JP2007242504A - Photoelectric conversion electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion electrode providing a photoelectric conversion element having light weight, high flexibility, and high heat resistance; and to provide the photoelectric conversion element typical in a solar cell, having high energy conversion efficiency using the photoelectric conversion electrode. <P>SOLUTION: In the photoelectric conversion electrode having a conductive layer and a semiconductor layer formed on a substrate, as the substrate, a self-supporting clay membrane satisfying the following conditions is used: (i) a layered inorganic compound and resin are essential ingredients; (ii) weight ratio of the layered inorganic compound to the whole solid is 70% or more; (iii) total light beam transmission factor exceeds 90%; (iv) gas barrier property is such that the oxygen gas permeability is less than 3.2×10<SP>-11</SP>cm<SP>2</SP>s<SP>-1</SP>cmHg<SP>-1</SP>at room temperature; (v) heat resistance is 250°C or more; and (vi) breaking strength as mechanical strength is 300 kg/cm<SP>2</SP>or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion electrode and a photoelectric conversion element such as a solar cell using the same.

In recent years, solar cells have attracted attention as photoelectric conversion elements that directly convert light energy into electric power from the viewpoints of energy saving measures and environmental pollution measures.
Examples of such solar cells include single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, III-V group compound solar cells such as cadmium telluride and indium copper selenide, and thin film silicon cells. Etc., and a power generation efficiency of around 10% is obtained as solar energy conversion efficiency.

Furthermore, research using organic pigments and organic dyes has been actively conducted as a method of converting sunlight into electrical energy using materials that are cheaper than silicon, easy to increase in area, and have a low environmental impact. Yes.
Under these circumstances, a photoelectric conversion element and a photovoltaic cell using semiconductor fine particles sensitized with a dye have been recently proposed (Patent Document 1).
This battery is said to be a dye-sensitized type using a porous titanium dioxide thin film spectrally sensitized with a ruthenium complex as a working electrode, and it is necessary to purify an inexpensive oxide semiconductor such as titanium dioxide to a high purity. In addition, the absorption of dyes is broad, sunlight can be converted to electricity over a wide visible wavelength range, and the color can be changed by the dyes, attracting attention as interior, exterior wall materials, and fashion materials. ing.

In this dye-type sensitized solar cell, conductive glass with good heat resistance on which a conductive film such as ITO or tin oxide is formed is used as a substrate (electrode substrate). This is because a high temperature exceeding 400 ° C. is required to produce a porous thin film in which semiconductor particles such as titanium dioxide are firmly bonded.
By the way, although a strong glass substrate can be used when using power devices, lightness and flexibility are required for applications such as interiors, portable materials, fashion materials, and solar cars.
For this reason, the use of a flexible substrate using a polymer such as PET has also been studied (Patent Document 2). However, since normal high-temperature firing is not possible, there is a problem that the bonding between semiconductor particles is poor and the performance is lowered. .
In addition, the metal film substrate has a problem that it is heavy and difficult to fire, and has no light transmittance.

  On the other hand, an inorganic layered compound such as swellable clay is dispersed in water or alcohol, and the dispersion is spread on a glass plate, allowed to stand, and dried to obtain a film with uniform particle orientation. For example, a fixed orientation sample for X-ray diffraction has been prepared by this film formation (Non-Patent Document 1).

However, when a film is formed on a glass plate, it is difficult to peel the inorganic layered compound thin film from the glass plate, and there is a problem that it is difficult to obtain a self-supporting film, such as a crack in the film when peeled off. Further, even if the film is peeled off, the obtained film is brittle and insufficient in strength, and it has been difficult to prepare a film having a uniform thickness with no pinholes and excellent gas barrier properties. It was.
In addition, recently, the present inventors have stated that “a self-supporting clay having mechanical strength that can be used as a self-supporting film, heat resistance, and highly oriented lamination of inorganic layered compound particles to provide gas barrier properties. "Membrane" was proposed (Patent Document 3).
Although this self-supporting clay film has good mechanical strength and heat resistance, the total light transmittance is not yet sufficient, and the haze value (cloudiness value) is 70% or more. Use as a substrate is limited.

US Pat. No. 4,927,721 JP 2001-357896 A International Publication No. 2005/023714 Pamphlet Haruo Shiramizu “Clay Mineralogy-Basics of Clay Science”, Asakura Shoten, p. 57 (1988)).

