JP2016119467A - Photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element in which electrolyte is sufficiently filled in a porous semiconductor electrode thereby to achieve excellent photoelectric conversion efficiency.SOLUTION: In a photoelectric conversion element 10 having a porous semiconductor electrode layer 13 having a photosensitizing compound and semiconductor nano-crystal particles, and an electrolyte layer 14 between an electrode 11 and a counter electrode 12 which are a pair of electrodes, the porous semiconductor electrode layer 13 has indefinite-shape gaps 13A and linear gaps 13B leading to the indefinite-shape gaps 13A, and the electrolyte layer 14 is composed of a solid electrolyte or a highly viscous electrolytic solution.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a photoelectric conversion element.

  As the introduction of renewable energy is becoming a global trend, there is a great interest in solar cells, which are photoelectric conversion elements. As solar cells, those using silicon such as single crystal silicon type, polycrystalline silicon type, and amorphous silicon type, and those using compound semiconductor such as copper indium selenide have been put into practical use. However, since any of these solar cells requires a large amount of energy for module production, there is a limitation in reducing the production cost, which is a limitation in the large-scale spread of solar cells.

  On the other hand, there is a dye-sensitized solar cell as a solar cell that is relatively low in production energy and advantageous for cost reduction. A dye-sensitized solar cell has a conductive transparent thin film, a porous semiconductor electrode, a photosensitizing compound (sensitizing dye, etc.), and an electrolyte-containing body (electrolytic solution, etc.) having a redox pair on a transparent substrate made of glass or the like. The counter electrode is laminated in order. By making the semiconductor electrode holding the sensitizing dye porous, the specific surface area is increased from several hundred times to 1000 times, and the amount of the sensitizing dye held is greatly increased, so that a large photocurrent can be obtained. This is a feature (see Non-Patent Documents 1 and 2, for example).

  Generally, a semiconductor electrode for a dye-sensitized solar cell is prepared by formulating a dispersion liquid containing semiconductor nanocrystal particles and a binder into a coating liquid whose viscosity is adjusted, and applying this to a substrate by a method such as screen printing. Thereafter, the binder is removed by heating and baking to obtain a porous structure. Titanium oxide is often used as the semiconductor nanocrystal particle.

  The power generation principle of the dye-sensitized solar cell is as follows: (1) the photosensitized compound fixed on the surface of the semiconductor electrode absorbs external light such as sunlight and enters an excited state. (2) This is an electron with respect to the semiconductor electrode. (3) The emitted electrons diffuse through the semiconductor electrode and arrive at the conductive transparent substrate, (4) move from the conductive substrate to the counter electrode via an external circuit, (5) at the counter electrode Reduce the redox couple in the electrolyte solution. (6) The reductant moves through the electrolyte solution and arrives at the dye, reducing the electron-sensitized photosensitized compound to the ground state (1). Based on cycle (6). By repeating this cycle, power generation is continuously performed while 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 sunlight absorption that is the starting point of the power generation cycle, the larger the amount of the sensitizing dye, the more advantageous. Therefore, it is desirable that the area of the semiconductor electrode surface that is the dye fixing surface is large. On the other hand, in order for the redox couple in the electrolyte to return the dye to the ground state and complete the power generation cycle, the electrolyte is sufficiently filled in the pores in the porous structure, and the electrolyte and the dye are in contact with each other. However, if the pores are too narrow, the electrolyte solution cannot penetrate sufficiently and is not filled in the pores, so it is necessary to construct pores that exceed the appropriately set diameter. In particular, this problem becomes significant when the electrolyte has a high viscosity and is difficult to penetrate into the pores.

  As a method for accelerating the filling of the porous semiconductor electrode layer with the electrolyte in the dye-sensitized photoelectric conversion element, a structure in which voids are provided in the porous semiconductor electrode layer has already been proposed. For example, in Patent Document 1, a porous semiconductor electrode layer having sufficient voids and specific surface area is formed by using nanotube-like crystalline titania (titania nanotube) as a single body or a mixture as a porous semiconductor layer material.

  Patent Document 2 proposes a method for producing a porous semiconductor electrode layer in which the void ratio and void size are controlled by adding a void-forming material to the coating liquid.

  The porous semiconductor electrode layer obtained by these methods can be smoothly filled with an electrolytic solution, and an improvement in photoelectric conversion characteristics can be expected.

  However, these conventional examples do not have an optimal semiconductor electrode layer structure for improving the photoelectric conversion characteristics. For example, in the method of adding titania nanotubes of Patent Document 1, since the arrangement of titania nanotubes is not controlled and is randomly arranged in the porous semiconductor, voids larger than necessary are formed, The number of sensitizing dyes is excessively reduced.

  Further, in the method of Patent Document 2 in which a material for forming voids is added to the coating liquid, the voids obtained are generally true spherical isolated holes. At this time, since the voids do not have a path to the outside of the film, the void forming purpose of sufficiently filling the electrolyte solution from the outside to the inside of the film cannot be sufficiently achieved.

  An object of the present invention is to solve the above-described problems and to provide a photoelectric conversion element in which an electrolyte is sufficiently filled in a porous semiconductor electrode layer, and thereby excellent photoelectric conversion efficiency can be obtained.

  A photoelectric conversion element according to the present invention for solving the above problems is a photoelectric conversion element in which a porous semiconductor electrode layer having a photosensitizing compound and semiconductor nanocrystal particles and an electrolyte layer are provided between a pair of electrodes. The porous semiconductor electrode layer has an irregularly shaped void and a streaky void connected to the irregularly shaped void, and the electrolyte layer is made of a solid electrolyte or a highly viscous electrolyte.

  ADVANTAGE OF THE INVENTION According to this invention, electrolyte can fully be filled in a porous semiconductor electrode layer, and the photoelectric conversion element from which the outstanding photoelectric conversion efficiency is obtained by this can be provided.

It is a schematic sectional drawing of a photoelectric conversion element. The cross-sectional SEM observation image of the semiconductor electrode obtained by Example 1 is shown.

