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WO2011028035A2 - Solar cell and paste composition for the same - Google Patents

Solar cell and paste composition for the same Download PDF

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Publication number
WO2011028035A2
WO2011028035A2 PCT/KR2010/005958 KR2010005958W WO2011028035A2 WO 2011028035 A2 WO2011028035 A2 WO 2011028035A2 KR 2010005958 W KR2010005958 W KR 2010005958W WO 2011028035 A2 WO2011028035 A2 WO 2011028035A2
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WO
WIPO (PCT)
Prior art keywords
paste composition
dispersing agent
phosphorous
solar cell
metal powder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/KR2010/005958
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French (fr)
Other versions
WO2011028035A3 (en
Inventor
In Jae Lee
Jin Gyeong Park
Sang Gon Kim
Soon Gil Kim
Jun Phil Eom
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LG Innotek Co Ltd
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LG Innotek Co Ltd
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Publication of WO2011028035A2 publication Critical patent/WO2011028035A2/en
Publication of WO2011028035A3 publication Critical patent/WO2011028035A3/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
    • H10K10/80—Constructional details
    • H10K10/82—Electrodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/20—Electrodes
    • H10F77/206—Electrodes for devices having potential barriers
    • H10F77/211—Electrodes for devices having potential barriers for photovoltaic cells
    • 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
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • 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 disclosure relates to a solar cell and a paste composition for the same.
  • next generation clean energy has become more important due to the lack of fossil fuel.
  • next generation clean energy a solar cell is spotlighted as an energy source for solving the future energy problem because it rarely causes environmental pollution and has the semi-permanent life span and there exists infinite resources for the solar cell.
  • Such a solar cell can be manufactured by forming a front electrode and a rear electrode on a silicon substrate having an N type semiconductor and a P type semiconductor.
  • a front electrode and a rear electrode on a silicon substrate having an N type semiconductor and a P type semiconductor.
  • it is very important to improve the photoelectronic transformation efficiency.
  • a method of controlling doping density in the N type semiconductor and the P type semiconductor there has been suggested a method of controlling doping density in the N type semiconductor and the P type semiconductor, and a method of improving the characteristic of top and the rear electrodes.
  • the embodiment provides a solar cell and a paste composition for an electrode of the solar cell, capable of improving the efficiency of the solar cell.
  • a paste composition for an electrode of a solar cell according to the embodiment includes a phosphorous-containing dispersing agent.
  • the phosphorous-containing dispersing agent may include at least one selected from the group consisting of an amphiphilic polymeric dispersing agent, an acidic polymeric dispersing agent, a basic polymeric dispersing agent, a neutral polymeric dispersing agent, a cationic dispersing agent, and an anionic dispersing agent.
  • the phosphorous-containing dispersing agent may include phosphoric ester salt having a metal-affinitive group.
  • the amount of the phosphorous-containing dispersing agent may be 0.1 to 10 wt% based on a total amount of the paste composition.
  • the paste composition includes a metal powder, a glass frit and an organic vehicle, and the organic vehicle may include the phosphorous-containing dispersing agent.
  • the paste composition may further include an additive, and the paste composition includes 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
  • the paste composition may include a metal powder, a glass frit, an organic vehicle, and an additive, and the additive may include the phosphorous-containing dispersing agent.
  • the paste composition may include 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
  • the metal powder may include a silver powder or an aluminum powder.
  • a solar cell according to the embodiment may include an electrode manufactured by using the paste composition.
  • the paste composition according to the embodiment may include a phosphorous-containing dispersing agent so that the dispersing characteristic of the paste composition can be improved. Therefore, the content of metal powder in the paste composition can be increased so that the electric and mechanical characteristics of the electrode manufactured by using the paste composition can be improved. As a result, the efficiency of the solar cell including the electrode manufactured by using the paste composition can be improved.
  • stability of the paste composition can be enhanced due to the phosphorous-containing dispersing agent, so that the productivity and reliability of the electrode can be improved.
  • FIG. 1 is a sectional view of a solar cell.
  • the paste composition for the electrode of the solar cell includes metal powder, a glass frit, and an organic vehicle.
  • the paste composition may further include an additive.
  • the paste composition includes a phosphorus-based dispersing agent, which is included in the organic vehicle or the additive.
  • the metal powder may include silver powder or aluminum powder having light weight and superior conductivity.
  • the paste composition including the silver powder can be used for manufacturing the front electrode and the paste composition including the aluminum powder can be used for manufacturing the rear electrode, but the embodiment is not limited thereto.
  • the metal powder may have a spherical shape, a plate shape, a bell shape or a flake shape.
  • the metal powder may consist of particles having the same shape or different shapes.
  • the mean grain size of the metal powder is about 1.5 to 10. If the mean grain size is less than 1.5, the organic substance may not penetrate into the metal powder due to the agglomeration of the metal powder so that the metal powder may not be easily dispersed. In addition, if the mean grain size exceeds 10, many pores are formed in the metal powder, so the density of the metal powder is lowered and electric resistance of the electrode is increased.
