JP2015154070A - Photoelectric conversion element using sensitizing dye of salicylaldehyde derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent photoelectric conversion element having high photoelectric conversion efficiency, and a solar cell including the element.SOLUTION: In the dye-sensitized photoelectric conversion element, at least a semiconductor layer obtained by carrying a sensitizing dye on a semiconductor and a charge transport layer are provided between a pair of electrodes facing each other. The sensitizing dye contains a compound represented by general formula [1]. [In the general formula [1], O is an oxygen atom; H is a hydrogen atom; and Rto Rare each selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.]

Description

      The present invention relates to a photoelectric conversion element and a solar cell using a sensitizing dye of a salicylaldehyde derivative.

  In recent years, the use of sunlight as a safe and secure energy has been energetically studied. Examples of products that are currently in practical use include residential single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide.

  For example, some silicon-based materials exhibit conversion efficiencies exceeding 30%, but the silicon used therein is required to have a very high purity, and it is necessary to input a large amount of power in the purification process. Therefore, if we consider purely the amount of electricity generated, we can't think it will be directly linked to solving the energy problem.

  Under such circumstances, a solar cell exhibiting good characteristics has been reported by Dr. Gretzell of Switzerland (see Non-Patent Document 1). The proposed battery is a dye-sensitized solar cell, which is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. The advantage of this method is that it is not necessary to purify an inexpensive metal compound semiconductor such as titanium oxide to a high purity. Therefore, the electric power input at the time of manufacture is overwhelmingly smaller than that of silicon solar cells, and it can be expected that the energy problem can be solved truly.

  The dye of this battery is not limited to the ruthenium complex, and a dye having a wide range of absorption region from visible light to infrared light can be used. However, even when a ruthenium complex that has been most actively studied is used, the conversion efficiency is as low as about 30% of the theoretical value, and a sensitizing dye exhibiting a higher photoelectric conversion efficiency is demanded.

JP2010-1000085

B. O'Regan, M.M. Gratzel, Nature, 353, 737 (1991) Y. Bai, J .; Zhang, D.C. Zhou, Y .; Wang, M .; Zhang, P.A. Wang, J .; Am. Chem. Soc. , 113, 11442 (2011)

  So far, many sensitizing dyes have been developed for improving the efficiency of dye-sensitized solar cells, but the efficiency is still insufficient. As a substituent (anchoring unit) for adsorbing the dye to the semiconductor electrode, a carboxyl group is used in the ruthenium complex disclosed in the patent document (Japanese Patent Application Laid-Open No. 2010-1000085). The D-π-A dye disclosed in Non-Patent Document 2 also uses a carboxyl group. In order to improve the photoelectric conversion efficiency, a novel anchoring unit replacing a carboxyl group is required.

  An object of the present invention is to provide a highly efficient photoelectric conversion element in which a sensitizing dye of a salicylaldehyde derivative according to the present invention is carried on a semiconductor electrode and the short-circuit current density is increased.

Therefore, the present invention provides a photoelectric conversion element using a salicylaldehyde compound, which is represented by the following general formula.

  According to the present invention, the photoelectric conversion element using the salicylaldehyde compound according to the present invention can provide a photoelectric light-emitting element having high photoelectric conversion efficiency.

FIG. 1 is a cross-sectional view showing an example of the photoelectric conversion element of the present invention.

  Hereinafter, the present invention will be described in detail. First, the salicylaldehyde compound of the present invention represented by the following general formula [1] will be described.

〔一般式［１］において、Ｏは酸素原子であり、Ｈは水素原子である。
Ｒ_１乃至Ｒ_４は、水素原子、ハロゲン原子、シアノ基、置換または無置換のアルキル基、アミノ基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、から選ばれる。〕The salicylaldehyde compound according to the present invention is represented by the following general formula [1].

[In General Formula [1], O is an oxygen atom, and H is a hydrogen atom.
R _{1 to} R ₄ are selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group. ]

  The halogen atom is preferably a fluorine atom, a chlorine atom, or a bromine atom. When purifying the dye by a vacuum deposition method, a fluorine atom is particularly preferable from the viewpoint of sublimation.

  Examples of the substituted or unsubstituted alkyl group include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a tertiary butyl group, an octyl group, and a cyclohexyl group. When the alkyl group has 2 or more carbon atoms, one or two or more methylene groups not adjacent to each other in the alkyl group may be substituted with -O-. A hydrogen atom in the alkyl group may be substituted with a fluorine atom to form, for example, a trifluoromethyl group.

  Of these alkyl groups, an isopropyl group, a tertiary butyl group, an octyl group, a cyclohexyl group, and a trifluoromethyl group are preferable from the viewpoint of suppressing aggregation of the dye. More preferred are isopropyl group, tertiary butyl group, and trifluoromethyl group. More preferred are isopropyl group and tertiary butyl group.

