JP2003249275A - Dye sensitized solar cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly efficient solar cell of which the light absorption wavelength range is large, and the light absorption amount is much. <P>SOLUTION: With respect to the dye sensitized solar cell in which a porous photoelectric conversion layer that is constituted by making a porous semiconductor layer absorb at least two kinds of coloring matter of which the optimum sensitivity wavelength range of an absorption spectrum differs, a conductive layer, and a counter electrode are laminated one by one on a conductive substrate, the porous photoelectric conversion layer has the multi-layer structure in the shape of layer parallel to the conductive substrate and is absorbed with the coloring matter, and at least one layer among them is the layer that absorbs one kind of the coloring matter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dye-sensitized solar cell and a method for manufacturing the same. More specifically, the present invention provides a dye-sensitized solar cell having a wide light absorption wavelength region, which includes a porous photoelectric conversion layer in which at least two kinds of spectral sensitizing dyes are adsorbed in a layered form on a porous semiconductor layer. The manufacturing method is related.

[0002]

2. Description of the Related Art Dye-sensitized solar cells have been widely noticed because of their high conversion efficiency among organic solar cells. Regarding the structure and operating principle of this dye-sensitized solar cell,
This will be specifically described. On the transparent conductor formed on the surface of the transparent support, a porous semiconductor layer such as titanium oxide is formed, and the porous semiconductor layer has a spectral sensitizing dye (a dye that functions as a photosensitizer, (Also referred to as "dye") is adsorbed to form a porous photoelectric conversion layer. On the other hand, the counter electrode is coated with a catalyst such as a platinum film, and the transparent support and the counter electrode are overlapped so that the porous semiconductor layer and the platinum film face each other, and an electrolytic solution is injected as a conductive layer between them to form a transparent support. By sealing the side surface of the counter electrode with a sealing material such as epoxy resin, a dye-sensitized solar cell is obtained.

In the dye-sensitized solar cell thus obtained, when the porous photoelectric conversion layer (semiconductor electrode) composed of the porous semiconductor layer and the dye is irradiated with light, the porous photoelectric conversion layer is formed. Electrons are generated, the electrons move to the counter electrode through the electric circuit, and the electrons that have moved to the counter electrode move as ions in the conductive layer and return to the porous photoelectric conversion layer. Energy is extracted.

In the dye-sensitized solar cell, as a porous photoelectric conversion layer that acts on photoelectric conversion, a porous semiconductor having a surface having a dye having an absorption in the visible light region adsorbed is used. For example, Japanese Patent No. 2664194 discloses a dye-sensitized solar cell using a metal oxide semiconductor in which a dye composed of a transition metal complex is adsorbed on the semiconductor surface. However, since this dye-sensitized solar cell uses a single dye, it has a problem that the absorption wavelength region of the dye that acts on photoelectric exchange is narrow and the photoelectric conversion efficiency is lower than that of a silicon-based solar cell. It was

Further, Japanese Patent Laid-Open No. 2000-243466 discloses a dye-sensitized solar cell having a porous photoelectric conversion layer having a structure in which a plurality of dyes are adsorbed in layers.
This dye-sensitized solar cell is manufactured as follows. First, the oligophenylene dye polyphenyl (short wavelength absorption: ultraviolet light to visible light) is adsorbed on titanium oxide particles and dried, and the mixture is mixed with a binder dissolved in alcohol to form a paste, which is then formed on a transparent conductive film. A film is formed by screen printing and dried. Then, a paste is prepared in the same manner as above using the xanthene dye Rhodamine B (medium wavelength absorption: visible light), and the paste is formed on the film formed in the above step and dried. Further, a paste is prepared in the same manner as above using IR140 (long wavelength absorption: visible light to infrared light) which is a cyanine dye, and is formed on the film formed in the above step and dried. In this way
A dye-sensitized solar cell having a porous photoelectric conversion layer in which a total of three kinds of dyes are adsorbed in layers can be obtained.

In this method for producing a dye-sensitized solar cell,
Dyes are adsorbed on oxide semiconductor (titanium oxide) particles, dried, and then mixed with a binder dissolved in alcohol to form a paste, and the steps of forming a film and drying are repeated to obtain each dye. An adsorbed oxide semiconductor layer is formed. In such a manufacturing method,
Since the sintering step was not performed, a large resistance was generated in the conductive path between the oxide semiconductor particles, and even if each of the dyes absorbed light, the photocurrent could not be effectively extracted.
In addition, the number of working steps is large, and the number of paste manufacturing apparatuses, film forming apparatuses, and the like used accordingly increases, which causes a problem of high cost.

