JP2005104760A - Metal oxide structure containing titanium oxide, method for producing the same, and use of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a titanium oxide structure high in a sensitizing dye adsorption, smooth in electron transfer, high in a photoelectric conversion efficiency, and suitable for use in solar cells and to provide a method for producing a metal oxide structure. <P>SOLUTION: The metal oxide structure is a titanium oxide structure having a BG of 2.7 to 3.1 eV (wherein BG is an optical band gap as calculated from an absoptivity measured with an integrating sphere spectrophotometer) or is a metal oxide structure prepared by dry-blending a plurality of metal oxide powders with different particle sizes or a dispersion thereof and satisfying BG0-BG1 of 0.01 to 0.45 eV (wherein BG0 is the BG of a starting metal oxide, and BG1 is the BG of the metal oxide after the dry blending). A dye-sensitized solar cell containing the metal oxide dispersion as a dye-sensitized electrode and a method for producing the same are also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a metal oxide structure containing titanium oxide suitable for solar cell applications and the like.

Silicon solar cells are the main current solar cells, but new types of solar cells have been researched and developed from the viewpoints of the use of harmful raw materials and high-cost manufacturing methods.
Dye-sensitized solar cells are one of them, and since being reported by Gretzell et al. Of Lausanne Institute of Technology in 1991 (see, for example, Non-Patent Document 1), research and development have been promoted as solar cells replacing silicon types. .

  A general dye-sensitized solar cell has a structure as shown in FIG. 1 and is composed of three parts: a dye electrode, an electrolytic layer, and a counter electrode. Here, the dye electrode 6 refers to an electrode such as conductive glass in which a metal oxide layer such as titanium oxide is bonded to an electrode substrate, and a counter electrode 7 is electrically conductive. An electrode in which a catalyst layer such as platinum or graphite is formed on an electrode substrate such as porous glass. The electrolytic layer 4 is a portion in which the electrolyte is dissolved and is sandwiched between the dye electrode and the counter electrode. The electrode substrate as used herein refers to a substrate obtained by applying FTO, ITO or the like to an electrode base material such as glass or organic polymer and drying it.

The photoelectric conversion mechanism is described as follows.
First, the sensitizing dye absorbs light and generates electrons and holes. The generated electrons reach the electrode substrate through the metal oxide layer and are extracted to the outside. On the other hand, the generated holes are carried to the counter electrode through the electrolytic layer, and are combined with the electrons supplied through the electrode substrate.
As an index indicating the characteristics of the dye-sensitized solar cell, there is a photoelectric conversion efficiency represented by the following formula: η (%) = Jsc × Voc × FF / incident light energy × 100
(Where η is the photoelectric conversion efficiency, Jsc is the short-circuit current density [mA / cm ² ], Voc is the open circuit voltage [V], and FF is the fill factor [−]. The incident light energy is the incident light per unit area. Energy [mW / cm ² ] is indicated.)

The photoelectric conversion efficiency η depends on the performance of the dye electrode. Factors that enhance the performance of the dye electrode include increasing the surface area per unit of metal oxide to increase the amount of sensitizing dye supported and increasing the amount of generated electrons, and increasing the necking of metal oxide particles to facilitate electron transfer. And so on. The term “particle necking” as used herein represents a structure as shown in FIG. 2 and is distinguished from a point contact structure between particles.
Hereinafter, titanium oxide will be described as an example of the metal oxide.

  As a method for increasing the surface area per unit of the metal oxide, a method using titanium oxide having a pore inner diameter of 3 to 10 nm (for example, see Patent Document 1) is described. In this method, a sol prepared from titanium tetrachloride is heated and dried to obtain titanium oxide particles. However, liquid phase titanium oxide obtained by hydrolyzing titanium tetrachloride or the like has a problem that the necking structure is small because the thermal history during synthesis is low.

  In order to increase the necking of metal oxide particles, a method in which a titanium oxide layer is formed on a substrate such as conductive glass and then treated with titanium tetrachloride has been proposed (see, for example, Non-Patent Document 2). Here, titanium tetrachloride has a function of reacting with titanium oxide particles to form new bonds and necking the particles. However, although such titanium tetrachloride treatment increases necking, there is a problem that the crystallinity of the surface of the titanium oxide particles is reduced or lattice defects are generated. When the crystallinity is low or lattice defects are present, the conduction band energy level of titanium oxide is lowered, so that the open-circuit voltage when the solar cell is formed is lowered, and the photoelectric conversion efficiency is lowered.

  As another electron transfer promoting method, there is a method of increasing the packing density of particles by mixing particle groups having different particle sizes. For example, a method using a group of semiconductor particles having a plurality of peaks in the particle size distribution has been proposed (see, for example, Patent Document 2). However, the efficiency of electron transfer is worse than that of the necking structure because it merely mixes a plurality of particle groups and only increases the point contact between the particles.

JP 2001-283942 A JP 2001-357899 A International Publication No. 01/16027 Pamphlet JP-A-6-304423 Japanese Patent Publication No.36-3359 M.M. Graezel, Nature, 353, 737, (1991) For example, C.I. J. et al. Barbe et al. , J .; Am. Ceram. Soc. , 80, 3157 (1997)) Manabu Seino, “Titanium Oxide”, Gihodo Co., Ltd., p. 129, (1991) L. D. Hart and L. K. Hadson, The American Ceramic Society Bulletin, 43, no. 1, (1964)) Edited by Kazuhito Hashimoto and Akira Fujishima, “All about Titanium Oxide Photocatalyst” CMC, Inc. (1998) “Advanced high-performance materials (6th electromagnetic functional material 2. Battery characteristic material)”, NGT Corporation, p. 439-447, 2001

  The present invention has been made to solve the above problems, and the problem of the present invention is that it is suitable for a solar cell having a high photoelectric conversion efficiency in which a large amount of sensitizing dye is adsorbed and electrons are smoothly transferred. Another object of the present invention is to provide a method for manufacturing a titanium oxide structure and a metal oxide structure.

As a result of intensive studies in view of the above problems, the present inventors have found a method capable of producing a metal oxide structure having a large surface area per unit mass and in which particles are necked, and solve the above problems. It came to.
That is, the present invention
[1] An optical band gap (hereinafter referred to as BG) calculated from absorbance by an integrating sphere spectrophotometer is 2.7 eV or more and 3.1 eV or less, and a tap density is 0.15 g / cm ³ or more. A titanium oxide structure characterized by being 0.45 g / cm ³ or less,
[2] A metal oxide structure obtained by dry-mixing a plurality of metal oxide powders having different particle sizes, wherein BG of the raw metal oxide is BG0, and BG of the metal oxide after dry-mixing is BG1, A metal oxide structure in which BG0-BG1 is 0.01 eV or more and 0.45 eV or less.

[3] A method for producing a metal oxide structure in which metal oxides are dry-mixed, and BG0-BG1 when BG of the raw metal oxide is BG0 and BG of the metal oxide after dry-mixing is BG1 A method for producing a metal oxide structure that is mixed so as to be 0.01 eV or more and 0.45 eV or less,
[4] The production of the metal oxide structure according to the above [3], wherein the dry mixing is a method selected from at least one of a ball mill, a high-speed rotary pulverizer, a stirring mill, and a jet pulverizer. Method,
[5] Dry mixing is performed by a ball mill, and the energy constant k1 in the dry mixing is such that the total mass of the powder to be mixed is wp (g), the media mass is wm (g), the inner diameter of the ball mill container is d (m), and rotation. When the number is n (rpm) and the mixing time is t (minutes),
k1 = wm / wp × d × n × t
The method for producing a metal oxide structure according to the above [3], wherein k1 represented by the relationship is 3,000 or more and 250,000 or less,
[6] The method for producing a metal oxide structure according to [3], wherein the energy constant k1 is 10,000 or more and 150,000 or less,
[7] The method for producing a metal oxide structure according to [3], wherein the energy constant k1 is 10,000 or more and 50,000 or less,

