WO2012161401A1 - METHOD OF MANUFACTURING DENSE CIGSe/CISe THIN FILM USING SELENIZATION OF CIGS/CIS NANOPARTICLES - Google Patents

METHOD OF MANUFACTURING DENSE CIGSe/CISe THIN FILM USING SELENIZATION OF CIGS/CIS NANOPARTICLES Download PDF

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WO2012161401A1
WO2012161401A1 PCT/KR2012/000811 KR2012000811W WO2012161401A1 WO 2012161401 A1 WO2012161401 A1 WO 2012161401A1 KR 2012000811 W KR2012000811 W KR 2012000811W WO 2012161401 A1 WO2012161401 A1 WO 2012161401A1
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Prior art keywords
thin film
cise
cigs
cis
cigse
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PCT/KR2012/000811
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French (fr)
Inventor
Sejin Ahn
Kyung-Hoon Yoon
Jae-Ho Yun
Jihye Gwak
Ara Cho
Kee-Shik Shin
SeoungKyu AHN
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Korea Institute Of Energy Research
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Publication of WO2012161401A1 publication Critical patent/WO2012161401A1/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
    • H01L31/0248—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
    • H01L31/0256—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 the material
    • H01L31/0264—Inorganic materials
    • H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
    • H01L31/0322—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
    • 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
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/0445—PV modules or arrays of single PV cells including thin film solar cells, e.g. single thin film a-Si, CIS or CdTe solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02568—Chalcogenide semiconducting materials not being oxides, e.g. ternary compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02587—Structure
    • H01L21/0259—Microstructure
    • H01L21/02601—Nanoparticles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02623—Liquid deposition
    • H01L21/02628—Liquid deposition using solutions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type
    • H01L31/0749—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/541—CuInSe2 material PV cells
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a method of manufacturing a CIGSe/CISe
  • Solar cells are classified into a variety of types depending on the material used for the light absorption layer.
  • the mainly available type is the Si solar cell.
  • Thin-film solar cells are manufactured to be thin so that smaller amounts of materials are consumed, and also are lightweight and thus the application field thereof is wide.
  • Thorough research is ongoing into using amorphous SI and CdTe, CKS, Se) or CIG(S, Se) as materials in such thin-film solar cells.
  • the CISe thin film or the CIGSe thin film corresponds to a Group I—111—
  • this film may be manufactured to a thickness of 10 im or less and is stable even upon extended use, so that an inexpensive high-efficiency solar cell capable of replacing Si that uses this film is expected.
  • the CISe thin film is a direct transition type semiconductor and may thus be provided in the form of a thin film, and has a band gap of 1.04 eV and is thus comparatively adapted for light conversion, and the coefficient of light absorption thereof is the greatest amongst the materials used in solar cells.
  • the CIGSe thin film is formed by replacing part of
  • Forming the CIGSe thin film may include for example a vapor deposition process in a vacuum, or a process comprising applying Cu-In-(Ga)-Se nanopart icles in a non-vacuum and then thermally treating them.
  • the non-vacuum process may decrease the process cost and enables the formation of a large area with a uniform structure, but may undesirably decrease the efficiency of the absorption layer.
  • the CIGSe thin film formed by applying CIGSe nanopart icles in a non-vacuum has many pores and is not dense. Thus, typical attempts are made to form a dense thin film via thermal post-treatment.
  • the melting point of CIGSe material is very high to the extent of 1000 ° C or more, even when using CIGSe compound nanopart icles of tens of nm, it is difficult to grow particles and achieve densif ication with thermal post-treatment .
  • an object of the present invention is to provide a method of manufacturing a dense thin film, wherein CIGSe nanopart icles for the absorption layer of a solar cell are applied in a non-vacuum, thus reducing the manufacturing cost and ensuring efficient densif ication.
