JP2014010901A - Dispersion of semiconductor particle for dye-sensitized solar cell, and dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a dispersion of semiconductor particles for a dye-sensitized solar cell, which is contamination-free and sufficiently dispersed; and a solar cell which is high in transparency, includes an electron transport layer with a large pore size formed therein, and has high conversion efficiency.SOLUTION: A dispersion of semiconductor particles for a dye-sensitized solar cell is dispersion-treated by pressure releasing a slurry, which is pressurized at 50 MPa or more and 350 MPa or less and includes semiconductor particles in a liquid medium, and applying a shearing force.

Description

  The present invention relates to a dispersion of semiconductor particles for a dye-sensitized solar cell, and a dye-sensitized solar cell using the dispersion.

  There are several types of solar cells, but most of them are diode type using silicon semiconductor junctions. These solar cells are currently expensive to manufacture, which is a factor that hinders their spread.

Recently, Graetzel et al. Of Lausanne University of Technology in Switzerland announced a high-efficiency solar cell (hereinafter referred to as a dye-sensitized solar cell) as a possibility of lowering costs. Patent Document 1, Non-Patent Documents 1 and 2).
This high-efficiency solar cell has a structure in which an electron transport layer is provided on a transparent conductive glass substrate, and a photosensitizing compound adsorbed on the surface thereof (hereinafter referred to as a photoelectric conversion layer). "), Comprising an electrolyte having a redox pair and a counter electrode.
Graetzel et al. Significantly improved the photoelectric conversion efficiency by making the electron transport layer made of titanium oxide or the like porous to increase the surface area and adsorbing a ruthenium complex as a photosensitizing compound as a single molecule.
The porous electron transport layer requires a large specific surface area in order to adsorb more photosensitizing compounds on the surface.
Furthermore, the electron transport layer is required to have high transparency in order to allow light to reach all the adsorbed dyes.
For this reason, a porous electron transport layer is often produced by applying a semiconductor particle dispersion having a primary particle size of several to several hundred nm and drying it.
Accordingly, there is a need for highly dispersible semiconductor particle dispersions.

As a method for obtaining a semiconductor particle dispersion, a method using a medium such as a bead mill is disclosed (for example, see Patent Document 2).
However, there is a problem that the dispersion treated with the media cannot avoid mixing media contamination.
And the dye-sensitized solar cell using the porous electron transport layer produced using the semiconductor particle dispersion in which the contamination is mixed has a problem that the resistance of the electron transport layer is increased and the conversion efficiency is lowered. .
In order to solve this problem, it has been proposed to perform dispersion treatment using an ultrasonic homogenizer or an ultrasonic stirrer (see, for example, Patent Document 2).
However, these dispersion treatments have a problem that the dispersion is insufficient and a highly transparent electron transport layer cannot be produced.

The dye-sensitized solar cell has an electrolyte having a redox pair. In order to smoothly move electrons, the electrolyte needs to have a sufficient contact area with the photoelectric conversion layer.
However, the porous electron transport layer with a large specific surface area has a problem that the pore diameter becomes small, so that the electrolyte does not enter the pores and the contact area of the photoelectric conversion layer becomes insufficient. .
In particular, when treated with media, the problem that the pore diameter becomes small due to the pulverization of the semiconductor particles was significant.
In particular, in recent years, in order to improve durability, a gel or solid electrolyte is often used, and in that case, it is difficult for the electrolyte to enter small pores, so the contact between the electrolyte and the photoelectric conversion layer is difficult. The problem of insufficient area was significant.

Therefore, the subject of this invention is providing the dispersion | distribution of the semiconductor particle for dye-sensitized solar cells fully disperse | distributed without contamination.
By using the dispersion of the present invention, an electron transport layer having high transparency and a large pore diameter is formed, and a solar cell having high conversion efficiency is provided.

The above-mentioned problems are described in the following (1) to (5) “dispersion of semiconductor particles for solar cells”, “dye-sensitized solar cell”, “method for producing dispersion of semiconductor particles for solar cells” and “dye enhancement” It is solved by the present invention which includes “a method for producing a solar cell”.
(1) “Dispersion of semiconductor particles for dye-sensitized solar cell that has been subjected to dispersion treatment by releasing the pressure of a slurry containing semiconductor particles in a liquid medium that has been pressurized to 50 MPa or more and 350 MPa or less and applying shearing force”.
(2) “Dispersion of semiconductor particles for dye-sensitized solar cell according to item (1), which is dispersed by reducing the pressure of the pressurized slurry in multiple stages and releasing the pressure”).
(3) “Dye-sensitized solar cell using the dispersion according to (1) or (2)”.
(4) “having a step of pressurizing a slurry containing semiconductor particles in a liquid medium to 50 MPa or more and 350 MPa or less, and a step of dispersing the pressurized slurry by applying a shearing force under pressure release. A method for producing a semiconductor particle dispersion for a dye-sensitized solar cell ".
(5) “A method for producing a dye-sensitized solar cell, comprising: a step of pressurizing a slurry containing semiconductor particles in a liquid medium to 50 MPa to 350 MPa in a dispersion of semiconductor particles used in the solar cell; A method for producing a dye-sensitized solar cell, comprising a step of producing a dispersion by subjecting the treated slurry to a dispersion treatment by applying a shearing force under pressure release ".

