WO2014073328A1 - 透明導電膜積層体及びその製造方法、並びに薄膜太陽電池及びその製造方法 - Google Patents
透明導電膜積層体及びその製造方法、並びに薄膜太陽電池及びその製造方法 Download PDFInfo
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- WO2014073328A1 WO2014073328A1 PCT/JP2013/077829 JP2013077829W WO2014073328A1 WO 2014073328 A1 WO2014073328 A1 WO 2014073328A1 JP 2013077829 W JP2013077829 W JP 2013077829W WO 2014073328 A1 WO2014073328 A1 WO 2014073328A1
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- transparent conductive
- conductive film
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- 239000010408 film Substances 0.000 title claims abstract description 470
- 239000010409 thin film Substances 0.000 title claims abstract description 103
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- 238000000034 method Methods 0.000 claims abstract description 50
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- 229910052710 silicon Inorganic materials 0.000 claims abstract description 36
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 181
- 239000011787 zinc oxide Substances 0.000 claims description 90
- 229910003437 indium oxide Inorganic materials 0.000 claims description 86
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 claims description 86
- 238000006243 chemical reaction Methods 0.000 claims description 67
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- 238000010521 absorption reaction Methods 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 4
- 229910052732 germanium Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 229910052725 zinc Inorganic materials 0.000 claims description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052796 boron Inorganic materials 0.000 claims description 3
- 229910052726 zirconium Inorganic materials 0.000 claims description 3
- 229910052684 Cerium Inorganic materials 0.000 claims description 2
- 229910052735 hafnium Inorganic materials 0.000 claims 1
- 239000010703 silicon Substances 0.000 abstract description 33
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 32
- 230000000694 effects Effects 0.000 abstract description 19
- 230000003287 optical effect Effects 0.000 abstract description 7
- FMRLDPWIRHBCCC-UHFFFAOYSA-L Zinc carbonate Chemical compound [Zn+2].[O-]C([O-])=O FMRLDPWIRHBCCC-UHFFFAOYSA-L 0.000 abstract description 4
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 abstract 2
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- 239000011135 tin Substances 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 9
- 229910052738 indium Inorganic materials 0.000 description 8
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 8
- 229910001887 tin oxide Inorganic materials 0.000 description 8
- 230000002159 abnormal effect Effects 0.000 description 7
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- 229910021419 crystalline silicon Inorganic materials 0.000 description 5
- 150000002431 hydrogen Chemical class 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 5
- 229910010271 silicon carbide Inorganic materials 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
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- 239000002245 particle Substances 0.000 description 3
- 238000010248 power generation Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
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- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 229910006404 SnO 2 Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
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- 238000005280 amorphization Methods 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
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- AJNVQOSZGJRYEI-UHFFFAOYSA-N digallium;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Ga+3] AJNVQOSZGJRYEI-UHFFFAOYSA-N 0.000 description 1
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- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
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- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
- H01L31/022483—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers composed of zinc oxide [ZnO]
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/08—Oxides
- C23C14/086—Oxides of zinc, germanium, cadmium, indium, tin, thallium or bismuth
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/24—Electrically-conducting paints
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3411—Constructional aspects of the reactor
- H01J37/3414—Targets
- H01J37/3426—Material
- H01J37/3429—Plural materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
- H01L31/022475—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers composed of indium tin oxide [ITO]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02366—Special surface textures of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1884—Manufacture of transparent electrodes, e.g. TCO, ITO
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- 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
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- 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 transparent conductive film laminate having a low light absorption loss and an excellent light confinement effect, a method for producing the same, and a thin film solar, useful as a surface electrode when producing a highly efficient silicon-based thin film solar cell.
- the present invention relates to a battery and a manufacturing method thereof.
- Transparent conductive film with high conductivity and high transmittance in the visible light region is used for electrodes of solar cells, liquid crystal display elements, and other various light receiving elements. It is also used as a transparent heating element for various types of anti-fogging, such as a film, an antistatic film, and a frozen showcase.
- tin oxide (SnO 2 ) -based, zinc oxide (ZnO) -based, and indium oxide (In 2 O 3 ) -based thin films are known.
- tin oxide those containing antimony as a dopant (ATO) and those containing fluorine as a dopant (FTO) are used.
- ATO antimony as a dopant
- FTO fluorine as a dopant
- zinc oxide system those containing aluminum as a dopant (AZO) and those containing gallium as a dopant (GZO) are used.
- the transparent conductive film most industrially used is an indium oxide type, and indium oxide containing tin as a dopant is referred to as an ITO (Indium-Tin-Oxide) film. Since it is obtained, it has been used widely.
- ITO Indium-Tin-Oxide
- a thin film solar cell that generates power by making light incident from the side of a light transmissive substrate such as a glass substrate, generally, a transparent conductive film, one or more semiconductor thin film photoelectric conversion units sequentially stacked on the light transmissive substrate, And a back electrode. Since silicon materials are abundant in resources, silicon-based thin-film solar cells using silicon-based thin films for photoelectric conversion units (light absorption layers) are quickly put into practical use, and research and development are expanding actively. Has been.
- silicon-based thin film solar cells are further diversified.
- amorphous thin film solar cells that use amorphous thin films such as amorphous silicon as the conventional light absorption layer
- fine crystalline silicon is mixed in amorphous silicon.
- a microcrystalline thin film solar cell using the microcrystalline thin film and a crystalline thin film solar cell using a crystalline thin film made of crystalline silicon have been developed, and a hybrid thin film solar cell in which these are laminated has been put into practical use.
- Such a photoelectric conversion unit or thin film solar cell has an amorphous photoelectric conversion layer that occupies the main part regardless of whether the p-type and n-type conductive semiconductor layers contained therein are amorphous, crystalline, or microcrystalline.
- Those having a high quality are referred to as amorphous units or amorphous thin-film solar cells, and those having a crystalline photoelectric conversion layer are referred to as crystalline units or crystalline thin-film solar cells, and the photoelectric conversion layer is microcrystalline.
- microcrystalline units or microcrystalline thin-film solar cells are called microcrystalline units or microcrystalline thin-film solar cells.
- the transparent conductive film is used for the surface transparent electrode of the thin film solar cell, and in order to effectively confine the light incident from the translucent substrate side in the photoelectric conversion unit, the surface thereof is usually fine. Many irregularities are formed.
- Haze rate is an index representing the degree of unevenness of this transparent conductive film. This is equivalent to the light that is transmitted when the light from a specific light source is incident on a transparent substrate with a transparent conductive film divided by the scattered component whose optical path is bent and divided by all components. Measured using a C light source containing Generally, the haze ratio increases as the height difference between the projections and depressions increases, or as the distance between the projections and depressions of the projections and projections increases, and the light incident into the photoelectric conversion unit is effectively confined. The effect is excellent.
- the transparent conductive film If the haze ratio can be increased and sufficient light confinement can be performed, a high short-circuit current density (Jsc) can be realized, and a thin film solar cell with high conversion efficiency can be manufactured.
- a metal oxide material mainly composed of tin oxide produced by a thermal CVD method is known as a transparent conductive film having a high haze ratio, and is generally used as a transparent electrode of a thin film solar cell.
- the photoelectric conversion unit formed on the surface of the transparent conductive film is generally manufactured using a high-frequency plasma CVD method, and as a source gas used at this time, a silicon-containing gas such as SiH 4 or Si 2 H 6 , or those A mixture of the above gas and H 2 is used. Further, as a dopant gas for forming a p-type or n-type layer in the photoelectric conversion unit, B 2 H 6, PH 3 or the like is preferably used.
- the substrate temperature is 100 ° C. or more and 250 ° C. or less (however, the amorphous p-type silicon carbide layer 3p is 180 ° C. or less), the pressure is 30 Pa or more and 1500 Pa or less, and the high frequency power density is 0.01 W / cm 2 or more and 0.5 W / cm 2 or less is preferably used.
- the photoelectric conversion unit when manufacturing the photoelectric conversion unit, if the formation temperature is increased, the reduction of the metal oxide is promoted by the existing hydrogen, and in the case of the transparent conductive film mainly composed of tin oxide, the hydrogen reduction is performed. There is a loss of transparency. If such a transparent conductive film with poor transparency is used, a thin film solar cell with high conversion efficiency cannot be realized.
- the transparent conductive film mainly composed of indium oxide also loses transparency due to this hydrogen reduction.
- the transparency is impaired as the film is blackened by hydrogen reduction, so that it is very difficult to use it as a surface electrode of a thin film solar cell.
