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WO2013094935A1 - 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
WO2013094935A1
WO2013094935A1 PCT/KR2012/010868 KR2012010868W WO2013094935A1 WO 2013094935 A1 WO2013094935 A1 WO 2013094935A1 KR 2012010868 W KR2012010868 W KR 2012010868W WO 2013094935 A1 WO2013094935 A1 WO 2013094935A1
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WIPO (PCT)
Prior art keywords
solar cell
light absorbing
electrode layer
absorbing layer
layer
Prior art date
Application number
PCT/KR2012/010868
Other languages
French (fr)
Inventor
Jin Woo Lee
Se Han Kwon
Chul Hwan Choi
Original Assignee
Lg Innotek Co., Ltd.
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Publication date
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Publication of WO2013094935A1 publication Critical patent/WO2013094935A1/en

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/14—Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
    • H10F77/143—Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies comprising quantum structures
    • H10F77/1433—Quantum dots
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/16—Photovoltaic cells having only PN heterojunction potential barriers
    • H10F10/167—Photovoltaic cells having only PN heterojunction potential barriers comprising Group I-III-VI materials, e.g. CdS/CuInSe2 [CIS] heterojunction photovoltaic cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/16—Material structures, e.g. crystalline structures, film structures or crystal plane orientations
    • H10F77/169—Thin semiconductor films on metallic or insulating substrates
    • H10F77/1694—Thin semiconductor films on metallic or insulating substrates the films including Group I-III-VI materials, e.g. CIS or CIGS
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/16—Material structures, e.g. crystalline structures, film structures or crystal plane orientations
    • H10F77/169—Thin semiconductor films on metallic or insulating substrates
    • H10F77/1698—Thin semiconductor films on metallic or insulating substrates the metallic or insulating substrates being flexible
    • H10F77/1699—Thin semiconductor films on metallic or insulating substrates the metallic or insulating substrates being flexible the films including Group I-III-VI materials, e.g. CIS or CIGS on metal foils or polymer foils
    • 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.
  • Solar cells may be defined as devices for converting light energy into electric energy by using a photovoltaic effect of generating electrons when light is incident onto a P-N junction diode.
  • the solar cell may be classified into a silicon solar cell, a compound semiconductor solar cell mainly including a group I-III-VI compound or a group III-V compound, a dye-sensitized solar cell, and an organic solar cell according to materials constituting the junction diode.
  • a solar cell made from CIGS (CuInGaSe), which is one of group I-III-VI Chalcopyrite-based compound semiconductors, represents superior light absorption, higher photoelectric conversion efficiency with a thin thickness, and superior electro-optic stability, so the CIGS solar cell is spotlighted as a substitute for a conventional silicon solar cell.
  • a light absorbing layer having a composition of Cu(In,Ga)Se2 and or a buffer layer consisting of CdS and other n-type chemical compound semiconductor may be the most core elements of the CIGS solar cell.
  • a CIS or CIGS light absorbing layer may be the most important element to determine performance of the solar cell.
  • the CIS or CIGS light absorbing layer is prepared by simultaneously evaporating metallic elements in the Se gas atmosphere or is prepared through a selenization process after depositing a Cu-Ga-In alloy layer in a vacuum state.
  • a Se compound which is a toxic material, is used in a gas state so that the possibility of air pollution is extremely high.
  • a CIGS solar cell fabricated through the above schemes represents high photoelectric conversion efficiency, vacuum equipment is required and a great amount of source metals is lost, so the manufacturing cost for the CIGS solar cell may be increased.
  • the embodiment provides a solar cell capable of improving photoelectric conversion efficiency, and a method of fabricating the same.
  • a solar cell including: a back electrode layer on a support substrate; a light absorbing layer disposed on the back electrode layer and comprising a carbon structure; and a front electrode layer on the light absorbing layer.
  • a method of fabricating a solar cell including: forming a back electrode layer on a support substrate; forming a light absorbing layer comprising a carbon structure on the back electrode layer; and forming a front electrode layer on the light absorbing layer.
