JP2012031373A - Optical functional material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensitizing dye for photoelectric conversion for a dye-sensitizing photoelectric conversion cell stable and high in conversion efficiency.SOLUTION: The optical functional material is expressed by general formula (1), wherein in the formula: Rand Reach independently represents a hydrogen atom or alkyl; Rto Reach independently represents a hydrogen atom or alkyl; Rand Reach independently represents an electron-withdrawing group; Xan Xeach independently represents a non-substituted or alkyl-bearing divalent thiophene residue or non-substituted or alkyl-bearing divalent condensed thiophene residue; and m and n each represents an integer, and the sum of m and n is 1-6.

Description

  The present invention relates to an optical functional material. The optical functional material can be used as a photoelectric conversion material, a light emitting material, a light absorbing material, or the like. The present invention also relates to a photoelectric conversion material using this optical functional material, a photoelectric conversion electrode, and a photoelectric conversion cell using the same.

  As for photovoltaic power generation, single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide have been put into practical use or research and development. In order to further spread these solar cells, it is necessary to overcome problems related to manufacturing costs, raw materials, energy payback time, and the like. On the other hand, many solar cells using organic materials aimed at increasing the area and price have been proposed so far, but they have a problem of low conversion efficiency and poor durability.

  Under such circumstances, a photoelectric conversion electrode and a photoelectric conversion cell using a semiconductor microporous material sensitized with a dye, and a material and a manufacturing technique for producing the photoelectric conversion electrode are disclosed. (See Non-Patent Document 1 and Patent Document 1) The disclosed battery comprises a porous titanium oxide layer spectrally sensitized with a ruthenium complex dye as a working electrode, an electrolyte layer mainly composed of iodine, and a counter electrode. This is a dye-sensitized photoelectric conversion cell. The first advantage of this method is that an inexpensive photoelectric conversion element can be provided because an inexpensive oxide semiconductor such as titanium oxide is used. The second advantage is that a relatively high conversion efficiency can be obtained because the ruthenium complex dye used has a wide absorption in the visible light region.

  One problem with such a dye-sensitized photoelectric conversion cell is that ruthenium is used as a raw material for the dye. Ruthenium has a relatively low Clark number of 0.01 ppm, and a small amount is present on the earth comparable to platinum and palladium. Therefore, there is a risk of depletion when used in large quantities. Furthermore, since ruthenium complex dyes are expensive, they hinder the mass diffusion of photoelectric conversion cells.

  Recently, researches on dyes other than ruthenium complexes have been actively conducted as sensitizing dyes in dye-sensitized solar cells. Examples thereof include phenylxanthene dyes, phthalocyanine dyes, coumarin dyes, cyanine dyes, porphyrin dyes, azo dyes, and the like. These organic dyes are expected to have high photoelectric conversion efficiency because they have a large extinction coefficient and a large degree of freedom in molecular design as compared with ruthenium complexes. However, organic sensitizing dyes with good performance have not yet been found due to the narrow light absorption region of the dyes and the inefficiency of charge injection into titanium oxide.

  In order to solve these problems, it has been disclosed that a sensitizing dye having a substituted acrylic acid moiety has a relatively high conversion efficiency as a sensitizing dye characterized by an adsorption terminal with titanium oxide (Patent Document). 2 and 3). A characteristic feature of these sensitizing dyes is that the electron-withdrawing effect at the end of acrylic acid is increased by the fact that the carbon atom to which the carboxyl group at the end of acrylic acid is bonded has an electron-withdrawing substituent such as a cyano group. It is in. The sensitizing dye is bonded to the surface of an inorganic oxide semiconductor such as titanium oxide at a terminal carboxy group, and excited electrons generated by light absorption of the sensitizing dye are injected into the inorganic oxide side through the carboxy group. Therefore, the electron injecting effect at this part is strengthened to promote the electron injecting effect, and as a result, high conversion efficiency is realized. As a representative example, a sensitizing dye combining a coumarin skeleton and an acrylic acid terminal having a cyano group achieves a high conversion efficiency of 5% or more. (See Non-Patent Document 2) In addition, a high conversion efficiency of 5% or more is also achieved in a sensitizing dye in which a similar acrylic acid terminal is introduced into a chromophore combining a polyene structure and an amino group. (See Non-Patent Document 3)

  However, since the absorption wavelength region such as the coumarin skeleton is biased to a relatively short wavelength side in the visible light region, in order to increase the absorption wavelength based on this skeleton, a long-chain double bond site ( Such as polyene structure). Long-chain double bond sites have low durability such as being easily oxidized to active oxygen or the like, and having low thermal stability. For the same reason, it is expected that the sensitizing dye having the polyene structure described in Non-Patent Document 3 also has a problem in durability. In addition, cyanine dyes that function as sensitizing dyes also have long-chain double bond sites, and thus are examples of dyes with low durability.