  As will be understood from the following detailed and specific description, the present invention can provide a dispersion of semiconductor particles for dye-sensitized solar cells that is sufficiently contaminated and dispersed, and uses the dispersion of the present invention. By doing so, an extremely excellent effect that an electron transport layer having high transparency and a large pore diameter is formed and a solar cell with high conversion efficiency can be provided is exhibited.

1 is an overall view of an example of a dispersion apparatus used in the present invention. It is sectional drawing of an example of the dispersion | distribution part (23) which releases the pressure of the slurry by which the pressurization process was carried out in the said dispersion apparatus to atmospheric pressure, and gives a shear. It is sectional drawing of an example of the dispersion | distribution part (23) which decompresses pressure release to the same atmospheric pressure in two steps, and gives a shear. It is sectional drawing of an example of the dispersion | distribution part (23) which decompresses pressure release to the same atmospheric pressure in five steps, and gives a shear. It is sectional drawing which shows an example of the dye-sensitized solar cell which concerns on this invention.

The present invention is described in detail below.
The dispersion of the present invention is produced by pressurizing a slurry prepared by mixing at least semiconductor particles with a solvent to 50 MPa or more and 350 MPa or less, releasing the pressure, and applying a shearing force.
The pressure of the slurry can be confirmed by a diaphragm gauge or a pressure sensor.
The pressure may be released once or a plurality of times.
Here, the pressure release is an operation of reducing the pressurized slurry to atmospheric pressure.

FIG. 1 shows an overall view of an example of a dispersing apparatus used in the present invention.
A hopper (21) into which slurry made by mixing semiconductor particles is charged, a pump (22) for pressurizing the slurry, a dispersion part (23), and a dispersion receiver (24) are provided.
The pressurization is preferably performed by a high pressure pump such as a plunger pump.
The pressurization is preferably 50 MPa or more and 350 MPa or less, more preferably 100 MPa or more and 350 MPa or less, and further preferably 200 MPa or more and 350 MPa or less.
When the pressurization is lower than 50 MPa, the dispersion becomes insufficient and a highly transparent electron transport layer cannot be produced.
When the pressure is 50 MPa or more, the aggregation of the semiconductor particles can be loosened, and a highly transparent photoelectron transport layer can be produced.
However, if the pressurization exceeds 350 MPa, the semiconductor particles may be crushed and re-agglomerated, and the apparatus becomes heavy and the equipment cost increases.
The shape of the pipe may be square or curved.
In FIG. 1, the material of the piping of the decompression unit (not shown) and the decompression member is preferably a hard material such as diamond or silicon carbide.
The viscosity of the slurry is preferably from 0.1 cP to 100 cP, more preferably from 1 cP to 10 cP.
Although there is no problem as dispersion for the low viscosity of the slurry, if it is 0.1 cP or less, the productivity is lowered or the relative amount of solvent is increased, so that the cost is increased.
When the slurry viscosity is 100 cP or more, a sufficient flow rate cannot be obtained at the dispersion portion, the dispersion becomes insufficient, and a highly transparent electron transport layer cannot be produced.

Next, the invention for releasing the pressure of the pressurized slurry and applying a shearing force will be described.
FIG. 2 is a cross-sectional view of an example of the dispersing portion (23) that opens to atmospheric pressure and applies shear.
The slurry pressurized by the pump (22) of FIG. 1 is branched and flows in from the inflow hole (11), is depressurized by the pressure reducing part (13), and flows out from the outflow hole (12).
The diameter of the decompression section (13) is preferably 0.5 mm or less and 0.05 mm or more. More preferably, it is 0.2 mm or less and 0.05 mm or more, More preferably, it is 0.1 mm or less and 0.05 mm or more.
The smaller the diameter, the higher the slurry pressure. However, if the diameter is too small, it will cause clogging.
The diameter of the outflow hole (12) may be the same as or different from the inflow hole (11).
The number of inflow holes (11) and outflow holes (12) may be one or plural.
When there are a plurality, the diameters may be the same or different.
The number of inflow holes (11) and outflow holes (12) may be the same or different.

