JP7429098B2 - Sensitizing dye, sensitizing dye composition for photoelectric conversion, photoelectric conversion element using the same, and dye-sensitized solar cell - Google Patents

Description

The present invention relates to a sensitizing dye, a sensitizing dye composition for photoelectric conversion used in a dye-sensitized photoelectric conversion element, a photoelectric conversion element using the sensitizing dye composition for photoelectric conversion, and a dye-sensitized solar cell. .

In recent years, carbon dioxide generated from fossil fuels such as coal, oil, and natural gas has become a greenhouse gas, causing global warming and environmental destruction due to global warming, and as global energy consumption increases due to population growth, There are concerns that environmental destruction will continue to progress on a global scale. Under these circumstances, the use of renewable energy, which unlike fossil fuels is less likely to run out, is being actively considered. The use of solar energy, mainly solar power generation, is important as a next-generation major renewable energy power generation method that can contribute to preventing global warming, replacing thermal power generation and nuclear power generation that consume fossil fuels. It is being developed and applied in a variety of fields, from power generation and charging for wristwatches and small portable electronic devices to small-scale power generation facilities for houses, buildings, and fallow land that can save on utility bills. is progressing.

As a means of solar power generation, photoelectric conversion elements that convert sunlight energy into electrical energy are used in solar cells.Solar cells include single crystal, polycrystal, amorphous silicon, gallium arsenide, and sulfide Inorganic solar cells, such as those based on compound semiconductors such as cadmium and indium copper selenide, have been mainly studied and are currently being put into practical use in homes and small-scale power generation facilities. However, these inorganic solar cells have problems such as high manufacturing costs and difficulty in securing raw materials.

On the other hand, organic solar cells such as organic thin-film solar cells and dye-sensitized solar cells using various organic materials have been developed, although their photoelectric conversion efficiency and durability are still significantly lower than inorganic solar cells. ing. Organic solar cells are said to be more advantageous than inorganic solar cells in terms of manufacturing costs, larger area, lighter weight, thinner film, translucency, wider absorption wavelength range, flexibility, and availability of raw materials. .

Among them, the dye-sensitized solar cell proposed by Gretzel et al. (see Non-Patent Document 1) uses a thin film electrode made of porous titanium oxide as a semiconductor, and a ruthenium complex dye adsorbed on the semiconductor surface to widen the sensitive wavelength range. , a wet solar cell composed of an electrolyte containing iodine, is expected to have high photoelectric conversion efficiency comparable to that of amorphous silicon solar cells. Dye-sensitized solar cells are attracting attention as next-generation solar cells because they have a simpler device structure than other solar cells and can be manufactured without large manufacturing equipment.

As a sensitizing dye used in dye-sensitized solar cells, ruthenium complexes are considered to be the most advantageous in terms of photoelectric conversion efficiency, but since ruthenium is a noble metal, it is disadvantageous in terms of manufacturing cost, and If a large amount of ruthenium complex is required for practical use, resource constraints will also become an issue. Therefore, research on dye-sensitized solar cells using organic dyes that do not contain noble metals such as ruthenium as sensitizing dyes is being actively conducted. As organic dyes that do not contain noble metals, coumarin dyes, cyanine dyes, merocyanine dyes, rhodacyanine dyes, phthalocyanine dyes, porphyrin dyes, xanthene dyes, etc. have been reported (for example, Patent Documents 1 to 3). reference).

Compounds with an indanone structure have also been proposed as adsorbed onto the surface of semiconductor particles such as titanium oxide and as electron-attracting parts for efficiently transporting excited electrons generated by sensitizing dyes to the semiconductor (for example, (See Patent Documents 4 to 6). However, although these organic dyes have the advantages of being inexpensive, having a large extinction coefficient, and being able to control their absorption characteristics due to their structural diversity, they do not meet the required characteristics in terms of photoelectric conversion efficiency and stability over time. The current situation is that we have not been able to obtain anything that satisfies us.

Japanese Patent Application Publication No. 11-214730 Japanese Patent Application Publication No. 11-238905 Japanese Patent Application Publication No. 2011-26376 Japanese Patent Application Publication No. 2011-207784 Japanese Patent Application Publication No. 2012-51854 Unexamined Japanese Patent Publication No. 2016-6811

"Nature" (UK), 1991, Vol. 353, p. 737-740

The problem to be solved by the present invention is to provide a sensitizing dye with a novel structure that can expand the photosensitive wavelength range, and furthermore, a sensitizing dye composition for photoelectric conversion that can efficiently extract current from the sensitizing dye. An object of the present invention is to provide a photoelectric conversion element having good photoelectric conversion characteristics and a dye-sensitized solar cell that can be used as a photoelectric conversion element.

In order to solve the above problems, the inventors conducted intensive studies on improving the photoelectric conversion properties of sensitizing dyes. By using a sensitizing dye with a specific structure as a sensitizing dye for photoelectric conversion, the inventors achieved high efficiency and high durability. It has been found that a photoelectric conversion element with high properties can be obtained. That is, the present invention consists of the following contents.

1. A sensitizing dye represented by the following general formula (1).

[wherein R ¹ is a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
Or represents an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent.
R ² and R ³ represent a hydrogen atom or a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent.
m represents an integer from 2 to 8.
X represents a divalent group, and Z represents a monovalent group. ]

2. A sensitizing dye in which, in the general formula (1), X is a divalent aromatic hydrocarbon group or a divalent heterocyclic group represented by the following general formula (2).

[In the formula, R ¹⁰ to R ¹⁵ may be the same or different,
hydrogen atom,
A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
A linear or branched alkenyl group having 2 to 18 carbon atoms which may have a substituent, an amino group having 0 to 18 carbon atoms which may have a substituent,
or a thio group having 0 to 18 carbon atoms which may have a substituent,
n represents 0 or 1.
When n is 0, R ¹⁰ and R ¹¹ and R ¹² and R ¹³ may be bonded to each other to form a ring.
Further, when n is 1, R ¹⁰ and R ¹¹ , R ¹¹ and R ¹⁴ , R ¹² and R ¹³ , or R ¹³ and R ¹⁵ may be bonded to each other to form a ring. ]

3. A sensitizing dye in which, in the general formula (1), X is a divalent bonding group represented by the following general formulas (X1) to (X7).

[In the formula, R ¹⁶ to R ¹⁹ may be the same or different,
hydrogen atom,
A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
Aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent,
or a heterocyclic group having 2 to 36 carbon atoms which may have a substituent,
Adjacent groups of R ¹⁸ and R ¹⁹ may be bonded to each other to form a ring. ]

4. A sensitizing dye in which Z in the general formula (1) is a monovalent group represented by the following general formula (3).

