Glass powder for front conductive paste of TOPCon solar cell and preparation method thereof

Abstract

This invention discloses a glass powder for the front conductive paste of TOPCon solar cells and its preparation method, belonging to the field of solar cell technology. The glass powder comprises a main glass material A and a secondary glass material B, with a weight ratio of 5:1 to 1:5. The main glass material A contains B2O3, SiO2, Bi2O3, Al2O3, Fe2O3, Ga2O3, and Li2O; the secondary glass material B contains B2O3, SiO2, Bi2O3, V2O5, Al2O3, and ZnO. The preparation method includes batching, melting, molding and cooling, and ball milling steps. When used in the front conductive paste of TOPCon cells, this glass powder can synergistically control corrosivity and electrical performance, achieving high photoelectric conversion efficiency while significantly reducing acetic acid degradation of the cell, thus resolving the contradiction between high efficiency and low environmental reliability in TOPCon cells. This invention has a simple process and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to a glass powder for the front conductive paste of TOPCon solar cells and its preparation method. Background Technology

[0002] TOPCon (Tunnel Oxide Passivated Contact) solar cells have become a research hotspot in the industry due to their excellent photoelectric conversion efficiency. Their front electrode is typically prepared using silver paste, where glass powder plays a crucial role. During sintering, it needs to moderately etch the silicon nitride antireflection layer and passivation layer on the cell surface to achieve good ohmic contact with the silicon substrate, while avoiding excessive etching that could exacerbate carrier recombination and affect the open-circuit voltage and fill factor.

[0003] Traditional glass powders mostly use the PbO system, which often struggles to balance corrosivity and passivation protection: excessive corrosivity damages the passivation layer, leading to increased recombination current and poorer environmental degradation resistance; insufficient corrosivity results in excessively high contact resistance, affecting fill factor and efficiency. While some glass powder components can improve contact performance, their poor acetic acid resistance causes significant degradation in photoelectric conversion efficiency after acetic acid environmental testing, impacting long-term battery reliability. Current technologies struggle to simultaneously achieve both high photoelectric conversion efficiency and low acetic acid degradation, often sacrificing one to ensure the other, thus limiting the industrial application of TOPCon batteries.

[0004] Therefore, developing a glass powder with controllable corrosion, low contact resistance, excellent resistance to acetic acid degradation, and high photoelectric conversion efficiency is crucial for improving the efficiency and long-term reliability of TOPCon batteries. Summary of the Invention

[0005] To address the problems of uncontrollable corrosion, high acetic acid attenuation, and difficulty in balancing photoelectric conversion efficiency and reliability in the glass powder used in the front conductive paste of TOPCon solar cells in the prior art, this invention provides a composite glass powder system, along with a preparation method for the glass powder, a conductive paste based on the glass powder, and its preparation method, achieving synergistic optimization of low corrosion, low contact resistance, low acetic acid attenuation, and high photoelectric conversion efficiency.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a glass powder for the front conductive paste of TOPCon solar cells, comprising a main glass powder A and a secondary glass powder B, wherein the weight ratio of the main glass powder A to the secondary glass powder B is 5:1 to 1:5. The main glass material A comprises the following components by weight percentage: 5-30% B2O3, 1-15% SiO2, 10-70% Bi2O3, 2-20% Al2O3, 5-15% Fe2O3, 0-10% Ga2O3, and 0-5% Li2O. The secondary glass material B comprises the following components by weight percentage: 5-40% B2O3, 1-35% SiO2, 10-60% Bi2O3, 1-10% V2O5, 1-10% Al2O3, and 0-5% ZnO.

