High efficiency high soldering tensile force main grid silver paste adapting leco process and application thereof

Abstract

This invention discloses a high-efficiency, high-weld-strength main grid silver paste adapted to the LECO process and its application. The silver paste comprises silver powder, glass powder, and an organic carrier; wherein the glass powder comprises a Pb-B-Te-Zn glass system. This invention introduces a novel Pb-B-Te-Zn glass system into the paste, thereby giving the glass components better fluidity and etching ability during sintering. The silver powder and silicon wafer act as a strong bond, greatly improving the weld pull value. Furthermore, the paste fuses better with the solder ribbon, exhibits strong tin melting ability, and possesses a good weld fracture surface. It has a wide sintering window, making it compatible with the LECO process where the peak temperature of the existing sintering furnace decreases, reducing the fabrication cost of solar cells. It also enhances the fusion between the front main grid paste and the front fine grid paste, effectively improving the cell's on-state voltage and open-circuit flyback (FF), further improving the cell's photoelectric conversion efficiency.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a high-efficiency, high-welding-stretch main grid silver paste adapted to the LECO process and its application. Background Technology

[0002] TOPCon cells, short for Tunnel Oxide Passivated Contact solar cells, are an advanced technology in the photovoltaic field designed to improve the conversion efficiency and performance of solar cells. The core structure of TOPCon cells is developed from the traditional passivated emitter and PERC (Performance-Reverse Conversion) cell, with the main difference being its back contact layer. It utilizes an ultra-thin layer of silicon oxide (SiO2). x A tunneling oxide layer and a doped polycrystalline silicon layer serve as the passivated contact layer. This structural design effectively reduces the recombination rate of electrons and holes, thereby increasing the open-circuit voltage (Voc) and short-circuit current (Isc) of the battery, and thus improving the conversion efficiency.

[0003] Typically, the N-type TOPCon front-side grid paste includes key components such as silver powder, organic carrier, glass powder, additives, and solvents. It is then processed through screen printing, drying, sintering, light injection, and LECO laser sintering (laser-enhanced contact optimization process) to form the front electrode of the solar cell. The LECO process is an advanced technology used in solar cell manufacturing, particularly for optimizing tunneling oxide passivation contact cell structures.

[0004] Currently, due to the widespread adoption of the LECO laser sintering process, the paste can precisely and locally disrupt the passivation layer. Under high temperatures, silver particles begin to react with silicon, forming a silver-silicon alloy. This process involves silver atoms diffusing into the silicon wafer surface and forming good ohmic contacts in the contact area. However, at the junction of the main grid and the fine grid, due to the difference in their systems, the excessive corrosivity of the front main grid paste can cause it to erode downwards excessively after being combined with the fine grid, severely damaging the ultrathin silicon oxide layer, reducing the turn-on voltage and open-circuit (FF) of the solar cell, and thus affecting efficiency. Furthermore, the LECO process is a post-sintering treatment. Its emergence allows for further reduction in the temperature of the front-end sintering furnace, lowering the cost of cell manufacturing. However, this results in insufficient sintering of the front main grid paste, reduced adhesion between the paste and the cell, and consequently, decreased long-term stability.

[0005] In summary, under the influence of LECO laser sintering technology, the application of front-side grid paste is crucial for improving the photoelectric conversion efficiency of solar cells. However, the current N-type TOPCon front-side grid paste has a narrow sintering window, weak tensile strength, poor long-term environmental stability, and excessively high corrosion intensity, which causes excessive damage to the silicon oxide layer, greatly affecting the cell's on-state voltage and open-circuit flyback (FF), reducing cell efficiency and failing to meet market demands. Improvement is urgently needed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-efficiency, high-welding-tensile main grid silver paste adapted to the LECO process and its application.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] In a first aspect, the present invention provides a high-efficiency, high-welding-strength main grid silver paste adapted to the LECO process, which includes silver powder, glass powder and an organic carrier.

[0009] The glass powder contained in the glass system is a Pb-B-Te-Zn glass system.

