JP2011253741A - Semiconductor electrode layer, method of manufacturing the same, and electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor electrode layer composed of a metal oxide semiconductor porous layer, which can be manufactured by low temperature calcination and which has all of the performance as an electrode, the hardness and the adhesion to a support member and achieves a higher photoelectric conversion performance when it is used to form a dye-sensitized-type solar cell, and to provide a method of manufacturing the semiconductor electrode layer, and an electrochemical device having the semiconductor electrode layer.SOLUTION: The method of manufacturing a semiconductor electrode layer includes: preparing a coating liquid by adding, to metal oxide semiconductor fine particles 2, a first compound yielding titanium oxide on hydrolysis, and a second compound consisting of a niobium (V) compound yielding oxide or hydroxide on hydrolysis, or phosphoric acid or phosphoric ester; and putting a layer of the coating liquid on a support member 5 followed by low temperature calcination. The semiconductor electrode layer 1 formed by the method has a first oxide layer 3 made of titanium oxide and binding between the metal oxide semiconductor fine particles 2 and between the fine particle 2 and support member 5, and is improved in its conductivity by niobium (V) oxide or a phosphorous (V) compound.

Description

  The present invention relates to a semiconductor electrode layer comprising a porous metal oxide semiconductor layer, a method for producing the same, and an electrochemical device having the semiconductor electrode layer and useful as a dye-sensitized solar cell.

  Carbon dioxide is generated when fossil fuels such as coal and oil are used as energy sources. Carbon dioxide is one of the causative substances that cause global warming. In the use of nuclear energy, radioactive elements are generated and there is a risk of radioactive contamination. Moreover, these energy resources are limited and will eventually be exhausted. Therefore, reliance on these energy sources is problematic. In recent years, sunlight has attracted attention as an alternative and clean and inexhaustible energy source. A solar cell is a photoelectric conversion device that converts the energy of sunlight into electrical energy, and uses sunlight as an energy source, and therefore has a very small influence on the global environment. For this reason, further spread of solar cells is expected. A solar cell is a device that converts light energy into electrical energy.

  Various things are proposed as a principle and constituent material of a solar cell. Among them, solar cells using a semiconductor pn junction are currently most popular, and many solar cells using silicon as a semiconductor material are commercially available. However, manufacturing a solar cell using a pn junction requires a process for manufacturing a high-purity semiconductor material and a process for forming a pn junction. For this reason, there exists a problem that energy consumption in manufacturing processes, such as a high temperature process, is large. In addition, since the number of manufacturing processes is large and a large-scale apparatus such as a clean room or a vacuum apparatus is necessary, there is a problem that the manufacturing cost increases.

  On the other hand, a dye-sensitized solar cell using photoinduced electron transfer photosensitized by a dye has been proposed by Gretzel et al. (Patent Publication No. 2664194 (2nd and 3rd pages, FIG. 1)) and B (See O'Regan and M. Graetzel, Nature, 353, p. 737-740 (1991).)

  FIG. 5 is a cross-sectional view of the main part showing the structure of a general dye-sensitized solar cell 100. The dye-sensitized solar cell 100 mainly includes a transparent substrate 101 such as glass, a transparent conductive layer (negative electrode current collector) 102, a semiconductor electrode layer 103 (negative electrode) holding a photosensitizing dye, an electrolyte layer 104, a counter electrode. (Positive electrode) 105, counter substrate 106, and sealing material (not shown).

The transparent conductive layer 102 is made of ITO (Indium Tin Oxide) or FTO (fluorine-doped tin oxide), and is provided on the transparent substrate 101 as a negative electrode current collector. Function. The semiconductor electrode layer 103 that is a negative electrode is provided in contact with the transparent conductive layer 102. As the semiconductor electrode layer 103, a porous layer obtained by sintering fine particles of a metal oxide semiconductor such as titanium oxide TiO ₂ is often used. The photosensitizing dye is adsorbed on the surface of the metal oxide constituting the semiconductor electrode layer 103. As the electrolyte layer 104, an electrolytic solution containing a redox species (redox pair) or the like is used. The counter electrode 105 is composed of a platinum layer or the like, and is provided on the counter substrate 106.

  The dye-sensitized solar cell 100 is configured such that light enters from the transparent substrate 101 side. A part of the incident light is absorbed by the photosensitizing dye, and a part of the electrons excited by the light absorption is extracted to the semiconductor electrode layer 103. On the other hand, the photosensitizing dye that has lost electrons is reduced by the reducing agent in the electrolyte layer 104. The oxidizing agent generated in the electrolyte layer 104 by this reaction receives electrons from the counter electrode (positive electrode) 105 and is reduced. As a result, the dye-sensitized solar cell 100 operates as a photovoltaic cell having the transparent conductive layer 102 and the semiconductor electrode layer 103 as a negative electrode and the counter electrode 105 as a positive electrode. A dye-sensitized solar cell is an example of an electrochemical device having a semiconductor electrode layer.

  Dye-sensitized solar cells do not require a vacuum treatment process for manufacturing, so large-scale equipment is not required, and inexpensive oxide semiconductors such as titanium oxide are used to manufacture with low productivity and high productivity. There are advantages. In addition, there are various photosensitizing dyes that can absorb light in each wavelength region in a wide wavelength region centered on the visible light region. Therefore, the wavelength of light to be absorbed can be selected by changing the dye used, or multiple By combining these dyes, there is an advantage that light in a wide wavelength region can be used. In addition, there is a possibility that it can be manufactured with high productivity and low cost by a roll-to-roll process using a lightweight and flexible base material such as plastic. For this reason, it has attracted much attention in recent years as a new generation solar cell.

  FIG. 6 is a flowchart showing a general manufacturing process of the conventional semiconductor electrode layer 103 made of a metal oxide semiconductor porous layer. Hereinafter, the case where the semiconductor electrode layer 103 is manufactured using titanium oxide or the like as a material will be described.

  In order to produce the metal oxide semiconductor porous layer, first, a paste-like dispersion liquid in which metal oxide semiconductor fine particles having a particle size of several tens to several tens of nm are dispersed is prepared. Next, a dispersion liquid is deposited on the transparent conductive layer 102 provided on the transparent substrate 101 by a coating method or the like, and then the solvent is evaporated to form a metal oxide semiconductor fine particle layer.

  Next, a sintering process is performed in which the metal oxide semiconductor fine particle layer is heated in air at a high temperature of about 450 to 550 ° C. for about 30 minutes. In this sintering process, the metal oxide semiconductor porous layer in which the fine particles are fused in the vicinity of the contacts, the fine particles are connected in a network via thin connecting portions, and the voids between the fine particles are left as pores. (Hereinafter, the phenomenon in which the fine particles are connected through a thin connecting portion by fusion in the vicinity of the contact is called necking, and the process of forming such a connection may be called the necking process.) . This metal oxide semiconductor porous layer can be used as the semiconductor electrode layer 103 when a photosensitizing dye is adsorbed.

  The connecting portion between the fine particles formed in the sintering process forms an electron path (path) between the fine particles. Accordingly, the photoelectric conversion characteristics of the dye-sensitized solar cell 100 greatly depend on the state of necking, and the more the necking process is performed, the higher the connectivity between the fine particles, the smoother the electron flow and the photoelectric conversion characteristics are. improves. However, since the necking treatment usually involves heating, if it is performed excessively, the fine particles are fused more than necessary, the pores are crushed, and the actual surface area of the porous layer is reduced. This reduction in the actual surface area is disadvantageous for the retention of the photosensitizing dye on the surface of the semiconductor electrode layer 103 and the progress of the electrode reaction. Therefore, it is necessary to control the sintering process at an appropriate processing temperature and processing time.

  In the porous layer, the area of the surface of the constituent fine particles facing the pores inside the porous layer reaches several times to several thousand times the area of the outer surface (projected area). Therefore, the retention of the photosensitizing dye in the porous layer and the progress of the electrode reaction are mainly performed on the surface facing the pores inside the porous layer. Therefore, in the present specification, hereinafter, the total surface area of the fine particles constituting the porous layer including the surface facing the pores inside the porous layer is referred to as an actual surface area, and is distinguished from the projected area of the porous layer. . Moreover, the surface treatment of the porous layer as used in this specification shall mean the process performed with respect to the whole surface mainly having the surface which faces the void | hole inside a porous layer.

  After sintering, for the purpose of increasing the actual surface area of the porous layer or increasing the necking between the fine particles, the surface treatment of the porous layer, for example, titanium tetrachloride aqueous solution treatment, titanium oxide ultrafine particles having a diameter of 10 nm or less In general, dip treatment with sol is performed. In the titanium tetrachloride aqueous solution treatment, for example, the titanium oxide porous layer is held at 70 ° C. for 30 minutes in a titanium tetrachloride aqueous solution having a concentration of about 0.05M. Subsequently, after washing with distilled water, heat treatment is performed at a high temperature of 450 to 550 ° C. for about 30 minutes (see Non-Patent Documents 1 and 2 described later).

In this titanium tetrachloride aqueous solution treatment, nanosized high-purity titanium oxide fine particles are formed on the surface of the titanium oxide fine particles constituting the porous layer by hydrolysis of titanium tetrachloride TiCl _{4 represented} by the following reaction formula. The
TiCl ₄ + 4H ₂ O → Ti (OH) ₄ + 4HCl
Ti (OH) ₄ → TiO ₂ + 2H ₂ O
The surface of the newly formed titanium oxide fine particles is supposed to function as a region having high photoelectric conversion activity (see Non-Patent Document 2 described later). Further, it is said that there is an effect of improving the conductivity between the fine particles by improving the connectivity between the fine particles (see Non-Patent Document 3 described later).

  Now, the sintering process at high temperature becomes an obstacle to reducing energy consumption in the manufacturing process. Moreover, since there is no plastic material that can withstand high temperatures of 400 to 500 ° C., it is impossible to use plastic as the transparent substrate 101 when performing high-temperature sintering.

  On the other hand, in the case where a plastic film is used as the transparent substrate 101 in order to reduce the cost of the dye-sensitized solar cell or to provide flexibility so that it can be installed on a curved surface or the like, the heat resistance temperature of the plastic substrate (glass In relation to the transition temperature, low-temperature baking is performed at a heat treatment temperature of about 150 ° C. However, since the metal oxide semiconductor porous layer obtained by low-temperature firing has poor crystallinity, the photoelectric conversion efficiency is low. Further, since the bonding state between the fine particles is poor, the titanium oxide porous layer may be damaged or peeled off in the manufacturing process of the solar cell by a roll-to-roll process or the like.

  Therefore, in Patent Document 1 described later, a metal oxide fine particle and a metal alkoxide for adhering the metal oxide fine particle are kneaded to form a paste, and the paste is applied to a conductive substrate. To form a porous film of the metal oxide fine particles on the surface of the conductive substrate, then perform ultraviolet irradiation in an oxygen atmosphere to generate ozone, so-called UV ozone treatment, Next, a method for producing a dye-sensitized solar cell is proposed in which a sensitizing dye is adsorbed on the porous film.

  FIG. 7 is a flowchart showing a manufacturing process of a semiconductor electrode layer made of a metal oxide semiconductor porous layer, as disclosed in Patent Document 1. Patent Document 1 explains as follows.

  In order to produce the metal oxide semiconductor porous layer, first, metal oxide semiconductor fine particles having a particle diameter of 5 to 100 nm are heat-treated at 300 to 500 ° C. Remove organics. This pretreatment improves the photoelectric conversion efficiency of the obtained dye-sensitized solar cell. In addition, the photoelectric conversion efficiency of the dye-sensitized solar cell is also improved by pretreatment for removing organic substances from the metal oxide semiconductor fine particles by ultraviolet irradiation.

  Next, metal oxide semiconductor fine particles and metal alkoxide are kneaded together with a solvent to prepare a paste-like coating liquid.

