WO2009145140A1

WO2009145140A1 - Dye-sensitized solar cell

Info

Publication number: WO2009145140A1
Application number: PCT/JP2009/059518
Authority: WO
Inventors: 隆彦野島; 修石毛; 貴宗服部
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2008-05-27
Filing date: 2009-05-25
Publication date: 2009-12-03
Also published as: JPWO2009145140A1

Abstract

Provided is a dye-sensitized solar cell having a high open voltage and also durability even when stored at a high temperature. The dye-sensitized solar cell sequentially has a porous n-type semiconductor electrode wherein a dye is adsorbed on the surface, a charge transfer layer and a counter electrode on a conductive base material. The charge transfer layer contains a radical compound composed of N-oxyl derivatives.

Description

Dye-sensitized solar cell

The present invention relates to a dye-sensitized solar cell using, as a charge transfer layer, an electrolyte containing an organic compound that generates a radical compound in at least one of an electrochemical oxidation reaction or a reduction reaction.

In recent years, as environmental and energy problems such as global warming have become more serious due to the burning of fossil fuels and the increase in carbon dioxide generation, the energy source is clean and inexhaustible, and air pollutants during power generation As a power generation system that does not generate noise and has a low environmental impact, various solar cells that efficiently extract solar energy as an energy source have been actively developed.

Among them, dye-sensitized solar cells can be manufactured in a simple manufacturing process under atmospheric pressure using a general printing process. It is attracting attention as a next-generation solar cell following silicon, polycrystalline silicon, amorphous silicon, CIGS, and the like.

In dye-sensitized solar cells, dye molecules adsorbed on the semiconductor surface absorb sunlight, and electrons are injected from the dye LUMO (lowest orbital) into the semiconductor CB (conduction band), so-called spectral sensitization. I do. Since the dye molecule is bonded to the semiconductor surface via an adsorbing group, it is generally considered to be a monomolecular layer. That is, in order to convert light incident on the solar cell into electrons with high efficiency, a technique for improving the light absorption ability of the dye is required.

In response to that, M. made a big breakthrough. There is a so-called Gratzel cell using a porous film made of fine particles of titanium oxide by Gratzel et al. And a photoelectrode formed of a Ru bipyridine complex dye (see, for example, Non-Patent Document 1).

A semiconductor that serves as a dye adsorption site that excites electrons by light absorption and injects electrons into the semiconductor by adsorbing single molecules of dye molecules that serve as photosensitizers on the surface of this porous semiconductor. The specific surface area can be increased to several thousand times, and sunlight incident on the solar battery cell can be efficiently converted into electrons.

The dye absorbs light energy and emits electrons, and the semiconductor titania receives the electrons and delivers them to the conductive substrate. On the other hand, the holes remaining in the dye oxidize iodine ions in the electrolyte, I ⁻ changes to I ₃ ⁻ , and this oxidized I ₃ ⁻ receives and reduces electrons again at the counter electrode, and the electrons cycle through both electrodes. To generate electricity.

The open-circuit voltage of the dye-sensitized solar cell is defined by the difference between the Fermi level of the oxide semiconductor and the redox potential of the redox in the electrolyte. In terms of the power generation principle, it is possible to change the open circuit voltage by appropriately designing the energy levels of the dye HOMO / LUMO, the oxide semiconductor VB / CB, and the redox level in the electrolyte. Iodine redox (I ⁻ / I ₃ ⁻ ) is typically used for charge transfer in conventional dye-sensitized solar cells.

However, iodine is highly corrosive to metals, and platinum generally used as a counter electrode is known to corrode under high temperature storage. Further, non-iodine redox and electrolytes have been studied from the viewpoints of sublimability of iodine itself and loss of conversion efficiency due to a decrease in transmitted light due to coloring.

For the above problems, bromine redox has been studied as a halogen-based redox similar to iodine redox (for example, see Non-Patent Documents 2 and 3). Since the redox potential of bromine redox is more noble (positive) than iodine redox, the energy level difference of HOMO / LUMO such as coumarin 343 and eosin Y is large, and the organic dye having a shorter absorption region has an open circuit voltage. Improvement is recognized.

However, when a dye having a relatively small HOMO / LUMO energy level difference such as Ru complex N719 and a longer absorption region is used, the redox potential of bromine redox is too low compared to the dye HOMO. Therefore, effective electron injection hardly occurs, and conversion efficiency is lowered.

As an inorganic redox, SCN ⁻ / (SCN) ₂ or the like has been studied, but its performance is inferior to iodine redox (see, for example, Non-Patent Document 4).

Also, a semiconductor comprising a tetramethylpiperidinyloxy (TEMPO) derivative that generates a radical compound in at least one of an electrochemical oxidation reaction or a reduction reaction, and a dense layer of indium / tin oxide formed by sputtering. A photoelectrochemical device composed of a layer and an electrolyte layer has been proposed (see, for example, Patent Document 1), but is not an invention related to a dye-sensitized solar cell, but is related to performance improvement and durability in a dye-sensitized solar cell. No performance improvement is suggested.

On the other hand, conductive polymers having hole transport properties have been studied, but conversion efficiency is inferior to iodine redox, and it has not been sufficient (for example, see Patent Document 2).

JP 2003-100360 A JP 2003-264304 A

The present invention is to solve the above-described problems, and an object thereof is to provide a dye-sensitized solar cell having a high open-circuit voltage and durability under high-temperature storage.

The problem of the present invention has been solved by using an electrolyte containing a specific radical compound in producing a dye-sensitized solar cell. Specifically, this was achieved by the following configuration.

1. A dye-sensitized solar cell having, on a conductive substrate, a porous n-type semiconductor electrode having a dye adsorbed on its surface, a charge transfer layer, and a counter electrode, wherein the charge transfer layer is an N-oxyl derivative A dye-sensitized solar cell comprising a radical compound comprising:

2. 2. The dye-sensitized solar cell as described in 1 above, wherein the N-oxyl derivative is an azaadamantane N-oxyl derivative or an azabicyclo N-oxyl derivative.

3. 3. The dye-sensitized solar cell according to 2 above, wherein the azabicyclo N-oxyl derivative is represented by the following general formula (1).

(Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom, an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heterocyclic group, and X is necessary for forming a cyclic structure. 2 or 3 atomic groups.)
4). 4. The dye-sensitized solar cell according to any one of 1 to 3, wherein the charge transfer layer contains an organic solvent.

5. 5. The dye-sensitized solar cell as described in 4 above, wherein the organic solvent is 3-methoxypropionitrile, ethylene carbonate, propylene carbonate, or γ-butyrolactone.

According to the present invention, it is possible to provide a dye-sensitized solar cell that has a high open-circuit voltage and has durability under high-temperature storage.

It is a schematic sectional drawing which shows the basic structure of the dye-sensitized solar cell of this invention.

Hereinafter, the best mode for carrying out the present invention will be described in detail.

