WO2013094943A1 - Solar cell and method of fabricating the same - Google Patents

Solar cell and method of fabricating the same Download PDF

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Publication number
WO2013094943A1
WO2013094943A1 PCT/KR2012/010980 KR2012010980W WO2013094943A1 WO 2013094943 A1 WO2013094943 A1 WO 2013094943A1 KR 2012010980 W KR2012010980 W KR 2012010980W WO 2013094943 A1 WO2013094943 A1 WO 2013094943A1
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Prior art keywords
support substrate
conductive layer
layer
thermal conductive
solar cell
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PCT/KR2012/010980
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French (fr)
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Suk Jae Jee
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Lg Innotek Co., Ltd.
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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
    • H01L31/0248—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
    • 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
    • H01L31/0248—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
    • H01L31/03925—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 AIIBVI compound materials, e.g. CdTe, CdS
    • 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
    • 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 embodiment relates to a solar cell and a method of fabricating the same.
  • a solar cell (or photovoltaic cell) is a core element in solar power generation to directly convert solar light into electricity.
  • the solar light having energy greater than bandgap energy of a semiconductor is incident into a solar cell having the PN junction structure, electron-hole pairs are generated. As electrons and holes are collected into an N layer and a P layer, respectively, due to the electric field formed in a PN junction part, photovoltage is generated between the N and P layers. In this case, if a load is connected to electrodes provided at both ends of the solar cell, current flows through the solar cell.
  • a CIGS-based solar cell which is a PN hetero junction apparatus having a substrate structure including a glass substrate, a metallic back electrode layer, a P-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N-type window layer, has been extensively used.
  • non-uniform thermal distribution occurs between a center and an outer peripheral region of a support substrate so that thermal characteristics between centers and edges of a back electrode layer, a p-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N-type window layer, which are formed on the support substrate, may vary, thereby lowering light efficiency.
  • a technology for improving hardware such as a heater structure and control circuits of a deposition device is applied to improve temperature uniformity of the support substrate.
  • a high investment cost is required to achieve temperature uniformity within 5%.
  • the embodiment provides a solar cell which can improve the output and photoelectric conversion efficiency of the solar cell by improving temperature uniformity of a layer formed on a support substrate by forming a thermal conductive layer on the support substrate.
  • a solar cell including: a support substrate; and a thermal conductive layer on the support substrate.
  • thermal distribution uniformity between a central region and an outer peripheral region of the support substrate used for the solar cell can be improved by thinly coating the peripheral region of the support substrate with materials having specific thermal conductivity so that the output and photoelectric conversion efficiency of the solar cell can be improved.
  • the thermal gradient can be improved by depositing a material having high thermal conductivity on the support substrate without a high hardware investment cost.
  • the embodiment is applicable to a case where the support substrate is a rigid substrate or a flexible metal substrate so that the productivity can be improved.
  • FIG. 1 is a perspective view showing a solar cell according to the embodiment.
  • FIG. 2 is a sectional view showing a support substrate and a thermal conductive layer of the solar cell according to the embodiment.
  • FIGS. 3 to 5 are views illustrated a method of fabricating a solar cell panel according to the embodiment.
  • FIG. 6 is a view showing morphology of a light absorbing layer according to a temperature difference.
  • FIG. 1 is a perspective view showing a solar cell according to the embodiment.
  • FIG. 2 is a sectional view showing a support substrate and a thermal conductive layer of the solar cell according to the embodiment.
  • a solar cell includes a support substrate 100, a thermal conductive layer 150, a back electrode layer 200, a light absorbing layer 300, a buffer layer 400, and a window layer 500.
  • the support substrate 100 has a plate shape, and supports the thermal conductive layer 150, the back electrode layer 200, the light absorbing layer 300, the buffer layer 400, and the window layer 600.
  • the support substrate 100 may be an insulator.
  • the support substrate 100 may be a glass substrate, a plastic substrate such as a polymer substrate, or a metal substrate.
  • the support substrate 100 may be formed of a ceramic material such as alumina, stainless steel, or flexible polymer.
  • the support substrate 100 may be transparent, rigid or flexible.
  • the support substrate 100 includes soda lime glass
  • sodium (Na) contained in the soda lime glass may be diffused into the light absorbing layer prepared by CIGS, so that a charge concentration may be increased. This may be a factor to increase the photoelectric conversion efficiency of the solar cell.
  • the thermal conductive layer 150 is formed on the support substrate 100.
  • the thermal conductive layer 150 may be formed at an outer peripheral region of the support substrate 100.
  • a width b of the thermal conductive layer 150 may be in the range of 10% to 40% based on a total length a from a central portion of the support substrate 100 to an outer peripheral region of the support substrate 100.
  • the width b of the thermal conductive layer 150 is applicable to a horizontal axis and a vertical axis.
  • a ratio of the width of the thermal conductive layer 150 in the horizontal axis may be different from a ratio of the width of the thermal conductive layer 150 in the vertical axis.
  • a deposition thickness of the thermal conductive layer 150 may be determined corresponding to a thickness of the support substrate 100.
  • the thermal conductive layer 150 may be in the range of 20 nm to 140 nm.
  • the thermal conductive layer 150 may be in the range of 5 nm to 40 nm. That is, the thickness of the thermal conductive layer 150 may be in the range of 1/160 to 1/140 of the thickness of the support substrate 100.
  • the thermal conductive layer 150 may include a material having superior electric conductivity and superior electric insulation.
  • the thermal conductive layer 150 may include a material having thermal expansion coefficient in the range of 3.5 ppm/K to 4.5 ppm/K, and a melting point of 2000 or above.
  • the thermal conductive layer 150 may include SiC, and thermal conductivity and thermal expansion coefficient of the thermal conductive layer 150 may be controlled by a combination with other metallic material.
  • the thermal conductive layer 150 has thermal conductivity in the range of 0.9 W/mK to 1.3 W/mK, and the thermal expansion coefficient of the thermal conductive layer 150 is in the range of 8.5 ppm/K to 9.5 ppm/K.
  • the thermal conductive layer 150 includes SiC
  • the thermal conductivity of the thermal conductive layer 150 is in the range of 360 W/mK to 490 W/mK
  • the thermal expansion coefficient of the thermal conductive layer 150 is 4 ppm/K.
  • the back electrode layer 200 molybdenum (Mo) the thermal conductivity of the thermal conductive layer 150 is 138 W/mK, and the thermal expansion coefficient of the thermal conductive layer 150 is 4.8 ppm/K.
  • the back electrode layer 200 is disposed on the support substrate 100.
  • the back electrode layer 200 is a conductive layer.
  • the back electrode layer 200 transfers charges produced in the light absorbing layer 300 of the solar cell, thereby allowing current to flow to the outside of the solar cell.
  • the back electrode layer 200 must represent higher electric conductivity and lower resistivity in order to perform the above function.
  • the back electrode layer 200 must maintain high-temperature stability when heat treatment is performed under the atmosphere of sulfur (S) or selenium (Se) required when a CIGS compound is formed.
  • the back electrode layer 200 must represent a superior adhesive property with respect to the support substrate 100 such that the back electrode layer 200 is prevented from being delaminated from the substrate 100 due to the difference in the thermal expansion coefficient between the back electrode layer 200 and the support substrate 100.
  • a material for the back electrode layer 200 may include Mo.
  • the light absorbing layer 300 may be formed on the back electrode layer 200.
  • the light absorbing layer 300 includes a P-type semiconductor compound.
  • the light absorbing layer 300 includes a group I-III-VI-based compound.
  • the light absorbing layer 300 may have a Cu(In,Ga)Se 2 (CIGS) crystal structure, a Cu(In)Se 2 crystal structure, or a Cu(Ga)Se2 crystal structure.
  • the light absorbing layer 300 may have an energy bandgap in the range of 1.1 eV to 1.2 eV.
  • a lattice constant may be about 0.575 nm.
  • the buffer layer 400 is disposed on the light absorbing layer 300.
  • a P-N junction is formed between a CIGS compound thin film, which serves as a P-type semiconductor, and the window layer 500 which is an N-type semiconductor.
  • a buffer layer having the intermediate bandgap between the bandgaps of the two materials is required to form the superior junction between the two materials.
  • the buffer layer 400 may have an energy bandgap in the range of 2.2 eV to 2.5 eV.
  • the material used for forming the buffer layer 400 includes CdS and ZnS. Since the CdS is relatively superior to any other materials in the aspect of the solar cell generation efficiency.
  • the buffer layer 400 has a thickness in the range of 10 to 100 . It is preferable that the buffer layer 400 may have a thickness in the range of 50 to 80 .
  • the high-resistance buffer layer (not shown) may be disposed on the buffer layer 400.
  • the high-resistance buffer layer may include i-ZnO, which is zinc oxide not doped with impurities.
  • the high-resistance buffer layer may have an energy bandgap in the range of about 3.1eV to about 3.3eV.
  • the window layer 500 is disposed on the buffer layer 400.
  • the window layer 500 is transparent and a conductive layer.
  • the resistance of the window layer 500 is higher than that of the back electrode layer 200.
  • the window layer 500 includes oxide.
  • the window layer 500 may include zinc oxide, indium tin oxide (ITO), or indium zinc oxide (IZO).
  • the window layer 500 may include Al doped zinc oxide (AZO) or Ga doped zinc oxide (GZO).
  • thermal distribution uniformity between a central region and an outer peripheral region of the support substrate used for the solar cell can be improved by thinly coating the peripheral region of the support substrate with materials having specific thermal conductivity so that the output and photoelectric conversion efficiency of the solar cell can be improved.
  • the thermal gradient can be improved by depositing a material having high thermal conductivity on the support substrate without a high hardware investment cost.
  • the embodiment is applicable to a case where the support substrate is a rigid substrate or a flexible metal substrate so that the productivity can be improved.
  • FIGS. 3 to 5 are views illustrated a method of fabricating a solar cell panel according to the embodiment.
  • the description about the method of fabricating the solar cell will be made based on the above description about the solar cell apparatus.
  • the description about the solar cell apparatus may be essentially incorporated herein by reference.
  • a thermal conductive layer 150 is formed on a support substrate 100.
  • the thermal conductive layer 150 is formed on an entire surface of the support substrate 100, but the thermal conductive layer 150 is formed around the support substrate 100 as shown in FIG. 1.
  • the thermal conductive layer 150 may be deposited by an epitaxial process, but the embodiment is limited thereto.
  • a back electrode layer 200 is formed on the thermal conductive layer 150.
  • the back electrode layer 200 may be deposited using Mo.
  • the light absorbing layer 300 is formed on the thermal conductive layer 150.
  • Various schemes such as a scheme of forming a Cu(In,Ga)Se 2 (CIGS) based-light absorbing layer 300 by simultaneously or separately evaporating Cu, In, Ga, and Se and a scheme of performing a selenization process after a metallic precursor film has been formed, have been extensively used in order to form the light absorbing layer 300.
  • CGS Cu(In,Ga)Se 2
  • the metallic precursor layer is formed on the back electrode layer 200 through a sputtering process employing a Cu target, an In target, or a Ga target.
  • the metallic precursor layer is subject to the selenization process so that the Cu (In, Ga) Se 2 (CIGS) based light absorbing layer 300 is formed.
  • the sputtering process employing the Cu target, the In target, and the Ga target and the selenization process may be simultaneously performed.
  • a CIS or a CIG based light absorbing layer 300 may be formed through the sputtering process employing only Cu and In targets or Cu and Ga targets and the selenization process.
  • the light absorbing layer 300 may have a thickness in the range of 1.5 m to 2.5 m, but the embodiment is not limited thereto.
  • a buffer layer 400 400 is formed on the light absorbing layer 300.
  • the back electrode layer 200 may be formed using CdS through a Physical Vapor Deposition (PVD) scheme or a plating scheme.
  • PVD Physical Vapor Deposition
  • the window layer 500 is formed on the buffer layer 400.
  • the window layer 500 may be formed on the buffer layer 500 by depositing a transparent conductive material.
  • FIG. 6 is a view showing morphology of a light absorbing layer according to a temperature difference.
  • FIG. 6 illustrates morphology of the light absorbing layer formed on a soda lime support substrate on which the thermal conductive layer is not formed. Based on the drawing, a left side indicates a central portion and a right side indicates an outer peripheral region. A temperature of 630 was measured at the left side and a temperature of 600 was measured at the right side.
  • the growth patterns of a CIGS light absorbing layer at a central portion and an outer peripheral region of the same support substrate are different from each other under the condition of superior temperature uniformity of 5% or less and the same composition ratio. That is, the grains have large sizes and relatively uniform surfaces at the central portion having a high temperature.
  • the thermal conductive layer 150 is formed at the outer peripheral region of the support substrate 100 so that a CIGS light absorbing layer formed with grains having the large size and superior surface profile can be formed at the outer peripheral region of the support substrate 100.
  • any reference in this specification to one embodiment, an embodiment, example embodiment, etc. means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention.
  • the appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment.

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Abstract

A solar cell apparatus according to the embodiment includes a support substrate; and a thermal conductive layer on the support substrate.

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME
The embodiment relates to a solar cell and a method of fabricating the same.
A solar cell (or photovoltaic cell) is a core element in solar power generation to directly convert solar light into electricity.
If the solar light having energy greater than bandgap energy of a semiconductor is incident into a solar cell having the PN junction structure, electron-hole pairs are generated. As electrons and holes are collected into an N layer and a P layer, respectively, due to the electric field formed in a PN junction part, photovoltage is generated between the N and P layers. In this case, if a load is connected to electrodes provided at both ends of the solar cell, current flows through the solar cell.
Recently, as energy consumption is increased, solar cells to convert the solar light into electrical energy have been developed.
In particular, a CIGS-based solar cell, which is a PN hetero junction apparatus having a substrate structure including a glass substrate, a metallic back electrode layer, a P-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N-type window layer, has been extensively used.
In general, as the size of a substrate becomes enlarged in the solar cell, non-uniform thermal distribution occurs between a center and an outer peripheral region of a support substrate so that thermal characteristics between centers and edges of a back electrode layer, a p-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N-type window layer, which are formed on the support substrate, may vary, thereby lowering light efficiency.
In order to solve the above problem, according to the related art, a technology for improving hardware such as a heater structure and control circuits of a deposition device is applied to improve temperature uniformity of the support substrate. However, a high investment cost is required to achieve temperature uniformity within 5%.
The embodiment provides a solar cell which can improve the output and photoelectric conversion efficiency of the solar cell by improving temperature uniformity of a layer formed on a support substrate by forming a thermal conductive layer on the support substrate.
According to the embodiment, there is provided a solar cell including: a support substrate; and a thermal conductive layer on the support substrate.
According to the solar cell of the embodiment, thermal distribution uniformity between a central region and an outer peripheral region of the support substrate used for the solar cell can be improved by thinly coating the peripheral region of the support substrate with materials having specific thermal conductivity so that the output and photoelectric conversion efficiency of the solar cell can be improved.
In addition, the thermal gradient can be improved by depositing a material having high thermal conductivity on the support substrate without a high hardware investment cost.
Further, the embodiment is applicable to a case where the support substrate is a rigid substrate or a flexible metal substrate so that the productivity can be improved.
FIG. 1 is a perspective view showing a solar cell according to the embodiment.
FIG. 2 is a sectional view showing a support substrate and a thermal conductive layer of the solar cell according to the embodiment.
FIGS. 3 to 5 are views illustrated a method of fabricating a solar cell panel according to the embodiment.
FIG. 6 is a view showing morphology of a light absorbing layer according to a temperature difference.
In the description of the embodiments, it will be understood that when a substrate, a layer, a film or an electrode is referred to as being on or under another substrate, another layer, another film or another electrode, it can be directly or indirectly on the other substrate, the other layer, the other film, or the other electrode, or one or more intervening layers may also be present. Such a position of the layer has been described with reference to the drawings. The size of the elements shown in the drawings may be exaggerated for the purpose of explanation and may not utterly reflect the actual size.
FIG. 1 is a perspective view showing a solar cell according to the embodiment. FIG. 2 is a sectional view showing a support substrate and a thermal conductive layer of the solar cell according to the embodiment. Referring to FIGS. 1 and 2, a solar cell includes a support substrate 100, a thermal conductive layer 150, a back electrode layer 200, a light absorbing layer 300, a buffer layer 400, and a window layer 500.
The support substrate 100 has a plate shape, and supports the thermal conductive layer 150, the back electrode layer 200, the light absorbing layer 300, the buffer layer 400, and the window layer 600.
The support substrate 100 may be an insulator. The support substrate 100 may be a glass substrate, a plastic substrate such as a polymer substrate, or a metal substrate. In addition, the support substrate 100 may be formed of a ceramic material such as alumina, stainless steel, or flexible polymer. The support substrate 100 may be transparent, rigid or flexible.
When the support substrate 100 includes soda lime glass, sodium (Na) contained in the soda lime glass may be diffused into the light absorbing layer prepared by CIGS, so that a charge concentration may be increased. This may be a factor to increase the photoelectric conversion efficiency of the solar cell.
The thermal conductive layer 150 is formed on the support substrate 100. The thermal conductive layer 150 may be formed at an outer peripheral region of the support substrate 100. A width b of the thermal conductive layer 150 may be in the range of 10% to 40% based on a total length a from a central portion of the support substrate 100 to an outer peripheral region of the support substrate 100. The width b of the thermal conductive layer 150 is applicable to a horizontal axis and a vertical axis. A ratio of the width of the thermal conductive layer 150 in the horizontal axis may be different from a ratio of the width of the thermal conductive layer 150 in the vertical axis.
A deposition thickness of the thermal conductive layer 150 may be determined corresponding to a thickness of the support substrate 100. For example, when the support substrate 100 has a thickness of 2.8 mm, the thermal conductive layer 150 may be in the range of 20 nm to 140 nm. When the support substrate 100 has a thickness of 0.8 mm, the thermal conductive layer 150 may be in the range of 5 nm to 40 nm. That is, the thickness of the thermal conductive layer 150 may be in the range of 1/160 to 1/140 of the thickness of the support substrate 100.
The thermal conductive layer 150 may include a material having superior electric conductivity and superior electric insulation. In detail, the thermal conductive layer 150 may include a material having thermal expansion coefficient in the range of 3.5 ppm/K to 4.5 ppm/K, and a melting point of 2000 or above.
For example, the thermal conductive layer 150 may include SiC, and thermal conductivity and thermal expansion coefficient of the thermal conductive layer 150 may be controlled by a combination with other metallic material.
When the support substrate 100 includes soda lime glass, the thermal conductive layer 150 has thermal conductivity in the range of 0.9 W/mK to 1.3 W/mK, and the thermal expansion coefficient of the thermal conductive layer 150 is in the range of 8.5 ppm/K to 9.5 ppm/K. When the thermal conductive layer 150 includes SiC, the thermal conductivity of the thermal conductive layer 150 is in the range of 360 W/mK to 490 W/mK, and the thermal expansion coefficient of the thermal conductive layer 150 is 4 ppm/K. When the back electrode layer 200 molybdenum (Mo), the thermal conductivity of the thermal conductive layer 150 is 138 W/mK, and the thermal expansion coefficient of the thermal conductive layer 150 is 4.8 ppm/K.
The back electrode layer 200 is disposed on the support substrate 100. The back electrode layer 200 is a conductive layer. The back electrode layer 200 transfers charges produced in the light absorbing layer 300 of the solar cell, thereby allowing current to flow to the outside of the solar cell. The back electrode layer 200 must represent higher electric conductivity and lower resistivity in order to perform the above function.
In addition, the back electrode layer 200 must maintain high-temperature stability when heat treatment is performed under the atmosphere of sulfur (S) or selenium (Se) required when a CIGS compound is formed. In addition, the back electrode layer 200 must represent a superior adhesive property with respect to the support substrate 100 such that the back electrode layer 200 is prevented from being delaminated from the substrate 100 due to the difference in the thermal expansion coefficient between the back electrode layer 200 and the support substrate 100. A material for the back electrode layer 200 may include Mo.
The light absorbing layer 300 may be formed on the back electrode layer 200. The light absorbing layer 300 includes a P-type semiconductor compound. In more detail, the light absorbing layer 300 includes a group I-III-VI-based compound. For example, the light absorbing layer 300 may have a Cu(In,Ga)Se2 (CIGS) crystal structure, a Cu(In)Se2 crystal structure, or a Cu(Ga)Se2 crystal structure. The light absorbing layer 300 may have an energy bandgap in the range of 1.1 eV to 1.2 eV. When the light absorbing layer 300 includes CIGS, a lattice constant may be about 0.575 nm.
The buffer layer 400 is disposed on the light absorbing layer 300. According to the solar cell having the light absorbing layer 300 including the CIGS compound, a P-N junction is formed between a CIGS compound thin film, which serves as a P-type semiconductor, and the window layer 500 which is an N-type semiconductor. However, since two materials represent the great difference in the lattice constant and the bandgap energy therebetween, a buffer layer having the intermediate bandgap between the bandgaps of the two materials is required to form the superior junction between the two materials.
The buffer layer 400 may have an energy bandgap in the range of 2.2 eV to 2.5 eV. The material used for forming the buffer layer 400 includes CdS and ZnS. Since the CdS is relatively superior to any other materials in the aspect of the solar cell generation efficiency.
The buffer layer 400 has a thickness in the range of 10 to 100 . It is preferable that the buffer layer 400 may have a thickness in the range of 50 to 80 .
The high-resistance buffer layer (not shown) may be disposed on the buffer layer 400. The high-resistance buffer layer may include i-ZnO, which is zinc oxide not doped with impurities. The high-resistance buffer layer may have an energy bandgap in the range of about 3.1eV to about 3.3eV.
The window layer 500 is disposed on the buffer layer 400. The window layer 500 is transparent and a conductive layer. The resistance of the window layer 500 is higher than that of the back electrode layer 200.
The window layer 500 includes oxide. For example, the window layer 500 may include zinc oxide, indium tin oxide (ITO), or indium zinc oxide (IZO). In addition, the window layer 500 may include Al doped zinc oxide (AZO) or Ga doped zinc oxide (GZO).
According to the solar cell of the embodiment, thermal distribution uniformity between a central region and an outer peripheral region of the support substrate used for the solar cell can be improved by thinly coating the peripheral region of the support substrate with materials having specific thermal conductivity so that the output and photoelectric conversion efficiency of the solar cell can be improved.
In addition, the thermal gradient can be improved by depositing a material having high thermal conductivity on the support substrate without a high hardware investment cost.
Further, the embodiment is applicable to a case where the support substrate is a rigid substrate or a flexible metal substrate so that the productivity can be improved.
FIGS. 3 to 5 are views illustrated a method of fabricating a solar cell panel according to the embodiment. The description about the method of fabricating the solar cell will be made based on the above description about the solar cell apparatus. The description about the solar cell apparatus may be essentially incorporated herein by reference.
Referring to FIG. 3, a thermal conductive layer 150 is formed on a support substrate 100. When viewed in a sectional view, the thermal conductive layer 150 is formed on an entire surface of the support substrate 100, but the thermal conductive layer 150 is formed around the support substrate 100 as shown in FIG. 1. The thermal conductive layer 150 may be deposited by an epitaxial process, but the embodiment is limited thereto.
Referring to FIG. 4, a back electrode layer 200 is formed on the thermal conductive layer 150. The back electrode layer 200 may be deposited using Mo.
Next, the light absorbing layer 300 is formed on the thermal conductive layer 150. Various schemes, such as a scheme of forming a Cu(In,Ga)Se2 (CIGS) based-light absorbing layer 300 by simultaneously or separately evaporating Cu, In, Ga, and Se and a scheme of performing a selenization process after a metallic precursor film has been formed, have been extensively used in order to form the light absorbing layer 300.
Regarding the details of the selenization process after the formation of the metallic precursor layer, the metallic precursor layer is formed on the back electrode layer 200 through a sputtering process employing a Cu target, an In target, or a Ga target.
Thereafter, the metallic precursor layer is subject to the selenization process so that the Cu (In, Ga) Se2 (CIGS) based light absorbing layer 300 is formed.
In addition, the sputtering process employing the Cu target, the In target, and the Ga target and the selenization process may be simultaneously performed.
Further, a CIS or a CIG based light absorbing layer 300 may be formed through the sputtering process employing only Cu and In targets or Cu and Ga targets and the selenization process. The light absorbing layer 300 may have a thickness in the range of 1.5 m to 2.5 m, but the embodiment is not limited thereto.
Referring to FIG. 5, a buffer layer 400 400 is formed on the light absorbing layer 300. The back electrode layer 200 may be formed using CdS through a Physical Vapor Deposition (PVD) scheme or a plating scheme.
Then, the window layer 500 is formed on the buffer layer 400. The window layer 500 may be formed on the buffer layer 500 by depositing a transparent conductive material.
FIG. 6 is a view showing morphology of a light absorbing layer according to a temperature difference. FIG. 6 illustrates morphology of the light absorbing layer formed on a soda lime support substrate on which the thermal conductive layer is not formed. Based on the drawing, a left side indicates a central portion and a right side indicates an outer peripheral region. A temperature of 630 was measured at the left side and a temperature of 600 was measured at the right side.
According to the observation result of the growth patterns of a CIGS light absorbing layer at a central portion and an outer peripheral region of the same support substrate, the growth patterns of the CIGS light absorbing layer at the central portion and the outer peripheral region of the same support substrate are different from each other under the condition of superior temperature uniformity of 5% or less and the same composition ratio. That is, the grains have large sizes and relatively uniform surfaces at the central portion having a high temperature.
According to the embodiment, the thermal conductive layer 150 is formed at the outer peripheral region of the support substrate 100 so that a CIGS light absorbing layer formed with grains having the large size and superior surface profile can be formed at the outer peripheral region of the support substrate 100.
Any reference in this specification to one embodiment, an embodiment, example embodiment, etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effects such feature, structure, or characteristic in connection with other ones of the embodiments.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims (13)

  1. A solar cell comprising:
    a support substrate; and
    a thermal conductive layer on the support substrate.
  2. The solar cell of claim 1, wherein the thermal conductive layer is formed at an outer peripheral region of the support substrate.
  3. The solar cell of claim 2, wherein a width of the thermal conductive layer is in a range of 10% to 40% based on a total length from a central portion of the support substrate to the outer peripheral region of the support substrate.
  4. The solar cell of claim 1, wherein a thickness of the thermal conductive layer is in a range of 1/160 to 1/140 based on a thickness of the support substrate.
  5. The solar cell of claim 1, wherein the thermal conductive layer comprises SiC.
  6. The solar cell of claim 1, wherein the thermal conductive layer has thermal conductivity in a range of 360 W/mK to 490 W/mK.
  7. The solar cell of claim 6, wherein the support substrate comprises soda lime glass.
  8. A method of fabricating a solar cell, the method comprising:
    forming a thermal conductive layer on a support substrate; and
    forming a back electrode layer on the thermal conductive layer.
  9. The method of claim 8, wherein the thermal conductive layer is formed at an outer peripheral region of the support substrate, a width of the thermal conductive layer is in a range of 10% to 40% based on a total length a from a central portion of the support substrate to the outer peripheral region of the support substrate.
  10. The method of claim 8, wherein the thermal conductive layer comprises SiC.
  11. The method of claim 8, wherein a thickness of the thermal conductive layer is in a range of 1/160 to 1/140 of a thickness of the support substrate.
  12. The method of claim 8, wherein the support substrate comprises soda lime glass.
  13. The method of claim 8, wherein the thermal conductive layer has thermal conductivity in a range of 360 W/mK to 490 W/mK.
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