Next, the coating liquid is deposited on a conductive substrate provided with a conductive layer or the like by a coating method or the like, and then the solvent is evaporated. At this time, the metal alkoxide reacts with moisture in the air, and a metal oxide is generated by hydrolysis of the metal alkoxide, as shown by the following reaction formula. The reaction formula shows an example in which the metal alkoxide is a titanium alkoxide, in which OR represents an alkoxy group.
Ti (OR) ₄ + 4H ₂ O → Ti (OH) ₄ + 4ROH
Ti (OH) ₄ → TiO ₂ + 2H ₂ O

  The generated metal oxide is amorphous and adheres to the surface of the metal oxide semiconductor fine particles, and serves to bond between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the conductive substrate. As a result, a metal oxide semiconductor porous layer is formed on the conductive substrate. When the metal oxide semiconductor fine particles are titanium oxide fine particles, the photoelectric conversion efficiency of the dye-sensitized solar cell is increased when the newly generated metal oxide is also titanium oxide. However, it is also possible to deposit oxides of different metal elements such as zirconium and niobium.

  Next, this metal oxide semiconductor porous layer is irradiated with ultraviolet rays in an oxygen atmosphere to generate ozone, and the remaining organic matter is oxidized and removed. Furthermore, it is preferable to heat-process after this at 80-200 degreeC. These post-treatments improve the photoelectric conversion efficiency of the dye-sensitized solar cell. Thereafter, the photosensitizing dye is adsorbed on the metal oxide semiconductor porous layer.

  The reason why the photoelectric conversion efficiency of the dye-sensitized solar cell is improved by the pre-treatment of the metal oxide semiconductor fine particles and the post-treatment of the metal oxide semiconductor porous layer is that the removal of moisture and organic substances causes the metal oxide semiconductor porous It is mentioned that the amount of the photosensitizing dye adsorbed on the quality layer increases. In addition, since the organic substance in the metal oxide semiconductor porous layer acts as an electron recombination center, the removal of the organic substance has the effect of suppressing the electron recombination, increasing the electron lifetime, and improving the quantum efficiency. Explained.

  According to the manufacturing method disclosed in Patent Document 1, a semiconductor electrode layer composed of a metal oxide semiconductor porous layer can be produced by low-temperature firing. As a result, energy consumption in the manufacturing process can be suppressed, and a material having low heat resistance such as a lightweight, inexpensive, and flexible plastic film can be used as the substrate, which is preferable.

  However, according to the manufacturing method shown in Patent Document 1, there is a trade-off relationship in relation to the mixing ratio between the metal oxide semiconductor fine particles and the metal alkoxide. That is, when the amount of the metal alkoxide is too small compared to the amount of the metal oxide semiconductor fine particles, the metal oxide generated by the decomposition of the metal alkoxide is insufficient, and between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the conductive material. Adhesion with the conductive substrate becomes insufficient, and the mechanical strength of the metal oxide semiconductor porous layer is insufficient, or the metal oxide semiconductor porous layer is easily peeled off from the conductive substrate. On the other hand, if the amount of the metal alkoxide is too large compared to the amount of the metal oxide semiconductor fine particles, the surface of the metal oxide semiconductor fine particles may be thickly covered with an amorphous metal oxide layer, or the actual surface area of the metal oxide semiconductor fine particles Or the performance as an electrode is reduced. Therefore, if importance is attached to the performance as an electrode, the hardness of the metal oxide semiconductor porous layer may be insufficient, or the adhesion to the conductive substrate may be insufficient.

Therefore, the applicant has recently
A metal oxide semiconductor fine particle, a first compound that generates a first oxide when hydrolyzed, and is harder to hydrolyze than the first compound and is harder than the first oxide when hydrolyzed A step of preparing a coating liquid in which a second compound that produces an oxide of 2 is dispersed or dissolved in an organic solvent;
Applying a layer of the coating liquid to a support;
An evaporation step of evaporating the organic solvent from the coating liquid layer;
After the evaporation step, the temperature is increased, and a baking step for heat treatment is included.
The first oxide layer is mainly bonded directly to the metal oxide semiconductor fine particles and the support;
The second oxide layer is bound to the metal oxide semiconductor fine particles and the support mainly through the first oxide layer;
A metal oxide semiconductor in which the metal oxide semiconductor fine particles and the metal oxide semiconductor fine particles and the support are bound by the first oxide layer and the second oxide layer. A first manufacturing method of a semiconductor electrode layer for producing a porous layer was invented and a patent application was filed (Japanese Patent Application No. 2009-298384).

  Further, the applicant of the present invention provides a first fine particle having an average primary particle size of 100 nm or less and a second fine particle having an average primary particle size of more than 100 nm and 10000 nm or less as the metal oxide semiconductor fine particles. And inventing a second method for producing a semiconductor electrode layer, wherein the metal oxide semiconductor porous layer is produced using metal oxide semiconductor fine particles containing at least two kinds of fine particles. An application was filed (Japanese Patent Application No. 2010-26483).

  In the first method for producing a semiconductor electrode layer, volume contraction occurs due to a dehydration condensation reaction that generates a first oxide and a second oxide in the evaporation step and / or the firing step, and the metal oxide semiconductor porous layer Cracks may occur. This crack does not have a great adverse effect on the hardness of the metal oxide semiconductor porous layer and the adhesion to the support. However, when cracks occur, the formation of necking between the metal oxide semiconductor fine particles is insufficient, the conductivity between the metal oxide semiconductor fine particles decreases, and the dye using the metal oxide semiconductor fine particle layer The photoelectric conversion performance of the sensitized solar cell is lowered. In the second manufacturing method of the semiconductor electrode layer, this inconvenience is solved. However, considering practical application, further improvement in the photoelectric conversion performance of the dye-sensitized solar cell is desired.

  The present invention has been made in view of such a situation, and the object thereof can be produced by low-temperature firing, and achieves both performance as an electrode, hardness, and adhesion to a support. A semiconductor electrode layer comprising a metal oxide semiconductor porous layer, a method for producing the same, and a semiconductor electrode layer capable of obtaining higher photoelectric conversion performance when a dye-sensitized solar cell is configured An object of the present invention is to provide an electrochemical device useful as a dye-sensitized solar cell.

That is, the present invention
Metal oxide semiconductor fine particles disposed on a support;
A first oxide layer made of titanium oxide TiO ₂ and bound directly to the metal oxide semiconductor fine particles and the support;
Niobium Nb that is contained in the first oxide layer or that forms a second oxide layer that binds to the metal oxide semiconductor fine particles and the support mainly through the first oxide layer. V) an oxide or hydroxide, or at least one of phosphoric acid or phosphate covering at least part of the surface of the first oxide layer, the first oxide layer, or the The first oxide layer and the second oxide layer relate to a semiconductor electrode layer formed by binding between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support. is there.

Also,
at least,
Metal oxide semiconductor fine particles,
A first compound that yields titanium oxide TiO ₂ upon hydrolysis;
Niobium (V) compound, phosphoric acid or niobium (V) compound that is less likely to hydrolyze than the first compound, or is easily hydrolyzed to the same extent, and generates niobium Nb (V) oxide or hydroxide upon hydrolysis. A step of preparing a coating liquid in which a second compound that is one of phosphate esters is dispersed or dissolved in an organic solvent;
Applying a layer of the coating liquid to a support;
An evaporation step of evaporating the organic solvent from the coating liquid layer;
After the evaporation step, the temperature is increased, and a baking step for heat treatment is included.
The first oxide layer made of titanium oxide is mainly directly bonded to the metal oxide semiconductor particles and the support;
The niobium Nb (V) oxide or hydroxide contains at least one of the niobium Nb (V) oxide or hydroxide, and the phosphoric acid or phosphate ester, and the niobium Nb (V) oxide or hydroxide contains the first oxide layer. Or the second oxide layer bound to the metal oxide semiconductor fine particles and the support mainly through the first oxide layer. The phosphoric acid or phosphorous The acid ester covers at least part of the surface of the first oxide layer,
The first oxide layer or the first oxide layer and the second oxide layer bind the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support. The present invention relates to a method for producing a semiconductor electrode layer for producing a porous metal oxide semiconductor layer.

  The present invention also relates to an electrochemical device having at least the semiconductor electrode layer of the present invention, a counter electrode, and an electrolyte layer sandwiched therebetween.

  According to the method for producing a semiconductor electrode layer of the present invention, at least the metal oxide semiconductor fine particles, the first compound that generates titanium oxide when hydrolyzed, and the hydrolyzate is less difficult or comparable to the first compound. A niobium (V) compound that is easily hydrolyzed and generates a niobium Nb (V) oxide or hydroxide upon hydrolysis, or a second compound that is either phosphoric acid or a phosphate ester, and an organic solvent A coating solution dispersed or dissolved in is prepared. The unpurified metal oxide semiconductor fine particles and the organic solvent usually contain more or less adsorbed or occluded moisture. As a result, the hydrolysis of the first compound proceeds in the coating liquid, the generated titanium oxide is bonded to the surface of the metal oxide semiconductor fine particles, the metal oxide semiconductor fine particles are connected, A network between the metal oxide semiconductor fine particles may be formed in the coating liquid. Next, when the layer of the coating liquid is deposited on a support and the organic solvent is evaporated from the layer of the coating liquid, the titanium oxide contained in the coating liquid is converted into the metal oxide semiconductor fine particles or Bonded to the support. In addition, hydrolysis of the first compound further proceeds by reaction with moisture in the air. As a result, the first compound largely changes to the titanium oxide before entering the next baking step. Then, a metal oxide semiconductor porous layer is formed in which the metal oxide semiconductor fine particles are bound to each other and between the metal oxide semiconductor fine particles and the support by the first oxide layer. Thereafter, the firing step is performed.

  When the second compound is the niobium (V) compound, it can be roughly divided into two cases. When the niobium (V) compound is easily hydrolyzed to the same extent as the first compound, the niobium (V) compound is hydrolyzed in the same manner as the first compound, and the resulting niobium (V) V) Oxide or hydroxide is contained in the first oxide layer, and reinforces the binding between the metal oxide semiconductor particles and between the metal oxide semiconductor particles and the support. When the niobium (V) compound is more difficult to hydrolyze than the first compound, the amount of the niobium (V) compound to be hydrolyzed before the firing step is small, and most of the niobium (V) compound is In the firing step, hydrolysis is performed by moisture supplied from the air. In this case, the niobium (V) oxide or hydroxide produced by hydrolysis of the niobium (V) compound is mainly bound on the first oxide layer to form the second oxide layer. To do. The second oxide layer reinforces the first oxide layer and strengthens the binding between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support.

  In addition, as shown in the examples described later, the semiconductor electrode layer (metal oxide semiconductor porous layer) having the above specific structure adsorbs the photosensitizing dye, and the semiconductor electrode layer of the dye-sensitized solar cell. When used as a metal oxide semiconductor porous layer in which the first oxide layer and the second oxide layer do not contain the niobium (V) oxide or hydroxide, the photoelectric conversion performance is large. It was found that can be achieved. Further, when the second compound is the phosphoric acid or the phosphoric acid ester, as shown in the examples described later, the photosensitizing dye is adsorbed and used as a semiconductor electrode layer of the dye-sensitized solar cell. It was found that large photoelectric conversion performance could be achieved.

  According to the production method of the present invention, a semiconductor electrode layer composed of a metal oxide semiconductor porous layer can be produced by low-temperature firing. As a result, energy consumption in the manufacturing process can be suppressed, and a material having low heat resistance such as a lightweight, inexpensive and flexible plastic film can be used as the support. In addition, the roll-to-roll process can be manufactured at a lower cost with higher productivity.

  Since the electrochemical device of the present invention has the semiconductor electrode layer of the present invention as an electrode, it can be manufactured using a flexible plastic film or the like as the support, which is lightweight, inexpensive, and can be manufactured with high productivity. It is a chemical device.

It is sectional drawing which shows the structure of the metal oxide semiconductor porous layer based on Embodiment 1 of this invention. It is a flowchart which shows the preparation processes of a metal oxide semiconductor porous layer equally. It is sectional drawing which shows the structure of the metal oxide semiconductor porous layer based on Embodiment 2 of this invention. It is sectional drawing which shows the structure of the dye-sensitized solar cell based on Embodiment 3 of this invention. It is principal part sectional drawing which shows the structure of a general dye-sensitized solar cell. It is a flowchart which shows the general manufacturing process of the conventional semiconductor electrode layer which consists of a metal oxide semiconductor porous layer. It is a flowchart which shows the preparation process of the semiconductor electrode layer which is shown by patent document 1 and consists of a metal oxide semiconductor porous layer.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these examples.