Next, an invention for applying a shearing force by reducing the pressure of the pressurized slurry in multiple stages and releasing the pressure will be described.
FIG. 3 is a cross-sectional view of an example of a dispersion section (23) that applies a shear by reducing the pressure to atmospheric pressure in two stages.
The slurry pressurized by the pump (22) of FIG. 1 flows in from the inflow hole (11), depressurizes by the pressure reducing sections (13) and (14), and flows out from the outflow hole (12).
The diameters of the decompression sections (13) and (14) may be different from each other.
Also, the number of decompression parts can be changed according to the purpose. By increasing the number of the pressure reducing parts, the pressure is gradually reduced when the pressure is released.

  FIG. 4 shows the dispersal part (23) that is released to atmospheric pressure, depressurized in five stages through the decompression parts (13), (14), (15), (16), (17) and (18), and gives shear. It is sectional drawing of an example.

The material of the semiconductor particles used in the present invention is not particularly limited, and known materials can be used.
Specifically, a single semiconductor such as silicon or germanium, a compound semiconductor typified by a metal chalcogenide, a compound having a perovskite structure, or the like can be given.
Metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, or tantalum oxides, cadmium, zinc, lead, silver, antimony, bismuth. Sulfide, cadmium, lead selenide, cadmium telluride and the like.
Other compound semiconductors are preferably phosphides such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide, and the like.
As the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.
Among these, an oxide semiconductor is preferable, and titanium oxide, zinc oxide, tin oxide, and niobium oxide are particularly preferable, and they may be used alone or in combination of two or more. The crystal type of these semiconductors is not particularly limited, and may be single crystal, polycrystal, or amorphous.

The primary particle size of the semiconductor particles is preferably 1 nm to 500 nm, more preferably 5 nm to 300 nm, and even more preferably 10 nm to 300 nm.
If the primary particle size is too small, there is a problem that the pore size of the electron transport layer is small. On the other hand, if the primary particle diameter is too large, there is a problem that the transparency of the electron transport layer is lowered.
The content of the semiconductor particles is preferably 5 to 70% by mass and more preferably 10 to 50% by mass in the dispersion.
Solvents for dispersing the semiconductor particles include water, alcohol solvents such as methanol, ethanol, isopropyl alcohol, α-terpineol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or n acetate. Ester solvents such as butyl, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone Amide solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene Zen, iodobenzene, or halogenated hydrocarbon solvents such as 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o Examples thereof include hydrocarbon solvents such as xylene, m-xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

In order to prevent re-aggregation of particles in the dispersion, acids such as hydrochloric acid, nitric acid and acetic acid, surfactants such as polyoxyethylene (10) octylphenyl ether, chelating agents such as acetylacetone, 2-aminoethanol and ethylenediamine Etc. can be added.
Further, a resin may be added.
Resins used at this time include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid esters, and methacrylic acid esters, silicone resins, phenoxy resins, polysulfone resins, polyvinyl butyral resins, and polyvinyl formal resins. Polyester resin, cellulose ester resin, cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin, polyimide resin and the like.
It is also an effective means to add a thickener for the purpose of improving the film forming property.
Examples of the thickener added at this time include polymers such as polyethylene glycol and polyvinyl alcohol, and thickeners such as ethyl cellulose.

Next, the structure of the dye-sensitized solar cell using the dispersion of this invention is demonstrated based on FIG.
FIG. 5 is a cross-sectional view of the dye-sensitized solar cell.
In the embodiment shown in FIG. 5, an electron current collecting electrode (3) is provided on a substrate (1), and consists of a dense electron transport layer (6) and a porous electron transport layer (7) having photoelectric conversion ability. It has an electron transport layer (5), and a structure in which a catalyst layer (10), a hole collecting electrode (4), and a substrate (2) are sequentially provided with an electrolyte layer (9) interposed therebetween.
A photosensitizing compound (12) that is excited from the ground state to near the conduction band level by absorbed light to generate exciton (exciton) is adsorbed on the surface of the porous electron transport layer (7).
The excitation level of excitons (excitons) is slightly lower than the excitation level of electrons in the compound, but the porous electron transport layer (7) is a semiconductor layer. The exciton (exciton) generated in the photosensitized compound (12) can drift to the adjacent compound even if its excited level is slightly lower than the conduction band level of the electrons in the compound, or Due to resonance, energy can propagate to adjacent compounds to reach the pn junction surface with the semiconductor particles, and the electrons captured by the electron collector electrode (3) at the pn junction surface and the hole electrode (3). To be separated into holes.
The porous electron transport layer (7) forms a porous state by applying the dispersion of the present invention, drying, sintering and the like.

