JP2000235874A - Photoelectric conversion element and photo electrochemical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coloring matter sensitization photoelectric conversion element with a high photoelectric conversion efficiency, and a photoelectrochemical battery. SOLUTION: A coloring matter sensitization photoelectric conversion element comprises a conductive support, a layer containing semiconductor fine particles that absorbs a coloring matter applied onto the conductive support, a charge transfer layer and a counter electrode. The contents of sulfur and phosphorus in the semiconductor fine particles range from 0.0001 to 0.3 wt.% and from 0.00001 to 0.01 wt.%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoelectric conversion element using semiconductor fine particles sensitized by a dye. Further, the present invention relates to a photoelectrochemical cell using the same.

[0002]

2. Description of the Related Art Photovoltaic power generation is a single-crystal silicon solar cell,
Polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide have been put into practical use or subject to major research and development.
It is necessary to overcome problems such as a long energy payback time. On the other hand, many solar cells using an organic material intended to have a large area and a low price have been proposed so far, but have a problem that conversion efficiency is low and durability is poor. Under these circumstances, Nature (Vol.353, 737-
(Pp. 740, 1991) and U.S. Pat. No. 4,492,721 disclose a photoelectric conversion element and a solar cell using semiconductor fine particles sensitized by a dye, as well as materials and manufacturing techniques for producing the same. The proposed battery is a wet solar battery using a titanium dioxide porous thin film spectrally sensitized by a ruthenium complex as a working electrode. The first advantage of this method is that an inexpensive raw material such as titanium dioxide can be used, so that an inexpensive photoelectric conversion element can be provided. In this wavelength range can be converted into electricity. However, there is a problem that the conversion efficiency is still low for practical use as a solar cell, and the conversion efficiency must be further improved.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dye-sensitized photoelectric conversion element and a photoelectrochemical cell having excellent conversion efficiency.

[0004]

The object of the present invention has been attained by the following items which specify the present invention and preferred embodiments thereof. (1) In a conductive support, a dye-sensitized photoelectric conversion element having a dye-adsorbed layer containing a dye coated on the conductive support, a charge transfer layer, and a counter electrode, the semiconductor fine particles contain sulfur. Not less than 0.0001 wt% 0.3
wt% or less, and 0.00001 wt% of phosphorus
A photoelectric conversion element characterized by containing at least 0.01 wt% or less. (2) The semiconductor fine particles contain at least 0.005 wt% and no more than 0.2 wt% of sulfur, and at least 0.00000 of phosphorus.
The above (1) containing 1 wt% or more and 0.001 wt% or less.
Photoelectric conversion element. (3) The photoelectric conversion element according to the above (1) or (2), wherein the semiconductor fine particles are titanium oxide and / or niobium oxide. (4) The photoelectric conversion element according to the above (1) or (2), wherein the semiconductor fine particles are titanium oxide, and the anatase content is 80 to 100%. (5) The photoelectric conversion element according to any one of (1) to (4), wherein the semiconductor fine particles are semiconductor fine particles adsorbing at least one of a ruthenium complex dye, a phthalocyanine dye, and a polymethine dye. (6) The above (1), wherein the semiconductor fine particles are semiconductor fine particles adsorbing at least two kinds of dyes a) and b) below.
To (5). a) The wavelength range of 4
A dye having a maximum value of the incident light quantum yield of 50 nm or more and less than 600 nm; b) a wavelength range of 6
Dye having a maximum value of the incident light quantum yield of not less than 00 nm and not more than 850 nm (7) A photoelectrochemical cell using the photoelectric conversion element of any of the above (1) to (6).

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, the configurations and materials of the photoelectric conversion element and the photoelectrochemical cell of the present invention will be described in detail. In the present invention, the dye-sensitized photoelectric conversion element includes a conductive support, a semiconductor film (photosensitive layer) sensitized by a dye or the like provided on the conductive support, a charge transfer layer, and a counter electrode. A photoelectrochemical cell that can use this photoelectric conversion element for a battery that works in an external circuit is used. The photosensitive layer is designed according to the purpose, and may have a single-layer structure or a multilayer structure. Light incident on the photosensitive layer excites dyes and the like. The excited dye or the like has high-energy electrons, which are transferred from the dye or the like to the conduction band of the semiconductor fine particles and reach the conductive support by diffusion. At this time, molecules such as dyes are oxidized. In a photoelectrochemical cell, electrons on a conductive support return to an oxidant such as a dye via a counter electrode and a charge transfer layer while working in an external circuit, and the dye or the like is regenerated. The semiconductor film functions as a negative electrode of this battery. In the present invention, at the boundaries between the layers (for example, the boundary between the conductive layer and the photosensitive layer of the conductive support, the boundary between the photosensitive layer and the charge transfer layer, the boundary between the charge transfer layer and the counter electrode, etc.) They may be mutually diffused and mixed.

In the present invention, the semiconductor is a so-called photoreceptor, which plays a role of absorbing light to separate 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 the semiconductor is responsible for receiving and transmitting the electrons. As the semiconductor, besides a simple semiconductor such as silicon or germanium, a so-called compound semiconductor represented by a metal chalcogenide (for example, oxide, sulfide, selenide, or the like) or a compound having a perovskite structure can be used. . Preferably as a metal chalcogenide titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium,
Cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc,
Lead, silver, antimony, bismuth sulfide, cadmium,
Examples include lead selenide and cadmium telluride. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide and the like. Further, as the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, and potassium niobate are preferably exemplified. More preferably, as the semiconductor used in the present invention, specifically, Si, TiO ₂ , SnO ₂ , Fe
₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S ₃ , Cd
Se, CdTe, GaP, InP, GaAs, CuInS ₂ , and CuInSe ₂ are mentioned. More preferably _{TiO 2, ZnO, SnO 2,} Fe 2 O 3, WO
_{3, Nb 2 O 5, CdS} , PbS, CdSe, InP, GaAs, CuInS 2, CuI
a nSe _2, particularly preferably TiO ₂ or Nb ₂ O _5, and most preferably TiO _2.

The semiconductor used in the present invention may be single crystal or polycrystal. Although a single crystal is preferable as the conversion efficiency, a polycrystal is preferable in terms of manufacturing cost, securing of raw materials, energy payback time, and the like, and a fine particle semiconductor having a nanometer to micrometer size is particularly preferable. The particle diameter of these semiconductor fine particles is an average particle diameter using the diameter when the projected area is converted into a circle, and is 5% as a primary particle.
It is preferably from 200 to 200 nm, particularly preferably from 8 to 100 nm. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is 0.01 to 100 μm.
It is preferred that Further, two or more kinds of fine particles having different particle size distributions may be mixed and used, and in this case, the average size of the small particles is preferably 5 nm or less. In addition, semiconductor particles having a large particle size, for example, about 300 nm may be mixed for the purpose of improving the light capture rate by scattering incident light. These semiconductor fine particles preferably contain sulfur in the range of 0.0001% to 0.3% by weight, and more preferably 0.001% to 0.3% by weight.
The content is preferably 2 wt% or less, particularly preferably 0.005 wt% or more and 0.2 wt% or less. In addition, these semiconductor fine particles contain phosphorus in an amount of 0.00001 wt% or more.
It is preferably contained in an amount of 0.01 wt% or less, and more preferably 0.0
It is preferable to contain 0001 wt% or more and 0.001 wt% or less. If the content of sulfur or phosphorus is too large, it is easy to cause inhibition of dye adsorption, which is not preferable.
It is not preferable to reduce the amount more than necessary because the cost is increased in the production of titanium dioxide. These sulfur and phosphorus can be quantified by fluorescent X-ray analysis, ICP-AES or ICP-MS analysis.

The method for producing semiconductor fine particles is described in "Sol-Gel Method Science" by Agao Shofusha (1988) by Sakubana Sakuhana, "Thin Film Coating Technology by Sol-Gel Method" (1995) by Technical Information Association, etc. Tadao Sugimoto, "Synthesis of Monodisperse Particles and Size Morphology Control by New Synthetic Gel-Sol Method", Materia, Vol. 35, No. 9, 1012
The gel-sol method described on pages 10 to 1018 (1996) is preferred. Further, a method of producing an oxide by hydrolyzing a chloride in an oxyhydrogen flame at a high temperature developed by Degussa is also preferable. In the case of titanium oxide, the above sol-gel method,
The gel-sol method and the high-temperature hydrolysis method of chloride in an oxyhydrogen flame are all preferable. Further, the sulfuric acid method described in Manabu Kiyono's "Titanium oxide physical properties and applied technology" Gihodo Shuppan (1997).
The chlorine method can also be used. In the case of titanium oxide, among the sol-gel methods described above, in particular, Barb et al., "Journal of American Ceramic Society No. 80
Vol. 12, No. 3, pp. 3157 to 3171 (1
997) ”and the method described in“ Chemical Materials Vol. 10, No. 9, pages 2419 to 2425 ”by Burnside et al.

