A method for preparing silver-aluminum paste to solve the clouding of the front side of N-type TOPCon batteries

Abstract

The present invention relates to the field of photovoltaic cell technology, and in particular to a method for preparing a silver-aluminum paste for resolving front-side fogging of N-type TOPCon cells. The method comprises the following steps: S1, screening spherical silver powder and spherical aluminum powder of suitable particle size; S2, weighing the raw materials according to a ratio and mixing them uniformly; firing the mixture, quenching, ball-milling, and drying to obtain a main boron glass powder and a low-melting glass powder; S3, mixing a resin and a solvent A according to a ratio, heating, and stirring to obtain an adhesive; S4, mixing all the raw materials according to a ratio, stirring at high speed to obtain a uniformly dispersed material, grinding, and sieving to obtain the target silver-aluminum paste. The method uses boron oxide as the main raw material to prepare the main boron glass powder, using it as the boron source and low-melting glass powder as the medium to promote the generation of additional boron diffusion, improve the breadth and density of the boron diffusion area, achieve a wider range of doping adaptability, and ensure uniform front-side boron diffusion, thereby avoiding fogging defects on the front side of N-type TOPCon cells.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a method for preparing silver-aluminum paste for solving the problem of front-side fogging of N-type TOPCon cells. Background Art

[0002] N-type TOPCon cells are an important mainstream photovoltaic cell technology. Research has shown that due to the difficulty of boron diffusion on the front side of N-type cells, which can lead to uneven doping, the contact resistance of various areas of the front side after sintering the silver-aluminum paste varies. When the contact resistance is too high, clouding appears in areas with poor current collection, indicating the presence of obvious point defects. As a result, the yield of N-type TOPCon cells is lower than that of P-type cells.

[0003] Currently, most silver-aluminum pastes have obvious front-side fogging after EL testing after sintering. In existing processes, equipment and processes are usually adjusted to improve the uniformity of boron diffusion doping on the front side of N-type batteries. However, existing technologies cannot completely solve this problem. A small amount of fog will still exist on the front side of the battery, which will affect the battery performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing silver-aluminum paste for solving the problem of fogging on the front side of N-type TOPCon batteries, so as to solve the problems raised in the above-mentioned background technology.

[0005] The present invention provides a method for preparing a silver-aluminum paste for solving the problem of front fogging of an N-type TOPCon battery. The silver-aluminum paste comprises the following components in parts by weight:

[0006] 82-88 parts of spherical silver powder, the particle size of the spherical silver powder is 1.0-2.5 μm, and the specific surface area is 0.4-1.6 m 2 / g, tap density is 5.0~6.5g / mL;

[0007] 0.1 to 2.5 parts of spherical aluminum powder, the particle size of the spherical aluminum powder is 1.0 to 3.0 μm, and the surface oxygen content is less than 2%;

[0008] 2-6 parts of glass powder, wherein the glass powder includes 1-4 parts of main boron glass powder and 1-2 parts of low-melting glass powder, wherein the average particle size of the main boron glass powder and the low-melting glass powder is 0.1-1.0 μm, the main boron glass powder is mainly made of oxide of the Group IIIA element boron, is used to provide a boron source, and has a softening point of 450-650°C; the low-melting glass powder is mainly made of lead oxide, is used to promote boron diffusion, and has a softening point of 300-400°C;

[0009] 7 to 12 parts of an organic additive, which includes 1 to 10 parts of an adhesive, 0.2 to 1 part of a thixotropic agent, 0.5 to 1 part of a dispersant, and 0 to 5 parts of a solvent B, wherein the adhesive is a resin dispersed in a solvent A;

[0010] The preparation method of the silver-aluminum paste specifically comprises the following steps:

[0011] S1. Screening: Screening spherical silver powder and spherical aluminum powder of appropriate particle size according to the above-mentioned raw material components of the silver-aluminum paste;

[0012] S2. Preparation of glass powder: weighing raw materials according to the corresponding ratio of glass powder and mixing them evenly, firing the mixture, quenching, ball milling, and drying to obtain main boron glass powder and low-melting glass powder;

[0013] S3. Preparing an adhesive: mixing the resin and solvent A in a ratio of 1-14:6-19 by weight, heating at 60-80° C. and stirring to obtain the target adhesive;

[0014] S4. Mix the spherical silver powder and spherical aluminum powder screened in S1, the main boron glass powder and low-melting glass powder obtained in S2, and the adhesive, thixotropic agent, dispersant and solvent B prepared in S3 according to the ratio, stir at high speed to obtain a uniformly dispersed material, grind the obtained material with a three-roll grinder, and sieve to obtain the target silver-aluminum paste.

