JP2007048580A - Oxide semiconductor electrode, method for producing the same, and dye-sensitized solar cell provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide semiconductor electrode capable of dramatically improving the photoelectric conversion efficiency of a dye-sensitized solar cell, a manufacturing method thereof, and a dye-sensitized solar cell provided with the same.
An oxide semiconductor electrode having an underlayer and an oxide semiconductor layer, the underlayer is thin, and the crystalline oxide semiconductor particles (A1) constituting the layer have a specific average particle size. An oxide semiconductor electrode having a high average porosity and a crystalline oxide semiconductor particle (B1) constituting the layer having a specific average particle size Embodiment), or an oxide semiconductor electrode having an underlayer, an intermediate layer, and an oxide semiconductor layer, wherein the thickness of the underlayer is thin and the crystalline oxide semiconductor particles (A2) constituting the layer are specified Oxidation having fine particles having an average particle size or less, and that the intermediate layer has a specific film thickness and a high porosity, and the crystalline oxide semiconductor particles (B2) constituting the layer have a specific average particle size Semiconductor electrode (second embodiment).
[Selection] Figure 1

Description

  The present invention relates to an oxide semiconductor electrode suitable for a dye-sensitized solar cell and a method for producing the same.

  Since a dye-sensitized solar cell having performance comparable to that of an amorphous silicon solar cell by Gretzell et al. Has been reported, research on a dye-sensitized solar cell with higher photoelectric conversion efficiency has been actively conducted.

  For example, in Patent Document 1, in the production of a porous titanium oxide thin film on a substrate by a spray pyrolysis method (SPD method), a titanium compound is added to a titanium oxide sol solution, which is a raw material solution, so Further, there is disclosed a technique for growing a neck and ensuring improvement in productivity by forming a film in a short time and improving conversion efficiency of a solar cell. In this document, the oxidation is performed by interposing a dense titanium oxide buffer layer made of an organic titanium compound as a raw material between the transparent electrode (fluorine-doped tin oxide thin film) on the substrate and the porous titanium oxide thin film. It is said that the difficulty of film formation due to the poor compatibility of the tin thin film and the titanium oxide sol solution is avoided, thereby eliminating the problem of short circuit due to contact between the electrolytic solution and the transparent electrode and the accompanying decrease in open circuit voltage. This is because the titanium oxide buffer layer is familiar with both the transparent electrode and the porous titanium oxide thin film and can easily form a bond.

  Further, in Patent Document 2, a conductive promote film such as an organometallic complex or an organic conductive material is formed between a conductive surface on a substrate and an oxide semiconductor film such as titanium oxide. It is assumed that the bonding property with the oxide semiconductor film can be improved, so that the oxide semiconductor film can be manufactured without using high temperature, and the energy conversion efficiency can be significantly improved.

  However, none of the documents focus on preventing the occurrence of cracks in the nanometer order between the conductive substrate and the porous oxide semiconductor thin film such as titanium oxide that are generated during high-temperature firing.

JP 2003-176130 A JP 2003-297443 A SAITO Y., KAMBE S., KITAMURA T., WADA Y., YANAGIDA S., Morphology control of mesoporous TiO2 nanocrystalline films for performance of dye sensitized solar cells, Solar Energy materials and Solar Cells, 2004, Vol.83, No. 1, Page 1-13 Yuki Saito, Shozo Yanagida Nanotechnology to improve the performance of titanium oxide solar cells (2003), Powder and Industry, Vol. 35, No. 4

  In the usual manufacturing method, the present inventors have a nanometer order between an oxide semiconductor film such as titanium oxide used as an n-type semiconductor in a dye-sensitized solar cell and a conductive substrate such as a glass electrode. It was discovered for the first time that the crack was generated, and one of the causes of the low performance of the dye-sensitized solar cell was thought to be the generation of this crack. That is, after applying the conventional method (oxide semiconductor nanoparticles dispersed in an aqueous solution containing an organic binder on a transparent conductive glass substrate by a squeegee method or the like so as to have a film thickness of 5 microns or more, firing at a temperature of about 450 ° C. Is observed with a focused ion beam (FIB) processing and observation device, and there are several gaps between the transparent electrode (fluorine-doped tin oxide thin film) and the porous titanium oxide thin film on the substrate. A 10 nm crack was observed. Moreover, as a result of observing the occurrence of cracks at various firing temperatures, it was found that cracks occurred during firing after the oxide semiconductor material was applied. The space of this crack is impossible for electrons to jump over at the electron density generated in the dye-sensitized solar cell, and only through a few columnar connecting parts that are connected in a form that bridges this crack, It was speculated that electrons were transmitted. If the generation of such cracks can be suppressed, electron transfer between the transparent electrode on the substrate and the porous titanium oxide thin film can be improved, and the photoelectric conversion efficiency can be dramatically improved.

  Accordingly, the present invention provides an oxide semiconductor electrode capable of dramatically improving the photoelectric conversion efficiency of a dye-sensitized solar cell by suppressing the occurrence of cracks on the order of nanometers, and a method for manufacturing the same. Is an issue.

  In order to suppress the occurrence of such cracks, we considered the provision of an underlayer between a transparent electrode (such as a fluorine-doped tin oxide thin film) on the substrate and a porous titanium oxide thin film. Even if it was possible to suppress the occurrence of cracks with the transparent electrode, it was difficult to simultaneously suppress the occurrence of cracks with the porous titanium oxide thin film. However, surprisingly, by setting the porosity of the oxide semiconductor layer to 55% or more, or even if the porosity of the oxide semiconductor layer is less than 55%, the gap between the base layer and the oxide semiconductor layer It has been found that the occurrence of cracks between the layers can be suppressed by interposing an intermediate layer having a porosity of 55% or more in each layer.

That is, the first aspect of the present invention is a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A1) formed on the conductive surface, and formed on the base layer. An oxide semiconductor electrode having an oxide semiconductor layer made of crystalline oxide semiconductor particles (B1), wherein the following requirements (1) and (2) are satisfied:
(1) The underlayer has a thickness of 50 to 1000 nm, and the crystalline oxide semiconductor particles (A1) have an average particle size of 25 nm or less.
(2) The porosity of the oxide semiconductor layer is 55% or more, and the average particle size of the crystalline oxide semiconductor particles (B1) is 10 to 30 nm.
It is characterized by satisfying the above requirements.

The second aspect of the present invention is a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A2) formed on the conductive surface, and formed on the base layer. An oxide semiconductor electrode having an intermediate layer made of crystalline oxide semiconductor particles (B2) and an oxide semiconductor layer formed on the intermediate layer and made of oxide semiconductor particles (C), The requirements of (1) and (2), ie
(1) The underlayer has a thickness of 50 to 1000 nm, and the crystalline oxide semiconductor particles (A2) have an average particle size of 25 nm or less.
(2) The porosity of the intermediate layer is 55% or more and the film thickness is 1 to 4 μm, and the average particle diameter of the crystalline oxide semiconductor particles (B2) is 10 to 30 nm.
It is characterized by satisfying the above requirements.

  Moreover, the 3rd aspect of this invention is a dye-sensitized solar cell characterized by having the oxide semiconductor electrode as described in the said 1st or 2nd aspect.