[0007] This invention provides a composite glass powder system specifically for the conductive paste on the front side of TOPCon solar cells. Through a specific ratio and composition design of the main glass powder A and the secondary glass powder B, it successfully solves the prominent contradiction of severe acetic acid degradation faced by current TOPCon cells in pursuing high photoelectric conversion efficiency. In this system, the main glass powder A is based on Bi2O3, and the introduction of Fe2O3 and Al2O3 effectively strengthens the glass network structure, significantly improving its resistance to acetic acid corrosion. Simultaneously, the addition of Ga2O3 and Li2O optimizes the conductivity and moderate corrosion activity of the glass, which is beneficial for forming good ohmic contacts and controlling excessive corrosion of the silicon nitride passivation layer. The secondary glass powder B uses V2O5 as a key fluxing component, effectively lowering the overall softening point of the glass system and improving wetting and spreading performance at high temperatures. Its combination with the main powder allows for synergistic effects within a wide sintering temperature window. The conductive paste using this glass powder enables TOPCon cells to achieve high conversion efficiency while stably controlling the acetic acid degradation value at a low level, effectively balancing the dual requirements of high efficiency output and high environmental reliability.

[0008] Optionally, the glass powder has a particle size D50 of 1.0-2.5 μm.

[0009] This particle size range ensures that the glass powder is uniformly dispersed in the conductive slurry and forms sufficient contact with the silver powder and silicon nitride film during sintering, avoiding poor contact or localized excessive corrosion caused by uneven particle size.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned glass powder, characterized by comprising the following steps: (1) Weigh each component of the main glass material A and the secondary glass material B, and mix them evenly to obtain the main glass material A mixed raw material and the secondary glass material B mixed raw material; (2) The main glass material A mixture and the secondary glass material B mixture are melted to obtain main glass material A molten glass and secondary glass material B molten glass; (3) The main glass material A and the secondary glass material B are respectively molded and cooled to room temperature to obtain the main glass material A glass blank and the secondary glass material B glass blank; (4) Add a dispersing medium to the main glass material A glass preform and the secondary glass material B glass preform respectively and perform ball milling to obtain the main glass material A and the secondary glass material B; (5) Mix the main glass material A and the secondary glass material B obtained in step (4) at a weight ratio of 5:1-1:5 to obtain the glass powder for the front conductive paste of the TOPCon solar cell.

[0011] Optionally, in step (2), the melting treatment temperature is 1000-1400℃ and the time is 30-60 min. In step (4), the dispersion medium is anhydrous ethanol and the ball milling treatment time is 3-12 h.

[0012] Thirdly, the present invention provides a conductive paste for the front side of a TOPCon solar cell, characterized in that it comprises the glass powder described in the first aspect.

[0013] Optionally, the conductive paste comprises the following components by weight percentage: 88-90% silver powder, 0.5-1% aluminum powder, 1-2% of the main glass material A, 0.2-1% of the secondary glass material B, 5-9% organic carrier, and 0.5-1.5% alcohol ester twelve.

[0014] Fourthly, the present invention provides a method for preparing the above-mentioned conductive paste, characterized by comprising the following steps: weighing each component according to the ratio and mixing them evenly; rolling them in a three-roll mill to obtain a paste with a fineness of 4-6 μm; filtering to obtain the TOPCon solar cell front conductive paste.

[0015] Beneficial effects 1. By combining the main glass material A and the auxiliary glass material B, precise control of corrosion resistance is achieved. The main material ensures moderate etching ability and excellent acetic acid resistance, while the auxiliary material lowers the overall softening point and improves wettability. Together, they achieve low contact resistance and high open-circuit voltage within a wider sintering window, thereby improving conversion efficiency.

[0016] 2. In the glass material A of this invention, Bi2O3 replaces traditional PbO, reducing glass corrosivity. Combined with the structural regulation effect of SiO2, the corrosion depth of the silicon nitride film can be precisely controlled, reducing silicon substrate surface recombination and improving the open-circuit voltage of the battery. In the secondary glass material B, V2O5 and Bi2O3 synergistically lower the glass softening point, resulting in excellent fluidity at low firing temperatures.

