JP2011076935A - Dye-sensitized solar cell, liquid for electrolyte layer formation, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell which has no deterioration due to volatilization of an electrolyte and has a superior battery performance. <P>SOLUTION: The dye-sensitized solar cell is constructed of a conductive substrate, a porous semiconductor layer which is formed on the conductive substrate and carries sensitized dye on the hole surface, a counter electrode which is arranged opposed to the porous semiconductor layer, and an electrolyte layer which is formed between the conductive substrate and the counter electrode and is composed of a redox pair and an ionic liquid of which anion is a carboxylic acid ion with bivalence or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell, a liquid used to form an electrolyte layer in the 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 with high photoelectric conversion efficiency and low cost.

  The dye-sensitized solar cell has, for example, a transparent substrate, a transparent conductive layer formed on the transparent substrate, an oxide semiconductor layer carrying a dye, a redox couple, and an electrolyte from the light incident side. The electrolyte layer and the substrate on which the counter electrode is formed are sequentially stacked to form a cell. In particular, the Gretcher cell is characterized by using a porous semiconductor layer obtained by firing titanium oxide, which is a nanoparticle, and by making the semiconductor layer porous, the adsorption amount of the sensitizing dye is increased and the light absorption ability is increased. It is improving.

  However, in the conventional dye-sensitized solar cell, since an organic solvent-based electrolyte is used, there is a problem of performance degradation due to evaporation of the liquid. On the other hand, a dye-sensitized solar cell using an ionic liquid that is relatively stable at room temperature as an electrolyte has been proposed.

  However, when an ionic liquid is used as the electrolyte, the viscosity of the electrolyte of the ionic liquid is generally higher than the viscosity of the organic solvent-based electrolyte. It tends to happen. Reverse electron transfer is a phenomenon in which electrons or holes once injected into a semiconductor layer or conductive layer move back to an electrolyte layer. When reverse electron transfer occurs, battery performance such as open-circuit voltage and photoelectric conversion efficiency decreases. A problem occurs.

  Therefore, in Patent Document 1, reverse electron transfer is performed by immersing a semiconductor layer carrying a dye in a carboxylic acid compound solution such as acetic acid and carrying acetic acid or the like on a portion of the semiconductor layer where the dye is not carried. A method to prevent is disclosed. However, the method disclosed in Patent Document 1 has a problem that acetic acid or the like carried on the semiconductor layer is detached from the electrolyte, and the battery performance deteriorates with time.

  Patent Document 2 discloses an electrolyte layer composed of iodine molecules, an ionic liquid of iodide, a carboxylic acid compound such as acetic acid and benzoic acid, and a gelling agent. However, when the content of acetic acid, benzoic acid or the like that does not contribute to ion conduction increases in the electrolyte layer, there is a problem that the diffusion of the redox couple is inhibited and the battery performance is lowered. In addition, it is necessary to use an ionic liquid having high solubility in acetic acid, benzoic acid, etc., and there is a problem that the selection range of the ionic liquid is narrowed.

JP-A-2004-227920 JP-A-2005-93370

  In view of the above situation, it is an object of the present invention to provide a dye-sensitized solar cell and a dye-sensitized solar cell module that have no deterioration due to volatilization of an electrolyte and have excellent battery performance. Another object of the present invention is to provide a liquid used for forming such an electrolyte layer.

  The present inventor has found that the above problems can be solved by using an ionic liquid whose anion is a divalent or higher carboxylic acid ion as an electrolyte, and has completed the present invention.

That is, the gist of the present invention is as follows.
1st invention is arrange | positioned facing the said porous semiconductor layer with the electroconductive base material, the porous semiconductor layer which was formed on the said electroconductive base material, and carried | supported the sensitizing dye on the hole surface. Dye enhancement comprising a counter electrode, an electrolyte layer formed between the conductive substrate and the counter electrode and comprising an oxidation-reduction pair and an ionic liquid whose anion is a divalent or higher carboxylic acid ion. It is a sensitive solar cell.

