WO2006123785A1

WO2006123785A1 - Electrolyte composition

Info

Publication number: WO2006123785A1
Application number: PCT/JP2006/310049
Authority: WO
Inventors: Satoshi Uchida; Akio Maeda; Shigeru Hagiwara
Original assignee: Nippoh Chemicals Co., Ltd.
Priority date: 2005-05-19
Filing date: 2006-05-19
Publication date: 2006-11-23
Also published as: TWI389966B; JP4982361B2; TW200643092A; JPWO2006123785A1

Abstract

This invention provides means that, in solar batteries such as dye-sensitized solar batteries, can suppress iodine-derived coloration of solar battery cells without causing a lowering in photoelectric conversion efficiency with the elapse of time. An electrolyte composition comprising a medium and an iodine-cyclodextrin inclusion compound, which is hardly soluble in the medium and has an average particle diameter of not more than 20 μm is incorporated in an electrolyte layer in a solar cell.

Description

Specification

Electrolyte composition

Technical field

[0001] The present invention relates to an electrolyte composition. Specifically, the present invention relates to an electrolyte composition that can improve durability and design performance of a dye-sensitized solar cell or the like.

Background art

In recent years, against the background of increasing awareness of environmental problems, solar cells, which are power generation systems using sunlight as an energy source, have been actively developed.

[0003] Conventionally, solar cells using organic pigments and organic dyes have been proposed as materials for elements constituting solar cells, in addition to silicon materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon. According to solar cells that employ these organic materials, relatively high conversion efficiency can be achieved by combining dye molecules that absorb light with molecules and substance species that transport electrons and hole transport molecules and substance species. Is obtained. Among them, the dye-sensitized solar cell developed by Dr. Gretzell of Switzerland has attracted attention in recent years because it can achieve particularly high conversion efficiency. Dye-sensitized solar cells can also be manufactured using inexpensive semiconductor materials, and have the advantage that the wavelength range of light that can be used for power generation is wide.

[0004] Here, an acid-reducing pair is used as the electrolyte of the dye-sensitized solar cell. However, as a powerful oxidation-reduction pair, iodine (I-) and iodide are used because of their excellent reaction rate. Ion (Γ)

Three

An organic electrolyte solution is generally used.

[0005] Traditionally, I _Zl_

3 A technology is disclosed in which a cyclodextrin, which is a cyclic polysaccharide, is further contained in an electrolytic solution containing a redox couple (see, for example, JP 2004-235011 A and JP 2005-71895 A). . Specifically, in the publication of Japanese Patent Application Laid-Open No. 2004-235011, an electrolytic solution containing an iodine-cyclodextrin inclusion product (hereinafter also simply referred to as “CDI”) and a photoelectric conversion element using the same ( Solar cells). According to the powerful technology, the inclusion of iodine in cyclodextrin reduces the toxicity of iodine and provides a safe photoelectric conversion element (solar cell). JP-A-2005-71895 discloses cyclodextrin, which is a cyclic polysaccharide, and an organic molten salt compound (so-called so-called compound). , An ionic liquid) and iodine. According to such a technique, the addition of cyclodextrin suppresses the decrease in ionic conductivity in the electrolyte accompanying the addition of the ionic liquid, and can improve the conversion efficiency.

Disclosure of the invention

Incidentally, a solar cell is a power generation system that uses sunlight as an energy source. For this reason, the members (semiconductor electrode and counter electrode) constituting the solar cell are substantially transparent. However, since iodine contained in the electrolyte exhibits a characteristic dark brown color, the electrolyte layer of the solar cell also exhibits a dark brown color. Therefore, since the solar cells cannot be arranged in places where the aesthetics may be impaired by the arrangement of dark brown cells, the places where the cells can be arranged are limited. For example, if solar cells are arranged side by side on the outer wall of a building, the entire outer wall of the building will exhibit a dark brown color, which is not preferable in view of the scenery. In addition, the restriction of the location of the solar cells in this way has resulted in restrictions on the use of solar cells, which has been one of the factors that hinder the spread of solar cells.

[0007] The problem of color tone due to iodine contained in the electrolyte of the solar cell has not been solved even by the technique of adding cyclodextrin as described in the above-mentioned document. As a means for suppressing the coloration of solar cells caused by iodine, it is conceivable to lower the iodine concentration in the electrolytic solution. However, the photoelectric conversion efficiency may decrease over time by such means. Is not realistic.

[0008] As described above, there is a strong demand for the development of means that can suppress the coloration of solar cells caused by iodine without causing a decrease in photoelectric conversion efficiency over time.

Accordingly, an object of the present invention is to provide a powerful means.

[0010] The present inventors have conducted intensive research to solve the above problems. As a result, in the electrolyte layer of the solar cell, iodine (specifically, I-)

It was found that when 3 was dissolved in the electrolyte, the electrolyte layer was dark brown. Based on this powerful knowledge, CDI, which is difficult to dissolve in the medium, is refined and dispersed in the electrolyte layer, so that the coloration caused by iodine can be significantly reduced while maintaining the same conversion efficiency as before. As a result, the present invention has been completed. [0011] That is, according to one aspect of the present invention, it includes a medium and an iodine-cyclodextrin inclusion compound having an average particle diameter of 20 m or less that is hardly soluble in the medium. Characteristic electrolyte compositions are provided.

