Glass powder for topcon crystalline silicon solar cell main grid paste and preparation method thereof

Abstract

This invention discloses a glass powder for the main grid paste of TOPCon crystalline silicon solar cells and its preparation method. The glass powder is obtained by mixing glass frits A and B obtained after cold rolling at a mass ratio of 1.5 to 2:1, followed by secondary melting and cold rolling. Glass frit A includes PbO, SiO2, B2O3, Li2O, Na2O, etc., and glass frit B includes Bi2O3, SiO2, AgNO3, B2O3, Li2O, Na2O, etc. Distilled water is added to glass frit B during the batching process to fully combine AgNO3 with other oxides, and the mixture is dried to a viscous state before sintering. During the sintering process, laser-enhanced contact optimization technology is used to reduce AgO in the glass to silver microcrystals, thereby improving the electrical performance of the main grid lines. The printed solar cells exhibit reduced damp heat decay, resulting in high module reliability and improved photoelectric conversion efficiency while ensuring high welding tensile strength. The resulting glass powder does not excessively etch the silicon nitride and aluminum oxide passivation layers, and the prepared slurry can be sintered at 650-800℃, which can meet the requirements of the front and back main grid electrodes of TOPCon batteries.

Description

Technical Field

[0001] This invention belongs to the field of solar photovoltaic cell technology, specifically relating to a glass powder for silver paste used in the main grid of TOPCon solar cells and its preparation method. Background Technology

[0002] TOPCon has entered an era of large-scale and rapid development. It is the largest share of the new generation of battery technology. The current production capacity of TOPCon has reached more than 70GW. Compared with conventional P-type crystalline silicon cells, TOPCon has higher efficiency, higher minority carrier lifetime, and lower light-induced degradation and temperature coefficient, which are significant advantages and are currently a research hotspot in solar cell technology.

[0003] TOPCon cells typically use an n-type substrate and a p-type emitter. An Al₂O₃ passivation film and a SiN₂ layer are placed in front of the cell. X The antireflective layer has an ultrathin tunneling oxide layer and an n-type antireflective coating on the back side. + The doped silicon layer effectively suppresses minority carrier recombination and improves electron collection efficiency. Simultaneously, the introduction of Laser Enhanced Contact Optimization (LECO) technology optimizes the entire battery system, enabling precise control over the microstructure of the battery surface. This provides more optimization avenues for the main grid silver paste in TOPCon batteries.

[0004] Furthermore, with the development of the photovoltaic industry and the increasing maturity of the market, photovoltaic modules need to be exposed to the outdoor natural environment for extended periods. External environmental factors such as water vapor, salt spray, high and low temperatures, and sandstorms can all affect the long-term reliability of the modules, especially in some extremely harsh natural environments, where the impact on the modules is even greater. This also places higher demands on the main grid silver paste of solar cells. Traditional TOPCon main grid pastes are generally made from a single glass powder using a melt-quenching method, which makes it difficult to improve the tensile strength and guarantee the electrical performance of the main grid lines. To further improve the photoelectric conversion efficiency of TOPCon cells, the main grid silver paste needs to improve the welding tensile strength to enhance the reliability of the module in harsh environments, and it also needs good electrical performance to conduct the charge carriers collected by the fine grid. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of low welding pull and poor electrical performance of the main grid when printing TOPCon paste using DUP technology. It provides a glass powder for silver paste of TOPCon battery main grid used in LECO technology and its preparation method. The glass powder has good wettability and matching softening temperature. The silver paste prepared has high welding pull and good electrical performance, and the battery has less damp heat decay.

