High-efficiency TOPCon battery back silver paste based on novel organic carrier combination and preparation method of high-efficiency TOPCon battery back silver paste

Abstract

The invention discloses efficient TOPCon battery back silver paste based on novel organic carrier combination and a preparation method of the efficient TOPCon battery back silver paste. The silver paste is composed of silver powder, glass powder and organic carriers. The silver powder is a mixture of core-shell structure silver powder and flake silver powder; the glass powder is prepared from the following raw materials: 40 to 50 percent of Bi2O3, 20 to 30 percent of B2O3, 10 to 15 percent of SiO2, 5 to 10 percent of ZnO, 3 to 5 percent of TeO2, 2 to 4 percent of Al2O3, 1 to 3 percent of P2O5 and 1 to 2 percent of TiO2; the organic carrier comprises 60-69 wt% of a solvent, 30-39 wt% of resin and 0.5-1.5 wt% of an auxiliary agent. The hyperbranched polymer, the ethylene acrylate rubber (AEM elastomer) and the phenolic resin are matched to serve as a novel organic carrier, and the comprehensive performance of the silver paste is further improved due to the unique performance of the novel organic carrier.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a high-efficiency TOPCon cell back silver paste based on a novel organic carrier combination and a preparation method thereof. Background Art

[0002] With the rapid development of photovoltaic technology, TOPCon (Tunnel Oxide Passivated Contact) cells, as a type of high-efficiency solar cells, have gradually become a research hotspot in the photovoltaic industry due to their excellent passivation effect and contact performance. The back silver paste, as one of the key materials for TOPCon cells, directly affects the conversion efficiency, reliability, and production cost of the cells. Traditional TOPCon cell back silver pastes usually use epoxy resin or acrylic resin as the organic carrier. Although they can meet the basic requirements of conductivity and adhesion, the following problems still exist in actual applications:

[0003] Insufficient conductivity: The resistance of traditional organic carriers is relatively high, which limits the conductivity of the silver paste and affects the fill factor (FF) and conversion efficiency of the cells.

[0004] Weak adhesion: The adhesion between the silver paste and the silicon substrate is insufficient, and the silver paste is prone to falling off during the long-term use of the cells, affecting the reliability of the cells.

[0005] Poor weather resistance: Traditional organic carriers are prone to aging in high-temperature and high-humidity environments, resulting in a decline in the performance of the silver paste and affecting the long-term stability of the cells.

[0006] Poor printing performance: The rheological properties of traditional organic carriers are poor, resulting in problems such as broken grids and missing printing during the printing process of the silver paste, affecting the yield of the cells. Summary of the Invention

[0007] In view of the above problems existing in the prior art, the present invention provides a high-efficiency TOPCon cell back silver paste based on a novel organic carrier combination and a preparation method thereof. By optimizing the silver powder, glass powder, organic carrier, and preparation process, the present invention significantly improves the conductivity, adhesion, and printing performance of the silver paste.

[0008] The technical solution of the present invention is as follows:

[0009] The first object of the present invention is to provide an organic carrier for a TOPCon cell back silver paste, which includes 60 - 69 wt% of a solvent, 30 - 39 wt% of a resin, and 0.5 - 1.5 wt% of an auxiliary agent; wherein, the resin is a mixture of 40 - 55 wt% of a hyperbranched polyester acrylate resin, 20 - 40 wt% of a phenolic resin, and 15 - 30 wt% of an ethylene acrylic ester rubber (AEM elastomer).

[0010] The second object of the present invention is to provide a TOPCon cell back silver paste, which is composed of silver powder, glass powder and an organic carrier; the mass ratio of silver powder, glass powder to the organic carrier is (75-85):(2-5):(10-20);

[0011] The silver powder is a mixture of core-shell structured silver powder and flake silver powder, and the mass ratio is 1:(1.5-4);

[0012] The glass powder is composed of raw materials with the following mass percentages: 40-50% Bi2O3, 20-30% B2O3, 10-15% SiO2, 5-10% ZnO, 3-5% TeO2, 2-4% Al2O3, 1-3% P2O5 and 1-2% TiO2;

[0013] The organic carrier includes 60-69wt% solvent, 30-39wt% resin and 0.5-1.5wt% additives; among them, the resin is a mixture of 40-55wt% hyperbranched polyester acrylate resin, 20-40wt% phenolic resin and 15-30wt% ethylene acrylic rubber (AEM elastomer).