The fourth aspect of the present invention is a method for manufacturing the oxide semiconductor electrode according to the first aspect. That is, this embodiment is a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A1) formed on the conductive substrate, and a crystalline oxide formed on the base layer A method for manufacturing an oxide semiconductor electrode having an oxide semiconductor layer made of semiconductor particles (B1), the following steps (1) and (2):
Process (1)
After applying crystalline oxide semiconductor particles (A1) having an average particle diameter of 25 nm or less or a precursor paste thereof onto a substrate having a conductive surface, the film thickness is 50 by baking at a temperature of 80 to 550 ° C. Forming a base layer of ˜1000 nm,
Process (2)
An oxide having a porosity of 55% or more is obtained by applying a paste of crystalline oxide semiconductor particles (B1) having an average particle size of 10 to 30 nm on the underlayer and then firing the paste at a temperature of 400 to 550 ° C. Forming a semiconductor layer;
Are performed in order.

Furthermore, a fifth aspect of the present invention is a manufacturing method for the oxide semiconductor electrode according to the second aspect. That is, the present embodiment includes a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A2) formed on the conductive substrate, and a crystalline oxide formed on the base layer. A method for manufacturing an oxide semiconductor electrode having an intermediate layer made of semiconductor particles (B2) and an oxide semiconductor layer formed on the intermediate layer and made of crystalline oxide semiconductor particles (C), comprising the following steps: (1)-(3) That is,
Process (1)
After applying a crystalline oxide semiconductor particle (A2) having an average particle diameter of 25 nm or less or a precursor paste thereof onto a substrate having a conductive surface, the film thickness is 50 by baking at a temperature of 80 to 550 ° C. Forming a base layer of ˜1000 nm,
Process (2)
After applying a paste of crystalline oxide semiconductor particles (B2) having an average particle diameter of 10 to 30 nm on the underlayer, the film thickness is 1 to 4 μm by firing at a temperature of 80 to 550 ° C. Forming an intermediate layer having a porosity of 55% or more;
Step (3)
A step of forming an oxide semiconductor layer by applying a paste of the oxide semiconductor particles (C) on the intermediate layer and firing at a temperature of 400 to 550 ° C .;
Are performed in order.

  According to the present invention, it is possible to prevent the occurrence of nanometer-order cracks generated between an oxide semiconductor film such as titanium oxide and a conductive substrate such as a glass electrode during high-temperature firing, and thus the photoelectric conversion efficiency of a dye-sensitized solar cell Can be dramatically improved.

(1) About the first aspect of the present invention In this aspect, a substrate having a conductive surface, a base layer comprising crystalline oxide semiconductor particles (A1) formed on the conductive surface, and the base layer An oxide semiconductor electrode having an oxide semiconductor layer made of crystalline oxide semiconductor particles (B1) formed thereon, the following requirements (1) and (2):
(1) The underlayer has a thickness of 50 to 1000 nm, and the crystalline oxide semiconductor particles (A1) have an average particle size of 25 nm or less.
(2) The porosity of the oxide semiconductor layer is 55% or more, and the average particle size of the crystalline oxide semiconductor particles (B1) is 10 to 30 nm.
An oxide semiconductor electrode characterized by satisfying the above requirements.
I will provide a.

(I) Substrate having a conductive surface A substrate having a conductive surface is a conductive metal oxide thin film such as indium oxide or tin oxide, a metal such as gold, silver or platinum on a heat resistant substrate such as glass. A thin film or a conductive thin film such as a conductive polymer is formed. When this is applied to a dye-sensitized solar cell and light is taken from the anode side, a transparent electrode such as a fluorine-doped tin oxide thin film can be preferably used from the viewpoint of heat resistance, chemical resistance, and translucency.

(Ii) About the crystalline oxide semiconductor particles (A1) and the crystalline oxide semiconductor particles (B1) (hereinafter referred to as “crystalline oxide semiconductor particles”) One compound or a mixture of two or more selected from the group consisting of titanium oxide, niobium oxide, zinc oxide, tin oxide, indium oxide, zirconium oxide, tantalum oxide, vanadium oxide, yttrium oxide, aluminum oxide, and magnesium oxide. Among them, from the viewpoint of photoelectric conversion efficiency, one or more selected from the group consisting of titanium oxide, niobium oxide, zinc oxide and tin oxide are preferable, and titanium oxide is particularly preferable. Further, from the viewpoint of suppressing the generation of cracks, it is preferable that the crystalline oxide semiconductor particles (A1) and the crystalline oxide semiconductor particles (B1) have the same chemical composition. For example, it is preferable that both the crystalline oxide semiconductor particles (A1) and the crystalline oxide semiconductor particles (B1) are titanium oxide.

  The crystalline oxide semiconductor particle is preferably a single crystal from the viewpoint of suppressing the generation of cracks. May be mixed in a small amount. When the crystalline oxide semiconductor particles are titanium oxide, three types of crystal systems of rutile, anatase, and brookite are known. Of these, anatase or brookite, particularly anatase is preferred.

(Iii) Underlayer The underlayer is made of crystalline oxide semiconductor particles (A1) and is formed on the conductive surface. By using crystallinity, thinness, and a fine particle form having an average particle diameter of 25 nm or less, generation of cracks between the conductive surface and the underlayer can be suppressed. The average particle diameter of the crystalline oxide semiconductor particles (A1) is 25 nm or less from the viewpoint of preventing cracks from occurring, and from the viewpoint of increasing the voltage by preventing infiltration of the electrolytic solution by obtaining a dense layer without gaps. 10-20 nm is more preferable, and 12-18 nm is more preferable.

  In addition, the thickness of the underlayer is 50 to 1000 nm, and preferably 100 to 300 nm, from the viewpoint of preventing cracking itself during high-temperature firing and suppressing crack generation.

  Here, the average particle diameter means the number average particle diameter throughout the present specification, and can be measured by FE-SEM or the like.

  As the crystalline oxide semiconductor particles (A1), for example, HPW-18NR (anatase type crystalline titanium oxide) manufactured by Catalytic Chemical Co., Ltd., NTB-13 (Brookite type crystalline titanium oxide) manufactured by Showa Denko KK Etc. can be used suitably.

(Iv) Oxide Semiconductor Layer The oxide semiconductor layer comprises crystalline oxide semiconductor particles (B1) having a porosity of 55% or more and an average particle size of 10 to 30 nm. It is formed on the formation.

  The porosity [measured by gas adsorption measurement (nitrogen isothermal adsorption measurement)] is more preferable from the viewpoint of adsorbing more organic dye on the surface, and from the viewpoint of mobility of the electrolytic solution and crack generation suppression. Is 55 to 80%, particularly preferably 60 to 75%. At this time, in order not to impair the dye adsorption amount, it is preferable to maintain the roughness factor at a value larger than 1000 by reducing the particle diameter or the like. By adopting the porosity as described above, the generation of cracks between the layers during high-temperature firing and cooling between the layers is suppressed. The details of the mechanism are unknown, but it is estimated that the interlayer expands and contracts flexibly, acting as a spring, which suppresses delamination between layers during high-temperature firing and cooling. .