  Hereinafter, the photoelectric conversion element 10 according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of the photoelectric conversion element 10. As shown in FIG. 1, the photoelectric conversion element 10 includes a pair of electrodes 11 and a counter electrode 12, and a porous semiconductor electrode layer 13 and an electrolyte layer 14 provided between the electrodes.

  The first electron collecting electrode that is the electrode 11 is provided on one surface of the substrate 15. The porous semiconductor electrode layer 13 is provided on the surface of the base material 15 having the electrode 11 and is connected to the photosensitizing compound, the semiconductor nanocrystal particles, the irregularly shaped void 13A, and the irregularly shaped void 13A. And the gap 13B. The electrolyte layer 14 is provided to face the electrode 11 so as to sandwich the porous semiconductor electrode layer 13. The counter electrode 12 has a second electron current collecting electrode 19 on one surface, and is provided with the second electron current collecting electrode 19 facing the porous semiconductor electrode layer 13 so as to sandwich the electrolyte layer 14. The electrolyte layer 14 is made of a solid electrolyte or a highly viscous electrolyte.

  Here, the indefinite shape means a shape having no regularity in the contour line unlike a true spherical shape or the like. Examples of the shape having no regularity include an amoeba shape.

  In the present invention, the porous semiconductor electrode layer has an irregularly shaped void and a streaky void connected to the irregularly shaped void, so that the solid or high-viscosity electrolyte permeates into the irregularly shaped void. Then, the electrolytic solution penetrates into the porous semiconductor electrode layer from the streak-like voids connected to the irregular-shaped voids, and the voids and the pores are sufficiently filled, so that the photoelectric conversion efficiency can be improved.

  Usually, the pores formed in the porous semiconductor electrode of the dye-sensitized solar cell are given as a gap between the semiconductor particles stacked densely. Assuming that the particle sizes are perfectly aligned and the particles are closest packed, the pore size given by the geometric calculation is approximately 1/3 of the particle size. For the purpose of increasing the specific surface area in the porous semiconductor electrode and increasing the amount of adsorbed dye, a particle size of 20 to 50 nm is generally selected as the semiconductor particle, and the pores formed at this time are determined to be about 7 to 17 nm. It is done. This is a very insufficient pore size for filling a solid electrolyte or a highly viscous electrolyte.

  In addition, even when a void forming material is added to the coating liquid and pores having a diameter larger than the gap between the particles are provided, if these are isolated pores, the pores connecting the isolated pores Has a diameter of 7 to 17 nm consisting of gaps between particles as described above. Therefore, it is difficult to sufficiently fill all the isolated holes formed in the film with the electrolytic solution.

  On the other hand, in the present invention, an irregularly shaped void necessary for improving the permeability of the electrolytic solution and a streaky void connected to the irregularly shaped void are provided. The streak-like voids connected to the irregularly shaped voids serve as a passage for the electrolyte that permeates from the outside of the membrane to communicate with the voids inside the membrane, and the irregularly shaped voids are sufficiently filled with electrolyte without stagnation. Making it possible. Further, not only as a passage for connecting the electrolyte solution from the outside of the membrane to the inside of the membrane, but also as a passage connecting the voids in the membrane, the electrolyte filling property is further improved.

  Thereby, even if it is a solid electrolyte or a highly viscous electrolyte, the porous semiconductor electrode layer can be sufficiently filled, and a photoelectric conversion element having high conversion efficiency can be obtained.

As a method for forming a porous semiconductor electrode layer having an irregularly shaped void and a streaky void connected to the irregularly shaped void, for example, in a dispersion of semiconductor nanocrystal particles, The method of forming a porous semiconductor electrode layer using the coating liquid obtained by adding the liquid containing an aggregate or a heat extinction fiber is mentioned.
In a preferred method for producing the photoelectric conversion element of the present invention, a porous semiconductor electrode layer having a photosensitizing compound and semiconductor nanocrystal particles and an electrolyte layer are provided between a pair of electrodes, and the electrolyte layer is a solid electrolyte or A method for producing a photoelectric conversion element comprising a highly viscous electrolytic solution, the coating obtained by adding a liquid containing aggregates of heat extinguishing particles or heat extinguishing fibers to the dispersion of the semiconductor nanocrystal particles A step of forming a porous semiconductor electrode layer using a liquid to form the porous semiconductor electrode layer having an irregularly shaped void and a streaky void connected to the irregularly shaped void;

  Next, an embodiment of the photoelectric conversion element 10 according to the present invention will be described in more detail. Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are attached thereto, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise described, the present invention is not limited to these embodiments.

<Electrode 11>
The electrode 11 is a transparent electron current collecting electrode disposed on the surface of the substrate 15.

  The type of the substrate 15 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, a transparent plastic plate, a transparent plastic film, an inorganic transparent crystal The body is used.

  The shape of the substrate 15 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 collecting electrode is not particularly limited as long as it is a conductive material transparent to visible light, and a known photoelectric conversion element or a known one used for a liquid crystal panel or the like can be used.

  Examples of the conductive material 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. A single layer or a plurality of layers may be stacked.

  The thickness of the electron collector electrode is preferably 5 nm to 100 μm, more preferably 50 nm to 10 μm.

  As the electrode 11, a known one in which the electron collector electrode and the base material 15 are integrated can be used. For example, FTO-coated glass, ITO-coated glass, zinc oxide: aluminum-coated glass, FTO-coated transparent plastic film, Examples thereof include an ITO-coated transparent plastic film.

  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, you may use a metal lead wire etc. as an electronic current collection electrode.

  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.

<Porous semiconductor electrode layer 13>
The porous semiconductor electrode layer 13 is provided on the electron collecting electrode 11 disposed on the base material 15 that is transparent to visible light.