  • the solar cell according to the embodiment provides a light absorbing layer including a graphene. Since the grapheme represents superior electric properties such as an electric conductivity and electron mobility, the solar cell according to the embodiment can increase electron mobility in the light absorbing layer by about 100 times or more, and obtain a sufficient Jsc in even a thinner thickness of a thin film so that device efficiency can be improved.
  • FIGS. 1 and 4 are sectional views showing a method of fabricating a solar cell according to the embodiment.
  • graphene refers to a polycyclic aromatic molecule consisting of a plurality of carbon atoms covalently bonded to each other.
  • the covalently bonded carbon atoms may from a six-member ring as repeating unit, and may further include at least one of a five-member ring and a seven-member ring.
  • the graphene includes a single layer of covalently bonded carbon atoms having sp2 hybridization.
  • the graphene may have various structures. The above structures may be changed according to a content of the five-member ring and/or the seven-member ring which may be included in the grapheme.
  • the grapheme may include a single layer of graphene or may include a plurality of layers of carbon. Typically, a side end of the grapheme is saturated with hydrogen atoms.
  • FIGS. 1 and 4 are sectional views showing a method of fabricating a solar cell according to the embodiment.
  • the solar cell and a method of fabricating the same according to the embodiment will be described with reference to FIGS. 1 to 4.
  • a back electrode layer 200 is formed on a substrate 100.
  • the support substrate 100 has a plate shape and supports the back electrode layer 200, a light absorbing layer 300, a buffer layer 400, a high-resistance layer 600, and a front electrode layer 700.
  • the support substrate 100 may include an insulator.
  • the support substrate 100 may include a glass substrate, a plastic substrate, or a metallic substrate.
  • the support substrate 100 may include a soda lime glass substrate.
  • the support substrate 100 may be transparent.
  • the support substrate 100 may be rigid or flexible.
  • the back electrode layer 200 may be formed on the substrate 100 through a Physical Vapor Deposition (PVD) scheme or a plating scheme.
  • PVD Physical Vapor Deposition
  • the back electrode layer 200 is a conductive layer.
  • the back electrode layer 200 may include at least of molybdenum (Mo), gold (Au), aluminum (Al), chrome (Cr), tungsten (W), and copper (Cu).
  • the back electrode layer 200 may include the Mo.
  • the Mo has a thermal expansion coefficient similar to that of the support substrate 100, so the Mo may improve the adhesive property and prevent the back electrode layer 200 from being delaminated from the substrate 100, and totally satisfying the characteristic required for the back electrode layer 200. That is, it is preferable that the back electrode layer 200 is a Mo layer.
  • the light absorbing layer 300 is disposed on the back electrode layer 200.
  • the light absorbing layer 300 includes a group I-III-VI compound.
  • the light absorbing layer 300 may include a plurality of nano particles 310 having a group I-III-VI compound.
  • the light absorbing layer 300 may have the CIGSS (Cu(IN,Ga)(Se,S)2) crystal structure, the CISS (Cu(IN)(Se,S)2) crystal structure or the CGSS (Cu(Ga)(Se,S)2) crystal structure.
  • the light absorbing layer 300 includes a carbon structure 320.
  • the carbon structure 320 includes a graphene, a graphite, or a carbon nano tube.
  • the carbon structure 320 may include the grapheme, but the embodiment is not limited thereto.
  • the graphene 320 may include a functional graphene which is vertically self-aligned with respect to the support substrate.
  • the vertically self-aligned graphene 320 may be formed on the nano particle 310 including the group I-III-VI compound.
  • graphene as used throughout the specification refers to a polycyclic aromatic molecule consisting of a plurality of carbon atoms covalently bonded to each other.
  • the covalently bonded carbon atoms may from a six-member ring as a basic repeating unit, and may further include at least one of a five-member ring and a seven-member ring.
  • the grapheme 320 represents superior electric properties such as an electric conductivity and electron mobility. Accordingly, charge mobility of the light absorbing layer 300 including the graphene 320 according to the embodiment is about 100 cm2/Vs, which may be higher by about 100 times or above as compared with the charge mobility (1 cm2/Vs) of the light absorbing layer according to the related art. Therefore, the solar cell according to the embodiment obtains a sufficient Jsc in a thinner thickness of a thin film so that device efficiency can be improved.
