JP5445121B2 - Dye-sensitized solar cell, electrolyte layer forming liquid, and solar cell module - Google Patents

Description

  The present invention relates to a dye-sensitized solar cell, a liquid used for forming an electrolyte layer in the dye-sensitized solar cell, and a dye-sensitized solar cell module formed by connecting two or more solar cells. .

  In recent years, global warming caused by carbon dioxide has become a global problem. In recent years, active research and development of solar cells using solar energy has been promoted as an environmentally friendly and clean energy source. . Among them, a dye-sensitized solar cell has attracted attention as a solar cell having relatively high photoelectric conversion efficiency and low cost.

  A dye-sensitized solar cell includes, for example, a conductive substrate, a porous semiconductor layer including metal oxide fine particles carrying a sensitizing dye, an electrolyte layer including a redox couple, and a counter electrode from the light incident side. Are arranged in order.

  Here, in the conventional dye-sensitized solar cell, an organic solvent is often used as a solvent for the redox couple of the electrolyte layer. However, in an electrolyte layer in which an organic solvent is used, there may be a problem of performance degradation due to evaporation of the liquid.

  Therefore, it has been proposed to employ an ionic liquid, which is a relatively stable substance at room temperature, as a solvent for the redox couple of the electrolyte layer. However, since the electrolyte layer using only the ionic liquid has high fluidity, even if the electrolyte layer is sealed with a sealant or the like, liquid leakage from the electrolyte layer occurs due to deterioration or damage of the sealant or the like. There was a problem that there was a fear that durability was insufficient.

  To solve the above problem, for example, in Patent Document 1, the electrolyte layer in which an ionic liquid is used as a solvent for the redox couple of the electrolyte layer, the first compound having three or more isocyanate groups and the active hydrogen are required. A technique of adding a second compound having two or more nucleus groups to form a gel electrolyte is disclosed. However, when a curing agent is added to the electrolyte layer as in the technique disclosed in Patent Document 1, unreacted or insufficiently reacted low molecular weight substances remain, which may impair power generation characteristics.

JP 2003-303630 A

  Therefore, a substance capable of stably holding the ionic liquid without using a curing agent is contained in the electrolyte layer, and the fluidity of the electrolyte layer in which the ionic liquid is used as a solvent for the redox couple may be reduced. desired.

  However, in general, when a substance that does not contribute to power generation is included in the electrolyte layer, the substance tends to inhibit the function of the redox couple and tend to cause a decrease in power generation characteristics of the dye-sensitized solar cell. Absent. On the other hand, when a substance that does not contribute to power generation is included in the electrolyte layer, by selecting a substance that has a relatively small adverse effect on the function of the redox couple, the degradation of power generation characteristics is suppressed as much as possible, and high power generation characteristics It can be said that expression is important.

  However, it is difficult to predict a substance that can stably hold the ionic liquid and has a small adverse effect on the function of the redox couple.

  This invention is made | formed in view of said situation, and makes it a subject to provide the dye-sensitized solar cell and the dye-sensitized solar cell module which were excellent in durability and electric power generation characteristic. It is another object of the present invention to provide a liquid for forming such an electrolyte layer.

  As a result of intensive studies based on the above problems, the present inventor has found that the styrene-butadiene rubber can stably hold the ionic liquid and has a small adverse effect on the function of the redox couple. It was found that the inclusion of rubber in the electrolyte layer can lower the fluidity of the electrolyte layer, while the power generation characteristics are not significantly reduced, thereby completing the present invention.

  That is, the gist of the present invention is as follows.

  According to a first aspect of the present invention, there is provided a conductive substrate, a porous semiconductor layer disposed on the conductive substrate and including metal oxide fine particles carrying a sensitizing dye, and facing the porous semiconductor layer. A dye-sensitized solar cell including a counter electrode disposed and an electrolyte layer disposed between the porous semiconductor layer and the counter electrode and including an oxidation-reduction pair, an ionic liquid, and styrene-butadiene rubber. is there.

  A second invention is an electrolyte layer forming solution for a dye-sensitized solar cell, and is an electrolyte layer forming solution containing a redox couple, an ionic liquid, and a styrene-butadiene rubber.

  A third invention is a dye-sensitized solar cell module formed by connecting two or more dye-sensitized solar cells of the first invention in series or in parallel.

