JP7003387B2 - Photoelectric conversion element, solar cell and synthesis method - Google Patents

Description

The present invention relates to a hole transport material, a photoelectric conversion element, and a solar cell provided with the photoelectric conversion element.

In recent years, the driving power in electronic circuits has become extremely small, and it has become possible to drive various electronic components such as sensors even with a weak power. Furthermore, when using sensors, it is expected to be applied to self-sustaining power sources (environmental power generation elements) that can generate and consume electricity on the spot. Among them, solar cells are attracting attention as elements that can generate electricity anywhere if there is light.

Among the solar cells, the dye-sensitized solar cell announced by Gratezel et al. Of Swiss Federal Institute of Technology has been reported to have higher photoelectric conversion characteristics than the amorphous silicon solar cell in a weak indoor light environment (non-amorphous silicon solar cell). See Patent Document 1).
Dye-sensitized solar cells that use conventional electrolytes with high power generation performance have concerns about volatilization and leakage of the electrolytes. Therefore, when it is assumed that the electrolytic solution will be put into practical use, it is desired that the electrolytic solution be solidified. Many have been reported, such as those using a small molecule organic hole transport material (see, for example, Patent Document 1, Non-Patent Documents 2 and 3). It has been reported that when weak light such as room light is converted into electricity, the loss current due to the internal resistance of the photoelectric conversion element is remarkable (see Non-Patent Document 4).

As described above, all of the solid-state photoelectric conversion elements that have been studied so far have reported only the power generation performance in pseudo-sunlight, and not the power generation performance in indoor light. Further, the hole transport material called spiro-OMeTAD described in Non-Patent Document 2 has a high material cost, and it is desired to reduce the cost. Further, a 60 ° C. heat resistance test on a solar cell using spiro-OMeTAD has been reported (Non-Patent Document 5). The results of the above test show a decrease in output over time.

Therefore, in view of the above problems, it is an object of the present invention to provide a hole transport material capable of obtaining a photoelectric conversion element having excellent photoelectric conversion property even under weak irradiation light such as indoor light even under high temperature storage. And.

（式中、Ｒ₁、及びＲ₂は、それぞれ独立に、水素原子、メチル基、及びメトキシ基のいずれかを表す。） In order to solve the above problems, the hole transport material of the present invention is as follows.
A hole transport material represented by the following general formula (1).

(In the formula, R ₁ and R ₂ each independently represent one of a hydrogen atom, a methyl group, and a methoxy group.)

According to the present invention, it is possible to provide a hole transport material capable of obtaining a photoelectric conversion element having excellent photoelectric conversion property even in a weak irradiation light such as indoor light even under high temperature storage.

It is a schematic diagram of an example showing the structure of the photoelectric conversion element which concerns on this invention. 6 is an IR spectrum of the hole transport material (Compound No. 1-2) obtained in Example I-1.

（式中、Ｒ₁、及びＲ₂は、それぞれ独立に、水素原子、メチル基、及びメトキシ基のいずれかを表す。）
なお、Ｒ₁とＲ₂とは同一であってもよい。 The hole transport material of the present invention is represented by the following general formula (1).

(In the formula, R ₁ and R ₂ each independently represent one of a hydrogen atom, a methyl group, and a methoxy group.)
It should be noted that R ₁ and R ₂ may be the same.

The spiro-OMeTAD described in Non-Patent Document 2 is represented by the following structural formula, and one of the factors in which a decrease in output is observed under high temperature storage is crystallization of spiro-OMeTAD. One method of suppressing this crystallization is to asymbolize the hole transport material, and as a result of diligent studies by the present inventors, eight methoxy groups are asymmetricalized with four ethoxy groups and four methoxy groups. As a result, it became clear that the crystallization of the hole transport material can be suppressed. In addition, the raw material cost using the ethoxy group can be obtained at a lower cost, which can contribute to the cost reduction.

When the conventional hole transport material is used, it is considered that the morphology of the hole transport material in the hole transport layer and the constituent materials such as basic compounds and lithium salts, which are additives, changes during the high temperature process, resulting in a decrease in output. ing.
In order to suppress the change in morphology, it is considered that one solution is to use a highly crystalline material for the hole transport material, but the hole transport material in the solid dye-sensitized solar cell has a high output unless it is in an amorphous state. Cannot be obtained. Therefore, as a result of diligent studies, the asymmetry of the eight methoxy groups with the four ethoxy groups and the four methoxy groups resulted in higher amorphousness and suppression of crystallization. As a result, it was possible to obtain a photoelectric conversion element having excellent photoelectric conversion property even in a weak irradiation light such as indoor light even under high temperature storage at 100 ° C.

Specific exemplary compounds in the hole transport material represented by the general formula (1) are described below, but are not limited thereto.

Hereinafter, the photoelectric conversion element and the solar cell according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments shown below, and can be modified within the range conceivable by those skilled in the art, such as other embodiments, additions, modifications, and deletions. However, as long as the action and effect of the present invention are exhibited, it is included in the scope of the present invention.

The photoelectric conversion element of the present invention has a first electrode, a hole blocking layer, an electron transport layer, a hole transport layer, and a second electrode, and the hole transport layer is the hole transport material of the present invention. including.
The configuration of the photoelectric conversion element and the solar cell will be described with reference to FIG. Note that FIG. 1 is an example of a cross-sectional view of a photoelectric conversion element and a solar cell.
In the embodiment shown in FIG. 1, the first electrode 2 is formed on the substrate 1, the hole blocking layer 3 is formed on the first electrode 2, and the electron transport layer 4 is formed on the hole blocking layer 3. An example of a configuration in which the photosensitizer 5 is adsorbed on the electron transporting material in the electron transport layer 4 and the hole transport layer 6 is sandwiched between the first electrode 2 and the second electrode 7 facing the first electrode 2 is shown. ing. Further, FIG. 1 shows an example of a configuration in which lead lines 8 and 9 are provided so that the first electrode 2 and the second electrode 7 conduct with each other. The details will be described below.

<Board>
The substrate 1 used in the present invention is not particularly limited, and known ones can be used. The substrate 1 is preferably made of a transparent material, and examples thereof include glass, a transparent plastic plate, a transparent plastic film, and an inorganic transparent crystal.