[0014] In an embodiment of the present invention, the hyperbranched polyester acrylate resin is H2004 of Perstorp of Sweden; the phenolic resin is 29502 of Sumitomo of Japan; the ethylene acrylic rubber (AEM elastomer) is GLS of DuPont.

[0015] Hyperbranched polyester acrylate resin: provides low viscosity, high reactivity, and improves the rheological properties and printing properties of the silver paste.

[0016] Phenolic resin: provides high adhesion, chemical corrosion resistance and mechanical strength.

[0017] Ethylene acrylic rubber (AEM elastomer): provides excellent flexibility, heat resistance and weather resistance.

[0018] In an embodiment of the present invention, the average particle size of the core-shell structured silver powder is 0.3-1.5μm; the core-shell structured silver powder has silver as the core and silver oxide as the shell layer. Supplier of the core-shell structured silver powder: Tongwa Electronic Materials of Japan; Product model: AgC-100 (core-shell structured silver powder, average particle size 0.5μm, silver oxide shell layer thickness 50nm). Characteristics: high purity (≥99.95%), excellent conductivity after sintering, suitable for high-efficiency solar cells.

[0019] In one embodiment of the present invention, the average particle size of the flaky silver powder is 0.5 - 2 μm. Supplier of the flaky silver powder: Fukuda Metal Foil Powder Co., Ltd. of Japan, Product Model: FSP-100 (flaky silver powder, average particle size 1.0 μm, thickness 0.15 μm), Characteristics: High purity (≥99.95%), Good dispersibility, Suitable for high-precision printing.

[0020] In one embodiment of the present invention, the softening point of the glass powder is 350 - 400 °C, and the coefficient of thermal expansion is 6.5 - 7.5×10 -6 / °C.

[0021] In one embodiment of the present invention, the solvent in the organic carrier consists of 30 - 40 wt% diethylene glycol monoethyl ether acetate, 20 - 30 wt% propylene glycol monomethyl ether acetate, 20 - 30 wt% diethylene glycol monobutyl ether acetate, 10 - 20 wt% phenoxyethanol, and 10 - 20 wt% dipropylene glycol monomethyl ether.

[0022] Diethylene glycol monoethyl ether acetate: High-boiling solvent, providing good leveling property and printing performance.

[0023] Propylene glycol monomethyl ether acetate: Medium-boiling solvent, improving the dispersibility and drying rate of the silver paste.

[0024] Diethylene glycol monobutyl ether acetate: High-boiling solvent, improving the leveling property and printing performance of the silver paste.

[0025] Phenoxyethanol: Low-boiling solvent, improving the wettability and initial fluidity of the silver paste.

[0026] Dipropylene glycol monomethyl ether: Medium-boiling solvent, improving the dispersibility and drying property of the silver paste.

[0027] In one embodiment of the present invention, the additives in the organic carrier include one or more of a dispersant, a leveling agent, and an antifoaming agent.

[0028] In one embodiment of the present invention, the dispersant is a polyurethane-based dispersant; the leveling agent is a fluorine-modified acrylate leveling agent; the antifoaming agent is a polyether-modified polysiloxane antifoaming agent.

[0029] In one embodiment of the present invention,

[0030] The dispersant is Disperbyk-190, and the dosage is 0.5 - 1.5% of the total mass of the organic carrier.

[0031] The leveling agent is BYK-381, and the dosage is 0.1 - 0.3% of the total mass of the organic carrier.

[0032] The antifoaming agent is TEGO Foamex 810, and the dosage is 0.05 - 0.2% of the total mass of the organic carrier.

[0033] The third object of the present invention is to provide a method for preparing the above-mentioned back silver paste for TOPCon battery, comprising the following steps:

[0034] Mix silver powder, glass powder and organic carrier in a mass ratio of (75 - 85):(2 - 5):(10 - 20), stir evenly, and then grind to obtain the back silver paste for TOPCon battery.

[0035] In an embodiment of the present invention, the process of stirring evenly is as follows: Stir in a planetary mixer at a rotation speed of 200 - 500 rpm for 0.5 - 1 h, and then stir at a rotation speed of 500 - 800 rpm for 1 - 2 h.