  For the above reasons, regardless of the introduction of sites with low durability such as long-chain double bond sites, etc., it has a highly durable skeleton structure, and further uses raw materials that are not subject to depletion. A sensitizing dye capable of providing a photoelectric conversion cell having high conversion efficiency has been demanded.

US Pat. No. 4,927,721 JP 2002-164089 A WO 02/11213 pamphlet

Nature (Vol. 353, 737-740, 1991) Chem. Commun. (569-570, 2001) Chem. Commun. (Pages 252-253, 2003)

  An object of the present invention is to use a sensitizing dye for a dye-sensitized photoelectric conversion cell that does not use a material that may be depleted such as ruthenium, has a highly durable skeleton structure, is inexpensive and has high conversion efficiency. Is to provide. Furthermore, a photoelectric conversion material in which this sensitizing dye is connected to the surface of the inorganic semiconductor porous body, a photoelectric conversion electrode formed by laminating the photoelectric conversion material on the conductive surface of a transparent substrate having a conductive surface, and An object of the present invention is to provide a photoelectric conversion cell in which a photoelectric conversion electrode is combined with a conductive counter electrode via an electrolyte layer.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a photoelectric property exhibiting good characteristics by linking a specific sensitizing dye to the surface of an inorganic oxide semiconductor laminated on a transparent conductive substrate. The inventors have found that a conversion cell can be produced and have reached the present invention.

  That is, the present invention relates to an optical functional material represented by the following general formula (1).

General formula (1)

[Wherein, R ¹ and R ² each independently represents a hydrogen atom or an alkyl group.
R ^{3 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group.
R ¹¹ and R ¹² each independently represents an electron withdrawing group.
X ¹ and X ² each independently represents an unsubstituted or divalent thiophene residue having an alkyl group or an unsubstituted or divalent fused thiophene residue having an alkyl group.
M and n represent integers, and the sum of m and n is 1 to 6. ]

The present invention also relates to the above optical functional material in which R ¹¹ is a cyano group.

The present invention also relates to the above optical functional material, wherein R ¹² is a carboxyl group.

  The present invention also relates to a sensitizing dye for photoelectric conversion comprising the optical functional material.

  The present invention also relates to a photoelectric conversion material obtained by connecting the sensitizing dye and an inorganic semiconductor porous body.

Moreover, this invention relates to the photoelectric conversion electrode formed by laminating | stacking the said photoelectric conversion material on a transparent electrode.

  The present invention also relates to a photoelectric conversion cell comprising the photoelectric conversion electrode, an electrolyte layer, and a conductive counter electrode.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the photoelectric conversion cell which has high photoelectric conversion efficiency with the material which does not have a possibility of exhaustion. In addition, by combining the sensitizing dye of the present invention with other sensitizing dyes, production of a photoelectric conversion material, a photoelectric conversion electrode, and a photoelectric conversion cell that exhibit a highly efficient photoelectric conversion function in a wide wavelength range with respect to sunlight. Is possible. Furthermore, since the optical functional material of the present invention has a structure in which the main skeleton is connected to a thiophene ring or a condensed thiophene ring and does not have a polyene structure, it is not deteriorated by light, heat, etc., and has a highly stable photoelectric conversion cell. Can be provided.

FIG. 1 shows the configuration of a photoelectric conversion cell test sample.

  Hereinafter, the present invention will be described in detail.

  In the present invention, the optical functional material means a sensitizing effect, a heat generating effect, a color developing effect, a color fading effect, a phosphorescent effect, a phase change effect, a photoelectric conversion effect, a photomagnetic effect, a photocatalytic effect, a light modulation effect by absorbing light, A material that exhibits functions such as an optical recording effect and a radical generation effect. Or it is the material which receives these effects and has a light emission function. The photofunctional material includes, for example, a photoelectric conversion material, a light emitting material, an optical recording material, an image forming material, a photochromic material, an electroluminescent material, a photoconductive material, a dichroic material, a radical generating material, an acid generating material, a base generating material, Phosphorescent material, nonlinear optical material, photosensitive material, light absorbing material, near infrared absorbing material, photochemical hole burning material, optical sensing material, optical marking material, sensitizing material for photochemical treatment, optical phase change recording material, photosintering It can be widely used for recording materials, magneto-optical recording materials, photodynamic therapy dyes, photocatalytic water decomposition sensitizing dyes, photoelectric conversion sensitizing dyes, and the like.

  In this specification, since the optical functional material represented by the general formula (1) is mainly used as a sensitizing dye for photoelectric conversion, this material is mainly referred to as a sensitizing dye for photoelectric conversion or a sensitizing dye. It does not deny a wide range of applications.