  According to the present invention, a dye-sensitized solar cell and a dye-sensitized solar cell module excellent in durability and power generation characteristics can be obtained. Moreover, the liquid for forming such an electrolyte layer can be obtained.

It is sectional drawing which shows one Embodiment of the dye-sensitized solar cell of this invention.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a cross-sectional view showing one embodiment of the dye-sensitized solar cell of the present invention. This dye-sensitized solar cell 1 includes a conductive substrate 10, a porous semiconductor layer 20 disposed on the conductive substrate 10 and having metal oxide fine particles carrying a sensitizing dye, and a porous semiconductor. The counter electrode 40 is disposed to face the layer 20, and the electrolyte layer 30 is disposed between the porous semiconductor layer 20 and the counter electrode 40. The electrolyte layer 30 includes at least a redox couple, an ionic liquid, and a styrene-butadiene rubber. Note that at least one of the conductive substrate 10 and the counter electrode 40 is light transmissive with respect to the excitation wavelength of the sensitizing dye.

  As a power generation mechanism of the dye-sensitized solar cell, first, sunlight incident from the conductive base material 10 side and / or the counter electrode 40 side having light permeability is used as the metal oxide fine particles of the porous semiconductor layer 20. Excites the sensitizing dye supported on the substrate. The excited electrons are conducted to the conductive substrate 10 and the counter electrode 40 through the metal oxide fine particles. Thereafter, the electrons return to the ground level of the sensitizing dye through the oxidation-reduction pair of the electrolyte layer 30, whereby the dye-sensitized solar cell 1 generates power.

  Hereinafter, the dye-sensitized solar cell of the present invention will be described in detail.

(Conductive substrate) The conductive substrate is a substrate having at least one surface having conductivity. A porous semiconductor layer, an electrolyte layer, and a counter electrode, which will be described later, are disposed above the conductive surface of the conductive substrate. As the conductive substrate, for example, a metal substrate can be used, or a conductive substrate formed on an insulating substrate such as a glass substrate or a resin substrate, or a glass substrate. A material obtained by bonding a metal base material to an insulating base material such as a material or a resin base material can be used. Specifically, as a metal, titanium (Ti), chromium (Cr), tungsten (W), molybdenum (Mo), silver (Ag), platinum (Pt), tantalum (Ta), niobium (Nb), zirconium ( Zr), zinc (Zn), nickel (Ni), copper (Cu), aluminum (Al), iron (Fe) and other simple substances, alloys of the metals such as stainless steel, and other metals to the metal Since it is easy to obtain and low cost, it is preferable to use titanium (Ti), chromium (Cr), aluminum (Al), or stainless steel. Examples of the glass include those containing silicate or borate as a main component. Examples of the resin include an ethylene-tetrafluoroethylene copolymer, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate, polyether sulfone, polyether ether ketone, polyether imide, and polyimide. In addition, an electroconductive base material may be used independently and may laminate | stack and use 2 or more types of different base materials.

  The conductive substrate may be transparent or opaque. However, when the conductive substrate is located on the light receiving surface side, the conductive substrate needs to have optical transparency with respect to the excitation wavelength of the sensitizing dye. The substrate excellent in light transmittance can be appropriately selected from a glass substrate, a resin substrate, and the like.

The conductive substrate preferably has flexibility. Since a flexible conductive substrate is difficult to break, by pressing the porous semiconductor layer placed on the conductive substrate, the metal oxide fine particles can be pressed between metal oxide particles or between the conductive substrate and the metal oxide. This is because the adhesion between the fine particles can be improved and the power generation characteristics of the dye-sensitized solar cell can be improved. Moreover, it is because the dye-sensitized solar cell which has flexibility can be expand | deployed for various uses. The substrate having flexibility can be appropriately selected from a metal substrate, a glass substrate, a resin substrate and the like having a relatively small thickness. In addition, the presence or absence of flexibility is determined by whether the bending is performed when a force of 5 × 10 ³ N is applied by performing a fine ceramic bending test method of JIS R1601 or a metal material bending test method of JISZ2248 depending on the material to be used. Can be judged.

  The conductive substrate preferably has high heat resistance. Conductive substrate with high heat resistance is fired at a high temperature to improve adhesion between metal oxide fine particles or between conductive substrate and metal oxide fine particles, and dye sensitization The power generation characteristics of the solar cell can be improved. The substrate having heat resistance can be appropriately selected from a glass substrate, a metal substrate and the like.

