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WO2014024850A1 - GLASS SUBSTRATE FOR Cu-In-Ga-Se SOLAR CELL, AND SOLAR CELL USING SAME - Google Patents

GLASS SUBSTRATE FOR Cu-In-Ga-Se SOLAR CELL, AND SOLAR CELL USING SAME Download PDF

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Publication number
WO2014024850A1
WO2014024850A1 PCT/JP2013/071172 JP2013071172W WO2014024850A1 WO 2014024850 A1 WO2014024850 A1 WO 2014024850A1 JP 2013071172 W JP2013071172 W JP 2013071172W WO 2014024850 A1 WO2014024850 A1 WO 2014024850A1
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Prior art keywords
glass
solar cell
glass substrate
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cigs
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PCT/JP2013/071172
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French (fr)
Japanese (ja)
Inventor
伸一 安間
裕 黒岩
朋美 安部
玲大 臼井
健 岡東
剛 富澤
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旭硝子株式会社
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Priority to JP2014529494A priority Critical patent/JPWO2014024850A1/en
Priority to KR20147034799A priority patent/KR20150040251A/en
Publication of WO2014024850A1 publication Critical patent/WO2014024850A1/en

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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/16—Material structures, e.g. crystalline structures, film structures or crystal plane orientations
    • H10F77/169—Thin semiconductor films on metallic or insulating substrates
    • H10F77/1694—Thin semiconductor films on metallic or insulating substrates the films including Group I-III-VI materials, e.g. CIS or CIGS
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
    • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
    • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
    • C03C3/093—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/12—Active materials
    • 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
    • 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
    • Y02E10/541—CuInSe2 material PV cells

