JP4453889B2 - Electrolytic solution composition, photoelectric conversion element and photovoltaic cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolyte composition excellent in charge transport ability, a photoelectric conversion element and a photovoltaic cell excellent in conversion efficiency using the same.
[0002]
[Prior art]
Photoelectric conversion elements are used in various optical sensors, copying machines, and photovoltaic power generation devices. Various systems such as those using metals, semiconductors, organic pigments and dyes, and combinations of these have been put to practical use as photoelectric conversion elements.
U.S. Pat. A photoelectric conversion element using a sensed semiconductor fine particle (hereinafter referred to as “dye-sensitized photoelectric conversion element”), a material for producing the photoelectric conversion element, and a manufacturing technique are disclosed. As a semiconductor fine particle, an inexpensive semiconductor such as titanium oxide can be used without being purified with high purity. Therefore, such a dye-sensitized photoelectric conversion element has an advantage that it can be produced at a low cost. However, in these dye-sensitized photoelectric conversion elements, since an electrolyte solution containing an organic solvent or water is used as an electrolyte, there is a problem that the element deteriorates due to volatilization of the organic solvent or water.
Journal of Electrochemical Society Vol. 143, No. 10, pages 3099-3108 (1996) discloses a method for solving the above problem by using a molten salt electrolyte which is substantially non-volatile. However, since the molten salt electrolyte has low ionic conductivity, a photoelectric conversion element using the molten salt electrolyte has low conversion efficiency and is desired to be improved.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide an electrolytic solution composition having high ionic conductivity and excellent charge transport ability, and a dye-sensitized photoelectric conversion element and a photovoltaic cell excellent in durability and conversion efficiency.
[0004]
[Means for Solving the Problems]
As a result of intensive studies in view of the above object, the present inventors have found that the electrolyte solution composition containing 1-methyl-3-alkylimidazolium iodide having a total carbon number of 7 or less and iodine is excellent in charge transporting ability, And it discovered that the photoelectric conversion element which has a charge transport layer containing this electrolyte solution composition, and a photovoltaic cell showed the outstanding photoelectric conversion efficiency, and came up with this invention.
[0005]
That is, the electrolytic solution composition of the present invention is an electrolytic solution composition containing 1-methyl-3-alkylimidazolium iodide having a total carbon number of 7 or less and iodine, and 70 mol of the cation in the electrolytic solution composition. % Or more is 1-methyl-3-alkylimidazolium ion having a total carbon number of 7 or less, and 30 mol% or more of anions in the electrolyte composition is iodide ion.
[0006]
It is preferable that 30 mol% or more of all cations in the electrolyte composition is 1-methyl-3-n-propylimidazolium ion, and 10 to 70 mol% is 1-methyl-3-ethylimidazolium ion. Preferably, 10 to 70 mol% is 1,3-dimethylimidazolium ion.
[0007]
The electrolytic solution composition preferably contains an anion selected from the group consisting of tetrafluoroborate ions, thiocyanate ions, and trifluoroacetate ions. Moreover, it is preferable to contain a pyridine or a pyridine derivative, and it is preferable to contain a lithium ion.
[0008]
The photoelectric conversion element of the present invention is a photoelectric conversion element having a semiconductor fine particle layer adsorbed with a dye, a conductive support, and a charge transport layer, wherein the charge transport layer is composed of the above electrolyte composition.
[0009]
The photovoltaic cell of the present invention uses the above photoelectric conversion element.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
[1] Electrolyte composition
The electrolytic solution composition of the present invention contains at least 1-methyl-3-alkylimidazolium iodide and iodine having a total carbon number of 7 or less, and 70 mol% or more of the cations in the electrolytic solution composition has a total carbon number of 7 The following 1-methyl-3-alkylimidazolium ions and an ionic liquid in which 30 mol% or more of the anions in the electrolyte composition are iodide ions. The electrolytic solution composition may appropriately contain an iodide salt other than imidazolium iodide, a molten salt for dilution, a gelling agent, or various additives. Examples of preferred additives include inorganic salts and pyridines. However, it does not contain volatile components that deteriorate the durability of the dye-sensitized photoelectric conversion element, which is the main use of the electrolyte composition of the present invention (for example, an organic solvent having a boiling point of 150 ° C. or lower, an additive having a boiling point of 150 ° C. or lower). .
[0011]
The most important property of the electrolyte composition is the charge transport ability when applied to a photoelectric conversion element, and the following four points are important for the charge transport ability.
(a) Ratio of ionic compound in the electrolyte composition
(b) Ratio of iodide ion to all anions in electrolyte composition
(c) Ratio of iodine in the electrolyte composition
(d) Ratio of 1-methyl-3-alkylimidazolium ion to all cations in the electrolyte composition
That is, the electrolytic solution composition of the present invention is mainly composed of an ionic compound, and when it contains a nonionic gelling agent or a nonionic additive, the total amount is preferably 40% by mass with respect to the electrolytic solution composition. Hereinafter, it is more preferably 20% by mass or less. In the present invention, the ratio of iodide ions to the total anions in the electrolytic solution composition is 30 mol% or more, preferably 40 mol% or more. The content of iodine in the electrolytic solution composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 5% by mass with respect to the entire electrolytic solution composition material. In addition, iodine reacts with iodide ions in the electrolyte composition and changes to polyiodide ions. In the present invention, the ratio of 1-methyl-3-alkylimidazolium ions having a total carbon number of 7 or less to all cations in the electrolytic solution composition is 70 mol% or more. When the ratio of iodide ion to the total anion in the electrolyte composition is less than 30 mol% or the ratio of 1-methyl-3-alkylimidazolium ion to the total cation is less than 70 mol%, the ionic conduction of the electrolyte composition The conversion efficiency is not sufficient when a photoelectric conversion element is produced using this.
[0012]
The electrolytic solution composition of the present invention is a uniform liquid at room temperature. The viscosity of the liquid is preferably as low as possible, and the viscosity at room temperature is preferably 1000 cp or less, more preferably 500 cp or less, and particularly preferably 300 cp or less. Moreover, you may add a gelatinizer to electrolyte solution composition. In this case, the electrolytic solution composition becomes a non-flowable gel as a whole, but even in that case, the mixture of the constituent components excluding the gelling agent is a uniform liquid.
