JP2007018891A - Manufacturing method of treated metal oxide semiconductor particle, manufacturing method of photoelectric conversion electrode using the treated metal oxide semiconductor particle manufactured by the method, and photoelectric conversion cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a treated metal oxide semiconductor particle, suitable for a compound semiconductor based material having strong durability and absorbing power over a wide wavelength region with respect to sunlight as a sensitizing part, by making the best use of the feature that a titanium oxide porous layer binding dyes, since the sensitizing part can efficiently carry out photoelectric conversion by utilizing the size of its surface area, in a dye-sensitized photoelectric conversion cell. <P>SOLUTION: In this manufacturing method of the treated metal oxide semiconductor particles, the metal oxide semiconductor particle, having an average particle diameter of not less than 1 nm and not more than 200 nm, is brought into contact with salt or a chelate compound of copper, a sulfur source compound, and salt or a chelate compound of a metal, other than copper if required, and a copper-containing metal sulfide is bound to the surface of the metal oxide semiconductor particle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing treated metal oxide semiconductor particles suitably used for producing a photoelectric conversion cell, a method for producing a photoelectric conversion electrode using the same, and a photoelectric conversion cell.

  As solar power generation, single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, compound semiconductor solar cells such as cadmium telluride and indium copper selenide have been put into practical use or are subject to research and development. . However, in widespread use of compound semiconductor solar cells, it is necessary to overcome problems such as manufacturing cost, securing raw materials, and long energy payback time. On the other hand, many solar cells using organic materials aimed at increasing the area and price have been proposed so far, but have the problems of low conversion efficiency and poor durability.

Under such circumstances, Nature (Vol. 353, 737-740, 1991) and US Pat. No. 4927721, etc., and a photoelectric conversion electrode and a photoelectric conversion cell using a semiconductor microporous material sensitized with a dye. , And materials and manufacturing techniques for making it have been disclosed. The proposed battery is a dye-sensitized photoelectric conversion cell comprising a titanium oxide porous layer spectrally sensitized with a sensitizing dye such as a ruthenium complex, an electrolyte mainly composed of iodine, and a counter electrode. The first advantage of this method is that an inexpensive photoelectric conversion element can be provided because an inexpensive oxide semiconductor such as titanium oxide is used. The second advantage is that the ruthenium complex used is widely used in the visible light range. Since it has absorption, a relatively high conversion efficiency is obtained.
In J. Am. Chem. Soc. (2001), Vol. 123, pp1613-1624, a tripyridylcarboxylate coordination was carried out on a titanium oxide porous film formed by baking after forming a film with a titanium oxide dispersion. It has been reported that a cell was produced using an electrode on which a ruthenium complex having a child was adsorbed and a conversion efficiency of 10.4% was achieved.

However, since the dye-sensitized photoelectric conversion cell has a dye as the sensitizing portion, it has a drawback of low durability against light and heat compared to a compound semiconductor solar cell such as a silicon-based or CIGS-based compound. .
On the other hand, there is a compound semiconductor solar cell as a group expected as a next generation solar cell. A compound semiconductor solar cell uses CuInS, CuInSe, CuGaSe, Cu ₂ InGaSe ₂ , Cu ₂ ZnSnS ₂ or the like as a photoreceptor, and is expected to be a low-cost and highly durable solar cell. CuInS ₂ , CuGaS ₂ , CuInSe, and CuGaSe have band gaps of 1.5 eV, 2.43 eV, 1.04 eV, and 1.68 eV, respectively, and have a large light absorption coefficient. Can contribute to conversion.
Adv. Mater. (2004), Vol. 16, No. 5, pp453-456 shows an example in which CuInS is used as a photosensitive layer by a AL-CVD method on a titanium oxide porous film. This is a method of forming a film by repeatedly reacting the raw material compound molecules on the substrate in the vacuum chamber one layer at a time and purging with nitrogen repeatedly, which requires a reduced pressure manufacturing device and requires a large number of repeated steps for atmosphere exchange. Therefore, mass production is difficult.
Nature (Vol.353, 737-740, 1991) US Patent 4927721 J. Am. Chem. Soc. (2001), Vol. 123, pp1613-1624 Adv.Mater. (2004), Vol.16, No.5, pp453-456

  In the dye-sensitized photoelectric conversion cell, the present invention makes use of the feature that the titanium oxide porous layer that binds the dye as a sensitizer can efficiently perform photoelectric conversion using the surface area, and is durable as a sensitizer. It is an object of the present invention to provide a method for producing treated metal oxide semiconductor particles suitable as a compound semiconductor material that is highly resistant and absorbs sunlight in a wide wavelength range. In that case, it aims at providing the manufacturing method which this sensitizing layer can form in a wet process aiming at an inexpensive photoelectric conversion cell with high safety and health.

