JP2002184475A - Method of manufacturing semiconductor electrode and photochemical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor electrode enabling use of not only glass but also a certain translucent base as the base material of the semiconductor electrode for a photochemical battery, while providing a practical current/voltage curve, and a photochemical battery using the semiconductor electrode. SOLUTION: The method of manufacturing the semiconductor electrode includes forming a layer containing an oxide semiconductor and/or its precursor on a heat resistant base, heating and baking the layer to obtain an oxide semiconductor film, and transferring the film onto a transfer base.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor electrode for a photochemical cell, a method for producing the same, and a photochemical cell using the electrode.

[0002]

2. Description of the Related Art A solar cell including an oxide semiconductor sensitized with a dye is known. For example, Japanese Patent Application Laid-Open No. 1-220380 discloses an oxide semiconductor electrode in which a photosensitizing dye such as a ruthenium metal complex is adsorbed on a semiconductor made of a metal oxide such as porous and crystalline titanium oxide. There has been proposed a dye-sensitized solar cell using the same. Specifically, the dye-sensitized solar cell includes a transparent substrate having a conductive surface and an oxide semiconductor film formed on the conductive surface and adsorbing a sensitizing dye serving as a photoelectrode, and a conductive material serving as a counter electrode. It is manufactured by using a transparent substrate having a neutral surface and sealing an electrolyte solution between these electrodes.

An oxide semiconductor film formed on a conductive surface is formed from a fired product of an aggregate of oxide semiconductor fine particles. Specifically, a metal alkoxide is used as a starting material, a sol-gel method of obtaining an oxide through hydrolysis and polycondensation, a method of applying oxide semiconductor fine particles as a slurry to a conductive surface, and a chemical reaction in an aqueous solution. Utilizing, for example, a liquid phase deposition method of depositing an oxide semiconductor thin film on a conductive surface is used, and the oxide semiconductor formed on the conductive surface and a precursor thereof are formed by sintering in these methods. You.

[0004] As described above, the oxide semiconductor electrode requires a firing step in order to obtain its durability and practical energy conversion efficiency. Therefore, the substrate serving as an electrode is required to have high heat resistance, and is actually limited to a transparent conductive glass substrate coated with tin oxide, tin-doped indium oxide, fluorine-doped tin oxide, antimony-doped tin oxide, and the like. It has been difficult to use a resin or the like having poor heat resistance as the semiconductor electrode substrate.

[0005]

According to the present invention, not only glass but also any light-transmitting substrate, particularly a synthetic resin having poor heat resistance, can be used as a substrate material of a semiconductor electrode for a photochemical battery. It is an object of the present invention to provide a method for manufacturing a semiconductor electrode capable of obtaining practical energy conversion efficiency, and a photochemical battery using the semiconductor electrode. It is a further object of the present invention to provide a semiconductor electrode and a photochemical cell which are excellent in flexibility and workability.

[0006]

Means for Solving the Problems As a result of studying the above problems, the present inventors formed a layer made of an oxide semiconductor and / or a precursor thereof on a heat-resistant substrate, and fired and fired the layer. It has been found that the problem can be solved by transferring the obtained oxide semiconductor film onto an arbitrary light-transmitting substrate to form an oxide semiconductor electrode.

That is, the present invention includes the following inventions. (1) A layer containing an oxide semiconductor and / or a precursor thereof is formed on a heat-resistant substrate, and an oxide semiconductor film obtained by heating and sintering the layer is transferred onto a substrate to be transferred. A method for manufacturing a semiconductor electrode. (2) The manufacturing method according to (1), wherein the substrate to be transferred is a synthetic resin. (3) A semiconductor obtained by forming a layer containing an oxide semiconductor and / or a precursor thereof on a heat-resistant substrate and heating and firing the layer to transfer an oxide semiconductor film onto a synthetic resin substrate. electrode. (4) A photochemical battery using the semiconductor electrode according to (3). (5) A layer containing an oxide semiconductor and / or a precursor thereof is formed over a heat-resistant substrate, and the layer is obtained by heating and baking.
A heat-resistant substrate having an oxide semiconductor film for transfer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oxide semiconductor used in the present invention is not particularly limited, and a conventionally known semiconductor can be used. For example, Ti, Nb, Zn, Sn, Zr, Y, La, Ta, H
f, Sr, In, V, Cr, Mo, other oxides of transition metals such as _{W, SrTiO 3, CaTiO 3, BaTiO} 3, MgTiO 3, SrNb 2 O 6, perovskite oxides etc., or their A composite oxide or an oxide mixture is exemplified. In particular, TiO ₂ and ZnO are preferred from the viewpoint of semiconductor characteristics, corrosion resistance, stability and safety. Note that these oxide semiconductors are preferably used as fine particles, and the average particle diameter is usually 1 to 1000 n.
m, preferably 5 to 200 nm.