Definitions

  • the present invention relates to a glass substrate for a solar cell in which a photoelectric conversion layer is formed between glass substrates and a solar cell using the same. More specifically, the glass substrate typically includes a glass substrate and a cover glass, and a Cu— layer in which a photoelectric conversion layer mainly composed of a group 11, group 13, or group 16 element is formed on the glass substrate.
  • the present invention relates to a glass substrate for an In—Ga—Se solar cell and a solar cell using the same.
  • Group 11-13, 11-16 compound semiconductors having a chalcopyrite crystal structure and cubic or hexagonal 12-16 group compound semiconductors have a large absorption coefficient for light in the visible to near-infrared wavelength range. have. Therefore, it is expected as a material for high-efficiency thin film solar cells.
  • Typical examples include Cu (In, Ga) Se 2 (hereinafter referred to as “CIGS” or “Cu—In—Ga—Se”) and CdTe.
  • CIGS thin film solar cells (hereinafter also referred to as “CIGS solar cells”) are inexpensive and have an average thermal expansion coefficient close to that of CIGS compound semiconductors, soda lime glass is used as a substrate to obtain a solar cell. ing. In order to obtain an efficient solar cell, a glass material that can withstand a high heat treatment temperature has been proposed (see Patent Documents 1 to 5).
  • a CIGS photoelectric conversion layer (hereinafter also referred to as “CIGS layer”) is formed on the glass substrate.
  • CIGS layer A CIGS photoelectric conversion layer
  • a solar cell with high power generation efficiency is produced at a higher temperature. Heat treatment is preferred, and the glass substrate is required to withstand it and satisfy a predetermined average thermal expansion coefficient.
  • Patent Document 1 proposes a glass composition having a relatively high annealing point, but the invention described in Patent Document 1 does not necessarily have high power generation efficiency.
  • Patent Documents 2 and 3 solar cell glass having a high strain point and satisfying a predetermined average thermal expansion coefficient is proposed.
  • the problem of Patent Document 2 is to secure heat resistance and improve productivity
  • Patent Document 3 is to improve surface quality and improve devitrification resistance, both of which solve problems related to power generation efficiency. Not. Therefore, it cannot be said that the inventions described in Patent Documents 2 and 3 have high power generation efficiency.
  • Patent Documents 4 and 5 there are proposals for high strain point glass substrates, but these are mainly intended for plasma display applications and have different problems.
  • the inventions described in Patent Documents 4 and 5 have high power generation. It is not necessarily efficient.
  • Patent Document 3 proposes a glass containing a large amount of boron oxide and having a high strain point and satisfying a predetermined average thermal expansion coefficient.
  • boron diffuses into the CIGS layer, which is a p-type semiconductor, and acts as a donor, which may reduce power generation efficiency.
  • a boron removal facility is required, which tends to increase costs.
  • boron in the glass is reduced, but the power generation efficiency is insufficient with the glass composition specifically described, and there is room for improvement in terms of further improvement in power generation efficiency.
  • Patent Document 7 discloses a method of improving efficiency by diffusing Na in glass into a CIGS layer.
  • the glass substrate used in the CIGS solar cell has a good balance between high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, solubility during plate glass production, formability, and devitrification prevention. Was difficult.
  • the present invention relates to a Cu—In—Ga—Se solar cell having a good balance of high power generation efficiency, high glass transition temperature, predetermined average coefficient of thermal expansion, solubility during plate glass production, formability, and devitrification prevention.
  • An object of the present invention is to provide a glass substrate for use and a solar cell using the same.
  • the inventors of the present application have found that a specific composition of the glass substrate for a Cu—In—Ga—Se solar cell enables high power generation efficiency, high glass transition temperature, predetermined It was found that a glass substrate for a Cu—In—Ga—Se solar cell having a good balance of the average thermal expansion coefficient, solubility during production of sheet glass, formability, and devitrification prevention properties can be obtained.
  • the glass substrate for a Cu—In—Ga—Se solar cell is expressed by a mass percentage based on the following oxide: 45 to 70% of SiO 2 10-20% Al 2 O 3 B 2 O 3 from 0 to 0.5%, 0-6% MgO CaO 0-4%, 9.5-20% of SrO, BaO 0-5%, ZrO 2 0-8%, 3-10% Na 2 O, 2 to 9.5% of K 2 O, contains.
  • the glass substrate for a Cu—In—Ga—Se solar cell of the present invention has high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, solubility during plate glass production, formability, and devitrification prevention characteristics. Can be provided in a balanced manner, and a solar cell with high power generation efficiency can be provided by using the glass substrate for CIGS solar cell of the present invention.
  • FIG. 1 is sectional drawing which represents typically an example of embodiment of the solar cell using the glass substrate for CIGS solar cells of this invention.
  • FIG. 2 shows a solar cell (a) produced on a glass substrate for evaluation in the example and a cross-sectional view (b) thereof.
  • FIG. 3 shows the top view of the several photovoltaic cell produced on the glass substrate for evaluation in an Example.
  • the glass substrate for a Cu—In—Ga—Se solar cell of the present invention is expressed by a mass percentage based on the following oxide, 45 to 70% of SiO 2 10-20% Al 2 O 3 B 2 O 3 from 0 to 0.5%, 0-6% MgO CaO 0-4%, 9.5-20% of SrO, BaO 0-5%, ZrO 2 0-8%, 3-10% Na 2 O, 2 to 9.5% of K 2 O, contains.
  • CGS Cu—In—Ga—Se is hereinafter referred to as “CIGS”.
  • the glass transition temperature (Tg) of the glass substrate for CIGS solar cell of the present invention is 640 ° C. or higher and 700 ° C. or lower, which is higher than the glass transition temperature of soda lime glass.
  • the glass transition temperature (Tg) is preferably 645 ° C. or higher, more preferably 650 ° C. or higher, and further preferably 655 ° C. or higher in order to ensure the formation of the CIGS layer at a high temperature.
  • the temperature is preferably 690 ° C. or lower. More preferably, it is 685 degrees C or less, More preferably, it is 680 degrees C or less.
  • the average thermal expansion coefficient at 50 to 350 ° C. of the glass substrate for CIGS solar cell of the present invention is 60 ⁇ 10 ⁇ 7 to 110 ⁇ 10 ⁇ 7 / ° C. If it is less than 60 ⁇ 10 ⁇ 7 / ° C. or more than 110 ⁇ 10 ⁇ 7 / ° C., the difference in thermal expansion from the CIGS layer becomes too large, and defects such as peeling tend to occur.
  • it is 65 ⁇ 10 ⁇ 7 / ° C. or more, more preferably 70 ⁇ 10 ⁇ 7 / ° C. or more, and further preferably 75 ⁇ 10 ⁇ 7 / ° C. or more.
  • the Mo (molybdenum) film that is a positive electrode it is preferably 100 ⁇ 10 ⁇ 7 / ° C. or less, more preferably 95 ⁇ 10 ⁇ 7 / ° C. or less, and still more preferably 90 ⁇ 10 ⁇ 7 / ° C. or less.
  • the relationship between the temperature (T 4 ) at which the viscosity is 10 4 dPa ⁇ s and the devitrification temperature (T L ) is T 4 ⁇ T L ⁇ ⁇ 30 ° C.
  • T 4 The -T L is lower than -30 ° C., devitrification is likely to occur at the time of sheet glass forming, there is a possibility that the molding of the glass plate becomes difficult.
  • T 4 -T L is preferably -10 ° C. or higher, more preferably 10 ° C. or higher, more preferably 30 ° C. or higher, particularly preferably 50 ° C. or higher.
  • the devitrification temperature refers to the maximum temperature at which crystals are not generated on the glass surface and inside when the glass is held at a specific temperature for 17 hours.
  • T 4 is 1230 ° C. or less.
  • T 4 is preferably 1220 ° C. or less, more preferably 1210 ° C. or less, more preferably 1200 ° C. or less, particularly preferably 1190 ° C. or less.
  • the glass substrate for CIGS solar cell of the present invention has a temperature (T 2 ) at which the viscosity becomes 10 2 dPa ⁇ s at 1620 ° C. in consideration of solubility of glass, that is, improvement in homogeneity and productivity.
  • T 2 is preferably 1590 ° C. or lower, more preferably 1570 ° C. or lower, further preferably 1560 ° C. or lower, and particularly preferably 1550 ° C. or lower.
  • a glass substrate for a CIGS solar cell of the present invention has a density of 2.45 g / cm 3 or more and 2.9 g / cm 3 or less. When the density exceeds 2.9 g / cm 3 , the product mass becomes heavy, which is not preferable. Moreover, the glass substrate becomes brittle and easily broken, which is not preferable. Density is more preferably 2.85 g / cm 3 or less, more preferably 2.82 g / cm 3 or less, particularly preferably 2.8 g / cm 3 or less.
  • the density is less than 2.45 g / cm 3 , only light elements having a small atomic number can be used as constituent elements of the glass substrate, and there is a possibility that desired power generation efficiency and glass viscosity cannot be obtained. . More preferably 2.5 g / cm 3 or more, more preferably 2.55 g / cm 3 or more, and particularly preferably 2.6 g / cm 3 or more.
  • SiO 2 is a component that forms a glass skeleton. If it is less than 45% by mass (hereinafter, “mass%” is simply referred to as “%”), the heat resistance and chemical durability of the glass substrate decrease, and the average heat The expansion coefficient may increase. Preferably it is 48% or more, More preferably, it is 50% or more, More preferably, it is 52% or more. However, if it exceeds 70%, the high-temperature viscosity of the glass is increased, and there is a possibility that a problem of deterioration of solubility occurs. Preferably it is 65% or less, More preferably, it is 60% or less, More preferably, it is 58% or less.
  • Al 2 O 3 increases the glass transition temperature, improves weather resistance (solarization), heat resistance and chemical durability, and increases Young's modulus. If the content is less than 10%, the glass transition temperature may be lowered. In addition, the average thermal expansion coefficient may be out of the predetermined range. Preferably it is 11% or more, More preferably, it is 14% or more, More preferably, it is 15% or more. However, if it exceeds 20%, the high-temperature viscosity of the glass is increased, and the solubility may be deteriorated. Further, the devitrification temperature is increased, and the moldability may be deteriorated. In addition, power generation efficiency may be reduced. Preferably it is 19% or less, More preferably, it is 18% or less, More preferably, it is 17% or less, Most preferably, it is 16% or less.
  • B 2 O 3 may be contained up to 0.5% in order to improve the solubility. If the content exceeds 0.5%, the glass transition temperature may decrease or the average thermal expansion coefficient may decrease, which is not preferable for the process of forming the CIGS layer. Moreover, devitrification temperature rises and it becomes easy to devitrify, and there exists a possibility that plate glass shaping
  • MgO may be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.05% or more, More preferably, it is 0.1% or more, More preferably, it is 0.2% or more. However, if it exceeds 6%, the devitrification temperature may increase. Furthermore, power generation efficiency may be reduced. Preferably it is 5% or less, More preferably, it is 4.5% or less, More preferably, it is 4% or less.
  • CaO may be contained because it has an effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.05% or more, More preferably, it is 0.1% or more, More preferably, it is 0.2% or more. However, since it has an effect of inhibiting Na diffusion, it is contained in a range of less than 4%, preferably 3.5% or less, more preferably 3% or less.
  • SrO has the effect of lowering the viscosity during melting of the glass, maintaining the average thermal expansion coefficient at a predetermined value, and promoting melting. Furthermore, since there exists an effect which accelerates
  • BaO can be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.1% or more, More preferably, it is 0.2% or more, More preferably, it is 0.5% or more. However, if the content exceeds 5%, the power generation efficiency decreases, the average thermal expansion coefficient of the glass substrate increases, the density increases, and the glass may become brittle. In addition, the Young's modulus may be reduced. Preferably it is 4% or less, More preferably, it is 3% or less, More preferably, it is 2% or less.
  • ZrO 2 can be contained because it has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. However, if the content exceeds 8%, the average thermal expansion coefficient of the glass substrate decreases, the power generation efficiency decreases, the devitrification temperature rises, and devitrification easily occurs, making it difficult to form a sheet glass. Preferably it is 7% or less, More preferably, it is 6% or less, More preferably, it is 5.5% or less. Further, it is preferably 0.5% or more, more preferably 1% or more, and further preferably 1.5% or more.
  • TiO 2 Since the inclusion of TiO 2 devitrification temperature increases, it is preferred that TiO 2 is not contained.
  • the glass substrate for a CIGS solar cell of the present invention is likely to generate a foam layer on the surface of the molten glass as compared with ordinary soda lime glass. When the foam layer is generated, the temperature of the molten glass does not rise, it becomes difficult to clarify, and the productivity tends to deteriorate.
  • a titanium compound may be supplied to the foam layer generated on the surface of the molten glass as an antifoaming agent. The titanium compound is taken into the molten glass and exists as TiO 2 .
  • This titanium compound may be an inorganic titanium compound (titanium tetrachloride, titanium oxide, etc.) or an organic titanium compound.
  • examples of the organic titanium compound include titanic acid esters or derivatives thereof, titanium chelates or derivatives thereof, titanium acylates or derivatives thereof, and oxalic acid titanates. For the above reason, TiO 2 is allowed to be contained in the glass by 0.2% or less as an impurity.
  • MgO, CaO, SrO and BaO are at least one selected from the group consisting of MgO, CaO, and BaO in order to lower the viscosity at the time of melting the glass, promote the melting, and bring the thermal expansion coefficient into a predetermined range.
  • the total amount of SrO and SrO (that is, (MgO + CaO + SrO + BaO)) is preferably 17% or more. 18% or more is more preferable, and 19% or more is more preferable. However, if the total amount exceeds 30%, the devitrification temperature rises and the moldability may be deteriorated. Therefore, 30% or less is preferable, 26% or less is more preferable, and 24% or less is more preferable.
  • the proportion of SrO in the MgO, CaO, SrO and BaO is preferably 0.6 or more. That is, the ratio of SrO to the total content of MgO, CaO, SrO and BaO (hereinafter, the total content of these alkaline earth metal oxides (RO) is also referred to as (MgO + CaO + SrO + BaO)), that is, SrO / (MgO + CaO + SrO + BaO) is preferably 0.6 or more.
  • the effect of promoting the diffusion of Na to the CIGS layer on the glass when the CIGS solar cell is produced can be further enhanced. More preferably, it is 0.65 or more, More preferably, it is 0.7 or more.
  • Na 2 O is a component that contributes to improving the power generation efficiency of CIGS solar cells, and is an essential component. Further, it has the effect of lowering the viscosity at the glass melting temperature and facilitating melting, so 3 to 10% is contained. Na diffuses into the CIGS layer formed on the glass substrate to increase the power generation efficiency. However, if the content is less than 3%, Na diffusion to the CIGS layer on the glass substrate becomes insufficient, and the power generation efficiency is also insufficient. There is a risk of becoming.
  • the content is preferably 3.5% or more, more preferably 4% or more, and even more preferably 4.5% or more. When the Na 2 O content exceeds 10%, the average thermal expansion coefficient is out of the predetermined range, and the glass transition temperature tends to decrease.
  • the Young's modulus may be reduced.
  • excessive Na may deteriorate the Mo (molybdenum) film formed as a positive electrode, leading to a decrease in power generation efficiency.
  • the content is preferably 9% or less, more preferably 8% or less, and even more preferably 7% or less.
  • K 2 O has the same effect as Na 2 O, and also has a function of suppressing changes in the CIGS composition in the crystal growth of CIGS at a high temperature in the CIGS solar cell manufacturing process. It is contained in an amount of 2 to 9.5% to prevent the decrease. However, if it exceeds 9.5%, the glass transition temperature is lowered, and the average thermal expansion coefficient may be out of the predetermined range. Alternatively, the Young's modulus may be reduced. Preferably it is 3% or more, More preferably, it is 3.5% or more, More preferably, it is 4% or more. Further, it is preferably 9% or less, more preferably 8% or less, and further preferably 7% or less.
  • the glass substrate for CIGS solar cell of the present invention consists essentially of the above-mentioned mother composition, but other components within the range that does not impair the purpose of the present invention are divided by 1% or less in total with respect to the above-mentioned glass mother composition. Or 5% or less.
  • ZnO, Li 2 O, WO 3 , Nb 2 O 5 , V 2 O 5 , Bi 2 O 3 , MoO 3 for the purpose of improving weather resistance, solubility, devitrification, ultraviolet shielding, refractive index, and the like.
  • P 2 O 5 or the like may be contained.
  • fining agents such as SO 3 , F, Cl, SnO 2 are divided into the glass matrix composition, and the total amount is 1% or less, respectively. You may add these raw materials to a mother composition raw material so that it may contain 2% or less. In order to improve the chemical durability of the glass substrate, Y 2 O 3 and La 2 O 3 may be contained in the glass substrate in a total amount of 2% or less.
  • the glass substrate for a CIGS solar cell of the present invention considering the environmental burden, it is preferred not to contain As 2 O 3, Sb 2 O 3 substantially. In consideration of stable float forming, it is preferable that ZnO is not substantially contained.
  • the glass substrate for CIGS solar cell of the present invention may be manufactured not only by the float method but also by the fusion method.
  • the manufacturing method of the glass substrate for CIGS solar cells of this invention > Then, the one aspect
  • molding process are implemented similarly to the time of manufacturing the conventional glass substrate for solar cells.
  • the glass substrate for CIGS solar cells of the present invention is an alkali glass substrate containing an alkali metal oxide (Na 2 O, K 2 O), SO 3 can be effectively used as a fining agent, Suitable for the float method and fusion method (down draw method) as the molding method.
  • a float method capable of easily and stably forming a large-area glass substrate with the enlargement of the solar cell is used. preferable.
  • molten glass obtained by melting raw materials is formed into a plate shape.
  • raw materials are prepared so that the obtained glass substrate has the above composition, the raw materials are continuously charged into a melting furnace, and heated to 1500 to 1700 ° C. to obtain molten glass.
  • the molten glass is formed into a ribbon-like glass plate by applying, for example, a float process.
  • After pulling out the ribbon-shaped glass plate from the float forming furnace it is cooled to room temperature by a cooling means, and after cutting, a CIGS solar cell glass substrate is obtained.
  • the glass substrate for CIGS solar cell of the present invention is not limited to the glass substrate on which the CIGS layer is formed, but is also suitable as a glass substrate for cover glass that protects the surface side of the solar cell element on which the CIGS layer is formed.
  • the thickness of the glass substrate for CIGS solar cell of the present invention is preferably 3 mm or less, more preferably 2 mm or less, and still more preferably 1.5 mm or less.
  • a method for forming a CIGS layer on a glass substrate is not particularly limited, but a selenization method in which a metal laminated film containing Cu, In or the like is heat-treated in a selenium-based gas atmosphere is particularly preferable.
  • the heating temperature when forming the CIGS layer can be set to 500 to 700 ° C., preferably 600 to 650 ° C.
  • the cover glass of the solar cell element using the CIGS solar cell glass substrate of the present invention may use the above-described CIGS solar cell glass substrate of the present invention, but is not limited to such a glass substrate, soda lime glass. A plate may be used.
  • the CIGS solar cell glass substrate of the present invention is preferably used in combination with a CIGS layer forming glass substrate and a cover glass because the average thermal expansion coefficient is the same, so that no thermal deformation or the like occurs during solar cell assembly.
  • the solar cell in the present invention includes a glass substrate, a cover glass, and a CIGS layer disposed as a photoelectric conversion layer between the glass substrate and the cover glass, and a CIGS layer is formed thereon. Is at least the glass substrate for a Cu—In—Ga—Se solar cell of the present invention described above.
  • FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of a solar cell in the present invention.
  • the CIGS solar cell 1 in the present invention has a glass substrate 5, a cover glass 19, and a CIGS layer 9 between the glass substrate 5 and the cover glass 19.
  • the glass substrate 5 consists of the glass substrate for CIGS solar cells of this invention demonstrated above.
  • the solar cell 1 has the back electrode layer of Mo film which is the plus electrode 7 on the glass substrate 5, and has the CIGS layer 9 on it.
  • An example of the composition of the CIGS layer is Cu (In 1-x Ga x ) Se 2 .
  • x represents the composition ratio of In and Ga, and 0 ⁇ x ⁇ 1.
  • a CdS (cadmium sulfide) layer, a ZnS (zinc sulfide) layer, a ZnO (zinc oxide) layer, a Zn (OH) 2 (zinc hydroxide) layer as a buffer layer 11, or a mixture thereof. It has a crystal layer.
  • a transparent conductive film 13 such as ZnO, ITO, or Al-doped ZnO (AZO) is provided via a buffer layer, and an extraction electrode such as an Al electrode (aluminum electrode) that is a negative electrode 15 is provided thereon. .
  • An antireflection film may be provided at a necessary place between these layers. In FIG. 1, an antireflection film 17 is provided between the transparent conductive film 13 and the negative electrode 15.
  • a cover glass 19 may be provided on the minus electrode 15, and if necessary, the minus electrode and the cover glass are sealed with a resin or bonded with a transparent resin for bonding.
  • a cover glass a glass substrate used as a substrate for forming the CIGS layer of the present invention may be used.
  • the end of the CIGS layer or the end of the solar cell may be sealed.
  • a material for sealing the same material as the glass substrate for CIGS solar cells of this invention, other glass, and resin are mentioned, for example. Note that the thickness of each layer of the solar cell shown in the accompanying drawings is not limited to the drawings.
  • Example and a manufacture example demonstrate this invention in more detail, this invention is not limited to these Examples and a manufacture example.
  • Examples (Examples 1 to 9) and comparative examples (Examples 10 to 11) of the glass substrate for CIGS solar cell of the present invention are shown.
  • the raw materials of each component are prepared so as to have the compositions shown in Table 1 and Table 2, and 100 parts by mass of the mother composition raw material of the component for glass substrate, 0.1 parts by mass of sulfate in terms of SO 3 , It added to the raw material, and it melt
  • GPa specific elastic modulus E / d (unit: GPa ⁇ cm 3 / g), temperature at which viscosity becomes 10 4 dPa ⁇ s (T 4 ) (unit: ° C), temperature at which viscosity becomes 10 2 dPa ⁇ s (T 2 ) (unit: ° C.), devitrification temperature (T L ) (unit: ° C.), and power generation efficiency were measured and shown in Tables 1 and 2.
  • the measuring method of each physical property is shown below.
  • each physical property is the same value with a glass plate and a glass substrate. By processing and polishing the obtained glass plate, a glass substrate can be obtained.
  • Tg is a value measured using a differential thermal dilatometer (TMA), and was obtained according to the standard of JIS R3103-3 (FY2001).
  • TMA differential thermal dilatometer
  • Average thermal expansion coefficient at 50 to 350 ° C . The average coefficient of thermal expansion was measured using TMA and determined from the standard of JIS R3102 (1995).
  • Density The density was measured by Archimedes' method for about 20 g of glass lump that did not contain bubbles and was cut out from the glass plate.
  • Viscosity The viscosity is measured using a rotational viscometer, and the temperature T 2 when the viscosity ⁇ is 10 2 dPa ⁇ s and the temperature T when the viscosity ⁇ is 10 4 dPa ⁇ s. 4 (formability reference temperature) was measured.
  • Devitrification temperature (T L ) As for the devitrification temperature, 5 g of a glass lump cut out from a glass plate was placed on a platinum dish and kept in an electric furnace at a predetermined temperature for 17 hours. The maximum temperature at which crystals do not precipitate on the surface and inside of the glass lump after being held was defined as the devitrification temperature.
  • the amount of Na diffusion was evaluated by using the obtained glass plate as a solar cell substrate, producing a solar cell for evaluation as shown below, and using this to evaluate the amount of Na diffusion.
  • the production of the solar cell for evaluation will be described below with reference to FIGS.
  • the layer configuration of the solar cell for evaluation is substantially the same as the layer configuration of the solar cell shown in FIG. 1 except that it does not have the cover glass 19 and the antireflection film 17 of the solar cell in FIG.
  • the obtained glass plate was processed into a size of 3 cm ⁇ 3 cm and a thickness of 1.1 mm to obtain a glass substrate.
  • a Mo (molybdenum) film was formed as a plus electrode 7a by a sputtering apparatus.
  • Mo film formation was performed at room temperature to obtain a Mo film having a thickness of 500 nm.
  • a CuGa alloy layer is formed with a CuGa alloy target by a sputtering apparatus, and then an In layer is formed using an In target, whereby an In—CuGa precursor film is formed.
  • a film was formed.
  • Film formation was performed at room temperature. The thickness of each layer was adjusted so that the composition of the precursor film measured by fluorescent X-rays was Cu / (Ga + In) ratio of 0.8 and Ga / (Ga + In) ratio of 0.25. Obtained.
  • the precursor film was heat-treated using a RTA (Rapid Thermal Annealing) apparatus in a mixed atmosphere of argon and hydrogen selenide (hydrogen selenide is 5% by volume with respect to argon, referred to as “selenium atmosphere”).
  • RTA Rapid Thermal Annealing
  • the CIGS layer 9a was obtained by growing the CIGS crystal by holding at 580 ° C. for 30 minutes. The thickness of the obtained CIGS layer 9a was 2 ⁇ m.
  • a CdS layer was formed as the buffer layer 11a on the CIGS layer 9a by the CBD (Chemical Bath Deposition) method. Specifically, first, cadmium sulfate having a concentration of 0.01M, thiourea having a concentration of 1.0M, ammonia having a concentration of 15M, and pure water were mixed in a beaker. Next, the CIGS layer was immersed in the mixed solution, and the beaker was placed in a constant temperature bath with a water temperature of 70 ° C. in advance to form a CdS layer having a thickness of 50 to 80 nm. Further, a transparent conductive film 13a was formed on the CdS layer by a sputtering apparatus by the following method.
  • a ZnO layer was formed using a ZnO target, and then an AZO layer was formed using an AZO target (that is, a ZnO target containing 1.5 wt% Al 2 O 3 ).
  • AZO target that is, a ZnO target containing 1.5 wt% Al 2 O 3 .
  • Each layer was formed at room temperature to obtain a transparent conductive film 13a having a two-layer structure having a thickness of 480 nm.
  • An aluminum film having a thickness of 1 ⁇ m was formed as a U-shaped negative electrode 15a on the AZO layer of the transparent conductive film 13a by EB vapor deposition (where the U-shaped electrode length is 8 mm in length, 4 mm in width, electrode The width is 0.5 mm).
  • FIG. 2A is a view of one solar battery cell as viewed from above
  • FIG. 2B is a cross-sectional view taken along line AA ′ in FIG. 2A.
  • One cell has a width of 0.6 cm and a length of 1 cm, and the area excluding the negative electrode 15a is 0.5 cm 2.
  • FIG. 3 a total of eight cells are placed on one glass substrate 5a. Obtained.
  • a CIGS solar cell for evaluation (evaluation glass substrate 5a on which the above eight cells were prepared) was installed in a solar simulator (YSS-T80A manufactured by Yamashita Denso Co., Ltd.) and added to the positive electrode 7a previously coated with InGa solvent.
  • a terminal (not shown) was connected to the voltage generator at the lower end of the U-shape of the negative electrode 15a.
  • the temperature in the solar simulator was controlled at a constant temperature of 25 ° C. with a temperature controller. Pseudo sunlight was irradiated, and after 60 seconds, the voltage was changed from -1 V to +1 V at an interval of 0.015 V, and the current values of each of the eight cells were measured.
  • the power generation efficiency was calculated by the following formula (2) from the current and voltage characteristics during irradiation. Tables 1 and 2 show the value of the most efficient cell among the eight cells as the value of the power generation efficiency of each glass substrate.
  • the illuminance of the light source used for the test was 0.1 W / cm 2 .
  • the power generation efficiency is obtained by multiplying the open circuit voltage (V oc ), the short circuit current density (J sc ), and the fill factor (FF).
  • the open circuit voltage (V oc ) is an output when the terminal is opened, and the short circuit current (I sc ) is a current when the terminal is short circuited.
  • the short-circuit current density (J sc ) is I sc divided by the area of the cell excluding the negative electrode. The point that gives the maximum output is called the maximum output point, the voltage at that point is called the maximum voltage value (V max ), and the current is called the maximum current value (I max ).
  • a value obtained by dividing the product of the maximum voltage value (V max ) and the maximum current value (I max ) by the product of the open circuit voltage (V oc ) and the short circuit current (I sc ) is obtained as a fill factor (FF). It is done. Using the above values, the power generation efficiency was determined.
  • the amount of Na diffusion was measured in order to observe the effect of the glass substrate on the diffusion of the alkali metal element into the CIGS layer.
  • the measurement method is as follows. After completion of the second stage of heating by the RTA apparatus, the sample is measured for the integrated intensity of 23 Na in the CIGS film by secondary ion mass spectrometry (SIMS).
  • SIMS secondary ion mass spectrometry
  • Tables 1 and 2 are relative amounts when Example 10 is taken as 100. If Na diffusion amount compared with Example 10 is 60 or more, it can be said that it is a glass substrate suitable for a solar cell with much Na diffusion amount and high power generation efficiency.
  • the SO 3 remaining amount in the glass in this example was 100 to 500 ppm.
  • the residual amount of SO 3 in the glass composition was measured by measuring a glass lump cut out from a glass plate in a powder form and evaluating with fluorescent X-rays.
  • the glass substrates of Examples 45 to 70% of SiO 2 10-20% Al 2 O 3 B 2 O 3 from 0 to 0.5%, 0-6% MgO CaO 0-4%, 9.5-20% of SrO, BaO 0-5%, ZrO 2 0-8%, 3-10% Na 2 O, 2 to 9.5% of K 2 O,
  • the glass transition temperature Tg is as high as 640 ° C.
  • the average thermal expansion coefficient is 60 ⁇ 10 ⁇ 7 to 110 ⁇ 10 ⁇ 7 / ° C., and the density is 2.9 g / cm 3 or lower. Therefore, it is possible to have a high power generation efficiency, a high glass transition temperature, and a predetermined average thermal expansion coefficient in a well-balanced manner. Therefore, the CIGS photoelectric conversion layer does not peel from the glass substrate with the Mo film, and when the solar cell in the present invention is further assembled (specifically, the glass substrate having the CIGS photoelectric conversion layer and the cover glass are heated). When bonding), the glass substrate is less likely to deform and has better power generation efficiency.
  • the glass substrate of the comparative example (Example 10) has a low Tg and is not suitable because the glass substrate is easily deformed during film formation at 600 ° C. or higher. Further, the glass substrate of the comparative example (Example 11) is not suitable because it has a small amount of SrO and has an insufficient effect of promoting the diffusion of Na into the CIGS layer, which contributes to high power generation efficiency.
  • the glass substrate for a Cu—In—Ga—Se solar cell of the present invention is suitable as a glass substrate for a CIGS solar cell.
  • the glass substrate for a Cu—In—Ga—Se solar cell of the present invention has high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, solubility during production of sheet glass, molding Therefore, it is possible to provide a solar cell with high power generation efficiency by using the CIGS solar cell glass substrate of the present invention.