[0006] To achieve the above objectives, the silver-containing glass powder for the TOPCon crystalline silicon solar cell grid paste provided by the present invention is prepared by the following method:

[0007] Step 1: According to the following mass percentages: 20%–60% PbO or Pb₂O₃ or Pb₃O₄ or PbF₂, 2%–30% SiO₂, 0%–10% Al₂O₃ or AlF₃, 5%–40% B₂O₃, 0%–30% Bi₂O₃, 0%–10% ZnO, 0%–10% MgO, 0%–5% TiO₂ or TiF₄, 0%–30% TeO₂, 0%–5% As₂O₅, 0%–5% CaO, 1%–5% Li₂O or LiF, 1%–5% Na₂O or NaF. Weigh out 0%–5% K₂O and 0%–5% WO₃ and place each component in an agate mortar. Grind for 20–30 minutes to ensure thorough mixing. Then place the mixed components in a corundum crucible and clamp the crucible into a high-temperature electric furnace preheated to 1100–1300°C. Melt the glass at high temperature for 10–40 minutes, shaking the molten glass in the furnace every 10 minutes to ensure uniform melting of each component. Then remove the corundum crucible and pour the molten glass into a roller mill for cold rolling. Collect the cold-rolled glass fragments to obtain glass frit A.

[0008] Step 2: Weigh out each component according to the following mass percentages: 20%–70% Bi₂O₃, 2%–30% SiO₂, 5%–35% AgNO₃, 0%–15% AlF₃, 5%–30% B₂O₃, 0%–10% MgO, 0%–10% Cr₂O₃, 0%–10% NiO, 0%–5% SO₃, 0%–5% TiF₄, 0%–5% Fe₂O₃, 0%–5% CaO, 1%–5% Li₂O / LiF, 1%–5% Na₂O / NaF, 0%–5% K₂O, and 0%–5% MnO₂. First, add AgNO₃ to the corundum crucible and then add distilled water, stirring thoroughly. Mix thoroughly, then add the remaining components and stir for 5-10 minutes to ensure complete mixing. Then, place the corundum crucible in an oven at 50-70°C and dry for 2-5 hours until the mixture becomes viscous. Remove the crucible and place it in a high-temperature electric furnace preheated to 1100-1300°C. Melt the mixture at high temperature for 20-40 minutes, shaking the molten glass in the furnace every 10 minutes to ensure uniform melting of all components. Remove the corundum crucible and pour the molten glass into a roller mill for cold rolling. Collect the cold-rolled glass fragments to obtain glass frit B.

[0009] Step 3: Grind glass frit A and glass frit B into glass powder using an air jet mill at a mass ratio of 1.5 to 2:1, controlling the particle size to be below 4 μm.

[0010] Step 4: Place the glass powder pulverized in Step 3 into a high-temperature electric furnace at 600-1000℃ for 5-10 minutes. After cold rolling the resulting mixed glass melt, obtain glass frit C. Pulverize glass frit C with an air jet mill until the particle size is below 4μm to obtain glass powder for TOPCon crystalline silicon solar cell grid paste.

[0011] In step 2 above, the preferred ratio of the amount of distilled water added to the mass of the melted glass block B is 0.5 to 1:1.

[0012] Furthermore, in steps 1 and 2 above, the high-temperature electric furnace preheated to 1100-1300℃ is first heated to 500℃ at a rate of 5℃ / min, held at that temperature for 1 hour, and then heated to 1100-1300℃ at a rate of 10℃ / min.

[0013] Furthermore, in steps 3 and 4, the conditions for pulverizing by the airflow pulverizer are as follows: the air pressure gauge of the air compressor is 0.5 MPa, the pressure reducing valve of the airflow pulverizer is 0.1 to 0.5 MPa, the pressure reducing valve of the pulse meter is 0.3 to 0.8 MPa, and the particle size of the pulverized glass powder must meet the following requirements: D50: 1.5 to 3.5 μm, D90: 3.5 to 4.5 μm.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. This invention involves adding AgNO3 to glass, pre-adding distilled water during the preparation process to ensure its complete combination with other oxides, and drying it to a viscous state before firing. The resulting main grid silver paste can be optimized using laser-enhanced contact technology. During sintering, the AgO remaining in the glass component of the paste is reduced to silver microcrystals, thereby significantly improving the electrical performance of the main grid line. This not only ensures high welding tensile strength of the solar cell but also enhances the photoelectron conduction capability of the main grid line, thus improving the photoelectric conversion efficiency and providing a new approach for the preparation of photovoltaic cell module materials.