  A second invention is the dye-sensitized solar cell according to the first invention, wherein the anion is a dicarboxylic acid ion.

  A third invention is the dye-sensitized solar cell according to the second invention, wherein the anion is a maleic acid ion or a maleic acid substituted ion.

  A fourth invention is a liquid for forming an electrolyte layer of a dye-sensitized solar cell, which is a liquid for forming an electrolyte layer including a redox pair and an ionic liquid whose anion is a divalent or higher carboxylic acid ion. .

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

  According to the present invention, it is possible to obtain a dye-sensitized solar cell and a dye-sensitized solar cell module that have no deterioration due to volatilization of the electrolyte and have excellent battery performance. Moreover, the liquid used in order to form 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 an embodiment of the dye-sensitized solar cell of the present invention. The dye-sensitized solar cell 1 includes a conductive substrate 10, a porous semiconductor layer 20 formed on the conductive substrate 10 and carrying a sensitizing dye on the pore surface, and a porous semiconductor layer 20. The counter electrode 40 is arranged roughly, and the electrolyte layer 30 is formed between the conductive substrate 10 and the counter electrode 40. The electrolyte layer 30 includes at least a redox pair and an ionic liquid in which an anion is a divalent or higher carboxylic acid ion.

(Conductive substrate)
As the conductive substrate 10, general conductive substrates such as various metal foils and metal plates can be used, or can be obtained by forming a conductive layer on a substrate such as glass or plastic. it can. The substrate may be transparent or opaque, but when it is located on the light receiving surface side, it is preferably a transparent substrate having excellent light transmittance. Furthermore, it is preferable that it is excellent in heat resistance, weather resistance, and gas barrier properties against water vapor and the like. Specifically, non-flexible transparent rigid materials such as quartz glass, Pyrex (registered trademark), and synthetic quartz glass, ethylene-tetrafluoroethylene copolymer film, polyethylene terephthalate film (PET), polyether Examples thereof include a sulfone film, a polyether ketone film, a polyetherimide film, a polyimide film, and a plastic film such as polyethylene naphthalate (PEN).

  Among the above, when using a conductive base material in which a rigid material is used as a substrate and a conductive layer is formed thereon, a sintering process is performed at a few hundred degrees after forming a porous semiconductor layer described later on the conductive base material. It is preferable to carry out. The sintering treatment of the porous semiconductor layer improves the retention function of the redox couple in the porous semiconductor layer, thereby preventing a decrease in photoelectric conversion efficiency due to the deterioration of the redox couple over time and increasing the durability of the solar cell.

  When using a conductive base material made of a flexible film with a conductive layer formed on a plastic film as a substrate, solar cells can be used for various applications. Cost reduction can be achieved. When a plastic film is used as a substrate, after the porous semiconductor layer is formed, the porous semiconductor layer is pressed and / or the porous semiconductor layer is sintered at a temperature that can withstand the plastic film. In addition, the retention function of the redox couple in the porous semiconductor layer can be improved. The plastic film may be used alone as a substrate, or may be used in a state where two or more different plastic films are laminated.

  The thickness of the conductive substrate or the substrate of the conductive substrate is preferably in the range of 10 μm to 500 μm.

The material of the conductive layer formed on the substrate is not particularly limited as long as it is excellent in conductivity, but the conductive layer located on the light receiving surface side is excellent in light transmission. Preferably there is. For example, as a material having excellent light permeability, can be cited SnO _2, ITO, FTO, ZnO, IZO, or the like. Among these, FTO and ITO are particularly preferably used because they are excellent in both conductivity and transparency.

Further, the material for the conductive layer formed on the substrate is preferably selected in consideration of each work function. For example, examples of materials having a high work function include Au, Ag, Co, Ni, Pt, C, ITO, FTO, SnO ₂ , and ZnO. On the other hand, examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, and Zr.

  Each conductive layer may be composed of a single layer, or may be composed of laminated materials having different work functions.

  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)
Next, the porous semiconductor layer 20 will be described. The porous semiconductor layer has metal oxide fine particles, on which a sensitizing dye is supported, and has a function of conducting charges generated from the sensitizing dye by light irradiation.