  In the semiconductor electrode layer according to the present invention, the metal oxide semiconductor fine particles include a first fine particle having an average primary particle size of 100 nm or less, and a second primary particle having an average primary particle size of greater than 100 nm and 10,000 nm or less. It is preferable to contain at least two kinds of fine particles together with the fine particles.

The metal oxide semiconductor fine particles are at least selected from the group consisting of titanium oxide TiO ₂ , zinc oxide ZnO, tungsten oxide WO ₃ , niobium oxide Nb ₂ O ₅ , strontium titanate SrTiO ₃ , and tin oxide SnO _2. It is good to consist of one kind of oxide.

The second oxide layer preferably contains a high-hardness oxide having a hardness higher than that of the titanium oxide forming the first oxide layer. At this time, the high-hardness oxide is at least one oxide selected from the group consisting of silicon oxide SiO ₂ , boron oxide B ₂ O ₃ , aluminum oxide Al ₂ O ₃ , and zirconium oxide ZrO ₂ . Is good.

  The material of the support is preferably a plastic material.

  Moreover, it is good to hold | maintain a photosensitizing dye on the surface and to comprise as a semiconductor electrode layer of a dye-sensitized solar cell. In this case, the support is a light-transmitting support having a light-transmitting conductive layer on one surface, and is preferably provided in contact with the light-transmitting conductive layer. Alternatively, the support is a light-transmitting support in which a light-transmitting conductive layer and a close-contact auxiliary layer are laminated on one surface, and the support is provided in contact with the close-contact support layer. Good. Alternatively, the support is an insulating light-transmitting support, and a porous conductive layer is provided on the surface of the semiconductor electrode layer opposite to the surface in contact with the support. Good.

  In the method for producing a semiconductor electrode layer of the present invention, a salt or alkoxide of titanium Ti (IV) is preferably used as the first compound. As the titanium salt or alkoxide, a compound that reacts with a small amount of water usually contained in the metal oxide semiconductor fine particles and / or the organic solvent at room temperature and is partially or fully hydrolyzed in the coating solution is used. It is good.

  In addition, a niobium (V) salt or alkoxide may be used as the second compound.

  Moreover, it is good to add to the said coating liquid the 3rd compound which produces a high-hardness oxide which is harder to hydrolyze than the said 1st compound and is harder than titanium oxide when hydrolyzed. At this time, as the third compound, an alkoxide of at least one element selected from the group consisting of silicon Si, boron B, aluminum Al, and zirconium Zr is preferably used.

  Moreover, it is good to keep the temperature in the said baking process at 40-200 degreeC.

  In the electrochemical device of the present invention, the semiconductor electrode layer holds a photosensitizing dye, and when light is incident, the electrons of the photosensitizing dye excited by absorbing the light enter the semiconductor electrode layer. The photosensitizing dye that has been removed and has lost the electrons is reduced by the reducing agent in the electrolyte layer. As a result, the oxidizing agent generated in the electrolyte layer is reduced by receiving electrons from the counter electrode. It is preferable to be configured as a dye-sensitized solar cell.

  In the dye-sensitized solar cell, the support is a light-transmitting support having a light-transmitting conductive layer provided on one surface, and the semiconductor electrode layer is in contact with the light-transmitting conductive layer. It is good to be provided. Alternatively, the support is a light-transmitting support in which a light-transmitting conductive layer and a close-contact auxiliary layer are laminated on one surface, and the support is provided in contact with the close-contact support layer. Good. Alternatively, the support is an insulating light-transmitting support, and a porous conductive layer is provided on the surface of the semiconductor electrode layer opposite to the surface in contact with the support. Good.

  Hereinafter, based on the embodiment of the present invention, details will be specifically described with reference to the drawings.

[Embodiment 1]
In the first embodiment, examples of the semiconductor electrode layer described in claims 1 and 3 to 6 and the manufacturing method thereof described in claims 11 to 17 will be described.

  FIG. 1A is a cross-sectional view of the semiconductor electrode layer 1 formed on the support 5. As will be described later, such a structure is formed when the semiconductor electrode layer 1 is formed using a niobium (V) compound that is more difficult to hydrolyze than the first compound as the second compound. The semiconductor electrode layer 1 includes a first oxide layer 3 and a second oxide between the metal oxide semiconductor fine particles 2 disposed on the support 5 and between the metal oxide semiconductor fine particles 2 and the support 5. It is a metal oxide semiconductor porous layer bound by the layer 4.

The metal oxide semiconductor fine particles 2 are composed of titanium oxide TiO ₂ , zinc oxide ZnO, tungsten oxide WO ₃ , niobium oxide Nb ₂ O ₅ , strontium titanate SrTiO ₃ , and tin oxide SnO ₂ according to the characteristics of the semiconductor electrode layer. It is preferable to consist of at least one oxide selected from the group consisting of:

  The first oxide layer 3 is made of titanium oxide, and is mainly bound directly to the metal oxide semiconductor fine particles 2 and the support 5. The second oxide layer 4 contains at least niobium (V) oxide or hydroxide, and is mainly bound to the metal oxide semiconductor fine particles 1 and the support 5 via the first oxide layer 3. .

The second oxide layer 4 preferably contains a high-hardness oxide having a hardness higher than that of titanium oxide forming the first oxide layer 3. This high-hardness oxide may be at least one oxide selected from the group consisting of silicon oxide SiO ₂ , boron oxide B ₂ O ₃ , aluminum oxide Al ₂ O ₃ , and zirconium oxide ZrO ₂ .

  In the semiconductor electrode layer 1 having this unique structure, the second oxide layer 4 reinforces the first oxide layer 3, and between the metal oxide semiconductor fine particles 1 and between the metal oxide semiconductor fine particles 1 and the support 5. It works to strengthen the bond between the two.

  When the semiconductor electrode layer 1 is formed using a niobium (V) compound that is easily hydrolyzed to the same extent as the first compound as the second compound, the niobium (V) compound is the same as the first compound. The niobium (V) oxide or hydroxide produced as a result of hydrolysis is contained in the first oxide layer 3 and is between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support. Reinforce the binding.

  As will be described later in the Examples, the semiconductor electrode layer (metal oxide semiconductor porous layer) 1 having such a unique structure adsorbs a photosensitizing dye and serves as a semiconductor electrode layer of a dye-sensitized solar cell. When used, the first oxide layer 3 and the second oxide layer 4 achieve greater photoelectric conversion performance than a metal oxide semiconductor porous layer that does not contain niobium (V) oxide or hydroxide. It turns out that you can.

  At present, the reason why the photoelectric conversion performance is improved is unknown. In the literature (Adv. Funct. Mater., (2010), 20, 509), there is an example in which niobium (V) is doped into titanium oxide fine particles by hydrothermal synthesis in a dye-sensitized solar cell to increase conductivity. It has been reported. If the action of niobium (V) in the present invention is the same as in this example, it is considered that niobium (V) acts as a dopant for supplying electron carriers to the first oxide layer 3 made of amorphous titanium oxide. It is done. In general, when the number of carriers in a semiconductor increases, the conductivity is improved and current flows easily. Therefore, when the semiconductor electrode layer having the first oxide layer 3 and the second oxide layer 4 into which niobium (V) is introduced is used as the semiconductor electrode layer of the dye-sensitized solar cell, niobium (V) Compared to the case of using a metal oxide semiconductor porous layer into which no oxygen is introduced, it is considered that more electrons transferred from the excited photosensitizing dye to titanium oxide can reach the negative electrode current collector. As a result, it is considered that the photoelectric conversion efficiency is improved.

On the other hand, in another document (Coord. Chem. Rev., (2004), 248, 1271), in a dye-sensitized solar cell, a niobium (V) Nb ₂ O ₅ layer is formed on the surface with a core-shell structure. An example in which a semiconductor electrode layer is produced using the formed titanium oxide fine particles has been reported. If the action of niobium (V) in the present invention is the same as in this example, the niobium (V) oxide layer covers the titanium oxide layer and allows the transfer of electrons from the dye to the titanium oxide. It is considered that the barrier due to the band structure (V) functions as a barrier that suppresses the movement of electrons from the titanium oxide to the electrolyte layer.

  When the semiconductor electrode layer 1 is produced using phosphoric acid or phosphoric acid ester as the second compound, phosphoric acid or phosphoric acid ester covers at least a part of the surface of the first oxide layer 3. It is thought that there is. Also in this case, as shown in Examples described later, it was found that a large photoelectric conversion performance can be achieved when a photosensitizing dye is adsorbed and used as a semiconductor electrode layer of a dye-sensitized solar cell. The reason is unknown, but phosphoric acid or phosphate ester allows the transfer of electrons from the dye to the titanium oxide by coating the titanium oxide layer, but suppresses the transfer of electrons from the titanium oxide to the electrolyte layer. The possibility of functioning as a barrier is considered.

  FIG. 1B is a cross-sectional view showing an example in which the adhesion auxiliary layer 6 is provided on the support 5 and the semiconductor electrode layer 1 is formed thereon. The adhesion auxiliary layer 6 is a layer provided to improve adhesion when the adhesion between the semiconductor electrode layer 1 and the support 5 is not sufficient. As an example in which the adhesiveness tends to be insufficient, an example in which the support 5 is a base material on which an ITO layer is provided can be given. Examples of the material of the adhesion auxiliary layer 6 include polyacrylic resins, polyamide resins, polyamideimide resins, polyester resins, metal element chlorides (such as titanium tetrachloride), peroxides (such as titanium peroxide), Hydrolysis / dehydration condensation products such as alkoxides can be used. When the semiconductor electrode layer 1 is used as a semiconductor layer of a dye-sensitized solar cell, it is desirable that the adhesion auxiliary layer 6 has a thickness that does not significantly reduce the photoelectric conversion efficiency of the solar cell.

  FIG. 2 is a flow diagram showing a process for producing the semiconductor electrode layer (metal oxide semiconductor porous layer) 1. FIG. 2 mainly corresponds to the case where the semiconductor electrode layer 1 is manufactured using a niobium (V) compound that is less hydrolyzed than the first compound as the second compound. Hereinafter, an explanation will be given with an emphasis on how the semiconductor electrode layer 1 having the unique structure shown in FIG. 1A is formed.

  In order to produce the semiconductor electrode layer 1, first, the metal oxide semiconductor fine particles 2 are dispersed in an appropriate organic solvent to prepare a paste-like dispersion. As the dispersion method, known methods such as stirring treatment, ultrasonic dispersion treatment, bead dispersion treatment, kneading treatment, and homogenizer treatment can be preferably used. The compounding amount of the metal oxide semiconductor fine particles 2 is 1 to 50% by mass, for example, about 20% by mass, based on the mass of the coating liquid formed by adding first to third compounds described later. When the amount is less than 1% by mass, there is a disadvantage that a metal oxide semiconductor fine particle layer having a sufficient thickness cannot be formed by a coating method. On the other hand, when it is larger than 50% by mass, the viscosity of the coating liquid becomes too high, which makes it difficult to handle the metal oxide semiconductor fine particle layer by a coating method or the like.

  As the solvent, a solvent that can disperse the metal oxide semiconductor fine particles 2 and can dissolve the first compound and the second compound is appropriately selected and used. Specifically, for example, it is selected from alcohols, ketones, hydrocarbons, amides, sulfides and the like.

  Next, a 1st compound and a 2nd compound are added to the said dispersion liquid, are stirred and dissolved, and it is set as a uniform coating liquid. Further, a third compound may be added. Any order of adding the first compound to the third compound may be first.