[0016] 2. This invention utilizes cold rolling and an airflow pulverizer to better match the different temperatures of the chain sintering process by mixing glass powder, effectively improving the welding pull of the main grid silver paste. More importantly, by improving the preparation process of silver-containing glass powder and using laser-enhanced contact optimization technology (LECO), the electrical performance of the main grid line is further improved. This not only meets the high welding pull requirements of the main grid silver paste, but also improves the photoelectric conversion efficiency of the TOPCon cell by reducing the resistance of the main grid line, providing a new development idea for the development of green and environmentally friendly photovoltaic modules.

[0017] 3. When the main grid silver paste prepared by this invention is printed onto the TOPCon cell, the cell has less damp heat degradation conversion efficiency and less welding pull force of the main grid silver paste during damp heat degradation, which greatly improves the reliability of photovoltaic modules when operating in harsh environments.

[0018] 4. The main grid silver paste prepared by the glass powder of this invention, after sintering, only bonds to the passivation layer substrate material (silicon nitride substrate) on the surface of the battery, providing excellent mechanical bonding force. It does not form metallization ohmic contacts with the PN junction substrate material constituting the silicon battery. This effectively reduces metal recombination on the battery surface and improves the photoelectric conversion efficiency of the battery. Furthermore, the preparation steps of this invention are simple, the required cost is low, and it conforms to the manufacturing process of battery cells. Attached Figure Description

[0019] Figure 1 These are high-temperature microscope images of different glass powders.

[0020] Figure 2 This is a schematic diagram of the contact angles of different glass powders after melting on a silicon substrate.

[0021] Figure 3 These are cross-sectional views of different main grid silver pastes after sintering. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. However, the scope of protection of the present invention is not limited to the following embodiments. Any omissions, substitutions or modifications made by those skilled in the art based on the embodiments of the present invention will be included in the scope of protection of the present invention.

[0023] Comparative Example 1

[0024] Weigh out 100g of each component according to the following mass percentages: 40% PbO, 18% SiO2, 4% Al2O3, 20% B2O3, 5% Bi2O3, 2% ZnO, 1% MgO, 1% TiO2, 2% TeO2, 1% Li2O, 2% Na2O, 1.5% K2O, and 2.5% WO3. Place the mixture in an agate mortar and grind for 30 minutes until thoroughly mixed. Then place the mixed components in a corundum crucible. Heat the furnace at a rate of 5℃ / min. The temperature is raised to 500℃ and held for 1 hour. Then, the temperature is raised to 1200℃ at a rate of 10℃ / min. The corundum crucible is clamped into a preheated high-temperature electric furnace and melted at high temperature for 30 minutes. During this period, the molten glass is shaken in the electric furnace every 10 minutes to ensure that the components melt evenly. Then, the corundum crucible is removed and the molten glass is poured into a roller mill for cold rolling. The cold-rolled glass fragments are collected and then subjected to vibration crushing and airflow crushing to obtain glass powder C1 with a particle size D100 < 4μm.

[0025] Comparative Example 2

[0026] Step 1: Weigh out 100g of each component according to the following mass percentages: 40% PbO, 18% SiO2, 4% Al2O3, 20% B2O3, 5% Bi2O3, 2% ZnO, 1% MgO, 1% TiO2, 2% TeO2, 1% Li2O, 2% Na2O, 1.5% K2O, and 2.5% WO3. Place them in an agate mortar and grind for 30 minutes to ensure thorough mixing. Then place the well-mixed components into a corundum crucible. Inside the crucible; the high-temperature electric furnace is heated to 500°C at a rate of 5°C / min and held for 1 hour, then heated to 1200°C at a rate of 10°C / min. The corundum crucible is clamped into the preheated high-temperature electric furnace and melted at high temperature for 30 minutes, during which the molten glass is shaken in the electric furnace every 10 minutes to ensure that the components melt evenly. Then the corundum crucible is clamped out, the molten glass is poured into a roller mill for cold rolling, and the cold-rolled glass fragments are collected to obtain glass frit A2.

