JP2002075474A - Photoelectric conversion element and photocell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element with excellent durability which does not make a photoelectric conversion efficiency deteriorate, and to provide a photocell and a solar cell module using the above. SOLUTION: For the photoelectric conversion element comprising a conductive layer, a semiconductor particle layer sensitized by pigment, a electric charge transfer layer, and an opposite pole, the pigment is bonded to the semiconductor particle with covalent bond, and inorganic and/or organic hole transfer material is used for the electric charge transfer layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoelectric conversion element using semiconductor fine particles sensitized with a dye and a photovoltaic cell using the same.

[0002]

2. Description of the Related Art For solar power generation, monocrystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide have been put to practical use or are subject to major research and development. However, it is necessary to overcome the problems such as production cost, securing of raw materials, and long energy payback time in order to spread the technology. On the other hand, there have been proposed many solar cells using an organic material intended to have a large area and a low price, but have a problem that conversion efficiency is low and durability is poor. Under these circumstances, Nature
e) Volume 353, 737-740 (1991) and US Patent 49
No. 27721 discloses 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 oxide semiconductor such as titanium dioxide can be used without purification to a high degree of purity, so that an inexpensive photoelectric conversion element can be provided. Since the absorption of the dye is broad, it is possible to convert light in almost all visible wavelength regions into electricity. However, since a low-boiling organic solvent is used as the charge transport material, its durability has been concerned. Therefore, various stabilized charge transport materials have been proposed. For example, to prevent electrolyte depletion over time, J. Phys.
D: Appl. Phys. 31 (1998) pp. 1492-1496 or Chem. Ma.
ter., Vol. 10, pp. 1501-1509 (1998) proposes a photoelectric conversion element solidified using an inorganic hole transport material such as CuI or CuSCN. However, photoelectric conversion elements using these hole transport materials are prone to short-circuits as a result of examination,
In addition, there is a problem that deterioration with time is severe. In addition, these methods have a problem that the dye adsorbed on the semiconductor is deteriorated (that is, the photoelectric conversion efficiency is reduced) in the step of forming the hole transport layer, and the deterioration of the photoelectric conversion performance is also caused with time. There was a problem of being big.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoelectric conversion element which is excellent in durability without deteriorating photoelectric conversion performance. Another object is to provide a photovoltaic cell and a solar cell module using the same.

[0004]

The object of the present invention is attained by the following items which specify the present invention, and the preferred embodiments thereof. (1) In a photoelectric conversion element having a conductive layer, a semiconductor fine particle layer sensitized by a dye, a charge transport layer, and a counter electrode, the dye has a covalent bond with the semiconductor fine particles, and the charge transport layer has an inorganic and / or inorganic charge. Alternatively, a photoelectric conversion element using an organic hole transport material. (2) In the above (1), the inorganic hole transporting material is
A photoelectric conversion element comprising a monovalent copper compound. (3) The photoelectric conversion element according to (2), wherein the monovalent copper compound is produced by a process including an electrolytic plating process. (4) The photoelectric conversion device according to (2), wherein the monovalent copper compound is produced by a process including an electroless plating process using a copper salt. (5) The photoelectric conversion device according to any one of (1) to (4), wherein the dye covalently bonded to the semiconductor particles is a metal complex dye and / or a merocyanine dye. (6) In the above (1) to (5), the semiconductor fine particles are Ti
A photoelectric conversion element comprising metal oxide particles selected from the group consisting of O ₂ , ZnO, SnO ₂ , Fe ₂ O ₃ , WO ₃ , Nb ₂ O ₅ , and SrTiO ₃ . (7) A photovoltaic cell using the photoelectric conversion element described in any one of the above (1) to (6). (8) A photovoltaic module comprising the photoelectric conversion element described in (1) to (6).

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [1] Photoelectric conversion device The configuration of a photoelectric conversion device of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view showing the structure of a preferred embodiment of the photoelectric conversion device of the present invention, and includes a conductive layer 10, an undercoat layer 60, a photosensitive layer (semiconductor particle layer) 20, a charge transport layer 30, and a counter electrode conductive layer. The photosensitive layer 20 is composed of a dye 22, semiconductor fine particles 21 sensitized by the dye 22, and a charge transport material 23 that has penetrated into voids of the semiconductor fine particles 21 (that is, The charge transport material is made to penetrate into the gaps of the sensitized semiconductor fine particle layer). The charge transport material 23 is composed of the same components as the materials used for the charge transport layer 30. Also, in order to impart strength to the photoelectric conversion element, a conductive layer
As a base for the conductive layer 10 and / or the counter electrode layer 40, a substrate 50 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”. The conductive layer 10, the counter electrode conductive layer 40, and the substrate 50 in FIG.
May be a transparent conductive layer 10a, a transparent counter electrode conductive layer 40a, and a transparent substrate 50a, respectively. A photovoltaic cell is made for the purpose of generating electrical work by connecting this photoelectric conversion element to an external load (power generation), and an optical sensor is made for the purpose of sensing optical information. Of the photovoltaic cells, a case where the charge transport material 23 is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and a case where the main purpose is power generation by sunlight is called a solar cell.

In the photoelectric conversion device of the present invention shown in FIG. 1, when the semiconductor fine particles are n-type, light incident on the photosensitive layer 20 containing the semiconductor fine particles 21 sensitized by the dye 22 excites the dye 22, The electrons that have been excited and transitioned to a high energy level in the dye 22 are transferred to the conduction band of the semiconductor fine particles 21 and reach the conductive layer 10 by diffusion. At this time, the molecule of the dye 22 is in an oxidized form. In photovoltaic cells,
Electrons in the conductive layer 10 return to the oxidized form of the dye 22 through the counter electrode conductive layer 40 and the charge transport layer 30 while working in an external circuit,
Dye 22 regenerates. The photosensitive layer 20 is a negative electrode (photo anode)
And the counter electrode 40 works as a positive electrode. At the boundary of each layer (for example, the boundary between the conductive layer 10 and the photosensitive layer 20, the boundary between the photosensitive layer 20 and the charge transport layer 30, the boundary between the charge transport layer 30 and the counter electrode conductive layer 40, etc.) They may be mutually diffused and mixed. Hereinafter, each layer will be described in detail.