  • the glass frit may include at least one or two selected from the group consisting of Bi 2 O 3 , B 2 O 3 , SiO 2 , Al 2 O 3 , CdO, CaO, BaO, ZnO, Na 2 O, Li 2 O, PbO, and ZrO. If the glass frit includes PbO-Bi 2 O 3 -B 2 O 3 -ZnO-SiO 2 , the bowing of the substrate formed with the electrode can be prevented. For instance, the bowing of the substrate can be prevented even if the electrode has a thin thickness of about 15 to 25. In addition, the glass frit has the grain size of about 1 to 10.
  • the organic vehicle allows the paste composition to have viscosity and rheological property adapted to be coated on the substrate.
  • the organic vehicle may include a solvent and a polymer dissolved in the solvent.
  • the organic vehicle may include a thixotropic agent, a leveling agent, and an anti-foaming agent.
  • the organic vehicle may also include the phosphorous-containing dispersing agent, which will be described later in detail.
  • the polymer may include acrylate resin, ethylcellulous, nitrocellulous, polymer of ethylcellulous and phenol resin, wood rosin, and polymethacrylate of alcohol.
  • ethylcellulous is used as the polymer.
  • the solvent may include at least one or two selected from the group consisting of butylcarbitolacetate, butylcarbitol, butylcellosolve, butylcellosolveacetate, propyleneglycolmonomethylether, dipropyleneglycolmonomethylether, propyleneglycolmonomethylpropionate, ethyletherpropionate, terpineol, propyleneglycolmonomethyletheracetate, dimethylamino, formaldehyde, methylethylketone, gamma-butyrolactone, ethyllactate, and texanol.
  • butylcarbitolacetate is used as the solvent.
  • the thixotropic agent may include urea type, amide type or urethane type polymer/organic substance or inorganic silica.
  • the paste composition according to the embodiment may further include various additives to improve the desired characteristics thereof.
  • the paste composition may further include sintering additive, thickener, stabilizer, or surfactant.
  • the paste composition may include the phosphorous-containing dispersing agent, which will be described later in detail.
  • the paste composition may include 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
  • the composition may not be prepared in the form of paste. If the amount of the metal powder is less than 60 wt%, the amount of conductive material is reduced, so that the resistance of the rear electrode may be increased. That is, when the solar cell has the above composition ratio, sinterability of the paste composition can be improved and the efficiency of the solar cell can be improved.
  • the amount of the glass frit is in the range of 0.3 to 15 wt%, adhesive property, sinterability and characteristics of the post-process of the solar cell can be improved.
  • the amount of the organic vehicle exceeds 39 wt%, the amount of the metal powder is reduced, so that the resistance of the electrode may be increased, thereby degrading the efficiency of the solar cell.
  • the amount of the organic vehicle is less than 4 wt%, the metal powder may not be easily mixed and distributed. In this case, the metal powder may not be easily coated on the substrate. As a result, the precision of patterns of the electrode formed by using the paste composition may be degraded.
  • the amount of the additive exceeds 10 wt%, the amount of the metal powder is reduced, so that the resistance of the rear electrode may be increased, thereby degrading the efficiency of the solar cell. In addition, if the amount of the additive is less than 0.1 wt%, the effect derived from the additive may be degraded.
  • the paste composition according to the embodiment includes the phosphorous-containing dispersing agent included in the organic vehicle and/or the additive. That is, the phosphorous-containing dispersing agent can be included in the organic vehicle of the paste composition and/or the phosphorous-containing dispersing agent can be included in the paste composition separately from the organic vehicle.
  • the phosphorous-containing dispersing agent strongly adsorbs on the surface of the metal powder to improve the dispersing property of the paste composition.
  • the phosphorous-containing dispersing agent can prevent agglomeration of the metal powder when the paste composition is prepared. Therefore, the content of the metal powder in the paste composition can be increased so that the electric and mechanical characteristics of the electrode manufactured by using the paste composition according to the embodiment can be improved. As a result, the efficiency of the solar cell including the electrode manufactured by using the paste composition can be improved. Since the3 mechanical characteristic of the solar cell can be improved, the bowing of the silicon substrate of the solar cell can be prevented.
  • stability of the paste composition can be enhanced due to the phosphorous-containing dispersing agent, so that the paste composition can be prevented from being deformed when preparing the paste composition. Accordingly, productivity can be improved when manufacturing the electrode by using the paste composition and reliability of the electrode can be improved.
  • the phosphorous-containing dispersing agent may include copolymer having a high molecular weight.
  • the phosphorous-containing dispersing agent may include phosphoric ester salt having a metal-affinitive group. Since the phosphorous-containing dispersing agent includes the metal-affinitive group as well as phosphorous strongly adsorbed onto the metal powder, the agglomeration of the metal powder can be more effectively prevented.