- Non Patent Literature 1 discloses a reduction resistance on a transparent conductive film made of tin oxide having a high degree of unevenness formed by a thermal CVD method. A method of forming a thin zinc oxide film having a good thickness by sputtering is proposed. Since zinc oxide has a strong bond between zinc and oxygen and has excellent resistance to hydrogen reduction, the transparency of the transparent conductive film can be kept high by using such a structure.
- the transparent conductive film having the above-described structure it is necessary to form a film by combining two methods. Moreover, about the method of manufacturing all the laminated films of a tin oxide type transparent conductive film and a zinc oxide type transparent conductive film by sputtering method, a highly transparent tin oxide type transparent conductive film cannot be manufactured by sputtering method etc. It is said that it is impossible to realize for the reason.
- Non-Patent Document 2 proposes a method of obtaining a transparent conductive film having a surface roughness and having a high haze ratio, mainly composed of zinc oxide, by a sputtering method.
- This method uses a zinc oxide sintered body target to which 2 wt% of Al 2 O 3 is added and performs sputtering film formation at a high gas pressure of 3 Pa to 12 Pa and a substrate temperature of 200 ° C. to 400 ° C. ing.
- the film is formed by applying power of DC 80 W to a 6 inch ⁇ target, and the input power density to the target is as extremely low as 0.442 W / cm 2 . For this reason, the film formation rate is extremely slow, 14 nm / min or more and 35 nm / min or less, and it is not practical for industrial use.
- Non-Patent Document 3 after obtaining a transparent conductive film with zinc oxide as a main component and produced by a conventional sputtering method and having small surface irregularities, the surface of the film is etched with acid to make the surface irregular.
- a method for producing a transparent conductive film having a high haze ratio is disclosed.
- this method after a film is manufactured by a sputtering process which is a vacuum process in a dry process, it is dried by performing acid etching in the atmosphere, and a semiconductor layer must be formed again by a CVD process in the dry process. There are problems such as complicated processes and high manufacturing costs.
- Patent Document 1 a zinc oxide-based transparent conductive film having surface irregularities for increasing the light conversion efficiency as a solar cell is used in a wet etching process.
- Patent Document 2 a method obtained only by a sputtering method by introducing hydrogen gas or the like has been proposed.
- a film is formed by RF magnetron sputtering using a zinc oxide-based sintered target at a gas pressure of 0.1 Pa to 4 Pa and a substrate temperature of 100 ° C. to 500 ° C. It is carried out.
- the RF magnetron sputtering method has an extremely low film formation rate compared with DC magnetron sputtering, and it has been found by the present inventors that grain growth due to substrate heating tends to be promoted.
- a transparent electrode film having s is obtained, it is industrially impractical.
- a transparent conductive film having surface irregularities is obtained with a zinc oxide-based single layer film, but in this case, a considerable film thickness is required to obtain the necessary conductivity as a surface electrode, which is industrially useful. It can not be said.
- the present applicant has proposed a sputtering target in which gallium oxide is mixed with zinc oxide as a main component and abnormal discharge is reduced by adding a third element (Ti, Ge, Al, Mg, In, Sn).
- a third element Ti, Ge, Al, Mg, In, Sn.
- the GZO sintered body containing gallium as a dopant is composed of a ZnO phase in which at least one selected from the group consisting of Ga, Ti, Ge, Al, Mg, In, and Sn is dissolved in an amount of 2 wt% or more.
- the main constituent phase, and the other constituent phases are a ZnO phase in which at least one of the above is not dissolved, and an intermediate compound phase represented by ZnGa 2 O 4 (spinel phase).
- the present applicant optimizes the content of aluminum and gallium in an oxide sintered body containing zinc oxide as a main component and further containing aluminum and gallium as additive elements.
- an oxide sintered body containing zinc oxide as a main component and further containing aluminum and gallium as additive elements By optimally controlling the type and composition of the crystalline phase produced during firing, especially the composition of the spinel crystalline phase, particles are unlikely to form even when film formation is continued for a long time with a sputtering device, even under high DC power input.
- a target oxide sintered body that does not cause any abnormal discharge has been proposed (see Patent Document 4).
- the present invention provides a transparent conductive film laminate that is useful as a surface electrode when producing a highly efficient silicon-based thin film solar cell, and has a low light absorption rate and an excellent light confinement effect. It is an object of the present invention to provide a thin film solar cell using the transparent conductive film laminate, and a method for manufacturing the thin film solar cell.
- the present inventors have conducted extensive research and studied various transparent conductive film materials as transparent conductive films for surface transparent electrodes of thin film solar cells.
- an indium oxide-based transparent conductive film (I) whose crystallinity and surface state are controlled is formed on the translucent substrate, and the indium oxide-based transparent conductive film (I) is dense and uneven.
- a laminated structure formed with a zinc oxide-based transparent conductive film (II) having excellent crystallinity has a low light absorption loss and an excellent light confinement effect, and the present invention has been completed. It came to do.
- the transparent conductive film laminate according to the present invention includes an indium oxide-based transparent conductive film (I) formed on a translucent substrate with a surface roughness (Ra) of 1.0 nm or less, and the indium oxide. And a zinc oxide-based transparent conductive film (II) formed on the transparent transparent conductive film (I), a surface roughness (Ra) as a laminate of 30 nm or more, and a haze ratio of 8%
- the resistance value is 30 ⁇ / ⁇ or less, and the absorptance with respect to light in the wavelength range of 400 nm to 1200 nm is 15% or less on average.
- the manufacturing method of the transparent conductive film laminated body which concerns on this invention is a film thickness on the conditions which a gas pressure is 0.1 Pa or more and 2.0 Pa or less and a substrate temperature is 50 degrees C or less on a translucent board
- the thin-film solar battery according to the present invention is a thin-film solar battery in which a transparent conductive film laminate, a photoelectric conversion layer unit, and a back electrode layer are formed in this order on a light-transmitting substrate.
- the film laminate includes an indium oxide-based transparent conductive film (I) formed on the translucent substrate with a surface roughness (Ra) of 1.0 nm or less, and the indium oxide-based transparent conductive film (I). It has a structure provided with the zinc oxide-based transparent conductive film (II) formed thereon, the surface roughness (Ra) as a laminate is 30 nm or more, the haze ratio is 8% or more, and the resistance value is 30 ⁇ . / ⁇ or less, and the absorptance to light in the wavelength range of 400 nm to 1200 nm is 15% or less on average.
- the manufacturing method of the thin film solar cell which concerns on this invention is a manufacturing method of the thin film solar cell in which the transparent conductive film laminated body, the photoelectric converting layer unit, and the back surface electrode layer were formed in order on the translucent board
- An indium oxide-based transparent conductive film having a film thickness of 10 nm to 300 nm on the translucent substrate under the conditions of a gas pressure of 0.1 Pa to 2.0 Pa and a substrate temperature of 50 ° C. or less by sputtering.
- the transparent conductive film laminate is formed by a transparent conductive film laminate forming step including a second film forming step of forming a zinc oxide-based transparent conductive film (II) having a thickness of 200 nm to 1000 nm under the following conditions: Characterized in that it formed.
- this transparent conductive film laminate can be produced only by a sputtering method at a low gas pressure excellent in mass productivity, and is not only excellent in conductivity etc. for the surface transparent electrode of a thin film solar cell, Cost can be reduced as compared with a transparent conductive film formed by a conventional thermal CVD method. Furthermore, by using DC magnetron sputtering without using production conditions that are disadvantageous for mass productivity such as high gas pressure and RF magnetron sputtering, a highly efficient silicon-based thin film solar cell can be provided at a low cost with a simple process. It is extremely useful industrially.
- FIG. 1A is a surface structure SEM photograph of a transparent conductive film laminate obtained by forming a zinc oxide-based transparent conductive film with a sputtering gas pressure of 0.1 Pa or more and 2.0 Pa or less.
- FIG. 2 is a cross-sectional view illustrating a configuration example of a thin film solar cell using an amorphous silicon thin film as a photoelectric conversion unit.
- FIG. 3 is a cross-sectional view showing a configuration example of a hybrid thin film solar cell in which an amorphous silicon thin film and a crystalline silicon thin film are stacked as a photoelectric conversion unit.
- Transparent conductive film laminate 1-1 Indium oxide-based transparent conductive film (I) 1-2. Zinc oxide based transparent conductive film (II) 1-3. 1. Properties of transparent conductive film laminate 2. Method for producing transparent conductive film laminate 2-1. First film forming step: film formation of indium oxide-based transparent conductive film (I) 2-2. 2. Second film forming step: Film formation of zinc oxide based transparent conductive film (II) Thin film solar cell and manufacturing method thereof
- the transparent conductive film laminate according to the present embodiment is based on an indium oxide-based transparent conductive film (I) formed on a light-transmitting substrate, and a zinc oxide-based transparent conductive film excellent in unevenness thereon.