  The substituted amino group is preferably a dimethylamino group, a diphenylamino group, or a ditolylamino group from the viewpoint of electron donating properties. Particularly preferred is a diphenylamino group.

  Examples of the alkenyl group which may have a substituent include an ethenyl group and a butenyl group. Ethethenyl is preferred from the viewpoint of light stability.

  Examples of the alkynyl group which may have a substituent include an ethynyl group and a diacetylenyl group, and the ethynyl group is preferable from the viewpoint of light stability.

  As an aryl group which may have a substituent, phenyl group, biphenyl group, terphenyl group, fluorenyl group, naphthyl group, fluoranthenyl group, anthryl group, phenanthryl group, pyrenyl group, tetracenyl group, pentacenyl group, triphenylenyl group And perylenyl group.

  From the viewpoint of intramolecular electron transfer, a phenyl group, a fluorenyl group, and a naphthyl group are preferable. More preferably, they are a fluorenyl group and a naphthyl group.

  As the heteroaryl group which may have a substituent, thienyl group, pyrrolyl group, pyridyl group, pyrazyl group, pyrimidyl group, pyridazinyl group, quinolinyl group, isoquinolinyl group, phenanthridinyl group, acridinyl group, naphthyridinyl group, quinoxalinyl Group, quinazolinyl group, cinnolinyl group, phthalazinyl group, thienothienyl group, phenanthroyl group, phenazinyl group, dibenzofuranyl group, dibenzothiophenyl group, dithienothienyl group, carbazolyl group, benzofuranyl group, benzothiophenyl group, indolyl group, cycloazyl group, Examples thereof include a benzoimidazolyl group, a benzothiazolyl group, a benzothiadiazolyl group, a porphyrinyl group, and a phthalocyanyl group.

  From the viewpoint of intramolecular conductivity, a quinolinyl group, a benzothienyl group, a thienothienyl group, a dibenzothienyl group, a carbazolyl group, a dithienothienyl group, a porphyrinyl group, or a phthalocyanyl group is preferable. More preferred are a thienothienyl group, a dithienothienyl group, and a porphyrinyl group.

The substituent that the aryl group and heterocyclic group may have is not particularly limited, but is preferably a halogen atom, an alkyl group having 1 to 20 carbon atoms, a substituted amino group, a substituted or unsubstituted aryl. Group, a heteroaryl group. When the alkyl group has 2 or more carbon atoms, one or two or more methylene groups not adjacent to each other in the alkyl group may be substituted with -O-. In the alkyl group, a hydrogen atom may be substituted with a fluorine atom. Specific examples of the alkyl group, the substituted amino group, the substituted or unsubstituted aryl group, and the heteroaryl group include the alkyl group, substituted amino group, aryl group, and heteroaryl which are substituents introduced into the above-described R _{1 to} R _4. This is the same as the specific example of the group.

  Of these substituents, a fluorine atom, a trifluoromethyl group, an octyl group, a tertiary butyl group, a ditertiary butylamino group, and a phenyl group are preferable from the viewpoint of intramolecular conductivity and dye aggregation suppression. More preferred are fluorine, trifluoromethyl group, methyl group, tertiary butyl group and octyl group. Particularly preferred are a tertiary butyl group and an octyl group.

So far, in the salicylaldehyde compound of the present invention, the substituents that R _{1 to} R ₄ in the formula [1] may have have been described.

〔一般式［２］において、Ｏは酸素原子であり、Ｈは水素原子である。
Ｒ_１乃至Ｒ_４は、水素原子、ハロゲン原子、シアノ基、置換または無置換のアルキル基、アミノ基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、から選ばれる。Ｒ_５乃至Ｒ_６は、水素原子、置換または無置換のアルキル基、アリール基、ヘテロアリール基、から選ばれる。Ｘ１は２価の連結基であり置換または無置換のアリーレン基、ヘテロアリーレン基、アゾ基、アミド基、エステル基、アルケニレン基、アルキニレン基のうちの少なくとも一つを含み、また、同種または異種を複数個の組み合わせた２価の連結基でもよい。〕The salicylaldehyde compound according to the present invention is represented by the following general formula [2].

[In General Formula [2], O is an oxygen atom, and H is a hydrogen atom.
R _{1 to} R ₄ are selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group. R _{5 to} R ₆ are selected from a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, and a heteroaryl group. X1 is a divalent linking group and includes at least one of a substituted or unsubstituted arylene group, heteroarylene group, azo group, amide group, ester group, alkenylene group, alkynylene group, and is the same or different. A plurality of combined divalent linking groups may be used. ]

A halogen atom, an alkyl group, a substituted amino group, a substituted or unsubstituted alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group, which are substituents introduced into R _{1 to} R ₄ of the above general formula [2], This is the same as the specific example of Formula [1].

