JP2017011066A - Photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element that can obtain excellent photoelectric conversion efficiency even when a second electrode having translucency is used.SOLUTION: A photoelectric conversion element includes: a first substrate; a first electrode having translucency which is arranged on the first substrate; a photoelectric conversion layer which is arranged on the first electrode; a second electrode having translucency which is arranged on the photoelectric conversion layer; a porous layer which is arranged on the second electrode; and a second substrate which is arranged on the porous layer. The porous layer includes light scattering particles composed of a metal oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoelectric conversion element.

  In recent years, the driving power in electronic circuits has become very small, and various electronic components such as sensors can be driven even with weak power (μW order). Furthermore, when using sensors, it is expected to be applied to energy harvesting elements as a self-sustaining power source that can generate and consume on the spot. Among them, solar cells (a type of photoelectric conversion element) are elements that can generate electricity anywhere if there is light. It attracts attention.

  Among solar cells (a type of photoelectric conversion element), dye-sensitized solar cells announced by Graetzel et al. Of Lausanne University of Technology have higher photoelectric conversion characteristics than amorphous silicon solar cells in a weak indoor light environment. Has been reported (for example, see Non-Patent Document 1). Usually, the illuminance of indoor light such as an LED light or a fluorescent lamp is about 200 Lux to 1000 Lux, which is very weak light compared to direct sunlight (approximately 100,000 Lux). This solar cell has a structure in which a porous metal oxide semiconductor is provided on a transparent conductive glass substrate, a dye adsorbed on the surface thereof, an electrolyte having a redox pair, and a counter electrode. Graetzel et al. Significantly improved the photoelectric conversion efficiency by making a metal oxide semiconductor electrode such as titanium oxide porous to increase the surface area and adsorbing a ruthenium complex as a dye on a single molecule basis (for example, Patent Documents). 1, Non-Patent Document 2 and Non-Patent Document 3).

  As the counter electrode of the dye-sensitized solar cell, a deposited film of a noble metal such as platinum, silver, or gold is generally used. However, these are scarce and expensive materials, and there is a problem that the manufacturing cost becomes high because the vapor deposition equipment is expensive. Therefore, alternative materials that replace precious metals have been studied. For example, materials using conductive polymer compounds have been studied (Non-Patent Document 4). Further, as a film forming method, reduction of manufacturing cost by simply forming a film made of the above-mentioned noble metal nanoparticles or the above-mentioned conductive compound by a coating process such as screen printing has been studied.

  Practically, the dye-sensitized solar cell takes the form of a module composed of a plurality of cells. For example, Patent Document 2 includes a substrate, a first electrode, an electron transport layer made of an electron transport semiconductor in which a photosensitizing compound is adsorbed on the surface, a hole transport layer, and a second electrode in this order. A solid dye-sensitized solar cell has been proposed in which the electrode and the second electrode are each composed of a plurality of divided electrodes. However, regarding the photoelectric conversion of the dye-sensitized solar cell module using the conductive polymer compound as a counter electrode, the light irradiated between the electrodes of the solar cells constituting the module almost contributes to the photoelectric conversion. However, since the conductive polymer compound has translucency, there is a problem 2 that the scattered light cannot be used unlike the metal counter electrode.

  As for problem 2, since the absorption coefficient of the dye is small and light is transmitted without being sufficiently absorbed in the photoelectric conversion layer, a photoelectric scattering efficiency is improved by providing a light scattering layer and also using scattered light. It is necessary to make it. For example, Patent Document 3 discloses light in which high refractive material particles (particle size is 200 to 500 nm) having a controlled particle size are deposited on the lower surface (electrolyte side) of a light absorbing particle layer (semiconductor particles having a particle size of 80 nm or less). A dye-sensitized solar cell provided with a reflective particle layer has been proposed. Patent Document 4 has a light reflecting layer disposed adjacent to the back surface (electrolyte side) facing the light receiving surface of the semiconductor electrode, and the thickness of the light reflecting layer is 3 to 50 μm. The light reflecting layer contains first particles having a refractive index of 1.8 or less, and second particles having an average particle diameter of 150 nm or more and a refractive index of 2.4 or more, and There has been proposed a photoelectrode characterized in that the volume ratio of the second particles in the light reflecting layer is 15 to 40%. In Patent Document 5, a transparent electrode, a photoelectric conversion layer, and a light reflection layer are laminated in this order, the photoelectric conversion layer is a porous semiconductor carrying a sensitizing dye, and the light reflection layer is a sensitizing dye. A photoelectrode configured as an unsupported porous body has been proposed.

Regarding the above problem 1, in order to scatter light transmitted between the electrodes of the solar battery cell, it is necessary to provide a light scattering base material straddling the solar battery cell on the opposite side of the photoelectric conversion layer with the counter electrode interposed therebetween. . However, when a conductor such as a metal is used as the light scattering base material, it is easily estimated that the counter electrodes are electrically connected to each other so that the parallelism or seriality cannot be maintained. When a light scattering base material having a smooth surface such as a glass substrate or a high refractive polymer is used, the conductive polymer compound electrode is thermally transferred to the reflective base material in a high temperature environment of, for example, 85 ° C. or higher. Therefore, the case where the electrical contact with the photoelectric conversion layer is deteriorated and the contact resistance is increased is easily estimated.
All the proposals for the above problem 2 are techniques for improving the photoelectric conversion efficiency by providing a light reflecting layer in the photoelectric conversion layer, but in the case of a solid dye-sensitized solar cell using an organic hole transport material, Since the hole diffusion movement distance is shorter than in the case of using the electrolytic solution, the current loss increases due to the increase of the hole diffusion movement distance by providing the reflective particle layer in the photoelectric conversion layer. For this reason, it is difficult to provide both a reflective particle layer in the photoelectric conversion layer and good photoelectric conversion efficiency in a solid dye-sensitized solar cell.
As described above, none of the light scattering techniques studied so far has been satisfactory.
In view of the above problems, an object of the present invention is to provide a photoelectric conversion element that can obtain good photoelectric conversion efficiency even when a counter electrode (second electrode) having translucency is used.

In order to solve the above problems, the photoelectric conversion element of the present invention is
(1) A first substrate, a first electrode having translucency disposed on the first substrate, a photoelectric conversion layer disposed on the first electrode, and the photoelectric conversion layer A translucent second electrode disposed on the second electrode, a porous layer disposed on the second electrode, and a second substrate disposed on the porous layer, the porous The quality layer is a photoelectric conversion element including light scattering particles made of a metal oxide.

  As will be apparent from the following detailed and specific description, according to the present invention, good photoelectric conversion efficiency can be obtained even in a room light environment even when a transparent electrode (second electrode) having translucency is used. Can be provided.