The present inventor has investigated dye-sensitized solar cells having a composite electrode, such as open-circuit voltage, short-circuit current, form factor fill factor, photoelectric conversion efficiency, etc., and as a result, dye-sensitized using iodine redox. It was confirmed that the photoelectric conversion efficiency has not yet reached a sufficiently satisfactory level in the type solar cell configuration.

As a result of intensive studies in view of the above problems, the present inventor has found that a dye-sensitized dye having a porous n-type semiconductor electrode having a dye adsorbed on its surface, a charge transfer layer, and a counter electrode in order on a conductive substrate. Dye-sensitized solar cell, which is characterized in that the charge transfer layer contains the radical compound of the present invention, and not only a high open-circuit voltage can be realized, but also excellent stability during high-temperature storage It is as soon as the present invention has been found out that it has the property.

Hereinafter, details of the N-oxyl derivative according to the present invention, its production method, and the dye-sensitized solar cell will be described.

<< N-oxyl derivative >>
N-oxyl (also called nitroxide radical) is an oxygen-centered radical generated by radically cleaving the oxygen-hydrogen bond of hydroxylamine. In the present invention, compounds having> NO structure in the molecule are generically called N-oxyl derivatives.

Many N-oxyl derivatives are more stable than other radical compounds and can be extracted as crystals. As N-oxyl derivatives, derivatives substituted with various substituents such as TEMPO (2,2,6,6-tetramethylpiperidinyl-N-oxyl) are commercially available.

Generally, when hydrogen is substituted on the α-position carbon of the N-oxyl group, it is easily disproportionated to hydroxyamine and nitrone. Therefore, the four methyl groups substituted at the N-oxyl group α-position of TEMPO are important structural chemical elements when present as stable radicals.

When an N-oxyl derivative is used as a redox couple in a dye-sensitized solar cell, the stability of the compound itself is important for enhancing the durability of the battery. Therefore, a compound in which no hydrogen is substituted on the α-position carbon of the N-oxyl group is preferable.

However, the TEMPO derivative may be less reactive due to steric hindrance of the four methyl groups. An azaadamantane N-oxyl derivative or an azabicyclo N-oxyl derivative is more preferable in that it does not cause such a decrease in activity. In these compounds, even if a hydrogen atom is substituted at the α-position carbon of the N-oxyl group, the Bredt rule prevents isomerization to nitrone and ensures the existence as a stable radical. When these polycyclic N-oxyl derivatives are used as a redox couple of a dye-sensitized solar cell, higher durability is obtained than that of a TEMPO derivative.

These azaadamantane N-oxyl derivatives or azabicyclo N-oxyl derivatives may have a substituent at a substitutable position, and a large amount such as a dimer, a trimer or the like can be obtained by using these substituents as a linking group. It may form a body or may be a polymer.

In the present invention, the most preferred N-oxyl derivative is an azaadamantane N-oxyl derivative or an azabicyclo N-oxyl derivative represented by the general formula (1).

In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heterocyclic group, and an aliphatic hydrocarbon group , The aromatic hydrocarbon group and the heterocyclic group may have a substituent. X represents a group of 2 or 3 atoms necessary for forming a cyclic structure. Specific examples include CH ₂ , CO, and C having a substituent.

The aliphatic hydrocarbon group includes chain and cyclic groups, and the chain group includes linear and branched groups. Such aliphatic hydrocarbon groups include methyl, ethyl, vinyl, propyl, isopropyl, propenyl, butyl, iso-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, iso-hexyl, cyclohexyl, cyclohexenyl, Examples include octyl, iso-octyl, cyclooctyl, 2,3-dimethyl-2-butyl and the like.

Examples of the aromatic hydrocarbon group include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a pyridyl group, a thiazolyl group, an oxazolyl group, an imidazolyl group, a furyl group, a pyrrolyl group, a pyrazinyl group, a pyrimidinyl group, and a pyridazinyl group. , Serenazolyl group, sulfolanyl group, piperidinyl group, pyrazolyl group, tetrazolyl group, morpholino group and the like.

These substituents may further have a substituent. These substituents are not particularly limited, and examples thereof include alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, Tetradecyl group, pentadecyl group etc.), cycloalkyl group (eg cyclopropyl group, cyclopentyl group, cyclohexyl group etc.), alkenyl group (eg vinyl group, allyl group, butenyl group, octenyl group etc.), cycloalkenyl group (eg 2-cyclopenten-1-yl group, 2-cyclohexen-1-yl group, etc.), alkynyl group (eg, propargyl group, ethynyl group, trimethylsilylethynyl group, etc.), aryl group (eg, phenyl group, naphthyl group, p -Tolyl group, m-chlorophenyl group, o-hexadecanoylaminophen Group), heterocyclic group (for example, pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, furyl group, pyrrolyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, selenazolyl group, sulfolanyl group, piperidinyl group, pyrazolyl group, Tetrazolyl group, morpholino group, etc.), heterocyclic oxy group (for example, 1-phenyltetrazol-5-oxy group, 2-tetrahydropyranyloxy group, pyridyloxy group, thiazolyloxy group, oxazolyloxy group, imidazolyloxy group, etc.) ), Halogen atoms (for example, chlorine atom, bromine atom, iodine atom, fluorine atom, etc.), alkoxy groups (for example, methoxy group, ethoxy group, propyloxy group, t-butoxy group, pentyloxy group, hexyloxy group, octyl) Oxy group, dodecyloxy group, etc.), Loalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, 2-naphthyloxy group, 2-methylphenoxy group, 4-t-butylphenoxy group, 3-nitrophenoxy group) 2-tetradecanoylaminophenoxy group, etc.), alkylthio groups (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio groups (eg, cyclopentylthio group, Cyclohexylthio group etc.), arylthio group (eg phenylthio group, 1-naphthylthio group etc.), heterocyclic thio group (eg pyridylthio group, thiazolylthio group, oxazolylthio group, imidazolylthio group, furylthio group, pyrrolylthio group etc.), Alkoxycarbonyl groups (eg, methoxycarbonyl group, ethoxycarbonyl group, butoxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl groups (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl Groups (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylamino group) Sulfonyl group, 2-pyridylaminosulfonyl group, morpholinosulfonyl group, pyrrolidinosulfonyl group, etc.), ureido group (eg methyl Raid group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group) Propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, formyloxy group, Acetyloxy, pivaloyloxy, stearoyloxy, benzoyloxy, p-methoxyphenylcarbonyloxy, ethylcarbonyloxy, butylcarbonyloxy Group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), acylamino group (for example, acetylamino group, benzoylamino group, formylamino group, pivaloylamino group, lauroylamino group, 3,4,5-tri -N-octyloxyphenylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group) 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, morpholinocar Bonyl group, piperazinocarbonyl group, etc.), alkanesulfinyl group or arylsulfinyl group (for example, methanesulfinyl group, ethanesulfinyl group, butanesulfinyl group, cyclohexanesulfinyl group, 2-ethylhexanesulfinyl group, dodecanesulfinyl group, phenylsulfinyl group) Group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkanesulfonyl group or arylsulfonyl group (for example, methanesulfonyl group, ethanesulfonyl group, butanesulfonyl group, cyclohexanesulfonyl group, 2-ethylhexanesulfonyl group, dodecanesulfonyl group) Phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, methylamino group, ethylamino group, di-amino group) Tilamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, N-methylanilino group, diphenylamino group, naphthylamino group, 2-pyridylamino group, etc.), silyloxy group (for example, trimethylsilyl group) Oxy group, tert-butyldimethylsilyloxy group, etc.), aminocarbonyloxy group (for example, N, N-dimethylcarbamoyloxy group, N, N-diethylcarbamoyloxy group, morpholinocarbonyloxy group, N, N-di-n) -Octylaminocarbonyloxy group, Nn-octylcarbamoyloxy group, etc.), alkoxycarbonyloxy group (for example, methoxycarbonyloxy group, ethoxycarbonyloxy group, t-butoxycarbonyloxy group, n-octylca) Bonyloxy group etc.), aryloxycarbonyloxy group (eg phenoxycarbonyloxy group, p-methoxyphenoxycarbonyloxy group, pn-hexadecyloxyphenoxycarbonyloxy group etc.), alkoxycarbonylamino group (eg methoxycarbonylamino) Group, ethoxycarbonylamino group, t-butoxycarbonylamino group, n-octadecyloxycarbonylamino group, N-methyl-methoxycarbonylamino group, etc.), aryloxycarbonylamino group (for example, phenoxycarbonylamino group, p-chlorophenoxy) Carbonylamino group, mn-octyloxyphenoxycarbonylamino group, etc.), sulfamoylamino group (eg, sulfamoylamino group, N, N-dimethylaminosulfonylamino group) Group, Nn-octylaminosulfonylamino group, etc.), mercapto group, arylazo group (eg, phenylazo group, naphthylazo group, p-chlorophenylazo group, etc.), heterocyclic azo group (eg, pyridylazo group, thiazolylazo group, etc.) Oxazolylazo group, imidazolylazo group, furylazo group, pyrrolylazo group, 5-ethylthio-1,3,4-thiadiazol-2-ylazo group, etc.), imino group (for example, N-succinimido-1-yl group, N-phthalimide- 1-yl group), phosphino group (for example, dimethylphosphino group, diphenylphosphino group, methylphenoxyphosphino group, etc.), phosphinyl group (for example, phosphinyl group, dioctyloxyphosphinyl group, diethoxyphosphinyl group) Group), phosphinyloxy group (for example, diphe Xyphosphinyloxy group, dioctyloxyphosphinyloxy group, etc.), phosphinylamino group (eg, dimethoxyphosphinylamino group, dimethylaminophosphinylamino group, etc.), silyl group (eg, trimethylsilyl group, t-butyldimethylsilyl group, phenyldimethylsilyl group, etc.), cyano group, nitro group, hydroxyl group, sulfo group, carboxyl group and the like.