  The thickness of the conductive substrate can be appropriately selected according to the degree of flexibility required for the conductive substrate, the use of the dye-sensitized solar cell, and the like, but is usually within a range of 5 μm to 2000 μm. It is preferable that it is within a range of 10 μm to 500 μm, and more preferably within a range of 20 μm to 200 μm.

The material of the conductive layer formed on the insulating substrate is not particularly limited as long as it has excellent conductivity, but the conductive layer located on the light receiving surface side has excellent light transmittance. It is preferable that As a material excellent in light transmittance, for example, tin oxide (SnO ₂ ), indium tin oxide (hereinafter referred to as “ITO”), and fluorine-doped tin oxide (hereinafter referred to as “FTO”) are described. ), Zinc oxide (ZnO), indium zinc oxide (hereinafter referred to as “IZO”), and the like. Among these, FTO and ITO are particularly preferably used because they are excellent in both conductivity and light transmittance. The thickness of the conductive layer is in the range of 0.1 nm to 500 nm, preferably in the range of 1 nm to 300 nm.

  A method for forming such a conductive layer is not particularly limited, and examples thereof include a vapor deposition method, a sputtering method, and a CVD method. Among these, the sputtering method is preferably used.

(Porous semiconductor layer) The porous semiconductor layer contains metal oxide fine particles carrying a sensitizing dye and has a function of conducting charges generated from the sensitizing dye by light irradiation.

(Metal oxide fine particles) The metal oxide fine particles are not particularly limited as long as they can conduct electrons generated from the sensitizing dye to the conductive substrate. Specifically, titanium oxide (TiO ₂ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), ITO, zirconium oxide (ZrO ₂ ), silicon oxide (SiO ₂ ), magnesium oxide (MgO), aluminum oxide ( Al ₂ O ₃ ), selenium oxide (CeO ₂ ), bismuth oxide (Bi ₂ O ₃ ), manganese oxide (Mn ₃ O ₄ ), yttrium oxide (Y ₂ O ₃ ), tungsten oxide (WO ₃ ), tantalum oxide ( Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), and the like. Any one kind of these metal oxide fine particles may be used, or two or more kinds may be mixed and used. Among these, TiO ₂ can be preferably used.

  The average particle diameter of the metal oxide fine particles is preferably in the range of 1 nm to 10 μm, particularly preferably in the range of 10 nm to 500 nm. Further, metal oxide fine particles having different average particle diameters may be mixed and used. The average particle size of the metal oxide semiconductor fine particles means the primary particle size.

  The content of the metal oxide fine particles in the porous semiconductor layer is preferably in the range of 40% by weight to 99.9% by weight, and more preferably in the range of 85% by weight to 99.5% by weight.

  A resin can be added as a binder for the metal oxide fine particles. As such a resin, for example, a cellulose resin can be used.

(Sensitizing dye) The sensitizing dye is not particularly limited as long as it can absorb light and generate an electromotive force. Specifically, an organic dye or a metal complex dye can be used. For example, examples of organic dyes include acridine dyes, azo dyes, indigo dyes, quinone dyes, coumarin dyes, merocyanine dyes, phenylxanthene dyes, indoline dyes, squalium dyes, and carbazole dyes. In particular, indoline dyes and carbazole dyes are preferably used. As the metal complex dye, a ruthenium dye, particularly a ruthenium bipyridine dye and a ruthenium terpyridine dye are preferably used. By carrying such a sensitizing dye on the metal oxide fine particles, it is possible to efficiently take in the visible light range and cause photoelectric conversion.

(Method for forming porous semiconductor layer) As a general method for forming a porous semiconductor layer, for example, a layer containing metal oxide semiconductor fine particles is formed on a conductive substrate, and then a sensitizing dye is subjected to metal oxidation. The method of making it support on a product fine particle can be mentioned.

  The method for forming the layer containing metal oxide fine particles on the conductive substrate is not particularly limited, but is preferably formed by a coating method. In the coating method, for example, a coating liquid is prepared by dispersing metal oxide fine particles in a solvent using a known disperser, and the coating liquid containing the metal oxide fine particles is conductive using a known coating method. A layer containing metal oxide fine particles is formed by coating on a conductive substrate and drying. By repeating the application and drying a single time or a plurality of times of application and drying, the layer containing the metal oxide fine particles can be adjusted and formed to have a desired film thickness.