  As a method for forming the porous semiconductor electrode layer 13, a coating liquid (6) described later containing semiconductor nanocrystal particles is applied to the surface of the substrate 15 on which the electrode 11 is provided by a method such as screen printing. Drying and firing can be mentioned. Therefore, in the following, a method for forming the porous semiconductor electrode layer 13 having the irregularly shaped void 13A and the streaky void 13B connected to the irregularly shaped void 13A by a coating method will be described, but the method is not necessarily limited to this method. Instead, for example, a widely known method can be used, such as formation by drying conditions after coating.

  The porous semiconductor electrode layer 13 having the irregularly shaped void 13A and the streaky void 13B connected to the irregularly shaped void 13A is formed by applying the coating liquid (6) to the base material 15 on which the transparent electron collector electrode is disposed. It can be obtained by a coating method in which it is applied and fired.

<Coating fluid (6)>
The coating liquid (6) comprises a semiconductor nanocrystal particle dispersion (2) containing semiconductor nanocrystal particles (1), an aggregate of heat extinguishing particles or heat extinguishing fibers (3), and a binder resin (4). And a dispersion solvent (5).

<Preparation of coating liquid (6)>
The coating liquid (6) is obtained by first dispersing the semiconductor nanocrystal particles (1) alone to obtain a semiconductor nanocrystal particle dispersion (2), and then agglomerates of heat extinguishing particles or heat extinguishing fibers (3 ), A binder resin (4), and a dispersion solvent (5) are mixed and dispersed, and dissolved to obtain a coating liquid (6). Each component will be described later.

  The method of mixing the semiconductor nanocrystal particles, the heat extinguishing particle aggregate or the heat extinguishing fiber, the binder resin, and the dispersion solvent is not limited to the above method, and is particularly limited as long as a uniform mixing effect can be obtained. is not.

  However, it is desirable to add a heat extinguishing particle aggregate or a heat extinguishing fiber, a binder resin, and a dispersion solvent while stirring the semiconductor nanocrystal particle dispersion. It is preferable to carry out a uniform mixing process after performing agitation.

  Specific examples of the uniform mixing treatment include a stirring blade 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. During the uniform mixing treatment, the heat extinguishing particles are aggregated in the liquid to form aggregates that give voids of irregular shapes including streaks.

  Moreover, you may perform a heating, cooling, pressurization, or pressure reduction for a uniform mixing process.

  In the coating liquid, in order to prevent re-aggregation of semiconductor nanocrystal particles, acids such as hydrochloric acid, nitric acid, acetic acid, surfactants such as polyoxyethylene (10) octylphenyl ether, acetylacetone, 2-aminoethanol, ethylenediamine, etc. A chelating agent or the like can be added. Further, a cationic dispersant such as polycarboxylic acid may be added. Acetylacetone that can uniformly disperse the titania powder with a medium and does not cause separation of the titania powder and the solvent is preferable. These can be used alone or as a mixed solvent of two or more. The dispersion solvent is preferably added in an amount of 1 to 5% by weight based on the dispersion.

<Semiconductor nanocrystal particles (1)>
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. The semiconductor nanocrystal particle may be an aggregate of a crystalline semiconductor.

  Specific examples of the semiconductor nanocrystal particles include a single semiconductor such as silicon and germanium, a compound semiconductor typified by a metal chalcogenide, or a compound having a perovskite structure.

  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. Among these, titanium oxide having a high conductor energy is most preferable. The semiconductor nanocrystal particles may be used alone or in combination of two or more.

  The average primary particle diameter of the titanium oxide used 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 average primary particle size is too small, the semiconductor porous membrane is excessively densified and the pore size formed in the porous membrane becomes small, so that there is a problem that permeation or filling of the electrolyte is restricted. On the other hand, if the average primary particle size is too large, the surface area contained in the semiconductor porous membrane is reduced, and thus there is a problem that the amount of adsorbed dye cannot be sufficiently secured.

<Semiconductor nanocrystal particle dispersion (2)>
A semiconductor nanocrystal particle dispersion liquid is obtained by dispersing the semiconductor nanocrystal particles in a dispersion solvent.

  Solvents for dispersing the semiconductor nanocrystal particles include water, methanol, ethanol, isopropyl alcohol, alcohol solvents such as α-terpineol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or Ester solvents such as n-butyl acetate, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone Amide solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, Halogenated hydrocarbon solvents such as lomobenzene, iodobenzene or 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.

  For the dispersion, a generally known method can be used. For example, the dispersion can be performed by a media dispersion such as a bead mill or a paint shaker, a homogenizer utilizing ultrasonic waves or shearing by a rotor, a jet mill, or the like.

<Aggregates of heat extinguishing particles or heat extinguishing fibers (3)>
In order to form the porous semiconductor electrode layer 13 having the irregularly shaped voids 13A and the streaky voids 13B connected to the irregularly shaped voids 13A by a coating method, a heat extinguishing particle aggregate or a heat extinguishing fiber is used. use.

  In the case of using the heat extinguishing particle aggregate, the heat extinguishing particle is not particularly limited as long as it burns and disappears at 500 ° C. in the air that is the normal firing atmosphere of the coating film, and is not particularly limited. Any material such as a polymer resin or a carbon material can be used.

As specific polymers, polymer resins such as polyethylene, polypropylene, polystyrene, polystyrene acrylic, polyester, polymethyl methacrylate, and polyurethane are preferable. Examples of the carbon material include graphene, carbon nanotube, fullerene, and carbon fiber.
In particular, polymethyl methacrylate is preferable, and polymethyl methacrylate having a weight average molecular weight (Mw) of 30,000 to 45,000 and a glass transition temperature (Tg) of 80 ° C. to 95 ° C. is particularly preferable. By using polymethylmethacrylate having Mw and Tg within this range, the heat extinguishing particles are softened and deformed and then burned and disappeared in the temperature rising process at 500 ° C. As a result, the irregularly shaped void formed inside the semiconductor porous electrode has a more desirable structure for injecting and permeating the high-viscosity electrolyte.

  It is desirable to prepare a coating liquid by preparing a liquid containing agglomerates of heat extinguishing particles and then adding it to the semiconductor nanoparticle dispersion.