The porous electron transport layer (7) produced by applying the dispersion of the present invention has a high specific surface area.
A larger specific surface area is preferable for adsorbing more photosensitizing compounds. It is preferably 10 m ² g ⁻¹ or more and 90 m ² g ⁻¹ or less, more preferably 50 m ² g ⁻¹ or more and 90 m ² g ⁻¹ or less, further preferably 60 m ² g ⁻¹ or more and 90 m ² g ⁻¹ or less.
The specific surface area can be measured by a specific surface area measuring device or the like. Generally, it is measured by a gas adsorption method and calculated using the BET equation.
The measurement sample can be prepared by applying the dispersion of the present invention and heating at 100 ° C. or more and 600 ° C. or less to form a coating film of 3 μm or more and 10 μm or less, and then peeling the coating film.

The porous electron transport layer (7) produced by applying the dispersion of the present invention has a large pore diameter.
If the pore diameter is large, all the pores of the porous electron transport layer (7) are filled with the electrolyte, so that the electrons move smoothly.
Particularly in recent years, in order to improve durability, a gel-like or solid electrolyte is often used. In that case, the electrolyte is sufficiently filled in the pores of the porous electron transport layer (7), so that the pore diameter is It is required to be large.
An average pore diameter can be used as an index of the pore diameter, and the average pore diameter is preferably 10 nm to 50 nm, more preferably 20 nm to 50 nm, and still more preferably 30 nm to 50 nm.
The average pore diameter can be measured by a specific surface area / pore diameter distribution measuring device or the like. It can be calculated from the specific surface area (A) and the total pore volume (V) and is represented by 4 V / A.
The measurement sample can be prepared by applying the dispersion of the present invention and heating at 100 ° C. or more and 600 ° C. or less to form a coating film of 3 μm or more and 10 μm or less, and then peeling the coating film.

The porous electron transport layer (7) may be a single layer or multiple layers.
In the case of multiple layers, a dispersion of semiconductor particles having different particle diameters can be applied in multiple layers, or different types of semiconductors, and application layers having different compositions of resins and additives can be applied in multiple layers.
In order to improve the light capture rate, the particle size on the light incident side is small, and the particle size can be gradually increased.
In order to improve the light capture rate, a layer using semiconductor particles having a large particle size is often provided with the layer farthest from the light incident side as a scattering layer.
Multi-layer coating is an effective means when the film thickness is insufficient with a single coating.
In general, as the film thickness of the electron transport layer increases, the amount of the photosensitized compound carried per unit projected area increases, so that the light capture rate increases. Loss due to coupling also increases. Therefore, the film thickness of the electron transport layer is preferably 100 nm to 100 μm.

The method for applying the porous electron transport layer (7) is not particularly limited, and can be performed according to a known method.
For example, various methods such as dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, letterpress, offset, gravure, intaglio, rubber plate, screen printing, etc. can be used. .
After applying the porous electron transport layer (7), the particles are brought into electronic contact with each other, and firing, microwave irradiation, electron beam irradiation, or laser light is used to improve film strength and adhesion to the substrate. Irradiation is preferred. These processes may be performed alone or in combination of two or more.
Microwave irradiation may be performed from the electron transport layer forming side or from the back side.
Although there is no restriction | limiting in particular in irradiation time, It is preferable to carry out within 1 hour.
When firing, the range of the firing temperature is not particularly limited, but if the temperature is raised too much, the resistance of the substrate may be increased or the substrate may be melted, so 30 to 700 ° C is preferable, and 100 to 600 ° C is more preferable. Moreover, although there is no restriction | limiting in particular also in baking time, 10 minutes-10 hours are preferable.
For the purpose of increasing the surface area of the semiconductor particles after firing and increasing the efficiency of electron injection from the photosensitizing compound into the semiconductor fine particles, for example, chemical plating or titanium trichloride using an aqueous solution of titanium tetrachloride or a mixed solution with an organic solvent. Electrochemical plating using an aqueous solution may be performed.

The electrodes (3) and (4) used in the present invention are not particularly limited as long as they are conductive materials that are transparent to visible light, and are used for ordinary photoelectric conversion elements, liquid crystal panels, and the like. A well-known thing can be used.
For example, indium tin oxide (hereinafter referred to as ITO), fluorine-doped tin oxide (hereinafter referred to as FTO), antimony-doped tin oxide (hereinafter referred to as ATO), and the like can be mentioned, and these can be used alone or in a plurality of layers. It may be.
The thickness of the electrodes (3) and (4) is preferably 5 nm to 100 μm, more preferably 50 nm to 10 μm.
The electrodes (3) and (4) are preferably provided on a substrate made of a material transparent to visible light in order to maintain a certain hardness. For example, glass, transparent plastic plate, transparent plastic film, inorganic transparent crystal Etc. are used.