  A 1st compound is a compound which hydrolyzes and produces a titanium oxide. Specifically, a salt or alkoxide of titanium Ti (IV) (hereinafter abbreviated as titanium compound) may be used as the first compound. Unpurified metal oxide semiconductor fine particles and organic solvents usually contain more or less adsorbed or occluded water, but as titanium compounds react with these water at room temperature, and part or all of them are coated. It is preferable to use a compound that is hydrolyzed in the liquid. In this case, it is observed that the viscosity increases during the preparation of the coating liquid. This is because, as the mixing of the titanium compound with the metal oxide semiconductor fine particles and the organic solvent proceeds, the titanium compound reacts with moisture, and the titanium oxide produced by hydrolysis of the titanium compound binds to the surface of the metal oxide semiconductor fine particles 2. This is considered to be because the metal oxide semiconductor fine particles 2 are connected.

  The second compound is a compound that is more difficult to hydrolyze than the first compound, and generates niobium Nb (V) oxide or hydroxide upon hydrolysis. Specifically, a niobium (V) salt or alkoxide may be used as the second compound.

  The third compound is a compound that is harder to hydrolyze than the first compound and that produces a high-hardness oxide having a higher hardness than titanium oxide when hydrolyzed. As the third compound, an alkoxide of at least one element selected from the group consisting of silicon Si, boron B, aluminum Al, and zirconium Zr is preferably used.

  The compounding amounts of the first compound and the third compound are 0.01 to 20% by mass of the mass of the coating liquid, respectively. In order to obtain the desired hardness and adhesion to the support of the semiconductor electrode layer 1, the compounding amounts of the first compound and the third compound are the materials and dispersibility of the metal oxide semiconductor fine particles 2, and the first compound. According to the material type of the compound and the third compound, it is appropriately selected within the above range. When the blending amounts of the first compound and the third compound are out of the above ranges, it tends to be difficult to achieve both the hardness of the semiconductor electrode layer 1 and the adhesion to the support 5. In addition, when the semiconductor electrode layer 1 is used as a semiconductor electrode layer of a dye-sensitized solar cell, the photoelectric conversion efficiency may be lowered depending on the material type of the first compound and the third compound.

  The compounding amount of the second compound is 0.01 to 20% by mass of the mass of the coating liquid. In order to obtain the desired hardness and adhesion to the support of the semiconductor electrode layer 1, the compounding amount of the second compound is such that the material and dispersibility of the metal oxide semiconductor fine particles 2, the first compound and the third compound Depending on the material type of the compound, it is appropriately selected within the above range. When the amount of the second compound is out of the above range, it tends to be difficult to achieve both the hardness of the semiconductor electrode layer 1 and the adhesion to the support 5.

  Next, the layer of the coating liquid is deposited on the support 5 by a known method such as a coating method or a printing method. Examples of the coating method include a micro gravure coating method, a wire bar coating method, a direct gravure coating method, a die coating method, a dip method, a spray coating method, a reverse roll coating method, a curtain coating method, a comma coating method, a knife coating method, and a spin coating method. A coating method or the like can be used. In addition, as a printing method, for example, a relief printing method, an offset printing method, a gravure printing method, an intaglio printing method, a rubber plate printing method, a screen printing method, and the like can be used.

  Next, the solvent is removed by evaporation from the coating liquid layer to form a metal oxide semiconductor fine particle layer containing the first compound to the third compound and titanium oxide. As a method for evaporating the solvent, the solvent may be evaporated at room temperature or may be evaporated by heating. However, in order to suppress uneven evaporation, it is preferable to adjust the evaporation rate of the solvent. Specifically, it is preferable to evaporate in a temperature range of 20 ° C. to 100 ° C. and a time range of 30 seconds to 20 minutes. When the solvent is removed by evaporation, the titanium oxide contained in the coating liquid binds to the metal oxide semiconductor fine particles 2. The titanium compound is hydrolyzed by reacting with moisture in the air. As a result, most of the titanium compound is converted to titanium oxide before entering the next firing step. A metal oxide semiconductor porous layer is formed in which the metal oxide semiconductor fine particles 2 and the metal oxide semiconductor fine particles 2 and the support 5 are bound by the first oxide layer 3 made of titanium oxide. Is done. At this time, in order to promote the hydrolysis of the titanium compound, the temperature during and / or after the evaporation step may be maintained at 25 to 200 ° C., for example, about 80 ° C. Moreover, it is also possible to perform an evaporation process and the following baking process simultaneously.

  Next, the metal oxide semiconductor porous layer is baked to improve electronic connection between the metal oxide semiconductor fine particles 2, and the mechanical strength of the metal oxide semiconductor porous layer and the support 5 To improve the adhesion. Although there is no restriction | limiting in particular in a calcination temperature, since the support body 5 may deteriorate with a heat | fever when temperature is too high, a calcination temperature is 40-1000 degreeC, and it is preferable that it is about 300-600 degreeC normally. When a plastic material is used as the material of the support 5, it is preferably below the glass transition point, usually 40 to 200 ° C. Moreover, although there is no restriction | limiting in particular in baking time, Usually, it is about 30 seconds-about 10 hours.

  At this time, the ratio of the second compound and the third compound that are hydrolyzed until the firing step is small, and most of the second compound and the third compound are caused by moisture supplied from the air in the firing step. It is preferably hydrolyzed. In this case, the niobium (V) oxide or hydroxide and the high-hardness oxide generated by hydrolysis of the second compound and the third compound are mainly bound on the first oxide layer 3. Then, the second oxide layer 4 is formed.

  As described above, when the first oxide layer 3 and the second oxide layer 4 containing niobium (V) oxide or hydroxide are formed, the semiconductor electrode layer (metal oxide layer) having this unique structure is formed. The porous semiconductor layer) adsorbs a photosensitizing dye, and when used as a semiconductor electrode layer of a dye-sensitized solar cell, the first oxide layer 3 and the second oxide layer 4 have niobium (V ) Greater photoelectric conversion performance can be achieved as compared with a metal oxide semiconductor porous layer containing no oxide or hydroxide. On the other hand, the high-hardness oxide strongly reinforces the first oxide layer 3 bonded between the metal oxide semiconductor particles 2 and between the metal oxide semiconductor particles 2 and the support 5. As a result, a semiconductor electrode layer (metal oxide semiconductor porous layer) 1 having excellent mechanical strength and high adhesion to the support 5 is obtained. As shown in the examples described later, it is considered that niobium (V) oxide also functions as a high-hardness oxide.

  Note that the adhesion between the semiconductor electrode layer (metal oxide semiconductor porous layer) 1 and the support 5 may be insufficient only with the first compound. This is because a considerable portion of the first compound that is prone to hydrolysis is hydrolyzed before the coating liquid is applied to the support 5. The titanium oxide generated before the coating liquid is applied to the support 5 connects the metal oxide semiconductor fine particles 2 and contributes to increase the mechanical strength of the metal oxide semiconductor porous layer 1. This is because it does not contribute to improving the adhesion to the support 5. On the other hand, most of the hydrolysis of the second compound or the third compound occurs after the coating liquid is applied to the support 5, so that niobium (V) oxide or hydroxide, or high-hardness oxidation. The thing contributes to the improvement of the mechanical strength of the metal oxide semiconductor porous layer 1 and the improvement of the adhesion to the support 5 as well. However, only the second compound or the third compound tends to cause surface layer peeling or damage. This is because the second compound or the third compound has a lower reactivity with the surface of the metal oxide semiconductor fine particle 2 than the first compound, so that the fine particle 2 can be obtained only with the second compound or the third compound. This is because the number of neckings in between decreases and the strength tends to be insufficient. That is, in order to achieve both the mechanical strength of the semiconductor electrode layer 1 and the adhesion to the support 5, both the first compound and the second compound or the third compound are required.

  When the semiconductor electrode layer 1 is formed using a niobium (V) compound that is easily hydrolyzed to the same extent as the first compound as the second compound, the niobium (V) compound is the same as the first compound. The niobium (V) oxide or hydroxide produced as a result of hydrolysis is contained in the first oxide layer 3 and is between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support. Reinforce the binding.

  When the semiconductor electrode layer 1 is produced using phosphoric acid or phosphoric acid ester as the second compound, phosphoric acid or phosphoric acid ester covers at least a part of the surface of the first oxide layer 3. It is thought that there is.

  After firing, for the purpose of increasing the actual surface area of the metal oxide semiconductor porous layer or increasing the necking between the metal oxide semiconductor fine particles 2, for example, a necking treatment using a titanium tetrachloride aqueous solution or titanium alkoxide is performed. Also good. Further, organic substances and unreacted substances remaining in the metal oxide semiconductor porous layer may be removed by washing with a solvent or the like.

  When a plastic material is used as the material of the support 5, it is possible to perform a process of pressure-bonding the semiconductor electrode layer (metal oxide semiconductor porous layer) 1 to the support 5 by a heat and pressure process, for example, a calendar process.

  Hereinafter, the semiconductor electrode layer (metal oxide semiconductor porous layer) 1 and the manufacturing method thereof will be described in more detail.

  When the semiconductor electrode layer 1 is used as a semiconductor electrode layer of a dye-sensitized solar cell, it is as follows.

As the material of the metal oxide semiconductor fine particles 2, various metal oxide semiconductors, compounds having a perovskite structure, and the like can be used. At this time, the material of the metal oxide semiconductor fine particles 2 is preferably an n-type semiconductor material in which conduction band electrons become carriers under photoexcitation to generate an anode current. Specific examples of such semiconductor materials include TiO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ , SrTiO ₃ , and SnO ₂ , and among these, TiO ₂ is particularly preferable. However, the material of the metal oxide semiconductor fine particles 2 is not limited to these. As the metal oxide semiconductor fine particles 2, commercially available products may be used, or those having a predetermined particle diameter may be obtained by hydrolyzing a chloride or an alkoxide by a known method such as a sol-gel method. It may be produced. Also, two or more of these materials can be mixed and used.

  The thickness of the metal oxide semiconductor porous layer 1 is preferably 1 to 30 μm. When the thickness is less than 1 μm, sufficient photoelectric conversion efficiency cannot be obtained. As the thickness is increased, the photoelectric conversion efficiency is improved. However, when the thickness exceeds 30 μm, the effect of improving the photoelectric conversion efficiency due to the increase in the film thickness becomes poor. Therefore, the thickness is preferably 30 μm or less. The shape of the metal oxide semiconductor fine particles 2 is not particularly limited, and may be a general shape.

  In order to transmit visible light and increase the specific surface area, the average particle diameter of the primary particles is preferably 1 to 100 nm (however, in this case, the metal oxide semiconductor fine particles 2 have a metal oxide). Cracks are generated in the semiconductor porous layer, the conductivity between the metal oxide semiconductor fine particles is lowered, and the photoelectric conversion performance of the dye-sensitized solar cell using the metal oxide semiconductor fine particle layer may be lowered. (For such a case, refer to Embodiment 2 described later.) As the metal oxide semiconductor fine particles 2 having an average primary particle diameter of 1 to 100 nm, the following commercially available products can be used.

  When titanium oxide is used as the material of the metal oxide semiconductor fine particles 2, the crystal form thereof may be one type selected from rutile type, anatase type, and brookite type, and may be a mixture of two or more types. P25 and P90 (trade name) manufactured by Ishihara Sangyo Co., Ltd., ST01 and ST21 (trade name) manufactured by Ishihara Sangyo Co., Ltd., Super Titania F-1 to F-6 (manufactured by Showa Denko KK) Name), SSP-25, SSP-20, SSP-M, and STR series (trade name) manufactured by Sakai Chemical Industry Co., Ltd., MT-150A, MT-500B, MT-600B manufactured by Teika Co., Ltd. , MT-700B, AMT-100, AMT-600, TKP-101, TKP-102 (above, trade name), NanoTek Powder series (trade name) manufactured by CI Kasei Co., Ltd., etc. Rukoto can.

  When zinc oxide is used as the material for the metal oxide semiconductor fine particles 2, for example, MZ-300 and MZ-500 (trade name) manufactured by Teika Co., Ltd., and FZO-50 (trade name) manufactured by Ishihara Sangyo Co., Ltd. ), NanoTek Powder series (trade name) manufactured by CI Kasei Co., Ltd., FINEX series (trade name) manufactured by Sakai Chemical Industry Co., Ltd., F-1, F-2, F-3 manufactured by Hakusui Tech Co., Ltd. Pazet CK and Pazet GK-40 (above, trade name) can be used.

