JP2010277722A - Dye sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye sensitized solar cell which has a photosensitized semiconductor porous layer formed on the surface of a metal electrode substrate via a rectifying barrier layer and whose performance deterioration due to corrosion on the surface of the metal electrode substrate is surely prevented. <P>SOLUTION: The dye sensitized solar cell includes the metal electrode substrate 10 and a transparent electrode substrate 1 arranged opposing each other, wherein a power generation region X consisting of an electrolyte layer 20 and a dye sensitized semiconductor porous layer 13 and a sealing region Y located around the power generation region and consisting of a sealing material 30 joining both electrode substrates to each other are formed between both electrode substrates. The rectifying barrier layer 15 is formed on the surface of the metal electrode substrate 10, and the semiconductor porous layer 13 is formed on the rectifying barrier layer 15. The rectifying barrier layer 15 includes the power generation region X and extends to the sealing region Y. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention comprises a metal electrode substrate and a glass electrode substrate arranged to face each other, and a power generation region comprising an electrolyte layer and a semiconductor porous layer sensitized with a dye between the electrodes. Relates to a dye-sensitized solar cell in which is formed.

  Currently, there is great expectation for photovoltaic power generation from the viewpoint of global environmental problems and fossil energy resource depletion problems, and single crystal and polycrystalline silicon photoelectric conversion elements are put into practical use as solar cells. However, this type of solar cell is expensive and has a problem of supply of silicon raw materials, and the practical application of solar cells using materials other than silicon is desired.

  From the above viewpoint, recently, dye-sensitized solar cells have attracted attention as solar cells using materials other than silicon. As a representative of this dye-sensitized solar cell, a transparent electrode substrate in which a transparent conductive film such as ITO is provided on the surface of a glass substrate or a transparent plastic substrate, and a metal electrode substrate are a dye-sensitized semiconductor porous layer The peripheral portion of the metal electrode substrate and the transparent electrode substrate is sealed with a sealing material so that the electrolyte layer does not leak. That is, the region where the metal electrode substrate and the transparent electrode substrate are opposed to each other with the dye-sensitized semiconductor porous layer and the electrolyte layer interposed therebetween is a power generation region, and the dye-sensitized semiconductor porous layer (hereinafter, The semiconductor porous layer may be simply provided on the transparent electrode substrate, but may be provided on the metal electrode substrate (see Patent Document 1).

  In the dye-sensitized solar cell having the above-described structure, when visible light is irradiated from the transparent electrode substrate side, the dye in the dye-sensitized porous layer is excited, transitioned from the ground state to the excited state, and excited. The electrons of the dye are injected into the conduction band in the semiconductor porous layer, and pass through an external circuit from the transparent electrode substrate or metal electrode substrate on which the semiconductor porous layer is formed. Move to transparent electrode substrate. The electrons that have moved to the counter electrode substrate are carried by the ions in the electrolyte layer and return to the dye. Electric energy is extracted by repeating such a process. The power generation mechanism of such a dye-sensitized solar cell is different from a pn junction photoelectric conversion element, in which light capture and electronic conduction are performed in different places, and is very similar to a plant photoelectric conversion process. Yes.

  By the way, in the structure in which the semiconductor porous layer is provided on the transparent electrode substrate, since the semiconductor porous layer is formed on the transparent conductive film having a large resistance, the cell (minimum unit of power generation functioning as a battery) is large-sized. However, there is a problem that the internal resistance (FF) and conversion efficiency are greatly reduced. For this reason, recently, a structure in which a semiconductor porous layer is provided on a metal electrode substrate is becoming mainstream. That is, in this case, since the semiconductor porous layer is directly formed on the low-resistance metal electrode substrate, it is possible to effectively avoid the FF and the reduction in conversion efficiency due to the enlargement of the cell. .

  However, in a dye-sensitized solar cell having a structure in which a semiconductor porous layer is formed on a low-resistance metal electrode substrate, this semiconductor porous layer is a dense oxide semiconductor layer mainly produced by a sol-gel method. There is a problem that the rectification barrier is incomplete and the conversion efficiency decreases with time.

  For this reason, it has been proposed to form a rectifying barrier layer (back-current prevention layer) on a low-resistance metal electrode substrate and to provide a semiconductor porous layer on the rectifying barrier layer (see Patent Documents 2 and 3). .

