JP2012043724A - Semiconductor electrode layer and manufacturing method thereof and electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor electrode layer, composed of metal oxide semiconductor porous layers, which can be manufactured by low temperature firing and can meet the requirements for both the performance as an electrode and the hardness and adhesion to a supporting body, and a manufacturing method thereof, and an electrochemical device which includes the semiconductor electrode layer and is useful as a dye-sensitized solar cell.SOLUTION: A coating liquid containing granular and needle-like metal oxide semiconductor particulates 2 and 3 and a first chemical compound and a second chemical compound is prepared. The first chemical compound hydrolyzes to generate a first oxide, and the second chemical compound is less liable to hydrolyze than the first chemical compound and, when it does hydrolyze, generates a second oxide which is higher in hardness than the first oxide. A layer of the coating liquid is deposited on a support medium 6, which, after organic solvent has been evaporated, is burned at low temperature. In this way, a semiconductor electrode layer 1 which has gaps between the metal oxide semiconductor particulates 2 and between the particulates 2 and the support medium 6 bound by a first oxide layer 4, with the binding reinforced by a second oxide layer 5, is formed.

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.

  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. 6 is a cross-sectional view of the main part showing the structure of a conventional 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 provided on the transparent substrate 101 is made of ITO (Indium Tin Oxide), FTO (fluorine-doped tin oxide), or the like, and functions as a negative electrode current collector. 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 105 b 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 the electrons is reduced by the reducing species (reducing agent) in the electrolyte layer 104. The oxidized species (oxidant) generated in the electrolyte layer 104 by this reaction receives electrons from the counter electrode (positive electrode) 105 and returns to the reduced species. 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. 7 is a flowchart showing a general manufacturing process of a 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, after contacting the transparent conductive layer 102 provided on the transparent substrate 101 and depositing the dispersion by a coating method or the like, 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). 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. In addition, since there is no plastic material that can withstand high temperatures of 400 to 500 ° C., it is impossible to use a plastic film as the transparent substrate 101 when performing high-temperature sintering.

  On the other hand, when 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 film (glass In relation to the transition temperature, it is necessary to perform low-temperature firing 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. 8 is a flow chart 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.

  Moreover, the photoelectric conversion efficiency of the dye-sensitized solar cell is currently lower than that of the silicon-based solar cell, and various efforts have been reported for improving the photoelectric conversion efficiency. As one of them, in Patent Document 2 described later, acicular titanium oxide fine particles (rutile crystal) having a diameter of 30 to 200 nm and a length of 0.5 to 20 μm and granular titanium oxide fine particles (anatase type) having a diameter of 5 to 400 nm are disclosed. And a dye-sensitized solar cell provided with the titanium oxide porous film as a semiconductor electrode layer have been proposed. Patent Document 2 explains as follows.

A value (aspect ratio) obtained by dividing the average length of the acicular titanium oxide fine particles by the average diameter is 5 or more, and the specific surface area is 5 to 30 m ² / g. The granular titanium oxide fine particles are mainly anatase-type crystal fine particles, but may partially contain a rutile-type crystal structure, and may contain a rutile-type crystal structure in some cases. . The mass ratio between the acicular titanium oxide fine particles and the granular titanium oxide fine particles is preferably 1:10 to 2: 1.

As a method for producing the porous titanium oxide film on a transparent substrate made of an organic material having insufficient heat resistance, granular titanium oxide fine particles and acicular titanium oxide fine particles are further added to titanium alkoxide, for example, tetraethoxy titanium Ti ( C ₂ H ₅ O) ₄ is added to form a slurry-like or paste-like coating liquid, and this coating liquid is applied and crosslinked by a hydrolysis reaction of titanium alkoxide to form a porous body made of granular titanium oxide. Fix acicular titanium oxide fine particles. Alternatively, a coating solution may be formed by adding a sol solution of titanium oxide instead of titanium alkoxide. As a method not using titanium alkoxide or titanium oxide sol solution, the surface of the substrate on which the titanium oxide fine particle layer is formed is exposed to high frequency plasma while cooling the back side of the transparent substrate, and only the surface is heated to a high temperature to oxidize. There is a method of firing the titanium fine particle layer.

  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 the first fine particles having an average primary particle diameter of 100 nm or less as the metal oxide semiconductor fine particles and the second granular particles having an average primary particle diameter of greater than 100 nm and 10000 nm or less. Invented a second method for producing a semiconductor electrode layer, wherein a metal oxide semiconductor porous layer is produced using metal oxide semiconductor fine particles containing fine particles of at least two kinds of fine particles, and patented 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. In the example of Patent Document 2, there is an example in which photoelectric conversion efficiency is improved by using a porous titanium oxide film in which acicular titanium oxide fine particles (rutile type crystals) and granular titanium oxide fine particles (anatase type crystals) are mixed. Although shown, these are examples of performing high-temperature firing. Regarding low-temperature firing, it is only described that is known in Patent Document 1 and the like.

  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 made of a metal oxide semiconductor porous layer, a method for producing the same, and a semiconductor electrode layer having a higher photoelectric conversion performance when a dye-sensitized solar cell is configured. And providing an electrochemical device useful as a dye-sensitized solar cell.

That is, the present invention
Metal oxide semiconductor fine particles including fine particles having at least two shapes, granular fine particles and acicular fine particles, and disposed on a support;
A first oxide layer that is mainly directly bonded to the metal oxide semiconductor fine particles and the support;
The second oxide is harder than the first oxide forming the first oxide layer, and the metal oxide semiconductor fine particles and the support mainly through the first oxide layer. A second oxide layer bound to the body, and the first oxide layer and the second oxide layer, and between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the The present invention relates to a semiconductor electrode layer formed by binding with a support.

Also,
Metal oxide semiconductor fine particles including fine particles of at least two types of granular fine particles and acicular fine particles;
A first compound that yields a first oxide upon hydrolysis;
A coating liquid obtained by dispersing or dissolving in a organic solvent a second compound that produces a second oxide that is harder to hydrolyze than the first compound and that has a higher hardness than the first oxide when hydrolyzed. A step of preparing;
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;
Metal oxide semiconductor porous material 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 The present invention relates to a method for producing a semiconductor electrode layer for producing a 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, metal oxide semiconductor fine particles including fine particles of at least two types of granular fine particles and acicular fine particles, and a first oxide that generates a first oxide when hydrolyzed. And a second compound that is harder to hydrolyze than the first compound and generates a second oxide having a higher hardness than the first oxide when hydrolyzed, is dispersed or dissolved in an organic solvent. Prepare a coating solution. 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 first oxide is bonded to the surface of the metal oxide semiconductor fine particles, and the metal oxide semiconductor fine particles are connected. Thus, 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 first oxide contained in the coating liquid becomes the metal oxide. It binds to semiconductor fine particles. 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 first 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 by the first oxide layer between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support.

  Thereafter, the firing step is performed. A small amount of the second compound is hydrolyzed until the baking step, and most of the second compound is hydrolyzed by moisture supplied from the air in the baking step. In this case, the second oxide having a high hardness generated by hydrolysis of the second compound is mainly bound on the first oxide layer to form the second oxide layer, The first oxide layer bonded between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the support is strongly reinforced. As a result, the semiconductor electrode layer (metal oxide semiconductor porous layer) of the present invention having excellent mechanical strength and high adhesion to the support can be obtained.

  Since this semiconductor electrode layer contains not only the granular fine particles but also the acicular fine particles as the metal oxide semiconductor fine particles, as shown in the examples described later, the semiconductor not containing the acicular fine particles The conductivity is improved as compared with the electrode layer. The reason for this is that when the needle-shaped fine particles are included, the electrons are less likely to pass through the joint between the fine particles, which has a large resistance, by using the conductive paths in the fine particles that are long in the length direction of the fine particles. It is conceivable that the semiconductor electrode layer can be moved.

  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 as an electrode, it is an electrochemical device that can be manufactured lightly, inexpensively and with high productivity using a flexible plastic film or the like as the support. . Moreover, since the semiconductor electrode layer has improved conductivity compared to the semiconductor electrode layer not containing the acicular fine particles, the performance of the electrochemical device, for example, when a dye-sensitized solar cell is configured The photoelectric conversion performance is improved.

It is sectional drawing which shows the structure of the semiconductor electrode layer based on Embodiment 1 of this invention. It is a flowchart which shows the manufacturing process of a semiconductor electrode layer similarly. It is sectional drawing which shows the structure of the semiconductor electrode 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 a Cole-Cole plot figure which shows the result of having measured the alternating current impedance of the dye-sensitized solar cell by the Example 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 of the present invention, it is preferable that an average diameter of primary particles of the acicular metal oxide semiconductor fine particles is 0.1 to 1 μm and an average length is 1 to 10 μm.

  The ratio of the blended mass of the acicular metal oxide semiconductor particles to the blended mass of the granular metal oxide semiconductor particles is preferably 0.05 to 0.25.

  Further, the granular metal oxide semiconductor fine particles include first granular fine particles having an average primary particle size of 100 nm or less, and second granular fine particles having an average primary particle size of greater than 100 nm and 10,000 nm or less. It is preferable to include granular fine particles having at least two kinds of sizes.

  The ratio of the blending mass of the second particulate fine particles to the blending mass of the first particulate particulates is preferably 0.06 to 6.

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 element constituting the first oxide layer may be the same element as the metal element constituting the metal oxide semiconductor fine particles.

In addition, the oxide constituting the second oxide layer having high hardness is 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. The at least one oxide selected is preferred.

  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 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 may be used as the first compound. The first compound may be a compound of at least one element selected from the group consisting of titanium Ti, aluminum Al, silicon Si, vanadium V, zirconium Zr, niobium Nb, and tantalum Ta. In addition, as the first compound, 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 liquid. It is good to use.

  As the second 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.

  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 species (reducing agent) in the electrolyte layer. As a result, the oxidizing species (oxidizing agent) generated in the electrolyte layer are It is good to be configured as a dye-sensitized solar cell that receives and reduces electrons from the counter electrode.

  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 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 layers described in claims 1 to 3 and 6 to 9 and the manufacturing method thereof described in claims 13 to 17 will be described.

  FIG. 1A is a cross-sectional view and a partially enlarged view of the semiconductor electrode layer 1 formed on the support 6. The semiconductor electrode layer 1 includes the first oxide layer 4 between the metal oxide semiconductor fine particles 2 and 3 disposed on the support 6 and between the metal oxide semiconductor fine particles 2 and 3 and the support 6. It is a metal oxide semiconductor porous layer bound by the second oxide layer 5. As one of the characteristics of the present invention, the semiconductor electrode layer 1 contains metal oxide semiconductor fine particles having at least two types of shapes, ie, granular metal oxide semiconductor fine particles 2 and needle-like metal oxide semiconductor fine particles 3. .

Depending on the characteristics of the semiconductor electrode layer, the metal oxide semiconductor fine particles 2 and 3 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. _It is preferable to comprise at least one oxide selected from the group consisting of ₂ .

  In many cases, the metal element constituting the first oxide layer 4 is preferably the same metal element as the metal element constituting the metal oxide semiconductor fine particles 2 and 3. In such a case, the adhesion between the metal oxide semiconductor fine particles 2 and 3 and the first oxide layer 4 is expected to be the best. The first oxide layer 4 is mainly bound directly to the metal oxide semiconductor fine particles 2 and 3 and the support 6.

The second oxide layer 5 contains a second oxide having a hardness higher than that of the first oxide forming the first oxide layer 4, and the metal oxide mainly passes through the first oxide layer 4. The solid semiconductor particles 2 and 3 and the support 6 are bound. The second oxide layer 5 reinforces the first oxide layer 4 and strengthens the bond between the metal oxide semiconductor fine particles 2 and 3 and between the metal oxide semiconductor fine particles 2 and 3 and the support 6. To work. The high-hardness oxide constituting the second oxide layer 5 is at least one 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 . It may be an oxide.

  The semiconductor electrode layer 1 contains not only particulate fine particles 2 but also needle-like fine particles 3 as metal oxide semiconductor fine particles. For this reason, as shown in the below-mentioned Example, electroconductivity improves compared with the semiconductor electrode layer which does not contain the acicular fine particle 3. FIG. For this reason, when the acicular fine particles 3 are included, the electrons pass through the junction between the fine particles having a large resistance by using the long intra-fine particle conductive path in the longitudinal direction of the acicular fine particles 3. It is conceivable that the semiconductor electrode layer 1 can be moved less frequently.

  The average particle diameter of the primary particles of the granular fine particles 2 is not particularly limited, but it is preferably 1 to 100 nm because visible light permeability can be increased and the specific surface area can be increased.

  On the other hand, the average diameter of the primary particles of the needle-shaped fine particles 3 is preferably 0.1 to 1 μm, and the average length is preferably 1 to 10 μm. When the average length is shorter than 1 μm, the acicular fine particles 3 cannot form an effective conductive path in the semiconductor electrode layer 1, and as a result, the performance of the electrochemical device using the semiconductor electrode layer 1 is improved. Tend to be insufficient. For example, when a dye-sensitized solar cell is configured, the effect of increasing current collection efficiency and improving photoelectric conversion efficiency tends to be insufficient. Moreover, when the average length is longer than 10 μm, the pot life of the paint tends to deteriorate.

  The ratio of the blending mass of the needle-shaped fine particles 3 to the blending mass of the granular microparticles 2 (= (the blending mass of the acicular microparticles 3) / (the blending mass of the granular microparticles 2)) is 0.05 to 0.25. Is desirable. If it is less than 0.05, the amount of acicular fine particles 3 is too small, and the effect of improving the conductivity of the semiconductor electrode layer 1 is insufficient. On the other hand, when exceeding 0.25, although the effect of improving the electroconductivity of the semiconductor electrode layer 1 is large, the real surface area of the metal oxide semiconductor porous layer 1 reduces and the performance as an electrode falls. As a result, for example, when a dye-sensitized solar cell having the semiconductor electrode layer 1 is configured, high photoelectric conversion efficiency cannot be realized.

  When preparing a paint containing the acicular fine particles 3, the degree of dispersion of the acicular fine particles 3 is more preferable as the dispersion progresses. Specifically, for example, the dispersion processing time such as bead dispersion may be increased. As the dispersion progresses, a large number of conductive paths are formed uniformly by the acicular fine particles 3 in the semiconductor electrode layer 1 and the actual surface area of the acicular fine particles 3 increases. As a result, the conductivity of the semiconductor electrode layer 1 containing the acicular fine particles 3 is improved, and the performance of an electrochemical device using the same is improved. For example, in an electrochemical device configured as a dye-sensitized solar cell, current collection efficiency is improved and photoelectric conversion efficiency is improved.

  FIG. 1B is a cross-sectional view showing an example in which the adhesion auxiliary layer 6 is provided on the support 6 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 6 is not sufficient. As an example in which the adhesiveness tends to be insufficient, an example in which the support 6 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 polyacrylate 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 dye-sensitized solar cell.

  FIG. 2 is a flow diagram showing a process for producing the semiconductor electrode layer 1. Hereinafter, an explanation will be given with an emphasis on how the metal oxide semiconductor porous layer 1 having the unique structure described above is formed.

<Preparation of coating liquid>
In order to produce the semiconductor electrode layer 1, first, the metal oxide semiconductor fine particles 2 and 3 are each dispersed in an appropriate organic solvent to prepare two paste-like dispersions. 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.

  As the solvent, a solvent that can disperse the metal oxide semiconductor fine particles 2 and 3 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.

  The compounding amount of the metal oxide semiconductor fine particles 2 and 3 is 1 to 50% by mass, for example, about 20% by mass of the mass of the coating liquid formed by adding the first compound and the second compound 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.

  Next, the above-mentioned two dispersions are mixed at a predetermined ratio, and the first compound and the second compound are added to this, and stirred to dissolve to obtain a uniform coating solution. A solvent may be further added to adjust the concentration. Either order may be sufficient as the order which adds a 1st compound and a 2nd compound. A 1st compound is a compound which hydrolyzes and produces | generates a 1st oxide. The second compound is a compound that is harder to hydrolyze than the first compound and that produces a second oxide having a higher hardness than the first oxide when hydrolyzed.

  Specifically, a metal element salt or alkoxide is preferably used as the first compound. This metal element may be at least one element selected from the group consisting of titanium Ti, aluminum Al, silicon Si, vanadium V, zirconium Zr, niobium Nb, and tantalum Ta, for example. In addition, unpurified metal oxide semiconductor fine particles and organic solvents usually contain more or less adsorbed or occluded water, but as a first compound, they react with these water at room temperature, and partly Alternatively, it is preferable to use a compound that is fully hydrolyzed in the coating solution. 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 first compound, the metal oxide semiconductor fine particles, and the organic solvent proceeds, the first compound reacts with moisture, and the first oxide generated by hydrolysis of the first compound is a metal. This is considered to be due to bonding to the surfaces of the oxide semiconductor fine particles 2 and 3 to connect the metal oxide semiconductor fine particles 2 and 3 together.

  On the other hand, as the second 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 quantity of a 1st compound shall be 0.01-20 mass% of the mass of a coating liquid. Moreover, the compounding quantity of a 2nd compound shall be 0.01-20 mass% of the mass of a coating liquid. 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 second compound are the materials and dispersibility of the metal oxide semiconductor fine particles 2 and 3, Depending on the material type of the first compound and the second compound, it is appropriately selected within the above range. When the blending amounts of the first compound and the second compound are outside 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 6. Further, when the semiconductor electrode layer 1 is used as a semiconductor electrode layer of a dye-sensitized solar cell, depending on the material type of the first compound and the second compound, the adsorption of the photosensitizing dye is inhibited, and the photoelectric Conversion efficiency may decrease.

<Formation of semiconductor electrode layer>
Next, the layer of the coating liquid is deposited on the support 6 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, the second compound, and the first 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 first oxide contained in the coating liquid is bound to the metal oxide semiconductor fine particles 2 and 3. The first compound reacts with moisture in the air and is hydrolyzed. As a result, most of the first compound is converted to the first oxide before entering the next baking step. Then, a metal oxide semiconductor porous layer in which the metal oxide semiconductor fine particles 2 and 3 and between the metal oxide semiconductor fine particles 2 and 3 and the support 6 are bound by the first oxide layer 4 is formed. Is done. At this time, in order to promote hydrolysis of the first 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 fired to improve the electronic connection between the metal oxide semiconductor fine particles 2 and 3, and the mechanical strength of the metal oxide semiconductor porous layer and the support 6 is improved. Although there is no restriction | limiting in particular in a calcination temperature, since the support body 6 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 6, 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 proportion of the second compound that is hydrolyzed until the firing step is small, and most of the second compound is preferably hydrolyzed by moisture supplied from the air in the firing step. In this case, the second oxide generated by hydrolysis of the second compound is mainly bound on the first oxide layer 4 to form the second oxide layer 5, and the metal oxide The first oxide layer 4 bonded between the semiconductor fine particles 2 and 3 and between the metal oxide semiconductor fine particles 2 and 3 and the support 6 is strongly reinforced. As a result, a semiconductor electrode layer (metal oxide semiconductor porous layer) 1 having excellent mechanical strength and high adhesion to the support 6 is obtained.

  In addition, the adhesion between the semiconductor electrode layer (metal oxide semiconductor porous layer) 1 and the support 6 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 6. The first oxide generated before the coating liquid is applied to the support 6 connects the metal oxide semiconductor fine particles 2 and 3 and increases the mechanical strength of the metal oxide semiconductor porous layer 1. This is because it contributes above, but does not contribute to improving the adhesion to the support 6. On the other hand, most of the hydrolysis of the second compound occurs after the coating liquid is applied to the support 6, so that the second oxide has the mechanical strength of the metal oxide semiconductor porous layer 1. The improvement contributes to the improvement of the adhesion to the support 6 as well. However, only the second compound tends to cause surface peeling or damage. This is because the second compound is less reactive with the surface of the metal oxide semiconductor fine particles 2 and 3 than the first compound, so that the number of necking between the fine particles 2 and 3 is reduced only with the second compound. This is because the strength tends to be insufficient. That is, both the first compound and the second compound are required to achieve both the mechanical strength of the semiconductor electrode layer 1 and the adhesion to the support 6.

  After firing, for the purpose of increasing the actual surface area of the metal oxide semiconductor porous layer 1 or increasing the necking between the metal oxide semiconductor fine particles 2 and 3, metal salts such as titanium tetrachloride and titanium alkoxide and metal alkoxides Necking processing may be performed using. Further, organic substances and unreacted substances remaining in the metal oxide semiconductor porous layer 1 may be removed by washing with a solvent or the like.

  When a plastic material is used as the material of the support 6, it is possible to perform a process of pressing the semiconductor electrode layer 1 to the support 6 by a heat and pressure process, for example, a calendar process.

  Hereinafter, the semiconductor electrode layer 1 and the manufacturing method thereof will be further described in detail.

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

  The thickness of the semiconductor electrode 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.

As the material of the metal oxide semiconductor fine particles 2 and 3, 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 and 3 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 and 3 is not limited to these. Also, two or more of these materials can be mixed and used.

  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 in the granular metal oxide semiconductor fine particles 2 (in this case, however, metal Cracks are generated in the oxide semiconductor porous layer 1, 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 porous layer 1 is lowered. (For such a case, see Embodiment 2 described later.) As the metal oxide semiconductor fine particles 2 and 3, commercially available products may be used, or a predetermined value may be obtained by subjecting chloride or alkoxide to hydrolysis treatment or hydrothermal treatment by a known method such as a sol-gel method. You may produce the thing of a particle size.

  When titanium oxide is used as the material of the metal oxide semiconductor fine particles 2 and 3, the crystal form thereof may be one type selected from rutile type, anatase type, and brookite type, or a mixture of two or more types. Examples of commercially available products include granular metal oxide semiconductor fine particles 2 having an average primary particle diameter of 1 to 100 nm, such as P25 and P90 (trade name) manufactured by Degussa, manufactured by Ishihara Sangyo Co., Ltd. ST-01 and ST-21 (above, trade names), Super Titania F-1, F-2, F-3, F-4, F-5, and F-6 (above, manufactured by Showa Denko KK) (Trade name), SSP-25, SSP-20, SSP-M, and STR series (trade name) manufactured by Sakai Chemical Industry Co., Ltd., MT-150A, MT-500B, MT- manufactured by Teika Co., Ltd. 600B, MT-700B, AMT-100, AMT-600, TKP-101, and TKP-102 (above, trade names), NanoTek Powder series (trade names) manufactured by CI Kasei Co., Ltd., and the like can be used.

  Further, as the needle-like metal oxide semiconductor fine particles 3, FTL-100, FTL-110, FTL-200, FTL-300, FT-1000, FT-2000, FT-3000, FS- manufactured by Ishihara Sangyo Co., Ltd. 10P and FS-10D (above, trade names) can be used.

  When zinc oxide is used as the material for the metal oxide semiconductor fine particles 2 and 3, commercially available products include, for example, granular metal oxide semiconductor fine particles 2 such as MZ-300 and MZ-500 (above Product name), FZO-50 (product name) manufactured by Ishihara Sangyo Co., Ltd., NanoTek Powder series (product name) manufactured by CI Kasei Co., Ltd., FINEX series (product name) manufactured by Sakai Chemical Industry Co., Ltd. F-1, F-2, F-3, Pazet CK, Pazet GK-40 (above, trade name) manufactured by Co., Ltd. can be used. As the needle-shaped metal oxide semiconductor fine particles 3, Panatetra (trade name) manufactured by Amtec Co., Ltd. can be used.

  When tin oxide is used as the material of the metal oxide semiconductor fine particles 2 and 3, commercially available products include, for example, granular metal oxide semiconductor fine particles 2 having an average particle diameter of 15 nm manufactured by Johnson Matthey Co., Ltd. The NanoTek Powder series (trade name) manufactured by Kasei Co., Ltd. can be used.

  Note that the materials of the metal oxide semiconductor fine particles 2 and 3 may be used in appropriate mixture.

  As the first compound, a salt or alkoxide that can be dissolved in an organic solvent can be used. The first compound may be a compound of at least one element such as Ti, Al, Si, V, Zr, Nb, and Ta. In many cases, the element is the same element as the metal element constituting the metal oxide semiconductor fine particle 2, and the first oxide generated from the first compound and the metal oxide semiconductor fine particle 2 are formed. The constituent metal oxide is preferably the same kind of oxide. It can be expected that the adhesion between the metal oxide semiconductor fine particles 2 and the first oxide layer 3 is the best.

  Moreover, it is good to use the 1st compound hydrolyzed at room temperature with the water | moisture content normally contained in the metal oxide semiconductor fine particle 2 and / or the organic solvent as a 1st compound. In this case, as described above, the hydrolysis of the first compound starts in the coating liquid, and the metal oxide semiconductor fine particles 2 are connected by the generated first oxide. A network is easily formed.

As the salt, any of nitrates, sulfates, acetates, oxalates, halides and the like that can be dissolved in a solvent can be used. Specifically, TiOSO ₄ , Zr (CH ₃ COO) ₂ O, Zr (CH ₃ COO) ₄ , Al (NO ₃ ) ₃ , Al (CH ₃ COO) ₃ , Al ₂ (SO ₄ ) ₃ , TiCl ₄ AlCl ₃ , Ti (C ₂ O ₄ ) ₂ , Zr (C ₂ O ₄ ) ₂ , and Al ₂ (C ₂ O ₄ ) ₃ 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 metal 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.

  As a commercial item, the following can be used, for example. That is, Nippon Soda Co., Ltd. A-1, B-1, TOT, TOG, T-50, T-60, A-10, B-2, B-4, B-7, B-10, TBSTA, DPSTA-25, S-151, S-152, S-181, TAT, and TLA-A-50 (above, trade names), TPT, TBT, DBT, TST, TEAT, TAA, manufactured by Mitsubishi Gas Chemical Co., Ltd. TEAA, TLA, and OGT (trade name), KR TTS, KR 46B, KR 55, KR 41B, KR 38S, KR 138S, KR 238S, 338X, KR 44, KR 9SA, KR manufactured by Ajinomoto Fine Techno Co., Ltd. ET, and AL-M (above, trade name), TA-10, TA-25, TA-22, TA-30, TC-100, manufactured by Matsumoto Fine Chemical Co., Ltd. C-401, TC-200, TC-750, TC-400, TC-300, TC-310, TC-315, TPHS, ZA-40, ZA-65, ZC-150, ZC-540, ZC-570, ZC-580, ZC-700, ZB-320, and ZB-126 (above, trade name), Colcoat Co., Ltd. ethyl silicate 28, ethyl silicate 28P, N-propyl silicate, N-butyl silicate, MCS-18, Methyl silicate 51, methyl silicate 53A, ethyl silicate 40, ethyl silicate 48, EMS-485, SS-101, HAS-6, HAS-1, HAS-10, SS-C1, Colcoat P, Colcoat N-103X, and magnesium Ethylate (above, trade name) can be used.

