JP5332739B2 - Photoelectric conversion element and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element having high photoelectric conversion efficiency, high durability, and flexibility, and to provide a solar cell using the photoelectric conversion element. <P>SOLUTION: The photoelectric conversion element includes an inorganic glass film having a thickness of 10-70 &mu;m, a transparent conductive layer, a semiconductor layer carrying sensitized dye, an electrolyte layer, a conductive layer, and an inorganic glass film having a thickness of 10-70 &mu;m in this order between a pair of facing flexible films. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a dye-sensitized photoelectric conversion element and a solar cell using the photoelectric conversion element.

  In recent years, the use of sunlight, which is infinite and does not generate harmful substances, has been energetically studied. What is currently put into practical use as solar energy, which is a clean energy source, includes residential single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide. .

  However, the disadvantages of these inorganic solar cells are that, for example, silicon-based solar cells are required to have a very high purity. Naturally, the purification process is complicated, the number of processes is large, and the production cost is high.

  On the other hand, many solar cells using organic materials have been proposed. As an organic solar cell, a Schottky photoelectric conversion element that joins a p-type organic semiconductor and a metal having a low work function, a p-type organic semiconductor and an n-type inorganic semiconductor, or a p-type organic semiconductor and an electron-accepting organic compound are joined. There are heterojunction photoelectric conversion elements and the like, and organic semiconductors used are synthetic dyes and pigments such as chlorophyll and perylene, conductive polymer materials such as polyacetylene, or composite materials thereof. These are thinned by a vacuum deposition method, a casting method, a dipping method or the like to form a battery material. Although organic materials have advantages such as low cost and easy area enlargement, there are many problems that the conversion efficiency is as low as 1% or less and the durability is poor.

  Under such circumstances, a solar cell exhibiting good characteristics has been reported by Dr. Gretzell of Switzerland (see Non-Patent Document 1). The proposed battery is a dye-sensitized solar cell, which is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. An advantage of this method is that an inexpensive metal semiconductor such as titanium oxide can be used without the need to purify it to a high purity, and thus a solar cell can be produced at a low cost. In addition, the spectral sensitization effect of the dye can effectively convert sunlight with many visible light components into electricity.

  The dye-sensitized solar cell is generally manufactured using a glass substrate. However, the glass substrate has a problem that it is heavy and easily broken. To compensate for these drawbacks, a dye-sensitized solar cell using a resin substrate has been reported (for example, see Patent Document 1). When a resin substrate is used, flexibility can be imparted, so that the degree of freedom of installation form and application is expected to increase. However, since the resin substrate is inferior in heat resistance to the glass substrate, the titanium oxide film cannot be sintered at a high temperature (around 500 ° C.), and the adhesion between the titanium oxide particles and between the titanium oxide and the conductive substrate is low. It becomes worse and the photoelectric conversion efficiency is also greatly reduced compared with the cell using a glass substrate. In addition, it has been pointed out that water is mixed into the electrolyte layer as a deterioration mechanism of the dye-sensitized solar cell. However, since resin substrates generally have poor gas barrier properties (water vapor permeability), they can be used in electrolyte solutions over long periods of use. There is a problem of incurring moisture.

JP 2005-56627 A

B. O'Regan, M.M. Gratzel, Nature, 353, 737 (1991)

  This invention is made | formed in view of the said subject, The objective combines the high photoelectric conversion efficiency and the outstanding durability, and also has the flexible photoelectric conversion element, and the solar cell using this photoelectric conversion element. It is to provide.

  The above object of the present invention is achieved by the following configurations.

  1. Between a pair of opposing flexible films, an inorganic glass film having a thickness of 10 to 70 μm, a transparent conductive layer, a semiconductor layer carrying a sensitizing dye, an electrolyte layer, a conductive layer, and a film having a thickness of 10 to 70 μm A photoelectric conversion element comprising an inorganic glass film disposed in this order.

2. ^{2. The} photoelectric conversion element as described in 1 above, wherein the inorganic glass film has a water vapor permeability measured by a method based on JIS K 7126-1987 of 0.01 g / (m ² · day) or less.

  3. 3. The photoelectric conversion element as described in 1 or 2 above, wherein the semiconductor layer is made of porous titanium oxide adsorbing a sensitizing dye.

  4). A solar cell comprising the photoelectric conversion element according to any one of 1 to 3 above.

