JP2008071605A - Counter electrode for dye-sensitized solar battery, and dye-sensitized solar battery equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a counter electrode for a dye-sensitized solar battery capable of being manufactured at low cost and processes, endowed with high durability with degradation of performance with time restrained, and showing excellent battery characteristics even in case electrolyte solution of high viscosity or pseudo-solidified electrolyte is used, as well as a dye-sensitized solar battery using the same. <P>SOLUTION: An electrode equipped with an electrode base body consisting of an electrode support body and a conductive material and containing a fine linear or cylindrical carbon material partially or wholly coated with conductive polymers on the electrode base body makes up a counter electrode capable of quickly reducing an oxidant of the redox pair. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a counter electrode of a dye-sensitized solar cell and a dye-sensitized solar cell including the same.

In recent years, dye-sensitized solar cells in which a semiconductor layer is loaded with a sensitizing dye that absorbs a visible light region have been studied. This dye-sensitized solar cell is expected to be put to practical use because of the advantages that the material used is inexpensive and that it can be manufactured by a relatively simple process.
In the dye-sensitized solar cell, electrons are injected from the sensitizing dye excited by absorbing visible light into the semiconductor electrode, and current is taken out through the current collector. On the other hand, the oxidized form of the sensitizing dye is reduced and regenerated by a redox pair in the electrolyte. The oxidized redox pair is reduced on the counter electrode surface facing the semiconductor electrode, and the cycle goes around.

Counter electrodes conventionally used for dye-sensitized solar cells include a method in which a chloroplatinic acid solution is applied or immersed on an electrode substrate and then heat-treated, or a platinum thin film on a substrate by vacuum deposition or sputtering. There is known a platinum electrode obtained by a method of forming a film. In this counter electrode, a redox pair in the electrolyte (e.g., I ₃ ^- / I ^-, etc.) a reduction reaction of reducing an oxidant to reductant of rapidly progressive (I ₃ ^{- -} The I reduction reaction reduced to) What has the electrode characteristic which can be made to be made is calculated | required.

  However, platinum is an expensive noble metal, and when a platinum electrode is formed by sputtering or vacuum deposition, productivity is low due to waste of material consumption, and equipment costs are high because vacuum equipment is required. As a result, there has been a problem that the manufacturing cost becomes high. Further, in the method of applying the chloroplatinic acid solution to the substrate and then performing the baking treatment, a high temperature of 400 ° C. or higher is required to thermally decompose the applied platinum precursor solution into platinum, and the substrate is not sensitive to heat. There was a problem that could not be applied.

  Furthermore, in recent years, considering the practical application, the increase in viscosity and gelation of electrolytes for dye-sensitized solar cells has been studied. However, the diffusion of iodine, which is a redox couple with the increase in the viscosity of the electrolyte, has been investigated. This is the rate-limiting process of the electron transfer reaction, and there is a problem that the solar cell characteristics are deteriorated. For this reason, it is calculated | required to advance the iodine reduction reaction on the surface of a counter electrode more rapidly. For this purpose, it is necessary to take measures such as forming irregularities and increasing the surface area. As a result, the amount of platinum used increases, or the manufacturing process becomes complicated and the manufacturing cost increases. Furthermore, it is known that platinum dissolves in an electrolyte solution in the presence of water or oxygen, and its use has a problem in terms of stability.

  Non-Patent Document 1 describes a dye-sensitized solar cell using a counter electrode including a carbon material such as a carbon nanotube as a catalyst. In this document, single-wall nanotubes show relatively good photoelectric conversion efficiency, but only a performance lower than that of a platinum counter electrode is obtained.

  Non-Patent Documents 2 and 3 describe a counter electrode using activated carbon, and it is reported that a photoelectric conversion efficiency superior to that of a platinum counter electrode was obtained. However, the characteristics of the platinum counter electrode being compared, in particular, the short-circuit current density is low, and it is unclear whether the current operation can be performed at a higher current density. In addition, when carbon is used as a catalyst, the catalytic ability is lower than that of platinum. Therefore, in order to obtain an equivalent photocurrent, the catalyst layer must be made thicker than the platinum counter electrode to increase the specific surface area. In the case of using a liquid or a quasi-solid electrolyte, there is a problem that high characteristics cannot be obtained because the problem of diffusion of the redox couple is more seriously affected.

  Moreover, in the said nonpatent literature 3, although the counter electrode which combined activated carbon and a conductive polymer is described, only the performance inferior to the counter electrode using only a carbon material is obtained.

Patent Document 1 discloses a dye-sensitized solar cell using a hole current collecting electrode (counter electrode) made of an organic film formed simultaneously with polymerization of a monomer.
In the Hall current collector preparation method exemplified in Patent Document 1, after applying a solution containing a monomer of a conductive polymer and a polymerization catalyst, the polymerization is advanced by heat treatment, and finally the solvent is removed. It is a method to do.

  In order to make the iodine reduction reaction on the counter electrode surface proceed more quickly, there is a method to increase the surface area, as with the counter electrode using platinum described above. This production method is difficult. In addition, the film obtained by the production method is dense and has a problem that it swells in the electrolyte solution and peels off from the substrate. Therefore, with this manufacturing method, a counter electrode with a desired high surface area cannot be obtained, and further performance improvement is difficult. In addition, although the production method describes that poly (3,4-ethylenedioxy) thiophene is polymerized by heat treatment, plastic or film is not suitable for use as an electrode substrate because heat treatment is performed. There was also a problem.

  Non-Patent Document 4 describes a production method in which a dispersion solution of a conductive polymer is applied onto a conductive substrate to remove the solvent, but the adhesion between the particles is insufficient only by laminating the particles. In addition, due to insufficient conductivity only by contact with the conductive polymer particles, an electrode having a high specific surface area cannot be obtained as in Patent Document 1, and further performance improvement cannot be expected.

  Moreover, in the conductive polymer used in the above-mentioned patent document and non-patent document, the dopant for increasing the electrical conductivity contained in the conductive polymer is liberated in the electrolyte, and the electrical resistance of the counter electrode over time. There remained concern that the value would increase.

  Various technologies have been proposed, but they can still be manufactured with a lower manufacturing cost and process, and the deterioration of performance over time is suppressed and the durability is high, and a highly viscous electrolyte or quasi-solid electrolyte is used. There is a need for a dye-sensitized solar cell exhibiting excellent battery characteristics even in the case of

JP 2003-317814 A Kazuharu Suzuki, Makoto Yamaguchi, Mikio Kumagai, and Shozo Yanagida, “Application of Carbon Nanotubes to Counter Electros. 32, no. 1, Chemistry Letters, 2003, p. 28-29 Kiyoaki Imoto, Kohshin Takahashi, Takahiro Yamaguchi, Teruhisa Komura, Jun-ichi Nakamura, Kazuhiko Murata, "High-performance carbon counter electrode for dye-sensitized solar cells", 79, Solar Energy Materials & Solar Cells, 2003, p. 459-469 Kiyoaki Imoto, Masatoshi Suzuki, Kohshin Takahashi, Takahiro Yamaguchi, Teruhisa Komura, Jun-ichi Nakamura, and Kazuhiko Murata, "Activated Carbon Counter electrode for dye-sensitized solar cell", 71, No. 11, Electrochemistry, 2003, p. 944-946. Abstracts of the 72nd Annual Meeting of the Electrochemical Society of Japan, April 1, 2005, p.471

  In view of the above circumstances, the present invention is a counter electrode for a dye-sensitized solar cell, which can be manufactured with an inexpensive manufacturing cost and process, has a high durability with a decrease in performance over time, and has a high viscosity. It is an object of the present invention to provide a dye-sensitized solar cell counter electrode exhibiting excellent battery characteristics even when an electrolytic solution or a quasi-solidified electrolyte is used, and a dye-sensitized solar cell using the same.