It is the schematic of an example showing the structure of the photoelectric conversion element which concerns on this invention. It is the schematic of the other example showing the structure of the photoelectric conversion element which concerns on this invention.

Hereinafter, the present invention will be described in detail.
Although this invention concerns on the "photoelectric conversion element" of said (1), since it also concerns on the "photoelectric conversion element" as described in the following (2)-(6), these are also combined. This will be described in detail.
(2) An electron comprising a hole-blocking layer disposed on the first electrode and an electron-transporting semiconductor in which a photosensitizing compound is adsorbed on the surface, wherein the photoelectric conversion layer is disposed on the first electrode. The photoelectric conversion element according to (1), comprising a transport layer and a hole transport layer connected to the electron transport layer and made of a hole transport material.
(3) The light scattering particle includes at least one selected from the group consisting of magnesium oxide, aluminum oxide, zinc oxide, titanium oxide, tin oxide, niobium oxide, yttrium oxide, and zirconium oxide ( The photoelectric conversion element as described in 1) or (2).
(4) The photoelectric conversion element according to any one of (1) to (3), wherein the second electrode includes at least one of A and B below.
A: Conductive polymer compound selected from the group consisting of polythiophene and derivatives thereof B: Nanowires made of Group 11 metal elements (5) A plurality of divided first electrodes and second electrodes, respectively It consists of an electrode, The photoelectric conversion element as described in any one of (1) thru | or (4) characterized by the above-mentioned.
(6) The photoelectric conversion element according to any one of (1) to (5), wherein the photoelectric conversion element is used as a solar cell.

  In this specification, the photoelectric conversion element refers to an element that converts light energy into electric energy or an element that converts electric energy into light energy, and specifically includes a solar cell or a photodiode.

The photoelectric conversion element of the present invention includes a first substrate, a first electrode having translucency disposed on the first substrate, a photoelectric conversion layer disposed on the first electrode, A second electrode having translucency disposed on the photoelectric conversion layer; a porous layer disposed on the second electrode; and a second substrate disposed on the porous layer. And the porous layer includes light scattering particles made of a metal oxide.
The porous layer is provided between the second electrode and the second substrate, contains light scattering particles, and returns transmitted light incident from the first substrate to the photoelectric conversion layer. Thereby, even if it used the 2nd electrode which has translucency, it discovered that a favorable photoelectric conversion efficiency was obtained, and resulted in this invention. Here, when a light scattering base material having a smooth surface such as a glass substrate or a highly refractive polymer is used, the conductive polymer compound electrode is thermally transferred to the reflective base material in a high temperature environment of, for example, 85 ° C. or higher. As a result, the electrical contact with the photoelectric conversion layer may deteriorate and the contact resistance may increase. Therefore, the above-mentioned concern can be reduced by making the light scattering layer porous and reducing the contact area with the conductive polymer compound electrode.
In the case where the photoelectric conversion element of the present invention takes the form of a module composed of a plurality of cells, it can scatter light irradiated between the electrodes of the solar battery cells constituting the module. Efficiency is obtained.
Further, by providing a porous layer between the second electrode and the second substrate, even if the photoelectric conversion layer is a solid type dye sensitized type using an organic hole transporting material, the hole diffusion movement distance is Without increasing, current loss can be reduced.

  The photoelectric conversion layer includes a hole blocking layer disposed on the first electrode, an electron transport layer composed of an electron transport semiconductor disposed on the hole blocking layer and having a photosensitizing compound adsorbed on a surface thereof, and The hole transport layer is preferably connected to the electron transport layer and made of a hole transport material. An organic thin film solar cell is also mentioned as a photoelectric converting layer.

Next, the photoelectric conversion element according to the present invention will be described with reference to the drawings.
The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.
The structure of the photoelectric conversion element will be described with reference to FIG. FIG. 1 is a schematic view of a cross section of the photoelectric conversion element.

In the embodiment shown in FIG. 1, a first substrate 1, a first electrode 2 having translucency disposed on the first substrate 1, and a hole disposed on the first electrode 2. A blocking layer 3, an electron transporting layer 4 made of an electron transporting semiconductor disposed on the hole blocking layer 3 and having a photosensitized compound 5 adsorbed on the surface thereof, and the electron transporting layer 4 connected to the hole transporting property. A hole transport layer 6 made of a material; a translucent second electrode 7 disposed on the hole transport layer 6; a porous layer 8 disposed on the second electrode 7; An example of a structure having a second substrate 9 disposed on a porous layer 8 and containing light scattering particles is shown in the porous layer 8.
Details will be described below.

<First substrate>
The first substrate 1 used in the present invention is not particularly limited, and a known substrate can be used. The first substrate 1 is preferably made of a transparent material, and examples thereof include glass, a transparent plastic plate, a transparent plastic film, and an inorganic transparent crystal.

<First electrode>
The first electrode 2 used in the present invention is not particularly limited as long as it is a conductive material that is transparent to visible light, and is a known one that is used for ordinary photoelectric conversion elements, liquid crystal panels, and the like. Can be used.
Examples of the material for the first electrode 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), indium / tin oxide, and the like. Examples thereof include zinc oxide, niobium / titanium oxide, and graphene, and these may be used alone or in a plurality of layers.
The thickness of the first electrode 2 is preferably 5 nm to 100 μm, and more preferably 50 nm to 10 μm.

The first electrode 2 is preferably provided on the substrate 1 made of a material transparent to visible light in order to maintain a certain hardness. For example, FTO-coated glass, ITO-coated glass, zinc oxide: aluminum-coated glass, FTO-coated transparent plastic film, ITO-coated transparent can be used. A plastic film etc. are mentioned.
In addition, a transparent electrode obtained by doping tin oxide or indium oxide with cations or anions having different valences, a metal electrode having a structure capable of transmitting light, such as a mesh shape or a stripe shape, on a substrate such as a glass substrate But you can.
These may be used alone or in combination of two or more. Further, for the purpose of reducing the resistance, a metal lead wire or the like may be used in combination.
Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. The metal lead wire can be formed by a method in which deposition is performed on the substrate by vapor deposition, sputtering, pressure bonding, or the like, and ITO or FTO is provided thereon.

<Hole blocking layer>
In general, the hole blocking layer 3 is provided in order to suppress a decrease in power due to recombination (so-called reverse electron transfer) of holes in the electrolyte and electrons on the electrode surface when the electrolyte is in contact with the electrode. The effect of the hole blocking layer 3 is particularly remarkable in the solid dye-sensitized solar cell. Compared with a wet dye-sensitized solar cell using an electrolyte solution, a solid dye-sensitized solar cell using an organic hole transport material or the like recombines holes in the hole transport material and electrons on the electrode surface ( This is due to the high speed of reverse electron transfer.
The material of the hole blocking layer 3 used in the present invention is not particularly limited as long as it is transparent to visible light and is an electron transporting material. As a material, for example,
Examples thereof include titanium oxide, niobium oxide, magnesium oxide, aluminum oxide, zinc oxide, tungsten oxide, and tin oxide, and these may be used alone, laminated, or mixed.