  It is preferable that the layer containing the metal oxide fine particles is fired after the coating liquid containing the metal oxide fine particles is applied and dried. Thereby, since the adhesiveness between metal oxide microparticles | fine-particles increases, the electrical conductivity of a charge can be improved. Moreover, the adhesiveness between a conductive base material and metal oxide fine particles can also be improved. The firing temperature and time vary depending on the thickness of the layer and are not limited, but are generally about 300 to 700 ° C. for about 5 to 120 minutes. However, when the conductive substrate is composed of a resin substrate, it is preferable to perform firing at a temperature lower than the heat resistant temperature of the resin substrate.

  Examples of the method of supporting the sensitizing dye on the metal oxide fine particles include, for example, a method in which a layer containing metal oxide fine particles is immersed in a solution of the sensitizing dye and then drying, or a solution of the sensitizing dye in the metal oxide Examples thereof include a method in which a known coating method is applied to a layer containing fine particles and the solution is allowed to penetrate and then dried. The solvent used in the sensitizing dye solution can be appropriately selected from known solvents according to the type of the sensitizing dye to be used.

  The film thickness of the porous semiconductor layer is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 5 μm to 30 μm. This is because the film resistance of the porous semiconductor layer can be reduced within the above range, and light absorption by the porous semiconductor layer is sufficiently performed.

(Counter electrode) As the counter electrode, a conductive substrate can be used. The conductive substrate of the counter electrode is a substrate on which at least one surface has conductivity. The conductive substrate on which the above-described electrolyte layer, porous semiconductor layer, and porous semiconductor layer are disposed is disposed above the conductive surface of the conductive substrate of the counter electrode. As the conductive substrate of the counter electrode, for example, a metal substrate can be used, or a conductive layer is formed on an insulating substrate such as a glass substrate or a resin substrate, or A material obtained by bonding a metal substrate on an insulating substrate such as a glass substrate or a resin substrate can be used. Specifically, as a metal, titanium (Ti), chromium (Cr), tungsten (W), molybdenum (Mo), silver (Ag), platinum (Pt), tantalum (Ta), niobium (Nb), zirconium ( Zr), zinc (Zn), nickel (Ni), copper (Cu), aluminum (Al), iron (Fe) and other simple substances, alloys of the metals such as stainless steel, and other metals to the metal Since it is easy to obtain and low cost, it is preferable to use titanium (Ti), chromium (Cr), aluminum (Al), or stainless steel. Examples of the glass include those containing silicate or borate as a main component. Examples of the resin include an ethylene-tetrafluoroethylene copolymer, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate, polyether sulfone, polyether ether ketone, polyether imide, and polyimide. In addition, the electroconductive base material of a counter electrode may be used independently, and may laminate | stack and use 2 or more types of different base materials.

  The counter electrode may be transparent or opaque. However, when the counter electrode is located on the light receiving surface side, the counter electrode needs to have light transmittance with respect to the excitation wavelength of the sensitizing dye. As a base material excellent in light transmittance, a glass base material or a resin base material can be appropriately selected. Moreover, when the electroconductive base material with which a porous semiconductor layer is arrange | positioned has flexibility, it is preferable that a counter electrode also has flexibility. The substrate having excellent flexibility can be appropriately selected from a metal substrate, a glass substrate, a resin substrate and the like having a relatively small thickness.

  The thickness of the counter electrode can be appropriately selected according to the degree of flexibility required for the counter electrode, the use of the dye-sensitized solar cell, and the like, but is usually preferably in the range of 5 μm to 2000 μm. In particular, it is preferably in the range of 10 μm to 500 μm, and more preferably in the range of 20 μm to 200 μm.

The material of the conductive layer formed on the insulating substrate is not particularly limited as long as it has excellent conductivity, but the conductive layer located on the light receiving surface side has excellent light transmittance. It is preferable that Examples of the material excellent in light transmittance include tin oxide (SnO ₂ ), ITO, FTO, zinc oxide (ZnO), and IZO. Among these, FTO and ITO are particularly preferably used because they are excellent in both conductivity and light transmittance. The thickness of the conductive layer is in the range of 0.1 nm to 500 nm, preferably in the range of 1 nm to 300 nm.

  A method for forming such a conductive layer is not particularly limited, and examples thereof include a vapor deposition method, a sputtering method, and a CVD method. Among these, the sputtering method is preferably used.

