JP6171773B2 - Titanium oxide particles, titanium oxide particle synthesis method, paste for dye-sensitized solar cell, oxide semiconductor film, oxide semiconductor electrode, and dye-sensitized solar cell - Google Patents

Description

  The present invention relates to a titanium oxide particle having a controlled crystal plane, a method for synthesizing titanium oxide particles, a paste for a dye-sensitized solar cell, an oxide semiconductor film, an oxide semiconductor electrode, and a dye-sensitized solar cell.

  Titanium oxide particles used high refractive index and white hiding paint, visible light transmitting UV light cut film using UV shielding effect, atmospheric purification device using photocatalytic property, super hydrophilicity and photocatalytic action It is used in various applications such as tiles for building exteriors and semiconductor electrodes for dye-sensitized solar cells utilizing photo-semiconductor properties.

Since titanium oxide particles used in various applications have different characteristics required for each application, the optimal crystal shape and exposed crystal plane cannot be determined in a single way, and oxidation suitable for each application is required. Titanium particles are being sought.
In order to make use of the characteristics of titanium oxide particles, it is desired that the titanium oxide particles have a narrow particle size distribution, a stable shape, and excellent crystallinity even in various applications. Therefore, for example, titanium oxide fine particles having a particle diameter range of 5 to 100 nm, having a crystal plane (101) as a main surface, and containing an anatase single phase have been proposed (for example, see Patent Document 1).

  Titanium oxide particles in photocatalyst and dye-sensitized solar cell applications are desired to have high electron reducing power and high mobility, so anatase-type titanium oxide that has a crystalline shape that meets these requirements Particles are used. In general, as anatase-type titanium oxide fine particles for use in dye-sensitized solar cells, rod-type structure acid fine particles having a (100) plane exposed as a main surface are used.

  On the other hand, a method of synthesizing titanium oxide particles having a (100) face exposed as a main surface using sodium oleate and sodium stearate as surfactants as surface control agents has been proposed (for example, non-patented). Reference 1).

Japanese Patent No. 4676877

Tadao Sugimoto, Xingping Zhou, and Atsushi Muramatsu, Synthesis of uniform anatase TiO2 nanoparticles by gel-sol method 4.Shape control, Journal of Colloid and Interface Science 259 (2003) 53-61

  However, there is no anatase-type titanium oxide particle that can be used as a dye-sensitized solar cell electrode material and has a (001) plane exposed as a main surface.

  Further, in the method of Non-Patent Document 1, since the surfactant contains sodium ions, the sodium ion component remains in the titanium oxide fine particles synthesized using the surfactant, and the photoelectric conversion efficiency is lowered. It is difficult to use as a dye-sensitized solar cell electrode material. In addition, since titanium tetraisopropoxide is used as it is as a titanium oxide raw material, hydrothermal synthesis is performed, so there is a problem that a large amount of isopropanol is generated from the raw material and the pressure may increase, which is not suitable for hydrothermal synthesis. there were.

  Accordingly, the present invention has been made in view of the above circumstances, and anatase-type titanium oxide particles having a (001) plane exposed as a main surface, a method for synthesizing titanium oxide particles, and a paste for dye-sensitized solar cells. An object of the present invention is to provide an oxide semiconductor film, an oxide semiconductor electrode, and a dye-sensitized solar cell.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a surfactant obtained by reacting an alkoxide with an amine as a condensation catalyst in advance as a crystal plane control agent. ) The present inventors have found that anatase-type titanium oxide particles with exposed surfaces can be formed, and have completed the present invention.

That is, the present invention provides the following [1] to [7].
[1] Anatase-type titanium oxide particles having a (001) surface exposed as a main surface,
Titanium oxide particles having a ratio of [001] direction particle length A / [100] direction particle length B of 0.1 or more and less than 2.5 and a sodium content of 500 ppm or less.
[2] The titanium oxide particles according to [1], which has a hexahedral shape.
[3] The titanium oxide particles according to [2], wherein the pair of opposed surfaces is a (001) surface and the other four surfaces are a (100) surface.
[4] A method for producing anatase-type titanium oxide particles according to any one of [1] to [3],
A step of reacting a titanium alkoxide with a hydroxyl group-containing amine to obtain a titanium oxide source;
A step of hydrothermal synthesis by adding an organic acid amine salt obtained by reacting an organic acid having 8 or more carbon atoms and an amine to the obtained aqueous solution in which the titanium oxide source is dissolved. Synthesis method.
[5] A dye-sensitized solar cell paste containing the titanium oxide particles according to any one of [1] to [3] and a dispersion medium in which the titanium oxide particles are dispersed.
[6] An oxide semiconductor film formed by firing the paste for a dye-sensitized solar cell according to [5] on a transparent conductive substrate.
[7] A dye-sensitized solar cell including the oxide semiconductor film according to [6].