When titanium oxide is used as the material of the metal oxide semiconductor fine particles 2 and 3, examples of the first compound include titanium tetrachloride TiCl ₄ , titania sulfate TiOSO ₄ , tetramethoxy titanium Ti (OCH ₃ ) ₄ , and tetrapropoxy titanium. _{Ti (OCH 2 CH 2 CH 3} ) 4, titanium tetrabutoxide _{Ti (OCH 2 CH 2 CH 2} CH 3) 4, tetra-pentoxy titanium _{Ti (OCH 2 CH 2 CH 2} CH 2 CH 3) 4, butoxy titanium dimer, butoxy titanium oligomer, butoxy titanium polymer, tetramethoxy zirconium Zr (OCH _{3) 4,} tetraethoxy zirconium _{Zr (OCH 2 CH 3) 4} , tetra propoxy zirconium _{Zr (OCH 2 CH 2 CH 3} ) 4, tetrabutoxyzirconium Zr (OCH _{2 CH 2 CH 2 CH 3)} 4, trimethoxy aluminum Al (OCH _{3) 3,} Li ethoxy aluminum _{Al (OCH 2 CH 3) 3} , tripropoxy aluminum _{Al (OCH 2 CH 2 CH 3} ) 3, tributoxy aluminum _{Al (OCH 2 CH 2 CH 2} CH 2 CH 3) can be preferably used ₃ .

On the other hand, as the second compound, alkoxides such as Si, B, Al, and Zr are used, and the oxide forming the second oxide layer 4 is SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , and An oxide having high hardness such as ZrO ₂ is preferable.

When titanium oxide is used as the material of the metal oxide semiconductor fine particles 2 and 3, examples of the second compound include 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, trimethoxy borane B (OCH _{3) 3,} triethoxy borane _{B (OCH 2 CH 3) 3} , triisopropoxyborane B (OCH ( H ₃₎ CH _{3) 3} or the like can be used preferably.

  As the solvent, a solvent capable of dissolving the first compound and the second compound and dispersing the metal oxide semiconductor fine particles 2 and 3 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 6 is not particularly limited as long as it is stable in the environment in which it is used. The material of the support 6 may be an inorganic material or an organic material. Further, the shape of the support 6 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 6 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 6 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 6 is not particularly limited, and can be appropriately selected 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 6 is required to be light transmissive, a material that easily transmits light as the support 6. 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 polymer and a polymer material such as a cycloolefin polymer resin (COP). Among these, it is preferable to use a substrate material having a particularly high visible light transmittance. Although the thickness of a plastic substrate is not specifically limited, It is preferable that it is 38-500 micrometers from a 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 claims 4 and 5 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 6. The semiconductor electrode layer 21 includes the first oxide layer 4 between the metal oxide semiconductor fine particles 2 and 3 disposed on the support 6 and between the metal oxide semiconductor fine particles 2 and 3 and the support 6. It is a metal oxide semiconductor porous layer bound by the second oxide layer 5. The second embodiment is different from the first embodiment in that the granular metal oxide semiconductor fine particles 2 forming the semiconductor electrode layer 21 are the first granular fine particles 2A having an average primary particle diameter of 100 nm or less, That is, the primary particles are composed of two types of fine particles having different sizes from the second granular fine particles 2B having an average particle diameter of more than 100 nm and 10000 nm or less. 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 granular metal oxide semiconductor fine particles 2, the first granular 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 granular fine particles 2B is larger than 100 nm and not larger than 10,000 nm. The larger the average particle diameter of the second granular fine particles 2B, the more the ratio of the blending mass of the second granular fine particles 2B to the blending mass of the first granular fine particles 2A (= (the blending mass of the second granular fine particles 2B). ) / (Mixed mass of first particulate fine particles 2A)), the cracks generated in the semiconductor electrode layer (metal oxide semiconductor porous layer) 21 decrease as shown in Japanese Patent Application No. 2010-26483. To do.

  The reason for this is not completely understood, but when relatively large second granular fine particles 2B coexist, the connection between the second granular fine particles 2B and the surrounding first granular fine particles 2A is as follows. Since the number of particles that need to be connected to form the conductive path of the same length is relatively small, it is surely formed on the surface of the granular fine particles 2B. It is conceivable that the number of connecting portions between the first granular fine particles 2A that tends to have insufficient strength is remarkably reduced. Therefore, FIG. 3 shows an example including two types of granular fine particles having different average particle diameters of primary particles, but it is obvious that a configuration including three or more types of granular fine particles having different average particle diameters may be used. is there.

  Further, when the second particulate fine particles 2B coexist, incident light is easily scattered, the internal HAZE of the semiconductor electrode 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 semiconductor electrode layer 21 as a semiconductor electrode, the light utilization rate is increased by scattering of incident light, and the photoelectric conversion performance is improved.

  The primary particle average particle size of the second granular 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 semiconductor electrode layer 21 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 granular fine particles 2B tend to precipitate in the coating liquid, and the pot life of the coating liquid tends to decrease.

  Moreover, as shown in Japanese Patent Application No. 2010-26483, the ratio of the blending mass of the second granular fine particles 2B to the blending mass of the first granular fine particles 2A is preferably 0.06 to 6. When it is less than 0.06, the effect of suppressing the occurrence of cracks in the semiconductor electrode layer 21 becomes insufficient, and the performance of scattering incident light tends to be insufficient. On the other hand, when it is larger than 6, the effect of suppressing the occurrence of cracks in the semiconductor electrode layer 21 is sufficient and the performance of scattering incident light is sufficient, but the actual surface area of the metal oxide semiconductor particles in the semiconductor electrode layer 21 is sufficient. This may decrease the performance of an electrochemical device using the semiconductor electrode layer 21, for example, a dye-sensitized solar cell.

  The larger the ratio of the blending mass of the needle-shaped fine particles 3 to the blending mass of the granular microparticles 2 (= (the blending mass of the needle-shaped microparticles 3) / (the blending mass of the granular microparticles 2)), the more the second granular microparticle 2B The larger the ratio of the blending mass to the blending mass of the first particulate fine particles 2A (= (the blending mass of the second particulate fine particles 2B) / (the blending mass of the first particulate fine particles 2A)), the larger the semiconductor electrode layer 1 becomes. A light scattering function is imparted to the semiconductor electrode layer 21 so that the internal HAZE of the semiconductor electrode layer 21 increases and the total light transmittance decreases. Further, by adsorbing the photosensitizing dye to the semiconductor electrode layer 21, the total light transmittance is further lowered. The blending mass of the granular fine particles 2A and 2B and the acicular fine particles 3 is selected within the above-described range so that the internal HAZE value is 85% or more and the total light transmittance is 50% or less. Good. By doing in this way, in the dye-sensitized solar cell using the semiconductor electrode layer 21, the light utilization rate is improved and the photoelectric conversion performance is improved.

  As will be shown later in the examples, when the acicular fine particles 3 are contained in the semiconductor electrode layer (metal oxide semiconductor porous layer) 21, the hardness of the semiconductor electrode layer 21 and the adhesion to the substrate are maintained. The photoelectric conversion efficiency can be improved. In addition, no cracks are generated in the semiconductor electrode layer 21 in the solvent evaporation step and / or the baking step after application or printing of the coating liquid due to the inclusion of the acicular fine particles 3. However, the acicular fine particles 3 do not have an effect of suppressing the occurrence of cracks or are not sufficient. Therefore, the internal HAZE and the total light transmittance can be made within the above ranges by including the needle-shaped fine particles 3 in the semiconductor electrode layer 21, but if the semiconductor electrode layer 21 does not contain the granular fine particles 2B, the semiconductor electrode In some cases, the occurrence of cracks in the layer 21 cannot be suppressed.