  By further forming a catalyst layer on the metal substrate or conductive layer of the counter electrode, the power generation efficiency of the dye-sensitized solar cell can be further improved. Examples of the catalyst layer include a layer deposited with Pt and a catalyst layer containing a conductive polymer such as polyaniline, polythiophene, or polypyrrole, but are not limited thereto.

(Electrolyte layer) The electrolyte layer is disposed between the porous semiconductor layer and the counter electrode, and contains at least a redox couple, an ionic liquid, and styrene-butadiene rubber.

(Redox pair) The redox pair can be appropriately selected from those generally used in the electrolyte layer of a dye-sensitized solar cell. Specifically, a redox couple of iodine and a redox couple of bromine are preferably used. As an oxidation-reduction pair of iodine, a combination of iodine and iodide such as lithium iodide, sodium iodide, potassium iodide, calcium iodide, TPAI (tetrapropylammonium iodide), and an iodide ionic liquid described later Can be mentioned. Examples of the redox pair of bromine include combinations of bromine and bromides such as lithium bromide, sodium bromide, potassium bromide, and calcium bromide.

  The concentration of the redox couple in the electrolyte layer varies depending on the type of the redox couple and is not particularly limited. However, when using the redox couple of iodine or bromine, iodine or bromine is 0.001 mol / l to 0. 5 mol / l, iodide or bromide is preferably 0.1 mol / l to 5 mol / l, and generally set so that the molar ratio of iodine or bromine to iodide or bromide is about 1:10. It is preferable to do.

(Ionic liquid) The electrolyte layer contains an ionic liquid. An ionic liquid has an extremely low vapor pressure, and hardly evaporates at room temperature, and there is no concern about volatilization or ignition like a general organic solvent. Therefore, by adding an ionic liquid to the electrolyte layer, This is because it is possible to prevent performance degradation due to evaporation. Moreover, it is because by making an electrolyte layer contain an ionic liquid, the electroconductivity of the ion in an electrolyte layer can be improved and a power generation characteristic can be improved.

  As ionic liquids, the anion is fluorine ion, tetrafluoroborate, hexafluoroborate, and fluorine-based such as trifluoromethanesulfonate and trifluoroacetate, iodine ion, bromine ion, chlorine ion, cyanate and thiocyanate-based. Examples thereof include those in which the cation is an imidazolium type, a pyridium type, a phosphonium type, a sulfonium type, an alicyclic amine type, or an aliphatic amine type. One of these ionic liquids may be used alone, or a plurality of these ionic liquids may be used in combination.

  Further, it is preferable to use an iodide ionic liquid having iodine ions as anions. This is because the iodide-based ionic liquid is a source of iodine ions and can function as the above-described redox pair. Specifically, for example, 1,2-dimethyl-3-n-propylimidazolium iodide, 1-methyl-3-n-propylimidazolium iodide, 1-propyl-3-methylimidazolium iodide, 1 -Butyl-2,3-dimethylimidazolium iodide and 1-hexyl-3-methylimidazolium iodide can be mentioned.

  The concentration of the ionic liquid in the electrolyte layer varies depending on the type of the ionic liquid and is not particularly limited. However, the electrolyte layer may contain 30 wt% to 95 wt%, particularly 40 wt% to 85 wt%. preferable. Note that an ionic liquid that also functions as a redox pair, such as an iodide-based ionic liquid, is included as a redox pair instead of an ionic liquid in determining the concentration of the ionic liquid in the electrolyte layer. It is preferable to use the concentration described for the redox couple of (i.e., 0.1 mol / l to 5 mol / l) in the electrolyte layer.

(Styrene-butadiene rubber) The electrolyte layer contains styrene-butadiene rubber. Since the styrene-butadiene rubber can stably hold the ionic liquid and has a small adverse effect on the function of the redox couple, in the present invention, by adding the styrene-butadiene rubber to the electrolyte layer, While the fluidity can be reduced, the power generation characteristics are not significantly reduced.

  Styrene-butadiene rubber may be modified, for example, to improve ionic liquid retention and solubility or dispersibility in the electrolyte layer forming liquid, or monomers such as acrylic acid esters and organic acids, It may be a copolymer with a copolymer component.

  The molecular weight of the styrene-butadiene rubber is not particularly limited, but the weight average molecular weight is preferably in the range of 10,000 to 2,000,000 from the viewpoint of obtaining good film forming properties when forming the electrolyte layer. The styrene content of the styrene-butadiene rubber is preferably 5% by weight to 70% by weight for compatibility with the ionic liquid. Moreover, it is preferable that the glass transition temperature of styrene-butadiene rubber is -50 degreeC-+120 degreeC.