The method for producing a treated metal oxide semiconductor particle according to the present invention comprises contacting a metal oxide semiconductor particle having an average primary particle diameter of 1 nm or more and 200 nm or less, a copper salt or a chelate compound, and a sulfur source compound to form a metal oxide semiconductor. It is characterized by binding copper sulfide to the surface of the particles.
Further, the method for producing the treated metal oxide semiconductor particles of the present invention comprises metal oxide semiconductor particles having an average primary particle diameter of 1 nm to 200 nm, a copper salt or chelate compound, a sulfur source compound, and a metal other than copper. It is characterized by contacting with a salt or a chelate compound to bind a copper-containing metal sulfide to the surface of the metal oxide semiconductor particles.
Moreover, the manufacturing method of the photoelectric conversion electrode of this invention is characterized by including the process of forming into a film the process metal oxide semiconductor particle manufactured by one of the said methods on a transparent electrode base material.
Moreover, the photoelectric conversion cell of this invention comprises the photoelectric conversion electrode manufactured by the said method, an electrolyte, and a conductive counter electrode, It is characterized by the above-mentioned.

  Since the photoelectric conversion electrode obtained by the present invention has a sensitized portion made of an inorganic material on the surface of a metal oxide semiconductor electrode having a large surface area, it is possible to achieve both efficient photoelectric conversion capability and high durability. Can do. Further, since the sensitizer can be processed in the liquid phase without using the vapor phase method, the photoelectric conversion electrode can be provided at a low production cost. As a result, an inexpensive and highly durable photoelectric conversion cell can be provided.

The photoelectric conversion cell in the present invention is mainly formed from a photoelectric conversion electrode that receives light such as sunlight and performs photoelectric conversion, an electrolyte, and a conductive counter electrode. The photoelectric conversion electrode in the present invention includes a transparent electrode substrate, a metal oxide semiconductor porous layer formed by forming metal oxide semiconductor particles on a conductive surface thereof, and a porous metal oxide semiconductor porous layer It consists of a sensitizing part formed on the surface. A configuration consisting only of a transparent electrode substrate and a metal oxide semiconductor porous layer is distinguished as a metal oxide semiconductor electrode.
The mode of the photoelectric conversion electrode in the present invention is similar to the photoelectric conversion electrode in the dye-sensitized solar cell, and its sensitization part is close to that in which the dye is replaced with copper sulfide or copper-containing metal sulfide.

(Metal oxide semiconductor particles)
In the present invention, the “metal oxide semiconductor particles” collectively includes the total of primary particle bodies, secondary particle bodies, and porous layers formed by film formation thereof in the dispersion. The primary particle body is the smallest unit recognized as a particle by observation with an electron microscope or the like, and this average value is the average primary particle diameter. The primary particle size is measured by image processing of an electron micrograph. The secondary particle body is a unit recognized as an aggregate due to aggregation of the primary particle body in the dispersion, and this average value is the average secondary particle diameter. The secondary particle size is measured with a particle size distribution meter in the dispersion. The metal oxide semiconductor electrode includes a transparent electrode and metal oxide semiconductor particles. The method for forming a photoelectric conversion electrode in the present invention includes a case where a sensitized portion is formed on the surface of a metal oxide semiconductor particle and then laminated on the surface of the transparent electrode, and the surface after the metal oxide semiconductor electrode is first formed. In some cases, a sensitization part is added to the film. Furthermore, the method for forming the sensitizing portion on the surface of the metal oxide semiconductor particle may be to form the sensitizing portion on the surface of the primary particle body or to form the sensitizing portion on the surface of the secondary particle body.
The metal oxide semiconductor particles may be composed of a single metal oxide as a composition, or may be composed of oxides of a plurality of metal species.

In the present invention, the metal oxide semiconductor particles also include a composite metal oxide semiconductor particle having a core-shell structure in which a metal oxide having a composition different from the composition inside the particle is included in the surface layer of the particle. In this case, in the present invention, the internal metal oxide corresponding to the core is defined as the first metal oxide semiconductor particles, and the surface metal oxide corresponding to the shell is defined as the second metal oxide semiconductor. The second metal oxide semiconductor may further comprise a laminated structure of a plurality of types of metal oxides.
In order to obtain the sensitization effect using copper sulfide and copper-containing metal sulfide, which will be described later, the level of the conduction band of the metal oxide porous layer is changed from the photoexcited level of the metal sulfide. It is desirable to be in a position where it can be easily received. For this reason, various metal oxides can be used as the material for the first metal oxide semiconductor particles, but those containing at least one of Ti, Zn, Sn, and Nb as metal species are particularly suitable. is there. More preferably, Ti is mentioned.
For the purpose of optimizing the photoexcitation order of the sensitizer, a metal other than copper may be used as a component of the copper-containing metal sulfide. Preferably, divalent zinc, trivalent indium, trivalent gallium, tetravalent tin and the like are used in combination for this purpose.

