JP2012059599A - Carbon based electrode and electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon based electrode formed by a simple low temperature process, such as application of a coating liquid and evaporation of a solvent from a coating liquid layer, and inexpensive and excellent in electrolyte resistance, and to provide an electrochemical device having the carbon based electrode and useful as a dye sensitized solar cell or the like.SOLUTION: The carbon based electrode comprises: a support body (equivalent to a counter substrate 6); and a porous electrode layer (equivalent to a counter electrode 5) disposed on the support body and containing a polyamide imide used as a binder, and carbon based fine particles consisting mainly of carbon, having affinity with the polyamide imide, and formed by evaporating and removing a solvent from a coating liquid layer including both materials, where the carbon based particles are untreated with oxidation and are carbon black without hollows (contents filled), a mixture with distilled water showing neutrality or weak base; the ratio of the mass of the polyamide imide to the mass of the carbon black in the porous electrode layer is 1/15 to 1/7; and the thickness of the porous electrode layer is 20 μm or less.

Description

  The present invention has a carbon-based electrode that can be formed by a simple low-temperature process such as application of a coating liquid or evaporation of a solvent from a coating liquid layer, is inexpensive and has good anti-electrolytic solution properties, and the carbon-based electrode. The present invention relates to an electrochemical device useful as a dye-sensitized solar cell.

  Carbon dioxide is generated when fossil fuels such as coal and oil are used as energy sources. Carbon dioxide is one of the causative substances that cause global warming. In the use of nuclear energy, radioactive elements are generated and there is a risk of radioactive contamination. Moreover, these energy resources are limited and will eventually be exhausted. Therefore, reliance on these energy sources is problematic. In recent years, sunlight has attracted attention as an alternative and clean and inexhaustible energy source. A solar cell is a photoelectric conversion device that converts the energy of sunlight into electrical energy, and uses sunlight as an energy source, and therefore has a very small influence on the global environment. For this reason, further spread of solar cells is expected.

  Various things are proposed as a principle and constituent material of a solar cell. Among them, solar cells using a semiconductor pn junction are currently most popular, and many solar cells using silicon as a semiconductor material are commercially available. However, manufacturing a solar cell using a pn junction requires a process for manufacturing a high-purity semiconductor material and a process for forming a pn junction. For this reason, there exists a problem that energy consumption in manufacturing processes, such as a high temperature process, is large. In addition, since the number of manufacturing processes is large and a large-scale apparatus such as a clean room or a vacuum apparatus is necessary, there is a problem that the manufacturing cost increases.

  On the other hand, a dye-sensitized solar cell using photoinduced electron transfer photosensitized by a dye has been proposed by Gretzel et al. (Patent Publication No. 2664194 (2nd and 3rd pages, FIG. 1)) and B (See O'Regan and M. Graetzel, Nature, 353, p. 737-740 (1991).)

  FIG. 7 is a cross-sectional view of a main part showing the structure of a conventional general dye-sensitized solar cell 100. The dye-sensitized solar cell 100 mainly includes a transparent substrate 101 such as glass, a transparent conductive layer (negative electrode current collector) 102, a semiconductor electrode layer 103 (negative electrode) holding a photosensitizing dye, an electrolyte layer 104, a counter electrode. (Positive electrode) 105, counter substrate 106, and sealing material (not shown).

The transparent conductive layer 102 provided on the transparent substrate 101 is made of ITO (Indium Tin Oxide), FTO (fluorine-doped tin oxide), or the like, and functions as a negative electrode current collector. The semiconductor electrode layer 103 that is a negative electrode is provided in contact with the transparent conductive layer 102. As the semiconductor electrode layer 103, a porous layer obtained by sintering fine particles of a metal oxide semiconductor such as titanium oxide TiO ₂ is often used. The photosensitizing dye is adsorbed on the surface of the metal oxide constituting the semiconductor electrode layer 103. As the electrolyte layer 104, an electrolytic solution containing a redox species (redox pair) or the like is used. The counter electrode 105 is composed of a platinum layer or the like, and is provided on the counter substrate 106.

  The dye-sensitized solar cell 100 is configured such that light enters from the transparent substrate 101 side. A part of the incident light is absorbed by the photosensitizing dye, and a part of the electrons excited by the light absorption is extracted to the semiconductor electrode layer 103. On the other hand, the photosensitizing dye that has lost the electrons is reduced by the reducing species (reducing agent) in the electrolyte layer 104. Oxidized species (oxidant) generated in the electrolyte layer 104 by this reaction receives electrons from the counter electrode 105 and returns to the reduced species. As a result, the dye-sensitized solar cell 100 operates as a photovoltaic cell having the transparent conductive layer 102 and the semiconductor electrode layer 103 as a negative electrode and the counter electrode 105 as a positive electrode.

  Dye-sensitized solar cells do not require a vacuum treatment process for manufacturing, so large-scale equipment is not required, and inexpensive oxide semiconductors such as titanium oxide are used to manufacture with low productivity and high productivity. There are advantages. In addition, there are various photosensitizing dyes that can absorb light in each wavelength region in a wide wavelength region centered on the visible light region. Therefore, the wavelength of light to be absorbed can be selected by changing the dye used, or multiple By combining these dyes, there is an advantage that light in a wide wavelength region can be used. In addition, there is a possibility that it can be manufactured with high productivity and low cost by a roll-to-roll process using a lightweight and flexible base material such as plastic. For this reason, it has attracted much attention in recent years as a new generation solar cell.

  Conventionally, as the counter electrode (positive electrode) 105 of the dye-sensitized solar cell, a platinum layer is mainly used because it has both excellent catalytic action and corrosion resistance. For the formation of the platinum layer, a sputtering method or a wet method in which a chloroplatinic acid solution is applied and then the chloroplatinic acid is thermally decomposed to liberate platinum is used. The platinum layer is excellent in catalytic activity, corrosion resistance, and conductivity, but there are also problems such as platinum is scarce in resources and expensive, and high vacuum process or high temperature process is required for production. . Therefore, a solar cell manufactured using a plastic substrate has an electrode material and an electrode structure that can form an electrode layer easily and inexpensively at a low temperature process of about 150 ° C. or lower, such as application of a coating liquid or evaporation of a solvent. (See Yuki Saito, “Development of Electrolyte and Counter Electrode Material for Dye-Sensitized Solar Cells”, Chemical Engineering, 2007, 71 (7), p. 452). Therefore, a configuration using carbon as a material for the counter electrode and a configuration using a conductive polymer have been reported.

For example, in Patent Document 1 described later, a carbon-containing conductive layer having a resistivity of 0.001 to 0.1 Ω · cm is provided on one surface of a counter electrode substrate, and a specific surface area of 500 to 3000 m ² / g is further provided on the surface thereof. A dye-sensitized solar cell having a counter electrode provided with a carbon-containing catalyst layer is proposed. Patent Document 1 explains as follows.

  According to the above configuration, sufficient conductivity can be obtained by the carbon-containing conductive layer, and sufficient catalytic action can be obtained by the carbon-containing catalyst layer, so that a dye-sensitized solar cell with high photoelectric conversion efficiency can be realized. it can. In addition, since the carbon-containing conductive layer and the carbon-containing catalyst layer are mainly composed of carbon, they have excellent corrosion resistance.