  • the present invention provides a method of manufacturing a dense CIGSe/CISe thin film using selenization of CIGS/CIS nanoparticles, comprising (a) preparing CIGS or CIS compound nanoparticles as a precursor; (b) preparing a slurry of the precursor nanoparticles obtained in (a); (c) applying the slurry on a substrate in a non-vacuum, thus forming a CIGS or CIS precursor thin film; and (e) thermally treating the CIGS or CIS precursor thin film at high temperature using a vapor including Se to replace S of the precursor thin film with Se, thus forming a CIGSe or CISe compound thin film.
  • preparing the nanoparticles may be performed using any one selected from among a low- temperature colloidal process, a solvent heat synthesis process, a microwave process, and an ultrasonic synthesis process.
  • preparing the slurry may be performed by subjecting the nanoparticles to mixing with a binder, dissolving in a solvent and treating with ultrasound to disperse them.
  • the solvent may be an alcoholic solvent.
  • the alcoholic solvent may include at least one selected from among ethanol, methanol, pentanol, propanol and butanol.
  • the binder may include at least one selected from among ethyleneglycol , propyleneglycol , ethylcel lulose, polyvinylpyrrolidone, ethyl enedi amine, monoethanol amine, diethanolamine and triethanolamine.
  • applying the slurry on the substrate may be performed using any one selected from among spraying, ultrasonic spraying, spin coating, doctor blading, screen printing, and ink-jet printing.
  • the method may further comprise (d) performing drying, after (c).
  • drying may be performed in two stages.
  • (c) and (d) may be sequentially repeated a plurality of times.
  • thermally treating may be performed at 400 ⁇ 530 ° C .
  • thermally treating may be performed for 10 ⁇ 60 min.
  • the present invention provides a solar cell comprising the
  • a Cu-In-(Ga)-S thin film is formed in a non-vacuum and then thermally treated at high temperature using a vapor including Se, so that S is replaced with Se having a comparatively large atomic size, whereby the CIGSe thin film is made dense via lattice expansion.
  • FIG. 1 is a flowchart sequentially showing a process of manufacturing a
  • FIG. 2 is an X-ray diffraction (XRD) graph which verifies the completion of selenization in the process according to an embodiment of the present invention
  • FIG. 3 is a scanning electron microscope (SEM) image showing the surface structure of a CISe compound thin film which is densified via selenization of CIS nanoparticles in an example according to the present invent ion;
  • FIG. 4 is a graph showing the output properties of a solar cell using the thin film obtained in the example.
  • FIG. 5 is an SEM image showing the surface structure of a CISe compound thin film obtained by selenizing CISe nanoparticles in a comparative example!
  • FIG. 6 is a graph showing the output properties of a solar cell manufactured using the CISe compound thin film obtained by selenizing CISe nanoparticles in the comparative example.
  • a method of manufacturing a CIGSe/CISe compound thin film having high density for a solar cell using selenization is first described, after which a manufacturing method according to a preferred example of the present invention is presented and the resulting CIGSe/CISe compound thin film is compared by means of a comparative example with a thin film obtained without performing selenization which increases the density of a thin film.
  • FIG. 1 is a flowchart sequentially showing a process of manufacturing a
  • the method of manufacturing a CI(G)Se compound thin film for a solar cell includes five steps.
  • the first step is preparing CIGS/CIS precursor nanoparticles (SI).
  • the CIGS/CIS precursor nanoparticles may include Cu-In-Ga-S or Cu-In-S nanoparticles as Group I—111—VI compound semiconductors, and S is replaced with Se in the thermal treatment for selenization which will be described later .
  • Ga of Cu-In-Ga-S which is replaced at the position of In, is appropriately added to increase the band gap so as to raise the energy conversion efficiency of a device.
  • a value of the Ga/(In+Ga) ratio of about 0.3 is preferable in terms of energy conversion efficiency. If the value of Ga/(In+Ga) exceeds 0.3, the band gap may increase but the energy conversion efficiency may decrease instead.
  • the CIS or CIGS nanoparticles may be prepared using any one selected from among a low-temperature colloidal process, a solvent heat synthesis process, a microwave process and an ultrasonic synthesis process.