  The film forming method of the hole blocking layer 3 is not particularly limited, but high internal resistance is required to suppress the loss current in room light, and the film forming method is also important. In general, a sol-gel method for forming a wet film can be mentioned, but the film current is low and the loss current cannot be sufficiently suppressed. For this reason, dry film formation such as sputtering is more preferable, and the film density is sufficiently high and loss current can be suppressed.

  The hole blocking layer 3 is also formed for the purpose of preventing electronic contact between the first electrode 2 and the hole transport layer 6. The thickness of the hole blocking layer 3 is not particularly limited, but is preferably 5 nm to 1 μm, more preferably 500 to 700 nm for wet film formation, and more preferably 10 nm to 30 nm for dry film formation.

<Electron transport layer>
The photoelectric conversion element of the present invention preferably has the electron transport layer 4 formed on the hole blocking layer 3 and is generally configured as a porous layer. The electron transport layer 4 includes an electron transport material such as semiconductor fine particles, and the electron transport material is preferably adsorbed with a photosensitizing compound 5 described later. The electron transporting material is not particularly limited, and may be a semiconductor material such as a rod shape or a tube shape. In the following, there will be described portions taking semiconductor fine particles as an example, but the present invention is not limited to this.
Further, the electron transport layer 4 may be a single layer or a multilayer. In the case of multiple layers, a dispersion of semiconductor fine particles having different particle diameters can be applied in multiple layers, or different types of semiconductors, and application layers having different compositions of resins and additives can be applied in multiple layers. Multi-layer coating is an effective means when the film thickness is insufficient with a single coating.

The semiconductor is not particularly limited, and a known semiconductor can be used. Specifically, a single semiconductor such as silicon or germanium, a compound semiconductor typified by metal chalcogenide, a compound having a perovskite structure, or the like can be given.
Metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, or tantalum oxides, cadmium, zinc, lead, silver, antimony, bismuth. Sulfide, cadmium, lead selenide, cadmium telluride and the like.
Other compound semiconductors are preferably phosphides such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide, and the like.
As the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.
Among these, as the electron transporting material, an oxide semiconductor is preferable, and at least one selected from titanium oxide, zinc oxide, tin oxide, and niobium oxide is particularly preferable. Therefore, you may use these individually or in mixture of 2 or more types. The crystal type of these semiconductors is not particularly limited, and may be single crystal, polycrystal, or amorphous.

The particle size of the semiconductor fine particles is not particularly limited, but the average particle size of the primary particles is preferably 1 to 100 nm, and more preferably 5 to 50 nm. Further, the efficiency can be improved by the effect of scattering incident light by mixing or laminating semiconductor fine particles having a larger average particle diameter. In this case, the average particle size of the semiconductor is preferably 50 to 500 nm.
Generally, as the film thickness of the electron transport layer 4 increases, the amount of the supported photosensitizing compound 5 per unit projected area also increases, so that the light capture rate increases, but the diffusion distance of injected electrons also increases. Loss due to charge recombination also increases. Therefore, the film thickness of the electron transport layer is preferably 100 nm to 100 μm, more preferably 100 nm to 50 μm, and further preferably 100 nm to 10 μm.

There is no restriction | limiting in particular in the preparation methods of the electron carrying layer 4, The method of forming a thin film in vacuum, such as sputtering, and the wet film forming method are mentioned. In view of manufacturing costs, etc., a wet film-forming method is particularly preferable. A paste in which semiconductor fine particle powder or sol is dispersed is prepared, and an electron collector electrode substrate (substrate 1, first electrode 2, hole blocking layer 3 is formed). A method of coating on the formed electrode substrate) 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.

When a dispersion of semiconductor fine particles is prepared by mechanical pulverization or using a mill, it is formed by dispersing at least semiconductor fine particles alone or a mixture of semiconductor fine particles and a resin in water or an organic solvent.
Examples of the resin used at this time include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid esters, and methacrylic acid esters, silicon resins, phenoxy resins, polysulfone resins, polyvinyl butyral resins, and polyvinyl formals. Examples thereof include resins, polyester resins, cellulose ester resins, cellulose ether resins, urethane resins, phenol resins, epoxy resins, polycarbonate resins, polyarylate resins, polyamide resins, and polyimide resins.

  Examples of the solvent for dispersing the semiconductor fine particles include alcohol solvents such as water, methanol, ethanol, isopropyl alcohol, and α-terpineol, ketone solvents such as acetone, methyl ethyl ketone, and 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 bromobenzene, iodobenzene, or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, Examples thereof include hydrocarbon solvents such as o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

In order to prevent re-aggregation of particles, a dispersion of semiconductor particles or a paste of semiconductor particles obtained by a sol-gel method, etc., an acid such as hydrochloric acid, nitric acid, acetic acid, or a surfactant such as polyoxyethylene octylphenyl ether Chelating agents such as acetylacetone, 2-aminoethanol, and ethylenediamine can be added.
It is also an effective means to add a thickener for the purpose of improving the film forming property.
Examples of the thickener added at this time include polymers such as polyethylene glycol and polyvinyl alcohol, and thickeners such as ethyl cellulose.

The semiconductor fine particles are preferably subjected to firing, microwave irradiation, electron beam irradiation, or laser light irradiation in order to bring the particles into electronic contact with each other after coating and to improve film strength and adhesion to the substrate. . These treatments may be performed alone or in combination of two or more.
In the case of firing, the range of the firing temperature is not particularly limited, but if the temperature is raised too much, the resistance of the substrate may increase or the substrate may melt, so 30 to 700 ° C is preferable, and 100 to 600 ° C is more. preferable. Moreover, although there is no restriction | limiting in particular also in baking time, 10 minutes-10 hours are preferable.
The microwave irradiation may be performed from the electron transport layer forming side or from the back side. Although there is no restriction | limiting in particular in irradiation time, It is preferable to carry out within 1 hour.

For example, chemical plating using an aqueous solution of titanium tetrachloride or a mixed solution with an organic solvent for the purpose of increasing the surface area of the semiconductor fine particles and increasing the efficiency of electron injection from the photosensitizing compound 5 described later to the semiconductor fine particles after firing. Electrochemical plating using a titanium trichloride aqueous solution may be performed.
A film in which semiconductor fine particles having a diameter of several tens of nanometers are stacked by sintering or the like forms a porous state. This nanoporous structure has a very high surface area, which can be expressed using a roughness factor.
The roughness factor is a numerical value representing the actual area inside the porous body relative to the area of the semiconductor fine particles applied to the substrate. Accordingly, the roughness factor is preferably as large as possible, but is also related to the film thickness of the electron transport layer 4 and is preferably 20 or more in the present invention.