- (II) has a laminated structure formed sequentially.
- the transparent conductive film laminate is formed by controlling the crystallinity and surface state of the indium oxide-based transparent conductive film (I) serving as a base.
- this transparent conductive film laminate is formed by forming an indium oxide-based transparent conductive film (I) as a base on a translucent substrate with a surface roughness (Ra) of 1.0 nm or less. And a laminated structure in which a zinc oxide-based transparent conductive film (II) is formed on the indium oxide-based transparent conductive film (I).
- the transparent conductive film laminate has a surface roughness (Ra) of 30 nm or more, a haze ratio of 8% or more, a resistance value of 30 ⁇ / ⁇ or less, and a wavelength range of 400 nm to 1200 nm.
- the absorptance with respect to light in is an average value of 15% or less.
- this transparent conductive film laminate In such a transparent conductive film laminate, it is possible to achieve a low absorption rate for light and not only ensure a sufficient amount of light that can be sent to the power generation layer, but particularly when laser cutting the silicon power generation layer, It is possible to prevent the occurrence of problems such as being cut together. Moreover, this transparent conductive film laminated body has a high haze ratio, and not only has a so-called light confinement effect, but also has an extremely low resistance. From these things, it can use very effectively as a surface electrode material for thin film solar cells.
- the laminated structure of the transparent conductive film laminate can be formed by a sputtering method at a low gas pressure with excellent mass productivity, and can be formed by using DC magnetron sputtering. Therefore, it can be manufactured at low cost as compared with a transparent conductive film obtained by a conventional thermal CVD method or a method disadvantageous in mass productivity such as high gas pressure or RF magnetron sputtering. From this, by using the transparent conductive film laminate according to the present embodiment as a surface electrode material for a thin film solar cell, a highly efficient silicon-based thin film solar cell can be provided at a low cost by a simple process, It is extremely useful industrially.
- the crystal grain size of the zinc oxide-based transparent conductive film (II) formed on the indium oxide-based transparent conductive film (I) serving as the base is determined in inverse proportion to the concentration of the base protrusions. Therefore, there is a protrusion in the transparent conductive film (I) that has a size and concentration that exceeds the above-mentioned surface roughness range due to the formation of microcrystals of the indium oxide-based transparent conductive film (I). In this case, the crystal grains of the zinc oxide-based transparent conductive film (II) deposited thereon become small, and as a result, a transparent conductive film having a sufficient uneven structure and haze ratio cannot be formed.
- the indium oxide-based transparent conductive film (I) uses indium oxide having high conductivity and transparency as a material.
- a film in which an additive element such as Ti, Ga, Mo, Sn, W, or Ce is included in the indium oxide is useful because it can exhibit more excellent conductivity.
- a film obtained by adding Ti or Ti and Sn to indium oxide can obtain a film with high mobility and low resistance without increasing the carrier concentration, so that transmission in the visible region to the near infrared region is achieved.
- a high-resistance low-resistance film can be realized.
- an ITiO film containing Ti as a dopant, and further an IToTO film containing Ti and Sn as dopants can be preferably used as the indium oxide-based transparent conductive film (I).
- the film thickness of the indium oxide-based transparent conductive film (I) is not particularly limited and depends on the composition of the material, but is preferably 10 nm to 300 nm, and preferably 30 nm to 100 nm. More preferred. When the film thickness is less than 10 nm, the conductivity decreases, and it becomes difficult to control fine crystal grains suitable for forming irregularities in the zinc oxide-based transparent conductive film (II).
- the zinc oxide-based transparent conductive film (II) is formed on the conductive film using the indium oxide-based transparent conductive film (I) whose crystallinity and surface state are controlled as a base film.
- the indium oxide-based transparent conductive film (I) whose crystallinity and surface state are controlled as described above when forming the zinc oxide-based transparent conductive film (I), adjacent crystals are formed. Without inhibiting the grain growth, a dense and uneven structure can be realized, and light can be prevented from being scattered and absorbed by voids formed between the grains. Thereby, the film
- the underlying indium oxide-based transparent conductive film (I) can be prevented from being exposed, hydrogen plasma resistance can be improved. Also from this, it is useful as a surface electrode of a thin film solar cell.
- the zinc oxide-based transparent conductive film (II) may contain an additive metal element as long as zinc oxide is a main component (90% or more by weight).
- an additive element that contributes to the conductivity of the oxide film Al, Ga, B, Mg, Si, Ti, Ge, Zr, And one or more elements selected from Hf are preferably added.
- zinc oxide as a main component, and one or more additive metal elements selected from Al or Ga are (Al + Ga) / (Zn + Al + Ga) atomic ratio of 0.3 to 6.5 atomic%, In addition, it is preferable that the Al / (Al + Ga) atomic ratio is within a range of 30 to 70 atomic%.
- the total content of Al and Ga in the zinc oxide-based transparent conductive film (II) exceeds 6.5 atomic%, transmission in the near infrared region (wavelength 800 to 1200 nm) is caused by an increase in carrier concentration. If the rate is less than 80%, the rate is lowered, and there is a possibility that sufficient transmittance cannot be obtained for use in solar cells.
- zinc oxide-based transparent conductive film (II) In addition to Zn, Al, Ga, and O, other elements (for example, In, W, Mo, Ru, Re, Ce, F, etc.) are included in the zinc oxide-based transparent conductive film (II). It may be included as long as it does not impair the purpose.
- the film thickness of the zinc oxide-based transparent conductive film (II) is not particularly limited, and depends on the composition of the material, but is preferably 200 nm or more and 1000 nm or less, and preferably 400 nm or more and 700 nm or less. More preferred.
- the film thickness is less than 200 nm, it is difficult to obtain sufficient surface roughness (Ra) and haze ratio.
- the film thickness exceeds 1000 nm, the light absorptivity is increased and the transmittance is lowered. Not only incurs, but also decreases productivity.
- the above-described indium oxide-based transparent conductive film (I) (base film) is formed on a light-transmitting substrate, and the above-described zinc oxide-based transparent film is formed on the base film. It has a laminated structure in which the conductive film (II) is laminated.
- the surface roughness (Ra) of the transparent conductive film laminate according to the present embodiment is 30.0 nm or more.
- the surface roughness (Ra) is less than 30.0 nm, the haze ratio decreases, so that when the silicon-based thin film solar cell is manufactured, the light confinement effect is inferior and high conversion efficiency cannot be realized. Therefore, when the surface roughness (Ra) is 30.0 nm or more, a sufficient light confinement effect can be exhibited and high conversion efficiency can be realized.
- the surface roughness (Ra) of the zinc oxide-based transparent conductive film (II) exceeds 80 nm, the silicon-based thin film formed on the zinc oxide-based transparent conductive film (II) in producing the silicon-based thin film solar cell.
- a gap is generated at the interface between the zinc oxide-based transparent conductive film (II) and the silicon-based thin film, the contact property is deteriorated, and the solar cell characteristics are deteriorated. Therefore, when laminating silicon-based thin films, it is preferable to pay attention to the lamination conditions.
- the transparent conductive film laminate according to the present embodiment has a surface resistance value (resistance value) of 30 ⁇ / ⁇ or less.
- the resistance value exceeds 30 ⁇ / ⁇ , when used for the surface electrode of the solar cell, power loss at the surface electrode increases, and a highly efficient solar cell cannot be realized.
- this transparent conductive film laminate has a laminated structure composed of the indium oxide-based transparent conductive film (I) and the zinc oxide-based transparent conductive film (II) as described above, the resistance value is 30 ⁇ / ⁇ or less. It can be.
- the resistance value of the transparent conductive film laminate is preferably 20 ⁇ / ⁇ or less, more preferably 13 ⁇ / ⁇ or less, still more preferably 10 ⁇ / ⁇ or less, and most preferably 8 ⁇ / ⁇ or less.
- the transparent conductive film laminate according to the present embodiment has a haze ratio of 8% or more.
- the haze ratio is preferably 12% or more, more preferably 16% or more, and most preferably 20% or more.
- a haze ratio of 12% or more is indispensable in order to achieve a conversion efficiency of 10% or more.
- it is effective to use a surface electrode having a haze ratio of 16% or more.
- it is effective to use a surface electrode having a haze ratio of 20% or more.