For example, FTO coated glass, ITO coated glass, zinc oxide: aluminum coated glass, FTO coated transparent plastic film, ITO coated can be used. A transparent plastic film etc. are mentioned.
In addition, a transparent electrode obtained by doping cations or anions with different valences into tin oxide or indium oxide, or a metal electrode having a structure capable of transmitting light, such as a mesh shape or a stripe shape, provided on a substrate such as a glass substrate Good. These may be used singly or as a mixture of two or more kinds or laminated ones.
Moreover, a metal lead wire or the like may be used for the purpose of reducing the resistance of the substrates (1) and (2).
Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. For example, the metal lead wire may be provided on the substrate by vapor deposition, sputtering, pressure bonding, or the like, and ITO or FTO may be provided thereon.

The photoelectric conversion element of this invention forms the thin film which consists of semiconductors as an electron carrying layer (5) on said electrode (3).
This electron transport layer (5) is a laminate in which a dense electron transport layer (6) is formed on an electrode (3), and further a porous electron transport layer (7) having photoelectric conversion ability is formed thereon. A structure is preferred.
The dense electron transport layer (6) prevents electronic contact between the hole collecting electrode (4) and the electrolyte layer (9) having hole transport ability (prevents injection of electrons as minority carriers). Is formed. Therefore, if the electrode (4) and the electrolyte layer (9) are not in physical contact, pinholes, cracks, or the like may be formed.
Moreover, although there is no restriction | limiting in the film thickness of this precise | minute electron carrying layer, 10 nm-1 micrometer are preferable and 20 nm-700 nm are more preferable.
The “dense” of the electron transport layer (6) means that the inorganic oxide semiconductor is filled at a higher density than the packing density of the semiconductor particles in the porous electron transport layer (7).
In order to further improve the light conversion efficiency, it is preferable to adsorb the photosensitizing compound (12) to the porous electron transport layer (7).
The photosensitizing compound (12) is not particularly limited as long as it is a compound that is photoexcited by the excitation light to be used to generate excitons, and specifically includes the following compounds.
The metal complex compounds described in JP 7-500630 A, JP 10-233238 A, JP 2000-26487 A, JP 2000-323191 A, JP 2001-59062 A, etc. 10-93118, JP-A No. 2002-164089, JP-A No. 2004-95450, J. Pat. Phys. Chem. C, 7224, Vol. 111 (2007), etc., JP-A-2004-95450, Chem. Commun. , 4887 (2007), etc., JP-A No. 2003-264010, JP-A No. 2004-63274, JP-A No. 2004-115636, JP-A No. 2004-200068, JP-A No. 2004-235052. J. et al. Am. Chem. Soc. , 12218, Vol. 126 (2004), Chem. Commun. , 3036 (2003), Angew. Chem. Int. Ed. , 1923, Vol. 47 (2008), etc .; Am. Chem. Soc. 16701, Vol. 128 (2006), J.M. Am. Chem. Soc. , 14256, Vol. 128 (2006), JP-A-11-86916, JP-A-11-214730, JP-A-2000-106224, JP-A-2001-76773, JP-A-2003-7359. And the merocyanine dyes described in JP-A-11-214731, JP-A-11-238905, JP-A-2001-52766, JP-A-2001-76775, JP-A-2003-7360, etc. 9-arylxanthene compounds described in JP-A-10-92477, JP-A-11-273754, JP-A-11-273755, JP-A-2003-3273, etc., JP-A-10-93118, Triarylmethane compounds described in Japanese Unexamined Patent Publication No. 2003-31273, JP-A-9- 99744, JP-A No. 10-233238, JP-A No. 11-204821, JP-A No. 11-265738, J. Phys. Chem. , 2342, Vol. 91 (1987), J. MoI. Phys. Chem. B, 6272, Vol. 97 (1993), Electroanaly. Chem. , 31, Vol. 537 (2002), JP-A-2006-032260, J. Pat. Porphyrins Phthalocyanines, 230, Vol. 3 (1999), Angew. Chem. Int. Ed. , 373, Vol. 46 (2007), Langmuir, 5436, Vol. 24 (2008) etc., and the phthalocyanine compound, porphyrin compound, etc. can be mentioned.
Among these, it is particularly preferable to use metal complex compounds, coumarin compounds, polyene compounds, indoline compounds, and thiophene compounds.

As a method for adsorbing the photosensitizing compound (12) to the porous electron transporting layer (7), the substrate (1) on which the electron transporting layer (5) is formed in the photosensitizing compound solution or dispersion is used. A dipping method, a method of applying a solution or dispersion liquid to the electron transport layer and adsorbing the same can be used.
In the former case, dipping method, dipping method, roller method, air knife method, etc. can be used, and in the latter case, wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray method, etc. Can be used.
Further, it may be adsorbed in a supercritical fluid using carbon dioxide or the like.