JP 2001-273937 A JP 2007-87744 A JP 2008-53024 A

However, in the case where the rectifying barrier layer as described above is provided, there is a problem that the electrolytic solution forming the electrolyte layer often causes corrosion on the metal substrate, resulting in deterioration of the cell performance, and improvement is required. ing.
Moreover, since the rectification | straightening barrier layer proposed by patent document 2, 3 is formed by chemical conversion treatment or plating, there exists a problem that production efficiency is bad. In order to solve such a problem, the present applicant first applied a coating liquid containing a metal compound capable of forming a metal oxide serving as an anti-electrostatic agent by heat treatment to the surface of the metal electrode substrate, and then heat-treated. By doing so, it was proposed to form a rectifying barrier layer (back-current prevention layer) (Japanese Patent Application No. 2008-178341). That is, this method has an advantage that the production efficiency is extremely high because the rectifying barrier layer is formed by a coating method such as screen printing. However, even when the rectifying barrier layer is formed by such a coating method, the problem that corrosion often occurs on the surface of the metal substrate and causes deterioration of the cell performance has not been solved.

Accordingly, an object of the present invention is to have a structure in which a photosensitized semiconductor porous layer is formed on the surface of a metal electrode substrate via a rectifying barrier layer, so that performance degradation due to corrosion of the surface of the metal electrode substrate is ensured. An object is to provide a dye-sensitized solar cell which is prevented.
Another object of the present invention is to provide a dye-sensitized solar cell in which the rectifying barrier layer is formed by a coating method and has high productivity.

  As a result of examining the problem of corrosion of the metal electrode substrate when the dye-sensitized semiconductor porous layer is formed on the surface of the metal electrode substrate via the rectifying barrier layer, the present inventors selected this rectifying barrier layer as the power generation region. Therefore, the rectifying barrier layer is not formed on the peripheral portion of the power generation region (that is, the boundary portion with the sealing region) due to a positioning error at the time of manufacture, and the metal electrode substrate surface may be exposed. As a result, the inventors have found that the electrolyte solution that has penetrated into the porous layer contacts the surface of the metal substrate to cause corrosion, and has completed the present invention.

That is, according to the present invention, a metal electrode substrate and a transparent electrode substrate disposed so as to face each other are provided, and an electrolyte layer and a semiconductor porous layer sensitized with a dye are interposed between the electrode substrates. In a dye-sensitized solar cell in which a power generation region formed of and a sealing region made of a sealing material that is located around the power generation region and combines both electrode substrates are formed,
A rectifying barrier layer is formed on the surface of the metal electrode substrate, and the semiconductor porous layer is formed on the rectifying barrier layer.
The rectifying barrier layer includes the power generation region and extends to the sealing region. A dye-sensitized solar cell is provided.

In the dye-sensitized solar cell of the present invention,
(1) The rectifying barrier layer is formed on the entire surface of the metal electrode substrate,
(2) The rectifying barrier layer is formed by a coating method,
(3) The rectifying barrier layer is a dense layer of metal oxide,
Is preferred.

  In the dye-sensitized solar cell of the present invention, the rectifying barrier layer extends not only to the power generation region but also to the sealing region at the periphery of the power generation region. Therefore, a rectification barrier layer is always formed in the power generation region portion on the surface of the metal electrode substrate without being affected by positioning errors at the time of manufacture, and the peripheral portion of the power generation region, that is, the sealing region. Exposure of the metal substrate surface at the boundary portion can be reliably prevented. As a result, the contact of the electrolytic solution in the electrolytic layer with the surface of the metal electrode substrate is reliably prevented by the rectifying barrier layer, and the performance degradation due to the corrosion of the surface of the metal electrode substrate can be reliably prevented.

  In particular, when the rectifying barrier layer is formed by the coating method, the rectifying barrier layer is formed by selectively applying the coating liquid for forming the rectifying barrier layer to the portion of the metal electrode substrate surface that will be the power generation region. As a result, the coating liquid is not applied to the boundary portion with the sealing region, and therefore, the portion where the metal substrate surface is exposed without forming the rectifying barrier layer is likely to be formed. Since the rectifying barrier layer is extended to the above, such inconvenience can be surely prevented.

It is a schematic sectional drawing which shows the structure of the dye-sensitized solar cell of this invention. It is sectional drawing which expands and shows the principal part of the other example in the structure of the dye-sensitized solar cell of this invention.

  The dye-sensitized solar cell of the present invention includes a transparent electrode substrate (positive electrode substrate) 1 and a metal electrode substrate (negative electrode substrate) 10, and has a structure in which the transparent electrode substrate 1 and the metal electrode substrate face each other. is doing.

  The transparent electrode substrate 1 has a structure in which a transparent conductive film 5 and an electron reducing conductive layer 7 are formed in this order on the surface of the transparent substrate 3. On the other hand, the metal electrode substrate 10 has a metal substrate 11 on which a dye-sensitized semiconductor porous layer 13 is formed. The metal substrate 11 and the dye-sensitized semiconductor porous layer are formed on the metal substrate 11. A rectifying barrier layer 15 is formed between the layer 13 and the layer 13.