  When tin oxide is used as the material of the metal oxide semiconductor fine particles 2, examples of the first fine particles 2A include those having an average particle diameter of 15 nm manufactured by Johnson Matthey, and NanoTek Powder series (manufactured by CI Kasei Co., Ltd.). Product name) can be used.

  As the first compound, a Ti (IV) salt or alkoxide (hereinafter abbreviated as a titanium compound) that can be dissolved in an organic solvent can be used. As the titanium compound, it is preferable to use a compound that is hydrolyzed at room temperature with moisture usually contained in the metal oxide semiconductor fine particles 2 and / or an organic solvent. In this case, as described above, hydrolysis of the titanium compound starts in the coating liquid, and the metal oxide semiconductor fine particles 2 are connected by the generated titanium oxide, so that a strong network between the fine particles 2 is easily formed. .

As the salt of Ti (IV), titanium tetrachloride TiCl ₄ , titania sulfate TiOSO ₄ , titanium oxalate Ti (C ₂ O ₄ ) _{2 and the} like can be used. Moreover, the alkoxide which can be used can be represented like the following general formula.
General formula of alkoxide:

  In the above general formula, the alkoxide may be any of a monomer (m = 0), an oligomer (m = 1 to 10), and a polymer (m> 10), and two or more kinds may be mixed and used. Examples of the alkoxy group include a methoxy group (n = 1), an ethoxy group (n = 2), an n-propoxy group, an i-propoxy group (n = 3), an n-butoxy group, an i-butoxy group, sec- A butoxy group, a tert-butoxy group (above, n = 4), a 2-ethylhexoxy group, and other alkoxy groups derived from lower and higher alcohols can be used. Moreover, the alkoxide may be modified with β-diketones such as acetylacetone. A part of the alkoxy group may be substituted with a hydroxy group.

Specifically, tetramethoxy titanium Ti (OCH ₃ ) ₄ , tetrapropoxy titanium Ti (OCH ₂ CH ₂ CH ₃ ) ₄ , tetrabutoxy titanium Ti (OCH ₂ CH ₂ CH ₂ CH ₃ ) ₄ , tetrapentoxy titanium Ti (OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ) ₄ , butoxy titanium dimer, butoxy titanium oligomer, butoxy titanium polymer, and the like can be used.

As the second compound, which is less easily hydrolyzed than the first compound or is easily hydrolyzed to the same extent and which generates niobium Nb (V) oxide or hydroxide upon hydrolysis, an inorganic salt, for example, chloride can be used as the niobium (V) NbCl _5, as alkoxide compounds, for example, pentamethoxy niobium Nb (OCH _{3) 5,} pentaethoxyniobium _{Nb (OCH 2 CH 3) 5} , penta-propoxy niobium Nb (OCH ₂ CH ₂ CH ₃ ) ₅ , pentabutoxy niobium Nb (OCH ₂ CH ₂ CH ₂ CH ₃ ) ₅ , and pentapentoxy niobium Nb (OCH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ) ₅ , and some or all of them Hydrolyzed ones can be used.

As the inorganic phosphoric acid compound, for example, phosphoric acid H ₃ PO ₄ and polyphosphoric acid (HPO ₃ ) _n can be used. Examples of phosphate esters include trimethyl phosphate PO (OCH ₃ ) ₃ , triethyl phosphate PO (OCH ₂ CH ₃ ) ₃ , tripropyl PO phosphate (OCH ₂ CH ₂ CH ₃ ) ₃ , and phosphoric acid Tributyl PO (OCH ₂ CH ₂ CH ₂ CH ₃ ) ₃ or the like can be preferably used.

As the third compound, an alkoxide such as Si, B, Al, and Zr is used. The oxide forming the second oxide layer 4 is SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , and ZrO _2. It is preferable that the oxide has high hardness.

For example, dimethyldimethoxysilane Si (CH ₃ ) ₂ (OCH ₃ ) ₂ , dimethyldiethoxysilane Si (CH ₃ ) ₂ (OCH ₂ CH ₃ ) ₂ , methyltrimethoxysilane Si (CH ₃ ) (OCH ₃ ) ₃ , Methyltriethoxysilane Si (CH ₃ ) (OCH ₂ CH ₃ ) ₃ , tetramethoxysilane Si (OCH ₃ ) ₄ , tetraethoxysilane Si (OCH ₂ CH ₃ ) ₄ , tetrapropoxysilane Si (OCH ₂ CH ₂ CH ₃ ) ₄ , tetrabutoxysilane Si (OCH ₂ CH ₂ CH ₂ CH ₃ ) ₄ , ethoxysilane dimer, ethoxysilane oligomer, ethoxysilane polymer, trimethoxyborane B (OCH ₃ ) ₃ , triethoxyborane B (OCH ₂ CH ₃ ) ₃ , triisopropoxyborane B (OCH (CH ₃ ) CH ₃ ) _{3 and the} like can be preferably used.

  As the solvent, a solvent capable of dissolving the first compound to the third compound and dispersing the metal oxide semiconductor fine particles 2 is used. For example, methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol (isobutyl alcohol), 3-methyl-2-propanol (sec-butyl alcohol), and 2-methyl-2 -Selected from alcohols such as propanol (tert-butyl alcohol), ketones such as cyclohexanone and cyclopentanone, hydrocarbon solvents such as hexane, amides such as dimethylformamide (DMF), sulfoxides such as dimethyl sulfoxide (DMSO), etc. At least one or more types can be used.

  In order to suppress drying unevenness on the surface of the coating liquid layer, a high boiling point solvent can be added to control the evaporation rate of the solvent. Examples of such high-boiling solvents include butyl cellosolve, diacetone alcohol, butyl triglycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol Monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol isopropyl ether, dipropylene glycol isopropyl ether Tripropylene glycol isopropyl ether, or the like can be used methyl glycol. Further, additives such as a surfactant, a viscosity modifier, and a dispersant can be added as necessary for the purpose of improving the coating property to the support and the pot life of the composition.

  The support 5 is not particularly limited as long as it is stable in the environment in which it is used. The material of the support 5 may be an inorganic material or an organic material. Further, the shape of the support 5 is not particularly limited, and is, for example, a film shape, a sheet shape, and a plate shape. However, when the material of the support 5 is a plastic material, it is particularly preferable because the feature of the present invention that the semiconductor electrode layer can be produced by low-temperature firing is best utilized. Moreover, it is preferable that the material of the support 5 is a material that has a high blocking performance to block moisture and gas from entering the electrochemical device from the outside and is excellent in solvent resistance and weather resistance. The thickness of the support 5 is not particularly limited, and can be selected as appropriate in consideration of light transmittance, blocking performance for blocking water vapor transmission, mechanical strength, and the like.

  When the semiconductor electrode layer 1 is used as a semiconductor electrode layer of a dye-sensitized solar cell, when the support 5 is required to be light transmissive, the support 5 is a material that easily transmits light. And shape. For example, transparent inorganic substrates such as quartz, sapphire, and glass, and triacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester (TPEE), polyimide (PI), polyamide (PA) , Aramid, polyethylene (PE), polyacrylate, polyethersulfone, polysulfone, polypropylene (PP), diacetylcellulose, polyvinyl chloride, acrylic resin (PMMA), polycarbonate (PC), epoxy resin, urea resin, urethane resin, melamine Examples thereof include a transparent plastic substrate made of a resin and a cycloolefin polymer resin (COP). Among these, it is preferable to use a substrate material having a particularly high visible light transmittance. The thickness of the plastic support is not particularly limited, but is preferably 38 to 350 μm from the viewpoint of productivity.

  Moreover, you may use the support body in which the transparent conductive layer is formed on the transparent base material. Known materials can be used for the transparent conductive layer. Specifically, ITO, FTO, antimony-doped tin oxide (ATO), tin oxide, zinc oxide, indium / zinc composite oxide (IZO) ) And the like, but is not limited thereto. The transparent conductive layer may be a single layer film or a laminated film of these materials, and two or more kinds of materials may be used in combination.

[Embodiment 2]
In the second embodiment, an example of the semiconductor electrode layer described in claim 2 will be described.

  FIG. 3 is a cross-sectional view and a partially enlarged view of the semiconductor electrode layer 21 formed on the support 5. The semiconductor electrode layer 21 includes a first oxide layer 3 and a second oxide between the metal oxide semiconductor fine particles 2 disposed on the support 5 and between the metal oxide semiconductor fine particles 2 and the support 5. It is a metal oxide semiconductor porous layer bound by the layer 4. The second embodiment is different from the first embodiment in that the metal oxide semiconductor fine particles 2 forming the semiconductor electrode layer 21 are different from the first fine particles 2A in which the average particle diameter of the primary particles is 100 nm or less, and the primary particles. That is, the second fine particles 2B having an average particle diameter of larger than 100 nm and 10000 nm or less are composed of two types of fine particles having different sizes. Other than this, the second embodiment is the same as the first embodiment, and therefore, description will be made with emphasis on the differences while avoiding duplication.

  Among the metal oxide semiconductor fine particles 2, the first fine particles 2 </ b> A have an average primary particle diameter of 1 to 100 nm, so that the visible light transmittance can be increased and the specific surface area can be increased. On the other hand, the primary particle average particle diameter of the second fine particles 2B is larger than 100 nm and not larger than 10,000 nm. As the average particle diameter of the second fine particles 2B is larger, the ratio of the blending mass of the second microparticles 2B to the blending mass of the first microparticles 2A (= (the blending mass of the second microparticles 2B) / (first As the blending mass of 1 fine particle 2A)) increases, the cracks generated in the metal oxide semiconductor porous layer 21 decrease as shown in Japanese Patent Application No. 2010-26483.

  Although the reason for this is not completely understood, the following can be considered. When the metal oxide semiconductor porous layer is formed only with the relatively small first particles 2A, the surface area of the first particles 2A is relatively small, and therefore the first oxide layer 3 is between the first particles 2A. And the second oxide layer 4 are difficult to reliably bond, and a connecting portion between fine particles having insufficient binding strength is likely to occur. Furthermore, in order to form a conductive path having a certain length, it is necessary to connect a relatively large number of first fine particles 2A. As a result, cracking is likely to occur in the metal oxide semiconductor porous layer, and the conductivity tends to be low. On the other hand, when the relatively large second fine particles 2B coexist, as shown in the enlarged view of FIG. 3, the surface area of the second fine particles 2B is relatively large. The connection with the surrounding first fine particles 2A is surely formed with sufficient binding strength on the surface of the fine particles 2B. In addition, since the number of particles that need to be connected to form a conductive path of the same length is relatively small, the number of connecting portions between the first fine particles 2A where the binding strength tends to be insufficient is significantly reduced. . As a result, in the metal oxide semiconductor porous layer in which the first fine particles 2A and the second fine particles 2B coexist, cracking hardly occurs and the conductivity is kept high. In addition, although the example which contains two types of microparticles | fine-particles from which the average particle diameter of a primary particle differs was shown in FIG. It is clear.

  Further, when the second fine particles 2B coexist, incident light is easily scattered, the internal HAZE of the metal oxide semiconductor porous layer 21 is increased, and the total light transmittance is decreased. As shown in Japanese Patent Application No. 2010-26483, in a dye-sensitized solar cell using the metal oxide semiconductor porous layer 21 as a semiconductor electrode, light utilization efficiency is increased by scattering of incident light, and photoelectric conversion performance is increased. Will improve.

  The primary particle average particle diameter of the second fine particles 2B is more preferably 200 nm to 5000 nm. When the average particle diameter of the primary particles is smaller than 200 nm, the effect of suppressing the occurrence of cracks in the metal oxide semiconductor porous layer 1 is insufficient, and the performance of scattering incident light tends to be insufficient. On the other hand, when the average particle diameter of the primary particles is larger than 5000 nm, the second fine particles 2B tend to precipitate in the coating liquid, and the pot life of the coating liquid tends to be reduced.

