WO2011028058A2 - Aluminum paste for a back electrode of solar cell - Google Patents

Aluminum paste for a back electrode of solar cell Download PDF

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Publication number
WO2011028058A2
WO2011028058A2 PCT/KR2010/005998 KR2010005998W WO2011028058A2 WO 2011028058 A2 WO2011028058 A2 WO 2011028058A2 KR 2010005998 W KR2010005998 W KR 2010005998W WO 2011028058 A2 WO2011028058 A2 WO 2011028058A2
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Prior art keywords
aluminum
aluminum paste
solar cell
paste
glass frit
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PCT/KR2010/005998
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French (fr)
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WO2011028058A3 (en
Inventor
Chang-Mo Lee
Seung-Yong Lee
Dae-Sung Lim
Hyung-Sub Choi
Seung-Kwon Hong
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Dongwoo Fine-Chem Co., Ltd.
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Application filed by Dongwoo Fine-Chem Co., Ltd. filed Critical Dongwoo Fine-Chem Co., Ltd.
Priority to CN2010800426748A priority Critical patent/CN102549760A/en
Priority to JP2012527829A priority patent/JP2013504199A/en
Priority to EP10813967.6A priority patent/EP2474040A4/en
Publication of WO2011028058A2 publication Critical patent/WO2011028058A2/en
Publication of WO2011028058A3 publication Critical patent/WO2011028058A3/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/062—Glass compositions containing silica with less than 40% silica by weight
    • C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
    • C03C8/02—Frit compositions, i.e. in a powdered or comminuted form
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
    • C03C8/14—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions
    • C03C8/18—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions containing free metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/02—Bonding areas ; Manufacturing methods related thereto
    • H01L24/03—Manufacturing methods
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/02—Bonding areas ; Manufacturing methods related thereto
    • H01L24/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
    • H01L24/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/02—Bonding areas; Manufacturing methods related thereto
    • H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
    • H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01005—Boron [B]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01006—Carbon [C]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01013—Aluminum [Al]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01023—Vanadium [V]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01033—Arsenic [As]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01038—Strontium [Sr]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01047—Silver [Ag]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01074—Tungsten [W]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01082—Lead [Pb]
    • 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

Definitions

  • the present invention relates to aluminum paste for a back electrode of a solar cell.
  • crystalline silicon solar cells use a P-type silicon substrate having a thickness of 180 ⁇ 220 ⁇ m.
  • An N-type impurity layer having a thickness of 0.2 ⁇ 0.6 ⁇ m is formed on the front surface of the P-type silicon substrate, and a SiNx layer for antireflection and a front electrode are sequentially formed on the N-type impurity layer.
  • an aluminum electrode is formed on the back surface of the P-type silicon substrate. This aluminum electrode is formed by applying aluminum paste using screen printing or the like, drying the applied aluminum paste and then two-stage-firing the dried aluminum paste at low temperature (about 600°C) and at high temperature (800 ⁇ 950°C).
  • an Al-Si alloy layer is formed while aluminum diffuses into the P-type silicon substrate.
  • This Al-Si alloy layer forms a back surface field (BSF) layer preventing the recoupling of electrons generated from a solar cell and improving the collection efficiency of carriers generated from the solar cell.
  • the efficiency of the solar cell is influenced by the thickness and uniformity of the BSF layer. That is, when the thickness of the BSF layer is decreased, the efficiency of the solar cell is decreased, and when the thickness thereof is increased, the efficiency thereof is increased.
  • the thickness of a silicon wafer has been recently decreased in order to reduce the cost of solar cells.
  • the silicon wafer bows due to the difference in the expansion coefficient between the silicon wafer and aluminum, and thus the silicon wafer cracks.
  • the thickness of an aluminum electrode that functions as a back electrode it is required to decrease the thickness of an aluminum electrode that functions as a back electrode, and this purpose can be accomplished by decreasing the amount of aluminum paste applied.
  • the thickness of the BSF layer which is a back electric field layer, is decreased, so that the efficiency of the solar cell is deteriorated, and aluminum balls and/or bumps are increasingly formed in an electrode layer during a co-firing process.
  • the aluminum balls and/or bumps formed in the electrode layer decrease the flatness of the back surface of the silicon wafer, and stress is focused on these aluminum balls and/or bumps, thereby causing the solar cell to break during the solar cell manufacturing process or solar cell module manufacturing process.
  • Korean Patent Registration No. 10-0825580 discloses aluminum paste including aluminum powder having a particle size of 0.5 ⁇ 10 ⁇ m, an organic vehicle and a metal alkoxide
  • Korean Unexamined Patent Application Publication No. 10-2008-0068638 discloses aluminum paste including aluminum powder having a particle size of 2 ⁇ 20 ⁇ m, glass frit, an organic vehicle and a metal hydroxide
  • Korean Unexamined Patent Application Publication No. 10-2008-0057230 discloses aluminum paste including aluminum powder having a particle size of 2 ⁇ 20 ⁇ m, glass frit, an organic vehicle and a plasticizer
  • Korean Unexamined Patent Application Publication No. 10-2008-0104179 discloses aluminum paste including aluminum powder having a particle size of 4 ⁇ 10 ⁇ m, alkaline glass frit, boron ethoxide, titanium ethoxide, and fumed silica.