  The operation mechanism of the dye-sensitized solar cell consists of the following processes. That is, the process of injecting electrons from the excited sensitizing dye into the conduction band of an inorganic semiconductor such as titanium oxide after photoexcitation of the sensitizing dye that has absorbed sunlight was injected and injected into the inorganic semiconductor. It is a reduction process by electron injection from a redox system including iodine to a sensitizing dye.

  Therefore, functions necessary for a sensitizing dye for photoelectric conversion include that the dye has a wide absorption region and can efficiently absorb sunlight, and that charges can be efficiently injected into an inorganic compound semiconductor such as titanium oxide. It is done.

  The sensitizing dye represented by the general formula (1) can be broadened by adjusting the absorption region of the sensitizing dye by adjusting the site in the chemical structure. In conventional cyanine dyes and dyes described in Chem. Commun., Pp. 252-253, 2003, the absorption region of the dye is broadened by using a polyene structure. When this method is used, the polyene structure is susceptible to oxidation by active oxygen, and thus tends to cause photodegradation. There is also a drawback that the thermal stability is low. In the sensitizing dye represented by the general formula (1), the main skeleton has a structure in which a thiophene ring or a condensed thiophene ring is connected, and since it does not take a polyene structure, such a problem can be avoided. .

  Moreover, since the sensitizing dye represented by the general formula (1) has an electron-withdrawing group such as an acidic functional group or a derivative thereof at the terminal, physical adsorption on the surface of an inorganic compound semiconductor such as titanium oxide. In addition, since chemical adsorption or the like via an ester bond is possible, electron injection into an inorganic semiconductor such as titanium oxide is efficiently performed.

Further, when R ¹¹ and R ¹² have a structure such as a cyano group or an acidic group, which is an electron-withdrawing group, the electron accepting property of the carbon atom to which these functional groups are bonded becomes extremely high. Since it is bonded to the dye skeleton represented by the general formula (1) via a double bond, excited electrons are injected very efficiently into an inorganic semiconductor such as titanium oxide via the π-conjugated system of the dye skeleton. The

  Further, the dye represented by the general formula (1) has an absorption region due to a chemical structure that has an electron-donating amino group at one end and an acidic group that is an electron-withdrawing group at the other end. It is expected to increase the efficiency of electron injection into inorganic compound semiconductors such as titanium oxide.

  Further, the chemical structure of the dye represented by the general formula (1) has a structure in which an electron accepting site and an electron donating site are divided by a double bond and connected by a π-conjugated system. Such a characteristic chemical structure tends to localize electrons to an electron-donating site in the ground state and localize electrons to an electron-accepting site in the excited state. Electron injection into an inorganic compound semiconductor such as can be performed very efficiently.

  That is, it can be said that the chemical structure of the dye represented by the general formula (1) is a structure that can achieve high photoelectric conversion efficiency and high stability.

  Next, each substituent in the pigment | dye represented by General formula (1) is demonstrated.

R ¹ and R ² in the dye represented by the general formula (1) each independently represent a hydrogen atom or an alkyl group.

  As the alkyl group, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, tert-pentyl group, hexyl group, Examples include isohexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group and the like.

R ¹ and R ² are preferably alkyl groups having a branched skeleton. Examples thereof include a tert-butyl group and a 1,1,3,3-tetramethylbutyl group. These alkyl groups have solubility and stability, and since they are bulky substituents, they are highly effective in preventing stacking between molecules, and can achieve high performance as sensitizing dyes.

R ^{3 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group.

When R ^{3 to} R ¹⁰ are alkyl groups, they are preferably alkyl groups having 1 to 12 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec -Butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, tert-pentyl group, hexyl group, isohexyl group and the like.

R ¹¹ and R ¹² each independently represents an electron withdrawing group. Preferably, R ¹¹ is an electron withdrawing group such as a cyano group or a trifluoroacetyl group, and R ¹² is an electron withdrawing group such as an acidic functional group or a derivative thereof.

  Although there is no restriction | limiting in particular as an acidic functional group, Preferably a carboxylic acid group, a phosphonic acid group, a sulfonic acid group, a phosphinic acid group, a hydroxy group, a hydroxamic acid group, a boronic acid group, a squaric acid group etc. are mention | raise | lifted. These acidic functional groups may be derivatives thereof. The derivative is not particularly limited, and examples thereof include esters, amides, and salts having a cation as a counter ion.

  The functional group that forms an ester with an acidic functional group is not particularly limited as long as it forms an ester with the above acidic group, but examples include an alkyl group, an aryl group, an alkoxyalkyl group, an acyl group, Examples thereof include an alkylsilyl group and an arylsilyl group.

  Among the functional groups that form an ester with an acidic functional group, preferred are alkyl groups having 1 to 20 carbon atoms such as methyl group, ethyl group, isopropyl group, and t-butyl group, phenyl group, tolyl group, and benzyl group. Group, phenacyl group, methoxymethyl group, tetrahydropyranyl group, tetrahydrofuranyl group, trimethylsilyl group, t-butyldimethylsilyl group, phenyldimethylsilyl group and the like.