  An object of the present invention is to provide a photoelectric conversion electrode that gives a photoelectric conversion element that is lightweight and excellent in flexibility and heat resistance, and a photoelectric conversion element typified by a solar cell that is excellent in energy conversion efficiency using the photoelectric conversion electrode. .

As a result of intensive studies on a photoelectric conversion element that is lightweight and excellent in flexibility and heat resistance, the present inventors have found that the above-mentioned problems can be solved by using a specific clay free-standing film as a substrate of a photoelectric conversion electrode. It came to be completed.
That is, according to this application, the following invention is provided.
<1> A photoelectric conversion electrode having a conductive layer and a semiconductor layer provided on a substrate, wherein a self-supporting clay film satisfying the following conditions is used as the substrate.
(I) having a layered inorganic compound and a resin as essential components;
(Ii) The weight ratio of the layered inorganic compound to the total solid is 70% or more,
(Iii) the total light transmittance exceeds 90%,
(Iv) a gas barrier property having a permeability coefficient for oxygen gas of less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ at room temperature;
(V) having a heat resistance of 250 ° C. or higher, and (vi) having a mechanical strength of 300 kg / cm ² or more at break strength,
<2> The photoelectric conversion electrode according to <1>, obtained by firing a conductive layer and a semiconductor layer formed on a substrate.
<3> The photoelectric conversion electrode as described in <1> or <2> above, wherein the firing temperature is 200 ° C. to 400 ° C.
<4> The photoelectric conversion element according to any one of <1> to <3>, wherein the semiconductor layer is a porous semiconductor film adsorbing a dye.
<5> A photoelectric conversion element comprising the photoelectric conversion electrode according to any one of <1> to <4> and a counter electrode thereof.
<6> The photoelectric conversion element as described in <5> above, wherein a charge transport layer is provided between the light conversion electrode and the counter electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion electrode and photoelectric conversion element which were lightweight and excellent in the softness | flexibility and heat resistance are obtained. In particular, a dye-sensitized solar cell that is lightweight, excellent in flexibility and heat resistance, and has good photoelectric conversion efficiency can be obtained.

The photoelectric conversion electrode according to the present invention is characterized in that a self-supporting clay film satisfying the following conditions is used as a substrate in a photoelectric conversion electrode in which a conductive layer and a semiconductor layer are provided on a substrate.
(I) having a layered inorganic compound and a resin as essential components;
(Ii) The weight ratio of the layered inorganic compound to the total solid is 70% or more,
(Iii) the total light transmittance exceeds 90%,
(Iv) a gas barrier property having a permeability coefficient for oxygen gas of less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ at room temperature;
(V) having a heat resistance of 250 ° C. or higher, and (vi) having a mechanical strength of 300 kg / cm ² or more at break strength,

In the self-supporting clay film used for the substrate which is the first requirement of the photoelectric conversion electrode of the present invention, the layered inorganic compound referred to in (i) is not particularly limited as long as it is transparent. Or a composite, preferably, for example, one or more of mica, vermiculite, montmorillonite, beidellite, saponite, hectorite, stevensite, magadiite, isralite, kanemite, titanium on flakes, more preferably, Any of these natural or synthetic products or a mixture thereof may be exemplified. At this time, organic clay can be used as the inorganic layered silicate to impart water resistance to the substrate.
Further, the resin referred to in (i) is not particularly limited as long as it is transparent, but preferably, for example, epsilon caprolactam, dextrin, starch, cellulosic resin, gelatin, agar, flour, Gluten, chitin, chitosan, polylactic acid, alkyd resin, polyurethane resin, epoxy resin, fluororesin, acrylic resin, methacrylic resin, phenol resin, polyamide resin, polyester resin, polyimide resin, polyvinyl resin, polycarbonate, polyethylene glycol, polyacrylamide , Polyethylene oxide, protein, deoxyribonucleic acid, ribonucleic acid and polyamino acids, benzoic acid compounds and the like.