The compound represented by the general formula (1) may be a multimer such as a dimer or a trimer linked by these substituents, or may be a polymer.

Specific examples of the compound represented by the general formula (1) are shown below, but the present invention is not limited only to these exemplified compounds.

Specific examples of the azaadamantane N-oxyl derivative which may have a substituent and are used in the present invention are shown below, but the present invention is not limited only to these exemplified compounds.

《Charge transfer layer》
The charge transfer layer constituting the dye-sensitized solar cell of the present invention is a layer containing a charge transport material having a function of replenishing electrons to the oxidant of the dye. Examples of typical charge transport materials that can be used in the present invention include a solvent in which a redox counter ion is dissolved, an electrolyte such as a room temperature molten salt containing the redox counter ion, and a solution of the redox counter ion as a polymer matrix. And a gel-like quasi-solidified electrolyte impregnated with a low-molecular gelling agent, and a polymer solid electrolyte.

In addition to charge transport materials involving ions, electron transport materials and hole transport materials can also be used as materials in which carrier transport in solids is involved in electrical conduction, and these can be used in combination. is there.

As a solvent, it is an electrochemically inert compound that has low viscosity and improved ion mobility, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ionic conductivity. Is desirable.

Specifically, carbonate compounds such as dimethyl carbonate, diethyl carbonate, ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol Chain ethers such as dialkyl ether, polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether, alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether , Ethylene glycol, diethylene glycol, trie Polyhydric alcohols such as lenglycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, nitrile compounds such as acetonitrile, glutarodinitrile, propionitrile, methoxypropionitrile, methoxyacetonitrile, benzonitrile, tetrahydrofuran, dimethyl sulfoxide An aprotic polar substance such as sulfolane and γ-butyrolactone can be used. Any of 3-methoxypropionitrile, ethylene carbonate, propylene carbonate, and γ-butyrolactone is more preferable.

The solvent preferably has a boiling point of 80 ° C. or higher, more preferably 100 ° C. or higher, and still more preferably 120 ° C. or higher from the viewpoint of durability. Specific examples include 3-methoxypropionitrile (165 ° C.), ethylene carbonate (243 ° C.), propylene carbonate (240 ° C.), and γ-butyrolactone (203 ° C.).

A preferable electrolyte concentration is 0.1 to 15 mol / L, and more preferably 0.2 to 10 mol / L.

The molten salt electrolyte is preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. As the molten salt electrolyte, for example, International Publication No. 95/18456 pamphlet, JP-A-8-259543, JP-A-2001-357896, Electrochemistry, Vol. 65, No. 11, page 923 (1997). And electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts described in the above. These molten salt electrolytes are preferably in a molten state at room temperature, and it is preferable not to use a solvent.

Gelled by techniques such as oligomers and polymers containing electrolytes or electrolyte solutions, addition of polymers, addition of low-molecular gelling agents and oil gelling agents, polymerization including polyfunctional monomers, polymer cross-linking reaction, etc. (Pseudo-solidification) can also be used.

In the case of gelation by adding a polymer, polyacrylonitrile and polyvinylidene fluoride can be preferably used. In the case of gelation by adding an oil gelling agent, a preferred compound is a compound having an amide structure in the molecular structure.

Also, when the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a crosslinkable reactive group and a crosslinking agent in combination. In this case, a preferable crosslinkable reactive group is a nitrogen-containing heterocyclic ring (for example, a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, a triazole ring, a morpholine ring, a piperidine ring, a piperazine ring, etc.), and a preferable crosslinking agent is It is a reagent (for example, alkyl halide, halogenated aralkyl, sulfonic acid ester, acid anhydride, acid chloride, isocyanate, etc.) capable of electrophilic reaction with a nitrogen atom. The concentration of the electrolyte is usually 0.01 to 99% by mass, preferably about 0.1 to 90% by mass.