  The transparent electrode substrate 1 and the metal electrode substrate 10 are opposed to each other with the electrolyte layer 20 interposed therebetween, so that the electrolyte layer 20 does not leak at the peripheral portion between the transparent electrode substrate 1 and the metal electrode substrate 10. Further, it is sealed with a sealing material 30. That is, the region where the metal electrode substrate 10 and the transparent electrode substrate 1 face each other with the dye-sensitized semiconductor porous layer 13 and the electrolyte layer 20 interposed therebetween is the power generation region X. A sealed region is a sealed region Y.

(Transparent substrate 3)
In the structure as described above, the transparent substrate 3 used for forming the transparent electrode substrate 1 (positive electrode substrate) only needs to have high light transmittance, and is formed of, for example, transparent glass or a transparent resin film. The The thickness and size are appropriately determined according to the intended use of the dye-sensitized solar cell to be finally formed.

(Transparent conductive film 5)
Typical examples of the transparent conductive film 5 formed on the transparent substrate 3 include a film made of an indium oxide-tin oxide alloy (ITO film), a film in which tin oxide is doped with fluorine (FTO film), and the like. An ITO film is preferable because of its high electron reducing property and particularly desirable characteristics as a cathode. These are formed on the transparent substrate 3 by vapor deposition, and the thickness is usually about 500 nm to 700 nm.

(Electron reduction layer 7)
The electron reduction conductive layer 7 formed on the transparent conductive film 5 is generally made of a thin platinum layer, and has a function of quickly transferring electrons flowing into the transparent conductive film 5 to the electrolyte layer 20. is there. Such an electron reduction conductive layer 20 is thinly formed by vapor deposition so that the average thickness thereof is about 0.1 to 1.5 nm so as not to impair the light transmittance.

(Metal substrate 11)
On the other hand, the metal substrate 11 used for forming the metal electrode substrate 10 (negative electrode substrate) is not particularly limited as long as it is formed from a metal material having a low electrical resistance, but generally 6 × 10 ⁻⁶ Ω. A metal or alloy having a specific resistance of m or less, such as aluminum, iron (steel), stainless steel, copper, nickel, etc. is used. Further, the thickness of the metal substrate 11 is not particularly limited as long as it has a thickness enough to maintain an appropriate mechanical strength. If productivity is not taken into consideration, the metal substrate 11 may be formed on a resin film or the like, for example, by vapor deposition. Of course, the substrate such as the resin film does not need to be transparent.

(Dye-sensitized semiconductor porous layer 13)
On the other hand, the dye-sensitized semiconductor porous layer 13 formed on the surface of the metal substrate 11 with the rectifying barrier layer 15 interposed therebetween is formed in a portion that becomes the power generation region X, and its periphery is involved in power generation. It becomes the sealing area | region Y which does not. This dye-sensitized semiconductor porous layer 13 has been conventionally used in dye-sensitized solar cells, and is obtained by adsorbing and supporting a dye on an oxide semiconductor layer.

The oxide semiconductor porous layer for adsorbing and supporting the dye is, for example, an oxide of a metal such as titanium, zirconium, hafnium, strontium, tantalum, chromium, molybdenum, tungsten, or a composite oxide containing these metals, such as SrTiO _3. And a perovskite type oxide such as CaTiO ₃ , and the thickness is usually about 3 to 15 μm.

  Further, the porous layer of the oxide semiconductor needs to be porous in order to carry the dye, and for example, the relative density by the Archimedes method is 50 to 90%, particularly about 50 to 70%. It is preferable that a large surface area can be secured and an effective amount of the dye can be supported.

Such an oxide semiconductor porous layer is, for example, a paste prepared by dispersing fine particles of the above-described oxide semiconductor in an organic solvent or an organic compound having chelate reactivity, or a titanium alkoxide (for example, tetraisopropoxy titanium). It is easily formed by applying a slurry or paste dispersed in an organic solvent together with a binder component such as) on the metal substrate 11 and baking at a temperature of 600 ° C. or less for a time to the above-described relative density. be able to. That is, by firing, the TiO ₂ gel formed by the gelation (dehydration condensation) of the binder component joins the semiconductor fine particles and becomes porous.