<First electrode>
The first electrode 2 used in the present invention is not particularly limited as long as it is a conductive substance transparent to visible light, and is a known electrode used for a normal photoelectric conversion element, a liquid crystal panel, or the like. Can be used.
Examples of the material of the first electrode include indium tin oxide (hereinafter referred to as ITO), fluorine-doped tin oxide (hereinafter referred to as FTO), antimonated tin oxide (hereinafter referred to as ATO), and indium tin oxide. Examples thereof include zinc oxide, niobium-titanium oxide, graphene and the like, and these may be used alone or in combination of two or more.
The thickness of the first electrode is preferably 5 nm to 10 μm, more preferably 50 nm to 1 μm.

Further, in order to maintain a certain degree of hardness, the first electrode is preferably provided on a substrate 1 made of a material transparent to visible light, and the substrate may be, for example, glass, a transparent plastic plate, a transparent plastic film, or an inorganic substance transparent. Crystals and the like are used.
A known one in which the first electrode and the substrate are integrated can also be used, for example, FTO-coated glass, ITO-coated glass, zinc oxide: aluminum-coated glass, FTO-coated transparent plastic film, ITO-coated transparent plastic film. And so on.
In addition, a transparent electrode in which tin oxide or indium oxide is doped with cations or anions having different valences, or a metal electrode having a structure capable of transmitting light such as a mesh or a stripe is provided on a substrate such as a glass substrate. But it may be.

These may be alone, mixed with two or more kinds, or laminated. Further, for the purpose of lowering the resistance, a metal lead wire or the like may be used together.
Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. The metal lead wire can be formed by installing it on a substrate by thin film deposition, sputtering, crimping or the like, and then providing ITO or FTO on the metal lead wire.

<Hole blocking layer>
The material constituting the hole blocking layer 3 used in the present invention is not particularly limited as long as it is transparent to visible light and is an electron transporting material, but titanium oxide is particularly preferable. The hole blocking layer is provided in order to suppress a decrease in power due to the electrolyte coming into contact with the electrode and recombination (so-called reverse electron transfer) between the holes in the electrolyte and the electrons on the surface of the electrode. The effect of the hole blocking layer 3 is particularly remarkable in the solid-state dye-sensitized solar cell. This is compared with the wet dye-sensitized solar cell using an electrolytic solution, and the solid-type dye-sensitized solar cell using an organic hole transport material or the like recombines electrons in the hole in the hole transport material and the electrode surface. (Reverse electron transfer) This is due to the high speed.

The film forming method of the hole blocking layer is not limited, but a high internal resistance is required in order to suppress the loss current in the room light, and the film forming method is also important. Generally, a sol-gel method in which a wet film is formed can be mentioned, but the film density is low and the loss current cannot be sufficiently suppressed. Therefore, more preferably, it is a dry film forming method such as a sputtering method, and the film density is sufficiently high and the loss current can be suppressed.

This hole blocking layer is also formed for the purpose of preventing electronic contact between the first electrode 2 and the hole transport layer 6. The film thickness of this hole blocking layer is not particularly limited, but is preferably 5 nm to 1 μm, more preferably 500 to 700 nm for wet film formation, and more preferably 10 nm to 30 nm for dry film formation.

<Electron transport layer>
The photoelectric conversion element and the solar cell of the present invention form a porous electron transport layer 4 on the hole blocking layer 3, and the electron transport layer may be a single layer or a multilayer. May be good.
The electron transport layer is composed of an electron transport material. Semiconductor particles are preferably used as the electron transporting material.
In the case of multiple layers, dispersions of semiconductor particles having different particle sizes can be applied in multiple layers, or different types of semiconductors, resins, and coating layers having different composition of additives can be applied in multiple layers.
Multilayer coating is an effective means when the film thickness is insufficient with one coating.
In general, as the film thickness of the electron transport layer increases, the amount of carried light sensitizing material per unit projected area also increases, so the light capture rate increases, but the diffusion distance of the injected electrons also increases, so the charge recombination The loss due to bonding also increases.
Therefore, the film thickness of the electron transport layer is preferably 100 nm to 100 μm.

The semiconductor is not particularly limited, and known semiconductors can be used.
Specific examples thereof include elemental semiconductors such as silicon and germanium, compound semiconductors typified by metallic chalcogenides, and compounds having a perovskite structure.
Metallic chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lantern, vanadium, niobium, or tantalum oxide, cadmium, zinc, lead, silver, antimony, bismuth. Examples include sulfide, cadmium, lead selenium, and cadmium telluride.
As other compound semiconductors, phosphides such as zinc, gallium, indium and cadmium, gallium arsenic, copper-indium-selenium, copper-indium-sulfide and the like are preferable.
Further, as the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.
Of these, oxide semiconductors are preferable, and titanium oxide, zinc oxide, tin oxide, and niobium oxide are particularly preferable, and they may be used alone or in admixture of two or more. The crystal type of these semiconductors is not particularly limited, and may be single crystal, polycrystal, or amorphous.

The size of the semiconductor particles is not particularly limited, but the average particle size of the primary particles is preferably 1 to 100 nm, more preferably 5 to 50 nm.
It is also possible to improve efficiency by the effect of mixing or laminating semiconductor particles having a larger average particle size to scatter incident light. In this case, the average particle size of the semiconductor is preferably 50 to 500 nm.

The method for producing the electron transport layer is not particularly limited, and examples thereof include a method of forming a thin film in a vacuum such as sputtering and a wet film forming method.
In consideration of manufacturing cost and the like, a wet film forming method is particularly preferable, and a method of preparing a paste in which a powder of semiconductor particles or a sol is dispersed and applying it on an electron collecting electrode substrate is preferable.
When this wet film forming method is used, the coating method is not particularly limited and can be carried out according to a known method.
For example, dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, and various wet printing methods such as letterpress, offset, gravure, intaglio, rubber plate, screen printing, etc. Method can be used.

When the dispersion liquid of the semiconductor particles is mechanically pulverized or produced by using a mill, it is formed by at least the semiconductor particles alone or a mixture of the semiconductor particles and the resin dispersed in water or an organic solvent.
Examples of the resin used at this time include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid ester, and methacrylate ester, silicon resin, phenoxy resin, polysulfone resin, polyvinyl butyral resin, and polyvinyl. Examples thereof include formal resin, polyester resin, cellulose ester resin, cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin, and polyimide resin.
Examples of the solvent for dispersing the semiconductor particles include an alcohol solvent such as water, methanol, ethanol, isopropyl alcohol, α-terpineol, a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or the like. Ester solvent such as n-butyl acetate, ether solvent such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone. Amido-based solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or halogenated hydrocarbons such as 1-chloronaphthalene. Solvents, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, cumene, etc. A hydrocarbon solvent can be mentioned. These can be used alone or as a mixed solvent of two or more kinds.