  • the phosphorous-containing dispersing agent may be classified into an amphiphilic polymeric dispersing agent, an acidic polymeric dispersing agent, a basic polymeric dispersing agent, a neutral polymeric dispersing agent, a cationic dispersing agent, and an anionic dispersing agent according to the type of the metal-affinitive group. If the amphiphilic polymeric dispersing agent is employed as the phosphorous-containing dispersing agent, productivity of the paste composition can be more improved.
  • the amphiphilic polymeric dispersing agent may includemetal-affinitive groups of carboxylic acid type, sulfonic acid type, sulfate type, phosphoric acid type orphosphoric ester type based onanionic active moiety groups ofhydrophilic moieties.
  • the amphiphilic polymeric dispersing agent may includemetal-affinitive groups of betaine type, imidazoline type, -alanine type, or amino type. These metal-affinitive groups can be included in the main chain of phosphoric ester salt or attached as functional groups.
  • the acidic polymeric dispersing agent may include metal-affinitive groups having a carboxylic acid group, a sulfonic acid group, a sulfate group, a phosphoric ester group, etc., asan acidic group. These metal-affinitive groups can be included in the main chain of phosphoric ester salt or attached as functional groups.
  • the cationic dispersing agent may include metal-affinitive groups of aliphatic amine salt and quaternary ammonium salt, aliphatic quaternary ammonium salt, and heterocyclic quaternary ammonium salt thereof. These metal-affinitive groups can be included in the main chain of phosphoric ester salt or attached as functional groups.
  • the neutral dispersing agent may be a block copolymer including metal-affinitive groups of ether type, esterether type, ester type or nitrogen-containing type.
  • the ether type metal-affinitive group may include a block copolymer including alkyl and alkyl aryl polyoxyethyleneether, alkyl aryl formaldehyde-condensatedpolyoxyethyleneether, polyoxypropylene, etc., as an oleophilic group.
  • the esterether type metal-affinitive group may include polyoxyethyleneether of glycerinester, polyoxyethyleneether of sorbitanester, polyoxyethyleneether of sorbitolester, etc.
  • the ester type metal-affinitive group may include polyethyleneglycolfattyacidester, glycerinester, sorbitanester, propyleneglycolester, sugarester, etc.
  • the nitrogen-containing metal-affinitive group may include fatty acid alkanolamide, polyoxyethylenefattyacidamid, polyoxyethylenealkylamine, amineoxide, etc.
  • the amount of the phosphorous-containing dispersing agent is about 0.1 to 10 wt% based on the total amount of the paste composition. If the amount of the phosphorous-containing dispersing agent exceeds 10 wt%, carbon may remain after the firing process and the excessive phosphorous-containing dispersing agent may increase the viscosity of the paste composition so that the paste composition may not be easily controlled during the process. If the amount of the phosphorous-containing dispersing agent is less than 0.1 wt%, the dispersing effect is insufficient.
  • the above elements are uniformly mixed with each other in a predetermined ratio by using a blender or a 3-axis roll, thereby preparing the paste composition.
  • the paste composition When measured by using a Brookfield HBT viscometer and a multi-purpose cup using a #51 spindle under 5rpm and 25, the paste composition may have viscosity of about 50 to 200PaS.
  • FIG. 1 is a sectional view showing the solar cell.
  • the solar cell includes a P type silicon substrate 10 provided on the top surface thereof with an N type semiconductor 11, a front electrode 12 electrically connected to the N type semiconductor 11 and a rear electrode 13 electrically connected to the P type silicon substrate 10.
  • An anti-reflective layer 14 can be formed on the top surface of the emitter 11 except for an area where the front electrode 12 is formed.
  • a BSF (back surface field) layer 15 is formed on the rear electrode 13 of the silicon substrate 10.
  • the paste composition according to the embodiment can be used to form the front electrode 12 or the rear electrode 13 of the solar cell. That is, the front electrode 12 or the rear electrode 13 can be manufactured by drying and firing the paste composition coated on the silicon substrate 10.
  • the paste composition including the silver powder can be used for manufacturing the front electrode 12 and the paste composition including the aluminum powder can be used for manufacturing the rear electrode 13, but the embodiment is not limited thereto.
  • the electrode of the solar cell can be formed by drying and firing the paste composition coated on the silicon substrate 10.
  • the paste composition can be coated on the silicon substrate 10 through the painting scheme.
  • the screen paining scheme can be employed to coat the paste composition on the silicon substrate.
  • the paste composition can be coated with a thickness of about 20 to 60 through the painting scheme. Details of this are disclosed in Korean Laid-open Patent Publication Nos. 10-2006-0108550 and 10-2006-0127813 and Japanese Laid-open Patent Publication Nos. 2001-202822 and 2003-133567, the contents of which are herein incorporated by reference in their entirety.
  • the drying process is performed under the temperature of 90 to 250? and the firing process is performed under the temperature of 600 to 950?.
  • the high-temperature/high-speed firing process is performed for 5 seconds to 1 minute at the temperature of about 800 to 900?.