As a result of intensive studies to solve the above problems, the present inventors have, in the counter electrode for the dye-sensitized solar cell,
An electrode substrate comprising an electrode support and a conductive material, and an electrode containing a fine linear or cylindrical carbon material partially or entirely coated with a conductive polymer is oxidized on the electrode substrate. It has been found that the oxidant of the reducing pair becomes a counter electrode that can be rapidly reduced.
The present inventors have also described that the conductive polymer interacts with a fine linear or cylindrical carbon material, in particular, the linear or cylindrical carbon material and the conductive polymer are π-π. It was found that a counter electrode excellent in electrode characteristics and durability can be obtained by interacting by stacking.
The present inventors further composited by the interaction between the functional group introduced on the surface of the linear or cylindrical carbon material and the conductive polymer, in particular, the linear or cylindrical carbon material. The counter electrode combined by the interaction caused by the functional group introduced on the surface being doped into the conductive polymer or chemically bonded to the conductive polymer has excellent electrode characteristics and durability. I found out.

Therefore, the present invention provides a dye-sensitized solar cell having at least a light-transmitting semiconductor electrode containing a dye having a photosensitizing action and an electrolyte layer containing a chemical species serving as a redox pair, with the electrolyte layer interposed therebetween. A counter electrode disposed opposite to the semiconductor electrode,
An electrode substrate comprising an electrode support and a conductive material, and on the substrate, at least a part thereof is coated with a conductive polymer as a catalytic substance that reduces an oxidized form of a chemical species that serves as a redox pair. The counter electrode is characterized by containing a fine linear or cylindrical carbon material.

  The present invention is also the counter electrode characterized in that the linear or cylindrical carbon material and the conductive polymer interact with each other, more preferably by π-π stacking.

  The present invention is also the counter electrode characterized in that the conductive polymer is doped with a functional group introduced on the surface of the linear or cylindrical carbon material. Furthermore, the present invention is the counter electrode characterized in that the functional group introduced on the surface of the linear or cylindrical carbon material has a chemical bond with the conductive polymer.

  Examples of the functional group introduced into the surface of the linear or cylindrical carbon material include a carboxyl group, a sulfo group, and a phosphonium group. Specific examples of the linear or cylindrical carbon material include single- and multi-walled carbon nanotubes, carbon nanohorns, and fullerenes.

  Examples of the monomer that forms the conductive polymer include aromatic amine compounds, and more specifically, aniline and aniline derivatives. Examples of the aniline derivative include anisidine, phenetidine, toluidine, phenylenediamine, hydroxyaniline, and N-methylaniline. Other examples of the aniline derivative include trifluoromethylaniline, nitroaniline, cyanoaniline, and halogenated aniline. A thiophene compound is mentioned as another monomer which forms the said conductive polymer. Thiophene compounds include thiophene and thiophene derivatives, which include tetradecylthiophene, isothianaphthene, 3-phenylthiophene, 3,4-ethylenedioxythiophene, and 3-methylthiophene, 3-butylthiophene, There are alkylthiophenes such as 3-octylthiophene. Examples of another monomer that forms the conductive polymer include pyrrole and pyrrole derivatives. Examples of the pyrrole derivative include alkyl pyrroles such as 3-methyl pyrrole, 3-butyl pyrrole, and 3-octyl pyrrole.

  The present invention is also a dye-sensitized solar cell including the counter electrode described above.

  According to the present invention, it can be produced with a low manufacturing cost and process, has a high durability by suppressing a decrease in performance over time, and is excellent in the case of using a high-viscosity electrolytic solution or a quasi-solidified electrolyte. A dye-sensitized solar cell counter electrode exhibiting battery characteristics, and a dye-sensitized solar cell using the same can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings as appropriate.

FIG. 1 is a schematic cross-sectional view showing an example of the dye-sensitized solar cell of the present invention. In the dye-sensitized solar cell, a porous metal oxide semiconductor layer 4 is formed on the surface of an electrode substrate 1 comprising a transparent substrate 2 and a transparent conductive film 3 formed thereon, and the porous metal oxide is further formed. A sensitizing dye layer 5 is adsorbed on the surface of the semiconductor layer 4. The counter electrode 7 of the present invention is disposed so as to face the electrolyte layer 6.
FIG. 2 is a schematic cross-sectional view showing an example of the counter electrode of the present invention. In the counter electrode 7, an electrode base 8 made of an electrode support and a conductive material, and a conductive polymer as an active part of the electrode are used. A catalyst layer 9 containing a fine linear or cylindrical carbon material coated on a part or the whole is provided on the surface of the electrode substrate 8.

Hereinafter, a suitable form is demonstrated about each structural material of the dye-sensitized solar cell of this invention.
[Transparent substrate]
As the transparent substrate 2 constituting the electrode substrate 1, one that transmits visible light can be used, and transparent glass can be suitably used. Moreover, the thing which processed the glass surface and scattered incident light, and a translucent ground glass-like thing can also be used. Moreover, not only glass but a plastic plate, a plastic film, etc. can be used if it transmits light.
The thickness of the transparent substrate 2 is not particularly limited because it varies depending on the shape and use conditions of the solar cell. For example, when glass or plastic is used, the thickness is about 1 mm to 1 cm in consideration of durability during actual use. Yes, flexibility is required, and when a plastic film or the like is used, it is about 1 μm to 1 mm.

[Transparent conductive film]
As the transparent conductive film 3, a material that transmits visible light and has conductivity can be used, and examples of such a material include metal oxide. Although not particularly limited, for example, tin oxide doped with fluorine (hereinafter abbreviated as “FTO”), indium oxide, a mixture of tin oxide and indium oxide (hereinafter abbreviated as “ITO”), and oxidation. Zinc or the like can be suitably used. In addition, an opaque conductive material can be used as long as visible light is transmitted through a treatment such as dispersion. Such materials include carbon materials and metals. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene, etc. are mentioned. Further, the metal is not particularly limited, and examples thereof include platinum, gold, silver, ruthenium, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, and alloys thereof. Therefore, the transparent conductive film 3 can be formed by providing a conductive material made of at least one of the above-described conductive materials on the surface of the transparent substrate 2. Alternatively, it is also possible to incorporate the conductive material into the material constituting the transparent substrate 2 and integrate the transparent substrate and the transparent conductive film into the electrode substrate 1.

As a method for forming the transparent conductive film 3 on the transparent substrate 2, in the case of forming a metal oxide, there are a sol-gel method, a vapor phase method such as sputtering and CVD, and a coating of a dispersion paste. Moreover, when using an opaque electroconductive material, the method of fixing a powder etc. with a transparent binder etc. is mentioned.
In order to integrate the transparent substrate and the transparent conductive film, a method such as mixing the conductive film material as a conductive filler at the time of molding the transparent substrate can be used.
The thickness of the transparent conductive film 3 is not particularly limited because the conductivity varies depending on the material to be used, but is generally 0.01 μm to 5 μm, preferably 0.1 μm to 1 μm in the FTO-coated glass. It is. Further, the required conductivity varies depending on the area of the electrode to be used, and a wider electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω. / □ or less. Exceeding 100Ω / □ is not preferable because the internal resistance of the solar cell increases and current does not sufficiently flow.
The thickness of the electrode substrate 1 composed of a transparent substrate and a transparent conductive film, or the electrode substrate 1 in which the transparent substrate and the transparent conductive film are integrated varies depending on the shape and use conditions of the solar cell as described above, and thus is particularly limited. Generally, it is about 1 μm to 1000 μm.