[0017] 3. The synergistic effect of Al2O3 and Fe2O3 in the main glass material A of this invention significantly improves the acetic acid resistance of the glass powder, so that the photoelectric conversion efficiency decay value of the battery cell is reduced after the acetic acid environment test, ensuring the long-term reliability of the battery.

[0018] 4. The preparation processes of glass powder and conductive paste both use conventional equipment, and the raw materials are all commercially available products, requiring no special customization, making them suitable for large-scale industrial production. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0020] Unless otherwise specified, the following embodiments are all conventional experimental methods and operating procedures in the art.

[0021] Example 1 A glass powder for conductive paste on the front side of a TOPCon solar cell comprises a main glass powder A and a secondary glass powder B in a weight ratio of 3:1. The main glass powder A has the following composition by weight percentage: 20% B2O3, 8% SiO2, 46.5% Bi2O3, 15% Al2O3, 6% Fe2O3, 3% Ga2O3, and 1.5% Li2O. The formula for secondary glass material B, by weight percentage, is: 30% B2O3, 10% SiO2, 48% Bi2O3, 5% V2O5, 5% Al2O3, and 2% ZnO.

[0022] Preparation steps: (1) Weigh each component of the main glass material A and the secondary glass material B, and mix them evenly to obtain the main glass material A mixed raw material and the secondary glass material B mixed raw material; (2) The main glass material A mixture and the secondary glass material B mixture are placed in a high-temperature furnace and melted at 1350°C for 45 minutes to obtain the main glass material A glass liquid and the secondary glass material B glass liquid; (3) The main glass material A and the secondary glass material B are rolled into sheets by a double-roll cold rolling mill and cooled to room temperature to obtain the main glass material A glass blank and the secondary glass material B glass blank; (4) Add anhydrous ethanol to the glass blanks of the main glass material A and the glass blanks of the secondary glass material B respectively, and ball mill vertically for 7 hours to obtain the main glass material A and the secondary glass material B.

[0023] (5) The main glass material A and the secondary glass material B obtained in step (4) are mixed evenly according to the weight ratio of 3:1 as described in claim 1 to obtain the glass powder for the front conductive paste of the TOPCon solar cell.

[0024] The particle size D50 of the prepared main glass material A is 1.35 μm; the particle size D50 of the prepared main glass material B is 1.50 μm.

[0025] A TOPCon solar cell front conductive paste, by weight percentage, comprises the following components: 89% silver powder, 0.8% aluminum powder, 1.5% main glass material A, 0.5% secondary glass material B, 7.2% organic carrier, and 11% alcohol ester. Preparation steps of conductive paste: Weigh each component according to the formula, mix them evenly using a centrifugal homogenizer, roll them 6 times with a three-roll mill to obtain a TOPCon solar cell front conductive paste with a fineness of 4-6μm, filter it through a 500-mesh stainless steel filter to obtain the finished TOPCon solar cell front conductive paste.

[0026] The organic carrier was prepared in-house using the following method: By weight, 15 parts dimethyl adipate, 10 parts diethylene glycol dibutyl ether, 10 parts dodecyl alcohol ester, 33 parts 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 1.5 parts ethyl cellulose, 10 parts acrylic resin, 1.5 parts polyvinyl butyral, 6 parts dispersant, 3 parts thixotropic polyamide, and 10 parts dimethyl silicone oil with a viscosity of 100 CPS are mixed and stirred evenly. The mixture is heated and stirred at a constant temperature of 60-80℃ for 1-2 hours, and dispersed at a high speed of 2000 rpm using a high-speed disperser. After cooling, the mixture is filtered to prepare the organic carrier.

[0027] The ethyl cellulose, model STD4, was purchased from Dow Chemical Company, USA. The acrylic resin used was ER2602 and was purchased from Kusumoto, Japan. The polyvinyl butyral ester, model B30HH, was purchased from Kuraray, Japan. The dimethyl silicone oil, model KF-96-100CS, was purchased from Shin-Etsu Chemical Co., Ltd., Japan. The dispersant is ED120, purchased from Kusumoto, Japan. The polyamide is model 6500 and was purchased from DISPARON, Japan.