Titanium oxide mainly has two types of crystal forms, anatase type and rutile type. Depending on the production method and heat history, any type can be used, and often it is obtained as a mixture of both. The titanium oxide of the present invention preferably has a high anatase content, and specifically preferably has a content of 80% or more. Anatase has a shorter long-wavelength wavelength of light absorption than rutile, and has less damage to the photoelectric conversion element due to ultraviolet rays. The anatase content can be determined by an X-ray diffraction method, and can be determined from the ratio of diffraction peak intensities derived from anatase and rutile.

As the conductive support, use is made of a support such as a metal which has conductivity, or a glass or plastic support having a conductive layer (conductive agent layer) containing a conductive agent on the surface. Can be. In the latter case, a preferable conductive agent is a metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, or a conductive metal oxide (indium-tin composite oxide, tin oxide doped with fluorine). And the like). The conductive agent layer preferably has a thickness of 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 100 Ω / cm ² or less, and more preferably 40 Ω / cm ² or less. The lower limit is not particularly limited, but is usually about 0.1 Ω / cm ² . Preferably, the conductive support is substantially transparent. Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more,
70% or more is particularly preferred. As the transparent conductive support, glass or plastic coated with a conductive metal oxide is preferable. Among them, 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 particularly preferable. In addition, for a low-cost and flexible photoelectric conversion element or solar cell, a transparent polymer film provided with the above conductive layer is preferably used. For the transparent polymer film, tetraacetyl cellulose (TA
C), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndioctatic polysterene (SPS), polyphenylene sulfide (P
PS), polycarbonate (PC), polyacrylate (PAr), polysulfone (PSF), polyestersulfone (PES), polyetherimide (PE)
I), cyclic polyolefins, brominated phenoxy and the like. When a transparent conductive support is used, it is preferable that light be incident from the support side. In this case, the coating amount of the conductive metal oxide is preferably 0.01 to 100 g per 1 m ² of a glass or plastic support.

It is also preferable to use metal leads for the purpose of lowering the resistance of the transparent conductive substrate. 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. It is preferable that the metal lead is provided on a transparent substrate by vapor deposition, sputtering, or the like, and a transparent conductive layer made of tin oxide doped with fluorine or an ITO film is provided thereon. It is also preferable to provide a metal lead on the transparent conductive layer after providing the transparent conductive layer on a transparent substrate. The decrease in the amount of incident light due to the installation of metal leads is 1 to 10%, more preferably 1 to 5%.
It is.

Examples of the method of applying the semiconductor fine particles on the conductive support include a method of applying a dispersion or colloidal solution of the semiconductor fine particles on the conductive support, and the above-mentioned sol-gel method. In consideration of mass production of photoelectric conversion elements, liquid physical properties, and flexibility of a support, a wet film forming method is relatively advantageous. As a wet type film applying method, a coating method and a printing method are typical. In addition to the sol-gel method described above, a method of preparing a dispersion of semiconductor fine particles, a method of grinding in a mortar, a method of dispersing while grinding using a mill, or a method of precipitating as fine particles in a solvent when synthesizing a semiconductor. And a method of using it as it is. 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, a polymer, a surfactant, an acid, a chelating agent, or the like may be used as a dispersing aid, if necessary. As a coating method, a roller method as an application system,
Dip method, air knife method, blade method and the like as metering system, and wire bar method disclosed in JP-B-58-4589, U.S. Pat.
The slide hopper method, the extrusion method, the curtain method, and the like described in JP-A Nos. 294, 2761419, and 2761791 are preferable. As a general-purpose machine, a spin method or a spray method is also preferably used. As a wet printing method, intaglio, rubber printing, screen printing, and the like are conventionally preferable, including three major printing methods of letterpress, offset, and gravure. From the above methods, a preferable film-forming method is selected according to the liquid viscosity and the wet thickness.

The liquid viscosity is greatly affected by the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as a surfactant and a binder. High viscosity liquid (for example, 0.01 to 500 Po
In ise), an extrusion method or a casting method is preferable, and in 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. It should be noted that even in the case of applying a low-viscosity liquid by the extrusion method, the application is possible as long as the application amount is a certain amount. Screen printing is often used for applying a high-viscosity paste of semiconductor fine particles, and this method can also be used. As described above, a method of applying a wet film may be appropriately selected according to parameters such as the liquid viscosity of the coating liquid, the coating amount, the support, and the coating speed.

Further, the semiconductor fine particle layer need not be limited to a single layer. It is also possible to apply a multi-layer coating of dispersions having different particle diameters of fine particles.Also, it is possible to apply a multi-layer coating of different types of semiconductors or different coating compositions of binders and additives. Even when the film thickness is insufficient, the multilayer coating is effective. The extrusion method or slide hopper method is suitable for multi-layer coating. In the case of multi-layer coating, multiple layers may be coated at the same time,
It may be applied several times to several tens of times sequentially. Furthermore, a screen printing method can also be preferably used in the case of successive coating.

Generally, as the thickness of the layer containing semiconductor fine particles increases, the amount of dye carried per unit projected area increases, so that the light capture rate increases. However, the diffusion distance of generated electrons increases, so that the loss due to charge recombination also increases. growing. Therefore, the semiconductor fine particle-containing layer has a preferable thickness, but typically has a thickness of 0.1 to 100 μm. When used as a photoelectrochemical cell, the thickness is preferably 1 to 30 μm, and more preferably 2 to 25 μm. The coating amount of the semiconductor fine particles per 1 m ² of the support is 0.5 to 400.
g, more preferably 5 to 100 g. The semiconductor fine particles are preferably subjected to a heat treatment in order to electronically contact the particles after being applied to the conductive support, and to improve the strength of the coating film and the adhesion to the support. A preferred range of the heat treatment temperature is 40 ° C. or more and less than 700 ° C., and more preferably 100 ° C. or more and 600 ° C. or less. The heat treatment 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 the support is deteriorated. Further, it is preferable that the temperature is as low as possible from the viewpoint of cost. The lowering of the temperature can be achieved by the above-mentioned combination of small semiconductor particles having a size of 5 nm or less, heat treatment in the presence of a mineral acid, and the like. Further, after the heat treatment, for example, chemical plating or trichloride using an aqueous solution of titanium tetrachloride for the purpose of increasing the surface area of the semiconductor particles, increasing the purity in the vicinity of the semiconductor particles, and increasing the efficiency of electron injection from the dye into the semiconductor particles. Electrochemical plating using an aqueous titanium solution may be performed. The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For this reason, the surface area in the state where the semiconductor fine particle layer is coated on the support is preferably at least 10 times, more preferably at least 100 times the projected area. The upper limit is not particularly limited, but is usually about 1000 times.

The dye used in the present invention is preferably a metal complex dye, a phthalocyanine dye or a polymethine dye.
In the present invention, it is preferable to mix two or more types of dyes in order to widen the wavelength range of the photoelectric conversion as much as possible and increase the conversion efficiency. Dyes to be mixed and their proportions can be selected so as to match the intended wavelength range and intensity distribution of the light source. Such a dye preferably has an appropriate interlocking group for the surface of the semiconductor fine particles. Preferred linking groups include COOH groups, SO
₃ H group, a cyano group, -P (O) (OH) 2 group, -OP (O) (OH) 2 group, or, oxime, dioxime, hydroxyquinoline, a π conductivity, such as salicylate and α- ketoenolate Chelating groups. Among them, COOH group,
Particularly preferred are -P (O) (OH) ₂ groups and -OP (O) (OH) ₂ groups. 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.

The dye used in the present invention is a metal complex dye.
Are preferably ruthenium complex dyes, and
The dye represented by (I) is preferred. Formula (I) (A₁)_pRuB_aB_bB_c In the formula, p is 0 to 2, preferably 2. Ru is
Represents ruthenium. A ₁Is Cl, SCN, H_TwoO, B
r, I, CN, NCO and SeCN
It is a child. B_a, B_b, B_cAre each independently
It is an organic ligand selected from B-1 to B-8.

[0018]

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[0019]

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Here, _Ra is a hydrogen atom, a halogen atom,
A substituted or unsubstituted alkyl group having 1 to 12 carbon atoms (hereinafter referred to as C number), an aralkyl group substituted or unsubstituted with 7 to 12 carbon atoms, or a substituted or unsubstituted with 6 to 12 carbon atoms Represents an aryl group. The above alkyl group,
The alkyl portion of the aralkyl group may be linear or branched, and the aryl portion of the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). . Examples of the ruthenium complex dye used in the present invention include, for example, U.S. Pat.Nos. 4,492,721, 4,684,537 and 5,084.
And complex dyes described in JP-A Nos. 365, 5350644, 5463057, 5525440 and JP-A-7-249790. Preferred specific examples of the metal complex dye and the phthalocyanine dye used in the present invention are shown below, but the present invention is not limited thereto.