When a second metal oxide semiconductor layer that becomes a buffer layer or a semi-insulating layer is formed on the surface of the first metal oxide semiconductor particle, when a photoelectric conversion electrode is formed, an efficient electron such as preventing a reverse electron process Contributes to the movement of.
Various metal oxides can be used as the material for the second metal oxide semiconductor layer. Although depending on the combination with the first metal oxide semiconductor particles, those having no unpaired electrons in the d orbital or the like in the oxide state are suitable because excitation electrons are hardly deactivated. This includes oxides such as Mg, Al, Si, Sc, Ti, Zn, Ga, Ge, Sr, Y, Zr, Nb, In, Sn, Ba, La, Ta.
Further, a metal sulfide such as InS or CdS may be inserted as a buffer layer between the metal oxide semiconductor particles and the sensitizer.

（式中、Ｍは、１価から6価の金属原子を示す。Ｒ₁、Ｒ₂、Ｒ₃は、それぞれ独立に水素原子または１価の置換基を示す。矢印は、酸素原子からＭへの配位結合またはイオン結合を示す。破線は、ジケトナート化合物構造中の非局在結合を示す。） The second metal oxide semiconductor layer can be easily formed by oxidizing the second metal oxide semiconductor precursor on the surface in the presence of the first metal oxide semiconductor particles.
As a precursor of the second metal oxide semiconductor, many metal alcoholates are known and may be used. The precursor containing the structure of the formula (1) is dispersed in the metal oxide semiconductor particles. Therefore, it is useful for forming a homogeneous and dense second metal oxide semiconductor layer.
General formula (1)

(In the formula, M represents a monovalent to hexavalent metal atom. R ₁ , R ₂ , and R ₃ each independently represents a hydrogen atom or a monovalent substituent. The arrow represents an oxygen atom to M. (The broken line indicates a delocalized bond in the diketonate compound structure.)

  Representative examples of the monovalent substituent in the present invention include an alkyl group, an alkoxyl group, an alkylthio group, an arylthio group, a halogen group, a nitro group, a cyano group, a thiocyanic acid group, an isothiocyanic acid group, an amino group, and a monoalkylamino. Group, dialkylamino group, aryl group, aryloxy group, monoarylamino group, diarylamino group, alkyl peptide group, aryl peptide group, alkylcarbonyl group (acyl group), arylcarbonyl group, sulfonic acid amide group, sulfonic acid ester Group, dialkyloxyphosphoryl group, diaryloxyphosphoryl group, alkyloxyaryloxyphosphoryl group, dialkylphosphoryl group, diarylphosphoryl group, alkyloxyarylphosphoryl group, dialkoxyphosphinooxy group, diaryloxy Sufinookishi group, alkoxy aryloxy phosphino group, a phthalimidomethyl group, polyether group, and the like, but not limited thereto.

The halogen group includes fluorine, chlorine, bromine and iodine.
The alkyl group may have a branch, an alicyclic ring, or an unsaturated bond.
As the aryl group, a heterocyclic group in which carbon in the aromatic ring is partially replaced with nitrogen, oxygen, or sulfur may be used.
Each of the substituents may further have a composite of the substituents.

As a method for oxidizing the second metal oxide semiconductor precursor, treatments such as baking, heat treatment, ozone treatment, and ultraviolet irradiation can be used alone or in combination. Further, when a metal alcoholate or the like is used as a precursor of the second metal oxide semiconductor, the operation of obtaining the metal oxide by hydrolyzing it is also the precursor of the second metal oxide semiconductor here. Called oxidation.
When the thing which has a 2nd metal semiconductor on the surface of a 1st metal semiconductor particle can be obtained by surface treatment etc. of another method, this can be used as a raw material for the following copper containing metal sulfide process.

  As the surface area of the photoelectric conversion electrode increases, the surface area of the sensitizer increases, and the conversion efficiency as a photoelectric conversion cell improves. For this purpose, the average primary particle diameter of the metal oxide semiconductor particles is preferably 1 nm or more and 200 nm or less. When the particle diameter is less than this range, the particles are too close to each other, and voids during film formation are hardly formed, and the surface area is decreased, which is not preferable. If the particle diameter exceeds this, voids can be secured, but the surface area per unit film thickness is reduced, which is not preferable. More preferably, the average primary particle diameter of the metal oxide semiconductor particles is 10 nm or more and 50 nm or more.

(Copper sulfide and copper-containing metal sulfide)
In the present invention, the treated metal oxide semiconductor particles are obtained by binding copper sulfide or copper-containing metal sulfide to the surface of the metal oxide semiconductor particles. Here, the copper sulfide includes at least monovalent copper or divalent copper sulfide. Specifically, it includes copper sulfide alone such as Cu (I) ₂ S, Cu (II) S, and mixed valence copper sulfide such as Cu (I) _1.2 Cu (II) _0.4 S. The copper-containing metal sulfide is a sulfide containing a different metal species in addition to the copper sulfide. Specifically, it is a metal sulfide containing a metal species other than copper, such as Cu (I) In (III) S ₂ and Cu (I) ₂ Sn (IV) Zn (II) S ₄ .