[In the formula, R ²⁰ to R ²² may be the same or different,
hydrogen atom,
A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
A linear or branched alkoxy group having 1 to 18 carbon atoms which may have a substituent,
Or represents a linear or branched alkenyl group having 2 to 18 carbon atoms which may have a substituent.
p represents 0 to 4,
R ²⁰ and R ²¹ may be the same or different, and may be bonded to each other to form a ring.
R ²² represents a hydrogen atom or a linear or branched alkyl group having 1 to 18 carbon atoms.
R ²³ and R ²⁴ represent a hydrogen atom or an acidic group, and at least one of R ²³ and R ²⁴ is an acidic group. ]

5. In the general formula (1), R ¹ is a linear or branched alkyl group having 1 to 6 carbon atoms, which may have a substituent, or an aromatic hydrocarbon group having 6 to 26 carbon atoms. and
R ² and R ³ are hydrogen atoms,
or a linear alkyl group having 1 to 6 carbon atoms which may have a substituent,
Also, a sensitizing dye in which m is 3 or 4.

6. A sensitizing dye composition for photoelectric conversion containing the sensitizing dye.

7. A photoelectric conversion element using the sensitizing dye composition for photoelectric conversion.

8. A dye-sensitized solar cell using the photoelectric conversion element.

According to the sensitizing dye according to the present invention, it is possible to obtain a sensitizing dye composition for photoelectric conversion that can efficiently extract current. Moreover, by using the sensitizing dye composition for photoelectric conversion, a highly efficient and highly durable photoelectric conversion element and dye-sensitized solar cell can be obtained.

FIG. 1 is a schematic cross-sectional view showing the configuration of photoelectric conversion elements of examples and comparative examples of the present invention.

Embodiments of the present invention will be described in detail below. The sensitizing dye composition for photoelectric conversion containing the sensitizing dye of the present invention is used as a sensitizer in a dye-sensitized photoelectric conversion element. In addition, in this specification, "sensitizing dye" refers to a compound represented by general formula (1), and "sensitizing dye composition for photoelectric conversion" refers to a compound represented by general formula (1). It refers to a composition containing one or more types of sensitizing dyes, and optionally containing other sensitizing dyes that do not belong to the present invention. The photoelectric conversion element of the present invention typically has a photoelectrode formed by adsorbing a dye on a semiconductor layer on a conductive support and a counter electrode, which are placed opposite to each other with an electrolyte layer interposed therebetween.

The sensitizing dye represented by the general formula (1) will be specifically explained below, but the present invention is not limited thereto.

In the general formula (1), in the "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ³ , 18 linear or branched alkyl groups" specifically include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, Examples include n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group, heptyl group, octyl group, isooctyl group, nonyl group, and decyl group.

In general formula (1), "aromatic hydrocarbon group having 6 to 36 carbon atoms" in "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ¹ "Specifically, phenyl group, biphenyl group, terphenyl group, naphthyl group, biphenyl group, anthracenyl group (anthryl group), phenanthryl group, fluorenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, Examples include triphenylenyl group. Here, in the present invention, the aromatic hydrocarbon group includes a "fused polycyclic aromatic group" and an "aryl group."

In the general formula (1), "a linear or branched alkyl group having 1 to ¹⁸ carbon atoms which may have a substituent" and "a linear ^or branched alkyl group having a substituent and Specifically, the "substituent" in the "optionally aromatic hydrocarbon group having 6 to 36 carbon atoms" is
Halogen atoms such as fluorine atom, chlorine atom, bromine atom, iodine atom; cyano group; hydroxyl group; nitro group; nitroso group; carboxyl group;
Carboxylic acid ester groups such as methyl ester groups and ethyl ester groups;
Methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group, Straight-chain or branched alkyl groups having 1 to 18 carbon atoms such as heptyl group, octyl group, isooctyl group, nonyl group, decyl group;
Straight chain or branched with 2 to 20 carbon atoms such as vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 1-hexenyl group, isopropenyl group, isobutenyl group alkenyl group;
Straight-chain or branched alkoxy groups having 1 to 18 carbon atoms such as methoxy, ethoxy, propoxy, t-butoxy, pentyloxy, hexyloxy groups;
Aromatic hydrocarbon groups having 6 to 30 carbon atoms such as phenyl group, naphthyl group, anthryl group, phenanthryl group, pyrenyl group;
Pyridyl group, pyrimidilinyl group, triazinyl group, thienyl group, furyl group (furanyl group), pyrrolyl group, imidazolyl group, pyrazolyl group, triazolyl group, quinolyl group, isoquinolyl group, naphthyldinyl group, acridinyl group, phenanthrolinyl group, benzofuranyl group Carbon atoms such as groups, benzothienyl groups, oxazolyl groups, indolyl groups, carbazolyl groups, benzoxazolyl groups, thiazolyl groups, benzothiazolyl groups, quinoxalinyl groups, benzimidazolyl groups, pyrazolyl groups, dibenzofuranyl groups, dibenzothienyl groups, carbonylyl groups, etc. Heterocyclic group having 2 to 30 atoms;
A straight or branched alkyl group having 1 to 18 carbon atoms, such as dimethylamino group, diethylamino group, ethylmethylamino group, methylpropylamino group, di-t-butylamino group, diphenylamino group, or carbon A mono- or di-substituted amino group having 0 to 18 carbon atoms having a substituent selected from aromatic hydrocarbon groups having 6 to 18 atoms;
Thio groups having 1 to 18 carbon atoms such as methylthio group, ethanethio group, propylthio group, di-t-butylthio group, hex-5-en-3-thio group, phenylthio group, biphenylthio group;
etc. can be given. These "substituents" may be included only one, or may be included in plurality, and when included in plurality, they may be the same or different from each other. Moreover, these "substituents" may further have the above-mentioned substituents.

In general formula (1), R ¹ is preferably an alkyl group having 1 to 18 carbon atoms which may have a substituent or an aromatic hydrocarbon group which may have a substituent. .

In general formula (1), R ² and R ³ are preferably a hydrogen atom or a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent, and a hydrogen atom Or, it is more preferably a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent.

In general formula (1), m is an integer from 2 to 8 and represents the number of CH ₂ , and m is preferably 3 or 4.

In general formula (1), X is preferably a divalent group represented by the above general formula (2).

In the general formula (2), in the "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹⁰ to R ¹⁵ , 18 straight-chain or branched alkyl group" in the general formula (1) above, "straight-chain alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ³ The same thing as "chain or branched alkyl group" can be mentioned.