  • a low-temperature colloidal process a solvent heat synthesis process
  • a microwave process a microwave process
  • an ultrasonic synthesis process a microwave process
  • the scope of the present invention is not limited thereto, and the other preparation process may be applied within the scope of the present invention.
  • the second step is preparing a slurry of the CIGS/CIS precursor nanoparticles (S2).
  • the CIGS/CIS precursor nanoparticles are added with a binder and a solvent, and may then be treated with ultrasound for a suitable period of time so that they are efficiently mixed and dispersed.
  • the solvent may be an alcoholic solvent, for example, methanol, ethanol , pentanol, propanol and butanol
  • examples of the binder may include ethyleneglycol , propyleneglycol , ethylcel lulose, polyvinylpyrrolidone, ethylenediamine, monoethanol amine, diethanolamine and triethanolamine.
  • the solvent and the binder are not limited to the above species and the other materials may be applied within the scope of the present invention.
  • CIGS/CIS precursor nanoparticles may be controlled, as necessary, and in order to adjust the viscosity, the kind or amount of binder may be control led.
  • the third step is applying the slurry of the CIGS/CIS precursor nanoparticles in a non-vacuum (S3).
  • Applying the slurry on a substrate may include for example spraying, ultrasonic spraying, spin coating, doctor blading, screen printing, ink-jet printing, etc., and any other coating process which may be performed in a non-vacuum as known in the art may be applied.
  • the non-vacuum coating process is advantageous because it is of lower cost and a more simple application, compared to a vapor deposition process in a vacuum.
  • the fourth step is drying the applied precursor thin film (S4).
  • the drying is carried out to remove the solvent and the binder from the precursor thin film that is the slurry coating layer and may be carried out in two stages.
  • the appropriate thickness of the precursor thin film after four steps may be adjusted by repetitively performing the third step and the fourth step in sequence. Specifically, if the thickness of the precursor thin film after four steps satisfies a desired thickness, the subsequent process step may be conducted, whereas if a desired thickness is not obtained, the process may be repeated again from the third step.
  • the appropriate thickness of the precursor thin film of the present invention is not particularly limited but may be 1.0 ⁇ 3.0 .
  • the third step and the fourth step may be repeated 3 ⁇ 5 times.
  • the fifth step is thermally treating the precursor thin film using gaseous Se to selenize the thin film (S5).
  • This step may be carried out at a substrate temperature of 400 ⁇ 530 ° C for 10 ⁇ 60 min.
  • the gaseous Se may include H 2 Se gas, Se vapor by unit Se, etc.
  • Such thermal treatment using gaseous Se enables the replacement of S contained in the CIGS/CIS precursor thin film with Se.
  • S and Se belong to the same Group VIA on the periodic table, wherein the atomic size of Se is larger than that of S, so that lattice expansion may occur in the thin film due to the replacement of S with Se, thus minimizing the pores to densify the thin film structure.
  • the density of the CIGSe/CISe thin film in which S was replaced by Se may be remarkably increased compared to the precursor thin film. As such, the time or temperature of the thermal treatment for selenization is adjusted, so that the degree of replacement of S with Se is controlled, thereby regulating the density of the final thin film.
  • the synthesized CIS colloid was centrifuged at 4000 rpm for about 30 min, treated with ultrasound for 5 min, and washed with distilled methanol, and these procedures were repeated to completely remove by-products and pyridine from the product, resulting in high-purity CIS compound nanoparticles.
  • the slurry thus prepared was applied using spin coating on a soda-lime glass substrate having deposited Mo.
  • the spin coating was carried out at 1000 rpm for 20 sec.
  • FIG. 2 is an XRD graph that verifies completion of the selenization in the process according to an embodiment of the present invention. As shown in FIG. 2, the main peak is seen to shift toward CuInSe 2 , from which the selenization of the precursor thin film can be ascertained to be successfully achieved using the method of manufacturing the high-density thin film according to the embodiment of the present invention.