Here, the porosity can be obtained by the following equation.
Porosity = ρV / (ρV + 1) × 100 (%)
ρ: Theoretical density of titanium oxide (single crystal density g / cm ³ )
V: pore volume per unit weight (cm ³ / g) by gas adsorption analysis

  In order to set the porosity of the oxide semiconductor layer to 55% or more, as will be described later in (4) the fourth aspect of the present invention, irregularly shaped particles or secondary particles are deposited. Thus, a layer having such a large gap and a high porosity can be obtained. For example, as the crystalline oxide semiconductor particles (B1), those having a structure such as one in which a plurality of spherical particles aggregate to form secondary particles (three-dimensional daisy chain structure) or a tube-like one are used. A layer having a high porosity can be formed.

  Even when the crystalline oxide semiconductor particles (B1) do not have such a structure, an appropriate amount or more of a binder, preferably polyethylene glycol or Triton X100 [octylphenoxyethoxylate (average polymerization degree) with respect to its weight. The porosity of the oxide semiconductor layer can be increased to 55% or more by preparing an oxide semiconductor layer using a paste containing a glycol additive such as polyethylene glycol monoether such as 9.5)]. is there. The amount of the binder added varies depending on the particle size of the particles used, but an amount sufficient to make the oxide semiconductor layer have a porosity of 55% or more is used. For example, the addition can be 50% by weight or more based on the weight of the crystalline oxide semiconductor particles (B1). Non-patent document 1 and non-patent document 2 can be referred to for a method for producing a layer having a high porosity using a binder.

  Further, the average particle diameter of the crystalline oxide semiconductor particles (B1) is 10 to 30 nm from the viewpoint of the amount of dye adsorption, but is preferably 15 to 25 nm. Further, the average particle diameter of the crystalline oxide semiconductor particles (B1) is preferably larger than the average particle diameter of the crystalline oxide semiconductor particles (A1) from the viewpoint of preventing the occurrence of cracks.

  The thickness of the oxide semiconductor layer is preferably 5 to 30 μm, particularly preferably 8 to 16 μm, from the viewpoint of electron diffusion length.

Furthermore, the roughness factor (ratio of the effective surface area to the projected area) that comprehensively evaluates the porosity, average particle diameter, and thickness of the oxide semiconductor layer is defined, and can be calculated by the following formula,
Roughness factor = (total surface area of oxide semiconductor layer ^{* 1} ) / (projected area of oxide semiconductor layer ^{* 2} )
* 1 Obtained by the BET equation in nitrogen isothermal adsorption measurement.
* 2 Effective area.
This is preferably 1000 or more.

  Examples of preferable crystalline oxide semiconductor particles (B1) that give an oxide semiconductor layer having a porosity of 55% or more without using a binder include, for example, titanium oxide for low-temperature firing (SP200 series) manufactured by Showa Denko K.K. Can

(2) Second Embodiment of the Present Invention In this embodiment, a substrate having a conductive surface, a ground layer made of crystalline oxide semiconductor particles (A2) formed on the conductive surface, the ground layer An oxide semiconductor having an intermediate layer made of crystalline oxide semiconductor particles (B2) formed on the surface, and an oxide semiconductor layer made of crystalline oxide semiconductor particles (C) formed on the intermediate layer An electrode having the following requirements (1) and (2):
(1) The underlayer has a thickness of 50 to 1000 nm, and the crystalline oxide semiconductor particles (A2) have an average particle size of 25 nm or less.
(2) The porosity of the intermediate layer is 55% or more and the film thickness is 1 to 4 μm, and the average particle diameter of the oxide semiconductor particles (B2) is 10 to 30 nm.
It is characterized by satisfying the above requirements.

(I) Substrate having conductive surface The same as (1) (i) above.
(Ii) Crystalline oxide semiconductor particles (A2), crystalline oxide semiconductor particles (B2), and crystalline oxide semiconductor particles (C) In the above (1) (ii), the crystalline oxide semiconductor particles ( A1) and crystalline oxide semiconductor particles (B1) are the same as those obtained by replacing crystalline oxide semiconductor particles (A2), crystalline oxide semiconductor particles (B2), and crystalline oxide semiconductor particles (C). It is.
(Iii) Underlayer The same as (1) (iii) above, in which the crystalline oxide semiconductor particles (A1) are replaced with the crystalline oxide semiconductor particles (A2).
(Iv) About the intermediate layer The intermediate layer comprises oxide semiconductor particles (B2) having an average particle diameter of 10 to 30 nm, the porosity of the layer is 55% or more, and the film thickness is 1 to 4 μm. It is formed on the underlayer.

  The porosity of the intermediate layer [measured by gas adsorption measurement (nitrogen isothermal adsorption measurement) method] is 55% or more, more preferably 55 to 90%, particularly preferably 60 to 85, from the viewpoint of suppressing crack generation. %.

  The definition of porosity is the same as the definition described in (1) (iv) above.

  It is preferable from the viewpoint of adhesion that the porosity of the intermediate layer is larger than the porosity of the oxide semiconductor layer described later.

  By adopting the porosity as described above, the generation of cracks between the layers during high-temperature firing and cooling between the layers is suppressed. The details of the mechanism are unknown, but it is estimated that the interlayer expands and contracts flexibly, acting as a spring, which suppresses delamination between layers during high-temperature firing and cooling. .

  In order to make the porosity of the intermediate layer 55% or more, as will be described later in (5) the fifth aspect of the present invention, it is possible to deposit irregularly shaped particles or secondary particles. A layer having a large gap and a high porosity can be obtained. For example, as the crystalline oxide semiconductor particles (B2), those having a structure such as one in which a plurality of spherical particles aggregate to form secondary particles (three-dimensional daisy chain structure) or a tube-like one are used. A layer having a high porosity can be formed.

  Alternatively, even if the crystalline oxide semiconductor particles (B2) do not have such a structure, an appropriate amount or more of a binder, preferably polyethylene glycol or Triton X100 [octylphenoxyethoxylate (average polymerization degree) with respect to its weight. The porosity of the intermediate layer can be 55% or more by preparing the intermediate layer using a paste containing a glycol additive such as polyethylene glycol monoether such as 9.5)]. The amount of the binder added varies depending on the particle size of the particles to be used, but can be, for example, 50% by weight or more based on the weight of the crystalline oxide semiconductor particles (B2). Non-patent document 1 and non-patent document 2 can be referred to for a method for producing a layer having a high porosity using a binder.

  The intermediate layer can be formed not only as a single layer but also as a plurality of layers.

  Moreover, although the average particle diameter of this crystalline oxide semiconductor particle (B2) is 10-30 nm, the thickness of this intermediate | middle layer is 1-4 micrometers from a viewpoint of crack generation | occurrence | production suppression. From the same viewpoint, the average particle diameter of the crystalline oxide semiconductor particles (B2) is preferably larger than the crystalline oxide semiconductor particles (A2).

  As a preferable crystalline oxide semiconductor particle (B2) that can obtain an intermediate layer having a porosity of 55% or more without using a binder, titanium oxide for low-temperature firing (SP200 series) manufactured by Showa Denko KK Can be mentioned.