  Examples of the divalent linking group introduced with X1 in the general formula [2] include a fluorenylene group, a pyrenylene group, a chrysenylene group and the like as a substituted or unsubstituted arylene group.

  As substituted or ignorant heteroarylene groups, thienyl, pyrrolyl, pyridyl, pyrazyl, pyrimidyl, pyridazinyl, quinolinyl, isoquinolinyl, phenanthridinyl, acridinyl, naphthyridinyl, quinoxalinyl, quinazolinyl Group, cinnolinyl group, phthalazinyl group, thienothienyl group, phenanthroyl group, phenazinyl group, dibenzofuranyl group, dibenzothiophenyl group, dithienothienyl group, carbazolyl group, benzofuranyl group, benzothiophenyl group, indolyl group, cycloazyl group, benzoimidazolyl group, Examples thereof include a benzothiazolyl group, a benzothiadiazolyl group, a porphyrinyl group, and a phthalocyanyl group.

  From the viewpoint of electron donating properties, a thienyl group, a benzothienyl group, a thienothienyl group, a dibenzothienyl group, a carbazolyl group, and a dithienothienyl group are preferable. More preferably, they are a thienyl group, a carbazolyl group, and a benzothienyl group.

The substituent that the aryl group and heteroaryl group may have is not particularly limited, but is preferably an alkyl group having 1 to 20 carbon atoms, a substituted amino group, a substituted or unsubstituted aryl group, a hetero group. An aryl group. When the alkyl group has 2 or more carbon atoms, one or two or more methylene groups not adjacent to each other in the alkyl group may be substituted with -O-. In the alkyl group, a hydrogen atom may be substituted with a fluorine atom. Specific examples of the alkyl group, the substituted amino group, the substituted or unsubstituted aryl group, and the heteroaryl group include the alkyl group, the substituted amino group, the aryl group, and the hetero group that are substituents introduced into the above-described R _{1 to} R _4. The same as the specific examples of the aryl group.

  Other examples of the linking group include, but are not limited to, an azo group, an amide group, an ester group, an alkenylene group, and an alkynylene group. From the viewpoint of intramolecular conductivity, those composed of atoms composed of SP or SP2 hybrid orbitals are preferred.

  X1 may be composed of a single linking group as described above, but a divalent linking group in which the above-mentioned couplers are combined in the same type or different types is preferable.

Examples of the substituted or unsubstituted alkyl group introduced into R ₅ and R ₆ of the general formula [2] include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a tertiary butyl group, and an octyl group. And a cyclohexyl group. A hydrogen atom in the alkyl group may be substituted with a fluorine atom to form, for example, a trifluoromethyl group.

  Of these alkyl groups, a methyl group, an isopropyl group, a tertiary butyl group, an octyl group, and a cyclohexyl group are preferable from the viewpoint of electron donating property and dye aggregation suppression. More preferred are an octyl group and a tertiary butyl group.

  As an aryl group which may have a substituent, phenyl group, biphenyl group, terphenyl group, fluorenyl group, naphthyl group, fluoranthenyl group, anthryl group, phenanthryl group, pyrenyl group, tetracenyl group, pentacenyl group, triphenylenyl group And perylenyl group.

  From the viewpoint of electron donating properties, a phenyl group, a fluorenyl group, and a naphthyl group are preferable. More preferably, they are a phenyl group and a fluorenyl group.

  As the heteroaryl group which may have a substituent, thienyl group, pyrrolyl group, pyridyl group, pyrazyl group, pyrimidyl group, pyridazinyl group, quinolinyl group, isoquinolinyl group, phenanthridinyl group, acridinyl group, naphthyridinyl group, quinoxalinyl Group, quinazolinyl group, cinnolinyl group, phthalazinyl group, thienothienyl group, phenanthroyl group, phenazinyl group, dibenzofuranyl group, dibenzothiophenyl group, dithienothienyl group, carbazolyl group, benzofuranyl group, benzothiophenyl group, indolyl group, cycloazyl group, Examples thereof include a benzoimidazolyl group, a benzothiazolyl group, a benzothiadiazolyl group, a porphyrinyl group, and a phthalocyanyl group.

  From the viewpoint of electron donating properties, a thienyl group, a benzothienyl group, a thienothienyl group, a dibenzothienyl group, a carbazolyl group, and a dithienothienyl group are preferable. More preferably, they are a thienyl group, a carbazolyl group, and a benzothienyl group.

The substituent that the aryl group and heteroaryl group may have is not particularly limited, but is preferably an alkyl group having 1 to 20 carbon atoms, a substituted amino group, a substituted or unsubstituted aryl group, a hetero group. An aryl group. When the alkyl group has 2 or more carbon atoms, one or two or more methylene groups not adjacent to each other in the alkyl group may be substituted with -O-. In the alkyl group, a hydrogen atom may be substituted with a fluorine atom. Specific examples of the alkyl group, the substituted amino group, the substituted or unsubstituted aryl group, and the heteroaryl group include the alkyl group, the substituted amino group, the aryl group, and the hetero group that are substituents introduced into the above-described R _{1 to} R _4. The same as the specific examples of the aryl group.