The dispersion liquid of the semiconductor particles or the paste of the semiconductor particles obtained by the sol-gel method or the like is prepared by using an acid such as hydrochloric acid, nitric acid or acetic acid, polyoxyethylene (10) octylphenyl ether or the like in order to prevent the particles from reaggregating. A surfactant, a chelating agent such as acetylacetone, 2-aminoethanol, ethylenediamine and the like can be added.
It is also an effective means to add a thickener for the purpose of improving the film-forming property.
Examples of the thickener to be added at this time include polymers such as polyethylene glycol and polyvinyl alcohol, and thickeners such as ethyl cellulose.

After coating the semiconductor particles, the particles are preferably electronically contacted with each other, and firing, microwave irradiation, electron beam irradiation, or laser light irradiation is preferably performed in order to improve the film strength and the adhesion to the substrate. .. These processes may be performed individually or in combination of two or more types.

In the case of firing, the range of the firing temperature is not particularly limited, but if the temperature is raised too much, the resistance of the substrate may increase or the substrate may melt, so 30 to 700 ° C is preferable, and 100 to 600 ° C is more preferable. preferable. Further, the firing time is not particularly limited, but 10 minutes to 10 hours is preferable.

The microwave irradiation may be performed from the electron transport layer forming side or from the back side.
The irradiation time is not particularly limited, but it is preferably performed within 1 hour.

After firing, for the purpose of increasing the surface area of the semiconductor particles and increasing the efficiency of electron injection from the photosensitizing material into the semiconductor particles, for example, chemical plating using an aqueous solution of titanium tetrachloride or a mixed solution with an organic solvent or titanium trichloride Electrochemical plating treatment using an aqueous solution may be performed.

A film obtained by laminating semiconductor particles having a diameter of several tens of nm by sintering or the like forms a porous state. This nanoporous structure has a very high surface area, which can be expressed using the roughness factor.
This roughness factor is a numerical value representing the actual area inside the porous medium with respect to the area of the semiconductor particles coated on the substrate. Therefore, the larger the roughness factor is, the more preferable it is, but in the present invention, it is preferably 20 or more because of the relationship with the film thickness of the electron transport layer.

<Light sensitizer material>
In the present invention, in order to further improve the conversion efficiency, it is preferable to adsorb the photosensitizer on the surface of the electron transporting material which is the electron transporting layer 4.

The photosensitizing material 5 is not limited to the above as long as it is a compound that is photoexcited by the excitation light used, and specific examples thereof include the following compounds.
Metal complex compounds described in JP-A-7-500630, JP-A-10-233238, JP-A-2000-26487, JP-A-2000-323191, JP-A-2001-59062, etc. 10-93118, JP-A-2002-164809, JP-A-2004-95450, J. Mol. Phys. Chem. C, 7224, Vol. 111 (2007) and the like, coumarin compound, JP-A-2004-95450, Chem. Commun. , 4887 (2007) and the like, JP-A-2003-264010, JP-A-2004-63274, JP-A-2004-115636, JP-A-2004-200068, JP-A-2004-235052. Gazette, J. Mol. Am. Chem. Soc. , 12218, Vol. 126 (2004), Chem. Commun. , 3036 (2003), Angew. Chem. Int. Ed. , 1923, Vol. 47 (2008) and the like. Am. Chem. Soc. , 16701, Vol. 128 (2006), J. Mol. Am. Chem. Soc. , 14256, Vol. The thiophene compound described in 128 (2006) and the like, JP-A-11-86916, JP-A-11-214730, JP-A-2000-106224, JP-A-2001-76773, JP-A-2003-7359. Cyanine dyes described in JP-A-11-214731, JP-A-11-238905, JP-A-2001-52766, JP-A-2001-7675, JP-A-2003-7360, etc. Dyes, 9-arylxanthene compounds described in JP-A-10-92477, JP-A-11-273754, JP-A-11-273755, JP-A-2003-31273, etc., JP-A-10-93118. , JP-A-2003-31273, Triarylmethane Compounds, JP-A-9-199744, JP-A-10-233238, JP-A-11-204821, JP-A-11-265738, J. .. Phys. Chem. , 2342, Vol. 91 (1987), J. Mol. Phys. Chem. B, 6272, Vol. 97 (1993), Electrical. Chem. , 31, Vol. 537 (2002), JP-A-2006-032260, J. Mol. Porphyrins Phthalocyanines, 230, Vol. 3 (1999), Angew. Chem. Int. Ed. , 373, Vol. 46 (2007), Langmuir, 5436, Vol. 24 (2008) and the like, the phthalocyanine compound, the porphyrin compound and the like can be mentioned. In particular, among these, it is preferable to use a metal complex compound, a coumarin compound, a polyene compound, an indoline compound, and a thiophene compound.

More preferably, D131 represented by the following structural formula (3), D102 represented by the following structural formula (4), and D358 represented by the following structural formula (5) manufactured by Mitsubishi Paper Mills Limited can be mentioned.

As a method of adsorbing the photosensitizing material 5 on the electron transport layer 4, a method of immersing an electron collecting electrode containing semiconductor particles in a photosensitizing material solution or a dispersion liquid, or a solution or a dispersion liquid in an electron transport layer. A method of applying to and adsorbing the particles can be used.
In the former case, a dipping method, a dip method, a roller method, an air knife method, or the like can be used.
In the latter case, a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, a spray method and the like can be used.
Further, it may be adsorbed in a supercritical fluid using carbon dioxide or the like.

When adsorbing the photosensitizer, a condensing agent may be used in combination.
The condensing agent has a catalytic action that seems to physically or chemically bind the photosensitizer and the electron transport compound to the surface of the inorganic substance, or acts stoichiometrically to advantageously move the chemical equilibrium. Any of them may be used.
Further, a thiol or a hydroxy compound may be added as a condensation aid.