  According to the present invention, anatase-type titanium oxide particles having a (001) face exposed as a main surface, a method for synthesizing titanium oxide particles, a paste for a dye-sensitized solar cell, an oxide semiconductor film, an oxide semiconductor electrode, and A dye-sensitized solar cell can be provided.

It is a conceptual diagram of the titanium oxide particle which concerns on embodiment of this invention. It is a TEM image of the titanium oxide particle synthesize | combined with the synthesis | combining method of the titanium oxide particle which concerns on embodiment of this invention. It is a schematic block diagram which shows an example of a dye-sensitized solar cell.

  Hereinafter, the present invention will be described with reference to embodiments. This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[Titanium oxide particles]
As shown in FIG. 1, the titanium oxide particles according to the present embodiment are anatase type in which the (001) plane is exposed as a main surface, and the particle length in the [001] direction is A / [100]. The ratio of thickness B is 0.1 or more and less than 2.5, and the sodium content is 500 ppm or less.
Here, “the (001) plane is exposed as the main surface” means that A / B <2.5. The unit cell of the anatase-type titanium oxide particles has a particle length A = 9.6 mm and B = 3.8 mm. Therefore, when A / B <2.5, the (001) plane is exposed on the surface. It can be said that.
When the (100) plane is exposed as the main surface, A / B ≧ 2.5.
The crystal orientations [001] and [100] shown here indicate the normal directions of the respective planes of (001) and (100). That is, the particle length A indicates the distance between the opposing (001) planes, and the particle length B indicates the distance between the opposing (100) planes. For example, when the particle length A and the particle length B are substantially equal, the shape of the titanium oxide particles is a cube.

  The A / B ratio of the titanium oxide particles is preferably from 0.1 to less than 2.5, and more preferably from 0.1 to 2.0. Furthermore, the relationship between the particle length A and the particle length B of the titanium oxide particles is preferably A ≦ B from the viewpoint that the surface of the titanium oxide particles is mainly composed of (001) planes, and A < B is more preferable. The average particle length of the titanium oxide particles is preferably 1 nm or more and 100 nm or less, and more preferably 10 nm or more and 50 nm or less from the viewpoint of not impairing the transparency of the titanium oxide particle-containing film.

The size and shape of the titanium oxide particles are observed with, for example, a field emission transmission electron microscope (FEM-2100F, manufactured by JEOL Ltd.). As an example of the synthesized titanium oxide particles, a TEM image is shown in FIG. From the TEM image of FIG. 2, the synthesized titanium oxide particles were exposed to (001) faces of titanium oxide particles having a face spacing of 2.4 mm and (100) faces of titanium oxide particles having a face spacing of 1.8 mm. ing. Further, A / B is 1.3, and the (001) plane is exposed as the main surface.
The average particle length can be determined by measuring the particle diameter of each of 100 or more particles, preferably 500 or more particles, and calculating the average value by observation with a microscope, for example.

The titanium oxide particles according to the present embodiment preferably have a sodium content of 500 ppm or less, and further preferably have an alkali metal and alkaline earth metal content of 500 ppm or less. Examples of the alkali metal contained in the titanium oxide particles include Li, Na, and K. Moreover, Ca, Sr, Ba etc. are mentioned as an alkaline-earth metal contained in a titanium oxide particle.
The sodium content of the titanium oxide particles is preferably 1 ppm or more and 400 ppm or less, more preferably 1 ppm or more and 300 ppm or less, more preferably 1 ppm or more and 200 ppm or less from the viewpoint of maintaining the photoelectric conversion efficiency at a desired value or more. More preferably.
Further, the content of alkali metal and alkaline earth metal in the titanium oxide particles is preferably not contained from the same viewpoint as described above, but is preferably 1 ppm or more and 400 ppm or less due to production limitations. More preferably, it is 1 ppm or more and 300 ppm or less.