  When the carbon-containing conductive layer is formed by evaporating a solvent from a paste containing conductive carbon and a resin, the current collecting resistance can be suppressed sufficiently low. The conductive carbon is not particularly limited, but when it is at least one of graphite, ketjen black and carbon nanotubes, the current collecting resistance can be further reduced, and graphite is particularly preferable. The resin is not particularly limited, and may be a thermosetting resin or a thermoplastic resin. As the thermosetting resin, phenol resin, epoxy resin, unsaturated polyester resin, polyimide resin, polyurethane resin, or the like can be used. Moreover, as a thermoplastic resin, a fluororesin, a polyester resin, a polyamide resin, etc. can be used.

  Moreover, in order to improve electroconductivity, another electroconductive substance can also be contained in a carbon containing electroconductive layer. As the conductive substance, metals, conductive oxides, conductive polymers, and the like can be used. Examples of the conductive polymer include polyaniline, polypyrrole, and polyacetylene. Since the conductive substance contained in the carbon-containing conductive layer does not come into contact with the electrolytic solution, any conductive substance can be used regardless of the corrosion resistance.

  The carbon-containing catalyst layer includes a porous resin sheet and carbon having a catalytic action that is held by the porous resin sheet. It is preferable that the porous resin sheet is bonded to the surface of the carbon-containing conductive layer because sufficient catalytic action is exhibited. The carbon having a catalytic action is not particularly limited, but is preferably activated carbon.

  The resin constituting the porous resin sheet is not particularly limited, and may be a thermoplastic resin or a thermosetting resin. As the thermoplastic resin, fluorine resin, polyester resin, polyamide resin, or the like can be used. Moreover, as a thermosetting resin, an epoxy resin, a phenol resin, an unsaturated polyester resin, a polyimide resin, a polyurethane resin, etc. can be used. Of these resins, a highly durable fluororesin is preferred.

  The carbon-containing catalyst layer must have sufficient porosity as well as conductivity. The porous resin sheet has communication holes, and the catalyst carbon is held on the wall surfaces of the communication holes. The production method of the porous resin sheet is not particularly limited. For example, the resin sheet can be cold-stretched to obtain a porous resin sheet having a large number of voids. The method for retaining the catalyst carbon in the porous resin sheet is not particularly limited. For example, the porous resin sheet is immersed in a dispersion liquid in which the catalyst carbon is dispersed in a solvent, impregnated with the dispersion liquid, and then the solvent is added. A method of removing by heating or the like can be used.

  The method for joining the carbon-containing catalyst layer and the carbon-containing conductive layer is not particularly limited. For example, a porous resin sheet holding catalyst carbon is laminated on a coating film for forming a carbon-containing conductive layer, and then the solvent is evaporated from the coating film, thereby simultaneously producing the carbon-containing conductive layer. The carbon-containing catalyst layer and the carbon-containing conductive layer can be joined. In addition, both members can be bonded with various adhesives.

  Patent Document 2 described later proposes a photoelectric conversion element having a semiconductor electrode containing light scattering particles and a counter electrode using a conductive polymer and / or a carbon-based material. Patent Document 2 explains as follows.

  As the conductive polymer used for the counter electrode, generally known polymers can be used. For example, polyacetylene, polypyrrole, polyaniline, polythiophene, polyphenylene, polyacene, polyazulene, polyindole or derivatives thereof can be used. Particularly, poly (3,4-ethylenedioxythiophene) (PEDOT), polyalkylthiophenes and the like can be used. It can be used suitably.

  Various carbon-based materials may be used for the counter electrode, such as acicular carbon, ketjen black, acetylene black, fullerene, and carbon nanotube. In order to realize rapid charge transfer, a metal such as platinum is preferably supported on the carbon-based material. The carbon-based material is typically combined with a binder (binder). The binder is preferably insoluble in the electrolytic solution, and synthetic resins such as pitch, fluororubber, and fluororesin can be used. In particular, polyvinylidene fluoride (PVDF) is preferable in that it can be dissolved using a solvent and has excellent stability to light and heat.

  Carbon-based materials have good catalytic performance and anti-electrolytic solution properties, and inexpensive materials can be easily obtained. As a material for counter electrodes, such as dye-sensitized solar cells manufactured using plastic substrates, Is preferred. However, since a carbon-based material alone cannot be used to form a film, when an electrode layer made of a carbon-based material is formed on a plastic substrate or the like, a structure in which activated carbon is held in a through-hole of a porous resin sheet or a carbon-based material is not And a structure in which the electrode layer is formed in a composite form. At this time, in order for the electrode layer to exhibit sufficient catalytic performance, the electrode layer has sufficient porosity, the content of the carbon-based material in the electrode layer is sufficiently large, and the electrode layer is sufficient It is necessary to have good electrical conductivity.

  Like the carbon-containing catalyst layer of Patent Document 1, it is considered difficult to satisfy these requirements at a high level with a configuration using a porous resin sheet. Because, in order to maintain the strength of the porous resin sheet, the porosity of the porous resin sheet cannot be extremely increased. Therefore, while maintaining the strength and preventing the activated carbon from falling off, It is considered that the content of the activated carbon that can be held in is limited to about 50% by mass at most. Moreover, since the material illustrated as a porous resin sheet in patent document 1 does not have electroconductivity, when a carbon containing catalyst layer becomes too thick, electroconductivity will fall and photoelectric conversion efficiency will fall. For this reason, although the thickness of a carbon containing catalyst layer is restrict | limited, since it will restrict | limit the amount of activated carbon per unit area, it will become difficult to obtain a big current density.

  The configuration proposed in Patent Document 1 for sharing the function of the counter electrode between the carbon-containing conductive layer and the carbon-containing catalyst layer seems reasonable at first glance, but uses the porous resin sheet described above. Considering the configuration problems, it is difficult to actually obtain the expected performance. Furthermore, considering the decrease in conductivity due to the joint between the carbon-containing catalyst layer and the carbon-containing conductive layer, the increase in the number of manufacturing steps and the cost due to the two-layer configuration of the electrode layer, and the decrease in durability and reliability. The merit of the electrode layer having two layers is small, and it is considered desirable to solve the problem with a single layer electrode layer.

  When a carbon material is combined with a binder to form an electrode layer, the binder preferably has conductivity. However, when the film forming performance of the binder is high, the film can be formed with the addition of a small amount of binder, and the conductivity is ensured by the contact between the carbon-based materials, the binder does not have to be conductive. In order to ensure long-term reliability, the binder must not react with the electrolyte or dissolve in the electrolyte. In order to form an electrode layer by a simple method such as a coating method or a printing method, it is necessary that the carbon-based material and the binder can be applied together using a suitable solvent. From such a viewpoint, conventionally, a fluororesin and a conductive polymer exemplified in Patent Document 1 and Patent Document 2 have been suitable as the binder. However, since solar cells manufactured using plastic substrates are strongly required to be able to form electrode layers at a lower cost, it is possible to reduce the amount of fluororesin or conductive polymer used, or replace with other cheaper materials. Is required.

  The present invention has been made in view of such a situation, and the object thereof is to be formed by a simple low-temperature process such as application of a coating liquid or evaporation of a solvent from a coating liquid layer, and is inexpensive and is resistant to electrolysis. An object of the present invention is to provide a carbon-based electrode having good liquid characteristics and an electrochemical device having the carbon-based electrode and useful as a dye-sensitized solar cell.

  As a result of earnest research on an inexpensive binder added to form a carbon-based fine particle, the present inventors have completed the present invention.

That is, the present invention
A support;
It is disposed on the support and contains a polyamideimide as a binder and carbon-based fine particles mainly composed of carbon and having an affinity for the polyamideimide, and the solvent is evaporated and removed from the coating layer containing both. And a porous electrode layer.

  The present invention also relates to an electrochemical apparatus having the carbon-based electrode.