Examples of the solvent for dissolving or dispersing the photosensitizing material include alcohol-based solvents such as water, methanol, ethanol, and isopropyl alcohol.
Ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone,
Ester solvents such as ethyl formate, ethyl acetate, or n-butyl acetate,
Ethereal solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane,
Amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone,
Halogenated hydrocarbon solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichlorethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or 1-chloronaphthalene,
Hydrocarbons such as n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, or cumene. Examples of the system solvent can be mentioned, and these can be used alone or as a mixture of two or more kinds.

Further, depending on the type of the photosensitizer, there is a material that works more effectively if the aggregation between the compounds is suppressed, so that an aggregation dissociating agent may be used in combination.
As the coagulation dissociator, a steroid compound such as cholic acid or chenodeoxycholic acid, a long-chain alkylcarboxylic acid or a long-chain alkylphosphonic acid is preferable, and a photosensitizing material to be used is appropriately selected.
The amount of these coagulation dissociators added is preferably 0.01 to 500 parts by mass, more preferably 0.1 to 100 parts by mass with respect to 1 part by mass of the photosensitizer.

Using these, the temperature at which the photosensitizer or the photosensitizer and the agglutination dissociator are adsorbed is preferably −50 ° C. or higher and 200 ° C. or lower.
Further, this adsorption may be carried out by allowing it to stand still or stirring it.

Examples of the method for stirring include, but are not limited to, a stirrer, a ball mill, a paint conditioner, a sand mill, an attritor, a disperser, and ultrasonic dispersion.
The time required for adsorption is preferably 5 seconds or more and 1000 hours or less, more preferably 10 seconds or more and 500 hours or less, and even more preferably 1 minute or more and 150 hours.
Further, it is preferable that the adsorption is performed in a dark place.

（式中、Ｒ₁、及びＲ₂は、それぞれ独立に、水素原子、メチル基、及びメトキシ基のいずれかを表す。） <Hall transport layer>
Generally, the hole transport layer includes an electrolytic solution in which an oxidation-reduction pair is dissolved in an organic solvent, a gel electrolyte in which a liquid in which an oxidation-reduction pair is dissolved in an organic solvent is impregnated in a polymer matrix, a molten salt containing an oxidation-reduction pair, and a solid. An electrolyte, an inorganic hole transport material, an organic hole transport material, and the like are used, and the hole transport layer 6 of the photoelectric conversion element of the present invention contains an organic hole transport material represented by the following general formula (1).

(In the formula, R ₁ and R ₂ each independently represent one of a hydrogen atom, a methyl group, and a methoxy group.)

The hole transport layer preferably contains 50 to 95% by mass, more preferably 70 to 85% by mass, of the organic hole transport material represented by the general formula (1).
The hole transport material of the present invention can obtain photoelectric conversion characteristics excellent in storage in a high temperature environment. Furthermore, it was possible to verify that the superiority appears particularly remarkably in the case of photoelectric conversion in weak light such as indoor light, which is rarely reported.

（式中、Ｒ₃、及びＲ₄は、それぞれ独立に、アルキル基または芳香族炭化水素基を表す。ただし、Ｒ₃とＲ₄は互いに結合し、窒素原子を含む、複素環基を形成する場合を含む。）
前記Ｒ₃、及びＲ₄は、同一であっても良い。
前記アルキル基としては、炭素数が１～１２のアルキル基が好ましく、分岐鎖を有しても良い。前記芳香族炭化水素基としては、フェニル基、ナフチル基が好ましい。前記アルキル基は、置換基を有するアルキル基及び置換基を有しないアルキル基を含み、前記芳香族炭素水基は、置換基を有する芳香族炭化水素基及び置換基を有しない芳香族炭化水素基を含む。前記置換基としては、フェニル基等が挙げられる。
また、Ｒ₃とＲ₄は互いに結合し、窒素原子を含む、複素環基を形成する場合、該複素環基中に酸素原子や窒素原子が含まれても良い。また、前記複素環基は、置換基を有する複素環基及び置換基を有しない複素環基を含み、該置換基としては、フェニル基等が挙げられる。 Further, in the present invention, it is preferable to add the basic compound represented by the following general formula (2) to the hole transport layer 6, and by adding the basic compound, a particularly high open circuit voltage can be obtained. can. In addition, the internal resistance of the photoelectric conversion element is increased, and the loss current in weak light such as indoor light can be reduced. Therefore, a higher open circuit voltage than the conventional basic compound can be obtained.

(In the formula, R ₃ and R ₄ each independently represent an alkyl group or an aromatic hydrocarbon group, where R ₃ and R ₄ bond with each other to form a heterocyclic group containing a nitrogen atom. Including cases.)
The R ₃ and R ₄ may be the same.
As the alkyl group, an alkyl group having 1 to 12 carbon atoms is preferable, and an alkyl group may have a branched chain. As the aromatic hydrocarbon group, a phenyl group and a naphthyl group are preferable. The alkyl group contains an alkyl group having a substituent and an alkyl group having no substituent, and the aromatic carbon aqueous group is an aromatic hydrocarbon group having a substituent and an aromatic hydrocarbon group having no substituent. including. Examples of the substituent include a phenyl group and the like.
Further, when R ₃ and R ₄ are bonded to each other to form a heterocyclic group containing a nitrogen atom, the heterocyclic group may contain an oxygen atom or a nitrogen atom. Further, the heterocyclic group includes a heterocyclic group having a substituent and a heterocyclic group having no substituent, and examples of the substituent include a phenyl group and the like.

Conventionally, some of the compounds classified into the basic compounds represented by the general formula (2) are known. Further, some of the compounds are known to be used as basic compounds in an iodine electrolyte type dye-sensitized solar cell. However, it has been reported that although the iodine electrolyte type dye-sensitized solar cell using the basic compound has a high open circuit voltage, the short-circuit current density is significantly reduced and the photoelectric conversion characteristics are significantly deteriorated.

The hole transport layer in the present invention uses an organic hole transport material and is different from the hole transport model using the iodine electrolytic solution or the like. Therefore, even if the basic compound represented by the general formula (2) is used, excellent photoelectric conversion characteristics can be obtained by obtaining a high open circuit voltage with a small decrease in short-circuit current density. Furthermore, it was possible to verify that the superiority appears particularly remarkably in the case of photoelectric conversion in weak light such as indoor light, which is rarely reported.