<Photosensitizing compound>
In the present invention, the photosensitizing compound 5 is adsorbed on the surface of the electron transporting semiconductor in order to further improve the conversion efficiency.
The photosensitizing compound 5 is not particularly limited as long as it is a compound that is photoexcited by the excitation light used, and specific examples thereof 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.

More preferably, D131 represented by the following structural formula (1) manufactured by Mitsubishi Paper Industries, D102 represented by the following structural formula (2), and D358 represented by the following structural formula (3) are exemplified.

As a method of adsorbing the photosensitizing compound 5 to the electron transporting semiconductor, a method of immersing an electron collecting electrode containing electron transporting semiconductor fine particles in a photosensitizing compound solution or dispersion, or photosensitization. A method of applying a compound solution or dispersion to an electron transporting semiconductor and adsorbing it can be used.
In the former case, an immersion method, a dip method, a roller method, an air knife method, or the like can be used.
In the latter case, a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, a spray method, or the like can be used.
Further, it may be adsorbed in a supercritical fluid using carbon dioxide or the like.

When the photosensitizing compound 5 is adsorbed, a condensing agent may be used in combination.
The condensing agent has a catalytic action such that the photosensitizing compound 5 is physically or chemically bonded to the surface of the electron transporting semiconductor, or acts stoichiometrically to advantageously move the chemical equilibrium. Any of them may be used.
Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

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

Further, depending on the type of the photosensitizing compound 5, there are compounds that work more effectively when the aggregation between the compounds is suppressed. Therefore, an aggregating and dissociating agent may be used in combination.
The aggregating / dissociating agent is preferably a steroid compound such as cholic acid or chenodeoxycholic acid, a long-chain alkyl carboxylic acid or a long-chain alkyl phosphonic acid, and is appropriately selected according to the dye used.
The addition amount of these aggregating and dissociating agents is preferably 0.01 to 500 parts by mass, more preferably 0.1 to 100 parts by mass with respect to 1 part by mass of the photosensitizing compound.
The temperature at which the photosensitizing compound 5 or the photosensitizing compound 5 and the aggregation / dissociation agent are adsorbed using these is preferably −50 ° C. or higher and 200 ° C. or lower.

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 or less.
Adsorption is preferably performed in a dark place.

<Hole transport layer>
The hole transport layer 6 includes an electrolytic solution obtained by dissolving a redox couple in an organic solvent, a gel electrolyte obtained by impregnating a polymer matrix obtained by dissolving a redox couple in an organic solvent, a molten salt containing a redox couple, a solid electrolyte, An inorganic hole transport material, an organic hole transport material, or the like is used. Among these, an organic hole transport material is preferable. In addition, although there exists a part demonstrated below as an example for an organic hole transport material, it is not restricted to this.
The hole transport layer 6 in the present invention may be a single layer structure made of a single material or a laminated structure made of a plurality of compounds. In the case of a laminated structure, it is preferable to use a polymer material for the hole transport layer 6 close to the second electrode 7. By using a polymer material having excellent film forming properties, the surface of the porous electron transport layer 4 can be further smoothed, and the photoelectric conversion characteristics can be improved.

In addition, since the polymer material does not easily penetrate into the porous electron transport layer 4, it is excellent in covering the surface of the porous electron transport layer 4 and is effective in preventing a short circuit when an electrode is provided. Higher performance can be obtained.
A known organic hole transporting compound is used as the organic hole transporting material used in a single layer structure used as a single layer.
Specific examples thereof include oxadiazole compounds disclosed in JP-B No. 34-5466, triphenylmethane compounds disclosed in JP-B No. 45-555, JP-B No. 52-4188, and the like. Pyrazoline compounds shown, hydrazone compounds shown in JP-B-55-42380, oxadiazole compounds shown in JP-A-56-123544, etc., JP-A-54-58445 And the stilbene compounds disclosed in JP-A-58-65440 and JP-A-60-98437.

  Among them, Adv. Mater. , 813, vol. 17, (2005), the hole transport material (2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamino) -9,9'-spirobifluorene: spiro-OMeTAD) is particularly preferred. In spiro-OMeTAD, in addition to high hole mobility, two benzidine skeleton molecules are twisted and bonded. Therefore, a nearly spherical electron cloud is formed, and excellent photoelectric conversion characteristics are exhibited due to good hopping transmission between molecules. In addition, it is highly soluble, soluble in various organic solvents, and is amorphous (amorphous material having no crystal structure), so it is easy to be densely packed in the porous electron transport layer, which is useful for solid dye-sensitized solar cells. Has useful properties. Furthermore, since it does not have a light absorption characteristic of 450 nm or more, the photosensitizing compound can efficiently absorb light, and has a characteristic useful for a solid dye-sensitized solar cell. The film thickness of the hole transport layer made of spiro-OMeTAD is not limited, but preferably has a structure that enters the pores of the porous electron transport layer, preferably 0.01 μm or more on the electron transport layer. About 1 to 10 μm is more preferable.

As the polymer material used for the hole transport layer 6 close to the second electrode 7 used in the laminated structure, a known hole transport polymer material is used.
Specific examples thereof include poly (3-n-hexylthiophene), poly (3-n-octyloxythiophene), poly (9,9′-dioctyl-fluorene-co-bithiophene), poly (3,3 ″ '-Didodecyl-quarterthiophene), poly (3,6-dioctylthieno [3,2-b] thiophene), poly (2,5-bis (3-decylthiophen-2-yl) thieno [3,2-b Thiophene), poly (3,4-didecylthiophene-co-thieno [3,2-b] thiophene), poly (3,6-dioctylthieno [3,2-b] thiophene-co-thieno [3, 2-b] thiophene), poly (3,6-dioctylthieno [3,2-b] thiophene-co-thiophene), poly (3.6-dioctylthieno [3,2-b] thiophene-co-bithiophene) Polythiophene compounds such as poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene], poly [2-methoxy-5- (3,7-dimethyloctyloxy) -1,4-phenylenevinylene ], Poly [(2-methoxy-5- (2-ethylphenyloxy) -1,4-phenylenevinylene) -co- (4,4'-biphenylene-vinylene)] and the like, poly (9 , 9′-didodecylfluorenyl-2,7-diyl), poly [(9,9-dioctyl-2,7-divinylenefluorene) -alt-co- (9,10-anthracene)], poly [ (9,9-dioctyl-2,7-divinylenefluorene) -alt-co- (4,4′-biphenylene)], poly [(9,9-dioctyl-2,7-divinyle) Fluorene) -alt-co- (2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene)], poly [(9,9-dioctyl-2,7-diyl) -co- (1, 4- (2,5-dihexyloxy) benzene)] and the like, poly [2,5-dioctyloxy-1,4-phenylene], poly [2,5-di (2-ethylhexyloxy-1, Polyphenylene compounds such as 4-phenylene], poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (N, N′-diphenyl) -N, N′-di (p- Hexylphenyl) -1,4-diaminobenzene], poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (N, N′-bis (4-octyloxyphenyl) benzidine -N, N'- 1,4-diphenylene)], poly [(N, N′-bis (4-octyloxyphenyl) benzidine-N, N ′-(1,4-diphenylene)], poly [(N, N′-bis ( 4- (2-ethylhexyloxy) phenyl) benzidine-N, N ′-(1,4-diphenylene)], poly [phenylimino-1,4-phenylenevinylene-2,5-dioctyloxy-1,4-phenylene Vinylene-1,4-phenylene], poly [p-tolylimino-1,4-phenylenevinylene-2,5-di (2-ethylhexyloxy) -1,4-phenylenevinylene-1,4-phenylene], poly [ 4- (2-ethylhexyloxy) phenylimino-1,4-biphenylene] and other polyarylamine compounds, poly [(9,9-dioctylfluorenyl-2,7-dii) ) -Alt-co- (1,4-benzo (2,1 ′, 3) thiadiazole], poly (3,4-didecylthiophene-co- (1,4-benzo (2,1 ′, 3) thiadiazole) ) And the like.
Of these, polythiophene compounds and polyarylamine compounds are particularly preferred in consideration of carrier mobility and ionization potential.

