JP6432728B2 - Photoelectric conversion element, diketopyrrolopyrrole derivative, photosensitizing dye containing the diketopyrrolopyrrole derivative - Google Patents

Description

  The present invention relates to a photoelectric conversion element, a diketopyrrolopyrrole derivative, and a photosensitizing dye containing the diketopyrrolopyrrole derivative.

  In recent years, the importance of solar cells has been increasing as an alternative energy to fossil fuels and as a countermeasure against global warming. However, current solar cells typified by silicon-based solar cells are expensive at present and are factors that hinder their spread.

  Therefore, various low-cost solar cells are being researched and developed, and among them, dye-sensitized solar cells announced by Graetzel et al. Of Lausanne University of Technology in Switzerland are expected to be put to practical use (for example, patents). Reference 1, Non-Patent Documents 1 and 2). This solar cell has a porous metal oxide semiconductor provided on a transparent conductive glass substrate, and is composed of a sensitizing dye adsorbed on the surface thereof, an electrolyte having a redox couple, and a counter electrode. Graetzel et al. Significantly improved the photoelectric conversion efficiency by making a metal oxide semiconductor electrode such as titanium oxide porous to increase the surface area, and by adsorbing a ruthenium complex as a dye on a single molecule basis.

  However, the ruthenium complex used for the sensitizing dye is a rare metal and has resource limitations. Therefore, there is a demand for the development of organic dyes that are less resource-constrained. As sensitizing dyes already proposed, xanthene dyes such as eosin Y (see Non-patent Document 3), perylene dyes (see Non-Patent Document 4), cyanine dyes (see Patent Document 2), merocyanine dyes (patents) Reference 3), coumarin dye (see Non-patent document 5), polyene dye (see Non-patent document 6), porphyrin dye (see Non-patent document 7), phthalocyanine dye (see Non-patent document 8) and the like have been reported. .

  Xanthene dyes and perylene dyes such as eosin Y have an absorption wavelength region of only about 600 nm, and have a disadvantage of low conversion efficiency. Since cyanine dyes, merocyanine dyes, polyene dyes, coumarin dyes and the like have many conjugated double bonds, cis-trans isomerization is likely to occur due to light irradiation, and their durability is very low. Porphyrin dyes and phthalocyanine dyes are disadvantageous in that they have low solubility and low adsorptive power to titanium oxide, and are easily desorbed from titanium oxide. Also, it is difficult for phthalocyanine dyes to match the energy level with titanium oxide.

  Patent Document 4 discloses a method of adsorbing a dye in a supercritical fluid (supercritical fluid dye adsorption method). It is believed that this method can adsorb the dye to the inside of the titanium oxide pores and increase the amount of adsorbed dye, but conventional dyes have low solubility in supercritical fluids, Since it is not sufficiently dissolved in the supercritical fluid, it is difficult to increase the adsorption amount by adsorbing the dye to the inside of the titanium oxide pores.

As described above, none of the sensitizing dyes of dye-sensitized solar cells that have been studied so far has been obtained with satisfactory characteristics.
In addition, there is currently no dye suitable for the supercritical fluid dye adsorption method.

  An object of the present invention is to provide a photoelectric conversion element having high efficiency and good characteristics in order to solve the above-described problems.

As a result of intensive studies to solve the above problems, it is possible to provide a high-efficiency and high-performance photoelectric conversion element by adsorbing a specific compound to the electron transporting material constituting the electron transport layer on the first electrode. And reached the present invention.
The above problem is solved by the present invention described in (1) below.

(1) A photoelectric conversion element comprising a first electrode coated with an electron transport layer and a second electrode facing the electron transport layer of the first electrode, wherein the electron transport material comprises the electron transport layer A photoelectric conversion element, wherein a diketopyrrolopyrrole derivative represented by the following general formula (1) is adsorbed.
(In general formula (1), X represents a group represented by the following general formula A,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E, where n is 0-2 and m is 1-2 . Represents an integer, n + m does not exceed 3. )

  As will be understood from the following detailed and specific description, according to the present invention, it is possible to obtain a photoelectric conversion element having high efficiency and good characteristics.

It is an example of sectional drawing showing the structure of the photoelectric conversion element which concerns on this invention. It is a figure which shows an example of the apparatus which implements a supercritical fluid adsorption method. It is IR spectrum of the compound b represented by Structural formula b synthesize | combined in the Example. It is IR spectrum of exemplary compound D-14 synthesize | combined in the Example.

The photoelectric conversion element of the present invention will be described in detail.
The photoelectric conversion element of the present invention is a photoelectric conversion element comprising a first electrode covered with an electron transport layer and a second electrode facing the electron transport layer of the first electrode, and constitutes the electron transport layer. A diketopyrrolopyrrole derivative represented by the following general formula (1) is adsorbed on the electron transporting material.
The structure of the photoelectric conversion element of this invention is demonstrated based on FIG.
FIG. 1 is a cross-sectional view of an example of the photoelectric conversion element of the present invention.
In the embodiment shown in FIG. 1, a first electrode 2 is provided on a substrate 1, the first electrode 2 is covered with an electron transport layer 3, and a photosensitizing compound 4 ( A structure in which the charge transfer layer 5 is sandwiched between the second electrode 6 facing the electron transport layer 3 and the electron transport layer 3 is adsorbed by the diketopyrrolopyrrole derivative represented by the general formula (1). Yes.

<First electrode>
The first electrode 2 used in the present invention is not particularly limited as long as it is a conductive material that is transparent to visible light, and a known one that is used for a normal photoelectric conversion element, a liquid crystal panel, or the like. Can be used.

  For example, indium / tin oxide (hereinafter referred to as ITO), fluorine-doped tin oxide (hereinafter referred to as FTO), antimony-doped tin oxide (hereinafter referred to as ATO), indium / zinc oxide, niobium / titanium oxide , Graphene and the like, and these may be used alone or in a plurality of layers.

The thickness of the first electrode is preferably 5 nm to 100 μm, and more preferably 50 nm to 10 μm.
The first electrode is preferably provided on a substrate made of a material transparent to visible light in order to maintain a certain hardness. For example, glass, a transparent plastic plate, a transparent plastic film, an inorganic transparent crystal, or the like is 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, etc. Can be mentioned.
In addition, a transparent electrode obtained by doping cations or anions with different valences into tin oxide or indium oxide, or a metal electrode having a structure capable of transmitting light, such as a mesh shape or a stripe shape, provided on a substrate such as a glass substrate Good. These may be used singly or as a mixture of two or more kinds or laminated ones.

  Further, for the purpose of reducing the resistance, a metal lead wire or the like may be used in combination. Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. For example, the metal lead wire may be provided on the substrate by vapor deposition, sputtering, pressure bonding, or the like, and ITO or FTO may be provided thereon.