[0021]

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[0022]

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[0023]

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When the dye used in the present invention is a polymethine dye, a dye represented by the following formula (II) or (III) is preferred.

[0025]

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[0026] In the formula, each represents a hydrogen atom R _b and R _f, an alkyl group, an aryl group or a heterocyclic group,, R _c to R _e
Represents a hydrogen atom or a substituent. R _{b to} R _f may combine with each other to form a ring. X ₁₁ and X ₁₂ each represent nitrogen, oxygen, sulfur, selenium, or tellurium. m ₁₁ and m
₁₃ represents an integer of 0 to 2, and m ₁₂ represents an integer of 1 to 6. The compound represented by the formula (II) may have a counter ion depending on the charge of the whole molecule. The alkyl group in the above,
The aryl group and the heterocyclic group may have a substituent.
The alkyl group may be linear or branched, and the aryl group and the heterocyclic group may be monocyclic or polycyclic (condensed ring, ring assembly). The ring formed by R _{b to} R _f may have a substituent and may be a single ring or a condensed ring.

[0027]

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[0028] In the formula, Z _a represents a non-metallic atomic group necessary for forming a nitrogen-containing heterocyclic ring. R _g is an alkyl group or an aryl group. Q _a represents a methine group or a polymethine group necessary for compounds of the formula (III) to form a methine dye. X ₁₃ represents a charge balancing counter ion, and m ₁₄ represents an integer of 0 or more and 10 or less necessary for neutralizing the charge of the molecule. Nitrogen-containing heterocyclic ring formed by the above Z _a may have a substituent, it may be a condensed ring may be a single ring. Further, the alkyl group and the aryl group may have a substituent, the alkyl group may be linear or branched, and the aryl group may be monocyclic or polycyclic (condensed ring, Ring set). The dye represented by the formula (III) is preferably a dye represented by the following formulas (III-a) to (III-d).

[0029]

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In the formulas (III-a) to (III-d), R _a1 to
R _a5 , R _{b1 to} R _b4 , R _{c1 to} R _c3 , and R _{d1 to} R _d3 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group, and Y ₁₁ , Y ₁₂ , Y ₂₁ , Y _22, Y ₃₁ ~Y
₃₅ and Y ₄₁ to Y ₄₆ each independently represent oxygen, sulfur, selenium, tellurium, -CR _e1 R _e2 - represents a -, or -NR _e3. Y ₂₃ represents O ⁻ , S ⁻ , Se ⁻ , Te ⁻ , or NR _e4 ⁻ . R _{e1 to} R _e4 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. V _11, V _12,
V ₂₁ , V ₂₂ , V ₃₁ and V ₄₁ each independently represent a substituent, and m ₁₅ , m ₃₁ and m ₄₁ each independently represent an integer of 1 to 6. The alkyl group, aryl group and heterocyclic group in the above may have a substituent, the alkyl group may be linear or branched, and the aryl group and heterocyclic group may be monocyclic. Or polycyclic (condensed ring, ring assembly). Specific examples of such polymethine dyes are described in M. Okawar
a, T.Kitao, T.Hirasima, M.Matuoka by Organic Colorants
(Elsevier) and the like.

[0031]

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The formula (IV), Q _b represents an atomic group necessary to complete a nitrogen-containing heterocyclic ring of 5- or 6-membered, Q _b
May be condensed, and may have a substituent. Preferred examples of the heterocycle completed by Q _b include:
Benzothiazole nucleus, benzoxazole nucleus, benzoselenazole nucleus, benzotellurazole nucleus, 2-quinoline nucleus, 4-quinoline nucleus, benzimidazole nucleus, thiazoline nucleus, indolenine nucleus, oxadiazole nucleus, thiazole nucleus, imidazole nucleus Among them, benzothiazole nucleus, benzoxazole nucleus, benzimidazole nucleus, benzoselenazole nucleus, 2-quinoline nucleus, 4-quinoline nucleus and indolenine nucleus are more preferable, and benzothiazole nucleus and benzoxazole nucleus are particularly preferable. , 2-
They are a quinoline nucleus, a 4-quinoline nucleus and an indolenine nucleus. Examples of the substituent on the ring include carboxylic acid, phosphonic acid, sulfonic acid, halogen atom (F, Cl, Br, I), cyano,
Alkoxy group (methoxy, ethoxy, methoxyethoxy, etc.), aryloxy group (phenoxy, etc.), alkyl group (methyl, ethyl, cyclopropyl, cyclohexyl, trifluoromethyl, methoxyethyl, allyl, benzyl, etc.), alkylthio group (methylthio, etc.) , Ethylthio, etc.), alkenyl groups (vinyl, 1-propenyl, etc.), aryl groups and heterocyclic groups (phenyl, thienyl, toluyl, chlorophenyl, etc.).

Z _b represents an atomic group composed of atoms selected from a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom and a hydrogen atom, which is necessary for completing a 3- to 9-membered ring. The ring completed by Z is preferably a ring in which a skeleton is formed by 4 to 6 carbons, and is more preferably a ring represented by the following (A) to (E):
Most preferably, (a).

[0034]

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L ₁ , L ₂ , L ₃ , L ₄ and L ₅ each independently represent a methine group which may have a substituent.
As the substituent, a substituted or unsubstituted alkyl group (preferably having 1 to 12 carbon atoms, more preferably 1 to 7 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, 2-carboxy) Ethyl, benzyl, etc.), a substituted or unsubstituted aryl group (preferably having 6 to 10 carbon atoms, more preferably 6 to 8 carbon atoms, for example, phenyl, toluyl, chlorophenyl, o-carboxyphenyl), a heterocyclic ring Groups (eg, pyridyl, thienyl, furanyl, pyridyl, barbituric acid), halogen atoms (eg, chlorine, bromine), alkoxy groups (eg, methoxy,
Ethoxy), an amino group (preferably having 1 to 12, more preferably 6 to 12 carbon atoms, such as diphenylamino, methylphenylamino,
Acetylpiperazin-1-yl), oxo group and the like. These substituents on the methine group may be linked to each other to form a ring such as a cyclopentene ring, a cyclohexene ring, a squarylium ring, or a ring with an auxochrome.

M ₅₁ represents an integer of 0 to 4, preferably 0 to 3. m ₅₂ is 0 or 1.

R _h represents a substituent. The substituent is preferably an aromatic group which may have a substituent or an aliphatic group which may have a substituent. The number of carbon atoms of the aromatic group is preferably 1 to 16, more preferably 5 to 16. Or 6
It is. The aliphatic group preferably has 1 to 1 carbon atoms.
0, more preferably 1 to 6. Examples of the unsubstituted aliphatic group and aromatic group include a methyl group, an ethyl group, n
-Propyl group, n-butyl group, phenyl group, naphthyl group and the like.

W ₁ represents a counter ion when a counter ion is required to neutralize the charge. Whether a dye is a cation, an anion, or has a net ionic charge depends on its auxochrome and substituents. When the substituent has a dissociable group, it may dissociate and have a negative charge,
Also in this case, the charge of the whole molecule is neutralized by W ₁ . Typical cations are inorganic or organic ammonium ions (eg, tetraalkylammonium ions, pyridinium ions) and alkali metal ions,
On the other hand, the anion may specifically be either an inorganic anion or an organic anion, such as a halogen anion (for example, a fluoride ion, a chloride ion, a bromide ion, or an iodide ion), or a substituted aryl. Sulfonate ion (for example, p-toluenesulfonate ion, p-
Chlorobenzenesulfonic acid ion), aryldisulfonic acid ion (for example, 1,3-benzenedisulfonic acid ion, 1,5-naphthalenedisulfonic acid ion, 2,6
-Naphthalenedisulfonic acid ion), alkyl sulfate ion (for example, methyl sulfate ion), sulfate ion, thiocyanate ion, perchlorate ion, tetrafluoroborate ion, picrate ion, acetate ion, trifluoromethanesulfonic acid ion. Can be Further, an ionic polymer or another dye having a charge opposite to that of the dye may be used as the charge-balancing counter ion, or a metal complex ion (for example, bisbenzene-1,2-dithiolatonic nickel) may be used.
(III)) is also possible.

[0039]

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In the formula (V), D represents an aromatic group having at least four or more functional groups, and X ₁ and X ₂ each independently represent a sulfur atom, a selenium atom, CR _k R _l or CR _m = CR _n . Here, R _{k to} R _n are each a hydrogen atom or an alkyl group. R _i and R _j are each an aliphatic group or an aromatic group, and P ₁ and P ₂ each independently represent a group of nonmetallic atoms necessary for forming a polymethine dye. W ₂ represents a counter ion when a counter ion is required to neutralize the charge. Formula (V) will be described in more detail. Equation (V)
In the formula, D represents at least a tetrafunctional or higher aromatic group. Examples of such aromatic groups include benzene, naphthalene, anthracene, and phenanthrene as aromatic hydrocarbons from which these groups are derived, and aromatic heterocycles as anthraquinone, carbazole, pyridine, quinoline, and the like. Examples thereof include thiophene, furan, xanthene, and thianthrene, and these may have a substituent other than the connecting portion. The aromatic group represented by D is preferably a derivative of an aromatic hydrocarbon, and more preferably a derivative of benzene or naphthalene.