[0027] Step 2: Weigh out 100g of each component according to the following mass percentages: 40% Bi₂O₃, 25% AgNO₃, 18% SiO₂, 0.5% AlF₃, 5% B₂O₃, 1.5% MgO, 3% NiO, 1.5% SO₃, 1.2% TiF₄, 1.3% Fe₂O₃, 0.5% Li₂O, 1% Na₂O, and 1.5% MnO₂. Place them in an agate mortar and grind for 20 minutes to ensure thorough mixing. Then, combine the well-mixed components... The components are placed in a corundum crucible; the high-temperature electric furnace is heated to 500°C at a rate of 5°C / min and held for 1 hour, then heated to 1200°C at a rate of 10°C / min. The corundum crucible is then clamped into the preheated high-temperature electric furnace and melted at high temperature for 30 minutes, during which the molten glass is shaken in the furnace every 10 minutes to ensure that the components melt evenly; then the corundum crucible is removed, the molten glass is poured into a roller mill for cold rolling, and the cold-rolled glass fragments are collected to obtain glass frit B2.

[0028] Step 3: Grind glass frit A2 and glass frit B2 at a mass ratio of 2:1 using an air jet mill. The conditions for controlling the air jet mill are: air compressor pressure gauge 0.5MPa, air jet mill pressure relief valve 0.1-0.5MPa, pulse meter pressure relief valve 0.3-0.8MPa. After grinding, the glass powder particle size reaches D50: 1.5-3.5μm and D90: 3.5-4.5μm, obtaining silver-containing glass powder C2.

[0029] Example 1

[0030] Step 1: Weigh out 100g of each component according to the following mass percentages: 40% PbO, 18% SiO2, 4% Al2O3, 20% B2O3, 5% Bi2O3, 2% ZnO, 1% MgO, 1% TiO2, 2% TeO2, 1% Li2O, 2% Na2O, 1.5% K2O, and 2.5% WO3. Place them in an agate mortar and grind for 30 minutes to ensure thorough mixing. Then place the well-mixed components into a corundum crucible. Inside the crucible; the high-temperature electric furnace is heated to 500°C at a rate of 5°C / min and held for 1 hour, then heated to 1200°C at a rate of 10°C / min. The corundum crucible is clamped into the preheated high-temperature electric furnace and melted at high temperature for 30 minutes, during which the molten glass is shaken in the electric furnace once every 10 minutes to ensure that the components melt evenly. Then the corundum crucible is clamped out, the molten glass is poured into a roller mill for cold rolling, and the cold-rolled glass fragments are collected to obtain glass frit A3.

[0031] Step 2: Weigh out 100g of each component according to the following mass percentages: 40% Bi₂O₃, 25% AgNO₃, 18% SiO₂, 0.5% AlF₃, 5% B₂O₃, 1.5% MgO, 3% NiO, 1.5% SO₃, 1.2% TiF₄, 1.3% Fe₂O₃, 0.5% Li₂O, 1% Na₂O, and 1.5% MnO₂. First, add AgNO₃ to the corundum crucible and add 50g of distilled water, stirring until fully mixed. Then add the remaining components and stir for 10 minutes to ensure thorough mixing. The mixture is homogenized, and then the corundum crucible is placed in an oven at 60°C for 5 hours and then removed. The temperature of the high-temperature electric furnace is increased to 500°C at a rate of 5°C / min and held for 1 hour. Then, the temperature is increased to 1200°C at a rate of 10°C / min. The corundum crucible taken from the oven is clamped into the preheated high-temperature electric furnace and melted at high temperature for 30 minutes. During this period, the molten glass is shaken in the electric furnace every 10 minutes to ensure that the components are melted evenly. Then, the corundum crucible is clamped out, and the molten glass is poured into a roller mill for cold rolling. The glass fragments after cold rolling are collected to obtain glass frit B3.

[0032] Step 3: Grind glass frit A3 and glass frit B3 at a mass ratio of 2:1 using an air jet mill. The conditions for controlling the air jet mill are as follows: air compressor pressure gauge 0.5MPa, air jet mill pressure relief valve 0.1-0.5MPa, pulse meter pressure relief valve 0.3-0.8MPa. After grinding, the glass powder particle size reaches D50: 1.5-3.5μm and D90: 3.5-4.5μm.