When adsorbing the photosensitizing compound, a condensing agent may be used in combination.
The condensing agent has a catalytic action that seems to physically or chemically bond the photosensitizing compound and the electron transport compound to the inorganic surface, or acts stoichiometrically to favorably shift the chemical equilibrium. Either may be sufficient.
Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

  Solvents for dissolving or dispersing the photosensitizing compound are water, methanol, ethanol, alcohol solvents such as isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or acetic acid. Ester solvents such as n-butyl, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone Amido solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromoben Halogenated hydrocarbon solvents such as ethylene, iodobenzene or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o Examples include hydrocarbon solvents such as -xylene, m-xylene, p-xylene, ethylbenzene, and cumene, and these can be used alone or as a mixture of two or more.

Some photosensitizing compounds work more effectively if they suppress aggregation between compounds (as is known, all adsorption is exothermic (reduction of surface active energy without exception)). Or a decrease in activity due to the release of internal latent heat)), and an aggregating and dissociating agent may be used in combination.
The aggregating / dissociating agent is preferably a steroid compound such as cholic acid or chenodeoxycholic acid, a long-chain alkyl carboxylic acid or a long-chain alkyl phosphonic acid, and is appropriately selected according to the dye used. The addition amount of these aggregating and dissociating agents is preferably 0.01 to 500 parts by mass, more preferably 0.1 to 100 parts by mass with respect to 1 part by mass of the dye.

The temperature at which these are used to adsorb the photosensitizing compound or the photosensitizing compound and the aggregation / dissociation agent is preferably −50 ° C. or more and 200 ° C. or less.
Moreover, this adsorption may be carried out while standing or stirring.
Examples of the stirring method include, but are not limited to, a stirrer, a ball mill, a paint conditioner, a sand mill, an attritor, a disperser, and ultrasonic dispersion.
The time required for adsorption is preferably 5 seconds or more and 1000 hours or less, more preferably 10 seconds or more and 500 hours or less, and further preferably 1 minute or more and 150 hours.
Adsorption is preferably performed in a dark place.
The electrolyte layer (9) may be a liquid containing a redox couple, a pseudo solid obtained by gelling the liquid electrolyte with an appropriate gelling agent, or a solid made of a hole transport material. There may be.

  In the case of a liquid, a redox couple such as iodine / iodide ion, ferricyanide / ferrocyanide, quinone / hydroquinone, and additives such as lithium iodide and tertiary butylpyridine are dissolved in a solvent. Things are used. As the solvent, organic solvents such as acetonitrile, methoxyacetonitrile, propionitrile, ethylene carbonate, propylene carbonate, and γ-butyrolactone, and ionic liquids such as imidazolium salt, pyridinium salt, and pyrrolidinium salt can be used. It is not limited. Moreover, 2 or more types of these solvents can also be mixed and used.

  A gelling agent can be added to the liquid electrolyte to use it as a pseudo-solid. As the gelling agent, a crosslinkable polymer, a layered silicate mineral, or the like can be used, but is not limited thereto.

As the hole transporting material, known hole transporting compounds are used, and specific examples thereof include oxadiazole compounds disclosed in Japanese Patent Publication No. 34-5466 and the like, and Japanese Patent Publication No. 45-555. Triphenylmethane compounds, pyrazoline compounds shown in JP-B-52-4188, hydrazone compounds shown in JP-B-55-42380, etc., and JP-A-56-123544 Oxadiazole compounds, tetraarylbenzidine compounds disclosed in JP-A-54-58445, stilbene compounds disclosed in JP-A-58-65440 or JP-A-60-98437 These may be used alone or in combination of two or more.
There is no particular limitation on the method for producing the electrolyte layer when using the hole transport material, but in consideration of the manufacturing cost and the like, the wet film-forming method is particularly preferable, and the method of coating on the porous semiconductor layer is preferable.
When this wet film-forming method is used, the coating method is not particularly limited, and can be performed according to a known method. For example, dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, and wet printing methods such as relief printing, offset, gravure, intaglio printing, rubber printing, screen printing, etc. Can be used. Alternatively, the film may be formed in a supercritical fluid or a subcritical fluid.

The material used for the catalyst layer (10) is not particularly limited as long as the material exhibits conductivity. And it is preferable that it is electrochemically stable.
For example, platinum, carbon, gold, a conductive polymer, etc. are mentioned.

  A known method can be used as a method for forming the catalyst layer, and examples thereof include a sputtering method, a vapor deposition method, a spray method, a spin coating method, and a chemical vapor deposition method (CVD method).

  Next, although an Example is shown, this invention is not limited to a following example.