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Abstract

Provided is a glass substrate for a CIGS solar cell and a solar cell using the substrate. The substrate demonstrates high power generation efficiency, high glass transition temperature, a predetermined average thermal expansion coefficient, high glass strength, low glass density, and an excellent balance between solubility, moldability and devitrification prevention during plate glass production. A Cu-In-Ga-Se-solar-cell glass substrate containing 45 to 70% of SiO2, 11 to 20% of Al2O3, 0 to 0.5% of B2O3, 0 to 6% of MgO, 0 to less than 4% of CaO, 9.5 to 20% of SrO, 0 to 5% of BaO, 0 to 8% of ZrO2, 3 to 10% of Na2O, and 2 to 9.5% of K2O, the amounts indicating percentage by mass expressed in terms of oxides.

Description

Ｃｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板およびそれを用いた太陽電池Glass substrate for Cu-In-Ga-Se solar cell and solar cell using the same

　本発明は、ガラス基板の間に光電変換層が形成されている太陽電池用ガラス基板およびそれを用いた太陽電池に関する。より詳しくは、ガラス基板として、典型的にはガラス基板とカバーガラスとを有し、ガラス基板上に１１族、１３族、１６族元素を主成分とした光電変換層が形成されているＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板、およびそれを用いた太陽電池に関するものである。 The present invention relates to a glass substrate for a solar cell in which a photoelectric conversion layer is formed between glass substrates and a solar cell using the same. More specifically, the glass substrate typically includes a glass substrate and a cover glass, and a Cu— layer in which a photoelectric conversion layer mainly composed of a group 11, group 13, or group 16 element is formed on the glass substrate. The present invention relates to a glass substrate for an In—Ga—Se solar cell and a solar cell using the same.

　カルコパイライト結晶構造を持つ１１－１３族、１１－１６族化合物半導体や立方晶系あるいは六方晶系の１２－１６族化合物半導体は、可視から近赤外の波長範囲の光に対して大きな吸収係数を有している。そのために、高効率薄膜太陽電池の材料として期待されている。代表的な例としてＣｕ（Ｉｎ，Ｇａ）Ｓｅ２（以下、「ＣＩＧＳ」または「Ｃｕ－Ｉｎ－Ｇａ－Ｓｅ」と記述する。）やＣｄＴｅがあげられる。 Group 11-13, 11-16 compound semiconductors having a chalcopyrite crystal structure and cubic or hexagonal 12-16 group compound semiconductors have a large absorption coefficient for light in the visible to near-infrared wavelength range. have. Therefore, it is expected as a material for high-efficiency thin film solar cells. Typical examples include Cu (In, Ga) Se 2 (hereinafter referred to as “CIGS” or “Cu—In—Ga—Se”) and CdTe.

　ＣＩＧＳ薄膜太陽電池（以下、「ＣＩＧＳ太陽電池」ともいう）では、安価であることと平均熱膨張係数がＣＩＧＳ化合物半導体のそれに近いことから、ソーダライムガラスが基板として用いられ、太陽電池が得られている。
　また、効率の良い太陽電池を得るため、高温の熱処理温度に耐えうるガラス材料の提案もされている（特許文献１～５参照）。 CIGS thin film solar cells (hereinafter also referred to as “CIGS solar cells”) are inexpensive and have an average thermal expansion coefficient close to that of CIGS compound semiconductors, soda lime glass is used as a substrate to obtain a solar cell. ing.
In order to obtain an efficient solar cell, a glass material that can withstand a high heat treatment temperature has been proposed (see Patent Documents 1 to 5).

日本特開平１１－１３５８１９号公報Japanese Unexamined Patent Publication No. 11-135819 日本特開２０１０－１１８５０５号公報Japanese Unexamined Patent Publication No. 2010-118505 日本特開２００８－２８０１８９号公報Japanese Unexamined Patent Publication No. 2008-280189 日本特開平８－２９０９３８号公報Japanese Unexamined Patent Publication No. 8-290938 日本特開平１０－２５１２９号公報Japanese Unexamined Patent Publication No. 10-25129 日本特開２０１０－２６７９６５号公報Japanese Unexamined Patent Publication No. 2010-267965 国際公開第２０１１／１５８８４１号International Publication No. 2011/158841

　ガラス基板にはＣＩＧＳ光電変換層（以下、「ＣＩＧＳ層」ともいう）が形成されるが、特許文献１に開示されているように、発電効率の良い太陽電池を作製するにはより高温での熱処理が好ましく、ガラス基板にはそれに耐えうること、および、所定の平均熱膨張係数を満たすことが要求される。特許文献１では比較的徐冷点の高いガラス組成物が提案されているが、特許文献１に記載された発明が高い発電効率を有するとは必ずしもいえない。 A CIGS photoelectric conversion layer (hereinafter also referred to as “CIGS layer”) is formed on the glass substrate. However, as disclosed in Patent Document 1, a solar cell with high power generation efficiency is produced at a higher temperature. Heat treatment is preferred, and the glass substrate is required to withstand it and satisfy a predetermined average thermal expansion coefficient. Patent Document 1 proposes a glass composition having a relatively high annealing point, but the invention described in Patent Document 1 does not necessarily have high power generation efficiency.

　特許文献２、３に記載の発明では、歪点が高く所定の平均熱膨張係数を満たす太陽電池用ガラスが提案されている。しかし、特許文献２の課題は耐熱性の確保と生産性の改善であり、特許文献３の課題は表面品位の向上と耐失透性の改善であり、いずれも発電効率に関する課題を解決するものでは無い。そのため、特許文献２、３に記載された発明が高い発電効率を有するとは必ずしもいえない。
　また、特許文献４、５では、高歪点ガラス基板の提案があるが、これらはプラズマディスプレイ用途を主眼としているもので、課題が異なるものであり、特許文献４、５記載の発明が高い発電効率を有するとは必ずしもいえない。 In the inventions described in Patent Documents 2 and 3, solar cell glass having a high strain point and satisfying a predetermined average thermal expansion coefficient is proposed. However, the problem of Patent Document 2 is to secure heat resistance and improve productivity, and the problem of Patent Document 3 is to improve surface quality and improve devitrification resistance, both of which solve problems related to power generation efficiency. Not. Therefore, it cannot be said that the inventions described in Patent Documents 2 and 3 have high power generation efficiency.
Further, in Patent Documents 4 and 5, there are proposals for high strain point glass substrates, but these are mainly intended for plasma display applications and have different problems. The inventions described in Patent Documents 4 and 5 have high power generation. It is not necessarily efficient.

　さらに、特許文献３では、酸化ホウ素を多く含有し、歪点が高く所定の平均熱膨張係数を満たすガラスが提案されている。しかしながら、ガラス中にホウ素が多く存在すると、特許文献６に記載されているように、ｐ型半導体であるＣＩＧＳ層中にホウ素が拡散してドナーとして働き、発電効率を低下させるおそれがある。さらに、ホウ素の除去設備が必要で、コスト増となりやすいという問題があった。
　特許文献６では、ガラス中のホウ素を低減させているが、具体的に記載されているガラス組成では発電効率は不十分であり、さらなる発電効率の向上という点では改善の余地がある。 Furthermore, Patent Document 3 proposes a glass containing a large amount of boron oxide and having a high strain point and satisfying a predetermined average thermal expansion coefficient. However, when a large amount of boron is present in the glass, as described in Patent Document 6, boron diffuses into the CIGS layer, which is a p-type semiconductor, and acts as a donor, which may reduce power generation efficiency. Furthermore, there is a problem in that a boron removal facility is required, which tends to increase costs.
In Patent Document 6, boron in the glass is reduced, but the power generation efficiency is insufficient with the glass composition specifically described, and there is room for improvement in terms of further improvement in power generation efficiency.

　さらに特許文献７では、ガラス中のＮａをＣＩＧＳ層に拡散させることで効率を向上させるという方法が開示されている。 Further, Patent Document 7 discloses a method of improving efficiency by diffusing Na in glass into a CIGS layer.

　このようにＣＩＧＳ太陽電池に使用されるガラス基板において高い発電効率、高いガラス転移点温度、所定の平均熱膨張係数、板ガラス生産時の溶解性、成形性、失透防止の特性をバランスよく有することは困難であった。 As described above, the glass substrate used in the CIGS solar cell has a good balance between high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, solubility during plate glass production, formability, and devitrification prevention. Was difficult.

　本発明は、高い発電効率、高いガラス転移点温度、所定の平均熱膨張係数、板ガラス生産時の溶解性、成形性、および失透防止の特性をバランスよく有するＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板およびそれを用いた太陽電池を提供することを目的とする。 The present invention relates to a Cu—In—Ga—Se solar cell having a good balance of high power generation efficiency, high glass transition temperature, predetermined average coefficient of thermal expansion, solubility during plate glass production, formability, and devitrification prevention. An object of the present invention is to provide a glass substrate for use and a solar cell using the same.

　本願発明者等は、上記課題を解決する上で鋭意検討した結果、Ｃｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板において、特定の組成とすることで高い発電効率、高いガラス転移点温度、所定の平均熱膨張係数、板ガラス生産時の溶解性、成形性、および失透防止の特性をバランスよく有するＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板とすることができることを見出した。 As a result of intensive investigations to solve the above problems, the inventors of the present application have found that a specific composition of the glass substrate for a Cu—In—Ga—Se solar cell enables high power generation efficiency, high glass transition temperature, predetermined It was found that a glass substrate for a Cu—In—Ga—Se solar cell having a good balance of the average thermal expansion coefficient, solubility during production of sheet glass, formability, and devitrification prevention properties can be obtained.