  Since the sensitizing dye is supported on the pore surface of the metal oxide fine particles, the metal oxide fine particles are preferably porous having communication holes. By setting it as such a porous, the surface area of a porous semiconductor layer becomes large, and sufficient quantity of a sensitizing dye can be carry | supported. Moreover, a contact area with the electrolyte layer mentioned later becomes large, and energy conversion efficiency can be improved.

  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.

The metal oxide fine particles forming the porous semiconductor layer are not particularly limited as long as the charge generated from the sensitizing dye can be conducted to the conductive substrate 10. _{Specifically, TiO 2, ZnO, SnO 2} , ITO, ZrO 2, SiO 2, MgO, Al 2 O 3, CeO 2, Bi 2 O 3, Mn 3 O 4, Y 2 O 3, WO 3, Ta ₂ O ₅ , Nb ₂ O ₅ , La ₂ O _{3 and the} like can be mentioned. 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. Further, a core-shell structure in which one of these is used as a core particle and the core particle is coated with another metal oxide fine particle to form a shell may be used.

  A resin can be added to the porous semiconductor layer as a binder for the metal oxide fine particles. Specific examples of the resin include cellulose or a derivative thereof.

  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 99.9% by weight.

  The particle diameter of the metal oxide fine particles is preferably in the range of 1 nm to 10 μm, particularly in the range of 10 nm to 500 nm. When the particle diameter is smaller than the above range, it is difficult to produce such particles, and it is not preferable because each particle may aggregate to form secondary particles. On the other hand, when the particle diameter is larger than the above range, the surface area of the porous semiconductor layer is reduced, and the sensitizing dye carried on the porous semiconductor layer is decreased, which may lower the photoelectric conversion efficiency. Therefore, it is not preferable.

  You may mix and use the metal oxide fine particle from which a particle size differs. Thereby, the light scattering effect can be enhanced and more light can be confined in the porous semiconductor layer, so that light absorption by the sensitizing dye can be efficiently performed. For example, a case where metal oxide fine particles of 10 nm to 50 nm and metal oxide fine particles of 50 nm to 200 nm are mixed and used can be exemplified.

  The sensitizing dye supported on the metal oxide fine particles 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. Examples of organic dyes include acridine, azo, indigo, quinone, coumarin, merocyanine, phenylxanthene, indoline, and squalium dyes. In particular, a coumarin system is preferably used.

  As the metal complex dye, a ruthenium dye, particularly a ruthenium bipyridine dye and a ruthenium terpyridine dye are preferably used. By supporting such a sensitizing dye on the pore surface of the metal oxide fine particles, it is possible to efficiently take in the visible light range and cause photoelectric conversion.

  The method for forming the porous semiconductor layer is not particularly limited, but it is preferably formed by a coating method. That is, using a known disperser such as a homogenizer, a ball mill, a sand mill, a roll mill, or a planetary mixer, a coating liquid in which metal oxide fine particles are dispersed in a solvent is prepared. It is applied to the top (the conductive layer side of the conductive substrate when a conductive layer is formed), dried, and further baked as necessary. Then, the porous semiconductor layer carrying the sensitizing dye can be formed by adsorbing the sensitizing dye on the surface of the metal oxide fine particles.

  The solvent used in the metal oxide fine particle coating solution is not particularly limited. Specifically, chlorine solvents such as chloroform, methylene chloride, dichloroethane, ether solvents such as tetrahydrofuran, aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone and methyl ethyl ketone, ethyl acetate, butyl acetate And ester solvents such as ethyl cellosolve acetate, alcohol solvents such as isopropyl alcohol, ethanol, methanol and butyl alcohol, N-methyl-2-pyrrolidone, and pure water.

  In addition, various additives may be used as necessary in order to improve the coating suitability of the coating liquid used for forming the porous semiconductor layer. As the additive, a surfactant, a viscosity adjuster, a dispersion aid, a pH adjuster and the like can be used. Examples of the pH adjuster include nitric acid, hydrochloric acid, acetic acid, ammonia and the like.