<Electron transport layer>
The photoelectric conversion element of the present invention forms a thin film made of an electron transporting material as the electron transport layer 3 on the first electrode 2.
The electron transport layer 3 may have a laminated structure in which a dense electron transport layer 3a is formed on the first electrode 2 and a porous electron transport layer 3b is further formed thereon.
The dense electron transport layer 3 a is formed for the purpose of preventing electronic contact between the first electrode 2 and the charge transfer layer 5. Therefore, if the first electrode 2 and the charge transfer layer 5 are not in physical contact, pinholes, cracks, or the like may be formed.
Moreover, although there is no restriction | limiting in the film thickness of this precise | minute electron carrying layer 3a, 10 nm-1 micrometer are preferable and 20 nm-700 nm are more preferable.
The “dense” of the dense electron transport layer 3a means that the inorganic oxide semiconductor is filled at a density higher than that of the semiconductor fine particles in the porous electron transport layer 3b.

The porous electron transport layer 3b formed on the dense electron transport layer 3a may be a single layer or multiple layers.
In the case of multiple layers, a dispersion of semiconductor fine particles having different particle diameters can be applied in multiple layers, or different types of semiconductors, and application layers having different compositions of resins and additives can be applied in multiple layers.
Multi-layer coating is an effective means when the film thickness is insufficient with a single coating.

  In general, as the film thickness of the electron transport layer 3 increases, the amount of supported photosensitizing compound per unit projected area also increases, so that the light capture rate increases. However, the diffusion distance of injected electrons also increases, so Loss due to recombination also increases. Therefore, the film thickness of the electron transport layer is preferably 100 nm to 100 μm.

Examples of the electron transporting material include a semiconductor. The semiconductor is not particularly limited, and a known semiconductor can be used.
Specifically, a single semiconductor such as silicon or germanium, a compound semiconductor typified by a metal chalcogenide, a compound having a perovskite structure, or the like can be given.

Metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, or tantalum oxides, cadmium, zinc, lead, silver, antimony, bismuth. Sulfide, cadmium, lead selenide, cadmium telluride and the like.
Other compound semiconductors are preferably phosphides such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide, and the like.
As the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.

  Among these, an n-type oxide semiconductor is preferable, and titanium oxide, zinc oxide, tin oxide, and niobium oxide are particularly preferable, and they may be used alone or in combination of two or more. The crystal type of these semiconductors is not particularly limited, and may be single crystal, polycrystal, or amorphous.

Although there is no restriction | limiting in particular in the size of a semiconductor fine particle, It is preferable that it is a nanoparticle, 1-100 nm is preferable and the average particle diameter of a primary particle has more preferable 5-50 nm.
Further, the efficiency can be improved by the effect of scattering incident light by mixing or laminating semiconductor fine particles having a larger average particle diameter. In this case, the average particle size of the semiconductor is preferably 50 to 500 nm.

  The electron transport material of the electron transport layer is preferably an n-type oxide semiconductor composed of nanoparticles. When the electron transport layer has a laminated structure in which a dense electron transport layer is formed on the first electrode and a porous electron transport layer is further formed thereon, the dense electron transport layer and the porous electrons are formed. More preferably, both electron transport materials of the transport layer are n-type oxide semiconductors composed of nanoparticles, but only the electron transport material of the porous electron transport layer is composed of nanoparticles. It may be preferable.

There is no restriction | limiting in particular in the preparation methods of an electron carrying layer, The method of forming a thin film in vacuum, such as sputtering, and the wet film forming method are mentioned.
In consideration of the manufacturing cost and the like, a wet film forming method is particularly preferable, and a method of preparing a paste in which semiconductor fine particle powder or sol is dispersed and applying the paste onto a first electrode (electron collecting electrode) substrate is preferable.
When this wet film-forming method is used, the coating method is not particularly limited, and can be performed 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 wet printing methods such as relief printing, offset, gravure, intaglio printing, rubber printing, screen printing, etc. Can be used.

  When a dispersion is prepared by mechanical pulverization or using a mill, it is formed by dispersing at least semiconductor fine particles alone or a mixture of semiconductor fine particles and a resin in water or an organic solvent.

  As the resin used at this time, polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid ester, methacrylic acid ester, silicon resin, phenoxy resin, polysulfone resin, polyvinyl butyral resin, polyvinyl formal resin, Examples include polyester resin, cellulose ester resin, cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin, polyimide resin, and the like.

  Solvents for dispersing the semiconductor fine particles include water, alcohol solvents such as methanol, ethanol, isopropyl alcohol, and α-terpineol, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethyl formate, ethyl acetate, and n acetate. Ester solvents such as butyl, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone Amide solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromo Halogenated hydrocarbon solvents such as benzene, iodobenzene or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o Examples thereof include hydrocarbon solvents such as xylene, m-xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

In order to prevent re-aggregation of particles, a paste of semiconductor fine particles obtained by a dispersion of semiconductor fine particles or a sol-gel method is used, such as acids such as hydrochloric acid, nitric acid, acetic acid, polyoxyethylene (10) octylphenyl ether, etc. Surfactants, chelating agents such as acetylacetone, 2-aminoethanol, and ethylenediamine 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 added at this time include polymers such as polyethylene glycol and polyvinyl alcohol, and thickeners such as ethyl cellulose.

The semiconductor fine particles are preferably subjected to firing, microwave irradiation, electron beam irradiation, or laser beam irradiation in order to bring the particles into electronic contact with each other after coating and to improve film strength and adhesion to the substrate. . These processes may be performed alone or in combination of two or more.
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. Moreover, although there is no restriction | limiting in particular also in baking time, 10 minutes-10 hours are preferable.

For the purpose of increasing the surface area of the semiconductor fine particles after firing and increasing the efficiency of electron injection from the photosensitizing compound to the semiconductor fine particles, for example, chemical plating using titanium tetrachloride aqueous solution or mixed solution with organic solvent, titanium trichloride Electrochemical plating using an aqueous solution may be performed.
Microwave irradiation may be performed from the electron transport layer forming side or from the back side.
Although there is no restriction | limiting in particular in irradiation time, It is preferable to carry out within 1 hour.

For example, a dense electron transport layer can be formed by applying titanium tetra-n-propoxide, which is a precursor in the so-called sol-gel method, and baking it.
A film in which semiconductor fine particles having a diameter of several tens of nanometers are stacked by sintering or the like forms a porous state. This nanoporous structure has a very high surface area, which can be expressed using a roughness factor. The roughness factor is a numerical value representing the actual area inside the porous body relative to the area of the semiconductor fine particles applied to the substrate. Accordingly, the roughness factor is preferably as large as possible, but it is also related to the film thickness of the electron transport layer, and is preferably 20 or more in the present invention.

<Photosensitizing compound>
In the present invention, in order to further improve the conversion efficiency, the photosensitizing compound is adsorbed on the electron transporting material constituting the electron transporting layer. The photoelectric conversion element in the present invention uses a diketopyrrolopyrrole derivative represented by the general formula (1) as a photosensitizing compound, and further a diketopyrrolopyrrole represented by the following general formula (2). A derivative is preferred.