[Method of synthesizing titanium oxide particles]
Below, the synthesis | combining method of the titanium oxide particle which concerns on this embodiment is demonstrated.

<Step of obtaining a titanium oxide source>
The titanium oxide particle synthesis method according to this embodiment first undergoes a step of obtaining a titanium oxide source by reacting titanium alkoxide with a hydroxyl group-containing amine.
In the step of obtaining a titanium oxide source, first, titanium tetraisopropoxide, which is a titanium oxide raw material, and an amine containing a hydroxyl group are mixed and reacted, and an alkoxide (titanium / amine alkoxide) composed of titanium and an amine is obtained by alcohol exchange. Synthesize. Subsequently, isopropanol generated by the reaction between titanium tetraisopropoxide and an amine containing a hydroxyl group is removed by heating under reduced pressure.

  Examples of the titanium alkoxide used in the step of obtaining the titanium oxide source include tetraethoxy titanium, tetraisopropoxy titanium, tetra normal propoxy titanium, tetra normal butoxy titanium and the like. From the viewpoint of stability and water solubility of the alcohol generated after the synthesis of titanium oxide, tetraisopropoxytitanium and tetranormalpropoxytitanium are preferred, and tetraisopropoxytitanium is particularly preferred.

  Specifically, the amine containing a hydroxyl group used in the step of obtaining a titanium oxide source is preferably at least one selected from the group of monoethanolamine, diethanolamine, and triethanolamine.

<Hydrothermal synthesis process>
In the method for synthesizing titanium oxide particles according to the present embodiment, an organic acid amine salt obtained by reacting an organic acid having 8 or more carbon atoms and an amine is then surface-activated in an aqueous solution in which the obtained titanium oxide source is dissolved. It passes through the process of adding as an agent and performing hydrothermal synthesis.

The raw materials used in the method for synthesizing titanium oxide particles according to the present embodiment are such that these impurities are contained so that the content of alkali metal and alkaline earth metal contained in the finally produced titanium oxide particles does not exceed 500 ppm. It is better to select and use a small amount of raw materials.
The term “surfactant” as used herein means one having a function of controlling the growth of the (001) plane of the titanium oxide particles to be synthesized. As the surfactant, from the viewpoint of controlling the growth of the (001) plane of the titanium oxide particles to be synthesized, an organic acid amine salt having 8 or more carbon atoms is preferably used, and an organic acid having 12 or more carbon atoms is used. It is more preferable to use an amine salt.

  The organic acid amine salt is a reaction product obtained by a neutralization reaction between an organic acid and at least one amine selected from the group consisting of monoethanolamine, diethanolamine, and triethanolamine. Specific examples of the organic acid include stearic acid, oleic acid, lauric acid, and the like. And as an organic acid amine salt used for this invention, an oleic acid is preferable.

The mixing molar ratio (amine / organic acid) of the organic acid and the amine used when producing the organic acid amine salt is preferably 1 or more and 20 or less, and more preferably 1 or more and 10 or less.
In the hydrothermal synthesis, the amount of the organic acid amine salt is preferably 2% by mass or more and 20% by mass or less in the reaction system from the viewpoint of adjusting the reaction rate of the titanium oxide particles and controlling the particle size. More preferably, it is at least 15% by mass.

  The reaction temperature in the hydrothermal synthesis is preferably 100 ° C. or higher and 250 ° C. or lower because titanium oxide particles are not generated at 100 ° C. or lower, and at 250 ° C. or higher, the reaction rate is too high to control the crystal plane. 140 degreeC or more and 210 degrees C or less are more preferable.

By the above-described method for synthesizing titanium oxide particles, anatase-type titanium oxide particles having a cubic structure or a rectangular parallelepiped structure mainly having a hexahedral shape with the (001) plane exposed are synthesized.
Since the synthesized titanium oxide particles are synthesized using a surfactant that does not contain metal ions such as sodium ions, the sodium ion component does not remain and the photoelectric conversion efficiency does not decrease.

According to the method for synthesizing titanium oxide particles according to the present embodiment, an organic acid amine salt as a surfactant functions as a crystal surface control agent, so that an anatase type titanium oxide having a (001) plane exposed as a main surface. Particles can be synthesized.
That is, since an organic acid amine salt that does not contain alkali metal such as sodium and alkaline earth metal is used as the surfactant, alkali metal such as sodium, potassium, calcium, and alkaline earth metal contain only impurities. . Therefore, it is possible to obtain anatase-type titanium oxide particles having excellent photoelectric conversion efficiency and having the (001) plane exposed as a main surface.