  According to the present invention, a photoelectric conversion element having high photoelectric conversion efficiency and excellent durability and having flexibility, and a solar cell using the photoelectric conversion element can be provided.

It is sectional drawing which shows an example of the photoelectric conversion element of this invention.

  As a result of intensive studies, the present inventors have determined that, in a dye-sensitized photoelectric conversion element, an inorganic glass film having a thickness of 10 to 70 μm, a transparent conductive layer, between a pair of opposing flexible films, By placing a semiconductor layer carrying a sensitizing dye, an electrolyte layer, a conductive layer, and an inorganic glass film having a thickness of 10 to 70 μm in this order, it has both high photoelectric conversion efficiency and excellent durability, and has flexibility. It discovered that the solar cell using a photoelectric conversion element and this photoelectric conversion element was obtained.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a cross-sectional view showing an example of the photoelectric conversion element of the present invention.

  As shown in FIG. 1, the photoelectric conversion element of the present invention includes a flexible film 1 and 8, an inorganic glass film 2 and 7 having a thickness of 10 to 70 μm, a transparent conductive layer 3, and a semiconductor carrying a sensitizing dye. It is composed of a layer 4, an electrolyte layer 5 and a conductive layer 6.

  The present invention relates to a preferable film material of a photoelectric conversion element having flexibility.

  In general, a resin film is often used as a flexible substrate. However, since the resin film has low heat resistance, it cannot be heat-treated at a high temperature. For this reason, high-temperature sintering (around 500 ° C.) of the semiconductor film on the substrate cannot be performed, the adhesiveness between the semiconductor particles and between the semiconductor particles and the conductive substrate is deteriorated, and the photoelectric conversion efficiency is also reduced with that of the glass substrate. Compared to the cell used, it drops significantly. It has been found that when a thin inorganic glass film is used as the substrate of the photoelectric conversion element instead of the resin film, a flexible substrate in which the semiconductor particles are strongly sintered can be obtained, and a good electron transfer capability can be expressed.

  Hereinafter, each of the flexible film, the inorganic glass film, the conductive layer and the transparent conductive layer, the semiconductor layer carrying the sensitizing dye, the electrolyte layer, and the conductive layer will be described.

(Flexible film)
The film having flexibility means that when the thickness of the film is x (μm), x ^1/2 × 10 (cm), preferably x ^1/2 × 5 (cm), more preferably x It means that the film does not break or crack even when it is wound around a round bar having a diameter of ^1/2 (cm).

  As such a film, a polyimide film, a polyester film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyamide film, a polycarbonate film, or the like can be used. As thickness, 50-500 micrometers is preferable.

(Inorganic glass film)
The film thickness of the inorganic glass film used in the present invention is 10 to 70 μm. When the film thickness of the inorganic glass exceeds 70 μm, flexibility is lost and breakage and cracks occur.

In addition, since the inorganic glass film is generally excellent in gas barrier properties (water vapor permeability), even when used for a long period of time in a high humidity environment, moisture is not mixed into the electrolytic solution and deterioration can be prevented. In order to obtain sufficient gas barrier properties, the water vapor permeability of the inorganic glass film measured by a method based on JIS K 7126-1987 is preferably 0.01 g / (m ² · day) or less. When the above conditions are satisfied, the thickness of the glass film is generally 10 μm or more.

Examples of the method for producing the inorganic glass used in the present invention include, for example, a method for producing SiO ₂ glass using a known sol-gel method, and after adding a resin to these to form a film, the organic components are burned out by firing. And a method of forming a coating film.

  Production examples of the inorganic glass film used in the present invention will be described below.

(Production Example 1)
As the colloidal silica sol, an aqueous solvent system in which silica fine particles having a particle diameter of 10 to 20 nm were dispersed was used (solid content 20% by mass, pH 2.8). 1.0 g of zirconyl nitrate dihydrate was dissolved in 1.9 g of distilled water. The obtained zirconyl nitrate aqueous solution was mixed with 5.3 g of colloidal silica sol. Separately, polyvinyl alcohol (Kuraray Poval PVA-105, manufactured by Kuraray Co., Ltd.) was dissolved in distilled water as a binder to prepare a 5% by weight polyvinyl alcohol solution. Further, 0.6 g of 2-aminoethanol was dissolved in 1.8 g of water, and 1.8 g of acetic acid was slowly added thereto for neutralization to prepare an aminoethanol solution. 0.1 g of a surfactant and 0.2 g of an aminoethanol solution were added to 6 g of a 5% by weight polyvinyl alcohol solution, and 4.8 g of the zirconyl nitrate-containing silica sol prepared above was added thereto to prepare a mixed solution.