  • All of the aluminum pastes disclosed in the above patent documents include organic or inorganic additives in addition to aluminum powder, glass frit and an organic vehicle.
  • these additives are problematic because they exist as residues or include pores during a process of co-firing aluminum paste, so that the resistance and uniformity of the aluminum paste is decreased, thereby badly influencing the efficiency of a solar cell.
  • the above aluminum pastes are problematic because aluminum powder has a maximum particle size of 10 ⁇ 20 ⁇ m, so that it is difficult for aluminum paste to uniformly come into contact with the textured back surface of a solar cell, with the result that aluminum bumps can be probably formed by pores formed therein.
  • an object of the present invention is to provide aluminum paste for a back electrode of a solar cell, which can prevent the bowing of a solar cell and minimize the formation of aluminum balls and/or bumps and the occurrence of yellow discoloration during a co-firing process, which can greatly increase the values of short circuit current (Isc) and open circuit voltage (Voc), and which can remarkably improve the efficiency of a solar cell.
  • Isc short circuit current
  • Voc open circuit voltage
  • an aspect of the present invention provides aluminum paste for a back electrode of a solar cell, including, based on the total amount thereof: 65 ⁇ 75 wt% of aluminum powder having an average particle size distribution of 0.01 ⁇ 5 ⁇ m; 0.01 ⁇ 5 wt% of glass frit; and 20 ⁇ 34.90 wt% of an organic vehicle solution.
  • Another aspect of the present invention provides a method of manufacturing a solar cell, including a process of forming a back electrode using the aluminum paste.
  • the contact between aluminum paste and a textured silicon wafer has improved, the bowing of a solar cell can be prevented and the formation of aluminum balls and/or bumps and the occurrence of yellow discoloration can be minimized during the co-firing process, the values of short circuit current (Isc) and open circuit voltage (Voc) can be greatly increased, and the efficiency of a solar cell can be remarkably improved.
  • the present invention provides aluminum paste for a back electrode of a solar cell, including, based on the total amount thereof: 65 ⁇ 75 wt% of aluminum powder having an average particle size distribution of 0.01 ⁇ 5 ⁇ m; 0.01 ⁇ 5 wt% of glass frit; and 20 ⁇ 34.90 wt% of an organic vehicle solution.
  • the aluminum powder used in the aluminum paste of the present invention may have an average particle size distribution of 0.01 ⁇ 5 ⁇ m.
  • the surfaces of silicon solar cells are textured in order to enlarge the area that receives the solar light.
  • a monocrystalline silicon wafer is textured in the form of a pyramid, and the pyramid has a height of 2 ⁇ 15 ⁇ m and a width of 2 ⁇ 20 ⁇ m.
  • a polycrystalline silicon wafer is textured in the form of an irregular maze.
  • the textured silicon wafer is coated on the back surface thereof with aluminum paste by screen printing, gravure printing or offset printing, dried, and then co-fired to form an aluminum electrode.
  • the average particle size distribution of aluminum powder included in the aluminum paste be 0.01 ⁇ 5 ⁇ m.
  • the average particle size of aluminum powder is smaller than 0.01 ⁇ m, there is a problem in that aluminum bumps occur during the co-firing process conducted after the printing process, and the silicon wafer becomes increasingly bowed. Further, when the average particle size thereof is greater than 5 ⁇ m, the packing factor of aluminum particles decreases, thus decreasing the efficiency of the solar cell.
  • the solar cell manufactured in this way is advantageous in that yellow discoloration occurring in the aluminum electrode after the co-firing process can be prevented.
  • aluminum powder having an particle size distribution of 0.01 ⁇ 5 ⁇ m may be used.
  • the aluminum powder may be included in an amount of 65 ⁇ 75 wt%.
  • the amount of the aluminum powder included in the aluminum paste is below 65 wt%, there is a problem in that the aluminum layer printed after the calicination process becomes thin, so that a back surface field (BSF) layer is not sufficiently formed, thereby decreasing the efficiency of a solar cell.
  • BSF back surface field
  • the amount of the aluminum powder included therein is greater than 75 wt%, there is a problem in that the printed aluminum layer becomes excessively thick, thereby causing the silicon wafer to bow.
  • the glass frit may be included in an amount of 0.01 ⁇ 5 wt%, preferably 0.05 ⁇ 3 wt%, more preferably 0.1 ⁇ 1 wt%.
  • the glass frit may be Bi 2 O 3 -SiO 2 -Al 2 O 3 -B 2 O 3 -SrO.
  • the glass frit may include, but is not limited to, 20 ⁇ 30 mol% of Bi 2 O 3 , 5 ⁇ 15 mol% of Al 2 O 3 , 25 ⁇ 35 mol% of SiO 2 , 1 ⁇ 10 mol% of SrO, and 20 ⁇ 40 mol% of B 2 O 3 .
  • the softening point of the glass frit is increased, so that the aluminum paste is not softened enough during the co-firing process, with the result that the adhesion between the aluminum paste and the silicon wafer decreases, thereby decreasing the efficiency of the solar cell.
  • the glass frit includes an excessive amount of SrO, the softening point of the glass frit is excessively lowered, resulting in bumps in the aluminum electrode.
