Glass powder for PERC back silver paste, preparation method and application thereof

Abstract

The present application relates to the field of silver paste for PERC, and particularly relates to a glass powder for silver paste of the back of PERC, a preparation method and application thereof.The glass powder is a two-component glass powder including glass powder A and glass powder B; the glass powder A at least includes: SiO2, CuO, MnO2, TiO2, Bi2O3, TeO2, B2O3 and Sb2O3; and the glass powder B at least includes: SiO2, CuO, MnO2, PbO, TiO2, TeO2, B2O3 and BaCO3.A glass powder for silver paste capable of effectively solving the problems of sintering range, high adhesion and low corrosion at the same time is provided in the application, which can effectively protect the contact surface of the silicon wafer and the silver layer, and provides a new direction for improving the photoelectric conversion efficiency of the PERC cell for the person skilled in the art.

Description

Technical Field

[0001] This invention relates to the field of silver paste for PERC, and more particularly to a glass powder for PERC backside silver paste, its preparation method, and its application. Background Technology

[0002] In recent years, passivated emitter and back surface passivated cells (PERC) have attracted increasing attention from researchers in the battery field because their back silver electrode no longer directly contacts the silicon cell, reducing carrier recombination on the back surface of the cell and thus significantly improving the photoelectric conversion efficiency. Improvements to their performance are ongoing.

[0003] However, due to the presence of the passivation layer, the back silver electrode cannot directly contact the silicon solar cell, resulting in reduced adhesion between the silver electrode and the silicon solar cell, affecting the reliability of the silicon wafer. If the glass powder in the back silver paste corrodes the back passivation layer of the silicon solar cell during sintering, although it can improve adhesion, the corrosiveness of the silver layer will greatly damage the passivation layer, significantly reducing the efficiency of the solar cell. Furthermore, this corrosion will intensify with increasing temperature, while if the sintering temperature is too low, insufficient softening of the glass will occur, further reducing adhesion.

[0004] The prior art CN107721183B provides a glass powder for the back electrode paste of a bifacial PERC solar cell, which adopts a Pb-Bi-B main system to form a glass powder composition. Although it claims that the prepared composition can adapt to the thinner passivation film thickness of bifacial PERC solar cells and has excellent reactivity with the passivation film and good adhesion, it still does not solve the technical problems such as the silver paste sintering range and low corrosion in detail.

[0005] Therefore, in order to solve the above problems, this application provides a glass powder for PERC back-side silver paste, which is applied to the preparation of silver paste, and the resulting silver paste has excellent wide sintering range, high adhesion and low corrosion. Summary of the Invention

[0006] To address the aforementioned problems, the first aspect of this invention provides a glass powder for PERC back-side silver paste, wherein the glass powder is a two-component glass powder comprising glass powder A and glass powder B; glass powder A comprises at least: SiO2, CuO, MnO2, TiO2, Bi2O3, TeO2, B2O3, and Sb2O3; and glass powder B comprises at least: SiO2, CuO, MnO2, PbO, TiO2, TeO2, B2O3, and BaCO3.

[0007] As a preferred embodiment, the glass powder A further includes additive I; additive I is at least two of Cr2O3, WO3, and Y2O3.

[0008] As a preferred embodiment, the auxiliary agent I is Cr2O3, WO3, and Y2O3, with a mass ratio of 0-2:0.5-2.5:0-3.

[0009] As a more preferred embodiment, the mass ratio of Cr2O3, WO3, and Y2O3 is 0.5:1:1.

[0010] As a preferred embodiment, the mass percentage of additive I in glass powder A is 2.5% to 5.5%.

[0011] In this application, by adding Cr2O3, WO3, and Y2O3 to glass powder A, the sintering activity of the glass powder can be effectively reduced, thereby giving the glass powder excellent weak corrosion resistance. This is mainly because the applicant found that when Cr2O3, WO3, and Y2O3 are added, the higher dissociation energy components they bring can directly introduce glass network reinforcing elements into the system. In particular, when the mass ratio of Cr2O3, WO3, and Y2O3 is 0.5:1:1, the viscosity increases with the increase in softening point. Under high-temperature sintering conditions, the softening time of the glass powder is shortened, and the high viscosity can help reduce the flow rate of the glass system in the high-temperature environment, thereby ensuring less corrosion of the silicon wafer surface. While ensuring low corrosion resistance, the open-circuit voltage and conversion efficiency are improved. However, the inventors also found that excessive addition of the above-mentioned additives can cause glass softening to be sluggish, making it impossible to form good silicon wafer contact, thereby causing the silicon wafer and silver layer to detach.

[0012] As a preferred embodiment, the glass powder B further includes additive ⅠⅠ; the additive ⅠⅠ is at least one of AlF3 and PbF2.

[0013] As a preferred embodiment, the auxiliary agent ⅠⅠ is AlF3 and PbF2, with a mass ratio of 0 to 2: 1 to 2.

[0014] As a more preferred embodiment, the auxiliary agent ⅠⅠ is AlF3 and PbF2, with a mass ratio of 1.5:1.

[0015] As a preferred embodiment, the mass percentage of additive ⅠⅠ in glass powder B is 2-4%.

[0016] In this application, by adding AlF3 and PbF2 additives to glass powder B, the high adhesion of the glass powder silver paste system is ensured. This is mainly because the inventors found that the addition of the above-mentioned additives can effectively reduce the softening point of the glass and improve its fluidity and activity; especially when the mass ratio of AlF3 to PbF2 is 1.5:1, it can further ensure that the glass has sufficient softening time under low-temperature sintering conditions, improve the sintering density of the silver layer, and at the same time, the silver layer can form good contact with the silicon wafer, thereby ensuring the low-temperature tensile strength between the silicon wafer and the silver layer.

[0017] As a preferred embodiment, the D50 particle size of glass powder A is 1.5–2.0 μm; and the D50 particle size of glass powder B is 1.5–2.0 μm.

[0018] As a preferred embodiment, the mass ratio of glass powder A to glass powder B is 1-2:1-2.

[0019] As a preferred embodiment, the mass ratio of glass powder A to glass powder B is 1.2 to 1.5:1.

[0020] As a more preferred embodiment, the mass ratio of glass powder A to glass powder B is 1.3:1.

[0021] In this application, the combined use of glass powder A and glass powder B ensures tensile strength and weak corrosion resistance under high temperature conditions with glass powder A, which has a higher softening point, and tensile strength under low temperature conditions with glass powder B, which has a lower softening point. In particular, when the mass ratio of glass powder A to glass powder B is 1.3:1, the dual glass powder system of glass powder A and glass powder B results in good tensile strength and weak corrosion resistance of the PERC back silver paste over a wide sintering range, ensuring tensile strength while promoting the improvement of Uoc and FF.

[0022] The second aspect of the present invention provides a method for preparing the above-mentioned glass powder for PERC back-side silver paste, comprising the following steps: S1: the raw material for preparing glass powder A is subjected to high-temperature melting, water quenching, ball milling, drying and sieving to obtain glass powder A; S2: the raw material for preparing glass powder B is subjected to high-temperature melting, water quenching, ball milling, drying and sieving to obtain glass powder B; S3: glass powder A and glass powder B are mixed in a certain proportion to obtain the final product.

[0023] As a preferred embodiment, the preparation method of the glass powder for the PERC back-side silver paste includes the following steps: S1: Mix the raw materials for preparing glass powder A evenly, melt it at 1450-1550℃, take out the molten glass liquid and quench it with water to obtain molten glass slag, ball mill it for 5-6 hours, dry it, and finally sieve it to obtain glass powder A; S2: Mix the raw materials for preparing glass powder B evenly, melt it at 1400-1500℃, take out the molten glass liquid and quench it with water to obtain molten glass slag, ball mill it for 5-6 hours, dry it, and finally sieve it to obtain glass powder B; S3: Mix glass powder A and glass powder B in a certain proportion to obtain the final product.

[0024] A second aspect of the present invention provides an application of the glass powder used in the back-side silver paste of PERC, including the application of the glass powder in silver paste for solar cells.

[0025] As a preferred embodiment, the composition of the silver paste for solar cells, by mass percentage, includes at least: 0.5-1% glass powder A, 0.5-1% glass powder A, 50-65% silver powder, 1-5% organic solvent, and the balance being an organic carrier.

[0026] As a preferred embodiment, the silver powder has a D50 particle size of 1.5–2.0 μm and a tap density of 3.5–5.0 g / cm³. 3 Specific surface area 1.0–2.0 m² 2 / g.