  • the light absorbing layer 300 including the carbon structure 320 according to the embodiment is formed under a non-vacuum atmosphere.
  • the light absorbing layer 300 prepared under a non-vacuum atmosphere according to the related art represents the electron mobility and shunt resistance characteristic significantly lower than those of a light absorbing layer prepare through vacuum deposition.
  • the carbon structure 320 having superior electric conductivity is formed when preparing the light absorbing layer 300.
  • the nana particle 310 including the group I-III-VI compound and the carbon structure 320 are dispersed in a solvent to form a paste and a mixed ink.
  • the nano particle 310 including the group I-III-VI compound may be fabricated by preparing a Cu precursor, an In precursor, a Ga precursor, and a Se precursor, and mixing the Cu precursor, the In precursor, the Ga precursor, and the Se precursor to produce a mixture, and performing heat treatment with respect to the mixture.
  • the Cu precursor, the In precursor, the Ga precursor, and the Se precursor may include a salt and an oxide of Cu, In, Ga and Se or a salt and an oxide of an alloy including at least two of the above metals, such as hydroxide, nitrate, sulfate, acetate, chloride, acetylacetonate, and formaldehyde.
  • a dispersing agent and a binder may be added according to a usage purpose of a finally obtained paste or ink.
  • the dispersing agent or the binder may include all dispersing agents or binders generally known in the art or a combination thereof.
  • the dispersing agent includes ⁇ -tefenol, ethylene glycol, and thioacetamide.
  • the binder includes ethyl cellulose, palmitic acid, polyethylene glycol, polypropylene glycol, and polypropylene carbonate.
  • a usage amount of the dispersing agent or the binder is not specifically limited.
  • the graphene may be vertically self-aligned on the support substrate 100 by an electrostatic self-assembly scheme during the above manufacturing procedure, but the embodiment is not limited thereto.
  • the paste or the ink fabricated by the above scheme is coated on the back electrode layer and performing heat treatment with respect to the back electrode layer 200 coated with the paste or the ink.
  • the coating scheme may include a doctor blade coating scheme, a screen coating scheme, a spin coating scheme, a spray coating scheme, and a paint coating scheme generally known in the art.
  • Heat treatment with respect to the coated paste may be performed at a temperature in the range of about 200 to about 700°C, preferably, about 350 °C to about 550 °C under an inert gas atmosphere and/or a reducing gas atmosphere, for example, a mixed gas atmosphere of hydrogen and inert gat such as hydrogen/argon, but the embodiment is not limited thereto.
  • the method of fabricating the light absorbing layer 300 according to the embodiment uses paste or ink instead of a vacuum deposition scheme according to the related art. According to the method of the embodiment, loss of a raw material during production of the light absorbing layer 300 can be reduced and the mass production of the light absorbing layer 300 having a large area can be achieved. In addition, a thin film may be fabricated at a low cost using a stable scheme without using toxic gas.
  • the light absorbing layer 300 fabricated by the above scheme represents superior crystallinity and has large-size particles, so that a problem, such as a pin-hole, may not be caused in film formation. Since the light absorbing layer 300 includes a self-aligned graphene, charge mobility in the light absorbing layer 300 is significantly increased so that a sufficient Jsc can be achieved in a thinner thickness of a thin film. Accordingly, device efficiency can be improved.
  • the buffer layer 400 is provided on the light absorbing layer 300.
  • the CIGS compound, a P-N junction is formed between the light absorbing player 300 of a CIGS or CIGSS compound thin film, which serves as a P-type semiconductor, and the front electrode layer 700 which is an N-type semiconductor.
  • a buffer layer having the intermediate band-gap between the band-gaps of the two materials is required to form the superior junction between the two materials.
  • the buffer layer 400 may have a thickness in the range of about 10 nm to about 30 nm, but the embodiment is not limited thereto.
  • the buffer layer 400 may include cadmium sulfide (CdS), zinc sulfide (ZnS), InXSY, and InXSeYZn(O, OH). It is preferable that the buffer layer 500 may be zinc sulfide (ZnS).
