JP6805490B2 - Method for forming porous semiconductor electrodes of coating liquid and dye-sensitized solar cells - Google Patents

Description

The present invention relates to a coating liquid for forming a porous semiconductor electrode.

With the introduction of renewable energy becoming a global trend, there is also a great deal of interest in solar cells. As the solar cell, one made of silicon such as single crystal silicon type, polycrystalline silicon type, and amorphous silicon type, and one made of compound semiconductor such as copper indium selenium are put into practical use. However, since all of these solar cells require a large amount of energy for module production, there are restrictions on the reduction of production costs, which is a restriction on the large-scale spread of solar cells.

On the other hand, there is a dye-sensitized solar cell as a solar cell which has a relatively low production energy and is advantageous for cost reduction. A dye-sensitized solar cell is an electrolyte-containing material (electrolyte solution, etc.) having a conductive transparent thin film, a porous semiconductor electrode, a photosensitizing compound (sensitizing dye, etc.), and a redox pair on a transparent substrate made of glass or the like. , The structure is such that the counter electrodes are laminated in order. By making the semiconductor electrode that holds the sensitizing dye porous, the specific surface area is expanded hundreds to thousands of times, and the amount of the sensitizing dye that is held is significantly increased, so that a large photocurrent can be obtained. This is a feature (see, for example, Non-Patent Documents 1 and 2).

Generally, in a semiconductor electrode for a dye-sensitized solar cell, a dispersion liquid containing semiconductor nanocrystal particles and a binder is formulated in a coating liquid having an adjusted viscosity, and this is applied to a substrate by a method such as screen printing. After that, it is obtained by removing the binder by heating and firing to make it porous. Titanium oxide is often used as the semiconductor nanocrystal particles.

The power generation principle of the dye-sensitized solar cell is as follows: (1) The photosensitizing compound fixed on the surface of the semiconductor electrode absorbs external light such as sunlight and becomes excited. (2) This is an electron with respect to the semiconductor electrode. (3) The emitted electrons diffuse and move around the semiconductor electrode and arrive at the conductive transparent substrate, (4) Move from the conductive substrate to the counter electrode via an external circuit, and (5) At the counter electrode. The oxidation-reduction pair in the electrolytic solution is reduced. (6) This reducing body moves in the electrolytic solution and arrives at the dye, and the photosensitizing compound emitted by electrons is reduced to return to the basal state (1). Based on the cycle of ~ (6). By repeating this cycle, power generation is continuously generated while the light is irradiated.

In view of such a power generation principle, the porous structure formed in the semiconductor electrode needs to have an appropriate surface area and an appropriate pore diameter at the same time. That is, in order to increase the absorption of sunlight, which is the starting point of the power generation cycle, the larger the amount of the sensitizing dye, the more advantageous it is. On the other hand, in order for the redox pair in the electrolytic solution to return the dye to the ground state and complete the power generation cycle, the electrolytic solution is sufficiently filled in the pores in the porous structure, and the electrolytic solution and the dye come into contact with each other. However, if the pores are too narrow, the electrolytic solution cannot sufficiently permeate and the pores are not filled, so that it is necessary to construct pores having a diameter exceeding an appropriately set diameter. In particular, this problem becomes remarkable when the viscosity of the electrolytic solution is high and it is difficult to penetrate into the pores.

The pore structure in the semiconductor electrode is uniquely that when a coating liquid containing semiconductor nanocrystal particles is applied to the substrate, the binder disappears by heating, and the remaining nanocrystal particles form a film. It is formed by creating a gap between them. In this case, the larger the particle size, the larger the pore diameter formed, but the surface area per unit volume decreases accordingly. Therefore, it is difficult to have an appropriate surface area and an appropriate pore diameter at the same time by simply forming pores by gaps between particles.

In order to solve the above problem, a particulate material that burns and disappears by heating to the same extent as ordinary heating and firing, and at the time of extinction, gives pores having a diameter larger than the gap formed by the contact between the particles ( Attempts have been made conventionally to add a heat-dissipating material (hereinafter referred to as a heat-dissipating material) as an additive for a coating liquid (see, for example, Patent Documents 1 to 4). For example, in Patent Document 1, polystyrene particles having an average particle size of 100 nm to 1,000 nm or carbon nanotubes having an average particle size of 50 nm are added to the titanium oxide paste as a heat-dissipating material to form a titanium oxide electrode film after firing. The size of the formed pores and the degree of porosity are controlled. Further, in Patent Document 4, a cross-linking agent having at least one of an oxypropylene unit or an oxytetramethylene unit and having two or more polymerizable unsaturated groups is reacted with a monomer having a polymerizable unsaturated group. The resin obtained by subjecting the mixture is used as a heat-dissipating material to form pores of about 200 nm to 1,000 nm.

However, in these conventional examples, since the heat-dissipating particles for forming pores are added as an additive in the semiconductor nanocrystal particle paste, the arrangement of the heat-dissipating particles in the coating film is left to chance. There is no choice but to control it precisely. For this reason, a portion where the pores are densely formed and a portion where the pores are sparsely formed are generated, and it is difficult to uniformly construct the pores in the film. Such a non-uniform arrangement is not desirable in view of the purpose of sufficiently filling the pores with the electrolytic solution. Further, in the portion where the pores are densely formed, a plurality of pores are merged into one pore, so that pores having a diameter larger than necessary may be formed. This reduces the arrangement of the sensitizing dye, which causes a decrease in power generation performance.

The present invention has been made in view of the above problems in the prior art, and the pores to be formed are uniformly present in the semiconductor electrode film, and the pores are composed of a combination of a plurality of heat-dissipating particles. It is an object of the present invention to provide a coating liquid in which deterioration of power generation performance is suppressed by suppressing formation.

The coating liquid according to the present invention for solving the above problems is a coating liquid containing composite particles composed of semiconductor nanocrystal particles and heat-disappearing particles, and the heat-disappearing particles are weight-averaged. For forming porous semiconductor electrodes of dye-sensitized solar cells, which are polymethylmethacrylate having a molecular weight (Mw) of 30,000 or more and 45,000 or less and a glass transition temperature (Tg) of 80 ° C. or more and 95 ° C. or less . It is a coating liquid of .

According to the present invention, the pores to be formed are uniformly present in the semiconductor electrode film, and the deterioration of power generation performance is suppressed by suppressing the formation of pores composed of the coalescence of a plurality of heat-dissipating particles. The coating liquid to be applied can be provided.