  The semiconductor fine particles used for forming the slurry or paste as described above should have a particle size in the range of 5 to 500 nm, particularly 5 to 350 nm from the viewpoint of making them porous. Further, as the chelate-reactive organic compound, β-diketone, β-ketoamine, and β-ketoester are representative and can be used without particular limitation as long as it is easily volatile. However, acetylacetone, which is a β-diketone, can be used. Is particularly suitable, and is preferably used in an amount of 5 to 35% by weight based on the weight of the semiconductor fine particles. Further, the titanium alkoxide as a binder component is preferably used in an amount of 10 to 60 parts by weight, particularly 20 to 50 parts by weight, per 100 parts by weight of titanium dioxide fine particles. In general, lower alcohols having 4 or less carbon atoms such as methanol, ethanol, isopropanol, n-butanol, sec-butanol, t-butanol and the like are suitable, and these organic compounds can be used without limitation. A solvent may be used independently and can also be used in the form of the mixed solvent which combined 2 or more types. The amount of the organic solvent may be used in such an amount that the slurry or paste exhibits an appropriate coating property. In general, the solid content concentration of the slurry or paste is 5 to 50% by weight, particularly 15 to 40% by weight. It is better to use it in an amount that is in the range. If the amount of solvent is too large, the slurry or paste becomes low-viscosity and it becomes difficult to form a coating layer with a stable thickness due to dripping, etc., and if the amount of solvent is small, the viscosity becomes high-viscosity and workability decreases. Because.

  The dye adsorbed on the oxide semiconductor porous layer formed as described above is adsorbed and supported by bringing the dye solution into contact with the porous layer. The contact of the dye solution is usually performed by dipping, and the adsorption treatment time (immersion time) is usually about 30 minutes to 24 hours, and after adsorption, the solvent of the dye solution is removed by drying, The dye-sensitized semiconductor porous layer 13 having the sensitizing dye adsorbed and supported on the surface and inside is formed.

The dye used can function as a sensitizing dye and has a linking group such as a carboxylate group, a cyano group, a phosphate group, an oxime group, a dioxime group, a hydroxyquinoline group, a salicylate group, and an α-keto-enol group. Those known per se are used. For example, a ruthenium complex, an osmium complex, an iron complex, etc. can be used without any limitation. Ruthenium-tris (2,2′-bispyridyl-4,4′-dicarboxylate), ruthenium-cis-diaqua-bis (2,2′-bispyridyl-4,4) in that it has a particularly broad absorption band. Ruthenium-based complexes such as' -dicarboxylate) are preferred. Such a dye solution of a sensitizing dye is prepared using an alcohol-based organic solvent such as ethanol or butanol as a solvent, and the dye concentration is usually about 3 × 10 ^{−4 to} 5 × 10 ⁻⁴ mol / l. It is good to do.

(Rectifying barrier layer 15)
The rectifying barrier layer 15 appropriately formed on the metal substrate 11 is also called a reverse current prevention layer, and is a layer made of a metal or metal oxide having a higher resistance than the metal substrate 11 and prevents reverse current. In addition to being an effective rectifying barrier, it has corrosion resistance and also has a function of preventing corrosion of the metal substrate 11 due to permeation of an electrolytic solution from the electrolyte layer 20 described later.

  Further, the rectifying barrier layer 14 as described above can be formed by chemical conversion treatment, plating method, cladding method or the like as disclosed in, for example, JP-A-2008-53165, but in the present invention, In particular, it is preferably formed by a coating method. That is, in the coating method, the rectifying barrier layer 15 can be formed very easily as compared with the above method, and the productivity can be improved.

  In the present invention, in the coating method, a rectifying barrier layer 15 is formed by applying a coating liquid having a predetermined composition to the surface of the metal substrate 11 and then heat-treating the rectifying barrier layer 15. It is made of a material, particularly an oxide semiconductor, and is a layer that is considerably denser than the above-described dye-sensitized porous layer 13, whereby a high rectifying barrier and corrosion resistance can be realized.

  The coating solution used in the above coating method is composed of an organic solvent solution of a metal compound, and a solute stabilizer is added to the solution to effectively prevent precipitation of the metal compound. The viscosity at 25 ° C. is adjusted to 10 cP or more, particularly 50 to 2000 cP, so that the coating property is improved and the coating property is improved and, for example, a coating layer having a uniform thickness can be formed by screen printing. Has been.

  The metal compound contained in the coating liquid forms a metal oxide by a heat treatment (firing) described later, and as long as such an oxide can be formed, the metal element is not particularly limited, For example, Ti, Al, Zn, Ni, Fe, Cu or the like may be used. The form of the compound is not particularly limited as long as it can form an oxide by heat treatment and can be dissolved in an organic solvent. In general, it can be easily obtained, and the oxide can be quickly obtained by heat treatment. And is preferably an alkoxide, hydroxide, or chloride because of its high solubility in organic solvents. Further, when the semiconductor porous layer 13 formed on the rectifying barrier layer 15 formed using this coating liquid is titanium dioxide, it is high between the rectifying barrier layer 15 and the semiconductor porous layer 13. Titanium alkoxide, in particular titanium isopropoxide, is preferable since titanium can be secured, and titanium tetraisopropoxide is most preferable.

