阅读说明：本技术 光电转换元件和太阳能电池 (Photoelectric conversion element and solar cell ) 是由 田中裕二 堀内保 兼为直道 于 2015-01-30 设计创作，主要内容包括：本申请涉及光电转换元件和太阳能电池。提供光电转换元件,其包括第一电极、空穴阻挡层、电子输送层、第一空穴输送层、和第二电极,其中所第一空穴输送层包括以下通式(1a)和通式(1b)表示的碱性化合物中的至少一种：<Image he="612" wi="679" file="DDA0002260412800000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>其中在式(1a)或(1b)中,R<Sub>1</Sub>和R<Sub>2</Sub>表示取代或未取代的烷基或芳香族烃基团,并且可以相同或不同,并且R<Sub>1</Sub>和R<Sub>2</Sub>可彼此结合形成取代或未取代的包含氮原子的杂环基团。(The present application relates to a photoelectric conversion element and a solar cell. Provided is a photoelectric conversion element including a first electrode, a hole blocking layer, an electron transport layer, a first hole transport layer, and a second electrode, wherein the first hole transport layer includes at least one of basic compounds represented by the following general formula (1a) and general formula (1 b): wherein in formula (1a) or (1b), R 1 And R 2 Represents a substituted or unsubstituted alkyl or aromatic hydrocarbon group, and may be the same or different, and R 1 And R 2 May be combined with each other to form a substituted or unsubstituted heterocyclic group containing a nitrogen atom.)

1. A solid photoelectric conversion element comprising:

a first electrode;

an electron transport layer;

a hole transport layer; and

a second electrode for applying a second voltage to the substrate,

wherein the electron transport layer comprises an electron transporting semiconductor and a photo-sensitizing material, and

wherein the hole transport layer includes an organic hole transport material and at least one of basic compounds represented by the following general formula (1a) and general formula (1 b):

wherein in formula (1a) or (1b), R₁And R₂Represents a substituted or unsubstituted alkyl or aromatic hydrocarbon group, and may be the same or different, and R₁And R₂May be combined with each other to form a substituted or unsubstituted heterocyclic group containing a nitrogen atom.

2. The solid photoelectric conversion element according to claim 1,

wherein the photo-sensitizing material is represented by the following general formula (2):

wherein in the formula, R₃Represents a substituted or unsubstituted alkyl group.

3. The solid photoelectric conversion element according to claim 1 or 2,

wherein the electron-transporting semiconductor includes at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide, and niobium oxide.

4. The solid photoelectric conversion element according to any one of claims 1 to 3,

wherein the solid photoelectric conversion element further comprises a hole blocking layer, and

wherein the hole blocking layer comprises titanium oxide.

5. The solid photoelectric conversion element according to any one of claims 1 to 4,

wherein the organic hole transport material comprises a compound selected from the group consisting of:oxadiazole compounds, triphenylmethane compounds, pyrazoline compounds, hydrazone compounds, tetraarylbenzidine compounds, stilbene compounds, and spirobifluorene compounds.

6. The solid photoelectric conversion element according to claim 5,

wherein the organic hole transporting material comprises spiro-OMeTAD.

7. The solid photoelectric conversion element according to any one of claims 4 to 6,

wherein the electron transport layer is provided on the hole blocking layer.

8. The solid photoelectric conversion element according to any one of claims 1 to 7,

wherein the hole transport layer is a first hole transport layer,

the solid photoelectric conversion element further comprises

A second hole transport layer between the first hole transport layer and the second electrode,

wherein the second hole transporting layer comprises a hole transporting polymeric material.

9. A solar cell comprising

The solid photoelectric conversion element according to any one of claims 1 to 8.

10. A photoelectric conversion element comprising:

a first electrode;

a layer of organic thin film material; and

a second electrode for applying a second voltage to the substrate,

wherein the organic thin film material layer includes at least one of basic compounds represented by the following general formula (1a) and general formula (1b), and

wherein the amount of the basic compound is 1% to 20% by weight;

wherein in formula (1a) or (1b), R₁And R₂Represents a substituted or unsubstituted alkyl or aromatic hydrocarbon group, and may be the same or different, and R₁And R₂May be combined with each other to form a substituted or unsubstituted heterocyclic group containing a nitrogen atom.

11. A solar cell comprising

The photoelectric conversion element according to claim 10.

Technical Field

The present invention relates to a method for producing a photoelectric conversion element and a solar cell.

Background

In recent years, solar cells have been increasingly important as an alternative energy source to fossil fuels and a measure against global warming. However, the conventional solar cell represented by a silicon solar cell is currently expensive, and the high cost is a factor that hinders the popularization.

Therefore, research and development of various low-cost solar cells have been promoted. Among such solar cells, dye-sensitized solar cells proposed by Graetzel et al of Swiss Federal Institute of Technology in Lausanne (see, for example, patent document 1 and non-patent documents 1 and 2) are expected to be highly practical.

The structure of the solar cell is formed by: a porous metal oxide semiconductor on a transparent conductive glass substrate; a pigment adsorbed to the surface of the porous metal oxide semiconductor; an electrolyte comprising a redox couple; and a counter electrode.

The dye-sensitized solar cells of patent document 1 and non-patent documents 1 and 2 have significantly improved photoelectric conversion efficiency by increasing the surface area and monomolecularly adsorbing a ruthenium complex compound as a dye using a porous material formed of a metal oxide semiconductor such as titanium oxide as an electrode.

In addition, since a printing technique can be applied as a method for producing a photoelectric conversion element, an expensive manufacturing facility is not required, and it is expected that the production cost can be reduced. However, the solar cell includes iodine and a volatile solvent, and has problems in that power generation efficiency may be reduced due to deterioration of an iodine redox system and an electrolyte may volatilize or leak.