  The content of the heat extinguishing particle aggregate or the heat extinguishing fiber is preferably 10 to 50% by mass with respect to the semiconductor nanocrystal particles which are particles giving the porous semiconductor electrode. When the content is 10% or less, almost no voids are generated, which is insufficient for filling the electrolytic solution. When the content exceeds 50%, voids increase excessively, so that when formed in the porous semiconductor layer, the strength is lowered, and deterioration as a dye-sensitized solar cell is likely to proceed. Accordingly, the heat extinguishing particles are preferably 10% or more and 50% or less with respect to the particles giving the porous semiconductor electrode.

  The average particle diameter of the heat extinguishing particles is not particularly limited as long as the aggregate particle diameter is 100 nm or more and 2,000 nm or less. Aggregate particle size is defined as the volume-based median diameter (Dv50). In the present invention, it is important that the particle diameter of the aggregate is within this range. When the particle size of the aggregate is less than 100 nm, it does not act as a hole that can sufficiently advance the electrolyte filling. On the other hand, when the particle size of the aggregate exceeds 2,000 nm, the pores formed after the heating disappears become larger than necessary, and sometimes exceeds the thickness of the semiconductor porous film. In this case, it is not desirable because it causes a coating film defect rather than a void in the porous film, resulting in a non-uniform semiconductor porous film.

  The method for forming the aggregate of the heat extinguishing particles is not particularly limited. For example, the heat extinguishing particles can be monodispersed in a solvent with high affinity and then put into a solvent with low affinity to be aggregated. Alternatively, the particles may be aggregated by heating or pressure bonding. Moreover, you may utilize the agglutination reaction in the gaseous phase by mechanochemical bonding or spray atomization.

  Alternatively, the solution containing the heat extinguishing particles may be irradiated with ultrasonic waves and aggregated by the cavitation action. The method of irradiating ultrasonic waves is not particularly limited, and a known method can be used.

  For example, a rod-shaped or flat plate-like vibrator is put into a container containing a solution containing heat extinguishing particles, and a method of generating ultrasonic waves inside the container, a solution containing heat extinguishing particles or a container containing a solution, A method in which a vibrator is placed in or installed in a liquid tank at the bottom and ultrasonic waves generated in the liquid tank are used, and a solution containing heat extinguishing particles is passed through a container in which a rod-like or flat vibrator is installed. And a method of generating ultrasonic waves only when passing through.

  When using a heat extinguishing fiber, the material is not particularly limited as long as it burns and disappears in air at 500 ° C., and any known polymer resin or carbon material may be used. Can do.

<Binder resin (4)>
The binder resin is added to adjust the coating property of the coating liquid, and has a thickening effect, is dissolved in a solvent, and is 500 ° C. in air, which is a normal firing atmosphere of the coating film. There is no particular limitation as long as it burns and disappears during firing. For example, polyethylene glycol, polyvinyl alcohol, ethyl cellulose and the like can be mentioned.

<Dispersion solvent (5)>
The solvent used for the dispersion is preferably the same solvent used when the semiconductor nanocrystal particle dispersion is prepared. However, if different, the solvent used for the coating solution may be replaced after the dispersion treatment.

  Solvents different from the semiconductor nanocrystal particle dispersion include water, methanol, ethanol, isopropyl alcohol, alcohol solvents such as α-terpineol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, acetic acid. Ester solvents such as ethyl or n-butyl acetate, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl- Amide solvents such as 2-pyrrolidone, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluoro Halogenated hydrocarbon solvents such as benzene, bromobenzene, iodobenzene, or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, Examples thereof include hydrocarbon solvents such as toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

<Preparation of porous semiconductor electrode layer 13>
The porous semiconductor electrode layer 13 is obtained by coating the coating liquid on the base material 15 on which the transparent electronic current collecting electrode 16 is disposed and baking it. That is, the aggregates of heat extinguishing particles or the heat extinguishing fibers (3) are dispersed in the semiconductor nanocrystal particle dispersion liquid (2) with the above-described particle size. Aggregates of heat extinguishing particles or heat extinguishing fibers (3) disappear due to vaporization, combustion, and the like due to heating in the heating step of baking. For this reason, in the porous semiconductor electrode layer 13 after firing, voids 13A having an irregular shape in the layer of semiconductor nanocrystal particles and streaky voids 13B connected to the voids 13A having an irregular shape are generated.

  There is no restriction | limiting in particular in the coating method of a coating liquid, According to a well-known method, it can carry out. As the coating 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, or 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.

  Firing of the coated film brings semiconductor nanocrystal particles contained in the coating solution into electrical and mechanical contact to improve film strength, improve adhesion with the substrate, and reduce electrical resistance. This is performed in order to eliminate components other than semiconductor particles such as aggregates of heat extinguishing particles, binder resin, and dispersion solvent contained in the dispersion.

  The firing method is not particularly limited, and a known method such as a muffle furnace can be used. Although there is no restriction | limiting in particular in the range of baking temperature, 30-700 degreeC is preferable and 100-600 degreeC is more preferable since resistance of an electron current collection electrode will become high or a base material will melt | melt if temperature is raised too much. . Moreover, although there is no restriction | limiting in particular also in baking time, 10 minutes-10 hours are preferable.

  After firing, for the purpose of increasing the surface area of the semiconductor particles and increasing the efficiency of electron injection from the photosensitizing compound to the semiconductor nanocrystal particles, for example, chemical plating using an aqueous solution of titanium tetrachloride or a mixed solution with an organic solvent, An electrochemical plating process using a titanium chloride aqueous solution may be performed.

  A porous semiconductor layer is formed on the semiconductor electrode obtained as described above, and the porous semiconductor layer has an irregularly shaped void and a streaky void connected to the irregularly shaped void. Such a structure can be confirmed by observing the cross section of the semiconductor electrode film with an electron microscope.

The specific surface area of the porous semiconductor electrode layer 13 is preferably 30 to 60 m ² / g. Here, the specific surface area is a surface area (m ² ) per unit mass (1 g) of the porous semiconductor electrode layer 13.