[0010] Secondly, the present invention also provides a method for preparing a TOPCon solar cell, characterized in that it includes:

[0011] The high-efficiency, high-welding-strength main grid silver paste is printed on the front side of the TOPCon solar cell and dried to form the main grid line precursor;

[0012] The main grid line precursor is thermally sintered;

[0013] After thermal sintering, the main grid line precursor is subjected to LECO laser sintering to form the front main grid line.

[0014] Thirdly, the present invention also provides a TOPCon solar cell prepared by the above-described preparation method.

[0015] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0016] This invention provides a front-side main grid paste for N-type TOPCon cells adapted to the LECO process. This paste introduces a novel Pb-B-Te-Zn glass system, resulting in better fluidity and etching ability of the glass components during sintering. It also provides excellent adhesion between the silver powder and the silicon wafer, significantly improving the solder pull strength. Furthermore, the paste integrates better with the solder ribbon, exhibits strong tin melting ability, and provides a good solder fracture surface. Simultaneously, it has a wide sintering window, making it compatible with the LECO process where the peak temperature of the existing sintering furnace is reduced by 30-50°C, thus lowering the manufacturing cost of solar cells. Additionally, it enhances the fusion between the front-side main grid paste and the front-side fine grid paste, effectively improving the cell's on-state voltage and open-circuit filter (FF), thereby further enhancing the cell's photoelectric conversion efficiency.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below. Detailed Implementation

[0018] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0019] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0020] This invention provides a high-efficiency, high-welding-strength main grid silver paste adapted to the LECO process, comprising silver powder, glass powder, and an organic carrier; wherein the glass powder comprises a Pb-B-Te-Zn glass system.

[0021] Some existing technologies propose low-temperature sintering slurries, but these are not designed for the low-temperature sintering + LECO process and are not suitable for this advanced process. For example, existing technologies propose that glass powders containing lead, tellurium, and silicon can achieve low-temperature sintering, but this invention uses boron and zinc to replace part of the silicon, which can effectively adjust the density of the glass network structure, making the glass's viscosity-temperature characteristics and other physicochemical properties more effectively achieved for SiN. xThe anti-reflective coating and the controlled etching reaction of Si are key features. High-Zn glass exhibits strong etching capabilities for silicon wafers, and its combination with highly fluid elements such as lead and bismuth enables the main grid to achieve high welding pull and a good welding condition. Te is a crucial factor in improving the efficiency of the main grid paste involved in this invention. Te increases the silver-dissolving capacity of the glass, and with the assistance of highly fluid lead-bismuth glass, the paste can form good contact during LECO laser sintering, increasing the fill factor of the cell and effectively improving the cell efficiency.

[0022] Furthermore, the Pb-B-Te-Zn system used in the main grid slurry of this invention requires the simultaneous presence of four key elements (in the form of oxides or salts) to achieve the high tensile strength and high efficiency of the main grid slurry. However, it is not limited to the presence of these four elements in a single glass powder; multiple glass powders can be combined to contain the aforementioned key elements.

[0023] In this system, boron (B) is essential for forming the glass network. Pb, Te, and Zn, as key elements for regulating the glass transition temperature, fluidity, and silver solubility, can be adjusted in different proportions depending on the sintering temperature and LECO process. This allows the grid paste to react with the Si wafer in a "pinning" manner under suitable temperature and process conditions. This results in good silver microcrystal diffusion at the contact points, forming a good electron transport channel and thus improving the photoelectric conversion efficiency of the solar cell.

[0024] Furthermore, regarding compatibility with the LECO process, which is a more precise process, it uses a high-intensity laser to precisely irradiate the surface of the cell's grid lines, generating localized high temperatures that cause the paste to react with the silicon wafer. The main grid paste involved in this invention, due to the addition of elements such as Pb, Bi, and Te, can undergo a silver melting and crystallization reaction with the silicon wafer during this process, forming contact. Moreover, its system is more compatible with the fine grid paste, resulting in better synergy. Previously, the main grid paste was a non-contact type, only providing welding pull strength. The paste involved in this invention can achieve contact by being paired with the LECO process, and can also possess high welding pull strength at low firing temperatures.