  The functional group that forms an amide with an acidic functional group is not particularly limited as long as it forms an amide with the above acidic functional group, but examples include dimethylamino group, diethylamino group, diisopropylamino group, diphenyl. Amino group, pyrrolidinyl group, piperidinyl group, 7-nitroindolyl group, 8-nitrotetrahydroquinolyl group and the like can be mentioned.

The cation for forming a salt with an acidic functional group is not particularly limited as long as it is a cation that forms a salt with the above acidic group. For example, metal ions such as lithium, sodium, potassium, magnesium, calcium, etc. And quaternary ammonium ions such as tetramethylammonium, tetrabutylammonium, pyridinium, and imidazolium.

  When the compound of the present invention is used by adsorbing to an inorganic semiconductor such as titanium oxide, the acidic functional group is preferably a quaternary ammonium salt or a free acidic functional group. When adsorbing to a semiconductor, it can be adsorbed while being hydrolyzed in the system using an appropriate catalyst or the like.

  The electron withdrawing group in the present invention represents a functional group having a positive Hammett substituent constant σ. These functional groups are not particularly limited, but in addition to the aforementioned acidic functional groups, cyano groups, carboxyl groups, nitro groups, acyl groups, alkyloxycarbonyl groups, aryloxycarbonyl groups, alkylsulfonyl groups, arylsulfonyl groups , Perfluoroalkyl group, perfluoroalkylcarbonyl group, optionally substituted sulfonamide group, 4-cyanophenyl group, halogen atom and the like.

  Among the electron withdrawing groups, examples of the acyl group include an acetyl group, a thioacetyl group, a benzenesulfonyl group, and a phosphononitridoyl group.

  Examples of the alkyloxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a propyloxycarbonyl group, a butoxycarbonyl group, a pentyloxycarbonyl group, a hexyloxycarbonyl group, a heptyloxycarbonyl group, and an octyloxycarbonyl group.

  Examples of the aryloxycarbonyl group include a phenoxycarbonyl group, a 1-naphthyloxycarbonyl group, and a 2-naphthyloxycarbonyl group.

  Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  Examples of the alkylsulfonyl group include a mesyl group, an ethylsulfonyl group, and a propylsulfonyl group.

  Examples of the arylsulfonyl group include a benzenesulfonyl group and a toluenesulfonyl group.

  Examples of the perfluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, and a heptafluoropropyl group.

  Examples of the perfluoroalkylcarbonyl group include a trifluoroacetyl group, a pentafluoroethylcarbonyl group, and a heptafluoropropylcarbonyl group.

  Examples of the sulfonamide group that may have a substituent include a sulfonamide group, a dimethylaminosulfonyl group, a diethylaminosulfonyl group, and a diphenylaminosulfonyl group.

  Of the electron-withdrawing groups listed above, preferred are a cyano group, an alkylsulfonyl group, an arylsulfonyl group, and a perfluoroalkylcarbonyl group.

X ¹ and X ² each independently represents an unsubstituted or divalent thiophene residue having an alkyl group or an unsubstituted or divalent fused thiophene residue having an alkyl group. When X ¹ and X ² have an alkyl group as a substituent, an alkyl group having 1 to 12 carbon atoms is preferable.

Here, the alkyl group having 1 to 12 carbon atoms has the same meaning as the alkyl group in R ^{3 to} R ¹⁰ .

  The condensed thiophene residue in the present invention is a residue having a structure in which 2 to 7 thiophene rings are condensed, and is represented by the following structural formulas (1) to (6).

Structural formula (1)

Structural formula (2)

Structural formula (3)

Structural formula (4)

Structural formula (5)

Structural formula (6)

  The condensed thiophenes represented by the above structural formulas (1) to (6) are described in, for example, Journal of Organic Chemistry Vol. 72, pages 442 to 451.

  Now, since the compound of this invention has a double bond, various structural isomers, such as a cis body and a trans body, can be taken. Any of these can be used favorably as a sensitizing dye for photoelectric conversion. Further, the same can be said when a substituent or the like has a double bond.

  The compound represented by the general formula (1) can be produced, for example, by the following method.

  First, a compound represented by the general formula (4) is produced by a reaction between an aldehyde represented by the following general formula (2) and a phosphonic acid ester represented by the general formula (3).

General formula (2)

General formula (3)

一般式（４）で表される化合物のメチル基を臭素化した後に亜リン酸トリエチルと反応させることにより一般式（５）で表される化合物を製造することが出来る。 General formula (4)

The compound represented by the general formula (5) can be produced by brominating the methyl group of the compound represented by the general formula (4) and then reacting with triethyl phosphite.