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

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

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

[0010] The transparent conductive support is preferably formed by forming a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic by coating or vapor deposition. Preferred as the transparent conductive layer,
It is tin dioxide or indium-tin oxide (ITO) doped with fluorine or antimony. As the transparent substrate, a glass substrate such as soda glass which is advantageous in terms of cost and strength and alkali-free glass which is not affected by alkali elution, and a transparent polymer film can be used. Materials for the transparent polymer film include triacetyl cellulose (TAC) and polyethylene terephthalate (P
ET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyimide (PI ), Polyetherimide (PEI), cyclic polyolefin, brominated phenoxy resin, and the like. In order to ensure sufficient transparency, the amount of the conductive metal oxide applied is preferably 0.01 to 100 g per 1 m ² of a glass or plastic support.

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

(B) Photosensitive layer In the photosensitive layer, the semiconductor acts as a photoreceptor, absorbs light to separate charges, and generates electrons and holes. In a dye-sensitized semiconductor, light absorption and thus generation of electrons and holes mainly occur in the dye, and semiconductor fine particles have a role of receiving and transmitting the electrons (or holes). The semiconductor used in the present invention is preferably an n-type semiconductor which gives an anode current by conducting electrons as carriers under photoexcitation.

(1) Semiconductors Semiconductors include simple semiconductors such as silicon and germanium, compound semiconductors of Group III-V elements of the periodic table, and metal chalcogenides (eg, oxides, sulfides, selenides, and the like). Or a compound having a perovskite structure (eg, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.).

Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium,
Hafnium, strontium, indium, cerium,
Examples include oxides of yttrium, lanthanum, vanadium, niobium, or tantalum, sulfides of cadmium, zinc, lead, silver, antimony or bismuth, selenides of cadmium or lead, tellurides of cadmium, and the like.
Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, selenides of gallium-arsenic or copper-indium, and sulfides of copper-indium. Furthermore, MxOySz or M ₁ xM ₂
yOz (M, M ₁ and M ₂ are each a metal element, O is oxygen, x, y, z are the number of combinations valence is neutral) can be preferably used a composite, such as.

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

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

The particle size of the semiconductor fine particles is generally 10 ^-9 to 1.
The average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably from 5 to 200 nm, and more preferably from 8 to 100 nm, although the level is from 0 to ⁶ m (1 nm to 1 μm). . The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 30 μm. Two or more types of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 25 nm or less, more preferably 10 nm or less. For the purpose of improving the light capture rate by scattering the incident light, a large particle size, for example, 100 nm to 300 nm
It is also preferable to mix a certain amount of semiconductor particles.

The type of the semiconductor fine particles may be a mixture of two or more different types. When two or more kinds of semiconductor fine particles are mixed and used, one kind is TiO ₂ , ZnO, Nb ₂ O ₅ or SrTi
Preferably it is O ₃ . Another type is Sn
O ₂ , Fe ₂ O ₃ and WO ₃ are preferred. More preferred combinations include ZnO and SnO ₂ , ZnO and WO ₃ or ZnO,
Combinations of SnO ₂ and WO ₃ can be mentioned. 2
When a mixture of two or more kinds of semiconductor fine particles is used, the respective particle diameters may be different. In particular, a combination in which the particle size of the semiconductor fine particles mentioned as the first type is large and the semiconductor fine particles mentioned as the second type is small is preferable. Preferably, the particles having a large particle diameter are 100 nm or more, for example, 100 to 500.
nm, particles having a small particle size of 15 nm or less, for example, 2 to 15
It is a combination of particles having a size of nm.

As a method for producing semiconductor fine particles, Sakuhana Shizuo's "Sol-Gel Method Science" Agne Shofusha (1998) and Technical Information Association "Sol-Gel Method for Thin Film Coating" (1995 )), Tadao Sugimoto's "Synthesis of Monodisperse Particles and Size Morphology Control by New Synthetic Method Gel-Sol Method", Materia, Vol. 35, No. 9, 1012-1018.
The gel-sol method described on page (1996) is preferred. Also De
Also preferred is a method developed by Gussa to produce oxides by high temperature hydrolysis of chlorides in oxyhydrogen salts.

When the semiconductor fine particles are titanium oxide, the above-mentioned sol-gel method, gel-sol method, and high-temperature hydrolysis method in chloride oxyhydrogen salt are all preferably applicable adjustment methods. Sulfuric acid method and chlorine method described in “Titanium oxide physical properties and applied technology”, Gihodo Shuppan (1997) can also be used. Examples of the sol-gel method include a method described in Barbe et al., Journal of American Ceramic Society, Vol. 80, No. 12, pp. 3157-3171 (1997), and Burnside.
The Chemistry of Materials, Vol. 10, No. 9
No. 2419-2425 are also preferred.

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

As a method for preparing a dispersion of semiconductor fine particles, in addition to the above-described sol-gel method, a method of grinding with a mortar, a method of dispersing while pulverizing using a mill, or a method of preparing a solvent when synthesizing a semiconductor. A method of precipitating as fine particles therein and using it as it is is exemplified.

Examples of the dispersion medium include water and various organic solvents (eg, methanol, ethanol, isopropyl alcohol, citronellol, terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). At the time of dispersion, for example, polyethylene glycol, hydroxyethyl cellulose, a polymer such as carboxymethyl cellulose, a surfactant, an acid,
Alternatively, 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 adjust the viscosity of the dispersion, to form a semiconductor layer that is difficult to peel off, and to control the porosity of the semiconductor layer. Therefore, it is preferable to add polyethylene glycol.