(In general formula (1) and general formula (2), X represents a group represented by the following general formula A,
Ar represents a thienylene group or a phenylene group,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-3. )

  The diketopyrrolopyrrole derivative represented by the general formula (1) can be synthesized, for example, as follows. In the following schemes (I) to (VII), X represents a group represented by the above general formula A, Ar represents a thienylene group or a phenylene group, Y represents a carboxyl group, and the structural formula C represents A group represented by the structural formula D, or a group represented by the structural formula E.

Method for synthesizing diketopyrrolopyrrole derivative represented by general formula (1) (first step)
In the presence of a base, the nitrile body and disuccinate are reacted, and then (second step)
By reacting with an ethylene glycol bromide derivative in the presence of a base, a diketopyrrolopyrrole derivative in which the N atom is substituted with an ethylene glycol derivative can be obtained.

(3rd step: Formylation with Vilsmeier reagent)
Next, when n is 1 in the general formula (1), the hydrogen atom is replaced with a formyl group.
Vilsmeier reagent can be prepared by mixing an amide derivative such as N, N-dimethylformamide or N-methylformanilide with phosphorus oxychloride.

(4th step: condensation reaction)
Next, by reacting the following formulas (structural formulas C ′, D ′, E ′), which are precursors of the structural formulas C, D, E, with the above formyl derivatives in acetic acid, the general formula (1) is obtained. Can be obtained. When Y is -COOH, it is obtained by oxidizing various oxidants (potassium permanganate, hydrogen peroxide, metachloroperbenzoic acid, chromium oxide-acetone-sulfuric acid mixture (Jones' reagent), etc.) and oxidizing the aldehyde. be able to.

(3rd step: halogenation)
In the general formula (1), when n is 2, after the second step, a hydrogen atom is substituted with a halogen atom such as a bromine atom to obtain a halogen derivative.
(B represents a chlorine atom, a bromine atom, or an iodine atom)
For halogenation, N-halogenated succinimide, simple iodine, bromine, or the like can be used.

(4th step: cross-coupling reaction)
Next, by using an aldehyde derivative represented by the following structure (Structural Formula F), a halogen atom is substituted with an —Ar—CHO group by a cross-coupling reaction.

The cross-coupling reaction represents various cross-coupling reactions between aromatic groups and heteroaromatic groups using known metal catalysts, and Z in the structural formula F includes derivatives as shown below. Can do.
(Boronic acid derivative)
(Tin derivative)
(R ⁵ represents an alkyl group having 1 to 10 carbon atoms)

A method using Suzuki coupling will be described as an example of cross coupling using a metal catalyst.
The Suzuki coupling reaction is performed with a halide and a boron compound. The halogen atom of the aryl halide is preferably an iodide or bromide from the viewpoint of reactivity. As the aryl boron compound, aryl boronic acid or aryl boronic acid ester or aryl boronic acid salt is used, but the aryl boronic acid ester does not produce a trimerized anhydride (boroxine) like aryl boronic acid. Moreover, it is more preferable because of high crystallinity and easy purification. As a method for synthesizing an aryl boronic acid ester, (i) a reaction in which an aryl boronic acid and an alkyl diol are heated in an anhydrous organic solvent, and (ii) a reaction in which an alkoxy boron ester is added after metalation of the halogen moiety of the aryl halide. (Iii) Reaction of adding alkoxyboron ester after preparing Grignard reagent of aryl halogen, and (iv) Heating aryl halide and bis (pinacolato) diboron or bis (neopentylglycolato) diboron under palladium catalyst It is obtained by reacting.

Examples of the palladium catalyst used include various catalysts such as Pd (PPh ₃ ) ₄ , PdCl ₂ (PPh ₃ ) ₂ , Pd (OAc) ₂ , PdCl ₂ , or palladium carbon to which triphenylphosphine is added as a separate ligand. Can be used. Of these, Pd (PPh ₃ ) ₄ is used most generally.

A base is always required in the Suzuki coupling reaction, but relatively weak bases such as Na ₂ CO ₃ , NaHCO ₃ , K ₂ CO ₃ give good results. When affected by steric hindrance or the like, strong bases such as Ba (OH) ₂ and K ₃ PO ₄ are effective, and caustic soda is also effective depending on the reaction substrate. Other caustic potash, metal alkoxides, etc., such as potassium t-butoxide, sodium t-butoxide, lithium t-butoxide, potassium 2-methyl-2-butoxide, sodium 2-methyl-2-butoxide, sodium methoxide, sodium ethoxide, potassium Ethoxide, potassium methoxide and the like can also be used. Further, a phase transfer catalyst may be used to make the reaction proceed more smoothly, preferably tetraalkylammonium halide, tetraalkylammonium hydrogensulfate, or tetraalkylammonium hydroxide. -N-butylammonium halide, benzyltriethylammonium halide, or tricaprylylmethylammonium chloride.
Although the reaction atmosphere can be carried out in the air, it is preferable to carry out the reaction under an inert gas atmosphere such as nitrogen or argon because the catalyst used may be deteriorated.

When n is 3, the 3 ′ step and the 4 ′ step are repeated. However, the following structural formula F ′ is used as the structural formula F in the first 4 ′ step.
After the aldehyde derivative is obtained, the general formula (I) can be obtained by the fourth step described above.

Alternatively, the compound of the general formula (1) can also be obtained by the following scheme (VII) instead of the 3 ′ step and the 4 ′ step.
(Direct array)
(B represents a chlorine atom, a bromine atom, or an iodine atom)
The direct arylation is similar to the cross coupling, and can be reacted under the same palladium catalyst, the same base, and the same atmosphere. By adding an aliphatic carboxylic acid such as acetic acid, propionic acid or pivalic acid as an additive specific to direct arylation, the yield is improved. Pivalic acid is preferred.

In schemes (I) to (VII), the reaction solvent can be a common organic solvent. For example, reaction solvents include methanol, ethanol, isopropanol, butanol, 2-methoxyethanol, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether and other alcohols and ethers, chloroform, dichloromethane, 1,2-dichloroethane. In addition to halogens such as carbon tetrachloride, chlorobenzene and 1,2-dichlorobenzene, cyclic ethers such as dioxane and tetrahydrofuran, benzene, toluene, xylene, dimethyl sulfoxide, N, N-dimethylformamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned.
The reactions of schemes (I) to (VII) are usually performed at a temperature from room temperature to 180 ° C, preferably at a temperature from room temperature to 100 ° C.

  Specific examples of the photosensitizing compound represented by the general formula (1) include the following exemplary compounds D-1 to D-15, but are not limited thereto.