[0041] X _1, X ₂ are each preferably a sulfur atom or a CR _k R _l, and most preferably from CR _k R _l.

P₁, P_TwoAre independently polymethine colors
Represents the group of non-metallic atoms necessary to form element. P₁, P
_TwoCan form any methine dye
There is preferably a cyanine dye, a merocyanine dye,
Rhodacyanine dye, trinuclear merocyanine dye, allopolar
-Dyes, hemicyanine dyes, styryl dyes, etc.
It is. At this time, methine which forms the dye
Substituents on the chain form squarium and croconium rings
Also includes those that have done. For more information on these dyes
Is a `` heterocycling '' by FM Harmer.
Click Compounds-Cyanine Soybean & Re
Heterocyclic Compounds-Cya
nine Dyes and Related Compounds), John Willi
-John Wiley & Sons
Talk, London, 1964, D.M.
ー (D.M.Sturmer), Heterocyclic Compound
Zoo Special Topics in Heterocyclic
K Chemistry (Heterocyclic Compounds-Special to
pics in heterocyclic chemistry), Chapter 18, Chapter 1
Section 4, 482 to 515, etc. Shi
Formulas of anine dyes, merocyanine dyes, rhodacyanine dyes
Is described in U.S. Pat. No. 5,340,694 at pages 21 and 22.
(XI), (XII) and (XIII) are preferred
No. Also, P ₁And P_TwoPolymethi formed by
At least one of the methine chains
Those having an allylium ring are preferable, and those having both
Is more preferred.

R _i and R _j are an aromatic group or an aliphatic group, and these may have a substituent. The number of carbon atoms of the aromatic group is preferably 5 to 16, more preferably 5 to 6. The number of carbon atoms in the aliphatic group is preferably 1 to 10, more preferably 1 to 6. Examples of the unsubstituted aliphatic group and aromatic group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a phenyl group, and a naphthyl group.

In the formula (V), it is preferred that at least one of R _i , R _j , P ₁ and P ₂ has an acidic group. Here, the acidic group is a substituent having a dissociable proton, for example, carboxylic acid, phosphonic acid, sulfonic acid,
Boric acid and the like are preferable, and carboxylic acid is preferable.
Further, such an acidic group may be in a form of dissociating by releasing a proton.

W ₂ has the same meaning as W _{1 in the} formula (IV).

Preferred specific examples of the polymethine dyes represented by formulas (II) to (V) are shown below, but the present invention is not limited thereto.

[0047]

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[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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The compounds represented by the formulas (II) and (III) are described in FM Harmer, "Heterocyclic Compounds-Cyan
ine Dyes and Related Compounds), John Wiley & Sons, Inc.- New York, London, 1964, DMSturmer, Complex Cyclic Compounds Special Topics. In complex cyclic
Chemistry (Heterocyclic Compounds-Special topics
in heterocyclic chemistry) ", Chapter 18, Section 14,
482-515, John Wiley & Sons, Inc.-New York, London, 1977, "Rodd's Chemistry of Carbon Co.
mpounds) "2nd.Ed.vol.IV, partB, 1977, No.15
Chapters, 369-422, Elsevier Science
Public Company, Inc. (Elsevier Science Pu
blishing Company Inc.), New York, UK Patent No. 1,077,611, and the like. The synthesis of the compound represented by the formula (IV) used in the present invention is described in Dyes and Pigments Vol. 21, 227 to 23.
This can be done by referring to the description of documents such as four pages. The synthesis of the compound represented by the formula (V) is described in Ukrainskii Khimich
eskii Zhurnal Vol. 40, No. 3, pp. 253-258, Dyes and
Pigments, Vol. 21, pp. 227 to 234 and the descriptions of the documents cited in these documents can be referred to.

In the present invention, two or more kinds of dyes to be adsorbed can be used in combination to increase the photoelectric conversion wavelength range as much as possible and to increase the photoelectric conversion efficiency. When two types of dyes are adsorbed on the photoelectric conversion element, when each type of the dyes is independently adsorbed on the semiconductor fine particle-containing layer, one type of dye is 300
It is preferable to use a dye having a maximum value of the incident light quantum yield of at least 600 nm and less than 600 nm, and one kind of dye having a maximum value of the incident light quantum yield of at least 600 nm and not more than 850 nm. Is 450n
A dye having a maximum value of the incident light quantum yield in the range of m to less than 600 nm and one kind of dye having a maximum value of the incident light quantum yield in the range of 600 nm to 850 nm is used. Here, the incident light quantum yield (abbreviation: IPCE) is a parameter indicating the photoelectric conversion ability, and is obtained by dividing the number of photoelectrons generated when light of a certain wavelength (or a certain wavelength range) is irradiated by the number of irradiated photons. In more detail, (the number of photons absorbed by the dye) × (the quantum yield of electron injection from the dye into the semiconductor) / (the number of irradiated photons) × 100, and the unit is%. 300 nm or more as dye 60
The dye having a maximum value of the incident light quantum yield of less than 0 nm is preferably a ruthenium complex represented by the formula (I) or a polymethine dye represented by the formula (II), (III), (IV) or (V). And more preferably a ruthenium complex or a polymethine dye having a partial structure derived from squaric acid represented by formula (III-b) or (IV). 600n
The dye having the maximum value of the incident light quantum yield in the range from m to 850 nm is a ruthenium complex represented by the formula (I) or a polymethine dye represented by the formula (II), (III), (IV) or (V). It is more preferable that the formula (III)
-B) a polymethine dye of formula (IV) or (V)
Is a polymethine dye having a partial structure derived from squaric acid among the polymethine dyes represented by

When three or more dyes to be adsorbed are used, when each dye alone is adsorbed to the semiconductor fine particle containing layer, at least one of the dyes has a maximum value of the incident light quantum yield of 300 nm or more and less than 550 nm, and at least One kind of dye has a maximum value of incident light quantum yield of 550 nm or more and less than 700 nm, and at least one kind of dye
It is preferable to use a dye having a maximum value of incident light quantum yield of 0 nm or more and 850 nm or less, more preferably at least one kind of dye has a maximum value of incident light quantum yield of 400 nm or more and less than 550 nm, and One type of dye has a maximum value of the incident light quantum yield at 550 nm or more and less than 700 nm, and at least one type of dye has a maximum value of the incident light quantum yield of 700 nm or more and 850 nm or less. As the dye, a dye having a maximum value of the incident light quantum yield of 300 nm or more and less than 550 nm is preferably a ruthenium complex represented by the formula (I) or a compound represented by the formula (II), (III), (IV) or (V). And more preferably a ruthenium complex or a polymethine dye represented by the formula (III-b) or the polymethine dye represented by the formula (IV), having a partial structure derived from squaric acid It is a polymethine dye. 550nm or more 700
The dye having the maximum value of the incident light quantum yield of less than nm is a ruthenium complex represented by the formula (I) or a compound represented by the formula (II) or (II)
It is preferably a polymethine dye represented by I), (IV) or (V), more preferably a ruthenium complex or a polymethine dye represented by formula (III-b) or a formula (IV)
Is a polymethine dye having a partial structure derived from squaric acid among the polymethine dyes represented by The dye having the maximum value of the incident light quantum yield at 700 nm or more and 850 nm or less is the ruthenium complex represented by the formula (I) or the formula (I)
It is preferably a polymethine dye represented by (I), (III), (IV) or (V), more preferably a formula (III-
Among the polymethine dyes shown in b) or the polymethine dyes represented by the formulas (IV) or (V), the polymethine dyes have a partial structure derived from squaric acid.

In a photoelectric conversion element having two or more kinds of dyes adsorbed thereon, the wavelength dependence of the incident light quantum yield of the element is measured. (Peak) is observed, and the ratio of the maximum maximum value to the minimum maximum value (minimum maximum value / maximum maximum value) is preferably 0.05 or more and 1 or less, more preferably 0.1 or less. It is 1 or more and 1 or less, particularly preferably 0.3 or more and 1 or less. Also, the maximum value of the incident light quantum yield of the photoelectric conversion element adsorbing two or more dyes is preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more.

In adsorbing the dye onto the semiconductor, all the dyes to be used may be dissolved and used as a single adsorbent, or the adsorbents may be prepared individually and adsorbed sequentially. When three or more types of dyes are used, a combination of two types of dyes adsorbed and then a type of dye may be adsorbed can be used.