[0012] According to another aspect of the present invention, there is provided a dye-sensitized solar cell (hereinafter, also simply referred to as "solar cell") in which an electrolyte layer includes the above electrolyte composition.

[0013] Still other objects, features, and characteristics of the present invention will become apparent by referring to the following description and preferred embodiments exemplified in the accompanying drawings.

Brief Description of Drawings

[0014] FIG. 1 is an explanatory diagram for explaining the absolute maximum length used to define the particle diameter of poorly soluble CDI.

FIG. 2 is a cross-sectional view showing one preferred embodiment of a solar cell provided by the present invention.

FIG. 3 is a diagram showing the results of absorbance measurement in Examples.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] In the following, the ability to describe a preferred embodiment for carrying out the present invention The technical scope of the present invention is not limited to the following form.

[0018] According to one aspect of the present invention, it includes a medium, and an iodine monocyclodextrin inclusion complex having an average particle diameter of 20 m or less that is hardly soluble in the medium. An electrolyte composition is provided.

[0019] First, the configuration of the electrolyte composition of the present embodiment will be described.

[0020] The electrolyte composition of the present embodiment first includes a medium.

There are no particular restrictions on the specific form of the medium. For example, a conventionally known solvent can be appropriately employed as a solvent for the electrolyte of the dye-sensitized solar cell. According to the strong form, the electrolyte composition of the present form is a liquid composition. As the characteristics of the solvent, it is preferable that the solvent is electrochemically inactive, the relative dielectric constant is high, and the viscosity is low. Examples of solvents having strong properties include: -tolyl solvents such as methoxypropio-tolyl and methoxyacetonitrile, y-petit-latatones, laterotonic solvents such as valerolatatane, ethylene carbonate Carbonate solvents such as propylene carbonate, ether solvents such as dioxane, jetyl ether, ethylene glycol dialkyl ether, methanol, ethanol Alcohols, alcohol solvents such as polypropylene glycol monoalkyl ether, aprotic polar solvents such as dimethyl sulfoxide and sulfolane, glycol solvents such as ethylene glycol and polyethylene glycol, aliphatic quaternary ammonium salts Examples include ionic liquids such as imidazolium salts. Among these, nitrile solvent, rataton solvent, carbonate solvent, glycol solvent, and ionic liquid are preferably used as the viewpoint power that is excellent in the above-described characteristics, and more preferably nitrile solvent is used. It is done. Note that only one of these solvents may be used alone, or two or more of them may be used in combination.

[0022] Note that the medium is not limited to a liquid (that is, a solvent), and may be a solid (for example, a gel). Examples of the solid medium include polypyrrole, copper iodide, and copper thiocyanide.

[0023] Secondly, the electrolyte composition of the present embodiment includes CDI.

[0024] The iodine-cyclodextrin inclusion compound (CDI) has a structure in which iodine is included in the cyclodextrin. When the electrolyte composition of this embodiment is used in the electrolyte layer of a dye-sensitized solar cell, the clathrated iodine is oxidized (I

By moving back and forth between 3-) and reductant (Γ), it functions as a redox pair in the electrolyte layer.

[0025] "Cyclodextrin" is a compound in which D-darcoviranose is bound cyclically by 1, 4 bonds. Cyclodextrins are roughly classified into ex-cyclodextrin (6), β-cyclodextrin (7), and γ-cyclodextrin (8), depending on the number of D-Dalcobilanose.

[0026] The CDI contained in the electrolyte composition of the present embodiment is CDI that is hardly soluble in the medium contained in the electrolyte composition (hereinafter, also simply referred to as “slightly soluble CDI”). Naturally, hardly soluble CDI hardly dissolves in the electrolyte composition, so that the dark brown coloration caused by iodine can be remarkably reduced in the electrolyte composition of this embodiment. Therefore, according to the electrolyte composition of this embodiment, the design performance of the solar cell can be improved. “Slightly soluble in the medium” means that when the medium is liquid (ie, the medium is a solvent), the solubility in a solvent at 25 ° C. is 5. OmgZmL or less. To do. As a method of measuring solubility, Experimental Chemistry Course 1—Basic Operation I, 4th edition, edited by The Chemical Society of Japan, 151—159 The method described on page shall be used. Further, even when the medium is in a solid state, if the CDI exhibits poor solubility as defined above in the liquid stage before the medium is solidified, the CDI may be dispersed and solidified in a suspended state. Thus, the function and effect of the electrolyte composition of the present embodiment can be exhibited.