[8] The metal oxide powder (hereinafter referred to as particle group A) in which the raw metal oxide is in the range of 100 to 500 nm in average primary particle diameter converted from the specific surface area by the BET method, and the average primary particle diameter is The metal oxide structure according to any one of the above [3] to [7], comprising a metal oxide powder (hereinafter referred to as particle group B) in a range of 10 to 40 nm. Production method,
[9] Particle group B has a metal oxide powder (hereinafter referred to as particle group C) having an average primary particle diameter converted from a specific surface area by the BET method of 20 to 40 nm and a metal oxide powder (hereinafter referred to as particle group C). , Referred to as particle group D), and the method for producing a metal oxide structure according to [8] above,
[10] The method for producing a metal oxide structure according to the above [8] or [9], wherein the particle group B has an average specific surface area of 60 m ² / g or more and 110 m ² / g or less,
[11] The method for producing a metal oxide structure according to any one of the above [8] to [10], wherein at least one of the particle groups A to D is a metal oxide synthesized by a vapor phase method,
[12] The method for producing a metal oxide structure according to any one of the above [3] to [11], wherein the tap density is 0.15 g / cm ³ or more and 1.0 g / cm ³ or less,

[13] The method for producing a titanium oxide structure according to any one of [3] to [12], wherein the metal oxide is titanium oxide,
[14] The metal oxide is a mixture of titanium oxide and at least one metal oxide selected from zinc oxide, niobium oxide, tantalum oxide, zirconium oxide, tin oxide, and tungsten oxide. The method for producing a metal oxide structure according to any one of the above [3] to [12],
[15] The method for producing a metal oxide structure according to the above [14], wherein the content of titanium oxide contained in the metal oxide mixture is 10% by mass or more,

[16] Dispersed in the titanium oxide structure of [1] or the metal oxide structure of [2] or the metal oxide structure obtained by the production method according to any of [3] to [15] This is a method for producing a metal oxide structure dispersion by adding a medium and performing wet mixing in a ball mill, where the energy constant k2 in the wet mixing is the total mass of the powder to be mixed, wp (g), and the media mass When wm (g), the ball mill container inner diameter is d (m), the rotation speed is n (rpm), and the mixing time is t (minutes),
k2 = wm / wp × d × n × t
The relationship between k2 expressed by the relationship and the energy constant k1 in dry mixing is
k2 ≧ k1
A method for producing a metal oxide dispersion characterized by being represented by:
[17] The relationship between the energy constant k2 in the wet mixing and the energy constant k1 in the dry mixing is
8.0 × k1 ≧ k2 ≧ 1.5 × k1
The method for producing a metal oxide dispersion according to the above [16], characterized by being represented by:
[18] The relationship between the energy constant k2 in wet mixing and the energy constant k1 in dry mixing is
5.0 × k1 ≧ k2 ≧ 2.5 × k1
The method for producing a metal oxide dispersion according to the above [16], characterized by being represented by:
[19] A metal oxide dispersion containing titanium oxide obtained by the production method according to any one of [16] to [18],

[20] The titanium oxide structure according to [1] or the metal oxide structure according to [2], or the metal oxide structure obtained by the production method according to any one of [3] to [15]. Or a composition comprising a metal oxide dispersion containing titanium oxide according to [19] above,
[21] The titanium oxide structure according to [1] or the metal oxide structure according to [2], or the metal oxide structure obtained by the production method according to any one of [3] to [15] Or a thin film containing a metal oxide dispersion containing titanium oxide according to [19] above,
[22] The thin film containing the metal oxide structure according to [21], wherein the film thickness is 1 μm or more and 40 μm or less,

[23] A method for producing a dye-sensitized solar cell comprising the metal oxide structure according to any one of [3] to [15] as a dye-sensitized electrode,
[24] The dye-sensitized electrode includes the metal oxide structure according to any one of [3] to [15] and the metal oxide dispersion according to any one of [17] to [19]. Method for producing dye-sensitized solar cell,
[25] A dye-sensitized solar cell produced by the production method of [23] or [24] above,
[26] A dye-sensitized solar cell including a dye electrode having a thin film containing the metal oxide structure according to [22] as a constituent element,
[27] A dye-sensitized solar cell, wherein BG of titanium oxide after removing the dye from the dye electrode is 2.7 to 3.1 eV,

[28] An article having a power generation function, comprising the dye-sensitized solar cell according to any one of [25] to [27],
[29] An article having a light emitting function, comprising the dye-sensitized solar cell according to any one of [25] to [27],
[30] An article having a heat generating function, comprising the dye-sensitized solar cell according to any one of [25] to [27],
[31] An article having a sound generating function, comprising the dye-sensitized solar cell according to any one of [25] to [27],
[32] An article having a movement function, comprising the dye-sensitized solar cell according to any one of [25] to [27],
By solving this problem, the above problems were solved.

According to the present invention, there are provided a metal oxide structure having a large amount of sensitizing dye adsorption and capable of facilitating electron transfer, and a method for producing them.
According to the metal oxide structure of the present invention, a dye-sensitized solar cell having high photoelectric conversion efficiency can be obtained, and the present invention has industrially practical value.

The metal oxide structure of the present invention is a structure including a microstructure of metal oxide particles. That is, the metal oxide structure of the present invention is a structure characterized by including a necking structure (partial surface contact structure) between particles.
The metal oxide structure of the present invention has a metal oxide powder (referred to as particle group A) having an average primary particle diameter in the range of 100 to 500 nm converted from a specific surface area according to the BET method, and an average primary particle diameter of 10. It is obtained by dry-mixing metal oxide powder (referred to as particle group B) in the range of ˜40 nm. Dry mixing here means a method of mixing without using a dispersion medium such as water or an organic solvent. In wet mixing using a dispersion medium, energy generated by collision, friction, etc. is diffused not only in the particles but also in the dispersion medium, so that a mechanochemical reaction hardly occurs. The important point is to advance the mechanochemical reaction by dry mixing and neck the particles.

  In the state where the particle group A and the particle group B are simply mixed, there is only a point contact portion between the particles, so that the electrons are compared with a particle structure having a necking structure (partial surface contact structure) as shown in FIG. The efficiency of movement is poor. In order to facilitate electron transfer, it is important that the particles have a necking structure.

  A so-called liquid phase metal oxide obtained by hydrolyzing a metal halide or the like in a wet manner has a low thermal history during synthesis and has a low necking structure as it is, so that the electron transfer efficiency is poor. On the other hand, metal oxide particles obtained by a so-called gas phase method in which a metal halide or the like is reacted with an oxidizing gas such as oxygen at a high temperature has high crystallinity due to a high thermal history during synthesis, and has a necking bond. It has a structure that facilitates electron transfer and is advantageous for diffusion of the electrolyte. Although there is no particular limitation on the production method of this vapor phase method, for example, in the case of titanium oxide, it can be synthesized by the methods of Patent Document 3, Patent Document 4, Patent Document 5, and the like.

In the production method of the present invention, it is preferable that the metal oxide constituting the metal oxide structure has at least one particle group obtained by a vapor phase method. As described above, the vapor phase metal oxide itself has a necking structure to some extent, and in this structure, electron transfer is easy to some extent. In order to further promote the electron transfer, the number of particles having a necking structure may be further increased, and it can be said that adoption of a mechanochemical reaction by dry mixing is more effective.
The gas phase method is preferable as the metal oxide structure of the present invention when used as the particle group A or the particle group B because a powder having a relatively narrow particle size distribution of primary particles is obtained as compared with other production methods. Easy to obtain primary particle size distribution.

  In the production method of the present invention, the particle group A constituting the metal oxide structure mainly has a function of scattering light rays that have entered the inside of the solar cell inside the cell, thereby increasing the light absorption efficiency. Since dye-sensitized solar cells absorb light from the ultraviolet to the near-infrared region and generate electrons, scattering light from the ultraviolet to the near-infrared region inside the solar cell causes the probability of light absorption by the sensitizing dye Will increase. In general, light scattering is maximized when the particle diameter is about ½ of the light wavelength, and it is said that light scattering is weakened when the particle diameter deviates from that (Non-Patent Document 3). In order to scatter ultraviolet rays to near-infrared rays, the average primary particle size is desirably in the range of 100 nm to 500 nm, and the particle size can be selected in accordance with the wavelength of the light rays to be scattered.