　すなわち、本発明の一態様に係るＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板は、下記酸化物基準の質量百分率表示で、
　　　ＳｉＯ２を４５～７０％、
　　　Ａｌ２Ｏ３を１０～２０％、
　　　Ｂ２Ｏ３を０～０．５％、
　　　ＭｇＯを０～６％、
　　　ＣａＯを０～４％未満、
　　　ＳｒＯを９．５～２０％、
　　　ＢａＯを０～５％、
　　　ＺｒＯ２を０～８％、
　　　Ｎａ２Ｏを３～１０％、
　　　Ｋ２Ｏを２～９．５％、
含有する。 That is, the glass substrate for a Cu—In—Ga—Se solar cell according to one embodiment of the present invention is expressed by a mass percentage based on the following oxide:
45 to 70% of SiO 2
10-20% Al 2 O 3
B 2 O 3 from 0 to 0.5%,
0-6% MgO
CaO 0-4%,
9.5-20% of SrO,
BaO 0-5%,
ZrO 2 0-8%,
3-10% Na 2 O,
2 to 9.5% of K 2 O,
contains.

　本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板は、高い発電効率、高いガラス転移点温度、所定の平均熱膨張係数、板ガラス生産時の溶解性、成形性、および失透防止の特性をバランスよく有することができ、本発明のＣＩＧＳ太陽電池用ガラス基板を用いることで発電効率の高い太陽電池を提供できる。 The glass substrate for a Cu—In—Ga—Se solar cell of the present invention has high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, solubility during plate glass production, formability, and devitrification prevention characteristics. Can be provided in a balanced manner, and a solar cell with high power generation efficiency can be provided by using the glass substrate for CIGS solar cell of the present invention.

図１は、本発明のＣＩＧＳ太陽電池用ガラス基板を用いた太陽電池の実施形態の一例を模式的に表す断面図である。FIG. 1: is sectional drawing which represents typically an example of embodiment of the solar cell using the glass substrate for CIGS solar cells of this invention. 図２は、実施例において評価用ガラス基板上に作製した太陽電池セル（ａ）とその断面図（ｂ）を示す。FIG. 2 shows a solar cell (a) produced on a glass substrate for evaluation in the example and a cross-sectional view (b) thereof. 図３は、実施例において評価用ガラス基板上に作製した複数の太陽電池セルの平面図を示す。FIG. 3: shows the top view of the several photovoltaic cell produced on the glass substrate for evaluation in an Example.

＜本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板＞
　以下、本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板について説明する。
　本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板は、下記酸化物基準の質量百分率表示で、
　　　ＳｉＯ２を４５～７０％、
　　　Ａｌ２Ｏ３を１０～２０％、
　　　Ｂ２Ｏ３を０～０．５％、
　　　ＭｇＯを０～６％、
　　　ＣａＯを０～４％未満、
　　　ＳｒＯを９．５～２０％、
　　　ＢａＯを０～５％、
　　　ＺｒＯ２を０～８％、
　　　Ｎａ２Ｏを３～１０％、
　　　Ｋ２Ｏを２～９．５％、
含有する。なお、Ｃｕ－Ｉｎ－Ｇａ－Ｓｅを以下「ＣＩＧＳ」と記載する。 <Glass substrate for Cu—In—Ga—Se solar cell of the present invention>
Hereinafter, the glass substrate for a Cu—In—Ga—Se solar cell of the present invention will be described.
The glass substrate for a Cu—In—Ga—Se solar cell of the present invention is expressed by a mass percentage based on the following oxide,
45 to 70% of SiO 2
10-20% Al 2 O 3
B 2 O 3 from 0 to 0.5%,
0-6% MgO
CaO 0-4%,
9.5-20% of SrO,
BaO 0-5%,
ZrO 2 0-8%,
3-10% Na 2 O,
2 to 9.5% of K 2 O,
contains. Note that Cu—In—Ga—Se is hereinafter referred to as “CIGS”.

　本発明のＣＩＧＳ太陽電池用ガラス基板のガラス転移点温度（Ｔｇ）は、６４０℃以上、７００℃以下であり、ソーダライムガラスのガラス転移点温度より高い。ガラス転移点温度（Ｔｇ）は、高温におけるＣＩＧＳ層の形成を担保するため６４５℃以上であるのが好ましく、６５０℃以上がより好ましく、６５５℃以上がさらに好ましい。一方、溶解時の粘性を上げ過ぎないようにするために、６９０℃以下とするのが好ましい。より好ましくは６８５℃以下、さらに好ましくは６８０℃以下である。 The glass transition temperature (Tg) of the glass substrate for CIGS solar cell of the present invention is 640 ° C. or higher and 700 ° C. or lower, which is higher than the glass transition temperature of soda lime glass. The glass transition temperature (Tg) is preferably 645 ° C. or higher, more preferably 650 ° C. or higher, and further preferably 655 ° C. or higher in order to ensure the formation of the CIGS layer at a high temperature. On the other hand, in order not to increase the viscosity at the time of dissolution, the temperature is preferably 690 ° C. or lower. More preferably, it is 685 degrees C or less, More preferably, it is 680 degrees C or less.

　本発明のＣＩＧＳ太陽電池用ガラス基板の５０～３５０℃における平均熱膨張係数は、６０×１０－７～１１０×１０－７／℃である。６０×１０－７／℃未満または１１０×１０－７／℃超ではＣＩＧＳ層との熱膨張差が大きくなりすぎ、剥がれ等の欠点が生じやすくなる。好ましくは６５×１０－７／℃以上、より好ましくは７０×１０－７／℃以上、さらに好ましくは７５×１０－７／℃以上である。また、プラス電極であるＭｏ（モリブデン）膜との膨張差による反りを低減するために、好ましくは１００×１０－７／℃以下、より好ましくは９５×１０－７／℃以下、さらに好ましくは９０×１０－７／℃以下である。 The average thermal expansion coefficient at 50 to 350 ° C. of the glass substrate for CIGS solar cell of the present invention is 60 × 10 −7 to 110 × 10 −7 / ° C. If it is less than 60 × 10 −7 / ° C. or more than 110 × 10 −7 / ° C., the difference in thermal expansion from the CIGS layer becomes too large, and defects such as peeling tend to occur. Preferably it is 65 × 10 −7 / ° C. or more, more preferably 70 × 10 −7 / ° C. or more, and further preferably 75 × 10 −7 / ° C. or more. Further, in order to reduce warpage due to a difference in expansion from the Mo (molybdenum) film that is a positive electrode, it is preferably 100 × 10 −7 / ° C. or less, more preferably 95 × 10 −7 / ° C. or less, and still more preferably 90 × 10 −7 / ° C. or less.

　本発明のＣＩＧＳ太陽電池用ガラス基板は、粘度が１０４ｄＰａ・ｓとなる温度（Ｔ４）と失透温度（ＴＬ）との関係がＴ４－ＴＬ≧－３０℃である。Ｔ４－ＴＬが－３０℃未満では、板ガラス成形時に失透が生じやすく、ガラス板の成形が困難になるおそれがある。Ｔ４－ＴＬは、好ましくは－１０℃以上、より好ましくは１０℃以上、さらに好ましくは３０℃以上、特に好ましくは５０℃以上である。ここで、失透温度とは、ガラスを特定の温度で１７時間保持するときに、ガラス表面および内部に結晶が生成しない最大温度を指す。ガラス板の成形性、即ち、平坦性向上、および生産性向上を考慮すると、Ｔ４は１２３０℃以下である。Ｔ４は１２２０℃以下が好ましく、１２１０℃以下がより好ましく、１２００℃以下がさらに好ましく、１１９０℃以下が特に好ましい。 In the CIGS solar cell glass substrate of the present invention, the relationship between the temperature (T 4 ) at which the viscosity is 10 4 dPa · s and the devitrification temperature (T L ) is T 4 −T L ≧ −30 ° C. T 4 The -T L is lower than -30 ° C., devitrification is likely to occur at the time of sheet glass forming, there is a possibility that the molding of the glass plate becomes difficult. T 4 -T L is preferably -10 ° C. or higher, more preferably 10 ° C. or higher, more preferably 30 ° C. or higher, particularly preferably 50 ° C. or higher. Here, the devitrification temperature refers to the maximum temperature at which crystals are not generated on the glass surface and inside when the glass is held at a specific temperature for 17 hours. In consideration of moldability of the glass plate, that is, improvement in flatness and productivity, T 4 is 1230 ° C. or less. T 4 is preferably 1220 ° C. or less, more preferably 1210 ° C. or less, more preferably 1200 ° C. or less, particularly preferably 1190 ° C. or less.

　また、本発明のＣＩＧＳ太陽電池用ガラス基板は、ガラスの溶解性、即ち、均質性向上、および生産性向上を考慮して、粘度が１０２ｄＰａ・ｓとなる温度（Ｔ２）を１６２０℃以下とする。Ｔ２は１５９０℃以下が好ましく、１５７０℃以下がより好ましく、１５６０℃以下がさらに好ましく、１５５０℃以下が特に好ましい。 In addition, the glass substrate for CIGS solar cell of the present invention has a temperature (T 2 ) at which the viscosity becomes 10 2 dPa · s at 1620 ° C. in consideration of solubility of glass, that is, improvement in homogeneity and productivity. The following. T 2 is preferably 1590 ° C. or lower, more preferably 1570 ° C. or lower, further preferably 1560 ° C. or lower, and particularly preferably 1550 ° C. or lower.

　本発明のＣＩＧＳ太陽電池用ガラス基板は、密度が２．４５ｇ／ｃｍ３以上、２．９ｇ／ｃｍ３以下である。密度が２．９ｇ／ｃｍ３を超えると、製品質量が重くなり好ましくない。また、ガラス基板が脆くなり破壊しやすくなり好ましくない。密度はより好ましくは２．８５ｇ／ｃｍ３以下、さらに好ましくは２．８２ｇ／ｃｍ３以下、特に好ましくは２．８ｇ／ｃｍ３以下である。
　また、密度が２．４５ｇ／ｃｍ３未満であると、ガラス基板の構成元素として、原子番号の小さい軽元素しか使用することができず、所望の発電効率、ガラス粘度を得られないおそれがある。より好ましくは２．５ｇ／ｃｍ３以上、さらに好ましくは２．５５ｇ／ｃｍ３以上、特に好ましくは２．６ｇ／ｃｍ３以上である。 A glass substrate for a CIGS solar cell of the present invention has a density of 2.45 g / cm 3 or more and 2.9 g / cm 3 or less. When the density exceeds 2.9 g / cm 3 , the product mass becomes heavy, which is not preferable. Moreover, the glass substrate becomes brittle and easily broken, which is not preferable. Density is more preferably 2.85 g / cm 3 or less, more preferably 2.82 g / cm 3 or less, particularly preferably 2.8 g / cm 3 or less.
Further, if the density is less than 2.45 g / cm 3 , only light elements having a small atomic number can be used as constituent elements of the glass substrate, and there is a possibility that desired power generation efficiency and glass viscosity cannot be obtained. . More preferably 2.5 g / cm 3 or more, more preferably 2.55 g / cm 3 or more, and particularly preferably 2.6 g / cm 3 or more.

　本発明のＣＩＧＳ太陽電池用ガラス基板において上記組成（以下、「母組成」ともいう）範囲に限定する理由は以下のとおりである。
　ＳｉＯ２：
　ＳｉＯ２は、ガラスの骨格を形成する成分で、４５質量％（以下、「質量％」を単に「％」と記載する）未満ではガラス基板の耐熱性および化学的耐久性が低下し、平均熱膨張係数が増大するおそれがある。好ましくは４８％以上であり、より好ましくは５０％以上であり、さらに好ましくは５２％以上である。
　しかし、７０％超ではガラスの高温粘度が上昇し、溶解性が悪化する問題が生じるおそれがある。好ましくは６５％以下であり、より好ましくは６０％以下であり、さらに好ましくは５８％以下である。 The reason why the glass substrate for CIGS solar cell of the present invention is limited to the above composition (hereinafter also referred to as “mother composition”) is as follows.
SiO 2 :
SiO 2 is a component that forms a glass skeleton. If it is less than 45% by mass (hereinafter, “mass%” is simply referred to as “%”), the heat resistance and chemical durability of the glass substrate decrease, and the average heat The expansion coefficient may increase. Preferably it is 48% or more, More preferably, it is 50% or more, More preferably, it is 52% or more.
However, if it exceeds 70%, the high-temperature viscosity of the glass is increased, and there is a possibility that a problem of deterioration of solubility occurs. Preferably it is 65% or less, More preferably, it is 60% or less, More preferably, it is 58% or less.

　Ａｌ２Ｏ３：
　Ａｌ２Ｏ３は、ガラス転移点温度を上げ、耐候性（ソラリゼーション）、耐熱性および化学的耐久性を向上し、ヤング率を上げる。その含有量が１０％未満では、ガラス転移点温度が低下するおそれがある。また平均熱膨張係数が所定の範囲から外れるおそれがある。好ましくは１１％以上であり、より好ましくは１４％以上、さらに好ましくは１５％以上である。
　しかし、２０％超では、ガラスの高温粘度が上昇し、溶解性が悪くなるおそれがある。また、失透温度が上昇し、成形性が悪くなるおそれがある。また発電効率が低下するおそれがある。好ましくは１９％以下、より好ましくは１８％以下、さらに好ましくは１７％以下、特に好ましくは１６％以下である。 Al 2 O 3 :
Al 2 O 3 increases the glass transition temperature, improves weather resistance (solarization), heat resistance and chemical durability, and increases Young's modulus. If the content is less than 10%, the glass transition temperature may be lowered. In addition, the average thermal expansion coefficient may be out of the predetermined range. Preferably it is 11% or more, More preferably, it is 14% or more, More preferably, it is 15% or more.
However, if it exceeds 20%, the high-temperature viscosity of the glass is increased, and the solubility may be deteriorated. Further, the devitrification temperature is increased, and the moldability may be deteriorated. In addition, power generation efficiency may be reduced. Preferably it is 19% or less, More preferably, it is 18% or less, More preferably, it is 17% or less, Most preferably, it is 16% or less.