  The method for applying the coating liquid containing metal oxide fine particles is not particularly limited as long as it is a known coating method, specifically, die coating, gravure coating, gravure reverse coating, roll coating, reverse roll coating, Examples thereof include bar coating, blade coating, knife coating, air knife coating, slot die coating, slide die coating, dip coating, micro bar coating, micro bar reverse coating, and screen printing. Using such a coating method, the porous semiconductor layer is formed so as to have a desired film thickness by repeating coating and drying once or a plurality of times.

  After coating and drying, baking is performed as necessary. Thereby, the porous semiconductor layer can be homogenized and densified, and the binding property between the metal oxide fine particles can be increased, so that the charge conductivity can be improved. In addition, the adhesion between the conductive substrate and the porous semiconductor layer can be improved. The firing temperature and time vary depending on the film thickness of the porous semiconductor layer and are not limited, but are generally about 300 to 700 ° C. and about 5 to 120 minutes. Moreover, when a conductive base material is comprised from a plastic film, it is preferable to perform drying and baking below the heat-resistant temperature of a film.

  As a method for supporting the sensitizing dye, for example, the dried and baked metal oxide fine particles are immersed in a sensitizing dye solution and then dried, or the sensitizing dye solution is applied onto the metal oxide fine particles. And a method of drying after permeation. The solvent used in the sensitizing dye solution is appropriately selected from an aqueous solvent and an organic solvent according to the type of the dye sensitizer used.

(Counter electrode)
As the counter electrode 40, it is possible to use various metal foils, metal plates, or the like, or those in which a conductive layer is formed on the surface of a substrate such as glass or plastic. The substrate may be transparent or opaque, but when it is located on the light receiving surface side, it is preferably a transparent substrate having excellent light transmittance. Furthermore, it is preferable that it is excellent in heat resistance, weather resistance, and gas barrier properties against water vapor and the like. Specifically, non-flexible transparent rigid materials such as quartz glass, Pyrex (registered trademark), and synthetic quartz glass, ethylene-tetrafluoroethylene copolymer film, polyethylene terephthalate film (PET), polyether Examples thereof include a sulfone film, a polyether ether ketone film, a polyether imide film, a polyimide film, and a plastic film such as polyethylene naphthalate (PEN).

  When a counter electrode made of a flexible film having a conductive layer formed on a plastic film as a substrate is used, solar cells can be used for various applications. Reduction can be achieved. The plastic film may be used alone as a substrate, or may be used in a state where two or more different plastic films are laminated.

  The thickness of the counter electrode or the substrate of the counter electrode is preferably in the range of 10 μm to 500 μm.

The material of the conductive layer formed on the substrate is not particularly limited as long as it is excellent in conductivity, but the conductive layer located on the light receiving surface side is excellent in light transmission. Preferably there is. For example, as a material having excellent light permeability, can be cited SnO _2, ITO, FTO, ZnO, IZO, or the like. Among these, FTO and ITO are particularly preferably used because they are excellent in both conductivity and transparency.

Further, the material for the conductive layer formed on the substrate is preferably selected in consideration of each work function. For example, examples of the material having a high work function include Au, Ag, Co, Ni, Pt, C, SnO ₂ , ITO, FTO, and ZnO. On the other hand, examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, and Zr.

  Each conductive layer may be composed of a single layer, or may be composed of laminated materials having different work functions.

  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 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 made of an organic material such as polyaniline, polythiophene, polypyrrole, but are not limited thereto.

(Electrolyte layer)
Next, the electrolyte layer 30 will be described. The electrolyte layer 30 is formed between the conductive substrate 10 on which the porous semiconductor layer 20 is formed and the counter electrode 40, and contains at least an ionic liquid in which the redox pair and the anion are divalent or higher carboxylic acid ions. .