[0028] Example 2 A glass powder for the front conductive paste of a TOPCon solar cell comprises a main glass powder A and a secondary glass powder B in a weight ratio of 5:1. The main glass powder A has the following composition by weight percentage: 30% B₂O₃, 10% SiO₂, 41% Bi₂O₃, 10% Al₂O₃, 5% Fe₂O₃, 2% Ga₂O₃, and 2% Li₂O. The secondary glass powder B has the following composition: 25% B₂O₃, 5% SiO₂, 54% Bi₂O₃, 10% V₂O₅, 3% Al₂O₃, and 3% ZnO. Glass powder preparation steps: Same as in Example 1.

[0029] The particle size D50 of the prepared main glass material A is 1.50 μm; the particle size D50 of the prepared main glass material B is 1.2 μm.

[0030] A TOPCon solar cell front conductive paste, by weight percentage, comprises the following components: 89.2% silver powder, 0.8% aluminum powder, 1.5% main glass material A, 0.3% secondary glass material B, 7.2% organic carrier, and 11% alcohol ester. The preparation steps for the conductive paste are the same as in Example 1.

[0031] The preparation method of the organic carrier is the same as in Example 1.

[0032] Example 3 A glass powder for the front conductive paste of a TOPCon solar cell comprises a main glass powder A and a secondary glass powder B in a weight ratio of 1:2. The main glass powder A has the following composition by weight percentage: 25% B₂O₃, 5% SiO₂, 34.5% Bi₂O₃, 20% Al₂O₃, 8% Fe₂O₃, 5% Ga₂O₃, and 2.5% Li₂O; the secondary glass powder B has the following composition: 15% B₂O₃, 5% SiO₂, 69% Bi₂O₃, 8% V₂O₅, 2% Al₂O₃, and 1% ZnO. Glass powder preparation steps: Same as in Example 1.

[0033] The particle size D50 of the prepared main glass material A is 1.2 μm; the particle size D50 of the prepared main glass material B is 1.45 μm.

[0034] A TOPCon solar cell front conductive paste, by weight percentage, comprises the following components: 89.2% silver powder, 0.8% aluminum powder, 1.3% main glass material A, 0.5% secondary glass material B, 7.2% organic carrier, and 11% alcohol ester. The preparation steps for the conductive paste are the same as in Example 1.

[0035] The preparation method of the organic carrier is the same as in Example 1.

[0036] Performance testing The conductive pastes from Examples 1-3 were printed on the front side of TOPCon solar cells, which were then sintered using conventional methods to produce the solar cells. The electrical performance and acetic acid degradation values ​​were measured using an offline solar cell IV tester (model KP-X-FXJ) from Nanjing Lixite Optoelectronics Technology Co., Ltd.

[0037] The acetic acid decay test method is as follows: 1. Take 10 experimental solar cells and use an offline IV tester to test the IV performance of the solar cells before degradation, and calculate the average efficiency before degradation.

[0038] 2. Weigh 18.9g of acetic acid, 345g of potassium chloride, and 582g of pure water using an electronic balance and pour them into the acetic acid test chamber. 3. Arrange the battery cells neatly in the battery cell basket, and place a fake cell at the top and bottom.

[0039] 4. Place the battery cell basket in the acetic acid test chamber, ensuring that the battery cells do not come into contact with the acetic acid test chamber. 5. Put the lid on the acetic acid test chamber, and then seal the acetic acid test chamber with stretch film.

[0040] 6. Open the oven door, place the acetic acid test chamber inside the oven, and close the door.

[0041] 7. Turn on the power switch, set the oven temperature to 85℃ and the time to 1200min, and you can start the test.