  • the high-resistance buffer layer 500 is disposed on the buffer layer 400.
  • the high-resistance buffer layer 500 may include i-ZnO which is zinc oxide not doped with impurities.
  • the high-resistance buffer layer 500 may be formed by depositing zinc oxide on the buffer layer 400 through a sputtering process.
  • the front electrode layer 600 is formed on the high-resistance buffer layer 500.
  • the front electrode layer 700 is transparent conductive layer.
  • the front electrode layer 600 may include B doped zinc oxide (ZnO:B, BZO), Al doped zinc oxide (AZO), or Ga doped zinc oxide (GZO).
  • the front electrode layer 600 may use Al doped zinc oxide (AZO) or B doped zinc oxide (ZnO:B, BZO) by taking bandgap and contact with the buffer layer 500 into consideration, but the embodiment is not limited thereto.
  • the front electrode layer 600 may be formed by depositing a transparent conductive material on the high-resistance buffer layer 500.
  • the front electrode layer 600 may be deposited through a sputtering scheme or a Metal-Organic Chemical Vapor Deposition (MOCVD) scheme.
  • MOCVD Metal-Organic Chemical Vapor Deposition
  • the front electrode layer 600 may be deposited through a sputtering process.
  • 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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  • Photovoltaic Devices (AREA)

Abstract

Disclosed are a solar cell and a method of fabricating the same. The solar cell solar cell including: a back electrode layer on a support substrate; a light absorbing layer disposed on the back electrode layer and comprising a carbon structure; and a front electrode layer on the light absorbing layer.

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME
The embodiment relates to a solar cell and a method of fabricating the same.
Solar cells may be defined as devices for converting light energy into electric energy by using a photovoltaic effect of generating electrons when light is incident onto a P-N junction diode. The solar cell may be classified into a silicon solar cell, a compound semiconductor solar cell mainly including a group I-III-VI compound or a group III-V compound, a dye-sensitized solar cell, and an organic solar cell according to materials constituting the junction diode.
A solar cell made from CIGS (CuInGaSe), which is one of group I-III-VI Chalcopyrite-based compound semiconductors, represents superior light absorption, higher photoelectric conversion efficiency with a thin thickness, and superior electro-optic stability, so the CIGS solar cell is spotlighted as a substitute for a conventional silicon solar cell.
Generally, a light absorbing layer having a composition of Cu(In,Ga)Se2 and or a buffer layer consisting of CdS and other n-type chemical compound semiconductor may be the most core elements of the CIGS solar cell. Particularly, a CIS or CIGS light absorbing layer may be the most important element to determine performance of the solar cell.
The CIS or CIGS light absorbing layer is prepared by simultaneously evaporating metallic elements in the Se gas atmosphere or is prepared through a selenization process after depositing a Cu-Ga-In alloy layer in a vacuum state. Thus, it is difficult to prepare a large-size CIS or CIGS light absorbing layer and a Se compound, which is a toxic material, is used in a gas state so that the possibility of air pollution is extremely high. In addition, although a CIGS solar cell fabricated through the above schemes represents high photoelectric conversion efficiency, vacuum equipment is required and a great amount of source metals is lost, so the manufacturing cost for the CIGS solar cell may be increased.
The embodiment provides a solar cell capable of improving photoelectric conversion efficiency, and a method of fabricating the same.
According to the embodiment, there is provided a solar cell including: a back electrode layer on a support substrate; a light absorbing layer disposed on the back electrode layer and comprising a carbon structure; and a front electrode layer on the light absorbing layer.
According to the embodiment, there is provided method of fabricating a solar cell, the method including: forming a back electrode layer on a support substrate; forming a light absorbing layer comprising a carbon structure on the back electrode layer; and forming a front electrode layer on the light absorbing layer.
The solar cell according to the embodiment provides a light absorbing layer including a graphene. Since the grapheme represents superior electric properties such as an electric conductivity and electron mobility, the solar cell according to the embodiment can increase electron mobility in the light absorbing layer by about 100 times or more, and obtain a sufficient Jsc in even a thinner thickness of a thin film so that device efficiency can be improved.