Specific exemplary compounds in the general formula (2) are described below, but the compound is not limited thereto. When a number is described next to the following structural formula, the number means the compound number in the chemical substance database "Japanese Chemical Substance Dictionary" published by the Japan Science and Technology Agency.

The amount of the basic compound represented by the general formula (2) added to the hole transport layer is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the organic hole transport material. More preferably, it is 20 parts by mass or less.

The organic hole transport layer in the present invention may have a single-layer structure or a laminated structure composed of different compounds. In the case of a laminated structure, it is preferable to use a polymer material for the organic hole transport material layer near the second electrode 7.
This is because the surface of the porous electron transport layer can be further smoothed and the photoelectric conversion characteristics can be improved by using a polymer material having excellent film forming properties.
In addition, since it is difficult for the polymer material to penetrate into the porous electron transport layer, it is also excellent in covering the surface of the porous electron transport layer, and is also effective in preventing short circuits when providing electrodes. Therefore, it is possible to obtain higher performance.

As the organic hole transporting material used in the single layer structure and the organic hole transporting material used in the organic hole transporting layer far from the second electrode in the laminated structure, the organic hole transporting compound represented by the general formula (1) is used. Used.

As the polymer material used for the organic hole transport layer close to the second electrode 7 used in the laminated structure, a known hole transport polymer material is used.
Specific examples thereof include poly (3-n-hexylthiophene), poly (3-n-octyloxythiophene), poly (9,9'-dioctyl-fluorene-co-bithiophene), and poly (3,3''. '-Gidodecyl-quarterthiophene), poly (3,6-dioctylthiophene [3,2-b] thiophene), poly (2,5-bis (3-decylthiophen-2-yl) thieno [3,2-b] ] Thiophene), Poly (3,4-didecylthiophene-thiophene [3,2-b] thiophene), Poly (3,6-dioctylthiophene [3,2-b] Thiophene-cothieno [3, 2-b] thiophene), poly (3,6-dioctylthiophene [3,2-b] thiophene-co-thiophene), poly (3.6-dioctylthiophene [3,2-b] thiophene-co-bithiophene) Polythiophene compounds, etc.
Poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene vinylene], poly [2-methoxy-5- (3,7-dimethyloctyloxy) -1,4-phenylene vinylene], poly Polyphenylene vinylene compounds such as [(2-methoxy-5- (2-ethylphenyloxy) -1,4-phenylene vinylene) -co- (4,4'-biphenylene-vinylene)],
Poly (9,9'-zidodecylfluorenyl-2,7-diyl), poly [(9,9-dioctyl-2,7-divinylenefluorene) -alt-co- (9,10-anthracene)] , Poly [(9,9-dioctyl-2,7-dibinylene fluorene) -alt-co- (4,4'-biphenylene)], poly [(9,9-dioctyl-2,7-dibinylene fluorene)) -Alt-co- (2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene)], poly [(9,9-dioctyl-2,7-diyl) -co- (1,4-diyl) (2,5-dihexyloxy) benzene)] and other polyfluorene compounds,
Polyphenylene compounds such as poly [2,5-dioctyloxy-1,4-phenylene] and poly [2,5-di (2-ethylhexyloxy-1,4-phenylene]],
Poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (N, N'-diphenyl) -N, N'-di (p-hexylphenyl) -1,4-diamino Benzene], poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (N, N'-bis (4-octyloxyphenyl) benzidine-N, N'-(1, 4-Diphenylene)], Poly [(N, N'-bis (4-octyloxyphenyl) benzidine-N, N'-(1,4-diphenylene)], Poly [(N, N'-bis (4-) (2-Ethylhexyloxy) phenyl) benzidine-N, N'-(1,4-diphenylene)], poly [Phenylimino-1,4-phenylenebinylene-2,5-dioctyloxy-1,4-phenylenebinylene- 1,4-Phenylene], Poly [p-triluimino-1,4-phenylenebinylene-2,5-di (2-ethylhexyloxy) -1,4-phenylenebinylene-1,4-phenylene], poly [4- (2-Ethylhexyloxy) Phenylimino-1,4-biphenylene] and other polyarylamine compounds,
Poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (1,4-benzo (2,1', 3) thiadiazole]], poly (3,4-didecylthiophene- Polythiadiazole compounds such as co- (1,4-benzo (2,1', 3) thiadiazole) can be mentioned.
Among these, polythiophene compounds and polyarylamine compounds are particularly preferable in consideration of carrier mobility and ionization potential.

Further, various additives may be added to the organic hole transport material shown above.
Examples of the additive include metal iodides such as iodine, lithium iodide, sodium iodide, potassium iodide, cesium iodide, calcium iodide, copper iodide, iron iodide, and silver iodide.
Quaternary ammonium salts such as tetraalkylammonium iodide and pyridinium iodide, metallic bromides such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, etc.
Bromates of quaternary ammonium compounds such as tetraalkylammonium bromide and pyridinium bromide,
Metal chlorides such as copper chloride and silver chloride, metal acetates such as copper acetate, silver acetate and palladium acetate,
Metal sulfates such as copper sulphate and zinc sulphate, metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ion,
Sulfur compounds such as polysodium sulfide, alkylthiols-alkyldisulfides,
Viologen dye, hydroquinone, etc., 1,2-dimethyl-3-n-propylimidazolinium iodide, 1-methyl-3-n-hexylmidazolinium iodide, 1,2-dimethyl-3-ethylimidazole Rium trifluoromethanesulfonate, 1-methyl-3-butylimidazolium nonafluorobutyl sulfonate, 1-n-hexyl-3-methylimidazolinium bis (trifluoromethylsulfonyl) imide, 1-methyl-3 -Inorg such as ethylimidazolium bis (trifluoromethyl) sulfonylimide. Chem. 35 (1996) 1168. Ionic liquid imidazolium compound, basic compound such as pyridine, 4-t-butylpyridine, benzimidazole, etc.
Examples thereof include lithium compounds such as lithium trifluoromethanesulfonylimide, lithium diisopropylimide, and lithium bis (trifluoromethanesulfonyl) imide.
An ionic liquid imidazolium compound may be used, and specifically, 1-n-hexyl-3-methylimidazolinium bis (trifluoromethylsulfonyl) imide is preferable.