  As shown in Japanese Patent Application No. 2010-26483, the ratio of the blending mass of the second fine particles 2B to the blending mass of the first microparticles 2A is preferably 0.06 to 6. When it is less than 0.06, the effect of suppressing the occurrence of cracks in the metal oxide semiconductor porous layer 1 is insufficient, and the performance of scattering incident light tends to be insufficient. On the other hand, when larger than 6, the effect of suppressing the occurrence of cracks in the metal oxide semiconductor porous layer 1 is sufficient, and the performance of scattering incident light is sufficient, but the ratio of the metal oxide semiconductor porous layer 21 The surface area is reduced, and the performance of the dye-sensitized solar cell using the semiconductor electrode layer 1 is reduced.

  When a commercially available product is used as the metal oxide semiconductor fine particles 2A, a commercially available product having an average primary particle diameter of 1 to 100 nm shown in Embodiment 1 can be used. When a commercially available product is used as the metal oxide semiconductor fine particle 2B, if it is a titanium oxide fine particle, for example, PT-301, CR-EL, ET-500W, ET-600W, and ST-41 (manufactured by Ishihara Sangyo Co., Ltd.) As mentioned above, Showa Denko Co., Ltd. G-1, G-2, and F-10 (above, trade name), Teika Co., Ltd. JR (trade name), Fuji Titanium Industry Co., Ltd. TA-100, TA-200, TA-300, TA-500 (above, trade name) and the like can be used. Moreover, if it is a zinc oxide microparticles | fine-particles, Sakai Chemical Industry Co., Ltd. LPZINC-2 and LPZINC-5 (above, brand name) etc. can be used.

  In order to produce the semiconductor electrode layer 21, first, the first fine particles 2A and the second fine particles 2B constituting the metal oxide semiconductor fine particles 2 are respectively dispersed in an appropriate organic solvent, and a paste-like dispersion liquid is prepared. Prepare two. Next, the above-mentioned two dispersions are mixed at a predetermined ratio, and the first compound to the third compound are added to this, and stirred to dissolve to obtain a uniform coating solution. Others are the same as in the first embodiment.

[Embodiment 3]
In Embodiment 3, an electrochemical device configured as a dye-sensitized solar cell will be described as an example of the semiconductor electrode layer described in claims 7 to 10 and the electrochemical device described in claims 18 to 20. .

  FIG. 4A is a cross-sectional view showing the structure of the dye-sensitized solar cell 30 based on the third embodiment. The dye-sensitized solar cell 30 mainly includes a transparent substrate 31, a transparent conductive layer (negative electrode current collector) 32, a semiconductor electrode layer (negative electrode) 33 holding a photosensitizing dye, an electrolyte layer 34, and a counter electrode (positive electrode). 35, a counter substrate 36, a sealing material 37, and the like.

As a feature of the present embodiment, the semiconductor electrode layer 33 is the metal oxide semiconductor porous layer 1 or 21 such as titanium oxide TiO ₂ described in the first or second embodiment, and the metal oxide semiconductor fine particles 2 or the like. A photosensitizing dye is held on the surface of the film. Others are the same as the conventional dye-sensitized solar cell. That is, the transparent substrate 31 is made of a glass plate or a plastic film such as PEN or PET. The transparent conductive layer (negative electrode current collector) 32 is made of ITO, FTO, or the like, and is provided on the transparent substrate 31. The electrolyte layer 34 is disposed between the semiconductor electrode layer 33 and the counter electrode 35, and I ⁻ / I ₃ ⁻ (triiodide ion I ₃ ⁻ is present as ions by combining I ₂ with iodide ion I ^−. It is composed of an electrolytic solution containing a redox species (redox pair). The counter electrode 35 is made of a platinum layer, a carbon layer, or the like laminated on the base layer, and is provided on the counter substrate 36. The counter substrate 36 is made of a glass plate or a plastic film.

  When light is incident, the dye-sensitized solar cell 30 operates as a battery having the counter electrode 35 as a positive electrode and the semiconductor electrode layer 33 as a negative electrode.

  That is, when the photosensitizing dye absorbs photons transmitted through the transparent substrate 31 and the transparent conductive layer 32, electrons in the photosensitizing dye are excited from the ground state to the excited state. Excited electrons are extracted to the conduction band of the semiconductor electrode layer 33 through electrical coupling between the photosensitizing dye and the semiconductor electrode layer 33, and reach the transparent conductive layer 32 through the semiconductor electrode layer 33. To do.

On the other hand, the photosensitizing dye that has lost the electrons is converted from the reducing agent in the electrolyte layer 34, for example, I ⁻ to the following reaction 2I ⁻ → I ₂ + 2e ^{−.
_{I 2 + I - → I 3}} -
To receive electrons and produce an oxidant, for example I ₃ ⁻ , in the electrolyte layer 34. The generated oxidant reaches the counter electrode 35 by diffusion, and the reverse reaction of the above reaction I ₃ ⁻ → I ₂ + I ⁻
I ₂ + 2e ^- → 2I ^-
Thus, electrons are received from the counter electrode 35 and reduced to the original reducing agent.

  The electrons that have flowed from the transparent conductive layer 32 to the external circuit return to the counter electrode 35 after performing electrical work in the external circuit. In this way, light energy is converted into electrical energy without leaving any change in the photosensitizing dye or the electrolyte layer 34.

  In order to fabricate the dye-sensitized solar cell 30, the metal oxide semiconductor porous layer as the semiconductor electrode layer 33 is formed on the transparent conductive layer 32 provided on the transparent substrate 31 as described in the first embodiment. 1 or 21 is formed. Next, the photosensitizing dye is adsorbed on the metal oxide semiconductor porous layer 33. The method for adsorbing the dye is not particularly limited. For example, a solution in which a dye molecule is dissolved is prepared, and the transparent substrate 31 on which the metal oxide semiconductor porous layer 33 is formed is immersed in the dye solution, or After the dye solution is soaked into the metal oxide semiconductor porous layer 33 by applying, spraying, or dropping the dye solution onto the metal oxide semiconductor porous layer 33, the solvent is evaporated. Next, the transparent substrate 31 and the counter substrate 36 are disposed so that the semiconductor electrode layer 33 and the counter electrode 35 face each other, and are bonded together with a sealant 37. Finally, an electrolyte solution is injected to form the electrolyte layer 34.

  The metal oxide semiconductor porous layer 33 preferably has a large actual surface area including the surface of fine particles facing pores inside the porous layer so that a large amount of photosensitizing dye can be adsorbed. The actual surface area of the physical semiconductor porous layer 33 is preferably 10 times or more, more preferably 100 times or more the area (projected area) of the outer surface.

  Generally, as the thickness of the semiconductor electrode layer 33 increases and the number of metal oxide semiconductor fine particles 2 contained per unit projected area increases, the actual surface area increases and the amount of dye that can be held per unit projected area increases. Therefore, the light absorption rate with respect to incident light becomes high. On the other hand, when the thickness of the semiconductor electrode layer 33 increases, the distance that electrons transferred from the photosensitizing dye to the semiconductor electrode layer 33 diffuse until reaching the transparent conductive layer 32 increases. Electron loss due to charge recombination also increases. Accordingly, the semiconductor electrode layer 33 has a preferable thickness, but is generally 0.1 to 100 μm, and more preferably 1 to 30 μm.

  FIG. 4B is a cross-sectional view showing the structure of another dye-sensitized solar cell 40 based on the third embodiment. The dye-sensitized solar cell 40 is a back contact type cell and is an example of the dye-sensitized solar cell according to claim 20. In the dye-sensitized solar cell 40, in order from the light incident side, at least the transparent substrate 41, the semiconductor electrode layer (negative electrode) 43 holding the photosensitizing dye, the light-reflective porous conductive layer (negative electrode current collector). 42, an electrolyte layer 44, a counter electrode (positive electrode) 45, and a counter substrate 46 are disposed.

  The semiconductor electrode layer 43 is an insulating light-transmitting support (transparent substrate 41) according to claim 10, and has a porous conductive surface on the opposite side to the surface in contact with the support. It is an example of the semiconductor electrode layer provided with the layer. Similar to the dye-sensitized solar cell 30, the semiconductor electrode layer 43 is the metal oxide semiconductor porous layer 1 or 21 such as titanium oxide TiO 2 described in the first or second embodiment, and the metal oxide semiconductor fine particles 2 are used. A photosensitizing dye is held on the surface. The electrolyte layer 44 is disposed such that the electrolyte solution infiltrates into the semiconductor electrode layer 43 through a large number of through holes provided in the conductive layer 42.

  In the solar cell 40, since there is no transparent conductive layer 32 on the light incident side, the loss of light due to the transparent conductive layer 32 can be eliminated, and the high cost of the transparent conductive layer 32 is not used, so that the cost can be reduced. There are advantages. Further, since the porous conductive layer (negative electrode current collector) 42 is light-reflective, the light that has not been absorbed by the photosensitizing dye and has been transmitted through the semiconductor electrode layer 43 is reflected, and again the semiconductor electrode layer. 43. As a result, the light utilization rate is improved. Since others are the same as that of the dye-sensitized solar cell 30, the description is omitted to avoid duplication.

  In order to manufacture the dye-sensitized solar cell 40, a metal oxide semiconductor porous layer is formed on the transparent substrate 41 as the semiconductor electrode layer 43 as described in the first embodiment. Next, in the same manner as the dye-sensitized solar cell 30, the photosensitizing dye is held in the metal oxide semiconductor porous layer 43. Next, a porous conductive layer 42 is formed by forming a metal layer such as titanium on the metal oxide semiconductor porous layer 43 by sputtering or vapor deposition. Next, the transparent substrate 41 and the counter substrate 46 are arranged so that the semiconductor electrode layer 43 and the counter electrode 45 face each other, and are bonded together with a sealing material 47. Finally, an electrolyte solution is injected to form the electrolyte layer 44.

  The dye-sensitized solar cell 30 is the same as the conventional dye-sensitized solar cell with respect to members other than the semiconductor electrode layer 33. The dye-sensitized solar cell 40 is the same as the conventional dye-sensitized solar cell with respect to members other than the porous conductive layer 42 and the semiconductor electrode layer 43. The main points will be described below.

  The photosensitizing dye to be held in the semiconductor electrode layer is not particularly limited as long as it exhibits a sensitizing action. Cyanine dyes such as cyanine, basic dyes such as phenosafranine, fog blue, thiocin and methylene blue, other azo dyes, porphyrin compounds such as chlorophyll, zinc porphyrin and magnesium porphyrin, phthalocyanine compounds, coumarin compounds, ruthenium Ru And bipyridine complexes, terpyridine complexes, anthraquinone dyes, polycyclic quinone dyes, squarylium dyes, and the like. Among them, a ruthenium Ru bipyridine complex whose ligand has a pyridine ring has a high quantum yield and is preferable as a photosensitizing dye. However, the photosensitizing dye is not limited to this, and can be used alone or in combination of two or more.

As the electrolyte layer, an electrolytic solution or a gel or solid electrolyte can be used. Examples of the electrolyte include a solution containing a redox system (redox _couple ). Specifically, a combination of iodine I ₂ and a metal iodide salt or an organic iodide salt, bromine Br ₂ and a metal bromide salt or an organic salt. A combination with a bromide salt is used. The cations constituting the metal halide salt are lithium Li ⁺ , sodium Na ⁺ , potassium K ⁺ , cesium Cs ⁺ , magnesium Mg ²⁺ , calcium Ca ²⁺ , and the cation constituting the organic halide salt is Quaternary ammonium ions such as tetraalkylammonium ions, pyridinium ions, and imidazolium ions are suitable, but are not limited to these, and can be used alone or in admixture of two or more.

Among these, an electrolyte combining iodine I ₂ and a quaternary ammonium compound such as lithium iodide LiI, sodium iodide NaI, or imidazolium iodide is particularly preferable. The concentration of the electrolyte salt in the electrolytic solution is preferably 0.05M to 5M, more preferably 0.1M to 3M. The concentration of iodine I ₂ or bromine Br ₂ is preferably 0.0005M to 1M, and more preferably 0.005 to 0.5M. Various additives such as 4-tert-butylpyridine and carboxylic acid can be added for the purpose of improving the open circuit voltage and the short circuit current.