Further, as a method for obtaining a dye-sensitized solar cell having a porous photoelectric conversion layer having a structure in which a plurality of dyes are adsorbed in layers, one kind of dye is adsorbed on the porous photoelectric conversion layer. A method of adsorbing another dye by using an electrochemical method can be considered. However, since another dye is adsorbed on the dye that is first adsorbed to form the second photoelectric conversion layer, the porous semiconductor layer is formed at the contact interface of the photoelectric conversion layers on which different dyes are adsorbed. However, there is a problem in that the carrier transport resistance of No. 2 becomes large and the performance of the dye-sensitized solar cell is deteriorated. When the second photoelectric conversion layer is formed by an electrochemical method,
There is a problem that the previously adsorbed dye is desorbed and the same dye is adsorbed in both the first layer and the second layer. In dye-sensitized solar cells, the light absorption range of the dye is limited, and sunlight in the visible to near-infrared region cannot be effectively absorbed, so it is difficult to obtain high conversion efficiency like silicon-based solar cells. There was a problem.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-performance dye-sensitized solar cell having a wide light absorption wavelength region and a large light absorption amount.

[0009]

As a result of intensive studies to solve the above problems, the present inventors have found that at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum are formed on a conductive support. In a dye-sensitized solar cell in which a porous photoelectric conversion layer in which a porous semiconductor layer is adsorbed, a conductive layer, and a counter electrode are sequentially laminated, the porous photoelectric conversion layer is a dye in a layer shape parallel to the conductive support. A multilayer dye-sensitized solar cell having a wide light absorption wavelength region and a large amount of light absorption is obtained by having a multilayer structure in which at least one layer has adsorbed one kind of dye. The present invention has been completed and the present invention has been completed. Further, by forming a part of the porous semiconductor layer having a multi-layer structure using a compound different from that of the porous semiconductor layer, it is possible to selectively adsorb the dye to any layer region of the porous semiconductor layer. Heading, it came to complete this invention.

According to the present invention, a porous photoelectric conversion layer, a conductive layer and a counter electrode in which at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum are adsorbed on a porous semiconductor layer are formed on a conductive support. In the dye-sensitized solar cell that is sequentially laminated, the porous photoelectric conversion layer has a multilayer structure in which dyes are adsorbed in a layer shape parallel to the conductive support, and at least one layer adsorbs one kind of dye. Provided is a dye-sensitized solar cell, which is a layer.

Further, according to the present invention, (a) a porous semiconductor layer having a multi-layer structure is formed on a conductive support, the semiconductor particles having no coating layer and the semiconductor particles having a coating layer. Then, (b) a solution separately containing at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum is prepared, and the porous semiconductor layer is immersed in the obtained solution to form a layer parallel to the conductive support. The dye is adsorbed in a layer shape parallel to the conductive support by repeating the step of adsorbing the dye to the porous semiconductor layer in a shape and the step of removing the film layer of the porous semiconductor layer composed of the semiconductor particles having the film layer. Forming a porous photoelectric conversion layer having an adsorbed multilayer structure, at least one layer of which adsorbs one kind of dye;
The porous photoelectric conversion layer on the conductive support and the counter electrode are opposed to each other, the conductive layer is filled between them, and (d) the conductive layer is optionally sealed with a sealing material to dye sensitize. Provided is a method for producing a dye-sensitized solar cell, which comprises producing a type solar cell.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The dye-sensitized solar cell of the present invention (hereinafter referred to as "solar cell") comprises at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum on a conductive support. In a solar cell in which a porous photoelectric conversion layer adsorbed on a porous semiconductor layer, a conductive layer and a counter electrode are sequentially laminated, the porous photoelectric conversion layer has a multilayer structure in which a dye is adsorbed in a layer shape parallel to the conductive support. And that at least one layer is a layer on which one type of dye is adsorbed.

The "maximum sensitivity wavelength region" in the present invention is
In the light absorption spectrum of the dye, in the peak wavelength (maximum light absorption wavelength) showing the maximum absorption sensitivity, the wavelength region in which the absorption sensitivity is -20% of the peak wavelength with the peak wavelength as the center and the peak wavelength as the center It means the wider one of the wavelength regions of 50 nm width.

A preferred embodiment of the present invention will be described with reference to the drawings. It should be noted that this embodiment is an example, and various embodiments can be implemented within the scope of the present invention. Figure 1
FIG. 3 is a schematic cross-sectional view of a main part showing a layer structure of a solar cell of the present invention. In the figure, 1 is a transparent support, 2 is a transparent conductor, 3 is a porous photoelectric conversion layer, 4 is a region where the first dye is adsorbed, 5 is a region where the second dye is adsorbed, and 6 is a conductive layer (oxidation-reduction). Electrolyte solution), 7 is a counter electrode, 8 is a platinum film, and 9 is a sealing material. The transparent support 1 and the transparent conductor 2 are combined to form a conductive support 1
Also called 0.