As a remedy for these drawbacks, the following solid-dye-sensitized solar cell is proposed:

1) a solid dye-sensitized solar cell using an inorganic semiconductor (see, for example, non-patent documents 3 and 4);

2) a solid dye-sensitized solar cell using a low-molecular-weight organic hole transporting material (see, for example, patent document 2 and non-patent documents 5 and 6); and

3) a solid dye-sensitized solar cell using a conductive polymer (see, for example, patent document 3 and non-patent document 7).

The solar cell described in non-patent document 3 utilizes copper iodide as a material constituting the p-type semiconductor layer. Such a solar cell has relatively good photoelectric conversion efficiency immediately after production, but it is known that the photoelectric conversion efficiency is halved within several hours due to, for example, deterioration caused by increase in copper iodide crystal grains.

Therefore, the solar cell described in non-patent document 4 further contains imidazoline thiocyanate (imidiazoliniumthiocyanato) to suppress crystallization of copper iodide. However, the inhibition is insufficient.

Hagen et al reported a solid pigment-sensitized solar cell of the type using an organic hole transporting material described in non-patent document 5, and Graetzel et al improved it (see non-patent document 6).

The solid pigment-sensitized solar cell using a triphenylamine compound described in patent document 2 includes a charge transport layer formed by vacuum vapor deposition of a triphenylamine compound.

Therefore, the triphenylamine compound cannot reach the inner pores of the porous semiconductor. Therefore, it can only obtain low conversion efficiency.

In the example of non-patent document 6, a spiro-type hole transporting material is dissolved in an organic solvent, and spin coating is used to obtain a composite of nano titanium dioxide particles and the hole transporting material.

However, in such a solar cell, the optimum value of the thickness of the nano titania particle film is specified to be about 2 μm, which is much smaller than the thickness when the iodine electrolyte is used, i.e., 10 μm to 20 μm. Therefore, the amount of the dye adsorbed to the titanium oxide is low, and it is difficult to achieve sufficient light absorption and sufficient carrier generation. Therefore, the characteristics obtained when the electrolytic solution is used cannot be achieved.

As a type of solid solar cell using a conductive polymer, a solid solar cell using polypyrrole has been reported by Yanagida et al of Osaka University (Osaka University) (see non-patent document 7). Such solid-state solar cells are also only capable of obtaining low conversion efficiencies. The solid pigment-sensitized solar cell using a polythiophene derivative described in patent document 3 includes a charge transport layer formed by electrolytic polymerization on a pigment-adsorbing porous titanium oxide electrode. However, there are problems that the pigment may be desorbed from the titanium oxide and the pigment may be decomposed. In addition, polythiophene derivatives also have a significant problem in terms of durability.

Due to recent technological development, the driving power of an electronic circuit has been significantly reduced, and various electronic parts such as sensors can be driven by converting weak light such as indoor light into electricity.

In addition, it has been reported that a conventional electrolyte type dye-sensitized solar cell (using, for example, iodine) has a photoelectric conversion characteristic equal to or higher than that of an amorphous silicon solar cell under weak indoor light (see non-patent document 8).

However, this electrolyte type dye-sensitized solar cell contains iodine and the above-mentioned volatile solvent, and has problems that the power generation efficiency may be lowered due to deterioration of the iodine redox system and the electrolyte may volatilize or leak.

Also, it has been reported that when weak light such as indoor light is converted into electricity, a loss current due to the internal impedance of the photoelectric conversion element is significant (see non-patent document 9).

When the internal impedance increases, the short-circuit current density deteriorates and the photoelectric conversion characteristics deteriorate. When the internal impedance is lowered, the open circuit voltage is deteriorated and the photoelectric conversion characteristic is deteriorated. That is, it is difficult to satisfy both: a raised internal impedance; and good photoelectric conversion characteristics.

The photoelectric conversion element obtains a lower open circuit voltage under weak light such as indoor light, as compared with simulated sunlight. Therefore, in order to obtain an output voltage required for driving the electronic circuit, it is necessary to obtain a high open-circuit voltage.

Hitherto, an alkaline substance capable of achieving a high open circuit voltage has been reported (see non-patent document 10). However, in a dye-sensitized solar cell of the type using an electrolytic solution such as iodine, no alkaline material can achieve a more excellent photoelectric conversion characteristic than 4-t-butylpyridine used hitherto.

As described above, in the present situation, satisfactory characteristics have not been obtained yet for solid-state photoelectric conversion elements studied so far.

Reference list

Patent document

Patent document 1: japanese patent No. 2664194

Patent document 2: japanese unexamined patent application publication No. 11-144773

Patent document 3: japanese unexamined patent application publication No. 2000-106223

Non-patent document

Non-patent document 1: nature, 353(1991)737

Non-patent document 2: j.am.chem.soc., 115(1993)6382

Non-patent document 3: Semicond.Sci.Technol, 10(1995)1689

Non-patent document 4: electrochemistry, 70(2002)432

Non-patent document 5: synthetic Metals, 89(1997)215

Non-patent document 6: nature 398(1998)583

Non-patent document 7: hem, Lett., (1997)471

Non-patent document 8: panasonic Technical Report, 56(2008)87

Non-patent document 9: fujikura Technical Report, 121(2011)42

Non-patent document 10: solar Energy Materials & Solar Cells, 181(2004)87

Non-patent document 11: chem., 67(2002)3029

Disclosure of Invention

Technical problem

An object of the present invention is to solve the above-described problems and to provide a solid-state photoelectric conversion element having more excellent photoelectric conversion characteristics than heretofore obtained.