  By using the latex of styrene-butadiene rubber, the adjustment of the electrolyte layer forming liquid becomes easy, and the styrene-butadiene rubber can be made uniform in the electrolyte layer. When latex is used, it is necessary to appropriately select a hydrophilic ionic liquid that can be dissolved or dispersed in the latex so that the latex is not destroyed.

  If the content of the styrene-butadiene rubber in the electrolyte layer is too small, the fluidity of the electrolyte layer becomes high. On the other hand, if the content is too large, the power generation characteristics are deteriorated. Specifically, it is preferable to contain 5 wt% to 70 wt% in the electrolyte layer. In order to obtain a dye-sensitized solar cell having a photoelectric conversion efficiency of 1% or more, it is more preferably 15% by weight to 55% by weight.

(Additives) The electrolyte layer can contain various additives for the purpose of improving durability, improving open-circuit voltage value, and the like. Specific examples of the additive include guanidinium thiocyanate, tertiary butyl pyridine, N-methylbenzimidazole and the like.

(Method for Forming Electrolyte Layer) As a general method for forming an electrolyte layer, for example, a conductive base material on which a porous semiconductor layer is disposed and a counter electrode are disposed so as to have a predetermined gap, and a sealing agent or the like. After sealing with, a method of injecting an electrolyte layer forming liquid containing a redox couple, an ionic liquid, and styrene-butadiene rubber into the gap (hereinafter referred to as “injection method”), a redox couple, Examples thereof include a method of applying an electrolyte layer forming solution containing an ionic liquid and styrene-butadiene rubber on the porous semiconductor layer of the conductive substrate or on the counter electrode (hereinafter referred to as “coating method”). .

  When forming the electrolyte layer by an injection method, first, prepare a conductive substrate and a counter electrode on which the porous semiconductor layer is arranged, arrange them so as to face each other with a predetermined gap, Fix with sealant. The gap at this time is preferably set so that the distance between the conductive substrate and the counter electrode is 2 μm to 150 μm. In order to stably provide the predetermined gap, a spacer can be provided on either or both of the conductive substrate side and the counter electrode side. Examples of such a spacer include known glass spacers and resin spacers. Next, an electrolyte layer forming solution containing an oxidation-reduction pair, an ionic liquid, and styrene-butadiene rubber is injected into the gap by utilizing a capillary phenomenon, and then sealed to form an electrolyte layer. Thereby, a dye-sensitized solar cell can be obtained.

  When the electrolyte layer is formed by a coating method, first, an electrolyte forming liquid including at least a redox couple, an ionic liquid, and a styrene-butadiene rubber is prepared.

  At this time, in order to stably dissolve or disperse styrene-butadiene rubber and other additives in the electrolyte layer forming solution, or to adjust the application suitability of the electrolyte layer forming solution, the electrolyte layer forming solution may be used as necessary. A solvent can be used for the liquid. In the present invention, the solvent includes not only a medium for dissolving a solute but also a medium for dispersing a solute. Solvents include volatile organic solvents such as alcohol solvents such as methanol, isopropanol, butanol, and ethanol, ketone solvents such as methyl ethyl ketone, and amide solvents such as N-methylpyrrolidone (NMP), and pure water. Preferably used. Specifically, from the viewpoint of the stability of the electrolyte layer forming solution, lower alcohols such as methanol, ethanol, isopropanol, and butanol, and solvents such as water and NMP are preferably used. When a solvent is used, the electrolyte layer can be formed by coating and then drying appropriately to remove the solvent.

  Next, the case where an electrolyte layer is formed by a coating method will be described. In the present invention, since the electrolyte layer contains styrene-butadiene rubber, the fluidity of the electrolyte layer is lowered. Therefore, after the electrolyte layer forming solution is applied, the periphery of the electrolyte layer forming region is not sealed. Also, the electrolyte layer can be retained. Therefore, the dye-sensitized solar cell of the present invention is excellent in that it can improve the productivity by adopting a coating method.

  In the coating method, as a means for coating the electrolyte layer forming liquid on the porous semiconductor layer or the counter electrode of the conductive substrate, a known coating means can be used, specifically, die coating, gravure coating, Gravure reverse coat, roll coat, reverse roll coat, bar coat, blade coat, knife coat, air knife coat, slot die coat, slide die coat, dip coat, micro bar coat, micro bar reverse coat, screen printing, etc. .