Further, as the gel electrolyte, an electrolyte composition containing an electrolyte and metal oxide particles and / or conductive particles can also be used. As the metal oxide particles, TiO ₂ , SnO ₂ , WO ₃ , ZnO, ITO, BaTiO ₃ , Nb ₂ O ₅ , In ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ , SrTiO ₃ , Y Examples thereof include one or a mixture of two or more selected from the group consisting of ₂ O ₃ , Ho ₂ O ₃ , Bi ₂ O ₃ , CeO ₂ , and Al ₂ O ₃ . These may be doped with impurities or complex oxides. Examples of the conductive particles include those made of a substance mainly composed of carbon.

Next, the polymer electrolyte is a solid substance capable of dissolving the redox species or binding with at least one substance constituting the redox species, for example, polyethylene oxide, polypropylene oxide, polyethylene succinate, Polyethers to polymer functional groups such as poly-β-propiolactone, polyethyleneimine, polyalkylene sulfide and the like, or cross-linked products thereof, polyphosphazene, polysiloxane, polyvinyl alcohol, polyacrylic acid, polyalkylene oxide, etc. Examples include those obtained by adding segments or oligoalkylene oxide structures as side chains, or copolymers thereof. Among them, those having oligoalkylene oxide structures as side chains, and polyether segments as side chains. Which is preferable.

In order to contain the redox species in the solid, for example, a method of polymerizing in the coexistence of a monomer that becomes a polymer compound and a redox species, a solid such as a polymer compound is dissolved in a solvent as necessary. Then, the above-mentioned method of adding the redox species can be used. The content of the redox species can be appropriately selected according to the required ion conduction performance.

In the present invention, instead of an ion conductive electrolyte such as a molten salt, a solid hole transport material which is organic or inorganic or a combination of both can be used.

Organic hole transport materials include aromatic amines and triphenylene derivatives, polyacetylene and derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof. Conductive polymers such as derivatives, polythiophene and derivatives thereof, polyaniline and derivatives thereof, polytoluidine and derivatives thereof can be preferably used.

In order to control the dopant level, the hole transport material may be added with a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate, or the potential of the oxide semiconductor surface. In order to perform control (space charge layer compensation), a salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added.

As the inorganic hole transport material, a p-type inorganic compound semiconductor can be used. The p-type inorganic compound semiconductor for this purpose preferably has a band gap of 2 eV or more, and more preferably 2.5 eV or more.

In addition, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye-adsorbing electrode from the condition that the holes of the dye can be reduced. Although the preferred range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 to 5.5 eV, more preferably 4.7 to 5.3 eV.

A preferred p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper, preferably CuI and CuSCN, and most preferably CuI. The preferred hole mobility of the charge transfer layer containing the p-type inorganic compound semiconductor is 1 × 10 ⁻⁴ to 1 × 10 ⁴ m ² / V · sec, more preferably 1 × 10 ⁻³ to 1 × 10 ³ cm. ² / V · sec. The preferred conductivity of the charge transport layer is 1 × 10 ⁻⁸ to 1 × 10 ² S / cm, more preferably 1 × 10 ⁻⁶ to 10 S / cm.

In the present invention, the method for forming the charge transfer layer between the porous n-type semiconductor electrode and the counter electrode is not particularly limited. For example, the porous n-type semiconductor electrode and the counter electrode are arranged to face each other. Then, the charge transfer layer is formed by filling the above-described electrolyte or various electrolytes between both electrodes to form a charge transfer layer, or by dropping or coating the electrolyte or various electrolytes on the porous n-type semiconductor electrode or the counter electrode. After forming the layer, a method of superimposing the other electrode on the charge transfer layer can be used.

Moreover, in order to prevent electrolyte from leaking out between the porous n-type semiconductor electrode and the counter electrode, sealing is performed using a film or a resin in the gap between the porous n-type semiconductor electrode and the counter electrode as necessary. It is also preferable to store the porous n-type semiconductor electrode, the charge transfer layer, and the counter electrode in an appropriate case.

In the case of the former forming method, as a method for filling the charge transfer layer, a normal pressure process using capillary action by dipping or the like, or a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used. .

In the latter formation method, microgravure coating, dip coating, screen coating, spin coating or the like can be used as a coating method. In the wet charge transfer layer, the counter electrode is provided in an undried state and measures for preventing liquid leakage at the edge portion are taken. 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 this case, the counter electrode can be applied after drying and fixing.

In the case of a solid electrolyte or a solid hole transport material, a charge transfer layer can be formed by a dry film formation process such as a vacuum deposition method or a CVD method, and then a counter electrode can be provided. Specifically, it can be introduced into the electrode by techniques such as vacuum deposition, casting, coating, spin coating, dipping, electropolymerization, and photoelectropolymerization. It is formed by evaporating the solvent by heating to an arbitrary temperature.

The thickness of the charge transfer layer is preferably 10 μm or less, more preferably 5 μm or less, and further preferably 1 μm or less. The electric conductivity of the charge transfer layer is preferably 1 × 10 ⁻¹⁰ S / cm or more, and more preferably 1 × 10 ⁻⁵ S / cm or more.

<< Dye-sensitized solar cell >>
The dye-sensitized solar cell of the present invention will be described with reference to FIG.

FIG. 1 is a schematic cross-sectional view showing the basic structure of the dye-sensitized solar cell of the present invention. As shown in FIG. 1, the dye-sensitized solar cell of the present invention includes a conductive substrate 1, a porous n-type semiconductor electrode 2 having a dye 3 adsorbed on the surface of a semiconductor, and a charge transfer layer (“electrolyte”). 4) and a counter electrode 5 (sometimes referred to as a “layer”). In FIG. 1, e ⁻ represents an electron, and an arrow represents the flow of the electron.

When constituting the dye-sensitized solar cell of the present invention, the porous n-type semiconductor electrode, the charge transfer layer and the counter electrode are housed in a case and sealed, or the whole is sealed with resin. It is preferable.

When the dye-sensitized solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, the dye 3 adsorbed on the semiconductor is excited by absorbing the irradiated sunlight or electromagnetic wave. Electrons generated by excitation move to the semiconductor, and then move to the counter electrode 5 via the conductive substrate 1 to reduce the redox electrolyte of the charge transfer layer 4.

On the other hand, the dye 3 that has moved electrons to the semiconductor is an oxidant, but is reduced to the original state by supplying electrons from the counter electrode 5 via the redox electrolyte of the charge transfer layer 4. At the same time, the iodine redox (in the present invention, the radical compound according to the present invention) of the charge transfer layer 4 is oxidized and returns to a state where it can be reduced again by the electrons supplied from the counter electrode 5. In this way, electrons flow and the dye-sensitized solar cell of the present invention can be configured.

《Metal oxide semiconductor layer》
The metal oxide semiconductor layer according to the present invention will be described.

The metal oxide constituting the metal oxide semiconductor layer according to the present invention is not particularly limited as long as it is a semiconductor that receives electrons generated by light irradiation with a dye adsorbed on the semiconductor and transmits the electrons to a conductive substrate. Various metal oxides used in the dye-sensitized solar cell can be used.