次に、一般式（５）で表される化合物と、次の一般式（６）で表される化合物を反応させることにより次の一般式（７）で表される化合物を製造することが出来る。なお、一般式（６）におけるＸ¹、Ｘ²、ｍ及びｎは一般式（１）におけるそれらと同様である。 General formula (5)

Next, the compound represented by the following general formula (7) can be produced by reacting the compound represented by the general formula (5) with the compound represented by the following general formula (6). . Note that the X ^1, X ^2, m and n in the general formula (6) is the same as those in formula (1).

General formula (6)

General formula (7)

  After reacting the compound represented by the above general formula (7) with alkyllithium at a low temperature, the aldehyde represented by the following general formula (8) is further reacted with N, N-dimethylformamide. Can be manufactured.

General formula (8)

  The compound represented by the general formula (1) can be produced by reacting the compound represented by the general formula (8) with the compound represented by the following general formula (9).

General formula (9)

  The reaction of the compound represented by the general formula (8) and the compound represented by the general formula (9) can be performed in a solvent in the presence of a catalyst. As the catalyst, piperidine, ammonium acetate, or the like can be used, but is not particularly limited thereto. For example, the catalyst described in Organic Reactions Volume 15 Chapter 2 can be used. Moreover, as a solvent, ethanol, tetrahydrofuran, or the like can be used, but is not particularly limited thereto, and for example, a solvent described in Organic Reactions Volume 15 Chapter 2 can be used. Further, when the reaction is difficult to proceed, it may be effective to perform the reaction without using a solvent. Furthermore, the reaction temperature may usually be room temperature, but the reaction can be carried out by heating if necessary.

  The following Table 1 shows representative examples of compounds that can be used as the sensitizing dye for photoelectric conversion of the present invention, but the present invention is not limited to these representative examples.

Table 1

  By the way, the sensitizing dye for photoelectric conversion used in the present invention is combined with other sensitizing dyes in order to supplement the absorption of sunlight in a region where the sensitizing dye represented by the general formula (1) cannot absorb. Can be used. Other sensitizing dyes here include azo dyes, quinacridone dyes, diketopyrrolopyrrole dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, Examples thereof include chlorophyll dyes, ruthenium complex dyes, indigo dyes, perylene dyes, dioxazine dyes, anthraquinone dyes, phthalocyanine dyes, naphthalocyanine dyes, and derivatives thereof. These sensitizing dyes preferably have a functional group capable of being linked to the surface of the inorganic semiconductor porous body in the chemical structure. The reason is that the excited electrons of the photoexcited dye can be quickly transmitted to the conduction band of the inorganic semiconductor porous body. The functional group mentioned here includes the above-mentioned acidic functional group, etc., but a sensitizing dye is connected to the surface of the inorganic semiconductor porous body, and the excited electrons of the dye are quickly transmitted to the conduction band of the inorganic semiconductor porous body. Any substituent may be used as long as it has a function to obtain.

  Hereinafter, materials other than the sensitizing dye for photoelectric conversion used in the present invention will be described.

(Inorganic oxide)
The photoelectric conversion sensitizing dye used in the present invention forms a photoelectric conversion material in which the inorganic semiconductor porous body is sensitized by connecting to the surface of the inorganic semiconductor porous body through a linking group. Inorganic semiconductors generally have a photoelectric conversion function for light in a certain region, but photoelectric conversion to the visible light and / or near infrared light region by connecting a sensitizing dye to this surface. Is possible. As the inorganic semiconductor porous body, an inorganic oxide is mainly used. However, the inorganic semiconductor porous body is not limited to this as long as it has a photoelectric conversion function by connecting a sensitizing dye. Examples of inorganic semiconductors include silicon, germanium, III-V group semiconductors, metal chalcogenides, and the like. Examples of the inorganic oxide semiconductor porous material used in the present invention include titanium oxide, tin oxide, tungsten oxide, zinc oxide, indium oxide, niobium oxide, iron oxide, nickel oxide, cobalt oxide, strontium oxide, tantalum oxide, and antimony oxide. , Lanthanoid oxides, yttrium oxides, vanadium oxides, and the like, but these surfaces can be combined with sensitizing dyes to enable visible and / or near-infrared photoelectric conversion. If it becomes, it will not be restricted to these. In order for the surface of the inorganic oxide semiconductor porous body to be sensitized by the sensitizing dye, it is desirable that the conduction band of the inorganic oxide exists at a level where electrons are easily accepted from the photoexcited level of the sensitizing dye. For this reason, titanium oxide, tin oxide, zinc oxide, niobium oxide and the like are particularly used among the inorganic oxide semiconductor porous bodies. Furthermore, titanium oxide is particularly used from the viewpoint of price and environmental hygiene. In the present invention, one or more types can be selected and combined from the inorganic oxide semiconductor porous body.