[0027] The hardly soluble CDI contained in the electrolyte composition of the present embodiment is not particularly limited as long as it is hardly soluble in the medium contained in the electrolyte composition. That is, when the medium is a solvent, the solubility in a solvent at 25 ° C. should be 5. OmgZmL or less. The solubility is preferably 1. OmgZmL or less, more preferably 0.1 mgZmL or less. Examples of the cyclodextrin constituting the hardly soluble CDI include / 3-cyclodextrin. In this embodiment, it is particularly preferable to use cyclodextrin because an excellent effect can be obtained. However, other cyclodextrins may be used in some cases. In addition, newly developed poorly soluble CDI may be used. The cyclodextrin constituting the hardly soluble CDI contained in the electrolyte composition of the present embodiment may be only one type or two or more types.

[0028] The poorly soluble CDI contained in the electrolyte composition of the present embodiment is controlled to a value having a small particle size. Specifically, the average particle diameter of the hardly soluble CDI contained in the electrolyte composition of the present embodiment is 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less. When the average particle size is within the range of force, the dispersibility of the hardly soluble CDI in the electrolyte composition can be improved. In addition, if the average particle diameter of poorly soluble CDI exceeds 20 m, the electrolyte composition may be damaged in materials such as titanium oxide and the like that constitute the semiconductor electrode when the electrolyte composition is used in, for example, a dye-sensitized solar cell. There is also a risk of it. The lower limit value of the average particle diameter of the hardly soluble CDI is not particularly limited, but is preferably 0.01 m or more, more preferably 0.1 m or more in consideration of ease of production. The shape of the hardly soluble CDI particles is not limited to a spherical shape, and may be a plate shape, a needle shape, a column shape, a square shape, or the like. The shape of the particles can be appropriately selected in consideration of desired characteristics. When the particle shape is other than spherical, the particle shape is not uniform. Therefore, in the case of force, the absolute maximum particle length is used as the average particle size. Here, the “absolute maximum length” means the maximum distance L among the distances between any two points on the contour line of the particle 1 as shown in FIG. Here, average particle diameter of poorly soluble CDI Examples of the measuring method include centrifugal sedimentation light transmission method, laser diffraction Z scattering method, electrical detection method, and image analysis method. Here, when the value of the average particle diameter obtained by the measurement method is different, the value obtained by the method described in Examples described later is adopted as the average particle diameter.

[0029] The content of poorly soluble CDI in the electrolyte composition of the present embodiment is not particularly limited, but is preferably 0.005 to 0.4M, more preferably 0.01 to 0, based on the total amount of the medium. 3M, more preferably 0.05-0.2M. If the content of the hardly soluble CDI is too small, there is a possibility that a sufficient generated current cannot be obtained. On the other hand, if the content of poorly soluble CDI is too large, the color of the electrolytic solution becomes dark and there is a risk that light transmission may be hindered.

[0030] The electrolyte composition of the present embodiment may contain other components as long as the effects of the present invention are not impaired.

[0031] Examples of other components that can be included in the electrolyte composition include electrolytes other than CDI, bases, and cyclodextrins that do not include iodine.

[0032] By adding an electrolyte other than CDI, the power generation characteristics when the electrolyte composition of the present embodiment is used for an electrolyte layer of a solar cell can be improved. Examples of powerful electrolytes include metal iodide salts such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide; tetraalkylammonium iodide and pyridinium iodide. Quaternary ammonium iodide salts such as sodium iodide, imidazolium iodide; metal bromide salts such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide; tetraalkylammonium bromide, Quaternary ammonium bromide salts such as pyridinium bromide; metal complexes such as ferrocyanate-ferricyanate, ferucene-ferricium ion; sodium polysulfate, alkylthiol alkyldis Sulfur compounds such as rufide; viologen dye; hydroquinone-quinone; organic molten salts such as 1 propyl 2, 3 dimethylimidazolium-iodine (DMPII) It is.

[0033] By adding a base, the efficiency of electron transfer between the electrolyte layer and the semiconductor electrode or the counter electrode can be improved. Examples of the base include 4-61: 1; -butylpyridine (4-8-?),? ^ -Methyl benzimidazole, 2 picoline, 2, 6-lutidine and the like. For the purpose of improving photoelectric conversion efficiency and durability, a pyrimidine ring-containing base may be added. [0034] Cyclodextrins that do not include iodine contain I — produced from soot as power generation proceeds.

3 Can be included to generate CDI. For this reason, when cyclodextrin that does not include iodine is present in the electrolyte composition of the present embodiment, the effects of storing iodine and forming a conductive path can be exhibited. The specific form of cyclodextrin to be added is not particularly limited, and conventionally known cyclodextrins can be added. However, if the amount of cyclodextrin (for example, methyl-β-cyclodextrin) that can form CDI that is easily soluble in the solvent by inclusion of iodine is too large, it will be difficult in the original electrolyte composition. The meaning of using soluble CDI may be attenuated, and as a result, the effects of the present invention may not be sufficiently obtained. For this reason, when cyclodextrin that does not include iodine is added to the electrolyte composition of the present embodiment, it is preferable to use the cyclodextrin described above as cyclodextrin constituting hardly soluble CDI. Better ,.