Specifically, various metal oxide semiconductors such as titanium oxide, zirconium oxide, zinc oxide, vanadium oxide, niobium oxide, tantalum oxide, tungsten oxide, strontium titanate, calcium titanate, magnesium titanate, barium titanate, niobium Various metal oxide semiconductors such as potassium oxide and strontium tantalate, transition metal oxides such as magnesium oxide, strontium oxide, aluminum oxide, cobalt oxide, nickel oxide and manganese oxide, cerium oxide, gadolinium oxide, samarium oxide, ytterbium oxide And metal oxides such as lanthanoid oxides, and inorganic insulators such as natural or synthetic silicate compounds represented by silica.

Also, these materials can be used in combination. Furthermore, the metal oxide particles may have a core-shell structure or may be doped with a different metal element, and a metal oxide having an arbitrary structure and composition can be applied.

The average particle diameter of the metal oxide particles is preferably from 10 nm to 300 nm, more preferably from 10 nm to 100 nm. Further, the shape of the metal oxide is not particularly limited, and may be spherical, acicular or amorphous crystals.

The method for forming metal oxide particles is not particularly limited, and various liquid phase methods such as hydrothermal reaction method, sol-gel method / gel sol method, colloid chemical synthesis method, coating pyrolysis method, spray pyrolysis method, and chemical vapor phase It can be formed using various gas phase methods such as a precipitation method.

Next, a method for manufacturing a metal oxide semiconductor layer according to the present invention will be described.

As a method for producing the metal oxide semiconductor layer of the dye-sensitized solar cell of the present invention, a known method can be applied, and (1) a suspension containing metal oxide fine particles or a precursor thereof. A method of forming a semiconductor layer by applying a liquid on a conductive substrate, drying and baking, and (2) immersing the conductive substrate in a colloidal solution and conducting the metal oxide semiconductor particles by electrophoresis. Electrophoretic electrodeposition method that adheres to a conductive substrate, (3) A method in which a foaming agent is mixed and applied to a colloidal solution or dispersion, and then sintered to make it porous. (4) A polymer microbead is mixed. After the coating, a method of removing the polymer microbeads by heat treatment or chemical treatment to form voids and making it porous can be applied.

Among the above preparation methods, as a coating method, a known method can be applied, and examples thereof include a screen printing method, an ink jet method, a roll coating method, a doctor blade method, a spin coating method, and a spray coating method. Can do.

In particular, in the case of the above method (1), the particle diameter of the metal oxide fine particles in the suspension is preferably fine and is preferably present as primary particles. The suspension containing the metal oxide fine particles is prepared by dispersing the metal oxide fine particles in a solvent, and the solvent is not particularly limited as long as the metal oxide fine particles can be dispersed, and water, Organic solvents, mixtures of water and organic solvents are included. As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, acetone and acetyl acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. A surfactant and a viscosity modifier (polyhydric alcohol such as polyethylene glycol) can be added to the suspension as necessary. The concentration range of the metal oxide fine particles in the solvent is preferably 0.1 to 70% by mass, and more preferably 0.1 to 30% by mass.

The suspension containing the metal oxide core fine particles obtained as described above is applied onto a conductive substrate, dried, etc., and then baked in air or in an inert gas to be conductive. A metal oxide semiconductor layer is formed on the conductive substrate. The semiconductor layer obtained by applying and drying the suspension on the conductive substrate is composed of an aggregate of metal oxide fine particles, and the particle size of the fine particles corresponds to the primary particle size of the metal oxide fine particles used. To do.

Since the metal oxide semiconductor layer formed on the conductive base material has low bonding strength with the conductive base material and fine particles, and the mechanical strength is low, this metal oxide fine particle assembly The body film is preferably fired to increase the mechanical strength, and is preferably a fired product film that is strongly fixed to the substrate.

In the present invention, the metal oxide semiconductor layer may have any structure, but is preferably a porous structure film (also referred to as a porous layer having voids). Here, the porosity of the metal oxide semiconductor layer is preferably 0.1 to 20% by volume, and more preferably 5 to 20% by volume. Note that the porosity of the metal oxide semiconductor layer means a porosity that is penetrable in the thickness direction of the dielectric, and can be measured using a commercially available apparatus such as a mercury porosimeter (Shimadzu Polarizer 9220 type). The thickness of the metal oxide semiconductor layer is preferably at least 10 nm or more, and more preferably 100 to 10,000 nm.

During the firing treatment, the actual surface area of the semiconductor layer is appropriately adjusted, and the firing temperature is preferably lower than 1000 ° C., more preferably in the range of 200 to 800 ° C. from the viewpoint of obtaining a semiconductor layer having the above porosity. .

In the metal oxide semiconductor layer according to the present invention, after the metal oxide semiconductor layer is formed on the metal oxide intermediate layer as described above, the metal oxide semiconductor layer is formed on the metal oxide semiconductor film as necessary for the purpose of improving electronic conductivity. You may perform the surface treatment by a metal oxide. The surface treatment composition is preferably the same type of composition as that of the metal oxide forming the metal oxide semiconductor layer, particularly from the viewpoint of electron conductivity between the metal oxide fine particles.

As a method of performing this surface treatment, after forming a metal oxide semiconductor film on a conductive substrate, a metal oxide precursor to be surface treated is applied to the semiconductor film, or the semiconductor film is a precursor. A surface treatment made of a metal oxide can be performed by immersing in a body solution and further performing a firing treatment as necessary.

Specifically, the surface treatment is performed by using an electrochemical treatment using a titanium tetrachloride aqueous solution or titanium alkoxide which is a precursor of titanium oxide, or using a precursor of an alkali metal titanate or an alkaline earth titanate metal. be able to. The firing temperature and firing time at this time are not particularly limited and can be arbitrarily controlled, but are preferably 200 ° C. or lower.

<Conductive substrate>
As the conductive substrate used in the present invention, the conductive substrate is preferably substantially transparent when the light-receiving surface is the conductive substrate side of the dye-sensitized solar cell. “Substantially transparent” means that the light transmittance is 10% or more, preferably 50% or more, and particularly preferably 80% or more.

As the conductive substrate, a substrate having conductivity by itself or a substrate having a conductive layer on the surface thereof can be used. In the latter case, it is possible to use a glass plate, a ceramic polishing plate such as titanium oxide or alumina, and various known plastic sheets as the base material, but considering the cost and flexibility, plastic It is preferable to use a sheet.

Specific examples of the plastic sheet include triacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), syndiotactic polyester (SPS), and polycarbonate (PC). , Polyarylate (PA), polyetherimide (PEI), polysulfone (PSF), polyethersulfone (PES), cyclic polyolefin, phenoxy resin, brominated phenoxy and the like.

Examples of the conductive material used for the conductive layer provided on these substrates include inorganic conductive materials made of various known metals and metal oxides, polymer conductive materials, and inorganic / organic composite conductive materials. Or any material such as a conductive material in which these are arbitrarily mixed can be used.