FIGS. 1 and 4 are sectional views showing a method of fabricating a solar cell according to the embodiment.
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.
The term “graphene” as used throughout the specification refers to a polycyclic aromatic molecule consisting of a plurality of carbon atoms covalently bonded to each other. The covalently bonded carbon atoms may from a six-member ring as repeating unit, and may further include at least one of a five-member ring and a seven-member ring. Thus, the graphene includes a single layer of covalently bonded carbon atoms having sp2 hybridization. The graphene may have various structures. The above structures may be changed according to a content of the five-member ring and/or the seven-member ring which may be included in the grapheme. The grapheme may include a single layer of graphene or may include a plurality of layers of carbon. Typically, a side end of the grapheme is saturated with hydrogen atoms.
FIGS. 1 and 4 are sectional views showing a method of fabricating a solar cell according to the embodiment. Hereinafter, the solar cell and a method of fabricating the same according to the embodiment will be described with reference to FIGS. 1 to 4.
Referring to FIG. 1, a back electrode layer 200 is formed on a substrate 100. The support substrate 100 has a plate shape and supports the back electrode layer 200, a light absorbing layer 300, a buffer layer 400, a high-resistance layer 600, and a front electrode layer 700.
The support substrate 100 may include an insulator. The support substrate 100 may include a glass substrate, a plastic substrate, or a metallic substrate. In detail, the support substrate 100 may include a soda lime glass substrate. The support substrate 100 may be transparent. The support substrate 100 may be rigid or flexible.
The back electrode layer 200 may be formed on the substrate 100 through a Physical Vapor Deposition (PVD) scheme or a plating scheme.
The back electrode layer 200 is a conductive layer. The back electrode layer 200 may include at least of molybdenum (Mo), gold (Au), aluminum (Al), chrome (Cr), tungsten (W), and copper (Cu). The back electrode layer 200 may include the Mo. The Mo has a thermal expansion coefficient similar to that of the support substrate 100, so the Mo may improve the adhesive property and prevent the back electrode layer 200 from being delaminated from the substrate 100, and totally satisfying the characteristic required for the back electrode layer 200. That is, it is preferable that the back electrode layer 200 is a Mo layer.
Referring to FIG. 2, the light absorbing layer 300 is disposed on the back electrode layer 200. The light absorbing layer 300 includes a group I-III-VI compound. In detail, the light absorbing layer 300 may include a plurality of nano particles 310 having a group I-III-VI compound. For example, the light absorbing layer 300 may have the CIGSS (Cu(IN,Ga)(Se,S)2) crystal structure, the CISS (Cu(IN)(Se,S)2) crystal structure or the CGSS (Cu(Ga)(Se,S)2) crystal structure.
The light absorbing layer 300 includes a carbon structure 320. The carbon structure 320 includes a graphene, a graphite, or a carbon nano tube. In more detail, the carbon structure 320 may include the grapheme, but the embodiment is not limited thereto.
As one example, the graphene 320 may include a functional graphene which is vertically self-aligned with respect to the support substrate. For example, the vertically self-aligned graphene 320 may be formed on the nano particle 310 including the group I-III-VI compound. The term “graphene” as used throughout the specification refers to a polycyclic aromatic molecule consisting of a plurality of carbon atoms covalently bonded to each other. The covalently bonded carbon atoms may from a six-member ring as a basic repeating unit, and may further include at least one of a five-member ring and a seven-member ring.
The grapheme 320 represents superior electric properties such as an electric conductivity and electron mobility. Accordingly, charge mobility of the light absorbing layer 300 including the graphene 320 according to the embodiment is about 100 cm2/Vs, which may be higher by about 100 times or above as compared with the charge mobility (1 cm2/Vs) of the light absorbing layer according to the related art. Therefore, the solar cell according to the embodiment obtains a sufficient Jsc in a thinner thickness of a thin film so that device efficiency can be improved.
The light absorbing layer 300 including the carbon structure 320 according to the embodiment is formed under a non-vacuum atmosphere. The light absorbing layer 300 prepared under a non-vacuum atmosphere according to the related art represents the electron mobility and shunt resistance characteristic significantly lower than those of a light absorbing layer prepare through vacuum deposition. To solve the above problem, in the method of fabricating the solar cell according to the embodiment, the carbon structure 320 having superior electric conductivity is formed when preparing the light absorbing layer 300.