[0035] In the electrolyte composition of the present embodiment, among the iodine atoms (I) present in the composition, the ratio of those that are clathrated to form a clathrate compound is particularly limited. However, it is preferably 40 to 99% by mass, more preferably 60 to 97% by mass or more, and still more preferably 80 to 95% by mass. If this ratio is too small, there is a problem that the ratio of iodine atoms dissolved in the medium is relatively increased, and the iodine color exhibited by the electrolyte becomes conspicuous. On the other hand, if this ratio is too large, the amount of iodine that functions as a redox system is reduced, and the battery performance may be reduced.

[0036] The content of each component other than the poorly soluble CDI in the electrolyte composition of the present embodiment is not particularly limited, and is appropriately adjusted in consideration of the content of the hardly soluble CDI that is an essential component and desired characteristics. sell.

[0037] The form of the electrolyte composition of the present embodiment is not particularly limited, and may be a liquid composition or a solid (eg, gel) composition depending on the type of medium. . However, from the viewpoint of carrier diffusion, the electrolyte composition of the present embodiment is preferably a liquid composition. In the case of a gel composition, in addition to a gelling agent and a polymerization initiator, a force that may contain a polymer or a polymerizable monomer that can constitute the matrix of the gel. Specific forms of these components are particularly limited. Instead, conventionally known knowledge can be referred to as appropriate.

[0038] The electrolyte composition of the present embodiment can be produced without using a special technique. For example, desired By preparing a slightly soluble CDI having an average particle size of 1 and other necessary additives, adding them to a separately prepared medium to a desired concentration, and stirring to obtain a uniform dispersion. The electrolyte composition of this embodiment is obtained. In addition, after adding a hardly soluble CDI to obtain a dispersion, an electrolyte composition may be obtained by removing the insoluble hardly soluble CDI. In other words, the supernatant of the dispersion after addition of poorly soluble CDI can also be used as a liquid electrolyte composition. In this embodiment, the means for removing poorly soluble CDI, the removal ratio, etc. are not particularly limited, taking into consideration the desired color tone of the electrolyte and the desired battery performance when the electrolyte is used in elements such as solar cells. Can be set as appropriate.

[0039] When preparing the poorly soluble CDI, it may be prepared by synthesizing itself, or when the product is sold, it may be prepared by purchasing the product. Conventionally known synthesis methods can be used without any particular limitation on the method of synthesizing poorly soluble CDI by itself. For example, by reacting j8-cyclodextrin, iodine, and an iodine solubilizing aid (for example, yowi potato) in water, poorly soluble CDI, 1 / 3-cyclodextrin, can be synthesized. However, other approaches can also be employed.

[0040] When the particle diameter of the prepared poorly soluble CDI is large, the average particle diameter can be controlled to a desired value by performing pulverization. Specific means for the pulverization process are not particularly limited. Examples thereof include a ball mill, a jet mill, a counter collision process, a roller mill, and a bead mill. The pulverization conditions such as the pulverization time are not particularly limited, and can be appropriately set in consideration of a desired average particle size value.

[0041] When the electrolyte composition of the present embodiment contains a polymerization initiator, a gel electrolyte composition can be produced by performing a polymerization treatment. The specific form of the polymerization treatment is not particularly limited, and can be appropriately selected depending on the kind of the polymerization initiator to be added. For example, when a azo initiator that is a thermal polymerization initiator is added, heat treatment may be performed as a polymerization treatment.

[0042] The electrolyte composition of the present embodiment can be preferably used as an electrolyte constituting an electrolyte layer of a dye-sensitized solar cell. That is, according to another embodiment of the present invention, a photoelectrode in which a transparent electrode and a semiconductor electrode are laminated, a counter electrode, and an electrolyte layer sandwiched between the semiconductor electrode and the counter electrode of the photoelectrode A dye-sensitized solar cell having Thus, the dye layer is a dye-sensitized solar cell, characterized in that the electrolyte layer contains the above-described electrolyte composition. Hereinafter, a preferred embodiment of the solar cell of the present embodiment will be described with reference to the drawings. In addition, in the solar cell of this embodiment, a conventionally known embodiment can be similarly adopted for the solar cell except that the electrolyte layer includes the above-described electrolyte composition. Therefore, the technical scope of the solar cell of this embodiment is not limited only to the following embodiment and the illustrated embodiment.

FIG. 2 is a cross-sectional view showing a preferred embodiment of the solar cell of the present embodiment. For convenience of explanation, the dimensional ratios in the drawings are exaggerated, and the illustrated form may be different from the actual one.

In the form shown in FIG. 2, solar cell 10 mainly includes photoelectrode 100, counter electrode 200, electrolyte layer 400 sandwiched between photoelectrode 100 and counter electrode 200 by spacer 300, and force. It is configured. The photoelectrode 100 mainly has a two-layer structure consisting of a transparent electrode 120, a semiconductor electrode 140, and the like, and the semiconductor electrode 140 is disposed on the electrolyte layer 400 side.