  • the glass frit used in the present invention may have a softening point of 400 ⁇ 600°C.
  • the softening point of the glass frit When the softening point of the glass frit is below 400°C, the thermal expansion coefficient of the glass frit is relatively increased, and thus the silicon wafer co-fired during the solar cell manufacturing process easily bows. Further, when the softening point thereof is above 600°C, the glass frit does not sufficiently melt in the co-firing process to such a degree that the adhesion is provided between the aluminum layer and the silicon wafer layer, thus deteriorating the adhesion therebetween.
  • the aluminum paste of the present invention may include, based on the total amount thereof, 20 ⁇ 34.90 wt% of an organic vehicle solution.
  • the organic vehicle solution is prepared by dissolving a polymer resin in an organic solvent, and, if necessary, may include a thixotropic agent, a wetting agent, an additive and the like.
  • the organic vehicle solution used in the present invention may include, based on the total amount thereof, 75 wt% or more of an organic solvent, 1 ⁇ 30 wt% of a polymer resin, 5 wt% or less of a wetting agent and a thixotropic agent, and 1 ⁇ 10 wt% of an additive.
  • the organic solvent may have a boiling point of 150 ⁇ 300°C such that it is possible to prevent the aluminum paste from drying and to control the flowability of the aluminum paste.
  • Examples of commonly-used organic solvents may include glycol ethers, such as tripropyleneglycol methyl ether, dipropyleneglycol n-propyl ether, dipropyleneglycol n-butyl ether, tripropyleneglycol n-butyl ether, propyleneglycol phenyl ether, diethyleneglycol ethyl ether, diethyleneglycol n-butyl ether, diethyleneglycol hexyl ether, ethyleneglycol hexyl ether, triethyleneglycol methyl ether, triethyleneglycol ethyl ether, triethyleneglycol n-butyl ether, ethyleneglycol phenyl ether, terpineol, Texanol®, ethyleneglycol,
  • the polymer resin may include polyvinylpyrrolidone, polyvinylalcohol, polyethyleneglycol, ethylcellulose, rosin, a phenol resin, an acrylate resin, and the like.
  • the amount of the polymer may be 1 ⁇ 30 wt%, preferably, 5 ⁇ 25 wt%, based on the total amount of the organic vehicle solution.
  • the amount of the polymer resin is below 1 wt%, the printability and dispersion stability of the aluminum paste are deteriorated. Further, the amount thereof is above 30 wt%, the aluminum paste cannot be printed.
  • thixotropic agent and wetting agent thixotropic agents and wetting agents commonly used in the related field may be used without limitation.
  • the additive may be a dispersant or the like commonly used in the related field.
  • the dispersant commercially available surfactants may be used, and they may be used independently or in combination with each other.
  • the surfactants may include: nonionic surfactants, such as ethers including alkyl polyoxyethylene ether, alkylaryl polyoxyethylene ether, polyoxyethylene-polyoxypropylene copolymer and the like, ester-ethers including polyoxyethylene ether of glycerin ester, polyoxyethylene ether of sorbitan ester, polyoxyethylene ether of sorbitol ester and the like, esters including polyethylene glycol fatty acid ester, glycerin ester, sorbitan ester, propylene glycol ester, sugar ester, alkyl polyglucoside and the like, and nitrogen-containing surfactants including fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, amine oxide and the like; and polymeric surfact
  • Examples of commercially available surfactant products may include hypermer KD (manufactured by Uniqema Corp.), AKM 0531 (manufactured by NOF Corp.), KP (manufactured by Shinetsu Kagaku Kogyo Corp.), POLYFLOW (manufactured by Kyoei Kagaku Corp.), EFTOP (manufactured by Tokemu Products Corp.), Asahi guard, Surflon (manufactured by Asahi Glass Corp.), SOLSPERSE (manufactured by Geneka Corp.), EFKA (manufactured by EFKA Chemicals Co., Ltd.), PB 821 (manufactured by Ajinomoto Co., Inc.), BYK-184, BYK-185, BYK-2160, Anti-Terra U (manufactured by BYK Corp.), and the like.
  • the amount of the dispersant may be 1 ⁇ 10 wt%, preferably, 1 ⁇ 5 wt%, based on the total amount of the organic vehicle solution.
  • the aluminum paste according to the present invention can be easily prepared using a planar mixer which simultaneously rotates and revolves. That is, this aluminum paste can be prepared by putting the above-mentioned components into a planar mixer in the corresponding composition ratio and then stirring and then properly mixing and dispersing the solids in an organic vehicle solution.
  • the aluminum paste prepared in this way has a viscosity of 20,000 ⁇ 200,000 cps at 5 rpm when its viscosity was measured at 25°C using a Brookfield HBDV-III Ultra Rheometer or a spindle CPE-52.
  • the aluminum paste may be prepared such that it has a viscosity of 40,000 ⁇ 100,000 cps.
  • the present invention provides a method of manufacturing a solar cell, including the step of forming a back electrode using the aluminum paste.
  • the solar cell manufactured in this way is advantageous in that it does not easily bows, and the minimum amount of aluminum balls and/or bumps are formed in the electrode layer, so that the values of short circuit current (Isc) and open circuit voltage (Voc) are greatly increased, and the efficiency thereof is remarkably improved.