  Thus, by bonding the conductive layer side of the counter electrode or the porous semiconductor layer side of the conductive substrate to the electrolyte layer formed on the porous semiconductor layer or the counter electrode of the conductive substrate in this way, A dye-sensitized solar cell can be obtained.

(Solar cell module) A dye-sensitized solar cell module can be obtained by connecting two or more dye-sensitized solar cells obtained as described above in series or in parallel. Specifically, for example, a plurality of dye-sensitized solar cells are arranged in a planar shape or a curved shape, and non-conductive partition walls are provided between the cells to partition each cell. These members can be used for electrical connection, and a positive or negative electrode lead can be drawn from the end portion to form a module. The number of dye-sensitized solar cells constituting the module is arbitrary, and can be freely designed so as to obtain a desired voltage.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, it is not limited to this.

(Preparation of electrolyte layer forming solution)
Example 1
Add 0.6 mol / l iodine, 6.0 mol / l hexylmethylimidazolium iodide, 0.45 mol / l N-methylbenzimidazole, and 0.1 mol / l guanidinium thiocyanate to ethylmethylimidazolium thiocyanate, The electrolytic solution was adjusted by stirring and dissolving. Subsequently, 1 g of the electrolyte solution and 1 g of styrene-butadiene rubber latex (manufactured by Nippon Zeon Co., Ltd .; BM-400B, concentration of styrene-butadiene rubber 39.3% by weight) are mixed and stirred with a stirrer. A coating solution for forming an electrolyte layer was prepared. At this time, the concentration of the styrene-butadiene rubber in the electrolyte layer coated with the electrolyte layer forming solution and dried is about 28.2% by weight.

(Example 2)
In Example 1, an electrolyte layer forming solution was prepared in the same manner as in Example 1 except that 1 g of the electrolytic solution and 1.5 g of styrene-butadiene rubber latex were mixed. At this time, the concentration of the styrene-butadiene rubber in the electrolyte layer coated with the electrolyte layer forming solution and dried is about 37.1% by weight.

(Example 3)
A liquid for forming an electrolyte layer was prepared in the same manner as in Example 1 except that 1 g of the electrolytic solution and 2 g of latex of styrene-butadiene rubber were mixed in Example 1. At this time, the concentration of the styrene-butadiene rubber in the electrolyte layer coated with the electrolyte layer forming solution and dried is about 44.0% by weight.

Example 4
A liquid for forming an electrolyte layer was prepared in the same manner as in Example 1 except that 1 g of the electrolytic solution and 3 g of styrene-butadiene rubber latex were mixed in Example 1. At this time, the concentration of the styrene-butadiene rubber in the electrolyte layer coated with the electrolyte layer forming solution and dried is about 54.1% by weight.

(Example 5)
In Example 1, an electrolyte layer forming solution was prepared in the same manner as in Example 1 except that 1 g of the electrolytic solution and 5 g of styrene-butadiene rubber latex were mixed. At this time, the concentration of the styrene-butadiene rubber in the electrolyte layer coated with the electrolyte layer forming solution and dried is about 66.3% by weight.

(Comparative Example 1 and Comparative Example 2)
In Example 1, a coating solution for forming an electrolyte layer was prepared using only the electrolytic solution without mixing the latex of styrene-butadiene rubber.

(Formation of conductive substrate and porous semiconductor layer)
(Examples 1-5, Comparative Examples 1-2)
A titanium oxide ink in which titanium oxide (manufactured by Nippon Aerosil Co., Ltd .; P25) was dispersed in ethanol was prepared. Subsequently, transparent conductive glass (manufactured by Nippon Sheet Glass Co., Ltd.) having an FTO layer formed on a glass plate as a conductive substrate is prepared, and the titanium oxide ink is applied to the FTO layer of the transparent conductive glass by a screen printing method. This was applied and baked at 550 ° C. to form a porous titanium oxide layer having a thickness of 10 μm. Next, the above-mentioned titanium oxide layer was added to a dye solution in which a ruthenium complex (manufactured by Solaronix; RuI ₂ (NCS) ₂ ) was dissolved in absolute ethanol so as to have a concentration of 3.0 × 10 ⁻⁴ mol / l. It was immersed for 20 hours. After the immersion, the pigment solution was pulled up and the pigment solution adhering to the titanium oxide layer was washed with acetonitrile and air-dried. Thereby, the porous semiconductor layer was formed on the conductive substrate.