  Solvents that make up the electrolyte include water, alcohols, ethers, esters, carbonates, lactones, carboxylic esters, phosphate triesters, heterocyclic compounds, nitriles, ketones, amides , Nitromethane, halogenated hydrocarbons, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, and hydrocarbons, but are not limited thereto, It can be used alone or in admixture of two or more. Moreover, it is also possible to use a room temperature ionic liquid of a tetraalkyl, pyridinium, or imidazolium quaternary ammonium salt as a solvent.

  In order to reduce the leakage of the electrolyte from the dye-sensitized solar cell and the volatilization of the solvent constituting the electrolyte, a gelling agent, a polymer, a crosslinking monomer, or various shapes of metal oxide semiconductors are added to the electrolyte composition. Fine particles (fibers) or the like can be dissolved or dispersed and mixed to be used as a gel electrolyte. As for the ratio of the gel material and the electrolyte composition, the more the electrolyte composition, the higher the ionic conductivity, but the lower the mechanical strength. On the contrary, when there are too few electrolyte components, although mechanical strength is large, ionic conductivity falls.

  There is no particular limitation on the method of injecting the electrolytic solution, but a method of dropping several drops of the solution into the injection port and introducing it by capillary action is simple. Further, if necessary, the injection operation can be performed under reduced pressure or under heating. After the solution is completely injected, the solution remaining at the inlet is removed and the inlet is sealed. Although there is no restriction | limiting in particular also in this sealing method, If necessary, it can also seal by sticking a glass plate or a plastic substrate with a sealing material.

  Further, when the electrolyte is an electrolyte gelled using a polymer or the like, or an all solid electrolyte, a polymer solution containing an electrolyte and a plasticizer is applied on the semiconductor electrode layer by a casting method or the like. Thereafter, the plasticizer is volatilized and completely removed, and then sealed with a sealing material in the same manner as described above. This sealing is preferably performed using a vacuum sealer or the like in an inert gas atmosphere or in a reduced pressure. After sealing, it is possible to perform heating and pressurizing operations as necessary so that the electrolyte solution of the electrolyte layer sufficiently penetrates into the semiconductor electrode layer.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

  In Example 1, first, the semiconductor electrode layers 1 and 21 described in the first and second embodiments were produced, and their characteristics were examined.

<Preparation of coating liquid>
Titanium oxide TiO ₂ fine particles were used as the metal oxide semiconductor fine particles 2. In Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2, P25 (trade name; manufactured by Degussa, anatase type crystal (80%) and rutile type crystal (20%) were used as titanium oxide fine particles. The mixture, the average particle size of primary particles was about 21 nm). On the other hand, in Examples 1-5 and 1-6 and Comparative Example 1-3, two types of particles having different sizes are used, P25 (trade name) is used as the first fine particles 2A, and the second fine particles 2B are used. TA-300 (trade name; manufactured by Fuji Titanium Industry Co., Ltd., anatase type crystal, average particle diameter of primary particles of about 390 nm) was used.

  The titanium oxide fine particle powder was mixed with ethanol so that the titanium oxide content was 20% by mass. After adding ethanol, P25 was subjected to bead dispersion treatment for 24 hours using a paint shaker and zirconia beads having a diameter of 0.65 mm to prepare a titanium oxide fine particle dispersion. TA-300 was subjected to a bead dispersion treatment using an agitator and zirconia beads having a diameter of 0.65 mm for 24 hours to prepare a titanium oxide fine particle dispersion. When two types of particles having different sizes are used, first, a dispersion of each fine particle is prepared, and then the two dispersions are mixed at a predetermined ratio.

  The longer the processing time of the bead dispersion treatment, the better the dispersibility of the titanium oxide fine particles. In this case, when the titanium oxide porous layer is formed, the titanium oxide fine particles are packed more densely, and the hardness of the titanium oxide porous layer and the adhesion to the support tend to be improved. On the other hand, as the treatment time of the dispersion treatment is shortened, a layer having a high degree of porosity (a layer having many gaps) is formed when the titanium oxide porous layer is formed. As a result, when this titanium oxide porous layer is used as the semiconductor electrode layer 33, the photoelectric conversion efficiency of the dye-sensitized solar cell 30 tends to be improved.

  Next, a predetermined amount of the first compound to the third compound is added to the dispersion, and the mixture is stirred and mixed uniformly. Ethanol is added to adjust the concentration, and the titanium oxide fine particles and the first compound to the third compound are added. A coating solution containing the compound was prepared. At this time, it was observed that the viscosity of the dispersion increased by the addition of the first compound.

  At this time, as the first compound, butoxy titanium dimer (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used in all Examples and Comparative Examples, and the blending amount in the coating liquid was kept constant at 2.5% by mass. As the second compound, Pentaboxyniobium (manufactured by Gelest) was used in Examples 1-1 to 1-5, and triethyl phosphate (manufactured by Kanto Chemical Co., Inc.) was used in Example 1-6. As the third compound, tetramethoxysilane (manufactured by Junsei Chemical Co., Ltd.) was used in Examples 1-1 and 1-2 and Comparative Example 1-1, and triisopropoxyborane was used in Comparative Examples 1-2 and 1-3. (Tokyo Chemical Industry Co., Ltd.) was used. In Examples 1-3 to 1-6, the third compound was not added. The blending amounts of the second compound and the third compound in the coating liquid are as shown in Table 2. As a solvent, ethanol was used in all examples.

<Preparation of semiconductor electrode layer (metal oxide semiconductor porous layer)>
The coating solution was applied onto the support by a bar coating method using a coil bar, and then the solvent was evaporated at 80 ° C. for 2 minutes. Then, it baked at 150 degreeC for 30 minutes. As the support 5, a 125 μm-thick PET film (trade name: 0300E; manufactured by Mitsubishi Resin Co., Ltd.) was used.

<Confirmation that there is no residual organic matter in the semiconductor electrode layer>
It is preferable that no organic matter remains in the semiconductor electrode layer. When the organic matter remains, the performance of the dye-sensitized solar cell using the semiconductor electrode layer may be deteriorated. Therefore, using Nicolet Magna 550 (trade name; manufactured by Thermo Fisher Scientific Co., Ltd.), the support on which the semiconductor electrode layer is formed is fixed on the DuraSampl II ATR attachment, and the FT-IR of the semiconductor electrode layer is fixed. The spectrum was measured, and the presence or absence of absorption based on stretching vibration (2800 to 3000 cm ⁻¹ ) of the carbon-hydrogen bond was examined. In both Example 1 and Comparative Example 1, the stretching vibration of the carbon-hydrogen bond was not measured, and it was confirmed that there was no residual organic substance in the semiconductor electrode layer.

<Evaluation method>
(Thickness of semiconductor electrode layer)
The thickness of the semiconductor electrode layer 1 or 21 is obtained by scraping a part of the layer from the support 5 and measuring a step from the layer surface to the surface of the support 5 with a stylus type surface roughness measuring instrument Surfcoder ET4000 (trade name; ( It was determined by measuring using Kosaka Laboratory).

(hardness)
The hardness was evaluated by Martens hardness and a rubbing test. Martens hardness was evaluated using PICODETOR HM500 (trade name; manufactured by Fisher Instruments Co., Ltd.). The load was 3 mN. In the rubbing test, Bencot M-3II was used, and the surface was vigorously rubbed once in one direction with a length of about 5 cm, and evaluation was performed according to the following criteria.
○: No scratch △: 10 or less scratches ×: 11 or more scratches

(Adhesion characteristics)
The adhesion property was evaluated by a peel test of a cell pattern (1 mm interval × 100 mass) cellophane tape CT24 (trade name; manufactured by Nichiban Co., Ltd.) of JIS K5400 using a semiconductor electrode layer produced on PET or a glass substrate as a test piece. .

  Table 1 is a table | surface which shows the compounding quantity of the titanium oxide microparticles | fine-particles in the coating liquid by Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3. In the table, the ratio of the blending amounts is the ratio of the blending mass of the second fine particles 2B to the blending mass of the first microparticles 2A (= (the blending mass of the second microparticles 2B) / (the blending of the first microparticles 2A). Mass)).

  Table 2 shows the blending amounts of the first compound to the third compound in the coating liquids according to Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3, and their coating liquids. It is a table | surface which shows evaluation of the produced semiconductor electrode layer. In the table, pentaboxyniobium is abbreviated as NPB, triethylphosphoric acid as PTE, tetramethoxysilane as TMOS, and tripropoxyborane as BTP.

  Next, the dye-sensitized solar cell 30 described in the third embodiment was fabricated and its performance was evaluated (see Adv. Mater. (2003), 15, 2101).

<Preparation of dye-sensitized solar cell 30>
(1) The above-mentioned coating solution was applied on a conductive glass substrate with an FTO layer (manufactured by Nippon Sheet Glass Co., Ltd., surface resistance 13Ω / □) by a bar coating method, and then the solvent was evaporated at 80 ° C. for 2 minutes. Next, an unnecessary part is scraped off from the obtained semiconductor electrode layer by using the edge of the glass plate, formed into a square of 5 mm × 5 mm, and then baked at 150 ° C. for 30 minutes to produce a semiconductor electrode layer. did.
(2) Next, the semiconductor electrode layer was immersed in the Z907 dye solution at room temperature for 10 hours to adsorb the dye to the semiconductor electrode layer. Z907 is cis-bis (isothiocyanato) (H ₂ dcbpy) (dnbpy) ruthenium complex (where H ₂ dcbpy is 4,4′-dicarboxy-2,2′-bipyridine and dnbpy is 4,4 ′ -Dinonyl-2,2'-bipyridine). Next, the semiconductor electrode was washed with acetonitrile, and then the acetonitrile was spontaneously evaporated to dry the semiconductor electrode.
(3) A counter electrode formed by sequentially laminating a chromium Cr layer with a thickness of 50 nm and a platinum Pt layer with a thickness of 100 nm on a glass substrate in advance by a sputtering method was used.
(4) Next, the two substrates were placed so that the semiconductor electrode layer and the counter electrode face each other, and bonded together via a silicon rubber sheet having a thickness of 30 μm. Next, an electrolyte solution was introduced between the electrodes using a capillary passage test phenomenon, and a dye-sensitized solar cell 30 was produced. As an electrolytic solution, a solution in which 0.6 M iodide (1-propyl-3-methylimidazolium) and 0.1 M iodine were dissolved in 3-methoxypropionitrile was used.

<Evaluation of dye-sensitized solar cell>
The short-circuit current, open-circuit voltage, and fill of the dye-sensitized solar cell produced while irradiating simulated sunlight (AM1.5, 100 mW / cm ² ) using a square mask with a square hole of 4.5 mm × 4.5 mm. Factors and photoelectric conversion efficiency were evaluated at 24 ° C.

Table 3 is a table | surface which shows the measurement result of the performance of the dye-sensitized solar cell produced in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3. Table 3 shows the average value of the evaluation results of N = 3.

  When Example 1-1 and Comparative Example 1-1 are compared in Table 3, it can be seen that by adding NPB as the second compound, photoelectric conversion efficiency was improved by 20% in Example 1-1. Similarly, when Example 1-1 and Example 1-2 are compared in Table 3, even if the blending amount of NPB is increased from 0.25% to 1.0%, the improvement in photoelectric conversion efficiency is 3%. You can see that it is small. On the other hand, it can be seen from Table 2 that the Martens hardness is improved by increasing the blending amount of NPB, and that NPB also exhibits the action as the third compound.

  Comparing Example 1-2 and Example 1-3 in Table 2, in Example 1-3, the third compound TMOS was omitted, so the Martens hardness decreased slightly, but the second compound NPB Has an action as a third compound, so that it is understood that necessary hardness and adhesion are maintained. On the other hand, by omitting TMOS from Table 3, the photoelectric conversion efficiency is improved by 2% in Example 1-3. This is presumably because TMOS slightly inhibits photoelectric conversion.

  When Example 1-3 is compared with Example 1-4, even if the blending amount of NPB is increased from 1.0% to 2.5%, the Martens hardness improvement is not so great from Table 2, while From FIG. 3, it can be seen that the photoelectric conversion efficiency decreases, and it is found that the policy of improving the hardness and adhesion by increasing the blending amount of NPB is not desirable.