  • Aluminum paste was prepared in the same manner as in Example 1, except that 65 wt% of aluminum powder having an average particle size distribution of 0.04 ⁇ 5 ⁇ m and 34.5 wt% of an organic vehicle solution were added.
  • Aluminum paste was prepared in the same manner as in Example 1, except that 75 wt% of aluminum powder having an average particle size distribution of 0.04 ⁇ 5 ⁇ m and 24.5 wt% of an organic vehicle solution were added.
  • Aluminum paste was prepared in the same manner as in Example 1, except that the glass frit was replace by glass frit having the composition ratio given in Table 2 below.
  • Aluminum paste was prepared in the same manner as in Example 1, except that 76 wt% of aluminum powder having an average particle size distribution of 0.04 ⁇ 5 ⁇ m and 23.5 wt% of an organic vehicle solution were added.
  • Aluminum paste was prepared in the same manner as in Example 1, except that aluminum powder having an average particle size distribution of 2 ⁇ 10 ⁇ m was used instead of the aluminum powder having an average particle size distribution of 0.04 ⁇ 5 ⁇ m.
  • Aluminum paste was prepared in the same manner as in Example 1, except that aluminum powder having an average particle size distribution of 5 ⁇ 15 ⁇ m was used instead of the aluminum powder having an average particle size distribution of 0.04 ⁇ 5 ⁇ m.
  • Test Example Manufacturing a solar cell and testing characteristics thereof
  • a monocrystalline silicon wafer having a size of 156 X 156 mm and a thickness of 200 ⁇ m was surface-textured such that the height of a pyramid is about 4 ⁇ 6 ⁇ m, and then the N-side of the surface-textured silicon wafer was coated with SiNx.
  • bus bars were printed on the back surface of the silicon wafer using silver paste and then dried, and then aluminum paste of each of Examples 1 to 3 and Comparative Examples 1 to 4 was applied thereon using a screen printing plate of 250 mesh such that the weight of the aluminum paste was 1.5 ⁇ 0.1 g and then dried. Further, finger lines were printed on the front surface of the silicon wafer using silver paste and then dried.
  • the silicon wafer that had undergone the above processes was co-fired in a continuous infrared furnace such that the temperature of a firing zone was 720 ⁇ 900°C, thereby manufacturing a solar cell.
  • the front and back surface of the silicon wafer can be simultaneously co-fired while passing through a belt furnace.
  • the belt furnace includes a burn-out zone of about 600°C and a firing zone of 800 ⁇ 950°C.
  • organic matter was removed from the aluminum paste and the silver paste, and then the aluminum paste and silver paste applied on the back surface and front surface of the silicon wafer were melted to form electrodes.
  • the degree of bowing of the manufactured solar cell was evaluated by matching four edges of the solar cell with the bottom and then measuring to what degree the central portion thereof had been lifted. Further, the occurrence of bumps and aluminum balls around an aluminum back electrode was observed with the naked eye, and the number thereof was counted. The results thereof are given in Table 3 below.
  • the efficiency of the manufactured solar cell was evaluated using an SCM-1000, which is an apparatus for evaluating the performance of solar cells, manufactured by FitTech Corporation. The results thereof are given in Table 4 below.

Abstract

Disclosed herein is an aluminum paste for a back electrode of a solar cell, including, based on the total amount thereof: 65 ~ 75 wt% of aluminum powder having an average particle size dis¬ tribution of 0.01 ~ 5 μm; 0.01 ~ 5 wt% of glass frit; and 20 ~ 34.90 wt% of an organic vehicle solution. The aluminum paste is advantageous in that since the contact between aluminum paste and a textured silicon wafer is improved, the bowing of a solar cell can be prevented, and the formation of aluminum balls and/or bumps and the occurrence of yellow discoloration can be minimized during a co-firing process, the values of short circuit current (Isc) and open circuit voltage (Voc) can be greatly increased and the efficiency of a solar cell can be remarkably improved.

Description

ALUMINUM PASTE FOR A BACK ELECTRODE OF SOLAR CELL
The present invention relates to aluminum paste for a back electrode of a solar cell.
Generally, crystalline silicon solar cells use a P-type silicon substrate having a thickness of 180 ~ 220μm. An N-type impurity layer having a thickness of 0.2 ~ 0.6μm is formed on the front surface of the P-type silicon substrate, and a SiNx layer for antireflection and a front electrode are sequentially formed on the N-type impurity layer. Further, an aluminum electrode is formed on the back surface of the P-type silicon substrate. This aluminum electrode is formed by applying aluminum paste using screen printing or the like, drying the applied aluminum paste and then two-stage-firing the dried aluminum paste at low temperature (about 600℃) and at high temperature (800 ~ 950℃). In this co-firing process, an Al-Si alloy layer is formed while aluminum diffuses into the P-type silicon substrate. This Al-Si alloy layer forms a back surface field (BSF) layer preventing the recoupling of electrons generated from a solar cell and improving the collection efficiency of carriers generated from the solar cell. The efficiency of the solar cell is influenced by the thickness and uniformity of the BSF layer. That is, when the thickness of the BSF layer is decreased, the efficiency of the solar cell is decreased, and when the thickness thereof is increased, the efficiency thereof is increased.