At least one of the conductive support 10 and the counter electrode 7 is transparent, and gold, silver, aluminum, indium, indium tin oxide (ITO film) is formed on a metal plate substrate or a substrate such as a glass plate and a transparent plastic sheet. )
And a film on which a conductive film such as tin oxide is formed. As a method of forming a conductive film on a substrate, a vacuum evaporation method, a sputtering method, a CVD method of a component serving as a material are used.
Examples of the known method include a vapor phase method such as a PVD method, a PVD method, and a coating method using a sol-gel method. The conductive support 10 in FIG. 1 is transparent and is composed of a transparent support 1 made of the above substrate and a transparent conductor 2 made of the above conductive film. Further, the counter electrode 7 may be coated with a platinum film 8 or a carbon film which acts as a catalyst.

The porous photoelectric conversion layer 3 has a layer shape parallel to the conductive support and has a multilayer structure in which at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum are adsorbed on the porous semiconductor layer. At least one layer is a layer in which one type of dye is adsorbed.

The porous semiconductor layer is made of, for example, TiO ₂ , S.
nO ₂ , ZnO, Nb ₂ O ₆ , ZrO ₂ , CeO ₂ , WO ₃ ,
SiO ₂ , Al ₂ O ₃ , NiO, CuAlO ₂ , SrCu ₂
It is formed from an oxide such as O ₂ or a composite oxide thereof, and among these, titanium oxide (TiO ₂ ) is particularly preferable. Examples of the form include particulate form and film form,
A film-like porous semiconductor formed on the conductive support 10 is particularly preferable.

The method for forming the film-like porous semiconductor layer on the conductive support 10 is not particularly limited and may be a known method. Specifically, (1) a method of forming a porous semiconductor layer by applying a suspension containing semiconductor particles on a conductive support, and drying and firing the solution, (2) using a desired source gas By the CVD method and the MOCVD method,
A method of forming a porous semiconductor layer on a conductive support,
(3) A method of forming a porous semiconductor layer on a conductive support by a PVD method, a vapor deposition method, a sputtering method, etc. using a raw material solid, (4) a sol-gel method, and an electrochemical redox reaction were used. Examples of the method include a method of forming a porous semiconductor layer on a conductive support by a method.

The thickness of the porous semiconductor layer is not particularly limited, but is preferably about 0.5 to 20 μm from the viewpoint of light transmittance, photoelectric conversion efficiency and the like. Further, in order to improve the photoelectric conversion efficiency, it is necessary to adsorb a larger amount of dye onto the porous semiconductor layer. Therefore, it is preferable that the porous semiconductor has a large specific surface area.
It is preferably about 00 m ² / g.

The method (1) for forming the above-mentioned porous semiconductor layer will be specifically described. Suspension by adding semiconductor particles as a material to a dispersant, solvent, etc. and dispersing
Is prepared, and the suspension is applied onto the conductive support 10. Examples of the coating method include known methods such as a doctor blade method, a squeegee method, a spin coating method, and a screen printing method.

Thereafter, the coating film is dried and baked to obtain a porous semiconductor layer. In drying and firing,
It is necessary to appropriately adjust the conditions such as temperature, time and atmosphere depending on the type of conductive support or semiconductor particles used. The firing is performed, for example, in the atmosphere or in the atmosphere of an inert gas in the range of about 50 to 800 ° C. for 10 seconds to 12 seconds.
It can be done in about an hour. This drying and firing is
It can be performed once at a single temperature or twice or more with varying temperatures.

Examples of the semiconductor particles include commercially available particles having a suitable average particle diameter, for example, the above-mentioned oxide or composite oxide semiconductor particles having an average particle diameter of about 1 to 500 nm. The solvent used to disperse the semiconductor particles includes a glyme solvent such as ethylene glycol monomethyl ether, an alcohol solvent such as isopropyl alcohol and terpineol, a mixed solvent such as isopropyl alcohol / toluene, and water. .

The dye that functions as a photosensitizer by adsorbing on the porous semiconductor layer has absorption in various visible light regions and / or infrared light regions, and the dye can be incorporated into the porous semiconductor layer. Those having an interlocking group such as a carboxylic acid group, a carboxylic acid anhydride group, an alkoxy group, a hydroxyl group, a hydroxyalkyl group, a sulfonic acid group, an ester group, a mercapto group, or a phosphonyl group in the dye molecule for strongly adsorbing Are preferred, and among these, a carboxylic acid group and a carboxylic acid anhydride group are particularly preferred. In addition,
The interlocking group provides an electrical bond that facilitates electron transfer between the excited state dye and the conductive band of the porous semiconductor.

As the dye having an interlock group,
For example, ruthenium bipyridine dye, azo dye, quinone dye, quinonimine dye, quinacridone dye, squarylium dye, cyanine dye, merocyanine dye, triphenylmethane dye, xanthene dye, porphyrin dye, phthalocyanine Examples thereof include dyes of the series, berylene dyes, indigo dyes, and naphthalocyanine dyes.

Examples of the method for adsorbing the dye on the porous semiconductor layer include a method of immersing the porous semiconductor layer formed on the conductive support in a solution in which the dye is dissolved (dye adsorbing solution). .