[0013]
(1) Imidazolium iodide
The imidazolium iodide used in the present invention is a 1-methyl-3-alkylimidazolium iodide having a total carbon number of 7 or less, preferably 1-methyl-3-n-propylimidazolium iodide, 1-methyl- 3-Isopropylimidazolium iodide, 1-methyl-3-ethylimidazolium iodide, or 1,3-dimethylimidazolium iodide. Of these, 1-methyl-3-n-propylimidazolium iodide is a liquid, and 1-methyl-3-isopropylimidazolium iodide, 1-methyl-3-ethylimidazolium iodide and 1,3-dimethylimidazole are used. Lilium iodide is a solid. Liquid iodide salts can be used alone. On the other hand, the solid iodide salt is used by dissolving in 1-methyl-3-n-propylimidazolium iodide, liquid iodide salt, diluted molten salt, or various additives. In general, a liquid iodide salt is more preferable than a solid iodide salt because there is no limitation in use such as solubility. Therefore, the imidazolium iodide used in the present invention is most preferably 1-methyl-3-n-propylimidazolium iodide.
[0014]
(2) Iodide salts other than imidazolium iodide
Iodide salts other than imidazolium iodide are preferably liquid at room temperature. Examples of the iodide salt that can be preferably used include those represented by any one of the following general formulas (Y-a), (Y-b), and (Y-c).
[0015]
[Chemical 1]
[0016]
Q in general formula (Y-a)_y1Represents an atomic group that forms a 5- or 6-membered aromatic cation with a nitrogen atom. Q_y1Is preferably composed of at least one atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom and sulfur atom. Q_y1The 5-membered ring formed by is preferably an oxazole ring, thiazole ring, imidazole ring, pyrazole ring, isoxazole ring, thiadiazole ring, oxadiazole ring, triazole ring, indole ring or pyrrole ring, A ring or an imidazole ring is more preferable, and an oxazole ring or an imidazole ring is particularly preferable. Q_y1The 6-membered ring formed by is preferably a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring or triazine ring, and more preferably a pyridine ring.
[0017]
In general formula (Y-b), A_y1Represents a nitrogen atom or a phosphorus atom.
[0018]
R in general formulas (Y-a), (Y-b) and (Y-c)_y1~ R_y11Each independently represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkenyl group, preferably an alkyl group having 2 to 6 carbon atoms.
[0019]
In addition, R in the general formula (Y-b)_y2~ R_y5Two or more of them connected to each other_y1May form a non-aromatic ring containing R in the general formula (Y-c)_y6~ R_y11Two or more of them may be connected to each other to form a ring.
[0020]
Q in general formulas (Y-a), (Y-b) and (Y-c)_y1And R_y1~ R_y11May have a substituent, and examples of preferred substituents include halogen atoms, cyano groups, alkoxy groups, alkylthio groups, alkoxycarbonyl groups, amide groups, dialkylcarbamoyl groups, alkyl groups, alkenyl groups, and trialkyls. A silyl group, a trialkylsilyloxy group, etc. are mentioned.
[0021]
The compounds represented by the general formula (Y-a), (Y-b) or (Y-c) may be used alone or in combination of two or more. However, basically, since the effect of the imidazolium iodide used in the present invention is reduced, it is desirable not to use it as much as possible. The total amount of iodide salt other than imidazolium iodide is preferably 50 mol% or less, more preferably 20 mol% or less, based on the imidazolium iodide used in the present invention.
[0022]
(3) Molten salt for dilution
It is preferable to add a diluting molten salt for the purpose of dissolving the solid iodide salt or lowering the viscosity of the electrolyte. The molten salt is a salt that is liquid at normal temperature, and examples of a preferable molten salt that can be used in the present invention include salts in which iodide ions of those exemplified as the preferable iodide salts are replaced with other anions. Preferred examples of anions that replace iodide ions include SCN.^-, BF_Four ^-, PF₆ ^-, ClO_Four ^-, (CF_ThreeSO₂)₂N^-, (CF_ThreeCF₂SO₂)₂N^-, CH_ThreeSO_Three ^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, Ph_FourB^-, (CF_ThreeSO₂)_ThreeC^-Etc. Above all, SCN^-, CF_ThreeCOO^-And BF_Four ^-Is particularly preferred because of its low viscosity and low molecular weight. The cation is preferably a 1-methyl-3-alkylimidazolium ion, more preferably a 1-methyl-3-alkylimidazolium ion having a total carbon number of 7 or less, a 1-methyl-3-ethylimidazolium ion and 1,3 -Dimethylimidazolium ion is particularly preferred. That is, the molten salt for dilution is most preferably thiocyanate of 1-methyl-3-ethylimidazolium or 1,3-dimethylimidazolium, trifluoroacetate, or tetrafluoroborate.
[0023]
In the present invention, the addition amount of the molten salt other than the iodide salt is preferably 1 to 70% by mass, more preferably 5 to 60% by mass, and particularly preferably 10 to 60% by mass with respect to the entire electrolyte composition. . Further, it is preferable that the proportion of 1-methyl-3-ethylimidazolium ion or 1,3-dimethylimidazolium ion in the electrolytic solution composition is high because the ionic conductivity of the electrolytic solution is increased. However, since iodide ions are present in the electrolyte composition, and the iodide salts of these two types of imidazolium ions are solid, attention must be paid to crystal precipitation. For this reason, the ratio of 1-methyl-3-n-propylimidazolium ion in the total cation of the electrolyte composition is preferably at least 30 mol% or more, and 1-methyl-3-ethylimidazolium is preferable. The proportion of ions or 1,3-dimethylimidazolium ions is preferably 10 to 70 mol%.
[0024]
(4) Solvent
The molten salt electrolyte is preferably in a molten state at room temperature, and preferably does not use a solvent. The following solvent may be added, but the content of the molten salt is preferably 50% by mass or more, particularly preferably 90% by mass or more, based on the entire electrolyte composition. Further, it is preferable that 50% by mass or more of the salt is an iodide salt.
[0025]
The solvent used for the electrolyte is desirably a compound having a low viscosity and an improved ion mobility, or a high dielectric constant and an effective carrier concentration, which can exhibit excellent ion conductivity. Examples of such solvents include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether. Chain ethers, ethylene glycol monoalkyl ethers, propylene glycol monoalkyl ethers, polyethylene glycol monoalkyl ethers, polypropylene glycol monoalkyl ethers and other alcohols, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin and many other alcohols Monohydric alcohols, glutarodinitrile, oxydipropio Nitrile compounds of tolyl, dimethyl sulfoxide, aprotic polar substances such as sulfolane and the like, may be used as a mixture thereof.