Further, for the purpose of improving the conductivity, an oxidizing agent for converting a part of the organic hole transport material into a radical cation may be added.
Examples of the oxidizing agent include tris (4-bromophenyl) aminium hexachloroantimonate, silver hexafluoroantimonate, nitrosonium tetrafluoroborate, silver nitrate, and cobalt complex compounds.
It is not necessary that all the organic hole transport materials are oxidized by the addition of this oxidizing agent, and only a part thereof needs to be oxidized. Further, the added oxidizing agent may or may not be taken out of the system after being added.

The organic hole transport layer directly forms a hole transport layer on the electron transport layer 4 carrying the photosensitizer. The method for producing the organic hole transport layer is not particularly limited, and examples thereof include a method of forming a thin film in vacuum such as vacuum deposition and a wet film forming method. In consideration of manufacturing cost and the like, the wet film forming method is particularly preferable, and the method of coating on the electron transport layer is preferable.
When this wet film forming method is used, the coating method is not particularly limited and can be carried out according to a known method. For example, dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, and various wet printing methods such as letterpress, offset, gravure, intaglio, rubber plate, screen printing, etc. Method can be used. Further, the film may be formed in a supercritical fluid or a subcritical fluid having a temperature and pressure lower than the critical point.

The supercritical fluid exists as a non-aggregating high-density fluid in a temperature / pressure region exceeding the limit (critical point) at which a gas and a liquid can coexist, does not aggregate even when compressed, and has a critical temperature or higher and a critical pressure. The fluid is not particularly limited as long as it is in the above state, and can be appropriately selected depending on the intended purpose, but a fluid having a low critical temperature is preferable.
Examples of the supercritical fluid include carbon monoxide, carbon dioxide, ammonia, nitrogen, water, methanol, ethanol, ercoal solvents such as n-butanol, ethane, propane, 2,3-dimethylbutane, benzene, toluene and the like. Hydrocarbon-based solvents, halogen-based solvents such as methylene chloride and chlorotrifluoromethane, and ether-based solvents such as dimethyl ether are suitable. Among these, carbon dioxide is particularly preferable because it has a critical pressure of 7.3 MPa and a critical temperature of 31 ° C., so that a supercritical state can be easily created, and it is nonflammable and easy to handle.
Further, these fluids may be used alone or in a mixture of two or more kinds.

The subcritical fluid is not particularly limited as long as it exists as a high-pressure liquid in the temperature and pressure regions near the critical point, and can be appropriately selected depending on the intended purpose.
The above-mentioned compounds listed as supercritical fluids can also be suitably used as subcritical fluids.

The critical temperature and critical pressure of the supercritical fluid are not particularly limited and can be appropriately selected depending on the intended purpose. However, the critical temperature is preferably -273 ° C or higher and 300 ° C or lower, and 0 ° C or higher and 200 ° C or lower. preferable.

Further, in addition to the above-mentioned supercritical fluid and subcritical fluid, an organic solvent or an entrainer can be used in combination.
By adding an organic solvent and an entrainer, the solubility in a supercritical fluid can be adjusted more easily.
The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose.
For example, a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone,
Ester solvents such as ethyl formate, ethyl acetate, or n-butyl acetate,
Ethereal solvents such as diisopropyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane,
Amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone,
Halogenated hydrocarbon solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichlorethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or 1-chloronaphthalene,
Hydrocarbons such as n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, or cumene. Examples include system solvents.

In the present invention, the organic hole transport layer may be provided on the first electrode provided with the electron transport layer carrying the photosensitizer material, and then the press treatment step may be performed.
It is believed that this press treatment will improve the efficiency because the organic hole transport material will be in close contact with the porous electrode.
The press processing method is not particularly limited, and examples thereof include a press molding method using a flat plate as typified by an IR tablet shaper, and a roll press method using a roller or the like.
The pressure is preferably 10 kgf / cm ² or more, and more preferably 30 kgf / cm ² or more. The press processing time is not particularly limited, but it is preferably performed within 1 hour. Further, heat may be applied during the pressing process.

Further, during the above-mentioned pressing process, a mold release material may be sandwiched between the press machine and the electrodes.
Examples of the release material include polytetrafluorinated ethylene, polychlorotrifluoroethylene, tetrafluorinated ethylene hexafluoropropylene copolymer, perfluoroalkoxyfluororesin, polyvinylidene fluoride, ethylene tetrafluorinated ethylene copolymer, and ethylene. Fluororesin such as chlorotrifluoroethylene copolymer and polyvinylidene fluoride can be mentioned.

After performing the above press processing step and before providing the counter electrode, a metal oxide may be provided between the organic hole transport layer and the second electrode. Examples of the metal oxide that may be provided include molybdenum oxide, tungsten oxide, vanadium oxide, and nickel oxide, and molybdenum oxide is particularly preferable.
The method of providing these metal oxides on the hole transport layer is not particularly limited, and examples thereof include a method of forming a thin film in vacuum such as sputtering and vacuum vapor deposition, and a wet film forming method.
In the wet film forming method, a method of preparing a paste in which a metal oxide powder or a sol is dispersed and applying the paste on the hole transport layer is preferable.
When this wet film forming method is used, the coating method is not particularly limited and can be carried out according to a known method.
For example, dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, and various wet printing methods such as letterpress, offset, gravure, intaglio, rubber plate, screen printing, etc. Method can be used. The film thickness is preferably 0.1 to 50 nm, more preferably 1 to 10 nm.

<Second electrode>
The second electrode is newly applied after the hole transport layer is formed or on the above-mentioned metal oxide.
Further, as the second electrode, the same one as the above-mentioned first electrode can be usually used, and the support is not always necessary in the configuration in which the strength and the sealing property are sufficiently maintained.
Specific examples of the second electrode material include metals such as platinum, gold, silver, copper and aluminum, carbon-based compounds such as graphite, fullerene, carbon nanotubes and graphene, and conductive metal oxides such as ITO, FTO and ATO. , Polythiophene, polyaniline and other conductive polymers.
The film thickness of the second electrode layer is not particularly limited, and may be used alone or in a mixture of two or more kinds.
The coating of the second electrode can be appropriately formed on the hole transport layer by a method such as coating, laminating, vapor deposition, CVD, or bonding, depending on the type of material used and the type of hole transport layer.