[Porous metal oxide semiconductor]
Examples of the porous metal oxide semiconductor 4 include, but are not limited to, titanium oxide, zinc oxide, tin oxide, and the like. Particularly, titanium dioxide and further anatase type titanium dioxide are preferable. Further, it is desirable that the metal oxide has few grain boundaries in order to reduce the electric resistance value. In order to adsorb more sensitizing dye, the semiconductor layer is desirably porous, and specifically has a specific surface area in the range of 10 to ²⁰⁰ m ² / g. Further, in order to increase the light absorption amount of the sensitizing dye, it is desirable to scatter the light by making the particle diameter of the oxide to be used wide.
Such a porous metal oxide semiconductor is not particularly limited and can be provided on the transparent conductive film 3 by a known method. For example, there are a sol-gel method, dispersion paste application, electrodeposition and electrodeposition. Further, the porous metal oxide semiconductor may be further subjected to a high temperature treatment in order to enhance the electronic contact between the semiconductor particles and improve the adhesion to the support.
The thickness of such a semiconductor layer is not particularly limited because the optimum value varies depending on the oxide used and its properties, but is 0.1 μm to 50 μm, preferably 5 to 30 μm.

[Sensitizing dye]
The sensitizing dye layer 5 is not particularly limited as long as it can be excited by sunlight and can inject electrons into the metal oxide semiconductor layer 4, and dyes generally used in dye-sensitized solar cells can be used. However, in order to improve the conversion efficiency, it is desirable that the absorption spectrum overlaps with the sunlight spectrum in a wide wavelength region and the light resistance is high. Although not particularly limited, a ruthenium complex, particularly a ruthenium polypyridine complex is desirable, and a ruthenium complex represented by Ru (L) 2 (X) 2 is more desirable. Here, L is 4,4′-dicarboxy-2,2′-bipyridine, or a quaternary ammonium salt thereof, and a polypyridine ligand into which a carboxyl group is introduced, and X is SCN, Cl, CN It is. Examples thereof include bis (4,4′-dicarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex.
Examples of other dyes include metal complex dyes other than ruthenium, such as iron complexes and copper complexes. Further, organic dyes such as cyan dyes, porphyrin dyes, polyene dyes, coumarin dyes, cyanine dyes, squaric acid dyes, styryl dyes, and eosin dyes, and conductive polymers can be used. These dyes preferably have a bonding group with the metal oxide semiconductor layer in order to improve the efficiency of electron injection into the metal oxide semiconductor layer. The linking group is not particularly limited, but a carboxyl group, a sulfonic acid group and the like are desirable.

The method for adsorbing the sensitizing dye to the porous metal oxide semiconductor 4 is not particularly limited. For example, the porous metal oxide is dissolved in a solution in which the dye is dissolved at room temperature and atmospheric pressure. A method of immersing the electrode substrate 1 on which the physical semiconductor 4 is formed may be mentioned. It is desirable that the immersion time is appropriately adjusted so that a monomolecular film of the dye is uniformly formed on the semiconductor layer depending on the type of the semiconductor, the dye, the solvent, and the concentration of the dye used. In addition, what is necessary is just to perform the immersion under a heating in order to perform adsorption | suction effectively.
Examples of the solvent used to dissolve the sensitizing dye include alcohols such as ethanol, nitrogen compounds such as acetonitrile, ketones such as acetone, ethers such as diethyl ether, halogenated aliphatic hydrocarbons such as chloroform, Examples thereof include aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, and esters such as ethyl acetate. It is desirable that the dye concentration in the solution is appropriately adjusted according to the type of dye and solvent used. For example, a concentration of 5 × 10 ⁻⁵ mol / L or more is desirable.

[Electrolyte layer]
The electrolyte layer 6 includes a supporting electrolyte, a redox pair capable of reducing the oxidized sensitizing dye, and a solvent in which they are dissolved. The solvent is not particularly limited, and can be arbitrarily selected from non-aqueous organic solvents, room temperature molten salts, water, protic organic solvents, and the like. For example, acetonitrile, dimethylformamide, ethylmethylimidazolium bistrifluoromethylsulfonylimide, methoxy Acetonitrile, methoxypropionitrile, propylene carbonate and the like can be mentioned, among which methoxyacetonitrile, methoxypropionitrile, propylene carbonate and the like can be suitably used. Further, the solvent can be used after gelation.
Examples of the supporting electrolyte include lithium salts, imidazolium salts, and quaternary ammonium salts.

The oxidation-reduction pair is not particularly limited as long as it can be generally used in a battery or a solar battery. For example, a combination of a halogen diatomic molecule and a halide salt, a thiocyanate anion and Examples include a combination of two thiocyanate molecules, a polypyridyl cobalt complex, and organic redox such as hydroquinone. Among these, a combination of iodine molecules and iodide is particularly preferable.
The supporting electrolyte, the redox couple, and the like are not particularly limited because the optimum concentration differs depending on the solvent, the semiconductor electrode, the dye, and the like used, but is about 1 mmol / L to 5 mol / L.
Further, t-butylpyridine, 1,2-dimethyl-3-propylimidazolium iodide, water, and the like can be added to the electrolyte layer as additives.

[Counter electrode-electrode substrate]
The counter electrode 7 has a structure in which a catalyst layer 9 containing a fine linear or cylindrical carbon material partially or wholly covered with a conductive polymer is formed on the surface of the electrode substrate 8. .
The linear or cylindrical carbon material is preferably at least partially covered with a conductive polymer, and more preferably, the coverage is 50% or more.
Since the electrode substrate 8 is used as a counter electrode support and current collector, at least the surface portion on which the catalyst layer 9 is formed must have electrical conductivity.
As such a material, for example, a conductive metal or metal oxide, a carbon material, a conductive polymer, or the like is preferably used. Examples of the metal include platinum, gold, silver, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, and alloys thereof. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene etc. are mentioned. Moreover, when metal oxides, such as FTO, ITO, an indium oxide, and zinc oxide, are used, since it is transparent or translucent, the incident light quantity to a sensitizing dye layer can be increased, and it can use it conveniently.

  In addition, an insulator such as glass or plastic may be used as long as at least the surface of the electrode substrate is treated. As a treatment method for maintaining conductivity in such an insulator, a method of covering a part or the whole surface of the insulating material with the above-described conductive material, for example, when using a metal, plating, electrodeposition, etc. And a gas phase method such as sputtering or vacuum deposition. When a metal oxide is used, a sol-gel method or the like can be used. In addition, one or more of the above conductive material powders may be used and mixed with an insulating material.