  In the carbon-based electrode of the present invention, the porous electrode layer comprising the carbon-based fine particles having an affinity for the polyamide-imide and having the polyamide-imide as a binder is excellent in an anti-electrolytic solution as shown in Examples described later. It exhibits characteristics and is inexpensive. In addition, the porous electrode layer exhibits the excellent catalytic performance and conductivity of the carbon-based fine particles, and the porous electrode layer functions as an excellent catalyst electrode. This porous electrode layer can be formed by a simple low-temperature process such as application of a coating liquid containing the carbon-based fine particles and the polyamideimide, and evaporation of the solvent from the coating liquid layer.

  Since the electrochemical device of the present invention has the carbon-based electrode of the present invention as an electrode, the electrochemical device in which it is desired to form the electrode in a simple low-temperature process and at low cost, for example, the support of the porous electrode layer It is suitable as an electrochemical device using a plastic substrate as a body.

It is the schematic which shows the cross-section of the dye-sensitized solar cell based on embodiment of this invention. It is a SEM observation image of the cross section of the porous electrode layer obtained in Example 2-2 of this invention, and the porous electrode layer obtained in Example 3-1. It is a graph which shows the current-voltage characteristic of the dye-sensitized solar cell by Example 1 and 2 of this invention. It is a graph which shows the impedance characteristic of a dye-sensitized solar cell similarly. It is a graph which shows the current-voltage characteristic of the dye-sensitized solar cell by Example 3 of this invention. It is a graph which shows the impedance characteristic of a dye-sensitized solar cell similarly. It is principal part sectional drawing which shows the structure of the conventional common dye-sensitized solar cell.

  In the carbon-based electrode of the present invention, the carbon-based fine particles are not oxidized, and the mixed solution with distilled water is neutral or weakly basic and is not hollow (filled with carbon black). There should be.

  The ratio of the mass of polyamideimide to the mass of carbon black in the porous electrode layer is preferably 1/15 to 1/7.

  The porous electrode layer may have a thickness of 20 μm or less.

  The solvent may be N-methylpyrrolidone.

  The material of the support is preferably a plastic material.

  The electrochemical device of the present invention preferably includes at least a semiconductor electrode layer made of a metal oxide porous layer, the carbon-based electrode as the counter electrode, and an electrolyte layer sandwiched therebetween.

  At this time, the semiconductor electrode layer holds a photosensitizing dye, and when light is incident, the electrons of the photosensitizing dye excited by absorbing this light are taken out to the semiconductor electrode layer, and The photosensitizing dye that has lost the electrons is reduced by the reducing species (reducing agent) in the electrolyte layer. As a result, the oxidizing species (oxidizing agent) generated in the electrolyte layer receives electrons from the counter electrode. It is preferable to be configured as a dye-sensitized solar cell that receives and returns to the reduced species.

  Hereinafter, based on the embodiment of the present invention, details will be specifically described with reference to the drawings. In this embodiment, an electrochemical device configured as a dye-sensitized solar cell will be described as an example of the electrochemical device described in claims 7 to 9. Moreover, the electrode used as a counter electrode of a dye-sensitized solar cell is demonstrated as an example of the electrode described in Claims 1-6.

  FIG. 1 is a schematic diagram showing a cross-sectional structure of a dye-sensitized solar cell 10 according to an embodiment of the present invention. The dye-sensitized solar cell 10 mainly includes a light-transmitting substrate 1, a light-transmitting conductive layer (negative electrode current collector) 2, a semiconductor electrode layer (negative electrode) 3 that holds a photosensitizing dye, an electrolyte layer 4, and a counter electrode. The electrode (positive electrode) 5, the counter substrate 6, and a sealing material (not shown) are included. Members other than the counter electrode (positive electrode) 5 and the counter substrate 6 are the same as those of the conventional dye-sensitized solar cell.

  That is, the light transmissive substrate 1 is made of a glass plate or a plastic film such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET). The light transmissive conductive layer (negative electrode current collector) 2 is made of ITO, FTO, or the like, and is provided on the light transmissive substrate 1.

The semiconductor electrode layer (negative electrode) 3 is a porous layer made of metal oxide semiconductor fine particles such as titanium oxide TiO _2, and the photosensitizing dye 13 is adsorbed on the surfaces of the metal oxide semiconductor fine particles 11 and 12. . The semiconductor electrode layer (negative electrode) 3 includes a transmission layer 3a composed of semiconductor fine particles 11 having a small average particle diameter, a semiconductor fine particle 11 having a small average particle diameter, and a semiconductor fine particle 12 having a large average particle diameter. It is preferable to include a scattering layer 3b having a function of scattering the transmitted light that has been transmitted without being absorbed by 3a and returning it to the transmission layer 3a. Thereby, the utilization factor of light can be increased.

The electrolyte layer 4 is disposed between the semiconductor electrode layer 3 and the counter electrode 5, and I ⁻ / I ₃ ⁻ (triiodide ion I ₃ ⁻ is present as ions by combining I ₂ with iodide ion I ^−. It is composed of an electrolytic solution containing a redox species (redox pair). The electrolytic solution is disposed so as to be able to infiltrate the semiconductor electrode layer 3.

  As a feature of the present embodiment, the counter electrode 5 and the counter substrate 6 are the carbon-based electrodes described in claims 1 to 6, the counter substrate 6 is the support, and the counter electrode 5 is on the support. It is the said porous electrode layer arrange | positioned.

  The counter electrode 5 which is a porous electrode layer is made of carbon-based fine particles having affinity for polyamideimide, and includes polyamideimide as a binder. This porous electrode layer exhibits excellent electrolytic solution resistance and is inexpensive as shown in Examples described later. In addition, in this porous electrode layer, the excellent catalytic performance and conductivity of the carbon-based fine particles are exhibited, and the counter electrode 5 functions as an excellent catalyst electrode.

  At this time, it is preferable that the carbon-based fine particles are not oxidized, the mixed solution with distilled water is neutral or weakly basic, and is not hollow (filled) carbon black. The ratio of the mass of polyamideimide to the mass of carbon black in the porous electrode layer is preferably from 1/15 to 1/7. The thickness of the porous electrode layer is preferably 20 μm or less. In such a case, the effect that the electrode layer is a porous layer is maximized.

  The porous electrode layer is formed by a simple low-temperature process such as application of a coating liquid containing carbon-based fine particles having affinity for polyamideimide and polyamideimide, and evaporation removal of the solvent from the coating liquid layer. At this time, the solvent used for forming the coating liquid is preferably a carbon-based fine particle having affinity for polyamideimide and a solvent capable of affinity for polyamideimide, such as N-methylpyrrolidone. By using a solvent that can be compatible with both the carbon-based fine particles and the polyamideimide, a porous electrode layer is reliably formed.

  The counter substrate 6 which is a support for the porous electrode layer (counter electrode 5) is made of a glass plate, a plastic film, or the like, but when made of a plastic material, the electrode layer can be formed at a low cost in the low temperature process of the present invention. This is preferable because the effect is best utilized.

  When light is incident, the dye-sensitized solar cell 10 operates as a photovoltaic cell having the semiconductor electrode layer 3 as a negative electrode and the counter electrode 5 as a positive electrode.

  That is, when the photosensitizing dye 13 absorbs photons transmitted through the light-transmitting substrate 1 and the light-transmitting conductive layer 2, the electrons in the photosensitizing dye 13 are excited from the ground state to the excited state. Excited electrons are extracted to the conduction band of the semiconductor electrode layer 3 through electrical coupling between the photosensitizing dye 13 and the semiconductor electrode layer 3 and pass through the semiconductor electrode layer 3 to form a light-transmitting conductive layer. 2 is reached.