  In addition, as the solute stabilizer used for preventing the precipitation of the metal compound, a compound which is itself soluble in an organic solvent and has a high affinity for the metal compound is used. (Cellosolve) and β-diketone are preferably used.

Glycol ether has the following formula:
HOCH ₂ CH ₂ OR
In the formula, R is an alkyl group, an aryl group, or an aralkyl group.
The alkyl group is typically a lower alkyl group having 8 or less carbon atoms such as a methyl group, an ethyl group, an isopropyl group, an n-propyl group, an isobutyl group, an n-butyl group, and an isoamyl group. The aryl group may be exemplified by a phenyl group and the aralkyl group may be exemplified by a benzyl group. Among these, a glycol ether in which R is an alkyl group is preferred, and butyl cellosolve (R = isobutyl group, n-butyl group) is preferred.

  Examples of the β-diketone include acetylacetone, 1,3-cyclohexadione, methylenebis-1,3-cyclohexadione, 2-benzyl-1,3-cyclohexadione, acetyltetralone, palmitoyltetralone, Stearoyltetralone, benzoyltetralone, 2-acetylcyclohexanone, 2-benzoylcyclohexanone, 2-acetyl-1,3-cyclohexanedione, bis (benzoyl) methane, benzoyl-p-chlorobenzoylmethane, bis (4-methylbenzoyl) Methane, bis (2-hydroxybenzoyl) methane, benzoylacetone, tribenzoylmethane, diacetylbenzoylmethane, stearoylbenzoylmethane, palmitoylbenzoylmethane, lauroylbenzoylmethane, dibe Zoylmethane, bis (4-chlorobenzoyl) methane, bis (methylene-3,4-dioxybenzoyl) methane, benzoylacetylphenylmethane, stearoyl (4-methoxybenzoyl) methane, butanoylacetone, distearoylmethane, stearoylacetone, Examples thereof include bis (cyclohexanoyl) -methane and dipivaloylmethane, and among these, acetylacetone is preferred.

  The glycol ethers and β-diketones described above are soluble in organic solvents and easily form coordinate bonds with metal elements, effectively suppressing the precipitation of the metal compounds and being excellent as solute stabilizers. It seems to show the characteristic. Of these, glycol ether is most suitable in the present invention. That is, since glycol ether is chemically stable as compared with β-diketone, it exhibits particularly excellent characteristics as a solute stabilizer that prevents precipitation of a metal compound in a coating solution.

  The organic solvent can be used without any particular limitation as long as it can dissolve the above-described metal compound. However, it forms a viscous coating solution particularly suitable for screen printing and is produced by heating. From the standpoint that it can be volatilized without adversely affecting the electrical properties (anti-electrostatic properties) of the oxide, a mixed solvent containing terpineol as a main component, particularly a mixed solvent containing two types of terpineol and ethyl cellulose is preferably used. .

Terpineol (C ₁₀ H ₁₈ O), which is the main component of this organic solvent, is an unsaturated alcohol produced by dehydrating one molecule of water from 1,8-terbin, and three types of α, β and γ are known. Any type can be used, but in general, α-terpineol (Bp: 219 to 221 ° C.) or α-terpineol as a main component, and other types such as β-terpineol are mixed. Mixtures (generally those that are commercially available are mixtures) are preferred.

  That is, the above-mentioned terpineol is a viscous liquid, can easily dissolve the above-mentioned metal compound uniformly, and adversely affects the electrical characteristics of the metal oxide (for example, titanium dioxide) produced by heating. It can be easily volatilized without giving.

  Ethylcellulose, like terpineol, can be easily decomposed and removed by heat treatment without adversely affecting the electrical properties of the metal oxide produced from the metal compound. It has the function of. That is, when a solution of a metal compound is prepared using only terpineol as an organic solvent, the viscosity (25 ° C.) of the coating solution can be 10 cP or more, but it is low viscosity for application by screen printing. This causes inconveniences such as non-uniform application during printing. Therefore, when coating is performed by a screen method, it is preferable to use ethyl cellulose mixed with terpione. In this case, the coating liquid is adjusted to a viscosity range suitable for screen printing (the above-mentioned 50 to 2000 cP) range without diluting the concentration of the metal compound, and a coating film having a uniform thickness is formed without causing any dripping. It becomes possible to do. Furthermore, since this ethyl cellulose also has a function as a binder, a metal oxide is produced in a state in which the metal compound is bound via ethyl cellulose at the time of heat treatment (firing) of the coating film described later, For this reason, the use of ethyl cellulose is extremely advantageous in that it forms a good anti-electrostatic layer without pinholes.