　Ｂ２Ｏ３：
　Ｂ２Ｏ３は、溶解性を向上させる等のために０．５％まで含有してもよい。含有量が０．５％を超えると、ガラス転移点温度が下がるおそれ、または平均熱膨張係数が小さくなるおそれがあり、ＣＩＧＳ層を形成するプロセスにとって好ましくない。また失透温度が上昇して失透しやすくなり、板ガラス成形が難しくなるおそれがある。さらに、大規模なホウ素の除去設備が必要となり、環境負荷が大きくなるため好ましくない。
　また、ｐ型半導体であるＣＩＧＳ層中にＢ（ホウ素）が拡散してドナーとして働き、発電効率を低下させるおそれがあり好ましくない。好ましくは含有量が０．３％以下である。実質的に含有しないことがより好ましい。
　なお、本発明において「実質的に含有しない」とは、原料等から混入する不可避的不純物以外には含有しないこと、すなわち、意図的に含有させないことを意味する。以下、同様である。 B 2 O 3 :
B 2 O 3 may be contained up to 0.5% in order to improve the solubility. If the content exceeds 0.5%, the glass transition temperature may decrease or the average thermal expansion coefficient may decrease, which is not preferable for the process of forming the CIGS layer. Moreover, devitrification temperature rises and it becomes easy to devitrify, and there exists a possibility that plate glass shaping | molding may become difficult. Furthermore, a large-scale boron removal facility is required, which increases the environmental load, which is not preferable.
Further, B (boron) diffuses into the CIGS layer, which is a p-type semiconductor, and acts as a donor, which is not preferable because power generation efficiency may be reduced. The content is preferably 0.3% or less. More preferably, it does not contain substantially.
In the present invention, “substantially does not contain” means that it is not contained other than inevitable impurities mixed from raw materials or the like, that is, it is not intentionally contained. The same applies hereinafter.

　ＭｇＯ：
　ＭｇＯは、ガラスの溶解時の粘性を下げ、溶解を促進する効果があるので含有してもよい。好ましくは０．０５％以上であり、より好ましくは０．１％以上であり、さらに好ましくは０．２％以上である。
　しかし、６％超では、失透温度が上昇するおそれがある。さらに、発電効率が低下するおそれがある。好ましくは５％以下、より好ましくは４．５％以下、さらに好ましくは４％以下である。 MgO:
MgO may be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.05% or more, More preferably, it is 0.1% or more, More preferably, it is 0.2% or more.
However, if it exceeds 6%, the devitrification temperature may increase. Furthermore, power generation efficiency may be reduced. Preferably it is 5% or less, More preferably, it is 4.5% or less, More preferably, it is 4% or less.

　ＣａＯ：
　ＣａＯは、ガラスの溶解時の粘性を下げ、溶解を促進する効果があるので含有してもよい。好ましくは０．０５％以上であり、より好ましくは０．１％以上であり、さらに好ましくは０．２％以上である。しかし、Ｎａ拡散を阻害する効果があるため、４％未満の範囲で含有させ、好ましくは３．５％以下、より好ましくは３％以下である。 CaO:
CaO may be contained because it has an effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.05% or more, More preferably, it is 0.1% or more, More preferably, it is 0.2% or more. However, since it has an effect of inhibiting Na diffusion, it is contained in a range of less than 4%, preferably 3.5% or less, more preferably 3% or less.

　ＳｒＯ：
　ＳｒＯは、ガラスの溶解時の粘性を下げ、平均熱膨張係数を所定の値に維持し、溶解を促進する効果がある。さらに、ＣＩＧＳ層へのＮａの拡散を促進する効果があるので、９．５％以上含有させる。好ましくは１０％以上、より好ましくは１０．５％以上、さらに好ましくは１１％以上である。しかし、２０％超含有するとガラス基板の平均熱膨張係数が増大するとともに密度が増大し、ガラスが脆くなるおそれがある。好ましくは１９％以下、より好ましくは１８％以下、さらに好ましくは１６％以下、特に好ましくは１５％以下である。 SrO:
SrO has the effect of lowering the viscosity during melting of the glass, maintaining the average thermal expansion coefficient at a predetermined value, and promoting melting. Furthermore, since there exists an effect which accelerates | stimulates the spreading | diffusion of Na to a CIGS layer, it contains 9.5% or more. Preferably it is 10% or more, More preferably, it is 10.5% or more, More preferably, it is 11% or more. However, if the content exceeds 20%, the average thermal expansion coefficient of the glass substrate increases, the density increases, and the glass may become brittle. Preferably it is 19% or less, More preferably, it is 18% or less, More preferably, it is 16% or less, Most preferably, it is 15% or less.

　ＢａＯ：
　ＢａＯは、ガラスの溶解時の粘性を下げ、溶解を促進する効果があるので含有させることができる。好ましくは０．１％以上、より好ましくは０．２％以上、さらに好ましくは０．５％以上である。しかし、５％超含有すると発電効率が低下し、またガラス基板の平均熱膨張係数が増大するとともに密度が増大し、ガラスが脆くなるおそれがある。また、ヤング率が低下するおそれがある。好ましくは４％以下、より好ましくは３％以下、さらに好ましくは２％以下である。 BaO:
BaO can be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.1% or more, More preferably, it is 0.2% or more, More preferably, it is 0.5% or more. However, if the content exceeds 5%, the power generation efficiency decreases, the average thermal expansion coefficient of the glass substrate increases, the density increases, and the glass may become brittle. In addition, the Young's modulus may be reduced. Preferably it is 4% or less, More preferably, it is 3% or less, More preferably, it is 2% or less.

　ＺｒＯ２：
　ＺｒＯ２は、ガラスの溶解時の粘性を下げ、溶解を促進する効果があるので含有させることができる。しかし、８％超含有するとガラス基板の平均熱膨張係数が低下し、発電効率が低下し、また失透温度が上昇して失透しやすくなり板ガラス成形が難しくなる。好ましくは７％以下、より好ましくは６％以下、さらに好ましくは５．５％以下である。また、好ましくは０．５％以上であり、より好ましくは１％以上、さらに好ましくは１．５％以上である。 ZrO 2 :
ZrO 2 can be contained because it has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. However, if the content exceeds 8%, the average thermal expansion coefficient of the glass substrate decreases, the power generation efficiency decreases, the devitrification temperature rises, and devitrification easily occurs, making it difficult to form a sheet glass. Preferably it is 7% or less, More preferably, it is 6% or less, More preferably, it is 5.5% or less. Further, it is preferably 0.5% or more, more preferably 1% or more, and further preferably 1.5% or more.

　ＴｉＯ２：
　ＴｉＯ２を含有させると失透温度が上昇するため、ＴｉＯ２は含有しないことが好ましい。ただし本発明のＣＩＧＳ太陽電池用ガラス基板は、通常のソーダライムガラスに比べて溶融ガラス表面に泡層が生成しやすい。泡層が生成すると、溶融ガラスの温度が上がらず、清澄しづらくなり、生産性が悪化する傾向がある。溶融ガラス表面に生成した泡層を薄化ないし消失させるために消泡剤としてチタン化合物が、溶融ガラス表面に生成した泡層に供給されることがある。チタン化合物は、溶融ガラス中に取り込まれ、ＴｉＯ２として存在する。このチタン化合物は、無機チタン化合物（四塩化チタン、酸化チタン等）であってもよく、有機チタン化合物であってもよい。有機チタン化合物としては、チタン酸エステルまたはその誘導体、チタンキレートまたはその誘導体、チタンアシレートまたはその誘導体、シュウ酸チタネート等が挙げられる。上記の理由により、ＴｉＯ２は、不純物として０．２％以下ガラス中に含有することが許容される。 TiO 2 :
Since the inclusion of TiO 2 devitrification temperature increases, it is preferred that TiO 2 is not contained. However, the glass substrate for a CIGS solar cell of the present invention is likely to generate a foam layer on the surface of the molten glass as compared with ordinary soda lime glass. When the foam layer is generated, the temperature of the molten glass does not rise, it becomes difficult to clarify, and the productivity tends to deteriorate. In order to make the foam layer generated on the surface of the molten glass thin or disappear, a titanium compound may be supplied to the foam layer generated on the surface of the molten glass as an antifoaming agent. The titanium compound is taken into the molten glass and exists as TiO 2 . This titanium compound may be an inorganic titanium compound (titanium tetrachloride, titanium oxide, etc.) or an organic titanium compound. Examples of the organic titanium compound include titanic acid esters or derivatives thereof, titanium chelates or derivatives thereof, titanium acylates or derivatives thereof, and oxalic acid titanates. For the above reason, TiO 2 is allowed to be contained in the glass by 0.2% or less as an impurity.

　ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯ：
　ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯは、ガラスの溶解時の粘性を下げ、溶解を促進させ、熱膨張係数を所定の範囲にするために、ＭｇＯ、ＣａＯ、およびＢａＯからなる群から選ばれる少なくとも１種とＳｒＯとの合量（すなわち、（ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ））は、１７％以上が好ましい。１８％以上がより好ましく，１９％以上がさらに好ましい。しかし、合量が３０％超では失透温度が上昇し、成形性が悪くなる恐れがある。そのため、３０％以下が好ましく、２６％以下がより好ましく、２４％以下がさらに好ましい。 MgO, CaO, SrO and BaO:
MgO, CaO, SrO, and BaO are at least one selected from the group consisting of MgO, CaO, and BaO in order to lower the viscosity at the time of melting the glass, promote the melting, and bring the thermal expansion coefficient into a predetermined range. The total amount of SrO and SrO (that is, (MgO + CaO + SrO + BaO)) is preferably 17% or more. 18% or more is more preferable, and 19% or more is more preferable. However, if the total amount exceeds 30%, the devitrification temperature rises and the moldability may be deteriorated. Therefore, 30% or less is preferable, 26% or less is more preferable, and 24% or less is more preferable.

　さらに、上記ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのうちＳｒＯの占める割合は、０．６以上が好ましい。すなわち、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのそれぞれの含有量の合量（以下、これらのアルカリ土類金属酸化物（ＲＯ）の合量を（ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ）とも記す。）に対するＳｒＯの占める割合、すなわち、ＳｒＯ／（ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ）は０．６以上であることが好ましい。０．６以上にすることによって、ＣＩＧＳ太陽電池を作製した時にＮａがガラス上のＣＩＧＳ層へ拡散するのを促進する効果をより強めることができる。より好ましくは０．６５以上であり、さらに好ましくは０．７以上である。 Furthermore, the proportion of SrO in the MgO, CaO, SrO and BaO is preferably 0.6 or more. That is, the ratio of SrO to the total content of MgO, CaO, SrO and BaO (hereinafter, the total content of these alkaline earth metal oxides (RO) is also referred to as (MgO + CaO + SrO + BaO)), that is, SrO / (MgO + CaO + SrO + BaO) is preferably 0.6 or more. By making it 0.6 or more, the effect of promoting the diffusion of Na to the CIGS layer on the glass when the CIGS solar cell is produced can be further enhanced. More preferably, it is 0.65 or more, More preferably, it is 0.7 or more.

　Ｎａ２Ｏ：
　Ｎａ２Ｏは、ＣＩＧＳの太陽電池の発電効率向上に寄与するための成分であり、必須成分である。また、ガラス溶解温度での粘性を下げ、溶解しやすくする効果があるので３～１０％含有させる。Ｎａは、ガラス基板上に構成されたＣＩＧＳ層中に拡散し、発電効率を高めるが、含有量が３％未満ではガラス基板上のＣＩＧＳ層へのＮａ拡散が不十分となり、発電効率も不十分となるおそれがある。含有量が３．５％以上であると好ましく、含有量が４％以上であるとより好ましく、４．５％以上であるとさらに好ましい。
　Ｎａ２Ｏ含有量が１０％を超えると、平均熱膨張係数が所定の範囲から外れ、ガラス転移点温度が低下する傾向がある。または化学的耐久性が劣化する。または、ヤング率が低下するおそれがある。または、過剰なＮａにより、プラス電極として形成されるＭｏ（モリブデン）膜を劣化させて発電効率の低下につながるおそれがある。含有量が９％以下であると好ましく、８％以下であるとより好ましく、７％以下であるとさらに好ましい。 Na 2 O:
Na 2 O is a component that contributes to improving the power generation efficiency of CIGS solar cells, and is an essential component. Further, it has the effect of lowering the viscosity at the glass melting temperature and facilitating melting, so 3 to 10% is contained. Na diffuses into the CIGS layer formed on the glass substrate to increase the power generation efficiency. However, if the content is less than 3%, Na diffusion to the CIGS layer on the glass substrate becomes insufficient, and the power generation efficiency is also insufficient. There is a risk of becoming. The content is preferably 3.5% or more, more preferably 4% or more, and even more preferably 4.5% or more.
When the Na 2 O content exceeds 10%, the average thermal expansion coefficient is out of the predetermined range, and the glass transition temperature tends to decrease. Or chemical durability deteriorates. Alternatively, the Young's modulus may be reduced. Alternatively, excessive Na may deteriorate the Mo (molybdenum) film formed as a positive electrode, leading to a decrease in power generation efficiency. The content is preferably 9% or less, more preferably 8% or less, and even more preferably 7% or less.

　Ｋ２Ｏ：
　Ｋ２Ｏは、Ｎａ２Ｏと同様の効果があるため、また、ＣＩＧＳ太陽電池の製造工程における高温でのＣＩＧＳの結晶成長において、ＣＩＧＳ組成の変化を抑える働きがあり、それにより、短絡電流の低下が抑えられるため２～９．５％含有させる。
　しかし、９．５％超ではガラス転移点温度が低下し、平均熱膨張係数が所定の範囲から外れるおそれがある。または、ヤング率が低下するおそれがある。好ましくは３％以上、より好ましくは３．５％以上、さらに好ましくは４％以上である。また、好ましくは９％以下、より好ましくは８％以下、さらに好ましくは７％以下である。　 K 2 O:
K 2 O has the same effect as Na 2 O, and also has a function of suppressing changes in the CIGS composition in the crystal growth of CIGS at a high temperature in the CIGS solar cell manufacturing process. It is contained in an amount of 2 to 9.5% to prevent the decrease.
However, if it exceeds 9.5%, the glass transition temperature is lowered, and the average thermal expansion coefficient may be out of the predetermined range. Alternatively, the Young's modulus may be reduced. Preferably it is 3% or more, More preferably, it is 3.5% or more, More preferably, it is 4% or more. Further, it is preferably 9% or less, more preferably 8% or less, and further preferably 7% or less.