On the other hand, the photosensitizing dye 13 that has lost electrons is converted from the reducing species (reducing agent) in the electrolyte layer 4, for example, I ⁻ to the following reaction 2I ⁻ → I ₂ + 2e ^{−.
_{I 2 + I - → I 3}} -
The electrons are received by the oxidant to generate an oxidizing species (oxidant), for example, I ₃ ⁻ in the electrolyte layer 4. The generated oxidized species reach the counter electrode 5 by diffusion, and the reverse reaction of the above reaction I ₃ ⁻ → I ₂ + I ⁻
I ₂ + 2e ^- → 2I ^-
To receive electrons from the counter electrode 5 and return to the original reduced species.

  The electrons flowing out from the light-transmissive conductive layer 2 to the external circuit return to the counter electrode 5 after performing electrical work in the external circuit. In this way, light energy is converted into electrical energy without leaving any change in the photosensitizing dye 13 or the electrolyte layer 4.

  In order to fabricate the dye-sensitized solar cell 10, first, a fine particle layer made of metal oxide semiconductor fine particles is formed on the light transmissive conductive layer 2 provided on the light transmissive substrate 1, and then fired. A metal oxide semiconductor porous layer (semiconductor electrode layer) 3 is formed. Next, the photosensitizing dye 13 is adsorbed on the semiconductor electrode layer 3. The method for adsorbing the dye is not particularly limited. For example, a solution in which a dye molecule is dissolved is prepared, and the light-transmitting substrate 1 on which the semiconductor electrode layer 3 is formed is immersed in the dye solution, or the semiconductor electrode The dye solution is soaked in the semiconductor electrode layer 3 by applying, spraying or dropping the dye solution on the layer 3, and then the solvent is evaporated. Next, the light-transmitting substrate 1 and the counter substrate 6 are disposed so that the semiconductor electrode layer 3 and the counter electrode 5 face each other, and are bonded together with a sealant. Finally, an electrolyte solution is injected to form the electrolyte layer 4.

  Hereinafter, although it is the same as that of the conventional dye-sensitized solar cell, it demonstrates in detail about the transparent substrate 1-the electrolyte layer 4. FIG.

  The semiconductor electrode layer 3 is typically provided on a light transmissive conductive substrate. As shown in FIG. 1, this light-transmitting conductive substrate may be one in which a light-transmitting conductive layer 2 is formed on a conductive or non-conductive light-transmitting substrate 1, or as a whole. A conductive light-transmitting substrate may be used. The material of the light transmissive substrate 1 is not particularly limited, and various base materials can be used as long as they are light transmissive. The light-transmitting substrate 1 is preferably one that is excellent in moisture and gas barrier properties, solvent resistance, weather resistance, and the like entering from the outside of the dye-sensitized solar cell 10, and specifically, quartz, sapphire, Light-transmitting inorganic material substrate such as glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride, tetraacetylcellulose, brominated phenoxy, aramids, polyimides, polystyrenes, poly Examples thereof include light-transmitting plastic substrates such as arylates, polysulfones, and polyolefins. Among these, it is particularly preferable to use a substrate having a high transmittance in the visible light region. In consideration of workability and light weight, it is preferable to use a light transmissive plastic substrate as the light transmissive substrate 1. The thickness of the light transmissive substrate 1 is not particularly limited, and can be selected depending on the light transmittance, the shielding property between the inside and the outside of the dye-sensitized solar cell 10, and the like.

  The lower the surface resistance (sheet resistance) of the light transmissive conductive substrate, the better. Specifically, the surface resistance of the light-transmitting conductive substrate is preferably 500Ω / □ or less, and more preferably 100Ω / □. When a light transmissive conductive film is formed on a light transmissive substrate, a known material can be used as the material of the light transmissive conductive film. Specifically, indium-tin composite oxide (ITO), Fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), tin oxide, zinc oxide, indium / zinc composite oxide (IZO), etc. are included, but are not limited to these. Two or more types can be used in combination. In addition, for the purpose of reducing the surface resistance of the light transmissive conductive substrate and improving the current collection efficiency, wiring made of a conductive material such as highly conductive metal or carbon is separately provided on the light transmissive conductive substrate. It may be provided. Although there is no restriction | limiting in particular in the electrically conductive material used for this wiring, It is desirable that corrosion resistance and oxidation resistance are high, and the leakage current of electrically conductive material itself is low. However, even a conductive material having low corrosion resistance can be used by separately providing a protective layer made of a metal oxide or the like. For the purpose of protecting the wiring from corrosion and the like, the wiring is preferably installed between the light-transmitting conductive substrate and the protective layer.

  The semiconductor electrode layer (metal oxide semiconductor porous layer) 3 has a large actual surface area including the surface of fine particles facing pores inside the porous layer so that a large amount of photosensitizing dye can be adsorbed. Preferably, the actual surface area of the semiconductor electrode layer 3 is preferably 10 times or more, more preferably 100 times or more the area (projected area) of the outer surface of the semiconductor electrode layer 3.

  In general, as the thickness of the semiconductor electrode layer 3 increases and the number of semiconductor fine particles 11 or 12 contained per unit projected area increases, the actual surface area increases and the amount of dye that can be held per unit projected area increases. , The light absorption rate with respect to the incident light is increased. On the other hand, when the thickness of the semiconductor electrode layer 3 increases, the distance that the electrons transferred from the photosensitizing dye 13 to the semiconductor electrode layer 3 diffuse until reaching the light-transmissive conductive layer 2 increases. Electron loss due to charge recombination in the inside also increases. Accordingly, the semiconductor electrode layer 3 has a preferable thickness, but is generally 0.1 to 100 μm, and more preferably 1 to 30 μm.

As a material of the semiconductor electrode layer 3, various metal oxide semiconductors, compounds having a perovskite structure, and the like can be used. At this time, the material of the semiconductor fine particles is preferably an n-type semiconductor material in which conduction band electrons become carriers under photoexcitation to generate an anode current. Specific examples of such semiconductor materials include TiO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ , SrTiO ₃ , and SnO ₂ , and among these, anatase TiO ₂ is particularly preferable. However, the material of the semiconductor fine particles is not limited to these. Also, two or more of these materials can be mixed and used. Furthermore, the semiconductor fine particles can take various forms such as particles, tubes, and rods as required.

  The thickness of the semiconductor electrode layer 3 is preferably 1 to 30 μm. When the thickness is less than 1 μm, sufficient photoelectric conversion efficiency cannot be obtained. As the thickness is increased, the photoelectric conversion efficiency is improved. However, when the thickness exceeds 30 μm, the effect of improving the photoelectric conversion efficiency due to the increase in the film thickness becomes poor. Therefore, the thickness is preferably 30 μm or less. The shape of the semiconductor fine particles is not particularly limited, and may be a general shape. As for the particle diameter of the semiconductor fine particles, the average particle diameter of the primary particles is preferably 1 to 100 nm in order to transmit visible light.

  Although there is no restriction | limiting in particular in the particle size of semiconductor fine particle, 1-200 nm is preferable at the average particle diameter of a primary particle, Most preferably, it is 5-100 nm. Further, as shown in FIG. 1, semiconductor fine particles having an average particle diameter larger than this are mixed with semiconductor fine particles having an average particle diameter, and incident light is scattered by the semiconductor fine particles having a large average particle diameter. It is also possible to improve. In this case, the average particle diameter of the semiconductor fine particles to be mixed separately is preferably 20 to 500 nm.

