Disclosure of Invention
The invention aims to solve the technical problem of providing the front silver paste for the crystalline silicon solar cell in a grading manner, which is low in cost and can ensure the photoelectric conversion efficiency of the cell.
The invention also provides a preparation method of the front silver paste for the fractional use of the crystalline silicon solar cell, which has the advantages of simple process, high production rate, rapid mass production and suitability for industrial mass production.
In order to solve the technical problem, the invention provides a front silver paste for a crystalline silicon solar cell in a grading mode, which comprises a first paste and a second paste, wherein the first paste is used for printing a secondary grid of the cell, the second paste is used for printing a main grid of the cell, the first paste comprises spherical silver powder, first glass powder and a first organic carrier, and the second paste comprises silver-coated copper powder, spherical silver powder, flaky silver powder, second glass powder and a second organic carrier.
As an improvement of the above scheme, the first slurry comprises the following components in percentage by mass: 85-95% of spherical silver powder, 1-3% of first glass powder and 4-13% of first organic carrier;
the second slurry comprises the following components in percentage by mass: 80-85% of silver-coated copper powder, 3-8% of spherical silver powder, 2-8% of flake silver powder, 2-4% of second glass powder and 5-17% of second organic carrier.
As an improvement of the above aspect, the first glass frit includes: PbO, Bi2O3、TeO2、SiO2And a first oxide additive;
the second glass frit comprises: na (Na)2O、TeO2、WO3、SiO2、Li2O and a second oxide additive.
As an improvement of the above scheme, the first glass frit comprises the following components in percentage by mass: 15-55% of PbO and Bi2O3 10~50%、TeO2 20~60%、SiO25-15% and 5-15% of a first oxide additive;
the second glass powder comprises the following components in percentage by mass: na (Na)2O10~20%、TeO2 15~35%、WO325~35%、SiO2 3~8%、Li2O2-6% and a second oxide additive 10-15%.
As a modification of the above, the first oxide additive comprises WO3、ZnO、CaO、MgO、Al2O3、Li2O、Na2O、Fe2O3、B2O3And BaO;
the second oxide additive comprises MgO and Al2O3、LaO、Bi2O3、Li2O、CaO、SnO2、Fe2O3、B2O3、BaO、ZrO2、K2O、CrO3And NiO.
As an improvement of the above scheme, the first glass frit comprises the following components in percentage by mass: 15-55% of PbO and Bi2O3 10~50%、TeO2 20~60%、SiO25-15% and 5-15% of a first oxide additive;
the second glass powder comprises the following components in percentage by mass: na (Na)2O10~20%、TeO2 15~35%、WO325~35%、SiO2 3~8%、Li2O2-6% and a second oxide additive 10-15%.
As a refinement of the above, the first organic vehicle includes a first thickener, a thixotropic agent, a first organic solvent, and an organic additive;
the first thickening agent is one or more of cellulose resin, acrylic resin, rosin resin and phenolic resin;
the first organic solvent is one or more of butyl carbitol, butyl carbitol acetate, terpineol and tributyl citrate;
the second organic vehicle comprises a second thickener, a thixotropic agent, a second organic solvent, and an organic additive;
the second thickening agent is one or more of ethyl cellulose, butyl cellulose, acrylic resin and phenolic resin;
the second organic solvent is one or more of butyl carbitol, butyl carbitol acetate and terpineol.
As an improvement of the above scheme, the first organic vehicle comprises the following components in percentage by mass: 30% of a first thickening agent, 30% of a thixotropic agent, 10% of a first organic solvent and 20% of an organic additive;
the second organic carrier comprises the following components in percentage by mass: 30% of a second thickening agent, 5-10% of a thixotropic agent, 40-45% of a second organic solvent and 20% of an organic additive.
As an improvement of the scheme, the thixotropic agent is polyamide wax, and the organic additive is one or more of a leveling agent, a dispersing agent and a surfactant.