Problem solving scheme

As a result of the earliest studies to solve the above problems, it has been found that a high-performance solid photoelectric conversion element can be provided by allowing a hole transport layer to contain a specific basic compound. Based on this finding, the present invention has been achieved.

That is, the problem is solved by: a photoelectric conversion element includes a first electrode, a hole blocking layer, an electron transport layer, a first hole transport layer, and a second electrode, wherein the first hole transport layer contains at least one of basic compounds represented by the following general formula (1a) and general formula (1 b).

In the formulae (1a) or (1b) to R₁And R₂Represents a substituted or unsubstituted alkyl or aromatic hydrocarbon group, and may be the same or different, and R₁And R₂May be combined with each other to form a substituted or unsubstituted heterocyclic group containing a nitrogen atom.

Effects of the invention

The present invention can provide a solid photoelectric conversion element having more excellent photoelectric conversion characteristics than those obtained heretofore.

Drawings

Fig. 1 is an example schematic diagram illustrating a cross section orthogonal to the lamination direction of the photoelectric conversion element structure of the present invention.

Detailed Description

The configurations of the photoelectric conversion element and the solar cell will be described below with reference to fig. 1.

Fig. 1 is an exemplary schematic diagram illustrating a cross section orthogonal to the lamination direction of a photoelectric conversion element and a solar cell.

In the embodiment illustrated in fig. 1, the configuration includes a first electrode 2 on a substrate 1, a hole blocking layer 3 formed of titanium oxide, an electron transport layer 4, a photosensitizing material 5 adsorbed to the electron transport layer, and a hole transport layer 6 provided between the photosensitizing material and a second electrode 7.

< first electrode >

The first electrode 2 is not particularly limited as long as the first electrode 2 is a conductive material transparent to visible light. A known conductive material used for, for example, a general photoelectric conversion element or a liquid crystal panel can be used.

Examples of the material of the first electrode 2 include indium tin oxide (hereinafter, ITO), fluorine-doped tin oxide (hereinafter, FTO), antimony-doped tin oxide (hereinafter, ATO), indium zinc oxide, niobium titanium oxide, and graphene (graphene). One of these materials may be deposited alone, or more than one of these materials may be layered.

The thickness of the first electrode 2 is preferably 5nm to 100 μm, more preferably 50nm to 10 μm.

It is preferable that the first electrode 2 is provided on the substrate 1 formed of a material transparent to visible light so as to maintain the hardness constant. For example, glass, a transparent plastic plate, a transparent plastic film, or an inorganic transparent crystalline body is used for the substrate 1.

A known integration of the first electrode 2 and the substrate 1 may also be used. Examples of the integrated body include FTO-coated glass, ITO-coated glass, zinc oxide: aluminum coated glass, FTO coated transparent plastic films, and ITO coated transparent plastic films.

It is also possible to use products such as: in which a tin oxide or indium oxide transparent electrode doped with cations or anions having different valence states or a metal electrode forming a light-transmitting structure such as a mesh or a stripe is provided on a substrate such as a glass substrate.

One of these materials may be used alone, or two or more of these materials may be mixed or laminated. In addition, in order to reduce the impedance, for example, a metal wire may be used in combination.

Examples of the material of the metal wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. The metal wire may be formed by: metal wires are arranged on the substrate 1 by, for example, vapor deposition, sputtering, or crimping, and ITO or FTO is provided on the metal wires.

< hole-blocking layer >

The hole blocking layer 3 is not particularly limited as long as the hole blocking layer is transparent to visible light and is an electron transporting material. However, titanium oxide is particularly preferred. In order to suppress the loss current to make the use possible under weak light such as indoor light, it is necessary to provide high internal resistance, and a film formation method of titanium oxide to form the hole blocking layer 3 is also important.

Examples of general methods for forming a titanium oxide film include a sol-gel method and a titanium tetrachloride hydrolysis method, i.e., wet film formation. However, the impedance obtained is slightly lower. Sputtering, dry film formation, is more preferable.

To prevent electron contact between the first electrode 2 and the hole transport layer 6, the hole blocking layer 3 is formed. The thickness of the hole-blocking layer 3 is not particularly limited, but is preferably 5nm to 1 μm, more preferably 500nm to 700nm, for wet film formation, and more preferably 10nm to 30nm for dry film formation.

< Electron transport layer >

The photoelectric conversion element and the solar cell of the present invention include the porous electron transport layer 4 on the hole blocking layer 3. The porous electron transport layer 4 may comprise a single layer or multiple layers.

In the case of multiple layers, the multiple layers may be formed by applying a dispersion of semiconductor particles having different particle diameters, or may also be formed by applying different kinds of semiconductors or different resin or additive compositions.

Multilayer coating is an effective means when a sufficient thickness is not obtained by one coating.

In general, as the thickness of the electron transport layer increases, the amount of photosensitizing material carried per unit projected area of the electron transport layer 4 increases, resulting in an increase in the capture rate. However, this also increases the diffusion distance of the injected electrons, thereby increasing the loss due to charge recombination.

Therefore, the thickness of the electron transport layer 4 is preferably 100nm to 100 μm.

The semiconductor is not particularly limited, and a known semiconductor can be used.

Specific examples of the semiconductor include elemental semiconductors such as silicon and germanium, compound semiconductors typified by metal chalcogenides, and compounds having a perovskite structure.

Examples of metal chalcogenides include: oxides of titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, and tantalum; sulfides of cadmium, zinc, lead, silver, antimony, and bismuth; selenides of cadmium and lead; and cadmium telluride.