(Sulfur source compound)
As a method for binding copper sulfide and copper-containing metal sulfide to the surface of the metal oxide semiconductor particle, in the present invention, Cu salt, In salt, Ga salt, Zn salt, Sn salt are present in the presence of the metal oxide semiconductor particle. A metal salt such as sulfur and a sulfur source compound are brought into contact with each other and precipitated on the particle surface as a metal sulfide.
The sulfur source compound in the present invention is a compound that can be used as a raw material for a photoelectric conversion electrode when it comes into contact with a metal salt or chelate compound used in the production of a photoelectric conversion electrode and the sulfur element is released from the sulfur source compound and forms a bond with the metal element.

(Binding method for copper sulfide and copper-containing metal sulfide)
One method for binding copper sulfide and copper-containing metal sulfide to the surface of metal oxide semiconductor particles is to disperse metal oxide semiconductor particles such as titanium oxide in a solution in which all of the metal salt is homogeneously dissolved. Next, the solution of the sulfur source compound is brought into contact. Although various divalent sulfide salts can be used as the sulfur source compound, in particular, when (NH ₄ ) ₂ S is used, the reaction is easier to proceed quantitatively and gently than when hydrogen sulfide is used. It is less likely to cause danger to workers due to hydrogen gas and corrosion in the work environment. Sodium sulfide or the like may deteriorate battery performance if alkali metal ions or the like remain. The use of (NH ₄ ) ₂ S is optimal as a sulfur source compound because of ease of handling in the process and ease of removal.
Metal salts including Cu salt, In salt, Ga salt, Zn salt and Sn salt include strong acid salts such as chlorides and halides, sulfates and nitrates, acetates, carbonates and oxalates. And chelate compounds such as weak acid such as phosphate, organic acid salt and acetylacetonate.

When performing the above contact treatment, when heating and ultraviolet irradiation are used in combination, crystallization of copper sulfide and copper-containing metal sulfide is promoted, and a photoelectric conversion electrode with higher conversion efficiency can be obtained.
The binding amount of the copper-containing metal sulfide is a content ratio of 1 part by weight to 300 parts by weight, preferably 10 parts by weight to 100 parts by weight with respect to 100 parts by weight of the metal oxide semiconductor particles. When the amount of binding is smaller than this, it is difficult to obtain a sensitizing effect, and when it is large, electron transfer in the metal oxide semiconductor is easily inhibited. In addition, raw material costs are also increased.
After binding copper sulfide or copper-containing metal sulfide to the surface of the metal oxide semiconductor particle, as post-treatment, heating, pressurization or ultrasonic welding treatment, microwave irradiation treatment, ultraviolet light irradiation treatment, ozone By performing the treatment or a combination treatment thereof, the binding force to the surface of the metal oxide semiconductor particles can be increased or crystallization can be promoted.

(Form of treated metal oxide semiconductor particles)
In the present invention, the definition of “treated metal oxide semiconductor particles” collectively includes the total of primary particle bodies, secondary particle bodies, and porous layers formed by film formation of these particles in the dispersion.
The form of the treated metal oxide semiconductor particles corresponding to the present invention is shown in FIGS.
1 to 6 represent partial structures of treated metal oxide semiconductor particles in a photoelectric conversion electrode.
In each figure, a is the first metal oxide semiconductor particle, b is the second metal oxide semiconductor, and c is copper sulfide or copper-containing metal sulfide. c absorbs light, and electrons generated by charge separation are injected into the conduction band of a. The second metal oxide semiconductor b enters between a and c as a buffer layer or a semi-insulating layer and contributes to efficient electron transfer such as preventing a reverse electron process. b may consist of a plurality of layers having different compositions. Copper sulfide or copper-containing metal sulfide is a metal once deposited on a substrate, whether it is bound to the primary particle surface of the metal oxide semiconductor particle or the secondary particle surface. It may be bound to the surface of the oxide semiconductor particle layer.

As shown in FIG. 1, a configuration in which b and c are formed on the surface of a particle conducted at the grain interface of a is most ideal for electron transfer in the electrode. In this configuration, after forming a metal oxide semiconductor electrode with only the first metal oxide semiconductor particles, the surface treatment is performed with the precursor of the second metal oxide semiconductor which can be b, and then the oxidation is performed. It is obtained by the method of forming c by the method of.
In another method, when b is formed on the particle surface in a state where the metal oxide semiconductor particles are dispersed up to the primary particles, and c is formed after the film formation, the structure shown in FIG. 2 is obtained. If the film is formed after the formation, the structure of FIG. 3 is likely to be obtained. Forming the film by forming b and c on the particle surface first in a dispersed state is advantageous in terms of the process because a post-processing step of performing chemical treatment on the metal oxide semiconductor particles of the coating film can be omitted.
When the step of forming b is omitted, the configurations of FIGS. 4 and 5 exist.