[0015] As a further solution of the present invention, the raw materials of the main boron glass powder include, by mass, 30-70% boron oxide, 10-30% zinc oxide, 0-40% gallium oxide, 0-40% lead oxide and 0-10% auxiliary oxide C, wherein the auxiliary oxide C is one or a combination of any multiple of bismuth oxide, indium oxide, silicon oxide, aluminum oxide, titanium oxide, calcium oxide and barium oxide.

[0016] As a further embodiment of the present invention, the raw materials of the low-melting glass powder include, by mass, 60-90% lead oxide, 1-20% boron oxide, 1-20% zinc oxide and 0-10% auxiliary oxide D, wherein the auxiliary oxide D is one or a combination of any two of bismuth oxide, silicon oxide, aluminum oxide and titanium oxide.

[0017] Preferably, the solvent A and solvent B are respectively one or a combination of any of ethyl cellulose, acrylic resin, PVB, CAB, rosin resin, phenolic resin, epoxy resin, and petroleum resin.

[0018] Preferably, the thixotropic agent is polyamide wax.

[0019] Preferably, the dispersant is an aliphatic dispersant or an alicyclic dispersant.

[0020] As a further solution of the present invention, step S2 specifically comprises weighing the raw materials according to the ratio of the main boron glass powder and the low-melting glass powder and mixing them evenly in a mixer, then placing the mixture in a crucible and firing it, quenching the fired mixture using a double-roll mill, repeating the ball milling and drying steps 2 to 3 times to obtain refined powder, and using air flow dispersion equipment to screen and obtain the required glass powder powder.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses boron oxide as the main raw material to prepare the main boron glass powder, uses it as the boron source, and uses low-melting glass powder as the medium to promote the generation of additional boron diffusion, improve the breadth and density of the boron diffusion effect area, achieve a wider range of doping adaptability, and make the boron diffusion on the front side of the N-type TOPCon battery uniform, thereby avoiding the cloud defect on the front side of the N-type TOPCon battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 Schematic diagram of EL test results for comparative example;

[0025] Figure 2 Schematic diagram of EL test results of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] Example 1:

[0028] This embodiment provides a method for preparing a silver-aluminum paste for solving the problem of front-side fogging of an N-type TOPCon battery, which specifically includes the following steps:

[0029] S1. Spherical silver powder with a particle size of 1.5 μm and spherical aluminum powder with a particle size of 2.0 μm were screened. After screening, the specific surface area of ​​the spherical silver powder was measured to be 0.6 m 2 / g, tap density is 6.0g / mL, and the surface oxygen content of spherical aluminum powder is 1.0±0.2%;

[0030] S2. Weigh raw materials in a ratio of 55% boron oxide, 20% zinc oxide, 20% lead oxide, and 5% barium oxide and mix them evenly in a mixer. Then, place the mixture in a crucible and sinter it. Use a double-roll mill to quench the sintered mixture. Repeat the ball milling and drying steps 2 to 3 times to obtain a refined powder. Use an airflow dispersion device to screen and obtain the desired main boron glass powder. The main boron glass powder provided in this embodiment has an average particle size of 0.4 μm and a softening point of 550° C.

[0031] Raw materials are weighed in a ratio of 75% lead oxide, 10% boron oxide, 10% zinc oxide, and 5% bismuth oxide and mixed uniformly in a mixer. The mixture is then placed in a crucible and fired. The fired mixture is quenched using a double-roll mill. The ball milling and drying steps are repeated 2 to 3 times to obtain a refined powder. The desired low-melting glass powder is screened using an air flow dispersion device. The low-melting glass powder provided in this embodiment has an average particle size of 0.6 μm and a softening point of 320° C.