[Dye-sensitized solar cell paste]
The dye-sensitized solar cell paste contains titanium oxide particles synthesized by the method for synthesizing titanium oxide particles obtained by the above-described production method and a dispersion medium in which the titanium oxide particles are dispersed. The paste for dye-sensitized solar cells can be obtained by appropriately mixing titanium oxide particles, a dispersion medium, and other contents.

  The dispersion medium is not particularly limited as long as the titanium oxide particles can be dispersed, but it is preferable to use diols such as hexylene glycol and propylene glycol, and high-boiling organic solvents such as terpineol.

  In the dye-sensitized solar cell paste, the content ratio of the titanium oxide particles and the dispersion medium is 1: 0.01 to 1: 1 in terms of mass ratio from the viewpoint of easily obtaining the performance of the obtained oxide semiconductor film. The range of 5 is preferable, and the range of 1: 0.1 to 1: 1 is more preferable.

The dye-sensitized solar cell paste may contain a cellulose resin such as ethyl cellulose and an acrylic resin for adjusting the viscosity and the film thickness.
In the dye-sensitized solar cell paste, generally used additives such as a leveling agent, a chelating agent, a surfactant, a titanium coupling agent, and a thickener may be appropriately added. Examples of the leveling agent include water, ethylene glycol, polyethylene glycol, and glycerin. Examples of chelating agents include acetylacetone, benzylacetone, acetic acid and the like. Examples of the surfactant include polyethylene glycol. Examples of the thickener include cellulose-based thickeners.

  According to the paste for a dye-sensitized solar cell according to the present embodiment, since the titanium oxide particles do not contain metal ions such as sodium ions, a decrease in photoelectric conversion efficiency can be prevented.

[Oxide semiconductor film]
The oxide semiconductor film is formed by baking the paste for a dye-sensitized solar cell according to this embodiment on a transparent conductive substrate.
The thickness of the oxide semiconductor film is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and further preferably 5 μm or more and 30 μm or less from the viewpoint of obtaining a surface area of the film sufficient for adsorbing the dye. Note that the oxide semiconductor film may have a plurality of layers.

  The transparent conductive substrate is not particularly limited, but generally, a transparent substrate such as a glass substrate, and tin oxide, fluorine-doped tin oxide, tin-doped indium oxide (ITO) formed on the transparent substrate, A substrate provided with antimony-doped tin oxide (ATO), aluminum-doped zinc oxide, or the like is used. The transparent conductive base material may further be a base material that constitutes a light-transmitting transparent conductive film provided with a coating of tin oxide or fluorine-doped tin oxide on the surface.

The manufacturing method of an oxide semiconductor film applies the dye-sensitized solar cell paste according to the present embodiment to the surface of a transparent conductive substrate to form a coating film, which is dried as necessary and then fired. Can be obtained.
As a method of applying a dye-sensitized solar cell paste to the surface of a transparent conductive substrate, a bar coater method, a screen printing method, a gravure printing method, a spin coating method, a dip method, a spray method, a knife coater method, etc. It is preferable to use, and it is more preferable to use a screen printing method and a gravure printing method which are excellent in patterning property.

The firing temperature is preferably 250 ° C. or higher and 600 ° C. or lower, more preferably 400 ° C. or higher and 550 ° C. or lower. When the firing temperature is in the above range, good interparticle bonding is obtained, and the manufactured oxide semiconductor film becomes a low-resistance film. Moreover, if a calcination temperature is said range, grain growth with the particle | grains of the vicinity will be suppressed and a specific surface area will increase and it can be set as the electrode of a suitable photoelectric conversion element.
Further, it is preferable to perform a step of applying or dipping a titanium tetrachloride aqueous solution to the oxide semiconductor film thus obtained and baking it in air at a temperature of about 550 ° C. or lower. By this step, the electron mobility at the contact portion between the oxide semiconductor fine particles in the oxide semiconductor film can be improved.

  According to the oxide semiconductor film according to the present embodiment, since the dye-sensitized solar cell paste according to the present embodiment is baked, a decrease in photoelectric conversion efficiency can be prevented.