In the general formula (2), in the "linear or branched alkenyl group having 2 to 18 carbon atoms which may have a substituent" represented by R ¹⁰ to R ¹⁵ , 18 linear or branched alkenyl groups" specifically include vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 1-hexenyl group, iso Examples include a propenyl group, an isobutenyl group, and a linear or branched alkenyl group having 2 to 18 carbon atoms in which a plurality of these alkenyl groups are bonded.

In general formula (2), the "amino group having 0 to 18 carbon atoms" in the "amino group having 0 to 18 carbon atoms which may have a substituent" represented by R ¹⁰ to R ¹⁵ is Specifically, a carbon atom number of 1 to 18 that may have a substituent, such as dimethylamino group, diethylamino group, ethylmethylamino group, methylpropylamino group, di-t-butylamino group, diphenylamino group, etc. A mono- or di-substituted amino group having a substituent selected from a linear or branched alkyl group, or an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, etc. etc. can be given.

In general formula (2), the "thio group having 0 to 18 carbon atoms" in the "thio group having 0 to 18 carbon atoms which may have a substituent" represented by R ¹⁰ to R ¹⁵ is specifically,
Examples include methylthio group, ethanethio group, propylthio group, di-t-butylthio group, hex-5-en-3-thio group, phenylthio group, and biphenylthio group.

In the general formula (2), R ¹⁰ to R ¹⁵ represent "a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent", "a linear or branched alkyl group having a substituent and "A linear or branched alkenyl group having 2 to 18 carbon atoms which may optionally have a substituent,""an amino group having 1 to 18 carbon atoms which may have a substituent," or "A linear or branched alkenyl group having 1 to 18 carbon atoms which may have a The "substituent" in the "thio group having 1 to 18 carbon atoms which may optionally have a substituent" is a "carbon atom which may have a substituent" represented by R ¹ to R ³ in the general formula (1). The same as the "substituent" in "linear or branched alkyl group having numbers 1 to 18" and "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" are mentioned. . Moreover, these "substituents" may further have the substituents exemplified in the general formula (1).

In general formula (2), n represents 0 or 1, and R ¹⁰ to R ¹⁵ represent the substituents as described above, but when n is 0, R ¹⁰ and R ¹¹ , R ¹² and R ¹³ may be bonded to each other by a single bond, a bond via a sulfur atom, or a bond via a nitrogen atom to form a ring.
In addition, when n is 1, R ¹⁰ and R ¹¹ or R ¹¹ and R ¹⁴ , R ¹² and R ¹³ or R ¹³ and R ¹⁵ are a single bond, a bond via a sulfur atom, or a bond via a nitrogen atom. They may be bonded to each other to form a ring.

It is preferably a divalent group represented by the general formula (2), more specifically a divalent group represented by the above general formulas (X1) to (X7).

In general formulas (X4) and (X7), the "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹⁶ to R ¹⁹ is the general formula described above. In formula (1), the same things as "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ³ can be mentioned. .

In general formulas (X4) and (X7), "C6 to C36 aromatic hydrocarbon group optionally having a substituent," represented by R ¹⁶ to R ¹⁹ . The "aromatic hydrocarbon group" is the same as the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by R ¹ in the general formula (1) above. can be given.

In the "heterocyclic group having 2 to 36 carbon atoms which may have a substituent" represented by R ¹⁶ to R ¹⁹ in general formulas (X4) and (X7), "heterocyclic group having 2 to 36 carbon atoms" Specifically, the ``ring group'' is as follows:
Pyridyl group, pyrimidilinyl group, triazinyl group, thienyl group, furyl group (furanyl group), pyrrolyl group, imidazolyl group, pyrazolyl group, triazolyl group, quinolyl group, isoquinolyl group, naphthyldinyl group, acridinyl group, phenanthrolinyl group, benzofuranyl group group, benzothienyl group, oxazolyl group, indolyl group, carbazolyl group, benzoxazolyl group, thiazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carbonylyl group, etc. be able to.

In general formulas (X4) and (X7), "linear or branched alkyl group having ¹ to ¹⁸ carbon atoms which may have a substituent" and "substituted As the "substituent" in the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a group", the "substituent" represented by R ¹ to R ³ in the general formula (1) is ``Substituted straight chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent'' and ``aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent'' The same thing as "Ki" can be mentioned. Moreover, these "substituents" may further have the substituents exemplified in the general formula (1).

In the general formula (1), Z is preferably a monovalent group represented by the above general formula (3).

The "straight chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ²⁰ to R ²² in the general formula (3) includes the general formula (1 ), the same ones as "a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by R ¹ to R ³ can be mentioned.

In the general formula (3), in the "linear or branched alkoxy group having 1 to 18 carbon atoms which may have a substituent" represented by R ²⁰ to R ²² , 18 straight-chain or branched alkoxy group" specifically,
Methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, nonyloxy group, decyloxy group, isopropoxy group, isobutoxy group, s-butoxy group, t-butoxy group , isooctyloxy group, etc.

In the general formula (3), R ²⁰ to R ²¹ represent the substituents as described above, but R ²⁰ to R ²¹ are mutually bonded by a single bond, a bond via a sulfur atom, or a bond via a nitrogen atom. They may be combined to form a ring.

In general formula (3), the "acidic group" represented by R ²³ and R ²⁴ includes a carboxyl group, a sulfonic acid group, a phosphoric acid group, a hydroxamic acid group, a phosphonic acid group, a boric acid group, and a phosphinic acid group. group, silanol group, etc. Among these, a carboxyl group or a phosphonic acid group is preferred, and a carboxyl group is more preferred.

Among the sensitizing dyes of the present invention represented by general formula (1), sensitizing dyes containing a carboxyl group or a phosphonic acid group as an acidic group can be easily adsorbed onto the surface of a semiconductor layer. This will lead to further improvements in the photoelectric conversion characteristics of photoelectric conversion elements using sensitizing dyes.

In the present invention, the sensitizing dye represented by general formula (1) includes all possible stereoisomers. Any stereoisomer can be suitably used as a sensitizing dye in the present invention. For example, in general formula (1), X is a divalent group represented by general formula (2), Z is a monovalent group represented by general formula (3), and n is 0 and R When ²² and R ²³ are hydrogen atoms and R ²⁴ is a carboxyl group, the sensitizing dye of the present invention includes compounds represented by the following general formulas (4) and (5). Moreover, a mixture of two or more types selected from these stereoisomers may be used.

Specific examples of the compound of the sensitizing dye of the present invention represented by the general formula (1) are shown in the following formula, but the present invention is not limited thereto.
Moreover, the following exemplified compounds are examples of stereoisomers that may exist, and are intended to include all other stereoisomers. Moreover, each may be a mixture of two or more stereoisomers.