[0032] S3, ethyl cellulose, acrylic resin and solvent A are mixed in a ratio of 1:3:6, so that the resin is evenly dispersed in solvent A, where solvent A is a mixture of butyl carbitol acetate, terpineol and alcohol ester dodecahydrate in a ratio of 6:1:3, and the target adhesive is obtained by heating and stirring at 70°C;

[0033] S4, in parts by weight, weigh 85 parts of spherical silver powder obtained by screening S1, 1 part of spherical aluminum powder obtained by screening 1, 2.5 parts of main boron glass powder obtained by S2 and 1.5 parts of low-melting glass powder obtained by S2, 5 parts of adhesive prepared by S3, 0.5 parts of polyamide wax, 0.5 parts of aliphatic dispersant ED420 and 4 parts of solvent B, wherein solvent B is a mixture of butyl carbitol and alcohol ester dodecahydrate, and the ratio of butyl carbitol to alcohol ester dodecahydrate is 1:3;

[0034] S5. The spherical silver powder, spherical aluminum powder, main boron glass powder, low-melting glass powder, adhesive, thixotropic agent, dispersant and solvent B obtained in step S4 are mixed and stirred at high speed to obtain a uniformly dispersed material. The obtained material is ground using a three-roll mill and sieved to obtain the target silver-aluminum paste.

[0035] Example 2:

[0036] This embodiment provides a method for preparing a silver-aluminum paste for solving the problem of front-side fogging of an N-type TOPCon battery, which specifically includes the following steps:

[0037] S1. The same as in Example 1, spherical silver powder with a particle size of 1.5 μm and spherical aluminum powder with a particle size of 2.0 μm were screened;

[0038] S2. Weigh raw materials in a ratio of 50% boron oxide, 20% zinc oxide, 5% gallium oxide, 15% lead oxide, 5% aluminum oxide, and 5% barium oxide and mix them evenly in a mixer. Then, place the mixture in a crucible and sinter it. Use a double-roll mill to quench the sintered mixture. Repeat the ball milling and drying steps 2 to 3 times to obtain a refined powder. Use an airflow dispersion device to screen and obtain the desired main boron glass powder. The main boron glass powder provided in this embodiment has an average particle size of 0.4 μm and a softening point of 560° C.

[0039] Raw materials are weighed in a ratio of 75% lead oxide, 10% boron oxide, 10% zinc oxide, and 5% silicon dioxide and mixed uniformly in a mixer. The mixture is then placed in a crucible and fired. The fired mixture is quenched using a double-roll mill. The ball milling and drying steps are repeated 2 to 3 times to obtain a refined powder. The desired low-melting glass powder is screened using an air flow dispersion device. The low-melting glass powder provided in this embodiment has an average particle size of 0.6 μm and a softening point of 350° C.

[0040] S3. The target adhesive was prepared in the same manner as in Example 1;

[0041] S4, in parts by weight, weighed 85 parts of the spherical silver powder obtained by screening in S1, 1.2 parts of the spherical aluminum powder obtained by screening in 1, 3 parts of the main boron glass powder obtained in S2, 1.8 parts of the low-melting glass powder obtained in S2, 4 parts of the adhesive prepared in S3, 0.5 parts of polyamide wax, 0.5 parts of the aliphatic dispersant ED420 and 4 parts of solvent B, where solvent B is the same as that in Example 1;

[0042] S5. The spherical silver powder, spherical aluminum powder, main boron glass powder, low-melting glass powder, adhesive, thixotropic agent, dispersant and solvent B obtained in step S4 are mixed and stirred at high speed to obtain a uniformly dispersed material. The obtained material is ground using a three-roll mill and sieved to obtain the target silver-aluminum paste.