[Oxide semiconductor electrode]
The oxide semiconductor electrode is formed by adsorbing a dye to the oxide semiconductor film according to this embodiment.
As the dye to be adsorbed on the oxide semiconductor film, for example, a metal complex dye or an organic dye can be used. Examples of the metal complex dye include metal complex salts such as metal phthalocyanine, chlorophyll, hemin and the like and complexes containing one or more of ruthenium, osmium, iron and zinc. Among these, a ruthenium metal complex can be preferably used, and among them, a ruthenium bipyridine complex and a ruthenium terpyridine complex are preferable. On the other hand, examples of organic dyes include coumarin derivative dyes, polyene dyes, merocyanine dyes, azo dyes, quinone dyes, squarylium dyes, cyanine dyes, styryl dyes, xanthene dyes, and the like. Of these, coumarin derivative dyes can be preferably used.

  The oxide semiconductor electrode can be obtained by adsorbing the dye to the oxide semiconductor film by immersing the substrate on which the oxide semiconductor film according to this embodiment is laminated in a dye solution in which the dye is dissolved.

  A solvent for dissolving the dye may be appropriately selected and used. For example, alcohols such as methanol, ethanol, 2 propanol, 1 butanol, and t-butanol, and acetonitrile, methoxyacetonitrile, propionitrile, 3 methoxypropyl, and the like. Nitriles such as pionitrile, or a mixed solvent thereof can be used.

  According to the oxide semiconductor electrode according to this embodiment, since the oxide semiconductor film according to this embodiment is provided, it is possible to prevent a decrease in photoelectric conversion efficiency.

[Dye-sensitized solar cell]
In the dye-sensitized solar cell according to the present embodiment, a counter electrode is arranged with respect to the oxide semiconductor electrode according to the present embodiment to constitute a cell, and an electrolyte is enclosed inside the side frame member. Become.

FIG. 3 schematically shows an example of a solar cell.
The dye-sensitized solar cell 10 shown in FIG. 3 is a cell in which a transparent electrode 11 and a counter electrode 12 are arranged to face each other, and an electrolyte 14 is sealed inside through a side frame member 15. The transparent electrode 11 is made of conductive glass and constitutes an anode electrode. The counter electrode 12 is made of conductive glass and constitutes a cathode electrode. On the transparent electrode 11, an oxide semiconductor electrode 13 on which a dye is adsorbed is provided. The oxide semiconductor electrode 13 is obtained by adsorbing a dye after forming an oxide semiconductor film by mixing, for example, titanium oxide particles with a solvent, and applying and baking the particles on the transparent electrode 11.

  The transparent electrode 11 and the counter electrode 12 are arranged to face each other via the electrolyte 14 with an interval of several tens of μm to several mm, and the dye adsorbed on the oxide semiconductor electrode 13 of the transparent electrode 11 is disposed. Power generation is performed by passing the generated electrons excited by visible light to the oxide semiconductor electrode (titanium oxide particles) 13.

  The counter electrode 12 is not particularly limited. For example, a substrate made of a metal such as Al or stainless steel, glass, plastic, and the like, and Pt, C, Ni, Cr, stainless steel, fluorine-doped oxidation formed thereon. It is composed of a conductive layer such as tin and ITO. In addition, the counter electrode 12 can also comprise conductive glass having a conductive layer such as fluorine-doped tin oxide on the surface.

The electrolyte 14 can be a solid or a liquid. Specifically, various electrolytes such as iodine-based electrolyte, bromine-based electrolyte, selenium-based electrolyte, and sulfur-based electrolyte can be used as the electrolyte 14, and I ₂ , LiI, dimethylpropylimidazolium iodide, etc. can be used as acetonitrile. A solution or the like dissolved in an organic solvent such as methoxyacetonitrile, propylene carbonate, or ethylene carbonate is preferably used.
In the case where the liquid electrolyte 14 is used, a partition wall is provided between the oxide semiconductor electrode 13 and the counter electrode 12, and the electrolyte 14 is injected into the space thus formed.

  According to the dye-sensitized solar cell according to this embodiment, since the oxide semiconductor electrode according to this embodiment is provided, a decrease in photoelectric conversion efficiency can be prevented.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely according to an Example, this invention is not limited to the content of an Example.