As the solvent for dissolving the dye, any solvent capable of dissolving the dye may be used. Specifically, alcohols such as ethanol, ketones such as acetone, diethyl ether, ethers such as tetrahydrofuran, acetonitrile and the like. Examples thereof include nitrogen compounds, halogenated aliphatic hydrocarbons such as chloroform, aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, esters such as ethyl acetate, and water . These solvents may be used as a mixture of two or more kinds.

The dye concentration in the solution can be appropriately adjusted depending on the type of dye and solvent used, but it is preferable that the dye concentration is as high as possible in order to improve the adsorption function. The dye concentration may be, for example, 5 × 10 ⁻⁵ mol / liter or more.

In the present invention, at least two kinds of the above dyes having different maximum sensitivity wavelength regions in the absorption spectrum are used, whereby light in a wide wavelength region can be effectively used. From this perspective, 2
When using different types of dye, the dye should be 400 nm or more 60
A combination of dyes having a maximum sensitivity wavelength region in the absorption spectrum in a range of less than 0 nm and a range of 600 nm or more and 1000 nm or less is preferable. In particular,
A combination of a phthalocyanine dye having a maximum sensitivity wavelength region of 630 to 800 nm and a merocyanine dye having a maximum sensitivity wavelength region of 450 to 600 nm, the phthalocyanine dye, and a xanthene dye having a maximum sensitivity wavelength region of 400 to 550 nm. A typical combination is with.

The porous photoelectric conversion layer adsorbs dyes from the light-receiving surface side in this order from a dye having the maximum sensitivity wavelength region in the absorption spectrum on the short wavelength side to a dye having the maximum sensitivity wavelength region in the absorption spectrum on the long wavelength side. Is preferred. Thereby, the light which could not be absorbed by the dye having the maximum sensitivity absorption wavelength region on the short wavelength side, can be absorbed by the dye having the maximum sensitivity absorption wavelength region on the long wavelength side,
Light in a wide wavelength range can be effectively used.

Theoretically, the interaction between the dyes should be such that at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum are individually adsorbed in the porous semiconductor layer in a layered manner at the single molecule level. And the electron injection is efficiently performed. However, although it varies depending on the absorbance of each dye and the quantum efficiency of the solar cell when each dye is used alone, the layer area where the dyes are mixed and adsorbed is 50% of the total thickness of the porous photoelectric conversion layer. Below, preferably 10
When the film thickness is less than or equal to%, the total film thickness of the porous photoelectric conversion layer can be made smaller than when there is no layer region in which the dyes are mixed and adsorbed. Thereby, resistance in carrier transport is reduced, and a more efficient solar cell can be obtained.

The method for producing a solar cell of the present invention comprises: (a) a porous semiconductor layer having a multi-layer structure, which comprises, on a conductive support, semiconductor particles having no coating layer and semiconductor particles having a coating layer. And (b) a solution separately containing at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum is prepared, and the porous semiconductor layer is immersed in the obtained solution to be parallel to the conductive support. The step of adsorbing the dye to the porous semiconductor layer in a layer shape different from that of the porous semiconductor layer and the step of removing the coating layer of the porous semiconductor layer composed of semiconductor particles having a coating layer are repeated to form a layer shape parallel to the conductive support. A porous photoelectric conversion layer having a multilayer structure in which a dye is adsorbed, at least one of which is a layer in which one kind of dye is adsorbed, and (c) a porous photoelectric conversion layer on a conductive support and a counter electrode To face them Filling a conductive layer between, sealing the conductive layer with a sealing material optionally (d), characterized in that the production of solar cells.

From the above steps (a) and (b), that is, the formation of the porous semiconductor layer, the dye is adsorbed to the porous semiconductor layer in a layer shape parallel to the conductive support to form the porous photoelectric conversion layer. The methods up to are specifically described. The following description is an example in which titanium oxide is used as the semiconductor particles, magnesium oxide is used as the compound for forming the coating layer, and a doctor blade method using a paste in which the semiconductor particles are dispersed is used as the method for forming the porous semiconductor layer. The invention is not limited to these.

Step (a) A titanium oxide paste is deposited on the transparent conductor 2 side of the conductive support 10 by the doctor blade method, and the obtained coating film is dried (layer A). Then, about 5 to 30 wt% of magnesium oxide powder as a compound for forming the coating layer is mixed with the titanium oxide paste and dispersed therein, and the pH is adjusted to about 1 with hydrochloric acid or the like to mix them. Prepare the paste. The obtained mixed paste is similarly formed on the previously formed titanium oxide film (layer A) by the doctor blade method, and the obtained coating film is dried (layer B). Then, the titanium oxide film composed of the layers A and B is fired to obtain a titanium oxide film having only the titanium oxide film on the transparent conductor 2 side and a magnesium oxide layer (coating layer) on the opposite side.

By adjusting the pH to about 1 when preparing the mixed paste, the dispersion stability of the contained particles is improved,
Magnesium oxide powder dissolves in the paste. As a result, the layer B in which magnesium oxide is layered on the titanium oxide can be formed.

