WO2013024642A1 - Photoelectric conversion element - Google Patents

Photoelectric conversion element Download PDF

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Publication number
WO2013024642A1
WO2013024642A1 PCT/JP2012/067306 JP2012067306W WO2013024642A1 WO 2013024642 A1 WO2013024642 A1 WO 2013024642A1 JP 2012067306 W JP2012067306 W JP 2012067306W WO 2013024642 A1 WO2013024642 A1 WO 2013024642A1
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WIPO (PCT)
Prior art keywords
photoelectric conversion
layer
conductive layer
conversion element
porous semiconductor
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PCT/JP2012/067306
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French (fr)
Japanese (ja)
Inventor
恵 扇谷
福井　篤
古宮　良一
山中　良亮
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シャープ株式会社
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Publication of WO2013024642A1 publication Critical patent/WO2013024642A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2004—Light-sensitive devices characterised by the electrolyte, e.g. comprising an organic electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M14/00—Electrochemical current or voltage generators not provided for in groups H01M6/00 - H01M12/00; Manufacture thereof
    • H01M14/005—Photoelectrochemical storage cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/542—Dye sensitized solar cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a photoelectric conversion element.
  • a solar cell using a crystalline silicon substrate has a problem that the manufacturing cost of the silicon substrate is high.
  • the thin film silicon solar cell has a problem in that the manufacturing cost is high because it is necessary to use many kinds of semiconductor manufacturing gases and complicated devices. For this reason, in any solar cell, efforts have been made to increase the efficiency of photoelectric conversion in order to reduce the cost per power generation output, but the above problem has not yet been solved sufficiently.
  • Patent Document 1 Japanese Patent No. 26641964 discloses a wet solar cell applying photo-induced electron transfer of a metal complex as a new type solar cell.
  • Patent Document 2 Japanese Patent Laid-Open No. 2008-287900 discloses a wet solar cell using quantum dots as a new type of solar cell.
  • Electrodes are respectively formed on the surfaces of two glass substrates, two glass substrates are arranged so that these electrodes are inside, and a photoelectric conversion layer and an electrolytic solution are placed between the electrodes. It is made so as to be sandwiched.
  • the photoelectric conversion layer is composed of a semiconductor layer in which a photosensitizing dye is adsorbed to give an absorption spectrum in the visible light region.
  • Such a wet solar cell is also called a dye-sensitized solar cell.
  • Patent Document 3 Japanese Patent Laid-Open No. 2001-357897 discloses a wet solar cell using two conductive substrates.
  • a porous semiconductor layer which is a photoelectrode, is formed on one conductive substrate, a catalyst layer is formed on the other conductive substrate, and the side surfaces of the wet solar cell are overlapped so as to match each other. It is produced by sealing with an epoxy adhesive.
  • a hardly volatile solvent as the solvent of the electrolyte of the wet solar cell.
  • the photoelectric conversion efficiency of the wet solar cell is higher than that when a volatile solvent such as acetonitrile is used as the solvent for the electrolyte. There was a problem of a significant drop.
  • an object of the present invention is to provide a photoelectric conversion element that is excellent in durability and can suppress a decrease in photoelectric conversion efficiency.
  • the present invention provides a light transmissive support, a transparent conductive layer provided on the light transmissive support, a photoelectric conversion layer including a porous semiconductor layer provided on the transparent conductive layer, and at least a photoelectric conversion layer.
  • a carrier layer comprising: a conductive layer provided in part; a counter electrode conductive layer provided to face the transparent conductive layer; and a carrier transport material provided between the transparent conductive layer and the counter electrode conductive layer.
  • the material includes a hardly volatile solvent and a redox species, and the conductive layer is a photoelectric conversion element that is electrically connected to the transparent conductive layer.
  • the hardly volatile solvent has no boiling point or the boiling point of the hardly volatile solvent is 100 ° C. or higher.
  • the thickness of the photoelectric conversion layer is preferably 4 ⁇ m or more and 30 ⁇ m or less.
  • the viscosity of the hardly volatile solvent is preferably 1 cp or more.
  • the carrier transport material preferably has an electric conductivity of 1.5 S / m or less.
  • the present invention it is possible to provide a photoelectric conversion element that is excellent in durability and can suppress a decrease in photoelectric conversion efficiency.
  • FIG. 1 shows a schematic cross-sectional view of a photoelectric conversion element of the present embodiment which is an example of the photoelectric conversion element of the present invention.
  • the photoelectric conversion element according to the present embodiment is provided between the transparent electrode plate 11, the counter electrode 12 disposed at a predetermined distance so as to face the transparent electrode plate 11, and the transparent electrode plate 11 and the counter electrode 12.
  • the sealing material 6 is disposed between the transparent electrode plate 11 and the counter electrode 12 so as to surround the carrier transporting material 8 and seals the carrier transporting material 8.
  • the transparent electrode plate 11 includes a light transmissive support 1 and a transparent conductive layer 2 provided on one surface of the light transmissive support 1.
  • the photoelectric conversion layer 3 is provided on the surface of the transparent conductive layer 2, and the conductive layer 4 is provided on at least a part of the photoelectric conversion layer 3.
  • the conductive layer 4 is electrically connected to the transparent conductive layer 2 of the transparent electrode plate 11.
  • a hole for injecting the carrier transport material 8 may be provided in a part of the transparent electrode plate 11.
  • the counter electrode 12 includes a counter electrode conductive layer 5 and a catalyst layer 7 provided on one surface of the counter electrode conductive layer 5.
  • the counter electrode conductive layer 5 and the catalyst layer 7 of the counter electrode 12 are configured to face the transparent conductive layer 2 of the transparent electrode plate 11, respectively.
  • the light transmissive support 1 constitutes at least a part of the light receiving surface of the photoelectric conversion element of the present embodiment, the light transmissive support 1 is, for example, the light receiving surface of the photoelectric conversion element.
  • a material having at least light transparency in the portion can be used. However, any material can be used as long as it is a material that substantially transmits light having a wavelength having effective sensitivity to at least a photosensitizer described later, and is not necessarily transparent to light in all wavelength regions.
  • Examples of the light transmissive material used for the light transmissive support 1 include glass substrates such as soda lime float glass, fused silica glass, and crystal quartz glass, or heat resistant resin plates such as flexible films. Can be used.
  • Examples of the flexible film used for the light transmissive support 1 include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), and polyarylate (PA). , Polyetherimide (PEI), phenoxy resin, or polytetrafluoroethylene (PTFE) can be used.
  • TAC tetraacetyl cellulose
  • PET polyethylene terephthalate
  • PPS polyphenylene sulfide
  • PC polycarbonate
  • PA polyarylate
  • PEI Polyetherimide
  • phenoxy resin phenoxy resin
  • PTFE polytetrafluoroethylene
  • the flexible film used for the light transmissive support 1 it is preferable to use a PTFE film. Since the PTFE film has a heat resistance of 250 ° C. or more, when the transparent conductive layer 2 is formed by heating the surface of the light transmissive support 1 to about 250 ° C., for example, the light transmissive support 1 is damaged by heat. There is a tendency to be able to suppress.
  • the thickness of the light transmissive support 1 is not particularly limited, but is preferably 0.2 mm or more and 5 mm or less. When the thickness of the light transmissive support 1 is 0.2 mm or more, the light transmissive support 1 tends to exhibit a function as a support. When the thickness of the light transmissive support 1 is 5 mm or less, the amount of light transmitted through the light transmissive support 1 is increased and the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
  • the photoelectric conversion element of this embodiment When the photoelectric conversion element of this embodiment is attached to another structure, it can be attached using the light transmissive support 1.
  • the light transmissive support 1 when the light transmissive support 1 is made of a glass substrate, the peripheral portion of the light transmissive support 1 can be easily attached to another structure with screws or the like.
  • the transparent conductive layer 2 constitutes at least a part of the light receiving surface of the photoelectric conversion element of the present embodiment, the transparent conductive layer 2 may be, for example, at least a portion of the light receiving surface of the photoelectric conversion element.
  • a material having transparency and conductivity can be used. However, any material can be used as long as it is a material that substantially transmits light having a wavelength having effective sensitivity to at least a photosensitizer described later, and is not necessarily transparent to light in all wavelength regions.
  • the light-transmitting material used for the transparent conductive layer 2 for example, indium tin composite oxide (ITO), tin oxide doped with fluorine (FTO), zinc oxide (ZnO), or the like can be used.
  • ITO indium tin composite oxide
  • FTO tin oxide doped with fluorine
  • ZnO zinc oxide
  • a metal wire may be provided on the transparent conductive layer 2.
  • the resistance of the transparent conductive layer 2 tends to be lowered.
  • the metal wire for example, a metal wire containing at least one metal selected from the group consisting of platinum, gold, silver, copper, aluminum, nickel and titanium can be used. From the viewpoint of avoiding a decrease in the amount of incident light due to the metal wire provided on the transparent conductive layer 2, the thickness of the metal wire is preferably about 0.1 to 4 mm, for example.
  • the thickness of the transparent conductive layer 2 is preferably 0.02 ⁇ m or more and 5 ⁇ m or less.
  • the thickness of the transparent conductive layer 2 is 0.02 ⁇ m or more, the resistance of the transparent conductive layer 2 is reduced and the amount of current that can be taken out of the photoelectric conversion element is increased. Photoelectric conversion efficiency tends to improve.
  • the thickness of the transparent conductive layer 2 is 5 ⁇ m or less, the amount of transmitted light of the transparent conductive layer 2 increases and the amount of photoelectrons generated in the photoelectric conversion layer 3 increases. Efficiency tends to improve.
  • the surface resistance of the surface of the transparent conductive layer 2 is preferably 40 ⁇ / ⁇ or less.
  • the surface resistance of the transparent conductive layer 2 is 40 ⁇ / ⁇ or less, the amount of current that can be taken out of the photoelectric conversion element increases, and thus the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
  • a transparent electrode plate 11 is composed of the light transmissive support 1 and the transparent conductive layer 2.
  • a transparent conductive material made of FTO is formed on a light transmissive support material 1 made of soda-lime float glass.
  • a transparent electrode plate 11 on which the layer 2 is laminated can be used.
  • Photoelectric conversion layer 3 As the photoelectric conversion layer 3, a layer including a porous semiconductor layer and a photosensitizer that is held by being adsorbed on the porous semiconductor layer can be used.
  • the porous semiconductor layer used for the photoelectric conversion layer 3 is not particularly limited as long as it is made of a porous semiconductor.
  • the porous semiconductor layer is made of a porous semiconductor having various shapes such as a bulk shape, a particle shape, or a film shape. Can be used.
  • the specific surface area (surface area per unit mass) of the porous semiconductor layer used for the photoelectric conversion layer 3 is preferably 0.5 m 2 / g or more and 300 m 2 / g or less.
  • the specific surface area of the porous semiconductor layer of the photoelectric conversion layer 3 is 0.5 m 2 / g or more, the photoelectric conversion layer 3 can hold many photosensitizers, so that light is efficiently absorbed. Tend to be able to.
  • the specific surface area of the porous semiconductor layer of the photoelectric conversion layer 3 is 300 m 2 / g or less, the durability of the photoelectric conversion layer 3 tends to be improved.
  • the specific surface area of the porous semiconductor layer used for the photoelectric conversion layer 3 can be calculated by, for example, the BET method (JIS Z8830: 2001) which is a gas adsorption method.
  • the porosity of the porous semiconductor layer used for the photoelectric conversion layer 3 (ratio of the volume of voids provided in the porous semiconductor layer to the total volume of the porous semiconductor layer) is preferably 20% or more. . When the porosity of the porous semiconductor layer of the photoelectric conversion layer 3 is 20% or more, the carrier transporting material 8 tends to be sufficiently diffused inside the porous semiconductor layer of the photoelectric conversion layer 3. .
  • the porosity of the porous semiconductor layer used for the photoelectric conversion layer 3 is, for example, the volume calculated from the film thickness and area of the porous semiconductor layer, the mass of the porous semiconductor layer, and the material of the porous semiconductor layer It can be calculated from the density.
  • porous semiconductor layer used for the photoelectric conversion layer 3 examples include titanium oxide, zinc oxide, tin oxide, iron oxide, niobium oxide, cerium oxide, tungsten oxide, nickel oxide, strontium titanate, cadmium sulfide, lead sulfide, A layer made of a porous semiconductor containing at least one selected from the group consisting of zinc sulfide, indium phosphide, copper indium sulfide (CuInS 2 ), CuAlO 2 and SrCu 2 O 2 can be used.
  • the porous semiconductor layer of the photoelectric conversion layer 3 preferably contains at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide and niobium oxide, and particularly preferably contains titanium oxide.
  • the stability and safety of the porous semiconductor layer of the photoelectric conversion layer 3 are improved, and the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
  • titanium oxide is not limited to various narrowly defined oxides of titanium, such as anatase-type titanium oxide, rutile-type titanium oxide, amorphous titanium oxide, metatitanic acid, and orthotitanic acid.
  • titanium compound containing oxygen such as titanium oxide, titanium hydroxide and hydrous titanium oxide, and these can be used alone or in combination.
  • Titanium oxide can be in any of two types of crystal systems, anatase type and rutile type, depending on the production method and thermal history, but anatase type is common.
  • the porous semiconductor layer of the photoelectric conversion layer 3 may be made of a polycrystalline sintered body. In this case, the stability of the porous semiconductor layer of the photoelectric conversion layer 3 is improved and the crystal growth is facilitated, so that the manufacturing cost of the photoelectric conversion element tends to be reduced.
  • the average particle size of the crystallites constituting the polycrystalline sintered body is preferably 5 nm or more and less than 50 nm, preferably 10 nm or more and 30 nm. The following is more preferable. In this case, since an effective surface area sufficiently large with respect to the projected area can be obtained, there is a tendency that it can be converted into electric energy with high efficiency by increasing the amount of incident light.
  • the average particle diameter of the crystallite can be calculated by applying Scherrer's equation to the X-ray diffraction spectrum of the porous semiconductor layer obtained by X-ray diffraction measurement, for example.
  • the light scattering property of the photoelectric conversion layer 3 can be adjusted by the particle diameter (average particle diameter) of the semiconductor particles used for forming the porous semiconductor layer.
  • the photoelectric conversion layer 3 includes a porous semiconductor layer formed of semiconductor particles having a large average particle diameter
  • the light capturing property is high and more light is scattered, so that the light capture rate can be improved. It tends to be possible.
  • the photoelectric conversion layer 3 includes a porous semiconductor layer formed of semiconductor particles having a small average particle diameter
  • the light scattering property is lowered, but the number of places where the photosensitizer can be held increases. There is a tendency that the amount of the photosensitizing element held in the photoelectric conversion layer 3 can be increased.
  • the porous semiconductor layer of the photoelectric conversion layer 3 is, for example, a semiconductor layer made of semiconductor particles having an average particle diameter of 50 nm or more, more preferably an average particle diameter of 50 nm or more and 600 nm or less on the polycrystalline sintered body. It is good also as a structure which provided.
  • the porous semiconductor layer of the photoelectric conversion layer 3 is not limited to a single layer, and may be a laminated structure of at least two layers.
  • the photosensitizing element held in the porous semiconductor layer of the photoelectric conversion layer 3 for example, a dye and / or a quantum dot can be used.
  • the dye for example, one or more of dyes such as organic dyes and / or metal complex dyes that can absorb light in the visible light region and / or infrared light region are selectively used. Can do.
  • organic dyes examples include azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, perylene dyes, and indigo. At least one selected from the group consisting of system dyes can be used.
  • the extinction coefficient of an organic dye is generally larger than that of a metal complex dye having a form in which molecules are coordinated to a transition metal.
  • the metal complex dye examples include 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, Tc, Te, Rh, etc. It is possible to use at least one kind of dye having molecules coordinated to the metal.
  • metal complex dyes include porphyrin dyes, phthalocyanine dyes, and naphthalocyanine dyes.
  • a phthalocyanine dye or a ruthenium metal complex dye is preferably used, more preferably a ruthenium metal complex dye, and particularly, a ruthenium metal complex represented by the following formulas (I) to (III): It is preferable to use a dye.
  • a phthalocyanine dye or a ruthenium metal complex dye is used as the dye, particularly when a ruthenium metal complex dye represented by the following formulas (I) to (III) is used, light having a wavelength in the near infrared region is used. Therefore, the photoelectric conversion efficiency of the photoelectric conversion element can be increased.
  • TAA represents tetrabutylammonium.
  • dye is a carboxylic acid group, a carboxylic anhydride, an alkoxy group, a hydroxyl group, a hydroxyalkyl group, a sulfonic acid group, an ester group. It preferably contains at least one selected from the group consisting of a mercapto group and a phosphonyl group, and particularly preferably contains a carboxylic acid group and / or a carboxylic acid anhydride.