(V) Oxide Semiconductor Layer The oxide semiconductor layer is made of crystalline oxide semiconductor particles (C) and is formed on the intermediate layer.

  In addition, more organic dye is adsorbed on the surface of the oxide semiconductor layer, and the porosity of the oxide semiconductor layer is preferably 40% or more from the viewpoint of the mobility of the electrolytic solution. Note that, when the porosity of the oxide semiconductor layer is 55% or more, the object can be achieved even with a simpler system excluding the intermediate layer as in the second embodiment. This is significant when the porosity of the oxide semiconductor layer is less than 55%.

  Further, in order to make the porosity of the oxide semiconductor layer 40% or more or even less than 55%, it will be described later in (5) the fifth embodiment of the present invention, but it was prepared from titania alkoxide. Or using commercially available nanoparticles (P25 made by Nippon Aerosil, F-5 made by Showa Titanium, etc.) as they are, or adding an adjusted amount of binder in the paste to produce an oxide semiconductor layer Can adjust the porosity (see Non-Patent Document 1 and Non-Patent Document 2).

  The average particle diameter of the crystalline oxide semiconductor particles (C) is preferably 10 to 30 nm, and particularly preferably 15 to 25 nm, from the viewpoint of the amount of dye adsorbed. The thickness of the oxide semiconductor layer is preferably 5 to 30 μm, and particularly preferably 8 to 16 μm, from the viewpoint of electron diffusion length.

(3) About 3rd aspect of this invention In this aspect, the dye-sensitized solar cell containing the oxide semiconductor electrode demonstrated in the said 1st or 2nd aspect of this invention of said (1)-(2). provide. In accordance with a conventional method, a sensitizing dye such as a Ru sensitizing dye is adsorbed and supported on the oxide semiconductor layer of the oxide semiconductor electrode of the first or second aspect, superimposed on the counter electrode, and then various ion additives. Alternatively, it can be completed by filling an electrode with an electrolyte containing an organic solvent containing iodine as an redox agent, an ionic liquid or the like, or a P-type hole transport layer such as a conductive polymer. In addition, as the counter electrode, a material obtained by laminating an element such as platinum or carbon or a conductive polymer such as PEDOT [poly (ethylenedioxy) thiophene] as a catalyst on a conductive substrate in a thin and porous form is preferable. Can be used.

(4) About the 4th aspect of this invention In this aspect, the manufacturing method of the oxide semiconductor electrode demonstrated in the said (1) 1st aspect of this invention is provided.

That is, the fourth aspect of the present invention is formed on a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A1) formed on the conductive substrate, and the base layer. A method of manufacturing an oxide semiconductor electrode having an oxide semiconductor layer made of the crystalline oxide semiconductor particles (B1), which includes the following steps (1) and (2):
Process (1)
After applying crystalline oxide semiconductor particles (A1) having an average particle diameter of 25 nm or less or a precursor paste thereof onto a substrate having a conductive surface, the film thickness is 50 by baking at a temperature of 80 to 550 ° C. Forming a base layer of ˜1000 nm,
Process (2)
An oxide having a porosity of 55% or more is obtained by applying a paste of crystalline oxide semiconductor particles (B1) having an average particle size of 10 to 30 nm on the underlayer and then firing the paste at a temperature of 400 to 550 ° C. Forming a semiconductor layer;
In order, and is a method for manufacturing an oxide semiconductor electrode.

By the method of this aspect, the crack which generate | occur | produces in the baking after oxide semiconductor paste application | coating can be suppressed effectively, and the significant improvement of a photoelectric conversion efficiency can be anticipated.
(I) Application method and paste Crystalline oxide semiconductor particles (A1) or precursors thereof (first step), crystalline oxide semiconductor particles (B1) (second step) used in the above steps (hereinafter, Examples of the coating method (abbreviated as “crystalline oxide semiconductor particles”) include spin coating, spraying, dipping, screen printing, doctor blade, and the like. From the viewpoint of mass production, a spin coating method, a spray method, and a dipping method are preferable, and a screen printing method is preferable.

  The paste such as the crystalline oxide semiconductor particles is obtained by obtaining the crystalline oxide semiconductor or the like in the form of sol or slurry, and the solvent used is water, an organic solvent, or those Can be mentioned. Examples of the organic solvent include one or more solvents selected from alcohols such as methanol, ethanol and propanol, ketones such as methyl ethyl ketone, acetone and acetylacetone, and basic solvents such as dimethylformamide and pyridine. Among these, water, ethanol and the like are particularly preferable from the viewpoint of adhesion. In addition, the content of the oxide semiconductor in these solvents is preferably 10 to 30% by weight in the case of a spin coating method, for example, from the viewpoint of the thickness after coating. In addition, a dispersion aid such as nitric acid and acetylacetone, and a viscosity modifier such as polyethylene glycol can be added to the paste. The pH is preferably in the range of 1 to 4 from the viewpoint of dispersion.

(Ii) First Step (Formation of Underlayer) In the first step, a paste of crystalline oxide semiconductor particles (A1) having an average particle size of 25 nm or less or a precursor thereof is formed on a substrate having a conductive surface. After coating, the base layer having a thickness of 50 to 1000 nm is formed by baking at a temperature of 80 to 550 ° C.

  As the firing temperature, a temperature of 80 to 550 ° C. is used, but from the viewpoint of necking between particles, in the case of a heat resistant substrate such as FTO glass, it is more preferably 450 to 500 ° C. However, this condition varies depending on the heat resistance of the substrate.

  As the crystalline oxide semiconductor particles (A1), commercially available oxide semiconductor particles having an average particle diameter of 25 nm or less, more preferably an average particle diameter of 10 to 25 nm can be used. For example, the NTB series manufactured by Showa Denko (particle diameter of 20 nm or less, dispersion medium is water / alcohol) or the HPW series of catalyst chemical industry (particle diameter of 20 nm or less, dispersion medium is water) is already in the form of slurry. Therefore, it can be used as it is for spin coating. Since these commercially available slurry products such as NTB series made by Showa Denko are commercially available in various concentrations, spin coating is performed so that the film thickness finally becomes 50 to 1000 nm, preferably 100 to 300 nm. The number of times may be adjusted. Moreover, ST-01 (average particle diameter 7 nm) manufactured by Ishihara Sangyo Co., Ltd., AM-100 (average particle diameter 6 nm) manufactured by Teika, Super Titania F-6 manufactured by Showa Titanium (commercially available in powder form) Many are known, such as P90 (average particle size of about 15 nm) manufactured by Nippon Aerosil Co., Ltd., and these commercially available powder products are water-alcohol type so as to be 15 to 30% by weight. What is necessary is just to apply | coat so that it may disperse | distribute with a solvent and a film thickness may be set to 50-1000 nm by the spin coat method.