[0036] In an embodiment of the present invention, the grinding process is as follows: Grind 5 - 6 times on a three-roll grinder until the fineness is ≤ 5 μm.

[0037] The beneficial technical effects of the present invention are as follows:

[0038] The present invention uses a combination of hyperbranched polymer, ethylene acrylic ester rubber (AEM elastomer), and phenolic resin as a novel organic carrier. Due to its unique properties, such as low viscosity, high reactivity, strong adhesion, excellent weather resistance, etc., the comprehensive performance of the silver paste is further improved. Specific Embodiments

[0039] The present invention will be specifically described below in conjunction with embodiments.

[0040] The raw material compositions used in the examples and comparative examples of the present invention:

[0041] Silver powder: A mixture of core-shell structured silver powder and flaky silver powder.

[0042] Supplier of core-shell structured silver powder: Tongwa Electronic Materials of Japan. The product model is AgC-100, with an average particle size of 0.5 μm and a silver oxide shell layer thickness of 50 nm.

[0043] Supplier of flaky silver powder: Fukuda Metal Foil Powder of Japan, product model: FSP-100, average particle size 1.0 μm, thickness 0.15 μm.

[0044] Glass powder: Composed of 45 wt% Bi2O3, 25% B2O3, 12.5% SiO2, 7.5% ZnO, 4% TeO2, 2.5% Al2O3, 2% P2O5, and 1.5% TiO2.

[0045] Solvent: Composed of 32 wt% diethylene glycol ethyl ether acetate, 22 wt% propylene glycol methyl ether acetate, 22 wt% diethylene glycol butyl ether acetate, 12 wt% phenoxyethanol, and 12 wt% dipropylene glycol methyl ether.

[0046] Auxiliaries: including 0.7% of dispersant Disperbyk-190 based on the total mass of the organic carrier, 0.2% of leveling agent BYK-381 based on the total mass of the organic carrier, and 0.1% of defoamer TEGO Foamex 810 based on the total mass of the organic carrier.

[0047] Resin: a mixture of 40-55 wt% of hyperbranched polyester acrylate resin, 20-40 wt% of phenolic resin, and 15-30 wt% of ethylene acrylic ester rubber (AEM elastomer).

[0048] The hyperbranched polyester acrylate resin is H2004 from Perstorp of Sweden; the phenolic resin is 29502 from Sumitomo of Japan; the ethylene acrylic ester rubber (AEM elastomer) is GLS from DuPont. GLS.

[0049] The epoxy resin is JER 828 from Mitsubishi Chemical of Japan.

[0050] The polyester acrylate resin is EBECRYL 8701 from Axalta.

[0051] Examples 1-8

[0052] A back silver paste for TOPCon battery, comprising components with the following mass percentages: 81% of silver powder (the mass ratio of core-shell structured silver powder to flaky silver powder is 1:2), 3.5% of glass powder, and 15.5% of organic carrier; wherein the composition of the organic carrier is shown in Table 1 below.

[0053] Mix the silver powder, glass powder, and organic carrier, stir at a speed of 500 rpm in a planetary mixer for 0.5 h, and then stir at a speed of 500 rpm for 2 h; then grind 5 times on a three-roll mill until the fineness is ≤ 5 μm to obtain the back silver paste for TOPCon battery.

[0054] Example 9

[0055] A back silver paste for TOPCon battery, comprising components with the following mass percentages: 81% of silver powder (the mass ratio of core-shell structured silver powder to flaky silver powder is 1:3), 3.5% of glass powder, and 15.5% of organic carrier; wherein the composition of the organic carrier is shown in Table 1 below.

[0056] Mix the silver powder, glass powder, and organic carrier, stir at a speed of 200 rpm in a planetary mixer for 1 h, and then stir at a speed of 800 rpm for 1 h; then grind 5 times on a three-roll mill until the fineness is ≤ 5 μm to obtain the back silver paste for TOPCon battery.

[0057] Example 10

[0058] A back silver paste for TOPCon cells, comprising components with the following mass percentages: silver powder (the mass ratio of core-shell structured silver powder to flaky silver powder is 1:2) 76.5%, glass powder 4.3%, organic carrier 19.2%; wherein the composition of the organic carrier is shown in Table 1 below.