  • the adsorptivity with the porous semiconductor layer is stable, and electron injection from the dye into the porous semiconductor layer tends to be performed efficiently. It is in. Note that these functional groups provide an electrical bond that facilitates electron transfer between the excited dye and the conduction band of the porous semiconductor layer.
  • the quantum dots for example, at least one kind of fine particles selected from the group consisting of CdS, CdSe, PbS and PbSe can be used.
  • the particle diameter of the fine particles constituting the quantum dot is appropriately adjusted according to the absorption wavelength or the like, but is preferably 1 nm or more and 10 nm or less from the viewpoint of functioning as a quantum dot.
  • the thickness of the photoelectric conversion layer 3 is preferably 4 ⁇ m or more and 30 ⁇ m or less.
  • the thickness of the photoelectric conversion layer 3 is 4 ⁇ m or more, the moving distance of electrons in the photoelectric conversion layer 3 becomes long, and thus the effect of providing the conductive layer 4 tends to be sufficiently exhibited.
  • the thickness of the photoelectric conversion layer 3 is 30 ⁇ m or less, a sufficient amount of light can be irradiated to the photosensitizer that is in contact with the photoelectric conversion layer 3, and thus the photoelectric conversion efficiency of the photoelectric conversion element Tend to improve.
  • the conductive layer 4 can be used without particular limitation as long as it is a conductive material.
  • a conductive material For example, at least one metal selected from the group consisting of silver, copper, aluminum, indium, titanium, nickel, tantalum, and iron, or Two or more kinds of alloys can be used, and among them, it is preferable to use a material that can make ohmic contact with the photoelectric conversion layer 3.
  • the contact resistance between the photoelectric conversion layer 3 and the conductive layer 4 can be reduced, and the conductive layer 4 can be taken out of the photoelectric conversion element. Since the amount of current can be increased, the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
  • Examples of the conductive layer 4 include transparent conductive metal oxides such as zinc oxide doped with at least one selected from the group consisting of boron, gallium, and aluminum, titanium oxide doped with niobium, ITO, or FTO. Etc. can be used.
  • the carrier transport material 8 When a material having a strong corrosive force such as iodine is used for the carrier transport material 8, it is preferable to use at least one selected from the group consisting of ITO, FTO, titanium and tantalum as the conductive layer 4. In this case, corrosion of the conductive layer 4 due to the carrier transport material 8 can be effectively suppressed. In addition, in the conductive layer 4, only the interface with the carrier transport material 8 is required to have corrosion resistance with respect to the carrier transport material 8, so that only the surface of the conductive layer 4 is covered with a material having corrosion resistance. Also good.
  • the space sealed with the sealing material 6 between the transparent conductive layer 2 and the counter electrode conductive layer 5 is filled with a carrier transport material 8.
  • the photoelectric conversion layer 3 is provided in the carrier transport material 8. That is, the carrier transport material 8 enters the pores of the photoelectric conversion layer 3.
  • a material containing a hardly volatile solvent and a redox species can be used as the carrier transport material 8.
  • a material containing a hardly volatile solvent and a redox species can be used.
  • a material in which a redox species is dissolved in a hardly volatile solvent can be used.
  • the hardly volatile solvent examples include ionic liquids having no boiling point such as ethylmethylimidazolium bis (trifluoromethanesulfonyl) imide, carbonate compounds such as propylene carbonate, nitrile compounds such as 3-methoxypropionitrile, or water. It is preferable to use a solvent having a boiling point of 100 ° C. or higher. When an ionic liquid having no boiling point or a solvent having a boiling point of 100 ° C. or higher is used as the hardly volatile solvent, the durability of the photoelectric conversion element tends to be improved. Moreover, not only one type of solvent but also two or more types can be mixed and used as the hardly volatile solvent. In the present specification, “boiling point” means a boiling point at a pressure of 1 atm.
  • the viscosity of the hardly volatile solvent is preferably 1 cp (0.001 Pa ⁇ s) or more.
  • the viscosity of the hardly volatile solvent is 1 cp or more, since the loss at the time of electron transport due to carrier transport in the carrier transport material 8 is large, the effect of forming the conductive layer 4 is easily obtained. There is a tendency.
  • the viscosity of the hardly volatile solvent can be measured, for example, with a conventionally known viscometer.
  • redox species for example, at least one selected from the group consisting of I ⁇ / I 3 ⁇ series, Br 2 ⁇ / Br 3 ⁇ series, Fe 2+ / Fe 3+ series and quinone / hydroquinone series is used. be able to.
  • a combination of salt and iodine (I 2 ) it is preferable to use a combination of salt and iodine (I 2 ). In this case, for example, a better IV curve can be obtained as compared with a case where a cobalt complex or ferrocene is used as the redox species.
  • the metal iodide for example, at least one selected from the group consisting of lithium iodide (LiI), sodium iodide (NaI), potassium iodide (KI), and calcium iodide (CaI 2 ) is used. Can be used.
  • LiI lithium iodide
  • NaI sodium iodide
  • KI potassium iodide
  • CaI 2 calcium iodide
  • the tetraalkylammonium salt is selected from the group consisting of, for example, tetraethylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), tetrabutylammonium iodide (TBAI), and tetrahexylammonium iodide (THAI). At least one selected from the above can be used.
  • TEAI tetraethylammonium iodide
  • TPAI tetrapropylammonium iodide
  • TBAI tetrabutylammonium iodide
  • THAI tetrahexylammonium iodide
  • metal bromide for example, at least one selected from the group consisting of lithium bromide (LiBr), sodium bromide (NaBr), potassium bromide (KBr), and calcium bromide (CaBr 2 ) is used. Can do.
  • LiBr lithium bromide
  • NaBr sodium bromide
  • KBr potassium bromide
  • CaBr 2 calcium bromide
  • an additive may be added to the carrier transport material 8 as necessary.
  • additives include iodide-based molten salts, nitrogen-containing aromatic compounds such as t-butylpyridine (TBP), guanidine thiocyanate, and N-methylbenzimidazole.
  • Iodide-based molten salt is preferable because it is a source of iodine ions and can function as the above-described redox species.
  • DMPII dimethylpropylimidazole iodide
  • MPII methylpropylimidazole iodide
  • EMII ethylmethylimidazole iodide
  • EII ethylimidazole iodide
  • HMII hexylmethylimidazole iodide
  • the concentration of the redox species in the carrier transport material 8 is appropriately selected depending on the type of the solvent, electrolyte, etc., and is preferably 0.001 mol / liter to 1.5 mol / liter. It is preferably from 01 mol / liter to 0.7 mol / liter. In this case, the redox species in the carrier transport material 8 tend to be transported efficiently.
  • the electric conductivity of the carrier transport material 8 is preferably 1.5 S / m or less.
  • the electric conductivity of the carrier transport material 8 is 1.5 S / m or less, the electron transfer from the carrier transport material 8 to the photosensitizer is not efficiently performed, so the conductive layer 4 was formed. There exists a tendency which can fully express the effect by this.
  • the counter electrode 12 includes a counter electrode conductive layer 5 and a catalyst layer 7 provided on the surface of the counter electrode conductive layer 5.
  • the counter electrode conductive layer 5 collects electrons and can be electrically connected to an adjacent photoelectric conversion element.
  • the catalyst layer 7 has catalytic ability and can reduce holes in the carrier transport material 8.
  • the counter electrode 12 is composed of the counter electrode conductive layer 5 and the catalyst layer 7.
  • the counter electrode 12 may be constituted by only one of the counter electrode conductive layer 5 and the catalyst layer 7.
  • a conductive material can be used as the counter electrode conductive layer 5.
  • a conductive material can be used.
  • metal oxides such as ITO, FTO, and ZnO, and / or titanium, tungsten, gold, silver, copper, nickel, and the like can be used.
  • a conductive material containing at least one kind of metal can be used.
  • titanium it is preferable to use titanium as the counter electrode conductive layer 5.
  • the strength of the counter electrode conductive layer 5 can be significantly improved.
  • the catalyst layer 7 for example, platinum and / or carbon is preferably used.
  • examples of carbon used in the catalyst layer 7 include a group consisting of carbon black, graphite, glass carbon, amorphous carbon, hard carbon, soft carbon, carbon whisker, carbon nanotube, and fullerene. It is preferable to use at least one selected from
  • the sealing material 6 can suppress the volatilization of the carrier transport material 8 and can suppress the intrusion of a liquid such as water into the photoelectric conversion element. Moreover, the sealing material 6 can absorb the stress (impact) which acts on the transparent support body 1, and can absorb the bending etc. which act on the transparent support body 1 at the time of long-term use of a photoelectric conversion element. .
  • the sealing material 6 for example, a single layer including at least one selected from the group consisting of a silicone resin, an epoxy resin, a polyisobutylene resin, a hot melt resin, and a glass frit, or the single layer is made into two or more layers. A plurality of stacked layers can be used.
  • the sealing material 6 is a silicone resin, a hot melt resin (for example, an ionomer resin), or a polyisobutylene resin. And at least one selected from the group consisting of glass frit. In this case, corrosion of the sealing material 6 with respect to the carrier transporting material 8 tends to be suppressed.
  • a step of preparing a transparent electrode plate 11 having a transparent conductive layer 2 provided on the surface of a light-transmissive support 1 is performed.
  • the step of preparing the transparent electrode plate 11 may be, for example, a commercially available one.
  • the transparent conductive layer 2 is formed on the surface of the light-transmissive support 1 by, for example, sputtering or thermal CVD. You may prepare by laminating
  • a step of forming a porous semiconductor layer 3a on the surface of the transparent conductive layer 2 is performed.
  • the step of forming the porous semiconductor layer 3a is not particularly limited, but can be performed, for example, by at least one of the following methods (i) to (iv).
  • a porous semiconductor layer 3a is formed on the surface of the transparent conductive layer 2 by applying a paste containing fine particles made of a semiconductor material on the surface of the transparent conductive layer 2 by a screen printing method or an ink jet method and then baking the paste. How to form.
  • a method of forming the porous semiconductor layer 3a on the surface of the transparent conductive layer 2 by a CVD method or an MOCVD method using a desired source gas.
  • the step of forming the porous semiconductor layer 3a is performed by applying a paste containing fine particles made of a semiconductor material on the surface of the transparent conductive layer 2 by the screen printing method (i) and then baking the paste. It is preferable to use a method of forming the porous semiconductor layer 3 a on the surface of the conductive layer 2. In this case, the porous semiconductor layer 3a having a relatively large thickness tends to be produced at a low cost.
  • the porous semiconductor layer 3a When forming the film-like and / or particulate porous semiconductor layer 3a, it is preferable to form the porous semiconductor layer 3a having a specific surface area of 10 m 2 / g or more and 200 m 2 / g or less. In this case, there is a tendency that the photoelectric conversion efficiency of the photoelectric conversion element can be improved by forming the photoelectric conversion layer 3 holding more photosensitizers.
  • 125 mL of titanium isopropoxide is dropped into 750 mL of a 0.1 M nitric acid aqueous solution for hydrolysis, and heated at 80 ° C. for 8 hours to prepare a sol solution.
  • the sol solution prepared as described above is heated in a titanium autoclave at 230 ° C. for 11 hours to grow titanium oxide particles, and then ultrasonic dispersion is performed at room temperature for 30 minutes to obtain an average particle size.
  • a colloidal solution containing titanium oxide particles having a diameter (average primary particle diameter) of 15 nm is prepared.
  • the titanium oxide particles are added to a solution in which ethylcellulose and terpineol are dissolved in absolute ethanol and stirred to disperse the titanium oxide particles.
  • a titanium oxide paste is obtained by heating the solution in which the above titanium oxide particles are dispersed under vacuum conditions to evaporate ethanol. And as a final composition, a density
  • a solvent used for preparing a paste containing semiconductor particles (suspended) in addition to the above, for example, a glyme solvent such as ethylene glycol monomethyl ether, an alcohol solvent such as isopropyl alcohol, isopropyl alcohol and the like
  • a mixed solvent such as a mixed solution with toluene, water, or the like can be used.
  • the porous oxide layer 3a can be produced by screen printing the titanium oxide paste produced as described above on the surface of the transparent conductive layer 2 and then drying and baking.
  • the drying conditions and firing conditions of the titanium oxide paste can be adjusted by appropriately setting conditions such as temperature, time, and atmosphere depending on the type of the light-transmissive support 1 and the semiconductor particles.
  • the titanium oxide paste can be baked, for example, in an air atmosphere or an inert gas atmosphere within a range of about 50 to 800 ° C. for about 10 seconds to 12 hours.
  • the titanium oxide paste can be dried and fired, for example, once at a single temperature or twice or more at different temperatures.
  • the specific surface area of the porous semiconductor layer 3a made of titanium oxide produced under the above conditions is in the range of 10 m 2 / g or more and 200 m 2 / g or less.
  • the average particle diameter of the semiconductor particles constituting the porous semiconductor layer 3a is not particularly limited. However, in terms of effectively using incident light for photoelectric conversion, the average particle diameter should be uniform to some extent like a commercially available semiconductor material powder. Is more preferable.
  • the conductive layer 4 can be formed on at least part of the surface of the photoelectric conversion layer 3 by vapor deposition or sputtering, for example, so as to be electrically connected to the transparent conductive layer 2.
  • the photoelectric conversion layer 3 can be formed, for example, by adsorbing a photosensitizing element to the porous semiconductor layer 3a.
  • a method for adsorbing the photosensitizer on the porous semiconductor layer 3a for example, the porous semiconductor layer 3a formed on the surface of the transparent conductive layer 2 is immersed in a solution in which the photosensitizer is dissolved. Can be used. In addition, immersion conditions can be adjusted suitably.
  • Solvents that dissolve the photosensitizer include, for example, alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether and tetrahydrofuran, nitrogen compounds such as acetonitrile, and halogenated aliphatic hydrocarbons such as chloroform.
  • alcohols such as ethanol
  • ketones such as acetone
  • ethers such as diethyl ether and tetrahydrofuran
  • nitrogen compounds such as acetonitrile
  • halogenated aliphatic hydrocarbons such as chloroform.
  • One kind selected from aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, esters such as ethyl acetate, and water, or a mixture of two or more kinds can be used.
  • the dye concentration in the dye adsorption solution is appropriately adjusted according to the type of the dye and the solvent.
  • the concentration is preferably as high as possible, for example, 5 ⁇ 10 ⁇ 4 mol / liter or more.
  • a step of forming the counter electrode 12 by forming the catalyst layer 7 on the surface of the counter electrode conductive layer 5 is performed.
  • the catalyst layer 7 is formed by a known method such as a PVD method such as a vapor deposition method or a sputtering method, thermal decomposition or electrodeposition of chloroplatinic acid, for example. Can do.
  • the thickness of the catalyst layer 7 can be 0.5 nm or more and 1000 nm or less, for example.
  • the catalyst layer 7 is, for example, a screen printing method in which carbon dispersed in an arbitrary solvent is pasted. Can be formed by coating on the surface of the counter electrode conductive layer 5. Also here, the thickness of the catalyst layer 7 can be, for example, not less than 0.5 nm and not more than 1000 nm.
  • the thickness of the counter electrode conductive layer 5 is preferably selected as appropriate according to the specific resistivity of the material of the counter electrode conductive layer 5. This is because if the counter electrode conductive layer 5 is too thin, the resistance is increased, and if it is too thick, the movement of the carrier transport material 8 is hindered.
  • a step of installing a carrier transport material 8 in a region between the transparent conductive layer 2 of the transparent electrode plate 11 and the catalyst layer 7 of the counter electrode 12 is performed.
  • the step of installing the carrier transport material 8 includes, for example, installing the sealing material 6 so as to surround the photoelectric conversion layer 3 of the transparent electrode plate 11, the transparent conductive layer 2 of the transparent electrode plate 11, and the counter electrode 12.
  • the transparent electrode plate 11 and the counter electrode 12 are arranged so that the catalyst layer 7 faces each other, and the transparent electrode plate 11 and the counter electrode 12 are fixed by the sealing material 6.
  • the carrier transport material 8 is injected into the region surrounded by the sealing material 6 from the hole provided in the transparent electrode plate 11, and then the hole is closed, whereby the photoelectric conversion element of the embodiment shown in FIG. Can be produced.
  • the probability that the photosensitizer present on the counter electrode 12 side of the photoelectric conversion layer 3 absorbs light increases, while the electrons generated on the counter electrode 12 side of the photoelectric conversion layer 3 reach the transparent conductive layer 2. Therefore, the probability that electrons are trapped inside the photoelectric conversion layer 3 is increased, and the current density is significantly reduced.
  • the photoelectric conversion element of the embodiment manufactured as described above a hardly volatile solvent is used as the solvent of the carrier transport material 8 and the counter electrode 12 of the photoelectric conversion layer 3 is used.