The sensitizing dye of the present invention represented by general formula (1) can be synthesized by a known method. Below, a synthesis example will be shown where, in the general formula (1), X is, for example, a divalent group represented by the following formula (X2).

The following general formula ( The formyl compound represented by 8) can be synthesized.

Alternatively, a cross-coupling reaction such as Suzuki coupling between a boronic acid compound such as a boronic acid ester having a corresponding substituent represented by the following general formula (7) and 6-bromo-2-naphthaldehyde can be performed. The formyl compound represented by the following general formula (8) can also be synthesized by performing the following steps.

Subsequently, by carrying out a condensation reaction between the formyl compound represented by the general formula (8) obtained as described above and an indenone compound represented by the following general formula (9), the increase in the present invention can be obtained. It is possible to synthesize sensitive dyes. In the following general formula (9), R ²³ and R ²⁴ represent a hydrogen atom or an acidic group, and at least one of R ²³ or R ²⁴ is an acidic group. However, m, R ¹ to R ³ , R ²³ and R ²⁴ in general formulas (6) to (9) in the above synthesis examples are the same as m and R ¹ in general formulas (1) and (3) in the present invention. ～R Expresses the same meaning as ³ .

In addition, regarding the above-mentioned general formula (6) and the like that serve as starting materials, commercially available ones may be used, or those synthesized by known methods may be used. The indenone compound represented by the above general formula (9) can be easily synthesized by the methods described in Patent Documents 4 to 6 mentioned above. Furthermore, in addition to the divalent group represented by the above formula (X2), compounds in which X is a divalent group represented by the formulas (X1) to (X7) shown above can also be synthesized in the same manner. can.

Purification methods for the sensitizing dye compound of the present invention represented by general formula (1) include purification by column chromatography; purification by adsorption with silica gel, activated carbon, activated clay, etc.; recrystallization with a solvent, crystallization method, etc. Known methods may be used. Further, these compounds can be identified by nuclear magnetic resonance analysis (NMR) or the like.

The sensitizing dyes of the present invention may be used alone or in combination of two or more. Furthermore, the sensitizing dye of the present invention can be used in combination with other sensitizing dyes that do not belong to the present invention. Specific examples of other sensitizing dyes include ruthenium complexes, coumarin dyes, cyanine dyes, merocyanine dyes, rhodacyanine dyes, phthalocyanine dyes, porphyrin dyes, and xanthene dyes represented by the general formula (1). Sensitizing dyes other than the sensitizing dyes represented can be mentioned. When the sensitizing dye of the present invention and these other sensitizing dyes are used in combination as a composition for photoelectric conversion, the amount of the other sensitizing dye to be used is 10 to 200% by weight relative to the sensitizing dye of the present invention. The amount is preferably 20 to 100% by weight, and more preferably 20 to 100% by weight.

The sensitizing dye of the present invention can be applied as a spectral sensitizing dye for photoreceptors, photocatalysts, photofunctional materials, etc. for various imaging materials such as silver halide, zinc oxide, and titanium oxide, and can be used for dye-sensitized photoelectric conversion. It can also be applied as a sensitizing dye composition for photoelectric conversion used in devices, etc. In the present invention, the method for producing a dye-sensitized photoelectric conversion element is not particularly limited, but a semiconductor layer is formed on a conductive support (electrode), and the sensitizing dye composition for photoelectric conversion of the present invention is applied to the semiconductor layer. A method of fabricating a photoelectrode by adsorbing (supporting) an object is preferable (see FIG. 1. Needless to say, the drawing is not to a faithful scale of the actual device, as priority is given to facilitating understanding). A common method for adsorbing the dye is to immerse the semiconductor layer for a long time in a solution obtained by dissolving the dye in a solvent. When using two or more sensitizing dyes of the present invention in combination, or when using the sensitizing dye of the present invention in combination with other sensitizing dyes, prepare a mixed solution of all the dyes to be used and immerse the semiconductor layer. Alternatively, separate solutions may be prepared for each dye and the semiconductor layer may be immersed in each solution in turn.

In the present invention, in addition to a metal plate, a glass substrate or a plastic substrate provided with a conductive layer having a conductive material on the surface can be used as the conductive support. Specific examples of conductive materials include metals such as gold, silver, copper, aluminum, and platinum, conductive transparent oxide semiconductors such as fluorine-doped tin oxide, indium-tin composite oxide, and carbon. However, it is preferable to use a glass substrate coated with a fluorine-doped tin oxide thin film.

Specific examples of semiconductors forming the semiconductor layer in the present invention include metals such as titanium oxide, zinc oxide, tin oxide, indium oxide, zirconium oxide, tungsten oxide, tantalum oxide, iron oxide, gallium oxide, nickel oxide, and yttrium oxide. Oxides: Metal sulfides such as titanium sulfide, zinc sulfide, zirconium sulfide, copper sulfide, tin sulfide, indium sulfide, tungsten sulfide, cadmium sulfide, silver sulfide; titanium selenide, zirconium selenide, indium selenide, tungsten selenide Examples include metal selenides such as; elemental semiconductors such as silicon and germanium. These semiconductors can be used not only alone, but also in combination of two or more types. In the present invention, it is preferable to use one or more selected from titanium oxide, zinc oxide, and tin oxide as the semiconductor.

Although the form of the semiconductor layer in the present invention is not particularly limited, a thin film having a porous structure made of fine particles is preferable. When the substantial surface area of the semiconductor layer increases due to the porous structure and the amount of dye adsorbed to the semiconductor layer increases, a highly efficient photoelectric conversion element can be obtained. The semiconductor particle diameter is preferably 5 to 500 nm, more preferably 10 to 100 nm. The thickness of the semiconductor layer is usually 2 to 100 μm, more preferably 5 to 20 μm. The method for producing the semiconductor layer is to apply a paste containing semiconductor fine particles onto a conductive substrate using a wet coating method such as a spin coating method, a doctor blade method, a squeegee method, or a screen printing method, and then remove solvents and additives by baking. Examples include, but are not limited to, a method of forming a film by removing it, and a method of forming a film by sputtering, vapor deposition, electrodeposition, microwave irradiation, and the like.

In the present invention, a commercially available paste containing semiconductor fine particles may be used, or a paste prepared by dispersing commercially available semiconductor fine powder in a solvent may be used. Specific examples of solvents used when preparing the paste include water; alcohol solvents such as methanol, ethanol, and isopropyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; n-hexane, cyclohexane, benzene, Examples include, but are not limited to, hydrocarbon solvents such as toluene. Moreover, these solvents can be used alone or as a mixed solvent of two or more.