Moreover, you may add various additives to the organic hole transport material shown above.
Additives include iodine, lithium iodide, sodium iodide, potassium iodide, cesium iodide, calcium iodide, copper iodide, iron iodide, silver iodide and other metal iodides, tetraalkylammonium iodide, Quaternary ammonium salts such as pyridinium iodide, metal bromides such as lithium bromide, sodium bromide, potassium bromide, cesium bromide and calcium bromide, quaternary ammonium compounds such as tetraalkylammonium bromide and pyridinium bromide Metal chlorides such as bromine salts, copper chloride and silver chloride, metal acetates such as copper acetate, silver acetate and palladium acetate, metal sulfates such as copper sulfate and zinc sulfate, ferrocyanate-ferricyanate, ferrocene -Sulfur compounds such as metal complexes such as ferricinium ions, sodium polysulfide, alkylthiol-alkyl disulfides Viologen dye, hydroquinone, 1,2-dimethyl-3-n-propylimidazolinium iodide, 1-methyl-3-n-hexylimidazolinium iodide, 1,2-dimethyl-3-ethylimidazo Inorg. Such as lithium trifluoromethanesulfonate, 1-methyl-3-butylimidazolium nonafluorobutylsulfonate, 1-methyl-3-ethylimidazolium bis (trifluoromethyl) sulfonylimide. Chem. 35 (1996) 1168, basic compounds such as pyridine, 4-t-butylpyridine and benzimidazole, lithium compounds such as lithium trifluoromethanesulfonylimide and lithium diisopropylimide.

In the present invention, by adding a basic compound represented by the following general formula (4) to the hole transport layer, the internal resistance of the photoelectric conversion element is increased and the loss current in weak light such as room light is reduced. And a higher open circuit voltage can be obtained.
(Wherein R ₂ and R ₃ represent a substituted or unsubstituted alkyl group or an aromatic hydrocarbon group, which may be the same or different. R ₂ and R ₃ are bonded to each other and contain a nitrogen atom. (A substituted or unsubstituted heterocyclic group may be formed.)

Conventionally, the following compound No. which is a compound represented by the general formula (4) is used. The basic compound represented by 4-1 is known per se. Some of these compounds are known to be used as basic compounds in liquid dye-sensitized solar cells using iodine electrolyte. However, when the basic compound is used in a liquid dye-sensitized solar cell using an iodine electrolyte, the open circuit voltage is high, but the short-circuit current density is greatly reduced, and the photoelectric conversion characteristics are significantly deteriorated. It has been.
In the present invention, the hole transport layer is preferably made of an organic hole transport material. When the basic compound is used in a solid dye-sensitized solar cell using an organic hole transporting material, the amount of decrease in the short-circuit current density is small and a high open-circuit voltage is obtained, thereby obtaining excellent photoelectric conversion characteristics. be able to. Further, in photoelectric conversion in weak light such as room light, which is rarely reported, a particularly significant advantage appears.

Specific examples of the compound represented by the general formula (4) are shown below, but are not limited thereto. The Nikkaji number is shown next to the structural formula.

  The addition amount of the basic compound represented by the general formula (4) in the hole transport layer is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the organic hole transport material. It is more preferable that the amount is not less than 15 parts by mass.

Moreover, you may add the oxidizing agent for making a part of organic hole transport material into a radical cation for the purpose of improving electroconductivity.
Examples of the oxidizing agent include tris (4-bromophenyl) aminium hexachloroantimonate, silver hexafluoroantimonate, nitrosonium tetrafluorate, silver nitrate, and a cobalt complex compound.
It is not necessary for all organic hole transport materials to be oxidized by the addition of the oxidizing agent, and only a part of the hole transporting material needs to be oxidized. The added oxidizing agent may be taken out of the system after the addition or may not be taken out.

The hole transport layer 6 can be directly formed by being connected to the electron transport layer 4 containing the photosensitizing compound 5. There is no restriction | limiting in particular in the preparation methods of the hole transport layer 6, The method of forming a thin film in vacuum, such as vacuum deposition, and the wet film forming method are mentioned. In consideration of the manufacturing cost and the like, a wet film forming method is particularly preferable, and a method of coating on the electron transport layer 4 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 having a temperature and pressure lower than the critical point.

The supercritical fluid exists as a non-aggregating high-density fluid in a temperature / pressure region that exceeds the limit (critical point) at which gas and liquid can coexist, and does not aggregate even when compressed. The fluid is not particularly limited as long as it is in the above state, and can be appropriately selected according to the purpose. However, a fluid having a low critical temperature is preferable.
Examples of the supercritical fluid include carbon monoxide, carbon dioxide, ammonia, nitrogen, water, methanol, ethanol, n-butanol and other ercol solvents, ethane, propane, 2,3-dimethylbutane, benzene, toluene and the like. Hydrocarbon solvents, halogen solvents such as methylene chloride and chlorotrifluoromethane, and ether solvents such as dimethyl ether are preferred. Among these, carbon dioxide is particularly preferable because it has a critical pressure of 7.3 MPa and a critical temperature of 31 ° C., so that it can easily create a supercritical state and is nonflammable and easy to handle.
These fluids may be used alone or in combination of two or more.
The subcritical fluid is not particularly limited as long as it exists as a high pressure liquid in a temperature and pressure region near the critical point, and can be appropriately selected according to the purpose.
The compound mentioned as a supercritical fluid mentioned above can be used conveniently also as a subcritical fluid.