The amount of the layered inorganic compound used in the present invention is required to be 70% or more, preferably 70% to 90% in weight ratio with respect to the total solid, as defined in (ii).
When only layered inorganic compounds are added without adding additives such as resin, the inorganic compounds shrink and dry during film formation, causing cracks inside and causing haze, resulting in a decrease in total light transmittance. There is a problem. Therefore, it is better to add 10% or more of additives. On the other hand, if the additive exceeds 30%, the heat resistance is lowered, and there is a problem that the color develops when heated. Therefore, the weight ratio of the layered inorganic compound to the total solid is 70% or more, preferably 70% to 90%.

The total light transmittance of the self-supporting clay film of the present invention needs to be 90% or more as defined in (iii).
Here, the total light transmittance is defined in JIS K7105: 1981 “Testing methods for optical properties of plastics”, and is an index for evaluating what percentage of the sunlight passes through the material. If this value is close to 100%, there is no absorption or reflection of the sunlight of the material, and sunlight can be used effectively.
For the performance as a photoelectric conversion electrode, it is important to use sunlight effectively for the following. Therefore, the higher the total light transmittance, the better. However, it is practical photoelectric conversion that the total light transmittance is 90% or more. Although it has been considered to be at a certain required level for use as an electrode, the conventional clay film is made of natural clay, and even a very thin one having a thickness of 10 micrometers is JIS.
The total light transmittance based on K7105: 1981 “Testing method for optical properties of plastics” was about 86.9% at the maximum, and haze (cloudiness value) sometimes exceeded 78.2%.
In contrast, the self-supporting clay film of the present invention has a total light transmittance of 90% or more and a haze (cloudiness value) of less than 10%.

In addition, the self-supporting clay film of the present invention has a gas barrier property that the permeability coefficient for oxygen gas is less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ at room temperature as defined in (iv). is required.
The gas barrier property is evaluated from the amount of gas permeation and the elapsed time by introducing oxygen, which is a measurement gas, into one side of the membrane material and generating a differential pressure with the other side. Due to the high oxygen gas barrier property, it is possible to prevent oxidative deterioration of the constituent materials of the electrode substrate. In order to keep the electrode substrate for several years, in the present invention, the permeability coefficient for oxygen gas is 3. The value is less than 2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ .

  The self-supporting clay film of the present invention needs to have a heat resistance of 250 ° C. or higher as defined in (v). Conventional transparent plastic films and the like tend to be colored by heating and have a tendency to deteriorate their characteristic values, such as a decrease in gas barrier properties. As a photoelectric conversion electrode, even after heat treatment in the manufacturing process, transparency In addition, it is necessary to maintain gas barrier properties, and the total light transmittance should be high, and it is important that this value is not reduced by heating. The substrate used in the present invention is characterized in that the transparency is not lowered and the gas barrier property is not lowered even after the heat treatment at 250 ° C. or higher.

Further, the self-supporting clay film of the present invention needs to have a breaking strength of 300 kg / cm ² or more. This breaking strength means the mechanical strength that can be resisted without being damaged in the processing step of the manufacturing process during the production and the mechanical strength that can be resisted without being damaged under the use conditions.
The self-supporting clay film of the present invention has an excellent mechanical strength with a breaking strength of 300 kg / cm ² or more. Therefore, the self-supporting clay film is not damaged in the process of manufacturing a photoelectric conversion electrode or in the process of use.

  In the self-supporting clay film of the present invention, for example, a highly transparent inorganic layered compound and a highly transparent resin are dispersed in a solvent at a ratio of 95: 0 to 70:30, preferably 90:10 to 70:30. After obtaining a uniform dispersion containing no lumps, this dispersion is applied to a substrate having a flat surface and a water-repellent surface to deposit inorganic layered compound particles, and a solvent as a dispersion medium is appropriately added. After separation by solid-liquid separation method and forming into a film shape, the layered inorganic compound particles are oriented and transparent by peeling them from the substrate by methods such as drying, heating and cooling as necessary. An inorganic layered compound film that is high, excellent in flexibility, excellent in gas barrier properties, and high in heat resistance can be obtained.