In order to adsorb a dye to semiconductor fine particles, a method of immersing well-dried semiconductor fine particles in a solution of a dye or the like for several hours is general. The dye may be adsorbed at room temperature or may be heated and refluxed as described in JP-A-7-249790. The dye may be adsorbed before or after coating the semiconductor fine particles on the conductive support, or the semiconductor fine particles and the dye may be simultaneously coated and adsorbed. Is preferably adsorbed on the semiconductor fine particle film. The method of adsorbing the dye on the semiconductor fine particle film coated on the conductive support is performed by immersing the dried semiconductor fine particle film in the dye solution or by applying the dye solution onto the semiconductor fine particle film and adsorbing the dye solution. be able to.
In the former case, a dipping method, a dipping method, a roller method, an air knife method, or the like can be used. As the latter coating method, a wire bar method, a slide hopper method, an extrusion method,
There are a curtain method, a spin method, and a spray method, and examples of the printing method include letterpress, offset, gravure, and screen printing.

As in the case of the formation of the semiconductor fine particle layer, the liquid viscosity can be determined by various printing methods besides the extrusion method for a high-viscosity liquid (for example, 0.01 to 500 Poise) and the low-viscosity liquid (for example, 0.1 Poise or less). A slide hopper method, a wire bar method, or a spin method is suitable, and a uniform film can be obtained.

As described above, the viscosity of the dye coating solution, the coating amount,
An application method may be appropriately selected according to parameters such as a support and a coating speed. The time required for dye adsorption after coating should be as short as possible in consideration of mass production.

Since the presence of unadsorbed dye causes disturbance of device performance, it is preferable to remove the dye by washing immediately after adsorption. It is preferable to perform cleaning with a polar solvent such as acetonitrile and an organic solvent such as an alcohol solvent using a wet cleaning tank. In order to increase the amount of the adsorbed dye, it is preferable to perform the heat treatment before the adsorption. After the heat treatment, in order to avoid adsorption of water on the surface of the semiconductor fine particles, it is also preferable to quickly adsorb the dye at 40 to 80 ° C. without returning to normal temperature.

The total amount of the dye used is preferably 0.01 to 100 mmol per 1 m ² of the support. The amount of the dye adsorbed on the semiconductor fine particles is preferably 0.01 to 1 mmol per 1 g of the semiconductor fine particles. With such an amount of the dye, a sensitizing effect in the semiconductor can be sufficiently obtained. On the other hand, if the amount of the dye is 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.

A colorless compound may be co-adsorbed for the purpose of reducing the interaction between dyes such as association. Examples of the hydrophobic compound to be co-adsorbed include steroid compounds having a carboxyl group (for example, cholic acid). Further, for the purpose of promoting the removal of excess dye, the surface of the semiconductor fine particles may be treated with an amine after the dye is adsorbed. Preferred amines are pyridine, 4-tert
-Butylpyridine, polyvinylpyridine and the like. When these are liquids, they may be used as they are or may be used by dissolving them in an organic solvent.

Hereinafter, the charge transfer layer and the counter electrode will be described in detail. The charge transfer layer is a layer having a function of replenishing the oxidized dye with electrons. Examples of typical charge transfer layers that can be used in the present invention include a liquid (electrolytic solution) in which a redox couple is dissolved in an organic solvent, and a so-called gel in which a liquid in which a redox couple is dissolved in an organic solvent is impregnated in a polymer matrix. Examples include an electrolyte and a molten salt containing a redox couple.
Further, a solid electrolyte or a hole transporting material can be used.

The electrolyte used in the present invention comprises an electrolyte, a solvent,
And additives. The electrolyte of the present invention comprises a combination of I ₂ and iodide (for example, metal iodide such as LiI, NaI, KI, CsI, and CaI ₂ , or tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide and the like). Iodine salts of secondary ammonium compounds), B
Combination of r ₂ and bromide (bromide is LiBr,
NaBr, KBr, CsBr, metal bromide such as CaBr _2, or tetraalkylammonium bromide, pyridinium bromine salts of di-bromide and quaternary ammonium compounds). In addition, ferrocyanate - ferricyanide or ferrocene - ferricinium ion such as Metal complex, sodium polysulfide, sulfur compounds such as alkylthiol-alkyldisulfide, viologen dyes, hydroquinone-quinone, and the like.
I ₂ and LiI or pyridinium iodide Among these, an electrolyte that combines iodine salt of imidazolium iodide and quaternary ammonium compounds are preferred in the present invention.
The above-mentioned electrolytes may be used as a mixture. The electrolyte is EP-718288, WO95 / 18456, J. Electrochem. Soc
Vol.143, No.10, 3099 (1996), Inorg.
A salt in a molten state at room temperature (molten salt) described in 35, 1168-1178 can also be used. When a molten salt is used as an electrolyte, a solvent need not be used.

The preferred electrolyte concentration is 0.1M or more and 15M or less, more preferably 0.2M or more and 10M or less. When iodine is added to the electrolyte, a preferable concentration of iodine is 0.01 M or more and 0.5 M or less.

The solvent used for the electrolyte in the present invention is a compound capable of exhibiting excellent ionic conductivity by increasing the ionic mobility or increasing the effective carrier concentration with a low viscosity. Desirably. Examples of such a solvent include carbonate compounds such as ethylene carbonate (EC) and propylene carbonate (PC), heterocyclic compounds such as 3-methyl-2-oxazolidinone (NMO), dioxane, diethyl ether, and dimethoxyethane (DME). Ether compounds, chain ethers such as ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether, methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl Ethers, alcohols such as polypropylene glycol monoalkyl ether, ethylene glycol Polyhydric alcohols such as propylene glycol, polyethylene glycol, polypropylene glycol, and glycerin; nitrile compounds such as acetonitrile (AN), glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile; dimethyl sulfoxide (DMSO); An aprotic polar substance, water, or the like can be used.

Further, according to the present invention, J. Am. Ceram. Soc., 8
0 (12) Basic compounds such as ter-butylpyridine, 2-picoline and 2,6-lutidine as described in 3157-3171 (1997) can also be added. A preferred concentration range when a basic compound is added is 0.05M or more and 2M or less.

In the present invention, the electrolyte can be gelled (solidified) by a method such as addition of a polymer, addition of an oil gelling agent, polymerization containing a polyfunctional monomer, or crosslinking reaction of a polymer. In the case of gelation by adding a polymer, "Polymer Electrolyte Reviews-1 and 2" (J.
R.MacCallum and CA Vincent co-edited, ELSEVIER APPLIEDS
CIENCE), and polyacrylonitrile and polyvinylidene fluoride can be particularly preferably used. When gelling by adding an oil gelling agent, use J. Chem Soc. Japan, Ind. C
hem. Soc., 46779 (1943), J. Am. Chem. Soc., 111,5542.
(1989), J. Chem. Soc., Chem. Commun., 1993, 390, An
gew. Chem. Int. Ed. Engl., 35, 1949 (1996), Chem. Le
tt., 1996, 885, J. Chm. Soc., Chem. Commun., 1997,
Although the compounds described in 545 can be used, preferred compounds are compounds having an amide structure in the molecular structure.

When the gel electrolyte is formed by polymerization of a polyfunctional monomer, a solution is prepared from the polyfunctional monomer, a polymerization initiator, an electrolyte and a solvent, and the solution is prepared by a method such as a casting method, a coating method, a dipping method, and an impregnation method. A method in which a sol-like electrolyte layer is formed on an electrode supporting a dye and then gelled by radical polymerization is preferable. The polyfunctional monomer is preferably a compound having two or more ethylenically unsaturated groups, for example, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate. Ethylene glycol diacrylate, triethylene glycol dimethacrylate,
Preferred examples include pentaerythritol triacrylate and trimethylolpropane triacrylate. The monomers constituting the gel electrolyte may contain a monofunctional monomer in addition thereto, and may include acrylic acid or α-
Esters or amides derived from alkylacrylic acids (such as methacrylic acid) (for example, N-
iso-propylacrylamide, acrylamide, 2-
Acrylamide-2-methylpropanesulfonic acid, acrylamidopropyltrimethylammonium chloride, methyl acrylate, hydroxyethyl acrylate, n-propyl acrylate, n-butyl acrylate, 2-methoxyethyl acrylate, cyclohexyl acrylate, etc.), vinyl esters (for example, vinyl acetate) ), Esters derived from maleic acid or fumaric acid (eg, dimethyl maleate, dibutyl maleate, diethyl fumarate, etc.), maleic acid, fumaric acid,
p-styrenesulfonic acid sodium salt, acrylonitrile, methacrylonitrile, dienes (eg, butadiene, cyclopentadiene, isoprene), aromatic vinyl compound (eg, styrene, p-chlorostyrene, sodium styrenesulfonate), nitrogen-containing heterocycle A vinyl compound having a quaternary ammonium salt,
N-vinylformamide, N-vinyl-N-methylformamide, vinyl sulfonic acid, sodium vinyl sulfonate, vinylidene fluoride, vinylidene chloride, vinyl alkyl ethers (eg, methyl vinyl ether), ethylene, propylene, 1-butene, isobutene, N-phenylmaleimide and the like can be preferably used. The preferred weight composition range of the polyfunctional monomer in the total amount of the monomers is preferably from 0.5% by weight to 70% by weight, more preferably from 1.0% by weight to 50% by weight.
% By weight or less.