First, the nana particle 310 including the group I-III-VI compound and the carbon structure 320 are dispersed in a solvent to form a paste and a mixed ink. The nano particle 310 including the group I-III-VI compound may be fabricated by preparing a Cu precursor, an In precursor, a Ga precursor, and a Se precursor, and mixing the Cu precursor, the In precursor, the Ga precursor, and the Se precursor to produce a mixture, and performing heat treatment with respect to the mixture. The Cu precursor, the In precursor, the Ga precursor, and the Se precursor may include a salt and an oxide of Cu, In, Ga and Se or a salt and an oxide of an alloy including at least two of the above metals, such as hydroxide, nitrate, sulfate, acetate, chloride, acetylacetonate, and formaldehyde.
During the mixing and stirring reaction procedures, at least one of a dispersing agent and a binder may be added according to a usage purpose of a finally obtained paste or ink. The dispersing agent or the binder may include all dispersing agents or binders generally known in the art or a combination thereof. For example, the dispersing agent includes α-tefenol, ethylene glycol, and thioacetamide. For example, the binder includes ethyl cellulose, palmitic acid, polyethylene glycol, polypropylene glycol, and polypropylene carbonate. A usage amount of the dispersing agent or the binder is not specifically limited.
When the carbon structure 320 is the graphene, the graphene may be vertically self-aligned on the support substrate 100 by an electrostatic self-assembly scheme during the above manufacturing procedure, but the embodiment is not limited thereto.
The paste or the ink fabricated by the above scheme is coated on the back electrode layer and performing heat treatment with respect to the back electrode layer 200 coated with the paste or the ink. For example, the coating scheme may include a doctor blade coating scheme, a screen coating scheme, a spin coating scheme, a spray coating scheme, and a paint coating scheme generally known in the art.
Heat treatment with respect to the coated paste may be performed at a temperature in the range of about 200 to about 700℃, preferably, about 350 ℃ to about 550 ℃ under an inert gas atmosphere and/or a reducing gas atmosphere, for example, a mixed gas atmosphere of hydrogen and inert gat such as hydrogen/argon, but the embodiment is not limited thereto.
The method of fabricating the light absorbing layer 300 according to the embodiment uses paste or ink instead of a vacuum deposition scheme according to the related art. According to the method of the embodiment, loss of a raw material during production of the light absorbing layer 300 can be reduced and the mass production of the light absorbing layer 300 having a large area can be achieved. In addition, a thin film may be fabricated at a low cost using a stable scheme without using toxic gas.
The light absorbing layer 300 fabricated by the above scheme represents superior crystallinity and has large-size particles, so that a problem, such as a pin-hole, may not be caused in film formation. Since the light absorbing layer 300 includes a self-aligned graphene, charge mobility in the light absorbing layer 300 is significantly increased so that a sufficient Jsc can be achieved in a thinner thickness of a thin film. Accordingly, device efficiency can be improved.
Referring to FIG. 3, the buffer layer 400 is provided on the light absorbing layer 300. According to the solar cell, the CIGS compound, a P-N junction is formed between the light absorbing player 300 of a CIGS or CIGSS compound thin film, which serves as a P-type semiconductor, and the front electrode layer 700 which is an N-type semiconductor. However, since two materials represent the great difference in the lattice constant and the band-gap energy therebetween, a buffer layer having the intermediate band-gap between the band-gaps of the two materials is required to form the superior junction between the two materials. The buffer layer 400 may have a thickness in the range of about 10 nm to about 30 nm, but the embodiment is not limited thereto.
The buffer layer 400 may include cadmium sulfide (CdS), zinc sulfide (ZnS), InXSY, and InXSeYZn(O, OH). It is preferable that the buffer layer 500 may be zinc sulfide (ZnS).