  • the conductive layer 4 is provided on at least a part of the surface on the side, and the conductive layer 4 is electrically connected to the transparent conductive layer 2.
  • the durability of the photoelectric conversion element can be improved, and electrons generated on the counter electrode 12 side of the photoelectric conversion layer 3 are guided from the conductive layer 4 to the transparent conductive layer 2.
  • the probability that electrons are trapped inside the photoelectric conversion layer 3 can be lowered, so that a significant decrease in current density can be suppressed and a decrease in photoelectric conversion efficiency can be suppressed.
  • the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples.
  • the thickness of each layer was measured with a step gauge (E-VS-S28A, manufactured by Tokyo Seimitsu Co., Ltd.).
  • Example 1 a photoelectric conversion element having the structure shown in FIG. 1 was produced. First, a transparent electrode plate 11 having a width of 30 mm ⁇ a length of 30 mm ⁇ a thickness of 1 mm, in which a transparent conductive layer 2 made of tin oxide (FTO) doped with fluorine is formed on a light-transmitting support 1 made of glass. (Nippon Sheet Glass Co., Ltd. glass with SnO 2 film) was prepared.
  • FTO tin oxide
  • a screen plate having a pattern of a porous semiconductor layer having a width of 5 mm ⁇ a length of 5 mm and a screen printing machine manufactured by Neurong Precision Industry Co., Ltd., model number: LS-150
  • a commercially available titanium oxide paste manufactured by Solaronix, trade name: D / SP was applied and leveled at room temperature for 1 hour.
  • the coating film obtained as described above was dried in an oven set at 80 ° C. for 20 minutes, and further using a baking furnace (model number: KDF P-100 manufactured by Denken Co., Ltd.) set at 500 ° C. Baked for 60 minutes in air.
  • the above coating, drying and firing steps were repeated to obtain a porous semiconductor layer having a thickness of about 12 ⁇ m.
  • a titanium oxide paste manufactured by JGC Catalysts & Chemicals Co., Ltd., PST-400C
  • a porous semiconductor layer having a thickness of about 18 ⁇ m was formed.
  • a metal mask in which rectangular openings having a width of 6 mm and a length of 12 mm are arranged is prepared, and an electron beam evaporator ei-5 (manufactured by ULVAC, Inc.) is formed on the surfaces of the porous semiconductor layer and the transparent conductive layer 2.
  • a conductive film 4 having a thickness of about 300 nm was formed by depositing a titanium film at a deposition rate of 150 nm / sec.
  • the transparent electrode plate 11 after the formation of the conductive layer 4 is immersed in a dye adsorption solution prepared in advance at room temperature for 100 hours, and the transparent electrode plate 11 after the formation of the conductive layer 4 is immersed in ethanol. And dried at about 60 ° C. for about 5 minutes, thereby adsorbing the dye to the porous semiconductor layer to form the photoelectric conversion layer 3.
  • the dye adsorption solution was prepared by dissolving the dye of the above formula (II) (manufactured by Solaronix, trade name: Ruthenium 620 1H3TBA) in a mixed solvent of acetonitrile and t-butanol having a volume ratio of 1: 1.
  • the solution was ⁇ 10 -4 mol / liter.
  • a counter electrode 12 was formed by forming a platinum film having a thickness of about 7 nm by sputtering.
  • an electrolytic solution is injected as a carrier transporting material 8 from a hole provided in advance in the transparent electrode plate 11, and then the hole is sealed using an ultraviolet curable resin (manufactured by ThreeBond, model number: 31X-101).
  • an ultraviolet curable resin manufactured by ThreeBond, model number: 31X-101.
  • the above electrolytic solution was prepared by using 3-methoxypropionitrile (boiling point: 165 ° C., viscosity: 1.1 cp) as a solvent and I 2 (made by Kishida Chemical Co.) as a redox species at a concentration of 0.15 mol / liter.
  • methylpropylimidazole iodide (manufactured by Shikoku Kasei Kogyo Co., Ltd.) was added to a concentration of 0.8 mol / liter, and guanidine thiocyanate was added at a concentration of 0.1 mol / liter and N-methylbenzimidazole was added at a concentration of 0 It was added and dissolved so as to be 5 mol / liter.
  • the electric conductivity of this electrolytic solution was 1.5 S / m or less.
  • Example 2 the photoelectric conversion element of Example 2 was produced by the same method as Example 1 except that the photoelectric conversion layer 3 (see Table 1) having different pore diameters was formed.
  • Example 1 the photoelectric conversion element of Comparative Example 1 was produced in the same manner as in Example 1 except that the conductive layer 4 was not formed.
  • Example 2 a photoelectric conversion element of Comparative Example 2 was produced in the same manner as in Example 2 except that the conductive layer 4 was not formed.
  • Example 3 In Example 1, instead of 3-methoxypropionitrile, acetonitrile (boiling point: 82 ° C., viscosity: 0.341 cp), which is a volatile solvent, was used, and a comparative example was prepared in the same manner as in Example 1. 3 photoelectric conversion elements were produced.
  • Comparative Example 4 a photoelectric conversion element of Comparative Example 4 was produced by the same method as Comparative Example 3 except that the conductive layer 4 was not formed.
  • the photoelectric conversion elements of Examples 1 and 2 that satisfy the constituent requirements of the present invention are more photoelectrical than the photoelectric conversion elements of Comparative Examples 1 and 2 that are conventional photoelectric conversion elements. It was confirmed that the conversion efficiency was improved. Further, as apparent from Comparative Example 3 and Comparative Example 4, when acetonitrile, which is a volatile solvent having a low boiling point and a low viscosity solvent, is used, the photoelectric conversion efficiency due to the formation of the conductive layer 4 is improved. The improvement effect could not be confirmed.
  • the photoelectric conversion element of the present invention can be suitably used for wet solar cells such as dye-sensitized solar cells.
  • 1 light transmissive support 2 transparent conductive layer, 3 photoelectric conversion layer, 3a porous semiconductor layer, 4 conductive layer, 5 counter electrode conductive layer, 6 sealing material, 7 catalyst layer, 8 carrier transport material, 11 transparent electrode plate 12 Counter electrode.

Abstract

A photoelectric conversion element provided with a light-transmitting support body (1), a transparent electroconductive layer (2) provided on the light-transmitting support body (1), a photoelectric conversion layer (3) including a porous semiconductor layer (3a) provided on the transparent electroconductive layer (2), an electroconductive layer (4) provided on at least a part of the photoelectric conversion layer (3), a counter electrode electroconductive layer (5) provided so as to face the transparent electroconductive layer (2), and a carrier transport material (8) provided between the transparent electroconductive layer (2) and the counter electrode electroconductive layer (5); the carrier transport material (8) containing a poorly volatile solvent and an oxidation-reduction species, and the electroconductive layer (4) being electrically connected to the transparent electroconductive layer (2).

Description

光電変換素子Photoelectric conversion element
　本発明は、光電変換素子に関する。 The present invention relates to a photoelectric conversion element.
　化石燃料に代るエネルギー源として、太陽光を電力に変換することができる電池、すなわち太陽電池が注目されている。現在、結晶系シリコン基板を用いた太陽電池および薄膜シリコン太陽電池が一部実用化され始めている。 As an energy source that replaces fossil fuel, a battery that can convert sunlight into electric power, that is, a solar cell, has attracted attention. At present, some solar cells and thin film silicon solar cells using a crystalline silicon substrate are beginning to be put into practical use.
　しかしながら、結晶系シリコン基板を用いた太陽電池は、シリコン基板の製造コストが高いという問題があった。また、薄膜シリコン太陽電池は、多くの種類の半導体製造用ガスや複雑な装置を用いる必要があるため、製造コストが高くなるという問題があった。そのため、いずれの太陽電池においても、発電出力当たりのコストを低減するために光電変換の高効率化の努力が続けられているが、上記の問題を十分に解決できるまでには至っていない。 However, a solar cell using a crystalline silicon substrate has a problem that the manufacturing cost of the silicon substrate is high. In addition, the thin film silicon solar cell has a problem in that the manufacturing cost is high because it is necessary to use many kinds of semiconductor manufacturing gases and complicated devices. For this reason, in any solar cell, efforts have been made to increase the efficiency of photoelectric conversion in order to reduce the cost per power generation output, but the above problem has not yet been solved sufficiently.
　また、たとえば特許文献１（特許第２６６４１９４号）には、新しいタイプの太陽電池として、金属錯体の光誘起電子移動を応用した湿式太陽電池が開示されている。また、たとえば特許文献２（特開２００８－２８７９００号公報）には、新しいタイプの太陽電池として、量子ドットを用いた湿式太陽電池が開示されている。 Further, for example, Patent Document 1 (Japanese Patent No. 2664194) discloses a wet solar cell applying photo-induced electron transfer of a metal complex as a new type solar cell. For example, Patent Document 2 (Japanese Patent Laid-Open No. 2008-287900) discloses a wet solar cell using quantum dots as a new type of solar cell.
　これらの湿式太陽電池は、２枚のガラス基板の表面にそれぞれ電極を形成し、これらの電極が内側となるように２枚のガラス基板を配置し、電極間に光電変換層と電解液とを挟み込むようにして作製されている。光電変換層は、光増感色素を吸着させて可視光領域に吸収スペクトルを持たせた半導体層からなる。このような湿式太陽電池は、色素増感太陽電池とも呼ばれる。 In these wet solar cells, electrodes are respectively formed on the surfaces of two glass substrates, two glass substrates are arranged so that these electrodes are inside, and a photoelectric conversion layer and an electrolytic solution are placed between the electrodes. It is made so as to be sandwiched. The photoelectric conversion layer is composed of a semiconductor layer in which a photosensitizing dye is adsorbed to give an absorption spectrum in the visible light region. Such a wet solar cell is also called a dye-sensitized solar cell.
　上記のような湿式太陽電池に光が入射すると、光電変換層で電子が発生し、光電変換層で発生した電子は光電変換層を通って電極に到達する。そして、電極に到達した電子は、電極間を接続する外部電気回路を通って他方の電極に移動して電解液に供給され、電解液中のイオンによって運ばれて再度光電変換層に戻る。湿式太陽電池においては、このような電子の流れにより電気エネルギーが取り出される。 When light enters the wet solar cell as described above, electrons are generated in the photoelectric conversion layer, and the electrons generated in the photoelectric conversion layer reach the electrode through the photoelectric conversion layer. Then, the electrons that have reached the electrodes move to the other electrode through an external electric circuit that connects the electrodes, are supplied to the electrolytic solution, are carried by the ions in the electrolytic solution, and return to the photoelectric conversion layer again. In a wet solar cell, electric energy is taken out by such a flow of electrons.
　また、特許文献３（特開２００１－３５７８９７号公報）には、２枚の導電性基板を用いた湿式太陽電池が開示されている。この湿式太陽電池は、一方の導電性基板上に光電極である多孔質半導体層を形成し、他方の導電性基板上に触媒層を形成し、両者を合わせるように重ねた上で、側面をエポキシ系接着剤で封止することにより作製されている。 Further, Patent Document 3 (Japanese Patent Laid-Open No. 2001-357897) discloses a wet solar cell using two conductive substrates. In this wet solar cell, a porous semiconductor layer, which is a photoelectrode, is formed on one conductive substrate, a catalyst layer is formed on the other conductive substrate, and the side surfaces of the wet solar cell are overlapped so as to match each other. It is produced by sealing with an epoxy adhesive.
特許第２６６４１９４号Japanese Patent No. 2664194 特開２００８－２８７９００号公報JP 2008-287900 A 特開２００１－３５７８９７号公報JP 2001-357897 A
　湿式太陽電池の耐久性を向上させる観点からは、湿式太陽電池の電解液の溶媒としては難揮発性溶媒を用いることが好ましい。しかしながら、湿式太陽電池の電解液の溶媒として難揮発性溶媒を用いた場合には、電解液の溶媒にアセトニトリルなどの揮発性溶媒を用いた場合と比較して、湿式太陽電池の光電変換効率が大きく低下してしまうという問題があった。 From the viewpoint of improving the durability of the wet solar cell, it is preferable to use a hardly volatile solvent as the solvent of the electrolyte of the wet solar cell. However, when a hardly volatile solvent is used as the solvent for the electrolyte of the wet solar cell, the photoelectric conversion efficiency of the wet solar cell is higher than that when a volatile solvent such as acetonitrile is used as the solvent for the electrolyte. There was a problem of a significant drop.
　上記の事情に鑑みて、本発明の目的は、耐久性に優れ、かつ光電変換効率の低下を抑制することができる光電変換素子を提供することにある。 In view of the above circumstances, an object of the present invention is to provide a photoelectric conversion element that is excellent in durability and can suppress a decrease in photoelectric conversion efficiency.
　本発明は、光透過性支持体と、光透過性支持体上に設けられた透明導電層と、透明導電層上に設けられた多孔質半導体層を含む光電変換層と、光電変換層の少なくとも一部に設けられた導電層と、透明導電層と向かい合うようにして設けられた対極導電層と、透明導電層と対極導電層との間に設けられたキャリア輸送材料と、を備え、キャリア輸送材料は難揮発性溶媒と酸化還元種とを含み、導電層は透明導電層と電気的に接続されている光電変換素子である。 The present invention provides a light transmissive support, a transparent conductive layer provided on the light transmissive support, a photoelectric conversion layer including a porous semiconductor layer provided on the transparent conductive layer, and at least a photoelectric conversion layer. A carrier layer comprising: a conductive layer provided in part; a counter electrode conductive layer provided to face the transparent conductive layer; and a carrier transport material provided between the transparent conductive layer and the counter electrode conductive layer. The material includes a hardly volatile solvent and a redox species, and the conductive layer is a photoelectric conversion element that is electrically connected to the transparent conductive layer.
　ここで、本発明の光電変換素子においては、難揮発性溶媒が沸点を有しない、または難揮発性溶媒の沸点が１００℃以上であることが好ましい。 Here, in the photoelectric conversion element of the present invention, it is preferable that the hardly volatile solvent has no boiling point or the boiling point of the hardly volatile solvent is 100 ° C. or higher.
　また、本発明の光電変換素子においては、光電変換層の厚さが４μｍ以上３０μｍ以下であることが好ましい。 Moreover, in the photoelectric conversion element of the present invention, the thickness of the photoelectric conversion layer is preferably 4 μm or more and 30 μm or less.
　また、本発明の光電変換素子においては、難揮発性溶媒の粘度が１ｃｐ以上であることが好ましい。 In the photoelectric conversion element of the present invention, the viscosity of the hardly volatile solvent is preferably 1 cp or more.
　また、本発明の光電変換素子においては、キャリア輸送材料の電気伝導率が１．５Ｓ／ｍ以下であることが好ましい。 Moreover, in the photoelectric conversion element of the present invention, the carrier transport material preferably has an electric conductivity of 1.5 S / m or less.
　本発明によれば、耐久性に優れ、かつ光電変換効率の低下を抑制することができる光電変換素子を提供することができる。 According to the present invention, it is possible to provide a photoelectric conversion element that is excellent in durability and can suppress a decrease in photoelectric conversion efficiency.
本実施の形態の光電変換素子の模式的な断面図である。It is typical sectional drawing of the photoelectric conversion element of this Embodiment. 本実施の形態の光電変換素子の製造方法の一例の製造工程の一部を図解する模式的な断面図である。It is typical sectional drawing illustrating a part of manufacturing process of an example of the manufacturing method of the photoelectric conversion element of this Embodiment. 本実施の形態の光電変換素子の製造方法の一例の製造工程の他の一部を図解する模式的な断面図である。It is typical sectional drawing illustrating other one part of the manufacturing process of an example of the manufacturing method of the photoelectric conversion element of this Embodiment. 本実施の形態の光電変換素子の製造方法の一例の製造工程の他の一部を図解する模式的な断面図である。It is typical sectional drawing illustrating other one part of the manufacturing process of an example of the manufacturing method of the photoelectric conversion element of this Embodiment. 本実施の形態の光電変換素子の製造方法の一例の製造工程の他の一部を図解する模式的な断面図である。It is typical sectional drawing illustrating other one part of the manufacturing process of an example of the manufacturing method of the photoelectric conversion element of this Embodiment.
　以下、本発明の実施の形態について説明する。なお、本発明の図面において、同一の参照符号は、同一部分または相当部分を表わすものとする。 Hereinafter, embodiments of the present invention will be described. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.