6 is a cross-sectional SEM observation image of the semiconductor electrode obtained in Example 5. It is a volume-based particle size distribution when the composite particles shown by Examples 7 to 8 and Reference Examples 1 and 2 are measured by a laser diffraction type particle size distribution meter.

The coating liquid according to the present invention is a coating liquid containing particles for forming a porous semiconductor electrode, a binder resin, and a dispersion solvent, and the particles are semiconductor nanocrystal particles and heat-disappearing particles. It is characterized in that it is a composite particle composed of.

Next, the coating liquid according to the present invention will be described in more detail.
It should be noted that the embodiments described below are technically preferable because they are preferred embodiments of the present invention, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise stated, the present invention is not limited to these aspects.

In the present invention, first, composite particles (3) composed of semiconductor nanocrystal particles (1) and heat-dissipating particles (2) are prepared, and then the composite particles (3), a binder resin, and a solvent for dispersion are used. A coating liquid (4) containing the above is prepared. Further, the dye-sensitized solar cell manufactured from the coating liquid (4) is a semiconductor electrode obtained by applying the coating liquid on the base material (5) on which the transparent electron collecting electrode is arranged and firing the coating liquid (5). After producing 6), it is formed by combining with a photosensitizing compound (7), an electrolyte-containing substance (8), and a counter electrode (9).
Hereinafter, the coating liquid and each material constituting the dye-sensitized solar cell manufactured by using the coating liquid will be described in order.

(1) Semiconductor nanocrystal particles The semiconductor nanocrystal particles used in the present invention are not particularly limited as long as they are crystalline semiconductor particles, and known ones can be used.
Specific examples thereof include elemental semiconductors such as silicon and germanium, compound semiconductors typified by metallic chalcogenides, and compounds having a perovskite structure.

Metallic chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lantern, vanadium, niobium, or tantalum oxides, cadmium, zinc, lead, silver, antimony, bismuth. Examples include sulfide, cadmium, lead selenium, and cadmium telluride.
As other compound semiconductors, phosphides such as zinc, gallium, indium and cadmium, gallium arsenic, copper-indium-selenium, copper-indium-sulfide and the like are preferable.
Further, as the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.
Among these, oxide semiconductors are preferable, titanium oxide, zinc oxide, tin oxide and niobium oxide are particularly preferable, and titanium oxide is particularly preferable. These crystalline semiconductors may be used alone or in a mixture of two or more kinds.

The average primary particle size of the semiconductor nanocrystal particles is preferably 1 nm or more and 500 nm or less, more preferably 5 nm or more and 300 nm or less, further preferably 10 nm or more and 300 nm or less, and particularly preferably 20 nm or more and 135 nm or less. If the primary particle size is too small, the semiconductor porous membrane will still be excessively densified even if heat-dissipating particles are added, and the pore size formed in the porous membrane will be small, which limits the penetration or filling of the electrolyte. There is a problem of being done. On the other hand, if the primary particle size is too large, the surface area contained in the semiconductor porous film decreases, so that there is a problem that a sufficient amount of adsorbed dye cannot be secured.

The content of the semiconductor nanocrystal particles is preferably 5 to 50% by mass, more preferably 10 to 30% by mass in the coating liquid (4).

If necessary, it is desirable that the semiconductor nanocrystal particles are previously disaggregated to several tens of nm to several hundreds of nm in the liquid phase before being composited with the heat-dissipating particles. The method for loosening the agglomeration is not particularly limited as long as it can give an impact force exceeding the agglomeration force in the liquid phase, and a known method can be used.
Specifically, a crushing method based on collision with ceramic beads such as a bead mill or shear stress between the beads and the wall surface of the mill can be selected. It is also possible to select a method that does not use ceramic beads, in which a method of applying impact force by pressurizing and accelerating the dispersion liquid with a high-pressure pump and causing the dispersion liquids to collide with each other or with the dispersion liquid and a collision member. , A method in which the dispersion liquid is pressurized by a high-pressure pump to accelerate it, and an impact force is applied by the shear stress generated between the dispersion liquid and the wall surface when passing through the flow path at high speed. The distance between the dispersion liquid and the wall surface or the bottom surface of the container is constant. There are a method of agitating with a stirring blade kept in place and applying an impact force by a shear stress with the wall surface or the bottom surface of the container, a method of irradiating the dispersion liquid with ultrasonic waves, and applying an impact force based on the cavitation phenomenon.

(2) Heat-disappearing particles The heat-disappearing particles used in the present invention are not particularly limited as long as they are burned and extinguished by firing at 500 ° C. in the air which is the normal firing atmosphere of the coating film. Known resin fine particles can be used.
Specifically, fine particles such as polyethylene, polypropylene, polystyrene, polystyrene acrylic, polyester, polymethylmethacrylate, and polyurethane are preferable.
Among them, polymethylmethacrylate having a weight average molecular weight (Mw) of 30,000 or more and 45,000 or less and a glass transition temperature (Tg) of 80 ° C. or more and 95 ° C. or less is particularly preferable. By using polymethylmethacrylate having Mw and Tg in the above ranges, the heat-disappearing particles are softened and deformed in the process of raising the temperature in firing at 500 ° C., and then burned and disappeared. The pores formed thereby have improved connectivity as compared with the case without such deformation, and are more desirable for injecting and permeating the high-viscosity electrolytic solution into the inside of the semiconductor porous electrode. It has a structure.

The particle size of the heat-dissipating particles is preferably 10 nm or more and less than 2,000 nm, and more preferably 50 nm or more and less than 1,000 nm. The heat-dissipating particles are added for the purpose of expanding the pores formed in the semiconductor porous electrode membrane to a size that allows the electrolytic solution to sufficiently permeate, so that the particles can be adjusted to the target pore size. desirable. When the particle size of the heat-disappearing particles is less than 10 nm, the pores formed by the extinction of the particles are also less than 10 nm, which is no different from the pore diameter formed when the heat-disappearing particles are not added. On the other hand, if the particle size of the heat-disappearing particles exceeds 2,000 nm, excessively large pores are formed for the purpose, the arrangement of the sensitizing dye is reduced, and the power generation performance is deteriorated, which is not desirable.

The content of the heat-dissipating particles is preferably 5 to 70% by mass, more preferably 10 to 50% by mass in the coating liquid (4).