[0009] The term "precursor of an oxide semiconductor" as used herein means a precursor of an oxide semiconductor finally obtained, which can be turned into an oxide semiconductor by heating and baking. . As such, for example, a metal alkoxide and a hydrolyzate or a condensate thereof, which can form the above-described oxide semiconductor, a metal complex, a metal organic acid salt, a metal halide, and the like; And the like which exhibit physical properties. For example, as a precursor of the TiO ₂ semiconductor, titanium ethoxide, metal alkoxide such as titanium propoxide, or a hydrolysis product of such a metal alkoxide, a condensate obtained by polycondensation, or a metal such as titanium acetylacetonate A complex, a metal organic acid salt such as titanium octylate, or a metal halide such as titanium tetrachloride as a raw material, and a solution obtained by hydrolyzing these solutions can be used.

The material of the heat-resistant substrate used in the present invention is not particularly limited as long as it can withstand ordinary firing conditions, but it does not cause deformation or chemical change even under firing conditions of 300 to 1000 ° C. Is preferred. Such substrate materials include stainless steel, nickel, platinum, gold,
Examples include metals such as titanium, glass, and heat-resistant resins such as polyimide. A plate or sheet made of the above material can be used as a heat-resistant substrate. These heat-resistant substrates may be used alone, but may be subjected to a surface treatment for the purpose of imparting transferability (ease of peeling) of the oxide semiconductor film. As such a treatment, a release layer made of a fluororesin such as an ethylene-tetrafluoroethylene copolymer, polyvinyl fluoride, or polychlorotrifluoroethylene may be provided, or a synthesis such as burning and decomposing by heat during firing. A method of providing a layer of a resin, for example, a layer of a (meth) acrylate resin such as poly (2-ethylhexyl (meth) acrylate) or polyethyl (meth) acrylate, a cellulosic resin such as ethyl cellulose, or a thermally decomposable resin such as polyethylene glycol; There is.

A method for forming a layer of an oxide semiconductor and / or a precursor thereof on the heat-resistant substrate can be, for example, as follows. A solution in which fine particles of an oxide semiconductor are dispersed in water or an organic solvent or a mixed solvent thereof, a solution or suspension of a precursor of an oxide semiconductor, or a liquid or slurry in which these are mixed to prepare a coating liquid And The concentration of the oxide semiconductor and / or its precursor in the coating solution is 1 to
Preferably it is 70% by weight. Next, the coating solution is spin-coated, dip-coated, screen-printed,
Apply on heat-resistant substrate by blade coating method, etc.
By drying as necessary, a layer of an oxide semiconductor and / or a precursor can be formed. In addition, additives such as a surfactant, a viscosity modifier, and a dispersant may be added to the coating liquid as needed.

Next, the heat-resistant substrate on which the layer containing the oxide semiconductor and / or the precursor is formed is heated and fired. The heating and firing conditions are preferably at 300 to 1000 ° C. for 1 to 120 minutes. If the temperature is lower than 300 ° C., sintering does not proceed sufficiently, and sufficient film strength may not be obtained, or the mobility of electrons in the film may be reduced, so that energy conversion efficiency may be reduced. On the other hand, if the temperature is higher than 1000 ° C., the sintering proceeds too much to make it porous, and the amount of dye adsorbed as described below decreases, so that the energy conversion efficiency decreases. By baking the heat-resistant substrate over which the layer containing the oxide semiconductor and / or the precursor is formed, an oxide semiconductor film is formed over the heat-resistant substrate.

An oxide semiconductor film obtained by heating and baking is
It is a film having a porous structure, and its thickness is usually about 1 to 50 μm, preferably about 5 to 20 μm. Also,
The ratio of the actual surface area to the apparent area is 10 or more, preferably 100 or more. The actual surface area is the total surface area of the porous membrane determined by the BET method.