The shape of the electrode substrate is not particularly limited because it can be changed according to the shape of the dye-sensitized solar cell used as the counter electrode, and may be a plate shape or a film shape that can be curved. Further, the electrode substrate may be transparent or opaque. However, it is desirable that the electrode substrate be transparent or translucent because the amount of light incident on the sensitizing dye layer can be increased and, in some cases, the design can be improved. . Generally, glass with an FTO film or a PEN film with an ITO film is used as the electrode substrate, but the conductivity is different depending on the material used, and therefore the thickness of the electrode substrate is not particularly limited. For example, in the FTO-coated glass, the thickness is 0.01 μm to 5 μm, preferably 0.1 μm to 1 μm. Further, the required conductivity varies depending on the area of the electrode to be used, and a wider electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω. / □ or less. Exceeding 100Ω / □ is not preferable because the internal resistance of the solar cell increases and current does not sufficiently flow.
The thickness of the electrode substrate 8 is not particularly limited because it varies depending on the shape and use conditions of the solar cell as described above, but is generally about 1 μm to 1 cm.

[Counter electrode-catalyst layer]
The catalyst layer 9 containing a fine linear or cylindrical carbon material partially or wholly coated with the conductive polymer in the counter electrode of the present invention reduces the oxidant of the redox pair contained in the electrolyte layer. It functions as an active part of the catalyst. The catalyst layer 9 is preferably present in a porous state so that the electron transfer reaction can be performed efficiently.

  Specific examples of the linear or cylindrical carbon material included in the catalyst layer 9 in the counter electrode of the present invention include single-walled and multi-walled carbon nanotubes, carbon nanohorns, or fullerene aggregates, and particularly single-walled and multi-walled carbon nanotubes. Can be suitably used.

  In the present invention, it is required that the linear or cylindrical carbon material interacts with the conductive polymer. More specifically, the interaction by π-π stacking can be exemplified. In order for the linear or cylindrical carbon material and the conductive polymer to undergo π-π stacking, it is desirable to coat the linear or cylindrical carbon material with a π-conjugated conductive polymer.

  As another example of the above interaction in the present invention, it can be exemplified that the functional group introduced in advance on the surface of the linear or cylindrical carbon material interacts with the conductive polymer. Specific examples of the interaction between the functional group and the conductive polymer include doping of the functional group into the conductive polymer and a covalent bond. The interaction between the functional group and the conductive polymer and the interaction by the π-π stacking may be formed at the same time.

  Such a functional group is not particularly limited as long as it can be doped into a conductive polymer or can form a chemical bond with the conductive polymer, such as a carboxyl group, a sulfo group, or a phosphonium. Among them, a sulfo group is preferable when doping a conductive polymer, and a carboxyl group is preferable when chemically bonding.

The method for confirming the interaction is not particularly limited, and can be determined using a known method. For example, it can be discriminated by the difference between the absorption spectrum of the conductive polymer as a raw material and the linear or cylindrical carbon material and the absorption spectrum after the action by ultraviolet visible absorption spectroscopy, infrared spectroscopy, etc. . As an example of specific evaluation such as π-π stacking, it is possible to discriminate when absorption peaks appear, shift or broaden at positions different from individual raw materials.
Similarly, the confirmation method when the functional group is doped into the conductive polymer can also be determined from the change in the absorption spectrum.
In addition, when a covalent bond is formed between the functional group and the conductive polymer, it can also be determined by the disappearance or change of the spectrum of the functional group that forms the covalent bond, similarly using infrared spectroscopy. .

  The method for introducing the functional group onto the surface of the linear or cylindrical carbon material is not particularly limited, and a known method can be used. For example, a hydroxyl group, a carboxyl group, a sulfo group, or the like can be introduced by heating and refluxing a linear or cylindrical carbon material in a mixed acid of sulfuric acid and nitric acid and oxidizing the surface.

The conductive polymer contained in the catalyst layer 9 and covering at least a part of the linear or cylindrical carbon material is one or more homopolymers, one or more copolymers, or a mixture thereof. Good.
As a monomer which forms the conductive polymer contained in the catalyst layer 9 in the counter electrode of the present invention, an aromatic amine compound represented by the following general formula (1) or (2), represented by the following general formula (3) Examples include at least one monomer selected from the group consisting of a thiophene compound and a pyrrole compound represented by the following general formula (4).

（式（１）又は（２）中、Ｒ₁及びＲ₆はそれぞれ独立に水素原子、メチル基又はエチル基を示し、Ｒ₂〜Ｒ₅及びＲ₇〜Ｒ₁₀はそれぞれ独立に水素原子、炭素原子数１〜８のアルキル基又はアルコキシ基、炭素原子数６〜１２のアリール基、炭素原子数６〜１２のアラルキル基（例えばベンジル基）、シアノ基、チオシアノ基、ハロゲン基、またはニトロ基を示し、式（１）中、Ｒ₂とＲ₃、又はＲ₄とＲ₅はそれぞれ連結して環を形成していてもよく、式（２）中、Ｒ₈とＲ₉、又はＲ₉とＲ₁₀はそれぞれ連結して環を形成していてもよい。）

(In the formula (1) or (2), R ₁ and R ₆ each independently represent a hydrogen atom, a methyl group or an ethyl group, and R _{2 to} R ₅ and R _{7 to} R ₁₀ each independently represent a hydrogen atom or carbon. An alkyl group or alkoxy group having 1 to 8 atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 6 to 12 carbon atoms (for example, benzyl group), a cyano group, a thiocyano group, a halogen group, or a nitro group; In formula (1), R ₂ and R ₃ , or R ₄ and R ₅ may be linked to form a ring, respectively, and in formula (2), R ₈ and R ₉ , or R ₉ and R ₁₀ may be linked to each other to form a ring.)

（式（３）中、Ｒ₁₁、Ｒ₁₂はそれぞれ独立に水素原子、炭素原子数１〜８のアルキル基又はアルコキシ基、炭素原子数６〜１２のアリール基、シアノ基、チオシアノ基、ハロゲン基、又はニトロ基を示し、Ｒ₁₁とＲ₁₂は連結して環を形成していてもよい。）

(In Formula (3), R ₁₁ and R ₁₂ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alkoxy group, an aryl group having 6 to 12 carbon atoms, a cyano group, a thiocyano group, and a halogen group. Or a nitro group, and R ₁₁ and R ₁₂ may be linked to form a ring.)

（式（４）中、Ｒ₁₃、Ｒ₁₄はそれぞれ独立に水素原子、炭素原子数１〜８のアルキル基又はアルコキシ基、炭素原子数６〜１２のアリール基、シアノ基、チオシアノ基、ハロゲン基、ニトロ基、又はアミノ基を示し、Ｒ₁₃とＲ₁₄は連結して環を形成していてもよい。）

(In Formula (4), R <_13> , R <_14> is respectively independently a hydrogen atom, a C1-C8 alkyl group or an alkoxy group, a C6-C12 aryl group, a cyano group, a thiocyano group, and a halogen group. Nitro group or amino group, R ₁₃ and R ₁₄ may be linked to form a ring.)

  When using the aromatic amine compound, it is not particularly limited as long as the polymer polymerized by them has conductivity, but even if the polymer film of a certain aromatic amine compound alone does not have conductivity, What is necessary is just to have electroconductivity by setting it as a copolymer with aniline or another aromatic amine compound. Or what is necessary is just to have electroconductivity, after making it act with a linear or cylindrical carbon material. The polymer constituting the conductive polymer contained in the catalyst layer 9 may be a homopolymer or a copolymer, and the conductive polymer layer is formed using one or more aromatic amine compounds as monomer components. be able to.