　本発明のＣＩＧＳ太陽電池用ガラス基板は本質的に上記母組成からなるが、本発明の目的を損なわない範囲でその他の成分を、上記ガラス母組成に対し内割りで、それぞれ１％以下、合計で５％以下含有してもよい。例えば、耐候性、溶解性、失透性、紫外線遮蔽、屈折率等の改善を目的に、ＺｎＯ、Ｌｉ２Ｏ、ＷＯ３、Ｎｂ２Ｏ５、Ｖ２Ｏ５、Ｂｉ２Ｏ３、ＭｏＯ３、Ｐ２Ｏ５等を含有してもよい場合がある。 The glass substrate for CIGS solar cell of the present invention consists essentially of the above-mentioned mother composition, but other components within the range that does not impair the purpose of the present invention are divided by 1% or less in total with respect to the above-mentioned glass mother composition. Or 5% or less. For example, ZnO, Li 2 O, WO 3 , Nb 2 O 5 , V 2 O 5 , Bi 2 O 3 , MoO 3 for the purpose of improving weather resistance, solubility, devitrification, ultraviolet shielding, refractive index, and the like. , P 2 O 5 or the like may be contained.

　また、ガラスの溶解性、清澄性を改善するため、ガラス基板中にＳＯ３、Ｆ、Ｃｌ、ＳｎＯ２などの清澄剤を上記ガラス母組成に対し外割りで、それぞれ１％以下、合量で２％以下含有するように、これらの原料を母組成原料に添加してもよい。
　また、ガラス基板の化学的耐久性向上のため、ガラス基板中にＹ２Ｏ３、Ｌａ２Ｏ３を合量で２％以下含有させてもよい。 In addition, in order to improve the solubility and fining of the glass, fining agents such as SO 3 , F, Cl, SnO 2 are divided into the glass matrix composition, and the total amount is 1% or less, respectively. You may add these raw materials to a mother composition raw material so that it may contain 2% or less.
In order to improve the chemical durability of the glass substrate, Y 2 O 3 and La 2 O 3 may be contained in the glass substrate in a total amount of 2% or less.

　また、ガラスの色調を調整するため、ガラス中にＦｅ２Ｏ３等の着色剤を含有してもよい。このような着色剤の含有量は、合量で１％以下が好ましい。より好ましくは０．１％以下、さらに好ましくは０．０５％以下である。また好ましくは０．００５％以上、より好ましくは０．０１％以上である。
　また、本発明のＣＩＧＳ太陽電池用ガラス基板は、環境負荷を考慮すると、Ａｓ２Ｏ３、Ｓｂ２Ｏ３を実質的に含有しないことが好ましい。また、安定してフロート成形することを考慮すると、ＺｎＯを実質的に含有しないことが好ましい。しかし、本発明のＣＩＧＳ太陽電池用ガラス基板は、フロート法による成形に限らず、フュージョン法等による成形により製造してもよい。 Further, in order to adjust the color tone of the glass, it may contain a colorant such as Fe 2 O 3 in the glass. The total content of such colorants is preferably 1% or less. More preferably, it is 0.1% or less, More preferably, it is 0.05% or less. Further, it is preferably 0.005% or more, more preferably 0.01% or more.
Further, the glass substrate for a CIGS solar cell of the present invention, considering the environmental burden, it is preferred not to contain As 2 O 3, Sb 2 O 3 substantially. In consideration of stable float forming, it is preferable that ZnO is not substantially contained. However, the glass substrate for CIGS solar cell of the present invention may be manufactured not only by the float method but also by the fusion method.

＜本発明のＣＩＧＳ太陽電池用ガラス基板の製造方法＞
　続いて、本発明のＣＩＧＳ太陽電池用ガラス基板の製造方法の一態様について説明する。
　本発明のＣＩＧＳ太陽電池用ガラス基板を製造する場合、従来の太陽電池用ガラス基板を製造する際と同様に、溶解・清澄工程および成形工程を実施する。なお、本発明のＣＩＧＳ太陽電池用ガラス基板は、アルカリ金属酸化物（Ｎａ２Ｏ、Ｋ２Ｏ）を含有するアルカリガラス基板であるため、清澄剤としてＳＯ３を効果的に用いることができ、成形方法としてフロート法およびフュージョン法（ダウンドロー法）に適している。
　太陽電池用のガラス基板の製造工程において、ガラスを板状に成形する方法としては、太陽電池の大型化に伴い、大面積のガラス基板を容易に、安定して成形できるフロート法を用いることが好ましい。 <The manufacturing method of the glass substrate for CIGS solar cells of this invention>
Then, the one aspect | mode of the manufacturing method of the glass substrate for CIGS solar cells of this invention is demonstrated.
When manufacturing the glass substrate for CIGS solar cells of this invention, a melt | dissolution and clarification process and a shaping | molding process are implemented similarly to the time of manufacturing the conventional glass substrate for solar cells. In addition, since the glass substrate for CIGS solar cells of the present invention is an alkali glass substrate containing an alkali metal oxide (Na 2 O, K 2 O), SO 3 can be effectively used as a fining agent, Suitable for the float method and fusion method (down draw method) as the molding method.
In the manufacturing process of a glass substrate for a solar cell, as a method for forming glass into a plate shape, a float method capable of easily and stably forming a large-area glass substrate with the enlargement of the solar cell is used. preferable.

　以下、本発明のＣＩＧＳ太陽電池用ガラス基板の製造方法の好ましい態様について説明する。
　初めに、原料を溶解して得た溶融ガラスを板状に成形する。例えば、得られるガラス基板が上記組成となるように原料を調製し、上記原料を溶解炉に連続的に投入し、１５００～１７００℃に加熱して溶融ガラスを得る。そしてこの溶融ガラスを例えばフロート法を適用してリボン状のガラス板に成形する。
　次に、リボン状のガラス板をフロート成形炉から引出した後に、冷却手段によって室温状態まで冷却し、切断後、ＣＩＧＳ太陽電池用ガラス基板を得る。 Hereinafter, the preferable aspect of the manufacturing method of the glass substrate for CIGS solar cells of this invention is demonstrated.
First, molten glass obtained by melting raw materials is formed into a plate shape. For example, raw materials are prepared so that the obtained glass substrate has the above composition, the raw materials are continuously charged into a melting furnace, and heated to 1500 to 1700 ° C. to obtain molten glass. The molten glass is formed into a ribbon-like glass plate by applying, for example, a float process.
Next, after pulling out the ribbon-shaped glass plate from the float forming furnace, it is cooled to room temperature by a cooling means, and after cutting, a CIGS solar cell glass substrate is obtained.

＜本発明のＣＩＧＳ太陽電池用ガラス基板の用途＞
　本発明のＣＩＧＳ太陽電池用ガラス基板は、ＣＩＧＳ層を形成するガラス基板に限らず、ＣＩＧＳ層が形成された太陽電池素子の表面側を保護するカバーガラス用のガラス基板としても好適である。
　本発明のＣＩＧＳ太陽電池用ガラス基板の厚さは３ｍｍ以下とするのが好ましく、より好ましくは２ｍｍ以下、さらに好ましくは１．５ｍｍ以下である。またガラス基板上にＣＩＧＳ層を形成する方法は特に制限されないが、Ｃｕ、Ｉｎ等を含む金属積層膜をセレン系ガス雰囲気中で熱処理するセレン化法による方法が特に好ましい。本発明のＣＩＧＳ太陽電池用ガラス基板を用いることで、ＣＩＧＳ層を形成する際の加熱温度を５００～７００℃、好ましくは６００～６５０℃とすることができる。
　本発明のＣＩＧＳ太陽電池用ガラス基板を使用した太陽電池素子のカバーガラスは、上記した本発明のＣＩＧＳ太陽電池用ガラス基板を用いてもよいが、この様なガラス基板に限らず、ソーダライムガラス板を用いてもよい。 <Application of CIGS Solar Cell Glass Substrate of the Present Invention>
The glass substrate for CIGS solar cell of the present invention is not limited to the glass substrate on which the CIGS layer is formed, but is also suitable as a glass substrate for cover glass that protects the surface side of the solar cell element on which the CIGS layer is formed.
The thickness of the glass substrate for CIGS solar cell of the present invention is preferably 3 mm or less, more preferably 2 mm or less, and still more preferably 1.5 mm or less. A method for forming a CIGS layer on a glass substrate is not particularly limited, but a selenization method in which a metal laminated film containing Cu, In or the like is heat-treated in a selenium-based gas atmosphere is particularly preferable. By using the glass substrate for CIGS solar cell of the present invention, the heating temperature when forming the CIGS layer can be set to 500 to 700 ° C., preferably 600 to 650 ° C.
The cover glass of the solar cell element using the CIGS solar cell glass substrate of the present invention may use the above-described CIGS solar cell glass substrate of the present invention, but is not limited to such a glass substrate, soda lime glass. A plate may be used.

　なお、本発明のＣＩＧＳ太陽電池用ガラス基板を、ＣＩＧＳ層形成用のガラス基板およびカバーガラスに併用すると、平均熱膨張係数が同等であるため太陽電池組立時の熱変形等が発生せず好ましい。 The CIGS solar cell glass substrate of the present invention is preferably used in combination with a CIGS layer forming glass substrate and a cover glass because the average thermal expansion coefficient is the same, so that no thermal deformation or the like occurs during solar cell assembly.

＜本発明におけるＣＩＧＳ太陽電池＞
　次に、本発明における太陽電池について説明する。
　本発明における太陽電池は、ガラス基板と、カバーガラスと、上記ガラス基板と上記カバーガラスとの間に、光電変換層として配置されるＣＩＧＳ層と、を有し、ＣＩＧＳ層が形成されるガラス基板が少なくとも、上記した本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板である。 <CIGS solar cell in the present invention>
Next, the solar cell in this invention is demonstrated.
The solar cell in the present invention includes a glass substrate, a cover glass, and a CIGS layer disposed as a photoelectric conversion layer between the glass substrate and the cover glass, and a CIGS layer is formed thereon. Is at least the glass substrate for a Cu—In—Ga—Se solar cell of the present invention described above.

　以下、添付の図面を使用して本発明における太陽電池を詳細に説明する。なお本発明は添付の図面に限定されない。
　図１は本発明における太陽電池の実施形態の一例を模式的に表す断面図である。
　図１において、本発明におけるＣＩＧＳ太陽電池１は、ガラス基板５、カバーガラス１９、およびガラス基板５とカバーガラス１９との間にＣＩＧＳ層９を有する。ガラス基板５は、上記で説明した本発明のＣＩＧＳ太陽電池用ガラス基板からなる。太陽電池１は、ガラス基板５上にプラス電極７であるＭｏ膜の裏面電極層を有し、その上にＣＩＧＳ層９を有する。ＣＩＧＳ層の組成は、Ｃｕ（Ｉｎ１－ｘＧａx）Ｓｅ２が例示できる。ｘはＩｎとＧａの組成比を示すもので、０＜ｘ＜１である。
　ＣＩＧＳ層９上には、バッファ層１１としてのＣｄＳ（硫化カドミウム）層、ＺｎＳ（亜鉛硫化物）層、ＺｎＯ（酸化亜鉛）層、Ｚｎ（ＯＨ）２（水酸化亜鉛）層、またはこれらの混晶層を有する。バッファ層を介して、ＺｎＯまたはＩＴＯ、またはＡｌをドープしたＺｎＯ（ＡＺＯ）等の透明導電膜１３を有し、さらにその上にマイナス電極１５であるＡｌ電極（アルミニウム電極）等の取出し電極を有する。これらの層の間の必要な場所には反射防止膜を設けてもよい。図１においては、透明導電膜１３とマイナス電極１５との間に反射防止膜１７が設けられている。 Hereinafter, a solar cell according to the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the attached drawings.
FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of a solar cell in the present invention.
In FIG. 1, the CIGS solar cell 1 in the present invention has a glass substrate 5, a cover glass 19, and a CIGS layer 9 between the glass substrate 5 and the cover glass 19. The glass substrate 5 consists of the glass substrate for CIGS solar cells of this invention demonstrated above. The solar cell 1 has the back electrode layer of Mo film which is the plus electrode 7 on the glass substrate 5, and has the CIGS layer 9 on it. An example of the composition of the CIGS layer is Cu (In 1-x Ga x ) Se 2 . x represents the composition ratio of In and Ga, and 0 <x <1.
On the CIGS layer 9, a CdS (cadmium sulfide) layer, a ZnS (zinc sulfide) layer, a ZnO (zinc oxide) layer, a Zn (OH) 2 (zinc hydroxide) layer as a buffer layer 11, or a mixture thereof. It has a crystal layer. A transparent conductive film 13 such as ZnO, ITO, or Al-doped ZnO (AZO) is provided via a buffer layer, and an extraction electrode such as an Al electrode (aluminum electrode) that is a negative electrode 15 is provided thereon. . An antireflection film may be provided at a necessary place between these layers. In FIG. 1, an antireflection film 17 is provided between the transparent conductive film 13 and the negative electrode 15.

　また、マイナス電極１５上にカバーガラス１９を設けてもよく、必要な場合はマイナス電極とカバーガラスとの間は、樹脂封止される、または接着用の透明樹脂で接着される。カバーガラスには、本発明のＣＩＧＳ層の形成用基板として用いたガラス基板を用いてもよい。
　本発明において、ＣＩＧＳ層の端部または太陽電池の端部は封止されていてもよい。封止するための材料としては、例えば本発明のＣＩＧＳ太陽電池用ガラス基板と同じ材料、そのほかのガラス、樹脂が挙げられる。
　なお添付の図面に示す太陽電池の各層の厚さは図面に限定されない。 Further, a cover glass 19 may be provided on the minus electrode 15, and if necessary, the minus electrode and the cover glass are sealed with a resin or bonded with a transparent resin for bonding. As the cover glass, a glass substrate used as a substrate for forming the CIGS layer of the present invention may be used.
In the present invention, the end of the CIGS layer or the end of the solar cell may be sealed. As a material for sealing, the same material as the glass substrate for CIGS solar cells of this invention, other glass, and resin are mentioned, for example.
Note that the thickness of each layer of the solar cell shown in the accompanying drawings is not limited to the drawings.