[0025] Regarding the specific component ratios, in some embodiments, the mass fraction of the silver powder is 78-86%, the mass fraction of the glass powder is 1-2%, and the mass fraction of the organic carrier is 13-20%.

[0026] In some embodiments, the glass powder includes a first glass powder and a second glass powder, wherein the first glass powder has a mass fraction of 10-90% and the second glass powder has a mass fraction of 10-90%.

[0027] In some embodiments, the first glass powder comprises 20-70 wt% PbO, 1-30 wt% SiO2, 0-20 wt% TiO2, 0-10 wt% B2O3, and 0-10 wt% R2O; the second glass powder comprises 0-70 wt% PbO, 0-70 wt% Bi2O3, 0-40 wt% SiO2, 3-30 wt% TeO2, 5-30 wt% ZnO, 0-20 wt% B2O3, and 0-10 wt% R2O.

[0028] Where R represents alkali metal.

[0029] In some embodiments, the glass powder has an average particle size of 1-3 μm and a softening point of 350-500 °C.

[0030] In some embodiments, the silver powder has an average particle size of 1-2 μm, a D50 of 1-2 μm, a D90 of 1-6 μm, and a tap density of 4-6 g / m³. 3 .

[0031] In some embodiments, the organic carrier includes any one or a combination of two or more of ethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, acrylic resin, oleic acid, stearic acid, polyethylene glycol, shea butter propylene diamine oleate, dimethyl adipate, triphosphate, epoxy resin, dodecyl alcohol ester, butyl carbitol acetate, hexadecyl alcohol ester, and diethylene glycol dibutyl ether.

[0032] As typical application examples of the above technical solutions, the high-efficiency, high-welding-strength main grid silver paste adapted to the LECO process provided by the above technical solutions, calculated by mass fraction, contains the following components: 78-86 wt% silver powder, 1-2 wt% glass powder, and 13-20 wt% organic carrier, etc. The silver powder used in the first part is micron-sized silver powder; the glass powder in the second part consists of a composition of two types of glass powder, wherein the first glass powder is mainly composed of lead, silicon, titanium, metal oxides, etc., and the second glass powder is mainly composed of lead, silicon, zinc, tellurium, etc., and the two glass powders are mixed in a ratio of 1:9 to 9:1; the organic carrier in the third part is composed of resin, solvent, thixotropic agent, dispersant, and other additives, and commonly used organic carriers for silver pastes are usually selected.

[0033] The micron-sized silver powder mentioned above is generally spherical, with an average particle size of 1-2 μm, a D50 of 1-2 μm, a D90 of 1-6 μm, and a tap density of 4-6 g / m³. 3 Glass powder is composed of multiple raw materials selected from lead oxide, boron oxide, silicon oxide, silicon dioxide, aluminum oxide, zinc oxide, barium oxide, magnesium oxide, bismuth oxide, cerium oxide, iron oxide, titanium oxide, titanium dioxide, copper oxide, manganese oxide, tellurium oxide, calcium oxide, chromium oxide, tin oxide, sodium carbonate, and lithium carbonate, and at least meets the conditions for constituting a Pb-B-Te-Zn glass system.

[0034] The first glass powder can be prepared from the following components in mass fractions: 20-70 wt% PbO, 1-30 wt% SiO2, 0-20 wt% TiO2, 0-10 wt% B2O3, 0-10 wt% R2O, and other metal oxide components. The second glass powder is prepared from the following components: 0-70 wt% PbO, 0-70 wt% Bi2O3, 0-40 wt% SiO2, 3-30 wt% TeO2, 5-30 wt% ZnO, 0-20 wt% B2O3, 0-10 wt% R2O, and other metal oxide components. The alkali metal oxide R2O is one or more of Na2O, Li2O, and K2O.