  The mixture was cast on a polyethylene terephthalate (PET) film and dried overnight at room temperature. The dried precursor film was peeled off from the PET film and baked with an electric furnace on an alumina substrate. Firing was slowly heated from room temperature to 500 ° C. over 3 hours for the purpose of debinding. Furthermore, it heated up to 1200 degreeC over 1 hour, and baked over 30 minutes at the temperature. 0.5 g of the obtained film was taken and subjected to carbon analysis with a carbon / sulfur analyzer (EMIA-520, manufactured by Horiba Seisakusho). The result was less than 1 ppm and below the detection limit. Further, the obtained inorganic glass film had a thickness of 50 μm, and no breakage or cracking was observed even when it was wound around a round bar having a diameter of 7 cm.

(Production Example 2)
Dissolve 13.8 ml of dimethyldimethoxysilane, 9.3 ml of phenyltrimethoxysilane, 5.7 ml of tetraethoxysilane, and 0.57 ml of trimethoxyborane in 50 ml of tetrahydroxyfuran (THF). 1.25 ml of hydrochloric acid was added and refluxed for 3 hours. After 3 hours, the temperature of the oil bath was gradually raised, and after reaching 200 ° C., the reaction was continued for another 2 hours to obtain a very viscous syrupy substance. 7 g of this polymer was dissolved in 3 ml of THF, 0.53 ml of triethylamine was added, and the mixture was cast on a fluororesin film. Initially, it was dried in an oven at 120 ° C., gradually raised in temperature, and finally dried at 200 ° C. for 30 minutes. The film was peeled off from the fluororesin film and fixed to the frame, and heat treatment was performed at 300 ° C. for 30 minutes and at 400 ° C. for 30 minutes. 0.5 g of the obtained film was taken and subjected to carbon analysis with a carbon / sulfur analyzer (EMIA-520, manufactured by Horiba Seisakusho). The result was less than 1 ppm and below the detection limit. The obtained inorganic glass film had a thickness of 20 μm, and no breakage or cracking was observed even when it was wound around a round bar having a diameter of 7 cm.

  Moreover, a commercially available ultra-thin plate glass from Matsunami Glass Industry Co., Ltd. can be used.

(Conductive layer and transparent conductive layer)
Examples of materials used for the conductive layer include metals (eg, platinum, gold, silver, copper, aluminum, rhodium, indium, titanium) or conductive metal oxides (eg, indium, tin, zinc, gallium, etc.) And composite oxides of these elements) and carbon. When tin oxide is used, it is preferable to use fluorine-doped one. The conductive layer preferably has a surface resistance of 50 Ω / cm ² or less, and more preferably 10 Ω / cm ² or less.

  The transparent conductive layer refers to a layer that is substantially transparent among the conductive layers, and substantially transparent means that the light transmittance is 10% or more, and is 50% or more. Is more preferable, and 80% or more is most preferable.

The conductive layer, I ₃ ^- is preferably the reduction reaction of oxidation and other redox ions such as ions is a substance having a catalytic ability to perform fast enough. Examples of such a material include a platinum electrode, a conductive material surface subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, carbon, polypyrrole, and the like.

(Semiconductor layer carrying sensitizing dye)
A method for manufacturing a semiconductor layer (4 in FIG. 1) according to the present invention will be described.

  When the semiconductor according to the present invention is produced by firing, it is preferable that the semiconductor sensitization treatment (adsorption, penetration into the porous body, etc.) using the sensitizing dye is performed after the semiconductor is fired. It is particularly preferable to perform the sensitizing dye adsorption treatment quickly after the firing and before the water is adsorbed to the semiconductor.

  When the semiconductor according to the present invention is in the form of particles, the semiconductor is preferably manufactured by applying or spraying the semiconductor on the conductive layer. In the case where the semiconductor is in a film form and is not held on the conductive layer, the semiconductor is preferably bonded to the conductive layer.

  In the photoelectric conversion element of the present invention, as the semiconductor, a compound having a Group 3 to Group 5, Group 13 to Group 15 element of a periodic table (also referred to as an element periodic table), a metal chalcogenide (for example, Oxides, sulfides, selenides, etc.), metal nitrides, etc. can be used.

  Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides, cadmium, zinc, lead, silver, antimony or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Examples of other semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, copper-indium sulfides, and titanium nitrides.

Specific examples include TiO ₂ , ZrO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S ₃ , CdSe, CdTe, GaP. , InP, GaAs, CuInS ₂ , CuInSe ₂ , Ti ₃ N _{4 and the} like, but TiO ₂ , ZnO, SnO ₂ , Fe ₂ O ₃ , WO ₃ , Nb ₂ O ₅ , CdS, etc. are preferably used. PbS is more preferably used, and TiO ₂ or SnO ₂ is used. Of these, TiO ₂ is particularly preferably used.

As the semiconductor used for the photoelectrode, a plurality of the above-described semiconductors may be used in combination. For example, several kinds of the above-described metal oxides or metal sulfides can be used in combination, and a titanium oxide semiconductor may be used by mixing 20% by mass of titanium nitride (Ti ₃ N ₄ ). In addition, J.H. Chem. Soc. Chem. Commun. 15 (1999). At this time, when a component is added as a semiconductor in addition to the metal oxide or metal sulfide, the mass ratio of the additional component to the metal oxide or metal sulfide semiconductor is preferably 30% or less.

(Preparation of coating liquid containing semiconductor fine powder)
First, a coating solution containing fine semiconductor powder is prepared. The finer the primary particle diameter of the semiconductor fine powder, the better. The primary particle diameter is preferably 1 to 5000 nm, and more preferably 2 to 50 nm. The coating liquid containing the semiconductor fine powder can be prepared by dispersing the semiconductor fine powder in a solvent. The semiconductor fine powder dispersed in the solvent is dispersed in the form of primary particles. The solvent is not particularly limited as long as it can disperse the semiconductor fine powder.

  Examples of the solvent include water, an organic solvent, and a mixed solution of water and an organic solvent. As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, acetone and acetyl acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. A surfactant and a viscosity modifier (polyhydric alcohol such as polyethylene glycol) can be added to the coating solution as necessary. The range of the semiconductor fine powder concentration in the solvent is preferably 0.1 to 70% by mass, and more preferably 0.1 to 30% by mass.

(Application of coating solution containing fine semiconductor powder and baking treatment of the formed semiconductor layer)
The semiconductor fine powder-containing coating solution obtained as described above is applied or sprayed onto a conductive support, dried, etc., and then baked in air or an inert gas to provide a conductive support. A semiconductor layer (semiconductor film) is formed thereon.

  The film obtained by applying and drying the coating liquid on the conductive support is composed of an aggregate of semiconductor fine particles, and the particle size of the fine particles corresponds to the primary particle size of the semiconductor fine powder used. is there.

  Since the semiconductor fine particle aggregate film formed on the substrate such as the conductive support in this way has a low bonding strength with the conductive support or between the fine particles and a low mechanical strength. In order to increase the mechanical strength and to obtain a fired product film firmly adhered to the substrate, the semiconductor fine particle aggregate film is preferably subjected to a firing treatment.

  In the present invention, the fired product film obtained by this firing treatment may have any structure, but is preferably a porous structure film (also referred to as a porous layer having voids).

  Here, the porosity of the semiconductor thin film according to the present invention is preferably 10% by volume or less, more preferably 8% by volume or less, and particularly preferably 0.01 to 5% by volume or less. The porosity of the semiconductor thin film means a porosity that is penetrable in the thickness direction of the dielectric, and can be measured using a commercially available apparatus such as a mercury porosimeter (Shimadzu Polarizer 9220 type).

  As for the film thickness of the semiconductor layer used as the baked material film | membrane which has a porous structure, 10 nm or more is preferable, More preferably, it is 100-10000 nm.

  From the viewpoint of appropriately preparing the actual surface area of the fired product film during the firing treatment and obtaining a fired product film having the above porosity, the firing temperature is preferably lower than 1000 ° C, more preferably in the range of 200 to 800 ° C. Especially preferably, it is the range of 300-800 degreeC.

  The ratio of the actual surface area to the apparent surface area can be controlled by the particle size, specific surface area, firing temperature, etc. of the semiconductor fine particles. In addition, for example, an aqueous titanium tetrachloride solution is used for the purpose of increasing the surface area of the semiconductor particles after the heat treatment, increasing the purity in the vicinity of the semiconductor particles, and increasing the efficiency of electron injection from the sensitizing dye to the semiconductor particles. Chemical plating or electrochemical plating using a titanium trichloride aqueous solution may be performed.