  There are no particular restrictions on the method for producing the semiconductor electrode layer 3, but in view of physical properties, convenience, production costs, etc., a wet film-forming method is preferred, and the semiconductor fine particle powder or sol is used as a solvent such as water or an organic solvent. It is preferable to prepare a uniformly dispersed paste and deposit a coating liquid layer on a light-transmitting conductive substrate. There is no restriction | limiting in particular in the method, For example, it can carry out by the well-known method, for example, the apply | coating method or the printing method. As a coating method, for example, a dip method, a spray coating method, a wire bar coating method, a spin coating method, a roller coating method, a blade coating method, a gravure coating method, and as a wet printing method, for example, a relief printing method, an offset printing method, It can be performed by a printing method, a gravure printing method, an intaglio printing method, a rubber plate printing method, a screen printing method, or the like. When crystalline titanium oxide is used as the material of the semiconductor fine particles, the anatase type is preferable from the viewpoint of photocatalytic activity. The anatase-type titanium oxide may be a commercially available powder, sol, or slurry, or may be made with a predetermined particle size by a known method such as hydrolysis of titanium oxide alkoxide. When using a commercially available powder, it is preferable to eliminate secondary agglomeration of the particles, and it is preferable to disperse the particles using a mortar, ball mill, ultrasonic dispersion device or the like when preparing the coating solution. At this time, acetylacetone, hydrochloric acid, nitric acid, a surfactant, a chelating agent, or the like can be added in order to prevent the particles after the secondary aggregation from being aggregated again. For the purpose of thickening, various thickeners such as polymers such as polyethylene oxide and polyvinyl alcohol, and cellulose-based thickeners can be added.

  The semiconductor electrode layer 3 made of semiconductor fine particles, in other words, the semiconductor fine particle layer preferably has a large surface area so that a large amount of photosensitizing dye can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the substrate is preferably 10 times or more, more preferably 100 times or more the projected area. The upper limit is not particularly limited, but is usually about 1000 times. In general, as the thickness of the semiconductor fine particle layer increases, the amount of the supported dye increases per unit projected area and thus the light capture rate increases. However, the diffusion distance of injected electrons increases and the loss due to charge recombination also increases. . Accordingly, a preferable thickness exists in the semiconductor fine particle layer, but the thickness is generally 0.1 to 100 μm, more preferably 1 to 50 μm, and particularly preferably 3 to 30 μm. . The semiconductor fine particle layer is preferably fired in order to make the particles electronically contact each other after being applied to the substrate and to improve the film strength and the adhesion to the substrate. Although there is no restriction | limiting in particular in the range of baking temperature, Since resistance of a board | substrate will become high if it raises temperature too much and it may fuse | melt, it is usually 40-700 degreeC, More preferably, it is 40-650 degreeC. . The firing time is not particularly limited, but is usually about 10 minutes to 10 hours. After firing, for the purpose of increasing the surface area of the semiconductor fine particle layer or increasing the necking between the semiconductor fine particles, for example, chemical plating using a titanium tetrachloride aqueous solution or necking treatment using a titanium trichloride aqueous solution or a diameter of 10 nm or less. A dip treatment of the semiconductor ultrafine particle sol may be performed. In the case where a plastic substrate is used as the light-transmitting conductive substrate, it is possible to apply a paste containing a binder onto the substrate and perform pressure bonding to the substrate by a heating press.

  The photosensitizing dye to be held in the semiconductor electrode layer 3 is not particularly limited as long as it exhibits a sensitizing action. For example, xanthene dyes such as rhodamine B, rose bengal, eosin and erythrosine, merocyanine, quinocyanine, Cyanine dyes such as cryptocyanine, basic dyes such as phenosafranine, fog blue, thiocin and methylene blue, other azo dyes, porphyrin compounds such as chlorophyll, zinc porphyrin and magnesium porphyrin, phthalocyanine compounds, coumarin compounds, ruthenium Examples include Ru bipyridine complexes, terpyridine complexes, anthraquinone dyes, polycyclic quinone dyes, and squarylium dyes. Among them, a ruthenium Ru bipyridine complex whose ligand has a pyridine ring has a high quantum yield and is preferable as a photosensitizing dye. However, the photosensitizing dye is not limited to this, and can be used alone or in combination of two or more.

  The method for adsorbing the photosensitizing dye to the semiconductor electrode layer 3 is not particularly limited, but the above-described photosensitizing dye may be, for example, alcohols, nitriles, nitromethane, halogenated hydrocarbons, ethers, dimethyl sulfoxide, amides, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters, carbonates, ketones, hydrocarbons, water, and the like are dissolved in the semiconductor electrode layer 3 The dye solution can be applied onto the semiconductor electrode layer 3. In addition, when a dye having high acidity is used, deoxycholic acid or the like may be added for the purpose of reducing association between the dye molecules.

  After adsorbing the photosensitizing dye, the surface of the semiconductor electrode layer 3 may be treated with amines for the purpose of promoting the removal of the excessively adsorbed dye. Examples of amines include pyridine, 4-tert-butylpyridine, polyvinylpyridine, and the like. When these are liquid, they may be used as they are, or may be used after being dissolved in an organic solvent.

As the electrolyte layer 4, an electrolytic solution, or a gel or solid electrolyte can be used. Examples of the electrolyte include a solution containing a redox species (redox _couple ). Specifically, a combination of iodine I ₂ and a metal iodide salt or an organic iodide salt, bromine Br ₂ and a metal bromide salt or an organic salt. A combination with a bromide salt is used. In addition, metal complexes such as ferrocyanate / ferricyanate and ferrocene / ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol / alkyl disulfide, viologen dyes, hydroquinone / quinone, and the like can be used. The cations constituting the metal compound are lithium Li ⁺ , sodium Na ⁺ , potassium K ⁺ , cesium Cs ⁺ , magnesium Mg ²⁺ , calcium Ca ²⁺ , and the cation constituting the organic compound is a tetraalkyl. Quaternary ammonium ions such as ammonium ions, pyridinium ions, and imidazolium ions are suitable, but are not limited to these, and can be used alone or in admixture of two or more.

Among these, an electrolyte combining iodine I ₂ and a quaternary ammonium compound such as lithium iodide LiI, sodium iodide NaI, or imidazolium iodide is particularly preferable. The concentration of the electrolyte salt in the electrolytic solution is preferably 0.05M to 5M, more preferably 0.2M to 3M. The concentration of iodine I ₂ or bromine Br ₂ is preferably 0.0005M to 1M, and more preferably 0.001 to 0.3M.

  Solvents that make up the electrolyte include water, alcohols, ethers, esters, carbonates, lactones, carboxylic esters, phosphate triesters, heterocyclic compounds, nitriles, ketones, amides , Nitromethane, halogenated hydrocarbons, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, and hydrocarbons, but are not limited thereto, It can be used alone or in admixture of two or more. Moreover, it is also possible to use a room temperature ionic liquid of a tetraalkyl, pyridinium, or imidazolium quaternary ammonium salt as a solvent.