　＜光電変換素子＞
　図１に、本発明の光電変換素子の一例である本実施の形態の光電変換素子の模式的な断面図を示す。本実施の形態の光電変換素子は、透明電極板１１と、透明電極板１１と向かい合うようにして所定の距離を空けて配置された対極１２と、透明電極板１１と対極１２との間に設けられたキャリア輸送材料８と、透明電極板１１と対極１２との間において透明電極板１１と対極１２とを接合する封止材６とを備えている。なお、封止材６は、透明電極板１１と対極１２との間においてキャリア輸送材料８を取り囲むようにして設置されており、キャリア輸送材料８を封止している。 <Photoelectric conversion element>
FIG. 1 shows a schematic cross-sectional view of a photoelectric conversion element of the present embodiment which is an example of the photoelectric conversion element of the present invention. The photoelectric conversion element according to the present embodiment is provided between the transparent electrode plate 11, the counter electrode 12 disposed at a predetermined distance so as to face the transparent electrode plate 11, and the transparent electrode plate 11 and the counter electrode 12. And a sealing material 6 for joining the transparent electrode plate 11 and the counter electrode 12 between the transparent electrode plate 11 and the counter electrode 12. The sealing material 6 is disposed between the transparent electrode plate 11 and the counter electrode 12 so as to surround the carrier transporting material 8 and seals the carrier transporting material 8.
　透明電極板１１は、光透過性支持体１と、光透過性支持体１の一方の表面上に設けられた透明導電層２とから構成されている。そして、透明導電層２の表面上には光電変換層３が設けられており、光電変換層３の少なくとも一部に導電層４が設けられている。また、導電層４は、透明電極板１１の透明導電層２と電気的に接続されている。なお、透明電極板１１の一部にキャリア輸送材料８を注入するための孔が設けられていてもよい。 The transparent electrode plate 11 includes a light transmissive support 1 and a transparent conductive layer 2 provided on one surface of the light transmissive support 1. The photoelectric conversion layer 3 is provided on the surface of the transparent conductive layer 2, and the conductive layer 4 is provided on at least a part of the photoelectric conversion layer 3. The conductive layer 4 is electrically connected to the transparent conductive layer 2 of the transparent electrode plate 11. In addition, a hole for injecting the carrier transport material 8 may be provided in a part of the transparent electrode plate 11.
　対極１２は、対極導電層５と、対極導電層５の一方の表面上に設けられた触媒層７とから構成されている。ここで、対極１２の対極導電層５および触媒層７は、それぞれ、透明電極板１１の透明導電層２と向かい合うようにして構成されている。 The counter electrode 12 includes a counter electrode conductive layer 5 and a catalyst layer 7 provided on one surface of the counter electrode conductive layer 5. Here, the counter electrode conductive layer 5 and the catalyst layer 7 of the counter electrode 12 are configured to face the transparent conductive layer 2 of the transparent electrode plate 11, respectively.
　＜光透過性支持体＞
　光透過性支持体１は、本実施の形態の光電変換素子の受光面の少なくとも一部を構成していることから、光透過性支持体１としては、たとえば、光電変換素子の受光面となる部分で少なくとも光透過性を有する材料を用いることができる。ただし、少なくとも後述する光増感素子に実効的な感度を有する波長の光を実質的に透過させる材料であればよく、必ずしもすべての波長領域の光に対して透過性を有する必要はない。 <Light transmissive support>
Since the light transmissive support 1 constitutes at least a part of the light receiving surface of the photoelectric conversion element of the present embodiment, the light transmissive support 1 is, for example, the light receiving surface of the photoelectric conversion element. A material having at least light transparency in the portion can be used. However, any material can be used as long as it is a material that substantially transmits light having a wavelength having effective sensitivity to at least a photosensitizer described later, and is not necessarily transparent to light in all wavelength regions.
　光透過性支持体１に用いられる光透過性を有する材料としては、たとえば、ソーダ石灰フロートガラス、溶融石英ガラス、結晶石英ガラスなどのガラス基板、または可撓性フィルムなどの耐熱性樹脂板などを用いることができる。 Examples of the light transmissive material used for the light transmissive support 1 include glass substrates such as soda lime float glass, fused silica glass, and crystal quartz glass, or heat resistant resin plates such as flexible films. Can be used.
　また、光透過性支持体１に用いられる可撓性フィルムとしては、たとえば、テトラアセチルセルロース（ＴＡＣ）、ポリエチレンテレフタレート（ＰＥＴ）、ポリフェニレンスルファイド（ＰＰＳ）、ポリカーボネート（ＰＣ）、ポリアリレート（ＰＡ）、ポリエーテルイミド（ＰＥＩ）、フェノキシ樹脂、またはポリテトラフルオロエチレン（ＰＴＦＥ）などのフィルムを用いることができる。 Examples of the flexible film used for the light transmissive support 1 include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), and polyarylate (PA). , Polyetherimide (PEI), phenoxy resin, or polytetrafluoroethylene (PTFE) can be used.
　光透過性支持体１に用いられる可撓性フィルムとしては、なかでも、ＰＴＦＥフィルムを用いることが好ましい。ＰＴＦＥフィルムは２５０℃以上の耐熱性を有することから、光透過性支持体１の表面をたとえば２５０℃程度に加熱して透明導電層２を形成する場合に光透過性支持体１の熱ダメージを抑えることができる傾向にある。 As the flexible film used for the light transmissive support 1, it is preferable to use a PTFE film. Since the PTFE film has a heat resistance of 250 ° C. or more, when the transparent conductive layer 2 is formed by heating the surface of the light transmissive support 1 to about 250 ° C., for example, the light transmissive support 1 is damaged by heat. There is a tendency to be able to suppress.
　また、光透過性支持体１の厚さは、特に限定されないが、０．２ｍｍ以上５ｍｍ以下であることが好ましい。光透過性支持体１の厚さが０．２ｍｍ以上である場合には、光透過性支持体１が支持体としての機能を発揮することができる傾向にある。光透過性支持体１の厚さが５ｍｍ以下である場合には光透過性支持体１の透過光量が増大して光電変換素子の光電変換効率が向上する傾向にある。 The thickness of the light transmissive support 1 is not particularly limited, but is preferably 0.2 mm or more and 5 mm or less. When the thickness of the light transmissive support 1 is 0.2 mm or more, the light transmissive support 1 tends to exhibit a function as a support. When the thickness of the light transmissive support 1 is 5 mm or less, the amount of light transmitted through the light transmissive support 1 is increased and the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
　本実施の形態の光電変換素子を他の構造体に取り付けるときに光透過性支持体１を用いて取り付けることができる。たとえば、光透過性支持体１がガラス基板からなる場合には、光透過性支持体１の周縁部をねじ等により他の構造体に容易に取り付けることができる。 When the photoelectric conversion element of this embodiment is attached to another structure, it can be attached using the light transmissive support 1. For example, when the light transmissive support 1 is made of a glass substrate, the peripheral portion of the light transmissive support 1 can be easily attached to another structure with screws or the like.
　＜透明導電層＞
　透明導電層２は、本実施の形態の光電変換素子の受光面の少なくとも一部を構成していることから、透明導電層２としては、たとえば、光電変換素子の受光面となる部分で少なくとも光透過性を有するとともに導電性を有する材料を用いることができる。ただし、少なくとも後述する光増感素子に実効的な感度を有する波長の光を実質的に透過させる材料であればよく、必ずしもすべての波長領域の光に対して透過性を有する必要はない。 <Transparent conductive layer>
Since the transparent conductive layer 2 constitutes at least a part of the light receiving surface of the photoelectric conversion element of the present embodiment, the transparent conductive layer 2 may be, for example, at least a portion of the light receiving surface of the photoelectric conversion element. A material having transparency and conductivity can be used. However, any material can be used as long as it is a material that substantially transmits light having a wavelength having effective sensitivity to at least a photosensitizer described later, and is not necessarily transparent to light in all wavelength regions.
　透明導電層２に用いられる光透過性を有する材料としては、たとえば、インジウム錫複合酸化物（ＩＴＯ）、フッ素をドープした酸化錫（ＦＴＯ）、または酸化亜鉛（ＺｎＯ）などを用いることができる。 As the light-transmitting material used for the transparent conductive layer 2, for example, indium tin composite oxide (ITO), tin oxide doped with fluorine (FTO), zinc oxide (ZnO), or the like can be used.
　透明導電層２に金属線を設けてもよい。透明導電層２に金属線を設けた場合には、透明導電層２の抵抗を低くすることができる傾向にある。金属線としては、たとえば、白金、金、銀、銅、アルミニウム、ニッケルおよびチタンからなる群から選択された少なくとも１種の金属を含む金属線を用いることができる。なお、透明導電層２に設けられた金属線による入射光量の低下を避ける観点からは、金属線の太さは、たとえば０．１～４ｍｍ程度であることが好ましい。 A metal wire may be provided on the transparent conductive layer 2. When a metal wire is provided on the transparent conductive layer 2, the resistance of the transparent conductive layer 2 tends to be lowered. As the metal wire, for example, a metal wire containing at least one metal selected from the group consisting of platinum, gold, silver, copper, aluminum, nickel and titanium can be used. From the viewpoint of avoiding a decrease in the amount of incident light due to the metal wire provided on the transparent conductive layer 2, the thickness of the metal wire is preferably about 0.1 to 4 mm, for example.
　透明導電層２の厚さは、０．０２μｍ以上５μｍ以下とすることが好ましい。透明導電層２の厚さが０．０２μｍ以上である場合には、透明導電層２の抵抗が低減して光電変換素子の外部に取り出すことができる電流量が増大することから、光電変換素子の光電変換効率が向上する傾向にある。また、透明導電層２の厚さが５μｍ以下である場合には、透明導電層２の透過光量が増大して光電変換層３で発生する光電子量が増大することから、光電変換素子の光電変換効率が向上する傾向にある。 The thickness of the transparent conductive layer 2 is preferably 0.02 μm or more and 5 μm or less. When the thickness of the transparent conductive layer 2 is 0.02 μm or more, the resistance of the transparent conductive layer 2 is reduced and the amount of current that can be taken out of the photoelectric conversion element is increased. Photoelectric conversion efficiency tends to improve. Further, when the thickness of the transparent conductive layer 2 is 5 μm or less, the amount of transmitted light of the transparent conductive layer 2 increases and the amount of photoelectrons generated in the photoelectric conversion layer 3 increases. Efficiency tends to improve.
　また、透明導電層２の表面の面抵抗は４０Ω／□以下であることが好ましい。透明導電層２の面抵抗が４０Ω／□以下である場合には、光電変換素子の外部に取り出すことができる電流量が増大することから、光電変換素子の光電変換効率が向上する傾向にある。 The surface resistance of the surface of the transparent conductive layer 2 is preferably 40Ω / □ or less. When the surface resistance of the transparent conductive layer 2 is 40Ω / □ or less, the amount of current that can be taken out of the photoelectric conversion element increases, and thus the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
　＜透明電極板＞
　光透過性支持体１と透明導電層２とから透明電極板１１が構成され、透明電極板１１としては、たとえば、ソーダ石灰フロートガラスからなる光透過性支持体１上に、ＦＴＯからなる透明導電層２を積層した透明電極板１１などを用いることができる。 <Transparent electrode plate>
A transparent electrode plate 11 is composed of the light transmissive support 1 and the transparent conductive layer 2. As the transparent electrode plate 11, for example, a transparent conductive material made of FTO is formed on a light transmissive support material 1 made of soda-lime float glass. A transparent electrode plate 11 on which the layer 2 is laminated can be used.
　＜光電変換層＞
　光電変換層３は、多孔質半導体層と、多孔質半導体層に吸着すること等により保持された光増感素子とを含むものを用いることができる。 <Photoelectric conversion layer>
As the photoelectric conversion layer 3, a layer including a porous semiconductor layer and a photosensitizer that is held by being adsorbed on the porous semiconductor layer can be used.
　光電変換層３に用いられる多孔質半導体層としては、多孔質半導体から構成されるものであれば特に限定されず、たとえば、バルク状、粒子状または膜状などの種々の形状の多孔質半導体からなるものを用いることができる。なかでも、多孔質半導体層としては、膜状の多孔質半導体を用いることが好ましい。この場合には、光電変換層３の受光面積が増大して光電変換素子の光電変換効率が向上するとともに、光電変換素子の薄型化を促進することができる傾向にある。 The porous semiconductor layer used for the photoelectric conversion layer 3 is not particularly limited as long as it is made of a porous semiconductor. For example, the porous semiconductor layer is made of a porous semiconductor having various shapes such as a bulk shape, a particle shape, or a film shape. Can be used. Especially, it is preferable to use a film-like porous semiconductor as the porous semiconductor layer. In this case, the light receiving area of the photoelectric conversion layer 3 is increased, the photoelectric conversion efficiency of the photoelectric conversion element is improved, and the thinning of the photoelectric conversion element tends to be promoted.
　ここで、光電変換層３に用いられる多孔質半導体層の比表面積（単位質量当たりの表面積）は、０．５ｍ2／ｇ以上３００ｍ2／ｇ以下であることが好ましい。光電変換層３の多孔質半導体層の比表面積が０．５ｍ2／ｇ以上である場合には、光電変換層３が多くの光増感素子を保持することができるため光を効率的に吸収することができる傾向にある。光電変換層３の多孔質半導体層の比表面積が３００ｍ2／ｇ以下である場合には、光電変換層３の耐久性が向上する傾向にある。なお、光電変換層３に用いられる多孔質半導体層の比表面積は、たとえば、気体吸着法であるＢＥＴ法（ＪＩＳ　Ｚ８８３０：２００１）によって算出することができる。 Here, the specific surface area (surface area per unit mass) of the porous semiconductor layer used for the photoelectric conversion layer 3 is preferably 0.5 m 2 / g or more and 300 m 2 / g or less. When the specific surface area of the porous semiconductor layer of the photoelectric conversion layer 3 is 0.5 m 2 / g or more, the photoelectric conversion layer 3 can hold many photosensitizers, so that light is efficiently absorbed. Tend to be able to. When the specific surface area of the porous semiconductor layer of the photoelectric conversion layer 3 is 300 m 2 / g or less, the durability of the photoelectric conversion layer 3 tends to be improved. The specific surface area of the porous semiconductor layer used for the photoelectric conversion layer 3 can be calculated by, for example, the BET method (JIS Z8830: 2001) which is a gas adsorption method.
　光電変換層３に用いられる多孔質半導体層の空孔率（多孔質半導体層の全体の容積に対する多孔質半導体層に設けられている空隙の容積の割合）は、２０％以上であることが好ましい。光電変換層３の多孔質半導体層の空孔率が２０％以上である場合には、光電変換層３の多孔質半導体層の内部にキャリア輸送材料８を十分に拡散することができる傾向にある。なお、光電変換層３に用いられる多孔質半導体層の空孔率は、たとえば、多孔質半導体層の膜厚と面積とから算出した体積、多孔質半導体層の質量、および多孔質半導体層の材質の密度から算出することができる。 The porosity of the porous semiconductor layer used for the photoelectric conversion layer 3 (ratio of the volume of voids provided in the porous semiconductor layer to the total volume of the porous semiconductor layer) is preferably 20% or more. . When the porosity of the porous semiconductor layer of the photoelectric conversion layer 3 is 20% or more, the carrier transporting material 8 tends to be sufficiently diffused inside the porous semiconductor layer of the photoelectric conversion layer 3. . The porosity of the porous semiconductor layer used for the photoelectric conversion layer 3 is, for example, the volume calculated from the film thickness and area of the porous semiconductor layer, the mass of the porous semiconductor layer, and the material of the porous semiconductor layer It can be calculated from the density.
　光電変換層３に用いられる多孔質半導体層としては、たとえば、酸化チタン、酸化亜鉛、酸化錫、酸化鉄、酸化ニオブ、酸化セリウム、酸化タングステン、酸化ニッケル、チタン酸ストロンチウム、硫化カドミウム、硫化鉛、硫化亜鉛、リン化インジウム、銅インジウム硫化物（ＣｕＩｎＳ2）、ＣｕＡｌＯ2およびＳｒＣｕ2Ｏ2からなる群から選択された少なくとも１種を含む多孔質半導体からなる層を用いることができる。 Examples of the porous semiconductor layer used for the photoelectric conversion layer 3 include titanium oxide, zinc oxide, tin oxide, iron oxide, niobium oxide, cerium oxide, tungsten oxide, nickel oxide, strontium titanate, cadmium sulfide, lead sulfide, A layer made of a porous semiconductor containing at least one selected from the group consisting of zinc sulfide, indium phosphide, copper indium sulfide (CuInS 2 ), CuAlO 2 and SrCu 2 O 2 can be used.