Meanwhile, the thickness of a silicon wafer has been recently decreased in order to reduce the cost of solar cells. However, when the thickness of the silicon wafer is excessively decreased, the silicon wafer bows due to the difference in the expansion coefficient between the silicon wafer and aluminum, and thus the silicon wafer cracks.
In order to overcome the above problem, it is required to decrease the thickness of an aluminum electrode that functions as a back electrode, and this purpose can be accomplished by decreasing the amount of aluminum paste applied. However, when a smaller amount of aluminum paste is applied, the thickness of the BSF layer, which is a back electric field layer, is decreased, so that the efficiency of the solar cell is deteriorated, and aluminum balls and/or bumps are increasingly formed in an electrode layer during a co-firing process. In this case, the aluminum balls and/or bumps formed in the electrode layer decrease the flatness of the back surface of the silicon wafer, and stress is focused on these aluminum balls and/or bumps, thereby causing the solar cell to break during the solar cell manufacturing process or solar cell module manufacturing process.
In order to prevent the solar cell from bowing and to form fewer aluminum balls during the co-firing process, conventional technologies are proposed as follows. Korean Patent Registration No. 10-0825580 discloses aluminum paste including aluminum powder having a particle size of 0.5 ~ 10μm, an organic vehicle and a metal alkoxide; Korean Unexamined Patent Application Publication No. 10-2008-0068638 discloses aluminum paste including aluminum powder having a particle size of 2 ~ 20μm, glass frit, an organic vehicle and a metal hydroxide; Korean Unexamined Patent Application Publication No. 10-2008-0057230 discloses aluminum paste including aluminum powder having a particle size of 2 ~ 20μm, glass frit, an organic vehicle and a plasticizer; and Korean Unexamined Patent Application Publication No. 10-2008-0104179 discloses aluminum paste including aluminum powder having a particle size of 4 ~ 10μm, alkaline glass frit, boron ethoxide, titanium ethoxide, and fumed silica.
All of the aluminum pastes disclosed in the above patent documents include organic or inorganic additives in addition to aluminum powder, glass frit and an organic vehicle. However, these additives are problematic because they exist as residues or include pores during a process of co-firing aluminum paste, so that the resistance and uniformity of the aluminum paste is decreased, thereby badly influencing the efficiency of a solar cell. Further, the above aluminum pastes are problematic because aluminum powder has a maximum particle size of 10 ~ 20μm, so that it is difficult for aluminum paste to uniformly come into contact with the textured back surface of a solar cell, with the result that aluminum bumps can be probably formed by pores formed therein.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide aluminum paste for a back electrode of a solar cell, which can prevent the bowing of a solar cell and minimize the formation of aluminum balls and/or bumps and the occurrence of yellow discoloration during a co-firing process, which can greatly increase the values of short circuit current (Isc) and open circuit voltage (Voc), and which can remarkably improve the efficiency of a solar cell.
In order to accomplish the above object, an aspect of the present invention provides aluminum paste for a back electrode of a solar cell, including, based on the total amount thereof: 65 ~ 75 wt% of aluminum powder having an average particle size distribution of 0.01 ~ 5 μm; 0.01 ~ 5 wt% of glass frit; and 20 ~ 34.90 wt% of an organic vehicle solution.
Another aspect of the present invention provides a method of manufacturing a solar cell, including a process of forming a back electrode using the aluminum paste.
According to the aluminum paste of the present invention, since the contact between aluminum paste and a textured silicon wafer has improved, the bowing of a solar cell can be prevented and the formation of aluminum balls and/or bumps and the occurrence of yellow discoloration can be minimized during the co-firing process, the values of short circuit current (Isc) and open circuit voltage (Voc) can be greatly increased, and the efficiency of a solar cell can be remarkably improved.
The present invention provides aluminum paste for a back electrode of a solar cell, including, based on the total amount thereof: 65 ~ 75 wt% of aluminum powder having an average particle size distribution of 0.01 ~ 5 μm; 0.01 ~ 5 wt% of glass frit; and 20 ~ 34.90 wt% of an organic vehicle solution.
The aluminum powder used in the aluminum paste of the present invention may have an average particle size distribution of 0.01 ~ 5 μm.
Generally, the surfaces of silicon solar cells are textured in order to enlarge the area that receives the solar light. Generally, a monocrystalline silicon wafer is textured in the form of a pyramid, and the pyramid has a height of 2 ~15 μm and a width of 2 ~ 20 μm. In contrast, a polycrystalline silicon wafer is textured in the form of an irregular maze. The textured silicon wafer is coated on the back surface thereof with aluminum paste by screen printing, gravure printing or offset printing, dried, and then co-fired to form an aluminum electrode. In this process, when the size of aluminum particles is excessively large, aluminum paste does not easily come into contact with the silicon wafer, and thus a gap is formed between aluminum paste and the textured surface of the silicon wafer after being printed and dried. During the co-firing process, the gab moves to the surface of an aluminum electrode through the aluminum paste layer, being accompanied by the occurrence of aluminum balls and/or bumps. Therefore, it is preferred that the average particle size distribution of aluminum powder included in the aluminum paste be 0.01 ~ 5μm. When the average particle size of aluminum powder is smaller than 0.01μm, there is a problem in that aluminum bumps occur during the co-firing process conducted after the printing process, and the silicon wafer becomes increasingly bowed. Further, when the average particle size thereof is greater than 5μm, the packing factor of aluminum particles decreases, thus decreasing the efficiency of the solar cell.