(3) Composite Particles of Semiconductor Nanocrystal Particles and Heat-Disappearing Particles Composite particles are obtained by compounding the semiconductor nanocrystal particles (1) and heat-disappearing particles (2). Here, it is preferable to obtain composite particles by irradiating a solution containing semiconductor nanocrystal particles (1) and heat-dissipating particles (2) with ultrasonic waves and combining the two by a cavitation action.
The compounding treatment is preferably performed by irradiating the above solution with ultrasonic waves and combining them by a cavitation action, but the method is not particularly limited as long as the composite particles having a desired shape can be obtained, and is a known method. Can be used. It can also be done in the gas phase.

As the solvent for dispersing the particles, an alcohol solvent such as water, methanol, ethanol, isopropyl alcohol, α-terpineol, a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or n-acetate Estel solvents such as butyl, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, amides such as N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone. System solvent, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or halogenated hydrocarbon solvent such as 1-chloronaphthalene, n -Carbonites such as pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, or cumene. A solvent can be mentioned. These can be used alone or as a mixed solvent of two or more kinds.

The semiconductor nanocrystal particles and the heat-dissipating particles may be simultaneously charged into a solvent consisting of one or more of the above solvents, or may be charged separately into a solvent consisting of one or more of the above solvents and then mixed. You may. When charged separately, the respective solvents may be the same or different.

In the solution containing semiconductor nanocrystal particles and heat-dissipating particles, in order to prevent reaggregation of the particles, acids such as hydrochloric acid, nitric acid and acetic acid, surfactants such as polyoxyethylene (10) octylphenyl ether, acetylacetone, 2 -A chelating agent such as aminoethanol or ethylenediamine can be added.

The method of irradiating the solution containing the semiconductor nanocrystal particles and the heat-dissipating particles with ultrasonic waves is not particularly limited as long as it can give the impact force required for compounding the particles, and a known method is used. can do.
For example, a method in which a rod-shaped or flat plate-shaped transducer is put into a container containing a solution containing semiconductor nanocrystal particles and heat-dissipating particles to generate ultrasonic waves inside the container, semiconductor nanocrystal particles and heat-dissipating particles are used. A method of charging or installing the containing solution or a container containing the solution in a liquid tank having a vibrator at the bottom and using ultrasonic waves generated in the liquid tank, or a container in which a rod-shaped or flat-plate-shaped vibrator is installed. There is a method of passing a solution containing semiconductor nanocrystal particles and heat-dissipating particles and generating ultrasonic waves only when the particles pass through.

When it is carried out in the gas phase, surface modification of the child material particles to the base material particles using mechanochemical bonding, coating by a fluidized bed device, or the like can be used.

Further, it is preferable that the weight of the composite particles when heated at a temperature equal to or higher than the extinction temperature of the heat-disappearing particles is reduced by 30% or more as compared with that before heating. There is no particular limitation on the heating method at the time of measurement. For example, by using an electric muffle furnace (manufactured by Shirota Electric Furnace Material Co., Ltd.) or the like to hold the particles at a predetermined temperature and for a predetermined time, the heat-extinguishing particles are burnt and removed, and the weights before and after firing are measured. The weight loss rate when the composite particles are heated above the extinction temperature of the heat-disappearing particles can be calculated.

(4) Coating liquid A coating liquid is obtained by adding composite particles (3) of semiconductor nanocrystal particles and heat-dissipating particles and a binder resin into a dispersion solvent and mixing them.

The binder resin is added to adjust the coatability of the liquid, has a thickening effect, dissolves in a solvent, and is fired at 500 ° C. in the air, which is the normal firing atmosphere of the coating film. It is not particularly limited as long as it burns and disappears.
For example, polyethylene glycol, polyvinyl alcohol, ethyl cellulose and the like can be mentioned.

The solvent used in the coating liquid may be the same as or different from the solvent used when the composite treatment of the semiconductor nanocrystal particles and the heat-dissipating particles is performed. If they are different, when the compounding treatment is completed and then replaced with the solvent used for the coating liquid, or when the solvent used for the coating liquid is combined with the semiconductor nanocrystal particles and the heat-dissipating particles. After mixing the solvent used in the above, the solvent used in the compounding treatment of the semiconductor nanocrystal particles and the heat-dissipating particles is removed. When the solvent is different from the solvent used for the compounding treatment, an alcohol solvent such as water, methanol, ethanol, isopropyl alcohol, α-terpineol, a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, etc. Estel solvents such as ethyl formate, ethyl acetate, or n-butyl acetate, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or Amid solvents such as N-methyl-2-pyrrolidone, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or 1-chloronaphthalene. Halogenated hydrocarbon solvents such as n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene. , Ethylbenzene, or a hydrocarbon solvent such as xylene. These can be used alone or as a mixed solvent of two or more kinds.

The method for mixing the composite particles of the semiconductor nanocrystal particles and the heat-dissipating particles, the binder resin, and the solvent for dispersion is not particularly limited as long as a uniform mixing effect can be obtained.
Specific examples thereof include a stirring blade type mixer, a three-roll mill, a stirrer, a ball mill, a paint conditioner, a sand mill, an attritor, a disperser, a jet mill, and ultrasonic dispersion.
Further, heating, cooling, pressurization or depressurization may be performed at the time of mixing.

(5) Base material on which a transparent electron collecting electrode is arranged The type of base material is not particularly limited as long as it is made of a material transparent to visible light and has a certain mechanical strength, for example. , Glass, transparent plastic plate, transparent plastic film, inorganic transparent crystal, etc. are used.
The shape of the base material is not particularly limited, and may be a flat plate shape, a curved surface shape, a linear shape, an annular shape, or the like.

The electron current collecting electrode is not particularly limited as long as it is a conductive substance that is transparent to visible light, and ordinary photoelectric conversion elements, known ones used for liquid crystal panels, and the like can be used.
Examples thereof include 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, and these are individually or laminated. May be.
The thickness of the electron current collecting electrode is preferably 5 nm to 100 μm, more preferably 50 nm to 10 μm.

Further, a known one in which the electron collecting electrode and the substrate are integrated can also be used. For example, FTO coated glass, ITO coated glass, zinc oxide: aluminum coated glass, FTO coated transparent plastic film, ITO coated transparent plastic. Examples include a film.
Further, a transparent electrode obtained by doping tin oxide or indium oxide with cations or anions having different valences, or a metal electrode having a structure capable of transmitting light such as a mesh or a stripe is provided on a substrate such as a glass substrate. Good. These may be used alone, or a mixture of two or more kinds, or a laminated one.