When the specific surface area is less than 30 m ² / g, the amount of dye adsorbed decreases and the exchange of electrons decreases, so that the battery performance may deteriorate. On the other hand, if the specific surface area exceeds 60 m ² / g, the voids are reduced, so that the electrolyte solution is not sufficiently filled, and the conversion efficiency may be lowered.

  The porosity of the porous semiconductor electrode layer 13 is preferably 10 to 50%. The porosity is the ratio of the area of the void to the cross-sectional area of the porous semiconductor electrode layer 13. If the porosity is less than 10%, the electrolyte solution is not sufficiently filled, and the conversion efficiency may be lowered. When the porosity exceeds 50%, the specific surface area decreases, so that the amount of dye adsorbed decreases, conversion efficiency may decrease, and the film strength of the porous semiconductor layer may decrease.

<Photosensitizing compound>
A photosensitizing compound is disposed on the surface of the porous semiconductor electrode layer 13. The photosensitizing compound absorbs external light such as sunlight and enters an excited state, and emits electrons to the porous semiconductor electrode layer 13. The photosensitizing compound for absorbing external light is not particularly limited as long as it is a compound that is photoexcited by the excitation light used. Specific examples of the photosensitizing compound include 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.

<Method for Arranging Photosensitizing Compound to Porous Semiconductor Electrode Layer 13>
As a method for disposing the photosensitizing compound on the porous semiconductor electrode layer 13, a method of immersing the semiconductor electrode in a photosensitizing compound solution or dispersion and adsorbing it, or applying the solution or dispersion to the electron transport layer. 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.

  In addition, depending on the type of photosensitizing compound, there are compounds that work more effectively when aggregation between the compounds is suppressed, and therefore, an aggregation dissociator 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.

<Electrolyte layer 14>
In the present invention, as the electrolyte-containing body constituting the electrolyte layer 14, a solid electrolyte or a highly viscous electrolyte can be used. The solid electrolyte may be a pseudo solid obtained by gelling an electrolyte-containing body using an appropriate gelling agent, or may be a solid made of a hole transport material. Further, the high viscosity electrolyte refers to an electrolyte having a viscosity of 5 mPa · s or more. Examples of the highly viscous electrolytic solution include an electrolytic solution containing iodine ions and using the ionic liquid as a solvent, but are particularly limited as long as the electrolytic solution has a viscosity of 5 mPa · s or more and includes a redox couple. is not.

  When the electrolyte-containing material is a liquid, redox couples such as iodine / iodide ions, ferricyanide / ferrocyanide, quinone / hydroquinone, and additives such as lithium iodide and tertiary butylpyridine are added to the solvent. What is dissolved is 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 may be added to the liquid electrolyte-containing body 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.

<Counter electrode 12>
When the electrolyte-containing material of the electrolyte layer 14 is a liquid, the counter electrode 12 is formed by forming a catalyst layer on the surface of a conductive material such as a substrate 18 or a metal plate on which a transparent electron current collecting electrode is disposed. The material used for the catalyst layer 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. The base material 18 can use the same material as the base material 15 of the electrode 11.

  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).

  Moreover, when the electrolyte containing body of the electrolyte layer 14 is solid, the counter electrode 12 can be directly provided on the electrolyte containing body. At this time, the material used as the counter electrode 12 is not particularly limited as long as it is a material exhibiting conductivity. However, metals such as platinum, gold, silver, copper, and aluminum, carbon-based compounds such as graphite, graphene, fullerene, and carbon nanotubes, Examples thereof include conductive metal oxides such as ITO and FTO, and conductive polymers such as polythiophene and polyaniline.

  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.

The superior effects of the present invention are illustrated in the following examples. In addition, this description is for demonstrating the effect of invention specifically, Comprising: Invention content is not limited.
Example 1
<Semiconductor nanoparticle dispersion>

  A solution composed of 10 parts by weight of titanium oxide and 90 parts by weight of ethanol was prepared by introducing titanium oxide aggregates (P25 manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter of 21 nm) as semiconductor nanocrystal particles into ethanol. This was agitated with a magnetic stirrer for 16 hours, so that the titanium oxide aggregates were well wetted in advance.

  The solution prepared as described above is irradiated with ultrasonic waves having a frequency of 40 kHz for 30 minutes using an ultrasonic homogenizer (Sonifier SLPe40 manufactured by BRANSON), thereby giving an impact force derived from cavitation, and the titanium oxide aggregates. A dispersed semiconductor nanoparticle dispersion was obtained.

<Agglomerates of heat extinguishing particles or heat extinguishing fibers>
On the other hand, a solution composed of 20 parts by weight of heat extinguishable particles A and 80 parts by weight of water was prepared by adding powder of heat extinguisher particles A (polystyrene acrylic resin) to water. After stirring this with a magnetic stirrer for 1 hour, an ultrasonic homogenizer (Sonifier SLPe40 manufactured by BRANSON) was used to irradiate ultrasonic waves with a frequency of 40 kHz for 30 minutes, thereby giving an impact force derived from cavitation, and heat extinguishing particles. An aqueous dispersion of A was obtained. This was treated with a centrifuge (Himac CT6E manufactured by Hitachi Koki Co., Ltd.), and then the supernatant was discarded and the same amount of ethanol was added three times to replace water and ethanol. Since the heat extinguishing particles A have good affinity for water and poor affinity for ethanol, an ethanol solution containing aggregates of the heat extinguishing particles A was obtained by this operation.

  The particle size distribution of the thus obtained aggregate (pore forming agent) was measured with a laser diffraction particle size distribution meter (LA-950, manufactured by Horiba, Ltd.), and the volume-based median diameter (Dv50) was calculated.