The photosensitizing dye of the present invention contains a diketopyrrolopyrrole derivative represented by the general formula (1).
The photosensitizing dye of the present invention may be used alone as a diketopyrrolopyrrole derivative represented by the general formula (1), but may be used in a mixture of two or more. Examples of photosensitizing compounds that may be mixed include JP 7-500630 A, JP 10-233238 A, JP 2000-26487 A, JP 2000-323191 A, JP 2001-59062 A. No. 10-93118, JP-A No. 2002-164089, JP-A No. 2004-95450, J. Pat. Phys. Chem. C, 7224, Vol. 111 (2007), etc., JP-A-2004-95450, Chem. Commun. , 4887 (2007), etc., JP-A No. 2003-264010, JP-A No. 2004-63274, JP-A No. 2004-115636, JP-A No. 2004-200068, JP-A No. 2004-235052. Gazette, J.A. Am. Chem. Soc. , 12218, Vol. 126 (2004), Chem. Commun. , 3036 (2003), Angew. Chem. Int. Ed. , 1923, Vol. 47 (2008), etc .; Am. Chem. Soc. 16701, Vol. 128 (2006), J.M. Am. Chem. Soc. , 14256, Vol. 128 (2006), JP-A-11-86916, JP-A-11-214730, JP-A-2000-106224, JP-A-2001-76773, JP-A-2003-7359. Described in JP-A-11-214731, JP-A-11-238905, JP-A-2001-52766, JP-A-2001-76775, 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-2003-3273, etc., JP-A-10-93118 And triarylmethane compounds described in JP-A-2003-31273 JP-9-199744, JP-A No. 10-233238, JP-A No. 11-204821, JP-A No. 11-265738, JP-J. Phys. Chem. , 2342, Vol. 91 (1987), J. MoI. Phys. Chem. B, 6272, Vol. 97 (1993), Electroanaly. Chem. , 31, Vol. 537 (2002), JP-A-2006-032260, J. Pat. Porphyrins Phthalocyanines, 230, Vol. 3 (1999), Angew. Chem. Int. Ed. , 373, Vol. 46 (2007), Langmuir, 5436, Vol. 24 (2008) etc., and the phthalocyanine compound, porphyrin compound, etc. can be mentioned.
The photoelectric conversion element of the present invention can adsorb the photosensitizing compound represented by the general formula (1) to the electron transporting material using the photosensitizing dye of the present invention.

As a method of adsorbing the photosensitizing compound 4 to the electron transporting material constituting the electron transporting layer 3, a method of immersing an electron current collecting electrode containing semiconductor fine particles in a photosensitizing compound solution or dispersion, a solution Or the method of apply | coating and adsorb | sucking a dispersion liquid to an electron carrying layer can be used.
In the former case, dipping method, dipping method, roller method, air knife method, etc. can be used, and in the latter case, wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray method, etc. Can be used.
Further, it may be adsorbed in a supercritical fluid using carbon dioxide (CO ₂ ) or the like.
In the present invention, a supercritical fluid adsorption method in which adsorption is performed using a supercritical fluid is preferable. By adsorbing by the supercritical fluid adsorption method, the amount of adsorption can be increased, and the characteristics (particularly the short-circuit current density) are improved. For example, the short-circuit current density can be 7.5 mA / cm ² or more.

When adsorbing the photosensitizing compound, a condensing agent may be used in combination.
The condensing agent has a catalytic action that seems to physically or chemically bond the photosensitizing compound and the electron transporting material to the inorganic surface, or acts stoichiometrically to favorably shift the chemical equilibrium. Any of them may be used.
Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

  Solvents for dissolving or dispersing the photosensitizing compound are water, methanol, ethanol, alcohol solvents such as isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or acetic acid. Ester solvents such as n-butyl, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone Amido solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromoben Halogenated hydrocarbon solvents such as ethylene, iodobenzene or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o Examples include hydrocarbon solvents such as -xylene, m-xylene, p-xylene, ethylbenzene, and cumene, and these can be used alone or as a mixture of two or more.

Further, depending on the type of the photosensitizing compound, there are compounds that work more effectively when the aggregation between the compounds is suppressed. Therefore, a co-adsorbent (aggregation dissociation agent) may be used in combination.
The coadsorbent is preferably a steroid compound such as cholic acid or chenodeoxycholic acid, a long-chain alkyl carboxylic acid or a long-chain alkyl phosphonic acid, and is appropriately selected according to the dye used. The addition amount of these aggregating and dissociating agents 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 dye.

The temperature at which the photosensitizing compound or the photosensitizing compound and the coadsorbent are adsorbed using these is preferably −50 ° C. or higher and 200 ° C. or lower.
Moreover, this adsorption may be carried out while standing or stirring.
Examples of the stirring method 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 further preferably 1 minute or more and 150 hours or less.
Adsorption is preferably performed in a dark place.

  The supercritical fluid when adsorbed by the supercritical fluid adsorption method exists as a non-aggregating high-density fluid in the temperature / pressure range that exceeds the limit (critical point) where gas and liquid can coexist, and even when compressed, it agglomerates The fluid is not particularly limited as long as the fluid is in a state of a critical temperature or higher and a critical pressure or higher, and can be appropriately selected according to the purpose, but a fluid having a low critical temperature is preferable.

  This supercritical fluid includes, for example, carbon monoxide, carbon dioxide, ammonia, nitrogen, water, methanol, ethanol, ercol solvents such as n-butanol, ethane, propane, 2,3-dimethylbutane, benzene, toluene and the like. Hydrocarbon solvents, halogen solvents such as methylene chloride and chlorotrifluoromethane, and ether solvents such as dimethyl ether are preferred. 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 it can easily create a supercritical state and is nonflammable and easy to handle.

These fluids may be used alone or in combination of two or more.
The critical temperature and critical pressure of the supercritical fluid are not particularly limited and can be appropriately selected according to the purpose. However, the critical temperature is preferably −273 ° C. or more and 300 ° C. or less, particularly 0 ° C. or more and 200 ° C. or less. preferable.

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

  The photosensitizing compound represented by the general formula (1) is adsorbed to the electron transporting material constituting the electron transporting layer by the above method. When the electron transport layer is composed of a dense electron transport layer and an electron transport layer having a porous structure, a large amount of the photosensitizing compound is adsorbed to the electron transport layer having a porous structure, and the electron transport layer is dense. However, if the photosensitizing compound is adsorbed in a large amount at least in the electron transporting material constituting the electron transport layer having a porous structure, the effect of the present invention can be obtained. Can do.

<Charge transfer layer>
As the charge transfer layer, an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a liquid in which the redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, a molten salt containing the redox couple, a solid electrolyte, An inorganic hole transport material, an organic hole transport material, or the like can be used.