  • the paste composition according to the embodiment can improve dispersing property of the metal powder, so that the content of the metal powder can be increased.
  • the front electrode 12 or the rear electrode 13 manufactured by using the paste composition may have superior electric and mechanical characteristics.
  • the paste composition can be stably stored, so that the stability and reliability of the front electrode 12 or the rear electrode 13 manufactured by using the paste composition can be improved.
  • the paste composition was prepared by mixing 80g of metal powder with 5g of glass frit, 15g of organic vehicle, and 1g of phosphorous-containing dispersing agent. Silver powder was used as the metal powder, and the glass frit was PbO-Bi 2 O 3 -B 2 O 3 -ZnO-SiO 2 .
  • the organic vehicle was prepared by adding 10 wt% of polymer, which was prepared by mixing two types of ethyl cellulous having molecular weights different from each other in a ratio of 3:1, to 90 wt% of solution, which was prepared by mixing butylcarbitolacetate with terpineol in a ratio of 50:50.
  • the amphiphilic polymeric dispersing agent was used as the phosphorous-containing dispersing agent.
  • Phosphoric ester salt of copolymer having a high molecular weight with a metal-affinitive group was used as the amphiphilic polymeric dispersing agent.
  • Example 2 is similar to Example 1 except that the acidic dispersing agent was used as the phosphorous-containing dispersing agent.
  • the acidic dispersing agent was a copolymer having an acidic group including phosphorous.
  • Example 3 is similar to Example 1 except that the cationic dispersing agent was used as the phosphorous-containing dispersing agent.
  • the cationic dispersing agent was alkylol ammonium salt having multi-functional polymer including phosphorous.
  • Example 4 is similar to Example 1 except that the neutral dispersing agent was used as the phosphorous-containing dispersing agent.
  • the neutral dispersing agent was a block copolymer having a metal-affinitive group and including phosphorous.
  • the paste composition was prepared similarly to Example 1 except that the phosphorous-free dispersing agent was used instead of the phosphorous-containing dispersing agent.
  • the phosphorous-free dispersing agent was a block copolymer having a high molecular weight with a metal-affinitive group.
  • the efficiency of the solar cell was measured by using a solar simulator.
  • Examples 1 to 4 represent superior efficiencies as compared with the efficiency of the Comparative Example.
  • the minimum efficiency of Examples 1 to 4 is 16.56% and the mean efficiency of Examples 1 to 4 is 16.77%, but the efficiency of the Comparative Example is 16.37%.
  • the efficiency grade is classified in the unit of 0.2%, so the efficiency increment of 0.2% may have serious meaning. That is, Examples 1 to 4 represent excellent efficiencies.
  • the embodiments are applicable to the electrode of the solar cell.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Photovoltaic Devices (AREA)
  • Conductive Materials (AREA)

Abstract

A paste composition for an electrode of a solar cell according to the embodiment includes a phosphorous-containing dispersing agent. The phosphorous-containing dispersing agent includes at least one selected from the group consisting of an amphiphilic polymeric dispersing agent, an acidic polymeric dispersing agent, a basic polymeric dispersing agent, a neutral polymeric dispersing agent, a cationic dispersing agent, and an anionic dispersing agent.

Description

SOLAR CELL AND PASTE COMPOSITION FOR THE SAME
The disclosure relates to a solar cell and a paste composition for the same.
Recently, the development of next generation clean energy has become more important due to the lack of fossil fuel. Among the next generation clean energy, a solar cell is spotlighted as an energy source for solving the future energy problem because it rarely causes environmental pollution and has the semi-permanent life span and there exists infinite resources for the solar cell.
Such a solar cell can be manufactured by forming a front electrode and a rear electrode on a silicon substrate having an N type semiconductor and a P type semiconductor. In the solar cell, it is very important to improve the photoelectronic transformation efficiency. In order to improve the photoelectronic transformation efficiency, there has been suggested a method of controlling doping density in the N type semiconductor and the P type semiconductor, and a method of improving the characteristic of top and the rear electrodes.
The embodiment provides a solar cell and a paste composition for an electrode of the solar cell, capable of improving the efficiency of the solar cell.
A paste composition for an electrode of a solar cell according to the embodiment includes a phosphorous-containing dispersing agent.
The phosphorous-containing dispersing agent may include at least one selected from the group consisting of an amphiphilic polymeric dispersing agent, an acidic polymeric dispersing agent, a basic polymeric dispersing agent, a neutral polymeric dispersing agent, a cationic dispersing agent, and an anionic dispersing agent.
The phosphorous-containing dispersing agent may include phosphoric ester salt having a metal-affinitive group.
The amount of the phosphorous-containing dispersing agent may be 0.1 to 10 wt% based on a total amount of the paste composition.
The paste composition includes a metal powder, a glass frit and an organic vehicle, and the organic vehicle may include the phosphorous-containing dispersing agent.