(Preparation of counter electrode)
(Examples 1-5, Comparative Examples 1-2)
A counter electrode was prepared by laminating platinum with a thickness of 150 mm on an FTO layer of transparent conductive glass (manufactured by Nippon Sheet Glass Co., Ltd.) having an FTO layer formed on a glass plate.

(Preparation of dye-sensitized solar cell)
(Examples 1-5, Comparative Example 1)
By applying each electrolyte layer forming solution in Examples 1 to 5 and Comparative Example 1 on a porous semiconductor layer (4 mm × 4 mm) on a conductive substrate with a doctor blade and drying at about 100 ° C., Except for Comparative Example 1, an electrolyte layer having a thickness of 4 μm was formed. Next, the electrolyte layer of the conductive base material on which the electrolyte layer and the porous semiconductor layer were formed and the platinum layer of the counter electrode were bonded to each other and pressed with a clip. This produced the desired dye-sensitized solar cell.

  However, since the electrolyte layer forming solution in Comparative Example 1 was not coated with a doctor blade and dried at about 100 ° C., the electrolyte layer forming solution flowed and could not hold the electrolyte layer. A sensitive solar cell could not be produced.

(Comparative Example 2)
The porous semiconductor layer (4 mm × 4 mm) on the conductive substrate and the platinum layer of the counter electrode were faced to each other and bonded using an ionomer resin having a thickness of 30 μm. And what was bonded together was immersed in the electrolyte layer forming solution in Comparative Example 2, so that the ionomer resin was impregnated with the electrolyte layer forming solution to form an electrolyte layer. This produced the desired dye-sensitized solar cell.

(Evaluation method of fluidity of electrolyte layer)
The fluidity of the electrolyte layer was evaluated based on whether or not the shape of the electrolyte layer was maintained after the electrolyte layer forming solution was applied on the porous semiconductor layer and dried. The evaluation criteria are high fluidity when the width of the electrolyte layer exceeds 1.2 times the width of the application region, and flow when the width of the electrolyte layer is within 1.2 times the width of the application region. Judgment was low.

(Evaluation method of power generation performance)
Evaluation of the power generation performance of the solar cell is performed by using pseudo-sunlight (AM1.5, incident light intensity of 100 mW / cm ² ) as a light source and entering from the side of the conductive substrate having a porous semiconductor layer on which a sensitizing dye is adsorbed. A voltage was applied using a source measure unit (type 2400, manufactured by Keithley) to measure the current-voltage characteristics of the solar cell, and the photoelectric conversion efficiency was obtained. The area of the porous semiconductor layer used for the measurement is 0.16 cm ² (4 mm × 4 mm).

(Evaluation results)
Table 1 shows the evaluation results of the dye-sensitized solar cells prepared in the above examples and comparative examples.

  In Table 1, it can be seen that the fluidity of the electrolyte layer can be lowered by including the styrene-butadiene rubber in the electrolyte layer by comparing the example and the comparative example. Moreover, even if it is a case where styrene-butadiene rubber is made into Examples 1-5 with respect to the photoelectric conversion efficiency 3.95 of the comparative example 2 which does not contain a styrene-butadiene rubber, a power generation characteristic falls significantly. There is no. In particular, in Examples 1 to 4, a dye-sensitized solar cell having a photoelectric conversion efficiency of 1% or more was obtained. Therefore, the dye-sensitized solar cell of the present invention is excellent in durability and power generation characteristics.

1 Dye-sensitized solar cell 10 Conductive base material 20 Porous semiconductor layer 30 Electrolyte layer 40 Counter electrode

Claims (3)

A conductive substrate;
A porous semiconductor layer comprising metal oxide fine particles disposed on the conductive substrate and carrying a sensitizing dye; and
A counter electrode disposed to face the porous semiconductor layer;
A dye-sensitized solar cell, which is disposed between the porous semiconductor layer and the counter electrode and includes an oxidation-reduction pair, an ionic liquid, and an electrolyte layer containing styrene-butadiene rubber. A liquid for forming an electrolyte layer of a dye-sensitized solar cell,
An electrolyte layer forming liquid comprising a redox couple, an ionic liquid, and a styrene-butadiene rubber. A dye-sensitized solar cell module formed by connecting two or more dye-sensitized solar cells according to claim 1 in series or in parallel.

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