[0035] The first glass powder may also contain one or more oxides or salts of bismuth, tellurium, zinc, magnesium, aluminum, calcium, copper, manganese, and antimony, wherein the content of the oxides or salts of bismuth, tellurium, zinc, boron, magnesium, aluminum, calcium, copper, manganese, and antimony is 1-20 wt%. The second glass powder may also contain one or more oxides or salts of titanium, magnesium, aluminum, calcium, barium, tungsten, copper, manganese, and antimony, wherein the content of the oxides or salts of titanium, magnesium, aluminum, calcium, barium, tungsten, copper, manganese, and antimony is 1-30 wt%.

[0036] The average particle size of these two glass powders is 1-3 μm, and the softening point is 350-500℃.

[0037] The mixing ratio of the two glass powders is usually 10% to 90% of the total mass of the mixed glass powder, and the second glass powder accounts for 10% to 90% of the total mass of the mixed glass powder.

[0038] The organic carrier is composed of a combination of various materials such as ethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, acrylic resin, oleic acid, stearic acid, polyethylene glycol, tallow-based propylene diamine oleate, dimethyl adipate, triphosphate, epoxy resin, dodecyl alcohol ester, butyl carbitol acetate, hexadecyl alcohol ester, and diethylene glycol dibutyl ether. Specifically, you can choose an existing or self-prepared organic carrier with similar functions and physicochemical properties.

[0039] As a more specific example, the process for preparing the first glass powder and the second glass powder in a specific embodiment of the present invention may include the following steps:

[0040] Step 1: Prepare the ingredients according to the glass material ratio. Each component is weighed by mass percentage and then thoroughly mixed in the mixer.

[0041] Step 2: The batch material is loaded into a corundum crucible and melted in a lifting furnace at 1000-1300℃ for 1-1.5 hours. After the glass melt is homogenized, the glass material is obtained by high-temperature water quenching or cold rolling pressing.

[0042] Step 3: The glass material is dry-milled using a planetary ball mill at a speed of 300-650 r / min for 1-4 h. It is then wet-milled using a horizontal ball mill with alcohol as the solvent at a speed of 100-300 r / min for 10-30 h. After drying, glass powder with D50 < 3 μm is obtained.

[0043] The above-mentioned method for preparing high-efficiency, high-welding-strength main grid silver paste adapted to the LECO process may include the following steps:

[0044] Step 1: Mix the micron-sized silver powder, glass powder, and organic carrier according to the specified ratio, and stir until homogeneous;

[0045] Step 2: Grind the above mixture 6-8 times with a three-roll mill, filter and centrifuge to obtain a front grid slurry with a fineness ≤7μm and a viscosity of 30Pa·S~100Pa·S.

[0046] Of course, the above-mentioned methods for preparing glass powder and slurry are all exemplary. If the same method as the above-mentioned preparation process is not used in actual implementation to obtain glass powder / slurry with the same composition, proportion and physical properties, or if equivalent glass powder is purchased directly or a slurry with corresponding composition is prepared by others, it can also be used as an equivalent substitute for the above-mentioned exemplary scheme.

[0047] As a further application of the above technical solution, this embodiment of the invention also provides a method for preparing a TOPCon solar cell, which includes the following steps:

[0048] The high-efficiency, high-welding-tensile-strength main grid silver paste provided in any of the above embodiments is printed on the front side of the TOPCon solar cell and dried to form the main grid line precursor;

[0049] The main grid line precursor is thermally sintered;

[0050] After thermal sintering, the main grid line precursor is subjected to LECO laser sintering to form the front main grid line.

[0051] In some implementations, the sintering process of the main gate line can also be combined with that of the fine gate line (referred to as the auxiliary gate line or secondary gate line in some technical solutions). Therefore, the above preparation method may also include the following steps:

[0052] Simultaneously print the fine grid line paste on the front side and dry it to form the fine grid line precursor;

[0053] The fine grid line precursor and the main grid line precursor are thermally sintered simultaneously to ultimately form a front-side fine grid line that is connected to the main grid line.

[0054] As a typical example of the above technical solution, the specific process steps of the above TOPCon solar cell fabrication method are as follows:

[0055] Step 1: Using a screen printing machine, conventional back grid and back main grid pastes are printed onto the back of the silicon wafer, which is then further dried in a drying oven at a temperature of 250-350℃.