  The redox couple can be appropriately selected from those generally used in the electrolyte layer. Specifically, a redox couple of iodine or a redox couple of bromine is preferably used. Examples of the redox pair of iodine include combinations of iodine and iodides such as lithium iodide, sodium iodide, potassium iodide, calcium iodide, and TPAI (tetrapropylammonium iodide). 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 30 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 to 0.001. 5 mol / l and iodide or bromide are preferably 0.1 to 5 mol / l. In general, the molar ratio of iodine or bromine to iodide or bromide is set to about 1:10.

  The ionic liquid lowers the viscosity of the electrolyte, improves the conductivity of ions, and improves the photoelectric conversion efficiency. Since the ionic liquid has an extremely low vapor pressure, it hardly evaporates at room temperature, and there is no fear of volatilization or ignition like a general organic solvent, so that deterioration due to volatilization of the electrolyte can be prevented.

  In the present invention, at least an ionic liquid in which the anion (anion) is a divalent or higher carboxylic acid ion is used. Here, the divalent or higher carboxylic acid ion is an ion of a compound having two or more anionic groups, and at least one of the two or more anionic groups is a carboxyl group. Examples of the anionic group include a carboxyl group, a hydroxy group, a sulfo group, a phosphoric acid group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  By using an ionic liquid whose anion is a divalent or higher carboxylic acid ion for the electrolyte layer of the dye-sensitized solar cell, deterioration due to volatilization of the electrolyte can be prevented and a high open-circuit voltage can be obtained. The ionic liquid in which the anion is a divalent or higher carboxylic acid ion has at least one carboxyl group, and is thought to be supported on the portion of the semiconductor layer where the dye is not supported, thereby preventing reverse electron transfer. It is done. Further, according to the present invention, since the ionic liquid itself is a carboxylic acid, the solubility of the carboxylic acid in the ionic liquid is not questioned, and the electrolyte layer can easily contain the carboxylic acid. Further, even when other ionic liquids such as an iodide ionic liquid described later are used in combination, the ionic liquids are mixed together, so that the compatibility is good. Furthermore, an ionic liquid in which the anion is a divalent or higher carboxylic acid ion contributes to ion conduction as an electrolyte, and can improve the diffusion rate of the redox couple.

  The divalent or higher carboxylic acid ion is preferably a dicarboxylic acid ion. This is because dicarboxylic acids can be obtained relatively easily among divalent or higher carboxylic acids. Specific examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, terephthalic acid, isophthalic acid, and substituted products thereof. In addition, a substituted body is a compound which replaced the hydrogen atom of the hydrocarbon of an organic compound with another atom or another atomic group.

  In particular, a dye-sensitized solar cell with high conversion efficiency can be obtained by using, for the electrolyte layer, an ionic liquid whose anion is maleate ion or maleate substituted ion. The ionic liquid in which the anion is a maleate ion or a maleate-substituted substance ion has a low viscosity, which is considered to improve the diffusion rate of the redox couple.

  Examples of the cation (cation) of the ionic liquid include 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-butyl-3-methyl. Imidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-octadecyl-3-methylimidazolium, 1-methyl-2,3-dimethylimidazolium, 1-butyl-2 1,3-dimethylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1-octyl-2,3-dimethylimidazolium, and 1-octadecyl-2,3-dimethylimidazolium series, 1 -Pyridi such as methyl-pyridinium, 1-butyl-pyridinium, and 1-hexyl-pyridinium Beam system, phosphonium such as tetrabutylphosphonium, sulfonium system such as triethyl sulfonium, alicyclic amine-based, and may include those aliphatic amine.