The application method includes a roller method and a dipping method as an application (application liquid application) system.
Air knife method, blade method, etc., as a metering (coating amount control) system.
No. 9 discloses a wire bar method, U.S. Pat.
The slide hopper method, extrusion method, and curtain coating method described in each gazette such as Nos. 1294, 2761419, and 2761791 are preferable. Further, as other general-purpose means, a spin coating method or a spray coating method is also preferable. Further, a wet printing method is also preferable, and an intaglio, rubber plate, screen printing and the like are preferable, including three major printing methods of relief printing, offset printing and gravure printing. From these, a preferable film forming method can be selected according to the liquid viscosity and the wet thickness.

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

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) increases, the amount of dye carried per unit projected area increases, so that the light capture rate increases, but the diffusion distance of generated electrons increases. Therefore, the loss due to charge recombination also increases. Therefore, the preferred thickness of the semiconductor fine particle layer is
It is 0.1-100 μm. When used for a photovoltaic cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, more preferably 2 to 25 μm. Support 1 m ² per coating amount of the semiconductor fine particles 0.5
-100 g is preferable, and 3-50 g is more preferable.

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

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

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

(3) Dye The sensitizing dye used in the photosensitive layer is a dye having an absorption in the visible or near infrared region, capable of sensitizing a semiconductor, and capable of forming a covalent bond with semiconductor fine particles. Any dye may be used as long as it has the following. The group capable of forming a covalent bond with the semiconductor fine particles forms a bond such as an ether bond, a thioether bond, an amino bond, an ester bond, an amide bond, a urethane bond, and a urea bond by replacing the element constituting the semiconductor fine particles. Any group can be used as long as it is a suitable group, but preferably a carbonyl group-containing group and a precursor-containing group thereof (a carboxylic acid group, an acid halogen group, an acid anhydride group, and an ester group), a hydroxyl group-containing group and a precursor thereof. And a hydroxyl group, a metal salt of a hydroxyl group, an alkyloxy group, a hydroxyl group bonded to a silicon atom, a hydroxyl group bonded to a metal such as a titanium atom, a zinc atom, and a tin atom. The above-described covalent bond formed between the dye and the semiconductor fine particles can be detected by, for example, infrared absorption analysis.

Hereinafter, preferred sensitizing dyes for use in the photosensitive layer will be specifically described. The sensitizing dye is preferably an organometallic complex dye, a methine dye, a porphyrin dye or a phthalocyanine dye, and particularly preferably the following organometallic complex dye or merocyanine dye. 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.

(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 preferred, and a ruthenium complex dye is particularly preferred. Ruthenium complex dyes include, for example, U.S. Pat.
684537, 5084365, 5350644, 5463057,
No. 5525440, JP-A-7-249790, JP-T10-504512,
The complex dyes described in each gazette such as World Patent No. 98/50393 and JP-A-2000-26487 are exemplified.

The ruthenium complex dye used in the present invention is preferably a dye represented by the following general formula (I). (A1) pRu (Ba) (Bb) (Bc) (I) In the general formula (I), A1 represents a monodentate or bidentate ligand, and Cl, SCN, H2O, Br, I, CN , NCO and SeCN, and ligands selected from the group consisting of β-diketones, oxalic acid and dithiocarbamic acid derivatives. p is an integer of 0 to 3. Ba, Bb and Bc each independently represent an organic ligand selected from compounds represented by the following chemical formulas B-1 to B-10. Ba, Bb and Bc may be the same or different, and may be any one or two.

[0034]

Embedded image

In each of the above chemical formulas, Ra represents _a hydrogen atom or a substituent. Examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and a substituent having 7 to 12 carbon atoms. A substituted or 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 moiety of the alkyl group and the aralkyl group may be linear or branched, and the aryl moiety of the aryl group and the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly).

Preferred specific examples of the organometallic complex dyes are shown below as R-1 to R-17, but the present invention is not limited thereto.

[0037]

Embedded image

[0038]

Embedded image

[0039]

Embedded image

(B) Methine Dye Preferred methine dyes for use in the present invention are polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes. In the present invention, a dye more preferably used is a merocyanine dye. Examples of the polymethine dye preferably used in the present invention are described in JP-A-11-35
No. 836, JP-A-11-67285, JP-A-11-8
6916, JP-A-11-97725, JP-A-11-977
No. 158395, JP-A-11-163378, JP-A-11-214730, JP-A-11-214731,
JP-A-11-238905, JP-A-2000-2648
No. 7, EP 892411, EP 911841 and EP 991092. Specific examples of preferred methine dyes are shown below.

[0041]

Embedded image

(4) Adsorption of Dye on Semiconductor Particles In order to adsorb the dye on the semiconductor particles, a conductive support having a well-dried semiconductor particle layer is immersed in a solution of the dye, or the dye solution is applied to the semiconductor particles. 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. 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.), 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.

In order to bond the dye to the semiconductor fine particles by covalent bond, when the dye is treated with the semiconductor, heating, coexistence of an acid or base, or dehydration such as accelerating bond formation is performed. It is preferable to use a catalyst such as a catalyst, and these means may be used in combination. In addition, in the case of a dye that is difficult to form a bond directly with semiconductor fine particles, it is also preferable to use a compound having both binding groups capable of connecting both. As such a compound, any compound having at least one group capable of forming a bond with a semiconductor and one functional group capable of bonding with a dye can be used. Preferred compounds include so-called silane coupling agents. Preferred examples of the silane coupling agent include those described in “Silicone Material Handbook” (edited by Dow Corning Toray Silicone) and those described in “Silicone Handbook” (edited by Kunio Ito, published by Nikkan Kogyo Shimbun 1990). It is listed as. These compounds may be bonded to semiconductor particles in advance and then reacted with the dye, or may be bonded to the dye and then reacted with the semiconductor. Preferably the former.

The total adsorption amount of the dye is preferably from 0.01 to 100 mmol per unit surface 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, the temperature of the semiconductor electrode substrate is maintained at 60 to 150
It is preferable to carry out the dye adsorption operation quickly at a temperature of between ° C. 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.