When aluminum paste is prepared using aluminum powder having the average particle size distribution, the aluminum paste deeply infiltrates into the textured silicon wafer, and the porosity in the aluminum paste also decreases. For this reason, a back surface field (BSF) layer is uniformly formed on the silicon wafer, the resistance of an aluminum electrode becomes low, and the bowing of the silicon wafer is prevented. Therefore, when a solar cell is manufactured using the aluminum paste prepared using the aluminum powder, the value of the short-circuit current of the solar cell increases, and the efficiency thereof also increases. Further, the solar cell manufactured in this way is advantageous in that yellow discoloration occurring in the aluminum electrode after the co-firing process can be prevented.
Further, in the aluminum paste of the present invention, aluminum powder having an particle size distribution of 0.01 ~ 5 μm may be used.
In the aluminum paste of the present invention, the aluminum powder may be included in an amount of 65 ~ 75 wt%. When the amount of the aluminum powder included in the aluminum paste is below 65 wt%, there is a problem in that the aluminum layer printed after the calicination process becomes thin, so that a back surface field (BSF) layer is not sufficiently formed, thereby decreasing the efficiency of a solar cell. Further, when the amount of the aluminum powder included therein is greater than 75 wt%, there is a problem in that the printed aluminum layer becomes excessively thick, thereby causing the silicon wafer to bow.
In the aluminum paste of the present invention, the glass frit may be included in an amount of 0.01 ~ 5 wt%, preferably 0.05 ~ 3 wt%, more preferably 0.1 ~ 1 wt%.
The glass frit may be Bi2O3-SiO2-Al2O3-B2O3-SrO. The glass frit may include, but is not limited to, 20 ~ 30 mol% of Bi2O3, 5 ~ 15 mol% of Al2O3, 25 ~ 35 mol% of SiO2, 1 ~ 10 mol% of SrO, and 20 ~ 40 mol% of B2O3.
In the glass frit, SrO is effectively used to lower the softening point of the glass frit. When the glass frit does not include SrO, the softening point of the glass frit is increased, so that the aluminum paste is not softened enough during the co-firing process, with the result that the adhesion between the aluminum paste and the silicon wafer decreases, thereby decreasing the efficiency of the solar cell. However, when the glass frit includes an excessive amount of SrO, the softening point of the glass frit is excessively lowered, resulting in bumps in the aluminum electrode.
Further, the glass frit used in the present invention may have a softening point of 400 ~ 600℃. When the softening point of the glass frit is below 400℃, the thermal expansion coefficient of the glass frit is relatively increased, and thus the silicon wafer co-fired during the solar cell manufacturing process easily bows. Further, when the softening point thereof is above 600℃, the glass frit does not sufficiently melt in the co-firing process to such a degree that the adhesion is provided between the aluminum layer and the silicon wafer layer, thus deteriorating the adhesion therebetween.
The aluminum paste of the present invention may include, based on the total amount thereof, 20 ~ 34.90 wt% of an organic vehicle solution. The organic vehicle solution is prepared by dissolving a polymer resin in an organic solvent, and, if necessary, may include a thixotropic agent, a wetting agent, an additive and the like.
The organic vehicle solution used in the present invention may include, based on the total amount thereof, 75 wt% or more of an organic solvent, 1 ~ 30 wt% of a polymer resin, 5 wt% or less of a wetting agent and a thixotropic agent, and 1 ~ 10 wt% of an additive.
The organic solvent may have a boiling point of 150 ~ 300℃ such that it is possible to prevent the aluminum paste from drying and to control the flowability of the aluminum paste. Examples of commonly-used organic solvents may include glycol ethers, such as tripropyleneglycol methyl ether, dipropyleneglycol n-propyl ether, dipropyleneglycol n-butyl ether, tripropyleneglycol n-butyl ether, propyleneglycol phenyl ether, diethyleneglycol ethyl ether, diethyleneglycol n-butyl ether, diethyleneglycol hexyl ether, ethyleneglycol hexyl ether, triethyleneglycol methyl ether, triethyleneglycol ethyl ether, triethyleneglycol n-butyl ether, ethyleneglycol phenyl ether, terpineol, Texanol®, ethyleneglycol, and the like.
Examples of the polymer resin may include polyvinylpyrrolidone, polyvinylalcohol, polyethyleneglycol, ethylcellulose, rosin, a phenol resin, an acrylate resin, and the like. The amount of the polymer may be 1 ~ 30 wt%, preferably, 5 ~ 25 wt%, based on the total amount of the organic vehicle solution. When the amount of the polymer resin is below 1 wt%, the printability and dispersion stability of the aluminum paste are deteriorated. Further, the amount thereof is above 30 wt%, the aluminum paste cannot be printed.
As the thixotropic agent and wetting agent, thixotropic agents and wetting agents commonly used in the related field may be used without limitation.