〔一般式［３］において、Ｏは酸素原子であり、Ｈは水素原子である。
Ｒ_１乃至Ｒ_４は、水素原子、ハロゲン原子、シアノ基、置換または無置換のアルキル基、アミノ基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、から選ばれる。Ｒ_５乃至Ｒ_６は、水素原子、置換または無置換のアルキル基、アリール基、ヘテロアリール基、から選ばれる。Ｘ１は２価の連結基であり置換または無置換のアリーレン基、ヘテロアリーレン基、アゾ基、アミド基、エステル基、アルケニレン基、アルキニレン基のうちの少なくとも一つを含み、また、同種または異種を複数個の組み合わせた２価の連結基でもよい。〕The salicylaldehyde compound according to the present invention is represented by the following general formula [3].

[In General Formula [3], O is an oxygen atom, and H is a hydrogen atom.
R _{1 to} R ₄ are selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group. R _{5 to} R ₆ are selected from a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, and a heteroaryl group. X1 is a divalent linking group and includes at least one of a substituted or unsubstituted arylene group, heteroarylene group, azo group, amide group, ester group, alkenylene group, alkynylene group, and is the same or different. A plurality of combined divalent linking groups may be used. ]

A halogen atom, an alkyl group, a substituted amino group, a substituted or unsubstituted alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group, which are substituents introduced into R _{1 to} R ₄ of the above general formula [3], This is the same as the specific example of Formula [1].

  The divalent linking group introduced with X1 in the general formula [3] is a substituted or unsubstituted arylene group and the heteroarylene group is the same as the specific example of the general formula [2].

  Other examples of the linking group include, but are not limited to, an azo group, an amide group, an ester group, an alkenylene group, and an alkynylene group. From the viewpoint of intramolecular conductivity, those composed of atoms composed of SP or SP2 hybrid orbitals are preferred.

  X1 may be composed of the above-described linking group alone, but a divalent linking group obtained by combining the above-mentioned couplers of the same or different types is preferable.

The substituted or unsubstituted alkyl group, aryl group, and heteroaryl group introduced into R ₅ and R ₆ of the general formula [3] are the same as the specific examples of the general formula [2].

  The sensitizing dye of the present invention is supported on a semiconductor by the carbonyl group and hydroxyl group of salicylaldehyde. The sensitizing dye of the present invention improves the injectability of electrons from the excited dye to the semiconductor conductor than the one supported on the semiconductor using the carboxyl group used in general sensitizing dyes. Can be expected.

Considering the case where salicylaldehyde is supported on titanium oxide as a semiconductor, for example, it is considered that the following form is taken. Salicylaldehyde coordinates at the bidentate. Since the π electron of salicylaldehyde exists in the same plane as the oxygen atom connected to the titanium oxide electrode, the excited electron can be efficiently injected from the π conjugated system to the semiconductor electrode, and from the sensitizing dye to the semiconductor. The electron injecting property is improved, and the sensitizing dye of the present invention exhibits high electron injecting property.

  The injection property of electrons from the sensitizing dye to the semiconductor is improved, and the sensitizing dye of the present invention exhibits a high electron injection property.

  In order to have high efficiency as a sensitizing dye, it is preferable that excitation can be performed in a wide wavelength region. The longest absorption wavelength of the sensitizing dye according to the present invention is preferably 500 nm or more, and more preferably 550 nm or more.

Further, R ₁ and R ₄ in the general formulas [1] to [3] according to the present invention are preferably a hydrogen atom or an alkyl group. When R ₃ has a structure having a large conjugated substituent having long wavelength absorption, the distance between the semiconductor and the dye molecule can be kept the longest, and the reverse electron transfer to the semiconductor and the cationic sensitizing dye Can be suppressed. Further, when R ₁ and R ₄ are hydrogen atoms, the steric hindrance with the semiconductor is minimized, so that they can be supported more strongly. In addition, it can be expected that the steric hindrance with a large conjugated substituent having a long wavelength absorption bonded to R ₃ is minimized and the intramolecular conductivity of electrons is maximized.

(Examples of salicylaldehyde compounds according to the present invention)
Specific examples of the compound in the general formula [1] or the general formula [3] are shown below. However, the present invention is not limited to these.

  By sensitizing the dye of the present invention on a semiconductor, the effects described in the present invention can be achieved. Here, loading a dye on a semiconductor means various modes such as adsorption onto the surface of the semiconductor, and when the semiconductor has a porous structure such as a porous structure, the semiconductor porous structure is filled with the dye. Can be mentioned.