  The method for producing the dye-sensitized solar cell 10 is not particularly limited. For example, the electrolyte composition can be liquid or gelled inside the battery, and in the case of a liquid electrolyte composition before introduction, the semiconductor electrode layer 3 and the counter electrode face each other, and the substrate portion on which the semiconductor electrode layer 3 is not formed is sealed so that these electrodes are not in contact with each other. At this time, although there is no restriction | limiting in particular in the magnitude | size of the clearance gap between the semiconductor electrode layer 3 and a counter electrode, Usually, it is 1-100 micrometers, More preferably, it is 1-50 micrometers. If the distance between the electrodes is too long, the photocurrent decreases due to the decrease in conductivity. The sealing method is not particularly limited, but it is preferable to use a material having light resistance, insulation, and moisture resistance. Epoxy resin, ultraviolet curable resin, acrylic adhesive, EVA (ethylene vinyl acetate), ionomer resin, ceramic Various heat-sealing films can be used, and various welding methods can be used. The method for injecting the electrolyte composition solution is not particularly limited, but a method in which the outer periphery is sealed in advance and the solution is injected under reduced pressure inside the cell in which the solution inlet is opened is preferable. In this case, a method of dropping a few drops of the solution at the injection port and injecting the solution by capillary action is simple. In addition, the injection operation can be performed under reduced pressure or under heating as necessary. After the solution is completely injected, the solution remaining at the inlet is removed and the inlet is sealed. Although there is no restriction | limiting in particular also in this sealing method, If necessary, it can also seal by affixing a glass plate or a plastic substrate with a sealing agent. In addition to this method, an electrolytic solution can be dropped on a substrate and bonded together under reduced pressure as in a liquid crystal drop injection (ODF: One Drop Filling) process of a liquid crystal panel. In the case of a gel electrolyte using a polymer or the like or an all solid electrolyte, the polymer solution containing the electrolyte composition and the plasticizer is volatilized and removed on the semiconductor electrode layer 3 by a casting method. After completely removing the plasticizer, sealing is performed in the same manner as in the above method. This sealing is preferably performed using a vacuum sealer or the like under an inert gas atmosphere or under reduced pressure. After sealing, in order to fully immerse the electrolyte in the semiconductor electrode layer 3, operations of heating and pressurization can be performed as necessary.

  The dye-sensitized solar cell 10 can be produced in various shapes depending on the application, and the shape is not particularly limited. The dye-sensitized solar cell 10 is typically a photoelectric conversion device that converts light energy of sunlight into electric power, but may be other than that, for example, a dye-sensitized photosensor.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. In Examples 1 to 3, the porous electrode layer described in the embodiment and the dye-sensitized solar cell 10 (see FIG. 1) having the porous electrode layer as the counter electrode 5 were produced, and the photoelectric conversion characteristics thereof were measured. .

<Preparation of dye-sensitized solar cell 10>
(Formation of semiconductor electrode layer (metal oxide semiconductor porous layer) 3)
(1) As the light-transmissive substrate 1 and the light-transmissive conductive layer 2, a conductive glass substrate with an FTO layer for amorphous solar cells (manufactured by Nippon Sheet Glass Co., Ltd., sheet resistance 10Ω / □, thickness 1.1 mm) Using. This conductive glass substrate was processed into a square of 25 mm in length and 25 mm in width, subjected to ultrasonic cleaning using acetone, alcohol, alkaline cleaning liquid, and ultrapure water as cleaning solvents in order, and then sufficiently dried.

  (2) Next, using a screen printer and a circular screen mask having a diameter of 5 mm, a titanium oxide fine particle paste layer having a thickness of 20 μm was formed at the center of the conductive glass substrate. At this time, a transparent Ti-Nanoxide TSP paste (trade name; manufactured by Solaronix) layer is first formed on the FTO layer with a thickness of 7 μm, and then a Ti-Nanoxide DSP paste (trade name; Solaronix) containing scattering particles is formed. The product was laminated with a thickness of 13 μm to form a titanium oxide fine particle paste layer having a total thickness of 20 μm.

(3) Next, using an electric furnace, the titanium oxide paste layer was baked at 500 ° C. for 30 minutes to produce a titanium oxide porous layer. After being allowed to cool, the titanium oxide porous layer was immersed in a 0.1 mol / L titanium tetrachloride TiO ₄ aqueous solution and kept at 70 ° C. for 30 minutes. Next, the titanium oxide porous layer was sufficiently washed with pure water and ethanol and dried. Thereafter, the porous titanium oxide layer was fired again at 500 ° C. for 30 minutes using an electric furnace. In these steps, the following formula: TiCl ₄ + 2H ₂ O → TiO ₂ + 4HCl
The necking between the titanium oxide fine particles in the titanium oxide porous layer is strengthened by the generated titanium oxide.

  Next, the excimer lamp was used to irradiate the titanium oxide porous layer with ultraviolet light for 3 minutes to perform a treatment for increasing the activity of the titanium oxide porous layer. At this time, impurities such as organic substances contained in the titanium oxide porous layer are oxidatively decomposed and removed by the catalytic action of titanium oxide.

  (4) Next, the titanium oxide porous layer was immersed in the N719 dye solution at room temperature for 48 hours, and the photosensitizing dye N719 was adsorbed on the titanium oxide porous layer. N719 is cis-bis (isothiocyanato) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) ruthenium (II) ditetrabutylammonium salt. As the dye solution, a solution in which N719 was dissolved at a concentration of 0.5 mM in a mixed solvent in which tert-butyl alcohol and acetonitrile were mixed at a volume ratio of 1: 1 was used. Next, after the titanium oxide porous layer was washed with acetonitrile, acetonitrile was evaporated in the dark and the titanium oxide porous layer was dried. As a result, the semiconductor electrode layer 3 on which the photosensitizing dye was adsorbed was obtained.

(Preparation of counter electrode (porous electrode layer) 5)
(5) Next, as the counter substrate 6, a conductive glass substrate with FTO layer (made by Nippon Sheet Glass Co., Ltd., sheet resistance 10Ω / □, substrate having a thickness of 1.1 mm) is 25 mm long × 25 mm wide. Processed into a square. A hole having a diameter of 0.5 mm was formed as an electrolyte injection port at a position off the center of the counter substrate.

Carbon black # 40 (trade name; manufactured by Mitsubishi Chemical Corporation) and HR11NN (trade name; manufactured by Toyobo Co., Ltd.) are used as coating liquid materials for producing the counter electrode (porous electrode layer) 5. It was. HR11NN is a solution in which polyamideimide is dissolved in N-methylpyrrolidone at a concentration of 15% by mass. Carbon black, HR11NN, and N-methylpyrrolidone are mixed at a predetermined ratio, and stirred for 5 hours using a zirconia bead (diameter 0.3 mm) having a mass 10 times the solid content and a paint shaker (frequency: 65 Hz). And carbon black and polyamideimide were uniformly dispersed in N-methylpyrrolidone to prepare a coating solution. The ratio of the solid content in the coating liquid was 15% by mass, and the ratio of the mass of polyamideimide to the mass of carbon black was 1/15.
(Mass of polyamideimide) / (mass of carbon black) = 1/15

  Next, the coating liquid was deposited on the FTO layer by hand coating using a squeegee, and then heated to 150 ° C. for 15 minutes on a hot plate to evaporate the solvent, thereby forming the porous electrode layer 5. . It was 20 micrometers when the thickness of the porous electrode layer 5 was measured using the film thickness measuring apparatus DEKTAC3 (brand name; ULVAC, Inc. make).

(Assembly of dye-sensitized solar cell)
(6) Next, an ultraviolet (UV) curable adhesive was deposited on the porous electrode layer 5 by a screen printing method. At this time, an adhesive layer having a size of 20 mm in length × 20 mm in width and 2 mm in width was formed so that a current collecting portion remained on the outside. Next, the two conductive glass substrates were opposed and bonded so that the semiconductor electrode layer 3 and the counter electrode (porous electrode layer) 5 face each other. At this time, the inlet provided in the counter substrate 6 described above functions as an air escape path. Thereafter, the ultraviolet curable adhesive layer was cured by irradiating with ultraviolet rays.