In the oxide semiconductor film thus formed, a current collecting electrode for extracting a current is disposed.
The formation of the current collecting electrode may be performed before or after the heating and baking treatment. As the method, a metal or oxide conductor is deposited over an oxide semiconductor or a precursor thereof by an evaporation method or a sputtering method. Method, a method of mixing metal fine particles or oxide conductive fine particles with a resin or a solvent and applying the mixture on an oxide semiconductor or a precursor thereof, disposing a light-transmitting metal mesh on a heat-resistant substrate, and applying the above-mentioned coating on the mesh And a method of applying a liquid to form an oxide semiconductor film integrated with the metal mesh.

A dye may be adsorbed (chemical adsorption, physical adsorption, deposition, etc.) as a sensitizer to the oxide semiconductor film formed in this manner. The dye may be adsorbed before or after the transfer to the substrate to be transferred. As a method for adsorbing the dye, for example, the substrate provided with the oxide semiconductor film may be immersed in a solution in which the dye is dissolved in an organic solvent. If necessary, the solution may be subjected to a reduced pressure treatment or the solution may be heated for the purpose of promoting adsorption so that the solution quickly enters the inside of the semiconductor film.

As the dye which can be used in the present invention
Has absorption in the visible light region and / or infrared light region
Is not particularly limited as long as it is a metal complex, an organic dye, or the like.
Is mentioned. Metal complexes include ruthenium, osmium
Metal complexes of aluminum, iron, zinc, platinum, etc., copper phthalocyanine
Metal phthalocyanines such as titanyl phthalocyanine,
Chlorophyll or derivatives thereof. Among these,
Ruthenium complexes are preferred in terms of sensitizing effect and durability.
You. As ruthenium complex, RuL_Two(CN)_Two, RuL_Two(SC
N)_Two, RuL _Three(CN) and the like. Where L is 2,2'-bipi
A ligand such as lysyl-4,4'-dicarboxylate,
Functional groups such as ruboxyl group, hydroxyl group and sulfone group
Are preferred in terms of their ability to adsorb to oxide semiconductor films.
No.

The organic dyes include phthalocyanine, cyanine dye, merocyanine dye, xanthene dye, triphenylmethane dye, rose bengal,
Rhodamine B and the like are mentioned, and for the same reason, it is preferable to introduce a functional group such as a carboxyl group, a hydroxyl group or a sulfone group.

Next, a method for transferring an oxide semiconductor film formed on a heat-resistant substrate to a substrate to be transferred will be described.
The substrate to be transferred is not particularly limited as long as it is light-transmitting, and a substrate made of a synthetic resin can be used in addition to a conventionally used glass substrate.

Examples of the synthetic resin include polyolefins such as polyethylene, polypropylene, polyisobutylene, polystyrene, and ethylene-propylene rubber; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; ethylene-vinyl acetate copolymer; Acrylic acid copolymers, cellulose derivatives such as ethyl cellulose and cellulose triacetate, poly (meth) acrylic acid and its ester compounds, polyvinyl acetals such as polyvinyl acetate, polyvinyl alcohol and polyvinyl butyral, polyacetals, polyamides, polyimides, nylons and urethanes Resin, epoxy resin, silicone resin, fluororesin, polycarbonate,
Examples include urea resin, melamine resin, phenol resin, resorcinol resin, furan resin and the like. Among these synthetic resins, good light transmittance and resistance to electrolytes,
Polyolefin or polyester resins are preferred because they have low gas transmission.

When a synthetic resin is used, a thickness of 10 to 10
A film having a thickness of 00 μm can also be used as the substrate to be transferred. As a method of transferring the oxide semiconductor film to the substrate to be transferred, a method in which the oxide semiconductor film and the substrate to be transferred are bonded to each other using an adhesive or the like and then peeled off from the heat-resistant substrate, and the adhesive itself is used. After the substrate is bonded to an oxide semiconductor film as a substrate to be transferred, the substrate is peeled off from the heat-resistant substrate.