  The electrolytic solution used in the present invention is preferably composed of an electrolyte, a solvent, and an additive. Preferred electrolytes include metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide, tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, and the like. Iodine salts of quaternary ammonium compounds-iodine combinations, metal bromides such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide-bromine combinations, quaternary compounds such as tetraalkylammonium bromide, pyridinium bromide Bromine-bromine combinations of ammonium compounds, metal complexes such as ferrocyanate-ferricyanate, ferrocene-ferricinium ion, sulfur compounds such as sodium polysulfide, alkylthiol-alkyldisulfide, viologen Dye, hydroquinone - quinones, metal complexes such as cobalt, include the nitroxide radical compounds. The above-mentioned electrolytes may be a single combination or a mixture. Further, when an ionic liquid such as imidazolinium iodide is used, it is not particularly necessary to use a solvent.

  The electrolyte concentration in the electrolytic solution is preferably 0.05 to 20M, and more preferably 0.1 to 15M. Solvents used for the electrolyte include carbonate solvents such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether solvents such as dioxane, diethyl ether and ethylene glycol dialkyl ether, methanol, ethanol , Alcohol solvents such as polypropylene glycol monoalkyl ether, nitrile solvents such as acetonitrile and benzonitrile, aprotic polar solvents such as dimethyl sulfoxide and sulfolane, etc. are preferable, and t-butylpyridine, 2-picoline, 2, A basic compound such as 6-lutidine may be used in combination.

  In the present invention, the electrolyte can be gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. Preferable polymers in the case of gelation by polymer addition include polyacrylonitrile, polyvinylidene fluoride and the like. Preferred gelling agents for gelation by adding an oil gelling agent include dibenzylden-D-sorbitol, cholesterol derivatives, amino acid derivatives, alkylamide derivatives of trans- (1R, 2R) -1,2-cyclohexanediamine, alkylureas Derivatives, N-octyl-D-gluconamide benzoate, double-headed amino acid derivatives, quaternary ammonium derivatives and the like can be mentioned.

Preferred monomers for polymerization with a polyfunctional monomer include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, and the like. be able to. Furthermore, esters and amides derived from acrylic acid such as acrylamide and methyl acrylate and α-alkyl acrylic acid, esters derived from maleic acid and fumaric acid such as dimethyl maleate and diethyl fumarate, butadiene, cyclohexane and the like. Dienes such as pentadiene, aromatic vinyl compounds such as styrene, p-chlorostyrene and sodium styrene sulfonate, vinyl esters, acrylonitrile, methacrylonitrile, vinyl compounds having a nitrogen-containing heterocyclic ring, vinyl having a quaternary ammonium salt A monofunctional monomer such as a compound, N-vinylformamide, vinylsulfonic acid, vinylidene fluoride, vinyl alkyl ethers, N-phenylmaleimide may be contained.
0.5-70 mass% is preferable and the polyfunctional monomer which occupies for the monomer whole quantity has more preferable 1.0-50 mass%.

  The above-mentioned monomers can be polymerized by radical polymerization. The monomer for gel electrolyte that can be used in the present invention can be radically polymerized by heating, light, electron beam or electrochemical. The polymerization initiator used when the crosslinked polymer is formed by heating is 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2. Azo initiators such as 2,2′-azobis (2-methylpropionate) and peroxide initiators such as benzoyl peroxide are preferable. The addition amount of these polymerization initiators is preferably 0.01 to 20% by mass and more preferably 0.1 to 10% by mass with respect to the total amount of monomers.

  When the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a reactive group necessary for the crosslinking reaction and a crosslinking agent in combination. Preferable examples of the crosslinkable reactive group include nitrogen-containing heterocycles such as pyridine, imidazole, thiazole, oxazole, triazole, morpholine, piperidine, piperazine, etc. Preferred crosslinking agents include alkyl halides, halogens Bifunctional or higher functional reagents capable of electrophilic reaction with nitrogen atoms such as aralkyl fluoride, sulfonic acid ester, acid anhydride, acid chloride, and isocyanate can be exemplified.

(Inorganic hole transport layer)
When the charge transfer layer is an inorganic hole transport layer using an inorganic hole transport material and an inorganic solid compound is used instead of the electrolyte, copper iodide, copper thiocyanide, etc. are cast, coating, spin coating, immersion It can be introduced into the electrode by a method such as electroplating.

(Organic hole transport layer)
In the present invention, the charge transfer layer can be an organic hole transport layer using an organic hole transport material instead of the electrolyte. The organic hole transport layer in the present invention may have a single layer structure made of a single material or a laminated structure made of a plurality of compounds. In the case of a laminated structure, it is preferable to use a polymer material for the organic hole transport material layer close to the second electrode (6). 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 to penetrate into the porous electron transport layer, it is excellent in covering the surface of the porous electron transport layer, and also effective in preventing a short circuit when an electrode is provided. As a result, higher performance can be obtained.

  As the organic hole transporting material used in a single layer structure used in a single manner, a known organic hole transporting compound is used, and specific examples thereof include oxadiazole disclosed in Japanese Patent Publication No. 34-5466. Compounds, triphenylmethane compounds shown in JP-B-45-555, pyrazoline compounds shown in JP-B-52-4188, hydrazone shown in JP-B-55-42380, etc. Compounds, oxadiazole compounds shown in JP-A-56-123544, etc., tetraarylbenzidine compounds shown in JP-A-54-58445, JP-A-58-65440 or JP The stilbene compound etc. which are shown by Unexamined-Japanese-Patent No. 60-98437 can be mentioned.

As the polymer material used for the organic hole transport layer close to the second electrode 6 used in the laminated structure, a known hole transport polymer material is used, and specific examples thereof include poly (3-n-hexylthiophene). ), Poly (3-n-octyloxythiophene), poly (9,9′-dioctyl-fluorene-co-bithiophene), poly (3,3 ′ ″-didodecyl-quarterthiophene), poly (3,6- Dioctylthieno [3,2-b] thiophene), poly (2,5-bis (3-decylthiophen-2-yl) thieno [3,2-b] thiophene), poly (3,4-didecylthiophene- Co-thieno [3,2-b] thiophene), poly (3,6-dioctylthieno [3,2-b] thiophene-co-thieno [3,2-b] thiophene), poly (3,6-dio Polythiophene compounds such as cutylthieno [3,2-b] thiophene-co-thiophene) and poly (3.6-dioctylthieno [3,2-b] thiophene-co-bithiophene), poly [2-methoxy-5- (2 -Ethylhexyloxy) -1,4-phenylenevinylene], poly [2-methoxy-5- (3,7-dimethyloctyloxy) -1,4-phenylenevinylene], poly [(2-methoxy-5- (2- Ethylphenylene oxy) -1,4-phenylene vinylene) -co- (4,4′-biphenylene-vinylene)] and the like, poly (9,9′-didodecylfluorenyl-2,7- Diyl), poly [(9,9-dioctyl-2,7-divinylenefluorene) -alt-co- (9,10-anthracene)], poly [(9,9 Dioctyl-2,7-divinylenefluorene) -alt-co- (4,4′-biphenylene)], poly [(9,9-dioctyl-2,7-divinylenefluorene) -alt-co- (2- Methoxy-5- (2-ethylhexyloxy) -1,4-phenylene)], poly [(9,9-dioctyl-2,7-diyl) -co- (1,4- (2,5-dihexyloxy) Benzene)] and the like, poly [2,5-dioctyloxy-1,4-phenylene], poly [2,5-di (2-ethylhexyloxy-1,4-phenylene] and other polyphenylene compounds, poly [ (9,9-Dioctylfluorenyl-2,7-diyl) -alt-co- (N, N′-diphenyl) -N, N′-di (p-hexylphenyl) -1,4-diaminobenzene] , 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-phenylenevinylene-2,5-dioctyloxy-1,4-phenylenevinylene-1,4-phenylene ], Poly [p-tolylimino-1,4-phenylenevinylene-2,5-di (2-ethylhexyloxy) -1,4-phenylenevinylene-1,4-phenylene], poly [4- (2-ethylhexyl) Polyoxyamine compounds such as (oxy) phenylimino-1,4-biphenylene], poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (1,4-benzo (2, And polythiadiazole compounds such as poly (3,4-didecylthiophene-co- (1,4-benzo (2,1 ′, 3) thiadiazole)).
Of these, polythiophene compounds and polyarylamine compounds are particularly preferred in consideration of carrier mobility and ionization potential.