Examples of other compound semiconductors include: phosphides such as zinc, gallium, indium, and cadmium; gallium-arsenide; copper-indium-selenide; and copper-indium-sulfide.

Examples of the compound having a perovskite structure include strontium titanate, calcium titanate, sodium titanate, barium titanate, and potassium niobate. One of these semiconductors may be used alone, or two or more of these semiconductors may be mixed for use.

Among these semiconductors, an oxide semiconductor is preferable, and titanium oxide, zinc oxide, tin oxide, and niobium oxide are particularly preferable. The crystal type of these semiconductors is not particularly limited, and may be single crystal, polycrystalline, or amorphous.

The size of the semiconductor particles is not particularly limited. However, the average diameter of the primary particles is preferably 1nm to 100nm, more preferably 5nm to 50 nm.

Efficiency can also be improved based on the incident light scattering effect obtained by mixing or stacking semiconductor particles having a larger average particle diameter. In this case, the average particle diameter of the semiconductor particles is preferably 50nm to 500 nm.

The method of producing the electron transport layer 4 is not particularly limited. Examples of the method include a method of forming a thin film in vacuum such as sputtering, and a wet film formation method.

When production cost and other factors are taken into consideration, a wet film formation method is preferable, and a method of preparing a slurry in which a semiconductor particle powder or a sol is dispersed and coating an electron collecting electrode substrate with the slurry is more preferable.

When a wet film-forming method is used, the coating method is not particularly limited and may be performed according to a known method. Examples of the coating method include a dip coating method, a spray coating method, a wire bar method, a spin coating method, a roll coating method, a blade coating method, and a gravure coating method. In addition, as the wet printing method, various methods such as relief printing, offset printing, intaglio printing, flexographic printing, and screen printing can be employed.

In producing a semiconductor particle dispersion by mechanical pulverization or with a grinder, a dispersion is formed by dispersing at least semiconductor particles alone or a mixture of semiconductor particles and a resin in water or an organic solvent.

Examples of the resin include polymers or copolymers based on vinyl compounds such as styrene, vinyl acetate, acrylic esters, and methacrylic esters, silicone resins, phenoxy resins, polysulfone resins, polyvinyl butyral resins, polyvinyl formal resins, polyester resins, cellulose ester resins, cellulose ether resins, polyurethane resins, phenol resins, epoxy resins, polycarbonate resins, polyallyl ester resins, polyamide resins, and polyimide resins.

Examples of the solvent in which the semiconductor particles are dispersed include water; alcohol-based solvents such as methanol, ethanol, isopropanol, and α -terpineol; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based solvents such as ethyl formate, ethyl acetate, and n-butyl acetate; ether-based solvents, such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, and dioxane

An alkane; amide-based solvents such as N, N-dimethylformamide, N-dimethylacetamide, and N-methyl-2-pyrrolidone; halogenated hydrocarbon solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, and 1-chloronaphthalene; and hydrocarbon-based solvents such as n-pentane, n-hexane, n-octane, 1, 5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene. Can be used forOne of these solvents is used alone, or two or more of these solvents may be used as a mixed solvent.

To prevent the particles from reagglomerating, for example, acids such as hydrochloric acid, nitric acid, and acetic acid; surfactants such as polyoxyethylene (10) octylphenyl ether; and chelating agents such as acetylacetone, 2-aminoethanol, and ethylenediamine are added to the semiconductor particle dispersion liquid or the semiconductor particle paste obtained by, for example, a sol-gel method.

In addition, it is effective to add a thickener to improve film formability.

Examples of the tackifier include polymers such as polyethylene glycol and polyvinyl alcohol and tackifiers such as ethyl cellulose.

In order to provide electron contact between particles, improve film strength, and improve adhesion to a substrate, it is preferable to perform firing, microwave irradiation, electron beam irradiation, or laser irradiation on the semiconductor particles after coating. These treatments may be applied alone, or two or more of these treatments may be applied in combination.

In firing, the firing temperature is not limited to a specific range, but is preferably 30 ℃ to 700 ℃, more preferably 100 ℃ to 600 ℃, because if the temperature is too high, the resistance of the substrate may increase or the substrate may melt. The firing time is also not particularly limited, but is preferably 10 minutes to 10 hours.

The microwave irradiation may be given from the electron transport layer 4 formation side or the back side.

The irradiation time is not particularly limited, but is preferably within 1 hour.

After firing, in order to increase the surface area of the semiconductor particles and increase the electron injection efficiency from the photosensitizing material to the semiconductor particles, chemical plating using an aqueous titanium tetrachloride solution or a mixed solution with an organic solvent, or electrochemical plating treatment using an aqueous titanium trichloride solution may be performed.

A porous state is formed in a film obtained by depositing semiconductor particles having a diameter of several tens of nanometers by, for example, sintering. Such nanoporous structures have a very large surface area. The surface area may be represented by a roughness factor.

The roughness factor is a numerical value representing the actual area inside the porous texture relative to the area of coating of the semiconductor particles on the substrate. Therefore, a larger roughness factor is more preferable. However, in view of the relationship with the film thickness of the electron transport layer 4, the roughness factor is preferably 20 or more in the present invention.

< photo-sensitizing Material >

In the present invention, to further improve the conversion efficiency, the photosensitizing material is adsorbed to the surface of the electron transporting semiconductor, that is, the electron transporting layer 4. The substance represented by the general formula (2) is preferable as the photosensitizing material.

In the formula, R₃Represents a substituted or unsubstituted alkyl group.

Specific exemplary compounds of the general formula (2) will be shown below. These compounds are non-limiting examples.

The compounds represented by the general formula (2) can be synthesized by the method described in Dye and Pigments 91(2011) pp.145-152.