  In addition, although ethyl cellulose having various molecular weights is commercially available, from the viewpoint of adjusting the coating liquid to a viscosity particularly suitable for screen printing, toluene is used as a solvent, and a solid ethylcellulose concentration 10% solution is used. What has a viscosity (25 degreeC) in the range of 30-50 cp is suitable.

  From the above viewpoint, the organic solvent (mixed solvent) used as the organic solvent in the coating liquid generally has an ethylcellulose / terpineol (weight ratio) = 0.1 / 99.9 to 20/80, particularly 3 to It should be in the 97 range.

  In the coating liquid containing each component described above, the content of each component is desirably determined so that the function of each component is effectively exhibited, provided that a viscosity suitable for screen printing is obtained. .

  For example, the concentration of the metal compound in the coating solution is preferably 0.01 to 20%, particularly 0.1 to 5% in terms of metal element. If this concentration is too high, the solid content of the coating solution may become too high, and it may be difficult to form a coating layer having a uniform thickness, and the thickness of the rectifying barrier layer 15 to be formed becomes too thick. As a result, the generation of cracks in the layer and the formation of an insulating layer may adversely affect power generation. On the other hand, if the concentration is too low, the thickness of the rectifying barrier layer 15 to be formed becomes thin, the function as the rectifying barrier is impaired, and the conversion efficiency is lowered.

  The concentration of the solute stabilizer described above is preferably 0.01 to 20% by weight, particularly 1 to 10% by weight. If this concentration is excessively dilute, precipitation of the metal compound is likely to occur, and even if it is used in a larger amount than necessary, no further effect can be expected, and the solubility of the metal compound decreases. This is because there is a risk that it may occur.

  In addition, in the coating liquid containing the above-described components, if the amount is small enough not to adversely affect the above-described screen printing suitability and the characteristics of the rectifying barrier layer to be formed, a leveling agent, surfactant, thickener Alternatively, other volatile solvents or the like may be added.

  The coating liquid described above is applied to the surface of the metal substrate 11 used as an electrode, and is subjected to heat treatment (firing), whereby the rectifying barrier layer 15 is formed. That is, by this heat treatment, the organic solvent and the like are removed by volatilization, thermal decomposition, etc., and an oxide of a metal compound is generated, and the generated metal oxide particles are sintered to form a dense rectifying barrier layer without a pinhole. 15 is obtained.

  As described above, the coating liquid can be applied by screen printing. Of course, if productivity is not taken into consideration, known application means such as spraying, brushing, spin coating, dipping, etc. are used. However, screen printing is applied in terms of efficient and continuous application.

  The heat treatment conditions after coating vary depending on the type of metal compound used, but are generally performed by heating and holding the coating film at a high temperature of 300 to 600 ° C. for 10 to 180 minutes.

  The rectifying barrier layer 15 formed as described above generally has a thickness of 10 to 500 nm, particularly 50 to 200 nm, and the rectifying barrier layer 15 having such a thickness is formed. The coating amount of the coating solution is adjusted. In other words, if the thickness of the rectifying barrier layer 15 is excessively large, the current to the metal substrate 11 is hindered due to the formation of an insulating film, and the battery may not function as a battery. Furthermore, the occurrence of defects such as pinholes impairs durability, and the metal substrate 11 is corroded by the electrolytic solution from the electrolyte layer 20 when used as a battery, and the conversion efficiency tends to decrease with time. End up. Moreover, when the thickness is too thin, the function as a rectification | straightening barrier will be impaired, and there exists a possibility that conversion efficiency may fall by generation | occurrence | production of a reverse current.

  In the present invention, the rectifying barrier layer 15 is provided on the entire surface of the metal substrate 11 as understood from FIG. That is, the rectifying barrier layer 15 has a function as a rectifying barrier at the time of power generation and is provided to prevent corrosion due to the electrolytic solution from the electrolytic layer 20 coming into contact with the metal substrate 11. Basically, it is only necessary to be provided only in the power generation region X. In this case, however, the peripheral portion of the power generation region X, that is, the seal between the power generation region X and the like due to, for example, a screen positioning error during screen printing. There is a possibility that the rectifying barrier layer 15 is not formed at the boundary with the stop region Y, and a portion where the surface of the metal substrate 11 is exposed is formed. Even if the dye-sensitized porous layer 13 is formed on the exposed portion of the metal substrate 11, since the layer 13 is porous, the electrolyte in the electrolytic layer 20 penetrates and the metal substrate 11. As a result, the surface of the metal substrate 11 is corroded, and the performance of the cell is deteriorated. That is, with time, the corrosion progresses and the conversion efficiency is lowered. However, if the rectifying barrier layer 15 is formed on the entire surface of the metal substrate 11 as described above, the exposure of the metal substrate 1 at the boundary between the power generation region X and the sealing region Y can be reliably prevented. Thus, it is possible to effectively prevent performance degradation due to corrosion of the surface of the metal substrate 1.