  As the ionic liquid, an ionic liquid other than the ionic liquid in which the anion is a divalent or higher carboxylic acid ion may be used in combination, on the condition that the anion is a divalent or higher carboxylic acid ion. . Examples of other ionic liquid anions include fluorine ions, tetrafluoroborate, hexafluoroborate, trifluoromethanesulfonate, trifluoroacetate and other fluorine-based, iodine ion, bromine ion, chlorine ion, cyanate-based, and thiocyanate-based materials. Examples of other ionic liquid cations include 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, and 1-butyl. -3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-octadecyl-3-methylimidazolium, 1-methyl-2,3-dimethylimidazolium, 1 -Butyl-2,3-dimethylimidazoli Imidazoliums such as 1-hexyl-2,3-dimethylimidazolium, 1-octyl-2,3-dimethylimidazolium, and 1-octadecyl-2,3-dimethylimidazolium, 1-methyl-pyridium, Mention may be made of pyridiums such as 1-butyl-pyridinium and 1-hexyl-pyridium, phosphoniums such as tetrabutylphosphonium, sulfoniums such as triethylsulfonium, alicyclic amines, and aliphatic amines. it can. These other ionic liquids may be used alone or in combination with an ionic liquid whose anion is a divalent or higher carboxylic acid ion, or may be used in combination.

  When an ionic liquid whose anion is iodine (hereinafter referred to as “iodide-based ionic liquid”) is used, the iodide-based ionic liquid functions as a redox pair because it serves as a source of iodine ions. Can be made. Specific examples of the iodide ionic liquid include 1,2-dimethyl-3-n-propylimidazolium iodide, 1-methyl-3-n-propylimidazolium iodide, 1-propyl-3-methylimidazolium. Examples thereof include iodide, 1-butyl-2,3-dimethylimidazolium iodide, 1-hexyl-3-methylimidazolium iodide, and the like.

  The concentration of the ionic liquid in the electrolyte layer 30 varies depending on the type of the ionic liquid and the like, but it is preferable to contain 5 wt% to 95 wt%, particularly 10 wt% to 85 wt% in the electrolyte layer 30. Of all the ionic liquids contained in the electrolyte layer, the ionic liquid in which the anion is a divalent or higher carboxylic acid ion preferably occupies at least 5% by weight or more. Note that an ionic liquid that also functions as a redox pair, such as an iodide 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 30 described above. It is preferable to contain 0.1 mol / l to 60 mol / l in the electrolyte layer 30. At this time, the iodine concentration is preferably 0.001 mol / l to 6 mol / l, and it may or may not contain iodides other than the iodide ionic liquid.

  In addition, the electrolyte layer 30 can contain various additives and resins for the purpose of improving the battery performance and durability of the dye-sensitized solar cell. Specific examples of the additive include guanidinium thiocyanate, tertiary butyl pyridine, N-methylbenzimidazole and the like. The concentration of the additive in the electrolyte layer 30 is preferably 1 mol / l or less in total of various additives. Specific examples of the resin include cellulose or a derivative thereof. By causing the electrolyte layer to contain a resin and solidifying the electrolyte, it is possible to prevent liquid leakage due to deterioration or breakage of the sealing material. The concentration of the resin in the electrolyte layer 30 is preferably 5% to 60% by weight of the electrolyte layer.

  As a method of forming the electrolyte layer 30, a method of forming the electrolyte layer by disposing the porous semiconductor layer 20 and the counter electrode 40 so as to have a predetermined gap and injecting an electrolyte layer forming liquid into the gap ( Hereinafter, it may be referred to as an injection method), or a method of forming an electrolyte layer forming solution by applying it on the porous semiconductor layer 20 and drying it (hereinafter referred to as a coating method).

  When the electrolyte layer 30 is formed by an injection method, first, the counter electrode 40 on which the conductive layer is formed is prepared, and the porous semiconductor layer 20 and the counter electrode 40 are arranged so as to face each other with a predetermined gap. . The gap at this time is preferably set so that the distance between the conductive substrate 10 and the counter electrode 40 is 2 μm to 150 μm. In order to arrange the counter electrode 40 with a predetermined gap, a spacer can be provided on either the conductive substrate 10 side or the counter electrode 40 side. Examples of such a spacer include known glass spacers and resin spacers.

  Next, an electrolyte layer forming solution containing at least an oxidation-reduction pair and an ionic liquid in which an anion is a divalent or higher carboxylic acid ion is prepared, and the electrolyte layer forming solution is obtained by utilizing a capillary phenomenon or the like. The electrolyte layer 30 is formed by injecting into the gap, and the periphery of the side portion of the electrolyte layer is sealed with a curable resin or the like. Thereby, a dye-sensitized solar cell can be obtained.