Step (b) The titanium oxide film comprising layers A and B is immersed in a dye adsorbing solution containing the dye A to adsorb the dye A on the titanium oxide film. At this time, the dye A is adsorbed on the titanium oxide in the layer A, and the dye A is adsorbed on the magnesium oxide in the layer B. Then, the titanium oxide film is immersed in an acidic solution to dissolve the magnesium oxide in layer B. As a result, the dye A on the layer B is removed (desorbed).
Examples of the acidic solution include hydrochloric acid, nitric acid and the like.
It is preferably about 2 to 2N (N: normality).

Next, the titanium oxide film consisting of layer A and layer B is immersed in a dye adsorbing solution containing dye B to adsorb dye B on the titanium oxide film. As a result, a porous photoelectric conversion layer having a multilayer structure in which the dye A (partly, the dye B) is adsorbed in the layer A and the dye B is adsorbed in the layer B in a layer shape parallel to the conductive support is obtained. As described above, in the present invention, at least one layer of the multilayer structure may be a layer adsorbing one kind of dye, and the other layers may be layers adsorbing two or more kinds of dyes. In FIG. 1, the former is shown as a region 4 where the first dye is adsorbed, and the latter is shown as a region 5 where the second dye is adsorbed. After each dye is adsorbed, the porous semiconductor layer may be washed and dried by a known method using a polar solvent such as acetonitrile or an organic solvent such as an alcohol solvent.

Among the dyes adsorbed on the titanium oxide film, the dye A adsorbed on the layer on the light receiving surface side has the maximum sensitivity absorption wavelength region in the absorption spectrum on the short wavelength side,
As the dye B, it is preferable to use a dye having a maximum sensitivity absorption wavelength region in the absorption spectrum on the long wavelength side. In general,
Since the one having the maximum sensitivity absorption wavelength region on the short wavelength side has a small molecular weight (molecular size), the dye A is adsorbed on the titanium oxide film first, and the magnesium oxide in the layer B is removed with an acidic solution. Then, the dye B is adsorbed on the titanium oxide film, so that the dye B is also adsorbed on the layer A.

As a method of forming a coating layer on semiconductor particles, in addition to the method of using magnesium oxide powder as described above, a colloid solution or a metal alkoxide is used to hydrolyze the surface of the semiconductor particles to form a coating layer. There is also a method of forming. In these cases, the formed titanium oxide film is immersed in an aqueous solution of metal alkoxide, the metal alkoxide is hydrolyzed with titanium oxide particles to modify the surface thereof, and the film is baked to form a coating layer on the surface of the titanium oxide particles. . By adding ethanol to the aqueous metal alkoxide solution used at this time, the surface tension is lowered, and the aqueous metal alkoxide solution can be efficiently permeated into the titanium oxide film.

As the compound for forming the coating layer, there is no problem as long as it is an oxide which can be dissolved in an acidic solution and a basic solution. Specifically, when an acidic solution is used, magnesium oxide, zinc oxide, copper oxide are used. , Nickel oxide, molybdenum oxide, etc., when using a basic solution,
Examples thereof include zinc oxide, niobium oxide and lead oxide. The acidic solution and the basic solution in which the above compound is dissolved are not particularly limited. The acidic solution is particularly preferably one in which the anions after dissolution evaporate during sintering, and specific examples thereof include hydrochloric acid and nitric acid, and the basic solution includes sodium hydroxide, potassium hydroxide and the like. . These concentrations are influenced by the dissolution time and the dye used, but are preferably about 0.2 to 2N (N: normality).

Although it changes depending on the combination of dyes used, there is no problem even if the porous semiconductor layer (layer B) made of semiconductor particles having a coating layer is on the light receiving surface side. Specifically, it is effective to adapt to the following cases. For example, when adsorbing a dye with weak acid resistance on the light receiving surface side,
When magnesium oxide is removed with an acidic solution, it is considered that the dye adsorbed on titanium oxide (light-receiving surface side) is also dissolved in the acidic solution. In such a case, the dye is adsorbed on the porous semiconductor layer in the order of dye B having the maximum sensitivity absorption wavelength region in the absorption spectrum on the long wavelength side and dye A having the maximum sensitivity absorption wavelength region in the absorption spectrum on the short wavelength side. You can do it. That is, the dye B is added to the porous semiconductor layer.
Is adsorbed and magnesium oxide and the dye B adsorbed thereto are removed with an acidic solution, and then the dye A is attached to the porous semiconductor layer.
Adsorb.

When the magnesium oxide and the dye B adsorbed thereto are removed with an acidic solution as described above, the layer A is used.
It is expected that magnesium oxide will remain near the interface between the layer B and the layer B, and the electrical interface contact will deteriorate. But p
Layer B using a mixed paste in which H is adjusted to an acidity of about 1
When the layer A is applied using a titanium oxide paste and the magnesium oxide in the layer B near the applied layer A is dissolved, titanium oxide particles in the vicinity of the interface between the layer A and the layer B are separated from each other. The contact is made without the intermediary of magnesium oxide, and the problem of increase in resistance in carrier transport due to deterioration of interfacial contact expected as described above does not occur.