[0026]
(5) Gelling agent
The electrolyte composition of the present invention may be gelled by adding a gelling agent. Examples of the gelation method include addition of a polymer, addition of an oil gelling agent, addition of polyfunctional monomers and subsequent polymerization, addition of a polymer, and subsequent crosslinking. In the case of gelation by polymer addition, compounds described in “Polymer Electrolyte Reviews-1 and 2” (JRMacCallum and CA Vincent, edited by ELSEVIER APPLIED SCIENCE) can be used. Vinylidene chloride can be preferably used. In the case of gelation by adding an oil gelling agent, Journal of Industrial Science (J. Chem Soc. Japan, Ind. Chem. Sec.), 46,779 (1943), J. Am. Chem. Soc., 111,5542 (1989), J. Chem. Soc., Chem. Com mun., 1993, 390, Angew. Chem. Int. Ed. Engl., 35, 1949 (1996), Chem. Lett., 1996, 885, J. Chm. Soc. The compounds described in Chem. Commun., 1997, 545 can be used, but preferred compounds are those having an amide structure in the molecular structure. The gelation method described in JP-A-2000-58140 can also be applied to the present invention.
[0027]
Further, 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, the crosslinkable reactive group is preferably an amino group or a nitrogen-containing heterocyclic group (a group containing 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.). The crosslinking agent is preferably a bifunctional or higher functional reagent capable of electrophilic reaction with a nitrogen atom (alkyl halide, halogenated aralkyl, sulfonic acid ester, acid anhydride, acid chloride, isocyanate compound, α, β-inactive Saturated sulfonyl group-containing compounds, α, β-unsaturated carbonyl group-containing compounds, α, β-unsaturated nitrile group-containing compounds, etc.). The crosslinking techniques described in JP-A Nos. 2000-17076 and 2000-86724 can also be applied. The addition amount of the gelling agent is usually preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass.
[0028]
(6) Additive
An inorganic salt may be added for the purpose of improving the short-circuit current of the photoelectric conversion element. Preferred inorganic salts include alkali metal or alkaline earth metal salts (LiI, NaI, KI, MgI₂, CaI₂, SrI₂, CF_ThreeCOOLi, CF_ThreeCOONa, LiSCN, LiBF_Four, LiN (SO₂CF_Three)₂, LiPF₆, LiClO_Four, NaSCN, KSCN, RbBF_Four, CsPF₆Etc.). Of these, lithium salts are particularly preferred. The amount of these salts added is preferably about 0.02 to 2% by mass, and more preferably 0.1 to 1% by mass.
Pyridines may be added for the purpose of improving the open circuit voltage of the photoelectric conversion element. A substituted pyridine having a liquid temperature at normal temperature and a boiling point of 150 ° C. or higher is preferred, and a pyridine having an ionic substituent is particularly preferred. The addition amount of pyridines is preferably 1 to 40% by mass, particularly preferably 5 to 30% by mass with respect to the electrolytic solution composition. Specific examples of preferred pyridines are shown below, but the present invention is not limited thereto.
[0029]
[Chemical 2]
[0030]
[2] photoelectric conversion element
The photoelectric conversion element of the present invention has at least a semiconductor fine particle layer to which a dye is adsorbed, a charge transport layer, and a conductive support. Hereinafter, the semiconductor fine particle layer on which the dye is adsorbed is referred to as a photosensitive layer.
[0031]
As shown in FIG. 1, the photoelectric conversion device of the present invention is preferably formed by laminating a conductive layer 10, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 in this order. The semiconductor fine particles 21 sensitized by 22 and the liquid or gel charge transporting material 23 that permeates into the gaps between the semiconductor fine particles 21. The charge transport material 23 in the photosensitive layer 20 is usually the same material used for the charge transport layer 30. Further, a substrate 50 may be provided as a base for the conductive layer 10 and / or the counter electrode conductive layer 40 in order to impart strength to the photoelectric conversion element. In the present invention, the layer composed of the conductive layer 10 and the optionally provided substrate 50 is referred to as “conductive support”, and the layer composed of the counter electrode conductive layer 40 and the optionally provided substrate 50 is referred to as “counter electrode”.
[0032]
(A) Conductive support
The conductive support is composed of (1) a single layer of a conductive layer, or (2) two layers of a conductive layer and a substrate. If a conductive layer that can maintain sufficient strength and sealing properties is used, a substrate is not always necessary.
[0033]
In the case of (1), it is possible to use a material having sufficient strength as a conductive layer, such as metal, and having conductivity. In the case of (2), a substrate having a conductive layer containing a conductive agent on the photosensitive layer side can be used. Preferred conductive agents include metals (platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, and conductive metal oxides (indium-tin composite oxide, tin oxide doped with fluorine, etc.). Can be mentioned. The thickness of the conductive layer is preferably about 0.02 to 10 μm.
[0034]
The lower the surface resistance of the conductive support, the better. The range of the surface resistance is preferably 100Ω / □ or less, more preferably 40Ω / □ or less. The lower limit of the surface resistance is not particularly limited, but is usually about 0.1Ω / □.
[0035]
When irradiating light from the conductive support side, the conductive support is preferably substantially transparent. Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more, and more preferably 70% or more.
[0036]
The transparent conductive support is preferably formed by applying or vapor-depositing a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic. In particular, conductive glass in which a conductive layer made of tin dioxide doped with fluorine is deposited on a transparent substrate made of low-cost soda-lime float glass is preferable. Moreover, in order to obtain a flexible photoelectric conversion element or solar cell at low cost, it is preferable to use a transparent polymer film provided with a conductive layer. Transparent polymer film materials include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like can be used. In order to ensure sufficient transparency, the amount of conductive metal oxide applied is 1 m of glass or plastic support.²The amount is preferably 0.01 to 100 g.
[0037]
It is preferable to use a metal lead for the purpose of reducing the resistance of the transparent conductive support. The material of the metal lead is preferably a metal such as aluminum, copper, silver, gold, platinum, nickel, and particularly preferably aluminum and silver. The metal lead is preferably installed on a transparent substrate by vapor deposition, sputtering, or the like, and a transparent conductive layer made of tin oxide doped with fluorine or an ITO film is provided thereon. Moreover, it is also preferable to install a metal lead on the transparent conductive layer after providing the transparent conductive layer on the transparent substrate. The decrease in the amount of incident light due to the installation of the metal lead is preferably within 10%, more preferably 1 to 5%.