When the electrolyte layer 30 is formed by a coating method, first, an electrolyte layer forming solution including at least an oxidation-reduction pair and an ionic liquid whose anion is a divalent or higher carboxylic acid ion is prepared. Next, the electrolyte layer forming solution is applied onto the porous semiconductor layer 20 by a known application means to form the electrolyte layer 30. Specific application methods include die coating, gravure coating, gravure reverse coating, roll coating, reverse roll coating, bar coating, blade coating, knife coating, air knife coating, slot die coating, slide die coating, dip coating, and micro bar coating. , Microbar reverse coating, screen printing, and the like.

  In addition, in order to contain an additive, resin, etc., or to adjust the coating suitability of the electrolyte layer forming solution, a solvent can be used in the electrolyte layer forming solution as necessary. Examples of the solvent include an alcohol-based solvent such as ethanol, an ionic liquid whose anion is a divalent or higher carboxylic acid ion and an anion whose solubility is soluble, a ketone solvent such as methyl ethyl ketone, N-methylpyrrolidone (NMP), and the like. Volatile organic solvents such as amide solvents, pure water, and the like are preferably used. Specifically, lower alcohols such as methanol, ethanol, isopropanol, and butanol, and solvents such as water and NMP are preferably used from the viewpoints of the stability of the electrolyte layer forming solution and the film forming property of the electrolyte. When a solvent is used, the electrolyte layer 30 can be formed by applying the electrolyte layer forming solution and then drying it appropriately to remove the solvent.

  The conductive layer side of the counter electrode 40 is bonded to the electrolyte layer 30 thus formed, and the periphery of the side portion of the electrolyte layer is sealed with a curable resin or the like, whereby the dye-sensitized solar cell of the present invention. Can be obtained.

(Solar cell module)
A dye-sensitized solar cell module can be obtained by connecting two or more dye-sensitized solar cells 1 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
To 5 ml of 1-ethyl-3-methylimidazolium maleate (EMIm-M), 1-propyl-3-methylimidazolium iodide (PMIm-I) and iodine (I ₂ ) were respectively 12 mol / l and 1. It was added to a concentration of 2 mol / l and dissolved by stirring. Thereby, the electrolyte layer forming solution was prepared.

(Example 2)
A mixture of 2.5 ml of 1-ethyl-3-methylimidazolium maleate (EMIm-M) and 2.5 ml of 1-ethyl-3-methylimidazolium bis (trifluorosulfonyl) imide (EMIm-TFSI) 1-propyl-3-methylimidazolium iodide (PMIm-I) and iodine (I ₂ ) were added to a concentration of 12 mol / l and 1.2 mol / l, respectively, and dissolved by stirring. . Thereby, the electrolyte layer forming solution was prepared.

(Example 3)
In Example 1, an electrolyte layer forming solution was prepared in the same manner as in Example 1 except that tetrabutylphosphonium maleate (TBP-M) was used instead of EMIm-M.

Example 4
In Example 1, a liquid for forming an electrolyte layer was prepared in the same manner as in Example 1 except that 1-ethyl-3-methylimidazolium succinate (EMIm-S) was used instead of EMIm-M. did.

(Example 5)
In Example 1, an electrolyte layer forming solution was prepared in the same manner as in Example 1 except that tetrabutylphosphonium succinate (TBP-S) was used instead of EMIm-M.

(Comparative Example 1)
In Example 1, an electrolyte layer was formed in the same manner as in Example 1 except that 1-ethyl-3-methylimidazolium bis (trifluorosulfonyl) imide (EMIm-TFSI) was used instead of EMIm-M. The working solution was adjusted.

(Comparative Example 2)
In Example 1, in place of EMIm-M, adjustment of the electrolyte layer forming solution was attempted in the same manner as in Example 1 except that tetrabutylphosphonium bis (trifluorosulfonyl) imide (TBP-TFSI) was used. However, the liquid was solidified and could not be prepared.