The photo-sensitizing material 5 is not limited to the above-mentioned compounds as long as the photo-sensitizing material is a compound that can be photo-excited by the excitation light used. Specific examples of the light-sensitizing material also include the following.

Specific examples of the light-sensitizing material include: metal complex compounds described in, for example, Japanese translation of PCT International application publication No. JP-T-07-500630, Japanese unexamined patent application publication Nos. 10-233238, 2000-; coumarin compounds described in, for example, Japanese unexamined patent application publication Nos. 10-93118, 2002-164089 and 2004-95450, and J.Phys.chem.C, 7224, Vol.111 (2007); polyene compounds described in, for example, japanese unexamined patent application publication nos. 2004-95450 and chem.commun., 4887 (2007); indoline compounds described in, for example, japanese unexamined patent application publication nos. 2003-264010, 2004-63274, 2004-115636, 2004-200068, and 2004-235052, j.am.chem.soc., 12218, vol.126(2004), chem.commun., 3036(2003), and angelw.chem.int.ed., 1923, vol.47 (2008); thiophene compounds described, for example, in j.am.chem.soc., 16701, vol.128(2006) and j.am.chem.soc., 14256, vol.128 (2006); cyanine pigments described in, for example, Japanese unexamined patent application publication Nos. 11-86916, 11-214730, 2000-106224, 2001-76773, and 2003-7359; cyanine pigments described in, for example, Japanese unexamined patent application publication Nos. 11-214731, 11-238905, 2001-52766, 2001-76775, and 2003-7360; 9-arylxanthene compounds described in, for example, Japanese unexamined patent application publication Nos. 10-92477, 11-273754, 11-273755, and 2003-31273; compounds described in, for example, Japanese unexamined patent application publication Nos. 10-93118 and 2003-31273; and phthalocyanine compounds and porphyrin compounds described in, for example, japanese unexamined patent application publication nos. 09-199744, 10-233238, 11-204821 and 11-265738, j.phys.chem., 2342, vol.91(1987), j.phys.chem.b, 6272, vol.97(1993), electroananal.chem., 31, vol.537(2002), japanese unexamined patent application publication nos. 2006-032260, j.porphyrins Phthalocyanines, 230, vol.3(1999), angelw.chem.int.ed., 373, vol.46(2007), and Langmuir, 5436, vol.24 (2008).

Among these photosensitizing materials, metal complex compounds, coumarin compounds, polyene compounds, indoline compounds, and thiophene compounds are preferable.

As a method of adsorbing the photosensitizing material 5 to the electron transport layer 4, a method of immersing an electron collecting electrode containing semiconductor particles in a photosensitizing material solution or dispersion, and a method of coating the electron transport layer with the solution or dispersion to adsorb the photosensitizing material can be employed.

As a method of dipping the electron collecting electrode containing the semiconductor particles into the photo-sensitizing material solution or dispersion, for example, a dipping method, a dip coating method, a roll coating method, and a gas knife method can be employed.

As a method for coating the electron transport layer with a solution or a dispersion to adsorb the photo-sensitizing material, for example, a wire bar method, a slide hopper method, an extrusion method, a curtain coating method, a spin coating method, and a spray coating method can be employed.

The photosensitizing material can be adsorbed under supercritical fluid using, for example, carbon dioxide.

When the photosensitizing material 5 is adsorbed, a condensing agent may be used in combination.

The condensing agent may be any of the following: a substance that exhibits a physical or chemical bond that catalyzes the physical or chemical binding of a photosensitizing material and an electron transporting compound to the surface of an inorganic substance; and substances that act stoichiometrically to cause favorable shifts in chemical equilibrium.

In addition, a thiol or hydroxyl compound may be added as a condensation assistant.

Examples of the solvent that dissolves or disperses the photosensitizing material 5 include: water; alcohol-based solvents such as methanol, ethanol, and isopropanol; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based solvents such as ethyl formate, ethyl acetate, and n-butyl acetate; ether-based solvents, such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, and dioxane

An alkane; amide-based solvents such as N, N-dimethylformamide, N-dimethylacetamide, and N-methyl-2-pyrrolidone; halogenated hydrocarbon solvents such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, and 1-chloronaphthalene; and hydrocarbon-based solvents such as n-pentane, n-hexane, n-octane, 1, 5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene. One of these solvents may be used alone, or a mixture of two or more of these solvents may be used.

Some classes of photosensitizing materials work more effectively when aggregation between different compounds is inhibited. Therefore, an aggregation-dissociation agent may be used in combination.

As the agglutination dissociation agent, steroid compounds such as cholic acid and chenodeoxycholic acid, long-chain alkyl carboxylic acids, or long-chain alkyl phosphonic acids are preferable. An appropriate aggregation-dissociation agent is selected depending on the pigment used.

The addition amount of the aggregation-dissociation agent is preferably 0.01 to 500 parts by mass, more preferably 0.1 to 100 parts by mass, relative to 1 part by mass of the pigment.

The temperature at which the photosensitizing material is adsorbed alone or the temperature at which the photosensitizing material and the aggregation-dissociation agent are adsorbed is preferably-50 ℃ or higher but 200 ℃ or lower.

The adsorption may be carried out in a static state or under stirring.

The stirring method is not particularly limited and may be appropriately selected depending on the intended purpose. Examples of the method include an agitator, 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 but 1,000 hours or less, more preferably 10 seconds or more but 500 hours or less, and still more preferably 1 minute or more but 150 hours or less.

In addition, it is preferable to perform adsorption in a dark place.

< hole transport layer >

The hole transporting material 6 is not particularly limited and may be appropriately selected depending on the intended purpose, as long as the hole transporting material contains an organic hole transporting material and at least one of the basic compounds represented by the general formulae (1a) and (1 b).