[Example 1]
<Synthesis of titanium oxide particles>
In a separable flask, 170.6 g (0.6 mol) of titanium tetraisopropoxide (manufactured by Kosei Chemical Co., Ltd.) and 179.0 g (1.2 mol) of triethanolamine (manufactured by Nippon Shokubai Co., Ltd.) are blended for 30 minutes. Stir. Then, using an evaporator, the mixture was heated and depressurized until the weight of the formulation became 218.0 g, and isopropanol was removed to obtain a titanium oxide source composed of titanium and triethanolamine.
A flask in which the obtained titanium oxide source was dissolved in 450 g of pure water was charged with a neutralized product (amine salt) of 83.9 g of triethanolamine having 33.9 g of oleic acid, dissolved by stirring, and then completely dissolved. Was added in an amount of 1000 g to obtain a reaction solution.
The obtained reaction liquid was put into an autoclave and maintained at 180 ° C. for 8 hours, and a dispersion liquid containing titanium oxide particles of Example 1 was obtained by hydrothermal synthesis.

<Observation and evaluation of titanium oxide particles>
When the obtained titanium oxide dispersion was observed using a transmission electron microscope, cubic particles were synthesized, and the upper and lower surfaces of the cube were the (001) plane and the side surfaces were the (100) plane. I confirmed that there was. The average particle length of the titanium oxide particles was 20 nm, and the A / B ratio was 1.0.
Moreover, 1 mol / L nitric acid was added to 100 g of this dispersion to adjust the pH to 2 and the titanium oxide powder dried on a hot plate at 200 ° C. was analyzed for diffraction peaks using an X-ray diffractometer (manufactured by Philips). As a result, it was confirmed that the synthesized particles consisted of a single phase of anatase-type titanium oxide.
As a result of measuring this dispersion by ICP emission analysis, the sodium content contained in the titanium oxide particles was 200 ppm or less, the potassium content was 100 ppm or less, and the calcium content was 100 ppm or less.

<Preparation of paste for dye-sensitized solar cell>
The obtained titanium oxide particles, ethyl cellulose used for viscosity and film thickness adjustment, and terpineol as a dispersion medium were mixed to prepare a dye-sensitized solar cell paste of Example 1.
The composition ratio of this oxide semiconductor particle-containing paste was 26% by mass of titanium oxide, 8% by mass of ethyl cellulose, and 66% by mass of terpineol.

<Preparation of oxide semiconductor film>
The obtained paste for dye-sensitized solar cell was screen-printed on a transparent conductive substrate so as to have a fired film thickness of 7 μm and fired to produce the oxide semiconductor film of Example 1.

<Production of oxide semiconductor electrode>
The obtained oxide semiconductor film was immersed in a 0.3 mM Ru metal dye (Black Dye dye, manufactured by Daisol) for 24 hours to obtain an oxide semiconductor electrode of Example 1.

<Preparation of dye-sensitized solar cell>
In acetonitrile, the iodine salt of 1,2-dimethyl-3-propylimidazolium as the supporting electrolyte is 0.6M, lithium iodide is 0.1M, iodine is 0.05M, and tertiary butylpyridine is 0.5M. To prepare an electrolytic solution.

  The obtained oxide semiconductor electrode and the counter electrode substrate having a platinum film formed on the surface thereof are arranged so as to face each other, and the electrolyte obtained between the substrates is injected and sealed, whereby the dye of Example 1 A sensitized solar cell was produced.

<Evaluation of photoelectric conversion efficiency>
Using a solar simulator (manufactured by Yamashita Denso Co., Ltd.), the dye-sensitized solar cell of this example is irradiated with pseudo-sunlight, and the IV characteristics are measured with a current-voltage measuring device (manufactured by Yamashita Denso Co., Ltd.). Thus, the photoelectric conversion efficiency was obtained. The results are shown in Table 1.

[Example 2]
A dispersion containing titanium oxide particles of Example 2 was obtained in the same manner as Example 1 except that the reaction temperature in hydrothermal synthesis was 140 ° C.
When the obtained titanium oxide dispersion was evaluated in the same manner as in Example 1, the sodium content was 200 ppm or less, the potassium content was 100 ppm or less, the calcium content was 100 ppm or less, and cubic particles were synthesized, It was confirmed that the upper and lower surfaces were the (001) plane, the side surfaces were the (100) plane, and an anatase-type titanium oxide single phase. The average particle length of the titanium oxide particles was 15 nm, and the A / B ratio was 1.0.