The above-mentioned monomers are generally described in Takatsu Otsu and Masayoshi Kinoshita: Experimental Methods for Polymer Synthesis (Chemical Doujin) and Takatsu Otsu: Lecture Polymerization Reaction Theory 1 Radical Polymerization (I) (Chemical Doujin) It can be polymerized by radical polymerization which is a simple polymer synthesis method. The monomer for gel electrolyte that can be used in the present invention can be radically polymerized by heating, light, electron beam, or electrochemically, but it is particularly preferable to radically polymerize by heating. The polymerization initiator preferably used when the crosslinked polymer is formed by heating,
For example, 2,2'-azobisisobutyronitrile, 2,2
2'-azobis (2,4-dimethylvaleronitrile),
Azo initiators such as dimethyl 2,2'-azobis (2-methylpropionate) (dimethyl 2,2'-azobisisobutyrate); and peroxide initiators such as benzoyl peroxide. The preferable addition amount of the polymerization initiator is 0.01% by weight or more and 20% by weight or less, more preferably 0.1% by weight or more and 10% by weight based on the total amount of the monomers.
It is as follows. The weight composition range of the monomers in the gel electrolyte is preferably from 0.5% by weight to 70% by weight, more preferably from 1.0% by weight to 50% by weight. When the electrolyte is gelled by a crosslinking reaction of the polymer, it is preferable to use a polymer containing a crosslinkable reactive group and a crosslinking agent together. In this case, a preferable crosslinkable reactive group is 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, etc.), and a preferable crosslinking agent. Is a bifunctional or higher functional reagent capable of electrophilic reaction with a nitrogen atom (for example,
Alkyl halide, aralkyl halide, sulfonic ester, acid anhydride, acid chloride, isocyanate, etc.).

In the present invention, an organic or inorganic hole transporting material or a combination thereof can be used in place of the electrolyte. Organic hole transport materials applicable to the present invention include N, N'-diphenyl-N, N'-bis (4-methoxyphenyl)-(1,1'-biphenyl) -4,4'-diamine
(J. Hagen et al., Synthetic Metal 089 (1997) 215-22
0), 2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamine) 9,9'-spirobifluorene (Nature, Vol. 395,
8 Oct. 1998, p583-585 and WO97 / 10617), aromatic diamine compounds linked to tertiary aromatic amine units of 1,1-bis {4- (di-P-tolylamino) phenyl} cyclohexane No. 59-194393), two or more fused aromatic rings containing two or more tertiary amines represented by 4,4-bis [(N-1-naphthyl) -N-phenylamino] biphenyl Aromatic amine substituted with a nitrogen atom
-234681), an aromatic triamine having a starburst structure as a derivative of triphenylbenzene (US Pat. No. 4,923,774, JP-A-4-308688), N, N'-diphenyl-N, N Aromatic diamines such as' -bis (3-methylphenyl)-(1,1'-biphenyl) -4,4'-diamine (US Pat. No. 4,764,625), α, α, α ′, α '-Tetramethyl-α, α'-bis (4-di-p-tolylaminophenyl) -p-
Xylene (JP-A-3-269084), p-phenylenediamine derivative, triphenylamine derivative which is sterically asymmetric as a whole molecule (JP-A-4-129271), and a pyrenyl group substituted with a plurality of aromatic diamino groups (JP-A-4-175395) and an aromatic diamine in which a tertiary aromatic amine unit is linked by an ethylene group (JP-A-4-264189).
JP-A-5-25473, an aromatic diamine having a styryl structure (JP-A-4-290851), a benzylphenyl compound (JP-A-4-364153), and a tertiary amine linked by a fluorene group (JP-A-5-25473). Japanese Patent Application Laid-Open No. 5-197455), triamine compounds (Japanese Patent Application Laid-Open No. 5-239455), pisdipyridylaminobiphenyl (Japanese Patent Application Laid-Open No. 5-320634), N, N, N-triphenylamine derivatives (Japanese Patent Application Laid-Open No. 6-1972) Aromatic diamine having a phenoxazine structure (Japanese Patent Application No. 5-29072)
No. 8), diaminophenylphenanthridine derivatives (Japanese Patent Application No. 6-45669), aromatic amines such as α-octylthiophene and α, ω-dihexyl-α-octylthiophene (Adv. Mater. 1997) , 9, N0.7, p557), hexadodecyldodecithiophene (Angew. Chem. Int. Ed. En.
gl.1995, 34, No.3, p303-307), 2,8-dihexylanthra [2,3-b: 6,7-b '] dithiophene (JACS, Vol120, N0.
Oligothiophene compounds such as polypyrrole (K. Murakoshi et al., Chem. Lett. 1997, p47).
1), "Handbook of Organic Conductive Molecules an
d 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, polyaniline and its derivatives, polytoluidine and its conductive polymers are preferably used. can do. Nature, Vol. 395, 8
As described in Oct. 1998, p583-585, a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate is added to control the dopant level, or an oxide semiconductor is used. A salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added for controlling the potential of the surface (compensating the space charge layer). Organic hole transport materials include vacuum deposition, casting, coating, spin coating, dipping, electrolytic polymerization,
It can be introduced into the inside of the electrode by a method such as photoelectrolytic polymerization. When a hole transport material is used in place of the electrolyte, Electorochim. Acta 40, 643-6
52 (1995), it is preferable to apply a thin layer of titanium dioxide as an undercoat layer using a technique such as spray pyrolysis.

When an inorganic solid compound is used instead of the electrolyte, copper iodide (p-CuI) (J. Phys. D: Appl. Phys. 31
(1998) 1492-1496), copper thiocyanate (Thin Solid Film)
s 261 (1995) 307-310, J. Appl. Phys. 80 (8), 15 Octobe
r 1996, p4749-4754, Chem. Mater. 1998, 10, 1501-150.
9, Semicond. Sci. Technol. 10, 1689-1693) can be introduced into the inside of the electrode by a method such as a casting method, a coating method, a spin coating method, a dipping method, and an electrolytic plating method.

There are two methods for forming the charge transfer layer. One is a method in which a counter electrode is first adhered to a semiconductor fine particle-containing layer carrying a sensitizing dye, and a liquid charge transfer layer is sandwiched between the counter electrodes. Another one
The first is a method in which the charge transfer layer is directly provided on the semiconductor fine particle-containing layer, and the counter electrode is subsequently provided. As the method of sandwiching the charge transfer layer in the former case, a normal pressure process utilizing a capillary phenomenon due to immersion or the like and a vacuum process of replacing the gas phase with a liquid phase at a pressure lower than normal pressure can be used. In the latter case, the wet charge transfer layer is provided with a counter electrode in an undried state, and measures are taken to prevent liquid leakage at the edge. In the case of a gel electrolyte, there is also a method of solidifying by a method such as polymerization by coating in a wet manner, in which case drying,
A counter electrode may be provided after immobilization. As a method of applying a wet organic hole transport material or a gel electrolyte in addition to the electrolytic solution, as in the case of providing the semiconductor fine particle-containing layer and the dye,
An immersion method, a roller method, a dipping method, an air knife method, an extrusion method, a slide hopper method, a wire bar method, a spin method, a spray method, a casting method, various printing methods, and the like can be considered. In the case of a solid electrolyte or a solid hole transport material, the charge transfer 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.

In consideration of mass production, in the case of an electrolyte that cannot be solidified or a wet hole transport material, it is possible to cope by sealing the edge portion immediately after coating, but it is possible to solidify. In the case of a hole transport material, it is more preferable to solidify the film by a method such as photopolymerization or thermal radical polymerization after forming the hole transport layer by wet application. As described above, the film application method may be appropriately selected depending on the physical properties of the liquid and the process conditions.

The water content in the charge transfer layer was 10,
2,000 ppm or less, more preferably 2,0 ppm
It is at most 00 ppm, particularly preferably at most 100 ppm.

The counter electrode functions as a positive electrode of the photoelectrochemical cell when the photoelectric conversion element is a photoelectrochemical cell. As the counter electrode, a support having a conductive layer can be used as in the case of the above-described conductive support. However, the support is not necessarily required in a configuration in which the strength and the sealing property are sufficiently maintained. Specifically, as the conductive material used for the counter electrode, a metal (for example, platinum, gold, silver, copper, aluminum, rhodium,
Indium, etc.), carbon, or a conductive metal oxide (indium-tin composite oxide, tin oxide doped with fluorine, or the like). The thickness of the counter electrode is not particularly limited, but is preferably 3 nm or more and 10 μm or less. If it is a metal material, its thickness is preferably 5 μm.
m, more preferably 5 nm or more and 3 μm or less. In order for light to reach the photosensitive layer, at least one of the conductive support and the counter electrode described above must be substantially transparent. In the photoelectrochemical cell of the present invention, it is preferable that the conductive support is transparent and sunlight is incident from the support side. In this case, it is more preferable that the counter electrode has a property of reflecting light. In the present invention, as the counter electrode, glass or plastic on which a metal or a conductive oxide is deposited, or a metal thin film can be used.