Correspondingly, the invention also provides a preparation method of the front silver paste for the fractional use of the crystalline silicon solar cell, which comprises the following steps:
first, preparing a first slurry
a1, uniformly mixing and drying the components of the first glass powder to obtain a first mixture;
b1, smelting the first mixture obtained in the step (a1), and then extracting with water and drying;
c1, performing ball milling, drying and screening on the first mixture obtained in the step (b1) to obtain first glass powder;
d1, uniformly mixing the components of the first organic carrier, heating to 80-120 ℃, and continuously stirring for 60-90 minutes to obtain the first organic carrier;
e1, uniformly stirring the first glass powder obtained in the step (c1), the first organic carrier obtained in the step (d1) and the spherical silver powder at the temperature of 30-60 ℃ to form slurry, and rolling the stirred slurry to ensure that the fineness of the slurry is 10-15 microns and the viscosity is 50-500 Pascal seconds;
second, preparing a second slurry
a2, uniformly mixing and drying the components of the second glass powder to obtain a second mixture;
b2, smelting the second mixture obtained in the step (a2), and then extracting with water and drying;
c2, performing ball milling, drying and screening on the second mixture obtained in the step (b2) to obtain second glass powder;
d2, uniformly mixing the components of the second organic carrier, heating to 90-130 ℃, and continuously stirring for 80-100 minutes to obtain a second organic carrier;
e2, uniformly stirring the second glass powder obtained in the step (c2), the second organic carrier obtained in the step (d2) and the spherical silver powder at 40-60 ℃ to form slurry, and rolling the stirred slurry to ensure that the fineness of the slurry is 8-12 microns and the viscosity is 30-300 Pascal seconds.
The implementation of the invention has the following beneficial effects:
1. according to the invention, through the mutual matching of the first slurry and the second slurry, the silver-coated copper powder and a small amount of spherical silver powder and flake silver powder are printed on the main grid in a multi-printing mode, and a large amount of spherical silver powder is printed on the auxiliary grid, so that the battery can keep good light receiving performance and electric conductivity, and the use amount of silver can be greatly reduced.
2. The content of the spherical silver powder in the first paste is 85-95%, the content of the spherical silver powder is slightly higher than that of the conventional paste, the content of the glass powder is 1-3%, the content of the glass powder is slightly lower than that of the conventional paste, and compared with the existing paste, the grid line printed by the first paste is more compact, so that the loss of the fine grid in the current transmission process is reduced. The content of the silver-coated copper powder in the second slurry is 80-85%, wherein a large amount of silver-coated copper powder, a small amount of flaky silver powder and spherical silver powder in the second slurry form a conductive phase of the second slurry, so that the electrical property of the second slurry is ensured, and the cost of the slurry is reduced.
3. The first paste can burn through the SiNx antireflection layer of the cell to form good silver-silicon contact, the second paste cannot burn through the SiNx antireflection layer of the cell, current collected by the fine grid is mainly led out effectively, welding tension of the main grid is guaranteed, meanwhile, compounding of metal on the surface of the cell is reduced, and photoelectric conversion efficiency of the cell is improved effectively.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below.
The invention provides a front-side silver paste for crystalline silicon solar cells in a grading mode, which comprises a first paste and a second paste, wherein the first paste is used for printing secondary grids of the cells, the second paste is used for printing primary grids of the cells, the first paste comprises spherical silver powder, first glass powder and a first organic carrier, and the second paste comprises silver-coated copper powder, spherical silver powder, flaky silver powder, second glass powder and a second organic carrier.
At present, the front printing of the battery is divided into single printing and step-by-step printing, and the main grid paste and the auxiliary grid paste are printed together by the single printing, so that only one paste is available; the main grid slurry and the auxiliary grid slurry are printed step by step and are printed separately, the main grid slurry does not burn through the antireflection layer, the auxiliary grid slurry needs to burn through the antireflection layer to collect current, and therefore the two slurries have different components.
Specifically, the first slurry comprises the following components in percentage by mass: 85-95% of spherical silver powder, 1-3% of first glass powder and 4-13% of first organic carrier; the second slurry comprises the following components in percentage by mass: 80-85% of silver-coated copper powder, 3-8% of spherical silver powder, 2-8% of flake silver powder, 2-4% of second glass powder and 5-17% of second organic carrier.
According to the invention, through the mutual matching of the first slurry and the second slurry, the silver-coated copper powder and a small amount of spherical silver powder and flake silver powder are printed on the main grid in a multi-printing mode, and a large amount of spherical silver powder is printed on the auxiliary grid, so that the battery can keep good light receiving performance and electric conductivity, and the use amount of silver can be greatly reduced.