Specific examples of the inorganic conductive material include metals such as platinum, gold, silver, copper, zinc, titanium, aluminum, rhodium, and indium, conductive carbon, tin-doped indium oxide (ITO), and tin oxide (SnO ₂ ). And metal oxides such as fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), and zinc oxide (ZnO ₂ ).

Specific examples of the polymer-based conductive material include conductive polymers obtained by polymerizing thiophene, pyrrole, furan, aniline, etc., which may or may not be variously substituted, and polyacetylene. From the viewpoint of high properties, polythiophene is preferable, and polyethylenedioxythiophene (PEDOT) is particularly preferable.

As a method of forming a conductive layer on a substrate, a known appropriate method according to a conductive material can be used. For example, when forming a conductive layer made of a metal oxide such as ITO, a sputtering method is used. And thin film forming methods such as CVD, SPD (spray pyrolysis deposition), and vapor deposition. Further, when forming a conductive layer made of a polymer-based conductive material, it is preferably formed by various known coating methods.

The thickness of the conductive layer is preferably about 0.01 to 10 μm, more preferably about 0.05 to 5 μm. As a conductive base material, the lower the surface resistance, the better. Specifically, it is preferably 50 Ω / cm ² or less, more preferably 10 Ω / cm ² or less.

In addition, in order to improve the current collection efficiency of the conductive substrate and further increase the conductivity, the area ratio in a range that does not significantly impair the light transmittance, gold, silver, copper, platinum, aluminum, nickel, indium, titanium, A metal wiring layer made of tungsten or the like may be used in combination with the conductive layer. In the case of using a metal wiring layer, it is preferable that light is uniformly transmitted through the conductive substrate as a pattern such as a lattice shape, a stripe shape, or a comb shape. When a metal wiring layer is used in combination, it is preferable to install the conductive layer on the substrate by vapor deposition, sputtering, or the like.

<Short-circuit prevention layer>
In the dye-sensitized solar cell of the present invention, a short-circuit prevention layer can be provided between the conductive layer and the metal oxide semiconductor electrode described above. Thereby, the short circuit current of electrolyte and a metal oxide semiconductor can be reduced. In particular, when a solid p-type semiconductor is used as the electrolyte, it is preferable to have this layer.

The short-circuit preventing layer is not particularly limited as long as it is an n-type semiconductor that is an insulating substance that transmits visible light and has a conduction band energy level close to that of a metal oxide semiconductor. For example, silicon oxide, magnesium oxide, aluminum oxide, calcium carbonate, polyvinyl alcohol, polyurethane and the like can be mentioned. Moreover, what is generally used for a photoelectric conversion material may be used, for example, titanium oxide, niobium oxide, tungsten oxide, etc. are mentioned.

As a method for forming the short-circuit prevention layer, it can be produced by a vacuum film formation process, a liquid phase coating method, or the like, as in the case of the transparent conductive layer. When using a vacuum film formation process, the transparent conductive layer, the short-circuit prevention layer, and the metal oxide film can be formed in-line under vacuum without being exposed to the atmosphere.

The film thickness of the short-circuit prevention layer is preferably 0.001 to 0.02 μm, but can be adjusted as appropriate.

<Dye>
In the present invention, the dye adsorbed on the surface of the porous n-type semiconductor electrode 2 shown in FIG. 1 has absorption in various visible light regions and / or infrared light regions, and is a metal oxide semiconductor. A dye having the lowest vacancy level higher than the conduction band is preferable, and various known dyes can be used.

For example, azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, cyanidin dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, perylene dyes And dyes, indigo dyes, phthalocyanine dyes, naphthalocyanine dyes, rhodamine dyes, and the like.

Metal complex dyes are also preferably used. In this case, Cu, Ni, Fe, Co, V, Sn, Si, Ti, Ge, Cr, Zn, Ru, Mg, Al, Pb, Mn, In, Mo Y, Zr, Nb, Sb, La, W, Pt, Ta, Ir, Pd, Os, Ga, Tb, Eu, Rb, Bi, Se, As, Sc, Ag, Cd, Hf, Re, Au, Ac Various metals such as Tc, Te, and Rh can be used.

Among the above, polymethine dyes such as cyanine dyes, merocyanine dyes and squarylium dyes are one of preferred embodiments. Specifically, JP-A Nos. 11-35836, 11-67285, 11-86916, 11-97725, 11-158395, 11-163378, 11-214730, 11-214731, 11-238905, JP-A-2004-207224, 2004-319202 Examples thereof include dyes described in each specification such as Gazette, European Patent Nos. 892,411 and 911,841.

Furthermore, a metal complex dye is one of the preferred embodiments, and a metal phthalocyanine dye, a metal porphyrin dye or a ruthenium complex dye is preferable, and a ruthenium complex dye is more preferable. Examples of ruthenium complex dyes include U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, Nos. 5,525,440, JP-A-7-249790, JP-A-10-504512, WO98 / 50393, JP2000-26487, 2001-2223037 And complex dyes described in JP-A Nos. 2001-226607 and 3430254.

The above-mentioned compound according to the present invention is, for example, “Cyanine Soybean and Related Compounds” (1964, published by Inter Science Publishers) by F. M. Hammer, US Pat. No. 2,454,629, It can be synthesized with reference to the methods described in the specifications of JP-A-2,493,748, JP-A-6-301136, JP-A-2003-203684, and the like.

These dyes preferably have a large extinction coefficient and are stable against repeated redox. The dye is preferably chemically adsorbed on the metal oxide semiconductor and has a functional group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amide group, an amino group, a carbonyl group, or a phosphine group. preferable.

Also, in order to widen the wavelength range of photoelectric conversion as much as possible and increase the conversion efficiency, two or more kinds of dyes can be used together or mixed. In this case, the dye used together or mixed and the ratio thereof can be selected so as to match the wavelength range and intensity distribution of the target light source.

In the present invention, the method for adsorbing the dye to the metal oxide semiconductor layer is not particularly limited, and a known method can be used. For example, a method of dissolving a pigment in an organic solvent to prepare a pigment solution and immersing the semiconductor layer on the transparent conductive film in the obtained pigment solution, or a method of applying the obtained pigment solution to the surface of the semiconductor layer, etc. Can be mentioned.

In the former, a dip method, a roller method, an air knife method or the like can be applied, and in the latter, a wire bar method, an application method, a spin method, a spray method, an offset printing method, a screen printing method, or the like can be applied. Prior to the adsorption of the pigment, the surface of the semiconductor layer may be subjected to a treatment such as a decompression treatment or a heat treatment in advance to activate the surface and remove bubbles in the film.

From the viewpoint of preferably obtaining a sensitizing effect on the semiconductor layer, the time for immersing the semiconductor film in the dye solution is preferably 3 to 48 hours, and more preferably 4 to 24 hours.

In addition, the dye solution may be heated to a temperature that does not boil as long as the dye does not decompose. The preferred temperature range is 10 to 50 ° C., particularly preferably 15 to 35 ° C., but this is not the case when the solvent boils in the temperature range as described above.