In the present invention, the semiconductor fine powder may be dispersed in a solvent by grinding the powder in a mortar or the like, or by using a dispersing machine such as a ball mill, paint conditioner, vertical bead mill, horizontal bead mill, or attritor. You can. When preparing the paste, it is preferable to add a surfactant or the like to prevent agglomeration of the semiconductor fine particles, and it is preferable to add a thickener such as polyethylene glycol to increase the viscosity.

The adsorption of the sensitizing dye composition for photoelectric conversion of the present invention onto the surface of the semiconductor layer can be carried out, for example, by immersing the semiconductor layer in the dye solution for 30 minutes to 100 hours at room temperature or for 10 minutes to 24 hours under heating conditions. This can be done by leaving it alone. In that case, it is preferable to leave it at room temperature for 10 to 20 hours, and the dye concentration in the dye solution is preferably 10 to 2000 μM, more preferably 50 to 500 μM.

Examples of the solvent used when adsorbing the sensitizing dye for photoelectric conversion of the present invention onto the surface of the semiconductor layer include alcoholic solvents such as methanol, ethanol, isopropyl alcohol, and t-butyl alcohol; acetone, methyl ethyl ketone, Ketone solvents such as methyl isobutyl ketone; Ester solvents such as ethyl formate, ethyl acetate, and n-butyl acetate; Ether solvents such as diethyl ether, 1,2-dimethoxyethane, tetrahydrofuran, and 1,3-dioxolane; N, Amide solvents such as N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; Nitrile solvents such as acetonitrile, methoxyacetonitrile, and propionitrile; dichloromethane, chloroform, bromoform, o-dichlorobenzene, etc. Examples include, but are not limited to, halogenated hydrocarbon solvents such as n-hexane, cyclohexane, benzene, and toluene. These solvents may be used alone or as a mixed solvent of two or more. Among these solvents, it is preferable to use one or more selected from methanol, ethanol, t-butyl alcohol, acetone, methyl ethyl ketone, tetrahydrofuran, and acetonitrile.

When adsorbing the sensitizing dye composition for photoelectric conversion of the present invention onto the surface of a semiconductor layer, cholic acid or a cholic acid derivative such as deoxycholic acid, chenodeoxycholic acid, lysocholic acid, or dehydrocholic acid is dissolved in the dye solution. However, it may also be co-adsorbed with the dye. By using cholic acid or a cholic acid derivative, association between dyes is suppressed, and electrons can be efficiently injected from the dye to the semiconductor layer in the photoelectric conversion element. When cholic acid or cholic acid derivatives are used, their concentration in the dye solution is preferably 0.1 to 100 mM, more preferably 0.5 to 10 mM.

The counter electrode (electrode) used in the photoelectric conversion element of the present invention is not particularly limited as long as it has conductivity, but in order to promote the redox reaction of redox ions, a conductive material with catalytic ability is used. It is preferable to do so. Specific examples of the conductive material include, but are not limited to, platinum, rhodium, ruthenium, and carbon. In the present invention, it is particularly preferable to use as a counter electrode a thin platinum film formed on a conductive support. In addition, as a method for producing a conductive thin film, a paste containing a conductive material is applied onto a conductive substrate by a wet coating method such as a spin coating method, a doctor blade method, a squeegee method, or a screen printing method, and then the solvent is removed by baking. Examples include, but are not limited to, a method of forming a film by removing additives and a method of forming a film by a sputtering method, a vapor deposition method, an electrodeposition method, an electrodeposition method, a microwave irradiation method, and the like.

In the photoelectric conversion element of the present invention, an electrolyte is filled between a pair of opposing electrodes to form an electrolyte layer. The electrolyte used is preferably a redox electrolyte. Redox electrolytes include, but are not limited to, redox ion pairs such as iodine, bromine, tin, iron, chromium, and anthraquinone. Among these, iodine electrolytes and bromine electrolytes are preferred. In the case of an iodine-based electrolyte, a mixture of potassium iodide, lithium iodide, dimethylpropylimidazolium iodide, etc. and iodine is used, for example. In the present invention, it is preferable to use an electrolytic solution obtained by dissolving these electrolytes in a solvent. The concentration of electrolyte in the electrolytic solution is preferably 0.05 to 5M, more preferably 0.2 to 1M.

Examples of solvents for dissolving the electrolyte include nitrile solvents such as acetonitrile, methoxyacetonitrile, propionitrile, 3-methoxypropionitrile, and benzonitrile; ether solvents such as diethyl ether, 1,2-dimethoxyethane, and tetrahydrofuran; , N-dimethylformamide, N,N-dimethylacetamide, and other amide solvents; ethylene carbonate, propylene carbonate, and other carbonate solvents; γ-butyrolactone, γ-valerolactone, and other lactone solvents. Not limited. These solvents may be used alone or as a mixed solvent of two or more. Among these solvents, nitrile solvents are preferred.

In the present invention, an amine compound may be contained in the electrolytic solution in order to further improve the open circuit voltage and fill factor of the dye-sensitized photoelectric conversion element. Examples of amine compounds include 4-t-butylpyridine, 4-methylpyridine, 2-vinylpyridine, N,N-dimethyl-4-aminopyridine, N,N-dimethylaniline, and N-methylbenzimidazole. . The concentration of the amine compound in the electrolytic solution is preferably 0.05 to 5M, more preferably 0.2 to 1M.

As the electrolyte in the photoelectric conversion element of the present invention, a gel electrolyte obtained by adding a gelling agent, a polymer, etc., or a solid electrolyte using a polymer such as a polyethylene oxide derivative may be used. By using a gel electrolyte or a solid electrolyte, volatilization of the electrolyte can be reduced.

In the photoelectric conversion element of the present invention, a solid charge transport layer may be formed between a pair of opposing electrodes instead of an electrolyte. The charge transport material contained in the solid charge transport layer is preferably a hole transport material. Specific examples of charge transport materials include inorganic hole transport materials such as copper iodide, copper bromide, and copper thiocyanide, polypyrrole, polythiophene, poly-p-phenylene vinylene, polyvinylcarbazole, polyaniline, oxadiazole derivatives, and Examples include, but are not limited to, organic hole transport substances such as phenylamine derivatives, pyrazoline derivatives, fluorenone derivatives, hydrazone compounds, and stilbene compounds.

In the present invention, when a solid charge transport layer is formed using an organic hole transport material, a film-forming binder resin may be used in combination. Specific examples of the film-forming binder resin include polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polysulfone resin, polyester resin, polyphenylene oxide resin, polyarylate resin, alkyd resin, acrylic resin, phenoxy resin, etc. , but not limited to. These resins can be used alone or in combination as a copolymer. The amount of these binder resins used relative to the organic hole transport material is preferably 20 to 1000% by weight, more preferably 50 to 500% by weight.