(Sensitizing dye)
In the present invention, a sensitizing dye is supported on the semiconductor layer. From the viewpoint of efficient injection of charges into the semiconductor thin film, the sensitizing dye preferably has a carboxyl group. Although the specific example of a sensitizing dye is shown below, this invention is not limited to these.

(Semiconductor sensitization treatment)
The semiconductor sensitization treatment is performed by dissolving the sensitizing dye in an appropriate solvent as described above, and immersing the substrate on which the semiconductor is baked and fixed in the solution. In that case, a semiconductor layer (also referred to as a semiconductor film) is formed by baking, the substrate is preliminarily decompressed or heated to remove bubbles in the film, and the sensitizing dye is deep inside the semiconductor layer (semiconductor film). It is preferable to allow entry, and it is particularly preferable when the semiconductor layer (semiconductor film) is a porous structure film.

  The solvent used for dissolving the sensitizing dye is not particularly limited as long as it can dissolve and does not dissolve the semiconductor or react with the semiconductor, but is dissolved in the solvent. In order to prevent moisture and gas from entering the semiconductor film and hindering the sensitizing treatment such as adsorption of the sensitizing dye, it is preferable to degas and purify in advance.

  Solvents preferably used include alcohol solvents such as methanol, ethanol, n-propanol, and t-butyl alcohol, ketone solvents such as acetone and methyl ethyl ketone, and ether solvents such as diethyl ether, diisopropyl ether, tetrahydrofuran, and 1,4-dioxane. Solvents, nitrile solvents such as acetonitrile and propionitrile, halogenated hydrocarbon solvents such as methylene chloride and 1,1,2-trichloroethane, and mixed solvents may be used. Particularly preferred are ethanol, t-butyl alcohol and acetonitrile.

  The time for immersing the substrate on which the semiconductor has been baked in the solution containing the sensitizing dye is sufficient to cause the sensitizing dye to enter the semiconductor layer (semiconductor film) deeply so that the adsorption proceeds sufficiently and the semiconductor is sufficiently sensitized. In addition, from the viewpoint of suppressing degradation products generated by decomposition of the sensitizing dye in the solution from interfering with the adsorption of the sensitizing dye, 1 to 48 hours are preferable at 25 ° C., more preferably 3 to 24 hours. It is. This temperature and time are particularly preferred when the semiconductor film is a porous structure film. However, the immersion time is a value at 25 ° C., and this is not the case when the temperature condition is changed.

  In soaking, the solution containing the sensitizing dye may be heated to a temperature that does not boil as long as the sensitizing dye does not decompose. A preferable temperature range is 10 to 100 ° C., more preferably 25 to 80 ° C., but this is not the case when the solvent boils in the temperature range as described above.

  When the sensitizing treatment is performed using a sensitizing dye, the sensitizing dye may be used alone or a plurality thereof may be used in combination.

  Moreover, the sensitizing dye which has a carboxyl group preferable for the present invention and other sensitizing dyes can be used in combination. As the sensitizing dye that can be used in combination, any sensitizing dye that can spectrally sensitize the semiconductor layer according to the present invention can be used. It is preferable to mix two or more types of sensitizing dyes in order to make the wavelength range of photoelectric conversion as wide as possible and increase the photoelectric conversion efficiency. Further, it is possible to select the sensitizing dye to be mixed and its ratio so as to match the wavelength range and intensity distribution of the target light source.

  In particular, when the use of the photoelectric conversion element of the present invention is a solar cell to be described later, two or more types of absorption having different absorption wavelengths are used so that the wavelength range of photoelectric conversion can be made as wide as possible to effectively use sunlight. It is preferable to use a mixture of dyes.

  Among the sensitizing dyes used in combination, metal complex dyes, phthalocyanine dyes, porphyrin dyes, and polymethine dyes are preferably used from the comprehensive viewpoints such as photoelectron transfer reaction activity, light durability, and photochemical stability. It is done.

  Examples of the sensitizing dye that can be used in combination with the sensitizing dye having a carboxyl group preferable in the present invention include, for example, U.S. Pat. Nos. 4,684,537 and 4,927,721. 5,084,365, 5,350,644, 5,463,057, 5,525,440, JP-A-7-249790, JP2000 And sensitizing dyes described in JP-A-15-150007.