　なかでも、光電変換層３の多孔質半導体層は、酸化チタン、酸化亜鉛、酸化錫および酸化ニオブからなる群から選択された少なくとも１種を含むことが好ましく、酸化チタンを含むことが特に好ましい。この場合には、光電変換層３の多孔質半導体層の安定性および安全性が向上するとともに、光電変換素子の光電変換効率が向上する傾向にある。 Among these, the porous semiconductor layer of the photoelectric conversion layer 3 preferably contains at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide and niobium oxide, and particularly preferably contains titanium oxide. In this case, the stability and safety of the porous semiconductor layer of the photoelectric conversion layer 3 are improved, and the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
　なお、本明細書において、「酸化チタン」は、たとえば、アナターゼ型酸化チタン、ルチル型酸化チタン、無定形酸化チタン、メタチタン酸、およびオルソチタン酸などの各種の狭義のチタンの酸化物だけでなく、酸化チタン、水酸化チタンおよび含水酸化チタンなどの酸素を含むチタン化合物をも含む概念であり、これらを単独で、または混合して用いることができる。なお、酸化チタンは、その製法や熱履歴によって、アナターゼ型とルチル型の２種類のいずれの結晶系にもなり得るが、アナターゼ型が一般的である。 In this specification, “titanium oxide” is not limited to various narrowly defined oxides of titanium, such as anatase-type titanium oxide, rutile-type titanium oxide, amorphous titanium oxide, metatitanic acid, and orthotitanic acid. In addition, it is a concept including a titanium compound containing oxygen such as titanium oxide, titanium hydroxide and hydrous titanium oxide, and these can be used alone or in combination. Titanium oxide can be in any of two types of crystal systems, anatase type and rutile type, depending on the production method and thermal history, but anatase type is common.
　また、光電変換層３の多孔質半導体層は、多結晶焼結体からなっていてもよい。この場合には、光電変換層３の多孔質半導体層の安定性が向上するとともに、結晶成長が容易となるために光電変換素子の製造コストを低減することができる傾向にある。 Moreover, the porous semiconductor layer of the photoelectric conversion layer 3 may be made of a polycrystalline sintered body. In this case, the stability of the porous semiconductor layer of the photoelectric conversion layer 3 is improved and the crystal growth is facilitated, so that the manufacturing cost of the photoelectric conversion element tends to be reduced.
　光電変換層３の多孔質半導体層が多結晶焼結体からなる場合に、当該多結晶焼結体を構成する結晶子の平均粒径は、５ｎｍ以上５０ｎｍ未満であることが好ましく、１０ｎｍ以上３０ｎｍ以下であることがより好ましい。この場合には、投影面積に対して十分に大きい実効表面積を得ることができるため、光の入射光量の増大により高効率で電気エネルギに変換することができる傾向にある。なお、結晶子の平均粒径は、たとえば、Ｘ線回折測定によって得られる多孔質半導体層のＸ線回折スペクトルにシェラーの式を適用することによって算出することができる。 When the porous semiconductor layer of the photoelectric conversion layer 3 is made of a polycrystalline sintered body, the average particle size of the crystallites constituting the polycrystalline sintered body is preferably 5 nm or more and less than 50 nm, preferably 10 nm or more and 30 nm. The following is more preferable. In this case, since an effective surface area sufficiently large with respect to the projected area can be obtained, there is a tendency that it can be converted into electric energy with high efficiency by increasing the amount of incident light. The average particle diameter of the crystallite can be calculated by applying Scherrer's equation to the X-ray diffraction spectrum of the porous semiconductor layer obtained by X-ray diffraction measurement, for example.
　光電変換層３の光散乱性は、多孔質半導体層の形成に用いられる半導体粒子の粒子径（平均粒径）により調整することができる。 The light scattering property of the photoelectric conversion layer 3 can be adjusted by the particle diameter (average particle diameter) of the semiconductor particles used for forming the porous semiconductor layer.
　たとえば、光電変換層３が平均粒径の大きい半導体粒子で形成した多孔質半導体層を含む場合には、光散乱性が高く、より多くの光が散乱するため、光捕捉率を向上させることができる傾向にある。また、たとえば、光電変換層３が平均粒径の小さい半導体粒子で形成した多孔質半導体層を含む場合には、光散乱性が低くなるが、光増感素子を保持できる箇所が増加するため、光電変換層３における光増感素子の保持量を増加させることができる傾向にある。 For example, in the case where the photoelectric conversion layer 3 includes a porous semiconductor layer formed of semiconductor particles having a large average particle diameter, the light capturing property is high and more light is scattered, so that the light capture rate can be improved. It tends to be possible. For example, when the photoelectric conversion layer 3 includes a porous semiconductor layer formed of semiconductor particles having a small average particle diameter, the light scattering property is lowered, but the number of places where the photosensitizer can be held increases. There is a tendency that the amount of the photosensitizing element held in the photoelectric conversion layer 3 can be increased.
　光電変換層３の多孔質半導体層は、たとえば、上記の多結晶焼結体上に、好ましくは平均粒径が５０ｎｍ以上、より好ましくは平均粒径が５０ｎｍ以上６００ｎｍ以下の半導体粒子からなる半導体層を設けた構造としてもよい。このように、光電変換層３の多孔質半導体層は、単層に限定されず、少なくとも２層の積層構造体であってもよい。 The porous semiconductor layer of the photoelectric conversion layer 3 is, for example, a semiconductor layer made of semiconductor particles having an average particle diameter of 50 nm or more, more preferably an average particle diameter of 50 nm or more and 600 nm or less on the polycrystalline sintered body. It is good also as a structure which provided. Thus, the porous semiconductor layer of the photoelectric conversion layer 3 is not limited to a single layer, and may be a laminated structure of at least two layers.
　光電変換層３の多孔質半導体層に保持された光増感素子としては、たとえば、色素および／または量子ドットなどを用いることができる。 As the photosensitizing element held in the porous semiconductor layer of the photoelectric conversion layer 3, for example, a dye and / or a quantum dot can be used.
　色素としては、たとえば、可視光領域および／または赤外光領域の波長の光を吸収することができる有機色素および／または金属錯体色素などの色素の１種または２種以上を選択的に用いることができる。 As the dye, for example, one or more of dyes such as organic dyes and / or metal complex dyes that can absorb light in the visible light region and / or infrared light region are selectively used. Can do.
　有機色素としては、たとえば、アゾ系色素、キノン系色素、キノンイミン系色素、キナクリドン系色素、スクアリリウム系色素、シアニン系色素、メロシアニン系色素、トリフェニルメタン系色素、キサンテン系色素、ペリレン系色素およびインジゴ系色素からなる群から選択された少なくとも１種を用いることができる。 Examples of organic dyes include azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, perylene dyes, and indigo. At least one selected from the group consisting of system dyes can be used.
　なお、有機色素の吸光係数は、一般的に、遷移金属に分子が配位結合した形態を有する金属錯体色素の吸光係数に比べて大きい。 The extinction coefficient of an organic dye is generally larger than that of a metal complex dye having a form in which molecules are coordinated to a transition metal.
　金属錯体色素としては、たとえば、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、Ｔｃ、ＴｅまたはＲｈなどの金属に分子が配位結合した色素の少なくとも１種を用いることができる。このような金属錯体色素としては、たとえば、ポルフィリン系色素、フタロシアニン系色素、およびナフタロシアニン系色素などを挙げることができる。 Examples of the metal complex dye include 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, Tc, Te, Rh, etc. It is possible to use at least one kind of dye having molecules coordinated to the metal. Examples of such metal complex dyes include porphyrin dyes, phthalocyanine dyes, and naphthalocyanine dyes.
　色素としては、フタロシアニン系色素またはルテニウム系金属錯体色素を用いることが好ましく、ルテニウム系金属錯体色素を用いることがより好ましく、特に、以下の式（Ｉ）～（ＩＩＩ）で表わされるルテニウム系金属錯体色素を用いることが好ましい。色素としてフタロシアニン系色素またはルテニウム系金属錯体色素を用いた場合、特に、以下の式（Ｉ）～（ＩＩＩ）で表わされるルテニウム系金属錯体色素を用いた場合には、近赤外線領域の波長の光をも吸収することができるため、光電変換素子の光電変換効率を高めることができる。なお、以下の式（ＩＩ）および（ＩＩＩ）において、「ＴＢＡ」はテトラブチルアンモニウムを示している。 As the dye, a phthalocyanine dye or a ruthenium metal complex dye is preferably used, more preferably a ruthenium metal complex dye, and particularly, a ruthenium metal complex represented by the following formulas (I) to (III): It is preferable to use a dye. When a phthalocyanine dye or a ruthenium metal complex dye is used as the dye, particularly when a ruthenium metal complex dye represented by the following formulas (I) to (III) is used, light having a wavelength in the near infrared region is used. Therefore, the photoelectric conversion efficiency of the photoelectric conversion element can be increased. In the following formulas (II) and (III), “TBA” represents tetrabutylammonium.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
　また、光電変換層３の多孔質半導体層に色素を強固に吸着させるためには、色素は、カルボン酸基、カルボン酸無水物、アルコキシ基、ヒドロキシル基、ヒドロキシアルキル基、スルホン酸基、エステル基、メルカプト基およびホスホニル基からなる群から選択された少なくとも１種を含むことが好ましく、なかでも、カルボン酸基および／またはカルボン酸無水物を含むことが特に好ましい。色素が、カルボン酸基および／またはカルボン酸無水物を含む場合には、多孔質半導体層との吸着性が安定し、かつ、色素から多孔質半導体層への電子注入が効率的に行われる傾向にある。なお、これらの官能基は、励起状態の色素と多孔質半導体層の伝導帯との間の電子移動を容易にする電気的結合を提供するものである。 Moreover, in order to make a pigment | dye adsorb | suck firmly to the porous semiconductor layer of the photoelectric converting layer 3, a pigment | dye is a carboxylic acid group, a carboxylic anhydride, an alkoxy group, a hydroxyl group, a hydroxyalkyl group, a sulfonic acid group, an ester group. It preferably contains at least one selected from the group consisting of a mercapto group and a phosphonyl group, and particularly preferably contains a carboxylic acid group and / or a carboxylic acid anhydride. When the dye contains a carboxylic acid group and / or a carboxylic acid anhydride, the adsorptivity with the porous semiconductor layer is stable, and electron injection from the dye into the porous semiconductor layer tends to be performed efficiently. It is in. Note that these functional groups provide an electrical bond that facilitates electron transfer between the excited dye and the conduction band of the porous semiconductor layer.
　また、量子ドットとしては、たとえば、ＣｄＳ、ＣｄＳｅ、ＰｂＳおよびＰｂＳｅからなる群から選択された少なくとも１種の微粒子を用いることができる。量子ドットを構成する微粒子の粒径は、吸収波長などに応じて適宜調節されるが、量子ドットとして機能させる観点からは、１ｎｍ以上１０ｎｍ以下とすることが好ましい。 Further, as the quantum dots, for example, at least one kind of fine particles selected from the group consisting of CdS, CdSe, PbS and PbSe can be used. The particle diameter of the fine particles constituting the quantum dot is appropriately adjusted according to the absorption wavelength or the like, but is preferably 1 nm or more and 10 nm or less from the viewpoint of functioning as a quantum dot.
　光電変換層３の厚さは、４μｍ以上３０μｍ以下であることが好ましい。光電変換層３の厚さが４μｍ以上である場合には、光電変換層３における電子の移動距離が長くなるため、導電層４を設けたことによる効果が十分に発現する傾向にある。また、光電変換層３の厚さが３０μｍ以下である場合には、光電変換層３に接触する光増感素子に十分な量の光を照射することができるため、光電変換素子の光電変換効率が向上する傾向にある。 The thickness of the photoelectric conversion layer 3 is preferably 4 μm or more and 30 μm or less. When the thickness of the photoelectric conversion layer 3 is 4 μm or more, the moving distance of electrons in the photoelectric conversion layer 3 becomes long, and thus the effect of providing the conductive layer 4 tends to be sufficiently exhibited. In addition, when the thickness of the photoelectric conversion layer 3 is 30 μm or less, a sufficient amount of light can be irradiated to the photosensitizer that is in contact with the photoelectric conversion layer 3, and thus the photoelectric conversion efficiency of the photoelectric conversion element Tend to improve.
　＜導電層＞
　導電層４としては、導電性材料であれば特に限定なく用いることができ、たとえば、銀、銅、アルミニウム、インジウム、チタン、ニッケル、タンタルおよび鉄からなる群から選択された少なくとも１種の金属または２種以上の合金などを用いることができ、なかでも光電変換層３とオーミック接触可能な材料を用いることが好ましい。導電層４に光電変換層３とオーミック接触可能な材料を用いた場合には、光電変換層３と導電層４との接触抵抗を低減することができ、光電変換素子の外部に取り出すことができる電流量を増大させることができるため、光電変換素子の光電変換効率が向上する傾向にある。 <Conductive layer>
The conductive layer 4 can be used without particular limitation as long as it is a conductive material. For example, at least one metal selected from the group consisting of silver, copper, aluminum, indium, titanium, nickel, tantalum, and iron, or Two or more kinds of alloys can be used, and among them, it is preferable to use a material that can make ohmic contact with the photoelectric conversion layer 3. When a material that can make ohmic contact with the photoelectric conversion layer 3 is used for the conductive layer 4, the contact resistance between the photoelectric conversion layer 3 and the conductive layer 4 can be reduced, and the conductive layer 4 can be taken out of the photoelectric conversion element. Since the amount of current can be increased, the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.
　導電層４としては、たとえば、ボロン、ガリウムおよびアルミニウムからなる群から選択された少なくとも１種がドープされた酸化亜鉛、ニオブがドープされた酸化チタン、ＩＴＯ、またはＦＴＯなどの透明導電性金属酸化物などを用いることができる。 Examples of the conductive layer 4 include transparent conductive metal oxides such as zinc oxide doped with at least one selected from the group consisting of boron, gallium, and aluminum, titanium oxide doped with niobium, ITO, or FTO. Etc. can be used.
　キャリア輸送材料８にヨウ素などの腐食力の強い材料を用いた場合には、導電層４としては、ＩＴＯ、ＦＴＯ、チタンおよびタンタルからなる群から選択された少なくとも１種を用いることが好ましい。この場合には、キャリア輸送材料８による導電層４の腐食を有効に抑えることができる。なお、導電層４において、キャリア輸送材料８に対する耐腐食性が必要となる部分はキャリア輸送材料８との界面のみであるため、導電層４の表面のみを耐腐食性を有する材料で被覆してもよい。 When a material having a strong corrosive force such as iodine is used for the carrier transport material 8, it is preferable to use at least one selected from the group consisting of ITO, FTO, titanium and tantalum as the conductive layer 4. In this case, corrosion of the conductive layer 4 due to the carrier transport material 8 can be effectively suppressed. In addition, in the conductive layer 4, only the interface with the carrier transport material 8 is required to have corrosion resistance with respect to the carrier transport material 8, so that only the surface of the conductive layer 4 is covered with a material having corrosion resistance. Also good.
　＜キャリア輸送材料＞
　図１に示す実施の形態の光電変換素子においては、透明導電層２と、対極導電層５との間の封止材６で封止された空間には、キャリア輸送材料８が充填されており、キャリア輸送材料８中に光電変換層３が設けられている。すなわち、光電変換層３の空孔にはキャリア輸送材料８が入り込んでいる。 <Carrier transport material>
In the photoelectric conversion element of the embodiment shown in FIG. 1, the space sealed with the sealing material 6 between the transparent conductive layer 2 and the counter electrode conductive layer 5 is filled with a carrier transport material 8. The photoelectric conversion layer 3 is provided in the carrier transport material 8. That is, the carrier transport material 8 enters the pores of the photoelectric conversion layer 3.
　キャリア輸送材料８としては、難揮発性溶媒と、酸化還元種とを含むものを用いることができ、たとえば、難揮発性溶媒中に酸化還元種を溶解させたものなどを用いることができる。 As the carrier transport material 8, a material containing a hardly volatile solvent and a redox species can be used. For example, a material in which a redox species is dissolved in a hardly volatile solvent can be used.
　難揮発性溶媒としては、たとえば、エチルメチルイミダゾリウムビス（トリフルオロメタンスルホニル）イミドなどの沸点を有しないイオン性液体、プロピレンカーボネートなどのカーボネート化合物、３－メトキシプロピオニトリルなどのニトリル化合物、または水などの１００℃以上の沸点を有する溶媒を用いることが好ましい。難揮発性溶媒として沸点を有しないイオン性液体、または１００℃以上の沸点を有する溶媒を用いた場合には、光電変換素子の耐久性を向上させることができる傾向にある。また、難揮発性溶媒は、１種類の溶媒だけでなく、２種類以上を混合して用いることもできる。なお、本明細書において、「沸点」は、１ａｔｍの圧力における沸点を意味する。 Examples of the hardly volatile solvent include ionic liquids having no boiling point such as ethylmethylimidazolium bis (trifluoromethanesulfonyl) imide, carbonate compounds such as propylene carbonate, nitrile compounds such as 3-methoxypropionitrile, or water. It is preferable to use a solvent having a boiling point of 100 ° C. or higher. When an ionic liquid having no boiling point or a solvent having a boiling point of 100 ° C. or higher is used as the hardly volatile solvent, the durability of the photoelectric conversion element tends to be improved. Moreover, not only one type of solvent but also two or more types can be mixed and used as the hardly volatile solvent. In the present specification, “boiling point” means a boiling point at a pressure of 1 atm.