- a surface electrode having a haze ratio of 20% or more is particularly useful.
- the transparent conductive film laminate according to the present embodiment in addition to the indium oxide-based transparent conductive film (I) whose crystallinity is controlled being inserted as the base film, the zinc oxide-based transparent conductive film is formed on the base film. By laminating (II), a high haze ratio can be realized.
- the inventor's experience is that the film thickness needs to be 1500 nm or more. know. However, when doing so, the mass productivity is greatly reduced, which is not preferable.
- the transparent conductive film laminate according to the present embodiment has an average absorptance of 15% or less with respect to light in a wavelength range of 400 nm to 1200 nm.
- the light absorptance in the wavelength range of 400 nm to 1200 nm is 15% or less, the light absorption loss is reduced and it can be suitably used as a surface electrode for a solar cell.
- a surface roughness (Ra) is 1 nm or less by a sputtering method on a translucent substrate, and preferably the maximum height difference (Rmax) on the surface is 50 nm or less.
- the film forming process of each transparent conductive film and the film forming conditions will be described in more detail.
- First Film Formation Step Film Formation of Indium Oxide Transparent Conductive Film (I)>
- a protrusion having a surface roughness (Ra) of 1 nm or less, preferably a maximum height difference (Rmax) of 50 nm or less on the surface, or a diameter of 100 nm or less on the surface is formed on the translucent substrate.
- the indium oxide-based transparent conductive film (I) having a thickness of 100 or less per 5 ⁇ m square is formed by sputtering so that the film thickness is 10 nm or more and 300 nm or less.
- the film is formed using a sputtering method such as a magnetron sputtering method under the conditions of a substrate temperature of 50 ° C. or lower and a sputtering gas pressure of 0.1 to 2.0 Pa.
- a sputtering method such as a magnetron sputtering method under the conditions of a substrate temperature of 50 ° C. or lower and a sputtering gas pressure of 0.1 to 2.0 Pa.
- the type of sputtering gas to be used is not particularly limited, and basically argon gas is preferable, but for the purpose of amorphization, water vapor (H 2 O gas) or hydrogen ( H 2 ) gas may be mixed.
- H 2 O gas water vapor
- H 2 hydrogen
- the partial pressure of H 2 O gas and H 2 gas is preferably controlled from the viewpoint of the resistance value of the laminate, and specifically, the partial pressure of H 2 O gas is 0.05 Pa or less.
- the H 2 gas partial pressure is preferably 0.03 Pa or less.
- the indium oxide-based transparent conductive film (I) an oxidation mainly composed of indium oxide containing one or more metal elements selected from Ti, Ga, Mo, Sn, W, Ce, or the like.
- An object sintered compact target can be used. Note that when an oxide film is obtained by sputtering using an oxide sintered body target, the composition of the oxide film is equivalent to that of the target unless a volatile substance is contained.
- the zinc oxide-based transparent conductive film (II) it is preferable to form the zinc oxide-based transparent conductive film (II) immediately after the amorphous film is formed without heating the substrate, and immediately after the heat treatment.
- the crystal grain interfacial area of the zinc oxide-based transparent conductive film (II) can be suppressed, and large crystal grains can be obtained without the mutual growth being hindered by adjacent crystal grains.
- a film having a larger (Ra) and haze ratio can be formed. Further, since the grain growth is promoted, the film becomes dense, and a film having a low absorption rate can be effectively formed.
- the film thickness of the zinc oxide-based transparent conductive film (II) is 200 nm or more and 1000 nm or less on the indium oxide-based transparent conductive film (I) formed in the first film formation step. It forms into a film by sputtering method so that it may become.
- the film is formed under conditions of a substrate temperature of 200 ° C. to 450 ° C. and a sputtering gas pressure of 0.1 to 2.0 Pa.
- a sputtering method such as a magnetron sputtering method
- the film is formed under conditions of a substrate temperature of 200 ° C. to 450 ° C. and a sputtering gas pressure of 0.1 to 2.0 Pa.
- zinc oxide is the main component (90% or more by weight), Al, Ga, B, Mg, Si, Ti, Ge, Zr, And one or more metal elements selected from Hf may be contained.
- an oxide containing one or more metal elements selected from Al and Ga as an additive element that contributes to the conductivity of the oxide film from the viewpoint of preventing abnormal discharge under high DC power input.
- a sintered body target is preferably used.
- one or more metal elements selected from Al or Ga have an (Al + Ga) / (Zn + Al + Ga) atomic ratio of 0.3 to 6.5 atomic%, and Al / ( It is preferable to use an oxide sintered compact target that can form an oxide film containing Al + Ga) in an atomic ratio of 30 to 70 atomic%.
- the total content of Al and Ga in the formed zinc oxide-based transparent conductive film (II) deviates from the above-described range, a film having characteristics sufficient for use in solar cells may not be obtained.
- Al and Ga exceed 70% in the atomic ratio expressed by Al / (Al + Ga)
- the direct current input power is affected by the influence of the Al-rich spinel type oxide phase present in the sintered body. This is not preferable because arcing is likely to occur when DC sputtering is performed with a higher value.
- the composition of the oxide film is equivalent to that of the target unless a volatile substance is contained.
- the sputtering gas pressure is set to 0.1 Pa or more and 2.0 Pa or less as the film formation condition in the second film formation step.
- the crystallinity and the surface state are controlled so that the surface roughness of the indium oxide-based transparent conductive film (I) formed in the first film formation step is 1.0 nm or less. Therefore, the film can be formed with such a low gas pressure.
- the sputtering gas pressure is less than 0.1 Pa, it is difficult to obtain a film having large surface irregularities, and a film having an Ra value of 30.0 nm or more cannot be obtained.
- the sputtering gas pressure exceeds 2.0 Pa, an increase in absorption and a decrease in carrier mobility are caused as the density of the obtained film is reduced, and optical properties and conductivity are impaired. Further, such a low-density film has a high light absorption loss, and therefore, when used as a surface electrode of a thin-film solar battery, cell efficiency is greatly reduced, which is not preferable.
- FIG. 1A shows a surface texture SEM image of a transparent conductive film laminate obtained by forming a zinc oxide-based transparent conductive film (II) at a sputtering gas pressure of 0.1 Pa to 2.0 Pa
- FIG. 1B shows a surface texture SEM image of the transparent conductive film laminate obtained by forming the zinc oxide-based transparent conductive film (II) at a sputtering gas pressure higher than 2.0 Pa.
- the film density becomes rough when the film is formed at a gas pressure exceeding 2.0 Pa, while the film having a high density is formed by forming the film at a low pressure of 2.0 Pa or less. It can be seen that can be formed.
- a high gas pressure exceeding 2.0 Pa is not preferable in terms of mass productivity.
- the sputtering gas pressure is set to 2 0.0 Pa or less is necessary.
- the sputtering gas pressure exceeds 2.0 Pa, abnormal discharge frequently occurs due to dust induction in the film forming chamber, which is useful because it is difficult to control the film thickness and thus the film quality. Absent.
- the substrate temperature condition during the film formation in the second film formation step is set to 200 ° C. or higher and 450 ° C. or lower. By setting it as such temperature conditions, the crystallinity of a transparent conductive film becomes favorable, the mobility of a carrier electron increases, and the outstanding electroconductivity can be exhibited. When the substrate temperature is lower than 200 ° C., the film growth is inferior, so that a film having a large Ra value cannot be obtained.
- the high-speed film formation here refers to performing sputtering film formation by increasing the input power to the target to 2.76 W / cm 2 or more, and thereby, for example, 90 nm / min or more in static facing film formation.
- a zinc oxide-based transparent conductive film having a small light absorption loss and excellent surface unevenness can be obtained.
- the pass-type film formation transfer film formation
- the film was formed at a similar input power density of 5.1 nm ⁇ m / min (transfer speed (m / min)).
- a zinc oxide-based transparent conductive film having a small light absorption loss and excellent surface irregularity can be obtained even in high-speed transport film formation of the obtained film thickness (nm).
- Transparent conductive film laminate having a surface irregularity having an optical absorptance of 15% or less in an average range of 1200 nm, a surface roughness (Ra) of 30.0 nm or more, and a haze ratio of 8.0% or more can be efficiently manufactured.
- the above-described surface roughness (Ra) and surface resistance can be realized even with a thin film thickness of 500 nm or less, and the transmittance can be improved by reducing the film thickness.
- the film forming speed is not particularly limited.