The particle group B carries a sensitizing dye and has a role of transmitting electrons generated by the sensitizing dye. The sensitizing dye is supported on the metal oxide by a chemical bond with a surface hydroxyl group of the metal oxide or a metal atom (hereinafter referred to as a dye bonding portion), and moves electrons to the metal oxide through the bond. . Therefore, as the amount of the sensitizing dye bonded to the metal oxide increases, the number of electron transfer increases. It is known that the surface of metal oxide, for example, titanium oxide particles has 9 to 14 surface hydroxyl groups / nm ² (Non-patent Document 3, Kiyono “Titanium oxide”, p. 54, 55), Titanium oxide having a higher specific surface area has more dye binding portions. The specific surface area of the particle group B suitable for the solar cell is about 40 m ² / g to about 150 m ² / g, preferably about 60 m ² / g or more and about 110 m ² / g or less.

  In the case of titanium oxide, the average primary particle size is about 10 nm to about 40 nm, preferably about 13 nm to about 25 nm. Particle groups having an average primary particle size of less than about 10 nm are generally not suitable for solar cell applications because they have low crystallinity and electron transfer is not performed smoothly. This low crystallinity is attributed to a low thermal history in order to suppress particle growth during the synthesis. A group of particles having an average primary particle size larger than about 40 nm has a small specific surface area and an insufficient amount of dye adsorption. The mixing ratio of the particle group A and the particle group B is A / B = 5/95 to 30/70, preferably A / B = 10/90 to 20/80 in terms of mass ratio.

For smooth electron transfer, the particles should have a necking structure and be packed closely, and a method of combining particle groups having different average particle diameters is convenient for increasing the packing density. In particular, the particle group B classified as ultrafine particles may be the same (single particle group), but since the packing density is often low, it is better to increase the packing density by combining different diameter particle groups. Results are obtained. The average primary particle size of each particle group serving as the base of the combination is preferably selected from a particle size range suitable for the particle group B described above, and the particle group C having an average primary particle size of 20 to 40 nm and the average primary particle size. A combination of particle groups D having a particle size of 10 to 20 nm is preferable. The compounding ratio of the particle group C and the particle group D is a mass ratio, and is C / D = 10 / 90-80 / 20, preferably C / D = 15 / 85-75 / 25.
The chemical composition of the particle groups A, B, and C may be the same or different from each other.

One of the indexes indicating the particle filling state is the tap density. As the packing density increases, the value increases. The tap density is measured by the following method.
As the apparatus, a powder characteristic total measuring apparatus type PT-D manufactured by Hosokawa Micron Corporation is used. The sample is filled into a 100 cm ³ cup equipped with an auxiliary cup and tapped 100 times with a measuring device. After removing the auxiliary cup, the sample is accurately set to 100 cm ³ and the mass (g) of the sample is measured. The tap density is obtained by dividing the mass (g) of the powder by 100.
In the production method of the present invention, the tap density of the obtained metal oxide structure is preferably 0.15 g / cm ³ or more and 1.0 g / cm ³ or less. When the tap density is less than 0.15 g / cm ³ , this indicates that the packing density is insufficient. When the tap density is greater than 1.0 g / cm ³ , the metal oxide structure is used as a dispersion. It becomes difficult to disperse. The metal oxide structure dispersion having a poor dispersion state has few void portions in the metal oxide structure, and when the dye-sensitized solar cell is formed, the electrolyte is difficult to diffuse into the metal oxide layer. Insufficient electrolyte inside. If the electrolyte is insufficient, the charge transfer will not proceed smoothly.

  For dry mixing, for example, a ball mill, a high-speed rotary pulverizer, a stirring mill, a jet pulverizer, or the like is used. Any material can be used as long as it gives energy to cause a mechanochemical reaction to the particle group, but the material to be used is preferably a material that is not easily contaminated. Hereinafter, among the ball mills, a rolling ball mill will be described as an example.

The rolling ball mill is the most general mixing and pulverization method, and utilizes the collision between the powder in the container and the media, the frictional action, etc. that occur when the cylindrical container is rolled. The energy constant k in this case has been proposed as an index for unifying and evaluating the mixing and pulverization effect by the rolling ball mill (Non-Patent Document 4), and is expressed by the following equation.
k = wm / wp × d × n × t
(Wp is the total mass (g) of the powder to be mixed, wm is the media mass (g), d is the inner diameter of the ball mill container (m), n is the rotation speed (rpm), and t is the mixing time (minutes). .)

As the energy constant increases, the impact and frictional energy received by the powder increases and the mechanochemical reaction proceeds, but the agglomeration becomes intense accordingly.
In the method for producing a metal oxide structure of the present invention, k1 is desirably 3,000 or more and 250,000 or less, where k is an energy constant in dry mixing. When the energy constant k1 is lower than the lower limit, the mechanochemical reaction becomes insufficient and the particles are hardly bonded. When the energy constant k1 is higher than the upper limit, the mechanochemical reaction proceeds, but when the metal oxide structure is used as a dispersion, it is difficult to disperse and the resulting metal oxide structure has fewer voids. The reduction of the void portion adversely affects the electrolyte diffusion when the dye-sensitized solar cell is made, and the performance of the solar cell is lowered. Moreover, since an excessive mechanochemical reaction drastically lowers the conduction band energy level of the metal oxide structure, the open circuit voltage when the solar cell is formed is lowered, and the photoelectric conversion efficiency is lowered.

  Also in other mixing methods, it is desirable to adjust to a condition that gives sufficient energy to cause a mechanochemical reaction in the mixed particle group. For example, in the case of a high-speed rotary pulverizer, adjustment of the rotational speed, residence time, etc .; in the case of a stirring mill, adjustment of the stirring speed, media mass, stirring time, etc .; in the case of a jet pulverizer, the pressure of the carrier gas It is sufficient to adjust the residence time and advance the mechanochemical reaction.

As a method for detecting a mechanochemical reaction, there is a method for measuring a change in an optical band gap (hereinafter abbreviated as BG) before and after dry mixing.
It is considered that the change in BG of the metal oxide occurs because the molecular orbital near the surface of the metal oxide particle is changed by a mechanochemical reaction. Since particles having different primary particle diameters also have different lattice states on the particle surface, there is a difference in BG. When particles having different BGs are bonded to each other by a mechanochemical reaction, a new molecular orbital is generated, which becomes a value different from that of the BG before the mechanochemical reaction. In addition, the crystallinity of the particle surface is lowered, and a phenomenon in which BG changes can occur. Therefore, by measuring the BG difference before and after dry mixing (hereinafter abbreviated as ΔBG), the bonding and surface state of the particles of the particle group A and the particles of the particle group B can be defined. Here, a method for measuring BG and ΔBG will be described below.

  The relationship between wavelength and absorbance is measured using an integrating sphere spectrophotometer UV-2400, ISR-240A, etc. manufactured by Shimadzu Corporation. A tangent line is drawn with respect to the inflection point of the obtained absorbance pattern (see FIG. 3), and a point where the tangent line intersects the wavelength axis (absorption edge wavelength) is read. An example of the relationship between the absorbance pattern and the absorption edge wavelength is shown in FIG.

BG is E = 1240 / λ
(Wherein E represents BG [eV] and λ represents absorption edge wavelength [nm]), BG and absorption edge wavelength before dry mixing are represented by BG0 [eV], λ0 [nm], Further, assuming that the BG and the absorption edge wavelength after dry mixing are BG1 [eV] and λ1 [nm], respectively, the BG [eV] before and after dry mixing is BG0 = 1240 / λ0, respectively.
BG1 = 1240 / λ1
It becomes. Therefore, ΔBG [eV] before and after dry mixing is expressed by the following equation: ΔBG = BG0−BG1 = (1240 / λ0) − (1240 / λ1)
It is represented by

Generally, BG of anatase-type titanium oxide is said to be 3.2 eV (see Non-Patent Document 5), but BG tends to decrease due to mechanochemical reaction.
The same tendency to decrease BG is observed with other metal oxides or mixtures thereof.

