WO2012102476A2 - Solar cell apparatus and method of fabricating the same - Google Patents

Solar cell apparatus and method of fabricating the same Download PDF

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Publication number
WO2012102476A2
WO2012102476A2 PCT/KR2011/009147 KR2011009147W WO2012102476A2 WO 2012102476 A2 WO2012102476 A2 WO 2012102476A2 KR 2011009147 W KR2011009147 W KR 2011009147W WO 2012102476 A2 WO2012102476 A2 WO 2012102476A2
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layer
solar cell
electrode layer
backside electrode
cell according
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PCT/KR2011/009147
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French (fr)
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WO2012102476A3 (en
Inventor
Jung Hwan Gho
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Lg Innotek Co., Ltd.
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Priority to EP11856848.4A priority Critical patent/EP2668668A2/en
Priority to CN201180066301.9A priority patent/CN103339741B/en
Publication of WO2012102476A2 publication Critical patent/WO2012102476A2/en
Publication of WO2012102476A3 publication Critical patent/WO2012102476A3/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0392—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03923—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate including AIBIIICVI compound materials, e.g. CIS, CIGS
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0392—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03926—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate
    • H01L31/03928—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate including AIBIIICVI compound, e.g. CIS, CIGS deposited on metal or polymer foils
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type
    • H01L31/0749—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1892—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
    • H01L31/1896—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates for thin-film semiconductors
    • 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 solar cell apparatus and a method of fabricating the same.
  • a CIGS-base solar cell that is, p-n hetero junction device having a substrate structure including a glass substrate, a metal backside electrode layer, p-type CIGS-base light absorption layer, a buffer layer, n-type transparent electrode layer and the like is widely used.
  • the material included in the substrate during high temperature process such as light absorption layer forming may be diffused into the light absorption layer, thereby lowering the efficiency of the solar cell.
  • a CIGS film forming process grown at high temperatures proceeds using the glass as the growth substrate, and the sacrificial layer formed on the rigid glass substrate is removed by the electrolysis method.
  • an advantage of some aspects of the invention is that the bonding layer and the flexible substrate are formed under the backside electrode layer, thereby providing the solar cell having excellent curve and improved photoelectric conversion efficiency and reliability.
  • the solar cell according to the embodiment includes a backside electrode layer, a light absorption layer on the backside electrode layer, a buffer layer on the light absorption layer, a window layer on the buffer layer, and a bonding layer under the backside electrode layer.
  • a method of fabricating a solar cell includes forming a sacrificial layer on a growth substrate; forming a backside electrode layer on the sacrificial layer; forming a light absorption layer on the backside electrode layer; forming a top electrode layer on the light absorption layer; forming a sheet above the top electrode layer; and removing the sacrificial layer so that a bottom surface of the backside electrode layer is exposed by performing the electrolysis on the solar cell.
  • a solar cell and a method of fabricating the same having flexibility and improved photoelectric conversion efficiency and reliability is provided.
  • FIG. 1 is a section view of a solar cell according to an embodiment of the present invention.
  • FIGS. 2 to 7 show the method of fabricating the solar cell according to an embodiment of the present invention.
  • FIG. 1 is a section view showing a solar cell according to an embodiment of the present invention.
  • FIGS. 2 to 7 show the method of fabricating the solar cell according to an embodiment of the present invention.
  • the solar cell according to the embodiment includes a substrate 110, a bonding layer 250 on the substrate 110, a backside electrode layer 200 on the bonding layer 250, a light absorption layer 300 on the backside electrode layer 200, a buffer layer 400 and a high-resistant buffer layer 500 on the light absorption layer 300, a window layer 600 on the high-resistant buffer layer 500, and a first protection layer 700 on the window layer 600.
  • a second protection layer 800 may be formed under the substrate 110.
  • the substrate 110 has a plate shape, and supports the backside electrode layer 200, the light absorption layer 300, the buffer layer 400, the high-resistant buffer layer 500 and the window layer 600.
  • the substrate 110 may be a flexible substrate such as PET(polyethylene terephthalate), but is not limited thereto.
  • the backside electrode layer 200 is arranged on the substrate 110.
  • the backside electrode layer 200 becomes a conductive layer.
  • the backside electrode layer 200 allows charges produced from the light absorption layer 300 of the solar cell to move, such that current may flow outside the solar cell.