- the method for producing a transparent conductive film laminate according to the present embodiment since it can be produced only by a sputtering method, it only has excellent conductivity and the like for a surface transparent electrode of a thin film solar cell.
- the cost can be effectively reduced as compared with the transparent conductive film obtained by the conventional thermal CVD method, RF sputtering, high gas pressure, and DC sputtering by introducing hydrogen. Therefore, a high-efficiency silicon-based thin film solar cell can be provided at a low cost by a simple process, which is extremely useful industrially.
- the transparent conductive film laminate produced in this way has a low light absorption loss at a wavelength of 400 nm to 1200 nm, and has a high haze ratio and excellent conductivity. For this reason, the amount of light that can be sent to the power generation layer is large, solar energy can be converted into electrical energy very effectively, and it is very useful as a surface electrode for high-efficiency solar cells.
- a transparent conductive film laminate, a photoelectric conversion layer unit, and a back electrode layer are sequentially formed on a light transmitting substrate.
- the thin film solar cell according to the present embodiment is a photoelectric conversion element characterized by using the above-described transparent conductive film laminate as an electrode. That is, an indium oxide-based transparent conductive film (I) formed on a translucent substrate with a surface roughness (Ra) of 1.0 nm or less, and the indium oxide-based transparent conductive film (I).
- the surface roughness (Ra) as a laminate is 30 nm or more, the haze ratio is 8% or more, and the resistance value is 30 ⁇ / ⁇ .
- the transparent conductive film laminate having an average absorption value of 15% or less with respect to light in the wavelength range of 400 nm to 1200 nm is used as an electrode.
- the structure of the solar cell element is not particularly limited. For example, a PN junction type in which a p-type semiconductor and an n-type semiconductor are stacked, and an insulating layer (I layer) is interposed between the p-type semiconductor and the n-type semiconductor. PIN junction type.
- thin-film solar cells are roughly classified according to the type of semiconductor.
- Silicon-based solar cells using a silicon-based semiconductor thin film such as microcrystalline silicon and / or amorphous silicon as a photoelectric conversion element, CuInSe-based or Cu (In, Ga)
- Compound semiconductors represented by Se, Ag (In, Ga) Se, CuInS, Cu (In, Ga) S, Ag (In, Ga) S, solid solutions thereof, GaAs, CdTe, and the like are classified into a compound thin film solar cell using a thin film as a photoelectric conversion element, and a dye-sensitized solar cell using an organic dye (also referred to as a Gretzel cell solar cell).
- the thin film solar cell according to the present embodiment is included in any of the above cases, and high conversion efficiency can be realized by using the above-described transparent conductive film laminate as an electrode.
- a transparent conductive film is indispensable for an electrode on which sunlight is incident (light receiving unit side, front side), and the transparent conductive film lamination according to the present embodiment By using the body, characteristics of high conversion efficiency can be exhibited.
- the p-type and n-type conductive semiconductor layers in the photoelectric conversion unit serve to generate an internal electric field in the photoelectric conversion unit.
- the value of the open circuit voltage (Voc) which is one of the important characteristics of the thin film solar cell, depends on the magnitude of the internal electric field.
- the i-type layer is a substantially intrinsic semiconductor layer and occupies most of the thickness of the photoelectric conversion unit. The photoelectric conversion action mainly occurs in this i-type layer. Therefore, the i-type layer is usually called an i-type photoelectric conversion layer or simply a photoelectric conversion layer.
- the photoelectric conversion layer is not limited to an intrinsic semiconductor layer, and may be a layer doped with a small amount of p-type or n-type as long as loss of light absorbed by a doped impurity (dopant) does not become a problem. .
- FIG. 2 is a diagram showing an example of the structure of a silicon-based amorphous thin film solar cell.
- Silicon-based thin-film solar cells using silicon-based thin films for photoelectric conversion units include microcrystalline thin-film solar cells, crystalline thin-film solar cells, and laminated layers in addition to amorphous thin-film solar cells.
- the hybrid thin film solar cell is also in practical use.
- an amorphous photoelectric conversion layer occupying the main part thereof is called an amorphous unit or an amorphous thin film solar cell.
- a crystalline photoelectric conversion layer is called a crystalline unit or a crystalline thin film solar cell.
- the photoelectric conversion layer having a microcrystalline structure is called a microcrystalline unit or a microcrystalline thin film solar cell.
- a method for further improving the conversion efficiency of such a thin film solar cell there is a method of stacking two or more photoelectric conversion units into a tandem solar cell.
- a front unit including a photoelectric conversion layer having a large band gap is disposed on the light incident side of the thin film solar cell, and a rear unit including a photoelectric conversion layer having a small band gap is sequentially disposed behind the front unit.
- photoelectric conversion is enabled over the wide wavelength range of incident light, and the conversion efficiency as the whole solar cell can be improved.
- tandem solar cells those in which an amorphous photoelectric conversion unit and a crystalline or microcrystalline photoelectric conversion unit are stacked are called hybrid thin film solar cells.
- FIG. 3 is a diagram showing an example of the structure of a hybrid thin film solar cell.
- the wavelength range of light that can be photoelectrically converted by i-type amorphous silicon is up to about 800 nm on the long-wavelength side, but i-type crystalline or microcrystalline silicon is longer than about 800 nm.
- Light up to a wavelength of about 1150 nm can be photoelectrically converted.
- the thin-film solar cell according to the present embodiment includes a transparent conductive film 21 that is the above-described indium oxide-based transparent conductive film (I) and a zinc oxide-based film on a light-transmitting substrate 1.
- the transparent conductive film laminated body 2 which consists of the transparent conductive film 22 which is transparent conductive film (II) is formed.
- the translucent substrate 1 As the translucent substrate 1, a plate-like member or a sheet-like member made of glass, transparent resin or the like is used.
- An amorphous photoelectric conversion unit 3 is formed on the transparent conductive film laminate 2.
- the amorphous photoelectric conversion unit 3 includes an amorphous p-type silicon carbide layer 31, a non-doped amorphous i-type silicon photoelectric conversion layer 32, and an n-type silicon-based interface layer 33.
- the amorphous p-type silicon carbide layer 31 is formed at a substrate temperature of 180 ° C. or lower in order to prevent a decrease in transmittance due to reduction of the transparent conductive film stack 2.
- the crystalline photoelectric conversion unit 4 is formed on the amorphous photoelectric conversion unit 3.
- the crystalline photoelectric conversion unit 4 includes a crystalline p-type silicon layer 41, a crystalline i-type silicon photoelectric conversion layer 42, and a crystalline n-type silicon layer 43.
- a high frequency plasma CVD method is suitable for forming the amorphous photoelectric conversion unit 3 and the crystalline photoelectric conversion unit 4 (hereinafter, both units are simply referred to as “photoelectric conversion unit”).
- the substrate temperature is 100 ° C. or higher and 250 ° C. or lower (however, the amorphous p-type silicon carbide layer 31 is 180 ° C.
- the pressure is 30 Pa or higher and 1500 Pa or lower
- the high frequency power density is 0.01 W / cm. 2 or more and 0.5 W / cm 2 or less are preferably used.
- a silicon-containing gas such as SiH 4 or Si 2 H 6 or a mixture of these gases and H 2 is used.
- a dopant gas for forming the p-type or n-type layer in the photoelectric conversion unit B 2 H 6 or PH 3 is preferably used.
- the back electrode 5 is formed on the n-type silicon-based interface layer 33 shown in FIG. 2 or on the n-type silicon-based interface layer 43 shown in FIG.
- the back electrode 5 includes a transparent reflective layer 51 and a back reflective layer 52.
- the transparent reflective layer 51 is preferably made of a metal oxide such as ZnO or ITO.
- For the back reflective layer 52 it is preferable to use Ag, Al, or an alloy thereof.
- the back electrode 5 In forming the back electrode 5, a method such as sputtering or vapor deposition is preferably used.
- the back electrode 5 has a thickness of usually 0.5 ⁇ m to 5 ⁇ m, preferably 1 ⁇ m to 3 ⁇ m.
- the solar cell is completed by heating to near atmospheric pressure at an atmospheric temperature equal to or higher than the formation temperature of the amorphous p-type silicon carbide layer 31.
- the gas used in the heating atmosphere air, nitrogen, a mixture of nitrogen and oxygen, or the like is preferably used.
- the atmospheric pressure vicinity shows the range of 0.5 to 1.5 atmospheres in general.
- the thin film solar cell it is possible to provide a silicon-based thin film solar cell using the transparent conductive film laminate 2 described above as an electrode.