(Porous inorganic oxide)
The inorganic semiconductor porous body has a large surface area by making it porous for the purpose of linking a large amount of sensitizing dye to the surface and expressing a highly efficient photoelectric conversion capability. As a porous method, a method of sintering inorganic oxide particles such as titanium oxide having a particle diameter of several to several tens of nanometers after pasting into a paste is widely known. If it is a method to obtain, it will not restrict to this.

(Photoelectric conversion electrode)
The photoelectric conversion material used in this invention forms a photoelectric conversion electrode by laminating | stacking on the conductive surface of the transparent base material which has an electroconductive surface.

(Conductive surface)
The conductive surface used in the present invention is not particularly limited as long as it is a conductive material that absorbs little light from the visible region of the sunlight to the near infrared region. However, ITO (indium-tin oxide) or tin oxide ( Metal oxides having good electrical conductivity such as zinc oxide and the like are preferable.

(Transparent substrate)
The transparent substrate used is not particularly limited as long as it is a material that absorbs little light from the visible region of sunlight to the near infrared region. Glass substrates such as quartz, ordinary glass, BK7, lead glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyester, polyethylene, polycarbonate, polyvinyl butyrate, polypropylene, tetraacetylcellulose, syndiocta polystyrene, polyphenylene sulfide, polyarylate Resin base materials such as polysulfone, polyester sulfone, polyetherimide, cyclic polyolefin, and vinyl chloride can be used.

(Lamination method)
As a method of laminating the photoelectric conversion material used in the present invention on the conductive surface of a transparent substrate having a conductive surface, it is possible to apply inorganic oxide particles pasted on the conductive surface and then dry or sinter the inorganic surface. Forming an oxide semiconductor porous body and immersing it in a solution in which the sensitizing dye is dissolved together with the transparent substrate, and thereby sensitizing using the affinity between the inorganic porous surface and the linking group of the sensitizing dye A method of bonding the dye to the inorganic porous surface is common, but is not limited to this method. In order to paste the inorganic oxide particles, the inorganic oxide particles are dispersed in water or a suitable organic solvent. It is important to make a paste with good dispersibility for lamination as an inorganic porous surface having a large surface area, and if necessary, a dispersant such as an acid such as nitric acid or acetylacetone, polyethylene glycol, or Triton X-100. Is mixed with the paste component and made into a paste using a paint shaker or the like. As a method for applying the paste to the conductive surface of the transparent substrate, an application method using a spin coater, a screen printing method, an application method using a squeegee, a dipping method, a spraying method, a roller method, or the like is used. After the applied inorganic oxide paste is dried or baked, volatile components in the paste are removed, and an inorganic oxide semiconductor porous body is formed on the conductive surface of the transparent substrate. As a condition for drying or firing, for example, a method of applying thermal energy of about 30 minutes to 1 hour at a temperature of 400 ° C. to 500 ° C. is generally used, but the conductive surface of the transparent substrate has adhesion, It is not limited to this as long as it is a drying or firing method that provides a good electromotive force during light irradiation.

  Solvents used when preparing a solution in which a sensitizing dye is dissolved include alcohol solvents such as ethanol and benzyl alcohol, nitrile solvents such as acetonitrile and propionitrile, halogen solvents such as chloroform, dichloromethane and chlorobenzene, Ether solvents such as diethyl ether and tetrahydrofuran; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone; carbonate solvents such as diethyl carbonate and propylene carbonate; hexane, octane, benzene, Hydrocarbon solvents such as toluene, dimethylformamide, dimethylacetamide, dimethylsulfoxide, 1,3-dimethylimidazolinone, N-methylpyrrolidone, water and the like can be used, but are not limited thereto.

  The film thickness of the inorganic oxide semiconductor porous body formed on the conductive surface of the transparent substrate is desirably 0.5 μm to 200 μm. When the film thickness is less than this range, good conversion efficiency cannot be obtained. If the film thickness is thicker than this range, not only will it be difficult to produce such as cracking or peeling during film formation, but the distance between the surface of the inorganic oxide semiconductor porous body and the conductive surface will be longer, resulting in the generated charge. Cannot be effectively transmitted to the conductive surface, making it difficult to obtain good conversion efficiency.

(Photoelectric conversion cell)
The photoelectric conversion electrode used in the present invention forms a photoelectric conversion cell by combining a conductive counter electrode through an electrolyte layer.