[0033] Step 4: Place the glass powder pulverized in Step 3 into a high-temperature electric furnace at 900℃ for 8 minutes. After cold rolling the resulting mixed glass melt, obtain glass frit C3. Pulverize the glass frit C3 using an air jet mill according to the pulverization conditions in Step 3 to obtain silver-containing glass powder C3 for TOPCon crystalline silicon solar cell grid paste.

[0034] Depend on Figure 1 As can be seen, compared with glass powder C1 in Comparative Example 1, the softening point of glass powder C2 prepared by adding AgNO3 in Comparative Example 2 decreased from 699℃ to 672℃. After optimizing the sintering process of AgNO3-containing glass powder in Example 1, the softening point of the resulting glass powder C3 was further reduced to 612℃, while retaining the excellent wettability of glass powder C2.

[0035] Depend on Figure 2 It can be seen that, compared with glass powder C1 in Comparative Example 1, the wettability of glass powder C2 prepared by adding AgNO3 in Comparative Example 2 is greatly improved. After optimizing the sintering process of AgNO3-containing glass powder in Example 1, its softening point was further reduced, while its excellent wettability was also retained.

[0036] Silver pastes were prepared using glass powder C1 prepared in Comparative Example 1, glass powder C2 prepared in Comparative Example 2, and glass powder C3 prepared in Example 1, respectively. The mass percentage composition of the silver pastes was: 85% silver powder, 2% glass powder, 12.5% ​​organic carrier, and 0.5% dispersant. The organic carrier included 82% organic solvent, 6% binder, 1% thixotropic agent, 7% surfactant, and 4% coupling agent. The components were weighed and added to a sample container, then manually pre-stirred, and then mixed evenly in a planetary mixer. The mixture was then dispersed to below 10 μm on a three-roll mill and filtered through a 400-mesh sieve to obtain a uniformly dispersed grid silver paste with a viscosity of 159 Pa·s (25°C). The paste was screen-printed onto the front of a TOPCon cell, and its electrical performance and degree of silicon wafer erosion were tested. Subsequently, 0.3 mm solder ribbon was used for soldering at 350°C onto 0.8 mm × 1.2 mm pads. Six solder joints were randomly selected from each sample, and the tensile force was measured using a horizontal tensile tester. The average value was taken. The test results are shown in Table 1 and Figure 3 To test the damp heat degradation of the battery, 15 printed battery cells were randomly selected from each of the same batch and placed in an environmental chamber at 85°C and 85% relative humidity for 900 hours. IV test and welding tensile test were performed every 300 hours. The test results are shown in Table 2.

[0037] Table 1 Welding pull and series resistance of different busbar silver pastes

[0038]

[0039] Table 2 Battery efficiency damp heat degradation and welding tensile strength

[0040]

[0041]

[0042] As shown in Table 1, the main grid silver paste S2-C2 prepared using glass powder C2 has a higher pull strength and a lower series resistance. The main grid silver paste S3-C3 prepared using glass powder C3 obtained after optimizing the sintering process containing AgNO3 glass powder in Example 1 has a further reduced series resistance and maintains a high pull strength level.

[0043] As shown in Table 2, the S3-C3 solar cell printed with the main grid silver paste prepared with glass powder C3 showed the least efficiency degradation after 300h, 600h, and 900h damp heat tests. Furthermore, the welding tensile strength of the S2-C2 and S3-C3 solar cells printed with the main grid silver paste prepared with glass powder C2 and C3 remained greater than 1N after 600h of damp heat testing, although the welding tensile strength of S3-C3 was higher than that of S2-C2. This indicates that the main grid silver paste prepared with glass powder C3 has better reliability in harsh natural environments.

[0044] Depend on Figure 3 It can be seen that, except for the poor contact of the main gate silver paste S1-C1 prepared with glass powder C1, the main gate silver pastes S2-C2 and S3-C3 prepared with glass powder C2 and glass powder C3 have good contact with the emitter, can provide greater adhesion, and do not excessively corrode the emitter.