  • Cu-In-Se compound nanoparticles were prepared in the same manner as in the above example, with the exception that Na 2 Se was used as a starting material instead of Na 2 S, after which a slurry thereof was prepared, applied using spin coating on a glass substrate coated with a Mo back electrode, dried, and selenized, to yield a CISe compound thin film.
  • CISe nanoparticles are used instead of CIS nanoparticles and thus there is no replacement of S with Se upon selenization.
  • the formation of the CISe precursor thin film of the comparative example refers to the description of the above example.
  • the CISe thin film of the comparative example has comparatively many pores resulting in low density, whereas the number of pores of the CISe thin film of the example is comparatively low, and the structure thereof becomes dense.
  • the solar cell including the dense thin film according to the present invention is superior in terms of open-circuit voltage, short current, and fill factor, leading to increased solar cell efficiency.

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Abstract

Disclosed is a method of manufacturing a dense CISe/CIGSe thin film using selenization of CIS/CIGS nanopart icles, which includes (a) preparing CIGS or CIS compound nanopart icles as a precursor, (b) preparing a slurry of the nanopart icles, (c) applying the slurry on a substrate in a non-vacuum, thus forming a CIGS or CIS precursor thin film, and (e) thermally treating the precursor thin film at high temperature using a vapor including Se to replace S of the thin film with Se, thus forming a CIGSe or CISe compound thin film, whereby the structure of the CISe/CIGSe compound thin film is highly densified via lattice expansion, ultimately increasing the efficiency of a solar cell using such a thin film.

Description

[DESCRIPTION]
[Invention Title]
METHOD OF MANUFACTURING DENSE CIGSe/CISe THIN FILM USING SELENIZATION OF CIGS/CIS NANOPARTICLES
[Technical Field]
<i> The present invention relates to a method of manufacturing a CIGSe/CISe
(Cu-In-Ga-Se/Cu-In-Se) compound thin film using selenization of CIGS/CIS (Cu- In-Ga-S/Cu-In-S) nanoparticles, and more particularly to a method of manufacturing a dense CIGSe/CISe thin film by applying CIGS compound nanoparticles or CIS compound nanoparticles in a non-vacuum and then selenizing the coating layer.
[Background Art]
<2> Recently, the need to develop next-generation clean energy is gaining in importance in light of radiation leakage by nuclear and radiation accidents and the exhaustion of fossil energy. In particular, solar cells, which are used to directly convert solar energy into electric energy, are expected to become an energy source able to solve the energy problems of the future because they generate less pollution and use an unlimited resource and have a semi -permanent lifetime.
<3> Solar cells are classified into a variety of types depending on the material used for the light absorption layer. The mainly available type is the Si solar cell. However, as the price of Si has drastically increased attributable to a shortage of the Si supply in recent years, thin-film solar cells are receiving attention. Thin-film solar cells are manufactured to be thin so that smaller amounts of materials are consumed, and also are lightweight and thus the application field thereof is wide. Thorough research is ongoing into using amorphous SI and CdTe, CKS, Se) or CIG(S, Se) as materials in such thin-film solar cells.
<4> The CISe thin film or the CIGSe thin film corresponds to a Group I—111—
VI compound semiconductor, and achieves the greatest conversion efficiency among thin-film solar cells which have been experimentally produced. Furthermore, this film may be manufactured to a thickness of 10 im or less and is stable even upon extended use, so that an inexpensive high-efficiency solar cell capable of replacing Si that uses this film is expected.
<5> In particular, the CISe thin film is a direct transition type semiconductor and may thus be provided in the form of a thin film, and has a band gap of 1.04 eV and is thus comparatively adapted for light conversion, and the coefficient of light absorption thereof is the greatest amongst the materials used in solar cells.
<6> On the other hand, the CIGSe thin film is formed by replacing part of
In with Ga to improve the low open-circuit voltage of a CISe thin film. In order to increase the open-circuit voltage, Se may be replaced with S. Forming the CIGSe thin film may include for example a vapor deposition process in a vacuum, or a process comprising applying Cu-In-(Ga)-Se nanopart icles in a non-vacuum and then thermally treating them.