In the production method of the present invention, ΔBG before and after dry mixing of the obtained metal oxide structure is preferably 0.01 eV or more and 0.45 eV or less. When ΔBG is smaller than 0.01 eV, it means that there are few bonds between particles, and electron transfer between particles is difficult to be performed. When ΔBG is larger than 0.45 eV, the crystallinity of the particle surface is greatly reduced, the electron transfer rate is lowered, and the conduction band energy level of the metal oxide structure is extremely lowered. The open-circuit voltage at the time of doing will fall, and photoelectric conversion efficiency will fall.
In the titanium oxide structure of the present invention, BG1 is 2.7 eV or more and 3.1 eV or less.

The metal oxide structure obtained by the production method of the present invention is dispersed in a solvent in which the metal oxide can be dispersed, such as water, ethanol, acetone, acetonitrile, ethylene carbonate, propylene carbonate, or a mixed solvent thereof. And can be used as a dispersion of a titanium oxide structure. In addition, polyethylene glycol, polyvinyl alcohol, poly N-vinylacetamide, polyacrylate, N-vinylacetamide-sodium acrylate copolymer, N-vinylacetamide-acrylamide copolymer, polyacrylamide, acrylamide- Sodium acrylate copolymer, poly N-vinylformamide, polytetrafluoroethylene, tetrafluoroethylene-polyfluorinated propylene copolymer, tetrafluoroethylene-polyfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, polyvinylidene fluoride, styrene -One of polymer compounds selected from butadiene copolymer, polyvinyl pyridine, vinyl pyridine-methyl methacrylate copolymer, polyvinyl pyrrolidone, or a mixture thereof, etc. It can also be added Indah. The binder here refers to a substance having a function of preventing cracks generated when the dispersion is applied to a substrate or the like to form a film and peeling from the substrate. Among these, polyethylene glycol, polyvinyl alcohol, poly N-vinylacetamide, polyacrylamide, polyacrylate, N-vinylacetamide-sodium acrylate copolymer, acrylamide-sodium acrylate copolymer, and polytetrafluoroethylene are included. preferable. When using a polyacrylate, alkali metals or alkaline earth metals are preferable as the salt, and sodium, lithium, potassium, ammonium, and magnesium are more preferable.
Further, the higher the molecular weight of the binder, the higher the performance. Specifically, the average molecular weight is preferably 500 or more, and more preferably 10,000 or more.

  In the method for producing a metal oxide dispersion of the present invention, when a dispersion medium is added to the resulting metal oxide structure and the energy constant when wet-mixing with a ball mill is k2, the energy constant k1 in dry mixing is It is preferable that k2 ≧ k1. More preferably, 8.0 × k1 ≧ k2 ≧ 1.5 × k1, and most preferably 5.0 × k1 ≧ k2 ≧ 2.5 × k1.

In the metal oxide structure produced by dry mixing, the metal oxide structures are also agglomerated with each other, and void portions are reduced. If the tap density of the metal oxide structure obtained by dry mixing is 0.45 g / cm ³ or less, there is no significant effect on the electrolyte diffusibility when the solar cell is formed, but 0.45 g / cm ³ If it exceeds 1, the electrolyte diffusibility decreases, which may cause a decrease in the performance of the solar cell. In order to avoid degradation of the performance of the solar cell, it is preferable to disperse the aggregation of the metal oxide structures by wet mixing. The wet mixing method is not particularly limited as long as the metal oxide and the dispersion medium are mixed and the aggregation of the metal oxide structure is solved, such as a ball mill, a high-speed rotary pulverizer, and a stirring mill. In the case of wet mixing using a ball mill, the dispersibility increases as the energy constant k2 increases, but it is empirically effective to adjust the energy constant k1 to 1.0 times or more in the dry mixing. As k2 is larger, a dispersion effect is obtained, but the upper limit is determined from an economical viewpoint.
When the tap density of the metal oxide structure after dry mixing exceeds 1.0 g / cm ³ , the metal oxide cannot be dispersed unless k2 in the wet mixing is set large, which is economically disadvantageous. It is.
The metal oxide to which the production method of the present invention can be applied includes titanium oxide or titanium oxide and at least one metal oxide selected from zinc oxide, niobium oxide, tantalum oxide, zirconium oxide, tin oxide, and tungsten oxide. And a mixture thereof.

Further, the metal oxide structure of the present invention or the above-mentioned metal oxide structure dispersion can be applied to an electrode substrate such as a conductive glass substrate and thinned to be used as an electrode for a dye solar cell. .
The electrode substrate constituting the electrode substrate of the dye-sensitized solar cell containing the metal oxide of the present invention may be glass or an organic polymer.

  Specific examples of the organic polymer include polyolefins such as polyethylene, polypropylene and polystyrene, polyamides such as nylon 6, nylon 66 and aramid, polyesters such as polyethylene terephthalate, polyethylene naphthalate and unsaturated polyester, polyvinyl chloride, and polyvinylidene chloride. , Polyethylene oxide, polyethylene glycol, silicone resin, polyvinyl alcohol, vinyl acetal resin, polyacetate, ABS resin, epoxy resin, vinyl acetate resin, cellulose and rayon and other cellulose derivatives, urethane resin, polyurethane resin, polycarbonate resin, urea resin, Fluorine resin, polyvinylidene fluoride, phenol resin, celluloid, chitin, starch sheet, acrylic resin, melamine resin, alkyl Such as resin and the like. Of these, polyethylene terephthalate and polyethylene naphthalate are preferable.

  The transparent electrode substrate can be obtained by forming a conductive oxide thin film of tin oxide, fluorine-doped tin oxide, indium oxide, zinc oxide, antimony oxide, or a mixture thereof on the above-described electrode base material. Among these, fluorine-doped tin oxide (FTO), indium tin oxide (ITO), or a mixture thereof is preferable as the conductive oxide thin film. Thin film formation methods include, for example, a method of spraying an ethanol solution of indium chloride and tin chloride onto a heated electrode substrate, a method of sputtering a target conductive oxide target in an Ar gas atmosphere, and a target conductivity in an oxygen atmosphere. Examples thereof include a method of vacuum-depositing a functional oxide and an ion plating method. As post-treatment, it is also effective to increase the crystallinity by heating at a temperature according to the type of the electrode substrate in an oxidizing atmosphere. Although the surface resistance of the electrode substrate varies depending on the thin film forming method, it is preferable that the surface resistance value be 20 Ω / □ or less in any thin film forming method.

  The method of thinning the metal oxide structure on the electrode substrate is divided into a step of applying the metal oxide structure dispersion to the electrode substrate and a subsequent drying step. Examples of the dispersion coating method in the coating process include a squeegee method, a doctor blade method, a screen printing method, a spraying method, a spin coating method, and the like, but there are no particular limitations as long as the method can adjust the film thickness.

  Examples of the drying method in the drying process of the dispersion include a method of spraying warm air on the coating film with a dryer, a method of irradiating infrared rays, a method of heating the electrode substrate, and a method of spraying dry air on the coating film. In addition, any method can be used without limitation as long as the solvent is evaporated from the metal oxide structure dispersion liquid applied on the electrode substrate and the drying temperature is a temperature that does not deform or alter the electrode substrate.

  Since the thin film of the metal oxide structure obtained in this way may have microcracks or the like, the electrode substrate and the electrolytic solution are in direct contact with each other in the solar cell, and reverse electron transfer (leakage) Current). In order to prevent cracks, it is preferable to form a dense metal oxide layer in advance on the electrode substrate before applying the metal oxide structure dispersion. (Hereinafter, a dense metal oxide layer formed in advance is referred to as an undercoat layer, and a material for forming the undercoat layer is referred to as an undercoat agent.) As the undercoat agent, particles having a primary particle size of 20 nm or less are used. It is preferable to use a metal oxide having good dispersibility. Among these, it is most preferable to use ultrafine titanium oxide.