As a general hole transporting layer, for example, an electrolytic solution obtained by dissolving a redox couple in an organic solvent, a gel electrolyte obtained by immersing a liquid obtained by dissolving a redox couple in an organic solvent into a polymer matrix, a molten salt containing a redox couple, a solid electrolyte, an inorganic hole transporting material, and an organic hole transporting material are used.

< organic hole transporting Material >)

The organic hole transport material can be used for the hole transport layer 6 having a single-layer structure formed of a single material and the hole transport layer 6 having a laminated structure formed of a plurality of compounds.

As the organic hole transporting material used in the single-layer structure formed of a single material, a known organic hole transporting compound is used.

Specific examples of known organic hole transporting compounds include:

oxadiazole compounds, shown in, for example, Japanese unexamined patent publication No. 34-5466; triphenylmethane compounds, shown in, for example, Japanese unexamined patent publication No. 45-555; pyrazoline compounds shown in, for example, Japanese unexamined patent publication No. 52-4188; hydrazone compounds, shown in, for example, Japanese unexamined patent publication No. 55-42380;

oxadiazole compounds, shown in, for example, Japanese unexamined patent application publication No. 56-123544; tetraarylbenzidine compounds, shown in Japanese unexamined patent application publication No. 54-58445; stilbene compounds shown in Japanese unexamined patent application publication No. 58-65440 or Japanese unexamined patent application publication No. 60-98437; and spirobifluorene-based compounds, such as spiro-OMeTAD described by adv.mater., 813, vol.17, (2005).

Among these organic hole transporting compounds, the above-mentioned hole transporting material called spiro-OMeTAD is preferable because such a hole transporting material exhibits excellent photoelectric conversion characteristics.

In the hole transport layer 6 used in the form of a laminated structure, a known hole-transporting polymer material is used as a polymer material used in the vicinity of the second electrode 7.

Specific examples of known hole-transporting polymer materials include:

polythiophene compounds, such as poly (3-n-hexylthiophene), poly (3-n-octyloxythiophene), poly (9,9 '-dioctyl-fluorene-co-bithiophene), poly (3, 3' -dodecyl-tetrathiophene), poly (3, 6-dioctylthieno [3,2-b ] thiophene), poly (2, 5-bis (3-decylthiophen-2-yl) thieno [3,2-b ] thiophene), poly (3, 4-dodecylthiophene-co-thieno [3,2-b ] thiophene), poly (3, 6-dioctylthieno [3,2-b ] thiophene-co-thieno [3,2-b ] thiophene), poly (3, 6-dioctylthieno [3,2-b ] thiophene-co-thiophene), and poly (3.6-dioctylthieno [3,2-b ] thiophene-co-bithiophene);

polyphenylene vinylene compounds such as poly [ 2-methoxy-5- (2-ethylhexyloxy) -1, 4-phenylene vinylene ], poly [ 2-methoxy-5- (3, 7-dimethyloctyloxy) -1, 4-phenylene vinylene ], and poly [ (2-methoxy-5- (2-ethylp-hexyloxy) -1, 4-phenylene vinylene) -co- (4,4' -bisphenylene-vinylene) ];

polyfluorene compounds, such as poly (9,9 '-dodecylfluorenyl-2, 7-diyl), poly [ (9, 9-dioctyl-2, 7-divinylidenefluorene) -alt-co- (9, 10-anthracene) ], poly [ (9, 9-dioctyl-2, 7-divinylidenefluorene) -alt-co- (4,4' -biphenylene) ], poly [ (9, 9-dioctyl-2, 7-divinylidenefluorene) -alt-co- (2-methoxy-5- (2-ethylhexyloxy) -1, 4-phenylene) ], and poly [ (9, 9-dioctyl-2, 7-diyl) -co- (1,4- (2, 5-dihexyloxy) benzene) ];

polyphenylene compounds such as poly [2, 5-dioctyloxy-1, 4-phenylene ] and poly [2, 5-di (2-ethylhexyloxy-1, 4-phenylene ];

polyarylamine compounds, such as 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-di-phenylene) ], 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-bis (2-ethylhexyloxy) -1, 4-phenylenevinylene-1, 4-phenylene ], and poly [4- (2-ethylhexyloxy) phenylimino-1, 4-bisphenylene ]; and

polythiadiazole compounds, such as poly [ (9, 9-dioctylfluorenyl-2, 7-diyl) -alt-co- (1, 4-benzo (2,1',3) thiadiazole) ] and poly (3, 4-dodecylthiophene-co- (1, 4-benzo (2,1',3) thiadiazole).

Among these hole-transporting polymer materials, polythiophene compounds and polyarylamine compounds are particularly preferable in view of the degree of carrier mobility and ionization potential.

Various additives may be added to the organic hole transporting material.

Examples of additives include: iodine; metal iodides such as 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 pyridine iodide; metal bromides such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, and calcium bromide; bromine salts of quaternary ammonium compounds, such as tetraalkylammonium bromide and pyridine 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 sulfate and zinc sulfate; metal complexes such as ferrocyanide (ester) -ferricyanate and ferrocene-ferrocenium ion (ferrocene-ferricinium ion); sulfur compounds, such as sodium polysulfide and alkylthiol-alkyldisulfide; viologen pigments, hydroquinones, and the like; ionic liquids described by inorg. chem.35(1996)1168, such as 1, 2-dimethyl-3-n-propylimidazoline iodide, 1-methyl-3-n-hexylimidazoline iodide, 1, 2-dimethyl-3-ethylimidazole trifluoromethanesulfonate, 1-methyl-3-butylimidazole nonafluorobutylsulfonate, and 1-methyl-3-ethylimidazole bis (trifluoromethyl) sulfonimide; basic compounds such as pyridine, 4-t-butylpyridine, and benzimidazole; and lithium compounds such as lithium trifluoromethanesulfonylimide and lithium diisopropylimide.