　ここで、難揮発性溶媒の粘度は、１ｃｐ（０．００１Ｐａ・ｓ）以上であることが好ましい。難揮発性溶媒の粘度が１ｃｐ以上である場合には、キャリア輸送材料８中のキャリア輸送を起因とする電子輸送時のロスが大きいことから、導電層４を形成したことによる効果が得られやすい傾向にある。なお、難揮発性溶媒の粘度は、たとえば従来から公知の粘度計などによって測定することができる。 Here, the viscosity of the hardly volatile solvent is preferably 1 cp (0.001 Pa · s) or more. When the viscosity of the hardly volatile solvent is 1 cp or more, since the loss at the time of electron transport due to carrier transport in the carrier transport material 8 is large, the effect of forming the conductive layer 4 is easily obtained. There is a tendency. The viscosity of the hardly volatile solvent can be measured, for example, with a conventionally known viscometer.
　酸化還元種としては、たとえば、Ｉ-／Ｉ3-系、Ｂｒ2-／Ｂｒ3-系、Ｆｅ2+／Ｆｅ3+系およびキノン／ハイドロキノン系からなる群から選択された少なくとも１種を用いることができる。 As the redox species, for example, at least one selected from the group consisting of I − / I 3− series, Br 2− / Br 3− series, Fe 2+ / Fe 3+ series and quinone / hydroquinone series is used. be able to.
　酸化還元種としては、金属ヨウ化物とヨウ素（Ｉ2）との組み合わせ、テトラアルキルアンモニウム塩とヨウ素（Ｉ2）との組み合わせ、金属臭化物と臭素（Ｂｒ2）との組み合わせ、またはヨウ化物系溶融塩とヨウ素（Ｉ2）との組み合わせを用いることが好ましい。この場合には、たとえばコバルト錯体またはフェロセンなどを酸化還元種として用いた場合と比較して良好なＩ－Ｖ曲線を有することができる。 As a redox species, a combination of metal iodide and iodine (I 2 ), a combination of tetraalkylammonium salt and iodine (I 2 ), a combination of metal bromide and bromine (Br 2 ), or an iodide melt It is preferable to use a combination of salt and iodine (I 2 ). In this case, for example, a better IV curve can be obtained as compared with a case where a cobalt complex or ferrocene is used as the redox species.
　ここで、金属ヨウ化物としては、たとえば、ヨウ化リチウム（ＬｉＩ）、ヨウ化ナトリウム（ＮａＩ）、ヨウ化カリウム（ＫＩ）およびヨウ化カルシウム（ＣａＩ2）からなる群から選択された少なくとも１種を用いることができる。 Here, as the metal iodide, for example, at least one selected from the group consisting of lithium iodide (LiI), sodium iodide (NaI), potassium iodide (KI), and calcium iodide (CaI 2 ) is used. Can be used.
　また、テトラアルキルアンモニウム塩としては、たとえば、テトラエチルアンモニウムアイオダイド（ＴＥＡＩ）、テトラプロピルアンモニウムアイオダイド（ＴＰＡＩ）、テトラブチルアンモニウムアイオダイド（ＴＢＡＩ）およびテトラヘキシルアンモニウムアイオダイド（ＴＨＡＩ）からなる群から選択された少なくとも１種を用いることができる。 The tetraalkylammonium salt is selected from the group consisting of, for example, tetraethylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), tetrabutylammonium iodide (TBAI), and tetrahexylammonium iodide (THAI). At least one selected from the above can be used.
　また、金属臭化物としては、たとえば、臭化リチウム（ＬｉＢｒ）、臭化ナトリウム（ＮａＢｒ）、臭化カリウム（ＫＢｒ）および臭化カルシウム（ＣａＢｒ2）からなる群から選択された少なくとも１種を用いることができる。 Further, as the metal bromide, for example, at least one selected from the group consisting of lithium bromide (LiBr), sodium bromide (NaBr), potassium bromide (KBr), and calcium bromide (CaBr 2 ) is used. Can do.
　また、キャリア輸送材料８には、必要に応じて添加剤を加えてもよい。このような添加剤としては、たとえば、ヨウ化物系溶融塩、ｔ－ブチルピリジン（ＴＢＰ）などの窒素を含有する芳香族化合物、チオシアン酸グアニジン、Ｎ－メチルベンズイミダゾールなどを挙げることができる。ヨウ化物系溶融塩は、ヨウ素イオンの供給源であり上記の酸化還元種としても機能させることができるので好ましい。具体的には、ジメチルプロピルイミダゾールアイオダイド（ＤＭＰＩＩ）、メチルプロピルイミダゾールアイオダイド（ＭＰＩＩ）、エチルメチルイミダゾールアイオダイド（ＥＭＩＩ）、エチルイミダゾールアイオダイド（ＥＩＩ）、ヘキシルメチルイミダゾールアイオダイド（ＨＭＩＩ）などのイミダゾール塩などを用いることができる。 In addition, an additive may be added to the carrier transport material 8 as necessary. Examples of such additives include iodide-based molten salts, nitrogen-containing aromatic compounds such as t-butylpyridine (TBP), guanidine thiocyanate, and N-methylbenzimidazole. Iodide-based molten salt is preferable because it is a source of iodine ions and can function as the above-described redox species. Specifically, dimethylpropylimidazole iodide (DMPII), methylpropylimidazole iodide (MPII), ethylmethylimidazole iodide (EMII), ethylimidazole iodide (EII), hexylmethylimidazole iodide (HMII), etc. Imidazole salts and the like can be used.
　キャリア輸送材料８中の酸化還元種の濃度は、上記の溶媒、電解質などの種類により適宜選択されるが、０．００１モル／リットル以上１．５モル／リットル以下であることが好ましく、０．０１モル／リットル以上０．７モル／リットル以下であることが好ましい。この場合には、キャリア輸送材料８中の酸化還元種の輸送が効率的に行なわれる傾向にある。 The concentration of the redox species in the carrier transport material 8 is appropriately selected depending on the type of the solvent, electrolyte, etc., and is preferably 0.001 mol / liter to 1.5 mol / liter. It is preferably from 01 mol / liter to 0.7 mol / liter. In this case, the redox species in the carrier transport material 8 tend to be transported efficiently.
　キャリア輸送材料８の電気伝導率は、１．５Ｓ／ｍ以下であることが好ましい。キャリア輸送材料８の電気伝導率が１．５Ｓ／ｍ以下である場合には、キャリア輸送材料８から光増感素子への電子移動が効率的に行われないことから、導電層４を形成したことによる効果を十分に発現させることができる傾向にある。 The electric conductivity of the carrier transport material 8 is preferably 1.5 S / m or less. When the electric conductivity of the carrier transport material 8 is 1.5 S / m or less, the electron transfer from the carrier transport material 8 to the photosensitizer is not efficiently performed, so the conductive layer 4 was formed. There exists a tendency which can fully express the effect by this.
　＜対極＞
　対極１２は、対極導電層５と、対極導電層５の表面上に設けられた触媒層７とから構成されている。対極導電層５は、電子を収集するとともに隣接する光電変換素子と電気的に接続することができる。また、触媒層７は、触媒能を有し、キャリア輸送材料８中の正孔を還元することができる。 <Counter electrode>
The counter electrode 12 includes a counter electrode conductive layer 5 and a catalyst layer 7 provided on the surface of the counter electrode conductive layer 5. The counter electrode conductive layer 5 collects electrons and can be electrically connected to an adjacent photoelectric conversion element. Further, the catalyst layer 7 has catalytic ability and can reduce holes in the carrier transport material 8.
　なお、本実施の形態においては、対極１２は、対極導電層５と触媒層７とから構成されているが、対極導電層５が触媒能を有する場合、または触媒層７が高い導電性を有する場合には、対極導電層５および触媒層７のいずれか一方のみから対極１２を構成してもよい。 In the present embodiment, the counter electrode 12 is composed of the counter electrode conductive layer 5 and the catalyst layer 7. However, when the counter electrode conductive layer 5 has catalytic ability, or the catalyst layer 7 has high conductivity. In this case, the counter electrode 12 may be constituted by only one of the counter electrode conductive layer 5 and the catalyst layer 7.
　対極導電層５としては、導電性材料を用いることができ、たとえば、ＩＴＯ、ＦＴＯおよびＺｎＯ等の金属酸化物の少なくとも１種、および／または、チタン、タングステン、金、銀、銅およびニッケル等の金属の少なくとも１種を含む導電性材料を用いることができる。なかでも、対極導電層５としては、チタンを用いることが好ましい。対極導電層５としてチタンを用いた場合には、対極導電層５の強度を大幅に向上させることができる。 As the counter electrode conductive layer 5, a conductive material can be used. For example, at least one of metal oxides such as ITO, FTO, and ZnO, and / or titanium, tungsten, gold, silver, copper, nickel, and the like can be used. A conductive material containing at least one kind of metal can be used. Especially, it is preferable to use titanium as the counter electrode conductive layer 5. When titanium is used as the counter electrode conductive layer 5, the strength of the counter electrode conductive layer 5 can be significantly improved.
　触媒層７としては、たとえば、白金および／またはカーボンを用いることが好ましい。触媒層７がカーボンからなる場合には、触媒層７に用いられるカーボンとしては、たとえば、カーボンブラック、グラファイト、ガラス炭素、アモルファス炭素、ハードカーボン、ソフトカーボン、カーボンホイスカー、カーボンナノチューブおよびフラーレンからなる群から選択された少なくとも１種などを用いることが好ましい。 As the catalyst layer 7, for example, platinum and / or carbon is preferably used. When the catalyst layer 7 is made of carbon, examples of carbon used in the catalyst layer 7 include a group consisting of carbon black, graphite, glass carbon, amorphous carbon, hard carbon, soft carbon, carbon whisker, carbon nanotube, and fullerene. It is preferable to use at least one selected from
　＜封止材＞
　封止材６は、キャリア輸送材料８の揮発を抑制し、光電変換素子内への水など液体の浸入を抑制することができる。また、封止材６は、光透過性支持体１に作用する応力（衝撃）を吸収し、光電変換素子の長期使用時において光透過性支持体１に作用する撓みなどを吸収することができる。 <Encapsulant>
The sealing material 6 can suppress the volatilization of the carrier transport material 8 and can suppress the intrusion of a liquid such as water into the photoelectric conversion element. Moreover, the sealing material 6 can absorb the stress (impact) which acts on the transparent support body 1, and can absorb the bending etc. which act on the transparent support body 1 at the time of long-term use of a photoelectric conversion element. .
　封止材６としては、たとえば、シリコーン樹脂、エポキシ樹脂、ポリイソブチレン系樹脂、ホットメルト樹脂およびガラスフリットからなる群から選択された少なくとも１種を含む単層、または当該単層を２層以上に重ねた複数層などを用いることができる。なお、キャリア輸送材料８の難揮発性溶媒として、ニトリル系溶剤またはカーボネート系溶剤を用いた場合には、封止材６は、シリコーン樹脂やホットメルト樹脂（例えば、アイオノマー樹脂）、ポリイソブチレン系樹脂およびガラスフリットからなる群から選択された少なくとも１種を含むことが特に好ましい。この場合には、キャリア輸送材料８に対する封止材６の腐食を抑えることができる傾向にある。 As the sealing material 6, for example, a single layer including at least one selected from the group consisting of a silicone resin, an epoxy resin, a polyisobutylene resin, a hot melt resin, and a glass frit, or the single layer is made into two or more layers. A plurality of stacked layers can be used. When a nitrile solvent or a carbonate solvent is used as the hardly volatile solvent of the carrier transport material 8, the sealing material 6 is a silicone resin, a hot melt resin (for example, an ionomer resin), or a polyisobutylene resin. And at least one selected from the group consisting of glass frit. In this case, corrosion of the sealing material 6 with respect to the carrier transporting material 8 tends to be suppressed.
　＜製造方法＞
　以下、図２～図５の模式的断面図を参照して、実施の形態の光電変換素子の製造方法の一例について説明する。 <Manufacturing method>
Hereinafter, an example of a method for manufacturing the photoelectric conversion element of the embodiment will be described with reference to schematic sectional views of FIGS.
　まず、図２に示すように、光透過性支持体１の表面上に透明導電層２が設けられた透明電極板１１を準備する工程を行なう。ここで、透明電極板１１を準備する工程は、たとえば、市販されているものを準備してもよく、たとえば、光透過性支持体１の表面上に透明導電層２をたとえばスパッタリング法または熱ＣＶＤ法などの方法によって積層することにより準備してもよい。 First, as shown in FIG. 2, a step of preparing a transparent electrode plate 11 having a transparent conductive layer 2 provided on the surface of a light-transmissive support 1 is performed. Here, the step of preparing the transparent electrode plate 11 may be, for example, a commercially available one. For example, the transparent conductive layer 2 is formed on the surface of the light-transmissive support 1 by, for example, sputtering or thermal CVD. You may prepare by laminating | stacking by methods, such as a method.
　次に、図３に示すように、透明導電層２の表面上に多孔質半導体層３ａを形成する工程を行なう。ここで、多孔質半導体層３ａを形成する工程は、特に限定されないが、たとえば以下の（ｉ）～（ｉｖ）の少なくとも１つの方法により行なうことができる。
（ｉ）スクリーン印刷法またはインクジェット法などによって半導体材料からなる微粒子を含有するペーストを透明導電層２の表面上に塗布した後に焼成することによって透明導電層２の表面上に多孔質半導体層３ａを形成する方法。
（ｉｉ）所望の原料ガスを用いてＣＶＤ法またはＭＯＣＶＤ法などによって、透明導電層２の表面上に多孔質半導体層３ａを成膜する方法。
（ｉｉｉ）固体原料を用いたＰＶＤ法、蒸着法またはスパッタリング法などによって、透明導電層２の表面上に多孔質半導体層３ａを成膜する方法。
（ｉｖ）ゾル－ゲル法または電気化学的な酸化還元反応を利用した方法などによって、透明導電層２の表面上に多孔質半導体層３ａを形成する方法。 Next, as shown in FIG. 3, a step of forming a porous semiconductor layer 3a on the surface of the transparent conductive layer 2 is performed. Here, the step of forming the porous semiconductor layer 3a is not particularly limited, but can be performed, for example, by at least one of the following methods (i) to (iv).
(I) A porous semiconductor layer 3a is formed on the surface of the transparent conductive layer 2 by applying a paste containing fine particles made of a semiconductor material on the surface of the transparent conductive layer 2 by a screen printing method or an ink jet method and then baking the paste. How to form.
(Ii) A method of forming the porous semiconductor layer 3a on the surface of the transparent conductive layer 2 by a CVD method or an MOCVD method using a desired source gas.
(Iii) A method of forming the porous semiconductor layer 3a on the surface of the transparent conductive layer 2 by a PVD method, a vapor deposition method or a sputtering method using a solid material.
(Iv) A method of forming the porous semiconductor layer 3a on the surface of the transparent conductive layer 2 by a sol-gel method or a method using an electrochemical redox reaction.
　なかでも、多孔質半導体層３ａを形成する工程は、上記の（ｉ）のスクリーン印刷法によって半導体材料からなる微粒子を含有するペーストを透明導電層２の表面上に塗布した後に焼成することによって透明導電層２の表面上に多孔質半導体層３ａを形成する方法を用いることが好ましい。この場合には、比較的厚さのある多孔質半導体層３ａを低コストで作製することができる傾向にある。 In particular, the step of forming the porous semiconductor layer 3a is performed by applying a paste containing fine particles made of a semiconductor material on the surface of the transparent conductive layer 2 by the screen printing method (i) and then baking the paste. It is preferable to use a method of forming the porous semiconductor layer 3 a on the surface of the conductive layer 2. In this case, the porous semiconductor layer 3a having a relatively large thickness tends to be produced at a low cost.
　膜状および／または粒子状の多孔質半導体層３ａを形成する場合には、１０ｍ2／ｇ以上２００ｍ2／ｇ以下の比表面積の多孔質半導体層３ａを形成することが好ましい。この場合には、光増感素子をより多く保持した光電変換層３を形成することによって、光電変換素子の光電変換効率を向上させることができる傾向にある。 When forming the film-like and / or particulate porous semiconductor layer 3a, it is preferable to form the porous semiconductor layer 3a having a specific surface area of 10 m 2 / g or more and 200 m 2 / g or less. In this case, there is a tendency that the photoelectric conversion efficiency of the photoelectric conversion element can be improved by forming the photoelectric conversion layer 3 holding more photosensitizers.