[0059] Mix the silver powder, glass powder and organic carrier, stir at a speed of 300 rpm for 1 h in a planetary mixer, and then stir at a speed of 600 rpm for 2 h; then grind 6 times on a three-roll grinder until the fineness is ≤ 5 μm, thus obtaining the back silver paste for TOPCon cells.

[0060] Comparative Examples 1-5

[0061] A TOPCon back paste, comprising components with the following mass percentages: silver powder (the mass ratio of core-shell structured silver powder to flaky silver powder is 1:2) 81%, glass powder 3.5%, organic carrier 15.5%. The composition of the organic carrier is shown in Table 2 below.

[0062] Mix the silver powder, glass powder and organic carrier, stir at a speed of 500 rpm for 0.5 h in a planetary mixer, and then stir at a speed of 800 rpm for 1 h; then grind 6 times on a three-roll grinder until the fineness is ≤ 5 μm, thus obtaining the back silver paste for TOPCon cells.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067] Test Examples:

[0068] 1. Viscosity detection:

[0069] Take 15-20 g of the sampled paste, and use a Brookfield DV2 viscosity tester and rotor SC-14 to present the average viscosity value of the paste under the measurement conditions of 25 °C / rotation speed 50 rpm / 60 s.

[0070] 2. Electrical property detection:

[0071] Use a four-probe resistivity meter to test the resistivity. The grid line resistivity (ρ, unit: μΩ·cm) is determined by the material itself characteristics and geometric dimensions, and is calculated by measuring its resistance value (R), length (L), and cross-sectional area (A): ρ = R·L / A

[0072] The grid line resistivity directly affects the series resistance of the cell and needs to be controlled within the range of 1-3 μΩ·cm.

[0073] 3. Adhesion Detection:

[0074] Through screen printing technology, the conductive pastes in the above-mentioned examples and comparative examples were printed on the back of the silicon wafer. The specifications of the adhesion detection screen used were a non-knot screen with 500 mesh, 9 μm wire diameter, total thickness of 18 - 18.5 μm, and an opening of 13 μm. The battery cells were dried in an infrared drying oven, and then the adhesion was tested with 3M tape. The adhesion was judged according to the proportion of silver wires stuck on the tape. The best adhesion was 5B, and the worst was 0B.

[0075] 4. Battery Cell Efficiency Test:

[0076] The back silver paste was printed on the back of the silicon wafer. After drying, the front silver paste was printed on the front of the silicon wafer, dried and sintered. Then, a solar efficiency tester was used to measure the conversion efficiency (%) of the battery, and the conversion efficiency of the battery cells was evaluated under the same conditions.

[0077] 5. Printability Detection:

[0078] Through screen printing technology, the conductive pastes in the above-mentioned examples and comparative examples were printed on the back of the silicon wafer. The specifications of the printability detection screen used were a non-knot multi-opening screen with 500 mesh, 9 μm wire diameter, total thickness of 18 - 18.5 μm, and openings of 15 μm, 13 μm, 11 μm, and 9 μm respectively. The battery cells were dried in an infrared drying oven, and then the printability of the paste was observed by the naked eye and an optical microscope to judge whether there were broken grids and missing prints.

[0079] The silver pastes prepared in Examples 1 - 10 were subjected to performance tests, and the test results are shown in Table 3 below.

[0080] Table 3

[0081]

[0082] The silver pastes prepared in Comparative Examples 1 - 5 were subjected to performance tests, and the test results are shown in Table 4 below.

[0083] Table 4

[0084]

[0085] As can be seen from Table 3 above, the examples all showed excellent viscosity, electrical properties, adhesion (5B), battery cell efficiency (25.3 - 25.5%), and printability (uniform line type, excellent screen passing property, no broken wires, no missing prints). The introduction of ethylene acrylic ester rubber (AEM) significantly optimized the comprehensive performance of the silver paste. The AEM elastomer significantly improved the performance of the silver paste by enhancing heat resistance and flexibility, especially its application potential in high-temperature sintering and flexible substrates.