[0045] The solar cell 10 is a power generation system that uses energy of light such as sunlight. When power generation occurs in the solar cell 10, first, the sensitizing dye adsorbed on the semiconductor electrode 140 is excited by the energy of the irradiated light, and electrons are transferred from the excited sensitizing dye to the semiconductor electrode 140. Injected. Then, the electrons injected into the semiconductor electrode 140 are collected by the transparent electrode 120 and taken out to the outside, and perform electrical work on the external load. Hereinafter, each member constituting the solar cell 10 will be described in detail.

The transparent electrode 120 is an electrode that is disposed on the side on which irradiation light (for example, sunlight) that is an energy source of the solar cell 10 is incident, and constitutes the photoelectrode 100 together with a semiconductor electrode 140 described later. . In the form shown in FIG. 2, the transparent electrode 120 has a configuration in which a transparent conductive film 124 is formed on the semiconductor electrode 140 side of a glass substrate that is the transparent substrate 122. As a constituent material of the transparent conductive film 124, for example, a transparent electrode used for a liquid crystal panel or the like is illustrated. Examples of a strong transparent electrode include fluorine-doped tin oxide coated glass, indium tin oxide coated glass, zinc oxide: aluminum coated glass, and antimony doped oxide-tin coated glass. In the form shown in FIG. 2, a force in which a glass substrate is used as the transparent substrate 122 constituting the transparent electrode 124 The transparent substrate 122 may be made of other materials. Examples of other materials include a transparent plastic substrate and a transparent inorganic crystal. Note that the shape and size of the transparent electrode 120 are not particularly limited. In some cases, a protective layer (not shown) having a force such as an antireflection film may be further disposed on the surface of the transparent electrode 120 on the transparent substrate 122 side.

As the transparent electrode 120, a commercially available product may be purchased, or a transparent conductive film 124 may be formed on the surface of the transparent substrate 122. Examples of the method for forming the transparent conductive film 124 on the surface of the transparent substrate 122 include thin film formation techniques such as spray coating, vacuum deposition, sputtering, CVD, and sol-gel.

As shown in FIG. 2, a semiconductor electrode 140 is arranged on the surface of the transparent electrode 120 on the transparent conductive film 124 side. The semiconductor electrode 140 is in contact with an electrolyte contained in an electrolyte layer, which will be described later, and functions as a means for transmitting electrons injected from a sensitizing dye, which will be described later, to the transparent electrode 120. The material constituting the semiconductor electrode 120 is not particularly limited, and examples thereof include conventionally known oxide semiconductor particles. Specific examples include titanium oxide, zinc oxide, tin oxide, niobium oxide, indium oxide, tungsten oxide, zirconium oxide, lanthanum oxide, tungsten oxide, strontium titanate, and barium titanate. Among them, anatase-type titanium dioxide is preferably used from the viewpoint of high long-term stability against chemicals. The average particle size of the oxide semiconductor particles is not particularly limited, and is preferably about 10 to 30 nm.

[0050] As a method of forming the semiconductor electrode 140 on the surface of the transparent electrode 120 on the transparent conductive film 124 side, for example, a dispersion liquid containing oxide semiconductor particles is prepared, and the dispersion liquid is applied to the surface of the transparent conductive film 124. For example, it may be applied to the substrate, dried as necessary, and then fired.

[0051] To prepare the dispersion, oxide semiconductor particles, and other additives as required

(For example, a surfactant, a viscosity modifier, etc.) may be added to an appropriate solvent and uniformly dispersed by stirring. The solvent is not particularly limited, but examples thereof include water, organic solvents, and solvents. These mixed solvents can be widely used. The means for applying the obtained dispersion and the means for drying and baking the obtained coating film may be appropriately selected from conventionally known means without particular limitations.

A sensitizing dye (not shown) is attached to the particle surface of the constituent material of the semiconductor electrode 140 (for example, anatase type titanium dioxide). The sensitizing dye is excited by light energy of irradiation light such as sunlight (preferably having a wavelength in the visible light region to an infrared light region, more preferably 420 to 800 nm), and returns to a ground state. At this time, the semiconductor electrode 140 has a function of transmitting electrons to the particles of the constituent material. It should be noted that holes (h +) remain in the sensitizing dye after the electrons are transferred to the semiconductor electrode 140, but this hole is a reductant of a redox pair (for example, Γ) contained in the electrolyte in the electrolyte layer 400 described later. To an acid body (for example, I-)

3 disappears by oxidation.

[0053] The specific form of the sensitizing dye is not particularly limited as long as it has the above function, and conventionally known forms can be appropriately employed. Examples of sensitizing dyes include metal complexes and organic dyes. Examples of metal complexes include N3 dye (ruthenium (2, 2'-bipyridylo 4, 4, -dicarboxylate) (NCS) · 2Η 0), N719 dye (ruthenium (

2 2 2

2, 2'-bibilidyl 1,4'-dicarboxylate) (NCS) · 2 (tetraptyl ammo-

twenty two

Examples of organic dyes include ΝΚΧ-2877 coumarin dye (produced by Hayashibara Biochemical Laboratories Co., Ltd.), D-102 merocyanine dye (produced by Mitsubishi Paper Industries, Ltd.), D-149 indoline dye. (Mitsubishi Paper Co., Ltd.). Of course, other sensitizing dyes may be used.