  Examples of the aromatic amine compound include aniline and aniline derivatives. More specifically, examples include aniline, anisidine, phenetidine, toluidine, phenylenediamine, hydroxyaniline, N-methylaniline, trifluoromethaneaniline, nitroaniline, cyanoaniline, and halogenated aniline. Of these, anisidine, toluidine, phenylenediamine and aniline are preferably used. Among them, aniline is particularly preferably used, and examples thereof include polymers formed by polymerizing at least aniline as a monomer. In particular, polyaniline using aniline alone as a monomer can be suitably used because of its low cost and high catalytic ability.

Examples of the thiophene compound include thiophene and thiophene derivatives, and more specifically, alkylthiophenes such as thiophene, 3-methylthiophene, 3-butylthiophene, and 3-octylthiophene, tetradecylthiophene, isothianaphthene, 3- Examples include phenylthiophene and 3,4-ethylenedioxythiophene. When used as a homopolymer, 3,4-ethylenedioxythiophene can be preferably used.
A conductive polymer may be formed using one or more thiophene compounds.

  Examples of the pyrrole compound include pyrrole and pyrrole derivatives, and examples of the pyrrole derivative include those having an alkyl group having 1 to 8 carbon atoms at the 3-position. Specific examples of the pyrrole compound include pyrrole, 3-methylpyrrole, 3-butylpyrrole and alkylpyrrole such as 3-octylpyrrole. The conductive polymer may be formed using one or more pyrrole compounds.

The above aromatic amine compound, thiophene compound, and pyrrole compound may be used as one or more kinds, and may be one or more kinds of copolymers or a mixture thereof.
The monomer component that forms the conductive polymer preferably has a conductivity of 10 ⁻⁹ S / cm or more as a polymerized film.

The conductive polymer is preferably doped with a functional group introduced on the surface of the linear or cylindrical carbon material.
The conductive polymer is not particularly limited because the optimum value differs depending on the type of the conductive polymer used, but all of the theoretical doping amount is doped with a functional group introduced on the surface of the linear or cylindrical carbon material. It is particularly desirable. However, when the number of functional groups introduced on the surface of the linear or cylindrical carbon material is insufficient with respect to the theoretically doped amount of the conductive polymer, the functional group is defined as a conductive polymer. After making it act, you may supplement by adding another dopant.

  Such dopants are known materials, for example, halide anions such as hexafluoroline, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, perchloric acid, halogen anions such as iodine, bromine, chlorine, hexafluoroline, hexafluorohyd Element, hexafluoroantimony, tetrafluoroboron, halide anions such as perchloric acid, alkyl group-substituted organic sulfonic acid anions such as methanesulfonic acid and dodecylsulfonic acid, cyclic sulfonic acid anions such as camphorsulfonic acid, benzenesulfonic acid, Alkyl group-substituted or unsubstituted benzene mono- or disulfonic acid anions such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, benzenedisulfonic acid, etc. 1-3 such as 2-naphthalenesulfonic acid, 1,7-naphthalenedisulfonic acid Alkyl group-substituted or unsubstituted naphthalene sulfonate anion, anthracene sulfonic acid, anthraquinone sulfonic acid, alkyl biphenyl sulfonic acid, biphenyl disulfonic acid, etc. Polymer sulfonate anion such as acid, sulfonated polyether, sulfonated polyester, sulfonated polyimide, naphthalene sulfonate formalin condensate, substituted or unsubstituted aromatic sulfonate anion, bissartylate boron, biscatecholate boron And boron compound anions such as heteropoly acid anions such as molybdophosphoric acid, tungstophosphoric acid and tungstomolybdophosphoric acid. These dopants may be used alone or in combination of two or more.

  From the viewpoint of suppressing the desorption of the dopant, the dopant is preferably an organic acid anion rather than an inorganic anion, and it is desirable that the thermal decomposition or the like hardly occur. In addition, if the surface of the linear or cylindrical carbon material is coated with a dopant, the reduction reaction of the redox pair cannot be performed efficiently. It is desirable that

  Such a dopant can be used at an appropriate stage when the catalyst layer 9 is formed. For example, the dopant may be allowed to coexist with the conductive polymer and the linear or cylindrical carbon material after acting. it can. Moreover, after formation of the catalyst layer 9, it can also dope by the method of impregnating this catalyst layer in a dopant solution.

  As another example of the present invention, it is desirable that the conductive polymer and the functional group introduced on the surface of the linear or cylindrical carbon material have a chemical bond. Such chemical bonds are not particularly limited because they differ depending on the conductive polymer or functional group used, but examples include amide bonds, ether bonds, ester bonds, and sulfonate ester bonds, and particularly chemically stable amides. Bonding is desirable.

Various chemical bonds can be used depending on the functional group introduced on the surface of the linear or cylindrical carbon material. For example, in the case of a carboxyl group, an amide bond, an ester bond, an ether bond, etc. are mentioned, and in the case of a sulfo group, a sulfonate ester bond etc. are mentioned.
On the other hand, the functional group of the conductive polymer that forms the chemical bond is not particularly limited. Since it is convenient to use the functional group of the monomer that forms the conductive polymer, it is desirable to polymerize in advance using a monomer having a functional group that can react with the functional group on the surface of the linear or cylindrical carbon material.

In addition, when the conductive polymer and the functional group introduced on the surface of the linear or cylindrical carbon material are chemically bonded, it is desirable that the conductive polymer is doped separately from the chemical bond.
Such a dopant is not particularly limited because the type and the optimum amount differ depending on the type of the conductive polymer to be used, but can be used according to the dopant described above.

  The method for coating the linear or cylindrical carbon material with the conductive polymer is not particularly limited, and a known method can be used. For example, a method of adding and dispersing a linear or cylindrical carbon material in a conductive polymer solution or a dispersion of conductive polymer particles can be mentioned. At this time, it is desirable that the conductive polymer is dissolved in a solvent so that the conductive polymer can efficiently coat the linear or cylindrical carbon. In addition, in order to efficiently dope the functional group on the surface of the linear or cylindrical carbon material into the conductive polymer, or to form a chemical bond, the conductive polymer is previously undoped, and then the linear or It is desirable to work with a cylindrical carbon material.

  The solvent for such a conductive polymer solution is not particularly limited. For example, toluene, xylene, methyl ethyl ketone, tetrahydrofuran, ethyl acetate, butyl acetate, and N-methyl-2-pyrrolidone can be suitably used. These may be used alone or as a mixed solvent of two or more.

The method for preparing the conductive polymer solution or the conductive polymer particle dispersion is not particularly limited, and a known method can be used. For example, there is a chemical polymerization method in which polymerization is advanced by adding an oxidizing agent to a solution containing a conductive polymer monomer. This method can be suitably used because the conductive polymer particles can be easily obtained. In addition, as a method for preparing a conductive polymer solution, in the chemical polymerization method, a method of adjusting the degree of polymerization to directly dissolve the conductive polymer solution, or after separating the conductive polymer once obtained from the particles And a method of dissolving in a solvent again. A production method using such a chemical polymerization method can be suitably used because it is simple and has high productivity.
In any method, it is desirable to wash at an appropriate stage in order to remove residues and unreacted substances of the oxidizing agent and monomer, oligomers having a low polymerization degree, and the like.