(Electrolyte layer)
The electrolyte layer used in the present invention is preferably composed of an electrolyte, a medium, and an additive. The electrolyte of the present invention contains iodine and iodide (for example, lithium iodide, sodium iodide, potassium iodide, cesium iodide, magnesium iodide, calcium iodide, cuprous iodide, tetraalkylammonium iodide, pyridinium iodide). A mixture of bromine and bromide (for example, lithium bromide), a molten salt described in Inorganic Chemistry, 35, 1168-1178 (1996), and the like can be used. However, this is not the case. Among them, an electrolyte in which lithium iodide, pyridinium iodide, imidazolium iodide, or the like is mixed as a combination of iodine and iodide is preferable in the present invention, but is not limited to this combination. Preferred electrolyte concentrations are 0.01M to 0.5M iodine in the medium and 0.1M to 15M iodide mixture.

  The medium used for the electrolyte layer in the present invention is desirably a compound that can exhibit good ionic conductivity. Solution media include ether compounds such as dioxane and diethyl ether, chain ethers such as ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether, methanol, ethanol, and ethylene glycol monoalkyl. Alcohols such as ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin, acetonitrile, glutarodinitrile, Methoxyacetonitrile, propioni Nitrile compounds such as ril and benzonitrile, carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, aprotic polar solvents such as dimethyl sulfoxide and sulfolane, water, and the like can be used. .

  Further, for the purpose of using a solid (including gel) medium, a polymer may be included. In this case, a polymer such as polyacrylonitrile or polyvinylidene fluoride is added to the solution-like medium, or a polyfunctional monomer having an ethylenically unsaturated group is polymerized in the solution-like medium to make the medium solid. To do.

  As the electrolyte layer, an electrolyte that does not require any CuI or CuSCN medium, and 2,2 ′, 7,7′-tetrakis (N, N-dioxy) described in Nature, Vol. 395, pages 583-585 (1998) can be used. Hole transport materials such as -p-methoxyphenylamine) -9,9'-spirobifluorene can be used.

  In the electrolyte layer used in the present invention, an additive that functions to improve the electrical output of the photoelectric conversion cell or improve the durability can be added. Examples of additives that improve electrical output include 4-t-butylpyridine, 2-picoline, and 2,6-lutidine. Examples of the additive for improving durability include magnesium iodide.

(Conductive counter electrode)
The conductive counter electrode used in the present invention functions as a positive electrode of the photoelectric conversion cell. Specifically, the conductive material used for the counter electrode is metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), ITO (indium-tin oxide), tin oxide (doped with fluorine, etc.) A metal oxide such as zinc oxide, or carbon. The thickness of the counter electrode is not particularly limited, but is preferably 5 nm to 10 μm.

(How to assemble)
A photoelectric conversion cell is formed by combining the photoelectric conversion electrode and the conductive counter electrode via an electrolyte layer. In order to prevent leakage and volatilization of the electrolyte layer, sealing is performed around the photoelectric conversion cell as necessary. For sealing, a thermoplastic resin, a photocurable resin, glass frit, or the like can be used as a sealing material. The photoelectric conversion cell is made by connecting small-area photoelectric conversion cells as necessary. The electromotive voltage can be increased by combining the photoelectric conversion cells in series.

  Examples are shown below specifically, but the present invention is not limited to the following examples. In addition, unless otherwise indicated, a number represents a weight standard.

  As a method for evaluating a sensitizing dye for photoelectric conversion, a method for measuring the conversion efficiency of a photoelectric conversion cell assembled using a sensitizing dye will be described with reference to FIG. 1 showing a test sample of a photoelectric conversion cell.

Transparent electrode The glass substrate 3 with a fluorine dope type tin oxide layer (transparent electrode layer) (Asahi Glass Co., Ltd. type U-TCO) was used.

Conductive counter electrode A conductive counter electrode in which a platinum layer (platinum electrode layer) (thickness 150 nm) was laminated by sputtering on the conductive layer of a glass substrate 3 with fluorine-doped tin oxide layer (type U-TCO, manufactured by Asahi Glass Co., Ltd.) 4 was used.

Preparation of Titanium Oxide Paste Titanium oxide paste and zirconia beads were mixed according to the following formulation and dispersed using a paint shaker to obtain a titanium oxide paste.
Titanium oxide (Nippon Aerosil Co., Ltd., P25 particle size 21 nm) 6 parts Water (adjusted to pH 2 by addition of nitric acid) 14 parts Acetylacetone 0.6 parts Surfactant (ICN Triton X-100) 0.04 parts PEG- # 500 , 000 0.3 parts

Preparation of porous titanium oxide layer A 60μm thick mending tape is applied to the conductive surface (transparent electrode layer 3) of the transparent electrode, and a mask is made by removing the 1cm square tape. After dropping a few drops, the excess paste was removed with a squeegee. After air drying, all the masks were removed and baked in an oven at 450 ° C. for 1 hour to obtain a titanium oxide electrode having a titanium oxide porous layer having an effective area of 1 cm ² .