  When b and c are formed in a state where the metal oxide semiconductor particles are dispersed to secondary particles of an appropriate size, and these are formed, the structure shown in FIG. 6 is obtained according to the state of FIG. A post-processing step after the film formation is not necessary, and a film state having a configuration similar to that shown in FIG. In this case, if the secondary particle size is too large, the dispersion stability is also deteriorated, the density of the film is also roughened, and the conduction between the secondary particles and the adhesion to the transparent electrode are also deteriorated. A state with a particle diameter of 10 nm to 500 nm is appropriate. The secondary particle size is more suitably in a state where the average particle size is 50 nm or more and 200 nm or less.

(Create dispersion)
Solvents that can disperse the metal oxide semiconductor particles or the treated metal oxide semiconductor particles as raw materials are alcohol solvents such as ethanol, isopropyl alcohol, benzyl alcohol, 1-octanol, butyl cellosolve, and butyl carbitol, acetonitrile , Nitrile solvents such as propionitrile, halogen solvents such as chloroform, dichloromethane and chlorobenzene, ether solvents such as diethyl ether and tetrahydrofuran, ester solvents such as ethyl acetate and butyl acetate, ketones such as acetone, methyl ethyl ketone and cyclohexanone Solvents, carbonate esters such as diethyl carbonate and propylene carbonate, carbohydrate solvents such as hexane, octane, toluene and xylene, dimethylformamide, dimethylacetamide Dimethyl sulfoxide, 1,3-dimethyl imidazolinone, N-methylpyrrolidone, may be water or the like is not limited thereto. Two or more kinds of solvents may be mixed and used.

The dispersion treatment is generally carried out using, for example, a zirconia bead and a paint shaker or a mill, but is not limited thereto.
The dispersion can contain a binder resin in order to obtain an appropriate viscosity.
Examples of the binder resin include cellulose, polyethylene glycol, acrylic, urethane, polyol, polyethylene, and polyamide, but suitable viscosity and film formability of the dispersion, and characteristics as an electrode after film formation. It is not limited to this as long as it can obtain
When producing a photoelectric conversion electrode from metal oxide semiconductor particles, it is desirable that necking be formed between the particles during film formation in order to obtain a conductive electrode. For this purpose, pressure treatment, ultrasonic welding treatment is performed. If microwave treatment is effective, use it in combination.

(Conductive surface for transparent electrodes)
The transparent electrode used in the present invention comprises a conductive surface and a transparent substrate. In the present invention, the porous layer on the transparent electrode is formed on the conductive surface. The conductive surface is not particularly limited as long as it is a conductive material that absorbs little light from the visible to the near-infrared region of sunlight. However, ITO (indium-tin oxide) or tin oxide (a material doped with fluorine or the like) can be used. Metal oxides having good electrical conductivity such as zinc oxide are preferable. SPD method (spray pyrolysis method), sputtering method, etc. for the purpose of preventing reverse electron reaction before forming a layer of metal oxide semiconductor particles with copper-containing metal sulfide bound to the solid component surface on the conductive surface It is desirable to provide a titanium oxide layer or the like by this method.

(Transparent substrate for transparent electrodes)
The transparent substrate used for the electrode having a conductive surface is not particularly limited as long as it is a material that absorbs less light from the visible to the near infrared region of sunlight. Glass substrates such as quartz, ordinary glass, BK7, lead glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyester, polyethylene, polycarbonate, polyvinyl butyrate, polypropylene, tetraacetylcellulose, syndioctane polystyrene, polyphenylene sulfide, polyarylate Resin base materials such as polysulfone, polyester sulfone, polyetherimide, cyclic polyolefin, brominated phenoxy, and vinyl chloride can be used.

(Photoelectric conversion cell)
The photoelectric conversion electrode used in the present invention forms a photoelectric conversion cell by combining a conductive counter electrode through an electrolyte layer.
(Electrolyte layer)
The electrolyte layer used in the present invention is preferably composed of an electrolyte, a medium, and an additive. The electrolyte of the present invention is a mixture of I ₂ and iodide (for example, LiI, NaI, KI, CsI, MgI ₂ , CaI ₂ , CuI, tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, etc.), Br ₂ Mixtures of bromide and bromide (for example, LiBr, etc.), molten salts described in Inorg. Chem. 1996, 35, 1168-1178, etc. can be used, but not limited thereto. Among these, an electrolyte in which LiI, pyridinium iodide, imidazolium iodide, or the like is mixed as a combination of I ₂ and iodide is preferable in the present invention.
The preferable electrolyte concentration is 0.01 M to 0.5 M in the medium I ₂ and 0.1 M to 15 M in the iodide mixture.