Furthermore, in the first step, a precursor thereof can be used instead of the crystalline oxide semiconductor particles (A1). Examples of the precursor include metal alkoxides and metal halides that are converted into a corresponding crystalline oxide semiconductor during firing. From the viewpoint of improving adhesion, Ti (O ⁱ Pr) ₄ and TiCl ₄ are particularly preferable. Is preferred. For example, when 0.2M Ti (O ⁱ Pr) ₄ solution is spin-coated several times and fired at 450 ° C., crystalline titanium oxide particles having an average particle size of 20 nm or less (anatase type) have a thickness of 50 to 1000 nm. Can be applied.

(Iii) Second Step (Formation of Oxide Semiconductor Layer) In the second step, after applying a paste of crystalline oxide semiconductor particles (B1) having an average particle size of 10 to 30 nm on the underlayer, By baking at a temperature of 400 to 550 ° C., an oxide semiconductor layer having a porosity of 55% or more is formed.

  For the production of an oxide semiconductor layer having a high porosity of 55% or more, an irregularly shaped particle or secondary particle can be deposited to obtain a layer having a large gap and a high porosity. . For example, as the crystalline oxide semiconductor particles (B1), those having a structure such as one in which a plurality of spherical particles aggregate to form secondary particles (three-dimensional daisy chain structure) or a tube-like one are used. A layer having a high porosity can be formed.

  Alternatively, even when the crystalline oxide semiconductor particle (B1) does not have such a structure, an oxide semiconductor layer is formed using a paste containing a binder in an appropriate amount or more with respect to its weight. The porosity of the oxide semiconductor layer can be 55% or more. The amount of the binder added varies depending on the particle size of the particles to be used, but an amount sufficient for the porosity of the obtained oxide semiconductor layer to be 55% or more is used. For example, the addition can be 50% by weight or more based on the weight of the crystalline oxide semiconductor particles (B1). Non-Patent Document 1 and Non-Patent Document 2 can be referred to for a method for manufacturing an oxide semiconductor capable of forming a layer with a high porosity using a binder.

  As a commercial product that can produce an oxide semiconductor layer with a porosity of 55% or more without using a binder, the SP200 series made by Showa Denko is commercially available, and this can be used as it is in the stock solution and applied and fired. Can form an intermediate layer. High porosity can also be obtained by using titanium oxide nanotubes.

  In addition, as a method for obtaining a high porosity by adding a binder, for example, various titanium oxides such as ST-21 (average particle diameter 20 nm) manufactured by Ishihara Sangyo, which is a commercially available titanium oxide nanoparticle, AM manufactured by Teika -600 (average particle size: 30 nm), Super Titania F-5 (average particle size: about 20 nm) made by Showa Titanium, Nippon Aerosil P25 (average particle size: about 25 nm), etc., and a binder, preferably polyethylene glycol or Triton X100 Applying and baking a large amount of glycol additives such as polyethylene glycol monoether such as [octylphenoxyethoxylate (average degree of polymerization 9.5)] (for example, 50% by weight or more based on titanium oxide). Can provide an oxide semiconductor layer with high porosity.A sufficiently high porosity can be obtained by using 50 wt% or more of glycol additives with respect to titanium oxide. However, since the addition amount of polyethylene glycol and the like varies depending on the particle diameter and may vary depending on the molecular weight of polyethylene glycol and the like, the addition amount is appropriately adjusted. For example, according to Non-Patent Document 1, the following results are disclosed.

  In the second step, a firing temperature of 400 to 550 ° C., more preferably 450 to 500 ° C., is used from the viewpoint of promoting the bonding between particles and firing of the additive.

  In the second step, the thickness of the oxide semiconductor layer to be formed is preferably 5 to 30 μm, more preferably 8 to 16 μm. However, the dipping method is repeatedly applied to a predetermined thickness or the viscosity is increased. It can also be applied at once by a squeegee method or a screen printing method.

  Further, the crystalline oxide semiconductor particles (B1) used in the second step have a larger particle size than the crystalline oxide semiconductor particles (A1) used in the first step from the viewpoint of suppressing the generation of cracks. Is preferred.

(5) About 5th aspect of this invention In this aspect, the manufacturing method of the oxide semiconductor electrode demonstrated in said (2) 2nd aspect is provided. Also by the method of this aspect, the crack which generate | occur | produces at the time of baking after oxide semiconductor paste application | coating can be suppressed effectively, and the significant improvement of a photoelectric conversion efficiency can be anticipated.

That is, the fifth aspect of the present invention is formed on a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A2) formed on the conductive substrate, and the base layer. An oxide semiconductor electrode having an intermediate layer made of crystalline oxide semiconductor particles (B2) and an oxide semiconductor layer made of crystalline oxide semiconductor particles (C) formed on the intermediate layer. The following steps (1) to (3), that is,
Process (1)
After applying a crystalline oxide semiconductor particle (A2) having an average particle diameter of 25 nm or less or a precursor paste thereof onto a substrate having a conductive surface, the film thickness is 50 by baking at a temperature of 80 to 550 ° C. Forming a base layer of ˜1000 nm,
Process (2)
After applying a paste of crystalline oxide semiconductor particles (B2) having an average particle diameter of 10 to 30 nm on the underlayer, the film thickness is 1 to 4 μm by firing at a temperature of 80 to 550 ° C. Forming an intermediate layer having a porosity of 55% or more;
Step (3)
A step of forming an oxide semiconductor layer by applying a paste of the crystalline oxide semiconductor particles (C) on the intermediate layer and then baking at a temperature of 400 to 550 ° C .;
Are performed in order.

(I) Application method and paste In the description of (4) and (i) above, “crystalline oxide semiconductor particles (A1) or precursors thereof (first step), crystalline oxide semiconductor particles (B1) (first 2 steps) (hereinafter abbreviated as “crystalline oxide semiconductor particles, etc.”) is referred to as “crystalline oxide semiconductor particles (A2) or precursors thereof (first step), crystalline oxide semiconductor particles (B2)” (Second step) and crystalline oxide semiconductor particles (C) (third step) (hereinafter abbreviated as “crystalline oxide semiconductor particles and the like”) ”.

(Ii) First Step (Formation of Underlayer) In the first step, a paste of crystalline oxide semiconductor particles (A2) having an average particle size of 25 nm or less or a precursor thereof is formed on a substrate having a conductive surface. After coating, the base layer having a thickness of 50 to 1000 nm is formed by baking at a temperature of 80 to 550 ° C.

  About this process, in the description of said (4) (ii), it is the same as what replaced the crystalline oxide semiconductor particle (A1) or its precursor with the crystalline oxide semiconductor particle (A2) or its precursor. It is.

(Iii) Second Step (Formation of Intermediate Layer) In the second step, after applying a paste of crystalline oxide semiconductor particles (B2) having an average particle size of 10 to 30 nm on the underlayer, 80 to By baking at a temperature of 550 ° C., an intermediate layer having a film thickness of 1 to 4 μm and a porosity of 55% or more is formed.

  As the crystalline oxide semiconductor particles (B2), particles having an average particle diameter of 10 to 30 nm, preferably 15 to 25 nm are used, and the porosity of the intermediate layer is 55% or more, preferably 55 to 90%, more preferably. The intermediate layer is made to have a high porosity of 60-85%.