[0056] Step 2: After drying, the silicon wafer with the back side paste already printed is flipped over and re-printed with the front main grid paste and conventional front fine grid paste on the front side using a screen printing machine. After drying in a drying oven, it is heated and sintered in a sintering furnace to obtain an N-type TOPCon solar cell. The drying temperature is 150-300℃, the sintering temperature is 600-800℃, and the peak time is 1-4s.

[0057] The selected front grid paste, back grid paste, and main grid paste are all conventional pastes in the field of photovoltaic N-type TOPCon cells, while the front main grid paste is the paste involved in this invention.

[0058] Step 3: The printed solar cells need to be further passivated by a light injection annealing device. The peak temperature of the LED illumination area is 200-320℃ and the light intensity is 10-60%.

[0059] Step 4: After the solar cells have been passivated by light injection, a high-intensity laser is used to irradiate the solar cells with LECO laser-assisted sintering equipment, while a deflection voltage of 10V or higher is applied to obtain the final N-type TOPCon solar cell sample.

[0060] Furthermore, a third aspect of the present invention provides a TOPCon solar cell prepared by the preparation method provided in any of the above embodiments.

[0061] Based on the above technical solution, the main advantages of this invention compared to some existing technologies are as follows:

[0062] The front grid paste of the N-type TOPCon cell adapted to the LECO process (laser-enhanced contact optimization) of this invention introduces a new Pb-B-Te-Zn glass system, which contains high contents of Pb, Bi, Si, Ti, Te, Zn, etc., thus giving it good etching depth for the cell and good fusion ability with the solder ribbon, ensuring that the grid has excellent welding performance and long-term stability.

[0063] The front grid paste of the N-type TOPCon cell adapted to the LECO process described in this invention, which includes inorganic components such as silver powder and glass powder, is a wide-window system designed for the LECO process. It can maintain good welding performance and photoelectric conversion efficiency even when the sintering furnace temperature drops by 30-50°C.

[0064] The front grid paste of the N-type TOPCon cell adapted to the LECO process described in this invention, through the adjustment of the combination and compounding ratio of glass powder and various organic components, enables the glass material to have good fluidity and compatibility with the fine grid system, which can effectively improve the photoelectric conversion efficiency of the N-type TOPCon cell and improve its turn-on voltage and open-circuit voltage.

[0065] In summary, the two types of glass powders involved in the front-side main grid paste provided by this invention are a mixture of lead-silicon-zinc system and lead-silicon-boron system glass powders. Through the combination of the two types of glass powders, the lead-silicon-zinc system glass powder has a strong etching ability on the silicon wafer, which can ensure that the main grid has high tensile strength. In addition, the metal oxides contained therein can better fuse with the solder ribbon, and increase the long-term stability of the main grid, with good aging tensile strength. The lead-silicon-boron system glass powder controls the etching depth and fluidity of the main grid on the silicon wafer, forming a good glass layer and reducing the impact on the photoelectric conversion efficiency of crystalline silicon solar cells. The component content and system of the mixed glass powder have little impact on the front-side fine grid, and can be better adapted to the fine grid, with good synergy. It can enhance the turn-on voltage and FF of the solar cell, effectively improving the shortcomings of traditional front-side main grids, which have strong corrosion and are not compatible with the fine grid, thus reducing the photoelectric conversion efficiency of the cell.

[0066] The technical solution of the present invention will be further described in detail below through several embodiments. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0067] Example 1

[0068] This embodiment illustrates two methods for preparing glass powder, as shown in Tables 1 and 2 below:

[0069] Table 1

[0070]

[0071] Table 2

[0072]

[0073] After weighing the raw materials according to the table above, dry grinding was carried out using a planetary ball mill at a speed of 300-650 r / min for 1-4 h. Further wet grinding was carried out using a horizontal ball mill with alcohol as the solvent at a speed of 100-300 r / min for 10-30 h. After drying, glass powder with D50 < 3 μm was obtained.