Further, a metal lead wire or the like may be used as the electron current collecting electrode.
Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. Examples of the metal lead wire include a method in which the metal lead wire is installed on a substrate by vapor deposition, sputtering, crimping or the like, and ITO or FTO is provided on the metal lead wire.

(6) Semiconductor electrode A semiconductor electrode is obtained by coating the coating liquid (4) on a base material (5) on which a transparent electron current collecting electrode is arranged and firing it.

The method of applying the coating liquid is not particularly limited and can be applied according to a known method.
For example, a printing method, a dip method, a spray method, a wire bar method, a spin coating method, a roller coating method, a blade coating method, a gravure coating method and the like can be used. As a printing method, various methods such as letterpress, offset, gravure, intaglio, rubber plate, and screen printing can be used.

The firing of the coated film causes the semiconductor nanocrystal particles contained in the coated film to come into contact with each other electrically and mechanically to improve the film strength, improve the adhesion to the substrate, and reduce the electrical resistance. This is performed to eliminate components other than semiconductor nanocrystal particles such as heat-disappearing particles, binder resin, and solvent contained in the coating film.

The firing method is not particularly limited, and a known method such as a muffle furnace can be used.
The range of the firing temperature is not particularly limited, but if the temperature is raised too much, the resistance of the electron current collecting electrode increases and the base material melts. Therefore, 30 to 700 ° C. is preferable, and 100 to 600 ° C. is more preferable. .. The firing time is also not particularly limited, but is preferably 10 minutes to 10 hours.

After firing, for the purpose of increasing the surface area of semiconductor nanocrystal particles and increasing the efficiency of electron injection from photosensitizing compounds into semiconductor fine particles, for example, chemical plating using an aqueous solution of titanium tetrachloride or a mixed solution with an organic solvent. Electrochemical plating treatment using an aqueous solution of titanium chloride may be performed.

(7) Photosensitizing compound The photosensitizing compound arranged on the surface of the semiconductor electrode and for absorbing external light is not particularly limited as long as it is a compound photoexcited by the excitation light used, but specifically. The following compounds are mentioned.
Metal complex compounds described in JP-A-7-500630, JP-A-10-233238, JP-A-2000-26487, JP-A-2000-323191, JP-A-2001-59062, etc. Kumarin compounds described in JP-A-10-93118, JP-A-2002-164809, JP-A-2004-954450, J. Phys. Chem. C, 7224, Vol. 111 (2007), etc., JP-A-2004- Polyene compounds described in JP-A-95450, Chem. Commun., 4887 (2007), etc., JP-A-2003-264010, JP-A-2004-63274, JP-A-2004-115636, JP-A-2004-200068. , JP-A-2004-235502, J. Am. Chem. Soc., 12218, Vol. 126 (2004), Chem. Commun., 3036 (2003), Angelw. Chem. Int. Ed., 1923, Vol. Indolin compounds described in 47 (2008), etc., J. Am. Chem. Soc., 16701, Vol.128 (2006), J. Am. Chem. Soc., 14256, Vol.128 (2006), etc. Thiophen compounds, cyanine dyes described in JP-A-11-86916, JP-A-11-214730, JP-A-2000-106224, JP-A-2001-76773, JP-A-2003-7359, etc. Described in Kaihei 11-214731, JP-A-11-238905, JP-A-2001-52766, JP-A-2001-76775, JP-A-2003-7360, etc. Merosinin dyes, JP-A-10-92477. , JP-A-11-273754, JP-A-11-273755, JP-A-2003-31273 and the like, 9-arylxanthene compounds, JP-A-10-93118, JP-A-2003-31273, etc. , JP-A-9-199744, JP-A-10-233238, JP-A-11-204821, JP-A-11-265738, J. Phys. Chem., 2342, Vol.91 ( 1987), J. Phys. Chem. B, 6272, Vol.97 (1993), Electroanal. Chem., 3 1, Vol.537 (2002), JP-A-2006-032260, J. Porphyrins Phthalocyanines, 230, Vol.3 (1999), Angelw. Chem. Int. Ed., 373, Vol.46 (2007), Langmuir , 5436, Vol.24 (2008) and the like, and examples thereof include phthalocyanine compounds and porphyrin compounds.
In particular, among these, it is preferable to use a metal complex compound, a coumarin compound, a polyene compound, an indoline compound, and a thiophene compound.

As a method of arranging the photosensitizer compound (7) on the semiconductor electrode (6), a method of immersing the semiconductor electrode in a photosensitizer compound solution or a dispersion liquid and adsorbing the semiconductor electrode, or a method of adsorbing the solution or the dispersion liquid on an electron transport layer. A method of applying and adsorbing can be used.
In the former case, the dipping method, dip method, roller method, air knife method, etc. can be used, and in the latter case, the wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray method, etc. can be used. Can be used.
Further, it may be adsorbed in a supercritical fluid using carbon dioxide or the like.

A condensing agent may be used in combination when adsorbing the photosensitizer compound.
The condensing agent has a catalytic action that seems to physically or chemically bind the photosensitizing compound and the electron transporting compound to the surface of the inorganic substance, or acts stoichiometrically to favorably shift the chemical equilibrium. It may be either.
Further, a thiol or a hydroxy compound may be added as a condensation aid.

The solvent for dissolving or dispersing the photosensitizing compound is water, an alcohol solvent such as methanol, ethanol, or isopropyl alcohol, a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or acetate. Ester solvent such as n-butyl, ether solvent such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, etc. Amid solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or halogenated hydrocarbon solvents such as 1-chloronaphthalene. , N-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, or cumene. Hydrogen-based solvents can be mentioned, and these can be used alone or as a mixture of two or more kinds.

In addition, depending on the type of photosensitizer, there are some that work more effectively if the aggregation between the compounds is suppressed, so that a coagulation dissociator may be used in combination.
As the coagulation dissociator, steroid compounds such as cholic acid and chenodeoxycholic acid, long-chain alkylcarboxylic acids or long-chain alkylphosphonic acids are preferable, and they are appropriately selected for the dye to be used. The amount of these coagulation / dissociating agents added 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.
Using these, the temperature at which the photosensitizer compound or the photosensitizer compound and the coagulation / dissociator are adsorbed is preferably −50 ° C. or higher and 200 ° C. or lower.
Further, this adsorption may be carried out while standing or stirring.
Examples of the method for stirring 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.
Further, the adsorption is preferably performed in a dark place.