[0043] Example 3:

[0044] This embodiment provides a method for preparing a silver-aluminum paste for solving the problem of front-side fogging of an N-type TOPCon battery, which specifically includes the following steps:

[0045] S1. The same as in Example 1, spherical silver powder with a particle size of 1.5 μm and spherical aluminum powder with a particle size of 2.0 μm were screened;

[0046] S2. Weigh raw materials according to a ratio of 60% boron oxide, 20% zinc oxide, 5% gallium oxide, 10% lead oxide, and 5% indium oxide and mix them evenly in a mixer. Then, place the mixture in a crucible and sinter it. Use a double-roll mill to quench the sintered mixture. Repeat the ball milling and drying steps 2 to 3 times to obtain a refined powder. Use an airflow dispersion device to screen and obtain the desired main boron glass powder. The main boron glass powder provided in this embodiment has an average particle size of 0.4 μm and a softening point of 560° C.

[0047] Raw materials are weighed in a ratio of 70% lead oxide, 10% boron oxide, 10% zinc oxide, 5% bismuth oxide, and 5% silicon dioxide and mixed uniformly in a mixer. The mixture is then placed in a crucible and fired. The fired mixture is quenched using a double-roll mill. The ball milling and drying steps are repeated 2 to 3 times to obtain a refined powder. The desired low-melting glass powder is screened using an air flow dispersion device. The low-melting glass powder provided in this embodiment has an average particle size of 0.6 μm and a softening point of 340° C.

[0048] S3. The target adhesive was prepared in the same manner as in Example 1;

[0049] S4, in parts by weight, weighed 88 parts of the spherical silver powder obtained by screening in S1, 1 part of the spherical aluminum powder obtained by screening in 1, 2.5 parts of the main boron glass powder obtained in S2, 1.5 parts of the low-melting glass powder obtained in S2, 3 parts of the adhesive prepared in S3, 0.5 parts of polyamide wax, 0.5 parts of the aliphatic dispersant ED420 and 3 parts of solvent B, where solvent B is the same as that in Example 1;

[0050] S5. The spherical silver powder, spherical aluminum powder, main boron glass powder, low-melting glass powder, adhesive, thixotropic agent, dispersant and solvent B obtained in step S4 are mixed and stirred at high speed to obtain a uniformly dispersed material. The obtained material is ground using a three-roll mill and sieved to obtain the target silver-aluminum paste.

[0051] The target silver-aluminum paste was prepared by the methods provided in Examples 1-3, and coated on the corresponding pole pieces respectively. The pole pieces were rolled with a 2kg roller to obtain N-type TOPCon battery pole pieces after compaction.

[0052] Taking the existing similar products on the market as comparative examples, EL test was performed on the N-type TOPCon cells prepared with the silver-aluminum paste provided in Examples 1-3 and the comparative examples respectively using an EL tester. The image was used to determine whether the front of the N-type TOPCon cell was foggy. The test results are shown in the attached figure. Figure 1-2 And shown in the table below.

[0053] Conversion efficiency change △EFF Frontal cloud ratio Example 1 +0.05％ 0％ Example 2 +0.03％ 0％ Example 3 +0.06％ 0％ Comparative Example / 5％

[0054] As can be seen from the accompanying drawings, the comparative example produces fog on the front and corners, and the fog at the corners is more obvious. When the silver-aluminum paste provided in the present application is used for the N-type TOPCon battery, the boron diffusion on the front of the N-type TOPCon battery is uniform, and the image shows no fog, which can effectively avoid the fog defect on the front of the N-type TOPCon battery.