[0045]

Embedded image

The unadsorbed dye is preferably removed by washing immediately after the adsorption. For cleaning, use a wet cleaning tank,
It is preferable to perform washing with a polar solvent such as acetonitrile and an organic solvent such as an alcohol solvent. After the dye is adsorbed, the surface of the semiconductor fine particles may be treated with an amine or a quaternary salt. Preferable amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like, and preferable quaternary salts include tetrobutylammonium iodide, tetrahexylammonium iodide 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.

(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 transporting materials that can be used in the present invention include (i) a solution in which redox pair ions are dissolved (electrolyte solution) and a redox pair solution as a polymer matrix gel as an ion transporting material. A so-called gel electrolyte, a molten salt electrolyte containing an oxidation-reduction counter ion, and a solid electrolyte are further impregnated. 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. In the present invention, it is preferable to use an inorganic or organic hole (hole) transport material.

(1) Molten Salt Electrolyte A molten salt electrolyte is preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. The molten salt electrolyte is a liquid electrolyte at room temperature or a solid electrolyte having a low melting point. Examples thereof include WO95 / 18456, JP-A-8-259543, and other publications and Electrochemistry, Vol. 65, No. 11. 923, p. 923 (1997), and other known electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts. 10
A molten salt which becomes liquid at 0 ° C. or lower, particularly around room temperature, is preferred.

Examples of the molten salt that can be preferably used include those represented by any of the following formulas (Ya), (Yb) and (Yc).

[0050]

Embedded image

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. The five-membered ring formed by Q _{y 1} is 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. It is more preferable that each is a cation type of an oxazole ring, a thiazole ring or an imidazole ring, and it is particularly preferable that each is a cation type of an oxazole ring or an imidazole ring. The 6-membered ring formed by Q _y1 is a pyridine ring,
It is preferably a cationic type of a pyrimidine ring, a pyridazine ring, a pyrazine ring or a triazine ring, and more preferably a pyridinium 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, branched, or cyclic; for example, methyl Group, ethyl group, propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, t-
Octyl, decyl, dodecyl, tetradecyl,
2-hexyldecyl group, octadecyl group, cyclohexyl group, 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 or an allyl group), more preferably an alkyl group having 2 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms, and particularly preferably an alkyl group having 2 to 6 carbon atoms. .

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 , 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, etc.), a cyano group, an alkoxy group (e.g., methoxy group,
Ethoxy group, methoxyethoxy group, methoxyethoxyethoxy group, etc.), aryloxy group (eg, phenoxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, etc.), alkoxycarbonyl group (eg,
Ethoxycarbonyl group, etc.), carbonate group (eg, ethoxycarbonyloxy group, etc.), acyl group (eg, acetyl group, propionyl group, benzoyl group, etc.), sulfonyl group (eg, methanesulfonyl group, benzenesulfonyl group, etc.), Acyloxy group (for example,
Acetoxy group, benzoyloxy group, etc.), sulfonyloxy group (eg, methanesulfonyloxy group, toluenesulfonyloxy group, etc.), phosphonyl group (eg,
Diethylphosphonyl group, etc.), amide group (eg, acetylamino group, benzoylamino group, etc.), carbamoyl group (eg, N, N-dimethylcarbamoyl group, etc.), alkyl group (eg, methyl group, ethyl group, propyl group) ,
Isopropyl group, cyclopropyl group, butyl group, 2-carboxyethyl group, benzyl group, etc., aryl group (eg, phenyl group, toluyl group, etc.), heterocyclic group (eg, pyridyl group, imidazolyl group, furanyl group, etc.) ,
Examples include an alkenyl group (eg, a vinyl group, a 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 can 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 -}} , PF
_{^{6 -, ClO 4 -, (}} CF 3 SO 2) 2 N -, (CF 3 CF 2 SO 2) 2 N -, CH 3 SO 3 -, C
Preferred examples include F 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 amount of the alkali metal salt to be added is preferably about 0.02 to 2% by mass, more preferably 0.1 to 1% by mass, based on the whole chargeable composition.

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 electrolyte composition. In this case, the content of iodine is preferably 0.1 to 20% by mass relative to 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_Two Such
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_Two Such
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 I_TwoAnd LiI and pyridinium iodide,
Quaternary ammonium compounds such as imidazolium iodide
The electrolyte which combines the iodine salt of the above is preferable. Mentioned above
The electrolytes may be used as a mixture.

The preferred electrolyte concentration is 0.1M or more and 10M or less, more preferably 0.2M or more and 4M 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 to improve the effective carrier concentration, thereby exhibiting 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, non-proton polar substances such as sulfolane, water and the like, Can also be used as a mixture.

Further, in the present invention, J. Am. Ceram. Soc.,
80 (12) Vol. 3157-3171 (1997)
It is preferable to add a basic compound such as rt-butylpyridine, 2-picoline and 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 electrolyte is gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization containing a polyfunctional monomer, and crosslinking reaction of the polymer. (Solidification). To gel by adding a polymer, use “Polymer Electrol
yte Reviews-1 and 2 "(JRMacCallum and CA Vince
Compounds described in ELSEVIER APPLIED SCIENCE) can be used, and particularly, polyacrylonitrile and polyvinylidene fluoride can be preferably used. When gelling by adding an oil gelling agent
J. Chem Soc. Japan, Ind. Chem. Sec., 46, 779 (194
3), J. Am. Chem. Soc., 111, 5554 (1989), J. Che.
m. Soc., Chem. Commun., 1993, p. 390, Angew. Chem.
Int. (English), 35, 1949 (1996), Chem. Lett., 1996,
The compounds described in page 885, J. Chm. Soc., Chem. Commun., 1997, page 545 can be used, but preferred compounds are compounds having an amide structure in the molecular structure. An example in which the electrolyte is gelled is disclosed in JP-A-11-1858.
No. 63 discloses an example in which a molten salt electrolyte is gelled.
No. 00-58140, which is also applicable 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 respect to a nitrogen atom (for example, alkyl halides, aralkyl halides, sulfonic esters, acid anhydrides, acid chlorides, isocyanate compounds, α, β-unsaturated sulfonyl group-containing compound, α, β-unsaturated carbonyl group-containing compound, α, β-unsaturated nitrile group-containing compound, etc.)
And JP-A-2000-17076 and 2000-
The crosslinking technique described in 86724 can also be applied.