(8) Electrolyte-containing material The electrolyte-containing material may be a liquid containing a redox pair, a pseudo-solid obtained by gelling the liquid electrolyte-containing material with an appropriate gelling agent, or a hole. It may be a solid made of a transport material.

In the case of a liquid, redox pairs such as iodine / iodide ion, ferricianide / ferrocyanide, and 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. In addition, two or more of these solvents can be mixed and used.

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

As the hole transporting material, a known hole transporting compound is used, and specific examples thereof are shown in oxadiazole compounds published in Japanese Patent Publication No. 34-5466 and the like, and published in Japanese Patent Publication No. 45-555. Triphenylmethane compound, pyrazoline compound shown in Japanese Patent Publication No. 52-4188, hydrazone compound shown in Japanese Patent Publication No. 55-42380, etc., shown in JP-A-56-1235444, etc. Oxadiazole compounds, tetraarylbenzidine compounds shown in JP-A-54-58445, stillben compounds shown in JP-A-58-65440 or JP-A-60-98437. Etc., and may be used alone or as a mixture of two or more kinds.

The method for producing the electrolyte layer when the hole transport material is used is not particularly limited, but in consideration of the production 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 carried out 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 various wet printing methods such as letterpress, offset, gravure, concave plate, rubber plate, screen printing, etc. Method can be used. Further, the film may be formed in a supercritical fluid or a subcritical fluid.

(9) In the counter electrode, when the electrolyte-containing body (8) is a liquid, a catalyst layer is formed on the surface of a conductive material such as a base material (5) or a metal plate on which a transparent electron current collecting electrode is arranged. It becomes. The material used for the catalyst layer is not particularly limited as long as it is a material exhibiting conductivity. And it is preferable that it is electrochemically stable. For example, platinum, carbon, gold, conductive polymers and the like can be mentioned.

As a method for forming the catalyst layer, a known method can be used, for example, a sputtering method, a vapor deposition method, etc.
Examples thereof include a spray method, a spin coating method, and a chemical vapor deposition method (CVD method).
When the electrolyte-containing body (8) is a solid, it can be provided directly on the electrolyte-containing body.

At this time, the material used as the counter electrode is not particularly limited as long as it is a material exhibiting conductivity, but metals such as platinum, gold, silver, copper and aluminum, carbon-based compounds such as graphite, graphene, fullerene and carbon nanotubes, and ITO , FTO and other conductive metal oxides, polythiophene, polyaniline and other conductive polymers.

The method of providing the counter electrode on the solid electrolyte-containing body can be appropriately selected from methods such as coating, laminating, vapor deposition, CVD, and bonding.

Next, the present invention will be further described with reference to examples. It should be noted that the examples shown below are for specifically explaining the effects of the present invention, and do not limit the present invention in any way.

(Example 1)
A solution consisting of 10 parts by weight of titanium oxide and 90 parts by weight of ethanol was prepared by adding titanium oxide aggregates (semiconductor nanocrystal particles (1), Nippon Aerosil P25, average primary particle diameter of 21 nm) to ethanol. The titanium oxide aggregate was well wetted in advance by stirring this with a magnetic stirrer for 16 hours.
By irradiating the solution prepared in this manner with ultrasonic waves having a frequency of 40 kHz for 30 minutes using an ultrasonic homogenizer (Soniffier SLPe 40 manufactured by BRANSON), an impact force derived from cavitation is given to the titanium oxide aggregates. Was dispersed to obtain a dispersion.
The particle size distribution after dispersion was measured with a laser diffraction type particle size distribution meter (LA-950 manufactured by HORIBA, Ltd.), and the volume-based median diameter (Dv50) was calculated. (Titanium oxide alone)

On the other hand, by adding an aggregate (the heat-disappearing particles (2)) composed of polymethylmethacrylate A fine particles having a Dv50 of 400 nm according to the manufacturer's nominal to ethanol, the polymethylmethacrylate fine particles are composed of 20 parts by weight and 80 parts by weight of ethanol. The solution was adjusted. The polymethylmethacrylate A aggregate was well wetted in advance by stirring this with a magnetic stirrer for 2 hours.
The solution prepared in this way is irradiated with ultrasonic waves having a frequency of 40 kHz for 5 minutes using the ultrasonic homogenizer to give an impact force derived from cavitation to disperse polymethylmethacrylate A aggregates. I got the liquid.
The particle size distribution after dispersion was measured by the laser diffraction type particle size distribution meter, and Dv50 was calculated. (Polymethylmethacrylate A alone)

After mixing the titanium oxide dispersion prepared as described above and the polymethylmethacrylate A dispersion, the mixture is stirred with a magnetic stirrer for 20 minutes, and then irradiated with ultrasonic waves having a frequency of 40 kHz for 30 minutes using the ultrasonic homogenizer. , An impact force derived from cavitation was applied to obtain a dispersion liquid containing composite particles composed of titanium oxide particles and polymethylmethacrylate A particles (composite particles (3) of the semiconductor nanocrystal particles and heat-disappearing particles).
The volume-equivalent particle size distribution after the compounding treatment was measured by the laser diffraction type particle size distribution meter, and Dv50 was calculated. (Example 1)

(Example 2)
As the heat-dissipating particles (2), composite particles were produced in the same manner as in Example 1 except that polymethylmethacrylate B fine particles having a Dv50 of 800 nm according to the manufacturer's nominal were used. (Polymethylmethacrylate B alone, Example 2)

(Example 3)
As a composite treatment method, a water tank type ultrasonic cleaner (W-118 manufactured by Honda Electronics Co., Ltd.) was used, and composite particles were irradiated in the same manner as in Example 1 except that ultrasonic waves having a frequency of 45 kHz were irradiated for 30 minutes. Was produced.

(Example 4)
As a composite treatment method, a water tank type ultrasonic cleaner (W-118 manufactured by Honda Electronics Co., Ltd.) was used, and composite particles were irradiated in the same manner as in Example 2 except that ultrasonic waves having a frequency of 45 kHz were irradiated for 30 minutes. Was produced.

(Comparative Example 1)
After mixing the titanium oxide dispersion and the polymethylmethacrylate A dispersion prepared by the same method as in Example 1, a dispersion was prepared by stirring only for 5 hours with a magnetic stirrer, and the laser diffraction type particle size distribution meter was used. It was measured and Dv50 was calculated.

(Comparative Example 2)
After mixing the titanium oxide dispersion and the polymethylmethacrylate B dispersion prepared by the same method as in Example 3, a dispersion was prepared by stirring only for 5 hours with a magnetic stirrer, and the laser diffraction type particle size distribution meter was used. It was measured and Dv50 was calculated.