Specifically, the content of the spherical silver powder in the first paste is 85-95%, which is slightly higher than that of the conventional paste, and the content of the glass powder is 1-3%, which is slightly lower than that of the conventional paste. The content of the silver-coated copper powder in the second slurry is 80-85%, wherein a large amount of silver-coated copper powder, a small amount of flaky silver powder and spherical silver powder in the second slurry form a conductive phase of the second slurry, so that the electrical property of the second slurry is ensured, and the cost of the slurry is reduced. The price of the copper powder is lower than that of the silver powder, and in addition, the flaky silver powder is filled in the middle of the spherical silver powder, so that the conductivity can be improved.
The granularity of the silver powder has influence in many aspects, the silver powder can not pass through a screen plate for screen printing if the granularity is too large, and the filling gaps among the silver powder are large, so that the conductivity is influenced to a certain extent; too small particle size can affect the dispersibility of the silver powder in the slurry, resulting in uneven distribution of the silver powder in the slurry, thereby affecting electrical properties; in addition, silver powders of different particle sizes also have some effect on the viscosity of the paste.
Preferably, the particle size of the spherical silver powder in the first slurry is 0.1-0.3 micrometer, the content of silver in the silver-coated copper powder in the second slurry is 20-50%, the particle size is 0.2-0.5 micrometer, the particle size of the spherical silver powder in the second slurry is 0.05-0.2 micrometer, and the particle size of the flaky silver powder is 0.1-0.3 micrometer.
Due to the structure of the silver-coated copper powder in the second slurry, the total content of silver in the silver paste can be reduced, the total content of silver in the light receiving layer after the silver paste is printed is greatly reduced, and therefore the production cost of the battery is reduced.
The first paste can burn through the SiNx antireflection layer of the cell to form good silver-silicon contact, the second paste cannot burn through the SiNx antireflection layer of the cell, current collected by the fine grid is mainly led out effectively, welding tension of the main grid is guaranteed, meanwhile, compounding of metal on the surface of the cell is reduced, and photoelectric conversion efficiency of the cell is improved effectively.
The first glass powder in the first paste and the second glass powder in the second paste have larger difference in components. Specifically, the first glass frit comprises: PbO, Bi2O3、TeO2、SiO2And a first oxide additive; the second glass frit comprises: na (Na)2O、TeO2、WO3、SiO2、Li2O and a second oxide additive.
The first glass powder in the first paste has a strong erosion effect on the SiNx antireflection layer, so that the paste has better silver-silicon contact while burning through the antireflection layer. The second glass powder in the second paste has a weak erosion effect on the SiNx antireflection layer, and mainly plays a role in effectively guiding out current collected by the fine grid, so that the welding tension is ensured, the composition of metal on the surface of the cell is reduced, the filling factor of the cell is ensured, and the photoelectric conversion efficiency of the cell is effectively improved.
Preferably, the first glass powder comprises the following components in percentage by mass: 15-55% of PbO and Bi2O3 10~50%、TeO2 20~60%、SiO25-15% and 5-15% of a first oxide additive; the second glass powder comprises the following components in percentage by mass: na (Na)2O10~20%、TeO2 15~35%、WO3 25~35%、SiO2 3~8%、Li2O2-6% and a second oxide additive 10-15%.
Specifically, the PbO in the first glass powder can reduce the melting point of the glass, improve the glass forming range of the glass and widen the process window. Meanwhile, PbO has good silver melting capability and etching capability to the passivation layer on the surface of the polysilicon battery piece. The Bi2O3The method is beneficial to reducing the melting point of glass and has better etching effect on the passivation layer on the surface of the polycrystalline silicon cell. Bi2O3Can be addedThe excessive corrosion of the glass material to the polycrystalline silicon battery plate can be improved by relatively reducing the dosage of PbO. The TeO2The method is beneficial to forming a glass network structure, improving the silver melting and silver precipitation capacity of the glass powder and reducing the corrosion of glass components to the surface of the polycrystalline silicon cell to a certain degree. The SiO2The network structure of the glass powder can be enhanced, and the stability is improved.