[0086] As can be seen from Table 4 above, in Comparative Example 1, due to the absence of AEM elastomer, the electrical performance is poor, there are occasional wire breaks, and the performance is lower than that of the examples. In Comparative Example 2, due to the absence of the resin combination of the examples, the wire type is uneven, there are many wire breaks, and the adhesion is poor, and the performance is significantly lower than that of the examples. In Comparative Example 3, due to the absence of additives, the wire type is uneven, there are many wire breaks, the adhesion performance decreases, and the performance also decreases. In Comparative Example 4, due to the high resin addition amount, the slurry viscosity is high, the electrical performance is poor, the printed wire type is uneven, the screen passing property is poor, the wire break is serious, the adhesion is poor, and the efficiency is low. In Comparative Example 5, due to the low resin addition amount, the slurry viscosity is low, the electrical performance is poor, the printability is average, and there are occasional wire breaks.

[0087] The examples provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit the order of their execution. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A TOPCon cell back silver paste, characterized in that, It consists of silver powder, glass powder and an organic carrier; the mass ratio of silver powder, glass powder to the organic carrier is (75 - 85):(2 - 5):(10 - 20); The silver powder is a mixture of core-shell structured silver powder and flaky silver powder, and the mass ratio is 1:(1.5 - 4); The glass powder is composed of raw materials with the following mass percentages: 40 - 50% Bi2O3, 20 - 30% B2O3, 10 - 15% SiO2, 5 - 10% ZnO, 3 - 5% TeO2, 2 - 4% Al2O3, 1 - 3% P2O5 and 1 - 2% TiO2; The organic carrier includes 60 - 69wt% solvent, 30 - 39wt% resin and 0.5 - 1.5wt% additives; among them, the resin is a mixture of 40 - 55wt% hyperbranched polyester acrylate resin, 20 - 40wt% phenolic resin and 15 - 30wt% ethylene acrylic ester rubber.

2. The TOPCon cell back silver paste according to claim 1, characterized in that, The hyperbranched polyester acrylate resin is from Perstorp of Sweden H2004; the phenolic resin is from Sumitomo of Japan 29502; the ethylene acrylate rubber is from DuPont GLS 3. The TOPCon cell back silver paste according to claim 1, characterized in that, The average particle size of the core-shell structured silver powder is 0.3 - 1.5μm; the core-shell structured silver powder has silver as the core and silver oxide as the shell layer; the average particle size of the flaky silver powder is 0.5 - 2μm.

4. The TOPCon cell back silver paste according to claim 1, wherein The softening point of the glass powder is 350 - 400 °C, and the coefficient of thermal expansion is 6.5 - 7.5×10 -6 / °C.

5. The TOPCon cell back silver paste according to claim 1, characterized in that, The solvent in the organic carrier consists of 30 - 40wt% diethylene glycol ethyl ether acetate, 20 - 30wt% propylene glycol methyl ether acetate, 20 - 30wt% diethylene glycol butyl ether acetate, 10 - 20wt% phenoxyethanol and 10 - 20wt% dipropylene glycol methyl ether.

6. The TOPCon cell back silver paste according to claim 1, wherein The additives in the organic carrier include one or more of a dispersant, a leveling agent and an antifoaming agent.

7. The TOPCon battery back silver paste according to claim 6, wherein The dispersant is a polyurethane type dispersant; the leveling agent is a fluorine-modified acrylate leveling agent; the antifoaming agent is a polyether-modified polysiloxane antifoaming agent.

8. The TOPCon cell back silver paste according to claim 7, characterized in that, The dispersant is Disperbyk-190; the leveling agent is BYK-381; the antifoaming agent is TEGO Foamex 810.

9. The preparation method of the back silver paste of the TOPCon battery according to any one of claims 1-8, characterized in that, It includes the following steps: Mix the silver powder, glass powder and organic carrier according to the mass ratio (75 - 85):(2 - 5):(10 - 20), stir evenly, and then grind to obtain the silver paste for the back side of the TOPCon battery.

10. The preparation method according to claim 9, characterized in that, The process of stirring evenly is: stir in a planetary mixer at a speed of 200 - 500rpm for 0.5 - 1h, and then stir at a speed of 500 - 800rpm for 1 - 2h; The grinding process is: grind 5 - 6 times on a three-roll grinder until the fineness ≤ 5μm.

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