The conductive layer 7 filled between the porous photoelectric conversion layer 3 and the counter electrode 7 is made of a conductive material capable of transporting electrons, holes and ions. For example, hole-transporting materials such as polycarbazole; electron-transporting materials such as tetranitrofluorolenone; conductive polymers such as polypyrrole; ionic conductors such as liquid electrolytes and polymer electrolytes; copper iodide, copper thiocyanate, etc. Type semiconductors.

Among the above conductive materials, the ionic conductor is preferable, and the liquid electrolyte containing the redox electrolyte is particularly preferable. Such redox electrolyte is not particularly limited as long as it can be generally used in batteries, solar cells and the like. Specifically, LiI, Na
Combinations of metal iodides such as I, KI, CaI ₂ and iodine and LiBr, NaBr, KBr, CaBr ₂
A combination of a metal bromide such as bromine and bromine is preferable, and among these, a combination of LiI and iodine is particularly preferable.

Examples of the solvent for the electrolyte include carbonate compounds such as propylene carbonate, nitrile compounds such as acetonitrile, alcohols such as ethanol, and water and aprotic polar substances. Among these, carbonate compounds And nitrile compounds are particularly preferred. The electrolyte concentration is about 0.1 to 1.5 mol / liter, preferably about 0.1 to 0.7 mol / liter.

The sealing material 9 is not particularly limited as long as it can seal the solar cell so that the material forming the conductive layer 7 does not leak out. For example, epoxy resin, silicone resin, thermoplastic resin, etc. may be mentioned. Further, when the material forming the conductive layer 7 is solid and there is no risk of outflow from the solar cell, the sealing material 9 may not be necessarily provided.

[0046]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The following examples and comparative examples will be described with reference to FIG. 1, which is a schematic cross-sectional view of an essential part showing the layer structure of the solar cell of the present invention. In FIG. 1, 1 is a transparent support, 2 is a transparent conductor, 3 is a porous photoelectric conversion layer, 4 is a region where the first dye is adsorbed, 5 is a region where the second dye is adsorbed, and 6 is a conductive layer (oxidized). (Reducing electrolytic solution), 7 is a counter electrode, 8 is a platinum film, and 9 is a sealing material. The transparent support 1 and the transparent conductor 2 are collectively referred to as a conductive support 10.

Example 1 A solar cell using a porous photoelectric conversion layer in which two kinds of dyes were adsorbed in layers on the porous semiconductor layer was manufactured and its performance was evaluated. First, as a coating liquid for forming a titanium oxide film to be the porous semiconductor layer of the porous photoelectric conversion layer 3, a commercially available titanium oxide paste (manufactured by Solaronix, trade name: D) is used.
Prepared. On the transparent conductive film 2 side of the transparent support 1 made of a glass substrate on which a SnO ₂ film is formed as the transparent conductor 2,
Titanium oxide paste was applied using a doctor blade method to obtain a coating film having a film thickness of about 10 μm and an area of about 10 mm × 10 mm. The obtained coating film was pre-dried at 80 ° C. for 20 minutes (first layer).

Next, 10 wt% of magnesium oxide powder (manufactured by Kishida Chemical Co., Ltd.) was mixed in the titanium oxide paste with respect to titanium oxide, the pH was adjusted to about 1 with hydrochloric acid, and the mixture was stirred for 10 minutes. Then, ultrasonic dispersion was performed for 10 minutes to obtain a mixed paste in which magnesium oxide was dispersed in a titanium oxide paste. The mixed paste obtained by using the doctor blade method was applied onto the titanium oxide film (first layer) which had been preliminarily dried to obtain a coating film having a thickness of about 5 μm. The obtained coating film was pre-dried at 80 ° C. for 20 minutes (second layer) and baked at about 500 ° C. for 60 minutes in an oxygen atmosphere to obtain a porous semiconductor layer having a thickness of about 4 μm.

Next, as a dye (first dye) having the maximum sensitivity absorption wavelength region in the absorption spectrum on the short wavelength side, a merocyanine dye represented by the formula (1) (produced by Hayashibara Biochemical Laboratory Co., Ltd., a product Name: NK2684) was dissolved in ethanol to prepare a dye solution for adsorption of the first dye having a concentration of 4 × 10 ⁻⁴ mol / liter. The transparent support 1 including the dye solution for adsorption and the porous semiconductor layer obtained above is placed in a container and heated and immersed at about 50 ° C. for about 10 minutes to adsorb the first dye on the porous semiconductor layer. Let
After that, wash with absolute ethanol several times, and at about 60 ℃ for about 2
It was dried for 0 minutes.