(Example 5)
As a solvent with respect to the dispersion liquid containing the composite particles composed of titanium oxide particles and polymethylmethacrylate A particles (composite particles of the semiconductor nanocrystal particles and heat-disappearing particles (3)) produced by the method of Example 1 as a solvent. Ethyl cellulose (manufactured by Kanto Chemical Co., Ltd., toluene: ethanol = 80:20, viscosity of 5% solution in solvent = 45 cP at 25 ° C.), α-terpineol (manufactured by Kanto Chemical Co., Ltd.) was added as a solvent, and magnetic. After stirring with a stirrer for 1 hour, ethanol was removed with a rotary evaporator to obtain a coating solution having a viscosity suitable for screen printing (the coating solution (4)).
The amount of each coating liquid added was adjusted so that the amount of titanium oxide was 15 parts by weight after ethanol was removed.

This coating liquid is applied to a glass substrate (base material (5) on which the transparent electron collecting electrode is arranged) on which FTO (F-topped Tin Oxide) is formed on the surface by screen printing, and then air is applied. It was fired at medium 500 ° C. for 30 minutes to form a porous semiconductor electrode (semiconductor electrode (6)). The results of observing the cross section of the semiconductor electrode obtained at this time with a scanning electron microscope (SEM) are shown in FIG.

This titanium oxide semiconductor electrode was adjusted to 0.5 mM as a ruthenium complex, and the N719 dye (cis-bis (isothiocianate) bis (2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (II)- Bis-tetra-n-butylammonium, manufactured by Solaronix) (photosensitizing compound (7)) in an acetonitrile / t-butanol (1: 1 volume ratio) mixed solution at room temperature for 2 days in the dark. The photosensitizing compound was adsorbed on the surface of the semiconductor electrode.

1-Ethyl-3-methylimidazolinium disianamide (manufactured by Sigma Aldrich) in a chlorobenzene (solid content 10%) solution in which the following compound (1), which is a self-synthesized product, is dissolved on a semiconductor electrode carrying a photosensitizing compound. , 27 mM) and 4-t-butylpyridine (manufactured by ACROSS, 55 mM) were added dropwise to the solution obtained by dropping the solution onto a semiconductor electrode carrying a photosensitizer and air-drying. Further, a solution obtained by adding 1-ethyl-3-methylimidazolinium disianamide (manufactured by Sigma Aldrich, 5 mM) to chlorobenzene (solid content 2%) in which the following compound (2), which is an in-house synthesized product, is dissolved, is prepared. The film was spin-coated to form a solid electrolyte-containing compound (the electrolyte-containing compound (8)). Gold was vacuum-deposited on this by 100 nm to form a counter electrode (the counter electrode (9)), and a solar cell was produced.
The IV measurement of the manufactured solar cell was performed to calculate the conversion efficiency. The IV measurement was performed under simulated sunlight irradiation (AM1.5, 100 mW / cm ² ).

(Example 6)
As the composite particles, a solar cell was manufactured in the same manner as in Example 5 except that the composite particles composed of titanium oxide particles and polymethylmethacrylate B particles prepared by the method of Example 2 were used, and the conversion efficiency was calculated. did.

(Comparative Example 3)
A solar cell was prepared in the same manner as in Example 5 except that the coating solution prepared by using the mixed solution of titanium oxide and polymethylmethacrylate A prepared by the method of Comparative Example 1 was used, and the conversion efficiency was calculated. did.

Table 1 shows the dispersions of titanium oxide alone, the dispersions of polymethylmethacrylate A alone, the dispersions of polymethylmethacrylate B alone, and the titanium oxide dispersions and polymethylmethacrylates obtained by Examples 1 to 4 and Comparative Examples 1 and 2. The Dv50 of the mixed solution containing the dispersion liquid is shown.

It can be seen that in Examples 1 to 4, it is larger than the Dv50 observed in the dispersion liquid of titanium oxide alone and the dispersion liquid of polymethylmethacrylate alone. On the other hand, Dv50 in Comparative Examples 1 and 2 is an intermediate value between Dv50 observed in the dispersion of titanium oxide alone and the dispersion of polymethylmethacrylate alone. This is because in Examples 1 to 4, composite particles composed of titanium oxide and polymethylmethacrylate were obtained by the cavitation action associated with ultrasonic irradiation, whereas in Comparative Examples 1 and 2, ultrasonic waves were not irradiated. Therefore, it is shown that the titanium oxide particles and the polymethylmethacrylate particles are present separately. Further, it is clear from FIG. 1 that the formation of such composite particles causes pores derived from heat-dissipating particles to be formed evenly in the semiconductor electrode, and the object of the present invention is achieved.

Next, Table 2 shows the conversion efficiencies of the solar cells obtained in Examples 5 to 6 and Comparative Example 3.

In these examples, a solid electrolyte-containing material is used, and the difficulty of filling the pores becomes remarkable as compared with the liquid electrolyte-containing material, which is suitable for determining the effect of the present invention. In Examples 5 to 6, titanium oxide and polymethylmethacrylate are compounded, and pores derived from heat-disappearing particles are formed evenly in the semiconductor electrode, as compared with Comparative Example 1 which has no such effect. High conversion efficiency can be obtained.

From Examples 1 to 6 and Comparative Examples 1 to 3 described above, according to the present invention, composite particles composed of semiconductor nanocrystal particles and heat-disappearing particles for providing a porous semiconductor electrode suitable for a photoelectric conversion element are formed. I found that I could do it.
In particular, since the compounding treatment is performed in the liquid phase in Examples 1 to 6, it is possible to easily achieve compounding without reaggregating the semiconductor nanocrystal particles. Therefore, according to these, it is possible to solve the problem that the heat-disappearing particles and the semiconductor nanoparticles are previously composited to form pores at the time of firing.

(Example 7)
A solution consisting of 10 parts by weight of titanium oxide and 90 parts by weight of ethanol was prepared by adding titanium oxide aggregates (semiconductor nanocrystal particles (1), Nippon Aerosil P25, average primary particle diameter of 21 nm) to ethanol. The titanium oxide aggregate was well wetted in advance by stirring this with a magnetic stirrer for 16 hours.
By irradiating the solution prepared in this manner with ultrasonic waves having a frequency of 40 kHz for 30 minutes using an ultrasonic homogenizer (Soniffier SLPe 40 manufactured by BRANSON), an impact force derived from cavitation is given to the titanium oxide aggregates. Was dispersed to obtain a dispersion.
The obtained volume-based particle size distribution after dispersion was measured with a laser diffraction type particle size distribution meter (LA-950 manufactured by HORIBA, Ltd.), and the volume-based median diameter (Dv50) was calculated. The volume-based median diameter (Dv50) was 0.138 μm.