As described in the application of the charge transfer layer, the counter electrode is applied on the charge transfer layer or first on the semiconductor fine particle containing layer. In either case, depending on the type of counter electrode material and the type of charge transfer layer,
The counter electrode material can be appropriately formed on the charge transfer layer or the semiconductor fine particle-containing layer by a method such as coating, laminating, vapor deposition, or bonding. For example, in the case of attaching a counter electrode, a substrate provided as a conductive layer can be attached by a method such as application, evaporation, or CVD of the above conductive material. When the charge transfer layer is solid, the above-mentioned conductive material is directly applied thereon, plated, PVD, CV
The counter electrode can be formed by a technique such as D.

Further, a layer having other necessary functions such as a protective layer and an antireflection film can be provided on the conductive support or the counter electrode of the working electrode. When such layers are separated in function by multiple layers, simultaneous multilayer coating and sequential coating can be performed, but simultaneous multilayer coating is more preferable in terms of productivity. In the simultaneous multi-layer coating, the slide hopper method and the extrusion method are suitable in consideration of productivity and uniformity of film formation. In addition, these functional layers can be provided by a technique such as vapor deposition or pasting depending on the material.

In the photoelectrochemical cell of the present invention, it is preferable to seal the side surface of the cell with a polymer, an adhesive or the like in order to prevent deterioration of components and volatilization of contents.

Next, a cell structure and a module structure when the photoelectric conversion element of the present invention is applied to a so-called solar cell will be described. The structure inside the cell of the dye-sensitized solar cell is basically the same as that of the above-mentioned photoelectric conversion element or photoelectrochemical cell, but various forms are possible according to the purpose as shown in FIG. 2 or FIG. It is. If it is roughly divided into two,
A structure that allows light to enter from both sides [FIGS. 2 (a) (d) and 3 (g)] and a type that allows light from only one side [FIG. 2 (b)
(C) and FIGS. 3 (e) (f) (h)]. FIG. 2 (a)
Has a structure in which a TiO ₂ layer 10 as a dye-adsorbing semiconductor fine particle layer and a charge transfer layer 11 are interposed between two transparent conductive layers 12. FIG. 2 (b) shows that a metal lead 9 is partially provided on a transparent substrate 13, a transparent conductive layer 12 is further provided, and an undercoat layer 14, a dye-adsorbed TiO ₂ layer 10, a charge transfer layer 11 and a metal layer 8 are arranged in this order. And a support substrate 15 is further disposed. FIG. 2C shows a metal layer 8 on a support substrate 15, and a dye-adsorbed TiO ₂ layer 1 via an undercoat layer 14.
0, a charge transfer layer 11 and a transparent conductive layer 12 are further provided, and a transparent substrate 13 partially provided with a metal lead 9 is arranged with the metal lead 9 inside. FIG. 2 (d)
A metal lead 9 is partially provided on a transparent substrate 13, an undercoat layer 14 and a dye-adsorbed TiO 2 are provided between the metal lead 9 and the transparent conductive layer 12.
_This is a structure in which _two layers 10 and a charge transfer layer 11 are interposed.
FIG. 3 (e) has a transparent conductive layer 12 on a transparent substrate 13, a dye-adsorbed TiO ₂ layer 10 is provided via an undercoat layer 14, and a charge transfer layer 11 and a metal layer 8 are further provided thereon. This is a structure in which a support substrate 15 is arranged. FIG. 3 (f)
Has a metal layer 8 on a support substrate 15, a dye-adsorbed TiO ₂ layer 10 is provided via an undercoat layer 14, a charge transfer layer 11 and a transparent conductive layer 12 are further provided, and a transparent substrate 13 is disposed thereon. It is the structure which did. FIG. 3G shows a structure in which an undercoat layer 14, a dye-adsorbed TiO ₂ layer 10, and a charge transfer layer 11 are interposed between a transparent substrate 13 having a transparent conductive layer 12 with the transparent conductive layer 12 inside. FIG. 3 (h)
A metal layer 8 is provided on a support substrate 15, a dye-adsorbed TiO ₂ layer 10 is provided via an undercoat layer 14, a solid charge transfer layer 16 is further provided, and a metal layer 8 or a metal lead 9 is partially provided thereon. Structure.

The module structure of the dye-sensitized solar cell of the present invention can have basically the same structure as a conventional solar cell module. In general, a cell is formed on a supporting substrate such as a metal or ceramic, and the cell is covered with a filling resin or a protective glass, etc., so that light can be taken in from the opposite side of the supporting substrate. It is also possible to use a transparent material such as tempered glass for the substrate, form a cell thereon, and take in light from the transparent support substrate side. Specifically, a module structure called a superstrate type, a substrate type, or a potting type, or a module structure such as a substrate integrated type used in an amorphous silicon solar cell or the like is possible. These module structures can be appropriately selected depending on the purpose of use and the place of use (environment). FIG. 4 shows an example in which the element of the present invention is formed into a module with an integrated substrate. The module shown in FIG. 4 has a transparent conductive layer 12 on one side of a transparent substrate 13 and a cell in which a dye-adsorbed TiO ₂ layer 10, a solid charge transfer layer 16 and a metal layer 8 are further provided thereon. An antireflection layer 17 is provided on the other surface of the transparent substrate 13. In this case, in order to increase the utilization efficiency of incident light, it is preferable to increase the area ratio of the dye-adsorbed TiO ₂ layer 10 as the photosensitive portion (the area ratio when viewed from the transparent substrate 13 side which is the light incident surface). .

A typical structure of a superstrate type or a substrate type is that cells are arranged at regular intervals between supporting substrates which are transparent on one or both sides and have been subjected to antireflection treatment, and metal leads or adjacent cells are provided between adjacent cells. They are connected by a flexible wiring or the like, and have a structure in which current collecting electrodes are arranged on the outer edge to take out generated power to the outside. Various types of plastic materials such as ethylene vinyl acetate (EVA) can be used between the substrate and the cell in the form of a film or a filling resin, depending on the purpose, in order to protect the cell and increase current collection efficiency. When using in places where it is not necessary to cover the surface with a hard material, such as places where there is little external impact, make the surface protective layer a transparent plastic film or cure the above-mentioned filling and sealing material. It is also possible to provide a protective function and eliminate the support substrate on one side. The periphery of the support substrate is fixed in a sandwich shape with a metal frame in order to seal the inside and ensure the rigidity of the module, and the space between the support substrate and the frame is hermetically sealed with a sealing material.

If a flexible material is used for the cell itself, the support substrate, the filler and the sealing member, a solar cell can be formed on a curved surface. In this way, solar cells having various shapes and functions according to the purpose of use and environment of use can be manufactured.

The super-straight type solar cell module, for example, conveys a front substrate sent from a substrate supply device by a belt conveyor or the like, and seals the cells thereon with a sealing material, inter-cell connection lead wires, and back surface sealing. After laminating sequentially with materials and the like, a back substrate or a back cover can be placed, and a frame can be set on the outer edge portion to make it.
On the other hand, in the case of the substrate type, while the support substrate sent from the substrate supply device is conveyed by a belt conveyor or the like, the cells are sequentially laminated thereon with lead wires for cell connection, sealing material, etc. It can be manufactured by placing a frame on the periphery.

The module having the structure shown in FIG. 4 is formed by selective plating, selective etching, and CVD so that transparent electrodes, photosensitive layers, charge transfer layers, back electrodes, and the like are arranged three-dimensionally at regular intervals on a supporting substrate.・ Laser scribing or plasma CVM (Solar Ener) after semiconductor process technology such as PVD, or pattern application or wide application
gy Materials and Solar Cells, 48, p373-381) or a mechanical method such as grinding or the like, and a desired module structure can be obtained.

The other members and steps will be described below in detail. Examples of the sealing material include liquid-state EVA (ethylene vinyl acetate) and EVA in the form of a film of a mixture of vinylidene fluoride copolymer and an acrylic resin. Various materials can be used according to the purpose of improving (impact). these,
Depending on the properties of the encapsulant, the film can be fixed on the cell according to the physical properties of the encapsulant. There are various methods such as coating and screen printing. In addition, a transparent filler can be mixed into the sealing material to increase the strength or increase the light transmittance. The space between the outer periphery of the module and the frame surrounding the periphery may be sealed with a resin having high weather resistance and moisture resistance.

When a flexible material such as PET or PEN is used as the support substrate, a roll-shaped support is drawn out to form a cell thereon, and then the sealing layer is continuously laminated by the above method. And a highly productive process can be created.