[0050]

[Chemical 1]

The transparent support 1 having the porous semiconductor layer on which the first dye is adsorbed is immersed in 0.5N hydrochloric acid for about 10 minutes to dissolve the magnesium oxide adsorbed on the first dye in hydrochloric acid. The first dye adsorbed on magnesium oxide was desorbed and dried at about 60 ° C. for about 20 minutes.

Next, the phthalocyanine dye represented by the formula (2) was used as the dye (second dye) having the maximum sensitivity absorption wavelength region on the long wavelength side in the absorption spectrum. The synthesis method is described in J. Porphyrins Phtha
locyanines 3,230-237 (199
The method described in 9) was used. Dissolving the phthalocyanine dye represented by the formula (2) in dimethylformamide,
A dye solution for adsorption of the second dye having a concentration of 4 × 10 ⁻⁴ mol / liter was prepared. The transparent support 1 having the adsorbing dye solution and the porous semiconductor layer obtained above is placed in a container,
The second dye was adsorbed on the porous semiconductor layer by immersing the porous semiconductor layer at room temperature and atmospheric pressure for about 15 minutes. Then, it was washed with absolute ethanol several times and dried at about 60 ° C. for about 20 minutes.

[0053]

[Chemical 2]

Next, in a 3-methoxypropionitrile solvent, dimethylpropyl imidazolium iodide has a concentration of 0.5 mol / liter, lithium iodide has a concentration of 0.1 mol / liter, and iodine has a concentration of 0.05 mol / liter. It was dissolved so as to be 1 liter to prepare an oxidation-reduction electrolytic solution.
The porous photoelectric conversion layer 3 side of the transparent support 1 having the porous photoelectric conversion layer 3 adsorbing the first dye and the second dye, and the counter electrode 7 made of ITO glass having a platinum film as the counter electrode layer 8 The solar cell was completed by placing it so as to face the platinum film side of, and injecting the prepared redox electrolytic solution between them, and sealing the periphery with the epoxy resin sealing material 9. Measurement conditions of the obtained solar cell: AM-1.5 (100 m
Current value (Jsc): 1 when evaluated by W / cm ² )
It was 0.1 mA / cm ² .

Comparative Example 1 Similar to Example 1 except that only the merocyanine dye represented by the formula (1) which is the first dye of Example 1 is used as the dye to be adsorbed on the porous semiconductor layer 3. Then, a solar cell was manufactured and evaluated. The obtained solar cell had a current value of 8.5 mA / cm ² .

Comparative Example 2 Similar to Example 1 except that only the phthalocyanine dye represented by the formula (2) which is the second dye of Example 1 is used as the dye to be adsorbed on the porous semiconductor layer 3. Then, a solar cell was manufactured and evaluated. The obtained solar cell had a current value of 2.7 mA / cm ² .

From the above results, the solar cell of the present invention (Example 1) absorbs a wider range of light than the solar cells using only a single dye (Comparative Example 1 and Comparative Example 2). It can be effectively used) and has high photoelectric conversion efficiency.

Example 2 In the same manner as in Example 1, except that the order of forming the first layer and the second layer of the titanium oxide film to be the porous semiconductor layer of the porous photoelectric conversion layer 3 was changed. The conversion layer 3 was formed. That is, a titanium oxide film (first layer) having a thickness of 6 μm and a titanium oxide film (second layer) having a thickness of 10 μm were obtained. Example 1 except that a xanthene-based dye represented by formula (3) (manufactured by ACROS, trade name: EOSIN-Y) was used as the first dye to be adsorbed on the first layer of the porous semiconductor layer. Similarly, a solar cell was manufactured and evaluated. That is, as the second dye to be adsorbed on the second layer of the porous semiconductor layer, the phthalocyanine dye represented by the formula (2) was used as in Example 1.

[0059]

[Chemical 3]

Measurement conditions of the obtained solar cell: AM-1.
When evaluated at 5 (100 mW / cm ² ), the current value:
It was 3.8 mA / cm ² .

Comparative Example 3 The same as Example 1 except that only the xanthene dye represented by the formula (3) which is the second dye of Example 2 was used as the dye to be adsorbed on the porous semiconductor layer 3. Then, a solar cell was manufactured and evaluated. The obtained solar cell had a current value:
It was 1.2 mA / cm ² .

From the above results, the solar cell of the present invention (Example 2) absorbs a wider range of light than the solar cells using only a single dye (Comparative Examples 2 and 3). It can be effectively used) and has high photoelectric conversion efficiency.

Example 3 In the same manner as in Example 1, a titanium oxide paste was applied,
A titanium oxide porous film was formed as the first layer. Next, niobium (V) ethoxide (manufactured by Kishida Chemical Co., Ltd.) was added to a mixed solvent of ion-exchanged water and ethanol with a volume ratio of 1: 1.
Was added at a concentration of 0.1 mol / liter to prepare a film layer forming solution. A titanium oxide porous film was allowed to penetrate into this solution at room temperature for 30 minutes, and then, under an oxygen atmosphere,
A niobium oxide film was formed on the titanium oxide porous film by firing at 500 ° C. for 30 minutes. Then, a titanium oxide porous film was formed, and a solar cell was manufactured and evaluated in the same manner as in Example 2. However, when removing niobium oxide, a 0.5 N sodium hydroxide solution was used. In this case, since sodium ions may remain in the titanium oxide porous film after removing niobium oxide, the second dye was adsorbed after sufficiently washing with ion-exchanged water. The obtained solar cell had a current value of 3.6 mA / cm ^2.
Met.