  Further, in order to bind the undercoat agent to the electrode substrate, there is exemplified a method of baking at 300 ° C. or higher after applying the undercoat agent, but depending on the material of the electrode base material, it is deformed when baked at this temperature, May be altered. In this case, it is effective to add a binder component to the undercoat agent. The binder component is a substance that has a function of binding the metal oxide structure and the electrode substrate, and silica compounds, zirconia compounds, alumina compounds, titania compounds that are soluble in water or an organic solvent are used. Examples thereof include metal oxychlorides, hydroxychlorides, nitrates, ammonium carbonates, propionates and the like. These binder components can bind the undercoat agent and the electrode substrate even when drying at room temperature or at a relatively low temperature.

  The addition amount of the binder component needs to be adjusted so as not to inhibit the electron transfer, and is 3 to 3 by weight ratio in which the metal contained in the binder component is converted to metal oxide with respect to 100 parts by weight of the metal oxide structure. A range of 200 parts by weight is preferred.

  As an example of a method for obtaining a thin film, an ultrafine titanium oxide sol added with a binder is applied to a conductive substrate using polyethylene terephthalate as an electrode base material, dried at 120 ° C., and then obtained by the production method of the present invention. An example is a method in which the obtained metal oxide dispersion is applied by a spraying method and heated in a hot air drying furnace at 120 ° C. for 20 minutes.

A highly transparent photocatalyst film or UV absorbing film can also be provided on the outer surface side (two surfaces) of the electrode substrate.
By providing the photocatalyst film, the electrode surface can be kept clean, whereby the time-dependent reduction of the incident light into the battery can be suppressed. The photocatalyst particles constituting the photocatalyst film are not particularly limited, but ultrafine oxides of transition metals are preferable, and ultrafine particles of titanium oxide and zinc oxide are particularly preferable.
The photocatalytic film will be described below. (Configuration 1) On the outer interface of the electrode base material, a photocatalytic thin film having at least 50%, preferably 80% or more of a linear optical transmittance for light having a wavelength of 550 nm at the same time as photocatalytic activity is formed. As an aspect of Configuration 1, (Configuration 2) The photocatalytic thin film has a thickness of 0.1 μm to 5 μm. As one of the configurations 1 and 2, a precoat thin film having light transmittance may be provided between the outer interface of the electrode base material and the photocatalytic thin film. It is preferable that the film thickness of this precoat thin film is 0.02-0.2 micrometer. The precoat thin film is preferably made of a material mainly composed of SiO ₂ or a precursor thereof.
Moreover, the photocatalyst film manufacturing method can form a photocatalyst thin film on the outer interface of the electrode substrate by a pyrosol method, a dip method, a printing method, or a CVD method. Moreover, a photocatalyst film may be formed after the battery is assembled, or an electrode base material on which a photocatalyst film has been formed in advance may be prepared.
By forming a photocatalytic thin film having at least 50%, preferably 80% or more of linear light transmittance with respect to light having a wavelength of 550 nm at the same time as photocatalytic activity, the surface on the outside side of the electrode is kept clean for a long period of time. be able to. Thereby, the amount of light entering the battery can be kept high, and the photoelectric conversion efficiency can be maintained. In addition, if the photocatalyst particles are ultrafine titanium oxide or ultrafine zinc oxide, the photocatalyst film shields the ultraviolet rays well, thereby suppressing deterioration of the organic matter (pigment, electrolyte component, etc.) present in the battery over time due to the ultraviolet rays. be able to.

As a material for forming the titanium oxide thin film, the following ultrafine titanium oxide sol can be used. JP-A-11-43327 can be exemplified as a method for producing ultrafine titanium oxide sol. For example, titanium tetrachloride can be hydrolyzed to obtain an ultrafine titanium oxide sol.
In this case, if the concentration of titanium tetrachloride in the aqueous solution of titanium tetrachloride to be hydrolyzed is too low, the productivity is poor, and the efficiency is reduced when forming a thin film from the water-dispersed titanium oxide sol to be produced. On the other hand, if the concentration is too high, the reaction becomes violent, and the resulting titanium oxide particles are difficult to become fine, and the dispersibility also deteriorates. Therefore, a method of adjusting the titanium oxide concentration to 0.05 to 10 mol / liter by producing a sol having a high titanium oxide concentration by hydrolysis and diluting it with a large amount of water is not preferable. The concentration of titanium oxide is preferably in the range of 0.05 to 10 mol / liter at the time of sol formation. For this purpose, the concentration of titanium tetrachloride in the aqueous solution of titanium tetrachloride to be hydrolyzed is the titanium oxide produced. It is sufficient that the value is not significantly different from the concentration of the liquid, that is, about 0.05 to 10 mol / liter, and if necessary, the concentration is reduced to 0.05 to 10 mol / liter by adding or concentrating a small amount of water in the subsequent steps. You may adjust.

  The temperature in the hydrolysis is preferably in the range of 50 ° C. or higher and the boiling point of the aqueous titanium tetrachloride solution. If it is less than 50 degreeC, since a long time is required for a hydrolysis reaction, it is not preferable. The hydrolysis is carried out by raising the temperature to a predetermined temperature and holding for about 10 minutes to 12 hours. This holding time may be shorter as the hydrolysis temperature is higher. The hydrolysis of the aqueous solution of titanium tetrachloride may be carried out by a method in which a mixed solution of titanium tetrachloride and water is heated to a predetermined temperature in a reaction vessel, and water is preheated in the reaction vessel, Titanium tetrachloride may be added to this, and you may make it predetermined temperature. This hydrolysis generally provides titanium oxide in which an anatase type and / or a blue kite type are mixed with a blue kite type.

In order to increase the content of brookite-type titanium oxide, water is heated in advance to 75 to 100 ° C. in a reaction vessel, and titanium tetrachloride is added thereto, and the temperature ranges from 75 ° C. to the boiling point of the solution. A method of hydrolysis is suitable. According to this method, it is possible to make the brookite-type titanium oxide 70% by weight or more of the total titanium oxide produced.
The faster the temperature increase rate of the aqueous titanium tetrachloride solution in the hydrolysis, the more preferable particles are obtained because the obtained particles become finer. Therefore, a preferable temperature increase rate is 0.2 ° C./min or more, and a more preferable temperature increase rate is 0.5 ° C./min or more. According to this method, the average particle diameter of the titanium oxide particles in the sol is 0.5 μm or less, preferably in the range of 0.01 to 0.1 μm, and particles with higher crystallinity are obtained.

  The production method of the water-dispersed titanium oxide sol of the present invention is not limited to a batch type, and while continuously feeding titanium tetrachloride and water with the reaction tank as a continuous tank, the reaction solution is taken out on the opposite side of the inlet, and subsequently dechlorinated. Such a continuous method is also possible. The produced sol is adjusted so that the chlorine ion becomes 50 to 10,000 ppm by dechlorination treatment or addition of water or dehydration within a range that does not hinder. The dechlorination treatment may be performed by a general known means, and electrodialysis, ion exchange resin, electrolysis and the like are possible. The degree of dechlorination may be based on the pH of the sol. When the chlorine ion is 50 to 10,000 ppm, the pH is about 5 to 0.5, and when the preferred range is 100 to 4,000 ppm, the pH is about 4 to 1. An organic solvent can be added to the water-dispersed sol of the present invention, and the titanium oxide particles can be dispersed in a mixture of water and the organic solvent. When forming a titanium oxide thin film from this water-dispersed titanium oxide sol, it is preferable to use the sol produced by the hydrolysis reaction as it is. A titanium oxide powder is produced from this sol and dispersed in water to form a sol. Use is not a preferred method.