[0074] Example 2

[0075] Weigh 83 wt% conductive silver powder, 1.2 wt% type I glass powder XZ-1, 0.7 wt% type II glass powder XF-1, and 15.1 wt% organic phase, wherein the organic phase is commercially available and is mainly an activated mixture of terpineol, ethyl cellulose, polyurethane, epoxy resin, and silane coupling agent.

[0076] First, conductive silver powder and glass powder are premixed using a homogenizer. After the materials are homogenized, they are then stirred and centrifuged to ensure thorough mixing. The slurry is then ground eight times sequentially using a three-roll mill, and the fineness is tested using a scraper fineness meter. The slurry fineness is ≤6µm. The resulting slurry is named XY-1.

[0077] Example 3

[0078] Weigh 83 wt% conductive silver powder, 1.2 wt% type I glass powder XZ-2, 0.7 wt% type II glass powder XF-2, and 15.1 wt% organic phase, wherein the organic phase is commercially available and is mainly an activated mixture of terpineol, ethyl cellulose, polyurethane, epoxy resin, and silane coupling agent.

[0079] First, conductive silver powder and glass powder are premixed using a homogenizer. After the materials are homogenized, they are then stirred and centrifuged to ensure thorough mixing. The slurry is then ground eight times sequentially using a three-roll mill, and the fineness is tested using a scraper fineness meter. The slurry fineness is ≤6µm. The resulting slurry is named XY-2.

[0080] Example 4

[0081] Weigh 83 wt% conductive silver powder, 1.2 wt% type I glass powder XZ-3, 0.7 wt% type II glass powder XF-3, and 15.1 wt% organic phase, wherein the organic phase is commercially available and is mainly an activated mixture of terpineol, ethyl cellulose, polyurethane, epoxy resin, and silane coupling agent.

[0082] First, conductive silver powder and glass powder are premixed using a homogenizer. After the materials are homogenized, they are then stirred and centrifuged to ensure thorough mixing. The slurry is then ground eight times sequentially using a three-roll mill, and the fineness is tested using a scraper fineness meter. The slurry fineness is ≤6µm. The resulting slurry is named XY-3.

[0083] Comparative Example 1

[0084] This comparative example provides a control over the above embodiments using commercially available BSL slurry.

[0085] Comparative Example 2

[0086] This comparative example is largely the same as Example 1 above, except that in XY-1, TeO2 is removed, while the other components and their amounts remain unchanged, and the slurry is designated as D-1.

[0087] Comparative Example 3

[0088] This comparative example is largely the same as Example 1 above, except that ZnO is removed in XY-1, while the other components and their amounts remain unchanged, and the slurry is designated as D-2.

[0089] Comparative Example 4

[0090] This comparative example is largely the same as Example 1 above, except that in XY-1, B2O3 is removed, while the other components and their amounts remain unchanged, and the slurry is designated as D-3.

[0091] The XY-1 / 2 / 3 paste from the example and the BSL paste from the comparative example were printed on N-type 183 solar cell wafers using a Maiwei printing press as the front main grid paste, along with other back fine, back main, and front fine pastes, in one, two, three, or four passes. Each front main grid paste was printed on 30 wafers. The wafers were sintered in a DESPATCH sintering furnace at a peak temperature of 700°C. After sintering, they were further passivated by Maiwei light injection equipment with an annealing temperature of 320°C and an illumination intensity of 30%. Then, the solar cells were irradiated with a high-intensity laser using an Autowell LECO laser-assisted sintering equipment, while a deflection voltage of 10V or higher was applied to obtain the finished N-type solar cell.

[0092] IV efficiency and tensile tests were conducted, and the recorded data are shown in Table 3.