<Coating fluid>
A liquid containing the heat extinguishing particle A aggregate was added to the prepared semiconductor nanoparticle dispersion so that the heat extinguishing particle A was 50 parts by weight with respect to 100 parts by weight of titanium oxide. Furthermore, ethyl cellulose (manufactured by Kanto Chemical Co., Inc., toluene: ethanol = 80: 20, 5% solution in a solvent at 25 ° C. viscosity = 45 cP) as a binder resin, α-terpineol (manufactured by Kanto Chemical Co., Inc.) as a solvent, After stirring for 1 hour with a magnetic stirrer, ethanol was removed with a rotary evaporator to obtain a coating solution having a viscosity suitable for screen printing.

  Each addition amount of the coating liquid was adjusted so that titanium oxide would be 15 parts by weight after ethanol removal.

<Porous semiconductor electrode layer 13>
This coating solution was applied to a glass substrate having FTO (F-doped Tin Oxide) formed on the surface thereof by screen printing, and then baked in air at 500 ° C. for 30 minutes to form a porous semiconductor electrode.

  In order to observe the cross section of the semiconductor electrode obtained at this time, the cross section of the electrode exposed by a cross section exposing device (JEOL cross section polisher) was observed with an electron scanning microscope (SEM).

Moreover, the ratio which the space | gap occupied with respect to the cross-sectional film | membrane of a titanium oxide was calculated for the obtained image using the binarization processing software (Image Pro Plus by Media Cybernetics), and porosity (%) was computed. In parallel, the obtained porous semiconductor layer was peeled off from the electrode substrate, and the BET specific surface area (m ² / g) was measured using a BET specific surface area measuring apparatus (Tristar III 3020 manufactured by Shimadzu Corporation) by a nitrogen adsorption method.

<Arrangement of photosensitizing compound on porous semiconductor electrode layer 13>
N719 dye (cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium) in which the obtained porous semiconductor electrode layer 13 was adjusted to 0.5 mM as a ruthenium complex. (II) -bis-tetra-n-butylammonium (manufactured by Solaronix) (the photosensitizing compound) in acetonitrile / t-butanol (volume ratio 1: 1) 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 dicyanamide (manufactured by Sigma-Aldrich) in a chlorobenzene (solid content 10%) solution in which the compound (1) of the in-house synthesized product is dissolved on a semiconductor electrode carrying a photosensitizing compound, 27 mM) and 4-t-butylpyridine (manufactured by Acros, 55 mM) were added dropwise onto a semiconductor electrode carrying a photosensitizer and dried naturally.

  Furthermore, spin a solution obtained by adding 1-ethyl-3-methylimidazolinium dicyanamide (Sigma Aldrich, 5 mM) to chlorobenzene (solid content 2%) in which the compound (2) of the in-house synthesized product is dissolved. Coating was performed to form a solid electrolyte-containing body. On this, gold was vacuum-deposited to a thickness of 100 nm to form a counter electrode, and a solar cell was produced.

The produced solar cell was subjected to IV measurement, and the conversion efficiency was calculated. The IV measurement was performed under simulated sunlight irradiation (AM1.5, 100 mW / cm ² ).

(Example 2)
As the heat extinguishing particles, heat extinguishing particles B (polyurethane resin particles) are used, and the concentration of the heat extinguishing particles B in the coating liquid is 30 parts by weight with respect to 100 parts by weight of titanium oxide. A solar cell was produced and evaluated in the same manner as in Example 1 except that.

(Example 3)
A solar cell was prepared and evaluated in the same manner as in Example 1 except that the heat extinguishing particles C (polystyrene acrylic resin particles) were used as the heat extinguishing particles.

Example 4
Carbon nanotubes were used as the heat extinguishing particles. A solution composed of 20 parts by weight of carbon nanotubes and 80 parts by weight of ethanol was prepared by introducing carbon nanotubes (SMW100, diameter 10 nm, manufactured by Sigma-Aldrich) into ethanol. This was stirred with a magnetic stirrer for 1 hour, and then an ultrasonic dispersion of carbon nanotubes was obtained by irradiating ultrasonic waves with a frequency of 40 kHz for 4 hours using an ultrasonic homogenizer (Sonifier SLPe40 manufactured by BRANSON).

  With respect to the semiconductor nanoparticle dispersion prepared in the same manner as in Example 1, the above carbon nanotube dispersion was added so that the carbon nanotubes were 50 parts by weight with respect to 100 parts by weight of titanium oxide.

  Thereafter, solar cells were prepared and evaluated in the same manner as in Example 1.

(Example 5)
A solar cell was prepared and evaluated in the same manner as in Example 1 except that zinc oxide (TECNAPOW manufactured by TECNAN, average primary particle diameter of 30 nm) was used for the semiconductor nanocrystal particles.

(Example 6)
A solar cell was produced in the same manner as in Example 1 except that the semiconductor nanoparticle dispersion produced in the same manner as in Example 1 was changed to 80 parts by weight of the heat extinguishing particles A with respect to 100 parts by weight of titanium oxide. evaluated.

(Example 7)
A solar cell was produced in the same manner as in Example 1 except that the heat-extinguishing particles A were 70 parts by weight with respect to 100 parts by weight of titanium oxide with respect to the semiconductor nanoparticle dispersion produced in the same manner as in Example 1. evaluated.

(Example 8)
A solar cell was produced in the same manner as in Example 1 except that 60 parts by weight of the heat extinguishing particles A were added to 100 parts by weight of titanium oxide with respect to the semiconductor nanoparticle dispersion prepared in the same manner as in Example 1. evaluated.

Example 9
A solar cell was produced in the same manner as in Example 1 except that the heat-extinguishing particles A were 20 parts by weight with respect to 100 parts by weight of titanium oxide with respect to the semiconductor nanoparticle dispersion produced in the same manner as in Example 1. evaluated.

(Example 10)
A solar cell was produced in the same manner as in Example 1, except that the heat-extinguishing particles A were 10 parts by weight with respect to 100 parts by weight of titanium oxide with respect to the semiconductor nanoparticle dispersion produced in the same manner as in Example 1. evaluated.