Further, the total supported amount of the dye of the present invention per 1 m ² of the semiconductor layer (which may be a semiconductor) is preferably in the range of 0.01 to 100 mmol, more preferably 0.1 to 60 mmol, particularly preferably 0.8. 5-20 mmol.

  When the sensitization treatment is performed using the dye of the present invention, the dye may be used alone or in combination.

  In order to support the dye of the present invention on a semiconductor, a method in which a semiconductor which has been dissolved in an appropriate solvent (tetrahydrofuran) and dried well in the solution is immersed for a long time is generally used.

  When sensitizing by combining a plurality of the dyes of the present invention or using other dyes in combination, a mixed solution of each dye may be prepared and used. It is also possible to prepare a solution and immerse it in each solution in order.

  In the case of a semiconductor with a high porosity, it is preferable to complete the adsorption treatment of the dye or the like before water is adsorbed on the semiconductor thin film and in the voids inside the semiconductor thin film due to moisture, water vapor or the like.

  Next, the photoelectric conversion element of the present invention will be described.

[Photoelectric conversion element]
The photoelectric conversion element of the present invention has, on a conductive support, at least a semiconductor layer in which the dye of the present invention is supported on a semiconductor, a charge transport layer, and a counter electrode. Hereinafter, the semiconductor, the electrolyte, and the counter electrode will be sequentially described.

"semiconductor"
Semiconductors used for the photoelectrode include simple substances such as silicon and germanium, compounds having elements of Group 3 to Group 5 and Group 13 to Group 15 of the periodic table (also referred to as element periodic table), metals Chalcogenides (for example, oxides, sulfides, selenides, etc.), metal nitrides, and the like can be used.

  Preferred metal chalcogenides include oxides of titanium, tin, zinc, iron, tungsten, zirconium, strontium, indium, cerium, vanadium, niobium, or tantalum. Examples of other compound semiconductors include phosphides such as zinc, gallium, and indium, sulfides of copper-indium, nitrides of titanium, and the like.

  Specific examples include TiO2, SnO2, Fe2O3, WO3, ZnO, Nb2O5, CdS, ZnS, Bi2S3, CdSe, GaP, InP, CuInS2, Ti3N4, and the like. TiO2, ZnO, SnO2, Fe2O3, WO3, and Nb2O5 are preferably used, and TiO2 or Nb2O5 is preferably used, and TiO2 (titanium oxide) is particularly preferably used.

  As the semiconductor used for the semiconductor layer, a plurality of the above-described semiconductors may be used in combination.

  Further, the semiconductor according to the present invention may be surface-treated using an organic base. Examples of the organic base include diarylamine, triarylamine, pyridine, 4-t-butylpyridine, quinoline, piperidine, amidine, and the like, among which pyridine and 4-t-butylpyridine are preferable.

  When the organic base is a liquid, the surface treatment can be carried out by preparing a solution dissolved in an organic solvent and immersing the semiconductor according to the present invention in a liquid amine or an amine solution.

(Conductive support)
The conductive support used in the photoelectric conversion element of the present invention and the solar battery of the present invention is provided with a conductive material such as a conductive material such as a metal plate or a non-conductive material such as a glass plate or a plastic film. A structure having a different structure can be used. Examples of materials used for the conductive support include metals (for example, platinum, gold, silver, aluminum), conductive metal oxides (for example, indium-tin composite oxide, tin oxide doped with fluorine), carbon, etc. It is.

  Further, the conductive support is preferably substantially transparent, and substantially transparent means that the light transmittance is 10% or more, more preferably 50% or more, Most preferably, it is 80% or more. In order to obtain a transparent conductive support, it is preferable to provide a conductive layer made of a conductive metal oxide on the surface of a glass plate or a plastic film.

<< Fabrication of semiconductor layer >>
A method for manufacturing a semiconductor layer according to the present invention will be described.

  When the semiconductor of the semiconductor layer according to the present invention is in the form of particles, the semiconductor layer is preferably manufactured by coating or spraying the semiconductor on a conductive support. In the case where the semiconductor according to the present invention is in a film form and is not held on the conductive support, it is preferable to produce a semiconductor layer by bonding the semiconductor onto the conductive support.

  A preferred embodiment of the semiconductor layer according to the present invention includes a method of forming the semiconductor layer on the conductive support by firing using fine particles of semiconductor.

  When the semiconductor according to the present invention is produced by firing, the semiconductor sensitization (adsorption, filling in a porous layer, etc.) treatment with a dye is preferably performed after firing. It is particularly preferable to perform the compound adsorption treatment quickly after the firing and before the water is adsorbed to the semiconductor.

  Hereinafter, a method for forming a photoelectrode preferably used in the present invention by baking using semiconductor fine powder will be described in detail.