In the photoelectric conversion element of the present invention, the electrode (photoelectrode) provided with the semiconductor layer to which the sensitizing dye composition for photoelectric conversion is adsorbed serves as the cathode, and the counter electrode serves as the anode. Light such as sunlight may be irradiated from either the photoelectrode side or the counter electrode side, but it is preferable to irradiate it from the photoelectrode side. When irradiated with sunlight, the pigment absorbs the light, becomes excited, and emits electrons. These electrons flow outside through the semiconductor layer and move to the opposite electrode. On the other hand, the dye, which has become oxidized by releasing electrons, returns to the ground state by receiving electrons supplied from the counter electrode via ions in the electrolyte. This cycle causes current to flow, allowing it to function as a photoelectric conversion element.

When evaluating the performance (characteristics) of the photoelectric conversion element of the present invention, short circuit current, open circuit voltage, fill factor, and photoelectric conversion efficiency are measured. The short-circuit current represents the current per 1 cm ² that flows between both terminals when the output terminals are short-circuited, and the open-circuit voltage represents the voltage between the two terminals when the output terminals are opened. Fill factor is the value obtained by dividing the maximum output (the product of current and voltage) by the product of short circuit current and open circuit voltage, and is mainly influenced by internal resistance. The photoelectric conversion efficiency is determined as a value obtained by dividing the maximum output (W) by the light intensity (W) per 1 cm ² and multiplying it by 100, expressed as a percentage.

The photoelectric conversion element of the present invention can be applied to dye-sensitized solar cells, various optical sensors, and the like. In the dye-sensitized solar cell of the present invention, a photoelectric conversion element containing a sensitizing dye composition for photoelectric conversion containing a sensitizing dye represented by the above general formula (1) serves as a cell, and a required number of cells are arranged. It can be obtained by modularizing and providing predetermined electrical wiring.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples. In the synthesis examples, compounds were identified by ¹ H-NMR analysis (Nuclear magnetic resonance apparatus, JNM-ECA-600 or JMN-ECZ-400S, manufactured by JEOL Ltd.).

[Synthesis Example 1] Synthesis of sensitizing dye (A-1) In a reaction vessel purged with nitrogen, 8.11 g of 2-(4-bromophenyl)-1,1-diphenylethylene, 1,2,3,3a, 4.24 g of 4,8b-hexahydrocyclopenta[b]indole and 56 mL of xylene were added, and 0.127 g of triphenylphosphine, 5.43 g of potassium t-butoxide, and 0.27 g of palladium acetate were added and degassed under reduced pressure. . The reaction was carried out at 125° C. for 10 hours while stirring. The mixture was cooled to 50° C., 9.4 g of activated clay was added, and after stirring for 1 hour, suction filtration was performed, 100 mL of water was added and stirred, and the organic layer was extracted. After washing the organic layer with water, it was separated, dried over sodium sulfate, and concentrated under reduced pressure to obtain an oily crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane/toluene = 10/1 (volume ratio)) to obtain a yellow solid (9.98 g).
2 g of the obtained yellow solid was brominated according to a conventional method to obtain 2.35 g of bromine compound represented by the following formula (10).

In a reaction vessel purged with nitrogen, 1.53 g of the bromo compound represented by the above formula (10), 34 mL of dimethyl sulfoxide, 0.93 g of bis(pinacolato)diboron, and 0.90 g of potassium acetate were placed and stirred. Depressurization, degassing, and nitrogen substitution were repeated five times. Next, 0.18 g of tetrakis(triphenylphosphine)palladium and 0.09 g of 1,1'-bis(diphenylphosphino)ferrocene were added and stirred at 80° C. for 3 hours. After the reaction solution was allowed to cool to 25° C., 100 mL of toluene and 100 mL of water were added and stirred, and the organic layer was extracted. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane/toluene = 2/1 (volume ratio)) and dried to obtain a yellow-green solid of a boronate ester compound represented by the following formula (11). (0.80g) was obtained.

0.14 g of 4-bromobenzaldehyde, 0.35 g of the boronic acid ester compound represented by the above formula (11), 12 mL of dried dimethyl sulfoxide, and 0.19 g of potassium acetate were placed in a reaction vessel purged with nitrogen, and after stirring, the reaction was started. Reducing the pressure inside the container, degassing it, and replacing it with nitrogen were repeated 5 times. Next, 0.018 g of palladium acetate and 0.057 g of di(1-adamantyl)-n-butylphosphine were added, and the pressure inside the reaction vessel was reduced, degassed, and replaced with nitrogen five times. Thereafter, the mixture was stirred at 80°C for 9 hours. After the reaction solution was allowed to cool to 25° C., 10 mL of methylene chloride and 30 mL of water were added and stirred, and the organic layer was extracted. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene/hexane = 2/1 (volume ratio)), dried, and a yellow solid (0 .25g) was obtained.

In a reaction vessel purged with nitrogen, 0.241 g of the formyl compound represented by the above formula (12), 0.126 g of the indenone compound represented by the following formula (13), and acetic acid/toluene = 5/2 (volume ratio) mixture. 14 mL of liquid was added thereto, and the mixture was stirred at 90°C for 14 hours. After the reaction solution was allowed to cool to 25° C., 25 mL of methylene chloride and 50 mL of water were added and stirred, and the organic layer was extracted. The organic layer was washed successively with water and saturated brine and dried to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: methylene chloride/methanol = 5/1 (volume ratio)) and dried to obtain the desired sensitizing dye as a reddish-purple solid (0.247 g , yield 73%).

The obtained reddish-purple solid was analyzed by NMR, and the following 34 hydrogen signals were detected, and the structure was identified as represented by the following formula (A-1) (no hydrogen in the carboxyl group was observed). .

¹ H-NMR (600 MHz, CDCl ₃ ): δ (ppm) = 1.21-1.34 (1H), 1.59-1.72 (2H), 1.85-1.89 (2H), 2 .02-2.06 (1H), 3.84-3.88 (1H), 4.83-4.87 (1H), 6.98-7.13 (6H), 7.18-7.23 (2H), 7.27-7.36 (5H), 7.40-7.49 (3H), 7.54-7.60 (1H), 7.65-7.69 (1H), 7. 83-7.91 (3H), 8.05-8.09 (1H), 8.30-8.45 (2H), 8.59-8.63 (2H).

[Synthesis Example 2] Synthesis of sensitizing dye (A-2) Synthesis Example except that 6-bromobenzo[b]thiophene-2-carbaldehyde was used instead of the raw material 4-bromobenzaldehyde in Synthesis Example 1. It was synthesized in the same manner as in 1 to obtain the desired sensitizing dye as a purple solid (0.29 g, yield 57%).