In order to operate as a photoelectric conversion element, at least one of the first electrode and the second electrode must be substantially transparent.
In the photoelectric conversion element of the present invention, the method in which the first electrode side is transparent and sunlight is incident from the first electrode side is preferable. In this case, it is preferable to use a material that reflects light on the second electrode side, and a metal, glass on which a conductive oxide is vapor-deposited, plastic, or a metal thin film is preferable.
It is also an effective means to provide an antireflection layer on the incident side of sunlight.

<Use>
The photoelectric conversion element of the present invention can be applied to a solar cell and a power supply device including the solar cell.
As an application example, any device that has conventionally used a solar cell or a power supply device using the solar cell can be used.
For example, it may be used for a solar cell for an electronic desk computer or a wristwatch, and an example of utilizing the features of the photoelectric conversion element of the present invention is a power supply device such as a mobile phone, an electronic personal organizer, or an electronic paper. It can also be used as an auxiliary power source for prolonging the continuous use time of rechargeable or dry battery type electric appliances. Furthermore, it can be used as a self-supporting power source for a sensor and as a substitute for a primary battery in combination with a secondary battery.

（式中、Ｒ₁、及びＲ₂は、それぞれ独立に、水素原子、メチル基、及びメトキシ基のいずれかを表す。） <Synthesis method of whole transport material of the present invention Reported example (J. Org .Chem., 67 (2002) 3029) Similarly, it can be easily synthesized from the following route.

(In the formula, R ₁ and R ₂ each independently represent one of a hydrogen atom, a methyl group, and a methoxy group.)

Hereinafter, the present invention will be specifically described with reference to Examples, but the embodiments of the present invention are not limited to these Examples.

Phenacetin（東京化成社製）：５．３７ｇと5-Bromo-2-methoxytoluene（東京化成社製）：７．２３ｇと銅粉（関東化学社製）：２．８６ｇと炭酸カリウム（関東化学社製）：１８．６５ｇとオルトジクロロベンゼン（関東化学社製）：１００ｍｌを四つ口フラスコに秤量し、還流攪拌を２４時間実施した。反応物を、抽出し、硫酸マグネシウムを加えた後、濾過し、濃縮した。無色粉末状のアセトアニリド中間体（１０．３ｇ）を得た。
次に、得られたアセトアニリド中間体：１０．３ｇと水酸化カリウム（関東化学社製）：５ｇをエタノール：１５０ｍｌを四つ口フラスコに秤量し、還流攪拌を１０時間実施した。反応物を、抽出し、硫酸マグネシウムを加えた後、濾過し、濃縮した。粗収物をカラムクロマトグラフィー（トルエン／酢酸エチル＝９／１）で精製し、無色粉末状のアミン中間体（４．６ｇ）を得た。 [Example I-1]
(Synthesis of Hall Transport Material (Compound No. 1-2))

Phenacetin (manufactured by Tokyo Kasei Co., Ltd.): 5.37 g and 5-Bromo-2-methoxytoluene (manufactured by Tokyo Kasei Co., Ltd.): 7.23 g and copper powder (manufactured by Kanto Chemical Co., Inc.): 2.86 g and potassium carbonate (manufactured by Kanto Chemical Co., Inc.) ): 18.65 g and orthodichlorobenzene (manufactured by Kanto Chemical Co., Inc.): 100 ml were weighed in a four-necked flask, and reflux stirring was carried out for 24 hours. The reaction was extracted, added with magnesium sulfate, filtered and concentrated. A colorless powdery acetanilide intermediate (10.3 g) was obtained.
Next, 10.3 g of the obtained acetanilide intermediate and 5 g of potassium hydroxide (manufactured by Kanto Chemical Co., Inc.) were weighed in a four-necked flask with 150 ml of ethanol, and reflux stirring was carried out for 10 hours. The reaction was extracted, added with magnesium sulfate, filtered and concentrated. The crude product was purified by column chromatography (toluene / ethyl acetate = 9/1) to obtain a colorless powdery amine intermediate (4.6 g).

合成したアミン中間体：１．２３ｇと2,2’,7,7’-Tetrabromo-9,9’-spirobi(9H-fluorene)（東京化成社製）：０．６３ｇと酢酸パラジウム（東京化成社製）：９０ｍｇ、炭酸ナトリウム（関東化学社製）：０．５７ｇとキシレン：１５ｍｌを秤量し、アルゴンガス雰囲気下にて攪拌した。その後、ターシャルブチルホスフィン（関東化学社製）：２４０ｍｇを加えて、５時間還流攪拌した。反応物を抽出し、硫酸マグネシウムを加えた後、濾過し、濃縮した。粗収物をカラムクロマトグラフィー（トルエン／酢酸エチル＝４／１）で精製した。得られた粗収物を、アセトン／メタノールにて再沈殿処理を行い、無色粉末状のホール輸送材料（化合物Ｎｏ．１－２）（１．３１ｇ）を得た。得られたホール輸送材料のＩＲスペクトルを図２に示す。

Synthesized amine intermediates: 1.23 g and 2,2', 7,7'-Tetrabromo-9,9'-spirobi (9H-fluorene) (manufactured by Tokyo Kasei Co., Ltd.): 0.63 g and palladium acetate (Tokyo Kasei Co., Ltd.) (Manufactured): 90 mg, sodium carbonate (manufactured by Kanto Chemical Co., Inc.): 0.57 g and xylene: 15 ml were weighed and stirred under an atmosphere of argon gas. Then, Tarsal butylphosphine (manufactured by Kanto Chemical Co., Inc.): 240 mg was added, and the mixture was refluxed and stirred for 5 hours. The reaction was extracted, magnesium sulfate was added, and then the mixture was filtered and concentrated. The crude product was purified by column chromatography (toluene / ethyl acetate = 4/1). The obtained crude product was reprecipitated with acetone / methanol to obtain a colorless powdery whole transport material (Compound No. 1-2) (1.31 g). The IR spectrum of the obtained hole transport material is shown in FIG.

[Example II-1]
(Manufacturing of titanium oxide semiconductor electrode)
A dense hole blocking layer of titanium oxide was formed on an ITO-based glass substrate by reactive sputtering with oxygen gas using a target made of metallic titanium.
Next, bead mill with 3 g of titanium oxide (P90 manufactured by Nippon Aerodil), 0.2 g of acetylacetone, 0.3 g of surfactant (polyoxyethylene octylphenyl ether manufactured by Wako Pure Chemical Industries, Ltd.) with 5.5 g of water and 1.0 g of ethanol. The treatment was carried out for 12 hours.
1.2 g of polyethylene glycol (# 20,000) was added to the obtained dispersion to prepare a paste.
This paste was applied onto the hole blocking layer to a film thickness of 1.5 μm, dried at room temperature, and then calcined in air at 500 ° C. for 30 minutes to form a porous electron transport layer.

