyridine 0.1 mol / l) was introduced into the titanium oxide electrode to obtain a photoelectric conversion element CA shown in Table 2,
CB-1 to CB-5 and CC-1 to CC-5 were obtained.

According to this embodiment, as shown in FIG.
A photoelectric conversion element in which a conductive glass 1 (a conductive agent layer 3 is provided on a glass 2), a titanium oxide electrode 4 on which a dye is adsorbed, an electrolytic solution 5, a platinum layer 6, and a glass 7 are sequentially laminated. Was created.

4. Measurement of Photoelectric Conversion Efficiency Simulated sunlight was generated by passing light of a 500 W xenon lamp (manufactured by Ushio) through a spectral filter (AM1.5 manufactured by Oriel). The intensity of this light in the vertical plane
It was 98 mW / cm ² . A silver paste is applied to the end of the conductive glass of the photoelectrochemical cell to form a negative electrode.
238). The current-voltage characteristics were measured while simulating sunlight vertically, and the conversion efficiency was determined. Table 3 shows the conversion efficiencies of the photoelectric conversion elements prepared in the examples.

[0106]

[Table 2]

A cell using the titanium oxide of the present invention (CB-
1 to CC-5) have a higher conversion efficiency than the comparison cell (CA). Above all, C corresponding to the use of a compound in which R ₃ and R _{4 in} formula (1) are hydrogen atoms is used.
B-1, CB-2, CB-4, and CB-5 have higher conversion efficiency than CB-3. In addition, a cell containing no large particles (C
B-1 to CB-5) and cells containing large particles (CC-1 to C-C)
In comparison with C-5), the latter has higher conversion efficiency.

[0108]

The titanium oxide fine particles produced by the method of the present invention, when used in a dye-sensitized photoelectric conversion element,
The conversion efficiency of the element is improved. Further, the dye-sensitized photoelectric conversion element and the photovoltaic cell of the present invention use titanium oxide fine particles produced by the method of the present invention, so that the conversion efficiency is improved.

[Brief description of the drawings]

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

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

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

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

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

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

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

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

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

FIG. 10 is a schematic sectional view illustrating a configuration of a photoelectric conversion element prepared in an example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 conductive layer 10 a transparent conductive layer 11 metal lead 20 photosensitive layer 21 semiconductor fine particle 22 dye 23 charge transport material 30 charge transport layer 40 counter electrode conductive layer 40 a transparent counter electrode conductive layer 50 substrate 50 a transparent substrate 60 undercoat layer

Claims (9)

[Claims] 1. A method for producing titanium oxide fine particles, comprising a step of heating a titanium oxide sol or a titanium oxide precursor in the presence of a urea compound represented by the following general formula (1). Embedded image In the formula, R ₁ , R ₂ , R ₃ , and R ₄ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a primary amino group, an alkylamino group, or a dialkylamino group. However, R ₁ , R ₂ , R ₃ , and R ₄ may be bonded to each other to form a ring. 2. The method for producing titanium oxide fine particles according to claim 2, wherein both R ₃ and R ₄ in the general formula (1) are hydrogen atoms. 3. The method for producing titanium oxide fine particles according to claim 1, wherein the molecular weight of the urea compound is 200 or less. 4. The method for producing titanium oxide fine particles according to claim 1, wherein the urea compound is water-soluble. 5. The step of heating is performed using a pressure vessel.
The method for producing titanium oxide fine particles according to any one of claims 1 to 4, wherein the method is performed at a temperature of 0 ° C to 300 ° C. 6. A photoelectric conversion element having at least a layer of a semiconductor fine particle film to which a dye is adsorbed and a conductive support, wherein the semiconductor fine particle film is produced by the method according to claim 1. A photoelectric conversion element characterized by using fine titanium oxide particles. 7. The semiconductor fine particle film layer having an average particle diameter of 100
7. The photoelectric conversion element according to claim 6, wherein titanium oxide fine particles having a diameter of from 400 to 400 nm are used in combination. 8. The photoelectric conversion device according to claim 6, wherein a ruthenium complex dye is used as the dye. 9. A photovoltaic cell using the light conversion element according to claim 6. Description: