High-efficiency topcon cell back silver paste based on organic carrier combination and preparation method thereof

Abstract

The application discloses a kind of efficient TOPCon battery back silver paste based on novel organic carrier combination and preparation method thereof, and silver paste is composed of silver powder, glass powder and organic carrier;Silver powder is the mixture of core-shell structure silver powder and flaky silver powder;The raw material composition of glass powder is: 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;Organic carrier includes 60-69wt% solvent, 30-39wt% resin and 0.5-1.5wt% auxiliary agent.The present application adopts hyperbranched polymer, ethylene acrylate rubber (AEM elastomer), phenolic resin collocation, as a new type of organic carrier, due to its unique performance, further improves the comprehensive performance of silver paste.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a high-efficiency TOPCon cell back silver paste based on a novel organic carrier combination and its preparation method. Background Technology

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

[0003] Insufficient conductivity: The high resistance of traditional organic carriers limits the conductivity of silver paste, affecting the fill factor (FF) and conversion efficiency of the battery.

[0004] Weak adhesion: Insufficient adhesion between the silver paste and the silicon substrate can easily lead to silver paste detachment during long-term battery use, affecting battery reliability.

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

[0006] Poor printing performance: Traditional organic carriers have poor rheological properties, which makes it easy for silver paste to have problems such as grid breakage and missing printing during the printing process, affecting the yield of batteries. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, this invention provides a high-efficiency TOPCon battery back-side silver paste based on a novel organic carrier combination and its preparation method. This invention significantly improves the conductivity, adhesion, and printability of the silver paste by optimizing the silver powder, glass powder, organic carrier, and preparation process.

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

[0009] The first objective of this invention is to provide an organic carrier for silver paste on the back of a TOPCon battery, comprising 60-69 wt% solvent, 30-39 wt% resin and 0.5-1.5 wt% additives; wherein the resin is a mixture of 40-55 wt% hyperbranched polyester acrylate resin, 20-40 wt% phenolic resin and 15-30 wt% ethylene acrylate rubber (AEM elastomer).

[0010] The second objective of this invention is to provide a silver paste for the back of a TOPCon battery, which is composed of silver powder, glass powder and an organic carrier; the mass ratio of silver powder, glass powder and 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, with a mass ratio of 1:(1.5-4);

[0012] The glass powder is composed of the following raw materials in 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 comprises 60-69 wt% solvent, 30-39 wt% resin and 0.5-1.5 wt% additives; wherein the resin is a mixture of 40-55 wt% hyperbranched polyester acrylate resin, 20-40 wt% phenolic resin and 15-30 wt% ethylene acrylate rubber (AEM elastomer).

[0014] In one embodiment of the present invention, the hyperbranched polyester acrylate resin is from Perstork, Sweden. H2004; the phenolic resin is from Sumitomo, Japan. 29502; Ethylene acrylate rubber (AEM elastomer) is a DuPont product. GLS.

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

[0016] Phenolic resins offer high adhesion, chemical resistance, and mechanical strength.

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

[0018] In one embodiment of the present invention, the average particle size of the core-shell structured silver powder is 0.3-1.5 μm; the core-shell structured silver powder has a silver core and a silver oxide shell. The supplier of the core-shell structured silver powder is Dowa Electronic Materials Co., Ltd. of Japan; product model: AgC-100 (core-shell structured silver powder, average particle size 0.5 μm, silver oxide shell thickness 50 nm). Features: 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 flake silver powder is 0.5-2 μm. The supplier of the flake silver powder is Fukuda Metal Foil Powder, Japan; product model: FSP-100 (flake silver powder, average particle size 1.0 μm, thickness 0.15 μm); features: high purity (≥99.95%), good dispersibility, suitable for high-precision printing.

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

[0021] In one embodiment of the present invention, the solvent in the organic carrier is composed of 30-40 wt% diethylene glycol ethyl ether acetate, 20-30 wt% propylene glycol methyl ether acetate, 20-30 wt% diethylene glycol butyl ether acetate, 10-20 wt% phenoxyethanol and 10-20 wt% dipropylene glycol methyl ether.

[0022] Diethylene glycol ethyl ether acetate: a high-boiling-point solvent that provides good leveling and printing properties.

[0023] Propylene glycol methyl ether acetate: a medium-boiling-point solvent that improves the dispersibility and drying speed of silver paste.

[0024] Diethylene glycol butyl ether acetate: a high-boiling-point solvent that improves the leveling and printing performance of silver paste.

[0025] Phenoxyethanol: a low-boiling-point solvent that improves the wettability and initial flowability of silver paste.

[0026] Dipropylene glycol methyl ether: a medium-boiling-point solvent that improves the dispersibility and drying properties of silver paste.

[0027] In one embodiment of the present invention, the additives in the organic carrier include one or more of dispersants, leveling agents, and defoamers.

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

[0029] In one embodiment of the present invention

[0030] The dispersant is Disperbyk-190, and the amount used 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 defoamer is TEGO Foamex 810, and the dosage is 0.05-0.2% of the total mass of the organic carrier.

[0033] A third objective of this invention is to provide a method for preparing the silver paste on the back of the TOPCon battery described above, comprising the following steps:

[0034] Silver powder, glass powder and organic carrier are mixed in a mass ratio of (75-85):(2-5):(10-20), stirred evenly, and then ground to obtain the silver paste on the back of the TOPCon battery.

[0035] In one embodiment of the present invention, the process of uniform mixing is as follows: mixing in a planetary mixer at a speed of 200-500 rpm for 0.5-1 h, and then mixing at a speed of 500-800 rpm for 1-2 h.

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

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

[0038] This invention uses a combination of hyperbranched polymer, ethylene acrylate rubber (AEM elastomer), and phenolic resin as a novel organic carrier. Due to its unique properties, such as low viscosity, high reactivity, strong adhesion, and excellent weather resistance, it further enhances the overall performance of silver paste. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the embodiments.

[0040] The raw material composition used in the embodiments and comparative examples of this invention is as follows:

[0041] Silver powder: a mixture of core-shell structured silver powder and flake-shaped silver powder.

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

[0043] Supplier of flake silver powder: Fukuda Metal Foil Powder, Japan; Product model: FSP-100; Average particle size: 1.0μm; Thickness: 0.15μm.

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

[0045] Solvent: 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] Additives: including Disperbyk-190 dispersant (0.7% of the total organic carrier mass), BYK-381 leveling agent (0.2% of the total organic carrier mass), and TEGO Foamex 810 defoamer (0.1% of the total organic carrier mass).

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

[0048] Hyperbranched polyester acrylate resin is from Perstork, Sweden. H2004; the phenolic resin is from Sumitomo, Japan. 29502; Ethylene acrylate rubber (AEM elastomer) is a DuPont product. GLS.

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

[0050] The polyester acrylate resin is Zhanxin's EBECRIL 8701.

[0051] Examples 1-8

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

[0053] Silver powder, glass powder and organic carrier are mixed and stirred in a planetary mixer at 500 rpm for 0.5 h, then stirred at 500 rpm for 2 h; then ground 5 times on a three-roll mill until the fineness is ≤5 μm, thus obtaining the silver paste on the back of the TOPCon battery.

[0054] Example 9

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

[0056] Silver powder, glass powder and organic carrier are mixed and stirred in a planetary mixer at 200 rpm for 1 hour, then stirred at 800 rpm for 1 hour; then ground 5 times on a three-roll mill until the fineness is ≤5μm, thus obtaining the silver paste on the back of the TOPCon battery.

[0057] Example 10

[0058] A silver paste for the back of a TOPCon battery comprises the following components by mass percentage: 76.5% silver powder (the mass ratio of core-shell structured silver powder to flake silver powder is 1:2), 4.3% glass powder, and 19.2% organic carrier; wherein the composition of the organic carrier is shown in Table 1 below.

[0059] Silver powder, glass powder and organic carrier are mixed and stirred in a planetary mixer at 300 rpm for 1 hour, then stirred at 600 rpm for 2 hours; then ground 6 times on a three-roll mill until the fineness is ≤5μm, thus obtaining the silver paste on the back of the TOPCon battery.

[0060] Comparative Examples 1-5

[0061] A TOPCon backing paste comprises the following components by mass percentage: 81% silver powder (the mass ratio of core-shell silver powder to flake silver powder is 1:2), 3.5% glass powder, and 15.5% organic carrier. The composition of the organic carrier is shown in Table 2 below.

[0062] Silver powder, glass powder and organic carrier are mixed and stirred in a planetary mixer at 500 rpm for 0.5 h, then stirred at 800 rpm for 1 h; then ground 6 times on a three-roll mill until the fineness is ≤5 μm, thus obtaining the TOPCon back silver paste.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067] Test example:

[0068] 1. Viscosity testing:

[0069] Take a 15-20g sample of slurry and use a Brookfield DV2 viscometer and a rotor SC-14 to measure the average viscosity of the slurry under the conditions of 25℃ / 50rpm / 60s.

[0070] 2. Electrical performance testing:

[0071] Resistivity is measured using a four-probe resistor. The grid resistivity (ρ, unit: μΩ·cm) is determined by the material's inherent properties and geometry. It is calculated by measuring its resistance (R), length (L), and cross-sectional area (A): ρ = RL / A

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

[0073] 3. Adhesion test:

[0074] The conductive paste used in the above embodiments and comparative examples was printed onto the back of the silicon wafer using screen printing technology. The adhesion testing screen used was a knotless 500-mesh screen with a 9μm wire diameter, a total thickness of 18-18.5μm, and an aperture of 13μm. The solar cells were dried in an infrared drying oven, and then the adhesion was tested using 3M tape. The adhesion was judged based on the proportion of silver wires that were removed from the tape, with the best adhesion being 5B and the worst being 0B.

[0075] 4. Cell efficiency test:

[0076] The back silver paste is printed on the back of the silicon wafer, dried, and then the front silver paste is printed on the front of the silicon wafer. After drying and sintering, the conversion efficiency (%) of the cell is measured using a solar energy efficiency tester. The conversion efficiency of the cell is evaluated under the same conditions.

[0077] 5. Printability test:

[0078] The conductive pastes used in the above embodiments and comparative examples were printed onto the back of silicon wafers using screen printing technology. The screen specifications used for printability testing were a knotless, multi-aperture screen with 500 mesh, 9μm wire diameter, 18-18.5μm total thickness, and aperture sizes of 15μm, 13μm, 11μm, and 9μm respectively. The solar cells were dried in an infrared drying oven, and the printability of the paste was then observed visually and under an optical microscope to determine the presence of broken grids and incomplete printing.

[0079] The performance of the silver pastes prepared in Examples 1-10 was tested, and the test results are shown in Table 3 below.

[0080] Table 3

[0081]

[0082] The performance of the silver pastes prepared in Comparative Examples 1-5 was tested, and the test results are shown in Table 4 below.

[0083] Table 4

[0084]

[0085] As shown in Table 3 above, all examples exhibit excellent viscosity, electrical properties, adhesion (5B), cell efficiency (25.3-25.5%), and printability (uniform line shape, excellent screen passability, no broken lines, and no missing prints). The introduction of ethylene acrylate rubber (AEM) significantly optimizes the overall performance of the silver paste. AEM elastomer significantly improves the performance of the silver paste by enhancing its heat resistance and flexibility, particularly its application potential in high-temperature sintering and flexible substrates.

[0086] As shown in Table 4 above, Comparative Example 1, due to the absence of AEM elastomer, exhibited poor electrical properties, occasional line breaks, and lower performance than the Example. Comparative Example 2, due to the absence of the resin combination used in the Example, resulted in uneven line patterns, numerous line breaks, and poor adhesion, with performance significantly lower than the Example. Comparative Example 3, due to the lack of additives, also exhibited uneven line patterns, numerous line breaks, and decreased adhesion, leading to a decline in overall performance. Comparative Example 4, due to a high resin content, resulted in high slurry viscosity, poor electrical properties, uneven printed line patterns, poor screen transfer, severe line breaks, poor adhesion, and low efficiency. Comparative Example 5, due to a low resin content, resulted in low slurry viscosity, poor electrical properties, generally poor printability, and occasional line breaks.

[0087] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A silver paste for the back of a TOPCon battery, characterized in that, It is composed of silver powder, glass powder and organic carrier; the mass ratio of silver powder, glass powder and organic carrier is (75-85):(2-5):(10-20); The silver powder is a mixture of core-shell structured silver powder and flake silver powder, with a mass ratio of 1:(1.5-4); The glass powder is composed of the following raw materials in 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 comprises 60-69 wt% solvent, 30-39 wt% resin and 0.5-1.5 wt% additives; wherein the resin is a mixture of 40-55 wt% hyperbranched polyester acrylate resin, 20-40 wt% phenolic resin and 15-30 wt% ethylene acrylate rubber.

2. The TOPCon battery back silver paste according to claim 1, characterized in that, Hyperbranched polyester acrylate resin is from Perstork, Sweden. H2004; the phenolic resin is from Sumitomo, Japan. 29502; Ethylene acrylate rubber is from DuPont. GLS.

3. The TOPCon battery back silver paste according to claim 1, characterized in that, The average particle size of core-shell structured silver powder is 0.3-1.5 μm; core-shell structured silver powder has silver as the core and silver oxide as the shell; the average particle size of plate-like silver powder is 0.5-2 μm.

4. The TOPCon battery back silver paste according to claim 1, characterized in that, The softening point of glass powder is 350-400℃, and its coefficient of thermal expansion is 6.5-7.5×10⁻⁶. -6 / ℃.

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

6. The TOPCon battery back silver paste according to claim 1, characterized in that, The additives in organic carriers include one or more of dispersants, leveling agents, and defoamers.

7. The TOPCon battery back silver paste according to claim 6, characterized in that, The dispersant is a polyurethane type dispersant; the leveling agent is a fluorinated acrylate leveling agent; and the defoamer is a polyether-modified polysiloxane defoamer.

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

9. A method for preparing the silver paste on the back of a TOPCon battery according to any one of claims 1-8, characterized in that, Includes the following steps: Silver powder, glass powder and organic carrier are mixed in a mass ratio of (75-85):(2-5):(10-20), stirred evenly, and then ground to obtain the silver paste on the back of the TOPCon battery.

10. The preparation method according to claim 9, characterized in that, The process of mixing evenly is as follows: mix at 200-500 rpm for 0.5-1 hour in a planetary mixer, and then mix at 500-800 rpm for 1-2 hours. The grinding process is as follows: grind 5-6 times on a three-roll mill until the fineness is ≤5μm.

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