(4) Hole transporting material In the present invention, it is preferable to use an organic or inorganic or a solid hole transporting material combining both, instead of an ion-conductive electrolyte such as a molten salt. More preferably, the charge transport layer contains an inorganic hole transport material. More preferably, the charge transport layer contains a monovalent copper compound as the inorganic hole transport material.

(A) Organic Hole Transport Material Organic hole transport materials applicable to the present invention include Hagen (J. Hagen) et al., Synthetic Metal Vol. 89 (1997) 215-2.
20, Nature, 395, 8 Oct. 1998, 583-
585 pages and WO97 / 10617, JP-A-59-194393, JP-A-5-234681, U.S. Pat.No. 4,923,774, JP-A-4-3
08688, U.S. Patent No. 4,764,625, JP-A-3-269084
No., JP-A-4-129271, JP-A-4-175395, JP-A-4
No. -264189, JP-A-4-290851, JP-A-4-364153,
JP-A-5-25473, JP-A-5-239455, JP-A-5-3206
No. 34, JP-A-6-1972, JP-A-7-138562, JP-A-7-2
No. 52474, aromatic amines shown in each publication such as JP-A-11-144773, JP-A-11-149821, JP-A-11-148067
And the triphenylene derivatives described in JP-A-11-176489 and other publications can be preferably used. Also,
Adv. Mater. 1997, 9, N0.7, 557, Angew. Chem. (English) 1995, 34, No. 3, pp. 303-307, JACS, 120, N0.
Oligothiophene compounds described in 4, 1998, 664-672, etc., polypyrrole described in K. Murakoshi et al., Chem. Lett. 1997, 471, "Handbook of Organic Conduc
tive Molecules and Polymers Volumes 1-4 ”(NALWA, WI
Polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly
Conductive polymers such as (p-phenylenevinylene) and its derivatives, polythienylenevinylene and its derivatives, polythiophene and its derivatives, polyaniline and its derivatives, and polytoluidine and its derivatives can be preferably used.

Hole transporting materials include tris (4-bromophenyl) to control dopant levels as described in Nature, Volume 395, (8 Oct. 1998), pp. 583-585. ) Li [(CF3SO) to add a compound containing a cation radical such as aminium hexachloroantimonate, or to control the potential of the oxide semiconductor surface (compensate for the space charge layer).
2) A salt such as 2N] 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
A compound semiconductor containing monovalent copper, examples of the compound semiconductor containing monovalent copper include CuI, CuSCN, CuInSe ₂ , Cu (I
(n, Ga) Se ₂ , CuGaSe ₂ , Cu ₂ O, CuS, CuGaS ₂ , CuInS ₂ , CuAl
Se _{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 , C
r ₂ O ₃ or the like 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 between the gaps. 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 present invention, it is preferable to provide the charge transport layer by the latter method.

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, or a vacuum process for replacing the gas phase in the gap with a liquid phase at a pressure lower than normal pressure can be used. .

When the charge transporting layer is directly provided on the photosensitive layer, the wet type charge transporting 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 by wet method and solidifying it by a method such as polymerization. In this 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 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. Organic hole transport materials are vacuum deposited, cast,
It can be introduced into the inside of the electrode by a method such as a coating method, a spin coating method, a dipping method, an electrolytic polymerization method and a photoelectrolytic polymerization method. In the case of an inorganic solid compound, it can be introduced into the electrode by a method such as a casting method, a coating method, a spin coating method, a dipping method, an electrolytic deposition method, and an electroless plating method. In the present invention, when a monovalent copper compound is contained as a hole transporting material, it is preferable to use an electrolytic plating method or an electroless plating method. Among the electroplating methods, the preferred methods for the present invention are the methods described in Japanese Patent Application Nos. 11-351838, 11-336370, and 2000-006969. It is also preferable to use an electroless plating method.
-351842. More preferably, it is a method by electroless plating. As a method for producing a hole transport layer containing copper iodide by electroless plating, the following 1. And a reduction method using the two steps described in 2. There is a one-step oxidation method shown in FIG.

1. Reduction Method The reduction method includes a “plating step” for performing general electroless metal plating on the dye-adsorbed semiconductor fine particle layer, and a “post-process” for converting the plated metal to a p-type semiconductor. In the plating process, “(Metal Surface Technology Course Vol. 9) Electroless Plating”
(1971, edited by The Metal Surface Technology Association, published by Asakura Shoten)
"Latest Electroless Plating Technology" (1986, published by the General Technology Center), "Plating Technology Guidebook" (1987,
Tokyo Plating Materials Cooperative), "Amorphous Plating Method and Its Application" (1990, edited by Ken Masumoto and Toru Watanabe, published by Nikkan Kogyo Shimbun), "Application of Electroless Plating" (1991)
, Published by Toshio Okamura et al., Published by Maki Shoten), etc.).

Electroless plating is different from electrolytic plating in that metal cations are reduced by a reducing agent coexisting in a plating solution without supplying electricity from the outside, and are deposited on a surface to be plated. The plating solution used in the plating step comprises a metal salt, a reducing agent and an additive. As the metal salt, a sulfate, an acetate, a carbonate and the like are used.
In the case of copper plating, copper sulfate, copper acetate and copper carbonate are preferably used. Particularly, copper sulfate is preferable. Examples of the reducing agent include hypophosphite (eg, sodium hypophosphite), borohydride (eg, sodium borohydride), hydrazine, formaldehyde (HCHO), dimethylamine borane ((CH ₃ ) 2 NH.BH ₃ ), and the like. Is used. The preferred reducing agent used depends on the metal to be plated. In the case of copper plating, formaldehyde or dimethylamine borane, which is catalytically oxidized on the surface of the plated copper, is preferably used. In the case of nickel plating, sodium hypophosphite, sodium borohydride, hydrazine and the like are preferably used. The concentration of the metal salt constituting the plating solution, the concentration of the reducing agent and the additive may vary depending on the respective combination, but as the metal salt,
5 × 10 ^{−3 to} 0.5 mol / L, 1 × as reducing agent
It is 10 ^{-3 to} 1.0 mol / L.