　以下に、半導体粒子としてアナターゼ型酸化チタンを用いて、多孔質半導体層を形成する方法について、具体的に説明する。 Hereinafter, a method for forming a porous semiconductor layer using anatase-type titanium oxide as semiconductor particles will be specifically described.
　まず、チタンイソプロポキシド１２５ｍＬを０．１Ｍの硝酸水溶液７５０ｍＬに滴下して加水分解し、８０℃で８時間加熱して、ゾル液を調製する。 First, 125 mL of titanium isopropoxide is dropped into 750 mL of a 0.1 M nitric acid aqueous solution for hydrolysis, and heated at 80 ° C. for 8 hours to prepare a sol solution.
　次に、上記のようにして調製したゾル液をチタン製オートクレーブ中で２３０℃で１１時間加熱することによって酸化チタン粒子を成長させ、その後室温下で超音波分散を３０分間行なうことにより、平均粒径（平均一次粒径）１５ｎｍの酸化チタン粒子を含むコロイド溶液を調製する。 Next, the sol solution prepared as described above is heated in a titanium autoclave at 230 ° C. for 11 hours to grow titanium oxide particles, and then ultrasonic dispersion is performed at room temperature for 30 minutes to obtain an average particle size. A colloidal solution containing titanium oxide particles having a diameter (average primary particle diameter) of 15 nm is prepared.
　次に、上記のようにして得られたコロイド溶液に、該コロイド溶液の２倍容量のエタノールを加え、これを回転数５０００ｒｐｍで遠心分離して、酸化チタン粒子と溶剤とを分離させることによって、酸化チタン粒子を得る。 Next, to the colloid solution obtained as described above, ethanol twice the volume of the colloid solution is added, and this is centrifuged at a rotational speed of 5000 rpm to separate the titanium oxide particles and the solvent, Titanium oxide particles are obtained.
　次に、上記のようにして得られた酸化チタン粒子を洗浄した後、エチルセルロースとテルピネオールを無水エタノールに溶解させた溶液に酸化チタン粒子を加え、攪拌することによって、酸化チタン粒子を分散させる。 Next, after washing the titanium oxide particles obtained as described above, the titanium oxide particles are added to a solution in which ethylcellulose and terpineol are dissolved in absolute ethanol and stirred to disperse the titanium oxide particles.
　次に、上記の酸化チタン粒子を分散させた溶液を真空条件下で加熱してエタノールを蒸発させることによって、酸化チタンペーストを得る。そして、最終的な組成として、たとえば、酸化チタン固体濃度２０質量％、エチルセルロース１０質量％、テルピネオール７０質量％となるように濃度を調整する。なお、上記の最終的な組成は例示的なものであって、これに限定されるものではない。 Next, a titanium oxide paste is obtained by heating the solution in which the above titanium oxide particles are dispersed under vacuum conditions to evaporate ethanol. And as a final composition, a density | concentration is adjusted so that it may become titanium oxide solid concentration 20 mass%, ethyl cellulose 10 mass%, and terpineol 70 mass%, for example. Note that the above-mentioned final composition is illustrative and is not limited to this.
　半導体粒子を含有する（懸濁させた）ペーストを調製するために用いる溶剤としては、上記以外にも、たとえば、エチレングリコールモノメチルエーテルなどのグライム系溶剤、イソプロピルアルコールなどのアルコール系溶剤、イソプロピルアルコールとトルエンとの混合液などの混合溶剤、または水などを用いることができる。 As a solvent used for preparing a paste containing semiconductor particles (suspended), in addition to the above, for example, a glyme solvent such as ethylene glycol monomethyl ether, an alcohol solvent such as isopropyl alcohol, isopropyl alcohol and the like A mixed solvent such as a mixed solution with toluene, water, or the like can be used.
　次に、上記のようにして作製した酸化チタンペーストを透明導電層２の表面上にスクリーン印刷した後に乾燥させ、焼成することによって多孔質半導体層３ａを作製することができる。ここで、酸化チタンペーストの乾燥条件および焼成条件は、それぞれ、光透過性支持体１や半導体粒子の種類によって、温度、時間および雰囲気などの条件を適宜設定することによって調節することができる。 Next, the porous oxide layer 3a can be produced by screen printing the titanium oxide paste produced as described above on the surface of the transparent conductive layer 2 and then drying and baking. Here, the drying conditions and firing conditions of the titanium oxide paste can be adjusted by appropriately setting conditions such as temperature, time, and atmosphere depending on the type of the light-transmissive support 1 and the semiconductor particles.
　酸化チタンペーストの焼成は、たとえば、大気雰囲気下または不活性ガス雰囲気下で、５０～８００℃程度の範囲内で、１０秒～１２時間程度行なうことができる。また、酸化チタンペーストの乾燥および焼成は、それぞれ、たとえば、単一の温度で１回または温度
を変化させて２回以上行なうことができる。なお、上記の条件で作製した酸化チタンからなる多孔質半導体層３ａの比表面積は１０ｍ2／ｇ以上２００ｍ2／ｇ以下の範囲内にある。 The titanium oxide paste can be baked, for example, in an air atmosphere or an inert gas atmosphere within a range of about 50 to 800 ° C. for about 10 seconds to 12 hours. The titanium oxide paste can be dried and fired, for example, once at a single temperature or twice or more at different temperatures. The specific surface area of the porous semiconductor layer 3a made of titanium oxide produced under the above conditions is in the range of 10 m 2 / g or more and 200 m 2 / g or less.
　多孔質半導体層３ａを構成する半導体粒子の平均粒径は、特に限定されないが、入射光を光電変換に有効利用するという点では、市販の半導体材料粉末のようにある程度粒径が揃っていることがより好ましい。 The average particle diameter of the semiconductor particles constituting the porous semiconductor layer 3a is not particularly limited. However, in terms of effectively using incident light for photoelectric conversion, the average particle diameter should be uniform to some extent like a commercially available semiconductor material powder. Is more preferable.
　次に、図４に示すように、光電変換層３および透明導電層２の表面上にそれぞれ導電層４を形成する工程を行なう。 Next, as shown in FIG. 4, a process of forming the conductive layer 4 on the surface of the photoelectric conversion layer 3 and the transparent conductive layer 2 is performed.
　ここで、導電層４は、たとえば、透明導電層２と電気的に接続するようにして、蒸着法またはスパッタ法などによって光電変換層３の表面の少なくとも一部に形成することができる。 Here, the conductive layer 4 can be formed on at least part of the surface of the photoelectric conversion layer 3 by vapor deposition or sputtering, for example, so as to be electrically connected to the transparent conductive layer 2.
　また、光電変換層３は、たとえば、多孔質半導体層３ａに光増感素子を吸着させることによって形成することができる。ここで、多孔質半導体層３ａに光増感素子を吸着させる方法としては、たとえば、透明導電層２の表面上に形成された多孔質半導体層３ａを、光増感素子を溶解した溶液に浸漬する方法を用いることができる。なお、浸漬条件は適宜調整することができる。 The photoelectric conversion layer 3 can be formed, for example, by adsorbing a photosensitizing element to the porous semiconductor layer 3a. Here, as a method for adsorbing the photosensitizer on the porous semiconductor layer 3a, for example, the porous semiconductor layer 3a formed on the surface of the transparent conductive layer 2 is immersed in a solution in which the photosensitizer is dissolved. Can be used. In addition, immersion conditions can be adjusted suitably.
　光増感素子を溶解させる溶剤としては、たとえば、エタノールなどのアルコール類、アセトンなどのケトン類、ジエチルエーテルおよびテトラヒドロフランなどのエーテル類、アセトニトリルなどの窒素化合物類、クロロホルムなどのハロゲン化脂肪族炭化水素、ヘキサンなどの脂肪族炭化水素、ベンゼンなどの芳香族炭化水素、酢酸エチルなどのエステル類、ならびに水から選択された１種、または２種以上を混合して用いることができる。 Solvents that dissolve the photosensitizer include, for example, alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether and tetrahydrofuran, nitrogen compounds such as acetonitrile, and halogenated aliphatic hydrocarbons such as chloroform. One kind selected from aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, esters such as ethyl acetate, and water, or a mixture of two or more kinds can be used.
　なお、光増感素子を溶解した溶液として、上記の溶剤に色素を溶解させた色素吸着用溶液を用いた場合には、色素吸着用溶液中の色素濃度は、色素および溶剤の種類により適宜調整することができるが、吸着機能（効率）を向上させるためには、できるだけ高濃度であることが好ましく、たとえば５×１０-4モル／リットル以上であればよい。 When a dye adsorption solution in which a dye is dissolved in the above solvent is used as the solution in which the photosensitizer is dissolved, the dye concentration in the dye adsorption solution is appropriately adjusted according to the type of the dye and the solvent. However, in order to improve the adsorption function (efficiency), the concentration is preferably as high as possible, for example, 5 × 10 −4 mol / liter or more.
　次に、図５に示すように、対極導電層５の表面上に触媒層７を形成することによって対極１２を形成する工程を行なう。ここで、触媒層７として、白金を用いる場合には、触媒層７は、たとえば、蒸着法またはスパッタ法などのＰＶＤ法、塩化白金酸の熱分解または電着などの公知の方法により形成することができる。ここで、触媒層７の厚さは、たとえば、０．５ｎｍ以上１０００ｎｍ以下とすることができる。 Next, as shown in FIG. 5, a step of forming the counter electrode 12 by forming the catalyst layer 7 on the surface of the counter electrode conductive layer 5 is performed. Here, when platinum is used as the catalyst layer 7, the catalyst layer 7 is formed by a known method such as a PVD method such as a vapor deposition method or a sputtering method, thermal decomposition or electrodeposition of chloroplatinic acid, for example. Can do. Here, the thickness of the catalyst layer 7 can be 0.5 nm or more and 1000 nm or less, for example.
　触媒層７として、カーボンブラック、ケッチェンブラック、カーボンナノチューブ、フラーレンなどのカーボン材料を用いる場合には、触媒層７は、たとえば、任意の溶剤に分散してペースト状にしたカーボンをスクリーン印刷法などにより対極導電層５の表面上に塗布することにより形成することができる。ここでも、触媒層７の厚さは、たとえば、０．５ｎｍ以上１０００ｎｍ以下とすることができる。 When a carbon material such as carbon black, ketjen black, carbon nanotube, or fullerene is used as the catalyst layer 7, the catalyst layer 7 is, for example, a screen printing method in which carbon dispersed in an arbitrary solvent is pasted. Can be formed by coating on the surface of the counter electrode conductive layer 5. Also here, the thickness of the catalyst layer 7 can be, for example, not less than 0.5 nm and not more than 1000 nm.
　対極導電層５の厚さは、対極導電層５の材料の比抵抗率に応じて適宜選択することが好ましい。対極導電層５が薄すぎると抵抗が高くなり、厚すぎるとキャリア輸送材料８の移動の妨げとなるためである。 The thickness of the counter electrode conductive layer 5 is preferably selected as appropriate according to the specific resistivity of the material of the counter electrode conductive layer 5. This is because if the counter electrode conductive layer 5 is too thin, the resistance is increased, and if it is too thick, the movement of the carrier transport material 8 is hindered.
　その後、図１に示すように、透明電極板１１の透明導電層２と、対極１２の触媒層７との間の領域にキャリア輸送材料８を設置する工程を行なう。キャリア輸送材料８を設置する工程は、たとえば、透明電極板１１の光電変換層３の周囲を取り囲むようにして封止材６を設置し、透明電極板１１の透明導電層２と、対極１２の触媒層７とが向かい合うようにして透明電極板１１と対極１２とを配置して、透明電極板１１と対極１２とを封止材６により固定する。その後、透明電極板１１に設けられた孔からキャリア輸送材料８を封止材６で取り囲まれた領域内に注入し、その後、孔を塞ぐことにより、図１に示す実施の形態の光電変換素子を作製することができる。 Thereafter, as shown in FIG. 1, a step of installing a carrier transport material 8 in a region between the transparent conductive layer 2 of the transparent electrode plate 11 and the catalyst layer 7 of the counter electrode 12 is performed. The step of installing the carrier transport material 8 includes, for example, installing the sealing material 6 so as to surround the photoelectric conversion layer 3 of the transparent electrode plate 11, the transparent conductive layer 2 of the transparent electrode plate 11, and the counter electrode 12. The transparent electrode plate 11 and the counter electrode 12 are arranged so that the catalyst layer 7 faces each other, and the transparent electrode plate 11 and the counter electrode 12 are fixed by the sealing material 6. Thereafter, the carrier transport material 8 is injected into the region surrounded by the sealing material 6 from the hole provided in the transparent electrode plate 11, and then the hole is closed, whereby the photoelectric conversion element of the embodiment shown in FIG. Can be produced.
　＜作用・効果＞
　本発明者は、難揮発性溶媒の粘度が高いことに起因する従来の光電変換素子の光電変換効率の低下は、以下のメカニズムによるものであると考えた。すなわち、難揮発性溶媒の粘度が高いために、光を吸収して励起した色素を還元する役割を担うイオンが、キャリア輸送材料８中を拡散する速度が遅くなり、光電変換層３の透明電極板１１側に存在する色素などの光増感素子がカチオンである時間が長くなる。これにより、光電変換層３の対極１２側に存在する光増感素子が光を吸収する確率が高くなる一方で、光電変換層３の対極１２側で発生した電子が透明導電層２に到達するまでの距離が長くなるため、電子が光電変換層３の内部でトラップされてしまう確率が高くなり、電流密度の大幅な低下が引き起こされる。 <Action and effect>
This inventor considered that the fall of the photoelectric conversion efficiency of the conventional photoelectric conversion element resulting from the high viscosity of a hardly volatile solvent is based on the following mechanisms. That is, since the viscosity of the hardly volatile solvent is high, the rate of diffusion of ions that play a role of reducing the dye excited by absorbing light in the carrier transport material 8 is reduced, and the transparent electrode of the photoelectric conversion layer 3 The time during which the photosensitizer such as a dye existing on the plate 11 side is a cation becomes longer. Thereby, the probability that the photosensitizer present on the counter electrode 12 side of the photoelectric conversion layer 3 absorbs light increases, while the electrons generated on the counter electrode 12 side of the photoelectric conversion layer 3 reach the transparent conductive layer 2. Therefore, the probability that electrons are trapped inside the photoelectric conversion layer 3 is increased, and the current density is significantly reduced.
　そこで、本発明者が鋭意検討した結果、上記のようにして作製した実施の形態の光電変換素子においては、キャリア輸送材料８の溶媒として難揮発性溶媒を用いるとともに、光電変換層３の対極１２側の表面の少なくとも一部に導電層４を設け、導電層４を透明導電層２に電気的に接続されている。 Therefore, as a result of intensive studies by the present inventors, in the photoelectric conversion element of the embodiment manufactured as described above, a hardly volatile solvent is used as the solvent of the carrier transport material 8 and the counter electrode 12 of the photoelectric conversion layer 3 is used. The conductive layer 4 is provided on at least a part of the surface on the side, and the conductive layer 4 is electrically connected to the transparent conductive layer 2.
　これにより、実施の形態の光電変換素子においては、光電変換素子の耐久性を向上させることができるとともに、光電変換層３の対極１２側で発生した電子を導電層４から透明導電層２に導くことによって、電子が光電変換層３の内部でトラップされる確率を低くすることができることから、電流密度の大幅な低下を抑制して、光電変換効率の低下を抑制することができる。 Thereby, in the photoelectric conversion element of embodiment, the durability of the photoelectric conversion element can be improved, and electrons generated on the counter electrode 12 side of the photoelectric conversion layer 3 are guided from the conductive layer 4 to the transparent conductive layer 2. As a result, the probability that electrons are trapped inside the photoelectric conversion layer 3 can be lowered, so that a significant decrease in current density can be suppressed and a decrease in photoelectric conversion efficiency can be suppressed.
　本発明を実施例および比較例によりさらに具体的に説明する。ただし、これらの実施例および比較例により本発明が限定されるものではない。以下の実施例および比較例において、各層の厚みは段差計（（株）東京精密製　Ｅ－ＶＳ－Ｓ２８Ａ）により測定した。 The present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples. In the following examples and comparative examples, the thickness of each layer was measured with a step gauge (E-VS-S28A, manufactured by Tokyo Seimitsu Co., Ltd.).
　＜実施例１＞
　実施例１においては、図１に示す構造を有する光電変換素子を作製した。まず、ガラスからなる光透過性支持体１上にフッ素がドープされた酸化錫（ＦＴＯ）からなる透明導電層２が成膜された、幅３０ｍｍ×長さ３０ｍｍ×厚さ１ｍｍの透明電極板１１（日本板硝子株式会社製、ＳｎＯ2膜付ガラス）を準備した。 <Example 1>
In Example 1, a photoelectric conversion element having the structure shown in FIG. 1 was produced. First, a transparent electrode plate 11 having a width of 30 mm × a length of 30 mm × a thickness of 1 mm, in which a transparent conductive layer 2 made of tin oxide (FTO) doped with fluorine is formed on a light-transmitting support 1 made of glass. (Nippon Sheet Glass Co., Ltd. glass with SnO 2 film) was prepared.