[0054] The method for attaching the sensitizing dye to the particle surface of the constituent material of the semiconductor electrode 140 is not particularly limited, and a conventionally known method such as a chemical adsorption method or a physical adsorption method may be used. As an example of the physical adsorption method, first, a dye solution is prepared by adding a sensitizing dye to an appropriate solvent. The solvent is not particularly limited, but -tolyl solvents such as acetonitrile and petit-tolyl; alcohol solvents such as tert-butanol and ethanol; and mixed solvents thereof can be used. Next, the semiconductor electrode 140 is immersed in the dye solution. Further, if necessary, a sensitizing dye can be attached to the particle surface of the constituent material of the semiconductor electrode 140 by performing a drying treatment. When the dye solution is heated to reflux during immersion, the sensitizing dye adsorbs. Can be promoted.

The counter electrode 200 is an electrode disposed on the side facing the photoelectrode 100 (that is, the side facing the side on which the irradiation light is incident). The counter electrode 200 is an oxidant (for example, I ") of a redox pair contained in the electrolyte in the electrolyte layer 400 described later.

3 has a function to deliver electrons. This

The oxidant is reduced to a reductant (eg, Γ). In addition, the reduced body produced | generated by reduction | restoration is oxidized by the hole which a sensitizing dye has on the surface of the semiconductor electrode 140 as mentioned above, and returns to an oxidized body. By repeating this, the power generation cycle proceeds.

[0056] As a material constituting the counter electrode 200, for example, a material similar to that used for a liquid crystal panel, a silicon solar cell, or the like can be used. Specifically, the same material as exemplified for the transparent electrode 120 may be used. For example, a configuration in which a transparent substrate and a transparent conductive film are laminated is exemplified. In the case of a hook-like form, the transparent conductive film is disposed on the electrolyte layer 400 side.

[0057] On the surface of the counter electrode 200 on the electrolyte layer 400 side (when the counter electrode 200 has a laminated structure of a transparent substrate and a transparent conductive film, the surface of the transparent conductive film), as shown in FIG. A thin film electrode 220 is preferably disposed. By arranging the strong metal thin-film electrode 220, transfer of electrons between the counter electrode 200 and the oxidation-reduction pair in the electrolyte layer 400 can proceed smoothly. Although the material which comprises the metal thin film electrode 220 is not restrict | limited in particular, For example, electroconductive materials, such as metals, such as platinum and gold | metal | money, carbon, and a conductive polymer, are mentioned. In particular, when the metal thin film electrode 220 is made of platinum, the transfer of electrons can be performed more smoothly.

As the counter electrode 200, a commercially available product may be purchased, or the transparent electrode 120 may be produced by a method similar to the production method described above.

[0059] The method of forming the metal thin film electrode 220 on the surface of the counter electrode 200 on the electrolyte layer 400 side is not particularly limited, and the method described above as a method of forming the transparent conductive film 124 on the surface of the transparent substrate 122 (for example, Sputtering methods) can be used as well.

Spacer 300 functions as a means for providing a space for holding electrolyte layer 400 described later. The material constituting the spacer 300 is not particularly limited. For example, silica Examples thereof include beads and rosin beads. These materials are usually sealed with a noda for the purpose of preventing electrolyte leakage from the electrolyte layer 400. The noinder for sealing the spacer constituent material is not particularly limited, and examples thereof include epoxy resin, silicone resin, olefin-based resin, and ionomer resin.

[0061] The electrolyte layer 400 includes an electrolyte. The solar cell of this embodiment is characterized in that it includes the above-described electrolyte composition. Since the specific form of the electrolyte composition is as described above, detailed description thereof is omitted here.

[0062] As described above, the electrolyte composition provided by one embodiment of the present invention includes a hardly soluble CDI having a predetermined average particle diameter, and these are dispersed in a medium. I—and acting as a redox couple

3 Of Γ, I—

3 It is thought that during dismantling, it exists mainly in the form of inclusion in CDI. Therefore, it is not included in CDI and dissolved in the liquid.

3 Concentration is the minimum concentration necessary for the power generation reaction to proceed to a very low level. For this reason, in the electrolyte composition, the dark brown coloration caused by iodine is significantly reduced as compared with the conventional electrolyte composition for solar cells. Therefore, also in the electrolyte layer 400 of the solar cell of the present embodiment including the electrolyte composition, coloration caused by iodine can be reduced. Therefore, the solar cell of this embodiment can be placed at a place where it has been difficult to place the solar cell because of its iodine color. That is, according to this embodiment, a solar cell with excellent design performance can be provided.

[0063] In addition, the solar cell of this embodiment is also excellent in durability. This is presumed to be due to the following reasons. In other words, in conventional solar cells, I present in the electrolyte

Part of 3—

It is decomposed by the reaction of I "→ 1 + 厂 and the generated I is digested outside the electrolyte layer.

3 2 2

There was a problem. On the other hand, in the solar cell of this embodiment, as described above, only I— necessary for the progress of the power generation reaction is dissolved in the electrolyte, and other I— is included in CDI.