[0038]
(B) Photosensitive layer
In the photosensitive layer, the semiconductor acts as a photoconductor, absorbs light, separates charges, and generates electrons and holes. In a dye-sensitized semiconductor, light absorption and generation of electrons and holes thereby occur mainly in the dye, and the semiconductor fine particles receive and transmit these electrons (or holes). The semiconductor used in the present invention is preferably an n-type semiconductor in which conductor electrons become carriers under photoexcitation and give an anode current.
[0039]
(1) Semiconductor
Semiconductors include simple semiconductors such as silicon and germanium, III-V group compound semiconductors, metal chalcogenides (oxides, sulfides, selenides, composites thereof, etc.), compounds having a perovskite structure (strontium titanate) , Calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.) can be used.
[0040]
Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc, lead, silver, antimony or bismuth. Sulfides, cadmium or lead selenides, cadmium tellurides and the like. Examples of other compound semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, and copper-indium sulfides. Furthermore, M_xO_yS_zOr M_1xM_2yO_z (M, M₁And M₂In addition, composites such as are each a metal element, O is oxygen, and x, y, and z are the number of combinations in which the valence is neutral) can be preferably used.
[0041]
Preferred specific examples of the semiconductor used in the present invention include Si and TiO.₂, SnO₂, Fe₂O_Three, WO_Three, ZnO, Nb₂O_Five, CdS, ZnS, PbS, Bi₂S_Three, CdSe, CdTe, SrTiO_Three, GaP, InP, GaAs, CuInS₂, CuInSe₂And more preferably TiO₂, ZnO, SnO₂, Fe₂O_Three, WO_Three, Nb₂O_Five, CdS, PbS, CdSe, SrTiO_Three, InP, GaAs, CuInS₂Or CuInSe₂And particularly preferably TiO₂Or Nb₂O_FiveAnd most preferably TiO₂It is. TiO₂Among them, TiO containing 70% or more of anatase type crystals₂100% anatase type TiO₂Is particularly preferred. It is also effective to dope metals for the purpose of increasing the electron conductivity in these semiconductors. As a metal to dope, a bivalent or trivalent metal is preferable. In order to prevent a reverse current from flowing from the semiconductor to the charge transport layer, it is also effective to dope the semiconductor with a monovalent metal.
[0042]
The semiconductor used in the present invention may be single crystal or polycrystalline, but is preferably polycrystalline from the viewpoint of production cost, securing raw materials, energy payback time, etc., and the semiconductor fine particle layer is particularly preferably a porous film. Moreover, a part amorphous part may be included.
[0043]
The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably 5 to 200 nm, more preferably 8 to 100 nm. preferable. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 30 μm. Two or more kinds of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 25 nm or less, more preferably 10 nm or less. For the purpose of improving the light capture rate by scattering incident light, it is also preferable to mix semiconductor particles having a large particle size, for example, about 100 nm to 300 nm.
[0044]
Two or more different types of semiconductor fine particles may be mixed and used. When two or more kinds of semiconductor fine particles are mixed and used, one of them is TiO₂, ZnO, Nb₂O_FiveOr SrTiO_ThreeIt is preferable that The other is SnO₂, Fe₂O_ThreeOr WO_ThreeIt is preferable that A more preferable combination is ZnO and SnO.₂, ZnO and WO_Three, ZnO and SnO₂And WO_ThreeAnd the like. When two or more kinds of semiconductor fine particles are mixed and used, their particle sizes may be different. Especially the above TiO₂, ZnO, Nb₂O_FiveOr SrTiO_ThreeThe particle size of SnO₂, Fe₂O_ThreeOr WO_ThreeA combination with a small is preferred. Preferably, the large particle size is 100 nm or more, and the small particle size is 15 nm or less.
[0045]
Semiconductor fine particles are prepared by Sakuo Sakuo's “Science of Sol-Gel Method” Agne Jofusha (1998), Technical Information Association “Sol-gel Method for Thin Film Coating” (1995), etc. The sol-gel method described, Tadao Sugimoto, “Synthesis and size control of monodisperse particles by the new synthetic gel-sol method”, Materia, Vol. 35, No. 9, 1012-1018 (1996) Etc. are preferred. In addition, a method developed by Degussa for producing an oxide by high-temperature hydrolysis of a chloride in an oxyhydrogen salt can be preferably used.
[0046]
When the semiconductor fine particles are titanium oxide, the sol-gel method, gel-sol method, and high-temperature hydrolysis method in oxyhydrogen salt of chloride are all preferred, but Kiyoshi Manabu's “Titanium oxide properties and applied technology” The sulfuric acid method and the chlorine method described in Gihodo Publishing (1997) can also be used. Further, as a sol-gel method, the method described in Journal of American Ceramic Society, Volume 80, No. 12, pages 3157-3171 (1997), Barbe et al., Chemistry of Materials, Burnside et al. , Vol. 10, No. 9, pages 2419-2425 are also preferred.
[0047]
(2) Semiconductor fine particle layer
In order to apply the semiconductor fine particles on the conductive support, in addition to the method of applying a dispersion or colloidal solution of the semiconductor fine particles on the conductive support, the above-described sol-gel method or the like can also be used. In consideration of mass production of photoelectric conversion elements, physical properties of semiconductor fine particle liquid, flexibility of conductive support, etc., a wet film forming method is relatively advantageous. Typical examples of the wet film forming method include a coating method, a printing method, an electrolytic deposition method, and an electrodeposition method. In addition, a method of oxidizing metal, a method of depositing in a liquid phase from a metal solution by ligand exchange (LPD method), a method of vapor deposition by sputtering, a CVD method, or a metal that is thermally decomposed on a heated substrate An SPD method in which a metal oxide is formed by spraying an oxide precursor can also be used.
[0048]
In addition to the sol-gel method described above, a method for preparing a dispersion of semiconductor fine particles includes a method of grinding in a mortar, a method of dispersing while pulverizing using a mill, and fine particles in a solvent when synthesizing a semiconductor. The method of depositing and using as it is is mentioned.
[0049]
As the dispersion medium, water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, citronellol, terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.) can be used. At the time of dispersion, for example, a polymer such as polyethylene glycol, hydroxyethyl cellulose, carboxymethyl cellulose, a surfactant, an acid, a chelating agent, and the like may be used as a dispersion aid. By changing the molecular weight of the polyethylene glycol, the viscosity of the dispersion can be adjusted, and a semiconductor layer that is difficult to peel off can be formed and the porosity of the semiconductor layer can be controlled. Therefore, it is preferable to add polyethylene glycol.