　以下、実施例および製造例により本発明をさらに詳しく説明するが、本発明はこれら実施例および製造例に限定されない。
　本発明のＣＩＧＳ太陽電池用ガラス基板の実施例（例１～９）および比較例（例１０～１１）を示す。 EXAMPLES Hereinafter, although an Example and a manufacture example demonstrate this invention in more detail, this invention is not limited to these Examples and a manufacture example.
Examples (Examples 1 to 9) and comparative examples (Examples 10 to 11) of the glass substrate for CIGS solar cell of the present invention are shown.

　表１及び表２で表示した組成になるように各成分の原料を調合し、該ガラス基板用成分の母組成原料１００質量部に対し、硫酸塩をＳＯ３換算で０．１質量部、前記原料に添加し、白金坩堝を用いて１６００℃の温度で３時間加熱し溶解した。溶解にあたっては、白金スターラーを挿入し１時間攪拌しガラスの均質化を行った。次いで溶融ガラスを流し出し、板状に成形後冷却し、ガラス板を得た。
　こうして得られたガラス板の平均熱膨張係数（単位：×１０－７／℃）、ガラス転移点温度Ｔｇ（単位：℃）、密度ｄ（単位：ｇ／ｃｍ３）、ヤング率Ｅ（単位：ＧＰａ）、比弾性率Ｅ／ｄ（単位：ＧＰａ・ｃｍ３／ｇ）、粘度が１０４ｄＰａ・ｓとなる温度（Ｔ４）（単位：℃）、粘度が１０２ｄＰａ・ｓとなる温度（Ｔ２）（単位：℃）、失透温度（ＴＬ）（単位：℃）、発電効率を測定し、表１及び表２に示した。以下に各物性の測定方法を示す。
　なお、実施例では、ガラス板について測定しているが、各物性は、ガラス板とガラス基板とで同じ値である。得られたガラス板を加工、研磨を施すことで、ガラス基板とすることができる。 The raw materials of each component are prepared so as to have the compositions shown in Table 1 and Table 2, and 100 parts by mass of the mother composition raw material of the component for glass substrate, 0.1 parts by mass of sulfate in terms of SO 3 , It added to the raw material, and it melt | dissolved by heating at the temperature of 1600 degreeC for 3 hours using the platinum crucible. In melting, a platinum stirrer was inserted and stirred for 1 hour to homogenize the glass. Next, the molten glass was poured out, formed into a plate shape, and then cooled to obtain a glass plate.
The average thermal expansion coefficient (unit: × 10 −7 / ° C.), glass transition temperature Tg (unit: ° C.), density d (unit: g / cm 3 ), Young's modulus E (unit: unit) of the glass plate thus obtained. GPa), specific elastic modulus E / d (unit: GPa · cm 3 / g), temperature at which viscosity becomes 10 4 dPa · s (T 4 ) (unit: ° C), temperature at which viscosity becomes 10 2 dPa · s (T 2 ) (unit: ° C.), devitrification temperature (T L ) (unit: ° C.), and power generation efficiency were measured and shown in Tables 1 and 2. The measuring method of each physical property is shown below.
In addition, although measured about the glass plate in the Example, each physical property is the same value with a glass plate and a glass substrate. By processing and polishing the obtained glass plate, a glass substrate can be obtained.

（１）Ｔｇ：
Ｔｇは、示差熱膨張計（ＴＭＡ）を用いて測定した値であり、ＪＩＳ　Ｒ３１０３－３（２００１年度）の規格により求めた。
（２）５０～３５０℃の平均熱膨張係数：
平均熱膨張係数は、ＴＭＡを用いて測定し、ＪＩＳ　Ｒ３１０２（１９９５年度）の規格より求めた。 (1) Tg:
Tg is a value measured using a differential thermal dilatometer (TMA), and was obtained according to the standard of JIS R3103-3 (FY2001).
(2) Average thermal expansion coefficient at 50 to 350 ° C .:
The average coefficient of thermal expansion was measured using TMA and determined from the standard of JIS R3102 (1995).

（３）密度：
密度は、ガラス板から切り出した、泡を含まない約２０ｇのガラス塊をアルキメデス法によって測定した。 (3) Density:
The density was measured by Archimedes' method for about 20 g of glass lump that did not contain bubbles and was cut out from the glass plate.

（４）粘度：
粘度は、回転粘度計を用いて測定し、粘度ηが１０２ｄＰａ・ｓとなるときの温度Ｔ２（溶解性の基準温度）と、粘度ηが１０４ｄＰａ・ｓとなるときの温度Ｔ４（成形性の基準温度）を測定した。
（５）失透温度（ＴＬ）：
失透温度は、ガラス板から切り出したガラス塊５ｇを白金皿に置き、所定温度で１７時間電気炉中で保持した。保持した後のガラス塊表面および内部に結晶が析出しない温度の最大値を失透温度とした。
（６）Ｎａ拡散量：
Ｎａ拡散量は、得られたガラス板を太陽電池の基板に用い、以下に示すように評価用太陽電池を作製し、これを用いてＮａ拡散量について評価を行った。
　評価用太陽電池の作製について、図２、３およびその符号を用いて以下説明している。なお、評価用太陽電池の層構成は、図１の太陽電池のカバーガラス１９および反射防止膜１７を有さない以外は、図１に示す太陽電池の層構成とほぼ同様である。
　得られたガラス板を、大きさ３ｃｍ×３ｃｍ、厚さ１．１ｍｍに加工し、ガラス基板を得た。ガラス基板５ａの上に、スパッタ装置にて、プラス電極７ａとしてＭｏ（モリブデン）膜を成膜した。成膜は室温にて実施し、厚み５００ｎｍのＭｏ膜を得た。
　プラス電極７ａ（Ｍｏ膜）上にスパッタ装置にて、ＣｕＧａ合金ターゲットでＣｕＧａ合金層を成膜し、続いてＩｎターゲットを使用してＩｎ層を成膜することで、Ｉｎ－ＣｕＧａのプリカーサ膜を成膜した。成膜は室温にて実施した。蛍光Ｘ線によって測定したプリカーサ膜の組成が、Ｃｕ／（Ｇａ＋Ｉｎ）比が０．８、Ｇａ／（Ｇａ＋Ｉｎ）比が０．２５となるように各層の厚みを調整し、厚み６５０ｎｍのプリカーサ膜を得た。 (4) Viscosity:
The viscosity is measured using a rotational viscometer, and the temperature T 2 when the viscosity η is 10 2 dPa · s and the temperature T when the viscosity η is 10 4 dPa · s. 4 (formability reference temperature) was measured.
(5) Devitrification temperature (T L ):
As for the devitrification temperature, 5 g of a glass lump cut out from a glass plate was placed on a platinum dish and kept in an electric furnace at a predetermined temperature for 17 hours. The maximum temperature at which crystals do not precipitate on the surface and inside of the glass lump after being held was defined as the devitrification temperature.
(6) Na diffusion amount:
The amount of Na diffusion was evaluated by using the obtained glass plate as a solar cell substrate, producing a solar cell for evaluation as shown below, and using this to evaluate the amount of Na diffusion.
The production of the solar cell for evaluation will be described below with reference to FIGS. The layer configuration of the solar cell for evaluation is substantially the same as the layer configuration of the solar cell shown in FIG. 1 except that it does not have the cover glass 19 and the antireflection film 17 of the solar cell in FIG.
The obtained glass plate was processed into a size of 3 cm × 3 cm and a thickness of 1.1 mm to obtain a glass substrate. On the glass substrate 5a, a Mo (molybdenum) film was formed as a plus electrode 7a by a sputtering apparatus. Film formation was performed at room temperature to obtain a Mo film having a thickness of 500 nm.
On the positive electrode 7a (Mo film), a CuGa alloy layer is formed with a CuGa alloy target by a sputtering apparatus, and then an In layer is formed using an In target, whereby an In—CuGa precursor film is formed. A film was formed. Film formation was performed at room temperature. The thickness of each layer was adjusted so that the composition of the precursor film measured by fluorescent X-rays was Cu / (Ga + In) ratio of 0.8 and Ga / (Ga + In) ratio of 0.25. Obtained.

　プリカーサ膜をＲＴＡ（Ｒａｐｉｄ　Ｔｈｅｒｍａｌ　Ａｎｎｅａｌｉｎｇ）装置を用いてアルゴンおよびセレン化水素混合雰囲気（セレン化水素はアルゴンに対し５体積％、「セレン雰囲気」と呼ぶ）にて加熱処理した。 The precursor film was heat-treated using a RTA (Rapid Thermal Annealing) apparatus in a mixed atmosphere of argon and hydrogen selenide (hydrogen selenide is 5% by volume with respect to argon, referred to as “selenium atmosphere”).

　条件としては、まず、第１段階としてセレン雰囲気で５００℃で１０分保持を行い、ＣｕおよびＩｎおよびＧａとＳｅとを反応させて、その後、第２段階として硫化水素雰囲気（硫化水素はアルゴンに対し５体積％）に置換した後、さらに５８０℃で３０分保持してＣＩＧＳ結晶を成長させることでＣＩＧＳ層９ａを得た。得られたＣＩＧＳ層９ａの厚みは２μｍであった。 As conditions, first, hold at 500 ° C. for 10 minutes in a selenium atmosphere as a first stage, react Cu, In, Ga and Se, and then a hydrogen sulfide atmosphere (hydrogen sulfide into argon as a second stage). Then, the CIGS layer 9a was obtained by growing the CIGS crystal by holding at 580 ° C. for 30 minutes. The thickness of the obtained CIGS layer 9a was 2 μm.

　ＣＩＧＳ層９ａ上にＣＢＤ(Ｃｈｅｍｉｃａｌ　Ｂａｔｈ　Ｄｅｐｏｓｉｔｉｏｎ)法にて、バッファ層１１ａとしてＣｄＳ層を成膜した。具体的には、まず、ビーカー内で、濃度０．０１Ｍの硫酸カドミウム、濃度１．０Ｍのチオウレア、濃度１５Ｍのアンモニア、および純水を混合させた。次に、ＣＩＧＳ層を前記混合液に浸し、ビーカーごと予め水温を７０℃にしておいた恒温バス槽に入れ、ＣｄＳ層を５０～８０ｎｍ成膜した。
　さらにＣｄＳ層上にスパッタ装置にて、透明導電膜１３ａを以下の方法で成膜した。まず、ＺｎＯターゲットを使用してＺｎＯ層を成膜し、次に、ＡＺＯターゲット（すなわち、Ａｌ２Ｏ３を１．５ｗｔ％含有するＺｎＯターゲット）を使用してＡＺＯ層を成膜した。各層の成膜は室温にて実施し、厚み４８０ｎｍの２層構成の透明導電膜１３ａを得た。
　透明導電膜１３ａのＡＺＯ層上にＥＢ蒸着法により、Ｕ字型のマイナス電極１５ａとして膜厚１μｍのアルミ膜を成膜した（ここにおいて、Ｕ字の電極長は、縦８ｍｍ、横４ｍｍ、電極幅は、０．５ｍｍ）。 A CdS layer was formed as the buffer layer 11a on the CIGS layer 9a by the CBD (Chemical Bath Deposition) method. Specifically, first, cadmium sulfate having a concentration of 0.01M, thiourea having a concentration of 1.0M, ammonia having a concentration of 15M, and pure water were mixed in a beaker. Next, the CIGS layer was immersed in the mixed solution, and the beaker was placed in a constant temperature bath with a water temperature of 70 ° C. in advance to form a CdS layer having a thickness of 50 to 80 nm.
Further, a transparent conductive film 13a was formed on the CdS layer by a sputtering apparatus by the following method. First, a ZnO layer was formed using a ZnO target, and then an AZO layer was formed using an AZO target (that is, a ZnO target containing 1.5 wt% Al 2 O 3 ). Each layer was formed at room temperature to obtain a transparent conductive film 13a having a two-layer structure having a thickness of 480 nm.
An aluminum film having a thickness of 1 μm was formed as a U-shaped negative electrode 15a on the AZO layer of the transparent conductive film 13a by EB vapor deposition (where the U-shaped electrode length is 8 mm in length, 4 mm in width, electrode The width is 0.5 mm).

　最後に、メカニカルスクライブによって透明導電膜１３ａ側からＣＩＧＳ層９ａまでを削り、図２に示すようなセル化を行った。図２（ａ）は、１つの太陽電池セルを上面から見た図であり、図２（ｂ）は、図２（ａ）中のＡ－Ａ’の断面図である。一つのセルは幅０．６ｃｍ、長さ１ｃｍで、マイナス電極１５ａを除いた面積が０．５ｃｍ２であり、図３に示すように、合計８個のセルが１枚のガラス基板５ａ上に得られた。
　ソーラーシミュレータ（山下電装株式会社製、ＹＳＳ－Ｔ８０Ａ）に、評価用ＣＩＧＳ太陽電池（上記８個のセルを作製した評価用ガラス基板５ａ）を設置し、あらかじめＩｎＧａ溶剤を塗布したプラス電極７ａにプラス端子を（不図示）、マイナス電極１５ａのＵ字の下端にマイナス端子１６ａをそれぞれ電圧発生器に接続した。ソーラーシミュレータ内の温度は２５℃一定に温度調節機にて制御した。疑似太陽光を照射し、６０秒後に、電圧を－１Ｖから＋１Ｖまで０．０１５Ｖ間隔で変化させ、８個のセルのそれぞれの電流値を測定した。 Finally, from the transparent conductive film 13a side to the CIGS layer 9a was scraped by mechanical scribing, and a cell was formed as shown in FIG. 2A is a view of one solar battery cell as viewed from above, and FIG. 2B is a cross-sectional view taken along line AA ′ in FIG. 2A. One cell has a width of 0.6 cm and a length of 1 cm, and the area excluding the negative electrode 15a is 0.5 cm 2. As shown in FIG. 3, a total of eight cells are placed on one glass substrate 5a. Obtained.
A CIGS solar cell for evaluation (evaluation glass substrate 5a on which the above eight cells were prepared) was installed in a solar simulator (YSS-T80A manufactured by Yamashita Denso Co., Ltd.) and added to the positive electrode 7a previously coated with InGa solvent. A terminal (not shown) was connected to the voltage generator at the lower end of the U-shape of the negative electrode 15a. The temperature in the solar simulator was controlled at a constant temperature of 25 ° C. with a temperature controller. Pseudo sunlight was irradiated, and after 60 seconds, the voltage was changed from -1 V to +1 V at an interval of 0.015 V, and the current values of each of the eight cells were measured.