3 3

The above I, which has been a problem in the past due to the existence of

Sublimation of 2 can be suppressed. As a result, the durability of the solar cell can be improved.

[0064] Although the use of the electrolyte composition provided by the present invention has been described in detail above by taking a dye-sensitized solar cell as an example, the solar cell to which the electrolyte composition can be applied is a dye-sensitized solar cell. It is not limited only to solar cells. The electrolyte composition provided by the present invention comprises The present invention can be widely applied to a system using an elementary redox medium. For example, it can be applied to a water splitting system using a combination with a dye-sensitized photocatalyst in addition to a battery. In addition, the battery provided by the present invention is parallel or in series with conventionally used single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, compound semiconductor solar cells, etc. It may be used as an assembled battery that is connected. The specific forms of these batteries and systems are not particularly limited, and conventionally known knowledge can be appropriately referred to.

[0065] Next, the present invention will be described in more detail with reference to examples. However, the following examples do not affect the technical scope of the present invention.

First, 3-methoxypropio-tolyl (3-MPN) was prepared as a solvent.

[0067] On the other hand, iodine-β-cyclodextrin inclusion complex (“BCDI-20”, manufactured by Niho Ho Chemical Co., Ltd.) was prepared as poorly soluble CDI. The solubility of CDI in 3-MPN at 25 ° C is less than 0.1 mgZmL.

Next, the hardly soluble CDI prepared in the above was pulverized using a ball mill to obtain a fine powder. The average particle size of the fine powder obtained was measured by the laser diffraction Z-scattering method.

[0069] To 3-MPN, the solvent prepared above, fine powder (0.05 M) of the poorly soluble CDI (BCDI-20) obtained above, lithium iodide (Lil) (0. 1M), the base 4-tert butyl pyridine (4 TBP) (0.5M), and the organic molten salt compound 1-propyl-2,3 dimethylimidazolium-iodine (DMPII) (0.6M) Then, a uniform dispersion was obtained by stirring, and this was used as the electrolyte composition (electrolyte) of this example.

Except that the concentration of the iodine-β-cyclodextrin inclusion complex at the time of preparing the electrolytic solution was set to 0.1% (Example 2) and 0.2% (Example 3). Uniform dispersions were obtained by the same method as in Example 1, and these were used as the electrolytic solutions in the Examples.

[0071] <Comparative Example 1> Instead of iodine-β-cyclodextrin inclusion compound, simple iodine (I)

2

A uniform dispersion exhibiting a roaring brown color was obtained in the same manner as in Example 1 except that it was added at a concentration, and this was used as the electrolyte of Comparative Example 1.

[0072] <Comparative Example 2>

Instead of iodine-β-cyclodextrin inclusion compound, 77 mgZmL (about 0.05 M ) Except that it was added in the same manner as in Example 1 above, a uniform solution showing B-brown color was obtained, and this was used as the electrolyte of Comparative Example 2. When the electrolyte solution obtained in this comparative example was subjected to absorbance measurement, it showed the same behavior as the electrolyte solution obtained in Example 1 above. However, the value of absorbance itself was 2.6 times that in Example 1 over the entire wavelength region.

[0073] <Comparative Example 3>

To the electrolyte obtained in Comparative Example 1 above, j8-cyclodextrin was added at a concentration of 57 mg / mL (0.05 M) to obtain a uniform dispersion showing a dark brown color. The electrolyte solution was as follows. The electrolyte solution obtained in this Comparative Example was not measured for the absorbance described later, but the change in color tone with time was not visually confirmed, and the dark brown color was observed despite the addition of j8-cyclodextrin. Was maintained. This indicates that even if cyclodextrin is separately added to the electrolyte containing simple iodine, the effect of improving the color tone of the electrolyte cannot be expected!

[0074] <Measurement of Absorbance for Visible Light>

For the electrolyte solutions obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the absorbance to visible light was measured.

[0075] For the measurement of absorbance, a UV-VIS absorbance detector (UV-2450; manufactured by Shimadzu Corporation) was used, and the wavelength of irradiated light was scanned in the range of 400 to 800 nm. The length of the sample cell set in the detector in the direction of light irradiation was 10 mm. A solution obtained by the same method as in Example 1 except that iodine-β-cyclodextrin and lithium iodide, which are iodine compounds, were not used was used as a control sample. Figure 3 shows the results obtained by measuring the absorbance. [0076] When the absorbance at 550 nm, which is the optimum wavelength of the sensitizing dye, is compared with the results shown in FIG. 3, it can be seen that the absorbance of the electrolyte solution of the example is significantly reduced compared to the electrolyte solution of the comparative example. . Of course, the lower the concentration of CDI added, the lower the absorbance. Therefore, according to the electrolyte composition provided by the present invention, it is suggested that the coloration caused by iodine can be remarkably reduced in the solar battery cell.

[0077] <Measurement of photoelectric conversion efficiency>

Using the electrolyte solutions of Example 1 and Comparative Example 1 obtained above, dye-sensitized solar cells were prepared by the following method, and the photoelectric conversion efficiency was measured.