(Example 11)
As the heat extinguishing particles, heat extinguishing particles A2 (polystyrene acrylic resin) were used. A solar cell was fabricated and evaluated in the same manner as in Example 1 except that the concentration of the superheat extinguishing particles A2 was changed to 10 parts by weight of the heat extinguishing particles A2 with respect to 100 parts by weight of titanium oxide.

(Example 12)
As the heat extinguishing particles, heat extinguishing particles A2 (polystyrene acrylic resin) were used. A solar cell was produced and evaluated in the same manner as in Example 1 except that the concentration of the superheat extinguishing particles A2 was changed to 15 parts by weight of the heat extinguishing particles A2 with respect to 100 parts by weight of titanium oxide.

(Example 13)
As the heat extinguishing particles, heat extinguishing particles A2 (polystyrene acrylic resin) were used. A solar cell was produced and evaluated in the same manner as in Example 1 except that the concentration of the superheat extinguishing particles A2 was changed to 30 parts by weight of the heat extinguishing particles A2 with respect to 100 parts by weight of titanium oxide.

(Example 14)
As the heat extinguishing particles, heat extinguishing particles A2 (polystyrene acrylic resin) were used. A solar cell was prepared and evaluated in the same manner as in Example 1 except that the concentration of the superheat extinguishing particles A2 was changed to 60 parts by weight of the heat extinguishing particles A2 with respect to 100 parts by weight of titanium oxide.

(Example 15)
As the heat extinguishing particles, heat extinguishing particles A2 (polystyrene acrylic resin) were used. A solar cell was prepared and evaluated in the same manner as in Example 1 except that the concentration of the superheat extinguishing particles A2 was changed to 65 parts by weight of the heat extinguishing particles A2 with respect to 100 parts by weight of titanium oxide.

(Example 16)
As the heat extinguishing particles, heat extinguishing particles G (polymethyl methacrylate resin) were used. A solar cell was prepared and evaluated in the same manner as in Example 1 except that the concentration of the heat extinguishing particles G was 30 parts by weight with respect to 100 parts by weight of titanium oxide. The weight average molecular weight (Mw) calculated | required by the gel permeation chromatography (Tosoh Corporation HLC-8220) of this polymethylmethacrylate G microparticles | fine-particles is 31,500, and a differential scanning calorimetry (Seiko Instruments Inc. make) The glass transition temperature (Tg) calculated | required by DSC6200) was 85 degreeC.

(Comparative Example 1)
A solar cell was prepared and evaluated in the same manner as in Example 1 except that no heat extinguishing particles were used.

(Comparative Example 2)
Solar electrons were prepared and evaluated in the same manner as in Example 1 except that zinc oxide (TECNAPOW manufactured by TECNAN, average primary particle diameter of 30 nm) was used for the semiconductor nanocrystal particles, and no heat extinguishing particles were used.

(Comparative Example 3)
As the heat extinguishing particles, heat extinguishing particles D (polystyrene acrylic resin particles) were used. In the powdered semiconductor nanoparticle dispersion, 50 parts by weight of the heat-extinguishing particles D were added to 100 parts by weight of titanium oxide while the heat-extinguishing particles D remained in powder form. Otherwise, solar cells were produced and evaluated in the same manner as in Example 1.

(Comparative Example 4)
Zinc oxide (TECNAPOW manufactured by TECNAN, average primary particle size of 30 nm) was used as the semiconductor nanocrystal particles, and the heat extinguishing particles D were used as the heat extinguishing particles. In the powdered semiconductor nanoparticle dispersion, 50 parts by weight of the heat-extinguishing particles D were added to 100 parts by weight of titanium oxide while the heat-extinguishing particles D remained in powder form. Otherwise, solar cells were produced and evaluated in the same manner as in Example 1.

(Comparative Example 5)
As the heat extinction particles, heat extinction particles E (polystyrene acrylic resin) were used. With the heat extinguishing particles E in powder form, 30 parts by weight of the heat extinguishing particles E were added to 100 parts by weight of titanium oxide with respect to the prepared semiconductor nanoparticle dispersion. Otherwise, solar cells were produced and evaluated in the same manner as in Example 1.

(Comparative Example 6)
As the heat extinction particles, the heat extinction particles E were used. A solar cell was prepared and evaluated in the same manner as in Example 1 except for the above. With the heat extinguishing particles E in a powder form, 60 parts by weight of the heat extinguishing particles E were added to 100 parts by weight of titanium oxide with respect to the prepared semiconductor nanoparticle dispersion. Otherwise, solar cells were produced and evaluated in the same manner as in Example 1.

(Comparative Example 7)
As the heat extinction particles, heat extinction particles F (polyurethane) were used. With the heat extinguishing particles F in a powder form, 30 parts by weight of the heat extinguishing particles F were added to 100 parts by weight of titanium oxide with respect to the prepared semiconductor nanoparticle dispersion. Otherwise, solar cells were produced and evaluated in the same manner as in Example 1.

(Comparative Example 8)
As the heat extinction particles, the heat extinction particles F were used. While the heat extinguishing particles F remained in powder form, 60 parts by weight of the heat extinguishing particles F were added to 100 parts by weight of titanium oxide with respect to the prepared semiconductor nanoparticle dispersion. Otherwise, solar cells were produced and evaluated in the same manner as in Example 1.

(Comparative Example 9)
As the heat extinguishing particles, heat extinguishing particles H (polymethyl methacrylate resin) were used. A solar cell was produced and evaluated in the same manner as in Example 1 except that the concentration of the heat extinguishing particles H was 30 parts by weight with respect to 100 parts by weight of titanium oxide. The weight average molecular weight (Mw) determined by gel permeation chromatography (HLC-8220, manufactured by Tosoh Corporation) of the polymethylmethacrylate H fine particles was 27,000, and a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc.). The determined glass transition temperature (Tg) was 75 ° C.