  In order to include a sensitizing dye in the semiconductor layer, a method in which the sensitizing dye is dissolved in an appropriate solvent (ethanol or the like) and a well-dried semiconductor is immersed in the solution for a long time is generally used.

  When a sensitizing dye is used in combination with a plurality of sensitizing dyes or in combination with a sensitizing dye other than the sensitizing dye having a carboxyl group preferable for the present invention, a mixed solution of each sensitizing dye May be prepared and used, or a solution may be prepared for each sensitizing dye and immersed in each solution in order. When preparing a separate solution for each sensitizing dye and immersing in each solution in order, the effects described in the present invention can be obtained regardless of the order in which the sensitizing dye is included in the semiconductor layer. Can be obtained. Alternatively, it may be produced by mixing semiconductor fine particles on which a sensitizing dye is adsorbed alone.

  The adsorption treatment may be performed when the semiconductor layer is in the form of particles, or may be performed after the film is formed on the support. A solution in which the compound used for the adsorption treatment is dissolved may be used at room temperature, or may be used by heating in a temperature range in which the compound does not decompose and the solution does not boil. Moreover, you may implement the said sensitizing dye adsorption | suction after application | coating of semiconductor fine particle like manufacture of the photoelectric conversion element mentioned later. Alternatively, the sensitizing dye may be adsorbed by simultaneously applying the semiconductor fine particles and the sensitizing dye. Unadsorbed sensitizing dye can be removed by washing.

  Further, the sensitization treatment of the semiconductor layer according to the present invention is performed by the semiconductor containing the sensitizing dye. The details of the sensitization treatment are specifically described in the photoelectric conversion element described later. explain.

  In the case of a semiconductor layer having a semiconductor thin film with a high porosity, before the water is adsorbed on the semiconductor thin film and in the voids inside the semiconductor thin film by moisture, water vapor, etc., the sensitizing dye adsorption treatment ( It is preferable to complete the sensitization treatment of the semiconductor layer.

(Electrolyte layer)
The electrolyte layer (also referred to as charge transfer layer) used in the present invention will be described.

A redox electrolyte is preferably used for the electrolyte layer. Here, examples of the redox electrolyte include I ⁻ / I ₃ ⁻ system, Br ⁻ / Br ₃ ⁻ system, and quinone / hydroquinone system. Such redox electrolyte can be obtained by a conventionally known method, for example, I ^- / I ₃ ^- system electrolyte can be obtained by mixing an ammonium salt of iodine and iodine. The electrolyte layer is composed of dispersions of these redox electrolytes. These dispersions are dispersed in liquid electrolytes when they are solutions, solid polymer electrolytes and gel substances when dispersed in polymers that are solid at room temperature. It is called a gel electrolyte. When a liquid electrolyte is used as the electrolyte layer, an electrochemically inert solvent is used as the solvent, for example, acetonitrile, propylene carbonate, ethylene carbonate, or the like is used. Examples of the solid polymer electrolyte include those described in JP-A No. 2001-160427, and examples of the gel electrolyte include those described in “Surface Science” Vol. 21, No. 5, pages 288 to 293.

(Solar cell)
The solar cell of the present invention will be described.

  The solar cell of the present invention has a structure in which the optimum design and circuit design for sunlight are performed as one aspect of the photoelectric conversion element of the present invention, and the optimum photoelectric conversion is performed when sunlight is used as a light source. . That is, the semiconductor is dye-sensitized and can be irradiated with sunlight.

  When the solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, the sensitizing dye adsorbed on the semiconductor is excited by absorbing the irradiated light or electromagnetic wave. Electrons generated by excitation move to the semiconductor, and then move to the counter electrode via the conductive support to reduce the redox electrolyte in the charge transfer layer. On the other hand, the sensitizing dye that has moved electrons to the semiconductor is an oxidant, but is reduced to the original state by supplying electrons from the counter electrode via the redox electrolyte of the charge transfer layer. At the same time, the redox electrolyte of the charge transfer layer is oxidized and returns to a state where it can be reduced again by electrons supplied from the counter electrode. In this way, electrons flow, and a solar cell using the photoelectric conversion element of the present invention can be configured.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example (Production of Photoelectric Conversion Element 1)
The inorganic glass film of Production Example 1 having a thickness of 30 μm was used as the inorganic glass film. An FTO (fluorine-doped tin oxide) thin film was provided on one surface of this inorganic glass film by a spray pyrolysis method to obtain a transparent conductive film having a sheet resistance of 10Ω / □ to be a transparent conductive layer. Even when this inorganic glass film was wound around a round bar having a diameter of 5 cm, no breakage or cracks were observed, and the water vapor permeability was 0.01 g / m ² / day or less. On this FTO thin film, a commercially available titanium oxide paste for low-temperature firing (a dispersion of titanium oxide particles having a particle diameter of 18 nm in an organic solvent) was applied by a screen printing method (application area 5 × 5 mm ² ). After drying at 120 ° C. for 3 minutes, baking was carried out at 200 ° C. for 10 minutes and at 500 ° C. for 15 minutes to obtain a titanium oxide thin film having a thickness of 2.5 μm. Overlaid on this thin film, a commercially available titanium oxide paste (particle size 400 nm) was applied in the same manner and a titanium oxide thin film having a thickness of 2.5 μm was overcoated, followed by the same baking treatment to obtain a semiconductor layer. It was.