Na in the second glass frit2O and Li2O can help to reduce the melting point of the glass, and Li can also adjust the expansion coefficient of the glass layer, improve the strength of the glass powder and help the tensile property of the glass powder. The TeO2The method is beneficial to forming a glass network structure, improving the silver melting and silver precipitation capacity of the glass powder, improving the pulling force of the grid line and reducing the corrosion of glass components to the surface of the polycrystalline silicon cell to a certain degree. The SiO2The network structure of the glass powder can be enhanced, and the stability is improved.
The first oxide additive comprises WO3、ZnO、CaO、MgO、Al2O3、Li2O、Na2O、Fe2O3、B2O3And BaO, but not limited thereto. The second oxide additive comprises MgO and Al2O3、LaO、Bi2O3、Li2O、CaO、SnO2、Fe2O3、B2O3、BaO、ZrO2、K2O、CrO3And NiO, but not limited thereto. The second oxide additive may also include other compounds.
Preferably, the first oxide additive comprises the following components in percentage by mass: WO3 0.5~10%、ZnO 0.5~5%、CaO 0~2%、Li2O 0.5~3%、Na2O 0~2%、Fe2O3 0.5~2%、B2O30.5-2% and BaO 1-2%. The second oxide additive comprises the following components in percentage by mass: 1-2% of MgO and Al2O 0~2%、LaO 1~2%、BiO3 1~2%、Li2O 1~2%、CaO 1~2%、B2O3 1~2%、SnO2 1~2%、Fe2O3 1~2%、BaO 1~2%、ZrO2 0~2%、K2O 0~2%、CrO30-2% and NiO 0-2%.
Specifically, the first organic vehicle comprises a first thickener, a thixotropic agent, a first organic solvent and an organic additive; the first thickener is one or more of cellulose resin, acrylic resin, rosin resin and phenolic resin, and the first organic solvent is one or more of butyl carbitol, butyl carbitol acetate, terpineol and tributyl citrate. The second organic vehicle comprises a second thickener, a thixotropic agent, a second organic solvent, and an organic additive; the second thickener is one or more of ethyl cellulose, butyl cellulose, acrylic resin and phenolic resin, and the second organic solvent is one or more of butyl carbitol, butyl carbitol acetate and terpineol.
Preferably, the first organic carrier comprises the following components in percentage by mass: 30% of a first thickening agent, 30% of a thixotropic agent, 10% of a first organic solvent and 20% of an organic additive. The second organic carrier comprises the following components in percentage by mass: 30% of a second thickening agent, 5-10% of a thixotropic agent, 40-45% of a second organic solvent and 20% of an organic additive.
Preferably, the thixotropic agent is polyamide wax, and the organic additive is one or more of a leveling agent, a dispersing agent and a surfactant.
Correspondingly, the invention also provides a preparation method of the front silver paste for the crystalline silicon solar cell in the grading way, which is characterized by comprising the following steps:
first, preparing a first slurry
a1, uniformly mixing and drying the components of the first glass powder to obtain a first mixture;
b1, smelting the first mixture obtained in the step (a1), and then extracting with water and drying;
c1, performing ball milling, drying and screening on the first mixture obtained in the step (b1) to obtain first glass powder;
d1, uniformly mixing the components of the first organic carrier, heating to 80-120 ℃, and continuously stirring for 60-90 minutes to obtain the first organic carrier;
e1, uniformly stirring the first glass powder obtained in the step (c1), the first organic carrier obtained in the step (d1) and the spherical silver powder at the temperature of 30-60 ℃ to form slurry, and rolling the stirred slurry to ensure that the fineness of the slurry is 10-15 microns and the viscosity is 50-500 Pascal seconds;
second, preparing a second slurry
a2, uniformly mixing and drying the components of the second glass powder to obtain a second mixture;
b2, smelting the second mixture obtained in the step (a2), and then extracting with water and drying;
c2, performing ball milling, drying and screening on the second mixture obtained in the step (b2) to obtain second glass powder;
d2, uniformly mixing the components of the second organic carrier, heating to 90-130 ℃, and continuously stirring for 80-100 minutes to obtain a second organic carrier;
e2, uniformly stirring the second glass powder obtained in the step (c2), the second organic carrier obtained in the step (d2) and the spherical silver powder at 40-60 ℃ to form slurry, and rolling the stirred slurry to ensure that the fineness of the slurry is 8-12 microns and the viscosity is 30-300 Pascal seconds.