The adhesive that can be used in the transfer step is not particularly limited, and various synthetic resins and inorganic adhesives can be used. As the synthetic resin, for example, polyethylene, polypropylene, polyisobutylene, polystyrene, polyolefins such as ethylene-propylene rubber, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethyl cellulose, cellulose derivatives such as cellulose triacetate, Copolymer of poly (meth) acrylic acid and its ester, polyvinyl acetal such as polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyamide, polyimide, nylon, polyester resin, urethane resin, epoxy resin, silicone resin, fluorine Resins. Examples of the inorganic adhesive include low-melting glass, alkali metal silicates such as sodium silicate, and the like. Among these adhesives, adhesion, resistance to electrolytes,
Polyolefin, ethylene-vinyl acetate copolymer, urethane resin, epoxy resin, and silicone resin are preferred from the viewpoint of light transmittance and transferability. Additives can be used as necessary for these adhesives. Examples of the additive include a crosslinking agent, a dispersant, a tackifier, a leveling agent, a plasticizer, an antifoaming agent, and the like.

A method for bonding an oxide semiconductor film and a transfer substrate using such an adhesive will be described more specifically. For example, an adhesive dissolved or dispersed in an organic solvent or water may be used as an oxide semiconductor. On the film, or coated on the substrate to be transferred, a method of bonding and drying the oxide semiconductor film and the substrate to be transferred, the adhesive melted and heated on the oxide semiconductor film,
Alternatively, a method of cooling after coating and bonding on a substrate to be transferred, a method of sandwiching a resin film made of a synthetic resin as described above between an oxide semiconductor film and a substrate to be transferred, and bonding by heating. No. The thickness of the adhesive layer is not particularly limited, but is 5 to 300 μm, preferably 10 to 200 μm.
μm. A photochemical battery can be manufactured using the semiconductor electrode manufactured as described above.

As the electrolyte layer, an electrolyte solution is usually used. In addition, a gel or solid electrolyte is also used. Electrolyte solution is not particularly limited, I / I ₃ , Br / B
r ₃ , a solution containing a redox couple such as quinone / hydroquinone. Specifically, in the case of I / I ₃ , a solution in which iodine and an ammonium salt of iodine are dissolved in an organic solvent such as acetonitrile, ethylene carbonate, propylene carbonate, or the like is used.

Materials for transporting electrons and holes can also be used, such as various metal phthalocyanines, perylenetetracarboxylic acids, charge transport materials such as polycyclic aromatics such as perylene and coronene, and arylamines, and conductive materials such as polypyrrole and polyphenylenevinylene. A hydrophilic polymer or the like can be used. The thickness of these electrolyte layers is usually about 1 to 50 μm.

As the counter electrode, any conductive material can be used. Examples thereof include metal materials such as gold, platinum, silver, and copper, and the above-described conductive glass and carbon. Those having a catalytic ability to perform the reaction at a sufficient speed are preferable, and examples thereof include platinum, platinum-plated or platinum-deposited conductive material surfaces, and carbon. When manufacturing a photochemical cell using the semiconductor electrode of the present invention, a photochemical cell such as a dye-sensitized solar cell can be manufactured by bringing the semiconductor electrode of the present invention and a counter electrode into contact with an electrolyte.

[0026]

EXAMPLES (Example 1) <Formation of TiO ₂ film> Crystalline titanium oxide particles (manufactured by Nippon Aerosil Co., Ltd.) in a mixture of 3.6 ml of water and 0.4 ml of acetylacetone
12 g of trade name P-25 (average particle size: 21 nm) was added and dispersed well in a mortar. Further, 16 ml of water was gradually added with stirring, and finally a surfactant (Triton X-100 manufactured by Aldrich) 0.2
The resulting mixture was stirred well, and a titanium oxide slurry containing 38% by weight of titanium oxide was prepared.

Next, poly (2-ethylhexyl methacrylate) was applied to a stainless steel plate having a thickness of 1.1 mm as a heat-resistant substrate at a thickness of about 10 μm, and a current collecting electrode was formed on the poly (2-ethylhexyl methacrylate). A 100-mesh gold net (made by Nilaco Co., Ltd.) to be used was separately prepared. On the substrate, the above slurry was applied in an area of 1.5 × 1.5 cm and a thickness of 50 μm, and dried at room temperature for 5 hours. next
Heating and baking was performed at 450 ° C. for 30 minutes in air, and poly (2-ethylhexyl methacrylate) was thermally decomposed to produce a titanium oxide semiconductor electrode having a current collecting electrode.