The additive may be a dispersant or the like commonly used in the related field. As the dispersant, commercially available surfactants may be used, and they may be used independently or in combination with each other. Examples of the surfactants may include: nonionic surfactants, such as ethers including alkyl polyoxyethylene ether, alkylaryl polyoxyethylene ether, polyoxyethylene-polyoxypropylene copolymer and the like, ester-ethers including polyoxyethylene ether of glycerin ester, polyoxyethylene ether of sorbitan ester, polyoxyethylene ether of sorbitol ester and the like, esters including polyethylene glycol fatty acid ester, glycerin ester, sorbitan ester, propylene glycol ester, sugar ester, alkyl polyglucoside and the like, and nitrogen-containing surfactants including fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, amine oxide and the like; and polymeric surfactants, such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, polyacrylic acid-maleic acid compolymers, poly-12-hydroxystearic acid and the like.
Examples of commercially available surfactant products may include hypermer KD (manufactured by Uniqema Corp.), AKM 0531 (manufactured by NOF Corp.), KP (manufactured by Shinetsu Kagaku Kogyo Corp.), POLYFLOW (manufactured by Kyoei Kagaku Corp.), EFTOP (manufactured by Tokemu Products Corp.), Asahi guard, Surflon (manufactured by Asahi Glass Corp.), SOLSPERSE (manufactured by Geneka Corp.), EFKA (manufactured by EFKA Chemicals Co., Ltd.), PB 821 (manufactured by Ajinomoto Co., Inc.), BYK-184, BYK-185, BYK-2160, Anti-Terra U (manufactured by BYK Corp.), and the like.
The amount of the dispersant may be 1 ~ 10 wt%, preferably, 1 ~ 5 wt%, based on the total amount of the organic vehicle solution.
The aluminum paste according to the present invention can be easily prepared using a planar mixer which simultaneously rotates and revolves. That is, this aluminum paste can be prepared by putting the above-mentioned components into a planar mixer in the corresponding composition ratio and then stirring and then properly mixing and dispersing the solids in an organic vehicle solution. The aluminum paste prepared in this way has a viscosity of 20,000 ~ 200,000 cps at 5 rpm when its viscosity was measured at 25℃ using a Brookfield HBDV-III Ultra Rheometer or a spindle CPE-52. Preferably, the aluminum paste may be prepared such that it has a viscosity of 40,000 ~ 100,000 cps.
Further, the present invention provides a method of manufacturing a solar cell, including the step of forming a back electrode using the aluminum paste.
The solar cell manufactured in this way is advantageous in that it does not easily bows, and the minimum amount of aluminum balls and/or bumps are formed in the electrode layer, so that the values of short circuit current (Isc) and open circuit voltage (Voc) are greatly increased, and the efficiency thereof is remarkably improved.
Hereinafter, the present invention will be described in more detail with reference to the following Examples. However, the following Examples are set forth to illustrate the present invention, and the scope of the present invention is not limited thereto. The following Examples can be properly modified by those skilled in the art without departing from the scope of the invention.
Example 1: Preparation of aluminum paste
70 wt% of aluminum powder having an average particle size distribution of 0.04 ~ 5μm, 0.5 wt% of glass frit having a composition ratio given in Table 1 below, and 29.5 wt% of an organic vehicle solution in which ethyl cellulose is dissolved in glycol ether were sequentially mixed with each other to form a mixture, and then the mixture was stirred at a rotation speed of 1000 rpm for 3 minutes using a mixer which simultaneously rotates and revolves to prepare aluminum paste.
Table 1
Ingredient Mol%
Al2O3 6.5%
SrO 5.5%
Bi2O3 26.0%
B2O3 30.0%
SiO2 32.0%
Tg (transition point) 453
Thermal expansion coefficient (10-7/℃) 77
Tdsp 507
Example 2: Preparation of aluminum paste
Aluminum paste was prepared in the same manner as in Example 1, except that 65 wt% of aluminum powder having an average particle size distribution of 0.04 ~ 5μm and 34.5 wt% of an organic vehicle solution were added.
Example 3: Preparation of aluminum paste
Aluminum paste was prepared in the same manner as in Example 1, except that 75 wt% of aluminum powder having an average particle size distribution of 0.04 ~ 5μm and 24.5 wt% of an organic vehicle solution were added.
Comparative Example 1: Preparation of aluminum paste
Aluminum paste was prepared in the same manner as in Example 1, except that the glass frit was replace by glass frit having the composition ratio given in Table 2 below.
Table 2
Ingredient Mol%
Al2O3 10.91%
SrO -
Bi2O3 12.94%
B2O3 46.93%
SiO2 28.61%
Tg (transition point) 473
Thermal expansion coefficient (10-7/℃) 73
Tdsp 523
Comparative Example 2: Preparation of aluminum paste
Aluminum paste was prepared in the same manner as in Example 1, except that 76 wt% of aluminum powder having an average particle size distribution of 0.04 ~ 5μm and 23.5 wt% of an organic vehicle solution were added.
Comparative Example 3: Preparation of aluminum paste
Aluminum paste was prepared in the same manner as in Example 1, except that aluminum powder having an average particle size distribution of 2 ~ 10μm was used instead of the aluminum powder having an average particle size distribution of 0.04 ~ 5μm.