[Example 1]
(Preparation of Dispersion 1)
The slurry was prepared by mixing and stirring with the following composition.
Titanium oxide (primary particle size is 15 nm): 1 part by weight ethanol: 9 parts by weight The above slurry is put into a hopper (21), pressurized to 50 MPa and released to atmospheric pressure at the dispersion part shown in FIG. A dispersion 1 was produced.
The pressure was measured with a pressure transducer TJE manufactured by Honeywell Sensotec.

(Preparation of dispersion for printing 101)
Furthermore, after mixing by the following composition, ethanol was removed and the dispersion 101 for printing was obtained.
Dispersion 1: 5 parts by weight Terpineol: 1 part by weight Cellulose: 0.1 part by weight

(Preparation of scattering layer dispersion 104 for printing)
The slurry was prepared by mixing and stirring with the following composition.
Titanium oxide (primary particle size is 400 nm): 1 part by weight Ethanol: 9 parts by weight The above slurry is put into the hopper (21), pressurized to 50 MPa and released to atmospheric pressure at the dispersion part shown in FIG. A dispersion 103 for scattering layer was produced.

Furthermore, after mixing with the following composition, ethanol was removed to obtain a dispersion 104 for a scattering layer for printing.
Dispersion for scattering layer 103: 5 parts by weight Terpineol: 1 part by weight Cellulose: 0.1 part by weight

(Production of semiconductor electrode)
Titanium tetra-n-propoxide (2 ml), acetic acid (4 ml), ion exchange water (1 ml), and 2-propanol (40 ml) were mixed, spin-coated on an FTO glass substrate, dried at room temperature, and baked at 450 ° C. for 30 minutes in air. Using the same solution again, it was applied on the obtained electrode by spin coating so as to have a film thickness of 100 nm, and baked in air at 450 ° C. for 30 minutes to form a dense electron transport layer.
The dispersion for printing 101 is applied on the dense electron transport layer so as to have a dry film thickness of 15 μm, and the dispersion for scattering layer 104 for printing is applied so as to have a dry film thickness of 2 μm, followed by drying at room temperature. Then, it baked for 30 minutes at 500 degreeC in the air. Furthermore, this electrode was immersed in an aqueous titanium tetrachloride solution adjusted to 40 mM and allowed to stand at 70 ° C. for 30 minutes. After washing with water, it was again fired in air at 500 ° C. for 30 minutes to form a porous electron transport layer.

(Preparation of photoelectric conversion element)
N719 dye [cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II) −] prepared by adjusting the titanium oxide semiconductor electrode to 0.5 mM as a ruthenium complex. Bis-tetra-n-butylammonium, manufactured by Solaronix] in a mixed solution of acetonitrile / t-butanol (1: 1 by volume) at room temperature for 2 days to adsorb the photosensitizing compound. It was.

(Production of solar cells)
On the FTO glass substrate, an electrolyte injection hole was formed in the counter electrode produced by sputtering Pt.
And the spacer film was installed, the photoelectric conversion element produced previously was match | combined, and it sealed using acrylic UV hardening resin.
Thereafter, lithium iodide (LiI) 0.1M, 1-propyl-2,3-dimethylimidazolium iodide 0.6M, iodine (I2) 0.05M, 4-tert-butylpyridine 0.5M were added to acetonitrile. The dissolved electrolyte was injected from a hole formed in the counter electrode, and then the hole was sealed to produce a solar cell 1.

[Example 2]
A slurry 2 similar to that of Example 1 was pressurized to 150 MPa, released to atmospheric pressure at the dispersion portion shown in FIG.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a printing dispersion 2.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 2 was obtained.

[Example 3]
A slurry 3 similar to that of Example 1 was pressurized to 250 MPa, released to atmospheric pressure at the dispersion portion shown in FIG.
Terpineol and cellulose were added and mixed in the same manner as in Example 1, and then ethanol was removed to obtain a printing dispersion 3.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 3 was obtained.

[Example 4]
A slurry 4 similar to that of Example 1 was pressurized to 350 MPa, released to atmospheric pressure at the dispersion portion shown in FIG.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain dispersion 4 for printing.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 4 was obtained.

[Example 5]
A slurry similar to that of Example 1 was pressurized to 50 MPa and depressurized to 10 MPa in the dispersion portion shown in FIG. 3, then released to atmospheric pressure and sheared to prepare Dispersion 5.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a printing dispersion 5.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 5 was obtained.

[Example 6]
A slurry similar to that of Example 1 was pressurized to 350 MPa and reduced in pressure to 70 MPa in the dispersion portion shown in FIG. 3, then released to atmospheric pressure and sheared to prepare dispersion 6.
Terpineol and cellulose were added and mixed in the same manner as in Example 1, and then ethanol was removed to obtain a printing dispersion 6.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 6 was obtained.