(Comparative Example 10)
As the heat extinguishing particles, heat extinguishing particles I (polymethyl methacrylate resin) were used. A solar cell was prepared and evaluated in the same manner as in Example 1 except that the concentration of the heat extinguishing particles I was 30 parts by weight with respect to 100 parts by weight of titanium oxide. The polymethyl methacrylate I fine particles had a weight average molecular weight (Mw) determined by the gel permeation chromatography of 48,400 and a glass transition temperature (Tg) determined by the differential scanning calorimeter of 99 ° C.

  In FIG. 2, the cross-sectional SEM (scanning electron microscope) image of the semiconductor electrode obtained by Example 1 is shown. From this image, the presence of the irregularly shaped gap 13A and the streaky gap 13B connected to the irregularly shaped gap 13A was confirmed.

  Table 1 shows the results of Examples 1 to 16 and Comparative Examples 1 to 10.

  In Examples 1 to 16, a highly efficient solar cell with a conversion efficiency of 1.5% or more could be obtained. Compared with the comparative example, the efficiency increased more than twice. It is considered that the permeability of the electrolytic solution is improved and the performance is improved by having the streak-shaped void connected to the irregular-shaped void and the irregular-shaped void.

  Example 1 shows that the use of heat extinguishing particles that provide voids having irregularly shaped voids and streaky voids connected to irregularly shaped voids can increase the conversion efficiency without limiting the type of material. It was confirmed by ~ 4. In Example 5, by using zinc oxide, an irregularly shaped void and a streaky void connected to the irregularly shaped void were formed, and a high-efficiency solar cell was obtained. However, it tends to be lower than titanium oxide. It was in.

Examples 6 to 11 are data obtained by changing the level of specific surface area. The conversion efficiency is high because of the irregularly shaped voids and the streaky voids connected to the irregularly shaped voids. However, when the specific surface area is 30 m ² / g or less, the battery performance decreases. This is probably because the amount of dye adsorbed and electron transfer decreased. In addition, when the specific surface area is 60 m ² / g or more, it is considered that the gap is reduced, so that the electrolyte solution is insufficiently filled and the conversion efficiency is lowered.

  Examples 12 to 15 are data with varying porosity. When the porosity is in the range of 10 to 50%, high conversion efficiency is obtained. However, when the porosity is 10% or less, the electrolytic solution is not sufficiently filled, and the conversion efficiency is considered to be lowered. When the porosity is 50% or more, the specific surface area decreases, so that the amount of dye adsorption decreases and the conversion efficiency decreases. Moreover, the film | membrane intensity | strength of a porous semiconductor layer also falls and can cause deterioration of a battery.

  In Comparative Examples 3 to 8, an irregularly shaped void was formed, but a streak-like void connected to the irregularly shaped void was not formed. Although the heat extinguishing particles dropped in a powder form can form an irregularly shaped void in the porous semiconductor layer, a streak-like void connected to the irregularly shaped void was not provided. Even if the addition amount of the heat extinguishing particles is changed or the material type is changed, no streak-like void connected to the irregular void is provided in the porous semiconductor layer. The present invention is achieved by producing and using the heat extinguishing particles as a dispersion.

  Of the solar cells obtained in Examples 1 to 16, Example 16 using polymethyl methacrylate as the heat extinguishing particles shows particularly high conversion efficiency. Polymethyl methacrylate does not give uniquely high conversion efficiency, and it is possible to obtain high conversion efficiency by placing the weight average molecular weight and glass transition temperature within appropriate ranges. Example 16 and Comparative Example 9 From the comparison with 10. That is, in Comparative Example 9, since the glass transition temperature is too low, the heat extinguishing particles are excessively softened. On the other hand, in Comparative Example 10, since the glass transition temperature is too high, the connectivity of the pores obtained by disappearance is insufficient. In these comparative examples 9 and 10, formation of one or both of irregularly shaped voids or streaky voids could not be confirmed. Therefore, when injecting and penetrating the high-viscosity electrolyte into the semiconductor porous electrode, It can be seen that the structure is not desirable.

  As mentioned above, the photoelectric conversion element which can give high conversion efficiency by this invention was able to be obtained.

10: Photoelectric conversion element 11: Electrode 12: Counter electrode 13: Porous semiconductor electrode layer 13A: Undefined-shaped void 13B: Streaky void 14: Electrolyte layer 15: Base material 18: Base material 20: Catalyst layer

JP 2003-332602 A Japanese Patent No. 4887664

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

Claims (6)

A photoelectric conversion element in which a porous semiconductor electrode layer having a photosensitizing compound and semiconductor nanocrystal particles and an electrolyte layer are provided between a pair of electrodes,
The porous semiconductor electrode layer has an irregularly shaped void, and a streaky void connected to the irregularly shaped void,
The photoelectric layer is made of a solid electrolyte or a highly viscous electrolytic solution.   The photoelectric conversion element according to claim 1, wherein the semiconductor nanocrystal particles contained in the porous semiconductor electrode layer are titanium oxide particles. The photoelectric conversion element according to claim 1, wherein the porous semiconductor electrode layer has a specific surface area of 30 to 60 m ² / g.   The photoelectric conversion element according to claim 1, wherein a porosity of the porous semiconductor electrode layer is 10 to 50%. A porous semiconductor electrode layer having a photosensitizing compound and semiconductor nanocrystal particles and an electrolyte layer are provided between a pair of electrodes, and the electrolyte layer is a method for producing a photoelectric conversion element comprising a solid electrolyte or a highly viscous electrolyte. There,
Using the coating liquid obtained by adding a liquid containing an aggregate of heat-extinguishing particles or a heat-extinguishing fiber to the dispersion of the semiconductor nanocrystal particles, the voids having an irregular shape and the voids having the irregular shape are formed. A method for producing a photoelectric conversion element comprising a porous semiconductor electrode layer forming step of forming the porous semiconductor electrode layer having connected streaky voids. 6. The heat extinguishing particles are polymethyl methacrylate having a weight average molecular weight (Mw) of 30,000 to 45,000 and a glass transition temperature (Tg) of 80 ° C. or more and 95 ° C. or less. The manufacturing method of the photoelectric conversion element of description.