< basic Compound >)

In the present invention, a particularly high open circuit voltage can be obtained by adding a basic compound represented by the following general formula (1a) or general formula (1b) to an organic hole transporting material.

In addition, the internal impedance of the photoelectric conversion element is increased, and the loss current can be reduced under weak light such as indoor light. Therefore, a higher open circuit voltage than that obtained by the existing basic compound can be obtained.

In the formula (1a) or (1b), R₁And R₂Represents substituted or notSubstituted alkyl or aromatic hydrocarbon radicals, and may be identical or different, and R₁And R₂May be combined with each other to form a substituted or unsubstituted heterocyclic group containing a nitrogen atom. Examples of the substituent include an alkyl group, an aromatic hydrocarbon group, and a substituted or unsubstituted alkoxy group.

Hitherto, there have been known compounds having a structure similar to general formula (1a) or general formula (1b) and classified as the following basic compounds. Some of these compounds have been known to be used as alkaline compounds for iodine electrolyte type dye-sensitized solar cells. These compounds provide high open circuit voltage, but have been reported to greatly reduce short circuit current density and significantly deteriorate photoelectric conversion characteristics.

The hole transport layer 6 uses the above-described organic hole transport material, and is different from a hole transport model based on an iodine electrolyte or the like.

Therefore, the reduction amount of the short-circuit current density is small and a high open-circuit voltage can be obtained, so that excellent photoelectric conversion characteristics can be obtained. In addition, it can be verified that particularly outstanding excellent performance is exhibited at the time of photoelectric conversion under weak light such as indoor light. Such photoelectric conversion is a rare reported case.

Specific exemplary compounds of the general formula (1a) or the general formula (1b) are shown in table 1 (tables 1 to 1 and 1 to 2) below. However, these compounds are non-limiting examples.

TABLE 1-1

Tables 1 to 2

The amount of the basic compound represented by the general formula (1a) or the general formula (1b) added to the hole transport layer 6 is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less, with respect to 100 parts by mass of the organic hole transport material.

< method for synthesizing the basic Material (1a) or (1b) used in the present invention >

The basic material can be easily synthesized by the following route in the same manner as in the report (j. org. chem., 67(2002) 3029).

In the formulae (a) and (b), R₁And R₂Represents a substituted or unsubstituted alkyl or aromatic hydrocarbon group, and may be the same or different. R₁And R₂May be combined with each other to form a substituted or unsubstituted heterocyclic group containing a nitrogen atom. X represents a halogen.

To improve conductivity, an oxidizing agent that changes a portion of the organic hole transporting material into radical cations may be added.

Examples of the oxidizing agent include ammonium tris (4-bromophenyl) hexachloroantimonate, silver hexafluoroantimonate, nitrosotetrafluoroborate, silver nitrate, and cobalt complex-based compounds s.

It is not necessary to oxidize all of the organic hole transporting material by adding an oxidizing agent. Only a portion of the organic hole transporting material needs to be oxidized. Whether the added oxidizing agent is removed outside the system after addition is optional.

The hole transport layer 6 is formed directly on the electron transport layer 4 carrying the photo-sensitizing material. The method for producing the hole transport layer 6 is not particularly limited. Examples of the method include a method of forming a thin film in vacuum such as vacuum vapor deposition, and a wet film formation method. In view of the manufacturing cost and other factors, a wet film-forming method is particularly preferable, and a method of coating the electron transport layer 4 with a hole transport layer is preferable.

When a wet film-forming method is employed, the coating method is not particularly limited and may be performed according to a known method. Examples of the coating method include a dip coating method, a spray coating method, a wire bar method, a spin coating method, a roll coating method, a blade coating method, and a gravure coating method. In addition, as the wet printing method, various methods such as relief printing, offset printing, intaglio printing, flexographic printing, and screen printing can be employed.

The film formation may be performed under a supercritical fluid or a subcritical fluid having a temperature/pressure lower than the critical point.

The supercritical fluid is not particularly limited and may be appropriately selected depending on the intended purpose, as long as the supercritical fluid exists as a non-agglutinative high-density fluid in a temperature and pressure range higher than the limit (critical point) at which a gas and a liquid can coexist, and does not agglutinate even when compressed, but is still a fluid in a state above the critical temperature or above the critical pressure. However, supercritical fluids with low critical temperatures are preferred.

Preferred examples of the supercritical fluid include carbon monoxide, carbon dioxide, ammonia, nitrogen, water, alcohol-based solvents such as methanol, ethanol, and n-butanol, hydrocarbon-based solvents such as ethane, propane, 2, 3-dimethylbutane, benzene, and toluene, halogen-based solvents such as dichloromethane and chlorotrifluoromethane, and ether-based solvents such as dimethyl ether. Among these supercritical fluids, carbon dioxide is particularly preferable because carbon dioxide has a critical pressure of 7.3MPa and a critical temperature of 31 ℃, and thus can be easily formed into a supercritical state and is nonflammable and easy to handle.

One of these fluids may be used alone, or a mixture of two or more of these fluids may be used.

The subcritical fluid is not particularly limited and may be appropriately selected depending on the intended purpose, as long as the subcritical fluid exists as a high-pressure liquid in the temperature and pressure range near the critical point.

The compounds mentioned as examples of supercritical fluids may also be suitable for use as subcritical fluids.