[0050]
As application methods, roller method, dip method, etc. as application system, air knife method, blade method, etc. as metering system, and application and metering can be made the same part, disclosed in Japanese Patent Publication No. 58-4589 The wire bar method, the slide hopper method, the extrusion method, the curtain method, etc. described in US Pat. Nos. 2,681,294, 2761419, 2761791 and the like are preferable. Moreover, a spin method and a spray method are also preferable as a general purpose machine. As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. Among these, a preferable film forming method may be selected according to the liquid viscosity and the wet thickness.
[0051]
The semiconductor fine particle layer is not limited to a single layer, and a multi-layer coating of a dispersion of semiconductor fine particles having different particle diameters, or a multi-layer coating of a coating layer containing different types of semiconductor fine particles (or different binders and additives) You can also Multi-layer coating is also effective when the film thickness is insufficient with a single coating.
[0052]
In general, as the semiconductor fine particle layer thickness (same as the photosensitive layer thickness) increases, the amount of supported dye increases per unit projected area and thus the light capture rate increases. Loss due to coupling also increases. Therefore, the preferable thickness of the semiconductor fine particle layer is 0.1 to 100 μm. When used in a photovoltaic cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, and more preferably 2 to 25 μm. Semiconductor fine particle support 1m²The hit application amount is preferably 0.5 to 100 g, more preferably 3 to 50 g.
[0053]
After the semiconductor fine particles are applied on the conductive support, the semiconductor fine particles are preferably brought into contact with each other electronically, and heat treatment is preferably performed in order to improve the coating strength and the adhesion to the support. A preferable heating temperature range is 40 ° C. or more and 700 ° C. or less, and more preferably 100 ° C. or more and 600 ° C. or less. The heating time is about 10 minutes to 10 hours. When using a support having a low melting point or softening point such as a polymer film, high temperature treatment is not preferable because it causes deterioration of the support. Moreover, it is preferable that it is as low temperature as possible (for example, 50 to 350 degreeC) also from a viewpoint of cost. The temperature can be lowered by heat treatment in the presence of small semiconductor particles of 5 nm or less, mineral acids, and metal oxide precursors, and by applying ultraviolet rays, infrared rays, microwaves, etc., electric fields, and ultrasonic waves. It can also be done. At the same time, for the purpose of removing unnecessary organic substances and the like, it is preferable to use a combination of irradiation, application, heating, decompression, oxygen plasma treatment, pure water cleaning, solvent cleaning, gas cleaning and the like in combination as appropriate.
[0054]
After the heat treatment, for example, chemical plating using titanium tetrachloride aqueous solution or titanium trichloride to increase the surface area of the semiconductor fine particles, increase the purity in the vicinity of the semiconductor fine particles, and increase the efficiency of electron injection from the dye into the semiconductor fine particles. You may perform the electrochemical plating process using aqueous solution. In order to prevent a reverse current from flowing from the semiconductor fine particles to the charge transport layer, it is also effective to adsorb an organic substance having a low electron conductivity other than the dye on the particle surface. The organic substance to be adsorbed is preferably an organic substance having a hydrophobic group.
[0055]
The semiconductor fine particle layer preferably has a large surface area so that a large amount of dye can be adsorbed. The surface area of the semiconductor fine particle layer coated on the support is preferably at least 10 times, more preferably at least 100 times the projected area. The upper limit is not particularly limited, but is usually about 1000 times.
[0056]
(3) Dye
The sensitizing dye used in the photosensitive layer can be arbitrarily used as long as it is a compound that has absorption in the visible region and near-infrared region and can sensitize semiconductors. A dye is preferred. Moreover, in order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, two or more kinds of dyes can be used in combination or mixed. In this case, it is possible to select the dye to be used or mixed and the ratio thereof so as to match the wavelength range and intensity distribution of the target light source.
[0057]
Such a dye preferably has an appropriate interlocking group capable of adsorbing to the surface of the semiconductor fine particles. Preferred linking groups include -COOH group, -OH group, -SO_ThreeH group, -P (O) (OH)₂Group and -OP (O) (OH)₂And chelating groups having π conductivity such as oximes, dioximes, hydroxyquinolines, salicylates and α-ketoenolates. -COOH group, -P (O) (OH)₂Group and -OP (O) (OH)₂The group is particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an internal salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case where the methine chain forms a squarylium ring or a croconium ring, this part may be used as a linking group. Hereinafter, preferred sensitizing dyes used in the photosensitive layer will be specifically described.
[0058]
(a) Metal complex dye
When the dye is a metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye or a ruthenium complex dye is preferable, and a ruthenium complex dye is particularly preferable. Examples of ruthenium complex dyes include, for example, U.S. Pat. / 50393, JP-A 2000-26487, and the like.
[0059]
The ruthenium complex dye used in the present invention has the following general formula (I):
(A₁)_pRu (B-a) (B-b) (B-c) (I)
Is preferably represented by: In general formula (I), A₁Represents a mono or bidentate ligand, preferably Cl, SCN, H₂It is a ligand selected from the group consisting of O, Br, I, CN, NCO, SeCN, β-diketone derivatives, oxalic acid derivatives and dithiocarbamic acid derivatives. p is an integer of 0-3. B-a, B-b and B-c each independently represents an organic ligand represented by any of the following formulas B-1 to B-10.
[0060]
[Chemical Formula 3]
[0061]
In formulas B-1 to B-10, R_ThreeRepresents a hydrogen atom or a substituent, and examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 12 carbon atoms, Examples thereof include substituted or unsubstituted aryl groups having 6 to 12 carbon atoms, the aforementioned acidic groups (these acidic groups may form a salt), and chelating groups. Here, the alkyl part of the alkyl group and the aralkyl group may be linear or branched, and the aryl part of the aryl group and the aralkyl group may be monocyclic or polycyclic (fused ring, ring assembly). B-a, B-b and B-c may be the same or different, and may be any one or two.
[0062]
Specific examples of preferable metal complex dyes are shown below, but the present invention is not limited thereto.
[0063]
[Formula 4]
[0064]
[Chemical formula 5]
[0065]
(B) Methine dye
A preferred methine dye used in the present invention is a polymethine dye such as a cyanine dye, a merocyanine dye, or a squarylium dye. Examples of preferred polymethine dyes include JP-A-11-35836, JP-A-11-67285, JP-A-11-86916, JP-A-11-97725, JP-A-11-158395, JP-A-11-163378, Examples thereof include the dyes described in JP-A-11-214730, JP-A-11-214731, JP-A-11-238905, JP-A-2000-26487, European Patents 892411, 911841 and 991092. Specific examples of preferable methine dyes are shown below.