Conventional self-supporting clay films include examples in which natural clay is the main component and a self-supporting flexible film is obtained (for example, Patent Document 3). However, although the gas barrier property and flexibility of this film measured by a visible ultraviolet spectrophotometer were excellent, the light transmittance at a wavelength of 500 nanometers was 13.1% or less and was low. Further, the total light transmittance of this film based on JIS K7105: 1981 “Testing method for optical properties of plastics” was about 86.9%, and the haze (haze value) was extremely high such as 78.2%.
On the other hand, the self-supporting clay film used in the present invention is made of a transparent clay raw material and a transparent resin, and thus has a total light transmittance of 90% or more and efficiently performs photoelectric conversion. It can be carried out. Further, the haze (cloudiness value) is about 10 to 6%, which is low, and it is a good substrate for a photoelectric conversion electrode. Furthermore, although the film using natural clay turns black by heating at 250 ° C., the self-supporting clay film used in the present invention remains transparent. Therefore, the self-supporting clay film used in the present invention is excellent as a substrate for photoelectric conversion electrodes.

The conductive layer which is the second requirement of the photoelectric conversion electrode of the present invention is formed by applying or vapor-depositing a conductor such as a conductive metal oxide on the surface of the substrate.
A preferable conductive layer is fluorine dioxide or antimony-doped tin dioxide or indium-tin oxide (ITO). Further, it is preferable to use a metal lead for the purpose of reducing the resistance of the transparent conductive substrate. The material of the metal lead is preferably a metal such as indium, platinum, gold, nickel, titanium, aluminum, copper, or silver. The metal lead is preferably attached to the transparent substrate by soldering, vapor deposition, sputtering or the like.

The semiconductor used for the semiconductor layer, which is the third requirement of the photoelectric conversion electrode of the present invention, is an n-type semiconductor in which conductor electrons become carriers under photoexcitation and give an anode current, or valence band holes under photoexcitation. A p-type semiconductor which becomes a carrier and gives a cathode current is preferable.
In this semiconductor layer, light is absorbed and charge separation is performed to generate electrons and holes. In order to enhance this function, a dye-sensitized semiconductor layer is used in the present invention. preferable. In this dye-sensitized semiconductor, light absorption and generation of electrons and holes thereby occur mainly in the dye, and the semiconductor fine particles play a role of receiving and transmitting these electrons (or holes).

  As a semiconductor forming the semiconductor layer, a single semiconductor such as silicon or germanium, a III-V compound semiconductor, a metal chalcogenide (for example, sulfide or selenide), or a general oxide or composite oxide is used. Can be used.

  Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides, cadmium, zinc, lead, silver, antimony or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Examples of other compound semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, and copper-indium sulfides.

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, ZnS, PbS, Bi ₂ S ₃ , CdSe, CdTe, GaP, InP. GaAs, CuInS ₂ , CuInSe _{2 and the} like, more preferably TiO ₂ , ZnO, SnO ₂ , Fe ₂ O ₃ , WO ₃ or Nb ₂ O ₅ , or an alkaline earth titanate or alkali metal titanate, Particularly preferred is TiO ₂ , ZnO, SnO ₂ or Nb ₂ O ₅ , and most preferred is TiO ₂ . These semiconductors may be used alone or as a composite (mixture, mixed crystal, solid solution, etc.).

The semiconductor used in the present invention may be single crystal or polycrystalline. More preferably, a porous film made of semiconductor fine particles having a large surface area is particularly preferable.
When the dye is adsorbed on the semiconductor, the semiconductor fine particle layer is preferably a porous film having a large surface area so that a large amount of the dye can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the substrate is preferably 10 times or more, more preferably 100 times or more the projected area. The upper limit is not particularly limited, but is usually about 1000 times.

  The particle size of the semiconductor fine particles is generally 2 nm to 10 μm. The film thickness is preferably such that the semiconductor itself or the adsorbed dye can sufficiently absorb light. The thickness is 4 nm to 1000 μm, preferably 10 nm to 100 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 10 nm or less. For the purpose of scattering incident light and improving the light capture rate, semiconductor particles having a large particle size, for example, about 300 nm may be mixed.

When a sensitizing dye is used in the semiconductor layer, any compound that has absorption in the visible region and near infrared region and can sensitize the semiconductor can be widely used. Specific examples include xanthene organic dyes, cyanine dyes, basic dyes, porphyrin compounds, phthalocyanine compounds, azo dyes, and organometallic complexes.
Further, by using or mixing a plurality of dyes, it is possible to widen the wavelength range of photoelectric conversion as much as possible and improve the conversion efficiency. In this case, the dye to be used or mixed and the ratio thereof can be selected so as to match the wavelength range and intensity distribution of the target light source. Such a dye preferably has an appropriate bonding group such as a carboxyl group, a sulfonic acid group, or a phosphoric acid group that has an adsorption ability to the surface of the semiconductor fine particles.