(Preparation of coating liquid containing semiconductor fine powder)
First, a coating liquid containing fine semiconductor powder can be prepared by dispersing fine semiconductor powder in a solvent. The solvent is not particularly limited as long as it can disperse the semiconductor fine powder.

  Examples of the solvent include water, an organic solvent, and a mixed solution of water and an organic solvent. As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone and acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. A surfactant and a viscosity modifier (polyhydric alcohol such as polyethylene glycol) can be added to the coating solution as necessary.

(Application of coating solution containing fine semiconductor powder and baking treatment of the formed semiconductor layer)
The semiconductor fine powder-containing coating solution obtained as described above is applied or sprayed onto a conductive support, dried, etc., and then baked in air or in an inert gas, on the conductive support. A semiconductor layer (also referred to as a semiconductor film) is formed.

  A film obtained by applying and drying a coating solution containing semiconductor fine powder on a conductive support is composed of an aggregate of semiconductor fine particles, and the particle size of the fine particles is equal to the primary particle size of the semiconductor fine powder used. Corresponding.

  Thus, the semiconductor fine particle layer formed on the conductive layer such as the conductive support may be subjected to a baking treatment.

  In the present invention, the semiconductor layer may have any structure, but is preferably a porous structure film (also referred to as a porous layer having voids).

  From the viewpoint of appropriately preparing the actual surface area of the fired film during the firing treatment and obtaining a fired film having the above porosity, the firing temperature is preferably in the range of 200 to 800 ° C., more preferably It is the range of 300-800 degreeC.

  Moreover, when using a plastic substrate, the range of 50 to 500 degreeC is preferable, More preferably, it is the range of 80 to 300 degreeC.

(Semiconductor sensitization treatment)
As described above, the semiconductor sensitization treatment is performed by dissolving the dye of the present invention in an appropriate solvent and immersing the substrate on which the semiconductor is baked in the solution.

  The solvent used for dissolving the dye of the present invention is not particularly limited as long as it can dissolve the compound and does not dissolve the semiconductor or react with the semiconductor. These solvents are preferably dehydrated by post-distillation purification using a preliminarily dried solvent, and degassed or bubbled with an inert gas when used.

  Solvents preferably used in dissolving the compound include nitrile solvents such as acetonitrile, alcohol solvents such as ethanol and t-butanol, ketone solvents such as acetone and methyl ethyl ketone, diisopropyl ether, tetrahydrofuran, 1,4-dioxane and the like. Ether solvents, halogenated hydrocarbon solvents such as methylene chloride, 1,1,2-trichloroethane, and a plurality of solvents may be mixed. Particularly preferred are acetonitrile, ethanol, acetone, methyl ethyl ketone, and tetrahydrofuran alone and mixed solvents.

(Sensitivity processing time)
The time for immersing the semiconductor-baked substrate in the solution containing the dye of the present invention is preferably 3 to 48 hours, and more preferably 4 to 24 hours. Moreover, after immersing once, after washing | cleaning a board | substrate, you may repeat immersion again.

<Charge transport layer>
The charge transport layer used in the present invention will be described.

  The charge transport layer is a layer having a function of rapidly reducing the oxidized oxidant and transporting holes injected at the interface with the dye to the counter electrode.

  The charge transport layer according to the present invention is mainly composed of a redox electrolyte dispersion or a p-type compound semiconductor (charge transport agent) as a hole transport material.

Redox electrolytes include I- / I3- and Br- / Br3.
-System, quinone / hydroquinone system and the like. Such a redox electrolyte can be obtained by a conventionally known method. For example, an I- / I3- type electrolyte can be obtained by mixing an ammonium salt of iodine and iodine. These dispersions are called liquid electrolytes when they are in solution, solid polymer electrolytes when dispersed in a polymer that is solid at room temperature, and gel electrolytes when dispersed in a gel-like substance. When a liquid electrolyte is used as the charge transport layer, an electrochemically inert solvent is used as the solvent, for example, acetonitrile, propylene carbonate, ethylene carbonate, or the like is used.

  The charge transfer agent preferably has a large band gap so as not to prevent dye absorption. In order to reduce the dye hole, the ionization potential of the charge transfer agent needs to be smaller than the dye adsorption electrode ionization potential.

  As the charge transport agent, an aromatic amine derivative having an excellent hole transport capability is preferable. For this reason, photoelectric conversion efficiency can be improved more by comprising a charge transport layer mainly with an aromatic amine derivative. As the aromatic amine derivative, it is particularly preferable to use a triphenyldiamine derivative. Moreover, such an aromatic amine derivative may use any of a monomer, an oligomer, a prepolymer, and a polymer, and may mix and use these.

《Counter electrode》
The counter electrode used in the present invention will be described.