  For the production of an intermediate layer having a high porosity of 55% or more, an irregularly shaped particle or secondary particle can be deposited to obtain a layer with a large gap and a high porosity. For example, as the crystalline oxide semiconductor particles (B2), those having a structure such as one in which a plurality of spherical particles aggregate to form secondary particles (three-dimensional daisy chain structure) or a tube-like one are used. A layer having a high porosity can be formed. Alternatively, even if the crystalline oxide semiconductor particles (B2) do not have such a structure, an appropriate amount or more of a binder, preferably polyethylene glycol or Triton X100 [octylphenoxyethoxylate (average polymerization degree) with respect to its weight. The porosity of the oxide semiconductor layer can be increased to 55% or more by preparing an oxide semiconductor layer using a paste containing a glycol additive such as polyethylene glycol monoether such as 9.5)]. is there. The amount of the binder added varies depending on the particle size of the particles used and the molecular weight of the binder used (glycols such as polyethylene glycol) [see (1) in Table 1 of (iv) (iii)]. A sufficient amount of binder is added. For example, the addition can be 50% by weight or more based on the weight of the crystalline oxide semiconductor particles (B2). Non-patent literature 1 and non-patent literature 2 can be referred to for a method for producing an intermediate layer capable of forming a layer having a high porosity using a binder.

  As a commercially available crystalline oxide semiconductor particle (B2) that can produce an intermediate layer having a porosity of 55% or more without using a binder, SP200 series manufactured by Showa Denko is commercially available. The intermediate layer can be formed by coating and baking the raw solution as it is. High porosity can also be obtained by using titanium oxide nanotubes.

  In addition, as a method for obtaining a high porosity by adding a binder, for example, various titanium oxides such as ST-21 (average particle diameter 20 nm) manufactured by Ishihara Sangyo, which is a commercially available titanium oxide nanoparticle, AM manufactured by Teika -Glycerol additives such as polyethylene glycol are added to slurry such as -600 (average particle size 30 nm), Super Titania F-5 (average particle size about 20 nm) made by Showa Titanium, Japan Aerosil P25 (average particle size about 25 nm), etc. An intermediate layer having a high porosity can be obtained by applying and baking a large amount (for example, 50% by weight or more based on titanium oxide). A sufficiently high porosity can be obtained by using 50 wt% or more of glycol additives with respect to titanium oxide.

  The thickness of the intermediate layer is 1 to 4 μm from the viewpoint of suppressing the occurrence of cracks, but is preferably 2 to 4 μm.

  Moreover, as a calcination temperature in a 2nd process, although the temperature of 80-550 degreeC is used, from the viewpoint of the necking between particle | grains, in the case of heat resistant substrates, such as FTO glass, More preferably, it is 450-500 degreeC. However, this condition varies depending on the heat resistance of the substrate.

  In addition, the crystalline oxide semiconductor particles (B2) used in the second step have a larger particle size than the crystalline oxide semiconductor particles (A2) used in the first step from the viewpoint of suppressing the generation of cracks. Is preferred.

(Iv) Third Step (Formation of Oxide Semiconductor Layer) In the third step, after applying the crystalline oxide semiconductor particle (C) paste on the intermediate layer, firing at a temperature of 400 to 550 ° C. Thus, an oxide semiconductor layer is formed.

  Any known method can be used for forming the oxide semiconductor layer.

  The oxide semiconductor layer preferably has a porosity of 40% or more. In particular, a porosity of less than 55% can be differentiated from the oxide semiconductor electrode of the first aspect, and has a unique meaning. Have When an oxide semiconductor layer having a porosity of 50% or more or even less than 55% is produced, the crystalline oxide semiconductor particles (C) are prepared from titania alkoxides or commercially available nanoparticles (Japan). Aerosil P25, Showa Titanium F-5, etc.) were used, or the paste was adjusted so that the porosity of the resulting oxide semiconductor layer was 40% or more, or even less than 55%. An oxide semiconductor layer is prepared by adding an amount of binder.

  For example, ST21 manufactured by Ishihara Sangyo (average particle size 20 nm), AM600 manufactured by Teika (average particle size 30 nm), Super Titanium F-5 manufactured by Showa Titanium (average particle size about 20 nm), P25 manufactured by Nippon Aerosil (average particle size) Obtain commercially available titanium oxide nanoparticles (such as about 25 nm), add a sufficient amount of binder (polyethylene glycol, etc.) to achieve the specified porosity, and use a shaker such as a paint shaker. An oxide semiconductor layer (having a thickness of about 10 μm) having a predetermined porosity can be obtained by applying and baking by a squeegee method using a slurry that has been stirred and dispersed as a slurry.

Alternatively, titanium oxide obtained by a method in which a Ti (O ⁱ Pr) ₄ solution hydrolyzed under weak acidic conditions is stirred and aged at about 80 ° C. and then autoclaved at about 240 ° C. for half a day (from Solaronix) (Also commercially available) may be overcoated by squeegee method 2-3 times and then fired.

  In the third step, a firing temperature of 400 to 550 ° C., more preferably 450 to 500 ° C. is used.

  In the third step, the thickness of the oxide semiconductor layer to be formed is preferably 5 to 30 μm, more preferably 8 to 16 μm. However, since the thickness is generally larger than the other two layers, The spin coating method, the spray method, and the dipping method as in the second step can be repeatedly applied so as to have a predetermined thickness, or the viscosity can be increased and the coating can be performed at once by a squeegee method or a screen printing method.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Preparation of titania particle dispersion A titania particle dispersion having a mean particle size of 18 nm and anatase type crystallinity (manufactured by Catalytic Chemicals, HPW-18NR) was prepared, and this was used as a particle dispersion A as it was.

  A stock solution of SP210 (primary particle diameter 30 nm, Showa Denko), which is porous titania particles, was used as a particle dispersion B.

Formation of an underlayer on a substrate having a conductive surface The particle dispersion A is used as a paste for the underlayer, and this is applied to a conductive substrate [Nippon Sheet Glass by spin coating (1000 rpm, 15 seconds, spin coating once). F-made SnO ₂ glass (FTO glass)] is applied to a thickness of about 300 nm. Then, this was baked at 450 degreeC for 30 minutes with the electric furnace, and the process conductive substrate 1 was obtained.

Formation of Oxide Semiconductor Electrode E1 (First Aspect of the Present Invention) Spin coating under conditions of 800 rpm and 15 seconds on the underlying layer formed on the treated conductive substrate 1 using the particle dispersion B. The particle dispersion B was applied so that the film thickness was 10 μm. Then, it baked for 30 minutes at 450 degreeC with the electric furnace. Thus, an oxide semiconductor electrode E1 of the present invention was obtained. The porosity of the oxide semiconductor layer was 57%.

Preparation of titania particle dispersion liquid After adding acetylacetone as a dispersion aid to P25 (particle size 25 nm, manufactured by Nippon Aerosil Co., Ltd.) as a titania particle and dispersing in water, Triton-X100 is added as a surfactant, and titania. Another dispersion was prepared so that the concentration was 40% by weight. The particle dispersion thus obtained was designated as Particle Dispersion C.