<Preparation of dye-sensitized solar cell>
Instead of using the titanium oxide particles of Example 1, the paste for the dye-sensitized solar cell of Example 2, the oxide semiconductor film, and the like, except that the titanium oxide particles of Example 2 were used, An oxide semiconductor electrode and a dye-sensitized solar cell were obtained.
Table 1 shows the photoelectric conversion efficiency measured in the same manner as in Example 1.

[Example 3]
A dispersion containing titanium oxide particles of Example 3 was obtained in the same manner as Example 1 except that the reaction temperature in hydrothermal synthesis was 210 ° C.
When the obtained titanium oxide dispersion was evaluated in the same manner as in Example 1, the sodium content was 200 ppm or less, the potassium content was 100 ppm or less, the calcium content was 100 ppm or less, and cubic particles were synthesized. And the lower surface was the (001) plane, the side surface was the (100) plane, and it was confirmed that it was an anatase-type titanium oxide single phase. The average particle length of the titanium oxide particles was 30 nm, and the A / B ratio was 1.0.

<Preparation of dye-sensitized solar cell>
Instead of using the titanium oxide particles of Example 1, the paste for the dye-sensitized solar cell of Example 3, the oxide semiconductor film, and the like, except that the titanium oxide particles of Example 3 were used, An oxide semiconductor electrode and a dye-sensitized solar cell were obtained.
Table 1 shows the photoelectric conversion efficiency measured in the same manner as in Example 1.

[Comparative Example 1]
<Synthesis of titanium oxide particles>
A dispersion containing titanium oxide particles of Comparative Example 1 in the same manner as in Example 1 except that 6.1 g of sodium oleate was used instead of the neutralized product of 33.9 g of oleic acid with 89.5 g of triethanolamine. Got. The particles were evaluated in the same manner as in Example 1. As a result, cubic particles were synthesized, the upper and lower surfaces were the (001) plane, the side surfaces were the (100) plane, and were anatase-type titanium oxide single phase. It was confirmed. The average particle length of the titanium oxide particles was 20 nm, and the A / B ratio was 1.0. Moreover, sodium content exceeded 500 ppm.

Instead of using the titanium oxide particles of Example 1, the paste for the dye-sensitized solar cell of Comparative Example 1, the oxide semiconductor film, except that the titanium oxide particles of Comparative Example 1 were used, An oxide semiconductor electrode and a dye-sensitized solar cell were obtained.
Table 1 shows the photoelectric conversion efficiency measured in the same manner as in Example 1.

  According to the method for synthesizing titanium oxide particles of the present invention, the titanium oxide is anatase type in which the (001) plane is exposed as the main surface, and the particle length in the [001] direction is equal to or less than the particle length in the [100] direction. Since particles can be synthesized, it can be used in a wide range of fields such as paints that can use these titanium oxide particles, visible light transmission ultraviolet light cut film, air purification equipment, tiles for building exteriors, etc. It is.

DESCRIPTION OF SYMBOLS 10 ... Dye-sensitized solar cell 11 ... Transparent electrode 12 ... Counter electrode 13 ... Oxide semiconductor electrode 14 ... Electrolyte 15 ... Side frame member

Claims (6)

Anatase-type titanium oxide particles with the (001) face exposed as the main surface,
[001] The ratio of the direction of the particle length A / [100] direction of the particle length B is less than 0.1 to 2.5 state, and are the 500ppm or less sodium content, the surface of a pair of opposed There (001) plane, and the other four surfaces (100) Mendea Ru titanium oxide particles.   The titanium oxide particles according to claim 1, wherein the shape is a hexahedral shape. A method for synthesizing titanium oxide particles according to claim 1 or 2 ,
A step of reacting a titanium alkoxide with a hydroxyl group-containing amine to obtain a titanium oxide source;
A step of hydrothermal synthesis by adding an organic acid amine salt obtained by reacting an organic acid having 8 or more carbon atoms and an amine to the obtained aqueous solution in which the titanium oxide source is dissolved. Synthesis method. Claim 1 or 2 and the titanium oxide particles according to the dispersion medium and the dye-sensitized solar cell paste containing dispersing the titanium oxide particles. The oxide semiconductor film formed by baking the paste for dye-sensitized solar cells of Claim 4 on a transparent conductive substrate. A dye-sensitized solar cell comprising the oxide semiconductor film according to claim 5 .