Moreover, you may add various additives to the organic hole transport compound shown above.
Additives include iodine, lithium iodide, sodium iodide, potassium iodide, cesium iodide, calcium iodide, copper iodide, iron iodide, silver iodide and other metal iodides, tetraalkylammonium iodide, Quaternary ammonium salts such as pyridinium iodide, metal bromides such as lithium bromide, sodium bromide, potassium bromide, cesium bromide and calcium bromide, quaternary ammonium compounds such as tetraalkylammonium bromide and pyridinium bromide Metal chlorides such as bromine salts, copper chloride and silver chloride, metal acetates such as copper acetate, silver acetate and palladium acetate, metal sulfates such as copper sulfate and zinc sulfate, ferrocyanate-ferricyanate, ferrocene -Sulfur compounds such as metal complexes such as ferricinium ions, sodium polysulfide, alkylthiol-alkyl disulfides Viologen dye, hydroquinone, 1,2-dimethyl-3-n-propylimidazolinium iodide, 1-methyl-3-n-hexylimidazolinium iodide, 1,2-dimethyl-3-ethylimidazo Inorg. Such as lithium trifluoromethanesulfonate, 1-methyl-3-butylimidazolium nonafluorobutylsulfonate, 1-methyl-3-ethylimidazolium bis (trifluoromethyl) sulfonylimide. Chem. 35 (1996) 1168, basic compounds such as pyridine, 4-t-butylpyridine and benzimidazole, and lithium compounds such as lithium trifluoromethanesulfonylimide and lithium diisopropylimide.

  Moreover, you may add the oxidizing agent for making a part of organic hole transport compound into a radical cation for the purpose of improving electroconductivity. Examples of the oxidizing agent include tris (4-bromophenyl) aminium hexachloroantimonate, silver hexafluoroantimonate, nitrosonium tetrafluorate, and silver nitrate. It is not necessary for all organic hole transport materials to be oxidized by the addition of the oxidizing agent, and only a part of the hole transporting material needs to be oxidized. The added oxidizing agent may be taken out of the system after the addition or may not be taken out.

The organic hole transport layer is formed directly on the electron transport layer 3 carrying the photosensitizing compound. There is no restriction | limiting in particular in the preparation methods of an organic hole transport layer, The method of forming a thin film in vacuum, such as vacuum deposition, and the wet film forming method are mentioned. In consideration of the manufacturing cost and the like, a wet film forming method is particularly preferable, and a 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 performed 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 wet printing methods such as relief printing, offset, gravure, intaglio printing, rubber printing, screen printing, etc. Can be used.
The organic hole transport layer may be formed in a supercritical fluid or a subcritical fluid.

  As a supercritical fluid, it exists as a non-aggregating high-density fluid in a temperature and pressure range that exceeds the limit (critical point) at which gas and liquid can coexist, and does not aggregate even when compressed. The fluid is not particularly limited as long as it is in the above state, and can be appropriately selected according to the purpose. However, a fluid having a low critical temperature is preferable.

  This supercritical fluid includes, for example, carbon monoxide, carbon dioxide, ammonia, nitrogen, water, methanol, ethanol, ercol solvents such as n-butanol, ethane, propane, 2,3-dimethylbutane, benzene, toluene and the like. Hydrocarbon solvents, halogen solvents such as methylene chloride and chlorotrifluoromethane, and ether solvents such as dimethyl ether are preferred. 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 it can easily create a supercritical state and is nonflammable and easy to handle.

These fluids may be used alone or in combination of two or more.
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 according to the purpose.
The compound mentioned as a supercritical fluid mentioned above can be used conveniently also as a subcritical fluid.
The critical temperature and critical pressure of the supercritical fluid are not particularly limited and can be appropriately selected according to the purpose. However, the critical temperature is preferably −273 ° C. or more and 300 ° C. or less, particularly 0 ° C. or more and 200 ° C. or less. preferable.

Furthermore, in addition to the above 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 the supercritical fluid can be adjusted more easily.
Such an organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethyl formate, ethyl acetate, and n acetate. Ester solvents such as -butyl, ether solvents such as diisopropyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or N-methyl-2-pyrrolidone Amide solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene Is a halogenated hydrocarbon solvent such as 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m- Examples thereof include hydrocarbon solvents such as xylene, p-xylene, ethylbenzene, and cumene.

In this invention, after providing an organic hole transport material on the 1st electrode coat | covered with the electron transport layer comprised with the electron transport material which the photosensitizing compound adsorb | sucked, you may give a press process process. By performing this press treatment, the organic hole transport material is more closely attached to the porous electrode, so that the efficiency is improved. Although there is no restriction | limiting in particular in a press processing method, The roll molding method using the press molding method using a flat plate represented by IR tablet shaping device, a roller, etc. can be mentioned. The pressure is preferably 10 kgf / cm ² or more, more preferably 30 kgf / cm ² or more. Although there is no restriction | limiting in particular in the time to press-process, It is preferable to carry out within 1 hour. Further, heat may be applied during the pressing process.
In the above pressing process, a release material may be sandwiched between the press and the electrode. Release materials include polytetrafluoroethylene, polychlorotrifluoride ethylene, tetrafluoroethylene hexafluoropropylene copolymer, perfluoroalkoxy fluoride resin, polyvinylidene fluoride, ethylene tetrafluoride ethylene copolymer, ethylene chloro Fluorine resins such as ethylene trifluoride copolymer and polyvinyl fluoride can be mentioned.