Formation of Intermediate Layer A few drops of the particle dispersion B of Example 1 are dropped on the underlying layer of the treated conductive substrate 1 of Example 1 and spin coating (1000 rpm, 15 seconds, spin coating once) is used. Then, it was applied to a thickness of about 4 μm on the base layer. Then, the process conductive board | substrate 2 which baked at 450 degreeC for 30 minute (s) with the electric furnace and deposited the intermediate | middle layer on the base layer was obtained. The porosity of the intermediate layer was 57%.

Formation of Oxide Semiconductor Electrode E2 (Second Aspect of the Present Invention) Using the particle dispersion C, a film thickness of 10 μm is formed on the intermediate layer formed on the treated conductive substrate 2 by the squeegee method. The particle dispersion C was applied as described above. Then, it baked for 30 minutes at 450 degreeC with the electric furnace. Thus, an oxide semiconductor electrode E2 of the present invention was obtained.

(Comparative Example 1)
Formation of Oxide Semiconductor Electrode E3 Using the particle dispersion C of Example 2 above, a squeegee method is used to form a film thickness of 10 μm on a conductive substrate [F-doped SnO ₂ glass (FTO glass) manufactured by Nippon Sheet Glass]. Particle dispersion C was applied to Then, it baked for 30 minutes at 450 degreeC with the electric furnace. As a result, an oxide semiconductor electrode E3 having neither a base layer nor an intermediate layer was obtained.

(Comparative Example 2)
Formation of Oxide Semiconductor Electrode E4 Using the particle dispersion C of Example 2 above, the squeegee method is used to form a film thickness of 10 μm on the underlying layer formed on the treated conductive substrate 1 of Example 1 above. Particle dispersion C was applied to Then, it baked for 30 minutes at 450 degreeC with the electric furnace. As a result, an oxide semiconductor electrode E4 having a base layer but no intermediate layer was obtained. The porosity of the oxide semiconductor layer was 49%.

(Comparative Examples 3-5)
In Comparative Example 2, the firing temperature of each layer was set at 350 ° C. to produce the oxide semiconductor electrode E5 (Comparative Example 3). Similarly, the firing temperature of each layer was set at 150 ° C. to produce the oxide semiconductor electrode E6 (Comparative Example 4). In the same manner, all the firing temperatures were replaced with room temperature, and oxide semiconductor electrodes E7 (Comparative Example 5) were produced. In the production of the electrodes E5 to E7, the one corresponding to the treatment conductive substrate 1 was also produced by substituting for each of the above temperatures instead of 450 ° C.

(Test Example 1)
When the cross section of each oxide semiconductor electrode E1-E7 obtained by the above was observed with the focused ion beam (FIB) processing observation apparatus, the FE-SEM image of FIGS. 2-8 was able to be obtained. Here, FIG. 2 shows the electrode E1 of the example, FIGS. 3 and 4 show the electrode E2 of the example, FIG. 5 shows the electrode E3 of the comparative example 1 (an electrode without an underlayer or an intermediate layer, firing temperature 450 ° C.), FIG. FIG. 7 shows an electrode E4 of Comparative Example 2 (an electrode with a base layer but no intermediate layer, firing temperature 450 ° C.), FIG. 7 shows an electrode E5 (replaced the firing temperature in electrode E4 with 350 ° C.), and FIG. FIG. 9 is a cross-sectional FE-SEM image of E7 (the electrode E4 with the firing temperature replaced with room temperature).

  2 to 6, it can be seen that cracks between the layers are not observed in the products E1 and E2 of the present invention, whereas cracks are observed in the comparative products E3 and E4.

  Moreover, by observing FIG. 9 to FIG. 6 in order, it was shown that the occurrence of cracks that were to be suppressed in the present application occurred in the process of high-temperature firing.

(Test Example 2)
On the oxide semiconductor layer of the oxide semiconductor electrode produced as described above, an organic dye film was formed as follows.

  That is, cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) -ruthenium (II) (manufactured by Solaronix), which is a Ru dye, is mixed into a mixed solution of acetonitrile and t-butanol. It was dissolved to a concentration of 0.3 mM and prepared as a dye solution. Each of the oxide semiconductor electrodes E1 to E4 prepared according to the above preparation examples was heated in advance at 120 ° C. for 20 minutes, then allowed to cool in a desiccator for a while, then immersed in the dye solution, and left in the dark overnight. The dye was adsorbed by allowing it to stand.

  Next, a dye-sensitized solar cell was produced as follows.

That is, the oxide semiconductor electrodes E1 to E4 on which the dye is adsorbed and the counter electrode carrying platinum are overlapped and fixed with a clip, and an electrolyte [LiI 0.1M, DMPImI (= 1,2-dimethyl) is interposed between the electrodes. -3-imidazolinium iodide) 0.3 M, tBP (= 4-tert-butylpyridine) 0.5 M, I ₂ 0.05 M, solvent MAN (= methoxyacetonitrile)] was inserted, and the open cell was Produced.

  For each dye-sensitized solar cell thus obtained, the photoelectric conversion efficiency was measured under the following conditions.

That is, with a solar simulator (manufactured by Yamashita Denso Co., Ltd.), AM (air mass, atmospheric mass) 1.5, 100 mW / cm ² of simulated sunlight is irradiated, and short circuit current density, open circuit voltage, and fill factor (FF) are measured. The photoelectric conversion efficiency was calculated based on the following calculation formula (Formula 1).
(Formula 1)
Photoelectric conversion efficiency = (short-circuit current density x open-circuit voltage x fill factor) / (irradiated solar energy)
As a result, photoelectric conversion efficiency results as shown in Table 2 below were obtained.

  It can be seen that the photoelectric conversion efficiency is remarkably improved.

  An organic dye film is formed on the oxide semiconductor layer of the oxide semiconductor electrode of the present invention and is used as an electrode for a dye-sensitized solar cell, thereby obtaining a dye-sensitized solar cell with greatly improved photoelectric conversion efficiency. Can do.

It is the outline of sectional drawing of the oxide semiconductor electrode of the 1st aspect and 2nd aspect of this invention. The FE-SEM image of the cross section of the oxide semiconductor electrode E1 of this invention (Example). Upper magnification of 50,000 times, lower magnification of 100,000 times The FE-SEM image of the cross section of the oxide semiconductor electrode E2 of this invention (Example). Upper left figure magnification 5,000 times, upper right figure magnification 50,000 times, lower left figure magnification 100,000 times, lower right figure magnification 100,000 times The FE-SEM image of the cross section of the oxide semiconductor electrode E2 of this invention (Example). The upper middle magnification is 20,000 times, the lower left magnification is 50,000 times, the lower right magnification is 50,000 times, The FE-SEM image of the cross section of the oxide semiconductor electrode E3 of the comparative example 1. FIG. Upper left figure magnification 5,000 times, upper right figure magnification 50,000 times, lower left figure magnification 100,000 times, lower right figure magnification 100,000 times The FE-SEM image of the cross section of the oxide semiconductor electrode E4 of the comparative example 2. Upper left figure magnification 5,000 times, upper right figure magnification 50,000 times, lower left figure magnification 100,000 times, lower right figure magnification 100,000 times 14 is an FE-SEM image of a cross section of the oxide semiconductor electrode E5 of Comparative Example 3. FIG. (Oxide semiconductor electrode obtained by replacing the baking temperature with 350 ° C. in Comparative Example 2) Upper left figure magnification 5,000 times, upper right figure magnification 50,000 times, lower left figure magnification 100,000 times, lower right figure magnification 100,000 times 14 is an FE-SEM image of a cross section of the oxide semiconductor electrode E6 of Comparative Example 4. FIG. (Oxide semiconductor electrode obtained by replacing the firing temperature with 150 ° C. in Comparative Example 2) Upper left figure magnification 5,000 times, upper right figure magnification 50,000 times, lower left figure magnification 100,000 times, lower right figure magnification 100,000 times The FE-SEM image of the cross section of the oxide semiconductor electrode E7 of the comparative example 5. FIG. (Oxide semiconductor electrode obtained by replacing firing temperature with room temperature in Comparative Example 2) Upper left figure magnification 5,000 times, upper right figure magnification 50,000 times, lower left figure magnification 100,000 times, lower right figure magnification 100,000 times