- the transparent conductive film laminated body 2 is formed on the translucent substrate by using the indium oxide-based transparent conductive film (I) whose crystallinity and surface state are controlled as a base, and has excellent unevenness on the transparent conductive film laminate 2.
- it can be set as the transparent conductive film for surface transparent electrodes of a thin film solar cell of lower resistance by having the laminated structure which formed the zinc oxide type transparent conductive film (II) sequentially.
- the transparent conductive film laminate 2 can be formed at a lower cost than the transparent conductive film obtained by the conventional thermal CVD method, RF sputtering, high gas pressure and DC sputtering by introducing hydrogen, and has high efficiency. Can be produced easily and at low cost, and is extremely useful industrially.
- FIG. 3 shows the structure of the hybrid thin film solar cell.
- the number of photoelectric conversion units is not necessarily two, but an amorphous or crystalline single structure, a stacked solar cell structure having three or more layers. It may be.
- the film thickness was measured by the following procedure. In other words, oil-based magic ink is applied to a part of the substrate in advance before film formation, the magic is wiped off with ethanol after film formation, a film-free part is formed, and the level difference between the part with and without the film is contacted. It was determined by measuring with an equation surface shape measuring instrument (Alpha-Step IQ manufactured by KLA Tencor).
- the light absorptivity of the transparent conductive film laminate is based on the transmittance and reflectance profiles of the substrate measured using a spectrophotometer (manufactured by Hitachi, Ltd., U-4000) and the substrate with the transparent conductive film laminate. Calculated.
- haze ratio of the film was evaluated with a haze meter (HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd.) based on JIS standard K7136.
- the resistance value of the transparent conductive thin film was measured by a four-probe method using a resistivity meter Loresta EP (MCP-T360 type manufactured by Dia Instruments).
- Example 1 In the following procedure, an indium oxide-based transparent conductive film (I) containing titanium (Ti) and a zinc oxide-based transparent conductive film (II) are sequentially laminated and formed on a light-transmitting substrate. A conductive film laminate was produced.
- an indium oxide-based transparent conductive film (I) serving as a base was formed under the conditions shown in Table 1 below.
- the composition of the target manufactured by Sumitomo Metal Mining Co., Ltd.
- the purity of the target was 99.999%, and the size was 6 inches in diameter ⁇ 5 mm in thickness.
- This sputtering target is applied to a cathode for a ferromagnetic target of a DC magnetron sputtering apparatus (SPF503K, manufactured by Tokki Co., Ltd.) (maximum horizontal magnetic field strength at a position 1 cm away from the target surface is about 80 kA / m (1 kG)).
- SPF503K DC magnetron sputtering apparatus
- maximum horizontal magnetic field strength at a position 1 cm away from the target surface is about 80 kA / m (1 kG)
- a Corning 7059 glass substrate having a thickness of 1.1 mm was attached to the opposing surface of the sputtering target. The distance between the sputtering target and the substrate was 50 mm.
- the inside of the chamber is evacuated, and when the degree of vacuum reaches 2 ⁇ 10 ⁇ 4 Pa or less, Ar gas having a purity of 99.9999% by mass is placed in the chamber.
- the gas pressure was 1.0 Pa.
- the film thickness, light absorption rate, surface roughness (Ra), haze rate, and resistance value of the obtained transparent conductive thin film laminate were measured by the evaluation methods (1) to (6).
- the film thickness is 700 nm
- the light absorptance is 9.9% in the average value from 400 nm to 600 nm
- 9.2% in the average value from 400 nm to 1200 nm
- the surface roughness (Ra) is 38.2 nm
- the haze ratio is It was 16.2% and the resistance value was 9.8 ⁇ / ⁇ .
- Table 2 below collectively shows the characteristic evaluation results of the obtained transparent conductive film laminate.
- Example 2 [Comparative Example 1] The transparent conductive film stack was formed in the same manner as in Example 1 except that the substrate temperature when forming the indium oxide-based transparent conductive film (I) was 50 ° C. (Example 2) and 100 ° C. (Comparative Example 1). A body was prepared and properties were measured and evaluated.
- Table 2 below shows the results obtained.
- the surface roughness (Ra) of the indium oxide-based transparent conductive film (I) is 3.2 nm and exceeds 1 nm, and the maximum height difference (Rmax) also exceeds 50 nm. Since 650 crystal grains having a diameter of more than 100 nm exist in 5 ⁇ m square, the grain growth of the zinc oxide-based transparent conductive film (II) is inhibited, and as a result, the surface roughness (Ra ) was 5.2 nm and the haze ratio was 2.1%, which was a very low value.
- Example 2 As described above, in Comparative Example 1, a transparent conductive film laminate having a small light absorption loss, a high haze ratio, an excellent light confinement effect, and a low resistance is obtained at high speed only by a magnetron sputtering method with a low gas pressure. I could't.
- Example 2 As in Example 1, a transparent conductive film laminate useful as a surface electrode of a solar cell could be formed.
- Example 3 and 4 [Comparative Examples 2 and 3] Except that the film thickness of the indium oxide-based transparent conductive film (I) was 0 nm (none) (Comparative Example 2), 10 nm (Example 3), 250 nm (Example 4), and 350 nm (Comparative Example 3). A transparent conductive film laminate was produced in the same manner as in Example 1, and the characteristics were measured and evaluated.
- Table 2 below shows the results obtained.
- the surface roughness (Ra) was 5.0 nm and the haze ratio was very low at 1.8%.
- the resistance value was as high as 36.3 ⁇ / ⁇ .
- Comparative Example 3 since the indium oxide transparent conductive film (I) was too thick, 350 nm, the generation of microcrystals progressed, and the surface roughness (Ra) was 1.2 nm, exceeding 1 nm.
- the maximum height difference (Rmax) exceeded 54.4 nm and 50 nm, and there were 112 crystal grains exceeding a diameter of 100 nm in a 5 ⁇ m square, so that the grain growth of the zinc oxide-based transparent conductive film (II) was As a result, the surface roughness (Ra) of the transparent conductive film laminate was as low as 28.2 nm and the haze ratio was as low as 6.0%.
- a transparent conductive film laminate having a low light absorption loss, a high haze ratio, an excellent optical confinement effect, and a low resistance can be obtained at high speed only by a magnetron sputtering method with a low gas pressure.
- a transparent conductive film laminate useful as a surface electrode of a solar cell could be formed.
- Example 5 H 2 O gas was introduced when forming the indium oxide-based transparent conductive film (I), and the H 2 O partial pressure was 0.007 Pa (Example 5), 0.03 Pa (Example 6), 0.05 Pa.
- a transparent conductive film laminate was produced in the same manner as in Example 1 except that it was changed to (Example 7), and the characteristics were measured and evaluated.
- Table 2 shows the results obtained. As shown in Table 2, by introducing H 2 O gas, the surface roughness (Ra) and the haze ratio are higher than those of Example 1, and the light confinement effect is excellent. A useful transparent conductive film laminate was obtained.
- the resistance value tends to increase as the H 2 O partial pressure increases. From this, it was found that the H 2 O partial pressure is preferably 0.05 Pa or less.
- Example 8 When forming the indium oxide-based transparent conductive film (I), H 2 gas was introduced, and the H 2 partial pressure was 0.005 Pa (Example 8), 0.02 Pa (Example 9), 0.03 Pa (implemented).
- a transparent conductive film laminate was produced in the same manner as in Example 1 except that Example 10) was used, and the characteristics were evaluated for evaluation.
- Table 2 shows the results obtained. As shown in Table 2, by introducing H 2 gas, the surface roughness (Ra) and haze ratio are higher than in Example 1, and the light confinement effect is excellent, and it is more useful as a surface electrode of a solar cell. A transparent conductive film laminate was obtained.
- the H 2 partial pressure is preferably 0.03 Pa or less.
- Example 4 Except that the gas pressure when forming the zinc oxide-based transparent conductive film (II) was 0.5 Pa (Example 11), 2.0 Pa (Example 12), and 2.5 Pa (Comparative Example 4), A transparent conductive film laminate was produced in the same manner as in Example 1, and the characteristics were measured and evaluated.
- Table 2 below shows the results obtained. As shown in Table 2, in Comparative Example 4, the light absorptance increased in the range of 400 to 600 nm and 400 to 1200 nm, and the light absorption loss increased. This is probably because the gas pressure was as high as 2.5 Pa, and the film density of the zinc oxide-based transparent conductive film (II) became coarse, thereby increasing the light absorption loss.