［式中、Ｒ1及びＲ3は水素またはアルキル基を表わし、Ｒ2及びＲ5はオキシアルキレン、フルオロカーボン、オキシフルオロカーボン及び／またはカーボネート基を含む２価の基、Ｒ4は炭素数１０以下の２価の基を表わす。Ｒ2、Ｒ4及びＲ5はヘテロ原子を含んでいてもよく、直鎖状、分岐状または環状のいずれの構造を有するものでもよい。ｘは０または１〜１０の整数を示す。但し、同一分子中に複数個の上記一般式（１）または（２）で表される重合性官能基が含まれる場合、それぞれの重合性官能基中のＲ1、Ｒ2、Ｒ3、Ｒ4、Ｒ5及びｘは、同一でもよいし異なってもよい。］で表される重合性官能基を有する化合物を含んでいることが好ましい。
また、ベンゼン環を有しない有機過酸化物である重合開始剤としては、以下の一般式（３）

［式中、Ｘは置換基を有してもよいアルキル基またはアルコキシ基を表わし、Ｙは置換基を有してもよいアルキル基を表わす。Ｘ及びＹは、直鎖状、分岐状または環状のいずれの構造を有するものでもよい。ｍ、ｎはそれぞれ０または１であるが、（ｍ，ｎ）＝（０，１）の組み合わせは除く。］で表される有機過酸化物であることが好ましい。
電極基材の材質がガラスである場合は、電気炉等を利用して比較的高温条件で乾燥させることもできる。
金属酸化物構造体の薄膜は、その膜厚が１μｍ以上４０μｍ以下であることが好ましい。膜厚が１μｍ未満の場合、薄膜内の光線の散乱や吸収が不十分となり、光電変換効率が低下する。膜厚が４０μｍを超えると、電解質の拡散抵抗が大きくなったり、あるいは電子の移動距離が長くなったりするため、必ずしも性能が向上しないばかりか、成膜作業が繁雑になってしまう。 Furthermore, as a means to prevent electrolyte leakage or electrode material elution from the outside of the battery, and to prevent problems such as internal impedance rise or internal short circuit due to electrolyte bias or liquid drainage within the battery, the solid electrolyte Or pseudo-solidification is effective. Specifically, a polymerization initiator that is an organic peroxide that does not have a benzene ring as a thermally polymerizable compound containing a (meth) acrylate having a methoxyacrylate, fluorocarbon, oxyfluorocarbon and / or carbonate group moiety in the molecule. A solid electrolyte obtained by thermosetting a thermopolymerizable composition in combination with can be used as the electrolyte.
More specifically, the thermopolymerizable compound that becomes a polymer having a cross-linked and / or side chain structure by polymerization is represented by the following general formula (1) and / or general formula (2).

[Wherein R 1 and R 3 represent hydrogen or an alkyl group, R 2 and R 5 represent a divalent group containing an oxyalkylene, fluorocarbon, oxyfluorocarbon and / or carbonate group, and R 4 represents a divalent group having 10 or less carbon atoms. Represent. R2, R4 and R5 may contain a hetero atom, and may have any of a linear, branched or cyclic structure. x represents 0 or an integer of 1 to 10. However, when a plurality of polymerizable functional groups represented by the above general formula (1) or (2) are contained in the same molecule, R1, R2, R3, R4, R5 in each polymerizable functional group and x may be the same or different. It is preferable that the compound which has a polymerizable functional group represented by this is included.
Moreover, as a polymerization initiator which is an organic peroxide having no benzene ring, the following general formula (3)

[Wherein, X represents an alkyl group or an alkoxy group which may have a substituent, and Y represents an alkyl group which may have a substituent. X and Y may have any of a linear, branched or cyclic structure. m and n are each 0 or 1, but the combination of (m, n) = (0, 1) is excluded. It is preferable that it is an organic peroxide represented by this.
When the material of the electrode substrate is glass, it can be dried at a relatively high temperature using an electric furnace or the like.
The thin film of the metal oxide structure preferably has a thickness of 1 μm to 40 μm. When the film thickness is less than 1 μm, scattering and absorption of light rays in the thin film are insufficient, and the photoelectric conversion efficiency is lowered. When the film thickness exceeds 40 μm, the diffusion resistance of the electrolyte increases or the distance of electron movement increases, so that not only the performance is not improved, but the film forming operation becomes complicated.

The method for producing a dye-sensitized solar cell of the present invention includes the step of preparing the particle groups A, B, and C, the step of mixing those particles by dry mixing that defines the BG, and the wet mixing. It includes a step of wet mixing the dry mixed particles.
Moreover, in such a dye-sensitized solar cell, BG of a metal oxide electrode can be confirmed as follows.

The metal oxide electrode of the dye-sensitized solar cell is immersed in a 0.1 mol / L sodium hydroxide aqueous solution or the like to sufficiently elute the dye from the metal oxide. The metal oxide electrode from which the dye is eluted is washed with water and dried at 120 ° C. for 2 hours to form a sample electrode. The BG of the metal oxide supported on the sample electrode can be obtained by the BG measurement method and the BG calculation formula described above.
When the metal oxide is titanium oxide, it can be confirmed that the BG is 2.7 to 3.1 eV.

The dye-sensitized solar cell including the metal oxide structure according to the present invention is provided with an article having functions such as generation of light, heat, sound, and movement, motion, etc., so that sunlight, room light, fluorescent light, and incandescent light bulb are provided. It can be used as a power source for its function in an environment where light from various other light sources as well as illumination lamps is irradiated.
In this case, the method described in Non-Patent Document 6 can be employed as a procedure for manufacturing the dye-sensitized solar cell.

  It can also be used as a composite charging element combined with a lithium ion battery, chemical capacitor, electric double layer capacitor, etc., a composite cooling element combined with a Peltier element, a composite display element combined with a display element such as an organic EL or liquid crystal. it can.

  Moreover, it can also be set as a composite element with a polymer battery. The polymer battery includes at least an electrode that takes out electron exchange accompanying the oxidation-reduction reaction of a compound as electric energy, and a polymer battery having an electrolyte solution, a solid electrolyte, or a gel electrolyte, and an active material of positive and negative electrodes constituting the electrode Is a π-conjugated polymer or / and a quinone-based compound containing a nitrogen atom, which can involve the binding and desorption of protons in the electron transfer associated with the oxidation-reduction reaction, and the electrolyte solution or solid electrolyte or gel electrolyte is a proton. The electron transfer accompanying the redox reaction of the active material of the positive electrode and the negative electrode is performed only in connection with the binding / desorption of the proton bonded or coordinated to the nitrogen atom or the proton of the generated hydroxyl group Thus, the proton concentration of the electrolyte, solid electrolyte or gel electrolyte is set so that the operating voltage is It is a polymer battery which is characterized in that it is your.

In particular, if a resin is employed for the electrode substrate of the dye-sensitized solar cell and the above-described combined elements and components are based on a flexible base material, the resulting composite element can be made flexible.
Examples of articles using such dye-sensitized solar cells and composite elements thereof include, for example, building materials, machines, vehicles, glass products, home appliances, agricultural materials, electronic devices, mobile phones, tools, tableware, and baths. Goods, toilet articles, furniture, stationery, clothing, emblems, hats, bags, shoes, umbrellas, blinds, design windows, fabric products, textiles, leather products, paper products, resin products, sporting goods, baskets, containers, glasses, Signboards, bulletin boards, piping, signboards, ad balloons, piping, wiring, metal fittings, lighting, LEDs, traffic lights, street lights, sanitary materials, automotive supplies, toys, traffic lights, road signs, ornaments, tents, cooler boxes and other outdoor equipment Examples include articles having functions of power generation, light emission, heat generation, sound generation, and movement, such as a power source for artificial flowers, objects, and cardiac pacemakers.
For example, it is possible to install the dye-sensitized solar cell of the present invention in a bathroom product and use it as a power source for a water heater, bathroom television, bathtub hot water circulation device, and the like.
Furthermore, the dye-sensitized solar cell of the present invention can be used as an alternative to all applications and articles in which Si-type solar cells are employed.
Moreover, it is possible to prepare a learning material set or a DIY set by arranging the members constituting the manufacturing process of the dye-sensitized solar cell and its composite element.