  • the backside electrode layer 200 needs to have high electricalconductivity and small specific resistance to perform above function.
  • the backside electrode layer 200 should be maintained to have high temperature stability when heat-treating under the atmosphere of sulfur(S) or selenium(Se) accompanied in forming CIGS compound.
  • Such a backside electrode layer 200 may be formed by any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W) and copper (Cu) Among them, particularly, the molybdenum (Mo) enables the characteristic required for the backside electrode layer 200 to generally satisfy as compared with other element.
  • Mo molybdenum
  • Au gold
  • Al aluminum
  • Cr chromium
  • W tungsten
  • Cu copper
  • Mo molybdenum
  • the backside electrode layer 200 may include at least two layers. In this case, each layer may be formed by same metals or metals different from each other.
  • the portion of a sacrificial layer 105(refer to FIG. 3) may remain under the backside electrode layer 200.
  • some of metallic crystals of the Cu may be present under the backside electrode layer 200.
  • a second protection layer 800 may be formed under the substrate 110.
  • the second protection layer 800 acts a role to protect the solar cell against water and air of the outside.
  • the second protection layer 800 may be formed by a polymer layer.
  • the second protection layer 800 for example, including material such as PVF, polyester, acrylic, EVA may be formed.
  • the backside electrode layer 200 may be directly connected to the second protection layer 800 without forming the substrate 110.
  • the light absorption layer 300 may be formed on the backside electrode layer 200.
  • the light absorption layer 300 includes p-type semiconductor compound.
  • the light absorption layer 300 includes group I-III-VI?base compound.
  • the light absorption layer 300 may has Cu-In-Ga-Se-base(Cu(In,Ga)Se 2 ;CIGS-base) or Cu-Ga-Se-base crystal structure.
  • the buffer layer 400 and the high-resistant buffer layer 500 may be formed on the light absorption layer 300.
  • the solar cell having CIGS compound as the light absorption layer 300 forms p-n junction between a p-type semiconductor, that is, a CIGS compound thin film and a n-type semiconductor, that is, a window layer 600 thin film.
  • the material forming the buffer layer 400 is CdS, ZnS and the like, the CdS is a relatively good in terms of power generation efficiency of the solar cell.
  • the high-resistant buffer layer 500 includes zinc oxide(i-ZnO) not doped with impurity.
  • the energy bandgap of the high-resistant buffer layer 500 is about 3.1eV to 3.3eV.
  • the window 600 is formed on the high-resistant buffer layer 500.
  • the window layer 600 is transparent and a conductive layer. Further, resistance of the window layer 600 is higher than that of the backside electrode layer 200.
  • the window layer 600 includes oxide.
  • the window layer 600 may include zinc oxide, indium tin oxide; ITO or indium zinc oxide; IZO and the like.
  • the oxide may include conductive impurities such as aluminum(Al), alumina(Al 2 O 3 ), magnesium(Mg) or gallium(Ga).
  • the window layer 600 may include Al doped zinc oxide; AZO, B doped zinc oxide; BZO or Ga doped zinc oxide; GZO.
  • the first protection layer 700 and the second protection layer 800 may be formed on the top and bottom surface of the solar cell.
  • FIGS. 2 to 7 are sectional views showing the method of fabricating the solar cell according to an embodiment of the present invention.
  • the description regarding the present fabricating method refers to the descrition regarding the solar cell described previously.
  • the sacrificial layer 105 grows on a growth substrate 100.
  • the growth substrate 100 may be an insulator.
  • the growth substrate 100 may be a glass substrate.
  • the growth substrate 100 may be a soda lime glass substrate.
  • the growth substrate 100 becomes a soda lime glass
  • Na contained in the soda lime glass may be diffused into the light absorption layer 300 formed by the CIGS during the fabricating process of the solar cell, which allows charge concentration of the light absorption layer 300 to increase. That may become a factor that may increase photoelectric conversion efficiency of the solar cell.
  • a ceramic substrate such as alumina, stainless steel, flexible polymer and the like are used as the material of the growth substrate 100.
  • the growth substrate 100 may be transparent and rigid or flexible.
  • the sacrificial layer 105 may include a metal.
  • the sacrificial layer 105 may include elements such as Cu, Ag, Au and the like.
  • the backside electrode layer 200 is formed on the sacrificial layer 105.