- Example 13 and 14 [Comparative Examples 5 and 6]
- the substrate temperature when forming the zinc oxide-based transparent conductive film (II) is 150 ° C. (Comparative Example 5), 200 ° C. (Example 13), 450 ° C. (Example 14), and 500 ° C. (Comparative Example 6). Except for the above, a transparent conductive film laminate was produced in the same manner as in Example 1, and the characteristics were measured and evaluated.
- Table 2 below shows the results obtained.
- Comparative Example 5 since the heating temperature when forming the zinc oxide-based transparent conductive film (II) was insufficient at 150 ° C., grain growth did not proceed, and as a result, transparent conductive
- the surface roughness (Ra) and haze ratio of the film laminate were as low as 5.3 nm and 2.3%, respectively.
- Comparative Example 6 since the heating temperature when forming the zinc oxide-based transparent conductive film (II) was as high as 500 ° C., the flattening of the film progressed with c-axis oriented crystal growth. As a result, the surface roughness (Ra) and the haze ratio of the transparent conductive film laminate were as low as 28.9 nm and 7.6%, respectively.
- a transparent conductive film laminate having a small light absorption loss, a high haze ratio, an excellent light confinement effect, and a low resistance can be obtained at high speed only by a magnetron sputtering method with a low gas pressure.
- a transparent conductive film laminate useful as a surface electrode of a solar cell could be formed.
- Example 15 and 16 [Comparative Examples 7 and 8] Example 1 except that the thickness of the zinc oxide-based transparent conductive film (II) was 150 nm (Comparative Example 7), 250 nm (Example 15), 1000 nm (Example 16), and 1050 nm (Comparative Example 8). In the same manner, a transparent conductive film laminate was produced, and the characteristics were measured and evaluated.
- a transparent conductive film laminate having a small light absorption loss, a high haze ratio, an excellent light confinement effect, and a low resistance can be obtained at high speed only by a magnetron sputtering method with a low gas pressure.
- a transparent conductive film laminate useful as a surface electrode of a solar cell could be formed.
- the additive element M of the target used for the production of the indium oxide-based transparent conductive film (I) was Ti to Ga (Example 17), Mo (Example 18), Sn (Example 19), W (Example 20).
- a transparent conductive film laminate was produced in the same manner as in Example 1 except that Ce (Example 21) was used, and the characteristics were evaluated.
- the quantitative analysis result by the said evaluation method (1) is respectively 0.70 atomic% (Example 17) by Ga / (In + Ga), Mo.
- Example 21 The Ce / (In + Ce) was 0.80 atomic% (Example 21).
- Table 2 below shows the results obtained. As shown in Table 2, in all of Examples 17 to 21, a transparent conductive film laminate having a low light absorption loss, a high haze ratio, an excellent light confinement effect, and a low resistance was formed into a low gas pressure magnetron sputter. It was obtained at high speed only by the method and was confirmed to be useful as a surface electrode of a solar cell.
- the additive element M of the target used for the production of the zinc oxide-based transparent conductive film (II) was changed from Al and Ga to B (Example 22), Mg (Example 23), Si (Example 24), Ti ( Example 25), Ge (Example 26), Zr (Example 27), Hf (Example 28), except that the transparent conductive film laminate was produced in the same manner as in Example 1 and the characteristics were measured. Evaluation was performed.
- the target used for preparation of the zinc oxide-based transparent conductive film (II) has a quantitative analysis result by the evaluation method (1) of 0.50 atomic% (M / (Zn + M)) with M as the additive element. Examples 22 to 28).
- Table 2 shows the results obtained. As shown in Table 2, in all of Examples 22 to 28, a transparent conductive film laminate having a low light absorption loss, a high haze ratio, an excellent light confinement effect, and a low resistance was formed into a low gas pressure magnetron sputter. It was obtained at high speed only by the method, and was confirmed to be useful as a surface electrode of a solar cell.
- Transparent substrate 2. Transparent conductive film laminate, 3. Amorphous photoelectric conversion unit, 4. Crystalline photoelectric conversion unit, 5. Back electrode, 21. Indium oxide-based transparent conductive film (I), 22. Zinc oxide-based transparent conductive film (II)
Abstract
Description
1.透明導電膜積層体
1-1.酸化インジウム系透明導電膜(I)
1-2.酸化亜鉛系透明導電膜(II)
1-3.透明導電膜積層体の特性
2.透明導電膜積層体の製造方法
2-1.第1の成膜工程:酸化インジウム系透明導電膜(I)の成膜
2-2.第2の成膜工程:酸化亜鉛系透明導電膜(II)の成膜
3.薄膜太陽電池及びその製造方法
本実施の形態に係る透明導電膜積層体は、透光性基板上に形成された酸化インジウム系透明導電膜(I)を下地として、その上に、凹凸性に優れた酸化亜鉛系透明導電膜(II)が順次形成された積層構造を有する。特に、この透明導電膜積層体では、下地となる酸化インジウム系透明導電膜(I)の結晶性及びその表面状態が制御されて形成されている。
酸化インジウム系透明導電膜(I)は、透光性基板上に、表面粗さ(Ra)が1.0nm以下の状態で形成されてなることを特徴とする。また、表面において最大高低差(Rmax)が50nm以下であることが好ましい。さらには、表面において直径が100nm以下である突起が5μm四方あたり100個以下で存在していてもよい。