  The critical temperature and critical pressure of the supercritical fluid are not particularly limited and can be appropriately selected according to the purpose. However, the critical temperature is preferably −273 ° C. or more and 300 ° C. or less, particularly 0 ° C. or more and 200 ° C. or less. preferable.

Furthermore, in addition to the above supercritical fluid and subcritical fluid, an organic solvent or an entrainer can be used in combination. By adding an organic solvent and an entrainer, the solubility in the supercritical fluid can be adjusted more easily.
There is no restriction | limiting in particular as such an organic solvent, According to the objective, it can select suitably. For example, a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone,
Ester solvents such as ethyl formate, ethyl acetate, or n-butyl acetate,
Ether solvents such as diisopropyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane;
Amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone,
Halogenated hydrocarbon solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or 1-chloronaphthalene,
Hydrocarbons such as n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene or cumene System solvents and the like.

  In the present invention, an organic hole transporting material may be provided on the electron transporting layer 4 containing the electron transporting material that has adsorbed the photosensitizing compound 5, and then a pressing process may be performed. By performing this press treatment, the organic hole transporting material is more closely attached to the electron transporting layer 4 so that the efficiency is improved.

Although there is no restriction | limiting in particular in a press processing method, The roll molding method using the press molding method using a flat plate represented by IR tablet shaping device, a roller, etc. can be mentioned.
The pressure is preferably 10 kgf / cm ² or more, more preferably 30 kgf / cm ² or more. Although there is no restriction | limiting in particular in the time to press-process, It is preferable to carry out within 1 hour. Further, heat may be applied during the pressing process.
In the above pressing process, a release material may be sandwiched between the press and the electrode.

  Materials used for the release material include polytetrafluoroethylene, polychlorotrifluoride ethylene, tetrafluoroethylene hexafluoropropylene copolymer, perfluoroalkoxy fluoride resin, polyvinylidene fluoride, ethylene tetrafluoride ethylene copolymer. Fluorine resins such as polymers, ethylene chlorotrifluoride ethylene copolymers, polyvinyl fluoride, and the like.

A metal oxide may be provided between the organic hole transport material and the second electrode 7 before the second electrode 7 is provided after the pressing process. Examples of the metal oxide that may be provided include molybdenum oxide, tungsten oxide, vanadium oxide, and nickel oxide, and molybdenum oxide is particularly preferable.
The method for providing these metal oxides on the hole transport layer 6 is not particularly limited, and examples thereof include a method of forming a thin film in a vacuum such as sputtering and vacuum deposition, and a wet film forming method.
In the wet film forming method, it is preferable to prepare a paste in which a metal oxide powder or sol is dispersed and apply the paste onto the hole transport layer.
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. The film thickness is preferably from 0.1 to 50 nm, more preferably from 1 to 10 nm.

<Second electrode>
The second electrode 7 can be formed on the hole transport layer 6 or on the metal oxide in the hole transport layer 6. In addition, the second electrode 7 can be generally the same as the first electrode 2 described above, and a support is not necessarily required in a configuration in which strength and sealability are sufficiently maintained.
Specific examples of the material of the second electrode 7 include metals such as platinum, gold, silver, copper, and aluminum, carbon compounds such as graphite, fullerene, carbon nanotube, and graphene, and conductive metals such as ITO, FTO, and ATO. Examples thereof include conductive polymer compounds such as oxide, polythiophene, polyaniline, polypyrrole, and derivatives thereof, and these may be used alone or in combination of two or more.
The film thickness of the second electrode 7 is not particularly limited, and the coating is appropriately applied, laminated, vapor deposited, CVD, affixed on the hole transport layer 6 depending on the type of material used and the type of the hole transport layer 6. It can be formed by a technique such as matching.

  In the photoelectric conversion element of the present invention, film formation by an inexpensive coating method is preferable. Therefore, it is preferable to use a conductive polymer compound such as polythiophene, polyaniline, polypyrrole and derivatives thereof as the material, and a conductive polymer compound selected from the group consisting of polythiophene having good conductivity and derivatives thereof. It is more preferable. Alternatively, it is preferable to use a paste made of nanomaterials such as nanoparticles, nanorods, and nanowires made of Group 11 metal atoms such as silver and copper, and a fibrous metal network can be formed. More preferred is a nanowire capable of obtaining the property. These may be used alone or in combination of two or more. Moreover, in the photoelectric conversion element of this invention, the electrode film formed using these has translucency.

<Porous layer>
In the present invention, the porous layer 8 is provided between the second electrode 7 and the second substrate 9, includes light scattering particles made of a metal oxide, and photoelectrically converts transmitted light incident from the first substrate 1. Return to the layer. Thereby, even if it uses the cheap and transparent 2nd electrode 7, favorable photoelectric conversion efficiency is obtained.

  In the module form, in order to use the transmitted light between the divided electrodes, it is preferable to install a porous layer containing the light scattering particles across the divided second electrode 7. At this time, the porous layer 8 may be arranged so as to fill a gap existing between the divided second electrodes, or may be arranged on the air layer with the gap as an air layer. The air layer is not particularly limited. For example, various gases such as air, oxygen, nitrogen, and argon can be used.

Specific examples of the light scattering particles made of a metal oxide are not particularly limited, but those having a refractive index of 1.6 or more are preferable, and particularly dye-sensitized solar having high sensitivity in the visible light region. In the battery, a substance that absorbs less in the visible light region is more preferable because the visible light scattering efficiency increases. Specific examples include magnesium oxide, aluminum oxide, zinc oxide, titanium oxide, tin oxide, niobium oxide, yttrium oxide, and zirconium oxide. The porous layer 8 may be a single layer or a multilayer, and may be used alone or in combination of two or more kinds.
The particle size of the light scattering particles is selected according to the wavelength of the scattered light. According to JP2012-181983, the particle size for scattering light is proportional to the wavelength of the scattered light, and the particle size is determined by substituting the wavelength of incident light into a plurality of empirical formulas (Sumitomo). Osaka Cement Co., Ltd. Technical Report, Titanium Oxide for Dye-Sensitized Solar Cells (2005) 36-40). In particular, in a dye-sensitized solar cell having high sensitivity in the visible light region, it is preferable to appropriately select scattering particles according to the wavelength in the visible light region. For wavelengths from 400 nm to 800 nm, the particle size is 0.15 μm. To 0.45 μm is reported to be preferable.
The particle diameter of the light scattering particles is the average diameter of the primary particles, and the particle diameter was measured using a scanning electron microscope (SEM).