(Electrolyte layer 20)
The electrolyte layer 20 is disposed between the metal electrode substrate (negative electrode substrate) 10 and the transparent electrode substrate (positive electrode substrate) 1 which are formed and face each other as described above. The power generation region X is formed by the semiconductor porous layer 13. Such an electrolyte layer 20 is formed of various electrolyte solutions containing cations such as lithium ions and anions such as chlorine ions as in the case of known solar cells.

  In the electrolyte layer 20, it is preferable that a redox pair capable of reversibly taking an oxidized structure and a reduced structure exists, and examples of such a redox pair include an iodine-iodine compound, bromine-bromine, and the like. Examples thereof include compounds and quinone-hydroquinone. The electrolyte layer 20 is sealed by the sealing material 30 provided in the sealing region Y located at the periphery of the power generation region X, and liquid leakage from between the electrodes is prevented. In general, the thickness of the electrolyte layer 20 is generally about 10 to 50 μm, although it varies depending on the size of the battery finally formed.

(Encapsulant 30)
In order to prevent leakage of the electrolyte layer 20, the sealing material 30 that is disposed around the power generation region X and forms the sealing region Y includes various types of thermoplastic resins or thermoplastic elastomers that can be heat sealed, such as low Random or block copolymer of α-olefins such as density polyethylene, high density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, or ethylene, propylene, 1-butene, 4-methyl-1-pentene Polyolefin resins such as polymers; ethylene-vinyl compound copolymer resins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer; polystyrene, acrylonitrile-styrene copolymer , ABS, α-methylstyrene-styrene copolymer and other styrene resins; poly Vinyl resins such as vinyl alcohol, polyvinylpyrrolidone, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate; nylon 6, nylon Polyamide resin such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; Polycarbonate; Polyphenylene oxide; Cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose; Oxidation Starch, etherified starch, starch such as dextrin; and a resin composed of a mixture thereof are used.

  That is, the sealing material 30 is obtained by molding into a ring shape having a width corresponding to the sealing region Y, for example, by extrusion molding, injection molding, or the like using the above-described thermoplastic resin. 30 is heat-sealed (thermocompression bonding) in a state of being sandwiched between the negative electrode substrate 10 and the transparent electrode substrate 1 arranged to face each other, thereby joining the metal electrode substrate 10 and the transparent electrode substrate 1, Next, an injection tube is inserted into the sealing material 30, and an electrolyte solution for forming the electrolyte layer 20 is injected into the space between the two electrode substrates through the injection tube, whereby the structure shown in FIG. The dye-sensitized solar cell can be obtained.

  When a transparent resin film or the like is used as the transparent substrate 3, for example, the negative electrode substrate 10 and the transparent electrode substrate 1 are sealed with a sealing agent 30, and then filled with an electrolyte solution from an unsealed opening, Finally, the dye-sensitized solar cell having the structure shown in FIG. 1 can also be produced by completely sealing the opening with the sealant 30.

(Power generation)
In the dye-sensitized solar cell thus formed, as described above, by irradiating visible light from the transparent electrode substrate 1 side, the dye in the dye-sensitized semiconductor porous layer 13 is excited, Transition from the ground state to the excited state, the excited dye electrons are injected into the conduction band in the porous layer 13, and the external circuit (not shown) passes through the metal electrode substrate 10 (metal substrate 11). It moves through to the transparent electrode substrate 1. The electrons that have moved to the transparent electrode substrate 1 are carried by the ions in the electrolyte layer 20 and return to the pigment. By repeating such a process, electric energy is extracted and electric power is generated. That is, in such a solar cell, since the rectification barrier layer 15 is formed between the surface of the metal substrate 11 (the metal substrate 11 and the dye-sensitized semiconductor porous layer 13), the reverse current is effectively prevented and high Conversion efficiency can be obtained. The rectifying barrier layer 15 is a dense layer having no defects such as pinholes, and is formed on the entire surface of the metal electrode substrate 10 (metal substrate 11). Therefore, the metal substrate by the electrolyte solution from the electrolyte layer 20 is used. 11 corrosion can be reliably prevented, and therefore, extremely high durability is exhibited, and a decrease in conversion efficiency with time can also be effectively prevented.