Explanation of symbols

2 Substrate 4 Transparent electrode 6 Underlayer 8 Intermediate layer 10 Oxide semiconductor layer

Claims (16)

A substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A1) formed on the conductive surface, and a crystalline oxide semiconductor particle (B1) formed on the base layer An oxide semiconductor electrode having an oxide semiconductor layer, wherein the following requirements (1) and (2) are satisfied:
(1) The underlayer has a thickness of 50 to 1000 nm, and the crystalline oxide semiconductor particles (A1) have an average particle size of 25 nm or less.
(2) The porosity of the oxide semiconductor layer is 55% or more, and the average particle size of the crystalline oxide semiconductor particles (B1) is 10 to 30 nm.
An oxide semiconductor electrode characterized by satisfying the above requirements.   2. The oxide semiconductor electrode according to claim 1, wherein an average particle diameter of the crystalline oxide semiconductor particles (B1) is larger than the crystalline oxide semiconductor particles (A1).   The oxide semiconductor electrode according to claim 1, wherein the oxide semiconductor layer has a thickness of 5 to 30 μm. From a substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A2) formed on the conductive surface, and a crystalline oxide semiconductor particle (B2) formed on the base layer An oxide semiconductor electrode having an intermediate layer and an oxide semiconductor layer formed on the intermediate layer and made of crystalline oxide semiconductor particles (C), the following requirements (1) and (2) That is,
(1) The underlayer has a thickness of 50 to 1000 nm, and the crystalline oxide semiconductor particles (A2) have an average particle size of 25 nm or less.
(2) The porosity of the intermediate layer is 55% or more and the film thickness is 1 to 4 μm, and the average particle diameter of the crystalline oxide semiconductor particles (B2) is 10 to 30 nm.
An oxide semiconductor electrode characterized by satisfying the above requirements.   The oxide semiconductor electrode according to claim 4, wherein an average particle diameter of the crystalline oxide semiconductor particles (B2) is larger than the crystalline oxide semiconductor particles (A2).   6. The oxide according to claim 4, wherein the oxide semiconductor layer has a thickness of 5 to 30 μm, and the crystalline oxide semiconductor particles (C) have an average particle size of 10 to 30 nm. Semiconductor electrode.   A dye-sensitized solar cell comprising the oxide semiconductor electrode according to claim 1. A substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A1) formed on the conductive substrate, and a crystalline oxide semiconductor particle (B1) formed on the base layer A method for producing an oxide semiconductor electrode having an oxide semiconductor layer comprising the following steps (1) and (2):
Process (1)
After applying crystalline oxide semiconductor particles (A1) having an average particle diameter of 25 nm or less or a precursor paste thereof onto a substrate having a conductive surface, the film thickness is 50 by baking at a temperature of 80 to 550 ° C. Forming a base layer of ˜1000 nm,
Process (2)
An oxide having a porosity of 55% or more is obtained by applying a paste of crystalline oxide semiconductor particles (B1) having an average particle size of 10 to 30 nm on the underlayer and then firing the paste at a temperature of 400 to 550 ° C. Forming a semiconductor layer;
A method for manufacturing an oxide semiconductor electrode, which is performed in order.   As a paste of the crystalline oxide semiconductor particles (B1) in the step (2), water, an organic solvent, or a mixture thereof of the crystalline oxide semiconductor particles (B1) having an average particle size of 10 to 30 nm is used as a medium. 9. The method for producing an oxide semiconductor electrode according to claim 8, wherein the paste further comprises a binder in an amount sufficient for the porosity of the obtained oxide semiconductor layer to be 55% or more. Method.   The method for manufacturing an oxide semiconductor electrode according to claim 8 or 9, wherein an average particle diameter of the crystalline oxide semiconductor particles (B1) is larger than the crystalline oxide semiconductor particles (A1).   The method for manufacturing an oxide semiconductor electrode according to claim 8, wherein the oxide semiconductor layer has a thickness of 5 to 30 μm. A substrate having a conductive surface, a base layer made of crystalline oxide semiconductor particles (A2) formed on the conductive substrate, and a crystalline oxide semiconductor particle (B2) formed on the base layer A method for producing an oxide semiconductor electrode having an intermediate layer and an oxide semiconductor layer formed on the intermediate layer and made of crystalline oxide semiconductor particles (C), comprising the following steps (1) to (3) That is,
Process (1)
After applying a crystalline oxide semiconductor particle (A2) having an average particle diameter of 25 nm or less or a precursor paste thereof onto a substrate having a conductive surface, the film thickness is 50 by baking at a temperature of 80 to 550 ° C. Forming a base layer of ˜1000 nm,
Process (2)
After applying a paste of crystalline oxide semiconductor particles (B2) having an average particle diameter of 10 to 30 nm on the underlayer, the film thickness is 1 to 4 μm by firing at a temperature of 80 to 550 ° C. Forming an intermediate layer having a porosity of 55% or more;
Step (3)
A step of forming an oxide semiconductor layer by applying a paste of the crystalline oxide semiconductor particles (C) on the intermediate layer and then baking at a temperature of 400 to 550 ° C .;
A method for manufacturing an oxide semiconductor electrode, which is performed in order.   As a paste of the crystalline oxide semiconductor particles (B2) in the step (2), water, an organic solvent, or a mixture thereof of the crystalline oxide semiconductor particles (B2) having an average particle size of 10 to 30 nm is used as a medium. 13. The method for manufacturing an oxide semiconductor electrode according to claim 12, wherein the paste further contains a binder in an amount sufficient to obtain a porosity of the intermediate layer of 55% or more.   14. The method for manufacturing an oxide semiconductor electrode according to claim 12, wherein an average particle diameter of the crystalline oxide semiconductor particles (B2) is larger than the crystalline oxide semiconductor particles (A2).   The film thickness of the said oxide semiconductor layer is 5-30 micrometers, and the average particle diameter of the said crystalline oxide semiconductor particle (C) is 10-30 nm, The any one of Claims 12-14 characterized by the above-mentioned. Of manufacturing an oxide semiconductor electrode.   The method for manufacturing an oxide semiconductor electrode according to claim 9 or 13, wherein glycols are used as the binder.

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