The photoelectric conversion electrode of the present invention can be produced by various methods such as spraying, screen printing, doctor blending, or spin coating, but is preferably produced by spraying or screen printing.
Specifically, the semiconductor fine particle dispersion is applied on a substrate using a spraying device or a screen printer and dried, followed by heat treatment at a temperature at which the metal oxide is sintered.
As firing conditions, the firing temperature is 200 to 400 ° C, preferably 300 to 400 ° C.

  The photoelectric conversion electrode of the present invention can be formed into a photoelectric conversion element by preferably providing a counter electrode with a charge transfer layer interposed therebetween.

Since this counter electrode does not need to be heated, ordinary substrates can be widely used. If transparency is required, a glass film, a transparent plastic film, or a metal film can be used because the counter electrode may not be transparent when the substrate is on the light incident side. In a metal film or the like, it can also serve as a catalyst or a conductive layer.
The counter electrode of the present invention can be provided with a catalyst such as a conductive layer or a noble metal such as Pt or RuO ₂ , an oxide, or carbon, if necessary.
In this case, the conductive layer can be the same as described above with respect to the photoelectric conversion electrode.

For the charge transfer layer, any of conventionally known electrolyte solutions, gel electrolytes, ionic liquids, solid electrolyte electron transport materials, and hole transport materials can be used, but it is preferable to use an electrolyte solution. The electrolyte solution used for the charge transfer layer is not particularly limited as long as it can be used for a normal dye-sensitized solar cell. Moreover, it is preferable that electrolyte solution is comprised from electrolyte, a solvent, and an additive.
For example, the electrolyte is a metal iodide such as a combination of I ₂ and iodide (LiI, NaI, KI, CsI, CaI ₂ as iodide), or pyridinium iodide, imidazolium iodide, tetraalkylammonium iodide, etc. 4 Iodine salts of quaternary ammonium compounds), Br ₂ and bromide combinations (bromide as metal bromides such as LiBr, NaBr, KBr, CsBr, CaBr ₂₎ or bromine salts of quaternary ammonium compounds such as tetraalkylammonium bromide and pyridinium bromide In addition, sulfur compounds such as sodium polysulfide, alkylthiol-alkyldisulfides, viologen dyes, hydroquinone-quinones, ferrocyanates-ferricyanates, and metal complexes such as ferrocene-ferricinium ions can be used. . Among these, electrolytes in which iodine salts of quaternary ammonium compounds such as I ₂ and LiI, pyridinium iodide, and imidazolium iodide are combined are preferable. The electrolytes described above may be used in combination.

  A preferable electrolyte concentration is 0.1 M or more and 15 M or less, and more preferably 0.2 M or more and 10 M or less. In addition, when iodine is added to the electrolyte, a preferable iodine concentration is 0.01 M or more and 0.5 M or less.

  The solvent used for the electrolyte is preferably a compound having a low viscosity and improving the ion mobility, or having a high dielectric constant and an effective carrier concentration, so that excellent ion conductivity can be expressed. Such solvents include heterocyclic compounds such as 3-methyl-2-oxazolidinone, carbonate compounds such as ethylene carbonate and propylene carbonate, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, 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, polypropylene glycol monoalkyl ether, ethylene glycol, Propylene glycol, polyethylene glycol, polypropylene Glycol, polyhydric alcohols such as glycerin, acetonitrile, glutarodinitrile, methoxy acetonitrile, propionitrile, nitrile compounds such as benzonitrile, dimethyl sulfoxide, can be used aprotic polar solvents such as sulfolane, water, and the like.

  In the present invention, basic compounds such as tert-butylpyridine, 2-picoline and 2,6-lutidine can also be added. A preferable concentration range when adding the basic compound is 0.05 M or more and 2 M or less.

  In the present invention, the electrolyte can be used after gelation (solidification) by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. In the present invention, an ion conductive electrolyte such as a molten salt, or a solid hole transport material that is organic or inorganic, or a combination of both can be used.