  The medium used for the electrolyte layer in the present invention is desirably a compound that can exhibit good ionic conductivity. Solution media include ether compounds such as dioxane and diethyl ether, chain ethers such as ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether, methanol, ethanol, and ethylene glycol monoalkyl. Alcohols such as ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin, acetonitrile, glutarodinitrile, Methoxyacetonitrile, propioni Lil, nitrile compounds such as benzonitrile, ethylene carbonate, carbonate compounds such as propylene carbonate, 3-methyl-2-oxazolidinone heterocyclic compounds such as dimethyl sulfoxide, can be used aprotic polar substances such as sulfolane, water, and the like.

Further, for the purpose of using a solid (including gel) medium, a polymer may be included. In this case, a polymer such as polyacrylonitrile or polyvinylidene fluoride is added to the solution-like medium, or a polyfunctional monomer having an ethylenically unsaturated group is polymerized in the solution-like medium to make the medium solid. To do.
As the electrolyte layer, an electrolyte that does not require CuI or CuSCN medium, and 2,2 ′, 7,7′-tetrakis (N, N described in Nature, Vol. 395, 8 Oct. 1998, p583-585) can be used. Hole transport materials such as -di-p-methoxyphenylamine) 9,9'-spirobifluorene can be used.

In the electrolyte layer used in the present invention, an additive that functions to improve the electrical output of the photoelectric conversion cell or improve the durability can be added. Examples of additives that improve electrical output include 4-t-butylpyridine, 2-picoline, 2,6-lutidine, and cyclodextrin. MgI etc. are mentioned as an additive which improves durability.
Further, if the photoelectric conversion element can be operated, electrolyte injection can be omitted. In this case, in order to ensure adhesion between the photoelectric conversion electrode and the counter electrode, a method such as directly depositing a counter electrode layer on the surface of the photoelectric conversion electrode is taken.

(Conductive counter electrode)
The conductive counter electrode used in the present invention functions as a positive electrode of a photoelectric conversion cell. Specifically, conductive materials used for the counter electrode include metals (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), metal oxides (ITO (indium-tin oxide), tin oxide (fluorine, etc.)). , Zinc oxide), or carbon. The thickness of the counter electrode is not particularly limited, but is preferably 5 nm or more and 10 μm or less.

(How to assemble)
A photoelectric conversion cell is formed by combining the photoelectric conversion electrode and the conductive counter electrode via an electrolyte layer. In order to prevent leakage and volatilization of the electrolyte layer as necessary, sealing is performed around the photoelectric conversion cell. For sealing, a thermoplastic resin, a photocurable resin, glass frit, or the like can be used as a sealing material. The photoelectric conversion cell is made by connecting small-area photoelectric conversion cells as necessary. The electromotive voltage can be increased by combining the photoelectric conversion cells in series.

  According to the present invention, metal oxide semiconductor particles and electrodes whose surfaces are treated with a copper-containing metal sulfide can be obtained. Since the treated metal oxide semiconductor particles obtained in the present invention are obtained by a reaction in a solution, they can be produced at a low cost. Furthermore, since a sensitizing dye is not used and light of a wide wavelength can be photoelectrically converted with an inorganic material, it is excellent in durability.

Examples are shown below specifically, but the present invention is not limited to the following examples.
(Example 1)
-Preparation of metal oxide semiconductor dispersion In Table 1, the dispersion composition of the metal oxide semiconductor particles of Example 1 was mixed with zirconia beads, and a dispersion was obtained using a paint shaker. As the first metal oxide particles, titanium oxide (P25 manufactured by Nippon Erosil Co., Ltd.) was used, and Zn acetylacetonate was used as the precursor of the second metal oxide semiconductor.
The solvent was removed by distillation under reduced pressure, the dispersion was sintered at 400 ° C., and after pulverization, 10 g was put into an aqueous ammonia solution of cuprous chloride and redispersed with a paint shaker until the secondary particle size became 200 nm.

Next, a (NH ₄ ) ₂ S aqueous solution containing sulfur in an amount capable of quantitatively reacting with copper ions is added dropwise with stirring, heat treatment at 60 ° C., the particles are filtered, air-dried, and dispersed in ethanol. A metal oxide semiconductor particle dispersion treated with sulfide was prepared.
The finished dispersion was applied to a transparent electrode substrate to prepare a 1 cm square cell in which a porous layer was formed to a thickness of 13 μm (+ −2 μm). The transparent electrode is made of a glass substrate (Asahi Glass Co., Ltd .; the transparent conductive film is FTO), and the conductive film surface is provided with a 100 nm thick titanium oxide layer. After heat treatment at 150 ° C. for 1 hour, the electrolyte and A cell was prepared by applying a counter electrode, and the conversion efficiency was measured.