On the other hand, polymethylmethacrylate C fine particles having a Dv50 of 60 nm according to the manufacturer's nominal were prepared. The weight average molecular weight (Mw) determined by gel permeation chromatography (HLC-8220 manufactured by Tosoh Corporation) of the polymethylmethacrylate C fine particles is 31,500, and a differential scanning calorimeter (manufactured by Seiko Instruments Inc.). The glass transition temperature (Tg) determined by DSC6200) was 85 ° C.
A solution composed of 20 parts by weight of polymethylmethacrylate fine particles and 80 parts by weight of ethanol by adding an aggregate (the heat-disappearing particles (2)) composed of polymethylmethacrylate C fine particles having an average primary particle diameter of 60 nm to ethanol. Was adjusted. The polymethylmethacrylate C aggregate was well wetted in advance by stirring this with a magnetic stirrer for 2 hours.
The solution prepared in this way is irradiated with ultrasonic waves having a frequency of 40 kHz for 5 minutes using the ultrasonic homogenizer to give an impact force derived from cavitation to disperse polymethylmethacrylate C aggregates. I got the liquid.

The titanium oxide dispersion and the polymethylmethacrylate C dispersion prepared as described above were mixed so that 45 parts by weight of polymethylmethacrylate C was contained in 100 parts by weight of titanium oxide, and then stirred with a magnetic stirrer for 20 minutes. After that, by irradiating ultrasonic waves having a frequency of 40 kHz for 30 minutes using the ultrasonic homogenizer, an impact force derived from cavitation is applied, and composite particles composed of titanium oxide particles and polymethylmethacrylate C particles (the semiconductor nanocrystal particles). And a dispersion containing composite particles (3) of heat-disappearing particles was obtained.

The volume-equivalent particle size distribution after the compounding treatment was measured by the above-mentioned laser diffraction type particle size distribution meter.
In addition, the dispersion liquid containing the composite particles is subjected to a centrifuge device (himac CT6e manufactured by Hitachi Koki Co., Ltd.), the supernatant liquid is discarded, and then the remaining slurry is placed in a clean oven (PVC-212 manufactured by Espec Co., Ltd.). The mixture was kept at 120 ° C. for 10 minutes to volatilize and remove ethanol. Next, this dry solid was placed in a heat-resistant glass petri dish and kept in an electric muffle furnace (manufactured by Shirota Electric Furnace Material Co., Ltd.) at 500 ° C. for 30 minutes to burn off and remove the polymethylmethacrylate C particles. By measuring the weight before and after firing in the electric muffle furnace, the weight loss rate when the composite particles were heated above the extinction temperature of the heat-disappearing particles was calculated.

Next, a solar cell was produced in the same manner as in Example 5 except that the dispersion liquid containing the obtained composite particles was used.
The IV measurement of the manufactured solar cell was performed to calculate the conversion efficiency. The IV measurement was performed under simulated sunlight irradiation (AM1.5, 100 mW / cm ² ).

(Example 8)
When the titanium oxide and the polymethylmethacrylate C were compounded, a coating liquid was prepared in the same manner as in Example 7 except that the polymethylmethacrylate C was mixed so as to contain 60 parts by weight with respect to 100 parts by weight of titanium oxide. did. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Reference example 1)
When the titanium oxide and the polymethylmethacrylate C were compounded, a coating liquid was prepared in the same manner as in Example 7 except that the polymethylmethacrylate C was mixed so as to contain 20 parts by weight with respect to 100 parts by weight of titanium oxide. did. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Reference example 2)
When the titanium oxide and the polymethylmethacrylate C were compounded, a coating liquid was prepared in the same manner as in Example 7 except that the polymethylmethacrylate C was mixed so as to contain 40 parts by weight with respect to 100 parts by weight of titanium oxide. did. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Example 9)
A coating liquid was prepared in the same manner as in Example 7 except that zinc oxide powder (average primary particle diameter of 30 nm) was used instead of titanium oxide. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Reference example 3)
A coating liquid was prepared in the same manner as in Reference Example 1 except that zinc oxide powder was used instead of titanium oxide. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Example 10)
As titanium oxide, titanium oxide having an average primary particle diameter of 133 nm was used, and a solution consisting of 10 parts by weight of this titanium oxide and 90 parts by weight of ethanol was prepared and then treated with a paint shaker for 48 hours to obtain a titanium oxide dispersion. A coating solution was prepared in the same manner as in Example 8 except for the above. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Example 11)
Titanium oxide having an average primary particle diameter of 18 nm was used as titanium oxide, and a solution consisting of 10 parts by weight of this titanium oxide and 90 parts by weight of ethanol was prepared and then treated with a paint shaker for 48 hours to obtain a titanium oxide dispersion. A coating solution was prepared in the same manner as in Example 8 except for the above. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Example 12)
Titanium oxide having an average primary particle diameter of 140 nm was used as titanium oxide, and a solution consisting of 10 parts by weight of this titanium oxide and 90 parts by weight of ethanol was prepared and then treated with a paint shaker for 48 hours to obtain a titanium oxide dispersion. A coating solution was prepared in the same manner as in Example 7 except for the above. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Reference example 4)
When the titanium oxide and the polymethylmethacrylate C were compounded, a coating liquid was prepared in the same manner as in Example 11 except that the polymethylmethacrylate C was mixed so as to contain 20 parts by weight with respect to 100 parts by weight of titanium oxide. did. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Reference example 5)
When the titanium oxide and the polymethylmethacrylate C were combined, a coating liquid was prepared in the same manner as in Example 12 except that the polymethylmethacrylate C was mixed so as to contain 20 parts by weight with respect to 100 parts by weight of the titanium oxide. did. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.

(Reference example 6)
A coating liquid was prepared in the same manner as in Example 7 except that polymethylmethacrylate D was used as the heat-dissipating particles. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.
The manufacturer's nominal Dv50 of polymethylmethacrylate D fine particles is 45 nm, the weight average molecular weight (Mw) determined by gel permeation chromatography (HLC-8220 manufactured by Tosoh Corporation) is 27,000, and a differential scanning calorimeter. The glass transition temperature (Tg) determined by (DSC6200 manufactured by Seiko Instruments, Inc.) was 75 ° C.