Claims

1. A method for preparing glass powder for the grid paste of TOPCon crystalline silicon solar cells, characterized in that... Includes the following steps: Step 1: According to the following mass percentages: 20%–60% PbO or Pb₂O₃ or Pb₃O₄ or PbF₂, 2%–30% SiO₂, 0%–10% Al₂O₃ or AlF₃, 5%–40% B₂O₃, 0%–30% Bi₂O₃, 0%–10% ZnO, 0%–10% MgO, 0%–5% TiO₂ or TiF₄, 0%–30% TeO₂, 0%–5% As₂O₅, 0%–5% CaO, 1%–5% Li₂O or LiF, 1%–5% Na₂O or NaF. Weigh out 0%–5% K₂O and 0%–5% WO₃ and place each component in an agate mortar. Grind for 20–30 minutes to ensure thorough mixing. Then, place the mixed components in a corundum crucible and clamp the crucible into a high-temperature electric furnace preheated to 1100–1300°C. Melt the glass at high temperature for 10–40 minutes, shaking the molten glass in the furnace every 10 minutes to ensure uniform melting of all components. Then, remove the corundum crucible and pour the molten glass into a roller mill for cold rolling. Collect the cold-rolled glass fragments to obtain glass frit A. Step 2: According to the mass percentage: 20%–70% Bi₂O₃, 2%–30% SiO₂, 5%–35% AgNO₃, 0%–15% AlF₃, 5%–30% B₂O₃, 0%–10% MgO, 0%–10% Cr₂O₃, 0%–10% NiO, 0%–5% SO₃, 0%–5% TiF₄, 0%–5% Fe₂O₃, 0%–5% CaO, 1%–5% Li₂O / LiF, 1%–5% Na₂O / NaF, 0%–5% K₂O 0%–5% MnO2, weigh each component, first add AgNO3 to the corundum crucible and add distilled water, stir to mix thoroughly and evenly, then add the remaining components, stir for 5–10 minutes to mix thoroughly and evenly, then put the corundum crucible into an oven at 50–70°C and dry for 2–5 hours until the mixture becomes viscous, then take it out and clamp it into a high-temperature electric furnace preheated to 1100–1300°C, melt at high temperature for 20–40 minutes, during which the glass melt is shaken once in the electric furnace every 10 minutes to make each component melt evenly; Next, the corundum crucible is clamped out, the molten glass is poured into a double-roll mill for cold rolling, and the glass fragments after cold rolling are collected to obtain glass frit B. Step 3: Grind glass frit A and glass frit B into glass powder using an air jet mill at a mass ratio of 1.5 to 2:1, and control the particle size to be below 4 μm; Step 4: Place the glass powder pulverized in Step 3 into a high-temperature electric furnace at 600-1000℃ for 5-10 minutes. After cold rolling the resulting mixed glass melt, obtain glass frit C. Pulverize glass frit C with an air jet mill until the particle size is below 4μm to obtain glass powder for TOPCon crystalline silicon solar cell grid paste.

2. The method for preparing glass powder for the main grid paste of TOPCon crystalline silicon solar cells according to claim 1, characterized in that: In step 2, the ratio of the amount of distilled water added to the mass of the melted glass block B is 0.5 to 1:

1.

3. The method for preparing glass powder for the main grid paste of TOPCon crystalline silicon solar cells according to claim 1, characterized in that: In steps 1 and 2, the high-temperature electric furnace preheated to 1100-1300℃ is first heated to 500℃ at a rate of 5℃ / min, held at that temperature for 1 hour, and then heated to 1100-1300℃ at a rate of 10℃ / min.

4. The method for preparing glass powder for the grid paste of TOPCon crystalline silicon solar cells according to claim 1, characterized in that: In steps 3 and 4, the conditions for pulverizing by the airflow pulverizer are as follows: the air pressure gauge of the air compressor is 0.5 MPa, the pressure reducing valve of the airflow pulverizer is 0.1 to 0.5 MPa, the pressure reducing valve of the pulse meter is 0.3 to 0.8 MPa, and the particle size of the glass powder after pulverization must meet the requirements of D50: 1.5 to 3.5 μm and D90: 3.5 to 4.5 μm.

5. Glass powder for the grid paste of TOPCon crystalline silicon solar cells prepared by the method according to any one of claims 1 to 4.

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