Examples of the additives include a base for adjusting the pH of the reaction solution to a basic condition, a buffer for suppressing a decrease in pH in the reaction process, a stabilizer for preventing metal deposition in the solution, and hydrogen generated in the reaction process. Surfactants and wetting agents that promote gas removal are preferably used. As the base, an inorganic base is preferable, and among them, sodium hydroxide is preferably used. As the buffer, salts of organic acids and inorganic acids are used. As the stabilizer, those having a metal complex-forming ability such as EDTA, bipyridyl, thiourea, MBT, and a cyanide are preferably used. Also, as a wetting agent, PE
G (polyethylene glycol) and the like are preferably used.

In order to improve the adhesion and the like of the electroless plating, a solvent treatment, an etching treatment,
It is preferable to perform a step such as a catalyst imparting / activity promoting treatment as a preceding step. Among them, the solvent treatment and the etching treatment clean the surface of the plating target and improve the adhesion by the anchor effect by providing some irregularities. For cleaning the fine particle semiconductor, a weak alkaline water, alcohols, a polar solvent such as acetonitrile, or the like is used as the solvent treatment liquid. For the etching treatment, for example, acids such as nitric acid and hydrogen fluoride are preferably used. The catalyst imparting / activity promoting treatment is performed to provide a portion having a catalytic function for promoting the deposition on a surface on which the metal is originally unlikely to be deposited. Preferred examples include a method of treating with a catalyst (a Pd colloid, for example, a Pd ²⁺ / Sn ²⁺ hydrochloric acid solution) followed by an accelerator (an acid, for example, a sulfuric acid solution), or a method of treating with a sensitizer (eg, a tin chloride / hydrochloride solution). Activator (for example, palladium chloride in hydrochloric acid solution) treatment, alkali ion cater method,
A heat treatment method (after immersion in an organic complex solvent of Pd or Ag, followed by heat treatment) or the like is preferably used.

As the electrolytic plating method, a general method described in “Electrochemical Measurement Method” (Gihodo Shuppan Co., Ltd.) can be used. That is, an electrode having the semiconductor layer of the present invention as a working electrode, an inert electrode (platinum, carbon, etc.) as a counter electrode, and a copper salt solution (for example, CuI
And KI using a solution of KI in acetonitrile or acetone, etc. (preferable current density: 0.1
５００500 mA / cm ² ).

As a post-process for converting the plated metal to a p-type semiconductor, for example, in the case of copper, there is a process of converting the metal into copper iodide, copper thiocyanate, or the like. As the step of converting to copper iodide, a method of aging in iodine vapor, a method of immersion in a potassium iodide solution, and the like are preferably used.

(2) Oxidation Method The oxidation method is, for example, a method using CuI ₂ anion and / or CuI ₃
There is a method in which copper iodide is directly precipitated from a solution containing an anion in the presence of an oxidizing agent. As the oxidizing agent, it is preferable that the oxidation potential is more noble than +0.25 V (vsAg / AgCl).

(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 include a counter electrode conductive layer and a support substrate. As the conductive material used for the counter electrode conductive layer, a metal (for example, platinum, gold, silver, copper, aluminum, magnesium, indium, or the like), carbon, or a 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. Examples of preferred support substrates for the counter electrode are glass or plastic,
The above-mentioned conductive agent is applied or vapor-deposited on this. 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 the light may be irradiated from one or both of the conductive support and the counter electrode, in order for the light to reach the photosensitive layer, at least one of the conductive support and the counter electrode is substantially transparent. I just 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 onto the charge transport layer, plated or vapor-deposited (PVD, CVD), or may be attached to the conductive layer side of the substrate having the conductive layer. As in the case of the conductive support, particularly when the counter electrode is transparent, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode. 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.
In addition to the spray pyrolysis method described on page (1995), 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. A structure that allows incidence and a structure that allows only 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 is a partial cross-sectional view of the internal structure of one embodiment of the photoelectric conversion element of the present invention. The photosensitive layer 20, the charge transport layer 30 and the transparent conductive layer 10a are disposed between the transparent conductive layer 10a and the transparent counter electrode conductive layer 40a. Are shown, and light is incident from both sides. The photoelectric conversion element according to another embodiment of the present invention illustrated in FIG. 3 includes a metal lead 11 partially provided on a transparent substrate 50a,
Further provided with a transparent conductive layer 10a, the undercoat layer 60, the photosensitive layer 20,
A charge transport layer 30 and a counter electrode conductive layer 40 are provided in this order, and a support substrate 50 is further provided, so that light is incident from the conductive layer side. In still another embodiment of the photoelectric conversion device of the present invention shown in FIG. 4, further having a conductive layer 10 on a support substrate 50, providing a photosensitive layer 20 via an undercoat layer 60,
Further, the charge transport layer 30 and the transparent counter electrode conductive layer 40a are provided, and the transparent substrate 50a, on which the metal leads 11 are partially provided, is
This is a structure in which light is incident from the counter electrode side, with one side being placed inside. In the embodiment shown in FIG.
A metal lead 11 is partially provided on 50a, and further a transparent conductive layer 10a
(Or 40a) in which the undercoat layer 60, the photosensitive layer 20, and the charge transport layer 30 are interposed between a pair, and light is incident from both sides. Further, in the embodiment shown in FIG. 6, the transparent conductive layer 10a, the undercoat layer 60,
The photosensitive layer 20, the charge transport layer 30, and the counter electrode conductive layer 40 are provided, and the support substrate 50 is disposed thereon. In this structure, light enters from the conductive layer side. In the embodiment shown in FIG. 7, the conductive layer 10 is provided on the support substrate 50, and the photosensitive layer 20 is provided via the undercoat layer 60.
Further provided, the charge transport layer 30 and the transparent counter electrode conductive layer 40a
Is provided, on which the transparent substrate 50a is arranged,
In this structure, light enters from the opposite electrode side. In the embodiment shown in FIG. 8, a transparent conductive layer 10a is provided on a transparent substrate 50a, and an undercoat layer
The photosensitive layer 20 is provided via 60, the charge transport layer 30 and the transparent counter electrode conductive layer 40a are further provided, and the transparent substrate 50a is disposed thereon. Light is incident from both sides. FIG. 9 shows that the conductive layer 10 is provided on the support substrate 50 and the undercoat layer is provided.
The photosensitive layer 20 is provided through 60, and the solid charge transport layer 30 is further provided.
On which a counter electrode conductive layer 40 or a metal lead 11 is provided.
And has a structure in which light is incident from the counter electrode side.