  Oxidizing agents used in the above chemical polymerization methods include iodine, bromine, bromine iodide, chlorine dioxide, iodic acid, periodic acid, chlorous acid and other halides, antimony pentafluoride, phosphorus pentachloride, pentafluoride. Metal halides such as phosphorus, aluminum chloride, molybdenum chloride, high valent metal salts such as permanganate, dichromate, chromic anhydride, ferric salt, cupric salt, sulfuric acid, nitric acid, trifluoromethane Protonic acids such as sulfuric acid, oxygen compounds such as sulfur trioxide and nitrogen dioxide, hydrogen peroxide, ammonium persulfate, peroxo acids such as sodium perborate or salts thereof, molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid, etc. And at least one of them can be used.

The catalyst layer 9 is formed on the electrode substrate 8. Examples of the method for forming the catalyst layer 9 include a method of forming a film from a solution in which a linear or cylindrical carbon material is added to the above conductive polymer solution / dispersion. In addition, a method of forming a film from a solution in which a linear or cylindrical carbon material coated with a conductive polymer is separated from the solution and then dispersed in a solvent may be used.
Moreover, after processing the linear or cylindrical carbon material powder coat | covered with the conductive polymer in the form of a paste or an emulsion, it forms into a film on this electrode base | substrate. The film forming method is not particularly limited, and can be performed by a known coating method such as spin coating, casting method, spray coating, dip coating, roll coating, die coating, bead coating, blade coating, bar coating, and the like. . Moreover, the catalyst layer 9 can be formed by removing a solvent by heating and pressure-reducing as needed after application | coating.

  Furthermore, you may add a binder as needed in order to suppress peeling of the catalyst layer 9. As the binder, for example, acrylic resin, urethane resin, epoxy resin, silicone resin, fluorine resin such as PVDF and PTFE, and polymer material such as carboxymethyl cellulose can be used.

  The thickness of the catalyst layer 9 in the counter electrode of the present invention is not particularly limited because the optimum value varies depending on the type of conductive polymer used, the type of electrolyte, the viscosity, and the like, but generally a range of 5 nm to 5 μm is appropriate. Preferably it is 100 nm-3 micrometers.

  The reason why the reduction reaction rate can be increased in the counter electrode of the present invention is unclear. However, the conductive polymer and the linear or cylindrical carbon material that are constituent materials of the catalyst layer 9 have catalytic properties to reduce the oxidized form of the redox couple by themselves. By covering the cylindrical or cylindrical carbon material, the conductive polymer and the linear or cylindrical carbon material interact with each other, for example, π orbitals interact with each other to efficiently exchange electrons with the redox couple. I think that it was possible to. This effect is due to the interaction between the functional group introduced into the surface of the linear or cylindrical carbon material and the conductive polymer, more specifically, the functional group doping into the conductive polymer, or It is further improved by chemical bonding with the molecule.

  In addition, 1) Conductive polymer that is inferior in conductivity compared to metal improves the conductivity by encapsulating the carbon material, and 2) The conductive polymer covers the leakage current to the electrolyte, which is a disadvantage of the carbon material. 3) Since the carbon material has a linear or cylindrical shape, the pores formed when supported on the surface of the electrode substrate are increased, resulting in an increase in the specific surface area of the catalyst layer 9 and the like. For the reason, even if the thickness is relatively thin, the oxidized form of the redox couple contained in the electrolyte can be quickly reduced, and the thickness of the conductive polymer layer can be reduced while maintaining high performance. Therefore, even when a high-viscosity electrolytic solution or a quasi-solidified electrolyte is used, excellent battery characteristics can be exhibited and the manufacturing cost can be reduced.

  Further, the reason why the counter electrode of the present invention has high durability by suppressing the deterioration of performance over time is considered as follows. That is, 1) the conductive polymer and the carbon material interact with each other to strengthen the bond between them, and the substituent fixed on the surface of the linear or cylindrical carbon material is doped into the conductive polymer. And the fact that the release of the conductive polymer into the electrolyte is suppressed by being chemically bonded, or 2) that the conductivity is not easily lowered by dedoping as a result.

Thus, the counter electrode is obtained by forming the catalyst layer 9 on the electrode substrate 8 made of the electrode support and the conductive material.
After preparing the respective constituent materials of the dye-sensitized solar cell as described above, the dye-sensitized solar cell is assembled so that the metal oxide semiconductor electrode and the counter electrode face each other through an electrolyte by a conventionally known method. To complete.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited at all by these.
[Example 1]
[Porous metal oxide semiconductor]
As a transparent substrate with a transparent conductive film, FTO glass (Japanese plate glass 25 mm × 50 mm) was used, and a titanium dioxide paste (Soralonix) was applied to the surface with a bar coater, dried and baked at 450 ° C. for 30 minutes. The porous titanium oxide semiconductor electrode having a thickness of 10 μm was formed by being allowed to stand at room temperature.

[Adsorption of sensitizing dye]
As a sensitizing dye, a bis (4,4′-dicarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex generally called N3dye was used. The porous titanium oxide semiconductor electrode once heated to 150 ° C. was immersed in an ethanol solution having a pigment concentration of 0.5 mmol / L, and left standing under light shielding overnight. Thereafter, excess pigment was washed with ethanol and then air-dried to produce a semiconductor electrode of a solar cell. Furthermore, the semiconductor layer was ground so that the projected area of titanium oxide of the obtained semiconductor electrode was 25 mm ² .

[Introduction of anionic substituent into linear or cylindrical carbon material]
Concentrated sulfuric acid: 1 g of multi-walled carbon nanotubes was added to 40 ml of a mixed acid solution in which concentrated nitric acid was 3: 1, and the mixture was heated to reflux for 70 minutes. After cooling to room temperature, it was washed with a large amount of pure water and then filtered through a 200 nm diameter filter. Further, the obtained multi-walled carbon nanotube was dispersed / dissolved in 100 ml of pure water, and then filtered using quartz fiber. The resulting filtrate had a multi-walled carbon nanotube concentration of about 0.4 mg / ml. This filtrate was freeze-dried to obtain a multi-walled carbon nanotube having an anionic substituent introduced on the surface. The multi-wall carbon nanotubes as raw materials were prepared using Ni-phthalocyanine as a raw material at 700 ° C. using a CVD method. The multi-walled carbon nanotubes at the time of preparation have an average length of 6 to 8 μm and an average diameter of 25 to 40 nm, and the multi-walled carbon nanotubes introduced with an anionic substituent obtained by a series of operations have an average length of 1 to 2 μm and an average diameter of 25 to 25 nm. 40 nm. Further, the obtained multi-walled carbon nanotube was analyzed by FT-IR, and it was confirmed that a carbonyl group, a hydroxyl group, and a sulfo group were introduced.

[Production of conductive polymer and action with linear or cylindrical carbon material]
Ammonium persulfate was dropped into an ice bathed sulfuric acid aqueous solution having an aniline concentration of 0.1 mol / L to polymerize aniline to obtain polyaniline particles. Ammonia water was allowed to act on the obtained polyaniline particles, and then dissolved in N-methylpyrrolidone (hereinafter abbreviated as “NMP”) to a polyaniline concentration of 1 g / 70 ml to obtain a polyaniline NMP solution.
To the polyaniline NMP solution, the multi-walled carbon nanotube introduced with the anionic substituent is added to 0.4 g / ml, dispersed and stirred, and the multi-walled carbon nanotube-doped polyaniline (hereinafter abbreviated as “MWCN-doped PAN”). .) A solution was obtained.