  When a commercially available product is used as the granular metal oxide semiconductor fine particles 2A, a commercially available product having an average primary particle size of 1 to 100 nm shown in Embodiment 1 can be used. When a commercially available product is used as the granular metal oxide semiconductor fine particles 2B, for example, PT-301, CR-EL, ET-500W, ET-600W, and ST- manufactured by Ishihara Sangyo Co., Ltd. 41 (above, trade name), G-1, G-2, and F-10 (above, trade name) manufactured by Showa Denko KK, JR (trade name) manufactured by Teika Corporation, Fuji Titanium Industry Co., Ltd. ) TA-100, TA-200, TA-300, TA-500 (above, trade name), etc. 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. Alternatively, a product having a predetermined particle diameter may be produced by subjecting chloride or alkoxide to hydrolysis or hydrothermal treatment by a known method such as a sol-gel method.

  In order to produce the semiconductor electrode layer 21, first, the first granular fine particles 2A, the second granular fine particles 2B, and the acicular fine particles 3 constituting the metal oxide semiconductor fine particles 2 and 3 are respectively prepared in an appropriate organic solvent. To prepare three paste dispersions. Next, the above three dispersions are mixed at a predetermined ratio, and the first compound and the second compound are added to this, and dissolved by stirring to obtain a uniform coating solution. Others are the same as in the first embodiment.

[Embodiment 3]
In Embodiment 3, as an example of the semiconductor electrode layer described in claims 10 to 12 and the electrochemical device described in claims 18 to 20, an electrochemical device configured as a dye-sensitized solar cell will be described. .

  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 composed of the semiconductor electrode layer (metal oxide semiconductor porous layer) 1 or 21 such as titanium oxide TiO ₂ described in the first or second embodiment, and is subjected to metal oxidation. The photosensitizing dye is held on the surface of the physical semiconductor fine particles 2 and 3. Since the electrochemical device 30 has the semiconductor electrode layer 33 as an electrode, the electrochemical device 30 is an electrochemical device that can be manufactured lightly, inexpensively and with high productivity using a flexible plastic film or the like as a support. In addition, since the semiconductor electrode layer 33 has improved conductivity compared to the semiconductor electrode layer that does not contain the acicular metal oxide semiconductor fine particles 3, photoelectric conversion when a dye-sensitized solar cell is configured. Performance is improved. Furthermore, the acicular metal oxide semiconductor fine particles 3 have a light diffusion function. For this reason, the utilization factor of incident light is improved, and this also improves the photoelectric conversion performance.

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 has a redox species (such as I ⁻ / I ₃ ⁻ (triiodide ion I ₃ ⁻ is a chemical species in which I ₂ is combined with iodide ion I ⁻ )). The electrolyte solution includes a redox pair) and is disposed between the semiconductor electrode layer 33 and the counter electrode 35 so that the electrolyte solution can infiltrate into the semiconductor electrode layer 33. 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 produce the dye-sensitized solar cell 30, the semiconductor electrode layer 1 or 21 is formed on the transparent conductive layer 32 provided on the transparent substrate 31 as described in the first embodiment. Next, the photosensitizing dye is adsorbed on the semiconductor electrode layer 1 or 21 to form the semiconductor electrode 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 semiconductor electrode layer 1 or 21 is formed is immersed in the dye solution, or the semiconductor electrode After the dye solution is soaked into the semiconductor electrode layer 1 or 21 by applying, spraying, or dropping the dye solution onto the layer 1 or 21, 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 semiconductor electrode 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 surface area is preferably 10 times or more with respect to the area (projected area) of the outer surface, and more preferably 100 times or more.

  Generally, as the thickness of the semiconductor electrode layer 33 increases and the number of metal oxide semiconductor fine particles 2 and 3 contained per unit projected area increases, the actual surface area increases, and the amount of dye that can be retained per unit projected area increases. Since it increases, 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.

  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 main points will be described below.

  The photosensitizing dye to be held in the semiconductor electrode layer 33 is not particularly limited as long as it exhibits a sensitizing action. For example, xanthene dyes such as rhodamine B, rose bengal, eosin and erythrosine, merocyanine and quinocyanine Cyanine dyes such as cryptocyanine, basic dyes such as phenosafranine, cabrio blue, thiocin and methylene blue, other azo dyes, porphyrin compounds such as chlorophyll, zinc porphyrin and magnesium porphyrin, phthalocyanine compounds, coumarin compounds, ruthenium Examples include Ru bipyridine complexes, terpyridine complexes, anthraquinone dyes, polycyclic quinone dyes, and squarylium dyes. 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 34, 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 30 and the volatilization of the solvent constituting the electrolyte, a gelling agent, a polymer, a crosslinking monomer, or various shapes of metal oxides are added to the electrolyte composition. Semiconductor 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.

  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 33 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 also possible to perform heating and pressurizing operations as necessary so that the electrolyte solution of the electrolyte layer 34 sufficiently penetrates into the semiconductor electrode layer 33.

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

  In this example, first, the semiconductor electrode layer 21 described in the second embodiment was manufactured, and the characteristics were examined.

<Preparation of coating liquid>
As the first granular fine particles 2A and the second granular fine particles 2B which are the granular metal oxide semiconductor fine particles 2, two types of titanium oxide TiO ₂ fine particles having a spherical shape and different sizes were used. As the first granular fine particles 2A, P25 (trade name; manufactured by Degussa, a mixture of anatase type crystal (80%) and rutile type crystal (20%), average particle size of primary particles is about 21 nm) was used. This fine particle powder is mixed with ethanol so that the titanium oxide content is 30% by mass, and using a zirconia bead with a diameter of 0.65 mm, the beads are dispersed for 15 hours with a paint shaker or 3 hours with an agitator. And a dispersion of the first granular titanium oxide fine particles 2A was prepared. Further, 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 as the second granular fine particles 2B. This fine particle powder is mixed with ethanol so that the titanium oxide content is 20% by mass, and is subjected to a bead dispersion treatment with an agitator for 24 hours using zirconia beads having a diameter of 0.65 mm, and the second granular oxidation. A dispersion of titanium fine particles 2B was prepared.

On the other hand, acicular titanium oxide TiO ₂ fine particles were used as the acicular metal oxide semiconductor fine particles 3. As acicular titanium oxide fine particles, FTL-100 (trade name; manufactured by Ishihara Sangyo Co., Ltd., rutile crystal, average diameter of primary particles is about 0.13 μm, average length is about 1.68 μm), FTL-200 ( Product name: manufactured by Ishihara Sangyo Co., Ltd., rutile crystals, average primary particle diameter of about 0.21 μm, average length of about 2.86 μm, and FTL-300 (trade name; manufactured by Ishihara Sangyo Co., Ltd., rutile type) The average diameter of crystals and primary particles was about 0.27 μm, and the average length was about 5.15 μm. Any one of these powders is mixed with ethanol so that the titanium oxide content is 20% by mass, and zirconia beads having a diameter of 0.65 mm are used for 3 hours or 24 hours with a paint shaker. The dispersion process was performed and the dispersion liquid of the acicular metal oxide semiconductor fine particle 3 was prepared.