  The counter electrode may be any material as long as it has conductivity, and any conductive material can be used. However, it has a catalytic ability to perform oxidation of I3- ions and other redox ions at a sufficiently high rate. Is preferred. Examples of such a material include a platinum electrode, a surface of a conductive material subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, ruthenium oxide, and carbon.

[Solar cell]
The solar cell of the present invention will be described.

  The solar cell of the present invention has a structure in which the optimum design and circuit design for sunlight are performed as one aspect of the photoelectric conversion element of the present invention, and the optimum photoelectric conversion is performed when sunlight is used as a light source. Have That is, the semiconductor is dye-sensitized and can be irradiated with sunlight. When configuring the solar cell of the present invention, it is preferable that the photoelectrode, the charge transport layer and the counter electrode are housed in a case and sealed, or the whole is sealed with a resin.

  When the solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, the dye according to the present invention supported on the semiconductor absorbs the irradiated light or electromagnetic wave and excites it. Electrons generated by excitation move to the semiconductor, and then move to the counter electrode via the conductive support to reduce the redox electrolyte in the charge transfer layer. On the other hand, the dye according to the present invention in which electrons are transferred to a semiconductor is an oxidant, but is reduced by the supply of electrons from the counter electrode via the redox electrolyte of the charge transport layer, thereby returning to the original state. At the same time, the redox electrolyte of the charge transfer layer is oxidized and returned to a state where it can be reduced again by the electrons supplied from the counter electrode. In this way, electrons flow, and a solar cell using the photoelectric conversion element of the present invention can be configured.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

Synthesis Example 1 (Exemplary Compound: XA-1)

  4-[[4- (Diphenylamino) phenyl] azo] phenylboronic acid pinacol ester 153.0 mg (0.322 mmol), 4-bromosalicylaldehyde 66.1 mg (0.329 mmol), tetrakistriphenylphosphine palladium 5.2 mg (0.00450 mmol), ethanol 10.0 mL, toluene 10.0 mL, 2M aqueous sodium carbonate solution 2.1 mL were placed in an eggplant flask and purged with nitrogen. It was immersed in an oil bath heated to 85 ° C. and heated to reflux. The reaction solution was extracted with dichloromethane and saturated brine, and the organic layer was dried over magnesium sulfate. Then, the desiccant was removed and the solvent was distilled off under reduced pressure. The residue was purified by chromatography to obtain 51.1 mg (0.103 mmol) of a red solid (XA-1) in a yield of 73.5%.

Synthesis Example 2 (Exemplary Compound: XE-1)

  4-[[4- (Diphenylamino) phenyl] azo] phenylboronic acid pinacol ester 105.6 mg (0.222 mmol), 5-bromosalicylaldehyde 41.0 mg (0.204 mmol), tetrakistriphenylphosphine palladium 5.2 mg (0.00450 mmol), ethanol 6.50 mL, toluene 6.50 mL, 2M-sodium carbonate aqueous solution 2.0 mL were placed in an eggplant flask, purged with nitrogen, and heated to reflux for 3 hours. The reaction solution was extracted with dichloromethane, the organic layer was dried over magnesium sulfate, the desiccant was removed, and the solvent was distilled off under reduced pressure. The residue was purified by chromatography to obtain 29.7 mg (0.0633 mmol) of red solid (XE-1) in a yield of 31.0%.

Synthesis Example 3 (Comparative Compound RR-1)

  4-[(4-Bromophenyl) azo] triphenylamine 400.7 mg (0.9339 mmol), 4-carboxyphenylboronic acid 187.6 mg (1.144 mmol), tetrakis (triphenylphosphine) palladium 19.4 mg (0 .00168 mmol) 2M-aqueous sodium carbonate solution (5.9 mL), ethanol (29 mL), and toluene (29 mL) were placed in an eggplant flask and heated and stirred at 85 ° C. in a nitrogen atmosphere. 2N-HCl was added to the reaction solution, and the mixture was extracted with dichloromethane. The organic layer was dehydrated with magnesium sulfate, filtered, and the solvent was removed under reduced pressure. The residue was purified by silica gel chromatography (chloroform: methanol = 8: 1) and recrystallized from toluene to obtain 214.6 mg (48.9%) of red crystals RR-1.

Example 1
[Production of Photoelectric Conversion Element 1]
A titanium oxide paste (anatase type, primary average particle size 15 to 20 nm, alcohol-water dispersion) was applied to a fluorine-doped tin oxide (FTO) conductive glass substrate by a doctor blade method (application area 5 × 5 mm ² ). Baking was performed at 200 ° C. for 10 minutes and at 450 ° C. for 15 minutes to obtain a titanium oxide thin film.

  XA-1 of the present invention was dissolved in tetrahydrofuran to prepare a 5 × 10 −4 mol / l solution. An FTO glass substrate coated and sintered with titanium oxide was immersed in this solution at room temperature for 12 hours to perform dye adsorption treatment to obtain an oxide semiconductor electrode.