(7) On the other hand, 1-propyl-3-methylimidazolium iodide (0.6M), N-methyl-benzimidazole (0.5M), and iodine I ₂ (0.1M) are respectively enclosed in the above parentheses. An electrolytic solution dissolved in 3-methoxypropionitrile at the molar concentration shown in 1 was prepared.

  (8) Next, the electrolyte solution was injected under reduced pressure from the inlet. Thereafter, the electrolyte solution was completely injected into the cell by being left still in a pressurized container filled with 0.4 MPa of nitrogen gas. Next, after filling the inlet with an ultraviolet curable adhesive and sealing, the adhesive was cured by irradiating with ultraviolet rays, and the dye-sensitized solar cell 10 was produced.

<Evaluation of dye-sensitized solar cell>
Short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoelectric conversion efficiency of the dye-sensitized solar cell 10 produced while irradiating simulated sunlight (AM1.5, 100 mW / cm ² ) (Η) was measured at 24 ° C.

  In Example 2, # 2300 (trade name; manufactured by Mitsubishi Chemical Corporation) was used as carbon black instead of # 40 (trade name; manufactured by Mitsubishi Chemical Corporation). Further, the ratio of the mass of polyamideimide to the mass of carbon black and the thickness of the counter electrode (porous electrode layer) 5 were changed, and the influences were examined. Except for these, a dye-sensitized solar cell 10 was produced in the same manner as in Example 1, and the photoelectric conversion efficiency was measured.

[Example 2-1]
The ratio of the mass of polyamideimide to the mass of carbon black was 1/7. The thickness of the counter electrode (porous electrode layer) 5 was kept at 20 μm.

[Example 2-2]
The ratio of the mass of polyamideimide to the mass of carbon black was 1/10. The thickness of the counter electrode (porous electrode layer) 5 was kept at 20 μm.

[Example 2-3]
The ratio of the mass of polyamideimide to the mass of carbon black was 1/10. The thickness of the counter electrode (porous electrode layer) 5 was 10 μm.

[Example 2-4]
The ratio of the mass of polyamideimide to the mass of carbon black was 1/10. The thickness of the counter electrode (porous electrode layer) 5 was 2 μm.

  In Example 3, as in Example 2, # 2300 (trade name; manufactured by Mitsubishi Chemical Corporation) was used as the carbon black, but the ratio of the mass of polyamideimide to the mass of carbon black and the counter electrode (porous electrode) The thickness of layer 5 was greatly changed, and the influence was examined. Except for these, a dye-sensitized solar cell 10 was produced in the same manner as in Example 1, and the photoelectric conversion efficiency was measured.

[Example 3-1]
In Example 3-1, the ratio of the mass of polyamideimide to the mass of carbon black was 1/1.

[Example 3-2]
In Example 3-2, the ratio of the mass of polyamideimide to the mass of carbon black was 1/3.

[Example 3-3]
In Example 3-3, the ratio of the mass of polyamideimide to the mass of carbon black was 1/5.

[Example 3-4]
In Example 3-4, the ratio of the mass of polyamideimide to the mass of carbon black was 1/20. Further, the thickness of the counter electrode layer 5 was set to 40 μm.

[Comparative Example 1]
In Comparative Example 1, # 2350 (trade name; manufactured by Mitsubishi Chemical Corporation) was used as carbon black. The ratio of the mass of polyamideimide to the mass of carbon black was 1/7.

[Comparative Example 2]
In Comparative Example 2, MA8 (trade name; manufactured by Mitsubishi Chemical Corporation) was used as carbon black. The ratio of the mass of polyamideimide to the mass of carbon black was 1/7.

[Comparative Example 3]
In Comparative Example 3, MA100 (trade name; manufactured by Mitsubishi Chemical Corporation) was used as carbon black. The ratio of the mass of polyamideimide to the mass of carbon black was 1/7.

[Comparative Example 4]
In Comparative Example 4, Ketjen Black EC300J (trade name; manufactured by Lion Corporation) was used as carbon black. The ratio of the mass of polyamideimide to the mass of carbon black was 1/1.

[Comparative Example 5]
In Comparative Example 5, a platinum layer was formed on the counter substrate similar to that of Example 1 by sputtering to form a counter electrode. Other than that was carried out similarly to Example 1, and produced the dye-sensitized solar cell. Based on the performance of the dye-sensitized solar cell, the performance of the dye-sensitized solar cell 10 according to the example was evaluated.

  Table 1 is a table showing the types of carbon black used in Examples 1 to 3 and Comparative Examples 1 to 5 and their characteristic physical properties (Mitsubishi Chemical Corporation carbon black http: //www.carbonblack. jp / product / list2.html, and Lion Corporation http://www.lion.co.jp/ja/chem/seihin/sangyo/carbon/k_proper.html.) In the table, the particle diameter is an arithmetic average diameter obtained by observing carbon black particles with an electron microscope. The adsorption specific surface area is a specific surface area (JIS K6217) determined from the nitrogen adsorption amount by the S-BET equation. Generally, the smaller the particle diameter, the larger the specific surface area. The DBP absorption amount is the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black (JIS K6221). Generally, the more the structure is developed, the larger the absorption amount. The volatile matter is a volatile matter (mass reduction rate) when carbon black is heated at 950 ° C. for 7 minutes. In general, the more surface functional groups, the more components that volatilize. The pH value is a value obtained by measuring a mixed solution of carbon black and distilled water with a glass electrode pH meter.

  Tables 2 and 3 are tables showing the types of carbon black, the composition and coating properties of the coating liquid, the coating film characteristics, and the performance of the dye-sensitized solar cell 10 in Examples 1 to 3 of the present invention. Table 3 also shows the performance of the dye-sensitized solar cell according to Comparative Example 5.

Table 4 is a table | surface which shows the kind of carbon black, the composition of a coating liquid, and applicability | paintability in Comparative Examples 1-4 of this invention.

<Evaluation of Examples 1 to 3>
As shown in Table 1, carbon black # 40 (trade name) and # 2300 (trade name) are not oxidized on the surface, and the mixture with distilled water is neutral or weakly basic. Moreover, it is a non-hollow (non-hollow) (filled) carbon black. In Examples 1 to 3 using these carbon blacks, coating solutions having good coating properties were obtained. Since these carbon blacks have good affinity with polyamideimide and N-methylpyrrolidone, it is considered that such a result was obtained.

  On the other hand, carbon black # 2350 (trade name), MA80 (trade name) and MA100 (trade name) are not hollow (the contents are clogged) in which the surface is oxidized and the mixture with distilled water is acidic. Carbon black. The coating liquids obtained in Comparative Examples 1 to 3 using these carbon blacks were gelled coating liquids such as glue, and a good coating film could not be formed by coating. These carbon blacks are considered to have obtained such a result because a large number of groups having a large polarity such as a carboxy group are introduced on the surface, and the affinity with polyamideimide is insufficient.

  The coating solution obtained in Comparative Example 4 using ketjen black # 2350 (trade name) as carbon black was a clay-like coating solution, and a good coating film could not be formed by coating. . Ketjen black has a hollow shape and a large specific surface area. For this reason, since the polyamideimide does not cover the ketjen black, it is considered that such a result was obtained. Carbon black having a large specific surface area requires a large amount of polyamideimide resin, making it difficult to produce the porous electrode layer 5 in which the ratio of the mass of polyamideimide to the mass of carbon black is small. From the above, the carbon-based fine particles used in the electrode of the present invention are carbon black that has not been oxidized, the mixture with distilled water is neutral or weakly basic, and is not hollow (filled) It turned out to be good.