The paste composition may further include an additive, and the paste composition includes 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
The paste composition may include a metal powder, a glass frit, an organic vehicle, and an additive, and the additive may include the phosphorous-containing dispersing agent.
The paste composition may include 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
The metal powder may include a silver powder or an aluminum powder.
A solar cell according to the embodiment may include an electrode manufactured by using the paste composition.
The paste composition according to the embodiment may include a phosphorous-containing dispersing agent so that the dispersing characteristic of the paste composition can be improved. Therefore, the content of metal powder in the paste composition can be increased so that the electric and mechanical characteristics of the electrode manufactured by using the paste composition can be improved. As a result, the efficiency of the solar cell including the electrode manufactured by using the paste composition can be improved.
In addition, stability of the paste composition can be enhanced due to the phosphorous-containing dispersing agent, so that the productivity and reliability of the electrode can be improved.
FIG. 1 is a sectional view of a solar cell.
Hereinafter, a paste composition and a solar cell including an electrode manufactured by using the paste composition according to the embodiment will be described in detail.
The paste composition for the electrode of the solar cell includes metal powder, a glass frit, and an organic vehicle. The paste composition may further include an additive. In addition, the paste composition includes a phosphorus-based dispersing agent, which is included in the organic vehicle or the additive.
The metal powder may include silver powder or aluminum powder having light weight and superior conductivity. The paste composition including the silver powder can be used for manufacturing the front electrode and the paste composition including the aluminum powder can be used for manufacturing the rear electrode, but the embodiment is not limited thereto.
The metal powder may have a spherical shape, a plate shape, a bell shape or a flake shape. The metal powder may consist of particles having the same shape or different shapes.
The mean grain size of the metal powder is about 1.5 to 10. If the mean grain size is less than 1.5, the organic substance may not penetrate into the metal powder due to the agglomeration of the metal powder so that the metal powder may not be easily dispersed. In addition, if the mean grain size exceeds 10, many pores are formed in the metal powder, so the density of the metal powder is lowered and electric resistance of the electrode is increased.
Various materials can be used for the glass frit. For instance, lead borosilicate glass having the softening point of 400 to 600, lead silicate glass, bismuth glass or lithium glass can be used as the glass frit. In more detail, the glass frit may include at least one or two selected from the group consisting of Bi2O3, B2O3, SiO2, Al2O3, CdO, CaO, BaO, ZnO, Na2O, Li2O, PbO, and ZrO. If the glass frit includes PbO-Bi2O3-B2O3-ZnO-SiO2, the bowing of the substrate formed with the electrode can be prevented. For instance, the bowing of the substrate can be prevented even if the electrode has a thin thickness of about 15 to 25. In addition, the glass frit has the grain size of about 1 to 10.
The organic vehicle allows the paste composition to have viscosity and rheological property adapted to be coated on the substrate.
The organic vehicle may include a solvent and a polymer dissolved in the solvent. In addition, the organic vehicle may include a thixotropic agent, a leveling agent, and an anti-foaming agent. The organic vehicle may also include the phosphorous-containing dispersing agent, which will be described later in detail.
The polymer may include acrylate resin, ethylcellulous, nitrocellulous, polymer of ethylcellulous and phenol resin, wood rosin, and polymethacrylate of alcohol. Preferably, ethylcellulous is used as the polymer.
The solvent may include at least one or two selected from the group consisting of butylcarbitolacetate, butylcarbitol, butylcellosolve, butylcellosolveacetate, propyleneglycolmonomethylether, dipropyleneglycolmonomethylether, propyleneglycolmonomethylpropionate, ethyletherpropionate, terpineol, propyleneglycolmonomethyletheracetate, dimethylamino, formaldehyde, methylethylketone, gamma-butyrolactone, ethyllactate, and texanol. Preferably, butylcarbitolacetate is used as the solvent.
The thixotropic agent may include urea type, amide type or urethane type polymer/organic substance or inorganic silica.
The paste composition according to the embodiment may further include various additives to improve the desired characteristics thereof. For instance, the paste composition may further include sintering additive, thickener, stabilizer, or surfactant. In addition, the paste composition may include the phosphorous-containing dispersing agent, which will be described later in detail.
For instance, the paste composition may include 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
If the amount of the metal powder exceeds 95 wt%, the composition may not be prepared in the form of paste. If the amount of the metal powder is less than 60 wt%, the amount of conductive material is reduced, so that the resistance of the rear electrode may be increased. That is, when the solar cell has the above composition ratio, sinterability of the paste composition can be improved and the efficiency of the solar cell can be improved.
If the amount of the glass frit is in the range of 0.3 to 15 wt%, adhesive property, sinterability and characteristics of the post-process of the solar cell can be improved.
If the amount of the organic vehicle exceeds 39 wt%, the amount of the metal powder is reduced, so that the resistance of the electrode may be increased, thereby degrading the efficiency of the solar cell. In addition, if the amount of the organic vehicle is less than 4 wt%, the metal powder may not be easily mixed and distributed. In this case, the metal powder may not be easily coated on the substrate. As a result, the precision of patterns of the electrode formed by using the paste composition may be degraded.