  • the backside electrode layer 200 may be formed by any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W) and copper (Cu).
  • Mo molybdenum
  • Au gold
  • Al aluminum
  • Cr chromium
  • W tungsten
  • Cu copper
  • the backside electrode layer 200 may include at least two layers. In this case, each layer may be formed by same metals or metals different from each other.
  • the backside electrode layer 200 may be formed by PVD(Physical Vapor Deposition) or plating.
  • the light absorption layer 300 is formed on the backside electrode layer 200.
  • the light absorption layer 300 is widely fabricated by the method forming the light absorption layer 300 of Cu-In-Ga-Se-base(Cu(In,Ga)Se 2 ;CIGS-base) while simultaneously or separately evaporating, for example, Cu, In, Ga and Se, and the method using a selenization process after forming a metal precursor film.
  • the metal precursor film is formed on the backside electrode layer 200 by a sputtering process using Cu target, In target and Ga target.
  • the metal precursor film becomes the light absorption layer 300 of Cu-In-Ga-Se-base(Cu(In,Ga)Se 2 ;CIGS-base) by the selenization process.
  • the sputtering process using the Cu target, the In target and the Ga target is simultaneously performed with the selenization process.
  • CIS-base or CIG-base light absorption layer 300 may be formed by the sputtering process using only the Cu target and the In target or the Cu target and the Ga target, and the selenization process.
  • cadmium sulfide is deposited by the sputtering process and a chemical bath depositon(CBD) method and the like to form the buffer layer 400.
  • the zinc oxide is deposited on the buffer layer 400 by the sputtering process to form the high-resistant buffer layer 500.
  • the buffer layer 400 and the high-resistant buffer layer 500 are deposited to a small thickness.
  • a thickness of the buffer layer 400 and the high-resistant buffer layer 500 is about 1nm to 100nm.
  • the window 600 is formed on the high-resistant buffer layer 500. That is, the window layer 600 is formed by depositing transparent conductive material on the high-resistant buffer layer 500. In detail, the window layer 600 may be formed by depositing the zinc oxide doped with the aluminum, but is not limited thereto.
  • the first protection layer 700 is formed on the window 600.
  • the first protection layer 700 may be formed by a deposition method.
  • the first protection layer 700 includes EVA sheets to prevent damage for the panel of the solar cell when performing electrolys is.
  • the aqueous solution may be formed depending on the material included to the sacrificial layer 105 in the embodiment of the present invention.
  • the aqueous solution may use copper sulfate (Cu 2 SO 4 ) contained with the copper (Cu).
  • an anode (+) thereof is connected to the backside electrode layer 200 and a cathode is connected to a separate metal plate 107 spaced apart from the solar cell, thereby performing the electrolysis.
  • the sacrificial layer 105 contained with the metal is difficult to perform the electrolysis, and therefore, it is preferable to connect the anode to the backside electrode layer 200.
  • the sacrificial layer 105 is etched by the electrolysis, such that the sacrificial layer 105 and the growth substrate 100 are separated from the backside electrode layer 200.
  • the sacrificial layer 105 is etched by the electrolysis, but some of sacrificial layer 105 as the crystal form may remain in the backside electrode layer 200.
  • FIG. 6 is a sectional view showing the solar cell after removing the sacrificial layer 105 by the electrolysis.
  • the backside electrode layer 200 is exposed by the electrolysis process. Some of he material included in the sacrificial layer 105 may remain, for example, as the crystal form under the backside electrode layer 200.
  • a bonding agent is applied below the backside electrode layer 200 to form the bonding layer 250.
  • the bonding layer 250 allows adhesion of the backside electrode layer 200 and the substrate 110 to improve.
  • the bonding layer 250 may be formed using polymeric material such as epoxy or ceramic series bond.
  • the substrate 110 may be a flexible substrate such as PET(polyethylene terephthalate), but is not limited thereto. Further, the substrate 110 may not be formed.
  • the second protection layer 800 may be formed under the substrate 110.
  • the second protection layer 800 may protect the solar cell from the outside, and may be formed by the same or different material as the first protection layer 700.
  • the first and second protection layer 800 may be composed of Siloxane, PDAS(poly dialkyl siloxane) or film types of EVA(Ethylene Vinyl Acetate).
  • the backside electrode layer 200 may contact the second protection layer 800.
  • a CIGS film forming process grown at high temperatures proceeds using the glass as the growth substrate, and the sacrificial layer 105 formed on the rigid glass substrate is removed by the electrolysis method.
  • the bonding layer 250 and the flexible substrate 110 are formed under the backside electrode layer 200, thereby providing the solar cell having excellent curve and improved photoelectric conversion efficiency and reliability.

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Abstract

The solar cell according to the embodiment includes a backside electrode layer, a light absorption layer on the backside electrode layer, a buffer layer on the light absorption layer, a window layer on the buffer layer, and a bonding layer under the backside electrode layer.

Description

SOLAR CELL APPARATUS AND METHOD OF FABRICATING THE SAME
The present invention relates to a solar cell apparatus and a method of fabricating the same.
In recent, as the demand of the energy increases, developments for the solar cell converting solar energy into electrical energy are proceeding.
Particularly, a CIGS-base solar cell, that is, p-n hetero junction device having a substrate structure including a glass substrate, a metal backside electrode layer, p-type CIGS-base light absorption layer, a buffer layer, n-type transparent electrode layer and the like is widely used.
Further, to increase the efficiency of the solar cell, various researches are proceeding.
In general, when forming the solar cell on the growth substrate containing metal foil material, as the forming process proceeds, the material included in the substrate during high temperature process such as light absorption layer forming may be diffused into the light absorption layer, thereby lowering the efficiency of the solar cell.
Accordingly, in this embodiment, a CIGS film forming process grown at high temperatures proceeds using the glass as the growth substrate, and the sacrificial layer formed on the rigid glass substrate is removed by the electrolysis method.
Then, an advantage of some aspects of the invention is that the bonding layer and the flexible substrate are formed under the backside electrode layer, thereby providing the solar cell having excellent curve and improved photoelectric conversion efficiency and reliability.
The solar cell according to the embodiment includes a backside electrode layer, a light absorption layer on the backside electrode layer, a buffer layer on the light absorption layer, a window layer on the buffer layer, and a bonding layer under the backside electrode layer.
A method of fabricating a solar cell according to the embodiment includes forming a sacrificial layer on a growth substrate; forming a backside electrode layer on the sacrificial layer; forming a light absorption layer on the backside electrode layer; forming a top electrode layer on the light absorption layer; forming a sheet above the top electrode layer; and removing the sacrificial layer so that a bottom surface of the backside electrode layer is exposed by performing the electrolysis on the solar cell.
In the embodiment, a solar cell and a method of fabricating the same having flexibility and improved photoelectric conversion efficiency and reliability is provided.
FIG. 1 is a section view of a solar cell according to an embodiment of the present invention.
FIGS. 2 to 7 show the method of fabricating the solar cell according to an embodiment of the present invention.
In the description of the embodiment, in a case where each substrate, layer, a film or a electrode and the like is described to be formed “on” or “under” thereof, “on” or “under” also means one to be formed "directly” or “indirectly(through other component)” to component. Also, the criteria regarding “on” or “under” of each component will be described based on the drawings. In the drawing, the size of each component may be exaggerated to describe, and does not mean the size that is actually applied.
FIG. 1 is a section view showing a solar cell according to an embodiment of the present invention. FIGS. 2 to 7 show the method of fabricating the solar cell according to an embodiment of the present invention.
FIG. 1, the solar cell according to the embodiment includes a substrate 110, a bonding layer 250 on the substrate 110, a backside electrode layer 200 on the bonding layer 250, a light absorption layer 300 on the backside electrode layer 200, a buffer layer 400 and a high-resistant buffer layer 500 on the light absorption layer 300, a window layer 600 on the high-resistant buffer layer 500, and a first protection layer 700 on the window layer 600.
Further, a second protection layer 800 may be formed under the substrate 110.
The substrate 110 has a plate shape, and supports the backside electrode layer 200, the light absorption layer 300, the buffer layer 400, the high-resistant buffer layer 500 and the window layer 600.
The substrate 110 may be a flexible substrate such as PET(polyethylene terephthalate), but is not limited thereto.
The backside electrode layer 200 is arranged on the substrate 110. The backside electrode layer 200 becomes a conductive layer. The backside electrode layer 200 allows charges produced from the light absorption layer 300 of the solar cell to move, such that current may flow outside the solar cell.
The backside electrode layer 200 needs to have high electricalconductivity and small specific resistance to perform above function.
Further, The backside electrode layer 200 should be maintained to have high temperature stability when heat-treating under the atmosphere of sulfur(S) or selenium(Se) accompanied in forming CIGS compound.
Such a backside electrode layer 200 may be formed by any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W) and copper (Cu) Among them, particularly, the molybdenum (Mo) enables the characteristic required for the backside electrode layer 200 to generally satisfy as compared with other element.
The backside electrode layer 200 may include at least two layers. In this case, each layer may be formed by same metals or metals different from each other.
The portion of a sacrificial layer 105(refer to FIG. 3) may remain under the backside electrode layer 200. For example, when the sacrificial layer 105 containing the Cu is formed, some of metallic crystals of the Cu may be present under the backside electrode layer 200.
Further, a second protection layer 800 may be formed under the substrate 110. The second protection layer 800 acts a role to protect the solar cell against water and air of the outside. The second protection layer 800 may be formed by a polymer layer. The second protection layer 800, for example, including material such as PVF, polyester, acrylic, EVA may be formed.
Further, the backside electrode layer 200 may be directly connected to the second protection layer 800 without forming the substrate 110.
The light absorption layer 300 may be formed on the backside electrode layer 200. The light absorption layer 300 includes p-type semiconductor compound. In more detail, the light absorption layer 300 includes group Ⅰ-Ⅲ-Ⅵ?base compound. For example, The light absorption layer 300 may has Cu-In-Ga-Se-base(Cu(In,Ga)Se2;CIGS-base) or Cu-Ga-Se-base crystal structure.
The buffer layer 400 and the high-resistant buffer layer 500 may be formed on the light absorption layer 300. The solar cell having CIGS compound as the light absorption layer 300 forms p-n junction between a p-type semiconductor, that is, a CIGS compound thin film and a n-type semiconductor, that is, a window layer 600 thin film.
However, since two materials have large difference in a lattice constant and bandgap energy, to form good junction, it needs a buffer layer to allow the bandgap to be positioned in the middle of the two materials.
The material forming the buffer layer 400 is CdS, ZnS and the like, the CdS is a relatively good in terms of power generation efficiency of the solar cell. The high-resistant buffer layer 500 includes zinc oxide(i-ZnO) not doped with impurity. The energy bandgap of the high-resistant buffer layer 500 is about 3.1eV to 3.3eV.
The window 600 is formed on the high-resistant buffer layer 500. The window layer 600 is transparent and a conductive layer. Further, resistance of the window layer 600 is higher than that of the backside electrode layer 200.
The window layer 600 includes oxide. For example, the window layer 600 may include zinc oxide, indium tin oxide; ITO or indium zinc oxide; IZO and the like.
Further, the oxide may include conductive impurities such as aluminum(Al), alumina(Al2O3), magnesium(Mg) or gallium(Ga). In more detail, the window layer 600 may include Al doped zinc oxide; AZO, B doped zinc oxide; BZO or Ga doped zinc oxide; GZO.
The first protection layer 700 and the second protection layer 800 may be formed on the top and bottom surface of the solar cell.
FIGS. 2 to 7 are sectional views showing the method of fabricating the solar cell according to an embodiment of the present invention. The description regarding the present fabricating method refers to the descrition regarding the solar cell described previously.
In FIG 2, the sacrificial layer 105 grows on a growth substrate 100.
The growth substrate 100 may be an insulator. The growth substrate 100 may be a glass substrate. In more detail, the growth substrate 100 may be a soda lime glass substrate.
When the growth substrate 100 becomes a soda lime glass, Na contained in the soda lime glass may be diffused into the light absorption layer 300 formed by the CIGS during the fabricating process of the solar cell, which allows charge concentration of the light absorption layer 300 to increase. That may become a factor that may increase photoelectric conversion efficiency of the solar cell.
In addition, a ceramic substrate such as alumina, stainless steel, flexible polymer and the like are used as the material of the growth substrate 100. The growth substrate 100 may be transparent and rigid or flexible.
The sacrificial layer 105 may include a metal. For example, the sacrificial layer 105 may include elements such as Cu, Ag, Au and the like.