<7> The non-vacuum process may decrease the process cost and enables the formation of a large area with a uniform structure, but may undesirably decrease the efficiency of the absorption layer. Specifically, the CIGSe thin film formed by applying CIGSe nanopart icles in a non-vacuum has many pores and is not dense. Thus, typical attempts are made to form a dense thin film via thermal post-treatment. However, because the melting point of CIGSe material is very high to the extent of 1000°C or more, even when using CIGSe compound nanopart icles of tens of nm, it is difficult to grow particles and achieve densif ication with thermal post-treatment .
[Disclosure]
[Technical Problem]
<8> Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a method of manufacturing a dense thin film, wherein CIGSe nanopart icles for the absorption layer of a solar cell are applied in a non-vacuum, thus reducing the manufacturing cost and ensuring efficient densif ication.
[Technical Solution]
<9> In order to accomplish the above object, the present invention provides a method of manufacturing a dense CIGSe/CISe thin film using selenization of CIGS/CIS nanoparticles, comprising (a) preparing CIGS or CIS compound nanoparticles as a precursor; (b) preparing a slurry of the precursor nanoparticles obtained in (a); (c) applying the slurry on a substrate in a non-vacuum, thus forming a CIGS or CIS precursor thin film; and (e) thermally treating the CIGS or CIS precursor thin film at high temperature using a vapor including Se to replace S of the precursor thin film with Se, thus forming a CIGSe or CISe compound thin film.
<io> In a preferred embodiment of the present invention, preparing the nanoparticles may be performed using any one selected from among a low- temperature colloidal process, a solvent heat synthesis process, a microwave process, and an ultrasonic synthesis process.
<ii> Also, preparing the slurry may be performed by subjecting the nanoparticles to mixing with a binder, dissolving in a solvent and treating with ultrasound to disperse them.
<12> The solvent may be an alcoholic solvent.
<13> The alcoholic solvent may include at least one selected from among ethanol, methanol, pentanol, propanol and butanol.
<14> The binder may include at least one selected from among ethyleneglycol , propyleneglycol , ethylcel lulose, polyvinylpyrrolidone, ethyl enedi amine, monoethanol amine, diethanolamine and triethanolamine.
<i5> Also, applying the slurry on the substrate may be performed using any one selected from among spraying, ultrasonic spraying, spin coating, doctor blading, screen printing, and ink-jet printing.
<i6> Also the method may further comprise (d) performing drying, after (c).
<17> As such, drying may be performed in two stages.
<18> Also, (c) and (d) may be sequentially repeated a plurality of times.
<19> Also, thermally treating may be performed at 400 ~ 530°C .
<20> Furthermore, thermally treating may be performed for 10 ~ 60 min.
<2i> In addition, the present invention provides a solar cell comprising the
CISe/CIGSe thin film manufactured using the above method. [Advantageous Effects]
<23> According to the present invention, a Cu-In-(Ga)-S thin film is formed in a non-vacuum and then thermally treated at high temperature using a vapor including Se, so that S is replaced with Se having a comparatively large atomic size, whereby the CIGSe thin film is made dense via lattice expansion.
Thus the efficiency of a solar cell can increase.
[Description of Drawings]
<24> FIG. 1 is a flowchart sequentially showing a process of manufacturing a
CI(G)Se compound thin film having high density for a solar cell using selenization according to the present invention;
<25> FIG. 2 is an X-ray diffraction (XRD) graph which verifies the completion of selenization in the process according to an embodiment of the present invention;
<26> FIG. 3 is a scanning electron microscope (SEM) image showing the surface structure of a CISe compound thin film which is densified via selenization of CIS nanoparticles in an example according to the present invent ion;
<27> FIG. 4 is a graph showing the output properties of a solar cell using the thin film obtained in the example;
<28> FIG. 5 is an SEM image showing the surface structure of a CISe compound thin film obtained by selenizing CISe nanoparticles in a comparative example! and
<29> FIG. 6 is a graph showing the output properties of a solar cell manufactured using the CISe compound thin film obtained by selenizing CISe nanoparticles in the comparative example.