[Production of counter electrode]
As an electrode substrate with a conductive film layer, FTO glass (Nippon Sheet Glass 25 mm × 50 mm) was used. The electrode substrate ultrasonically cleaned in an organic solvent was dipped in the MWCN dope-PAN dispersion obtained above and then pulled up and heated and dried in air at 150 ° C. for 1 hour to obtain a MWCN dope-PAN counter electrode. . The average film thickness was 0.5 μm.

[Assembly of solar cells]
The semiconductor electrode produced as described above was placed so as to face the counter electrode, and an electrolyte was impregnated between both electrodes by capillary action. As the electrolyte, a solution containing methoxyacetonyl as a solvent, lithium iodide as a reducing agent, iodine as an oxidizing agent, t-butylpyridine as an additive, and 1,2-dimethyl-3-propylimidazolium iodide was used.

[Measurement of photoelectric conversion characteristics of solar cells]
The above solar cell is irradiated with pseudo-sunlight with an amount of light of 100 mW / cm ² to open voltage (hereinafter abbreviated as “Voc”), short-circuit current density (hereinafter abbreviated as “Jsc”), and shape. When the factors (hereinafter abbreviated as “FF”) and photoelectric conversion efficiency were evaluated, the following results were obtained.
About each measured value of "Voc", "Jsc", "FF", and a photoelectric conversion efficiency, it represents that a larger value is preferable as a performance of a photovoltaic cell.

[Measurement results of Example 1]
Open circuit voltage (Voc): 0.75V
Short-circuit current density (Jsc): 10.2 mA / cm ²
Form factor (FF): 0.75
Photoelectric conversion efficiency: 5.7%

[Example 2]
The same procedure as in Example 1 was performed except for the production of the conductive polymer and the counter electrode. The counter electrode was performed as follows. That is, 3-hexylthiophene, which is a conductive polymer monomer, was slowly added dropwise to a chloroform solution in which about 3 equivalents of ferric chloride was dissolved in 3-hexylthiophene while cooling at 0 ° C. in an ice bath. Thereafter, the mixture was stirred for one day while being kept at 0 ° C., and then the reaction solution was poured into a methanol solution to obtain a black precipitate. After the precipitate was suction filtered, unreacted monomers and oligomers were removed by washing with methanol. The resulting precipitate was dispersed and stirred in an aqueous ammonia solution to remove the dopant. After washing with pure water, it was dried under reduced pressure to obtain poly (3-hexylthiophene) (hereinafter abbreviated as “PHT”). The obtained PHT was dissolved in toluene to obtain a red PHT toluene solution.
The polyaniline NMP solution of Example 1 was replaced with the PHT toluene solution obtained, and a multi-walled carbon nanotube-doped poly (3-hexylthiophene) (hereinafter abbreviated as MWCN-doped PHT) dispersion solution was obtained by using the same method. . Using the obtained MWCN dope-PHT dispersion, a solar cell was produced and evaluated using a counter electrode produced in the same manner as in Example 1.
[Measurement results of Example 2]
Open circuit voltage (Voc): 0.73V
Short circuit current density (Jsc): 9.2 mA / cm ²
Form factor (FF): 0.72
Photoelectric conversion efficiency: 4.8%

Example 3
The same procedure as in Example 1 was performed except for the production of the conductive polymer and the counter electrode. The counter electrode was performed as follows. That is, multi-walled carbon nanotubes were ultrasonically dispersed in an aniline hydrochloride aqueous solution and stirred for 12 hours at 0 ° C. in an ice bath to adsorb aniline on the surface of the multi-walled carbon nanotubes. The separated multi-walled carbon nanotubes were separated and then dispersed, stirred in pure water at 0 ° C. in an ice bath, and an aqueous solution of ammonium persulfate was dropped to polymerize the aniline adsorbed on the multi-walled carbon nanotube surface. I let you. Polyaniline-coated multi-walled carbon nanotubes (hereinafter “PAN-coated-MWCN”) obtained by suction filtration, pure water washing, and drying under reduced pressure were ultrasonically dispersed in chloroform. The prepared solution was applied and dried on the FTO glass washed in the same manner as in Example 1 by a spin coating method to obtain a target PAN-coated-MWCN counter electrode. The formed film thickness was about 0.2 μm. Using the produced counter electrode, a solar cell was produced and evaluated in the same manner as in Example 1.
[Measurement results of Example 3]
Open circuit voltage (Voc): 0.75V
Short-circuit current density (Jsc): 8.9 mA / cm ²
Form factor (FF): 0.73
Photoelectric conversion efficiency: 4.9%

Example 4
The same procedure as in Example 1 was performed except for the production of the conductive polymer and the counter electrode. The counter electrode was performed as follows. In the step of introducing an anionic substituent into the linear or cylindrical carbon material of Example 1, the same procedure was performed except that the mixed acid was changed to 2.6 mol / L nitric acid, whereby a carboxyl group was formed on the surface of the multi-walled carbon nanotube. Was introduced. Further, the obtained carboxyl group-introduced multi-walled carbon nanotubes are dispersed in thionyl chloride to which dimethylformamide has been added, and heat-treated for 24 hours with stirring at 70 ° C., whereby the carboxyl group is converted to acyl chloride (acetate chloride). did. The obtained product was dried under reduced pressure after centrifugation.
The above-mentioned multi-walled carbon nanotubes introduced with an acetic chloride group were dispersed in a dimethyl sulfoxide (hereinafter abbreviated as “DMSO”) solution in which phenylenediamine was dissolved, and then stirred at 100 ° C. for 4 days. Amide bonds were formed between the nanotubes. The resulting mixture was added to and stirred in excess methanol, filtered, and then washed with methanol. Furthermore, ultrasonic dispersion treatment was performed for 2 hours, followed by filtration using a membrane filter and drying to obtain a powder of multi-walled carbon nanotubes bonded with phenylenediamine. Confirmation of amide bond formation was identified by infrared spectroscopy.
The multi-walled carbon nanotubes formed with an amide bond with the phenylenediamine obtained above were ultrasonically dispersed in an aqueous solution in which aniline as a conductive polymer monomer and paratoluenesulfonic acid as a dopant were dissolved. The mixture was stirred at 0 ° C. for 12 hours in an ice bath to adsorb aniline on the surface of the multi-walled carbon nanotube. Thereafter, an aniline adsorbed on the surface of the multi-walled carbon nanotube by dripping an aqueous ammonium persulfate solution under an ice bath / stirring condition, and phenylenediamine and aniline bonded to the surface of the multi-walled carbon nanotube were polymerized. Polyaniline-coated multi-walled carbon nanotubes (hereinafter “PAN-coated-MWCN”) obtained by suction filtration, pure water washing, and drying under reduced pressure were ultrasonically dispersed in chloroform. The prepared solution was applied and dried on the FTO glass washed in the same manner as in Example 1 by a spin coating method to obtain a target PAN-bonded-MWCN counter electrode. Using the produced counter electrode, a solar cell was produced and evaluated in the same manner as in Example 1.
[Measurement results of Example 4]
Open-circuit voltage (Voc): 0.76V
Short-circuit current density (Jsc): 8.4 mA / cm ²
Form factor (FF): 0.68
Photoelectric conversion efficiency: 4.3%