[0066]
[Chemical 6]
[0067]
[Chemical 7]
[0068]
(4) Adsorption of dye to semiconductor fine particles
Adsorption of the dye to the semiconductor fine particles can be carried out by immersing a conductive support having a well-dried semiconductor fine particle layer in the dye solution or by applying a dye solution to the semiconductor fine particle layer. In the former case, an immersion method, a dip method, a roller method, an air knife method or the like can be used. In the case of the immersion method, the adsorption of the dye may be performed at room temperature or may be performed by heating and refluxing as described in JP-A-7-249790. Examples of the latter application method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. In addition, a dye can be applied in an image form by an inkjet method or the like, and the image itself can be used as a photoelectric conversion element.
[0069]
The solvent used for the dye solution (dye adsorption solution) is preferably alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane Halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc. ), Hydrocarbon (hexane, petroleum ether, benzene, toluene, etc.) or a mixed solvent thereof.
[0070]
The total amount of dye adsorbed is the unit area of the semiconductor fine particle layer (1 m²) Is preferably 0.01 to 100 mmol. The amount of the dye adsorbed on the semiconductor fine particles is preferably in the range of 0.01 to 1 mmol per 1 g of the semiconductor fine particles. By using such an amount of dye adsorbed, a sensitizing effect in a semiconductor can be sufficiently obtained. On the other hand, if the amount of the dye is too small, the sensitizing effect becomes insufficient, and if the amount of the dye is too large, the dye not attached to the semiconductor floats, which causes a reduction in the sensitizing effect. In order to increase the adsorption amount of the dye, it is preferable to perform a heat treatment before the adsorption. In order to avoid water adsorbing on the surface of the semiconductor fine particles after the heat treatment, it is preferable to quickly perform the dye adsorption operation at a temperature of the semiconductor electrode substrate of 60 to 150 ° C. without returning to normal temperature. Further, for the purpose of reducing the interaction such as aggregation between the dyes, a colorless compound may be added to the dye adsorbing solution and co-adsorbed on the semiconductor fine particles. Effective compounds for this purpose are compounds having surface active properties and structures, and examples thereof include steroid compounds having a carboxyl group (chenodeoxycholic acid) and sulfonates such as the following examples.
[0071]
[Chemical 8]
[0072]
The unadsorbed dye is preferably removed by washing immediately after adsorption. The washing is preferably performed using a wet washing tank with a polar solvent such as acetonitrile or an organic solvent such as an alcohol solvent.
[0073]
After adsorbing the dye, the surface of the semiconductor fine particles may be treated with amines or quaternary ammonium salts. Preferable amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. Preferred quaternary ammonium salts include tetrabutylammonium iodide and tetrahexylammonium iodide. These may be used by dissolving in an organic solvent, or may be used as they are in the case of a liquid.
[0074]
(C) Charge transport layer
The above electrolyte composition is used for the charge transport layer. There are two methods for forming the charge transport layer. One is a method in which a counter electrode is first bonded onto the photosensitive layer, and an electrolytic solution composition is sandwiched between the gaps. The other is a method in which a charge transport layer is provided directly on the photosensitive layer, and a counter electrode is subsequently provided.
[0075]
In the case of the former method, as a method for sandwiching the electrolyte composition, a normal pressure process using capillary action due to 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. .
[0076]
In the case of the latter method, when using the electrolytic solution composition, a counter electrode is provided without being dried, and measures for preventing liquid leakage at the edge portion are taken. Moreover, when using a gel-like electrolyte solution composition, there exists a method of apply | coating wetly and solidifying by methods, such as superposition | polymerization, In that case, a counter electrode can also be provided after drying and fixing.
[0077]
(D) Counter electrode
Similar to the conductive support described above, the counter electrode may have a single-layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate. As the conductive material used for the counter electrode conductive layer, metal (platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, and conductive metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, etc.) Is mentioned. Among these, platinum, gold, silver, copper, aluminum, and magnesium can be preferably used. The support substrate used for the counter electrode is preferably a glass substrate or a plastic substrate, and the conductive material is applied or vapor-deposited thereon for use. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. The lower the surface resistance of the counter electrode layer, the better. The range of the surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less.
[0078]
Since light may be irradiated from either or both of the conductive support and the counter electrode, in order for light to reach the photosensitive layer, at least one of the conductive support and the counter electrode may be substantially transparent. . From the viewpoint of improving the power generation efficiency, it is preferable to make the conductive support transparent so that light is incident from the conductive support 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.
[0079]
The counter electrode may be formed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive agent on the charge transport layer or attaching the conductive layer side of the substrate having the conductive layer. Further, as in the case of the conductive support, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode, particularly when the counter electrode is transparent. In addition, the material and installation method of a preferable metal lead, the fall of the incident light amount by metal lead installation, etc. are the same as the case of an electroconductive support body.
[0080]
(E) Other layers
In order to prevent a short circuit between the counter electrode and the conductive support, it is preferable that a dense semiconductor thin film layer is preliminarily applied as an undercoat layer between the conductive support and the photosensitive layer. This method of preventing a short circuit by the undercoat layer is particularly effective when an electron transport material or a hole transport material is used for the charge transport layer. The undercoat layer is preferably TiO₂, SnO₂, Fe₂O_Three, WO_Three, ZnO or Nb₂O_FiveMore preferably TiO₂Consists of. The undercoat layer can be applied by, for example, a spray pyrolysis method described in Electrochim. Acta 40, 643-652 (1995), a sputtering method, or the like. The preferred thickness of the undercoat layer is 5 to 1000 nm, and more preferably 10 to 500 nm.
[0081]
Moreover, you may provide functional layers, such as a protective layer and an antireflection layer, in the outer surface of one or both of the electroconductive support body which acts as an electrode, and a counter electrode, between an electroconductive layer and a board | substrate, or in the middle of a board | substrate. For forming these functional layers, a coating method, a vapor deposition method, a bonding method, or the like can be used depending on the material.
[0082]
(F) Specific example of internal structure of photoelectric conversion element
As described above, the internal structure of the photoelectric conversion element can take various forms depending on the purpose. If roughly divided into two, a structure that allows light to enter from both sides and a structure that allows only one side are possible. 2 to 9 illustrate the internal structure of a photoelectric conversion element that can be preferably applied to the present invention.