  In Example 1-5, the best photoelectric conversion efficiency and good hardness and adhesion were achieved in this example. Example 1-5 is an example in which the blending amount of NPB is 1.0%, TMOS is not blended, and two types of microparticles having different sizes are used as titanium oxide microparticles. This is considered to be due to the fact that the use of two types of fine particles having different sizes prevented the occurrence of cracks, the internal HAZE was improved, and the light utilization rate was improved. Compared with Comparative Example 1-3 using two types of fine particles having different sizes, the addition of NPB improves the photoelectric conversion efficiency by 19%.

  Example 1-6 is an example in which 1.0% of PTE is added as the second compound, but the photoelectric conversion efficiency is improved by 12.5% compared to Comparative Example 1-3.

  In Example 2, a plastic film was used as the support 5 and a semiconductor electrode layer was formed so as to be in direct contact with the plastic film. Then, using this semiconductor electrode layer, the back contact type dye-sensitized solar cell 40 described in the third embodiment was fabricated, and its performance was evaluated. At this time, the same coating liquid as that prepared in Example 1-5 was prepared, and a semiconductor electrode layer was formed using the same coating liquid.

<Preparation of dye-sensitized solar cell 40>
(1) As the transparent substrate 41 (support 5), a 125 μm thick PET film (trade name: 0300E; manufactured by Mitsubishi Resin Co., Ltd.) was used. After applying the above-mentioned coating liquid on the transparent substrate 41 by a bar coating method using a coil bar, the solvent was evaporated at 80 ° C. for 2 minutes. Then, it baked for 30 minutes at 150 degreeC, and the semiconductor electrode layer 43 was produced. The thickness of the semiconductor electrode layer 43 was 5 μm.
(2) Next, a titanium layer having a thickness of 100 nm was formed as the porous electrode layer 42 on the semiconductor electrode layer 43 by sputtering.
(3) Next, the semiconductor electrode layer 43 was immersed in a Z907 dye solution at room temperature for 10 hours to adsorb the dye to the semiconductor electrode layer 43. Next, after the semiconductor electrode layer 43 was washed with acetonitrile, the acetonitrile was naturally evaporated and the semiconductor electrode layer 43 was dried.
(4) A glass substrate was used as the counter substrate 46. On this counter substrate, a chromium layer with a thickness of 50 nm and a platinum layer with a thickness of 100 nm were sequentially laminated in advance by sputtering, and this was used as the counter electrode 45.
(5) Next, the substrate 41 and the substrate 46 were disposed so that the semiconductor electrode layer and the counter electrode face each other, and a silicon rubber sheet having a thickness of 100 μm was sandwiched as the sealing material 47 and bonded together. Next, an electrolyte solution was introduced between the electrodes using a capillary passage test phenomenon, and a dye-sensitized solar cell 40 was produced. As an electrolytic solution, a solution in which 0.6 M iodide (1-propyl-3-methylimidazolium) and 0.1 M iodine were dissolved in 3-methoxypropionitrile was used.

<Evaluation of dye-sensitized solar cell>
Similarly to Example 1, a short circuit of the dye-sensitized solar cell produced while irradiating simulated sunlight (AM1.5, 100 mW / cm ² ) using a square mask having a square hole of 4.5 mm × 4.5 mm. The current, open circuit voltage, fill factor, and photoelectric conversion efficiency were evaluated at 24 ° C.

Table 4 is a table showing the measurement results of the performance of the back contact type dye-sensitized solar cell 40 produced in Example 2.

  From the above results, according to the present invention, it is possible to form a semiconductor electrode layer so as to be in direct contact with a transparent substrate made of a plastic film, and back contact type dye sensitization produced using this semiconductor electrode layer The solar cell 40 was found to be able to achieve almost the same photoelectric conversion efficiency as the dye-sensitized solar cell 30 manufactured using the expensive FTO transparent conductive layer manufactured in Example 1.

  Although the present invention has been described based on the embodiments and examples, it is needless to say that the present invention is not limited to these examples and can be appropriately changed without departing from the gist of the invention. .

  The present invention provides an electrochemical device such as a dye-sensitized solar cell that can be manufactured with high productivity using a lightweight, inexpensive, flexible plastic film, and contributes to its spread.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor electrode layer, 2 ... Metal oxide semiconductor fine particle, 2A ... 1st fine particle,
2B ... second fine particles, 3 ... first oxide layer, 4 ... second oxide layer, 5 ... support,
6 ... Adhesion auxiliary layer, 21 ... Semiconductor electrode layer, 30 ... Dye-sensitized solar cell, 31 ... Transparent substrate,
32 ... Transparent conductive layer (negative electrode current collector), 33 ... Semiconductor electrode layer (negative electrode) holding a photosensitizing dye,
34 ... Electrolyte layer, 35 ... Counter electrode (positive electrode), 36 ... Counter substrate, 37 ... Sealing material,
40 ... dye-sensitized solar cell, 41 ... transparent substrate,
42 ... Light-reflective porous conductive layer (negative electrode current collector),
43 ... Semiconductor electrode layer (negative electrode) holding a photosensitizing dye, 44 ... Electrolyte layer,
45 ... Counter electrode (positive electrode), 46 ... Counter substrate, 47 ... Sealing material,
100 ... General dye-sensitized solar cell, 101 ... Transparent substrate,
102 ... Transparent conductive layer (negative electrode current collector),
103 ... Semiconductor electrode layer (negative electrode) holding a photosensitizing dye, 104 ... Electrolyte layer,
105 ... Counter electrode (positive electrode), 106 ... Counter substrate

Japanese Patent No. 3671183 (pages 3-8 and 10-14, FIG. 2)

Z-S.Wang, T.Yamaguchi, H.Sugihara, H.Arakawa, Langmuir, 21, p.4272-4276 (2005), (page 4273, left column) MKNazeeruddin, A.Kay, I.Rodicio, R.Humphry-Baker, E.Mueller, P.Liska, N.Vlachopoulos, M.Graetzel, J.Am.Chem.Soc., 115 (14), p.6382 -6390 (1993), (page 6384, left column)

2003 (Germany) New Energy and Industrial Technology Development Organization Commissioned Research (Consignment) Results Report, “Solar Power Generation Technology R & D Innovative Next Generation Solar Power Generation System Technology R & D High Performance Dye-Sensitized Solar Cell Technology Research and Development "(March 2004), (pp. 67, 88 and 89, Fig. 2-3-1)

Claims (20)

Metal oxide semiconductor fine particles disposed on a support;
A first oxide layer made of titanium oxide TiO ₂ and bound directly to the metal oxide semiconductor fine particles and the support;
Niobium Nb that is contained in the first oxide layer or that forms a second oxide layer that binds to the metal oxide semiconductor fine particles and the support mainly through the first oxide layer. V) an oxide or hydroxide, or at least one of phosphoric acid or phosphate covering at least part of the surface of the first oxide layer, the first oxide layer, or the A semiconductor electrode layer formed by binding between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support by the first oxide layer and the second oxide layer.   The metal oxide semiconductor fine particles include at least two kinds of first fine particles having an average primary particle size of 100 nm or less and second fine particles having an average primary particle size of more than 100 nm and 10000 nm or less. The semiconductor electrode layer according to claim 1, comprising fine particles having a size. The metal oxide semiconductor fine particles are at least one selected from the group consisting of titanium oxide TiO ₂ , zinc oxide ZnO, tungsten oxide WO ₃ , niobium oxide Nb ₂ O ₅ , strontium titanate SrTiO ₃ , and tin oxide SnO _2. The semiconductor electrode layer according to claim 1, comprising the oxide of   The semiconductor electrode layer according to claim 1 or 2, wherein the second oxide layer includes a high-hardness oxide having a hardness higher than that of titanium oxide forming the first oxide layer. The high hardness oxide, silicon oxide SiO _2, boron oxide B ₂ O _3, at least one oxide selected from the group consisting of aluminum oxide Al ₂ O _3, and zirconium oxide ZrO _2, claim 4 The semiconductor electrode layer described in 1.   The semiconductor electrode layer according to claim 1, wherein a material of the support is a plastic material.   3. The semiconductor electrode layer according to claim 1, wherein the semiconductor electrode layer is configured as a semiconductor electrode layer of a dye-sensitized solar cell by holding a photosensitizing dye on the surface.   The semiconductor electrode layer according to claim 7, wherein the support is a light-transmitting support having a light-transmitting conductive layer on one surface, and is provided in contact with the light-transmitting conductive layer. .   The said support body is a light-transmitting support body provided by laminating | stacking a light transmissive conductive layer and a close_contact | adherence auxiliary | assistance layer on one surface, and is provided in contact with this close_contact | adherence auxiliary | assistant layer. The semiconductor electrode layer described in 1.   The semiconductor electrode layer according to claim 7, wherein the support is an insulating light-transmitting support, and a porous conductive layer is provided on a surface opposite to a surface in contact with the support. . at least,
Metal oxide semiconductor fine particles,
A first compound that yields titanium oxide TiO ₂ upon hydrolysis;
Niobium (V) compound, phosphoric acid or niobium (V) compound that is less likely to hydrolyze than the first compound, or is easily hydrolyzed to the same extent, and generates niobium Nb (V) oxide or hydroxide upon hydrolysis. A step of preparing a coating liquid in which a second compound that is one of phosphate esters is dispersed or dissolved in an organic solvent;
Applying a layer of the coating liquid to a support;
An evaporation step of evaporating the organic solvent from the coating liquid layer;
After the evaporation step, the temperature is increased, and a baking step for heat treatment is included.
The first oxide layer made of titanium oxide is mainly directly bonded to the metal oxide semiconductor particles and the support;
The niobium Nb (V) oxide or hydroxide contains at least one of the niobium Nb (V) oxide or hydroxide, and the phosphoric acid or phosphate ester, and the niobium Nb (V) oxide or hydroxide contains the first oxide layer. Or the second oxide layer bound to the metal oxide semiconductor fine particles and the support mainly through the first oxide layer. The phosphoric acid or phosphorous The acid ester covers at least part of the surface of the first oxide layer,
The first oxide layer or the first oxide layer and the second oxide layer bind the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support. A method for producing a semiconductor electrode layer, comprising producing a porous metal oxide semiconductor layer.   The method for producing a semiconductor electrode layer according to claim 11, wherein a salt or alkoxide of titanium Ti (IV) is used as the first compound.   As the titanium salt or alkoxide, a compound that reacts with a small amount of water usually contained in the metal oxide semiconductor fine particles and / or the organic solvent at room temperature and is partially or fully hydrolyzed in the coating solution is used. A method for producing a semiconductor electrode layer according to claim 12.   The method for producing a semiconductor electrode layer according to claim 11, wherein a niobium (V) salt or alkoxide is used as the second compound.   12. The semiconductor electrode layer according to claim 11, wherein a third compound that is harder to hydrolyze than the first compound and generates a high-hardness oxide having a higher hardness than titanium oxide is added to the coating liquid. Production method.   The method for producing a semiconductor electrode layer according to claim 15, wherein an alkoxide of at least one element selected from the group consisting of silicon Si, boron B, aluminum Al, and zirconium Zr is used as the third compound.   The method for producing a semiconductor electrode layer according to claim 11, wherein the temperature during the firing step is maintained at 40 to 200 ° C.   An electrochemical device comprising at least the semiconductor electrode layer according to any one of claims 1 to 10, a counter electrode, and an electrolyte layer sandwiched therebetween.   When the semiconductor electrode layer holds a photosensitizing dye and light is incident, the electrons of the photosensitizing dye excited by absorbing this light are taken out to the semiconductor electrode layer, and the electrons are lost. The photosensitizing dye is reduced by the reducing agent in the electrolyte layer, and as a result, the oxidizing agent generated in the electrolyte layer serves as a dye-sensitized solar cell that receives electrons from the counter electrode and is reduced. The electrochemical device according to claim 18, which is configured.   The electrochemical device according to claim 19, wherein the semiconductor electrode layer is the semiconductor electrode layer according to any one of claims 8 to 10.

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