[0064]

In the solar cell of the present invention, at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum are used as the dyes which are adsorbed on the porous semiconductor layer to form the porous photoelectric conversion layer. It is possible to provide a high-performance solar cell having a wide light absorption wavelength region and a large amount of light absorption, as compared with the above solar cell.

In the method for producing a solar cell of the present invention, the dye is adsorbed on the porous semiconductor layer, a part of which is coated with another compound.
In addition, the dye can be adsorbed in layers. Therefore, it is possible to obtain a solar cell having a multi-layer structure in which the adsorption of another dye is avoided, that is, at least one porous semiconductor layer in which a single dye is adsorbed and a porous semiconductor layer in which the dyes are mixed and adsorbed. Therefore, the total thickness of the porous semiconductor layer can be reduced, the resistance in carrier transport can be reduced, and a high-performance solar cell can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing a layer structure of a dye-sensitized solar cell of the present invention.

[Explanation of symbols]

1 transparent support 2 transparent conductor 3 Porous photoelectric conversion layer 4 Area where the first dye is adsorbed 5 Area where the second dye is adsorbed 6 Conductive layer (redox electrolyte) 7 opposite poles 8 Platinum film 9 Sealant 10 Conductive support

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takehito             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F term (reference) 5F051 AA14 BA13 CB13 DA20 FA03                       GA03 HA20                 5H032 AA06 AS06 AS16 EE02 EE16                       HH07

Claims (7)

[Claims] 1. A porous photoelectric conversion layer in which at least two kinds of dyes having different maximum sensitivity wavelength regions in an absorption spectrum are adsorbed on a porous semiconductor layer, a conductive layer and a counter electrode are sequentially laminated on a conductive support. In the dye-sensitized solar cell, the porous photoelectric conversion layer has a multilayer structure in which the dye is adsorbed in a layer shape parallel to the conductive support, and at least 1
A dye-sensitized solar cell, wherein the layer is a layer on which one type of dye is adsorbed. 2. The porous photoelectric conversion layer adsorbs dyes from the light-receiving surface side in this order from dyes having the maximum sensitivity wavelength region in the absorption spectrum on the short wavelength side to dyes having the maximum sensitivity wavelength region in the absorption spectrum on the long wavelength side. The dye-sensitized solar cell according to claim 1. 3. A porous semiconductor layer having a multi-layered structure is formed on a conductive support, comprising a semiconductor particle having no coating layer and a semiconductor particle having a coating layer.
(B) preparing a solution separately containing at least two kinds of dyes having different maximum sensitivity wavelength regions in the absorption spectrum,
A step of immersing the porous semiconductor layer in the obtained solution to adsorb the dye in the porous semiconductor layer in a layer shape parallel to the conductive support, and a film of the porous semiconductor layer comprising semiconductor particles having a film layer By repeating the step of removing the layer, a multilayer structure in which the dye is adsorbed in a layer shape parallel to the conductive support,
A porous photoelectric conversion layer in which at least one layer is adsorbed with one kind of dye is formed, and (c) the porous photoelectric conversion layer on the conductive support and the counter electrode are opposed to each other, and a conductive layer is formed between them. A method for producing a dye-sensitized solar cell, which comprises filling a layer and (d) sealing a conductive layer with an optional encapsulating material to produce a dye-sensitized solar cell. 4. The method for producing a dye-sensitized solar cell according to claim 3, wherein the semiconductor particles are titanium oxide particles. 5. The coating layer is a layer made of a compound selected from magnesium oxide, zinc oxide, copper oxide, nickel oxide and molybdenum oxide, and the porous semiconductor layer is immersed in an acidic solution in the step (b). 5. The coating layer of the porous semiconductor layer is dissolved and removed by carrying out.
The method for producing a dye-sensitized solar cell according to item 1. 6. The coating layer is a layer made of a compound selected from zinc oxide, niobium oxide and lead oxide, and in step (b), the porous semiconductor layer is made porous by immersing it in a basic solution. The method for producing a dye-sensitized solar cell according to claim 3, wherein the coating layer of the semiconductor layer is dissolved and removed. 7. In the step (b), the dye is porous from the light-receiving surface side in the order of the dye having the maximum sensitivity wavelength region in the absorption spectrum on the short wavelength side to the dye having the maximum sensitivity wavelength region in the absorption spectrum on the long wavelength side. The method for producing a dye-sensitized solar cell according to claim 3, wherein the dye-sensitized solar cell is adsorbed on a photoelectric conversion layer.