  Next, each fine particle dispersion was mixed in a predetermined ratio. Next, a predetermined amount of the first compound and the second compound are added to the dispersion, and the mixture is stirred and mixed uniformly, a solvent is added to adjust the concentration, and the titanium oxide fine particles 2A, 2B and 3; A coating solution containing the first compound and the second 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, in all examples and comparative examples, butoxy titanium dimer (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used as the first compound, and the blending amount in the coating liquid was kept constant at 2.5% by mass. Moreover, pentabtonoxy niobium (manufactured by Gelest) was used as the second compound, and the blending amount in the coating liquid was kept constant at 1.0% by mass. As a solvent, ethanol was used in all examples.

  Table 1 is a table showing the blending amounts of the granular titanium oxide fine particles 2A and 2B and the acicular titanium oxide fine particles 3 in the coating liquids according to Examples 1 to 9 and Comparative Examples 1 and 2. In the column of the dispersion time in the table, the time is abbreviated as h, and in parentheses, P is added when a paint shaker is used, and A is added when an agitator is used.

<Preparation of semiconductor electrode layer (metal oxide semiconductor porous layer)>
As the support 6, a PET film O300E (trade name; manufactured by Mitsubishi Resin Co., Ltd.) having a thickness of 125 μm was used. The coating liquid was applied onto the support 6 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.

<Evaluation method>
(Presence or absence of cracks in the semiconductor electrode layer)
The presence or absence of cracks in the semiconductor electrode layer 21 was evaluated using a digital microscope VHX-100 (trade name; manufactured by Keyence Co., Ltd.) by observing the surface of the semiconductor electrode layer at 10 to 150 magnifications at a magnification of 150 to 750 times. .

(Evaluation of internal HAZE and total light transmittance of semiconductor electrode layer)
The internal HAZE of the semiconductor electrode layer is obtained by attaching a PET film O300E (trade name; manufactured by Mitsubishi Plastics) to the surface of the semiconductor electrode layer through a transparent adhesive sheet, and HM-150 (trade name; Murakami Color Technology Co., Ltd.). Evaluation was performed according to JIS K7136. The total light transmittance of the semiconductor electrode layer was evaluated according to JIS K7361 using HM-150 (trade name; manufactured by Murakami Color Research Laboratory Co., Ltd.).

(hardness)
The hardness of the semiconductor electrode layer was evaluated by a 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 of the semiconductor electrode layer was vigorously rubbed once in one direction at a length of about 5 cm, and evaluated according to the following criteria.
○: No scratch △: 10 or less scratches ×: 11 or more scratches

(Adhesion characteristics)
The adhesion characteristics of the semiconductor electrode layer are as follows. A PET film on which the semiconductor electrode layer is formed is attached to a glass plate via an adhesive sheet, and this is used as a test piece, and a grid of JIS K5400 (1 mm interval × 100 mass) cellophane tape. CT24 (trade name; manufactured by Nichiban Co., Ltd.) was evaluated by a peel test.

(Confirm that there are no residual organic substances 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 any of Examples 1 to 9 and Comparative Examples 1 to 5, 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.

  Table 2 is a table showing the presence / absence of cracks, internal haze, total light transmittance, hardness (Martens hardness and rubbing test results), and adhesion characteristics in the semiconductor electrode layers according to Examples 1 to 9 and Comparative Examples 1 and 2.

  As shown in Tables 1 and 2, the semiconductor electrode layers according to Examples 1 to 5 in which the first granular fine particles 2A were dispersed for 15 hours using a paint shaker had good adhesion. In contrast, in the semiconductor electrode layers according to Examples 6 to 8 and Comparative Examples 1 and 2 in which the dispersion treatment of the first granular fine particles 2A was performed for 3 hours using an agitator, the adhesion was poor. This is because the paint shaker is superior in the action of dispersing the particulate fine particles than the agitator, and the dispersion process is performed for a longer time. Therefore, Examples 1 to 5 are compared with Examples 6 to 8 and the comparison. This is probably because the dispersion of the first particulate fine particles 2A progressed more than in Examples 1 and 2, and as a result, a denser semiconductor electrode layer (metal oxide semiconductor porous layer) was formed. The fact that the Martens hardness of the semiconductor electrode layers according to Examples 1 to 5 is an order of magnitude larger than the Martens hardness of the semiconductor electrode layers according to Examples 6 to 8 and Comparative Examples 1 and 2 also indicates the same thing. .

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

<Preparation of dye-sensitized solar cell>
(1) The coating liquid described above was applied on a conductive glass substrate with FTO layer (manufactured by Nippon Sheet Glass Co., Ltd., surface resistance 13Ω / □) by a coil barber coating method, and then the solvent was evaporated at 80 ° C. for 2 minutes. . Next, an unnecessary part was scraped off from the obtained semiconductor fine particle layer using an edge of a glass plate and formed into a square having a size of 5 mm × 5 mm, and then fired at 150 ° C. for 30 minutes to produce a semiconductor electrode layer. .
(2) Next, the semiconductor electrode layer was immersed in a Z907 dye solution or a D358 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) (see the above-mentioned document). D358 dye solution is a solution obtained by dissolving D358 dye (trade name; manufactured by Mitsubishi Paper Industries Co., Ltd.) in a mixed solvent in which acetonitrile and tert-butyl alcohol are mixed at a volume ratio of 1: 1 at a concentration of 0.5 mM. It is. Next, the semiconductor electrode was washed with acetonitrile, and then the acetonitrile was spontaneously evaporated to dry the semiconductor electrode.
(3) On the other hand, the counter electrode was 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 sputtering.
(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 phenomenon to produce a dye-sensitized solar cell 30. 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>
(Thickness of semiconductor electrode layer)
The thickness of the semiconductor electrode layer is obtained by scraping a part of the electrode layer from the support 6 at the edge of the glass plate, and measuring the step from the surface of the semiconductor electrode layer to the FTO surface with a stylus type surface roughness measuring instrument Surfcoder ET4000 (product) Name: Obtained by measurement using Kosaka Laboratory Co., Ltd.

(Photoelectric conversion efficiency)
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, the short-circuit current, open-circuit voltage of the produced dye-sensitized solar cell, The fill factor and photoelectric conversion efficiency were evaluated at 24 ° C.

  Table 3 is a table showing the thickness of the semiconductor electrode layer and the photoelectric conversion efficiency in the dye-sensitized solar cells produced in Examples 1 to 9 and Comparative Examples 1 and 2. Table 3 shows the average value of the evaluation results of N = 3.