The obtained purple solid was subjected to NMR analysis, and the following 34 hydrogen signals were detected, and the structure was identified as represented by the following formula (A-2) (no hydrogen in the carboxyl group was observed).

¹ H-NMR (600 MHz, CDCl ₃ ): δ (ppm) = 1.31-1.37 (1H), 1.60-1.64 (1H), 1.70-1.74 (1H), 1 .83-1.93 (2H), 2.03-2.10 (1H), 3.83-3.90 (1H), 4.79-4.86 (1H), 6.98-7.03 (2H), 7.02-7.08 (2H), 7.07-7.12 (2H), 7.18-7.24 (2H), 7.24-7.32 (3H), 7. 31-7.37 (2H), 7.39-7.45 (1H), 7.44-7.50 (2H), 7.50-7.55 (1H), 7.62-7.66 ( 1H), 7.72-7.78 (1H), 7.97-8.07 (2H), 8.16-8.20 (1H), 8.30-8.37 (2H), 8.36 -8.43 (1H), 8.53-8.57 (1H).

[Synthesis Example 3] Synthesis of sensitizing dye (A-3) Instead of the raw material 4-bromobenzaldehyde in Synthesis Example 1, 7-bromo-2,1,3-benzothiadiazole-4-carboxaldehyde was used. Except for this, the synthesis was carried out in the same manner as in Synthesis Example 1, and the desired sensitizing dye was obtained as a black solid (0.13 g, yield 69%).

The obtained black solid was subjected to NMR analysis, and the following 32 hydrogen signals were detected, and the structure was identified as represented by the following formula (A-3) (no hydrogen in the carboxyl group was observed).

¹ H-NMR (600 MHz, CDCl ₃ ): δ (ppm) = 1.30-1.35 (1H), 1.58-1.69 (2H), 1.80-1.85 (2H), 2 .02-2.06 (1H), 3.79-3.83 (1H), 4.81-4.85 (1H), 6.92-7.00 (3H), 7.01-7.08 (3H), 7.17-7.23 (2H), 7.25-7.31 (3H), 7.26-7.37 (2H), 7.39-7.50 (3H), 7. 87-7.98 (4H), 8.18-8.25 (1H), 8.26-8.33 (1H), 8.48-8.52 (1H), 9.45-9.53 ( 1H).

[Synthesis Example 4] Synthesis of sensitizing dye (A-4) Same as Synthesis Example 1 except that 6-bromo-2-naphthaldehyde was used instead of the raw material 4-bromobenzaldehyde in Synthesis Example 1. The desired sensitizing dye was obtained as a black-purple solid (0.16 g, yield 84%).

NMR analysis of the obtained black-purple solid was performed, and the following 36 hydrogen signals were detected, and the structure was identified as represented by the following formula (A-4) (no hydrogen in the carboxyl group was observed). .

¹ H-NMR (600 MHz, CDCl ₃ ): δ (ppm) = 1.30-1.41 (1H), 1.60-1.75 (2H), 1.86-1.94 (2H), 2 .01-2.11 (1H), 3.85-3.93 (1H), 4.81-4.89 (1H), 6.98-7.05 (2H), 7.05-7.15 (4H), 7.19-7.24 (2H), 7.27-7.37 (5H), 7.40-7.50 (3H), 7.56-7.62 (1H), 7. 69-7.73 (1H), 7.92-7.98 (1H), 8.01-8.14 (4H), 8.21-8.25 (1H), 8.35-8.46 ( 2H), 8.69-8.77 (1H), 9.00-9.04 (1H).

[Synthesis Example 6] Synthesis of sensitizing dye (A-7) In a reaction vessel purged with nitrogen, 0.85 g of the boronic acid ester compound represented by the formula (11) and 4,7-dibromo-2-octyl- After adding 0.61 g of 2H-benzotriazole, 24 mL of toluene, 39 mL of 1-butanol, 1.7 g of sodium carbonate, and 12 mL of water and stirring, the inside of the reaction vessel was vacuumed, degassed, and replaced with nitrogen five times. Next, 0.196 g of tetrakis(triphenylphosphine)palladium was added, and the pressure reduction, degassing, and nitrogen substitution in the reaction vessel were repeated five times. Thereafter, the mixture was stirred at 80°C for 2 hours. After the reaction solution was allowed to cool to 25° C., 156 mL of water was added and stirred, and the organic layer was extracted. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene/hexane = 2/1 (volume ratio)) and dried to obtain a yellow solid (0. 54g) was obtained.

In a reaction vessel purged with nitrogen, 0.499 g of the bromo compound represented by the above formula (14) and 5 mL of dehydrated tetrahydrofuran were placed, and while stirring at -72°C, 0.48 mL of a 1.6 M n-butyllithium hexane solution was added. After the mixture was added dropwise and stirred for 1 hour, 0.11 mL of dehydrated dimethyl formaldehyde was added dropwise and the reaction was carried out for 2 hours. 10 mL of water was added dropwise to the reaction solution, and the organic layer was extracted with toluene. After washing the organic layer with water, it was separated, dried over magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane/toluene = 3/2 (volume ratio)) to obtain a red solid (0.095 g) of the formyl compound represented by the following formula (15). I got it.

In a reaction vessel purged with nitrogen, 0.082 g of the formyl compound represented by the above formula (15), 0.036 g of the indenone compound represented by the above formula (13), and acetic acid/toluene = 5/2 (volume ratio) mixture. 5.6 mL of liquid was added thereto, and the mixture was stirred at 90°C for 3 hours. After the reaction solution was allowed to cool to 25° C., 30 mL of toluene and 30 mL of water were added and stirred, and the organic layer was extracted. The organic layer was washed successively with water and saturated brine and dried to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: methylene chloride/methanol = 20/1 (volume ratio)) and dried to obtain the desired sensitizing dye as a black-purple solid (0.072 g , yield 70%).

NMR analysis of the obtained black-purple solid was performed, and the following 49 hydrogen signals were detected, and the structure was identified as represented by the following formula (A-7) (no hydrogen in the carboxyl group was observed). .

¹ H-NMR (600 MHz, CDCl ₃ ): δ (ppm) = 0.77-0.87 (4H), 1.21-1.36 (10H), 1.60-1.74 (2H), 1 .85-1.93 (2H), 2.07-2.11 (3H), 3.88-3.92 (1H), 4.83-4.95 (3H), 7.00-7.06 (2H), 7.06-7.10 (2H), 7.12-7.18 (2H), 7.19-7.25 (2H), 7.27-7.37 (5H), 7. 44-7.50 (3H), 7.92-7.98 (1H), 8.05-8.17 (3H), 8.31-8.42 (2H), 8.47-8.51 ( 1H), 9.40-9.48 (1H).