The following sensitizing dye (1) and 2 equivalents of chenodeoxycholic acid with respect to the sensitizing dye are dissolved in a mixed solvent of acetonitrile: t-butyl alcohol = 1: 1, and the sensitizing dye concentration is 5 × 10 ⁻⁴ mol / l. A solution was prepared. The inorganic glass film substrate carrying the semiconductor layer was immersed in this solution at room temperature for 3 hours, and the sensitizing dye was adsorbed to obtain a semiconductor layer carrying the sensitizing dye.

  As an electrolytic solution used in the electrolyte layer, 1-butyl-3-methylimidazolium iodide 0.6 mol / l, lithium iodide 0.1 mol / l, iodine 0.05 mol / l, 4- (t-butyl) ) A 3-methoxypropionitrile solution containing 0.05 mol / l of pyridine was used.

  Separately, an inorganic glass film substrate provided with an FTO thin film was prepared, and a platinum thin film (thickness 40 nm) was deposited on the conductive surface side by sputtering. These two inorganic glass film substrates were opposed to each other so that the conductive surface side was inside, and were bonded together using a silica / alumina inorganic adhesive. After injecting the electrolytic solution from the gap between the adhesives, the two inorganic glass film substrates were bonded by thermosetting at 100 ° C. for 30 minutes. One separator of the acrylic transparent adhesive having a thickness of 20 μm sandwiched between the double-sided separators was peeled off, and the exposed adhesive surface was adhered to one side of a polyethylene terephthalate film having a thickness of 40 μm using a rubber roller. Two single-sided adhesive films were prepared, and the photoelectric conversion element 1 was produced by sticking on both surfaces of the element produced previously using the rubber roller.

(Preparation of photoelectric conversion elements 2 and 3)
Photoelectric conversion elements 2 and 3 were produced in the same manner as the photoelectric conversion element 1 except that the thickness of the inorganic glass film was changed to 70 μm and 10 μm.

(Preparation of photoelectric conversion element 4)
A commercially available titanium oxide paste for low-temperature firing (dispersion of titanium oxide particles with a particle size of 18 nm in an organic solvent) is applied to a polyethylene terephthalate (PET) resin film substrate coated with an indium tin oxide (ITO) conductive film ( The coating area was 5 × 5 mm ² ). Heat drying was performed at 150 ° C. for 5 minutes to obtain a titanium oxide thin film having a thickness of 2.5 μm. This film substrate was immersed in a 0.1 mol / l titanium tetrachloride aqueous solution at 70 ° C. for 30 minutes, sufficiently washed with water, and then again dried by heating at 150 ° C. for 5 minutes. The resin film substrate was subjected to sensitizing dye adsorption treatment in the same manner as the photoelectric conversion element 1. A platinum sputtering treatment was performed on the resin film substrate in the same manner as the photoelectric conversion element 1.

  The photoelectric conversion element 4 was produced by producing and injecting an electrolytic solution in the same manner as the photoelectric conversion element 1 and bonding the two resin film substrates produced previously with an ultraviolet curable resin film.

(Preparation of photoelectric conversion element 5)
A photoelectric conversion element 5 was produced in the same manner as the photoelectric conversion element 1 except that a commercially available glass plate with an FTO conductive film (sheet resistance 10 Ω / □, thickness 1.1 mm) was used instead of the inorganic glass film.

(Preparation of photoelectric conversion element 6)
A photoelectric conversion element 6 was produced in the same manner as the photoelectric conversion element 1 except that one side of the inorganic glass film (the side opposite to the semiconductor layer, 7 in FIG. 1) was replaced with a PET resin film substrate coated with an ITO conductive film.