  From Table 1 and Table 3, the photoelectric conversion efficiency of the dye-sensitized solar cell using the Z907 dye is Comparative Examples 1 and 2 that do not contain the acicular fine particles 3 in Examples 1 to 9 containing the acicular fine particles 3. It can be seen that it is excellent in most cases and at least equal or better. In Examples 1 to 9, the ratio of the blending mass of the needle-shaped fine particles 3 to the blending mass of the granular microparticles is 0.05 to 0.25. Further, the conversion efficiency is 2.1% or more in Examples 1 to 3 and Examples 6 to 9 in which the content of the acicular fine particles 3 is 10% of the total mass of the titanium oxide fine particles, whereas the content is In Example 4 where 5% is 20%, and in Example 5 where 20% is 20%, it is 2.0% or less. This indicates that the content of the acicular fine particles 3 has an optimum value, which is about 10% of the total mass of the titanium oxide fine particles.

<Evaluation of local resistance value by AC impedance measurement>
The AC impedance of the dye-sensitized solar cell was measured in a frequency range of 0.1 to 100000 Hz using a Schlumberger SI 1260 impedance / gain-phase analyzer (trade name; manufactured by Solartron Analytical).

FIG. 5 shows a dye-sensitized solar cell using the semiconductor electrode layer 33 containing FTL300 as the acicular fine particles 3 according to Examples 6 to 8 and a dye not containing the acicular fine particles 3 according to Comparative Example 2. It is a Cole-Cole plot (Nyquist plot) figure which shows the result of having measured the alternating current impedance of the sensitized solar cell. In addition, the symbol in a figure respond | corresponds to the following dye-sensitized solar cell.
●: Dye-sensitized solar cell according to Example 6 ■: Dye-sensitized solar cell according to Example 7 ◆: Dye-sensitized solar cell according to Example 8 Δ: Dye-sensitized solar cell according to Comparative Example 2

  In the Cole-Cole plot (Nyquist plot) diagram of FIG. 5, the magnitude of the interfacial resistance between the titanium oxide fine particles is reflected in the peak value of the imaginary part that appears in the vicinity of the real part 25Ω (Toyohisa Hoshikawa et al., “AC impedance "Establishment of evaluation method of dye-sensitized solar cell using the method", Ceramics, 39 (2004), p.455-458). According to FIG. 5, in the dye-sensitized solar cell according to Comparative Example 2, the peak value of the imaginary part of about 11Ω appears in the vicinity of the real part of about 25Ω. In contrast, in the dye-sensitized solar cells according to Examples 6 to 8, the imaginary part peak value of about 7 to 9 Ω appears in the vicinity of the real part of about 20 to 23 Ω, and the imaginary part peak value is shifted to the lower left. . This is because when the acicular fine particles 3 are contained in the semiconductor electrode layer, a conductive path having a small internal resistance is formed in the semiconductor electrode layer 33 using the intra-fine particle conducting path of the acicular fine particles 3, and between the titanium oxide fine particles. This is considered to indicate that the interfacial resistance decreases. As shown in Table 3, the photoelectric conversion efficiencies of the dye-sensitized solar cells according to Examples 6 to 8 tend to be higher than the photoelectric conversion efficiency of the dye-sensitized solar cell according to Comparative Example 2. This is a result reflecting the result of AC impedance measurement.

  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 ... Granular metal oxide semiconductor fine particle, 2A ... 1st granular fine particle,
2B ... 2nd granular fine particle, 3 ... Acicular metal oxide semiconductor fine particle, 4 ... 1st oxide layer,
5 ... 2nd oxide layer, 6 ... Support, 7 ... Adhesion auxiliary layer, 21 ... Semiconductor electrode layer,
30 ... Photosensitized 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,
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), 105 ... Counter electrode (positive electrode), 105a ... Conductive layer,
105b ... platinum layer, 106 ... counter substrate

Japanese Patent No. 3671183 (pages 3-8 and 10-14, FIG. 2) JP 2008-115055 (Claim 1, pages 4-6 and 7-10, 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 including fine particles having at least two shapes, granular fine particles and acicular fine particles, and disposed on a support;
A first oxide layer that is mainly directly bonded to the metal oxide semiconductor fine particles and the support;
The second oxide is harder than the first oxide forming the first oxide layer, and the metal oxide semiconductor fine particles and the support mainly through the first oxide layer. A second oxide layer bound to the body, and the first oxide layer and the second oxide layer, and between the metal oxide semiconductor fine particles and between the metal oxide semiconductor fine particles and the A semiconductor electrode layer formed by binding with a support.   The semiconductor electrode layer according to claim 1, wherein an average diameter of primary particles of the acicular metal oxide semiconductor fine particles is 0.1 to 1 µm and an average length is 1 to 10 µm.   2. The semiconductor electrode layer according to claim 1, wherein a ratio of a mixing mass of the acicular metal oxide semiconductor fine particles to a mixing mass of the granular metal oxide semiconductor fine particles is 0.05 to 0.25.   The granular metal oxide semiconductor fine particles are first granular fine particles having an average primary particle size of 100 nm or less, and second granular fine particles having an average primary particle size of more than 100 nm and 10,000 nm or less. The semiconductor electrode layer according to claim 1, comprising granular fine particles having at least two kinds of sizes.   The semiconductor electrode layer according to claim 4, wherein a ratio of a blending mass of the second particulate fine particles to a blending mass of the first particulate particulates is 0.06 to 6. 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, wherein the element constituting the first oxide layer is the same element as the metal element constituting the metal oxide semiconductor fine particles. The oxide constituting the second oxide layer having high hardness was 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 . The semiconductor electrode layer according to claim 1, wherein the semiconductor electrode layer is at least one oxide.   The semiconductor electrode layer according to claim 1, wherein a material of the support is a plastic material.   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 10, wherein the support is a light-transmitting support having a light-transmitting conductive layer provided on one surface, and is provided in contact with the light-transmitting conductive layer. .   The semiconductor electrode layer according to claim 10, 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. . Metal oxide semiconductor fine particles including fine particles of at least two types of granular fine particles and acicular fine particles;
A first compound that yields a first oxide upon hydrolysis;
A coating liquid obtained by dispersing or dissolving in a organic solvent a second compound that produces a second oxide that is harder to hydrolyze than the first compound and that has a higher hardness than the first oxide when hydrolyzed. A step of preparing;
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;
Metal oxide semiconductor porous material 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 method for producing a semiconductor electrode layer, wherein a layer is produced.   The method for producing a semiconductor electrode layer according to claim 13, wherein a salt or an alkoxide is used as the first compound.   The first compound is a compound of at least one element selected from the group consisting of titanium Ti, aluminum Al, silicon Si, vanadium V, zirconium Zr, niobium Nb, and tantalum Ta. Semiconductor electrode layer manufacturing method.   As the first compound, 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 entirely hydrolyzed in the coating solution, A method for producing a semiconductor electrode layer according to claim 13.   The method for producing a semiconductor electrode layer according to claim 13, 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 second compound.   An electrochemical device comprising at least the semiconductor electrode layer according to any one of claims 1 to 12, 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 a reducing species (reducing agent) in the electrolyte layer. As a result, the oxidizing species (oxidizing agent) generated in the electrolyte layer receives electrons from the counter electrode and is reduced. The electrochemical device according to claim 18, which is configured as a dye-sensitized solar cell.   The electrochemical device according to claim 19, wherein the semiconductor electrode layer is the semiconductor electrode layer according to claim 11.

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