  Fig.2 (a) is the observation image which observed the cross section of the porous electrode layer 5 obtained in Example 2-2 using the scanning electron microscope (SEM). The structure of the “bunch of grapes” that can be seen over almost the whole of FIG. 2A is the structure formed by the carbon-based fine particles. From FIG. 2A, the porous electrode layer 5 obtained in Example 2-2 has a structure formed throughout, and a porous structure (porous structure) is developed, and the surface area of the carbon-based fine particles is large. It can be seen that it has a structure.

  FIG. 3 is a graph showing current-voltage characteristics of the dye-sensitized solar cell 10 according to Examples 1 and 2 and Comparative Example 5. As shown in Table 2, the photoelectric conversion efficiency of the dye-sensitized solar cell 10 according to Examples 1 and 2 is 0.80 times or more the photoelectric conversion efficiency of the dye-sensitized solar cell according to Comparative Example 5.

  FIG. 4 is a graph showing impedance characteristics of the dye-sensitized solar cells according to Examples 1 and 2 and Comparative Example 5. The radius Rct of the first arc indicating the electron transport resistance between the electrolytic solution and the counter electrode is 4Ω or less in the dye-sensitized solar cell 10 according to Examples 1 and 2, and in the dye-sensitized solar cell according to Comparative Example 5. Less than 6Ω.

  From the above, in the dye-sensitized solar cell 10 according to Examples 1 and 2 in which the ratio of the mass of polyamideimide to the mass of carbon black in the porous electrode layer 5 is 1/15 or more and 1/7 or less, as the counter electrode A photoelectric conversion efficiency substantially equal to or higher than that of the dye-sensitized solar cell 10 according to Comparative Example 5 using a platinum layer can be realized, and the catalytic performance of the porous electrode layer 5 can exceed the catalytic performance of the platinum layer. It has been found. Moreover, from the comparison of Example 2-2 to Example 2-4, the photoelectric conversion efficiency of the dye-sensitized solar cell 10 varies depending on the thickness of the porous electrode layer 5, and the thinner one is in the range of 2 to 20 μm. It was found that the photoelectric conversion efficiency was increased.

  On the other hand, from Table 3, although it consists of the same material as Example 2, the ratio of the mass of polyamide imide with respect to the mass of carbon black in porous electrode layer 5 is as large as 1/1 to 1/5, and Examples 3-1 to 1 In Example 3-3, the photoelectric conversion efficiency of the dye-sensitized solar cell 10 is as low as 0.4 to 2.9%. FIG. 5 is a graph showing the current-voltage characteristics of the dye-sensitized solar cell 10 according to Example 3. This graph also shows a low photoelectric conversion efficiency. FIG. 6 is a graph showing impedance characteristics of the dye-sensitized solar cell 10 according to Example 3. FIG. 6 shows that the radius Rct of the first arc indicating the electron transport resistance between the electrolytic solution and the counter electrode is so large that it cannot be measured.

  FIG. 2B is an observation image obtained by observing the cross section of the porous electrode layer 5 obtained in Example 3-1, using an SEM. The structure (structure) of the “bunch of grapes” seen almost throughout the whole of FIG. 2 (a) is hardly seen in FIG. 2 (b). FIG. 2B shows that the porous electrode layer 5 obtained in Example 3-1 does not have a sufficient porous structure (porous structure), and the surface area of the carbon-based fine particles is small. From the above, when the ratio of the mass of polyamideimide to the mass of carbon black in the porous electrode layer 5 is too large, a porous structure is difficult to be formed in the porous electrode layer 5, and the contact between the carbon black and the electrolytic solution is difficult. It turns out that it becomes inadequate and the catalyst performance of carbon black is not fully demonstrated.

  On the other hand, the ratio of the mass of polyamideimide to the mass of carbon black in the porous electrode layer 5 is 1/10 as in Examples 2-2 to 2-4, but the thickness of the porous electrode layer 5 is 40 μm. In certain Example 3-4, peeling of the porous electrode layer 5 occurred. Thus, when the porous electrode layer 5 becomes too thick, there is no problem in the state of the coating liquid layer, but the electrode layer may be peeled off during the process of removing the solvent by evaporation. This peeling of the electrode layer does not occur when the thickness of the electrode layer is 20 μm or less, so the upper limit of the thickness of the porous electrode layer 5 is between 20 μm and 40 μm.

  Although the present invention has been described based on the embodiments and examples, it is needless to say that the present invention is not limited to these examples and can be appropriately changed without departing from the gist of the invention. .

  The present invention provides an electrochemical device such as a dye-sensitized solar cell with good light utilization efficiency, and contributes to its spread.

DESCRIPTION OF SYMBOLS 1 ... Light transmissive board | substrate, 2 ... Light transmissive conductive layer (negative electrode collector),
3 ... Semiconductor electrode layer (negative electrode) holding photosensitizing dye, 3a ... Transmission layer, 3b ... Scattering layer,
4 ... electrolyte layer, 5 ... counter electrode (porous electrode layer) (positive electrode), 6 ... counter substrate,
10 ... Dye-sensitized solar cell, 11 ... Semiconductor fine particles with small average particle diameter,
12 ... Semiconductor fine particles having a large average particle diameter, 13 ... Photosensitizing dye,
14 ... high refractive index fine particles having anisotropic shape, 15 ... spherical fine particles,
DESCRIPTION OF SYMBOLS 100 ... Photosensitized solar cell, 101 ... Transparent substrate, 102 ... Transparent conductive layer (negative electrode collector),
103 ... Semiconductor electrode layer (negative electrode) holding a photosensitizing dye, 104 ... Electrolyte layer,
105 ... Counter electrode (positive electrode), 106 ... Counter substrate

JP 2009-218179 A (pages 3, 4 and 6-11, FIGS. 1 and 2) JP 2005-116302 A (page 4-7, FIG. 1)

Claims (9)

A support;
It is disposed on the support and contains a polyamideimide as a binder and carbon-based fine particles mainly composed of carbon and having an affinity for the polyamideimide, and the solvent is evaporated and removed from the coating layer containing both. A carbon-based electrode having a porous electrode layer.   2. The carbon-based fine particles according to claim 1, wherein the carbon-based fine particles are not oxidized, and the liquid mixture with distilled water is neutral or weakly basic and is not hollow (filled) carbon black. Carbon-based electrode.   The carbon electrode according to claim 2, wherein a ratio of the mass of the polyamideimide to the mass of the carbon black in the porous electrode layer is 1/15 to 1/7.   The carbon electrode according to claim 2, wherein the porous electrode layer has a thickness of 20 μm or less.   The carbon-based electrode according to claim 1, wherein the solvent is N-methylpyrrolidone.   The carbon-based electrode according to claim 1, wherein a material of the support is a plastic material.   An electrochemical device comprising the carbon-based electrode according to claim 1.   The electrochemical device according to claim 7, comprising at least a semiconductor electrode layer made of a metal oxide porous layer, the carbon-based electrode as the counter electrode, and an electrolyte layer sandwiched therebetween.   When the semiconductor electrode layer holds a photosensitizing dye and light is incident, the electrons of the photosensitizing dye excited by absorbing this light are taken out to the semiconductor electrode layer, and the electrons are lost. The photosensitizing dye is reduced by a reducing species (reducing agent) in the electrolyte layer. As a result, the oxidizing species (oxidizing agent) generated in the electrolyte layer receives electrons from the counter electrode, and reduces. The electrochemical device according to claim 8, which is configured as a dye-sensitized solar cell that returns to seeds.