(Other examples)
In the example described above, the rectifying barrier layer 15 is formed on the entire surface of the metal substrate 11 (metal electrode substrate 10). As long as 15 is formed, the rectifying barrier layer 15 may not be formed on the entire surface of the metal substrate 11 (metal electrode substrate 10). That is, as shown in FIG. 2, if the rectifying barrier layer 15 extends to the sealing region X, for example, even when the rectifying barrier layer 15 is formed by coating, it is not affected by positioning errors and the like. The rectifying barrier layer 15 can be reliably formed over the entire power generation region X, and corrosion of the metal substrate 11 by the electrolyte layer 20 can be prevented.

  The invention is illustrated by the following experimental example.

(Experimental example 1)
A commercially available aluminum plate (width 20 mm, length 70 mm, thickness 0.3 mm) was prepared as a metal substrate, and after the metal substrate was sufficiently washed and dried, a titanium sol-gel paste was applied to the entire surface of the substrate by a screen printing method. On top of that, a titanium oxide paste is applied to the central part of the metal substrate by a screen printing method with an area of 10 mm × 60 mm and heat-treated in an electric furnace at 420 ° C. for 30 minutes to form a rectifying barrier layer and a titanium oxide porous film did. The obtained titanium oxide porous membrane had a thickness of about 10 μm.

  The sol-gel paste used was composed mainly of titanium tetraisopropoxide, mixed with terpineol and ethylcellulose as a solvent at a weight ratio of 2/98, and mixed with butyl cellosolve as a stabilizer at a concentration of 3% to obtain a titanium concentration. The paste for forming the titanium layer which functions as a rectification | straightening barrier layer was prepared so that it might become 0.5%.

The titanium oxide paste is mainly composed of two types of commercially available TiO ₂ particles having a spherical particle size of 30 nm and a polyhedral (indeterminate) particle size of 15 nm, and terpineol as a solvent in an amount of 60% by weight in the paste. As an example, ethyl cellulose was prepared to have a viscosity of 5 to 15 cP.

The oxide semiconductor layer was immersed in a solution containing D149 dye manufactured by Mitsubishi Paper Industries, Ltd., which is an organic dye, for about 4 hours, and then dried to modify the dye to titanium oxide fine particles to obtain an electrode.
On the other hand, FTO having platinum formed by sputtering on a substrate was used as a counter electrode (positive electrode) and sealed with a sealing material having a thickness of 50 μm.

A dye-sensitized solar cell was produced by sandwiching an electrolyte solution between the counter electrode structure and the negative electrode structure produced above. As the electrolyte _solution, used was added 4-tert-butylpyridine LiI / I 2 a (0.5M / 0.025 M) to that dissolved in methoxypropionitrile. An electrolyte was injected into the cell to form a solar battery.

  When the obtained battery was subjected to a aging test at 50 ° C., corrosion did not occur on the aluminum substrate even after 500 hours.

(Experimental example 2)
As a metal substrate, a commercially available aluminum plate (width 20 mm, length 70 mm, thickness 0.3 mm) is prepared, and after the metal substrate is sufficiently washed and dried, the sol-gel paste is 10 mm × 60 mm at the center of the metal substrate. The area was applied by screen printing. Except for the application area of the sol-gel paste, a dye-sensitized solar cell was manufactured in the same manner as in Experimental Example 1, and a time-lapse test was performed at 50 ° C., and the boundary with the sealing region of the aluminum substrate was within 100 hours. Corrosion occurred on the part.

1: Transparent electrode substrate 3: Transparent substrate 5: Transparent conductive film 7: Electron reduction layer 10: Metal electrode substrate 11: Metal substrate 13: Dye-sensitized porous semiconductor layer 15: Rectification barrier layer 20: Electrolyte layer 30: Sealing Material X: Power generation area Y: Sealing area

Claims (4)

A power generation region comprising a metal electrode substrate and a transparent electrode substrate disposed so as to oppose each other, and comprising an electrolyte layer and a semiconductor porous layer sensitized with a dye between the electrode substrates, and the power generation In the dye-sensitized solar cell in which a sealing region made of a sealing material that is located around the region and combines both electrode substrates is formed,
A rectifying barrier layer is formed on the surface of the metal electrode substrate, and the semiconductor porous layer is formed on the rectifying barrier layer.
The rectifying barrier layer includes the power generation region and extends to the sealing region.   The dye-sensitized solar cell according to claim 1, wherein the rectifying barrier layer is formed on the entire surface of the metal electrode substrate.   The dye-sensitized solar cell according to claim 1 or 2, wherein the rectifying barrier layer is formed by a coating method.   The dye-sensitized solar cell according to claim 3, wherein the rectifying barrier layer is a dense layer of metal oxide.

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