[Mode for Invention]
<30> Hereinafter, a detailed description will be given of preferred embodiments of the present invention with reference to the appended drawings. The following embodiments may be variously modified and are not construed as limiting the scope of the present invention. The embodiments of the present invention are merely intended to provide a complete description to a person having ordinary knowledge in the art. <3i> In the present invention, a method of manufacturing a CIGSe/CISe compound thin film having high density for a solar cell using selenization is first described, after which a manufacturing method according to a preferred example of the present invention is presented and the resulting CIGSe/CISe compound thin film is compared by means of a comparative example with a thin film obtained without performing selenization which increases the density of a thin film.
<32> FIG. 1 is a flowchart sequentially showing a process of manufacturing a
CI(G)Se compound thin film having high density for a solar cell using selenization according to the present invention.
<33> As shown in FIG. 1, the method of manufacturing a CI(G)Se compound thin film for a solar cell includes five steps.
<34> The first step is preparing CIGS/CIS precursor nanoparticles (SI).
<35> The CIGS/CIS precursor nanoparticles may include Cu-In-Ga-S or Cu-In-S nanoparticles as Group I—111—VI compound semiconductors, and S is replaced with Se in the thermal treatment for selenization which will be described later .
<36> As such, Ga of Cu-In-Ga-S, which is replaced at the position of In, is appropriately added to increase the band gap so as to raise the energy conversion efficiency of a device. A value of the Ga/(In+Ga) ratio of about 0.3 is preferable in terms of energy conversion efficiency. If the value of Ga/(In+Ga) exceeds 0.3, the band gap may increase but the energy conversion efficiency may decrease instead.
<37> The CIS or CIGS nanoparticles may be prepared using any one selected from among a low-temperature colloidal process, a solvent heat synthesis process, a microwave process and an ultrasonic synthesis process. However, the scope of the present invention is not limited thereto, and the other preparation process may be applied within the scope of the present invention.
<38> The second step is preparing a slurry of the CIGS/CIS precursor nanoparticles (S2).
<39> Specifically, the CIGS/CIS precursor nanoparticles are added with a binder and a solvent, and may then be treated with ultrasound for a suitable period of time so that they are efficiently mixed and dispersed.
<40> The solvent may be an alcoholic solvent, for example, methanol, ethanol , pentanol, propanol and butanol, and examples of the binder may include ethyleneglycol , propyleneglycol , ethylcel lulose, polyvinylpyrrolidone, ethylenediamine, monoethanol amine, diethanolamine and triethanolamine.
<4i> The solvent and the binder are not limited to the above species and the other materials may be applied within the scope of the present invention.
<42> Also in order to adjust the concentration of the slurry, the amount of
CIGS/CIS precursor nanoparticles may be controlled, as necessary, and in order to adjust the viscosity, the kind or amount of binder may be control led.
<43> The third step is applying the slurry of the CIGS/CIS precursor nanoparticles in a non-vacuum (S3).
<44> Applying the slurry on a substrate may include for example spraying, ultrasonic spraying, spin coating, doctor blading, screen printing, ink-jet printing, etc., and any other coating process which may be performed in a non-vacuum as known in the art may be applied.
<45> The non-vacuum coating process is advantageous because it is of lower cost and a more simple application, compared to a vapor deposition process in a vacuum.
<46> The fourth step is drying the applied precursor thin film (S4).
<47> The drying is carried out to remove the solvent and the binder from the precursor thin film that is the slurry coating layer and may be carried out in two stages.
<48> The appropriate thickness of the precursor thin film after four steps may be adjusted by repetitively performing the third step and the fourth step in sequence. Specifically, if the thickness of the precursor thin film after four steps satisfies a desired thickness, the subsequent process step may be conducted, whereas if a desired thickness is not obtained, the process may be repeated again from the third step.
