Conductive paste for TOPCon battery and preparation method of conductive paste

Abstract

The invention relates to a conductive paste for a TOPCon battery and a preparation method thereof, and relates to the technical field of solar cells, the conductive paste is prepared from the following raw materials by weight: 70-80 parts of silver powder, 2-6 parts of glass powder, 0.5-2 parts of an additive, and 3-5 parts of an organic carrier; the additive is Ti (Ti)-Zn (Zn)-rare earth (Nb)-B (B)-O. The conductive paste is good in conductivity, strong in binding force with a passivation layer of the TOPCon battery and sufficient in printing performance, and the efficiency of the prepared TOPCon battery is high.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a conductive paste for a TOPCon cell and a preparation method thereof. Background Art

[0002] With the growing global demand for clean energy, crystalline silicon photovoltaic cell technology has garnered widespread attention and rapid development. TOPCon (Tunneling Oxide Passivated Contact) cells, a common type of crystalline silicon photovoltaic cell, have gradually become a mainstream technology in the solar cell market due to their high photoelectric conversion efficiency, low attenuation performance, and high cost-effectiveness in mass production. However, the production process of traditional TOPCon cells, particularly the conductive paste used in electrode preparation, has exposed numerous limitations when faced with the emerging LECO (Laser-Enhanced Contact Opening) technology.

[0003] As an advanced laser sintering technology, LECO technology works by irradiating the cell with a high-intensity laser to excite charge carriers, while applying a deflection voltage of more than 10V to generate a local current of several amperes, which promotes the mutual diffusion of silver paste and silicon, thereby significantly reducing the contact resistance between the metal and the semiconductor and improving the fill factor. During the entire sintering process, the carrier lifetime ends quickly after the laser passes, minimizing the loss of the original passivation layer. However, traditional conductive pastes are difficult to adapt to the LECO process. On the one hand, the components such as silver powder, glass powder and organic carrier in traditional pastes cannot achieve good synergistic effects with the silicon wafer surface and each other during the laser sintering process. On the other hand, the softening temperature of the traditional glass powder system does not match the LECO process. Within the laser sintering temperature range, it cannot fully react with the silicon wafer surface and silver powder, resulting in poor metal-semiconductor contact performance and affecting the electrical performance of the battery. In addition, traditional organic carriers cannot meet the slurry's requirements for rheological properties such as viscosity and thixotropy under the LECO process, resulting in reduced printing performance, incomplete printing patterns, broken lines, collapsed edges and other problems, reducing the yield and efficiency of battery preparation.

[0004] In order to solve the above problems, the Chinese invention patent application with publication number CN118800497A discloses a conductive paste for LECO laser sintering, its preparation method, electrode, and solar cell. The conductive paste includes: silver powder, glass powder, organic carrier, and inorganic additive; wherein the inorganic additive is at least one of yttrium hexaboride, lanthanum hexaboride, aluminum boride, titanium boride, and zirconium diboride. By adding inorganic additives to the conductive paste, the invention can reduce the porosity of the grid line, increase the density of the grid line, effectively reduce the line resistance, improve the open circuit voltage and photoelectric conversion efficiency, and meet the requirements of the electrode material for sintering N-type TOPcon cells using LECO technology. However, the conductivity, bonding strength, printing performance and battery efficiency of the conductive paste still need to be further improved.

[0005] It can be seen that it is particularly important to develop a conductive paste for TOPCon batteries and a preparation method thereof, which has good conductivity, strong bonding with the passivation layer of the TOPCon battery, sufficient printing performance, and high battery efficiency of the TOPCon battery. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a conductive paste for TOPCon batteries, which has good conductivity, strong bonding with the passivation layer of TOPCon batteries, sufficient printing performance, and high battery efficiency of the TOPCon batteries prepared.

[0007] To achieve the above-mentioned object, the technical solution adopted by the present invention is a conductive paste for TOPCon batteries, comprising the following raw materials in parts by weight: 70-80 parts of silver powder, 2-6 parts of glass powder, 0.5-2 parts of additives, and 3-5 parts of organic carriers; the additive is Ti-Zn-rare earth-Nb-BO.

[0008] Preferably, the silver powder has an average particle size of 0.3-1.5 μm and a spherical shape.

[0009] Preferably, the glass powder has a D50 of 1.2-1.5 μm and is made of the following components in parts by weight: 50-54 parts of SiO2, 18-22 parts of B2O3, 23-27 parts of PbO, 1-3 parts of Li2O, and 0.8-1.2 parts of Na2O.

[0010] Preferably, the preparation method of the additive comprises the following steps: uniformly mixing titanium salt, zinc salt, rare earth salt, niobium salt and boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 25-35% of the total mass of the mixture to the mixture, magnetically stirring at 65-75°C for 2-3 hours, and adjusting the pH of the solution to 3.5-4.0 with ammonia water to form a stable sol system; adding ethylene glycol as a crosslinking agent at 8-12% of the mass of the sol, continuing stirring for 1 hour, and then transferring to an oven and drying at 125-135°C for 15-20 hours to form a wet gel; crushing the wet gel and adding it to a spray dryer for spray drying to obtain a precursor powder; and calcining to obtain the additive.

[0011] Preferably, the titanium salt is titanium nitrate; and the zinc salt is zinc nitrate.

[0012] Preferably, the rare earth salt is at least one of scandium nitrate, yttrium nitrate, praseodymium nitrate and cerium nitrate.

[0013] Preferably, the niobium salt is niobium oxalate; and the boron source is ammonium borate.

[0014] Preferably, the mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source and deionized water is 1:(0.8-1.2):0.2:(0.1-0.2):0.01:(6-10).

[0015] Preferably, the calcination temperature is 550-800° C. and the calcination time is 3-5 hours.

[0016] Preferably, the organic carrier comprises the following components in parts by weight: 30-40 parts of melamine formaldehyde resin, 50-60 parts of polyester polyol, 700-800 parts of terpineol, 80-90 parts of ethyl cellulose, and 5-8 parts of hydrogenated castor oil.

[0017] Preferably, the melamine formaldehyde resin is PJ590 melamine formaldehyde resin.

[0018] Preferably, the polyester polyol is POL-737 polyester polyol.

[0019] Preferably, the viscosity of the ethyl cellulose is 100-200 mPa·s.

[0020] Another object of the present invention is to provide a method for preparing the conductive paste for TOPCon batteries, comprising the following steps: uniformly mixing the raw materials by weight, and then subjecting the mixture to three-roller milling, viscosity adjustment, and filtering to obtain the conductive paste for TOPCon batteries.

[0021] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The method for preparing the conductive paste for TOPCon batteries disclosed in the present invention has a simple process, convenient operation and control, high preparation efficiency and finished product qualification rate, low dependence on equipment, easy large-scale industrial production, and high promotion and application value.

[0022] (2) The conductive paste for TOPCon batteries disclosed in the present invention comprises the following raw materials, measured in parts by weight: 70-80 parts of silver powder, 2-6 parts of glass powder, 0.5-2 parts of an additive, and 3-5 parts of an organic vehicle; the additive is Ti-Zn-rare earth-Nb-BO. Through the interaction between the raw materials, the conductive paste has better conductivity than conventional products, stronger bonding with the passivation layer of the TOPCon battery, better printing performance, and higher battery efficiency of the TOPCon battery.

[0023] (3) The conductive paste for TOPCon cells disclosed in the present invention has a glass powder with a D50 of 1.2-1.5 μm and is made of the following components in parts by weight: 50-54 parts of SiO2, 18-22 parts of B2O3, 23-27 parts of PbO, 1-3 parts of Li2O, and 0.8-1.2 parts of Na2O. By rationally adjusting the proportions of the components, the prepared glass powder has a lower glass transition temperature. When used in the conductive paste, it can reduce the sintering temperature of the conductive paste and improve the silver dissolving and precipitation ability of the glass powder under low temperature conditions, thus solving the problem that TOPCon crystalline silicon cells cannot be metallized at low temperatures, improving the overall performance of the conductive paste, and further improving the open circuit voltage, contact resistance, and photoelectric conversion efficiency of the battery made with the conductive paste.

[0024] (4) The conductive paste for TOPCon batteries disclosed in the present invention comprises Ti-Zn-rare earth-Nb-BO, which can reduce the porosity of the grid lines, increase the density, effectively reduce the line resistance, and improve the open circuit voltage and photoelectric conversion efficiency through the rational design of the additive composition.

[0025] (5) The conductive paste for TOPCon batteries disclosed in the present invention comprises an organic carrier comprising the following components in parts by weight: 30-40 parts of melamine formaldehyde resin, 50-60 parts of polyester polyol, 700-800 parts of terpineol, 80-90 parts of ethyl cellulose, and 5-8 parts of hydrogenated castor oil. The melamine formaldehyde resin and polyester polyol compounding system is used to form a stable carbon skeleton at the high temperature of the LECO process, protecting the silver powder from excessive oxidation. The optimized thixotropic properties ensure that the paste has good fluidity during the printing process and maintains the pattern shape after printing. The volatile matter is strictly controlled to avoid holes in the electrode due to gas escape during the sintering process. The low residual carbon design ensures that the organic residue in the electrode after sintering has minimal impact on battery performance. DETAILED DESCRIPTION

[0026] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0027] Example 1 A conductive paste for TOPCon batteries is prepared from the following raw materials in parts by weight: 70 parts of silver powder, 2 parts of glass powder, 0.5 parts of additives, and 3 parts of organic carriers; the additive is Ti-Zn-rare earth-Nb-BO.

[0028] The silver powder has an average particle size of 0.3 μm and is spherical in shape; the glass powder has a D50 of 1.2 μm and is made of the following components in parts by weight: 50 parts of SiO2, 18 parts of B2O3, 23 parts of PbO, 1 part of Li2O, and 0.8 parts of Na2O.

[0029] The preparation method of the additive comprises the following steps: uniformly mixing a titanium salt, a zinc salt, a rare earth salt, a niobium salt and a boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 25% of the total mass of the mixture into the mixture, magnetically stirring at 65°C for 2 hours, and adjusting the pH of the solution to 3.5 with ammonia water to form a stable sol system; adding 8% of the mass of the sol as a cross-linking agent, continuing stirring for 1 hour, transferring to an oven, and drying at 125°C for 15 hours to form a wet gel; crushing the wet gel and adding it to a spray dryer for spray drying to obtain a precursor powder; and calcining to obtain the additive; the titanium salt is titanium nitrate; the zinc salt is zinc nitrate; the rare earth salt is scandium nitrate; the niobium salt is niobium oxalate; and the boron source is ammonium borate.

[0030] The mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source and deionized water is 1:0.8:0.2:0.1:0.01:6; the calcination temperature is 550° C. and the calcination time is 3 hours.

[0031] The organic carrier includes the following components in parts by weight: 30 parts of melamine formaldehyde resin, 50 parts of polyester polyol, 700 parts of terpineol, 80 parts of ethyl cellulose, and 5 parts of hydrogenated castor oil; the melamine formaldehyde resin is PJ590 melamine formaldehyde resin; the polyester polyol is POL-737 polyester polyol; and the viscosity of the ethyl cellulose is 100-200 mPa·s.

[0032] A method for preparing the conductive paste for TOPCon batteries comprises the following steps: uniformly mixing the raw materials according to parts by weight, and then sequentially subjecting the mixture to three-roller milling, viscosity adjustment, and filtering to obtain the conductive paste for TOPCon batteries.

[0033] Example 2 A conductive paste for TOPCon batteries is prepared from the following raw materials in parts by weight: 73 parts of silver powder, 3 parts of glass powder, 1 part of an additive, and 3.5 parts of an organic vehicle; the additive is Ti-Zn-rare earth-Nb-BO.

[0034] The silver powder has an average particle size of 0.6 μm and is spherical in shape; the glass powder has a D50 of 1.3 μm and is made of the following components in parts by weight: 51 parts of SiO2, 19 parts of B2O3, 24 parts of PbO, 1.5 parts of Li2O, and 0.9 parts of Na2O.

[0035] The preparation method of the additive comprises the following steps: uniformly mixing a titanium salt, a zinc salt, a rare earth salt, a niobium salt, and a boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 28% of the total mass of the mixture into the mixture, magnetically stirring at 68°C for 2.3 hours, and adjusting the pH of the solution to 3.7 with ammonia water to form a stable sol system; adding ethylene glycol as a cross-linking agent at 9% of the mass of the sol, continuing stirring for 1 hour, and then transferring to an oven and drying at 127°C for 17 hours to form a wet gel; crushing the wet gel and adding it to a spray dryer for spray drying to obtain a precursor powder; and calcining to obtain the additive; the titanium salt is titanium nitrate; the zinc salt is zinc nitrate; the rare earth salt is yttrium nitrate; the niobium salt is niobium oxalate; and the boron source is ammonium borate.

[0036] The mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source, and deionized water is 1:0.9:0.2:0.13:0.01:7; the calcination temperature is 650° C. and the time is 3.5 hours; the organic carrier includes the following components in parts by weight: 33 parts of melamine formaldehyde resin, 53 parts of polyester polyol, 730 parts of terpineol, 83 parts of ethyl cellulose, and 6 parts of hydrogenated castor oil; the melamine formaldehyde resin is PJ590 melamine formaldehyde resin; the polyester polyol is POL-737 polyester polyol; and the viscosity of the ethyl cellulose is 100-200 mPa·s.

[0037] A method for preparing the conductive paste for TOPCon batteries comprises the following steps: uniformly mixing the raw materials according to parts by weight, and then sequentially subjecting the mixture to three-roller milling, viscosity adjustment, and filtering to obtain the conductive paste for TOPCon batteries.

[0038] Example 3 A conductive paste for a TOPCon battery is prepared by including the following raw materials in parts by weight: 75 parts of silver powder, 4 parts of glass powder, 1.4 parts of an additive, and 4 parts of an organic vehicle; the additive is Ti-Zn-rare earth-Nb-BO; the silver powder has an average particle size of 1 μm and a spherical shape; the glass powder has a D50 of 1.3 μm. The conductive paste comprises the following components in parts by weight: 52 parts of SiO2, 20 parts of B2O3, 25 parts of PbO, 2 parts of Li2O, and 1 part of Na2O.

[0039] The preparation method of the additive comprises the following steps: uniformly mixing a titanium salt, a zinc salt, a rare earth salt, a niobium salt, and a boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 30% of the total mass of the mixture into the mixture, magnetically stirring at 70°C for 2.5 hours, and adjusting the pH of the solution to 3.8 with ammonia water to form a stable sol system; adding 10% of the mass of the sol as a cross-linking agent, continuing stirring for 1 hour, and then transferring to an oven and drying at 130°C for 18 hours to form a wet gel; crushing the wet gel and adding it to a spray dryer for spray drying to obtain a precursor powder; and calcining to obtain the additive; the titanium salt is titanium nitrate; the zinc salt is zinc nitrate; the rare earth salt is praseodymium nitrate; the niobium salt is niobium oxalate; and the boron source is ammonium borate.

[0040] The mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source, and deionized water is 1:1:0.2:0.15:0.01:8; the calcination temperature is 700°C and the time is 4 hours; the organic carrier includes the following components in parts by weight: 35 parts of melamine formaldehyde resin, 55 parts of polyester polyol, 750 parts of terpineol, 85 parts of ethyl cellulose, and 6.5 parts of hydrogenated castor oil; the melamine formaldehyde resin is PJ590 melamine formaldehyde resin; the polyester polyol is POL-737 polyester polyol; and the viscosity of the ethyl cellulose is 100-200 mPa·s.

[0041] A method for preparing the conductive paste for TOPCon batteries comprises the following steps: uniformly mixing the raw materials according to parts by weight, and then sequentially subjecting the mixture to three-roller milling, viscosity adjustment, and filtering to obtain the conductive paste for TOPCon batteries.

[0042] Example 4 A conductive paste for TOPCon batteries is prepared from the following raw materials in parts by weight: 78 parts of silver powder, 5 parts of glass powder, 1.8 parts of additives, and 4.5 parts of organic vehicles; the additive is Ti-Zn-rare earth-Nb-BO.

[0043] The silver powder has an average particle size of 1.3 μm and is spherical in shape; the glass powder has a D50 of 1.4 μm and is made of the following components in parts by weight: 53 parts of SiO2, 21 parts of B2O3, 26 parts of PbO, 2.5 parts of Li2O, and 1.1 parts of Na2O.

[0044] The preparation method of the additive comprises the following steps: uniformly mixing a titanium salt, a zinc salt, a rare earth salt, a niobium salt, and a boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 33% of the total mass of the mixture into the mixture, magnetically stirring at 73°C for 2.8 hours, and adjusting the pH of the solution to 3.9 with ammonia water to form a stable sol system; adding 11% of the mass of the sol as a cross-linking agent, continuing stirring for 1 hour, transferring to an oven, and drying at 133°C for 19 hours to form a wet gel; crushing the wet gel and adding it to a spray dryer for spray drying to obtain a precursor powder; and calcining to obtain the additive; the titanium salt is titanium nitrate; the zinc salt is zinc nitrate; the rare earth salt is a mixture of scandium nitrate, yttrium nitrate, praseodymium nitrate, and cerium nitrate in a mass ratio of 1:2:2:1; the niobium salt is niobium oxalate; and the boron source is ammonium borate.

[0045] The mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source, and deionized water is 1:1.1:0.2:0.19:0.01:9.5; the calcination temperature is 750° C. and the time is 4.5 hours; the organic carrier includes the following components in parts by weight: 38 parts of melamine formaldehyde resin, 58 parts of polyester polyol, 790 parts of terpineol, 88 parts of ethyl cellulose, and 7.5 parts of hydrogenated castor oil; the melamine formaldehyde resin is PJ590 melamine formaldehyde resin; the polyester polyol is POL-737 polyester polyol; and the viscosity of the ethyl cellulose is 100-200 mPa·s.

[0046] A method for preparing the conductive paste for TOPCon batteries comprises the following steps: uniformly mixing the raw materials according to parts by weight, and then sequentially subjecting the mixture to three-roller milling, viscosity adjustment, and filtering to obtain the conductive paste for TOPCon batteries.

[0047] Example 5 A conductive paste for TOPCon batteries is prepared from the following raw materials in parts by weight: 80 parts of silver powder, 6 parts of glass powder, 2 parts of additives, and 5 parts of organic carriers; the additive is Ti-Zn-rare earth-Nb-BO.

[0048] The silver powder has an average particle size of 1.5 μm and is spherical in shape; the glass powder has a D50 of 1.5 μm and includes the following components in parts by weight: 54 parts of SiO2, 22 parts of B2O3, 27 parts of PbO, 3 parts of Li2O, and 1.2 parts of Na2O.

[0049] The preparation method of the additive comprises the following steps: uniformly mixing titanium salt, zinc salt, rare earth salt, niobium salt and boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 35% of the total mass of citric acid to the mixture, magnetically stirring at 75°C for 3 hours, adjusting the pH of the solution to 4.0 with ammonia water to form a stable sol system; adding 12% of the mass of the sol as a cross-linking agent, continuing stirring for 1 hour, transferring to an oven, and drying at 135°C for 2 hours. 0h to form a wet gel; the wet gel is crushed and added into a spray dryer for spray drying to obtain a precursor powder; after calcination, an additive is obtained; the titanium salt is titanium nitrate; the zinc salt is zinc nitrate; the rare earth salt is cerium nitrate; the niobium salt is niobium oxalate; the boron source is ammonium borate; the mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source, and deionized water is 1:1.2:0.2:0.2:0.01:10; the calcination temperature is 800°C and the time is 5h.

[0050] The organic vehicle includes the following components in parts by weight: 40 parts of melamine formaldehyde resin, 60 parts of polyester polyol, 800 parts of terpineol, 90 parts of ethyl cellulose, and 8 parts of hydrogenated castor oil; the melamine formaldehyde resin is PJ590 melamine formaldehyde resin; the polyester polyol is POL-737 polyester polyol; and the viscosity of the ethyl cellulose is 100-200 mPa·s.

[0051] A method for preparing the conductive paste for TOPCon batteries comprises the following steps: uniformly mixing the raw materials according to parts by weight, and then sequentially subjecting the mixture to three-roller milling, viscosity adjustment, and filtering to obtain the conductive paste for TOPCon batteries.

[0052] Comparative Example 1 A conductive paste for TOPCon batteries and a preparation method thereof are basically the same as those in Example 1, except that an equal amount of yttrium hexaboride is used instead of the additive; ethyl cellulose is not added, and an equal amount of SiO2 is used instead of Li2O.

[0053] Comparative Example 2 A conductive paste for TOPCon batteries and a preparation method thereof are basically the same as those in Example 1, except that an equal amount of titanium salt is used instead of niobium salt, hydrogenated castor oil is not added, and an equal amount of SiO2 is used instead of Na2O.

[0054] In order to further illustrate the beneficial technical effects of the conductive paste for TOPCon batteries involved in each embodiment of the present invention, relevant performance tests were conducted on the conductive paste for TOPCon batteries involved in Examples 1-5 and Comparative Examples 1-2. The test results are shown in Table 1. The test method is as follows: (1) Conductivity: A four-probe tester (RT-9000) was used, equipped with 1mm diameter tungsten probes and 1mm probe spacing. LECO laser sintering parameters were: wavelength 1064nm, power density 2.5kW / cm², scanning speed 100mm / s, and bias voltage 12V. Each sample was tested at five different locations and the average value was taken. The square resistance test accuracy was required to reach 0.01mΩ / □. (2) Bonding strength: The test was conducted using an electronic universal testing machine (Instron 5967) with a 20 mm diameter fixture. 5 mm × 5 mm electrodes were printed on TOPCon cells (area 156.75 mm × 156.75 mm), LECO treated, and then attached to an aluminum pulling head. The tensile speed was 10 mm / min. The maximum tensile force at failure was recorded and the bonding strength (N / mm²) was calculated. Ten samples were tested in each group and the average value was calculated.

[0055] (3) Printing performance: A fully automatic screen printing machine (DEK 265GSX) was used, with a 200-mesh stainless steel screen, a scraper pressure of 1.2 kg / cm, a printing speed of 50 mm / s, and 500 sheets were printed continuously. The number of defective products such as broken lines and collapsed edges was counted, and the printing yield was calculated. The temperature in the printing workshop was 23 ± 2 °C, and the humidity was 45 ± 5% RH.

[0056] (4) Cell efficiency test: Each conductive paste was screen-printed on an N-type TOPCon crystalline silicon cell and the electrical performance was tested.

[0057] Table 1 Performance test results of conductive paste for TOPCon batteries project Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Square resistance (mΩ / □) 2.6 2.3 2.1 2.0 1.6 3.3 3.0 Bonding strength (N / mm²) 6.5 7.0 7.7 8.0 8.3 5.6 6.0 Printing yield (%) 99.2 99.5 99.6 99.8 99.9 94.5 95.7 Conversion efficiency (%) 26.15 26.20 26.27 26.30 26.34 25.75 25.80 As can be seen from Table 1, the conductive paste for TOPCon cells according to the embodiments of the present invention has better conductivity, more excellent bonding strength and printing performance than the comparative example product. The TOPCon cells made with this paste have higher photoelectric conversion efficiency. The combined use of additives, ethyl cellulose, Li2O, niobium salt, hydrogenated castor oil and Na2O is beneficial to improving the above-mentioned properties.

[0058] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A conductive paste for TOPCon batteries, characterized in that: The invention comprises the following raw materials in parts by weight: 70-80 parts of silver powder, 2-6 parts of glass powder, 0.5-2 parts of additives, and 3-5 parts of organic carriers; the additive is Ti-Zn-rare earth-Nb-BO.

2. The conductive paste for TOPCon batteries according to claim 1, characterized in that: The silver powder has an average particle size of 0.3-1.5 μm and a spherical shape.

3. The conductive paste for TOPCon batteries according to claim 1, characterized in that: The glass powder has a D50 of 1.2-1.5 μm and is made of the following components in parts by weight: 50-54 parts of SiO2, 18-22 parts of B2O3, 23-27 parts of PbO, 1-3 parts of Li2O, and 0.8-1.2 parts of Na2O.

4. The conductive paste for TOPCon batteries according to claim 1, characterized in that: The preparation method of the additive comprises the following steps: uniformly mixing titanium salt, zinc salt, rare earth salt, niobium salt and boron source to obtain a mixture, dissolving the mixture in deionized water to form a mixture solution, then adding 25-35% of citric acid in an amount of the total mass of the mixture to the mixture, magnetically stirring at 65-75°C for 2-3 hours, and adjusting the pH of the solution to 3.5-4.0 with ammonia water to form a stable sol system; adding 8-12% of the mass of the sol as a cross-linking agent, continuing stirring for 1 hour, transferring to an oven, and drying at 125-135°C for 15-20 hours to form a wet gel; crushing the wet gel and adding it to a spray dryer for spray drying to obtain a precursor powder; and calcining to obtain the additive.

5. The conductive paste for TOPCon batteries according to claim 4, characterized in that: The titanium salt is titanium nitrate; the zinc salt is zinc nitrate.

6. The conductive paste for TOPCon batteries according to claim 4, characterized in that: The rare earth salt is at least one of scandium nitrate, yttrium nitrate, praseodymium nitrate, and cerium nitrate; the niobium salt is niobium oxalate; and the boron source is ammonium borate.

7. The conductive paste for TOPCon batteries according to claim 4, characterized in that: The mass ratio of the titanium salt, zinc salt, rare earth salt, niobium salt, boron source and deionized water is 1:(0.8-1.2):0.2:(0.1-0.2):0.01:(6-10); the calcination temperature is 550-800°C and the calcination time is 3-5h.

8. The conductive paste for TOPCon batteries according to claim 1, characterized in that: The organic carrier comprises the following components in parts by weight: 30-40 parts of melamine formaldehyde resin, 50-60 parts of polyester polyol, 700-800 parts of terpineol, 80-90 parts of ethyl cellulose, and 5-8 parts of hydrogenated castor oil.

9. The conductive paste for TOPCon batteries according to claim 1, characterized in that: The melamine formaldehyde resin is PJ590 melamine formaldehyde resin; the polyester polyol is POL-737 polyester polyol; and the viscosity of the ethyl cellulose is 100-200 mPa·s.

10. A method for preparing a conductive paste for TOPCon batteries according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: uniformly mixing the raw materials according to parts by weight, and then sequentially subjecting the raw materials to three-roller milling, viscosity adjustment, and filtering to obtain a conductive slurry for TOPCon batteries.