Next, an example of a typical photoelectric conversion electrode and photoelectric conversion element obtained in the present invention is shown in FIG.
In FIG. 1, 1 is a substrate a, 2 is a conductive layer a, 3 is a semiconductor layer, 4 is a charge transfer layer, 5 is a catalyst, 6 is a conductive layer b, and 7 is a substrate b.
The photoelectric conversion electrode (working electrode) 8 of the present invention is composed of 1-3, and the counter electrode is composed of 5-7. In the photoelectric conversion element shown in FIG. 1, light may be irradiated from one or both of substrate a / conductive layer a and substrate b / conductive layer b, so that the light reaches the semiconductor layer. Is sufficient if at least one of the substrate a / conductive layer a and the counter electrode is substantially transparent. From the viewpoint of improving the power generation efficiency, it is preferable to make the substrate a / conductive layer a transparent so that light enters from the working electrode. In this case, the counter electrode preferably has a property of reflecting light.
When the photoelectric conversion element of the present invention is produced for the purpose of generating electrical work by connecting to an external load (power generation), a photovoltaic cell is obtained. Among the photovoltaic cells, when the charge transfer layer is mainly made of an ion transport material, a so-called photoelectrochemical cell is obtained. Moreover, a solar cell is obtained when the main purpose is power generation using sunlight.
Further, when the photoelectric conversion element of the present invention is connected to an external load and prepared for the purpose of sensing optical information, an optical sensor can be obtained.

Hereinafter, the present invention will be specifically described by way of examples.

Example 1

[Preparation of substrate]
The board | substrate used with a photoelectric conversion electrode was synthesize | combined as follows.
As an inorganic layered compound, 0.9 g of synthetic saponite “Smecton” (manufactured by Kunimine Kogyo Co., Ltd.) is added to 100 cm ³ of distilled water and placed in a plastic sealed container together with a Teflon (registered trademark) rotor, 25 The mixture was shaken vigorously at 2 ° C. for 2 hours to obtain a uniform dispersion. To this dispersion, 0.1 g of commercially available sodium polyacrylate was added as an additive and shaken vigorously to obtain a uniform dispersion containing synthetic saponite and sodium polyacrylate.
Next, this clay paste was deaerated with a vacuum deaerator. Next, this clay paste was applied to a polypropylene tray having a flat surface. For application, a stainless steel gravel was used. Using a spacer as a guide, a clay paste film having a uniform thickness was formed. The tray was dried in a forced air oven at 60 ° C. for 1 hour to obtain a uniform additive composite clay thin film having a thickness of about 10 μm. The produced clay film was peeled from the tray to obtain a self-supporting clay film having high transparency, self-supporting, and excellent flexibility.
The properties of this self-supporting clay film were as follows.
Total light transmittance: (Total light transmittance based on JIS K7105: 1981 “Testing method for optical properties of plastic” is 92.1%)
-Haze: (The haze value is 6.4% based on JIS K7105: 1981 “Testing methods for optical properties of plastics”)
Gas barrier property: (permeability coefficient for oxygen gas is less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ at room temperature)
-Heat resistance: (Normally 250 ° C in an air environment, transparency and gas barrier properties are not deteriorated even when heated for an hour)
And mechanical strength :( breaking strength: 300kg / cm ² or more)

[Create photoelectric conversion electrode]
ITO was vapor-deposited on one side of the self-supporting clay film obtained above to obtain an ITO vapor-deposited film having a surface resistance of about 200 ohm / sq.
Next, TiO ₂ fine particles (Nippon AERZIL P-25, anatase type, particle size 25 nm) were used as the oxide semiconductor electrode material, and 0.2 g of TiO ₂ fine particles, 0.1 ml of ethylacetone, and 5 ml of ethanol were mixed well. This suspension solution was set on an air brush. Then, the ITO-deposited film was placed on hot plate set at 0.99 ° C., thereon at a mask 5mm square hole in TiO ₂ suspension spray (0.2 kg / m ² pressure, 1 min), TiO ₂ A film was formed. This TiO ₂ / ITO vapor deposition film was air baked at 390 ° C. for 30 minutes to obtain a photoelectric conversion electrode.