[0027] As a preferred embodiment, the organic solvent is at least two of the following: dodecyl alcohol ester, terpineol, dimethyl adipic acid, and aliphatic hydrocarbon.

[0028] As a preferred embodiment, the organic carrier is composed of ethyl cellulose, dispersant DumeeTDO, DBE, Texanol Ester Alcohol, butyl carbitol, and butyl carbitol acetate.

[0029] Beneficial effects:

[0030] 1. This application provides a glass powder for silver paste that can effectively solve the problems of sintering range, high adhesion and low corrosion at the same time. It can effectively protect the contact surface between silicon wafer and silver layer, providing a new direction for those skilled in the art to improve the photoelectric conversion efficiency of PERC cells.

[0031] 2. This application provides a glass powder for silver paste on the back of PERC batteries. Its preparation method is simple, the raw materials are simple and readily available, which can greatly reduce labor and time costs and has excellent market value.

[0032] 3. This application provides a glass powder for silver paste on the back of PERC batteries. By adding Cr2O3, WO3, and Y2O3 to glass powder A, the sintering activity of the glass powder can be effectively reduced, thereby giving the glass powder excellent weak corrosion resistance. When Cr2O3, WO3, and Y2O3 are added, the higher dissociation energy components they bring can directly introduce glass network reinforcing elements into the system. In particular, when the mass ratio of Cr2O3, WO3, and Y2O3 is 0.5:1:1, the viscosity increases with the increase of the softening point. Under high-temperature sintering, the softening time of the glass powder is shortened, and the high viscosity can help reduce the flow rate of the glass system in the high-temperature environment, thereby ensuring less corrosion of the silicon wafer surface. While ensuring low corrosion resistance, the open-circuit voltage and conversion efficiency are improved.

[0033] 4. This application provides a glass powder for silver paste on the back of PERC batteries. By adding AlF3 and PbF2 additives to the glass powder B, the high adhesion of the glass powder silver paste system is ensured. The addition of the above additives can effectively reduce the softening point of the glass and improve the fluidity and activity of the glass. In particular, when the mass ratio of AlF3 to PbF2 is 1.5:1, it can further ensure that the glass has sufficient softening time under low temperature sintering conditions, improve the sintering density of the silver layer, and at the same time, the silver layer can form good contact with the silicon wafer.

[0034] 5. This application provides a glass powder for silver paste on the back of a PERC battery, which uses glass powder A and glass powder B together. Glass powder A, with a higher softening point, ensures tensile strength and weak corrosion resistance under high temperature conditions, while glass powder B, with a lower softening point, ensures tensile performance under low temperature conditions. In particular, when the mass ratio of glass powder A to glass powder B is 1.3:1, under the action of the dual glass powder system of glass powder A and glass powder B, the silver paste on the back of the PERC battery has good tensile performance and weak corrosion resistance over a wide sintering range, ensuring tensile strength while promoting the improvement of Uoc and FF. Attached Figure Description

[0035] Figure 1 The PL diagrams are for comparative examples and Examples 1, 2, and 3 silver pastes obtained at a sintering temperature of 750°C.

[0036] Figure 2 The PL diagrams are for comparative examples and Examples 1, 2, and 3 silver pastes obtained at a sintering temperature of 790°C.

[0037] Figure 3 The PL diagrams are for comparative examples and Examples 4, 5, and 6 silver pastes obtained at a sintering temperature of 750°C.

[0038] Figure 4 The PL diagrams are for comparative examples and Examples 4, 5, and 6 silver pastes obtained at a sintering temperature of 790°C. Detailed Implementation

[0039] Example 1

[0040] Example 1: The first aspect provides a glass powder for ERC back-side silver paste, wherein the glass powder is a two-component glass powder comprising glass powder A and glass powder B.

[0041] Glass powder A, by mass percentage, comprises: CuO 21%, MnO2 11%, TiO2 5%, Bi2O3 18%, TeO2 4%, B2O3 3.5%, Sb2O3 1%, Cr2O3 0.5%, WO3 1%, and SiO2 as the balance.

[0042] By mass percentage, glass powder B comprises: CuO 20%, MnO2 10.5%, PbO 17%, TiO2 10%, TeO2 3.5%, B2O3 2.5%, BaCO3 2.5%, PbF2 1%, and SiO2 as the balance.