・ Electrolyte with the following formulation Solvent Methoxyacetonitrile
LiI 0.1M
I ₂ 0.05M
4-t-butylpyridine 0.5M
1-propyl-2,3-dimethylimidazolium iodide 0.6M

-Assembly of photoelectric conversion cell The test sample of the photoelectric conversion cell was assembled as shown in FIG.
The conductive counter electrode was a glass substrate with a fluorine-doped tin oxide layer (type U-TCO manufactured by Asahi Glass Co., Ltd.) and a platinum layer having a thickness of 150 nm laminated on the conductive layer by sputtering.
As the resin film spacer, a 25 μm thick “High Milan” film manufactured by Mitsui DuPont Polychemical Co., Ltd. was used.

・ Measurement method of conversion efficiency Combined solar simulator (# 8116) manufactured by ORIEL with air mass filter, 1-SUN with a light meter The IV curve characteristics were measured using an IV curve tracer (MP160) manufactured by Eihiro Seiki Co., Ltd. while irradiating the test sample of the photoelectric conversion cell with light. The conversion efficiency η was calculated by the following equation using Voc (open circuit voltage value), Isc (short circuit current value), and ff (fill factor value) obtained from the IV curve characteristic measurement.

η (%) = Voc (V) × Isc (mA) × ff × 100
100 (mW / cm ² ) × 1 (cm ² )

(Examples 2 to 30)
Electrodes were similarly prepared for photoelectric conversion electrodes having other configurations.
The results are summarized in Tables 1-3.

[Explanation of symbols in the table]
acac (acetylacetonate group; in general formula (1), R ₁ and R ₃ are methyl groups, R ₂ is a hydrogen element), Me (methyl group), Et (ethyl group), Pr (propyl group), nPr (normal) Propyl group), iPr (isopropyl group), Bu (butyl group), nBu (normal butyl group)
(* 1) The “precursor of the second metal oxide semiconductor” is present in a dissolved or dispersed state in the solvent as a composition in the “dispersion of metal oxide semiconductor particles”.

(Examples 31-33)
In Table 4, the dispersion composition of metal oxide semiconductor particles was applied to a transparent electrode substrate, formed into a film, and then fired together with the substrate to form a second metal oxide semiconductor on the surface of the metal oxide semiconductor particles. Thereafter, a copper-containing metal salt aqueous solution in the table was dropped on the electrode, dried at 60 ° C., and a (NH ₄ ) ₂ S aqueous solution was dropped to obtain a photoelectric conversion electrode. The other tests were the same as in Examples 1-30.

[Explanation of symbols in the table]
acac (acetylacetonate group; in general formula (1), R ₁ and R ₃ are methyl groups, R ₂ is a hydrogen element), Me (methyl group), Et (ethyl group)
(* 1) The “precursor of the second metal oxide semiconductor” is present in a dissolved or dispersed state in the solvent as a composition in the “dispersion of metal oxide semiconductor particles”.

(Example 34)
When the same treatment as in Example 3 was performed, the process of forming the copper-containing metal sulfide was performed while performing ultraviolet irradiation. The resulting conversion efficiency was 3.17%.
(Comparative Example 1)
As a comparison with a dye-sensitized solar cell, a durability comparison test was performed.
The electrode was prepared by applying a dispersion of titanium oxide (P25) to a transparent electrode in a square of 1 cm 2 by a conventional method, firing at 450 ° C., and adsorbing a Ru dye (N719). A cell was prepared by a conventional method, and the change in conversion efficiency was compared with the cell of Example 3 using a fade meter equivalent to 1-Sun. After 3 days of irradiation, the conversion efficiency of the dye-sensitized solar cell decreased by 20%, but the cell of Example 3 remained at a decrease of 2%.

The partial structure in the photoelectric conversion electrode of a process metal oxide semiconductor particle (binding at the primary particle interface of a 1st metal oxide semiconductor). The partial structure in the photoelectric conversion electrode of a process metal oxide semiconductor particle (binding at the 2nd metal oxide semiconductor interface). Partial structure of the treated metal oxide semiconductor particles in the photoelectric conversion electrode (binding at the copper-containing metal sulfide interface). Partial structure of the treated metal oxide semiconductor particles in the photoelectric conversion electrode (binding at the primary particle interface of the first metal oxide semiconductor; no second metal oxide). Partial structure of the treated metal oxide semiconductor particles in the photoelectric conversion electrode (binding at the copper-containing metal sulfide interface. No second metal oxide). Partial structure of the treated metal oxide semiconductor particles in the photoelectric conversion electrode (after forming the second metal oxide semiconductor layer and the copper-containing metal oxide semiconductor layer on the secondary particle surface of the first metal oxide semiconductor particles) , Film formation). The schematic diagram of a photoelectric conversion cell test sample.