  For the charge transfer layer (electrolytic solution), an acetonitrile solution containing 1,2-dimethyl-3-propylimidazolium iodide, lithium iodide, iodine, and 4- (t-butyl) pyridine was used. The photoelectric conversion element 1 was produced using the produced semiconductor electrode and the glass plate which vapor-deposited platinum to the counter electrode.

Example 2
[Preparation of Photoelectric Conversion Element 2]
In Example 1, a device was produced in the same manner as in Example 1 except that the dye XA-1 of the present invention was replaced by the exemplified compound XE-1.

Comparative Example 1
[Preparation of Photoelectric Conversion Element 2]
In Example 1, a device was produced in the same manner as in Example 1 except that the dye XA-1 of the present invention was replaced with the comparative compound RR-1.

[Evaluation of photoelectric conversion element]
The produced photoelectric conversion element was irradiated with 100 mW / cm ² of pseudo-sunlight from a xenon lamp that passed through an AM filter (AM-1.5) using a solar simulator (manufactured by Pexel Technologies). About a photoelectric conversion element, current-voltage characteristics are measured at room temperature using a source meter (manufactured by Keithley Instruments), and a short circuit current density (Jsc), an open circuit voltage (Voc), and a form factor (FF) are obtained. From these, the photoelectric conversion efficiency (η (%)) was determined.

The obtained evaluation results are summarized in Table 1.

From Table 1, the photoelectric conversion element of the present invention, when exposed with AM-1.5, 100 mW / cm @ 2, than the carboxylic acid derivatives of the conformational isomers, showed about 2 times the _{J SC.} From this result, the photoelectric conversion element using the sensitizing dyes XA-1 and XE-1 having the salicylaldehyde skeleton of the present invention uses the dye RR-1 having a benzoic acid skeleton which is a structural isomer of the salicylaldehyde skeleton. It can be said that the electron injecting property from the dye molecule to the semiconductor electrode is greatly improved as compared with the photoelectric conversion element. This result is derived from the fact that the salicylaldehyde skeleton is improved in electron injection from the salicylaldehyde skeleton to the semiconductor because free rotation of the dye π-electron system and the coordination bond portion does not occur due to bidentate arrangement. Conceivable.

  In addition, the reason why the short-circuit current density of XE-1 is improved more than that of XA-1 is excluded because the molecular structure of XE-1 is superior to the linearity of the dye molecules arranged in the semiconductor. This is considered to be because the possibility of reverse electron donation is reduced because the deposition is small and the electron donor site is further away from the semiconductor surface.

Claims (9)

In a dye-sensitized photoelectric conversion element in which a semiconductor layer in which at least a sensitizing dye is supported on a semiconductor and a charge transport layer are provided between a pair of opposing electrodes, the sensitizing dye is represented by the following general formula [1]. The photoelectric conversion element characterized by containing the compound represented by these.

[In General Formula [1], O is an oxygen atom, and H is a hydrogen atom.
R _{1 to} R ₄ are selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group. ] 2. The photoelectric conversion element according to claim 1, wherein the sensitizing dye represented by the general formula [1] is represented by the following general formula [2].

[In General Formula [2], O is an oxygen atom, and H is a hydrogen atom.
R _{1 to} R ₄ are selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group. R _{5 to} R ₆ are selected from a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, and a heteroaryl group. X1 is a divalent linking group and includes at least one of a substituted or unsubstituted arylene group, heteroarylene group, azo group, amide group, ester group, alkenylene group, alkynylene group, and is the same or different. A plurality of combined divalent linking groups may be used. ] 2. The photoelectric conversion element according to claim 1, wherein the sensitizing dye represented by the general formula [1] is represented by the following general formula [3].

[In General Formula [3], O is an oxygen atom, and H is a hydrogen atom.
R _{1 to} R ₄ are selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, an amino group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group. R _{5 to} R ₆ are selected from a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, and a heteroaryl group. X1 is a divalent linking group and includes at least one of a substituted or unsubstituted arylene group, heteroarylene group, azo group, amide group, ester group, alkenylene group, alkynylene group, and is the same or different. A plurality of combined divalent linking groups may be used. ]     4. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion element is supported on a semiconductor by a carbonyl group and a hydroxyl group of the general formulas [1] to [3].     5. The photoelectric conversion element according to claim 1, wherein the longest absorption wavelength of the general formulas [1] to [3] is longer than 550 nm. 6. The photoelectric conversion device according to claim ₁ , wherein R ₁ and R _{4 in the} general formulas [1] to [3] are hydrogen atoms.     The photoelectric conversion element according to claim 1, wherein the semiconductor forming the semiconductor layer is titanium oxide.   A solar cell comprising the photoelectric conversion element according to claim 1.   A power storage device having a power storage device connected to the photoelectric conversion element according to claim 1.

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