Adsorption of sensitizing dye The sensitizing dye for photoelectric conversion is dissolved in tetrahydrofuran: acetonitrile = 1: 1 (volume ratio) (concentration 0.6 mmol / L), and insoluble matter is removed by a membrane filter. The titanium oxide electrode was immersed and left at room temperature for 24 hours. The immersion time was set so that the conversion efficiency was maximized by actually creating a cell and obtaining the conversion efficiency.
The colored electrode surface was washed with the solvent and alcohol used for dissolution, then immersed in a 2 mol% alcohol solution of 4-t-butylpyridine for 30 minutes, and then dried, and the titanium oxide porous material on which the sensitizing dye was adsorbed A photoelectric conversion electrode having the layer 1 was obtained.

Preparation of electrolyte solution An electrolyte solution having the following formulation was prepared. Methoxyacetonitrile was used as the solvent.
Lithium iodide 0.1M
Iodine 0.05M
4-t-butylpyridine 0.5M
1-propyl-2,3-dimethylimidazolium iodide 0.6M

Assembly of Photoelectric Conversion Cell As shown in FIG. 1, a test sample of the photoelectric conversion cell was assembled. That is, a transparent electrode (a glass substrate 3 with a fluorine-doped tin oxide layer) on which a titanium oxide porous layer 1 on which a sensitizing dye for photoelectric conversion is adsorbed by the above procedure is formed, and a glass with a fluorine-doped tin oxide layer A conductive counter electrode 4 in which a platinum layer is laminated on a conductive layer of a substrate is fixed with a spacer 6 made of resin film (“High Milan” film (25 μm thickness) made by Mitsui-DuPont Polychemical Co., Ltd.) sandwiched in the gap. The above electrolyte solution was injected to form the electrolyte solution layer 2. Conductive wires 7 for measuring conversion efficiency were fixed to the glass substrate 3 and the platinum counter electrode layer, respectively.

Measurement Method of Conversion Efficiency A solar simulator (# 8116) manufactured by ORIEL Co., Ltd. and an air mass filter were combined and adjusted to a light amount of 100 mW / cm ² with a light meter to obtain a measurement light source. While irradiating the test sample of the photoelectric conversion cell with light, the IV curve characteristics were measured using a KEITHLEY MODEL 2400 source meter. The conversion efficiency η was calculated by the following equation using Voc (open circuit voltage value), Isc (short circuit current value) and ff (fill factor value) obtained from the IV curve characteristic measurement.

η (%) = Voc (V) × Isc (mA) × ff × 100
100 (mW / cm ² ) × 1 (cm ² )

Examples 1-46
Of the exemplified compounds described in Table 1, the compounds shown in Table 2 were used as sensitizing dyes, and evaluation was performed using the cell assembled by the above method. The obtained results are shown in Table 2.

化合物ａ

化合物ｂ


In Table 2, as a comparative example, the results of the same evaluation as in Examples 1 to 46 with respect to compound a and compound b having the following structures described in Non-Patent Document 3 already exemplified in the description of background art Was also written.

Compound a

Compound b

Table 2

  As can be seen from the examples shown in Table 2, the device produced using the optical functional material of the present invention had almost the same conversion as that immediately after production after 24 hours under exposure to fluorescent light and after 100 hours of simulated sunlight irradiation. Shows efficiency. In contrast to these examples, it can be seen that in any of the comparative examples, the conversion efficiency is significantly reduced from the value immediately after fabrication under any of the conditions described above.

1. Titanium oxide porous layer (adsorbed sensitizing dye for photoelectric conversion)
2. 2. Electrolyte solution layer Transparent electrode layer (fluorine-doped tin oxide)
4). 4. Pt electrode layer 5. Glass substrate 6. Resin film spacer Conversion efficiency measurement lead

Claims (7)

An optical functional material represented by the following general formula (1).
General formula (1)

[Wherein, R ¹ and R ² each independently represents a hydrogen atom or an alkyl group.
R ^{3 to} R ¹⁰ each independently represents a hydrogen atom or an alkyl group.
R ¹¹ and R ¹² each independently represents an electron withdrawing group.
X ¹ and X ² each independently represents an unsubstituted or divalent thiophene residue having an alkyl group or an unsubstituted or divalent fused thiophene residue having an alkyl group.
M and n represent integers, and the sum of m and n is 1 to 6. ] The optical functional material according to claim 1, wherein R ¹¹ is a cyano group. The optical functional material according to claim 1, wherein R ¹² is a carboxyl group. A sensitizing dye for photoelectric conversion, comprising the optical functional material according to claim 1. A photoelectric conversion material obtained by linking the sensitizing dye according to claim 4 and an inorganic semiconductor porous body. A photoelectric conversion electrode obtained by laminating the photoelectric conversion material according to claim 5 on a transparent electrode. A photoelectric conversion cell comprising the photoelectric conversion electrode according to claim 6, an electrolyte layer, and a conductive counter electrode.

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