Explanation of symbols

a. First metal oxide semiconductor particles b. A second metal oxide semiconductor c. Copper-containing metal sulfide Processed metal oxide semiconductor porous layer (copper-containing sulfide has been bound)
2. 2. Electrolyte solution layer Transparent electrode layer (fluorine-doped tin oxide or ITO)
4). 4. Pt electrode layer Transparent electrode6. 6. Resin film spacer Conversion efficiency measurement lead

Claims (19)

  Metal oxide semiconductor particles having an average primary particle diameter of 1 nm or more and 200 nm or less, a copper salt or chelate compound, and a sulfur source compound are contacted to bind copper sulfide to the surface of the metal oxide semiconductor particles. A process for producing treated metal oxide semiconductor particles.   Metal oxide semiconductor particles having an average primary particle diameter of 1 nm or more and 200 nm or less, a copper salt or chelate compound, a sulfur source compound, and a metal salt or chelate compound other than copper are brought into contact with each other, and the surface of the metal oxide semiconductor particles A process for producing treated metal oxide semiconductor particles, wherein a copper-containing metal sulfide is bound to a metal.   3. The method for producing treated metal oxide semiconductor particles according to claim 1, wherein the average secondary particle diameter of the metal oxide semiconductor particles is 10 nm or more and 500 nm or less.   The treated metal oxide according to claim 1 or 3, wherein metal oxide semiconductor particles having an average primary particle diameter of 1 nm to 200 nm are added to a copper salt or chelate compound solution, and then a sulfur source compound is added. Of manufacturing semiconductor particles.   Claims characterized in that metal oxide semiconductor particles having an average primary particle diameter of 1 nm to 200 nm are added to a solution of copper salt or chelate compound and metal salt or chelate compound other than copper, and then a sulfur source compound is added. Item 4. A method for producing a treated metal oxide semiconductor particle according to Item 2 or 3. The process for producing treated metal oxide semiconductor particles according to claim 1, wherein the sulfur source compound contains (NH ₄ ) ₂ S.   The method for producing treated metal oxide semiconductor particles according to claim 1, wherein the contact treatment is performed while irradiating with ultraviolet rays.   The copper salt or chelate compound contains monovalent copper, and the metal salt or chelate compound other than copper contains any of divalent zinc, trivalent indium, trivalent gallium, and tetravalent tin. The method for producing treated metal oxide semiconductor particles according to any one of claims 2, 3, 5 and 6.   The treatment according to claim 1, wherein the metal oxide semiconductor particles are composite metal oxide semiconductor particles having a second metal oxide semiconductor on the surface of the first metal oxide semiconductor particles. A method for producing metal oxide semiconductor particles.   The process according to claim 9, wherein the composite metal oxide semiconductor particles are obtained by oxidizing the precursor of the second metal oxide semiconductor in the presence of the first metal oxide semiconductor particles. A method for producing metal oxide semiconductor particles.   The method for producing treated metal oxide semiconductor particles according to claim 9 or 10, wherein the first metal oxide semiconductor particles contain at least one metal selected from Ti, Zn, Sn, and Nb. The method for producing treated metal oxide semiconductor particles according to claim 10 or 11, wherein the precursor of the second metal oxide semiconductor includes a structure represented by the following general formula (1).
General formula (1)

(In the formula, M represents a monovalent to hexavalent metal atom. R ₁ , R ₂ , and R ₃ each independently represents a hydrogen atom or a monovalent substituent. The arrow represents an oxygen atom to M. (The broken line indicates a delocalized bond in the diketonate compound structure.)   The second metal oxide semiconductor is at least one metal selected from Mg, Al, Si, Sc, Ti, Zn, Ga, Ge, Sr, Y, Zr, Nb, In, Sn, Ba, La, Ta The process metal oxide semiconductor particle and manufacturing method in any one of Claims 9-12 containing this.   The content of the copper-containing metal sulfide is 1 part by weight or more and 300 parts by weight or less with respect to 100 parts by weight of the metal oxide semiconductor particles, The production of the treated metal oxide semiconductor particles according to any one of claims 1 to 13. Method.   The process metal oxide semiconductor particle manufactured by the method in any one of Claims 1-14.   The manufacturing method of the photoelectric conversion electrode including the process of forming into a film the process metal oxide semiconductor particle of Claim 15 on a transparent electrode base material.   Furthermore, the process of the photoelectric conversion electrode of Claim 16 including the process of performing a heating, pressurization, an ultrasonic welding process, a microwave irradiation process, an ultraviolet light irradiation process, an ozone process, or these combination processes to a process metal oxide semiconductor particle. Production method.   The photoelectric conversion electrode manufactured by the method of Claim 16 or 17. A photoelectric conversion cell comprising the photoelectric conversion electrode according to claim 18, an electrolyte, and a conductive counter electrode.

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