[0055] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing silver-aluminum paste for solving the clouding problem on the front side of N-type TOPCon batteries, characterized in that: The silver-aluminum paste includes the following components in parts by weight: 82-88 parts of spherical silver powder, with a particle size of 1.0-2.5 μm; 0.1 to 2.5 parts of spherical aluminum powder, the particle size of the spherical aluminum powder is 1.0 to 3.0 μm, and the surface oxygen content is less than 2%; 2 to 6 parts of glass powder, wherein the glass powder includes 1 to 4 parts of main boron glass powder and 1 to 2 parts of low-melting glass powder, wherein the average particle size of the main boron glass powder and the low-melting glass powder is 0.1 to 1.0 μm, the main boron glass powder is used to provide a boron source, and the low-melting glass powder is used to promote boron diffusion; 7 to 12 parts of an organic additive, which includes 1 to 10 parts of an adhesive, 0.2 to 1 part of a thixotropic agent, 0.5 to 1 part of a dispersant, and 0 to 5 parts of a solvent B, wherein the adhesive is a resin dispersed in a solvent A; The method for preparing silver-aluminum paste to solve the problem of front fogging of N-type TOPCon cells specifically comprises the following steps: S1. Screening spherical silver powder and spherical aluminum powder of appropriate particle size; S2. Weigh the raw materials according to the ratio and mix them evenly. After firing, the mixture is quenched, ball-milled, and dried to obtain the main boron glass powder and low-melting glass powder; S3, mixing the resin and solvent A in a proportion of 1-14:6-19 by weight, heating at 60-80° C., and stirring to obtain the target adhesive; S4. Mix the spherical silver powder and spherical aluminum powder screened in S1, the main boron glass powder and low-melting glass powder obtained in S2, and the adhesive, thixotropic agent, dispersant and solvent B prepared in S3 according to the ratio, stir at high speed to obtain a uniformly dispersed material, grind the obtained material with a three-roll grinder, and sieve to obtain the target silver-aluminum paste.

2. The method for preparing silver-aluminum paste for solving the clouding problem on the front side of N-type TOPCon cells according to claim 1, characterized in that: In terms of mass percentage, the raw materials of the main boron glass powder include 30-70% boron oxide, 10-30% zinc oxide, 0-40% gallium oxide, 0-40% lead oxide and 0-10% auxiliary oxide C, and the auxiliary oxide C is one or a combination of any two of bismuth oxide, indium oxide, silicon oxide, aluminum oxide, titanium oxide, calcium oxide and barium oxide.

3. The method for preparing silver-aluminum paste for solving the front fogging problem of N-type TOPCon batteries according to claim 1, characterized in that: In terms of mass percentage, the raw materials of the low-melting glass powder include 60-90% lead oxide, 1-20% boron oxide, 1-20% zinc oxide and 0-10% auxiliary oxide D, and the auxiliary oxide D is one or a combination of any two of bismuth oxide, silicon oxide, aluminum oxide and titanium oxide.

4. The method for preparing silver-aluminum paste for solving the clouding problem on the front side of N-type TOPCon cells according to claim 1, characterized in that: The resin mixed with the solvent A is one or a combination of any of ethyl cellulose, acrylic resin, PVB, CAB, rosin resin, phenolic resin, epoxy resin, and petroleum resin; solvent A is a mixture of butyl carbitol acetate, terpineol, and alcohol ester dodecahydrate; solvent B is a mixture of butyl carbitol and alcohol ester dodecahydrate.

5. The method for preparing silver-aluminum paste for solving the front fogging problem of N-type TOPCon batteries according to claim 1, characterized in that: The thixotropic agent is polyamide wax.

6. The method for preparing silver-aluminum paste for solving the clouding problem on the front side of N-type TOPCon cells according to claim 1, characterized in that: The dispersant is an aliphatic dispersant or an alicyclic dispersant.

7. A method for preparing silver-aluminum paste for solving front fogging of N-type TOPCon cells according to any one of claims 1 to 6, characterized in that: Step S2 specifically comprises weighing the raw materials according to the ratio of the main boron glass powder and the low-melting glass powder respectively and mixing them evenly in a mixer, then placing the mixture in a crucible and firing it, quenching the fired mixture, repeating the ball milling and drying steps 2 to 3 times to obtain refined powder, and using air flow dispersion equipment to screen and obtain the required glass powder powder.

8. The method for preparing silver-aluminum paste for solving the clouding problem on the front side of N-type TOPCon cells according to claim 4, characterized in that: The content ratio of the mixture of butyl carbitol acetate, terpineol and alcohol ester dodecahydrate in solvent A is 6:1:3; the content ratio of butyl carbitol and alcohol ester dodecahydrate in solvent B is 1:3.

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