  After performing the said press treatment process, before providing a 2nd electrode, you may provide the layer of a metal oxide between an organic hole transport compound and a 2nd electrode. Examples of the metal oxide include molybdenum oxide, tungsten oxide, vanadium oxide, and nickel oxide, and molybdenum oxide is particularly preferable.

The method for providing these metal oxide layers on the hole transport material is not particularly limited, and examples thereof include a method of forming a thin film in a vacuum such as sputtering and vacuum deposition, and a wet film forming method.
In the wet film forming method, it is preferable to prepare a paste in which a metal oxide powder or sol is dispersed and apply the paste onto the hole transport layer.
When this wet film-forming method is used, the coating method is not particularly limited, and can be performed 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 wet printing methods such as relief printing, offset, gravure, intaglio printing, rubber printing, screen printing, etc. Can be used. The film thickness is preferably from 0.1 to 50 nm, more preferably from 1 to 10 nm.

<Second electrode>
In the present invention, there are roughly two methods for forming the charge transfer layer.
One is pasting a second electrode (also called a counter electrode) opposite to the electron transport layer of the first electrode on the electron transport layer composed of an electron transport material adsorbed with a photosensitizing compound, A method in which a liquid charge transfer layer is sandwiched between the gaps, and the other is a method in which a charge transfer layer is provided directly on an electron transport layer composed of an electron transport material after adsorbing a photosensitizing compound.
In the latter case, the counter electrode is newly added thereafter.

In the former case, examples of the method for sandwiching the charge transfer layer include a normal pressure process using a capillary phenomenon due to immersion and a vacuum process in which the gas phase is replaced with a liquid phase at a pressure lower than normal pressure. In the latter case, in the wet charge transfer layer, it is necessary to provide a counter electrode without being dried to prevent liquid leakage at the edge portion. In the case of a gel electrolyte, there is a method in which it is applied in a wet manner and solidified by a method such as polymerization. In that case, you may provide a counter electrode after drying and fixing.
In addition to the electrolyte solution, the organic hole transport material solution and gel electrolyte can be applied in the same manner as the electron transport layer and the photosensitizing compound, as in the immersion method, roller method, dipping method, air knife method, and extensible method. Examples include a rouge method, a slide hopper method, a wire bar method, a spin method, a spray method, a casting method, and various printing methods.

As the counter electrode, a support having a conductive layer can be used as in the case of a normal conductive support. However, the support is not necessarily required in a configuration in which strength and sealability are sufficiently maintained.
Specific examples of the material used for the counter electrode include metals such as platinum, gold, silver, copper, aluminum, rhodium, and indium, and conductive metal oxides such as carbon, ITO, and FTO.
There is no particular limitation on the thickness of the counter electrode.

When an inorganic hole transport material or an organic hole transport material is used for the charge transfer layer, the hole collecting electrode as the second electrode is newly applied after the formation of the solid hole transport layer or on the metal oxide layer. As the hole collecting electrode, the same one as the above-described electron collecting electrode (first electrode) can be usually used, and the support is not necessarily required in a configuration in which the strength and the sealing performance are sufficiently maintained. Specific examples of hole collecting electrode materials include metals such as platinum, gold, silver, copper, and aluminum, carbon compounds such as graphite, fullerene, and carbon nanotubes, conductive metal oxides such as ITO and FTO, polythiophene, and polyaniline. And conductive polymers such as
There is no restriction | limiting in particular in the film thickness of a hole current collection electrode layer, and you may use individually or in mixture of 2 or more types. The hole collecting electrode can be applied by a method such as coating, laminating, vapor deposition, CVD, and bonding on the hole transport layer as appropriate 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 electron collector electrode and the hole collector electrode must be substantially transparent.
In the photoelectric conversion element of the present invention, a method in which the electron collecting electrode side is transparent and sunlight is incident from the electron collecting electrode side is preferable. In this case, it is preferable to use a material that reflects light on the side of the hole collecting electrode, and a metal, glass, plastic, or metal thin film on which a conductive oxide is deposited is preferable.
It is also effective to provide an antireflection layer on the sunlight incident side.

<Application>
The photoelectric conversion element of the present invention can be applied to a solar cell and a power supply device using the solar cell.
As an application example, any device using a conventional solar cell or a power supply device using the solar cell can be used.
For example, although it may be used for an electronic desk calculator or a solar cell for a wristwatch, examples of utilizing the characteristics of the solar cell using the photoelectric conversion element of the present invention include a power supply device such as a mobile phone, an electronic notebook, and electronic paper. It is done. It can also be used as an auxiliary power source for extending the continuous use time of a rechargeable or dry battery type electric appliance.

The present invention relates to the following photoelectric conversion element (1), and includes the following (2) to (7) as embodiments.
(1) A photoelectric conversion element comprising a first electrode coated with an electron transport layer and a second electrode facing the electron transport layer of the first electrode, wherein the electron transport material comprises the electron transport layer A photoelectric conversion element, wherein a diketopyrrolopyrrole derivative represented by the following general formula (1) is adsorbed.
(In general formula (1), X represents a group represented by the following general formula A,
Ar represents a thienylene group or a phenylene group,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-3. When n is plural, Ar may be the same or different. )
(2) The diketopyrrolopyrrole derivative represented by the general formula (1) is a diketopyrrolopyrrole derivative represented by the following general formula (2), wherein the photoelectric conversion element according to (1) .
(In the general formula (2), X represents a group represented by the following general formula A,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-3. )
(3) The photoelectric conversion element as described in (1) or (2), wherein the electron transporting material is an n-type oxide semiconductor composed of nanoparticles.
(4) The photoelectric conversion element according to (3), wherein the oxide semiconductor is at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide, and niobium oxide.
(5) A diketopyrrolopyrrole derivative represented by the following general formula (1).
(In general formula (1), X represents a group represented by the following general formula A,
Ar represents a thienylene group or a phenylene group,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-3. When n is plural, Ar may be the same or different. )
(6) The diketopyrrolopyrrole derivative represented by the general formula (1) is a diketopyrrolopyrrole derivative represented by the following general formula (2): Pyrrole derivative.
(In the general formula (2), X represents a group represented by the following general formula A,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-3. )
(7) A photosensitizing dye comprising the diketopyrrolopyrrole derivative according to (5) or (6).

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example.

[Example 1-1]
<Synthesis of photosensitizing compound>
(Synthesis of Exemplified Compound D-14)
A diketopyrrolopyrrole compound (3.0 g) represented by the following structural formula a, diethylene glycol 2-bromoethyl methyl ether (7.5 g), potassium carbonate (3.0 g) in acetone (100 ml) under a nitrogen stream. And stirred at reflux.

After 4 hours, the reaction residue was filtered, and the filtrate was concentrated. The concentrate was purified by silica gel column chromatography (eluent: toluene / methanol = 9/1) to obtain 5.1 g of compound b represented by the following structural formula b. Red amorphous. m / z = 593.64 (M + H). The IR spectrum of compound b is shown in FIG.
The diketopyrrolopyrrole compound represented by the structural formula a was synthesized by the method described in journal of Organic Chemistry (2011), 76 (8), 2426-2432.