(Formation of conductive substrate and porous semiconductor layer)
Titanium oxide ink (manufactured by Solaronix) containing anatase-type titanium oxide having an average primary particle size of about 10 nm to 20 nm, and a fluorine-doped tin oxide (FTO) film formed on a glass plate have a surface resistivity of 6 ohm / square Transparent conductive glass (manufactured by Nippon Sheet Glass Co., Ltd.) was prepared. On the conductive glass, the above-described titanium oxide ink was applied by screen printing and baked at 450 ° C. to form a porous titanium oxide layer having a thickness of 2 μm. Furthermore, the titanium oxide layer having a thickness of 8 μm was finally formed on the conductive glass by repeating the application and firing of the titanium oxide ink on the titanium oxide layer.
Next, ruthenium complex (manufactured by Solaronix; cis-bis (thiocyanato) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II) dihydrate) was dissolved in absolute ethanol The above-mentioned titanium oxide layer was immersed in a dye solution dissolved in a concentration of 3.0 × 10 ⁻⁴ mol / l for 12 hours at room temperature. After soaking, the dye solution was pulled up and the dye solution adhering to the titanium oxide layer was washed with absolute ethanol and air-dried. Thereby, the porous semiconductor layer was formed on the conductive substrate.

(Preparation of counter electrode)
A counter electrode is produced by laminating platinum with a thickness of 150 mm on transparent conductive glass (manufactured by Nippon Sheet Glass Co., Ltd.) having a surface resistivity of 6 ohms / square with a fluorine-doped tin oxide (FTO) film formed on a glass plate. did.

(Preparation of dye-sensitized solar cell)
On the conductive substrate on which the porous semiconductor layer (4 mm × 4 mm) is formed, an epoxy resin layer having a thickness of 30 μm is formed so as to surround the porous semiconductor layer, and then the porous semiconductor layer of the conductive substrate and The epoxy resin layer and the platinum layer of the counter electrode were bonded face to face. Subsequently, an electrolyte forming solution was injected from an injection port opened in the counter electrode substrate, and the injection port was sealed with an epoxy resin and a glass plate to produce a desired dye-sensitized solar cell.

(Evaluation method of power generation performance)
The evaluation of the power generation performance of the solar cell was 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. The voltage was applied using the 2400 type | mold), the current voltage characteristic of the solar cell was measured, and the photoelectric conversion efficiency was calculated | required. 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.

  By using the ionic liquids of Examples and Comparative Examples, deterioration due to volatilization of the electrolyte is not observed. At this time, by comparing Examples 1 to 5 and Comparative Example 1 in Table 1, when an ionic liquid whose anion is a divalent or higher carboxylic acid ion is used for the electrolyte layer, it does not contain a carboxyl group. It can be seen that a dye-sensitized solar cell having a higher open-circuit voltage than that obtained using only the ionic liquid was obtained.

  Furthermore, by comparing Examples 1-2, Example 4, and Comparative Example 1, when the cation of the ionic liquid is the same, when the anion is a maleate ion, a dye increase having high conversion efficiency is achieved. It can be seen that a sensitive solar cell was obtained.

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

Claims (5)

A conductive substrate;
A porous semiconductor layer formed on the conductive substrate and having a sensitizing dye supported on the pore surface;
A counter electrode disposed to face the porous semiconductor layer;
An electrolyte layer formed between the conductive substrate and the counter electrode, the redox pair, and an ionic liquid in which an anion is a divalent or higher carboxylic acid ion;
A dye-sensitized solar cell comprising:   The dye-sensitized solar cell according to claim 1, wherein the anion is a dicarboxylate ion.   The dye-sensitized solar cell according to claim 2, wherein the anion is a maleate ion or a maleate-substituted ion. A liquid for forming an electrolyte layer of a dye-sensitized solar cell,
An electrolyte layer forming solution comprising a redox pair and an ionic liquid whose anion is a divalent or higher carboxylic acid ion. A dye-sensitized solar cell module comprising two or more dye-sensitized solar cells according to any one of claims 1 to 3 connected in series or in parallel.

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