[0042] 8. After the oven stops cooling down to room temperature, remove the battery cell basket, let it dry, and then test the IV performance of 10 battery cells. Calculate the average efficiency after degradation. Divide the efficiency difference before and after acetic acid degradation by the efficiency before acetic acid degradation to obtain the percentage of efficiency degradation.

[0043] The results are shown in Table 1.

[0044] Table 1

[0045] As shown in Table 1, the TOPCon cells prepared using the front-side conductive paste of the glass powder of this invention all exhibit high photoelectric conversion efficiency, high open-circuit voltage, and low series resistance, while the acetic acid decay values ​​are all controlled at a low level. This invention successfully balances the contradiction between high efficiency and low decay, demonstrating the synergistic advantages of the main and auxiliary glass powder composite system.

Claims

1. A glass powder for a front conductive paste of a TOPCon solar cell, characterized by, It includes a main glass material A and a secondary glass material B, wherein the weight ratio of the main glass material A to the secondary glass material B is 5:1 to 1:5; The main glass material A comprises the following components by weight percentage: 5-30% B2O3, 1-15% SiO2, 10-70% Bi2O3, 2-20% Al2O3, 5-15% Fe2O3, 0-10% Ga2O3 and 0-5% Li2O; The secondary glass material B comprises, by weight percentage, the following components: 5-40% B2O3, 1-35% SiO2, 10-60% Bi2O3, 1-10% V2O5, 1-10% Al2O3 and 0-5% ZnO.

2. The glass powder for a front-side conductive paste of a TOPCon solar cell according to claim 1, characterized by, The particle size D50 of the glass powder used in the conductive paste on the front side of the TOPCon solar cell is 1.0-2.5μm.

3. A method for preparing glass powder for the front conductive paste of a TOPCon solar cell as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Weigh each component of the main glass material A and the secondary glass material B, and mix them evenly to obtain the main glass material A mixed raw material and the secondary glass material B mixed raw material; (2) The main glass material A mixture and the secondary glass material B mixture are melted to obtain main glass material A molten glass and secondary glass material B molten glass; (3) The main glass material A and the secondary glass material B are respectively molded and cooled to room temperature to obtain the main glass material A glass blank and the secondary glass material B glass blank; (4) Add a dispersing medium to the main glass material A glass preform and the secondary glass material B glass preform respectively and perform ball milling to obtain the main glass material A and the secondary glass material B; (5) Mix the main glass material A and the secondary glass material B obtained in step (4) at a weight ratio of 5:1-1:5 to obtain the glass powder for the front conductive paste of the TOPCon solar cell.

4. The preparation method according to claim 3, characterized in that, In step (2), the melting temperature is 1000-1400℃.

5. The preparation method according to claim 3, characterized in that, In step (2), the melting treatment time is 30-60 min.

6. The preparation method according to claim 3, characterized in that, In step (4), the ball milling process takes 3-12 hours.

7. The preparation method according to claim 3, characterized in that, In step (4), the dispersion medium is anhydrous ethanol.

8. A conductive paste for the front side of a TOPCon solar cell, characterized in that, This includes the glass powder used in the front conductive paste of the TOPCon solar cell as described in claim 1.

9. The TOPCon solar cell front conductive paste according to claim 8, characterized in that, The composition comprises, by weight percentage: 88-90% silver powder, 0.5-1% aluminum powder, 1-2% primary glass frit A as described in claim 1, 0.2-1% secondary glass frit B as described in claim 1, 5-9% organic carrier, and 0.5-1.5% alcohol ester twelve.

10. A method for preparing the front conductive paste of a TOPCon solar cell as described in claim 9, characterized in that, Includes the following steps: Weigh each component according to the ratio, mix them evenly, place them in a three-roll mill for rolling, and obtain a TOPCon solar cell front conductive paste with a fineness of 4-6μm. Filter to obtain the TOPCon solar cell front conductive paste.

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