酸化亜鉛系透明導電膜(II)は、上述したように、その結晶性及び表面状態が制御された酸化インジウム系透明導電膜(I)を下地膜として、その導電膜上に形成される。このように結晶性や表面状態を上述のように制御した酸化インジウム系透明導電膜(I)上に形成することにより、当該酸化亜鉛系透明導電膜(I)の成膜に際して、隣り合う結晶に粒成長が阻害されることなく、緻密で凹凸性を有する構造を実現し、粒と粒の間に生成する空隙部により光が散乱、吸収されることを抑制できる。これにより、薄膜太陽電池用の表面電極として優れた膜を得ることができる。また、下地の酸化インジウム系透明導電膜(I)が露出することを防ぐことができることから、耐水素プラズマ性を向上させることができる。このことからも、薄膜太陽電池の表面電極として有用である。
本実施の形態に係る透明導電膜積層体は、透光性基板上に、上述した酸化インジウム系透明導電膜(I)(下地膜)を形成し、その下地膜上に上述した酸化亜鉛系透明導電膜(II)を積層させてなる積層構造を有する。
次に、本実施の形態に係る透明導電膜積層体の製造方法について説明する。本実施の形態に係る透明導電膜積層体の製造方法は、透光性基板上に、スパッタリング法により表面粗さ(Ra)が1nm以下、また好ましくは表面における最大高低差(Rmax)が50nm以下、あるいは表面において直径が100nm以下である突起が5μm四方あたり100個以下で存在する酸化インジウム系透明導電膜(I)を成膜する第1の成膜工程と、その酸化インジウム系透明導電膜(I)上に、スパッタリング法により酸化亜鉛系透明導電膜(II)を成膜する第2の成膜工程とを有する。以下、各透明導電膜の成膜工程並びにその成膜条件についてより詳細に説明する。
第1の成膜工程では、透光性基板上に、表面粗さ(Ra)が1nm以下、また好ましくは表面における最大高低差(Rmax)が50nm以下、あるいは表面において直径が100nm以下である突起が5μm四方あたり100個以下で存在する酸化インジウム系透明導電膜(I)を、その膜厚が10nm以上300nm以下となるようにスパッタリング法により成膜する。
第2の成膜工程では、第1の成膜工程にて成膜した酸化インジウム系透明導電膜(I)上に、酸化亜鉛系透明導電膜(II)を、その膜厚が200nm以上1000nm以下となるようにスパッタリング法により成膜する。
本実施の形態に係る薄膜太陽電池は、透光性基板上に、透明導電膜積層体と、光電変換層ユニットと、裏面電極層とが順に形成されてなる。
(1)透明導電膜の作製に用いたターゲットは、ICP発光分光分析(セイコーインスツルメンツ社製、SPS4000)で定量分析した。
以下の手順で、透光性基板上に、チタン(Ti)を含有する酸化インジウム系透明導電膜(I)と酸化亜鉛系透明導電膜(II)とを順次積層形成した、表面凹凸の大きな透明導電膜積層体を作製した。
最初に、下記表1に示す条件で、下地となる酸化インジウム系透明導電膜(I)の成膜を行った。酸化インジウム系透明導電膜(I)の作製に用いたターゲット(住友金属鉱山株式会社製)の組成を上記(1)の方法にて定量分析したところ、Ti/(In+Ti)で0.50原子%であった。また、ターゲットの純度は99.999%であり、大きさは直径6インチ×厚さ5mmであった。
次に、下記表1に示す条件で、酸化インジウム系透明導電膜(I)の上に、アルミニウムとガリウムを添加元素として含有した酸化亜鉛系焼結体ターゲット(住友金属鉱山株式会社製)を用いて、表面凹凸の大きい酸化亜鉛系透明導電膜(II)を形成した。ターゲットの組成は、Al/(Zn+Al)で0.30原子%であり、Ga/(Zn+Ga)で0.30原子%であった。何れのターゲットとも純度は、99.999%であり、ターゲットの大きさは、直径6インチ×厚さ5mmであった。
酸化インジウム系透明導電膜(I)を成膜する際の基板温度を50℃(実施例2)、100℃(比較例1)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化インジウム系透明導電膜(I)の膜厚を0nm(無し)(比較例2)、10nm(実施例3)、250nm(実施例4)、350nm(比較例3)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化インジウム系透明導電膜(I)を成膜する際にH2Oガスを導入し、H2O分圧を0.007Pa(実施例5)、0.03Pa(実施例6)、0.05Pa(実施例7)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化インジウム系透明導電膜(I)を成膜する際にH2ガスを導入し、H2分圧を0.005Pa(実施例8)、0.02Pa(実施例9)、0.03Pa(実施例10)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化亜鉛系透明導電膜(II)を成膜する際のガス圧を0.5Pa(実施例11)、2.0Pa(実施例12)、2.5Pa(比較例4)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化亜鉛系透明導電膜(II)を成膜する際の基板温度を150℃(比較例5)、200℃(実施例13)、450℃(実施例14)、500℃(比較例6)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化亜鉛系透明導電膜(II)の膜厚を150nm(比較例7)、250nm(実施例15)、1000nm(実施例16)、1050nm(比較例8)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。
酸化インジウム系透明導電膜(I)の作製に用いたターゲットの添加元素Mを、TiからGa(実施例17)、Mo(実施例18)、Sn(実施例19)、W(実施例20)、Ce(実施例21)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。なお、酸化インジウム系透明導電膜(I)の作製に用いたターゲットは、それぞれ上記評価方法(1)による定量分析結果が、Ga/(In+Ga)で0.70原子%(実施例17)、Mo/(In+Mo)で1.00原子%(実施例18)、Sn/(In+Sn)で0.50原子%(実施例19)、W/(In+W)で0.60原子%(実施例20)、Ce/(In+Ce)で0.80原子%(実施例21)であった。
酸化亜鉛系透明導電膜(II)の作製に用いたターゲットの添加元素Mを、それぞれAl及びGaから、B(実施例22)、Mg(実施例23)、Si(実施例24)、Ti(実施例25)、Ge(実施例26)、Zr(実施例27)、Hf(実施例28)としたこと以外は、実施例1と同様にして透明導電膜積層体を作製し、特性の測定評価を行った。なお、酸化亜鉛系透明導電膜(II)の作製に用いたターゲットは、それぞれ上記評価方
法(1)による定量分析結果が、添加元素をMとして全てM/(Zn+M)で0.50原子%(実施例22~28)であった。
Claims (14)
- 透光性基板上に、表面粗さ(Ra)が1.0nm以下の状態で形成された酸化インジウム系透明導電膜(I)と、該酸化インジウム系透明導電膜(I)上に形成された酸化亜鉛系透明導電膜(II)とを備えた構造を有し、
積層体としての表面粗さ(Ra)が30nm以上で、ヘイズ率が8%以上、且つ抵抗値が30Ω/□以下であり、波長400nmから1200nmの範囲における光に対する吸収率が平均値で15%以下であることを特徴とする透明導電膜積層体。 - 上記酸化インジウム系透明導電膜(I)の表面最大高低差(Rmax)が高さ50nm以下であることを特徴とする請求項1に記載の透明導電膜積層体。
- 上記酸化インジウム系透明導電膜(I)の表面上に、直径が100nm以下である突起が5μm四方あたり100個以下の割合で存在することを特徴とする請求項1に記載の透明導電膜積層体。
- 波長400nmから600nmの範囲における光に対する吸収率が、平均値で15%以下であることを特徴とする請求項1に記載の透明導電膜積層体。
- 膜厚が10nm以上300nm以下である上記酸化インジウム系透明導電膜(I)と、膜厚が200nm以上1000nm以下である上記酸化亜鉛系透明導電膜(II)とを備えた構造を有することを特徴とする請求項1に記載の透明導電膜積層体。
- 上記酸化インジウム系透明導電膜(I)は、酸化インジウムを主成分とし、Ti、Ga、Mo、Sn、W、及びCeから選ばれる1種以上の添加金属元素を含むことを特徴とする請求項1に記載の透明導電膜積層体。
- 上記酸化亜鉛系透明導電膜(II)は、酸化亜鉛を主成分とし、Al、Ga、B、Mg、Si、Ti、Ge、Zr、及びHfから選ばれる1種以上の添加金属元素を含むことを特徴とする請求項1に記載の透明導電膜積層体。
- 上記酸化亜鉛系透明導電膜(II)は、酸化亜鉛を主成分とし、Al又はGaから選ばれる1種以上の添加金属元素を、(Al+Ga)/(Zn+Al+Ga)原子数比で0.3~6.5原子%、且つAl/(Al+Ga)原子数比で30~70原子%の範囲内で含むことを特徴とする請求項1に記載の透明導電膜積層体。
- 透光性基板上に、スパッタリング法によりガス圧が0.1Pa以上2.0Pa以下、基板温度が50℃以下の条件で、膜厚が10nm以上300nm以下の酸化インジウム系透明導電膜(I)を形成する第1の成膜工程と、
上記酸化インジウム系透明導電膜(I)上に、スパッタリング法によりガス圧が0.1Pa以上2.0Pa以下、基板温度が200℃以上450℃以下の条件で、膜厚が200nm以上1000nm以下の酸化亜鉛系透明導電膜(II)を形成する第2の成膜工程と
を有することを特徴とする透明導電膜積層体の製造方法。 - 上記第1の成膜工程では、H2Oガスを導入し、H2O分圧が0.05Pa以下の雰囲気下で酸化インジウム系透明導電膜(I)を成膜することを特徴とする請求項9に記載の透明導電膜積層体の製造方法。
- 上記第1の成膜工程では、H2ガスを導入し、H2分圧が0.03Pa以下の雰囲気下で酸化インジウム系透明導電膜(I)を成膜することを特徴とする請求項9に記載の透明導電膜積層体の製造方法。
- 上記酸化亜鉛系透明導電膜(II)を形成するためのスパッタリングターゲットが、酸化亜鉛を主成分とし、Al又はGaから選ばれる1種以上の添加金属元素を、(Al+Ga)/(Zn+Al+Ga)原子数比で0.3~6.5原子%、且つAl/(Al+Ga)原子数比で30~70原子%の範囲内で含むことを特徴とする請求項9に記載の透明導電膜積層体の製造方法。
- 透光性基板上に、透明導電膜積層体と、光電変換層ユニットと、裏面電極層とが順に形成された薄膜太陽電池であって、
上記透明導電膜積層体は、
上記透光性基板上に、表面粗さ(Ra)が1.0nm以下の状態で形成された酸化インジウム系透明導電膜(I)と、該酸化インジウム系透明導電膜(I)上に形成された酸化亜鉛系透明導電膜(II)とを備えた構造を有し、
積層体としての表面粗さ(Ra)が30nm以上で、ヘイズ率が8%以上、且つ抵抗値が30Ω/□以下であり、波長400nmから1200nmの範囲における光に対する吸収率が平均値で15%以下であることを特徴とする薄膜太陽電池。 - 透光性基板上に、透明導電膜積層体と、光電変換層ユニットと、裏面電極層とが順に形成された薄膜太陽電池の製造方法であって、
上記透光性基板上に、スパッタリング法によりガス圧が0.1Pa以上2.0Pa以下、基板温度が50℃以下の条件で、膜厚が10nm以上300nm以下の酸化インジウム系透明導電膜(I)を形成する第1の成膜工程と、
上記酸化インジウム系透明導電膜(I)上に、スパッタリング法によりガス圧が0.1Pa以上2.0Pa以下、基板温度が200℃以上450℃以下の条件で、膜厚が200nm以上1000nm以下の酸化亜鉛系透明導電膜(II)を形成する第2の成膜工程と
を有する透明導電膜積層体形成工程により上記透明導電膜積層体を形成することを特徴とする薄膜太陽電池の製造方法。
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