　次に、透明電極板１１の透明導電層２側の表面上に、幅５ｍｍ×長さ５ｍｍの多孔質半導体層のパターンを有するスクリーン版とスクリーン印刷機（ニューロング精密工業株式会社製、型番：ＬＳ－１５０）を用いて、市販の酸化チタンペースト（Ｓｏｌａｒｏｎｉｘ社製、商品名：Ｄ／ＳＰ）を塗布し、室温で１時間レベリングを行なった。 Next, on the surface of the transparent electrode plate 11 on the transparent conductive layer 2 side, a screen plate having a pattern of a porous semiconductor layer having a width of 5 mm × a length of 5 mm and a screen printing machine (manufactured by Neurong Precision Industry Co., Ltd., model number: LS-150), a commercially available titanium oxide paste (manufactured by Solaronix, trade name: D / SP) was applied and leveled at room temperature for 1 hour.
　次に、上記のようにして得られた塗膜を８０℃に設定したオーブンで２０分間乾燥し、さらに５００℃に設定した焼成炉（株式会社デンケン製、型番：ＫＤＦ　Ｐ－１００）を用いて空気中で６０分間焼成した。上記の塗布、乾燥および焼成工程を繰り返して、厚さ１２μｍ程度の多孔質半導体層を得た。さらに、得られた多孔質半導体層上に粒径の異なる酸化チタンペースト（日揮触媒化成株式会社製、ＰＳＴ－４００Ｃ）を用い、さらに上記の塗布、乾燥および焼成工程を経ることで、最終的に、厚さ１８μｍ程度の多孔質半導体層を形成した。 Next, the coating film obtained as described above was dried in an oven set at 80 ° C. for 20 minutes, and further using a baking furnace (model number: KDF P-100 manufactured by Denken Co., Ltd.) set at 500 ° C. Baked for 60 minutes in air. The above coating, drying and firing steps were repeated to obtain a porous semiconductor layer having a thickness of about 12 μm. Furthermore, by using a titanium oxide paste (manufactured by JGC Catalysts & Chemicals Co., Ltd., PST-400C) having a different particle size on the obtained porous semiconductor layer, it is finally subjected to the above-described coating, drying and firing steps. A porous semiconductor layer having a thickness of about 18 μm was formed.
　次に、幅６ｍｍ×長さ１２ｍｍの長方形状の開口部が並ぶメタルマスクを用意し、多孔質半導体層および透明導電層２の表面上に、電子ビーム蒸着器ｅｉ－５（アルバック株式会社製）を用いて蒸着速度１５０ｎｍ／ｓｅｃでチタン膜を成膜することによって、厚さ約３００ｎｍの導電層４を形成した。 Next, a metal mask in which rectangular openings having a width of 6 mm and a length of 12 mm are arranged is prepared, and an electron beam evaporator ei-5 (manufactured by ULVAC, Inc.) is formed on the surfaces of the porous semiconductor layer and the transparent conductive layer 2. A conductive film 4 having a thickness of about 300 nm was formed by depositing a titanium film at a deposition rate of 150 nm / sec.
　次に、予め調製しておいた色素吸着用溶液に上記の導電層４の形成後の透明電極板１１を室温で１００時間浸漬させ、上記の導電層４の形成後の透明電極板１１をエタノールで洗浄し、約６０℃で約５分間乾燥させることによって、多孔質半導体層に色素を吸着させて光電変換層３を形成した。 Next, the transparent electrode plate 11 after the formation of the conductive layer 4 is immersed in a dye adsorption solution prepared in advance at room temperature for 100 hours, and the transparent electrode plate 11 after the formation of the conductive layer 4 is immersed in ethanol. And dried at about 60 ° C. for about 5 minutes, thereby adsorbing the dye to the porous semiconductor layer to form the photoelectric conversion layer 3.
　上記の色素吸着用溶液は、上記の式（ＩＩ）の色素（Ｓｏｌａｒｏｎｉｘ社製、商品名：Ｒｕｔｈｅｎｉｕｍ６２０　１Ｈ３ＴＢＡ）を体積比１：１のアセトニトリルとｔ－ブタノールの混合溶剤に溶解させて調製した濃度４×１０-4モル／リットルの溶液であった。 The dye adsorption solution was prepared by dissolving the dye of the above formula (II) (manufactured by Solaronix, trade name: Ruthenium 620 1H3TBA) in a mixed solvent of acetonitrile and t-butanol having a volume ratio of 1: 1. The solution was × 10 -4 mol / liter.
　次に、上記の透明電極板（日本板硝子株式会社製、ＳｎＯ2膜付ガラス）をもう１枚用意して対極導電層５とし、対極導電層５のＳｎＯ2膜の表面上に、触媒層７として、スパッタ法により厚さ約７ｎｍの白金膜を成膜することによって、対極１２を形成した。 Next, another transparent electrode plate (Nippon Sheet Glass Co., Ltd., glass with SnO 2 film) is prepared as the counter electrode conductive layer 5, and the catalyst layer 7 is formed on the surface of the SnO 2 film of the counter electrode conductive layer 5. As a result, a counter electrode 12 was formed by forming a platinum film having a thickness of about 7 nm by sputtering.
　次に、透明電極板１１の透明電極層２と、対極１２の触媒層７とを、光電変換層３の周囲を囲う形に切り出した熱融着フィルム（デュポン社製、ハイミラン１８５５）を用いて貼り合せ、約１００℃に設定したオーブンで１０分間加熱することによって、これらを圧着した。 Next, using a heat-sealing film (manufactured by DuPont, High Milan 1855) in which the transparent electrode layer 2 of the transparent electrode plate 11 and the catalyst layer 7 of the counter electrode 12 are cut out to surround the photoelectric conversion layer 3. These were bonded and pressure-bonded by heating in an oven set at about 100 ° C. for 10 minutes.
　次に、透明電極板１１に予め設けてあった孔からキャリア輸送材料８として電解液を注入し、その後、紫外線硬化樹脂（スリーボンド社製、型番：３１Ｘ－１０１）を用いて孔を封止することによって、キャリア輸送材料８を充填して、実施例の光電変換素子を得た。 Next, an electrolytic solution is injected as a carrier transporting material 8 from a hole provided in advance in the transparent electrode plate 11, and then the hole is sealed using an ultraviolet curable resin (manufactured by ThreeBond, model number: 31X-101). Thus, the carrier transport material 8 was filled to obtain the photoelectric conversion element of the example.
　上記の電解液は、溶剤である３－メトキシプロピオニトリル（沸点：１６５℃、粘度：１．１ｃｐ）に、酸化還元種として、Ｉ2（キシダ化学社製）を濃度０．１５モル／リットル、メチルプロピルイミダゾールアイオダイド（四国化成工業社製）を濃度０．８モル／リットルになるように、さらに添加剤としてチオシアン酸グアニジンを濃度０．１モル／リットル、Ｎ－メチルベンズイミダゾールを濃度０．５モル／リットルになるように添加して溶解させたものである。この電解液の電気伝導率は１．５Ｓ／ｍ以下であった。 The above electrolytic solution was prepared by using 3-methoxypropionitrile (boiling point: 165 ° C., viscosity: 1.1 cp) as a solvent and I 2 (made by Kishida Chemical Co.) as a redox species at a concentration of 0.15 mol / liter. Further, methylpropylimidazole iodide (manufactured by Shikoku Kasei Kogyo Co., Ltd.) was added to a concentration of 0.8 mol / liter, and guanidine thiocyanate was added at a concentration of 0.1 mol / liter and N-methylbenzimidazole was added at a concentration of 0 It was added and dissolved so as to be 5 mol / liter. The electric conductivity of this electrolytic solution was 1.5 S / m or less.
　＜実施例２＞
　実施例１において、細孔径の異なる光電変換層３（表１参照）を形成したこと以外は、実施例１と同様の方法により実施例２の光電変換素子を作製した。 <Example 2>
In Example 1, the photoelectric conversion element of Example 2 was produced by the same method as Example 1 except that the photoelectric conversion layer 3 (see Table 1) having different pore diameters was formed.
　＜比較例１＞
　実施例１において、導電層４を形成しなかったこと以外は、実施例１と同様の方法により比較例１の光電変換素子を作製した。 <Comparative Example 1>
In Example 1, the photoelectric conversion element of Comparative Example 1 was produced in the same manner as in Example 1 except that the conductive layer 4 was not formed.
　＜比較例２＞
　実施例２において、導電層４を形成しなかったこと以外は、実施例２と同様の方法により比較例２の光電変換素子を作製した。 <Comparative example 2>
In Example 2, a photoelectric conversion element of Comparative Example 2 was produced in the same manner as in Example 2 except that the conductive layer 4 was not formed.
　＜比較例３＞
　実施例１において、３－メトキシプロピオニトリルに代えて、揮発性溶媒であるアセトニトリル（沸点：８２℃、粘度：０．３４１ｃｐ）を用いたこと以外は、実施例１と同様の方法により比較例３の光電変換素子を作製した。 <Comparative Example 3>
In Example 1, instead of 3-methoxypropionitrile, acetonitrile (boiling point: 82 ° C., viscosity: 0.341 cp), which is a volatile solvent, was used, and a comparative example was prepared in the same manner as in Example 1. 3 photoelectric conversion elements were produced.
　＜比較例４＞
　比較例３において、導電層４を形成しなかったこと以外は、比較例３と同様の方法により比較例４の光電変換素子を作製した。 <Comparative Example 4>
In Comparative Example 3, a photoelectric conversion element of Comparative Example 4 was produced by the same method as Comparative Example 3 except that the conductive layer 4 was not formed.
　＜光電変換効率の測定＞
　実施例１および２、ならびに比較例１～４の光電変換素子に、それぞれ、集電電極部としてＡｇペースト（藤倉化成株式会社製、商品名：ドータイト）を公知の方法により塗布した。次いで、それぞれの光電変換素子の受光面に、開口部の面積が０．２２ｃｍ2である黒色のマスクを設置して、それぞれの光電変換素子に１ｋＷ／ｍ2の強度の光（ＡＭ１．５ソーラーシミュレータ）を照射して、光電変換効率を測定した。 <Measurement of photoelectric conversion efficiency>
Ag paste (manufactured by Fujikura Kasei Co., Ltd., trade name: Dotite) was applied as a collecting electrode part to the photoelectric conversion elements of Examples 1 and 2 and Comparative Examples 1 to 4 by a known method. Next, a black mask having an opening area of 0.22 cm 2 is installed on the light receiving surface of each photoelectric conversion element, and light of 1 kW / m 2 intensity (AM1.5 solar) is applied to each photoelectric conversion element. The photoelectric conversion efficiency was measured by irradiating a simulator.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表１に示す結果から明らかなように、本発明の構成要件を満たす実施例１および２の光電変換素子は、従来の光電変換素子である比較例１および２の光電変換素子に比べて、光電変換効率が向上することが確認できた。また、比較例３および比較例４から明らかなように、低沸点を有する揮発性溶媒であり、かつ低粘度溶媒であるアセトニトリルを用いた場合は、導電層４を形成したことによる光電変換効率の向上効果を確認できなかった。 As is clear from the results shown in Table 1, the photoelectric conversion elements of Examples 1 and 2 that satisfy the constituent requirements of the present invention are more photoelectrical than the photoelectric conversion elements of Comparative Examples 1 and 2 that are conventional photoelectric conversion elements. It was confirmed that the conversion efficiency was improved. Further, as apparent from Comparative Example 3 and Comparative Example 4, when acetonitrile, which is a volatile solvent having a low boiling point and a low viscosity solvent, is used, the photoelectric conversion efficiency due to the formation of the conductive layer 4 is improved. The improvement effect could not be confirmed.
　また、溶媒粘度が高い場合、細孔径が大きな光電変換層３を有することで、細孔径が小さな光電変換層３を有する場合と比較して、キャリア輸送材料８中のキャリア輸送を起因とする電子輸送時のロスが小さくなり、これにより、導電層４を形成したことによる効果は低下すると予測された。しかしながら、実施例１および２ならびに比較例１および２の光電変換素子をそれぞれ比較することにより、細孔径が大きな光電変換層３を有する光電変換素子において、細孔径が小さな光電変換層３を有する光電変換素子よりも、導電層４を形成したことによる効果が顕著であることが確認できた。 In addition, when the solvent viscosity is high, by having the photoelectric conversion layer 3 having a large pore diameter, electrons due to carrier transport in the carrier transporting material 8 as compared with the case having the photoelectric conversion layer 3 having a small pore diameter. It was predicted that the loss during transportation was reduced, and the effect of forming the conductive layer 4 was reduced. However, by comparing the photoelectric conversion elements of Examples 1 and 2 and Comparative Examples 1 and 2, respectively, in the photoelectric conversion element having the photoelectric conversion layer 3 having a large pore diameter, the photoelectric conversion element having the photoelectric conversion layer 3 having a small pore diameter. It was confirmed that the effect of forming the conductive layer 4 was more remarkable than that of the conversion element.
　以上のように本発明の実施の形態および実施例について説明を行なったが、上述の各実施の形態および各実施例の構成を適宜組み合わせることも当初から予定している。 Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.
　今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて請求の範囲によって示され、請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
　本発明の光電変換素子は、色素増感太陽電池などの湿式太陽電池に好適に利用することができる。 The photoelectric conversion element of the present invention can be suitably used for wet solar cells such as dye-sensitized solar cells.
　１　光透過性支持体、２　透明導電層、３　光電変換層、３ａ　多孔質半導体層、４　導電層、５　対極導電層、６　封止材、７　触媒層、８　キャリア輸送材料、１１　透明電極板、１２　対極。 1 light transmissive support, 2 transparent conductive layer, 3 photoelectric conversion layer, 3a porous semiconductor layer, 4 conductive layer, 5 counter electrode conductive layer, 6 sealing material, 7 catalyst layer, 8 carrier transport material, 11 transparent electrode plate 12 Counter electrode.

Claims (5)

  1. 　光透過性支持体（１）と、
    　前記光透過性支持体（１）上に設けられた透明導電層（２）と、
    　前記透明導電層（２）上に設けられた、多孔質半導体層（３ａ）を含む光電変換層（３）と、
    　前記光電変換層（３）の少なくとも一部に設けられた導電層（４）と、
    　前記透明導電層（２）と向かい合うようにして設けられた対極導電層（５）と、
    　前記透明導電層（２）と前記対極導電層（５）との間に設けられたキャリア輸送材料（８）と、を備え、
    　前記キャリア輸送材料（８）は、難揮発性溶媒と、酸化還元種と、を含み、
    　前記導電層（４）は、前記透明導電層（２）と電気的に接続されている、光電変換素子。     A light transmissive support (1);
    A transparent conductive layer (2) provided on the light transmissive support (1);
    A photoelectric conversion layer (3) including a porous semiconductor layer (3a) provided on the transparent conductive layer (2);
    A conductive layer (4) provided on at least a part of the photoelectric conversion layer (3);
    A counter electrode conductive layer (5) provided to face the transparent conductive layer (2);
    A carrier transport material (8) provided between the transparent conductive layer (2) and the counter electrode conductive layer (5),
    The carrier transport material (8) includes a hardly volatile solvent and a redox species,
    The said conductive layer (4) is a photoelectric conversion element electrically connected with the said transparent conductive layer (2).
  2. 　前記難揮発性溶媒が沸点を有しない、または前記難揮発性溶媒の沸点が１００℃以上である、請求項１に記載の光電変換素子。 The photoelectric conversion element according to claim 1, wherein the hardly volatile solvent does not have a boiling point, or the boiling point of the hardly volatile solvent is 100 ° C or higher.
  3. 　前記光電変換層（３）の厚さが、４μｍ以上３０μｍ以下である、請求項１に記載の光電変換素子。 The photoelectric conversion element according to claim 1, wherein the thickness of the photoelectric conversion layer (3) is 4 µm or more and 30 µm or less.
  4. 　前記難揮発性溶媒の粘度が、１ｃｐ以上である、請求項１に記載の光電変換素子。 The photoelectric conversion element according to claim 1, wherein the hardly volatile solvent has a viscosity of 1 cp or more.
  5. 　前記キャリア輸送材料（８）の電気伝導率が、１．５Ｓ／ｍ以下である、請求項１に記載の光電変換素子。 The photoelectric conversion element according to claim 1, wherein the carrier transport material (8) has an electric conductivity of 1.5 S / m or less.
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