(Preparation of photoelectric conversion element 7)
A photoelectric conversion element 7 was produced in the same manner as the photoelectric conversion element 1 except that the inorganic glass film was changed to a thickness of 5 μm.

(Evaluation of photoelectric conversion element)
The following evaluation was performed about each obtained photoelectric conversion element.

The produced photoelectric conversion element was irradiated by irradiating 100 mW / cm ² of pseudo-sunlight from a xenon lamp through an AM filter (AM-1.5) using a solar simulator (manufactured by Eiko Seiki). Photoelectric conversion characteristics were measured under conditions where a 5 × 5 mm ² mask was put on the semiconductor layer. That is, current-voltage characteristics are measured at room temperature using an IV tester to determine a short circuit current (Jsc), an open circuit voltage (Voc), and a form factor (FF), and from these, the photoelectric conversion efficiency (η (% )). The photoelectric conversion efficiency (η (%)) of the photoelectric conversion element was calculated based on the following formula (A).

Formula (A) η = 100 × (Voc × Jsc × FF) / P
Here, P is an incident light intensity [mW · cm ⁻² ], Voc is an open circuit voltage [V], Jsc is a short circuit current density [mA · cm ⁻² ], and FF is a form factor.

  In addition to the initial photoelectric conversion efficiency immediately after production of the photoelectric conversion element, after each photoelectric conversion element is wound on a round bar having a diameter of 7 cm for 10 minutes, or after standing for 10 days under conditions of a temperature of 30 ° C. and a humidity of 90%. The photoelectric conversion efficiency was measured and compared. The water vapor permeability of each film was measured by a method based on JIS K 7126-1987.

  The evaluation results are shown in Table 1.

  From the table, the photoelectric conversion efficiency of the photoelectric conversion elements 1 to 3 of the present invention using a flexible substrate made of a heat-resistant inorganic glass film was a resin film substrate having flexibility but not heat resistance. It was higher than the comparative photoelectric conversion element 4 and showed a photoelectric conversion efficiency comparable to that of the comparative photoelectric conversion element 5 using a non-flexible glass substrate. In the comparative photoelectric conversion element 4, since the heat resistance of the PET resin film substrate was low, only heat treatment at 150 ° C. was possible, whereas the adhesion between the titanium oxide fine particles and between the titanium oxide fine particles and the transparent conductive layer was insufficient. In the photoelectric conversion elements 1 to 3 of the present invention, the baking treatment can be performed at 500 ° C., which can be explained by the fact that the above-described adhesiveness is greatly improved.

  Moreover, when comparing the photoelectric conversion efficiency after standing for 10 days in a high humidity condition (90%), the photoelectric conversion elements 1 to 3 of the present invention have a lower photoelectric conversion efficiency than the comparative photoelectric conversion elements 4 and 6. The degree is small, which reflects that the gas barrier property of the inorganic glass substrate is superior to that of the resin substrate. On the other hand, in the comparative photoelectric conversion element 7 having a thin film thickness of the inorganic glass film of 5 μm, sufficient gas barrier properties were not obtained.

  The photoelectric conversion element of the present invention can provide a flexible solar cell having both high photoelectric conversion efficiency and excellent durability.

DESCRIPTION OF SYMBOLS 1, 8 Film which has flexibility 2, 7 Inorganic glass film with a film thickness of 10-70 micrometers 3 Transparent conductive layer 4 Semiconductor layer which carried the sensitizing dye 5 Electrolyte layer 6 Conductive layer

Claims (4)

  Between a pair of opposing flexible films, an inorganic glass film having a thickness of 10 to 70 μm, a transparent conductive layer, a semiconductor layer carrying a sensitizing dye, an electrolyte layer, a conductive layer, and a film having a thickness of 10 to 70 μm A photoelectric conversion element comprising an inorganic glass film disposed in this order. ^{2. The} photoelectric conversion element according to claim 1, wherein the inorganic glass film has a water vapor permeability of 0.01 g / (m ² · day) or less as measured by a method based on JIS K 7126-1987.   The photoelectric conversion element according to claim 1, wherein the semiconductor layer is made of porous titanium oxide adsorbing a sensitizing dye.   It has a photoelectric conversion element of any one of Claims 1-3, The solar cell characterized by the above-mentioned.

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