The invention will now be illustrated by the following specific examples
The front-side silver paste for the crystalline silicon solar cell in the grading mode comprises a first paste and a second paste, wherein the first paste is used for printing a secondary grid of the cell, and the second paste is used for printing a main grid of the cell;
the first slurry comprises the following components in percentage by mass: 90% of spherical silver powder, 2.5% of first glass powder and 7.5% of first organic carrier, wherein the particle size of the spherical silver powder is 2-3 microns;
the second slurry comprises the following components in percentage by mass: 82% of silver-coated copper powder, 6% of spherical silver powder, 2% of flake silver powder, 2% of second glass powder and 8% of second organic carrier, wherein the particle size of the silver-coated copper powder is 1-2 microns, and the particle size of the spherical silver powder is 2-3 microns;
the first glass powder comprises the following components in percentage by mass: PbO 25% and Bi2O3 30%、TeO2 25%、SiO210% and 10% of first oxide;
the first oxide additive comprises the following components in percentage by mass: WO3 3%、ZnO 2%,CaO 1%、Li2O1%、Na2O 0.5%、Fe2O3 0.5%、B2O30.3%, BaO 1%, and other compounds 0.7%;
the first organic carrier comprises the following components in percentage by mass: 30% of a first thickening agent, 30% of a thixotropic agent, 10% of a first organic solvent and 20% of an organic additive;
the second glass powder comprises the following components in percentage by mass: na (Na)2O 17%,TeO2 31.5%,WO3 28%,SiO2 6.5%,Li2O3% and a second oxide additive 14%.
The second oxide additive comprises the following components in percentage by mass: MgO 1.5%, Al2O 2%、LaO 1.5%、BiO3 1%、Li2O 1.7%、CaO 1.8%、B2O3 1%、SnO2 1%、Fe2O31%, BaO 1% and other compounds 0.5%;
the second organic carrier comprises the following components in percentage by mass: 30% of a second thickener, 6% of a thixotropic agent, 45% of a second organic solvent and 19% of an organic additive.
A preparation method of front silver paste for crystalline silicon solar cells in multiple use comprises the following steps:
first, preparing a first slurry
a1, uniformly mixing the components of the first glass powder in proportion, putting the mixture into a ceramic crucible, and drying to obtain a first mixture;
b1, putting the first mixture obtained in the step (a1) into a muffle furnace, smelting for about 1h, and drying after water extraction;
c1, grinding the first mixture obtained in the step (b1) by adopting a planetary ball mill, and carrying out ball milling, drying and sieving to obtain first glass powder;
d1, uniformly mixing the components of the first organic carrier in proportion, heating to 80-120 ℃, and continuously stirring for 90 minutes to obtain a transparent first organic carrier;
e1, adding the first glass powder obtained in the step (c1), the first organic carrier obtained in the step (d1) and the spherical silver powder into a stirrer in proportion, stirring uniformly at the temperature of 30-60 ℃ to form slurry, and rolling the stirred slurry for 5-10 times in a three-roll mill to ensure that the fineness of the slurry is 12 microns and the viscosity is 50-300 Pascal per second;
second, preparing a second slurry
a2, uniformly mixing the components of the second glass powder in proportion, and then putting the mixture into a ceramic crucible to be dried to obtain a second mixture;
b2, putting the second mixture obtained in the step (a2) into a muffle furnace, smelting for about 2 hours, and drying after water extraction;
c2, grinding the second mixture obtained in the step (b2) by adopting a planetary ball mill, and carrying out ball milling, drying and sieving to obtain second glass powder;
d2, uniformly mixing the components of the second organic carrier in proportion, heating to 80-120 ℃, and continuously stirring for 90 minutes to obtain a transparent second organic carrier;
e2, adding the second glass powder obtained in the step (c2), the second organic carrier obtained in the step (d2) and the spherical silver powder into a stirrer in proportion, stirring uniformly at 30-60 ℃ to form slurry, and rolling the stirred slurry for 5-10 times in a three-roll mill to ensure that the fineness of the slurry is 12 microns and the viscosity is 50-300 Pascal per second.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.