Comparative Example 4: Preparation of aluminum paste
Aluminum paste was prepared in the same manner as in Example 1, except that aluminum powder having an average particle size distribution of 5 ~ 15μm was used instead of the aluminum powder having an average particle size distribution of 0.04 ~ 5μm.
Test Example: Manufacturing a solar cell and testing characteristics thereof
A monocrystalline silicon wafer having a size of 156 X 156 mm and a thickness of 200 μm was surface-textured such that the height of a pyramid is about 4 ~ 6 μm, and then the N-side of the surface-textured silicon wafer was coated with SiNx. Subsequently, bus bars were printed on the back surface of the silicon wafer using silver paste and then dried, and then aluminum paste of each of Examples 1 to 3 and Comparative Examples 1 to 4 was applied thereon using a screen printing plate of 250 mesh such that the weight of the aluminum paste was 1.5 ± 0.1 g and then dried. Further, finger lines were printed on the front surface of the silicon wafer using silver paste and then dried.
Subsequently, the silicon wafer that had undergone the above processes was co-fired in a continuous infrared furnace such that the temperature of a firing zone was 720 ~ 900℃, thereby manufacturing a solar cell.
In the co-firing process, the front and back surface of the silicon wafer can be simultaneously co-fired while passing through a belt furnace. Here, the belt furnace includes a burn-out zone of about 600℃ and a firing zone of 800 ~ 950℃. In this belt furnace, organic matter was removed from the aluminum paste and the silver paste, and then the aluminum paste and silver paste applied on the back surface and front surface of the silicon wafer were melted to form electrodes.
The degree of bowing of the manufactured solar cell was evaluated by matching four edges of the solar cell with the bottom and then measuring to what degree the central portion thereof had been lifted. Further, the occurrence of bumps and aluminum balls around an aluminum back electrode was observed with the naked eye, and the number thereof was counted. The results thereof are given in Table 3 below.
The efficiency of the manufactured solar cell was evaluated using an SCM-1000, which is an apparatus for evaluating the performance of solar cells, manufactured by FitTech Corporation. The results thereof are given in Table 4 below.
Table 3
Exp. 1 Exp. 2 Exp. 3 Co. Exp. 1 Co. Exp. 2 Co. Exp. 3 Co. Exp. 4
Al powder 0.04-5 μm 0.04-5 μm .04-5 μm 0.04-5μm 0.04-5μm 2-10 μm 5-15μm
Al content 70 wt% 65 wt% 75 wt% 70 wt% 76 wt% 72 wt% 72 wt%
bowing (mm) 0.3-0.5 0.3-0.5 0.7-1.2 0.2-0.3 1.8-2.5 1.5-2.0 2.5-3.0
Number of Bump 0 1 - 2 0 5 - 8 0 10 - 12 15 - 20
Table 4
Exp. 1 Exp. 2 Exp. 3 Co. Exp. 1 Co. Exp. 2 Co. Exp. 3 Co. Exp. 4
Pmax (W) 4.16 4.077 4.088 3.899 4.059 3.900 3.889
Efficiency (%) 17.419 17.07 17.11 16.32 16.98 16.32 16.275
FF(%) 78.15 78.2 77.59 77.13 77.24 75.91 77.93
Isc 8.52925 8.415 8.478 8.279 8.475 8.341 8.182
Voc 0.62443 0.6197 0.6125 0.6107 0.6200 0.6159 0.6095
Rs 0.00746 0.00688 0.00719 0.00767 0.00749 0.00796 0.00663
Pmax = maximum power of solar cell
Isc = short circuit current (A)
Voc = open circuit voltage (V)
Rs = Series Resistance
FF = Fill Factor
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 (5)

  1. Aluminum paste for a back electrode of a solar cell, comprising, based on the total amount thereof:
    65 ~ 75 wt% of aluminum powder having an average particle size distribution of 0.01 ~ 5 μm;
    0.01 ~ 5 wt% of glass frit; and
    20 ~ 34.90 wt% of an organic vehicle solution.
  2. The aluminum paste according to claim 1, wherein the glass frit is Bi2O3-SiO2-Al2O3-B2O3-SrO.
  3. The aluminum paste according to claim 2, wherein the glass frit comprises 20 ~ 30 mol% of Bi2O3, 5 ~ 15 mol% of Al2O3, 25 ~ 35 mol% of SiO2, 1 ~ 10 mol% of SrO, and 20 ~ 40 mol% of B2O3.
  4. The aluminum paste according to claim 3, wherein the glass frit has a softening point of 400 ~ 600℃.
  5. A method of manufacturing a solar cell, comprising a process of forming a back electrode using the aluminum paste of claim 1.
PCT/KR2010/005998 2009-09-04 2010-09-03 Aluminum paste for a back electrode of solar cell WO2011028058A2 (en)

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EP2590177A3 (en) * 2011-11-04 2013-06-26 Heraeus Precious Metals North America Conshohocken LLC Organic vehicle for electroconductive paste
CN103709572A (en) * 2011-11-04 2014-04-09 赫劳斯贵金属北美康舍霍肯有限责任公司 Organic vehicle for electroconductive paste
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RU2531519C1 (en) * 2013-05-27 2014-10-20 Закрытое акционерное общество "Монокристалл" ЗАО "Монокристалл" Aluminium paste for silicon solar cells

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