Also, ultrasonic irradiation can be performed on the dye solution in which the semiconductor film is immersed. A commercially available apparatus can be used for ultrasonic irradiation, and the irradiation time is preferably 30 minutes to 4 hours, more preferably 1 to 3 hours.

The solvent used in the dye solution may be any solvent that dissolves the dye, and a conventionally known solvent can be used. In addition, the solvent is preferably a solvent purified in accordance with a conventional method, or prior to use of the solvent, distilled and / or dried as necessary, and a higher purity solvent, for example, methanol, ethanol, Butanol, one or more hydrophobic solvents, aprotic solvents, hydrophobic and aprotic solvents or mixtures thereof.

Here, examples of the hydrophobic solvent include halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; hydrocarbons such as hexane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; chlorobenzene, And halogenated aromatic hydrocarbons such as dichlorobenzene; esters such as ethyl acetate, butyl acetate, and ethyl benzoate;

Examples of the aprotic solvent include ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether, diisopropyl ether and dimethoxyethane; nitrogen compounds such as acetonitrile, dimethylacetamide and hexamethylphosphoric triamide; carbon disulfide; Sulfur compounds such as dimethyl sulfoxide; phosphorus compounds such as hexamethylphosphoramide; and combinations thereof.

Solvents preferably used include alcohol solvents such as methanol, ethanol, n-propanol and butanol, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as diethyl ether, diisopropyl ether, tetrahydrofuran and 1,4-dioxane, methylene chloride 1,1,2-trichloroethane and the like, particularly preferably methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran and methylene chloride.

The concentration of the dye in the dye solution can be appropriately adjusted depending on the dye used, the type of solvent, and the dye adsorption step. For example, it is 1 × 10 ⁻⁵ mol / L or more, preferably 5 × 10 ⁻⁵ to 1 ×. About 10 ⁻² mol / L.

Note that if the adsorption amount of the dye is small, the sensitization effect becomes insufficient. Conversely, if the adsorption amount is large, the dye that is not adsorbed on the oxide semiconductor floats, which reduces the sensitization effect and reduces the photoelectric conversion efficiency. This is not preferable because it causes a decrease. From the above, it is preferable to quickly remove the unadsorbed dye by washing.

As the washing solvent, a solvent such as acetone having a relatively low solubility of the dye and relatively easy to dry is preferable. Moreover, it is preferable to perform washing in a heated state. In addition, after removing the excess dye by washing, the surface of the oxide semiconductor fine particles may be treated with an organic basic compound in order to make the adsorption state of the dye more stable, thereby promoting the removal of the unreacted dye. . Examples of the organic basic compound include derivatives such as pyridine and quinoline. When these compounds are liquid, they may be used as they are, but when they are solid, they may be dissolved in a solvent, preferably the same solvent as the dye solution.

When two or more dyes are used, the ratio of the dyes to be mixed is not particularly limited, and is selected and optimized from the respective dyes. Generally, about 10% mol or more per one dye is used after mixing in equimolar amounts. It is preferable to do this.

As a specific method when two or more dyes are used in combination, the dyes may be adsorbed on the semiconductor layer sequentially by mixing and dissolving them. When the dye is adsorbed to the oxide semiconductor layer using a solution in which the dye to be used in combination is mixed and dissolved, the total concentration of the dye in the solution may be the same as when only one kind is supported. As a solvent in the case of using a mixture of dyes, the above-mentioned solvents can be used. Even when a solution is prepared for each dye to be used in combination and adsorbed to the semiconductor layer, the solvent described above can be used as the solvent, and the solvent for each dye to be used may be the same or different.

When a separate solution is prepared for each dye and is prepared by sequentially immersing in each solution, the effect of the present invention can be obtained regardless of the order in which the dye is adsorbed on the semiconductor layer. Moreover, you may produce by mixing the semiconductor fine particle which adsorb | sucked each pigment | dye independently.

When the dye is supported on the thin film of oxide semiconductor fine particles, it is effective to support the dye in the coexistence of the inclusion compound in order to prevent the association between the dyes. Examples of the inclusion compound include steroidal compounds such as cholic acid, crown ether, cyclodextrin, calixarene, polyethylene oxide, and the like. Deoxycholic acid, dehydrodeoxycholic acid, chenodeoxycholic acid, cholic acid are preferable. Examples thereof include cholic acids such as methyl ester and sodium cholate, and polyethylene oxide.

Alternatively, after the dye is supported, the surface of the semiconductor layer may be treated with an amine compound such as 4-t-butylpyridine. The treatment method may be, for example, a method of immersing a substrate provided with a semiconductor fine particle thin film carrying a dye in an ethanol solution of amine.

《Counter electrode》
The counter electrode constituting the dye-sensitized solar cell of the present invention has a single-layer structure of a base material having conductivity as in the case of the conductive base material described above, or a base material having a counter electrode conductive layer on the surface thereof. Can be used. In the latter case, the conductive material and the base material used for the counter electrode conductive layer, and the manufacturing method thereof are the same as those of the conductive base material 1 described above, and various known materials and methods can be applied.

Among them, I ₃ ^- is preferable to use those having a catalytic ability to perform a reducing reaction fast enough for oxidation and other redox ions such as ions, specifically platinum electrodes, the conductive material surface Examples include platinum-plated or platinum-deposited materials, rhodium metal, ruthenium metal, ruthenium oxide, and carbon.

In the same manner as described above, in consideration of cost and flexibility, it is also a preferable aspect to use a plastic sheet as a base material and to apply a polymer material as a conductive material.

The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. When the counter electrode conductive layer is a metal, the thickness is preferably 5 μm or less, and more preferably in the range of 10 nm to 3 μm. The surface resistance of the counter electrode is preferably as low as possible. Specifically, the range of the surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less, still more preferably 10Ω / □ or less. .

Since light may be received from either one or both of the conductive base material and the counter electrode described above, it is sufficient that at least one of the conductive base material and the counter electrode is substantially transparent. From the viewpoint of improving the power generation efficiency, it is preferable to make the conductive base material transparent so that light is incident from the conductive base material side. In this case, the counter electrode preferably has a property of reflecting light. As such a counter electrode, glass or plastic deposited with a metal or a conductive oxide, or a metal thin film can be used.

The counter electrode is formed by directly applying a conductive material on the above-described charge transfer layer, plating or vapor deposition (for example, PVD, CVD), or a conductive layer side of a substrate having a counter electrode conductive layer or a conductive substrate single layer. Just paste. In addition, as in the case of the conductive base material, it is also a preferable aspect to use a metal wiring layer in combination when the counter electrode is transparent.

The counter electrode is preferably conductive and has a catalytic action on the reduction reaction of the redox electrolyte. For example, a method of depositing platinum, carbon, rhodium, ruthenium or the like on glass or a polymer film, a method of applying conductive fine particles, or the like can be applied.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Preparation of electrolyte L-01 >>
Using acetonitrile as a solvent, lithium iodide, iodine, 1,2-dimethyl-3-propylimidazolium iodide, and t-butylpyridine, each at a concentration of 0.1 mol / L, 0.05 mol / L, An iodine redox electrolyte L-01 dissolved at 0.6 mol / L and 0.5 mol / L was prepared.