[0083]
In the structure shown in FIG. 2, the photosensitive layer 20 and the charge transport layer 30 are interposed between the transparent conductive layer 10a and the transparent counter electrode conductive layer 40a, and light is incident from both sides. . In the structure shown in FIG. 3, a metal lead 11 is partially provided on a transparent substrate 50a, a transparent conductive layer 10a is provided thereon, and an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are arranged in this order. Further, a support substrate 50 is arranged, and light is incident from the conductive layer side. The structure shown in FIG. 4 has a conductive layer 10 on a support substrate 50, a photosensitive layer 20 provided through an undercoat layer 60, a charge transport layer 30 and a transparent counter electrode conductive layer 40a, and a metal in part The transparent substrate 50a provided with the leads 11 is arranged with the metal lead 11 side inward, and has a structure in which light enters from the counter electrode side. In the structure shown in FIG. 5, the primer layer 60, the photosensitive layer 20, and the charge transport layer 30 are provided between a pair of metal leads 11 provided on a transparent substrate 50 a and a transparent conductive layer 10 a (or 40 a). In this structure, light enters from both sides. In the structure shown in FIG. 6, a transparent conductive layer 10a, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30 and a counter electrode conductive layer 40 are provided on a transparent substrate 50a, and a support substrate 50 is disposed thereon. In this structure, light enters from the conductive layer side. The structure shown in FIG. 7 has a conductive layer 10 on a support substrate 50, a photosensitive layer 20 provided via an undercoat layer 60, a charge transport layer 30 and a transparent counter electrode conductive layer 40a, and a transparent substrate thereon. 50a is arranged, and light is incident from the counter electrode side. The structure shown in FIG. 8 has a transparent conductive layer 10a on a transparent substrate 50a, a photosensitive layer 20 is provided via an undercoat layer 60, a charge transport layer 30 and a transparent counter electrode conductive layer 40a are provided, and a transparent layer is provided thereon. The substrate 50a is disposed, and light is incident from both sides. In the structure shown in FIG. 9, the conductive layer 10 is provided on the support substrate 50, the photosensitive layer 20 is provided via the undercoat layer 60, and the solid charge transport layer 30 is further provided. It has a metal lead 11 and has a structure in which light is incident from the counter electrode side.
[0084]
[3] Photocell
The photovoltaic cell of the present invention is one in which the photoelectric conversion element of the present invention is caused to work with an external load. Of the photovoltaic cells, the case where the charge transport material is mainly composed of an ion transport material as in the present invention is particularly called a photoelectrochemical cell, and the case where the main purpose is power generation by sunlight is called a solar cell. In order to prevent deterioration of components and volatilization of the contents of the photovoltaic cell, it is preferable to seal the side surface with a polymer or an adhesive. The external circuit itself connected to the conductive support and the counter electrode via a lead may be a known one.
[0085]
When the photoelectric conversion element of the present invention is applied to a solar cell, the structure inside the cell is basically the same as the structure of the photoelectric conversion element described above. Moreover, the dye-sensitized solar cell using the photoelectric conversion element of the present invention can basically have the same module structure as a conventional solar cell module. The solar cell module generally has a structure in which cells are formed on a support substrate such as metal or ceramic, and the cell is covered with a filling resin or protective glass, and light is taken in from the opposite side of the support substrate. It is also possible to use a transparent material such as tempered glass for the support substrate, configure a cell thereon, and take in light from the transparent support substrate side. Specifically, module structures called super straight type, substrate type, potting type, and substrate integrated module structures used in amorphous silicon solar cells, etc. are known, and the dye-sensitized solar cell of the present invention is also used. Depending on the location and environment of use, the module structure can be selected as appropriate. Specifically, the structure and aspect described in JP-A-2000-268892 are preferable.
[0086]
【Example】
Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
[0087]
Reference example 1
1. Preparation of titanium oxide particle dispersion
  To a mixture of 360 g of water and 12 g of acetic acid, 62 g of tetraisopropyl orthotitanate (manufactured by Wako Pure Chemical Industries, Ltd.) was added all at once at 25 ° C. and stirred for 1 hour. To this solution was added 6 ml of concentrated nitric acid at 80 ° C., and the mixture was further stirred for 4 hours. 50 ml of the obtained titanium oxide sol was transferred to a stainless steel autoclave, stirred at 240 ° C. for 16 hours, and then centrifuged at 15,000 rpm for 30 minutes. Next, the supernatant is removed by decantation, 0.3 g of polyethylene glycol (molecular weight 20000, manufactured by Wako Pure Chemical Industries) and 11 g of water are added and stirred well, and 1 g of ethanol and 0.4 ml of concentrated nitric acid are added to disperse the titanium oxide. A liquid (A) was obtained. The titanium oxide content of (A) was 15% by mass. Further, the average particle diameter of the titanium oxide particles in (A) was determined by X-ray diffractometry to be 16 nm.
[0088]
2. Creation of dye-adsorbed titanium oxide electrode
Transparent conductive glass coated with tin oxide doped with fluorine (made by Nippon Sheet Glass, surface resistance: approx. 10Ω / cm²) Apply the above titanium oxide dispersion (A) to the conductive surface side using a doctor blade, dry it at 25 ° C for 30 minutes, and then use an electric furnace ("Muffle furnace FP-32 type" manufactured by Yamato Kagaku). The titanium oxide electrode was obtained by baking at 450 ° C. for 30 minutes. When the coating amount of titanium oxide per unit area was determined from the mass change before and after coating and baking, the coating amount was 16.2 g / m.²Met.
The obtained titanium oxide electrode was immersed in a dye adsorbing solution containing the following dye R-A at 25 ° C. for 16 hours and washed successively with ethanol and acetonitrile to produce a dye adsorbing titanium oxide electrode. The dye adsorbing solution is composed of the dye RA and a mixed solvent of ethanol, t-butanol and acetonitrile (ethanol: t-butanol: acetonitrile = 1: 1: 2 (volume ratio)), and the concentration of the dye RA in the dye adsorbing solution. Was 0.3 mmol / l.
[0089]
[Chemical 9]
[0090]
3. Production of photovoltaic cells
Apply the electrolyte composition 1-1 to 1-3 shown in Table 1 to a dye-adsorbed titanium oxide electrode (2cm x 2cm), and leave it in a dry room at 50 ° C under reduced pressure for 16 hours. Was sufficiently soaked into the electrode. Photovoltaic cells A-1 to A-3 were produced by superimposing platinum-deposited glass of the same size on these electrodes. As shown in FIG. 10, these photovoltaic cells include a conductive glass 1 (with a conductive layer 3 placed on a glass 2), a dye-adsorbed titanium dioxide layer 4, a charge transport layer 5, a platinum layer 6 and a glass 7. It has a stacked structure. The structures of iodide salt I-1 and diluted molten salt T-1 shown in Table 1 are shown below.