  If the film thickness of the porous layer 8 is 1 μm or more, the light scattering efficiency is good, and the incident transmitted light can be efficiently returned to the photoelectric conversion layer. Although the upper limit is not particularly limited, for example, when the porous layer is formed by baking at a high temperature of about 500 ° C., if the film is too thick, cracks are likely to occur and the film is likely to peel off. Therefore, it is preferably 20 μm or less.

  The method for forming the porous layer 8 is not particularly limited, but a wet film forming method capable of forming a cheaper film is preferable, and the coating method is not particularly limited, and may be performed according to a known method. it can. 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.

When a dispersion of metal oxide fine particles is prepared by mechanical pulverization or using a mill, it is formed by dispersing at least metal oxide fine particles alone or a mixture of metal oxide fine particles and a resin in water or an organic solvent. .
The resin used at this time is not particularly limited. For example, polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid ester, methacrylic acid ester, silicon resin, phenoxy resin, polysulfone resin, polyvinyl butyral resin, polyvinyl formal resin, polyester resin, cellulose ester resin, Cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin, polyimide resin, ionomer, ethylene-vinyl acetic anhydride copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl alcohol Examples thereof include resins such as copolymers, ultraviolet curable resins, thermosetting resins, and vinyl alcohol polymers.

  The solvent to be dispersed is not particularly limited. For example, alcohol solvents such as water, methanol, ethanol, isopropyl alcohol, α-terpineol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ester solvents such as ethyl formate, ethyl acetate, or n-butyl acetate Ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone, 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 Examples thereof include hydrocarbon solvents such as xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

The dispersion of light scattering particles or the paste of light scattering particles obtained by a sol-gel method, etc. is used to prevent re-aggregation of the particles, such as acids such as hydrochloric acid, nitric acid, acetic acid, polyoxyethylene, octylphenyl ether, etc. Surfactants, chelating agents such as acetylacetone, 2-aminoethanol, and ethylenediamine can be added.
It is also an effective means to add a thickener for the purpose of improving the film forming property.
Examples of the thickener added at this time include polymers such as polyethylene glycol and polyvinyl alcohol, and thickeners such as ethyl cellulose.

  The method for fixing the porous layer is not particularly limited, and can be performed according to a known method. For example, heat sintering, microwave irradiation, electron beam irradiation, laser light irradiation, ultraviolet curing, thermal curing, and the like can be given. These treatments may be performed alone or in combination of two or more. In the case of firing, the range of the firing temperature is not particularly limited, but if the temperature is raised too much, the resistance of the substrate may increase or the substrate may melt, so 30 to 700 ° C is preferable, and 100 to 600 ° C is more. preferable. Moreover, although there is no restriction | limiting in particular also in baking time, 10 minutes-10 hours are preferable.

<Second substrate>
The second substrate 9 used in the present invention is not particularly limited, and a known substrate can be used. Examples thereof include glass, a transparent plastic plate, a transparent plastic film, and an inorganic transparent crystal.

<Application>
The photoelectric conversion element of the present invention can be used as a solar cell. Further, it can be applied to a power supply device by combining with a circuit board for controlling the generated current. Examples of devices using such a power supply device include an electronic desk calculator and a wristwatch. In addition, the power supply device having the photoelectric conversion element of the present invention can be applied to a mobile phone, an electronic notebook, electronic paper, and the like. Moreover, the power supply device which has the photoelectric conversion element of this invention can also be used as an auxiliary power supply for extending the continuous use time of a rechargeable or dry battery type electric appliance.

  Hereinafter, the present invention will be described with reference to examples and comparative examples. In addition, this invention is not limited to the Example illustrated here.

Example 1
<Production of titanium oxide semiconductor electrode>
A dense hole blocking layer of titanium oxide was formed on the ITO glass substrate by reactive sputtering with oxygen gas using a target made of titanium metal.
Next, 3 g of titanium oxide (P90 manufactured by Nippon Aerosil Co., Ltd.), 0.2 g of acetylacetone, and 0.3 g of surfactant (polyoxyethylene octylphenyl ether manufactured by Wako Pure Chemical Industries, Ltd.) were mixed with 5.5 g of water and 1.0 g of ethanol in a bead mill. The treatment was applied for 12 hours. 1.2 g of polyethylene glycol (# 20,000) was added to the obtained dispersion to prepare a paste. This paste was applied on the substrate so as to have a film thickness of 1.5 μm, dried at room temperature, and then baked in air at 500 ° C. for 30 minutes to form a porous electron transport layer. In this embodiment, what has been formed so far is referred to as a titanium oxide semiconductor electrode for convenience.

<Production of photoelectric conversion element>
The titanium oxide semiconductor electrode is immersed in D358 (0.5 mM, acetonitrile / t-butanol (volume ratio 1: 1) solution) manufactured by Mitsubishi Paper Industries, Ltd. represented by the structural formula (3) as a sensitizing dye. The photosensitized material was adsorbed by allowing it to stand in the dark for a long time.
Organic hole transport material represented by the following structural formula (5) on a semiconductor electrode carrying a photosensitizing material (Merck Co., Ltd., brand: 2,2 ', 7,7'-tetrakis (N, N -di-p-methoxyphenylamino) -9,9'-spirobifluorene, product number: SHT-263, CAS number 207739-72-8) in chlorobenzene (solid content 14% by mass) solution with lithium bis (trifluoromethane) manufactured by Kanto Chemical Co., Inc. Sulfonyl) imide (compound represented by the following structural formula (6)) (solid content: 1% by mass), exemplified basic compound No. 1 represented by the general formula (4). A solution obtained by adding 4-3 (solid content: 1.4% by mass) was applied by spin coating to form a hole transport layer 6. The layer formed so far is referred to as a solid-type photoelectric conversion layer for convenience. A PEDOT / PSS (poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid) (Aldrich) paste was screen-printed thereon and dried at 100 ° C. for 30 minutes to produce a second electrode.

  The cover glass is made of titanium oxide (particle size 200 nm) paste (titanium oxide 16% by mass, α-terpineol 70% by mass, ethyl cellulose 10 cps 8% by mass, acetylacetone 3% by mass, acetic acid 3% by mass) as light scattering particles. The resultant was applied to 2.0 μm, dried at room temperature, and then baked in air at 500 ° C. for 30 minutes to form a porous layer. The cover glass provided with the porous layer was combined with the substrate provided up to the second electrode to produce a photoelectric conversion element.

<Evaluation of photoelectric conversion element>
About the photoelectric conversion element obtained by the above, the photoelectric conversion efficiency under white LED irradiation (1000Lux: 0.24mW / cm < ² >) was measured. The white LED was measured with a desk lamp CDS-90α (study mode) manufactured by Cosmo Techno, and the evaluation device was measured with a solar cell evaluation system As-510-PV03 manufactured by NF Circuit Design Block. The measurement results are shown in Table 1.
As a result, since the light transmitted through the second electrode was scattered back to the photoelectric conversion layer, a high current value was obtained and excellent characteristics were exhibited.