[Comparative Example 1]
Except for the method for producing the counter electrode, solar cells were produced and evaluated in the same manner as in Example 1.
For the counter electrode, FTO glass was used for the electrode substrate, washed in the same manner as in Example 1, and then a platinum layer was formed on the FTO glass by sputtering. The thickness of the platinum layer was about 150 nm.
[Measurement results of Comparative Example 1]
Open-circuit voltage (Voc): 0.72V
Short-circuit current density (Jsc): 8.9 mA / cm ²
Form factor (FF): 0.66
Photoelectric conversion efficiency: 4.2%

[Comparative Example 2]
In the counter electrode manufacturing method of Example 1, the multi-walled carbon nanotubes introduced with an anionic substituent prepared in the same manner as in Example 1 were ultrasonically dispersed. The obtained dispersion was spin-coated on FTO glass under conditions of 1000 rpm × 30 seconds, air-dried, and then heat-dried at 90 ° C. for 15 minutes for 5 times to form a multi-walled carbon nanotube layer. .
[Measurement results of Comparative Example 2]
Open-circuit voltage (Voc): 0.68V
Short circuit current density (Jsc): 5.6 mA / cm ²
Form factor (FF): 0.49
Photoelectric conversion efficiency: 1.9%

[Comparative Example 3]
Instead of the aqueous solution in which the multi-walled carbon nanotubes used in Comparative Example 2 were ultrasonically dispersed, a poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid aqueous dispersion (hereinafter abbreviated as “PEDOT / PSS”) (Aldrich) (Manufactured by Co., Ltd.), by using a solution in which multi-walled carbon nanotubes are added and ultrasonically dispersed, a PEDOT / PSS dispersion-MWCN counter electrode is produced. Otherwise, a solar battery cell is produced in the same manner as in Comparative Example 2, evaluated.
[Measurement results of Comparative Example 3]
Open-circuit voltage (Voc): 0.66V
Short-circuit current density (Jsc): 8.0 mA / cm ²
Form factor (FF): 0.63
Photoelectric conversion efficiency: 3.3%

  Table 1 below shows the counter electrode materials and measured values of the above examples. In addition, the presence or absence of the interaction between the conductive element molecule and the carbon material in each of the above examples was appropriately determined by a known method by ultraviolet-visible spectroscopy, infrared spectroscopy, or the like.

＊１ ＭＷＣＮ：多層カーボンナノチューブ

* 1 MWCN: Multi-walled carbon nanotube

  From the above results, it can be seen that the dye-sensitized solar cell provided with the counter electrode of the present invention has excellent photoelectric conversion efficiency.

  According to the present invention, it can be produced with a low manufacturing cost and process, has a high durability by suppressing a decrease in performance over time, and is excellent in the case of using a high-viscosity electrolytic solution or a quasi-solidified electrolyte. A dye-sensitized solar cell counter electrode exhibiting battery characteristics, and a dye-sensitized solar cell using the same can be provided.

It is a cross-sectional schematic diagram which shows an example of a structure of the dye-sensitized solar cell of this invention. It is a cross-sectional schematic diagram which shows an example of a structure of the counter electrode of this invention.

Explanation of symbols

1 Electrode Base 2 Transparent Base 3 Transparent Conductive Film 4 Porous Metal Oxide Semiconductor Layer 5 Sensitizing Dye Layer 6 Electrolyte Layer 7 Counter Electrode 8 Electrode Base 9 Catalyst Layer

Claims (14)

In a dye-sensitized solar cell having at least a light-transmitting semiconductor electrode containing a dye having a photosensitizing action and an electrolyte layer containing a chemical species that becomes a redox pair,
A counter electrode disposed opposite to the semiconductor electrode via the electrolyte layer,
An electrode substrate comprising an electrode support and a conductive material, and at least a part of the electrode substrate is coated with a conductive polymer as a catalytic substance for reducing an oxidized form of a chemical species as a redox pair. A counter electrode comprising a fine linear or cylindrical carbon material.   The counter electrode according to claim 1, wherein the conductive polymer and the fine linear or cylindrical carbon material interact with each other.   The counter electrode according to claim 2, wherein the conductive polymer and the fine linear or cylindrical carbon material interact by π-π stacking.   A functional group is introduced on the surface of the linear or cylindrical carbon material, and the conductive polymer and the linear or cylindrical carbon material are combined by the interaction between the functional group and the conductive polymer. The counter electrode according to claim 1, wherein the counter electrode is provided.   The counter electrode according to claim 4, wherein a functional group on a surface of the linear or cylindrical carbon material is doped in the conductive polymer.   The counter electrode according to claim 4, wherein the functional group on the surface of the linear or cylindrical carbon material and the conductive polymer have a chemical bond.   The counter electrode according to any one of claims 4 to 6, wherein the functional group is at least one selected from the group consisting of a carboxyl group, a sulfo group, and a phosphonium group.   The counter electrode according to claim 1, wherein the linear or cylindrical carbon material is at least one selected from the group consisting of single-walled and multi-walled carbon nanotubes, carbon nanohorns, and fullerenes. The conductive polymer is represented by an aromatic amine compound represented by the following general formula (1) or (2), a thiophene compound represented by the following general formula (3), and the following general formula (4). The counter electrode according to any one of claims 1 to 6, which is a polymer formed by polymerizing at least one monomer selected from the group consisting of pyrrole compounds.

(In the formula (1) or (2), R ₁ and R ₆ each independently represent a hydrogen atom, a methyl group or an ethyl group, and R _{2 to} R ₅ and R _{7 to} R ₁₀ each independently represent a hydrogen atom or carbon. An alkyl group or alkoxy group having 1 to 8 atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 6 to 12 carbon atoms, a cyano group, a thiocyano group, a halogen group, or a nitro group is represented by the formula (1 ), R ₂ and R ₃ , or R ₄ and R ₅ may be linked to form a ring. In Formula (2), R ₈ and R ₉ , or R ₉ and R ₁₀ are linked. And may form a ring.)

(In Formula (3), R ₁₁ and R ₁₂ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alkoxy group, an aryl group having 6 to 12 carbon atoms, a cyano group, a thiocyano group, and a halogen group. Or R ₁₁ and R ₁₂ may be linked to form a ring.

(In Formula (4), R <_13> , R <_14> is respectively independently a hydrogen atom, a C1-C8 alkyl group or an alkoxy group, a C6-C12 aryl group, a cyano group, a thiocyano group, and a halogen group. Or a nitro group, R ₁₃ and R ₁₄ may be linked to form a ring.)   The counter electrode according to claim 9, wherein the conductive polymer is a polymer formed by polymerizing at least aniline as a monomer.   The conductive polymer is a copolymer formed by polymerizing aniline and at least one selected from the aromatic amine compounds represented by the general formula (1) or (2) as monomers. Opposite electrode.   The counter electrode according to claim 9, wherein the conductive polymer is a polymer formed by polymerizing at least 3,4-ethylenedioxythiophene as a monomer.   The conductive polymer is a polymer formed by polymerizing at least one selected from the group consisting of pyrrole, 3-methylpyrrole, 3-butylpyrrole and 3-octylpyrrole as a monomer. Opposite electrode.   A dye having at least a light-transmitting semiconductor electrode containing a dye having a photosensitizing action, an electrolyte layer containing a chemical species serving as a redox pair, and a counter electrode disposed opposite to the semiconductor electrode via the electrolyte layer A dye-sensitized solar cell, which is a sensitized solar cell, wherein the counter electrode is the counter electrode according to claim 1.

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