(Manufacturing of photoelectric conversion element)
The titanium oxide semiconductor electrode is immersed as a sensitizing dye in D102 (0.5 mM, acetonitrile / t-butanol (volume ratio 1: 1) solution) manufactured by Mitsubishi Paper Mills Limited represented by the structural formula (4). It was allowed to stand in a dark place for a while to adsorb the photosensitizer.
On a semiconductor electrode carrying a photosensitizing material, an organic hole transport material represented by the general formula (1) (exemplified compound No. 1-1): 183.3 mg of a chlorobenzene solution was added to 1 ml, manufactured by Kanto Chemical Co., Ltd. A solution obtained by adding lithium bis (trifluoromethanesulfonyl) imide: 12.83 mg and the basic compound represented by the general formula (2) (Compound No. 2-1): 36.66 mg was used as a photosensitizing material. A hole transport layer was formed by spin coating on the semiconductor electrode carrying the above. Silver was vacuum-deposited on this by 100 nm to prepare a second electrode, and a photoelectric conversion element was manufactured.

(Evaluation of photoelectric conversion element)
The photoelectric conversion efficiency of the obtained photoelectric conversion element under white LED irradiation (100 lux: 25 μW / cm ² ) was measured. The white LED was measured by a desk lamp CDS-90α (study mode) manufactured by Cosmo Techno, and the evaluation device was measured by a solar cell evaluation system As-510-PV03 manufactured by NF Circuit Design Block. After measuring the initial characteristics, the photoelectric conversion element was stored in a vacuum at a constant temperature of 100 ° C. for 1000 hours. After taking out, it was left at room temperature for 24 hours, the photoelectric conversion rate was measured in the same manner, and the maintenance rate was obtained by the following formula and evaluated. The results are shown in Table 1.
Maintenance rate = (conversion efficiency after storage at 100 ° C for 1000 hours / initial conversion efficiency) x 100

[Examples II-2 to II-8]
The organic hole transport material and the basic compound in Example II-1 are listed in Compound No. 1 in Table 1. A photoelectric conversion element was produced and evaluated in the same manner as in Example II-1 except that the compound was changed to the above compound. The results are shown in Table 1.

[Example II-9]
Basic compound No. in Example II-1. A photoelectric conversion element was produced and evaluated in the same manner as in Example II-1 except that 2-1 was changed to tertiary butylpyridine (tBP: manufactured by Aldrich). The results are shown in Table 1.

[Comparative Example 1]
The organic hole transport material compound No. in Example II-1. 1-1 is an organic hole transport material Spiro-MeOTAD (2,2', 7,7'-tetrakis (N, N-di-p-methoxyphenylamino) -9,9'-spirobifluorene) (SHT-263, Merck Group, Inc. A photoelectric conversion element was produced and evaluated in the same manner as in Example II-1 except that it was changed to (manufactured). The results are shown in Table 1.

[Comparative Example 2]
The organic hole transport material compound No. in Example II-1. A photoelectric conversion element was produced and evaluated in the same manner as in Example II-1 except that 1-1 was changed to the organic hole transport material Spiro-MeOTAD-HTM1 (LT-S9170, manufactured by Luminescence Technology Co., Ltd.). The results are shown in Table 1.

The photoelectric conversion elements of Examples II-1 to II-9 using the hole transport material represented by the general formula (1) are slightly inferior in initial conversion efficiency to the photoelectric conversion elements of Comparative Examples 1 and 2. However, the conversion efficiency after 1000 hours at 100 ° C. was excellent, and the maintenance rate was very good. As is clear from the above, it can be seen that the photoelectric conversion element of the present invention has excellent photoelectric conversion characteristics in a weak light environment and also has excellent high-temperature storage stability.

Japanese Unexamined Patent Publication No. 11-144773

Panasonic Electric Engineering Report, 56 (2008) 87 J. Am. Chem. Soc., 133 (2011) 18042 J. Am. Chem. Soc., 135 (2013) 7378 Fujikura Technical Report, 121 (2011) 42 ACS Appl. Mater. Interfaces, 2015, 7 (21), pp 11107-11116

Claims (10)

It has a first electrode, an electron transport layer, a hole transport layer, and a second electrode, and the hole transport layer includes a hole transport material represented by the following general formula (1).
The hole transport layer is a photoelectric conversion element containing 50 to 95% by mass of an organic hole transport material represented by the following general formula (1).

(In the formula, R ₁ and R ₂ each independently represent one of a hydrogen atom, a methyl group, and a methoxy group.) The photoelectric conversion element according to claim 1, wherein the hole transport layer contains 70 to 85% by mass of an organic hole transport material represented by the general formula (1). A solar cell comprising the photoelectric conversion element according to claim 1 or 2. The photoelectric conversion element according to claim 1 , wherein the electron transport layer includes an oxide semiconductor. The photoelectric conversion element according to claim 4, wherein the oxide semiconductor contains at least one of titanium oxide, zinc oxide, tin oxide, and niobium oxide. The photoelectric conversion element according to claim 1, wherein the electron transport layer has a film thickness of 100 nm to 100 μm. The photoelectric conversion element according to any one of claims 1 to 6, wherein the hole transport layer contains a basic compound represented by the following general formula (2).

(In the formula, R ₃ and R ₄ each independently represent an alkyl group or an aromatic hydrocarbon group, where R ₃ and R ₄ bond with each other to form a heterocyclic group containing a nitrogen atom. Including cases.) The seventh aspect of claim 7, wherein the amount of the basic compound represented by the general formula (2) added to the hole transport layer is 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the organic hole transport material. Photoelectric conversion element. The seventh aspect of claim 7, wherein the amount of the basic compound represented by the general formula (2) added to the hole transport layer is 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the organic hole transport material. Photoelectric conversion element. A synthetic method comprising synthesizing a compound represented by the following general formula (1) by the reaction shown in the following synthetic reaction formula.

(In the formula, R ₁ and R ₂ each independently represent one of a hydrogen atom, a methyl group, and a methoxy group.)

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