  Further, the obtained compound b (1.0 g), 4-iodobenzoic acid (0.30 g), palladium acetate (0.05 g), potassium carbonate (0.2 g), and pivalic acid (0.10 g) were converted to dimethylacetamide. (20 ml) was stirred at 100 ° C. under a nitrogen stream. After 4 hours, the reaction solution was poured into methanol, and the precipitate was collected by filtration. The filtered product was purified by silica gel column chromatography (eluent: THF) to obtain 0.25 g of Exemplified Compound D-14. Red purple solid. m / z = 833.13 (M + H). An IR spectrum of Exemplified Compound D-14 is shown in FIG.

[Example 2-1]
(Production of titanium oxide semiconductor electrode)
Titanium tetra-n-propoxide (2 ml), acetic acid (4 ml), ion exchange water (1 ml), and 2-propanol (40 ml) were mixed, spin-coated on an FTO-coated glass substrate, dried at room temperature, and baked at 450 ° C. for 30 minutes in air. Using the same solution again, it was applied on the obtained electrode by spin coating so as to have a film thickness of 100 nm, and baked in air at 450 ° C. for 30 minutes to form a dense electron transport layer.

A bead mill treatment was performed for 12 hours with 3 g of titanium oxide (P-25 manufactured by Nippon Aerosil Co., Ltd.) and 0.3 g of acetylacetone together with 5.5 g of water and 1.2 g of ethanol.
A paste was prepared by adding 0.3 g of a surfactant (polyoxyethylene octylphenyl ether manufactured by Wako Pure Chemical Industries, Ltd.) and 1.2 g of polyethylene glycol (# 20,000) to the obtained dispersion.
This paste was applied onto the dense electron transport layer so as to have a film thickness of 2 μm, dried at room temperature, and then baked in air at 500 ° C. for 30 minutes to form a porous electron transport layer. The primary particle diameter of the semiconductor fine particles of the porous electron transport layer was 21 nm.

(Adsorption of photosensitized compounds)
Adsorption of photosensitized compounds was performed by supercritical fluid adsorption. In the supercritical fluid adsorption method, as shown in FIG. 2, a THF solution 14 of Exemplified Compound D-7 adjusted to 0.5 mM is placed in a pressure vessel 11, and the titanium oxide semiconductor electrode 13 is placed on a gantry 12 and the titanium oxide surface is a solution. The pressure vessel 11 was purged with CO ₂ gas. Further, the temperature and pressure were adjusted so as to be in a supercritical state, supercritical CO ₂ was formed, the photosensitized compound THF solution 14 was diffused into the pressure vessel 11, and the state was maintained for 10 minutes. After removing CO ₂ and returning to normal pressure, the electrode on which the photosensitizing compound was adsorbed was taken out of the pressure vessel 11.

(Production and evaluation of photoelectric conversion element)
As an electrolytic solution, iodine 0.05M, lithium iodide 0.1M, 1,3-dimethyl-2-imidazolinium iodide 0.6M, and t-butylpyridine 0.05M were acetonitrile / valeronitrile = 17/3. What was melt | dissolved in the liquid mixture of was used. As the counter electrode, platinum sputtered on FTO was used. A 30 μm thick spacer was sandwiched between both electrodes, and an electrolytic solution was injected to produce a photoelectric conversion element. This was irradiated with pseudo-sunlight generated from a solar simulator (AM1.5, 100 mW / cm ² ) from the working electrode side, and the photoelectric conversion element characteristics at 25 ° C. were evaluated. As a result, an open circuit voltage of 0.56 V, a short circuit current density of 9.6 mA / cm ² , a shape factor of 0.57, and a conversion efficiency of 3.06% were shown.

[Example 2-2]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the exemplified compound D-14.

[Example 2-3]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the exemplified compound D-9.

[Example 2-4]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the exemplified compound D-5.

[Example 2-5]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the exemplified compound D-8.

[Example 2-6]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the exemplified compound D-12.

[Example 2-7]
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the exemplified compound D-13.

(Comparative Example 1)
A photoelectric conversion element was produced and evaluated in the same manner as in Example 2-1, except that the exemplified compound D-7 was changed to the following comparative compound 1 in Example 2-1.

As can be seen from the above, although the comparative compound 1 is adsorbed by the supercritical fluid adsorption method, its solubility in supercritical CO ₂ is low and high conversion efficiency cannot be obtained. It can be seen that it is suitable for the critical fluid adsorption process and has good conversion efficiency.

DESCRIPTION OF SYMBOLS 1 Substrate 2 1st electrode 3 Electron transport layer 4 Photosensitizing material 5 Charge transfer layer 6 2nd electrode 7 Lead line 8 Lead line 11 Pressure vessel 12 Mount 13 Titanium oxide semiconductor electrode 14 Photosensitizing compound THF solution

Japanese Patent No. 2664194 Japanese Patent Application Laid-Open No. 11-86916 Japanese Patent Laid-Open No. 11-238925 Patent No. 5008034

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Claims (7)

A photoelectric conversion element comprising a first electrode coated with an electron transport layer and a second electrode facing the electron transport layer of the first electrode, wherein the electron transport material constituting the electron transport layer has the following general formula: A photoelectric conversion element comprising a diketopyrrolopyrrole derivative represented by (1) adsorbed thereon.
(In general formula (1), X represents a group represented by the following general formula A, Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or the following structure A group represented by formula E, n represents 0-2, m represents an integer of 1-2 , and n + m does not exceed 3. )
2. The photoelectric conversion device according to claim 1, wherein the diketopyrrolopyrrole derivative represented by the general formula (1) is a diketopyrrolopyrrole derivative represented by the following general formula (2).
(In the general formula (2), X represents a group represented by the following general formula A,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-2 . )
  The photoelectric conversion element according to claim 1, wherein the electron transporting material is an n-type oxide semiconductor made of nanoparticles.   The photoelectric conversion element according to claim 3, wherein the oxide semiconductor is at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide, and niobium oxide. A diketopyrrolopyrrole derivative represented by the following general formula (1):
(In general formula (1), X represents a group represented by the following general formula A, Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or the following structure. A group represented by formula E, n represents 0-2, m represents an integer of 1-2 , and n + m does not exceed 3.
The diketopyrrolopyrrole derivative represented by the general formula (1) is a diketopyrrolopyrrole derivative represented by the following general formula (2).
(In the general formula (2), X represents a group represented by the following general formula A,
Y represents a carboxyl group, a group represented by the following structural formula C, a group represented by the following structural formula D, or a group represented by the following structural formula E,
n represents an integer of 1-2 . )
  A photosensitizing dye comprising the diketopyrrolopyrrole derivative according to claim 5 or 6.