<< Preparation of dye-sensitized solar cell SC-101 >>
A TiO ₂ paste (Solaronix Ti-Nanoxide T) is dried at room temperature so that the dry film thickness becomes 10 μm on the FTO surface of an FTO glass substrate having a surface resistance of 10 Ω / □ to be a transparent conductive substrate, and further at 450 ° C. for 30 minutes. A porous metal oxide semiconductor layer was formed by performing a sintering process for a minute.

Next, after preparing a dye solution in which 0.1 part by mass of Ru complex dye N719 was dissolved in 200 parts by mass of acetonitrile: t-butanol = 1: 1 solution, the metal oxide semiconductor layer was immersed in the substrate for 24 hours. Then, it was washed with an acetonitrile: t-butanol = 1: 1 solution and dried to prepare a porous n-type semiconductor electrode in which a dye was adsorbed on the metal oxide semiconductor layer.

As a cathode electrode, platinum was vacuum-deposited on an ITO glass substrate, and a hole for injecting an electrolyte was provided. The glass substrate and the cathode electrode are bonded to each other by using a 25 μm thick sheet-like spacer / sealing material (SX-1170-25, manufactured by Solaronix) having a 6.5 mm square hole, and provided on the cathode electrode. From the electrolyte injection hole, the electrolyte L-01 was injected as a charge transfer layer, the hole was closed with a hot bond, and a cover glass was attached and sealed from above using the sealing material.

An antireflection film (Konica Minolta Op hard coat / antireflection type cellulose film) was bonded to the light receiving surface side of the glass substrate to prepare a dye-sensitized solar cell SC-101.

<< Preparation of electrolyte L-02 >>
Using acetonitrile as a solvent, lithium bromide, bromine, 1,2-dimethyl-3-propylimidazolium bromide, and t-butylpyridine were added at concentrations of 0.1 mol / L, 0.05 mol / L, 0, respectively. An iodine redox electrolyte L-02 dissolved to be 6 mol / L and 0.5 mol / L was prepared.

<< Preparation of electrolyte L-03 >>
TEMPO was dissolved in an acetonitrile: t-butanol = 1: 1 solution so as to be 20% by mass to obtain an electrolyte L-03.

<< Preparation of electrolyte L-04 >>
Exemplified compound (RA-1) was dissolved in acetonitrile: t-butanol = 1: 1 solution so as to be 20% by mass to obtain an electrolyte L-04.

<< Preparation of electrolyte L-05 >>
The exemplified compound (RA-1) was dissolved in 3-methoxypropionitrile so as to be 20% by mass to obtain an electrolyte L-05.

<< Preparation of electrolyte L-06 >>
Exemplified compound (RB-1) was dissolved in 3-methoxypropionitrile so as to be 20% by mass to obtain an electrolyte L-06.

<< Preparation of electrolyte L-07 >>
Exemplified compound (RE-2) was dissolved in 3-methoxypropionitrile so as to be 20% by mass to obtain an electrolyte L-07.

<< Preparation of electrolyte L-08 >>
Exemplified compound (RE-3) was dissolved in 3-methoxypropionitrile so as to be 20% by mass to obtain an electrolyte L-08.

<< Preparation of electrolyte L-09 >>
The exemplified compound (RA-1) was dissolved in propylene carbonate so as to be 20% by mass to obtain an electrolyte L-09.

<< Preparation of electrolyte L-10 >>
The exemplified compound (RA-1) was dissolved in γ-butyrolactone so as to be 20% by mass to obtain an electrolyte L-10.

<< Preparation of dye-sensitized solar cells SC-102 to 110 >>
The production of the dye-sensitized solar cell SC-101 was performed in the same manner as the production of the dye-sensitized solar cell SC-101 except that the electrolyte and the dye were changed as shown in Table 1. SC-102 to 110 were produced.

<< Preparation of dye-sensitized solar cell SC-111 >>
In preparing the dye-sensitized solar cell SC-101, instead of using a dye solution in which 0.1 part by mass of the Ru complex dye N719 was dissolved in 200 parts by mass of acetonitrile: t-butanol = 1: 1 solution, acetonitrile: Dye-sensitized solar cell SC-111 was produced in the same manner except that a dye solution in which 0.1 part by mass of organic dye D149 was dissolved in 200 parts by mass of t-butanol = 1: 1 solution.

<< Evaluation of photoelectric conversion characteristics of dye-sensitized solar cells >>
Each of the dye-sensitized solar cells SC-101 to 111 obtained above was irradiated with light having an intensity of 100 mW / m ² by a solar simulator (manufactured by JASCO (JASCO), low energy spectral sensitivity measuring device CEP-25). The open circuit voltage Voc (V) when irradiated was determined and shown in Table 1. The value was an average value of values obtained by producing three solar cells having the same configuration and production method.

<< Durability evaluation of dye-sensitized solar cells >>
Each of the dye-sensitized solar cells SC-101 to 111 obtained above was stored at 85 ° C. for 300 hours, and durability evaluation of the open circuit voltage reduction rate (%) was performed.

As can be seen from Table 1, in the dye-sensitized solar cells SC-103 to 111 produced using the electrolyte of the present invention, the open-circuit voltage was improved compared to the comparative dye-sensitized solar cells SC-101 and 102, Furthermore, it turns out that the stability in durability evaluation is improving. In particular, it can be seen that the dye-sensitized solar cells SC-104 to 111 using the azaadamantane N-oxyl derivative or azabicyclo N-oxyl derivative of the present invention are good.

DESCRIPTION OF SYMBOLS 1 Conductive base material 11 Substrate 12 Conductive layer 2 Porous n-type semiconductor electrode 3 Dye 4 Charge transfer layer 5 Counter electrode 51 Substrate 52 Counter electrode conductive layer

Claims

A dye-sensitized solar cell having, on a conductive substrate, a porous n-type semiconductor electrode having a dye adsorbed on its surface, a charge transfer layer, and a counter electrode, wherein the charge transfer layer is an N-oxyl derivative A dye-sensitized solar cell comprising a radical compound comprising:
2. The dye-sensitized solar cell according to claim 1, wherein the N-oxyl derivative is an azaadamantane N-oxyl derivative or an azabicyclo N-oxyl derivative.
The dye-sensitized solar cell according to claim 2, wherein the azabicyclo N-oxyl derivative is represented by the following general formula (1).

(Wherein R 1 , R 2 , R 3 and R 4 each independently represents a hydrogen atom, an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heterocyclic group, and X is necessary for forming a cyclic structure. 2 or 3 atomic groups.)
The dye-sensitized solar cell according to any one of claims 1 to 3, wherein the charge transfer layer contains an organic solvent.
5. The dye-sensitized solar cell according to claim 4, wherein the organic solvent is 3-methoxypropionitrile, ethylene carbonate, propylene carbonate, or γ-butyrolactone.