[0091]
[Table 1]
[0092]
[Chemical Formula 10]
[0093]
4). Measurement of photoelectric conversion efficiency
Simulated sunlight was generated by passing light from a 500 W xenon lamp (USHIO) through a spectral filter ("AM1.5D" manufactured by Oriel). The intensity of this simulated sunlight is 100mW / cm on the vertical plane.²Met. The negative electrode of the photovoltaic cell was connected to the negative electrode of the power source, and the positive electrode of the photovoltaic cell was connected to the positive electrode of the power source. While maintaining the temperature of the photovoltaic cell at 30 ° C. and irradiating simulated sunlight vertically, the current-voltage characteristics were measured to obtain the photoelectric conversion efficiency. The results are shown in Table 2.
[0094]
Comparative Example 1
  Except for changing the electrolyte composition to 1-4 to 1-8 in Table 1Reference example 1Photocells A-4 to A-8 were prepared in the same manner as above, and the photoelectric conversion efficiency was measured. The results are shown in Table 2. The structures of iodide salts I-2 to I-4 shown in Table 1 are shown below.
Embedded image
[0095]
[Table 2]
[0096]
  From the results in Table 2, 1-methyl-3-alkylimidazolium ions having a total carbon number of 7 or less account for 70 mol% or more of cations in the electrolyte composition, and iodide ions account for 30 mol% or more of anions.Reference example 1Photocells A-1 to A-3 have a high short circuit current due to their high ionic conductivity. For this reason, it turns out that photoelectric conversion efficiency is high and it is preferable as a photovoltaic cell.
[0097]
Reference Example 2 and Example 1
  Except for changing the electrolyte composition and diluted molten salt to 2-1 to 2-7 and T-1 to T-7 in Table 3, respectively.Reference example 1Photocells B-1 to B-7 were prepared in the same manner as above, and the photoelectric conversion efficiency was measured. The results are shown in Table 4. The structures of the diluted molten salts T-2 to T-7 shown in Table 3 are shown below.
[0098]
[Table 3]
[0099]
Embedded image
[0100]
Comparative Example 2
  Except for changing electrolyte composition and diluted molten salt to 2-8 and T-8 in Table 3, respectivelyReference example 1Photocell B-8 was prepared in the same manner as above, and the photoelectric conversion efficiency was measured. The results are shown in Table 4. The structure of the diluted molten salt T-8 shown in Table 3 is shown below.
[0101]
Embedded image
[0102]
[Table 4]
[0103]
From the results shown in Table 4, photovoltaic cells B-1 to B-7 in which the proportion of 1-methyl-3-alkylimidazolium ions having 7 or less carbon atoms in the cation in the electrolyte composition is 70 mol% or more are compared. Conversion efficiency is higher than B-8 in Example 2. Further, when 1-methyl-3-alkylimidazolium tetrafluoroborate is used as a diluted molten salt, the conversion efficiency of the alkyl group is high in the order of methyl> ethyl> propyl. This indicates that the smaller the molecular weight of the cation, the higher the ionic conductivity. PF as an anion of diluted molten salt₆ ^-And N (SO₂CF_Three)₂ ^-Than BF_Four ^-, SCN^-And CF_ThreeCO₂ ^-The conversion efficiency is higher.
[0104]
Example 2
  Except for changing the electrolyte composition to that shown in Table 5Reference example 1Photocells C-1 to C-8 were prepared in the same manner as described above, and the photoelectric conversion efficiency was measured. The results are shown in Table 6.
[0105]
[Table 5]
[0106]
[Table 6]
[0107]
From the results in Table 6, the photocells C-3 to C-5 added with pyridines have higher conversion efficiency than the non-added photocell C-1. Moreover, the conversion efficiency of the photovoltaic cells C-7 and C-8 to which pyridines and a lithium salt are added is further increased. Photovoltaic cell C-2 to which only a lithium salt is added without adding pyridines has a lower conversion efficiency than unadded photovoltaic cell C-1.
[0108]
【The invention's effect】
As described in detail above, it contains 1-methyl-3-alkylimidazolium iodide and iodine having a total carbon number of 7 or less.The electrolyte composition isExcellent charge transport capability. Therefore, a dye-sensitized photoelectric conversion element and a photovoltaic cell using such an electrolytic solution composition have excellent photoelectric conversion efficiency.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 2 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 3 is a schematic cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 4 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 5 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 6 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 7 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 8 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 9 is a partial cross-sectional view showing the structure of a preferred photoelectric conversion element of the present invention.
FIG. 10 is a partial cross-sectional view illustrating a structure of a photoelectric conversion element created in an example.
[Explanation of symbols]
1 ... conductive glass
2,7 ... Glass
3. Conductive layer
4 ... Dye adsorption titanium dioxide layer
5,30 ... Charge transport layer
6 ... Platinum layer
10 ... conductive layer
10a ・ ・ ・ Transparent conductive layer
11 ... Metal lead
20 ... Photosensitive layer
21 ... Semiconductor fine particles
22 ... Dye
23 ... Charge transport material
40 ... Counterelectrode conductive layer
40a ・ ・ ・ Transparent counter conductive layer
50 ... Board
50a ・ ・ ・ Transparent substrate
60 ... Undercoat layer

Claims (5)

An electrolytic solution composition containing 1-methyl-3-n-propylimidazolium iodide, 1,3-dimethylimidazolium tetrafluoroborate and iodine,
30 mol% or more of the cation in the electrolyte composition is 1-methyl-3-n-propylimidazolium ion, and 10 to 70 mol% is 1,3-dimethylimidazolium ion,
The sum of the 1-methyl-3-n-propylimidazolium ion and the 1,3-dimethylimidazolium ion accounts for 70 mol% or more of the cation in the electrolyte composition,
And 30 mol% or more of the anions in the said electrolyte composition is iodide ion, The electrolyte solution composition characterized by the above-mentioned. 2. The electrolytic solution composition according to claim 1 , wherein the electrolytic solution composition contains pyridine or a pyridine derivative. 3. The electrolytic solution composition according to claim 1 , wherein the electrolytic solution composition contains lithium ions. 4. A photoelectric conversion element comprising a semiconductor fine particle layer adsorbed with a dye, a conductive support, and a charge transport layer, wherein the charge transport layer comprises the electrolytic solution composition according to any one of claims 1 to 3. A photoelectric conversion element. A photovoltaic cell comprising the photoelectric conversion element according to claim 4 .