<Transfer> A hot-melt EVA (ethylene-vinyl acetate copolymer) sheet (trade name: Takemelt, 150 μm thick, manufactured by Takeda Pharmaceutical Co., Ltd.) on the obtained semiconductor electrode, 50 μm corona-treated biaxially stretched polyethylene Terephthalate
(PET) films were sequentially stacked and bonded with a heat roll laminator heated to 110 ° C. Then, the semiconductor electrode was peeled off from the stainless steel plate to obtain a PET substrate semiconductor electrode in which a titanium oxide semiconductor was formed on the PET film via EVA as a substrate to be transferred.

<Dye Adsorption> The obtained PET substrate semiconductor electrode was treated with an ethanol solution of cis-bis (isothiocyanate) bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (3 × 10 ^{− 4} M) for 24 hours to adsorb the sensitizing dye on the titanium oxide to produce a dye-sensitized titanium oxide semiconductor electrode.

<Preparation of Photochemical Battery> A photochemical battery was constructed by bringing a dye-sensitized titanium oxide semiconductor electrode and its counter electrode into contact with an electrolytic solution. For the counter electrode, surface resistance 50Ω /
The ITO coated PET film of □ was prepared by depositing platinum on the ITO surface. As an electrolyte, a mixed solution of ethylene carbonate and acetonitrile (volume ratio of 80/20) and 0.5 M tetrapropylammonium iodide as an electrolyte were used.
Those containing 0.05M iodine were used. A 25 μm PET film was sandwiched between both electrodes as a spacer, and the ends were sealed with epoxy resin.

<Characteristic Evaluation of Photochemical Battery> The characteristic evaluation of the fabricated photochemical battery was performed by irradiating the AM1.5 simulated sunlight (1000 W / m ² ) defined in JIS C8911. 5.5%. Furthermore, after repeating the operation of applying a rod having a diameter of 1 cm to the front side of the photochemical cell and then bending the photochemical cell on the back side and bending it to the opposite side ten times, the energy conversion efficiency was measured to be 5.0%. Was.

(Reference Example 1) A titanium oxide slurry prepared in the same manner as in the example was mixed with ITO-coated PE having a surface resistance of 50Ω / □.
Coated on ITO surface of T film. After drying at room temperature for 5 hours, heat treatment was performed at 100 ° C. for 30 minutes to produce a titanium oxide semiconductor electrode. Adsorption of the dye and fabrication of the photochemical cell were performed in the same manner as in the example. The measured energy conversion efficiency was 2.7%. Furthermore, bending operation was performed in the same manner as in the example, and the energy conversion efficiency was measured. As a result, it was 0.8%. When the state of the titanium oxide film was visually observed, a part of the titanium oxide film was peeled off from the ITO-coated PET substrate.

[0033]

According to the present invention, it is possible to provide a method for manufacturing a semiconductor electrode using a substrate of any material. In particular, according to the present invention, a semiconductor electrode having practical energy conversion efficiency can be provided by using a synthetic resin substrate or the like having inferior heat resistance, which cannot be applied under conventional heating and firing conditions, and furthermore, a highly durable semiconductor electrode can be provided by using the electrode. And a highly efficient photochemical battery can be provided. According to the present invention, as compared with glass that has been conventionally used as a substrate, since it is possible to use a lightweight synthetic resin that is excellent in flexibility and workability and can be used as a substrate, the degree of freedom of an installation place is high, and even in a flat surface. A semiconductor electrode and a photochemical battery which can be installed on a curved surface and which can be easily installed can be provided.

Claims (5)

[Claims] An oxide semiconductor film obtained by forming a layer containing an oxide semiconductor and / or a precursor thereof on a heat-resistant substrate and heating and firing the layer is transferred onto a substrate to be transferred. Of manufacturing a semiconductor electrode. 2. The method according to claim 1, wherein the substrate to be transferred is a synthetic resin. 3. A layer containing an oxide semiconductor and / or a precursor thereof is formed on a heat-resistant substrate, and an oxide semiconductor film obtained by heating and sintering the layer is transferred onto a synthetic resin substrate. Semiconductor electrodes. 4. A photochemical battery using the semiconductor electrode according to claim 3. 5. A heat-resistant substrate having an oxide semiconductor film for transfer, which is obtained by forming a layer containing an oxide semiconductor and / or a precursor thereof on a heat-resistant substrate and heating and firing the layer.