If the amount of the additive exceeds 10 wt%, the amount of the metal powder is reduced, so that the resistance of the rear electrode may be increased, thereby degrading the efficiency of the solar cell. In addition, if the amount of the additive is less than 0.1 wt%, the effect derived from the additive may be degraded.
The paste composition according to the embodiment includes the phosphorous-containing dispersing agent included in the organic vehicle and/or the additive. That is, the phosphorous-containing dispersing agent can be included in the organic vehicle of the paste composition and/or the phosphorous-containing dispersing agent can be included in the paste composition separately from the organic vehicle.
The phosphorous-containing dispersing agent strongly adsorbs on the surface of the metal powder to improve the dispersing property of the paste composition. Thus, the phosphorous-containing dispersing agent can prevent agglomeration of the metal powder when the paste composition is prepared. Therefore, the content of the metal powder in the paste composition can be increased so that the electric and mechanical characteristics of the electrode manufactured by using the paste composition according to the embodiment can be improved. As a result, the efficiency of the solar cell including the electrode manufactured by using the paste composition can be improved. Since the3 mechanical characteristic of the solar cell can be improved, the bowing of the silicon substrate of the solar cell can be prevented.
In addition, stability of the paste composition can be enhanced due to the phosphorous-containing dispersing agent, so that the paste composition can be prevented from being deformed when preparing the paste composition. Accordingly, productivity can be improved when manufacturing the electrode by using the paste composition and reliability of the electrode can be improved.
The phosphorous-containing dispersing agent may include copolymer having a high molecular weight. For instance, the phosphorous-containing dispersing agent may include phosphoric ester salt having a metal-affinitive group. Since the phosphorous-containing dispersing agent includes the metal-affinitive group as well as phosphorous strongly adsorbed onto the metal powder, the agglomeration of the metal powder can be more effectively prevented.
The phosphorous-containing dispersing agent may be classified into an amphiphilic polymeric dispersing agent, an acidic polymeric dispersing agent, a basic polymeric dispersing agent, a neutral polymeric dispersing agent, a cationic dispersing agent, and an anionic dispersing agent according to the type of the metal-affinitive group. If the amphiphilic polymeric dispersing agent is employed as the phosphorous-containing dispersing agent, productivity of the paste composition can be more improved.
For instance, the amphiphilic polymeric dispersing agent may includemetal-affinitive groups of carboxylic acid type, sulfonic acid type, sulfate type, phosphoric acid type orphosphoric ester type based onanionic active moiety groups ofhydrophilic moieties. In addition, the amphiphilic polymeric dispersing agent may includemetal-affinitive groups of betaine type, imidazoline type, -alanine type, or amino type. These metal-affinitive groups can be included in the main chain of phosphoric ester salt or attached as functional groups.
In addition, the acidic polymeric dispersing agent may include metal-affinitive groups having a carboxylic acid group, a sulfonic acid group, a sulfate group, a phosphoric ester group, etc., asan acidic group. These metal-affinitive groups can be included in the main chain of phosphoric ester salt or attached as functional groups.
The cationic dispersing agent may include metal-affinitive groups of aliphatic amine salt and quaternary ammonium salt, aliphatic quaternary ammonium salt, and heterocyclic quaternary ammonium salt thereof. These metal-affinitive groups can be included in the main chain of phosphoric ester salt or attached as functional groups.
The neutral dispersing agent may be a block copolymer including metal-affinitive groups of ether type, esterether type, ester type or nitrogen-containing type. The ether type metal-affinitive group may include a block copolymer including alkyl and alkyl aryl polyoxyethyleneether, alkyl aryl formaldehyde-condensatedpolyoxyethyleneether, polyoxypropylene, etc., as an oleophilic group. The esterether type metal-affinitive group may include polyoxyethyleneether of glycerinester, polyoxyethyleneether of sorbitanester, polyoxyethyleneether of sorbitolester, etc. The ester type metal-affinitive group may include polyethyleneglycolfattyacidester, glycerinester, sorbitanester, propyleneglycolester, sugarester, etc. The nitrogen-containing metal-affinitive group may include fatty acid alkanolamide, polyoxyethylenefattyacidamid, polyoxyethylenealkylamine, amineoxide, etc.
The amount of the phosphorous-containing dispersing agent is about 0.1 to 10 wt% based on the total amount of the paste composition. If the amount of the phosphorous-containing dispersing agent exceeds 10 wt%, carbon may remain after the firing process and the excessive phosphorous-containing dispersing agent may increase the viscosity of the paste composition so that the paste composition may not be easily controlled during the process. If the amount of the phosphorous-containing dispersing agent is less than 0.1 wt%, the dispersing effect is insufficient.