(Examples 2 to 8)
A photoelectric conversion element was produced in the same manner as in Example 1 except that the light scattering particles in Example 1 were changed to the light scattering particles shown in Table 1, and evaluated in the same manner. As a result, since the refractive index was smaller than that of titanium oxide, the light scattering effect was relatively small, but a high current value was obtained and excellent characteristics were exhibited.

Example 9
In Example 1, the first electrode was laser-etched with a laser device to form a 4-cell series substrate, and a PEDOT / PSS (Aldrich) paste was used using a mask patterned to be in 4-cell series. A photoelectric conversion element was produced in the same manner as in Example 1 except that the second electrode was produced by screen printing and drying at 100 ° C. for 30 minutes, and evaluated in the same manner (the structure is shown in FIG. 2). FIG. 2 is a schematic view of a cross section of the photoelectric conversion element). As a result, light transmitted through the second electrode and light transmitted between the electrodes were returned to the photoelectric conversion layer by light scattering, so that a high current value was obtained and excellent characteristics were exhibited.

(Example 10)
In Example 1, a photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that the silver nanowire paste was screen-printed on the PEDOT / PSS electrode and dried at 100 ° C. for 30 minutes. As a result, a high current value was obtained by the light scattering effect, and a high FF (curve factor) was obtained by the low resistance silver nanowire, which showed excellent characteristics.

(Example 11)
In Example 1, the hole transport layer was made of iodine electrolyte (lithium iodide (0.1M), iodine (0.05M), 1,2-dimethyl-3-propylimidazolium iodide (0.6M), 4-tert-butylpyridine. (0.5 M solution in acetonitrile) (referred to as a liquid photoelectric conversion layer for convenience), PEDOT / PSS (Aldrich) paste was screen printed on the porous layer formed on the cover glass, A second electrode was prepared by drying at 100 ° C. for 30 minutes, and the cover glass provided with the porous layer and the second electrode was combined with the titanium oxide semiconductor electrode substrate on which the sensitizing dye was adsorbed, and the gap between the electrodes was A photoelectric conversion element was prepared in the same manner as in Example 1 except that a photoelectric conversion element was prepared by filling with the iodine electrolyte solution, and was similarly evaluated. As a result, since the light transmitted through the second electrode was returned to the photoelectric conversion layer by light scattering, a high current value was obtained and excellent characteristics were obtained, but a lot of light was absorbed by the iodine electrolyte. The effect was small because it was closed.

(Comparative Example 1)
In Example 1, a photoelectric conversion element was prepared and evaluated in the same manner as in Example 1 except that the porous layer containing light scattering particles was not provided. As a result, compared with Example 1, it showed a low current value and remained at low performance. This is because the light transmitted through the second electrode could not be used sufficiently.

(Comparative Example 2)
In Example 1, a porous layer containing light scattering particles is formed on a titanium oxide semiconductor electrode, dried at room temperature, and then baked in air at 500 ° C. for 30 minutes. Light scattering particles are formed on the second electrode. A photoelectric conversion element was produced in the same manner as in Example 1 except that the porous layer was not provided, and evaluated in the same manner. As a result, the hole diffusion movement distance in the hole transport layer was increased and the power loss was increased, so that the performance remained low.

(Comparative Example 3)
In Example 11, a photoelectric conversion element was produced and evaluated in the same manner as in Example 11 except that the porous layer containing light scattering particles was not provided. As a result, the current value was lower than that of Example 11, and the performance was low. This is because the light transmitted through the second electrode could not be used sufficiently.

(Comparative Example 4)
In Example 11, a porous layer containing light scattering particles was formed on a titanium oxide semiconductor electrode, dried at room temperature, and then fired in air at 500 ° C. for 30 minutes. Light scattering particles were deposited on the second electrode. A photoelectric conversion element was produced in the same manner as in Example 11 except that the porous layer was not provided, and evaluated in the same manner. As a result, the performance was lower than that of Example 11. This is because by providing a porous layer in the photoelectric conversion layer, ion diffusion of the electrolytic solution is inhibited and resistance is increased.

(Comparative Example 5)
In Example 1, a silver nanowire paste was screen-printed on the PEDOT / PSS electrode, dried at 100 ° C. for 30 minutes, and a photoelectric conversion element was obtained in the same manner as in Example 1 except that no porous layer containing light scattering particles was provided. Were prepared and evaluated in the same manner. As a result, compared with Example 1, it showed a low current value and remained at low performance. This is because the light transmitted through the second electrode could not be used sufficiently.
As apparent from the above, it can be seen that the photoelectric conversion element of the present invention exhibits excellent photoelectric conversion characteristics.

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 1st electrode 3 Hole blocking layer 4 Electron transport layer 5 Photosensitizing compound 6 Hole transport layer 7 Second electrode 8 Porous layer 9 Second substrate

Japanese Patent No. 2664194 JP 2014-143333 A JP-A-10-255863 JP2003-142171A JP2012-119189

Panasonic Electric Works Technical Report, Vol. 56, no. 4 (2008) 87 Nature, 353 (1991) 737 J. et al. Am. Chem. Soc. , 115 (1993) 6382 Chinese Science Bulletin Vol.58 No.4-5 (2013) 559-566

Claims (6)

  A first substrate, a first electrode having translucency disposed on the first substrate, a photoelectric conversion layer disposed on the first electrode, and disposed on the photoelectric conversion layer. A second electrode having translucency, a porous layer disposed on the second electrode, and a second substrate disposed on the porous layer, the porous layer comprising: A photoelectric conversion element comprising light scattering particles made of a metal oxide.   The photoelectric conversion layer is a hole blocking layer disposed on the first electrode, and an electron transport layer composed of an electron transport semiconductor disposed on the hole blocking layer and having a photosensitizing compound adsorbed on the surface thereof. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element comprises a hole transport layer made of a hole transport material and connected to the electron transport layer.   The light scattering particles include at least one selected from the group consisting of magnesium oxide, aluminum oxide, zinc oxide, titanium oxide, tin oxide, niobium oxide, yttrium oxide, and zirconium oxide. 2. The photoelectric conversion element according to 2. 4. The photoelectric conversion element according to claim 1, wherein the second electrode is composed of at least one of the following A and B. 5.
A: Conductive polymer compound selected from the group consisting of polythiophene and derivatives thereof B: Nanowire made of Group 11 metal element   5. The photoelectric conversion element according to claim 1, wherein the first electrode and the second electrode are each composed of a plurality of divided electrodes.   It uses as a solar cell, The photoelectric conversion element as described in any one of Claims 1 thru | or 5 characterized by the above-mentioned.