Hereinafter, although titanium oxide is concretely demonstrated in an Example and a comparative example, this invention is not limited to these at all.
<Dye solution preparation>
In a mixed solvent of 50% by volume of acetonitrile (manufactured by Kanto Chemical Co., Ltd., reagent special grade) and 50% by volume of ethanol (manufactured by Kanto Chemical Co., Ltd., reagent special grade), 3 mmol / L ruthenium complex dye (Ru (dcbpy) ₂ ( NCS) ₂ Kojima Chemical Co., Ltd.) was dissolved.

<Preparation of electrolyte>
To acetonitrile, 0.1 mol / liter lithium iodide (manufactured by Kishida Chemical Co., Ltd., purity 97%), 0.05 mol / liter iodine (manufactured by Kanto Chemical Co., Ltd., reagent special grade), 0.5 mol / liter tetrabutylammonium Iodine salt (Acros Organics, purity 98%) was dissolved.

<Photoelectric conversion efficiency measurement method>
The prepared dye-sensitized solar cell was irradiated with a light of 100 mW / cm ² using a xenon lamp (manufactured by USHIO INC., UXL-150D-S) as a light source. The maximum photoelectric conversion efficiency at this time was measured using a potentiostat (manufactured by Hokuto Denko Corporation, HAB151).

(Example 1):
1.5 g of titanium oxide (manufactured by Showa Denko KK, Super Titania (registered trademark) F-10) obtained by a vapor phase method with an average primary particle diameter of 150 nm and titanium oxide having an average primary particle diameter of 25 nm (same as Super Titania) (Registered trademark) F-5) 13.5 g, 500 g of 3φ zirconia balls are put into an 800 cm ³ polyethylene container (φ96 × 133 mm), and 1 hour at a rotational speed of 80 rpm with a ball mill (Asahi Rika Seisakusho Co., Ltd., AV). And mixed mechanochemical reaction. The energy constant k1 was 15,360, the tap density of the obtained titanium oxide structure was 0.19 g / cm ³ , and ΔBG was 0.18 eV. In this titanium oxide structure, contamination due to wear of zirconia balls or the like was not observed.

Titanium oxide structure 15.0 g, pure water 70 g, ethanol 10 g, polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1, molecular weight 500,000) 5 g, 3φ zirconia ball 500 g in an 800 cm ³ polyethylene container (φ96 × 133 mm), and wet-mixed with a ball mill at 80 rpm for 1 hour so that the energy constant k2 was 15,360. The obtained titanium oxide structure dispersion was applied to a conductive glass substrate (Asahi Glass Co., Ltd.) and then baked at 500 ° C. for 20 minutes to form a 10-12 μm titanium oxide thin film on the conductive glass substrate. It was.

  This titanium oxide thin film was immersed in a dye solution at 20 to 25 ° C. overnight to adsorb the dye, thereby obtaining a dye electrode. Open type dye sensitization by fixing a platinum counter electrode with platinum supported on a conductive glass substrate and a dye electrode molded in 5 mm square with each active surface facing each other at 30 μm intervals and injecting an electrolyte between them. Type solar cells were produced. The photoelectric conversion efficiency of this solar cell was 3.1%. Table 1 shows the results of the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of the particle group B.

(Example 2):
The titanium oxide of Example 1 was vapor-phase-processed titanium oxide having an average primary particle size of 250 nm and 1.5 g of vapor-phase-process titanium oxide having an average primary particle size of 30 nm (manufactured by Showa Denko KK, Super Titania (registered trademark) G1). (Same as above, Super Titania (registered trademark) F-4) 6.8g, Gas phase method titanium oxide with the average primary particle diameter 15nm (Super Titania (registered trademark) F-6) 6.7g, wet mixing time A dye-sensitized solar cell was produced in the same manner as in Example 1 except that was changed to 5 hours. The photoelectric conversion efficiency of this solar cell was 4.0%. Table 1 shows the results of the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of the particle group B.

(Example 3):
Vapor phase titanium oxide of Example 1 having an average primary particle diameter of 150 nm, 3.0 g of titanium oxide (manufactured by Showa Denko KK, Super Titania (registered trademark) F-10), an average primary particle diameter of 25 nm Except for changing to 2.0 g of titanium oxide (same as Super Titania (registered trademark) F-5) and 10.0 g of vapor phase titanium oxide (same as Super Titania (registered trademark) F-6) having an average primary particle diameter of 15 nm. Prepared a dye-sensitized solar cell in the same manner as in Example 1. The photoelectric conversion efficiency of this solar cell was 4.2%. Table 1 shows the results of the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of the particle group B.

Example 4
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the dry mixing time and the wet mixing time were changed to 10 hours each. The photoelectric conversion efficiency of this solar cell was 4.4%. Table 1 shows the results of the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of the particle group B.

(Example 5):
The titanium oxide of Example 1 was vapor-phase-processed titanium oxide having an average primary particle size of 250 nm and 1.5 g of vapor-phase-process titanium oxide having an average primary particle size of 30 nm (manufactured by Showa Denko KK, Super Titania (registered trademark) G1). (Same as above, Super Titania (registered trademark) F-4) 10.1 g, Gas phase process titanium oxide having the average primary particle diameter of 15 nm (Same as Super Titania (registered trademark) F-6) was changed to 3.4 g. Further, the ball mill mixing was replaced with a jet mill (manufactured by Seishin Enterprise Co., Ltd., CP-04) at 5 ° C. and 65 MPa for 5 times. Otherwise, a dye-sensitized solar cell was produced in the same manner as in Example 1. The photoelectric conversion efficiency of this solar cell was 3.7%. Table 1 shows the results of the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of the particle group B.

(Example 6):
The titanium oxide of Example 1 was prepared by adding 1.0 g of titanium oxide having an average primary particle diameter of 150 nm (manufactured by Showa Denko KK, Super Titania (registered trademark) F-10) and titanium oxide having an average primary particle diameter of 25 nm (same as above). A dye-sensitized solar cell was produced in the same manner as in Example 1 except that 13.0 g of Super Titania (registered trademark) F-5) and 1.0 g of vapor phase zinc oxide having an average primary particle diameter of 30 nm were used. The photoelectric conversion efficiency of this solar cell was 2.7%. Table 1 shows the results of the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of the particle group B.

(Comparative Example 1):
Gas phase method titanium oxide with an average primary particle size of 150 nm (manufactured by Showa Denko KK, Super Titania (registered trademark) F-10) 1.5 g and gas phase method titanium oxide with an average primary particle size of 25 nm (same as Super Titania ( (Registered trademark) F-5) 13.5 g was put into a 500 ml polyethylene bag and mixed by shaking 50 times. The tap density of the obtained titanium oxide mixture was 0.11 g / cm ³ , and ΔBG was 0 eV.

  A dye-sensitized solar cell was produced from this titanium oxide mixture in the same manner as in Example 1. The photoelectric conversion efficiency of this solar cell was 2.1%. Table 2 shows the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of particle group B.

(Comparative Example 2):
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the dry mixing time in Example 1 was changed to 0.1 hour and the wet mixing time was changed to 5 hours. The photoelectric conversion efficiency of this solar cell was 2.2%. Table 2 shows the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of particle group B.

(Comparative Example 3):
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the dry mixing time in Example 1 was changed to 5 hours and the wet mixing time was changed to 2 hours. The photoelectric conversion efficiency of this solar cell was 2.4%. Table 2 shows the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of particle group B.

(Comparative Example 4):
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the dry mixing time was changed to 10 hours. The photoelectric conversion efficiency of this solar cell was 2.3%. Table 2 shows the weighted average specific surface area, tap density, BG after dry mixing, ΔBG, and photoelectric conversion efficiency of particle group B.