[Example 7]
A slurry similar to that of Example 1 was pressurized to 50 MPa, and the dispersion portion shown in FIG. 4 was used to release the pressure in a multistage manner, such as 10 MPa, 8 MPa, 6 MPa, 4 MPa, and 2 MPa. 7 was produced.
Terpineol and cellulose were added and mixed in the same manner as in Example 1, and then ethanol was removed to obtain a printing dispersion 7.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 7 was obtained.

[Example 8]
The same slurry as in Example 1 was pressurized to 350 MPa, and the dispersion part shown in FIG. 4 was used to release the pressure in a multistage manner, such as 70 MPa, 30 MPa, 15 MPa, 8 MPa, and 3 MPa. 8 was produced.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a printing dispersion 8.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 8 was obtained.

[Comparative Example 1]
A slurry 9 similar to that in Example 1 was pressurized to 40 MPa, released to atmospheric pressure at the dispersion portion shown in FIG.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a printing dispersion 9.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 9 was obtained.

[Comparative Example 2]
A slurry similar to that of Example 1 was pressurized to 40 MPa and reduced in pressure to 8 MPa in the dispersion portion shown in FIG. 3, then released to atmospheric pressure and sheared to prepare dispersion 10.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a printing dispersion 10.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 10 was obtained.

[Comparative Example 3]
A slurry similar to that in Example 1 was pressurized to 40 MPa, and the dispersion part shown in FIG. 4 was used to release the pressure in a multistage manner, such as 8 MPa, 6 MPa, 4 MPa, 3 MPa, and 2 MPa. 11 was produced.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a printing dispersion 11.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 11 was obtained.

[Comparative Example 4]
Dispersion 12 was produced by dispersing the same slurry as in Example 1 using a bead mill.
In the same manner as in Example 1, terpineol and cellulose were added and mixed, and then ethanol was removed to obtain a dispersion 12 for printing.
A semiconductor electrode, a photoelectric conversion element, and a solar cell were produced in the same manner as in Example 1, and a solar cell 12 was obtained.

(Evaluation)
The transmittance of the film produced with the printing dispersion was measured. The measurement was performed with a UV-visible spectrophotometer V-660 manufactured by JASCO. Evaluation was made with a transmittance of 10 μm in film thickness and 500 nm in wavelength.
The specific surface area and average pore diameter of the film produced from the printing dispersion were measured. The measurement was performed with Tristar 3020 manufactured by Shimadzu Corporation, and the BET method was used. Sample preparation was performed on a slide glass and fired at 500 ° C. to form a 5 μm film, which was peeled off.
Conversion efficiency was calculated by performing IV measurement of the solar cell. The test was performed under simulated sunlight irradiation (AM1.5, 100 mW / cm ² ).
The results are shown in Table 1.

  The dispersion of the present invention is suitable for dye-sensitized solar cell applications, and can produce a dye-sensitized solar cell with high conversion efficiency. Therefore, the dispersion of the present invention has a very large practical value industrially.

(About FIGS. 1-5)
5 Electron transport layer 11 Inflow hole 12 Outflow hole 13 Decompression unit 14 Decompression unit 15 Decompression unit 16 Decompression unit 17 Decompression unit 18 Decompression unit 21 Hopper 22 Pump 23 Dispersion unit 24 Dispersion receiver

Japanese Patent No. 2664194 Japanese Patent No. 4279264

Nature, 353 (1991) 737 J. et al. Am. Chem. Soc. , 115 (1993) 6382

Claims (5)

  A dispersion of semiconductor particles for a dye-sensitized solar cell that has been subjected to a dispersion treatment by releasing the pressure of a slurry containing semiconductor particles in a liquid medium that has been pressurized to 50 MPa or more and 350 MPa or less and applying a shearing force.   The dispersion of semiconductor particles for a dye-sensitized solar cell according to claim 1, wherein the dispersion is performed by reducing the pressure of the pressurized slurry in multiple stages and releasing the pressure.   A dye-sensitized solar cell using the dispersion according to claim 1.   A step of pressurizing a slurry containing semiconductor particles in a liquid medium to 50 MPa or more and 350 MPa or less, and a step of dispersing the pressurized slurry by applying a shearing force under pressure release. A method for producing a semiconductor particle dispersion for a dye-sensitized solar cell.   A method for producing a dye-sensitized solar cell, comprising a step of pressurizing a slurry containing semiconductor particles in a liquid medium to 50 MPa to 350 MPa in a dispersion of semiconductor particles used in the solar cell, and the pressure-treated slurry And a step of producing by a treatment including a step of performing a dispersion treatment by applying a shearing force under pressure release, a method for producing a dye-sensitized solar cell.

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