[2] Photocell The photocell of the present invention is designed so that an external load works by using the electric energy obtained by conversion by the photoelectric conversion element. 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 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, a cell is formed on a support substrate such as a metal or ceramic, and the cell is covered with a filling resin or protective glass to take light from the opposite side of the support substrate.
It is also possible to adopt a structure in which a transparent material such as tempered glass is used for the supporting substrate, cells are formed thereon, and light is taken in from the transparent supporting substrate side. Specifically, a superstrate type, a substrate type, a module structure called a potting type, a substrate-integrated module structure used in amorphous silicon solar cells 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. Particularly preferred specific structures and embodiments are described in Japanese Patent Application No. 11-8457.

[0089]

The present invention will be specifically described below with reference to examples. Example 1 1. Preparation of Titanium Dioxide Dispersion Solution Solaronics Co., Ltd.TI-Nanoxide-D (anatase type titanium oxide dispersion, pH =
0.9) 0.20 g of PEG (polyethylene glycol) having a molecular weight of 20,000 was added to 10 g, and sufficiently dissolved and dispersed to obtain a dispersion.

2. 2. Preparation of TiO2 electrode adsorbing dye 2-1. Electrode A Conductive glass coated with fluorine-doped tin oxide (manufactured by Nippon Sheet Glass; area resistance 10Ω / □, 25 mm ×
100mm) on the conductive surface side
electrochimica Acta), 40, 643-652 (199)
A titanium dioxide undercoat layer (thickness: 60 nm) was formed by the spray pyrolysis method described in 5). An adhesive tape was applied to a part of the substrate (3 mm from the peripheral edge) to form a spacer, and the above titanium dioxide dispersion was applied thereon using a stainless steel rod. After the application, the adhesive tape was peeled off and air-dried at room temperature for 30 minutes. Next, the coated glass was placed in an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific Co., Ltd.).
And fired in air at 550 ° C. for 30 minutes. The glass was taken out, cooled in a dry environment at a dew point of -40 ° C until the electrode surface reached 120 ° C, and then immersed in a dehydrated ethanol solution of dye A (3 x 10-4 mol / l) at 60 ° C for 2 hours. Dye A was adsorbed on titanium dioxide on glass. After the dye-adsorbed electrode is washed with dehydrated acetonitrile, it is air-dried and cut into 26 mm x 19 mm squares.
The electrode A was obtained by removing the undercoat layer and the semiconductor layer except for the central portion of 14 mm × 14 mm (light receiving portion). The coating amount of the thus obtained photosensitive layer (the titanium dioxide layer on which the dye was adsorbed) was about 7.0 g / m 2. When the electrode A was treated with an alkaline solution, the dye was easily desorbed, and thus it was confirmed that the dye and the semiconductor fine particles were not covalently bonded.

[0091]

Embedded image

2-2. Electrode B An electrode B was prepared in the same manner as the electrode A, except that the dye B was used instead of the dye A. Dye B was covalently bonded to titanium oxide. Even when the electrode B was treated with an alkali solution, desorption of the dye was hardly observed.

2-3. Electrode C Conductive glass coated with fluorine-doped tin oxide (manufactured by Nippon Sheet Glass; 25 mm × 100 mm, area resistance 10
Ω / □) on the conductive surface side
Ochimica Acta), Vol. 40, pp. 643-652 (1995), to form a titanium dioxide undercoat layer (film thickness: 60 nm) by a spray pyrolysis method. An adhesive tape was applied to a part of the substrate (3 mm from the peripheral edge) to form a spacer, and the above titanium dioxide dispersion was applied thereon using a stainless steel rod. After the application, the adhesive tape was peeled off and air-dried at room temperature for 30 minutes. Next, this glass was placed in an electric furnace (a muffle furnace FP-32 manufactured by Yamato Scientific Co., Ltd.) and fired at 550 ° C. for 30 minutes in air. Take out the glass and keep the electrode surface at 120 ° C in a dry environment with a dew point of -40 ° C.
After cooling to 50%, the mixture was immersed in a solution (5% by mass) of a silane coupling agent C in dehydrated acetonitrile at 50 ° C. for 6 hours to react. After washing with acetonitrile, it was air-dried and then immersed in a dehydrated DMF solution of dye A (3 × 10 −4 mol / l) at 80 ° C. for 2 hours to react. Dye A, silane coupling agent C and titanium oxide were covalently bonded. Even if this electrode C was treated with an alkaline solution, desorption of the dye was hardly observed. The dye-reacted electrode was treated and processed in the same manner as the electrode A to obtain an electrode C.