[Synthesis Example 5] Synthesis of sensitizing dye (A-14) Except for using 4-bromobiphenyl instead of the raw material 2-(4-bromophenyl)-1,1-diphenylethylene in Synthesis Example 1. Synthesis was carried out in the same manner as in Synthesis Example 1, and the desired sensitizing dye was obtained as a purple solid (0.35 g, yield 81%).

The obtained purple solid was subjected to NMR analysis, and the following 28 hydrogen signals were detected, and the structure was identified as represented by the following formula (A-14) (no hydrogen in the carboxyl group was observed).

¹ H-NMR (600 MHz, CDCl ₃ ): δ (ppm) = 1.39-1.45 (1H), 1.65-1.69 (1H), 1.82-1.86 (1H), 1 .87-1.96 (2H), 2.08-2.12 (1H), 3.91-3.97 (1H), 4.97-5.03 (1H), 7.11-7.16 (1H), 7.30-7.36 (1H), 7.42-7.49 (4H), 7.61-7.66 (1H), 7.65-7.70 (2H), 7. 68-7.75 (3H), 7.88-7.94 (3H), 8.05-8.11 (1H), 8.34-8.41 (1H), 8.39-8.46 ( 1H), 8.60-8.67 (2H).

[Example 1]
A titanium oxide paste (PST-18NR, manufactured by JGC Catalysts & Chemicals Co., Ltd.) was applied by a squeegee method onto a glass substrate coated with a fluorine-doped tin oxide thin film. After drying at 110°C for 1 hour, it was fired at 450°C for 30 minutes to obtain a titanium oxide thin film with a thickness of 6 μm. Next, the sensitizing dye (A-1) obtained in Synthesis Example 1 was dissolved in a mixture of acetonitrile/t-butyl alcohol = 1/1 (volume ratio) to prepare 50 mL of a solution with a concentration of 100 μM. A glass substrate coated with titanium oxide and sintered was immersed in the solution at 25±2° C. for 15 hours to adsorb the dye, thereby forming a photoelectrode.

A platinum thin film with a thickness of 15 nm was formed on a glass substrate coated with a fluorine-doped tin oxide thin film by sputtering using an auto fine coater (JFC-1600 manufactured by JEOL Ltd.), and was used as a counter electrode.

Next, a spacer (thermal adhesive film) with a thickness of 60 μm is sandwiched between the photoelectrode and the counter electrode, and they are bonded together by heat fusion, and an electrolytic solution (0.1M lithium iodide, 0.6M After injecting dimethylpropylimidazolium chloride, 0.05M iodine, 0.5M 4-t-butylpyridine/3-methoxypropionitrile solution), the holes were sealed to produce a photoelectric conversion element.

Light generated by a simulated sunlight irradiation device (Model 2400 General-Purpose Source Meter, manufactured by KEITHLEY) was irradiated from the photoelectrode side of the photoelectric conversion element. The current-voltage characteristics were measured. The light intensity was adjusted to 100 mW/ ^cm2 . Table 1 shows the measurement results and initial photoelectric conversion efficiency.

[Example 2 to Example 4]
Photoelectric conversion cells prepared in the same manner as in Example 1 except that the sensitizing dyes shown in Table 1 were used instead of the sensitizing dye (A-1) obtained in Synthesis Example 1 as the sensitizing dyes for photoelectric conversion. Table 1 summarizes the current-voltage characteristics and initial photoelectric conversion efficiency of the device.

[Comparative example 1 to comparative example 3]
As a sensitizing dye for photoelectric conversion, in place of the sensitizing dye (A-1) obtained in Synthesis Example 1, the following sensitizing dyes (B-1) to (B-3) that do not belong to the present invention may be used. Table 1 shows the current-voltage characteristics and initial photoelectric conversion efficiency of the photoelectric conversion element manufactured in the same manner as in Example 1 except that .

From the results in Table 1, by using the sensitizing dye composition for photoelectric conversion containing the sensitizing dye of the present invention, the photoelectric conversion efficiency is high and the high photoelectric conversion efficiency is maintained even if light irradiation is continued for a long time. It was found that a photoelectric conversion element could be obtained. On the other hand, the photoelectric conversion efficiency of the photoelectric conversion element using the sensitizing dye for photoelectric conversion of the comparative example was insufficient.

The sensitizing dye composition for photoelectric conversion comprising the sensitizing dye of the present invention is useful for highly efficient and highly durable photoelectric conversion elements and dye-sensitized solar cells, and can efficiently convert sunlight energy into electrical energy. As a solar cell, it can provide clean energy.

1 Conductive support 2 Dye-supporting semiconductor layer 3 Electrolyte layer 4 Counter electrode 5 Conductive support

Claims (5)

A sensitizing dye represented by the following general formula (1).

[wherein R ¹ is a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
Or represents an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent.
R ² and R ³ represent a hydrogen atom or a linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent.
m represents an integer from 2 to 8.
X is any one divalent bonding group represented by the following general formulas (X1) to (X7),
Z is a monovalent group represented by the following general formula (3).

[In the formula, R ¹⁶ to R ¹⁹ may be the same or different, and a hydrogen atom,
A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
Aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent,
or a heterocyclic group having 2 to 36 carbon atoms which may have a substituent,
R ¹⁸ and R ¹⁹ may be bonded to each other to form a ring. ]

[In the formula, R ²⁰ to R ²² may be the same or different,
hydrogen atom,
A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent,
A linear or branched alkoxy group having 1 to 18 carbon atoms which may have a substituent, or a linear or branched alkoxy group having 2 to 18 carbon atoms which may have a substituent. Represents an alkenyl group.
p represents 0 to 4, and R ²⁰ and R ²¹ may be bonded to each other to form a ring.
^R23 and ^R24 represent a hydrogen atom or an acidic group, and at least one of them is an acidic group. ] In the general formula (1), R ¹ is a linear or branched alkyl group having 1 to 6 carbon atoms, which may have a substituent, or an aromatic hydrocarbon group having 6 to 26 carbon atoms. Claim 1, wherein R ² and R ³ are a hydrogen atom or a linear alkyl group having 1 to 6 carbon atoms which may have a substituent, and m is 3 or 4. The sensitizing dye described in . A sensitizing dye composition for photoelectric conversion comprising the sensitizing dye according to claim 1 or 2 . A photoelectric conversion element using the sensitizing dye composition for photoelectric conversion according to claim 3 . A dye-sensitized solar cell using the photoelectric conversion element according to claim 4 .

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