First, a conductive glass substrate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 1 mm) was prepared as a transparent electrode. As shown in FIG. 2, the glass substrate is composed of two layers: a transparent substrate and a transparent conductive film (thickness: 750 A). Next, a dispersion (particle concentration: 30% by mass) in which anatase-type titanium dioxide particles (average particle size: 21 nm) are dispersed in a nitric acid aqueous solution (pH 7.0) as a solvent on one side of the prepared glass substrate Was applied and baked at 500 ° C. for 30 minutes to form a semiconductor electrode (thickness: 10 m) having a titanium dioxide-titanium force on the surface of the glass substrate. Then, 0. Asetonitoriru Zt- butanol mixed solvent solution containing 03 mass ^_0/0 of N3 dye (volume ratio 1: 1) during the immersed glass substrate after the semiconductor electrode formation, 12 at 30 ° C The photoelectrode was produced by allowing the N3 dye to be adsorbed on the surface of the semiconductor electrode by allowing it to stand for a period of time.

[0079] On the other hand, another conductive glass substrate similar to that prepared above was prepared, and platinum fine particles were supported on one side of the substrate by sputtering to form a metal thin film electrode, thereby producing a counter electrode. did.

[0080] The photoelectrode and counter electrode produced above were laminated via a spacer (thickness: 30 m) so that the semiconductor electrode and the platinum support layer faced each other. Next, the electrolytic solution obtained in Example 1 or Comparative Example 1 was injected into the gap provided by the spacer having ionomer resin film power, thereby completing the dye-sensitized solar cell.

[0081] The photoelectric conversion efficiency of the two dye-sensitized solar cells prepared above was measured.

Specifically, using a solar simulator (YSS-80; manufactured by Yamashita Denso Co., Ltd.), simulated sunlight from a xenon lamp light source was irradiated through an AM filter (AMI. 5), and current- The pressure characteristics were measured. At this time, the intensity of irradiated light was lOOmWZcm ² . The photoelectric conversion efficiency r? Was calculated by the following formula 1.

[0082] [Equation 1]

[Formula 1] η (%) =. ^{c sc} Π xl 0 0

[0083] where V is the open circuit voltage (V), J is the short circuit current density (mAZcm ² ), and FF is

OC SC

Filling factor, P is irradiation light intensity (mWZcm ² ).

0

As a result, the conversion efficiency of the solar cell using the electrolytic solution of Comparative Example 1 was 5.78%, whereas the conversion efficiency of the solar cell using the electrolytic solution of Example 1 was 5.55. %, The conversion efficiency was almost the same.

[0085] Therefore, even when the composition of the electrolyte that reduces the coloration caused by iodine is configured as in the present invention, there is almost no possibility that the conversion efficiency decreases with this. It is suggested.

[0086] <Comparative Example 4>

A uniform dispersion was obtained in the same manner as in Example 1 except that BCDI-20 having an average particle size of 30 μm was used, and this was used as the electrolyte of Comparative Example 4.

[0087] A dye-sensitized solar cell was prepared by the same method as described in the above-mentioned "Measurement of photoelectric conversion efficiency" except that the electrolytic solution of Comparative Example 4 obtained above was used. Tried.

[0088] As a result, even if an attempt was made to inject the pore force electrolyte provided by the spacer having ionomer resin film strength, not all BCDI-20 was injected uniformly, and moreover, the dioxide dioxide constituting the semiconductor electrode. Damage to the titanium surface was observed. This is presumed to be due to the fact that the particle size of BCDI-20 in the electrolyte is approximately the same as the thickness of the gap provided by the spacer.

[0089] This application is based on Japanese Patent Application No. 2005-147005 filed on May 19, 2005, the disclosure of which is incorporated by reference in its entirety.

Claims

The scope of the claims

[1] An electrolyte composition comprising a medium and an iodine-cyclodextrin inclusion compound which is hardly soluble in the medium and has an average particle diameter of 20 m or less.

[2] The electrolyte composition according to claim 1, wherein the cyclodextrin constituting the iodine-cyclodextrin inclusion complex is β-cyclodextrin.

[3] The electrolyte composition according to claim 1 or 2, wherein the concentration power of the iodine-cyclodextrin inclusion complex is 1 to 30% by mass relative to the total amount of the medium.

[4] The electrolyte composition according to any one of claims 1 to 3, which is a liquid composition.

[5] The solvent constituting the liquid composition is selected from a group force consisting of a nitrile solvent, a Rathan solvent, a carbonate solvent, a glycol solvent, and an ionic liquid force.

The electrolyte composition according to claim 4, wherein there are two or more kinds.

[6] a photoelectrode formed by laminating a transparent electrode and a semiconductor electrode;

With the counter electrode,

An electrolyte layer sandwiched between the semiconductor electrode and the counter electrode of the photoelectrode, and a dye-sensitized solar cell,

The dye-sensitized solar cell, wherein the electrolyte layer includes the electrolyte composition according to any one of claims 1 to 5.