(Reference example 7)
A coating liquid was prepared in the same manner as in Example 7 except that polymethylmethacrylate E was used as the heat-dissipating particles. Further, using this coating liquid, a solar cell was produced in the same manner as in Example 7, and the conversion efficiency was calculated.
The manufacturer's nominal Dv50 of polymethylmethacrylate E fine particles is 110 nm, the weight average molecular weight (Mw) determined by the gel permeation chromatography is 48,400, and a differential scanning calorimeter (manufactured by Seiko Instruments Inc.). The glass transition temperature (Tg) determined by DSC6200) was 99 ° C.

Table 3 shows the weight loss rate of the composite particles shown in Examples 7 to 8 and Reference Examples 1 and 2 by heating at 500 ° C. Further, FIG. 2 shows a volume-based particle size distribution when the composite particles shown in Examples 7 to 8 and Reference Examples 1 and 2 are measured with a laser diffraction type particle size distribution meter.

The weight loss rate of the composite particles shown in Examples 7 and 8 exceeds 30% from Table 3. At this time, as shown in FIG. 2, the peaks of the observed particles are in a region of 1 μm or more, which is larger than both the titanium oxide dispersion (120 nm) and polymethylmethacrylate C (60 nm), and show a mountainous distribution. ing. This indicates that the particle compositing is completely progressing. On the other hand, the weight loss rate of the composite particles shown in Reference Examples 1 and 2 is less than 30% from Table 3. At this time, the peaks of the observed particles are the one-mountain distribution of 180 nm, which is slightly larger than the titanium oxide dispersion in Reference Example 1, and the two-mountain distribution between Reference Example 1 and Example 7 in Reference Example 2. there were. From this, in Reference Examples 1 and 2, particle compositing has not progressed sufficiently.
From these results, when the weight reduction rate of the composite particles is 30% or more, the semiconductor nanocrystal particles and the heat-dissipating particles are completely composited.

Table 4 shows the conversion efficiency when a coating liquid was prepared using the composite particles obtained in Examples 7 to 12 and Reference Examples 1 to 7 to prepare a solar cell.

In the solar cells obtained in Examples 7 to 8, high conversion efficiency is obtained because the optimum pores for filling the high-viscosity electrolytic solution are uniformly formed in the semiconductor electrode film. On the other hand, in Reference Examples 1 and 2, since the compounding is insufficient, the filling of the electrolytic solution is insufficient, and the conversion efficiency is lower than that in Examples 7 to 8. Further, since zinc oxide is used as the semiconductor nanoparticles in Example 9, the conversion efficiency is lower than that of Examples 7 to 8, but the conversion efficiency is higher than that of Reference Example 3, so that the semiconductor nanoparticles are used. It can be seen that even zinc oxide has an effect of improving the filling of the electrolytic solution by compounding the particles. From Examples 10 to 12, when the primary particle size of titanium oxide is less than 20 nm or more than 135 nm, the pores formed by the contact between the titanium oxide particles are too small to be filled with the electrolytic solution, or are arranged. Since the amount of the sensitizing dye is reduced, the conversion efficiency is lower than that of Examples 7 to 8. However, by comparison with Reference Examples 4 to 5, if the particle compositing is incomplete, the conversion efficiency is further lowered, so it is clear that the effect of improving the electrolyte filling by the particle compositing can be seen even in this case. ..

Further, the solar cells obtained in Example 7 have higher conversion efficiencies than the solar cells obtained in Reference Examples 6 to 7. This is an effect obtained by setting the weight average molecular weight and the glass transition temperature of polymeryl methacrylate, which are heat-dissipating particles, in an appropriate range. That is, in Reference Example 6, the glass transition temperature is too low, so that the heat-disappearing particles are excessively softened. On the other hand, in Reference Example 7, since the glass transition temperature is too high, the connectivity of the pores obtained by extinction is insufficient. In either case, the structure is not more desirable for injecting and permeating the high-viscosity electrolytic solution into the inside of the semiconductor porous electrode.

From the above, according to the present invention, it was possible to provide a coating liquid containing composite particles composed of semiconductor nanocrystal particles and heat-disappearing particles for forming a porous semiconductor electrode suitable for a photoelectric conversion element.
Note that Reference Examples 1 to 5 do not have a configuration in which the weight of the composite particles when heated at a temperature equal to or higher than the extinction temperature of the heat-disappearing particles is reduced by 30% or more as compared with that before heating. By further improving the configurations other than this, it is expected that the effect is higher than the conversion efficiency of the solar cells shown in Reference Examples 1 to 5. Therefore, it can be said that Reference Examples 1 to 5 are test examples in which the effects of the present invention can be achieved by various improvements.

Japanese Patent No. 4887664 Japanese Unexamined Patent Publication No. 2010-118158 Japanese Unexamined Patent Publication No. 2011-181281 Japanese Unexamined Patent Publication No. 2012-072234

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

Claims (8)

A coating liquid containing composite particles composed of semiconductor nanocrystal particles and heat-dissipating particles.
The heat-disappearing particles are dye-sensitized as polymethylmethacrylate having a weight average molecular weight (Mw) of 30,000 or more and 45,000 or less and a glass transition temperature (Tg) of 80 ° C. or more and 95 ° C. or less . A coating liquid for forming porous semiconductor electrodes of solar cells . The coating liquid according to claim 1, wherein the semiconductor nanocrystal particles and the heat-dissipating particles are composited in a liquid phase. The coating liquid according to claim 1 or 2, wherein the semiconductor nanocrystal particles and the heat-dissipating particles are composited by a cavitation action. The coating liquid according to any one of claims 1 to 3, wherein the weight of the composite particles when heated at a temperature equal to or higher than the extinction temperature of the heat-disappearing particles is reduced by 30% or more as compared with that before heating. .. The coating liquid according to any one of claims 1 to 4, further comprising a binder resin and a solvent. The coating liquid according to any one of claims 1 to 5, wherein the semiconductor nanocrystal particles are titanium oxide particles. The coating liquid according to any one of claims 1 to 6, wherein the average primary particle size of the semiconductor nanocrystal particles is 20 nm or more and 135 nm or less. A coating step of applying the coating liquid according to any one of claims 1 to 7 .
A method for forming a porous semiconductor electrode of a dye-sensitized solar cell, which comprises a heating and firing step of heating and firing the coating film formed in the coating step.