[0094]

Embedded image

3. Formation of a hole transport layer The hole transport layer A was produced by the following coating step A. The hole transport layer B was prepared by performing the following post-process after the following electroless plating process. The hole transport layer C was prepared by performing the following electroless plating step, the following post-process, and further performing the coating step B. 3-1. Coating Step A The electrode prepared in section 2 was protected on the exposed portion of the conductive surface and the 1 mm width around the light receiving portion, and was left on a hot plate heated to 100 ° C. for 2 minutes. Acetonitrile solution of γ-CuI and Compound D (CuI: 3.2% by mass, Compound D: 0.05% by mass)
0.2 ml was slowly added to the electrode over about 10 minutes while evaporating acetonitrile. After coating, the mixture was allowed to stand on a hot plate for 2 minutes to form a CuI (hole transport) layer. It was confirmed from the cross-sectional SEM that the hole transporting layer was substantially penetrated into the porous film formed by the fine particles of the electrode.

[0096]

Embedded image

3-2. Electroless plating step A plating solution having the following composition was prepared. Plating solution composition ----------------------------------------------- - sodium 10g copper sulfate pentahydrate hydroxide 10g EDTA2Na ₂ dihydrate 30g formaldehyde 4g 2, 2 'dipyridyl _{50mg NaCN 30mg K 2 Ni (CN} ) 4 15mg PEG1000 whole amount was added to 25mg water 1L -------- ----------------------------------------- The pH of the plating solution was 11 . While the plating solution is aerated with air, the temperature is kept at 50 ° C, and the exposed part of the electrode and the 1mm width around the light receiving part of the electrode prepared in Section 2 are immersed and left for about 1 hour, and then washed. Then, a Cu layer was formed by drying.

3-3. Post-Process A Cu layer formed by electroless plating is aged in a sealed iodine vapor at room temperature for 1 hour to convert Cu to CuI and form a CuI layer. did. It was confirmed from the cross-sectional SEM that the hole transport layer formed by this method had deeply penetrated into the porous film.

3-4. Coating Step B Compound E was coated on the CuI layer formed in the previous step, and allowed to stand for 10 hours under a reduced pressure of 1000 Pa or less.
Thereafter, excess molten salt remaining on the surface was removed by blotting with filter paper.

4. Production of Photoelectric Conversion Element Each of the electrodes A, B, and C on which the charge transport layer (hole transport layer) was formed as described above, and platinum-evaporated glass of the same size (platinum layer thickness = 1 μm, glass thickness = 1.1) mm) were overlapped so that the arrangement of FIG. 10 was obtained. (The combination of the electrode and the hole transport layer is as shown in Table 1.) For the overlapping part other than the light receiving part, stretched film (25 μm thickness) of ionomer (Himilan 1702) of DuPont Mitsui Chemicals Co., Ltd. -
Crimping heating was performed for 30 seconds. Further, the overlapping edge portion was sealed using an epoxy resin sealant (manufactured by Solaronix).

5. 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 (AM1.5D manufactured by Oriel). The intensity of this light was 100 mW / cm2. Simulated sunlight was irradiated, and electricity generated between the conductive glass and the counter electrode layer of the photovoltaic cell was measured with a current / voltage measuring device (Keithley SMU2400 type). Table 1 shows the short-circuit current (Jsc). Furthermore, the photoelectric conversion element is shielded from light,
(± 5 ° C.) and left in the air for 24 hours, and then measured in the same manner. Table 1 shows the short-circuit current (Jsc) after lapse of time. Note that “fresh” in the table means a state in which the photoelectric conversion element has not been aged after being manufactured.

[0102]

[Table 1]

As shown in Table 1, the photoelectric conversion elements (2, 3, 5 to 8) of the present invention using a dye (electrodes B and C) bonded to a semiconductor by a covalent bond and using a hole transporting material are shown in Comparative Examples. It can be seen that the short-circuit current after lapse of time is significantly superior to (Photoelectric conversion elements 1 and 4). Furthermore, the elements (5 to 8) produced by a method including an electroless plating step in producing the hole transport layer have a larger short circuit current and are superior to the elements (2, 3) produced by other methods. I understand. Electrodes C (3, 6, 8) in which a semiconductor and a dye are combined using a silane coupling agent are the other (2, 5, 7)
It can be seen that the short-circuit current is large and superior to that of FIG.

[0104]

As described above, it can be seen that the photoelectric conversion element of the present invention has a large short-circuit current and is effective.

[Brief description of the drawings]

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

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

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

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

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

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

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

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

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

FIG. 10 is a schematic diagram illustrating a structure of a photoelectric conversion element manufactured in an example.

[Explanation of symbols]

 10: conductive layer 10a: transparent conductive layer 11: metal lead 20: photosensitive layer 21: semiconductor fine particles 22: dye 23: charge transport material 30: charge transport layer 40: Counter-electrode conductive layer 40a: Transparent counter-electrode conductive layer 50: Substrate 50a: Transparent substrate 60: Undercoat layer 1: Dye adsorption electrode 2: Platinum vapor-deposited glass 3: Light receiving unit (14mm x 14mm)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tadahiko Kubota 210 Nakanuma, Minamiashigara-shi, Kanagawa Prefecture Fuji Photo Film Co., Ltd. F-term (reference) 5F051 AA14 5H032 AA06 AS16 CC17 EE01 EE16 EE17

Claims (5)

[Claims] 1. A photoelectric conversion device having a conductive layer, a semiconductor fine particle layer sensitized by a dye, a charge transport layer, and a counter electrode, wherein the dye is covalently bonded to the semiconductor fine particles,
A photoelectric conversion element using an inorganic and / or organic hole transport material for the charge transport layer. 2. The photoelectric conversion device according to claim 1, wherein the inorganic hole transport material is a monovalent copper compound. 3. The photoelectric conversion device according to claim 2, wherein the monovalent copper compound is produced by a process including a copper electroplating process or an electroless plating process using a copper salt. 4. The photoelectric conversion device according to claim 1, wherein the dye covalently bonded to the semiconductor fine particles is an organometallic complex dye and / or a merocyanine dye. 5. A photovoltaic cell using the photoelectric conversion element according to claim 1. Description: