WO2009008672A2 - Solar cell and method of manufacturing the same - Google Patents

Solar cell and method of manufacturing the same Download PDF

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Publication number
WO2009008672A2
WO2009008672A2 PCT/KR2008/004059 KR2008004059W WO2009008672A2 WO 2009008672 A2 WO2009008672 A2 WO 2009008672A2 KR 2008004059 W KR2008004059 W KR 2008004059W WO 2009008672 A2 WO2009008672 A2 WO 2009008672A2
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WO
WIPO (PCT)
Prior art keywords
light
type semiconductor
semiconductor layer
conductive type
substrate
Prior art date
Application number
PCT/KR2008/004059
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French (fr)
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WO2009008672A3 (en
Inventor
Jae Ho Kim
Original Assignee
Jusung Engineering Co., Ltd.
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Publication date
Application filed by Jusung Engineering Co., Ltd. filed Critical Jusung Engineering Co., Ltd.
Publication of WO2009008672A2 publication Critical patent/WO2009008672A2/en
Publication of WO2009008672A3 publication Critical patent/WO2009008672A3/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
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • 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
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H01L31/02366—Special surface textures of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—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
    • H01L31/0376—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 amorphous semiconductors
    • H01L31/03762—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 amorphous semiconductors including only elements of Group IV of the Periodic System
    • 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
    • H01L31/03921—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 only elements of Group IV of the Periodic System
    • 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 at least one potential-jump barrier or surface barrier
    • 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 at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • 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
    • Y02E10/52—PV systems with concentrators
    • 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
    • Y02E10/548—Amorphous silicon PV cells

Definitions

  • the present invention relates to a solar cell and a method of manufacturing the same, and more particularly, to a solar cell having high efficiency by increasing the intensity (i.e., luminance) of solar light incident on a light-condensing sheet type substrate, and a method of manufacturing the same.
  • Background Art i.e., luminance
  • the performance of the solar cell greatly depends on the efficiency of converting optical energy into electrical energy.
  • extensive researches are being conducted to provide methods for increasing the efficiency of a solar cell.
  • An example of methods for increasing the efficiency of a solar cell is to maximize light absorption by texturing a wafer surface.
  • the texturing process increases light absorption through light scattering. Therefore, a device with a texturing pattern has a limitation in that the intensity of incident solar light decreases if light is scattered to the outside of the device.
  • the present invention provides a solar cell and a method of manufacturing the same, which forms a light-condensing pattern on a substrate to concentrate incident solar light and increases an effective area of a photoelectric element converting the incident solar light into electrical energy, thereby making it possible to increase the efficiency of the solar cell.
  • a solar cell includes: a substrate; a light-condensing sheet disposed on the substrate; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the light-condensing sheet; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
  • a solar cell includes: a substrate; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the substrate; first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer; and a light-condensing sheet disposed on a surface of the substrate over which the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are not disposed.
  • the light-condensing sheet may be a prism sheet.
  • the light-condensing sheet may have a surface on which a convexo-concave portion is formed and the convex of the convexo-concave portion is triangular, circular or elliptical.
  • the convexo-concave portion may have V-shaped concaves, wherein each of the V- shaped concaves may have a slope of approximately 20° to approximately 80° and the adjacent con vexes of the convexo-concave portion may have a pitch of approximately 10/M to approximately 1000/M therebetween.
  • the convex may be consecutive point-shaped or line-shaped.
  • a solar cell includes: a substrate having a light-condensing pattern formed at a surface thereof; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the light-condensing pattern; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
  • a solar cell includes: a substrate having a light-condensing pattern formed at a surface thereof; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over an opposite surface of the substrate where the light-condensing pattern is not formed; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
  • the light-condensing sheet may have a surface on which a convexo-concave portion is formed and the convex of the convexo-concave portion is triangular, circular or elliptical.
  • the convex may be consecutive point-shaped or line-shaped.
  • the first conductive type semiconductor layer, a light- absorbing layer, and a second conductive type semiconductor layer are sequentially stacked and the solar cell further includes transparent electrodes disposed at the outsides of the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively.
  • a method of manufacturing a solar cell includes: attaching a light-condensing sheet on a substrate; sequentially stacking a first conductive type semiconductor layer, a light- absorbing layer and a second conductive type semiconductor layer over the light- condensing sheet; and forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
  • a method of manufacturing a solar cell includes: providing a substrate; sequentially stacking a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer over the substrate; forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer; and attaching a light- condensing sheet on a surface of the substrate over which the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are not formed.
  • a method of manufacturing a solar cell includes: providing a substrate; forming a light- condensing pattern on a surface of the substrate; sequentially stacking a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer over the substrate; and forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
  • the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer may be formed over the light-condensing pattern, or over an opposite surface of the substrate where the light-condensing pattern is not formed.
  • the light-condensing pattern may be formed performing one of a laser-based process, a photoresist layer-based etching process, a sandblaster-based process, a mechanical process, or a molding process.
  • the method of manufacturing the solar cell may further include forming a front transparent electrode before sequentially stacking the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer and forming a rear transparent electrode after sequentially stacking the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer.
  • the light-condensing sheet attached on the substrate can concentrate the incident solar light and thus increase the intensity of light incident on the light-converting layer, thereby increasing the efficiency of the solar cell.
  • the light-condensing pattern formed on the substrate can concentrate solar light incident on the substrate, thereby increasing the efficiency of the solar cell.
  • the light-converting layer is formed on the substrate having the light-condensing sheet attached thereon or the light- condensing pattern formed thereon, so that it possible to increase the effective area of the photoelectric element of the solar cell.
  • FIG 1 is a cross-sectional view of a solar cell in accordance with a first embodiment of the present invention
  • FIG 2 is a cross-sectional view of a solar cell in accordance with a modification of the first embodiment of the present invention
  • FIG 3 is a cross-sectional view of a solar cell in accordance with another modification of the first embodiment of the present invention.
  • FIG 4 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the first embodiment of the present invention
  • FIG 5 is a cross-sectional view of a solar cell in accordance with a second embodiment of the present invention.
  • FIG 6 is a cross-sectional view of a solar cell in accordance with a modification of the second embodiment of the present invention.
  • FIG 7 is a cross-sectional view of a solar cell in accordance with another modification of the second embodiment of the present invention.
  • FIG 8 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the second embodiment of the present invention. Best Mode for Carrying Out the Invention
  • FIG 1 is a cross-sectional view of a solar cell in accordance with a first embodiment of the present invention.
  • FIG 2 is a cross-sectional view of a solar cell in accordance with a modification of the first embodiment of the present invention.
  • FIG 3 is a cross- sectional view of a solar cell in accordance with another modification of the first embodiment of the present invention.
  • FIG 4 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the first embodiment of the present invention.
  • the solar cell in accordance with the first embodiment includes a substrate 10, a light-condensing sheet 100 disposed over the substrate 10, a front transparent electrode 110 formed over the light-condensing sheet 100, a first conductive type semiconductor layer 120 formed over the front transparent electrode 110, a light- absorbing layer 130 formed over the first conductive type semiconductor layer 120, a second conductive type semiconductor layer 140 formed over the light- absorbing layer 130, a rear transparent electrode 150 formed over the second conductive type semiconductor layer 140 and an electrode unit 160 formed over the rear transparent electrode 150.
  • the substrate 10 may be a transparent insulating substrate.
  • the transparent insulating substrate are a glass substrate and a transparent resin substrate.
  • the light-condensing sheet 100 condenses light that is incident through the transparent insulating substrate 10, thereby increasing the light intensity.
  • this embodiment may use a prism sheet as the light-condensing sheet 100.
  • the prism sheet refracts and condenses light to increase the luminance of light incident on a light- converting layer.
  • the light-condensing sheet 100 may be formed of polyester (PET) or polycarbonate (PC). It is effective that the light-condensing sheet 100 has a prism pattern formed on a surface thereof. As illustrated in FIG 1, the prism pattern on the surface of the light-condensing sheet 100 has V-shaped concaves and mountain- shaped convexes.
  • the prism pattern may have wedged convexo-ooncaves in cross- section.
  • the prism pattern may have sinusoidal convexo-concaves, i.e., semicircular convexo-concaves, in cross-section.
  • Each of the V-shaped concaves may have a slope of approximately 20° to approximately 80° with respect to the surface of the substrate 10.
  • the adjacent mountain-shaped convexes may have a pitch of approximately 10/M to approximately 1000/M therebetween.
  • the prism pattern may have a plurality of point patterns that are polygonal horn-shaped and are arranged consecutively, or may have a plurality of lines that are triangular in cross-section and are arranged consecutively in the longitudinal or latitudinal direction.
  • the prism pattern is not limited to the above-described configurations, and may be circular or elliptical as illustrated in FIG 2. R>r example, as illustrated in FIG 2, the prism pattern may have a plurality of circular or elliptical microlens patterns that are arranged in an embossing configuration. Of course, the prism pattern may have a plurality of lines that are circular or elliptical in cross-section and are arranged consecutively in the longitudinal or latitudinal direction.
  • the prism pattern is not limited to the above-described configurations and may be any other types of patterns that can condense light.
  • the light-condensing sheet 100 of this embodiment has the prism pattern on the surface thereof to condense light incident thereon. Also, the formation of the convexo-concave prism pattern increases a light-receiving area of a photoelectric element and thus increases an effective area of the photoelectric element, thereby increasing the efficiency of the solar cell.
  • the light-condensing sheet 100 may be fabricated in a separate process and then attached on the substrate 10.
  • the front transparent electrode 110 may have a transparent conductive electrode.
  • the front transparent electrode 110 may be formed of transparent conductive oxide (TCO).
  • TCO transparent conductive oxide
  • the TCO may be deposited by low-pressure chemical vapor deposition (LPCVD) in order to form the front transparent electrode 110 along the step portion of the prism pattern.
  • LPCVD low-pressure chemical vapor deposition
  • the first conductive type semiconductor layer 120 may include a silicon layer that is doped with P- type impurities at a low concentration.
  • the light- absorbing layer 130 may include a silicon layer that is not doped with impurities.
  • the second conductive type semiconductor layer 140 may include a silicon layer that is doped with N-type impurities at a low concentration.
  • the semiconductor layers 120, 130 and 140 may be formed of amorphous silicon
  • the semiconductor layers 120, 130 and 140 may be formed of compound semiconductor.
  • Each of the first conductive type semiconductor layer 120 and the second conductive type semiconductor layer 140 may be multilayered. Also, the first conductive type semiconductor layer 120, the light-absorbing layer 130, and the second conductive type semiconductor layer 140 are sequentially stacked to constitute a light-converting layer, and the light-converting layer may be stacked several times. That is, although FIG 1 illustrates the light-converting layer including the first conductive type semiconductor layer 120, the light- absorbing layer 130, and the second conductive type semiconductor layer 140 that are stacked one time between the front transparent electrode 110 and the rear transparent electrode 150, the light-converting layer may be stacked several times between the front transparent electrode 110 and the rear transparent electrode 150.
  • the rear transparent electrode 150 may be formed of the same material as the front transparent electrode 110.
  • the electrode unit 160 is formed by depositing conductive material over the rear transparent electrode 150 and patterning the deposited material. Although it is not shown, the electrode unit 160 includes a first electrode electrically connected to the rear transparent electrode 150 and a second electrode electrically connected to the front transparent electrode 110. Herein, the second electrode may be formed in an empty region that is formed by partially removing the rear transparent electrode 150, the second conductive type semiconductor layer 140, the light-absorbing layer 130, and the first conductive type semiconductor layer 120 that are disposed over the front transparent electrode 110.
  • step SlO the light-condensing sheet 100 is attached on the transparent substrate 10. That is, the surface of the light-condensing sheet 100 where a light-condensing pattern, i.e., a convexo-concave portion, is not formed is attached on the transparent substrate 10.
  • step S20 the front transparent electrode 110 is formed over the light-condensing sheet 100, and the layers 120, 130 and 140 constituting the light-converting layer are sequentially formed over the front transparent electrode 110.
  • the rear transparent electrode 150 is formed over the light-converting layer 120, 130 and 140. Subsequentally, the light-converting layer 120, 130 and 140 and the rear transparent electrode 150 are partially removed to expose a portion of the front transparent electrode 110.
  • step S30 conductive material is deposited over the rear transparent electrode 150, and the resulting structure is etched to form the electrode unit 160 electrically connected to the rear transparent electrode 150 and the front transparent electrode 110, thereby completing the fabrication of the solar cell.
  • the solar cell in accordance with this embodiment is not limited to the above- described configurations.
  • the light-condensing sheet 100 may be disposed on the surface of the substrate 10 where the light-converting layer 120, 130 and 140 is not formed. That is, the front transparent electrode 110, the light-converting layer 120, 130 and 140, the rear transparent electrode 150, and the electrode unit 160 are formed over the top surface of the substrate 10, and then the light-condensing sheet 100 having the prism pattern is attached on the bottom surface of the substrate 10, thereby completing the fabrication of the solar cell.
  • the light- condensing sheet 100 can prevent the light- condensing sheet 100 from being deformed by heat generated during the process of forming the front transparent electrode 110, the light-converting layer 120, 130 and 140, the rear transparent electrode 150, and the electrode unit 160. Also, the light- condensing sheet 100 having the prism pattern may be disposed in a light incident region, thereby concentrating the light incident on the substrate 10.
  • the present invention is not limited to the above-described configurations.
  • the light-condensing sheet 100 having the prism pattern may be united with the substrate 10.
  • FIGs. 5 to 8 A description of an overlap between the second embodiment of FIGs. 5 to 8 and the above-described first embodiment of FIGs. 1 to 4 will be omitted for the simplicity of explanation. Furthermore, the following description for the second embodiment can be applied to the first embodiment.
  • FIG 5 is a cross-sectional view of a solar cell in accordance with the second embodiment of the present invention.
  • FIG 6 is a cross-sectional view of a solar cell in accordance with a modification of the second embodiment.
  • FIG 7 is a cross-sectional view of a solar cell in accordance with another modification of the second embodiment.
  • FIG 8 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the second embodiment.
  • the solar cell in accordance with this embodiment includes a substrate 10 having a light-condensing pattern 11 formed at a surface thereof, a front transparent electrode 110, a light-oon verting layer consisting of layers 120, 130 and 140, and a rear transparent electrode 150 that are sequentially formed over the substrate 10, and an electrode unit 160 formed over the rear transparent electrode 150.
  • the substrate 10 may be a transparent substrate, and the light-condensing pattern 11 is formed at the surface of the substrate 10.
  • the light- condensing pattern 11 is formed at the top surface of the substrate 10. That is, the light-condensing pattern 11 is formed at the surface on which the light-converting layer 120, 130 and 140 is to be formed.
  • the light-condensing pattern 11 may be formed at the bottom surface of the substrate 10, i.e., the surface where the light-converting layer 120, 130 and 140 is not formed. It is effective that a prism pattern is used as the light- condensing pattern 11.
  • the light-condensing pattern 11 does not scatter but condense light incident on the substrate 10, thereby increasing the luminance of the incident light.
  • the light- condensing pattern 11 may be consecutive mountain- shaped in cross-section as illustrated in FIG 5.
  • the light-condensing pattern 11 may be consecutive semicircle or semiellipse-shaped in cross-section as illustrated in FIG 6.
  • the mountain- shaped may be point-shaped, e.g., tetragon- shaped, or line-shaped.
  • the semicircle or semiellipse-shaped may be point-shaped, e.g., microlens-shaped, or line-shaped.
  • the light-condensing pattern 11 may be sine wave-shaped or sawtooth wave-shaped in cross-section.
  • a laser-based process, a photoresist layer-based etching process, a sandblaster-based process, a mechanical process, or a molding process may be used to form the substrate 10 having the light-condensing pattern 11.
  • a laser beam is irradiated on a substrate, which has no thin layer formed thereon, to remove a portion of the substrate, thereby forming the light-condensing pattern 11.
  • a photoresist pattern is formed on a substrate, and then a portion of the substrate, which is exposed by the photoresist pattern, is removed to form the light-condensing pattern 11.
  • sands are blasted on a substrate to cut off a portion of the substrate, thereby forming the light-condensing pattern 11.
  • a portion of a substrate is mechanically cut off to form the light- condensing pattern 11.
  • a mold is used to form the light-condensing pattern 11 at a surface of a substrate during the formation of the substrate 10.
  • a molding process may be used to form the light- condensing pattern 11 on the substrate 10.
  • the light-condensing pattern 11 formed on the top surface of the substrate 10 condenses light incident through the bottom surface of the substrate 10, thereby increasing the light intensity. That is, the light-condensing pattern 11 refracts and condenses light to increase the luminance of light incident on the light- converting layer 120, 130 and 140. Also, the formation of the light-condensing pattern 11 on the substrate 10 increases the effective area of the top surface of the substrate 10, thereby increasing the efficiency of the solar cell.
  • the front transparent electrode 110, the light-converting layer 120, 130 and 140, and the rear transparent electrode 150 are formed along the step portion of the light- condensing pattern 11 formed on the top surface of the substrate 10.
  • the front transparent electrode 110, the light-converting layer 120, 130 and 140, and the rear transparent electrode 150 may be formed performing a chemical vapor deposition (CVD) process or a physical vapor deposition (PVD) process.
  • CVD chemical vapor deposition
  • PVD physical vapor deposition
  • LPCVD low- pressure chemical vapor deposition
  • the transparent substrate 10 is prepared first. Thereafter, the light-condensing pattern 11 is formed on the top surface of the transparent substrate 10 in step Sl 10.
  • the light-condensing pattern 11 may be formed by removing a portion of the top surface of the transparent substrate 10 by means of a laser beam.
  • the light-condensing pattern 11 may be formed by removing a portion of the transparent substrate 10 through an etching process using a photoresist mask.
  • the light-condensing pattern 11 may be formed by blasting sands onto the surface of the substrate 10.
  • the light-condensing pattern 11 may be formed on the top surface of the substrate 10 by using a mechanical process or a molding process.
  • the front transparent electrode 110 may be formed performing an LPCVD process.
  • the front transparent electrode 110 may be formed performing a PVD process or an atmospheric pressure chemical vapor deposition (APCVD) process.
  • the light-converting layer i.e., a sequential stack structure of the first conductive type semiconductor layer 120, the light- absorbing layer 130, and the second conductive type semiconductor layer 140, is formed over the front transparent electrode 110 in step S 120.
  • the formation of the front transparent electrode 110 may be omitted, and a buffer layer may be formed between the transparent substrate 10 and the light-converting layer 120, 130 and 140.
  • the rear transparent electrode 150 is formed over the light-converting layer
  • a conductive layer e.g., a metal layer, is formed over the rear transparent electrode 150 and a portion of the conductive layer is etched to form the electrode unit 160 in step S 130.
  • the method of manufacturing the solar cell of this embodiment is not limited to this.
  • the light-converting layer 120, 130 and 140 may be formed over the surface of the transparent substrate 10 on which the light-condensing pattern 11 is not formed.
  • the electrode unit 160 is formed over the top surface of the substrate 10, the present invention is not limited to this. R>r example, a portion of the electrode unit 160 may be formed over the bottom surface of the substrate 10. Also, the electrode unit 160 may be formed performing a deposition process, a conductive paste, a plating process, or a screen printing process.
  • the solar cell in a ⁇ jordance with this embodiment may further include a separate internal pad that is to be connected to an external terminal.
  • the internal pad includes a first pad connected to the front transparent electrode 110 and a second pad connected to the rear transparent electrode 150.

Abstract

Provided are a solar cell and a method of manufacturing the same. The solar cell includes a substrate that has a light-condensing pattern formed at a surface thereof. A first conductive type semiconductor layer, A light-absorbing layer, and a second conductive type semiconductor layer are disposed over the light-condensing pattern. A first electrode and a second electrode are connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively. The light-condensing pattern is formed at the surface of the substrate, or a light-condensing sheet is attached on the surface of the substrate. Thus, incident solar light is condensed to increase the intensity of light incident on a light-converting layer. Therefore, the efficiency of the solar cell can be increased and an effective area of a photoelectric element of the solar cell can be increased.

Description

Description
SOLAR CELL AND METHOD OF MANUFACTURING
THE SAME
Technical Field
[1] The present invention relates to a solar cell and a method of manufacturing the same, and more particularly, to a solar cell having high efficiency by increasing the intensity (i.e., luminance) of solar light incident on a light-condensing sheet type substrate, and a method of manufacturing the same. Background Art
[2] In a solar cell, the absorption of light leads to the production of electron-hole pairs in a semiconductor, and an electric field induced at a PN junction of the semiconductor causes the electrons to move to a first conductive type semiconductor and the holes to move to a second conductive type semiconductor, thereby generating electricity.
[3] The performance of the solar cell greatly depends on the efficiency of converting optical energy into electrical energy. Thus, extensive researches are being conducted to provide methods for increasing the efficiency of a solar cell. An example of methods for increasing the efficiency of a solar cell is to maximize light absorption by texturing a wafer surface. The texturing process increases light absorption through light scattering. Therefore, a device with a texturing pattern has a limitation in that the intensity of incident solar light decreases if light is scattered to the outside of the device.
Disclosure of Invention Technical Problem
[4] The present invention provides a solar cell and a method of manufacturing the same, which forms a light-condensing pattern on a substrate to concentrate incident solar light and increases an effective area of a photoelectric element converting the incident solar light into electrical energy, thereby making it possible to increase the efficiency of the solar cell. Technical Solution
[5] In accordance with one embodiment of the present invention, a solar cell includes: a substrate; a light-condensing sheet disposed on the substrate; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the light-condensing sheet; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[6] In accordance with another embodiment of the present invention, a solar cell includes: a substrate; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the substrate; first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer; and a light-condensing sheet disposed on a surface of the substrate over which the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are not disposed.
[7] The light-condensing sheet may be a prism sheet.
[8] The light-condensing sheet may have a surface on which a convexo-concave portion is formed and the convex of the convexo-concave portion is triangular, circular or elliptical.
[9] The convexo-concave portion may have V-shaped concaves, wherein each of the V- shaped concaves may have a slope of approximately 20° to approximately 80° and the adjacent con vexes of the convexo-concave portion may have a pitch of approximately 10/M to approximately 1000/M therebetween.
[10] The convex may be consecutive point-shaped or line-shaped.
[11] In accordance with still another embodiment of the present invention, a solar cell includes: a substrate having a light-condensing pattern formed at a surface thereof; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the light-condensing pattern; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[12] In accordance with further still another embodiment of the present invention, a solar cell includes: a substrate having a light-condensing pattern formed at a surface thereof; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over an opposite surface of the substrate where the light-condensing pattern is not formed; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[13] The light-condensing sheet may have a surface on which a convexo-concave portion is formed and the convex of the convexo-concave portion is triangular, circular or elliptical. [14] The convex may be consecutive point-shaped or line-shaped.
[15] The first conductive type semiconductor layer, a light- absorbing layer, and a second conductive type semiconductor layer are sequentially stacked and the solar cell further includes transparent electrodes disposed at the outsides of the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively.
[16] In accordance with further still another embodiment of the present invention, a method of manufacturing a solar cell includes: attaching a light-condensing sheet on a substrate; sequentially stacking a first conductive type semiconductor layer, a light- absorbing layer and a second conductive type semiconductor layer over the light- condensing sheet; and forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[17] In accordance with further still another embodiment of the present invention, a method of manufacturing a solar cell includes: providing a substrate; sequentially stacking a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer over the substrate; forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer; and attaching a light- condensing sheet on a surface of the substrate over which the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are not formed.
[18] In accordance with further still another embodiment of the present invention, a method of manufacturing a solar cell includes: providing a substrate; forming a light- condensing pattern on a surface of the substrate; sequentially stacking a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer over the substrate; and forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[19] The first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer may be formed over the light-condensing pattern, or over an opposite surface of the substrate where the light-condensing pattern is not formed.
[20] The light-condensing pattern may be formed performing one of a laser-based process, a photoresist layer-based etching process, a sandblaster-based process, a mechanical process, or a molding process. [21] The method of manufacturing the solar cell may further include forming a front transparent electrode before sequentially stacking the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer and forming a rear transparent electrode after sequentially stacking the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer.
Advantageous Effects
[22] As described above, in accordance with the present invention, the light-condensing sheet attached on the substrate can concentrate the incident solar light and thus increase the intensity of light incident on the light-converting layer, thereby increasing the efficiency of the solar cell.
[23] Also, in accordance with the present invention, the light-condensing pattern formed on the substrate can concentrate solar light incident on the substrate, thereby increasing the efficiency of the solar cell.
[24] Also, in accordance with the present invention, the light-converting layer is formed on the substrate having the light-condensing sheet attached thereon or the light- condensing pattern formed thereon, so that it possible to increase the effective area of the photoelectric element of the solar cell. Brief Description of the Drawings
[25] FIG 1 is a cross-sectional view of a solar cell in accordance with a first embodiment of the present invention;
[26] FIG 2 is a cross-sectional view of a solar cell in accordance with a modification of the first embodiment of the present invention;
[27] FIG 3 is a cross-sectional view of a solar cell in accordance with another modification of the first embodiment of the present invention;
[28]
[29] *FIG 4 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the first embodiment of the present invention;
[30] FIG 5 is a cross-sectional view of a solar cell in accordance with a second embodiment of the present invention;
[31] FIG 6 is a cross-sectional view of a solar cell in accordance with a modification of the second embodiment of the present invention;
[32] FIG 7 is a cross-sectional view of a solar cell in accordance with another modification of the second embodiment of the present invention; and [33] FIG 8 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the second embodiment of the present invention. Best Mode for Carrying Out the Invention
[34] Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals refer to like elements throughout.
[35] FIG 1 is a cross-sectional view of a solar cell in accordance with a first embodiment of the present invention. FIG 2 is a cross-sectional view of a solar cell in accordance with a modification of the first embodiment of the present invention. FIG 3 is a cross- sectional view of a solar cell in accordance with another modification of the first embodiment of the present invention. FIG 4 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the first embodiment of the present invention.
[36] Referring to FIGs. 1 to 3, the solar cell in accordance with the first embodiment includes a substrate 10, a light-condensing sheet 100 disposed over the substrate 10, a front transparent electrode 110 formed over the light-condensing sheet 100, a first conductive type semiconductor layer 120 formed over the front transparent electrode 110, a light- absorbing layer 130 formed over the first conductive type semiconductor layer 120, a second conductive type semiconductor layer 140 formed over the light- absorbing layer 130, a rear transparent electrode 150 formed over the second conductive type semiconductor layer 140 and an electrode unit 160 formed over the rear transparent electrode 150.
[37] The substrate 10 may be a transparent insulating substrate. Examples of the transparent insulating substrate are a glass substrate and a transparent resin substrate.
[38] The light-condensing sheet 100 condenses light that is incident through the transparent insulating substrate 10, thereby increasing the light intensity. To this end, this embodiment may use a prism sheet as the light-condensing sheet 100. The prism sheet refracts and condenses light to increase the luminance of light incident on a light- converting layer. The light-condensing sheet 100 may be formed of polyester (PET) or polycarbonate (PC). It is effective that the light-condensing sheet 100 has a prism pattern formed on a surface thereof. As illustrated in FIG 1, the prism pattern on the surface of the light-condensing sheet 100 has V-shaped concaves and mountain- shaped convexes. That is, the prism pattern may have wedged convexo-ooncaves in cross- section. Alternatively, the prism pattern may have sinusoidal convexo-concaves, i.e., semicircular convexo-concaves, in cross-section. Each of the V-shaped concaves may have a slope of approximately 20° to approximately 80° with respect to the surface of the substrate 10. Also, the adjacent mountain-shaped convexes may have a pitch of approximately 10/M to approximately 1000/M therebetween. Herein, the prism pattern may have a plurality of point patterns that are polygonal horn-shaped and are arranged consecutively, or may have a plurality of lines that are triangular in cross-section and are arranged consecutively in the longitudinal or latitudinal direction.
[39] The prism pattern is not limited to the above-described configurations, and may be circular or elliptical as illustrated in FIG 2. R>r example, as illustrated in FIG 2, the prism pattern may have a plurality of circular or elliptical microlens patterns that are arranged in an embossing configuration. Of course, the prism pattern may have a plurality of lines that are circular or elliptical in cross-section and are arranged consecutively in the longitudinal or latitudinal direction. The prism pattern is not limited to the above-described configurations and may be any other types of patterns that can condense light.
[40] As described above, the light-condensing sheet 100 of this embodiment has the prism pattern on the surface thereof to condense light incident thereon. Also, the formation of the convexo-concave prism pattern increases a light-receiving area of a photoelectric element and thus increases an effective area of the photoelectric element, thereby increasing the efficiency of the solar cell. The light-condensing sheet 100 may be fabricated in a separate process and then attached on the substrate 10.
[41] The front transparent electrode 110 may have a transparent conductive electrode. In this embodiment, the front transparent electrode 110 may be formed of transparent conductive oxide (TCO). The TCO may be deposited by low-pressure chemical vapor deposition (LPCVD) in order to form the front transparent electrode 110 along the step portion of the prism pattern.
[42] The first conductive type semiconductor layer 120 may include a silicon layer that is doped with P- type impurities at a low concentration. The light- absorbing layer 130 may include a silicon layer that is not doped with impurities. The second conductive type semiconductor layer 140 may include a silicon layer that is doped with N-type impurities at a low concentration.
[43] The semiconductor layers 120, 130 and 140 may be formed of amorphous silicon
(a-Si) that is grown at low temperatures. The present invention is not limited to this. For example, the semiconductor layers 120, 130 and 140 may be formed of compound semiconductor.
[44] Each of the first conductive type semiconductor layer 120 and the second conductive type semiconductor layer 140 may be multilayered. Also, the first conductive type semiconductor layer 120, the light-absorbing layer 130, and the second conductive type semiconductor layer 140 are sequentially stacked to constitute a light-converting layer, and the light-converting layer may be stacked several times. That is, although FIG 1 illustrates the light-converting layer including the first conductive type semiconductor layer 120, the light- absorbing layer 130, and the second conductive type semiconductor layer 140 that are stacked one time between the front transparent electrode 110 and the rear transparent electrode 150, the light-converting layer may be stacked several times between the front transparent electrode 110 and the rear transparent electrode 150.
[45] The rear transparent electrode 150 may be formed of the same material as the front transparent electrode 110.
[46] The electrode unit 160 is formed by depositing conductive material over the rear transparent electrode 150 and patterning the deposited material. Although it is not shown, the electrode unit 160 includes a first electrode electrically connected to the rear transparent electrode 150 and a second electrode electrically connected to the front transparent electrode 110. Herein, the second electrode may be formed in an empty region that is formed by partially removing the rear transparent electrode 150, the second conductive type semiconductor layer 140, the light-absorbing layer 130, and the first conductive type semiconductor layer 120 that are disposed over the front transparent electrode 110.
[47] Hereinafter, a method of fabricating the above-described solar cell in accordance with the first embodiment of the present invention will be described with reference to FIG 4.
[48] Referring to FIG 4, in step SlO, the light-condensing sheet 100 is attached on the transparent substrate 10. That is, the surface of the light-condensing sheet 100 where a light-condensing pattern, i.e., a convexo-concave portion, is not formed is attached on the transparent substrate 10. In step S20, the front transparent electrode 110 is formed over the light-condensing sheet 100, and the layers 120, 130 and 140 constituting the light-converting layer are sequentially formed over the front transparent electrode 110. Thereafter, the rear transparent electrode 150 is formed over the light-converting layer 120, 130 and 140. Subsequentally, the light-converting layer 120, 130 and 140 and the rear transparent electrode 150 are partially removed to expose a portion of the front transparent electrode 110. Thereafter, in step S30, conductive material is deposited over the rear transparent electrode 150, and the resulting structure is etched to form the electrode unit 160 electrically connected to the rear transparent electrode 150 and the front transparent electrode 110, thereby completing the fabrication of the solar cell.
[49] The solar cell in accordance with this embodiment is not limited to the above- described configurations. R>r example, the light-condensing sheet 100 may be disposed on the surface of the substrate 10 where the light-converting layer 120, 130 and 140 is not formed. That is, the front transparent electrode 110, the light-converting layer 120, 130 and 140, the rear transparent electrode 150, and the electrode unit 160 are formed over the top surface of the substrate 10, and then the light-condensing sheet 100 having the prism pattern is attached on the bottom surface of the substrate 10, thereby completing the fabrication of the solar cell. This can prevent the light- condensing sheet 100 from being deformed by heat generated during the process of forming the front transparent electrode 110, the light-converting layer 120, 130 and 140, the rear transparent electrode 150, and the electrode unit 160. Also, the light- condensing sheet 100 having the prism pattern may be disposed in a light incident region, thereby concentrating the light incident on the substrate 10.
[50] The present invention is not limited to the above-described configurations. For example, the light-condensing sheet 100 having the prism pattern may be united with the substrate 10.
[51] Hereinafter, a solar cell in accordance with a second embodiment of the present invention will be described with reference to FIGs. 5 to 8. A description of an overlap between the second embodiment of FIGs. 5 to 8 and the above-described first embodiment of FIGs. 1 to 4 will be omitted for the simplicity of explanation. Furthermore, the following description for the second embodiment can be applied to the first embodiment.
[52] FIG 5 is a cross-sectional view of a solar cell in accordance with the second embodiment of the present invention. FIG 6 is a cross-sectional view of a solar cell in accordance with a modification of the second embodiment. FIG 7 is a cross-sectional view of a solar cell in accordance with another modification of the second embodiment. FIG 8 is a flow chart illustrating a method of manufacturing the solar cell in accordance with the second embodiment.
[53] Referring to FIGs. 5 to 7, the solar cell in accordance with this embodiment includes a substrate 10 having a light-condensing pattern 11 formed at a surface thereof, a front transparent electrode 110, a light-oon verting layer consisting of layers 120, 130 and 140, and a rear transparent electrode 150 that are sequentially formed over the substrate 10, and an electrode unit 160 formed over the rear transparent electrode 150.
[54] The substrate 10 may be a transparent substrate, and the light-condensing pattern 11 is formed at the surface of the substrate 10. Referring to FIGs. 5 and 6, the light- condensing pattern 11 is formed at the top surface of the substrate 10. That is, the light-condensing pattern 11 is formed at the surface on which the light-converting layer 120, 130 and 140 is to be formed. This embodiment is not limited to this. For example, as illustrated in FIG 7, the light-condensing pattern 11 may be formed at the bottom surface of the substrate 10, i.e., the surface where the light-converting layer 120, 130 and 140 is not formed. It is effective that a prism pattern is used as the light- condensing pattern 11.
[55] The light-condensing pattern 11 does not scatter but condense light incident on the substrate 10, thereby increasing the luminance of the incident light. The light- condensing pattern 11 may be consecutive mountain- shaped in cross-section as illustrated in FIG 5. Alternatively, the light-condensing pattern 11 may be consecutive semicircle or semiellipse-shaped in cross-section as illustrated in FIG 6. Herein, from the plan view, the mountain- shaped may be point-shaped, e.g., tetragon- shaped, or line-shaped. Also, from the plan view, the semicircle or semiellipse-shaped may be point-shaped, e.g., microlens-shaped, or line-shaped. The present invention is not limited to this. For example, the light-condensing pattern 11 may be sine wave-shaped or sawtooth wave-shaped in cross-section.
[56] A laser-based process, a photoresist layer-based etching process, a sandblaster-based process, a mechanical process, or a molding process may be used to form the substrate 10 having the light-condensing pattern 11.
[57] For example, a laser beam is irradiated on a substrate, which has no thin layer formed thereon, to remove a portion of the substrate, thereby forming the light-condensing pattern 11. Alternatively, a photoresist pattern is formed on a substrate, and then a portion of the substrate, which is exposed by the photoresist pattern, is removed to form the light-condensing pattern 11. Alternatively, sands are blasted on a substrate to cut off a portion of the substrate, thereby forming the light-condensing pattern 11. Alternatively, a portion of a substrate is mechanically cut off to form the light- condensing pattern 11. Alternatively, a mold is used to form the light-condensing pattern 11 at a surface of a substrate during the formation of the substrate 10. Herein, if the substrate 10 is a resin substrate, a molding process may be used to form the light- condensing pattern 11 on the substrate 10.
[58] As illustrated in FIG 5, the light-condensing pattern 11 formed on the top surface of the substrate 10 condenses light incident through the bottom surface of the substrate 10, thereby increasing the light intensity. That is, the light-condensing pattern 11 refracts and condenses light to increase the luminance of light incident on the light- converting layer 120, 130 and 140. Also, the formation of the light-condensing pattern 11 on the substrate 10 increases the effective area of the top surface of the substrate 10, thereby increasing the efficiency of the solar cell.
[59] The front transparent electrode 110, the light-converting layer 120, 130 and 140, and the rear transparent electrode 150 are formed along the step portion of the light- condensing pattern 11 formed on the top surface of the substrate 10. The front transparent electrode 110, the light-converting layer 120, 130 and 140, and the rear transparent electrode 150 may be formed performing a chemical vapor deposition (CVD) process or a physical vapor deposition (PVD) process. Herein, in order to prevent the formation of a void or empty space, it is effective that the front transparent electrode 110 and the rear transparent electrode 150 are formed performing a low- pressure chemical vapor deposition (LPCVD) process.
[60] Hereinafter, a method of fabricating the above-described solar cell in accordance with the second embodiment will be described with reference to FIG 8.
[61] Referring to FIG 8, the transparent substrate 10 is prepared first. Thereafter, the light-condensing pattern 11 is formed on the top surface of the transparent substrate 10 in step Sl 10. Herein, the light-condensing pattern 11 may be formed by removing a portion of the top surface of the transparent substrate 10 by means of a laser beam. Alternatively, the light-condensing pattern 11 may be formed by removing a portion of the transparent substrate 10 through an etching process using a photoresist mask. Alternatively, the light-condensing pattern 11 may be formed by blasting sands onto the surface of the substrate 10. Alternatively, the light-condensing pattern 11 may be formed on the top surface of the substrate 10 by using a mechanical process or a molding process.
[62] Thereafter, the front transparent electrode 110 is formed on the transparent substrate
10 having the light-condensing pattern 11. Herein, the front transparent electrode 110 may be formed performing an LPCVD process. Alternatively, the front transparent electrode 110 may be formed performing a PVD process or an atmospheric pressure chemical vapor deposition (APCVD) process. Thereafter, the light-converting layer, i.e., a sequential stack structure of the first conductive type semiconductor layer 120, the light- absorbing layer 130, and the second conductive type semiconductor layer 140, is formed over the front transparent electrode 110 in step S 120. Herein, the formation of the front transparent electrode 110 may be omitted, and a buffer layer may be formed between the transparent substrate 10 and the light-converting layer 120, 130 and 140.
[63] Then, the rear transparent electrode 150 is formed over the light-converting layer
120, 130 and 140. Thereafter, a conductive layer, e.g., a metal layer, is formed over the rear transparent electrode 150 and a portion of the conductive layer is etched to form the electrode unit 160 in step S 130.
[64] Although it has been described that the light-converting layer 120, 130 and 140 is formed over the light-condensing pattern 11 of the transparent substrate 10, the method of manufacturing the solar cell of this embodiment is not limited to this. R>r example, the light-converting layer 120, 130 and 140 may be formed over the surface of the transparent substrate 10 on which the light-condensing pattern 11 is not formed.
[65] Also, although it has been described that the electrode unit 160 is formed over the top surface of the substrate 10, the present invention is not limited to this. R>r example, a portion of the electrode unit 160 may be formed over the bottom surface of the substrate 10. Also, the electrode unit 160 may be formed performing a deposition process, a conductive paste, a plating process, or a screen printing process.
[66] Also, the solar cell in aαjordance with this embodiment may further include a separate internal pad that is to be connected to an external terminal. Herein, the internal pad includes a first pad connected to the front transparent electrode 110 and a second pad connected to the rear transparent electrode 150.
[67] Although the solar cell and the method of manufacturing the same have been described with reference to the specific embodiments, they are not limited thereto. Therefore, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

Claims
[1] A solar cell, comprising: a substrate; a light-condensing sheet disposed on the substrate; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the light-condensing sheet; transparent electrodes disposed at the outsides of the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[2] The solar cell of claim 1, wherein the light-condensing sheet has a surface on which a convexo-concave portion is formed, and an opposite surface attached on the substrate.
[3] The solar cell of claim 1, wherein the light-condensing sheet includes a prism sheet.
[4] The solar cell of claim 2, wherein the convexo-concave portion has V-shaped concaves and each of the V-shaped concaves has a slope of approximately 20° to approximately 80°.
[5] The solar cell of claim 2, wherein the adjacent convexes of the convexo-concave portion has a pitch of approximately 10/M to approximately 1000/M therebetween.
[6] A solar cell, comprising: a substrate; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the substrate; transparent electrodes disposed at the outsides of the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively; first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer; and a light-condensing sheet disposed on the surface of the substrate where the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are not disposed.
[7] The solar cell of claim 6, wherein the light-condensing sheet has a surface on which a convexo-concave portion is formed, and an opposite surface attached on the substrate.
[8] The solar cell of claim 6, wherein the light-condensing sheet includes a prism sheet.
[9] The solar cell of claim 7, wherein the convexo-concave portion has V-shaped concaves and each of the V-shaped concaves has a slope of approximately 20° to approximately 80°.
[10] The solar cell of claim 7, wherein the adjacent con vexes of the convexo-concave portion has a pitch of approximately 10/M to approximately 1000/M therebetween.
[11] A solar cell, comprising : a substrate having a light-condensing pattern formed at a surface thereof, wherein the light-condensing pattern has a convexo-concave portion and the convex of the convexo-concave portion is triangular, circular or elliptical; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over the light-condensing pattern; transparent electrodes disposed at the outsides of the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[12] A solar cell, comprising: a substrate having a light-condensing pattern formed at a surface thereof, wherein the light-condensing pattern has a convexo-concave portion and the convex of the convexo-concave portion is triangular, circular or elliptical; a first conductive type semiconductor layer, a light-absorbing layer, and a second conductive type semiconductor layer that are stacked over an opposite surface of the substrate where the light-condensing pattern is not formed; transparent electrodes disposed at the outsides of the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively; and first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[13] A method of manufacturing a solar cell, the method comprising: attaching a light-condensing sheet on a substrate; sequentially stacking a front transparent electrode, a first conductive type semiconductor layer, a light-absorbing layer, a second conductive type semiconductor layer, and a rear transparent electrode over the light-condensing sheet; and forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[14] A method of manufacturing a solar cell, the method comprising: providing a substrate; sequentially stacking a front transparent electrode, a first conductive type semiconductor layer, a light-absorbing layer, a second conductive type semiconductor layer, and a rear transparent electrode over the substrate; forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer; and attaching a light-condensing sheet on a surface of the substrate voer which the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are not formed.
[15] A method of manufacturing a solar cell, the method comprising: providing a substrate; forming a light-condensing pattern on a surface of the substrate; sequentially stacking a front transparent electrode, a first conductive type semiconductor layer, a light-absorbing layer, a second conductive type semiconductor layer, and a rear transparent electrode over the substrate; and forming first and second electrodes respectively connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer.
[16] The method of claim 15, wherein the first conductive type semiconductor layer, the light-absorbing layer, and the second conductive type semiconductor layer are formed on the light-condensing pattern, or on an opposite surface of the substrate on which the light-condensing pattern is not formed.
[17] The method of claim 15, wherein the light-condensing pattern is formed performing one of a laser-based process, a photoresist layer-based etching process, a sandblaster-based process, a mechanical process, or a molding process.
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