The above elements are uniformly mixed with each other in a predetermined ratio by using a blender or a 3-axis roll, thereby preparing the paste composition. When measured by using a Brookfield HBT viscometer and a multi-purpose cup using a #51 spindle under 5rpm and 25, the paste composition may have viscosity of about 50 to 200PaS.
Hereinafter, an example of the solar cell employing the paste composition according to the embodiment will be described with reference to FIG. 1. FIG. 1 is a sectional view showing the solar cell.
Referring to FIG. 1, the solar cell includes a P type silicon substrate 10 provided on the top surface thereof with an N type semiconductor 11, a front electrode 12 electrically connected to the N type semiconductor 11 and a rear electrode 13 electrically connected to the P type silicon substrate 10. An anti-reflective layer 14 can be formed on the top surface of the emitter 11 except for an area where the front electrode 12 is formed. In addition, a BSF (back surface field) layer 15 is formed on the rear electrode 13 of the silicon substrate 10.
The paste composition according to the embodiment can be used to form the front electrode 12 or the rear electrode 13 of the solar cell. That is, the front electrode 12 or the rear electrode 13 can be manufactured by drying and firing the paste composition coated on the silicon substrate 10. For instance, the paste composition including the silver powder can be used for manufacturing the front electrode 12 and the paste composition including the aluminum powder can be used for manufacturing the rear electrode 13, but the embodiment is not limited thereto.
In detail, the electrode of the solar cell can be formed by drying and firing the paste composition coated on the silicon substrate 10.
The paste composition can be coated on the silicon substrate 10 through the painting scheme. In more detail, the screen paining scheme can be employed to coat the paste composition on the silicon substrate. The paste composition can be coated with a thickness of about 20 to 60 through the painting scheme. Details of this are disclosed in Korean Laid-open Patent Publication Nos. 10-2006-0108550 and 10-2006-0127813 and Japanese Laid-open Patent Publication Nos. 2001-202822 and 2003-133567, the contents of which are herein incorporated by reference in their entirety.
The drying process is performed under the temperature of 90 to 250? and the firing process is performed under the temperature of 600 to 950?. Preferably, the high-temperature/high-speed firing process is performed for 5 seconds to 1 minute at the temperature of about 800 to 900?.
The paste composition according to the embodiment can improve dispersing property of the metal powder, so that the content of the metal powder can be increased. Thus, the front electrode 12 or the rear electrode 13 manufactured by using the paste composition may have superior electric and mechanical characteristics. In addition, the paste composition can be stably stored, so that the stability and reliability of the front electrode 12 or the rear electrode 13 manufactured by using the paste composition can be improved.
Hereinafter, the experimental examples and the comparative example of the embodiment will be described in detail. These examples are illustrative purposes only, and the embodiment is not limited thereto.
Example 1
The paste composition was prepared by mixing 80g of metal powder with 5g of glass frit, 15g of organic vehicle, and 1g of phosphorous-containing dispersing agent. Silver powder was used as the metal powder, and the glass frit was PbO-Bi2O3-B2O3-ZnO-SiO2. The organic vehicle was prepared by adding 10 wt% of polymer, which was prepared by mixing two types of ethyl cellulous having molecular weights different from each other in a ratio of 3:1, to 90 wt% of solution, which was prepared by mixing butylcarbitolacetate with terpineol in a ratio of 50:50. The amphiphilic polymeric dispersing agent was used as the phosphorous-containing dispersing agent. Phosphoric ester salt of copolymer having a high molecular weight with a metal-affinitive group was used as the amphiphilic polymeric dispersing agent.
Example 2
Example 2 is similar to Example 1 except that the acidic dispersing agent was used as the phosphorous-containing dispersing agent. The acidic dispersing agent was a copolymer having an acidic group including phosphorous.
Example 3
Example 3 is similar to Example 1 except that the cationic dispersing agent was used as the phosphorous-containing dispersing agent. The cationic dispersing agent was alkylol ammonium salt having multi-functional polymer including phosphorous.
Example 4
Example 4 is similar to Example 1 except that the neutral dispersing agent was used as the phosphorous-containing dispersing agent. The neutral dispersing agent was a block copolymer having a metal-affinitive group and including phosphorous.
Comparative Example
The paste composition was prepared similarly to Example 1 except that the phosphorous-free dispersing agent was used instead of the phosphorous-containing dispersing agent. The phosphorous-free dispersing agent was a block copolymer having a high molecular weight with a metal-affinitive group.
The paste composition of Examples 1 to 4 and Comparative Example was printed on the silicon substrate through the silk screen printing process and then the firing process was performed to manufacture the front electrode. The result of efficiency of the solar cell having the front electrode is shown in Table 1.
The efficiency of the solar cell was measured by using a solar simulator.