In order to increase the power generation efficiency, the surface of the substrate (generally tempered glass) on the light intake side of the module is subjected to an antireflection treatment. This includes a method of laminating an antireflection film and a method of coating an antireflection layer. In addition, it is possible to increase the utilization efficiency of incident light by treating the surface of the cell with a method such as grooving or texturing.

In order to increase the power generation efficiency, it is most important that the light is introduced into the module without loss. It is also important. For this purpose, a support substrate surface is mirror-polished, and then Ag or Al is deposited or plated. Al-Mg or Al is added to the lowermost layer of the cell.
There is a method of providing an alloy layer of -Ti or the like as a reflective layer, or a method of forming a texture structure in the lowermost layer by annealing to increase the reflectance.

In order to increase the power generation efficiency, it is important to reduce the connection resistance between cells in order to suppress the internal voltage drop. It is common to connect with wire bonding or conductive flexible sheet. There is a method of applying a pattern to a position.

In the case of a solar cell using a flexible support such as a polymer film, cells are sequentially formed and cut into a desired size by the method described in the description of the application of the semiconductor while feeding the roll-shaped support. In addition, the periphery can be sealed with a flexible and moisture-proof material to produce a battery body. Also, Solar Energy Materials and S
A module structure called “SCAF” described in olar Cells, 48, p383-391 can also be used. In a solar cell having a flexible support, it can be further used by bonding it to a curved glass or the like.

[0097]

[Example 1]

1. Preparation of Titanium Dioxide Dispersion 25 g of titanium dioxide SSP-M (manufactured by Sakai Chemical Co., particle size: 15 nm, anatase) was washed with 1000 ml of pure water and filtered. This is repeated 10 times, and titanium dioxide A
I got Teflon-coated inner volume 200
15 g of titanium dioxide A, 45 g of water, and a dispersant (Triton X, manufactured by Aldrich) in a ml stainless steel vessel.
-100) 1 g and 450 g of zirconia beads (manufactured by Nikkato Corporation) having a diameter of 0.5 mm are put in the container, and the mixture is mixed at 1500 rpm using a sand grinder mill (manufactured by Imex Corporation).
Time dispersed. The zirconia beads were removed by filtration from the dispersion. The average particle size of titanium dioxide in this case is 0.3μ
m. The particle size at this time was measured with a master sizer manufactured by MALVERN. Titanium dioxide A
Was measured with a fluorescent X-ray analyzer. The contents were 0.08 and 0.001 wt%, respectively. Also, using an X-ray diffractometer (the counter cathode is Cu), 2θ = 2
The anatase conversion was determined from the peak intensity ratio around 5.2 degrees (anatase) and around 27.3 degrees (rutile). Titanium dioxide A had an anatase conversion of 100%.

2. Preparation of TiO ₂ electrode adsorbing dyes Conductive glass coated with fluorine-doped tin oxide (TCO glass manufactured by Nippon Sheet Glass, size 25 mm × 1
(00 mm) was applied to the conductive surface side using an applicator having a clearance of 150 μm. After air-drying at room temperature for 1 hour after coating, the mixture was baked at 450 ° C. for 30 minutes in an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific Co., Ltd.), and TiO 2 was used.
_Two electrodes were obtained. After taking out the electrode and cooling, both the dye compound S-30 and the dye compound S-32 were mixed in DMSO / ethanol (volume ratio 2.5 / 97.5, cholic acid 40 mM).
) Was immersed for 15 hours in a solution (3 × 10 ⁻⁴ mol / l for each dye). T dyed with dye
After iO ₂ electrode was dipped 4-tert-butylpyridine for 15 minutes, washed with ethanol and air-dried. The thickness of the photosensitive layer thus obtained was 10 μm, and the coating amount of the semiconductor fine particles was 20 g / m ² . The surface resistance of the conductive glass was 10Ω / cm ² .

3. Preparation of Photoelectrochemical Cell The color-sensitized TiO ₂ electrode substrate (2 cm × 2 cm) prepared as described above was overlaid with platinum-evaporated glass of the same size. Next, an electrolytic solution (1-methyl-3-hexylimidazolium iodine salt 0.65 mol / l, iodine 0.0
A methoxypropionitrile solution containing 5 mol / l) was impregnated and introduced into a TiO ₂ electrode to obtain a photoelectrochemical cell. According to the present embodiment, as shown in FIG. 1, conductive glass 1 (having a conductive agent layer 2 provided on glass), TiO ₂ layer 3, dye layer 4, electrolytic solution 5, platinum layer 6, and glass 7 were laminated in order, and a photoelectrochemical cell E-1 sealed with an epoxy-based sealing agent was produced.

4. Measurement of photoelectric conversion wavelength and photoelectric conversion efficiency The photoelectric conversion efficiency of the photoelectric conversion element of the present invention was measured as follows. Simulated sunlight containing no ultraviolet light was generated by passing light of a 500 W xenon lamp (made by Ushio) through a spectral filter (AM1.5 made by Oriel) and a sharp cut filter (Kenko L-42).
The intensity of this light was 86 mW / cm ² . The produced photoelectrochemical cell was irradiated with simulated sunlight, and the generated electricity was measured with a current / voltage measuring device (Keithley SMU238). Table 1 shows the conversion efficiency (η) of the photoelectrochemical cell thus obtained.

Comparative Examples 1 and 2 Dyes were combined in the same manner as in Example 1 except that titanium dioxides B and C shown below were used, and comparative photoelectrochemical cells RE-1 and RE-2 were used.
Was prepared. The conversion efficiency (η) is shown in Table 1. Titanium dioxide B Titania sulfate titanium dioxide with a primary particle size of 15 nm Titanium dioxide C Titanium sulfate titanium dioxide with a primary particle size of 60 nm

[0102]

[Table 1]

The electrochemical cell E-1 using the titanium dioxide A of the present invention had a higher conversion efficiency than the cells using the titanium dioxides B and C of the comparative example, and was preferred.

Example 2 and Comparative Examples 3 and 4 Photoelectrochemical cells E-2 and R were respectively used in the same manner as in Example 1 and Comparative Examples 1 and 2, except that the dye compounds S-31 and S-34 were used.
E-3 and RE-4 were prepared, and the conversion efficiency was similarly obtained. The results are shown in Table 2.

[0105]

[Table 2]

The photoelectrochemical cell E-2 using the titanium dioxide A of the present invention had a higher conversion efficiency than the cells using the titanium dioxides B and C of the comparative example, and was preferred.

[Examples 3 and 4] Titanium dioxide A was added to 750
C. for 2 hours to obtain titanium dioxide D, and 850.degree. C. for 2 hours to obtain titanium dioxide E. The contents of sulfur and phosphorus in both were not significantly different from those before firing. Photoelectrochemical cells E-3 and E-4 were produced in the same manner as in Example 1 except that these titanium dioxides D and E were used, respectively. Table 3 shows the conversion efficiencies obtained in the same manner as in Example 1.

[0108]

[Table 3]

A photoelectrochemical cell E-3 using titanium dioxide D having an anatase rate of 83% has a high conversion efficiency and is preferable. Although the conversion efficiency was higher than that of the battery, it was insufficient, and it was found that the conversion efficiency was higher as the anatase conversion was higher.

[0110]

According to the present invention, a photoelectric conversion element and a photoelectrochemical cell having excellent photoelectric conversion efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a photoelectrochemical cell prepared in an example.

FIG. 2 is a cross-sectional view showing a basic configuration example of a photoelectrochemical cell.

FIG. 3 is a cross-sectional view illustrating a basic configuration example of a photoelectrochemical cell.

FIG. 4 is a cross-sectional view showing an example of a module configuration of a substrate integrated type.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 conductive glass 2 conductive agent layer 3 TiO ₂ layer 4 dye layer 5 electrolytic solution 6 platinum layer 7 glass 8 metal layer 9 metal lead 10 dye-adsorbed TiO ₂ layer 11 charge transfer layer 12 transparent conductive layer 13 transparent substrate 14 undercoat layer 15 Support substrate 16 Solid charge transfer layer 17 Antireflection layer

Claims (4)

[Claims] 1. A dye-sensitized photoelectric conversion element having a conductive support, a layer containing semiconductor fine particles adsorbed with a dye, a charge transfer layer, and a counter electrode coated on the conductive support, wherein the semiconductor fine particles are used. Contains 0.0001% to 0.3% by weight of sulfur and 0.00000% of phosphorus.
A photoelectric conversion element containing 1 wt% or more and 0.01 wt% or less. 2. The method according to claim 1, wherein the semiconductor fine particles are titanium oxide and / or titanium oxide.
2. The photoelectric conversion element according to claim 1, which is niobium oxide. 3. The semiconductor fine particles are titanium oxide,
2. The photoelectric conversion device according to claim 1, wherein the anatase content is 80% or more and 100% or less. 4. A photoelectrochemical cell using the photoelectric conversion element according to claim 1.