The critical temperature and critical pressure of the supercritical fluid are not limited and may be appropriately selected depending on the intended purpose. However, the critical temperature is preferably from-273 ℃ to 300 ℃ inclusive, and particularly preferably from 0 ℃ to 200 ℃ inclusive.

In addition to the supercritical fluid and the subcritical fluid, an organic solvent and an entrainer may be used in combination.

The addition of organic solvents and entrainers renders the adjustment of the solubility in the supercritical fluid easier.

The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples of the organic solvent include: ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based solvents such as ethyl formate, ethyl acetate, and n-butyl acetate; ether-based solvents, such as diisopropyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, and bis

An alkane; amide-based solvents such as N, N-dimethylformamide, N-dimethylacetamide, and N-methyl-2-pyrrolidone; halogenated hydrocarbon solvents, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, and 1-chloronaphthalene; and hydrocarbon-based solvents such as n-pentane, n-hexane, n-octane, 1, 5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene.

After the organic hole transporting material is provided on the first electrode 2 provided with the electron transporting material coated with the photo-sensitizing material, a pressure treatment step may be performed.

It is considered that the pressure treatment results in stronger adhesion of the organic hole transport material to the porous electrode, thereby improving efficiency.

The pressure treatment method is not particularly limited. Examples of the method include a press molding method using a flat plate typified by an IR lozenge former and a rolling method using, for example, a roller.

The pressure at the time of pressure treatment is preferably 10kgf/cm²Above, more preferably 30kgf/cm²The above. The time for performing the pressure treatment is not particularly limited, but is preferably within 1 hour.

Heating can be carried out during the pressure treatment.

During the pressure treatment, the release material may be sandwiched between the press and the electrode.

Examples of the release material include fluorine resins such as polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, perfluoroalkoxy fluorine resin, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and polyvinyl fluoride.

After the pressure treatment step, before the counter electrode is disposed, a metal oxide may be provided between the organic hole transporting material and the second electrode 7. Examples of the metal oxide include molybdenum oxide, tungsten oxide, vanadium oxide, and nickel oxide. Among these metal oxides, molybdenum oxide is particularly preferable.

As described above, the hole transport layer 6 may have a single-layer structure formed of a single material or a laminated structure formed of a plurality of compounds. In the case of a laminated structure, it is preferable to use a polymer material in the organic hole transporting material layer adjacent to the second electrode 7.

This is because the use of a polymer material excellent in film formability can render the surface of the porous electron transport layer 4 smoother and can improve the photoelectric conversion characteristics.

In addition, the polymer material hardly permeates the inside of the porous electron transport layer 4. This in turn makes the polymer material excellent in coating the surface of the porous electron transport layer 4 and effectively prevents short circuits when the electrode is disposed, resulting in higher performance.

< second electrode >

The method of providing the metal oxide on the organic hole transporting material is not particularly limited. Examples of the method include a method of forming a thin film in vacuum such as sputtering and vacuum vapor deposition, and a wet film formation method.

As the wet film formation method, a method of preparing a paste obtained by dispersing a powder or a sol of a metal oxide and coating the hole transport layer 6 with the paste is preferable.

When the wet film-forming method is applied, the coating method is not particularly limited and may be performed according to a known method. Examples of the coating method include a dip coating method, a spray coating method, a wire bar method, a spin coating method, a roll coating method, a blade coating method, and a gravure coating method. In addition, as the wet printing method, various methods such as relief printing, offset printing, intaglio printing, flexographic printing, and screen printing can be employed. The thickness of the second electrode is preferably 0.1nm to 50nm, more preferably 1nm to 10 nm.

The second electrode 7 is newly provided after the formation of the hole transport layer 6, or is newly provided on the metal oxide.

In general, the same configuration as that of the first electrode 2 described above can be applied as the second electrode 7. The support is not indispensable for its structural strength and sealing performance to be sufficiently maintained.

Examples of the material of the second electrode 7 include: metals, such as platinum, gold, silver, copper, and aluminum; carbon-based compounds such as graphite, fullerene, carbon nanotube, and graphene; conductive metal oxides such as ITO, FTO, and ATO; and conductive polymers such as polythiophene and polyaniline.

The thickness of the second electrode 7 is not particularly limited. Therefore, the material of the second electrode 7 may be used alone, or two or more of the materials may be used in a mixture.

The second electrode 7 may be coated by an appropriate method such as coating, lamination, vapor deposition, CVD, and attachment of the hole transport layer 6, depending on the kind of the material used and the kind of the hole transport layer 6.

To be able to function as a dye-sensitized solar cell, at least one of the first electrode 2 and the second electrode 7 needs to be substantially transparent.

In the dye-sensitized solar cell of the present invention, the first electrode 2 is transparent. It is preferable that the sunlight is made incident from the first electrode 2 side. In this case, it is preferable to use a light reflective material on the second electrode 7 side. Metals, glass of vapor deposited conductive oxides, plastics, and metal films are preferred.

In addition, it is effective means to provide an antireflection layer on the sunlight incident side.

< application >

The dye-sensitized solar cell of the present invention can be applied to a power supply device using a solar cell.

Examples of applications include all machine types that have heretofore utilized solar cells or power supply devices employing solar cells.

Needless to say, the pigment-sensitized solar cell can be used as a solar cell for, for example, a desktop electronic calculator or a wristwatch. However, a power supply device to be equipped on, for example, a portable phone, an electronic organizer, and electronic paper can be proposed as an example of utilizing the features of the photoelectric conversion element of the present invention. In addition, an auxiliary power supply for the purpose of extending the continuous use time of a rechargeable or dry-cell operated electrical appliance may be proposed as an application example.