[Creation of photoelectric conversion element]
The photoelectric conversion electrode obtained above was immersed in a ruthenium complex (manufactured by Solaronics, N719) in a t-butanol / acetonitrile (1: 1) solution (0.4 mM) for one day to adsorb the dye to TiO ₂ , and t- Wash and dry with a butanol / acetonitrile (1: 1) mixture.
Next, an electrolyte solution was prepared by dissolving 0.1M lithium iodide, 0.05M iodine, and 0.62M dimethylpropylimidazolium iodide using acetonitrile as a solvent. To this, t-butylpyridine was added and dissolved to a concentration of 0.5M. The electrolyte solution was clamped with a 60 mm spacer between the photoelectric conversion electrode (dye-sensitized titanium oxide semiconductor electrode) and the transparent platinum counter electrode. When the obtained photoelectric conversion element was irradiated with light having an intensity of 100 mW / cm ^{2 using} a solar simulator (AM-1.5, JIS-A) as a light source, the short-circuit current Isc: 0.144 mA, the open-circuit voltage Voc: 0.775 V, form factor ff: 0.262, solar energy conversion efficiency: 0.13%.

Comparative Example 1
In Example 1, except that the self-supporting clay film was replaced with a self-supporting clay film a having the following properties (described in the examples of the pamphlet of International Publication No. WO 2005/023714), the photoelectric conversion electrode and When a photoelectric conversion element was produced, the film was deformed by heating, and an electrode could not be produced.
[Properties of self-supporting clay film a]
The self-supporting clay film a was produced as follows.
As clay, 3.42 g of natural montmorillonite (Kunipia P, manufactured by Kunimine Kogyo Co., Ltd.) and 0.72 g of synthetic mica (Somasif ME-100, manufactured by Co-op Chemical Co., Ltd.) are added to 100 cm ³ of distilled water, and plastic The product was put in a sealed container together with a Teflon (registered trademark) rotor and shaken vigorously at 25 ° C. for 2 hours to obtain a uniform dispersion. To this dispersion, 0.18 g of epsilon caprolactam (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive and shaken vigorously to obtain a uniform dispersion containing natural montmorillonite and epsilon caprolactam. This was gradually dried to obtain a clay paste. Next, this clay paste was deaerated with a vacuum deaerator. Next, this clay paste was applied to a brass tray. For application, a stainless steel gravel was used. Using a spacer as a guide, a clay paste film having a uniform thickness was formed. Here, the thickness of the paste was 0.5 mm. The tray was dried in a forced air oven at 60 ° C. for 1 hour to obtain a uniform additive composite clay film having a thickness of about 10 μm. The produced clay film was peeled from the tray to obtain a self-supporting clay film a. The properties of this self-supporting clay film a were as follows.
Total light transmittance: (Total light transmittance based on JIS K7105: 1981 “Testing methods for optical properties of plastics” is 86.9%)
・ Haze: (Haze value based on JIS K7105: 1981 “Testing method for optical properties of plastics” is 78.2%)
Gas barrier property: (permeability coefficient for oxygen gas is less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ at room temperature)

It is explanatory drawing of the typical photoelectric conversion electrode and photoelectric conversion element which concern on this invention.

Claims (6)

In the photoelectric conversion electrode which provided the conductive layer and the semiconductor layer on the board | substrate, the self-supporting clay film which satisfy | fills the following conditions was used as a board | substrate, The photoelectric conversion electrode characterized by the above-mentioned.
(I) having a layered inorganic compound and a resin as essential components;
(Ii) The weight ratio of the layered inorganic compound to the total solid is 70% or more,
(Iii) the total light transmittance exceeds 90%,
(Iv) a gas barrier property having a permeability coefficient for oxygen gas of less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ at room temperature;
(V) having a heat resistance of 250 ° C. or higher, and (vi) having a mechanical strength of 300 kg / cm ² or more at break strength, The photoelectric conversion electrode of Claim 1 obtained by baking the conductive layer and semiconductor layer which were formed into a film on the board | substrate. Baking temperature is 200 to 400 degreeC, The photoelectric conversion electrode of Claim 1 or 2 characterized by the above-mentioned. The photoelectric conversion element according to claim 1, wherein the semiconductor layer is a porous semiconductor film that has adsorbed a dye. The photoelectric conversion element provided with the photoelectric conversion electrode in any one of Claims 1-4, and its counter electrode. 6. The photoelectric conversion element according to claim 5, wherein a charge transport layer is provided between the light conversion electrode and the counter electrode.