　この照射時の電流と電圧特性から発電効率を下記式（２）により算出した。８個のセルのうち最も効率の良いセルの値を、各ガラス基板の発電効率の値として表１、２に示す。試験に用いた光源の照度は０．１Ｗ／ｃｍ２であった。 The power generation efficiency was calculated by the following formula (2) from the current and voltage characteristics during irradiation. Tables 1 and 2 show the value of the most efficient cell among the eight cells as the value of the power generation efficiency of each glass substrate. The illuminance of the light source used for the test was 0.1 W / cm 2 .

　　発電効率［％］＝Ｖｏｃ［Ｖ］×Ｊｓｃ［Ａ／ｃｍ2］×ＦＦ［無次元］×１００／試験に用いる光源の照度［Ｗ／ｃｍ2］　　　　……　式（２） Power generation efficiency [%] = V oc [V] × J sc [A / cm 2 ] × FF [dimensionless] × 100 / illuminance [W / cm 2 ] of the light source used in the test (2)

　発電効率は、開放電圧（Ｖｏｃ）と短絡電流密度（Ｊｓｃ）と曲線因子（ＦＦ）の掛け算で求められる。
　なお、開放電圧（Ｖｏｃ）は、端子を開放した時の出力であり、短絡電流（Ｉｓｃ）は短絡した時の電流である。短絡電流密度（Ｊｓｃ）は、Ｉｓｃをマイナス電極を除いたセルの面積で割ったものである。
　また最大の出力を与える点が最大出力点と呼ばれ、その点の電圧が最大電圧値（Ｖｍａｘ）、電流が最大電流値（Ｉｍａｘ）と呼ばれる。最大電圧値（Ｖｍａｘ）と最大電流値（Ｉｍａｘ）の掛け算の値を、開放電圧（Ｖｏｃ）と短絡電流（Ｉｓｃ）の掛け算の値で割った値が曲線因子（ＦＦ）として求められる。上記の値を使用し、発電効率を求めた。 The power generation efficiency is obtained by multiplying the open circuit voltage (V oc ), the short circuit current density (J sc ), and the fill factor (FF).
The open circuit voltage (V oc ) is an output when the terminal is opened, and the short circuit current (I sc ) is a current when the terminal is short circuited. The short-circuit current density (J sc ) is I sc divided by the area of the cell excluding the negative electrode.
The point that gives the maximum output is called the maximum output point, the voltage at that point is called the maximum voltage value (V max ), and the current is called the maximum current value (I max ). A value obtained by dividing the product of the maximum voltage value (V max ) and the maximum current value (I max ) by the product of the open circuit voltage (V oc ) and the short circuit current (I sc ) is obtained as a fill factor (FF). It is done. Using the above values, the power generation efficiency was determined.

　ここで、ＣＩＧＳ層へのアルカリ金属元素の拡散に対するガラス基板の効果を観察するために、Ｎａ拡散量を測定した。測定方法は以下のとおりである。
　上記ＲＴＡ装置による加熱の第２段階終了後、試料を二次イオン質量分析法（ＳＩＭＳ）にてＣＩＧＳ膜中の２３Ｎａの積分強度を測定する。なお、表１及び表２に記載した値は、例１０を１００とした時の相対量である。例１０と比較したＮａ拡散量が６０以上であればＮａ拡散量が多く、高い発電効率を有する太陽電池に適したガラス基板であるということができる。 Here, the amount of Na diffusion was measured in order to observe the effect of the glass substrate on the diffusion of the alkali metal element into the CIGS layer. The measurement method is as follows.
After completion of the second stage of heating by the RTA apparatus, the sample is measured for the integrated intensity of 23 Na in the CIGS film by secondary ion mass spectrometry (SIMS). The values listed in Tables 1 and 2 are relative amounts when Example 10 is taken as 100. If Na diffusion amount compared with Example 10 is 60 or more, it can be said that it is a glass substrate suitable for a solar cell with much Na diffusion amount and high power generation efficiency.

　本実施例におけるガラス中のＳＯ３残存量は１００～５００ｐｐｍであった。
　なお、ガラス組成物中のＳＯ３の残存量は、ガラス板から切り出したガラスの塊を粉末状にして蛍光Ｘ線で評価し、測定した。 The SO 3 remaining amount in the glass in this example was 100 to 500 ppm.
In addition, the residual amount of SO 3 in the glass composition was measured by measuring a glass lump cut out from a glass plate in a powder form and evaluating with fluorescent X-rays.

Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

　表１及び表２より明らかなように、実施例（例１～９）のガラス基板は、
　　　ＳｉＯ２を４５～７０％、
　　　Ａｌ２Ｏ３を１０～２０％、
　　　Ｂ２Ｏ３を０～０．５％、
　　　ＭｇＯを０～６％、
　　　ＣａＯを０～４％未満、
　　　ＳｒＯを９．５～２０％、
　　　ＢａＯを０～５％、
　　　ＺｒＯ２を０～８％、
　　　Ｎａ２Ｏを３～１０％、
　　　Ｋ２Ｏを２～９．５％、
含有する組成を満たしているためＣＩＧＳ太陽電池を作製した時に、ガラス上のＣＩＧＳ層へ拡散するＮａ量が多く、太陽電池用ガラス基板の特性をバランスよく有している。
　加えて、ガラス転移点温度Ｔｇが６４０℃以上と高く、平均熱膨張係数が６０×１０－７～１１０×１０-7／℃であり、密度が２．９ｇ／ｃｍ３以下である。
　したがって、高い発電効率、高いガラス転移点温度、所定の平均熱膨張係数、をバランスよく有することができる。そのため、ＣＩＧＳ光電変換層がＭｏ膜付ガラス基板から剥離することがなく、さらに本発明における太陽電池を組立てる際（具体的にはＣＩＧＳの光電変換層を有するガラス基板とカバーガラスとを加熱してはりあわせる際）、ガラス基板が変形しにくく発電効率により優れる。 As is clear from Tables 1 and 2, the glass substrates of Examples (Examples 1 to 9)
45 to 70% of SiO 2
10-20% Al 2 O 3
B 2 O 3 from 0 to 0.5%,
0-6% MgO
CaO 0-4%,
9.5-20% of SrO,
BaO 0-5%,
ZrO 2 0-8%,
3-10% Na 2 O,
2 to 9.5% of K 2 O,
When the CIGS solar cell is manufactured because the composition contained is satisfied, the amount of Na diffused into the CIGS layer on the glass is large, and the characteristics of the glass substrate for solar cell are well balanced.
In addition, the glass transition temperature Tg is as high as 640 ° C. or higher, the average thermal expansion coefficient is 60 × 10 −7 to 110 × 10 −7 / ° C., and the density is 2.9 g / cm 3 or lower.
Therefore, it is possible to have a high power generation efficiency, a high glass transition temperature, and a predetermined average thermal expansion coefficient in a well-balanced manner. Therefore, the CIGS photoelectric conversion layer does not peel from the glass substrate with the Mo film, and when the solar cell in the present invention is further assembled (specifically, the glass substrate having the CIGS photoelectric conversion layer and the cover glass are heated). When bonding), the glass substrate is less likely to deform and has better power generation efficiency.

　一方、表１が示すように比較例（例１０）のガラス基板はＴｇが低く、６００℃以上での成膜時にガラス基板が変形しやすいため適していない。
　また、比較例（例１１）のガラス基板はＳｒＯが少なく、発電効率の高さの一因となるＣＩＧＳ層へのＮａの拡散を促進する効果が不十分であるため適していない。 On the other hand, as shown in Table 1, the glass substrate of the comparative example (Example 10) has a low Tg and is not suitable because the glass substrate is easily deformed during film formation at 600 ° C. or higher.
Further, the glass substrate of the comparative example (Example 11) is not suitable because it has a small amount of SrO and has an insufficient effect of promoting the diffusion of Na into the CIGS layer, which contributes to high power generation efficiency.

　本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板は、ＣＩＧＳの太陽電池用のガラス基板として好適である。 The glass substrate for a Cu—In—Ga—Se solar cell of the present invention is suitable as a glass substrate for a CIGS solar cell.

　本発明のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板は、高い発電効率、高いガラス転移点温度、所定の平均熱膨張係数、高いガラス強度、低いガラス密度、板ガラス生産時の溶解性、成形性、および失透防止の特性をバランスよく有することができ、本発明のＣＩＧＳ太陽電池用ガラス基板を用いることで発電効率の高い太陽電池を提供できる。
　なお、２０１２年８月６日に出願された日本特許出願２０１２－１７３６９８号の明細書、特許請求の範囲、図面および要約書の全内容をここに引用し、本発明の開示として取り入れるものである。 The glass substrate for a Cu—In—Ga—Se solar cell of the present invention has high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, solubility during production of sheet glass, molding Therefore, it is possible to provide a solar cell with high power generation efficiency by using the CIGS solar cell glass substrate of the present invention.
The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2012-173698 filed on August 6, 2012 are incorporated herein by reference. .

１　太陽電池
５、５ａ　ガラス基板
７、７ａ　プラス電極
９、９ａ　ＣＩＧＳ層
１１、１１ａ　バッファ層
１３、１３ａ　透明導電膜
１５、１５ａ　マイナス電極
１７　反射防止膜
１９　カバーガラス DESCRIPTION OF SYMBOLS 1 Solar cell 5, 5a Glass substrate 7, 7a Positive electrode 9, 9a CIGS layer 11, 11a Buffer layer 13, 13a Transparent conductive film 15, 15a Negative electrode 17 Antireflection film 19 Cover glass

Claims (9)

　酸化物基準の質量百分率表示で、
　　　ＳｉＯ２を４５～７０％、
　　　Ａｌ２Ｏ３を１０～２０％、
　　　Ｂ２Ｏ３を０～０．５％、
　　　ＭｇＯを０～６％、
　　　ＣａＯを０～４％未満、
　　　ＳｒＯを９．５～２０％、
　　　ＢａＯを０～５％、
　　　ＺｒＯ２を０～８％、
　　　Ｎａ２Ｏを３～１０％、
　　　Ｋ２Ｏを２～９．５％、
含有するＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 In mass percentage display based on oxide,
45 to 70% of SiO 2
10-20% Al 2 O 3
B 2 O 3 from 0 to 0.5%,
0-6% MgO
CaO 0-4%,
9.5-20% of SrO,
BaO 0-5%,
ZrO 2 0-8%,
3-10% Na 2 O,
2 to 9.5% of K 2 O,
A glass substrate for a Cu—In—Ga—Se solar cell containing the glass substrate. 　ガラス転移点温度が６４０℃～７００℃である、請求項１に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 The glass substrate for a Cu-In-Ga-Se solar cell according to claim 1, having a glass transition temperature of 640 ° C to 700 ° C. 　平均熱膨張係数が６０×１０－７～１１０×１０－７／℃である、請求項１または２に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 3. The glass substrate for a Cu—In—Ga—Se solar cell according to claim 1, wherein an average coefficient of thermal expansion is 60 × 10 −7 to 110 × 10 −7 / ° C. 　密度が２．９ｇ／ｃｍ３以下である、請求項１～３のいずれか１項に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 The glass substrate for a Cu-In-Ga-Se solar cell according to any one of claims 1 to 3, wherein the density is 2.9 g / cm 3 or less. 　酸化物基準の質量百分率表示で、ＳｒＯ／（ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ）が０．６以上である請求項１～４のいずれか１項に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 The glass substrate for a Cu-In-Ga-Se solar cell according to any one of claims 1 to 4, wherein SrO / (MgO + CaO + SrO + BaO) is 0.6 or more in terms of oxide-based mass percentage. 　前記ガラス基板の母組成原料１００質量部に対し、ＴｉＯ２の含有量が０．２％以下である請求項１～５のいずれか１項に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 The glass for a Cu-In-Ga-Se solar cell according to any one of claims 1 to 5, wherein a content of TiO 2 is 0.2% or less with respect to 100 parts by mass of a mother composition raw material of the glass substrate. substrate. 　酸化物基準の質量百分率表示で、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯの含有量の和が１７％以上、３０％以下である請求項１～６のいずれか１項に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板。 The glass substrate for a Cu-In-Ga-Se solar cell according to any one of claims 1 to 6, wherein the sum of the contents of MgO + CaO + SrO + BaO is 17% or more and 30% or less in terms of mass percentage based on oxide. . 　ガラス基板と、カバーガラスと、前記ガラス基板と前記カバーガラスとの間に配置されるＣｕ－Ｉｎ－Ｇａ－Ｓｅの光電変換層と、を有し、前記ガラス基板が、請求項１～７のいずれか１項に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板であるＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池。 8. A glass substrate, a cover glass, and a Cu—In—Ga—Se photoelectric conversion layer disposed between the glass substrate and the cover glass, wherein the glass substrate comprises: A Cu—In—Ga—Se solar cell, which is the glass substrate for a Cu—In—Ga—Se solar cell according to any one of the items. 　前記カバーガラスが請求項１～７のいずれか１項に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池用ガラス基板である請求項８に記載のＣｕ－Ｉｎ－Ｇａ－Ｓｅ太陽電池。 The Cu-In-Ga-Se solar cell according to claim 8, wherein the cover glass is a glass substrate for a Cu-In-Ga-Se solar cell according to any one of claims 1 to 7.
PCT/JP2013/071172 2012-08-06 2013-08-05 GLASS SUBSTRATE FOR Cu-In-Ga-Se SOLAR CELL, AND SOLAR CELL USING SAME WO2014024850A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10683231B2 (en) 2015-03-26 2020-06-16 Pilkington Group Limited Glasses

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009054419A1 (en) * 2007-10-25 2009-04-30 Asahi Glass Company, Limited Glass composition for substrate and method for producing the same
JP2010143790A (en) * 2008-12-19 2010-07-01 Nippon Electric Glass Co Ltd Method for producing glass substrate for solar cell

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009054419A1 (en) * 2007-10-25 2009-04-30 Asahi Glass Company, Limited Glass composition for substrate and method for producing the same
JP2010143790A (en) * 2008-12-19 2010-07-01 Nippon Electric Glass Co Ltd Method for producing glass substrate for solar cell

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10683231B2 (en) 2015-03-26 2020-06-16 Pilkington Group Limited Glasses

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