Next, the backside electrode layer 200 is formed on the sacrificial layer 105. The backside electrode layer 200 may be formed by any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W) and copper (Cu). Among them, particularly, since the molybdenum(Mo) has small difference in thermal expansion coefficient with the supporting substrate 100 as compared with other element, Mo has excellent adhesion and may prevent delamination. Therefore, the molybdenum (Mo) may allow the characteristic required for the backside electrode layer 200 to generally satisfy.
The backside electrode layer 200 may include at least two layers. In this case, each layer may be formed by same metals or metals different from each other. The backside electrode layer 200 may be formed by PVD(Physical Vapor Deposition) or plating.
In FIG.3, the light absorption layer 300 is formed on the backside electrode layer 200.
The light absorption layer 300 is widely fabricated by the method forming the light absorption layer 300 of Cu-In-Ga-Se-base(Cu(In,Ga)Se2;CIGS-base) while simultaneously or separately evaporating, for example, Cu, In, Ga and Se, and the method using a selenization process after forming a metal precursor film.
When subdividing the selenization process after forming the metal precursor film, the metal precursor film is formed on the backside electrode layer 200 by a sputtering process using Cu target, In target and Ga target.
Then, the metal precursor film becomes the light absorption layer 300 of Cu-In-Ga-Se-base(Cu(In,Ga)Se2;CIGS-base) by the selenization process.
In contrast, the sputtering process using the Cu target, the In target and the Ga target is simultaneously performed with the selenization process.
In contrast, CIS-base or CIG-base light absorption layer 300 may be formed by the sputtering process using only the Cu target and the In target or the Cu target and the Ga target, and the selenization process.
Then, cadmium sulfide is deposited by the sputtering process and a chemical bath depositon(CBD) method and the like to form the buffer layer 400.
Then, the zinc oxide is deposited on the buffer layer 400 by the sputtering process to form the high-resistant buffer layer 500.
The buffer layer 400 and the high-resistant buffer layer 500 are deposited to a small thickness. For example, a thickness of the buffer layer 400 and the high-resistant buffer layer 500 is about 1㎚ to 100㎚.
Next, The window 600 is formed on the high-resistant buffer layer 500. That is, the window layer 600 is formed by depositing transparent conductive material on the high-resistant buffer layer 500. In detail, the window layer 600 may be formed by depositing the zinc oxide doped with the aluminum, but is not limited thereto.
Next, in FIG. 4, the first protection layer 700 is formed on the window 600. The first protection layer 700 may be formed by a deposition method. The first protection layer 700 includes EVA sheets to prevent damage for the panel of the solar cell when performing electrolys is.
In FIGS. 5 and 6, it is possible to remove the sacrificial layer 105 by performing the electrolysis of the sacrificial layer 105 in aqueous solution.
The aqueous solution may be formed depending on the material included to the sacrificial layer 105 in the embodiment of the present invention.
For example, when the sacrificial layer 105 includes the copper (Cu), the aqueous solution may use copper sulfate (Cu2SO4) contained with the copper (Cu).
After dipping the solar cell into an electrolysis trillion included with the aqueous solution, an anode (+) thereof is connected to the backside electrode layer 200 and a cathode is connected to a separate metal plate 107 spaced apart from the solar cell, thereby performing the electrolysis.
When the cathode is connected to the backside electrode layer 200, the sacrificial layer 105 contained with the metal is difficult to perform the electrolysis, and therefore, it is preferable to connect the anode to the backside electrode layer 200.
The sacrificial layer 105 is etched by the electrolysis, such that the sacrificial layer 105 and the growth substrate 100 are separated from the backside electrode layer 200. The sacrificial layer 105 is etched by the electrolysis, but some of sacrificial layer 105 as the crystal form may remain in the backside electrode layer 200.
FIG. 6 is a sectional view showing the solar cell after removing the sacrificial layer 105 by the electrolysis. The backside electrode layer 200 is exposed by the electrolysis process. Some of he material included in the sacrificial layer 105 may remain, for example, as the crystal form under the backside electrode layer 200.
In FIG. 7, a bonding agent is applied below the backside electrode layer 200 to form the bonding layer 250. The bonding layer 250 allows adhesion of the backside electrode layer 200 and the substrate 110 to improve. The bonding layer 250 may be formed using polymeric material such as epoxy or ceramic series bond.
The substrate 110 may be a flexible substrate such as PET(polyethylene terephthalate), but is not limited thereto. Further, the substrate 110 may not be formed.
Further, the second protection layer 800 may be formed under the substrate 110. The second protection layer 800 may protect the solar cell from the outside, and may be formed by the same or different material as the first protection layer 700. The first and second protection layer 800 may be composed of Siloxane, PDAS(poly dialkyl siloxane) or film types of EVA(Ethylene Vinyl Acetate).
When the substrate 110 may not be formed, the backside electrode layer 200 may contact the second protection layer 800.
As reviewed above, in this embodiment, a CIGS film forming process grown at high temperatures proceeds using the glass as the growth substrate, and the sacrificial layer 105 formed on the rigid glass substrate is removed by the electrolysis method.
Then, the bonding layer 250 and the flexible substrate 110 are formed under the backside electrode layer 200, thereby providing the solar cell having excellent curve and improved photoelectric conversion efficiency and reliability.
It is appreciated that the present invention can be carried out in other specific forms without changing a technical idea or essential characteristics by one having ordinary skilled in the art to which the present invention pertains to. Therefore, embodiments described above are for illustration purpose in all respect but not limited to them. The scope of the present invention is represented by claims described below rather than the detailed description, and any change and variations derived from the meaning, the scope and the concept of equality of claims should be interpreted to be included to the scope of the present invention.
In addition, although the preferred embodiments of the present invention are shown and described above, the present invention is not limited to above-described specific embodiment and is variously modified by one skilled in the art without the gist of the present invention claimed in the claim, such that the modified embodiment is not to be understood separately from technical ideas or views of the present invention.

Claims (14)

  1. A solar cell, comprising:
    a backside electrode layer;
    a light absorption layer on the backside electrode layer;
    a buffer layer on the light absorption layer;
    a window layer on the buffer layer; and
    a bonding layer under the backside electrode layer.
  2. The solar cell according to claim 1, wherein the bonding layer includes polymeric material such as epoxy or ceramic series bond.
  3. The solar cell according to claim 1, further comprising a substrate under the backside electrode layer.
  4. The solar cell according to claim 1, wherein one surface of the backside electrode layer includes a polymer layer.
  5. The solar cell according to claim 1, wherein a metal crystal is included between the backside electrode layer and the bonding layer.
  6. The solar cell according to claim 1, wherein the metal crystal includes at least one of Cu, Ag, and Au.
  7. A method of fabricating a solar cell, comprising:
    forming a sacrificial layer on a growth substrate;
    forming a backside electrode layer on the sacrificial layer;
    forming a light absorption layer on the backside electrode layer;
    forming a top electrode layer on the light absorption layer;
    forming a first protection layer above the top electrode layer; and
    removing the sacrificial layer so that a bottom surface of the backside electrode layer is exposed by performing the electrolysis of the solar cell.
  8. The method of fabricating the solar cell according to claim 7, further comprising forming a bonding layer on the bottom surface of the backside electrode layer.
  9. The method of fabricating the solar cell according to claim 7, further comprising forming a flexible substrate on the bottom surface of the backside electrode layer.
  10. The method of fabricating the solar cell according to claim 7, wherein the sacrificial layer includes at least one of Cu, Ag and Au, and an aqueous solution includes the same material as the sacrificial layer.
  11. The method of fabricating the solar cell according to claim 7, wherein
    when performing the electrolysis using an electrolysis trillion, an anode (+) thereof is connected to the backside electrode layer and a cathode is connected to a separate metal plate spaced apart from the solar cell.
  12. The method of fabricating the solar cell according to claim 9, wherein a second protection layer is formed on a bottom surface of the flexible substrate.
  13. The method of fabricating the solar cell according to claim 12, wherein
    the first and second protection layer may be formed by at least one of Siloxane, PDAS(poly dialkyl siloxane) or film types of EVA(Ethylene Vinyl Acetate).
  14. The method of fabricating the solar cell according to claim 11, wherein the aqueous solution included in the electrolysis trillion is copper sulfate aqueous solution.
PCT/KR2011/009147 2011-01-27 2011-11-29 Solar cell apparatus and method of fabricating the same WO2012102476A2 (en)

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US9209341B2 (en) * 2014-02-19 2015-12-08 Tsmc Solar Ltd. Thin film solar cell and method of forming same
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KR20100090181A (en) * 2009-02-05 2010-08-13 (주)포인트엔지니어링 Manufacturing of thin film solar cell by porous materials and solar cell
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