(Comparative Example 5)
1.5 g of titanium oxide (manufactured by Showa Denko KK, Super Titania (registered trademark) F-10) obtained by a vapor phase method with an average primary particle diameter of 150 nm and titanium oxide having an average primary particle diameter of 25 nm (same as Super Titania) (Registered Trademark) F-5) 13.5 g, pure water 70.0 g, ethanol 10.0 g, polyethylene glycol (molecular weight 500,000) 5.0 g, 3φ zirconia balls 500 g in an 800 cm ³ polyethylene container (φ96 × 133 mm) And mixed with a ball mill at a rotation speed of 80 rpm for 1 hour to obtain a titanium oxide dispersion. A dye-sensitized solar cell was produced in the same manner as in Example 1 except that this titanium oxide dispersion was used in place of the titanium oxide structure dispersion. The photoelectric conversion efficiency of this solar cell was 2.2%. Table 2 shows the results of the weighted average specific surface area and photoelectric conversion efficiency of the particle group B.

Sectional drawing which shows the outline of a structure of a dye-sensitized solar cell. The electron micrograph which shows the necking state of a titanium oxide particle. Absorbance pattern for obtaining the absorption edge wavelength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive glass 2 Titanium oxide particle 3 Sensitizing dye 4 Electrolytic layer 5 Catalyst layer 6 Dye electrode 7 Counter electrode A necking part A Point contact part

Claims (32)

The optical band gap (hereinafter referred to as BG) calculated from the absorbance by an integrating sphere spectrophotometer is 2.7 eV or more and 3.1 eV or less, and the tap density is 0.15 g / cm ³ or more and 0.45 g. Titanium oxide structure characterized by being / cm ³ or less. A metal oxide structure obtained by dry-mixing a plurality of metal oxide powders having different particle sizes, where BG0 of the raw metal oxide is BG0, and BG of the metal oxide after dry-mixing is BG1. Is a metal oxide structure having 0.01 eV or more and 0.45 eV or less. A method for producing a metal oxide structure in which metal oxides are dry mixed, wherein BG0-BG1 is 0.00 when BG of the raw metal oxide is BG0 and BG of the metal oxide after dry mixing is BG1. A method for manufacturing a metal oxide structure, wherein the metal oxide structure is mixed so as to have a voltage of 01 eV or more and 0.45 eV or less. The method for producing a metal oxide structure according to claim 3, wherein the dry mixing is a method selected from at least one of a ball mill, a high-speed rotary pulverizer, a stirring mill, and a jet pulverizer. Dry mixing is performed by a ball mill, and the energy constant k1 in the dry mixing is such that the total mass of the powder to be mixed is wp (g), the media mass is wm (g), the inner diameter of the ball mill container is d (m), and the rotational speed is n. (Rpm), when the mixing time is t (minutes)
k1 = wm / wp × d × n × t
The method for producing a metal oxide structure according to claim 3, wherein k1 represented by the following relationship is 3,000 or more and 250,000 or less. The method for producing a metal oxide structure according to claim 3, wherein the energy constant k1 is 10,000 or more and 150,000 or less. The method for producing a metal oxide structure according to claim 3, wherein the energy constant k1 is 10,000 or more and 50,000 or less. The raw metal oxide is a metal oxide powder (hereinafter referred to as particle group A) having an average primary particle diameter in the range of 100 to 500 nm as converted from the specific surface area by the BET method, and the average primary particle diameter is 10 to 40 nm. The method for producing a metal oxide structure according to any one of claims 3 to 7, wherein the metal oxide powder is composed of a metal oxide powder (hereinafter referred to as a particle group B) in the range of. Particle group B is a metal oxide powder (hereinafter referred to as particle group C) having an average primary particle diameter converted from a specific surface area according to the BET method of 20 to 40 nm and a metal oxide powder (hereinafter referred to as particle group) of 10 to 20 nm. 9. The method for producing a metal oxide structure according to claim 8, wherein the metal oxide structure is a mixture. Method for producing a metal oxide structure according to claim 8 or 9 average specific surface area of the particle group B is less than ^{60 m} 2 / g or more 110m ² / g. The method for producing a metal oxide structure according to any one of claims 8 to 10, wherein at least one of the particle groups A to D is a metal oxide synthesized by a vapor phase method. The method for producing a metal oxide structure according to claim ^{3, wherein the} tap density is 0.15 g / cm ³ or more and 1.0 g / cm ³ or less. The method for producing a titanium oxide structure according to any one of claims 3 to 12, wherein the metal oxide is titanium oxide. The metal oxide is a mixture of titanium oxide and at least one metal oxide selected from zinc oxide, niobium oxide, tantalum oxide, zirconium oxide, tin oxide, and tungsten oxide. 13. The method for producing a metal oxide structure according to any one of items 1 to 12. The method for producing a metal oxide structure according to claim 14, wherein the content of titanium oxide contained in the mixture of metal oxides is 10% by mass or more. A dispersion medium is added to the titanium oxide structure according to claim 1, the metal oxide structure according to 2, or the metal oxide structure obtained by the production method according to any one of claims 3 to 15, and A method for producing a metal oxide structure dispersion by wet mixing, wherein the energy constant k2 in the wet mixing is such that the total mass of powder to be mixed is wp (g), the media mass is wm (g), and a ball mill container When the inner diameter is d (m), the rotation speed is n (rpm), and the mixing time is t (minutes),
k2 = wm / wp × d × n × t
The relationship between k2 expressed by the relationship and the energy constant k1 in dry mixing is
k2 ≧ k1
The manufacturing method of the metal oxide dispersion characterized by these. The relationship between the energy constant k2 in wet mixing and the energy constant k1 in dry mixing is
8.0 × k1 ≧ k2 ≧ 1.5 × k1
It is represented by these, The manufacturing method of the metal oxide dispersion of Claim 16 characterized by the above-mentioned. The relationship between the energy constant k2 in wet mixing and the energy constant k1 in dry mixing is
5.0 × k1 ≧ k2 ≧ 2.5 × k1
It is represented by these, The manufacturing method of the metal oxide dispersion of Claim 16 characterized by the above-mentioned. The metal oxide dispersion containing the titanium oxide obtained by the manufacturing method of any one of Claims 16 thru | or 18. The titanium oxide structure according to claim 1 or the metal oxide structure according to claim 2, the metal oxide structure obtained by the production method according to any one of claims 3 to 15, or the metal oxide structure according to claim 19. A composition comprising a metal oxide dispersion comprising titanium oxide. The titanium oxide structure according to claim 1 or the metal oxide structure according to claim 2, the metal oxide structure obtained by the production method according to any one of claims 3 to 15, or the metal oxide structure according to claim 19. A thin film containing a metal oxide dispersion containing titanium oxide. The thin film containing a metal oxide structure according to claim 21, wherein the film thickness is 1 μm or more and 40 μm or less. A method for producing a dye-sensitized solar cell, comprising the metal oxide structure according to any one of claims 3 to 15 as a dye-sensitized electrode. A dye-sensitized solar comprising the metal oxide structure according to any one of claims 3 to 15 and the metal oxide dispersion according to any one of claims 17 to 19 as a dye-sensitized electrode. Battery manufacturing method. A dye-sensitized solar cell manufactured by the manufacturing method according to claim 23 or 24. A dye-sensitized solar cell comprising a dye electrode comprising a thin film containing the metal oxide structure according to claim 22 as a constituent element. A dye-sensitized solar cell, wherein the BG of titanium oxide after removing the dye from the dye electrode is 2.7 to 3.1 eV. An article having a power generation function, comprising the dye-sensitized solar cell according to any one of claims 25 to 27. An article having a light emitting function, comprising the dye-sensitized solar cell according to any one of claims 25 to 27. An article having a heat generating function, comprising the dye-sensitized solar cell according to any one of claims 25 to 27. An article having a sound generating function, comprising the dye-sensitized solar cell according to any one of claims 25 to 27. An article having a motion function, comprising the dye-sensitized solar cell according to any one of claims 25 to 27.

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