Table 1
Efficiency (%)
Example 1 17.07
Example 2 16.77
Example 3 16.56
Example 4 16.66
Comparative Example 16.37
As can be understood from Table 1, Examples 1 to 4 represent superior efficiencies as compared with the efficiency of the Comparative Example. In detail, the minimum efficiency of Examples 1 to 4 is 16.56% and the mean efficiency of Examples 1 to 4 is 16.77%, but the efficiency of the Comparative Example is 16.37%. In the solar cell industrial field, the efficiency grade is classified in the unit of 0.2%, so the efficiency increment of 0.2% may have serious meaning. That is, Examples 1 to 4 represent excellent efficiencies.
Although a preferred embodiment of the present invention has been described 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.
The embodiments are applicable to the electrode of the solar cell.

Claims (10)

  1. A paste composition for an electrode of a solar cell, comprising a phosphorous-containing dispersing agent.
  2. The paste composition of claim 1, wherein the phosphorous-containing dispersing agent includes at least one selected from the group consisting of an amphiphilic polymeric dispersing agent, an acidic polymeric dispersing agent, a basic polymeric dispersing agent, a neutral polymeric dispersing agent, a cationic dispersing agent, and an anionic dispersing agent.
  3. The paste composition of claim 1, wherein the phosphorous-containing dispersing agent includes phosphoric ester salt having a metal-affinitive group.
  4. The paste composition of claim 1, wherein an amount of the phosphorous-containing dispersing agent is 0.1 to 10 wt% based on a total amount of the paste composition.
  5. The paste composition of claim 1, wherein the paste composition includes a metal powder, a glass frit and an organic vehicle, and the organic vehicle includes the phosphorous-containing dispersing agent.
  6. The paste composition of claim 5, further comprising an additive, wherein the paste composition includes 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
  7. The paste composition of claim 1, wherein the paste composition includes a metal powder, a glass frit, an organic vehicle, and an additive, and the additive includes the phosphorous-containing dispersing agent.
  8. The paste composition of claim 7, wherein the paste composition includes 60 to 95 wt% of the metal powder, 0.3 to 15 wt% of the glass frit, 4 to 39 wt% of the organic vehicle, and 0.1 to 10 wt% of the additive.
  9. The paste composition of claim 1, wherein the metal powder includes a silver powder or an aluminum powder.
  10. A solar cell including an electrode manufactured by using the paste composition of claim 1.
PCT/KR2010/005958 2009-09-02 2010-09-02 Solar cell and paste composition for the same Ceased WO2011028035A2 (en)

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
US20120234384A1 (en) * 2011-03-15 2012-09-20 E.I. Du Pont Nemours And Company Conductive metal paste for a metal-wrap-through silicon solar cell
US20120234383A1 (en) * 2011-03-15 2012-09-20 E.I.Du Pont De Nemours And Company Conductive metal paste for a metal-wrap-through silicon solar cell
EP2802545A4 (en) * 2012-01-13 2015-06-10 Hanwha Chemical Corp FRITTE DE VERRE AND CONDUCTIVE PULP AND PHOTOPILE COMPOSITION COMPRISING SAME
CN113257453A (en) * 2021-04-15 2021-08-13 中国科学院山西煤炭化学研究所 Phosphorus-containing organic carrier PERC solar front silver paste and preparation method thereof

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TWI562171B (en) * 2013-03-27 2016-12-11 Cheil Ind Inc The composition for forming solar cell electrode and electrode prepared using the same

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EP0851511A1 (en) * 1996-12-24 1998-07-01 IMEC vzw Semiconductor device with two selectively diffused regions
US8455753B2 (en) * 2005-01-14 2013-06-04 Semiconductor Energy Laboratory Co., Ltd. Solar cell and semiconductor device, and manufacturing method thereof
KR100790856B1 (en) 2005-07-15 2008-01-03 삼성전기주식회사 Multilayer Ceramic Capacitors Containing Phosphoric Acid Dispersant
US7718092B2 (en) * 2005-10-11 2010-05-18 E.I. Du Pont De Nemours And Company Aluminum thick film composition(s), electrode(s), semiconductor device(s) and methods of making thereof
US8309844B2 (en) * 2007-08-29 2012-11-13 Ferro Corporation Thick film pastes for fire through applications in solar cells

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120234384A1 (en) * 2011-03-15 2012-09-20 E.I. Du Pont Nemours And Company Conductive metal paste for a metal-wrap-through silicon solar cell
US20120234383A1 (en) * 2011-03-15 2012-09-20 E.I.Du Pont De Nemours And Company Conductive metal paste for a metal-wrap-through silicon solar cell
EP2802545A4 (en) * 2012-01-13 2015-06-10 Hanwha Chemical Corp FRITTE DE VERRE AND CONDUCTIVE PULP AND PHOTOPILE COMPOSITION COMPRISING SAME
CN113257453A (en) * 2021-04-15 2021-08-13 中国科学院山西煤炭化学研究所 Phosphorus-containing organic carrier PERC solar front silver paste and preparation method thereof

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TWI401298B (en) 2013-07-11
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KR101611456B1 (en) 2016-04-11
WO2011028035A3 (en) 2011-07-07

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