The high-resistance buffer layer 500 is disposed on the buffer layer 400. The high-resistance buffer layer 500 may include i-ZnO which is zinc oxide not doped with impurities. The high-resistance buffer layer 500 may be formed by depositing zinc oxide on the buffer layer 400 through a sputtering process.
Referring to FIG. 4, the front electrode layer 600 is formed on the high-resistance buffer layer 500. The front electrode layer 700 is transparent conductive layer. For example, the front electrode layer 600 may include B doped zinc oxide (ZnO:B, BZO), Al doped zinc oxide (AZO), or Ga doped zinc oxide (GZO). In detail, the front electrode layer 600 may use Al doped zinc oxide (AZO) or B doped zinc oxide (ZnO:B, BZO) by taking bandgap and contact with the buffer layer 500 into consideration, but the embodiment is not limited thereto.
The front electrode layer 600 may be formed by depositing a transparent conductive material on the high-resistance buffer layer 500. In detail, the front electrode layer 600 may be deposited through a sputtering scheme or a Metal-Organic Chemical Vapor Deposition (MOCVD) scheme. For example, the front electrode layer 600 may be deposited through a sputtering process.
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 (8)

  1. A solar cell comprising:
    a back electrode layer on a support substrate;
    a light absorbing layer disposed on the back electrode layer and comprising a carbon structure; and
    a front electrode layer on the light absorbing layer.
  2. The solar cell of claim 1, wherein the carbon structure comprises a graphene, a graphite, or a carbon nano tube.
  3. The solar cell of claim 1, wherein the carbon structure is vertically self-aligned with respect to the support substrate.
  4. The solar cell of claim 2, wherein the graphene comprises carbon atoms covalently bonded to each other.
  5. The solar cell of claim 3, wherein the light absorbing layer comprises a nano particle having a group I-III-VI compound, and
    the carbon structure is formed on the nano particle.
  6. A method of fabricating a solar cell, the method comprising:
    forming a back electrode layer on a support substrate;
    forming a light absorbing layer comprising a carbon structure on the back electrode layer; and
    forming a front electrode layer on the light absorbing layer.
  7. The method of claim 6, wherein the forming of the light absorbing layer is performed in a non-vacuum atmosphere.
  8. The method of claim 6, wherein the forming of the light absorbing layer comprises:
    forming a paste by dispersing a nano particle having a group I-III-VI compound and the carbon structure in a solvent;
    coating the paste on the back electrode layer; and
    heat-treating the coated paste.
PCT/KR2012/010868 2011-12-19 2012-12-13 Solar cell and method of fabricating the same WO2013094935A1 (en)

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CN112164867A (en) * 2020-09-21 2021-01-01 西安电子科技大学 Carbon nanotube antenna for solar energy collection

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US9577134B2 (en) * 2013-12-09 2017-02-21 Sunpower Corporation Solar cell emitter region fabrication using self-aligned implant and cap

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KR100649743B1 (en) * 2005-10-20 2006-11-27 삼성전기주식회사 Solar cell containing CNT and manufacturing method thereof
KR101003807B1 (en) * 2008-06-23 2010-12-23 한국기계연구원 Transparent solar cell and method for manufacturing same
KR20110085216A (en) * 2010-01-19 2011-07-27 한양대학교 산학협력단 Stacked organic-inorganic hybrid solar cell containing various kinds of nanoparticles and manufacturing method thereof

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KR100649743B1 (en) * 2005-10-20 2006-11-27 삼성전기주식회사 Solar cell containing CNT and manufacturing method thereof
KR101003807B1 (en) * 2008-06-23 2010-12-23 한국기계연구원 Transparent solar cell and method for manufacturing same
KR20110085216A (en) * 2010-01-19 2011-07-27 한양대학교 산학협력단 Stacked organic-inorganic hybrid solar cell containing various kinds of nanoparticles and manufacturing method thereof

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Publication number Priority date Publication date Assignee Title
CN112164867A (en) * 2020-09-21 2021-01-01 西安电子科技大学 Carbon nanotube antenna for solar energy collection
CN112164867B (en) * 2020-09-21 2022-09-06 西安电子科技大学 Carbon nanotube antenna for solar energy collection

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KR101349505B1 (en) 2014-01-10

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