<49> The appropriate thickness of the precursor thin film of the present invention is not particularly limited but may be 1.0 ~ 3.0 . In order to ensure such a thickness, the third step and the fourth step may be repeated 3 ~ 5 times.
<50> The fifth step is thermally treating the precursor thin film using gaseous Se to selenize the thin film (S5).
<5i> This step may be carried out at a substrate temperature of 400 ~ 530°C for 10 ~ 60 min.
<52> The gaseous Se may include H2Se gas, Se vapor by unit Se, etc.
<53> Such thermal treatment using gaseous Se enables the replacement of S contained in the CIGS/CIS precursor thin film with Se. S and Se belong to the same Group VIA on the periodic table, wherein the atomic size of Se is larger than that of S, so that lattice expansion may occur in the thin film due to the replacement of S with Se, thus minimizing the pores to densify the thin film structure. The density of the CIGSe/CISe thin film in which S was replaced by Se may be remarkably increased compared to the precursor thin film. As such, the time or temperature of the thermal treatment for selenization is adjusted, so that the degree of replacement of S with Se is controlled, thereby regulating the density of the final thin film.
<54> A better understanding of the present invention is obtained via the following example.
<55> Exam le
<56> First, Cu-In-S nanoparticles were prepared as precursor particles.
<57> In a glove box, 0.343 g of Cul and 0.991 g of Inl3 were mixed with 30
ml of a distilled pyridine solvent, and the resultant mixture was stirred for about 10 min on a hot plate at 50°C . After stirring for about 10 min, the opaque solution was made transparent. The Cu/In mixture was mixed with 0.312 g of Na2S in 20 ml of distilled methanol, so as to correspond to the atomic ratio of Cu : In : Se = 0.9 : 1 : 2. Thereafter, the mixture of methanol and pyridine was mechanically stirred in an ice bath at 0°C and reacted for 1 min, thus synthesizing CIS nanoparticles. The synthesized CIS colloid was centrifuged at 4000 rpm for about 30 min, treated with ultrasound for 5 min, and washed with distilled methanol, and these procedures were repeated to completely remove by-products and pyridine from the product, resulting in high-purity CIS compound nanoparticles.
<58> Thereafter, 0.3 g of the CIS precursor nanoparticles, 0.3 g of a propyl eneglycol binder, 0.5 g of monoethanol amine, and 1.2 g of a methanol solvent were mixed, and treated with ultrasound for 30 min to disperse them, thus preparing a slurry.
<59> Thereafter, the slurry thus prepared was applied using spin coating on a soda-lime glass substrate having deposited Mo. The spin coating was carried out at 1000 rpm for 20 sec.
<60> After completion of the application of the slurry on the Mo/glass substrate, two-stage drying was performed to remove the alcoholic solvent and the binder. Specifically, the coated glass substrate was primarily dried on a hot plate at 100°C for 3 min, and then secondarily dried at 300°C for 5 min.
<6i> The coating and drying procedures were repeated five times thus forming a CIS compound thin film on the glass substrate.
<62> Finally, selenization was performed to replace S of the CIS precursor thin film with Se. Specifically, while gaseous Se was supplied at a substrate temperature of 500°C, thermal treatment was performed for 30 min, thus obtaining a dense Cu-In-Se compound thin film.
<63> FIG. 2 is an XRD graph that verifies completion of the selenization in the process according to an embodiment of the present invention. As shown in FIG. 2, the main peak is seen to shift toward CuInSe2 , from which the selenization of the precursor thin film can be ascertained to be successfully achieved using the method of manufacturing the high-density thin film according to the embodiment of the present invention.
<64>
<65> Comparative Example
<66> Cu-In-Se compound nanoparticles were prepared in the same manner as in the above example, with the exception that Na2Se was used as a starting material instead of Na2S, after which a slurry thereof was prepared, applied using spin coating on a glass substrate coated with a Mo back electrode, dried, and selenized, to yield a CISe compound thin film.