[0093] Table 3

[0094]

[0095] The results are shown in Table 3. In this embodiment, the front grid paste XY-1 of the N-type TOPCon cell adapted to the LECO process (laser-enhanced contact optimization) shows a significant improvement in photoelectric conversion efficiency compared to BSL. XY-2 / 3 shows a slightly higher photoelectric conversion efficiency compared to BSL. Tensile testing results show that XY-1 / 2 / 3 exhibits significantly enhanced welding performance under the LECO process compared to BSL. In this embodiment, the first and second glass powders are mixed in a certain proportion to create the front grid paste XY-1 / 2 / 3 of the N-type TOPCon cell adapted to the LECO process (laser-enhanced contact optimization). This results in a certain improvement in photoelectric conversion efficiency, mainly reflected in the on-state voltage and fill factor FF. Furthermore, its welding performance is also enhanced, exhibiting good long-term stability. The comparative test results also show that Te element has a significant impact on the contact ability of the grid paste, Zn element on the welding performance of the grid paste, and B element on the corrosiveness of the grid paste.

[0096] In summary, the front-side grid paste for N-type TOPCon cells adapted to LECO (Laser Enhanced Contact Optimization) technology provided by the embodiments of the present invention ensures excellent welding performance and long-term stability of the grid by providing good etching depth and good fusion ability with the solder ribbon. Furthermore, by adjusting the glass powder compounding ratio, the glass material has good fluidity and compatibility with the fine grid system, which can effectively improve the photoelectric conversion efficiency of N-type TOPCon cells and increase their turn-on voltage and open-circuit voltage.

[0097] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high efficiency high solder pull main grid silver paste adapted for LECO process, characterized in that, Including silver powder, glass powder, and organic carriers; The glass powder contained in the glass system is a Pb-B-Te-Zn glass system.

2. The high efficiency high solder pull main grid silver paste of claim 1, wherein, The silver powder has a mass fraction of 78-86%, the glass powder has a mass fraction of 1-2%, and the organic carrier has a mass fraction of 13-20%.

3. The high efficiency high solder pull main grid silver paste of claim 1, wherein, The glass powder includes a first glass powder and a second glass powder, wherein the mass fraction of the first glass powder is 10-90% and the mass fraction of the second glass powder is 10-90%.

4. The high-efficiency, high-welding-tensile main grid silver paste according to claim 3, characterized in that, The first glass powder comprises 20-70 wt% PbO, 1-30 wt% SiO2, 0-20 wt% TiO2, 0-10 wt% B2O3, and 0-10 wt% R2O; The second glass powder comprises 0-70 wt% PbO, 0-70 wt% Bi2O3, 0-40 wt% SiO2, 3-30 wt% TeO2, 5-30 wt% ZnO, 0-20 wt% B2O3, and 0-10 wt% R2O. Where R represents alkali metal.

5. The high-efficiency, high-welding-tensile main grid silver paste according to claim 1, characterized in that, The glass powder has an average particle size of 1-3 μm and a softening point of 350-500℃.

6. The high efficiency high solder pull main grid silver paste of claim 1, wherein, The silver powder has an average particle size of 1-2 μm, a D50 of 1-2 μm, a D90 of 1-6 μm, and a tap density of 4-6 g / m³. 3 .

7. The high efficiency high solder pull main grid silver paste of claim 1, wherein, The organic carrier includes any one or a combination of two or more of the following: ethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, acrylic resin, oleic acid, stearic acid, polyethylene glycol, shea butter propylene diamine oleate, dimethyl adipate, triphosphate, epoxy resin, dodecyl alcohol ester, butyl carbitol acetate, hexadecyl alcohol ester, and diethylene glycol dibutyl ether.

8. A method for manufacturing a TOPCon solar cell, characterized by, include: The high-efficiency, high-welding-tensile silver paste of any one of claims 1-7 is printed on the front side of the TOPCon solar cell and dried to form the main grid line precursor; The main grid line precursor is thermally sintered; After thermal sintering, the main grid line precursor is subjected to LECO laser sintering to form the front main grid line.

9. The preparation method according to claim 8, characterized in that, Also includes: Simultaneously print the fine grid line paste on the front side and dry it to form the fine grid line precursor; The fine grid line precursor and the main grid line precursor are thermally sintered simultaneously to ultimately form a front-side fine grid line that is connected to the main grid line.

10. A TOPCon solar cell prepared by the preparation method according to any one of claims 8-9.

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