<67> Although the synthesis of particles and the formation of a thin film of the comparative example are the same as those of the example, CISe nanoparticles are used instead of CIS nanoparticles and thus there is no replacement of S with Se upon selenization. Thus, the formation of the CISe precursor thin film of the comparative example refers to the description of the above example.
<68> When comparing the CISe thin film structure of the comparative example with the CISe thin film structure of the example of the present invention with reference to FIGS. 3 and 5, the CISe thin film of the comparative example has comparatively many pores resulting in low density, whereas the number of pores of the CISe thin film of the example is comparatively low, and the structure thereof becomes dense.
<69> When comparing the output properties of a solar cell including the CISe thin film of the comparative example and a solar cell including the CISe thin film of the example with reference to FIGS. 4 and 6, the solar cell including the dense thin film according to the present invention is superior in terms of open-circuit voltage, short current, and fill factor, leading to increased solar cell efficiency.
<70> Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[CLAIMS]
[Claim 1]
<72> A method of manufacturing a dense CIGSe/CISe (Cu-In-Ga-Se/Cu-In-Se) thin film using selenization of CIGS/CIS (Cu-In-Ga-S/Cu-In-S) nanoparticles, comprising:
<73> (a) preparing CIGS or CIS compound nanoparticles as precursor nanopart icles ;
<74> (b) preparing a slurry of the precursor nanoparticles obtained in (a);
<75> (c) applying the slurry on a substrate in a non-vacuum, thus forming a
CIGS or CIS precursor thin film; and
<76> (e) thermally treating the CIGS or CIS precursor thin film using a vapor including Se to replace S of the precursor thin film with Se, thus forming a CIGSe or CISe compound thin film.
[Claim 2]
<77> The method of claim 1, wherein the preparing the nanoparticles is performed using any one selected from among a low-temperature colloidal process, a solvent heat synthesis process, a microwave process and an ultrasonic synthesis process.
[Claim 3]
<78> The method of claim 1, wherein the preparing the slurry is performed by subjecting the nanoparticles to mixing with a binder, dissolving in a solvent and treating with ultrasound to disperse them.
<79>
[Claim 4]
<80> The method of claim 3, wherein the solvent is an alcoholic solvent.
[Claim 5]
<8i > The method of claim 4, wherein the alcoholic solvent includes at least one selected from among ethanol, methanol, pentanol, propanol and butanol.
[Claim 6]
<82> The method of claim 3, wherein the binder includes at least one selected from among ethyleneglycol , propyleneglycol , ethylcel lulose, polyvinylpyrrolidone, ethyl enedi amine, monoethanolamine, diethanolamine and triethanolamine.
[Claim 7]
The method of claim 1, wherein the applying the slurry on the substrate is performed using any one selected from among spraying, ultrasonic spraying, spin coating, doctor blading, screen printing and ink-jet printing.
[Claim 8]
The method of claim 1, further comprising (d) performing drying, after
(c).
[Claim 9]
The method of claim 8, wherein the drying is performed in two stages.
[Claim 10]
The method of claim 8, wherein (c) and (d) are repeated.
[Claim 11]
The method of claim 1, wherein the thermally treating is performed at 400 ~ 530°C .
[Claim 12]
The method of claim 1, wherein the thermally treating is performed for 10 ~ 60 min.
[Claim 13]
A solar cell comprising the CISe/CIGSe thin film manufactured using the method of any one of claims 1 to 12.
PCT/KR2012/000811 2011-05-25 2012-02-02 METHOD OF MANUFACTURING DENSE CIGSe/CISe THIN FILM USING SELENIZATION OF CIGS/CIS NANOPARTICLES WO2012161401A1 (en)

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US20090242033A1 (en) * 2006-07-24 2009-10-01 Seok-Hyun Yoon Method For Preparing Cis Compounds and Thin Layer, and Solar Cell Having Cis Compound Thin Layer
US20100120192A1 (en) * 2007-11-14 2010-05-13 Sungkyunkwan University Synthesis of i-iii-vi2 nanoparticles and fabrication of polycrystalline absorber layers
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