[0043] The weight ratio of glass powder A to glass powder B is 1.3:1.

[0044] The second aspect of this embodiment provides a method for preparing the above-mentioned glass powder, comprising the following steps: S1: The raw materials for preparing glass powder A are mixed evenly, melted at 1530°C, the molten glass liquid is taken out and quenched with water to obtain molten glass slag, ball-milled for 5 hours, dried afterward, and finally sieved to obtain glass powder A; S2: The raw materials for preparing glass powder B are mixed evenly, melted at 1480°C, the molten glass liquid is taken out and quenched with water to obtain molten glass slag, ball-milled for 5 hours, dried afterward, and finally sieved to obtain glass powder B; S3: Glass powder A and glass powder B are mixed in a certain proportion to obtain the final product.

[0045] The third aspect of this embodiment also provides a silver paste for the back of a PERC containing the above-mentioned glass powder. By mass percentage, the raw materials include: 0.8% glass powder A, 0.6% glass powder B, 65% silver powder, 1.6% organic solvent, and the balance being an organic carrier.

[0046] The silver powder has a D50 particle size of 1.7 μm and a tap density of 3.8 g / cm³. 3 Specific surface area 1.5m² 2 / g.

[0047] The organic solvent is composed of dodecayl alcohol, terpineol, and dimethyl adipic acid in a mass ratio of 1:1:1.

[0048] The organic carrier is composed of ethyl cellulose, dispersant DumeeTDO, DBE, Texanol Ester Alcohol, butyl carbitol, and butyl carbitol acetate.

[0049] Preparation method: After mixing evenly with a V-type mixer, grind the mixture on a three-roll mill to obtain the final product.

[0050] Example 2

[0051] The specific implementation method of this embodiment is the same as that of embodiment 1, except that:

[0052] Glass powder A contains: CuO 20.5%, MnO2 10.5%, TiO2 5%, Bi2O3 18%, TeO2 4%, B2O3 3.5%, Sb2O3 1%, WO3 1.5%, Y2O3 1%, and SiO2 as a supplementary balance.

[0053] Example 3

[0054] The specific implementation method of this embodiment is the same as that of embodiment 1, except that:

[0055] Glass powder A contains: CuO 20.5%, MnO2 10.5%, TiO2 5%, Bi2O3 18%, TeO2 4%, B2O3 3.5%, Sb2O3 1%, WO3 1%, Y2O3 1%, Cr2O3 0.5%, and SiO2 as a supplement.

[0056] Example 4

[0057] The specific implementation method of this embodiment is the same as that of embodiment 1, except that:

[0058] Glass powder B contains: CuO 20%, MnO2 10.5%, PbO 17%, TiO2 10%, TeO2 3.5%, B2O3 2.5%, BaCO3 2%, PbF2 1%, AlF3 1.5%, and SiO2 as a supplement.

[0059] Example 5

[0060] The specific implementation method of this embodiment is the same as that of embodiment 1, except that:

[0061] Glass powder A contains: CuO 20.5%, MnO2 10.5%, TiO2 5%, Bi2O3 18%, TeO2 4%, B2O3 3.5%, Sb2O3 1%, WO3 1.5%, Y2O3 1%, and SiO2 as a supplementary balance.

[0062] Glass powder B contains: CuO 20%, MnO2 10.5%, PbO 17%, TiO2 10%, TeO2 3.5%, B2O3 2.5%, BaCO3 2%, PbF2 1%, AlF3 1.5%, and SiO2 as a supplement.

[0063] Example 6

[0064] The specific implementation method of this embodiment is the same as that of embodiment 1, except that:

[0065] Glass powder A contains: CuO 20.5%, MnO2 10.5%, TiO2 5%, Bi2O3 18%, TeO2 4%, B2O3 3.5%, Sb2O3 1%, WO3 1%, Y2O3 1%, Cr2O3 0.5%, and SiO2 as a supplement.

[0066] Glass powder B contains: CuO 20%, MnO2 10.5%, PbO 17%, TiO2 10%, TeO2 3.5%, B2O3 2.5%, BaCO3 2%, PbF2 1%, AlF3 1.5%, and SiO2 as a supplement.

[0067] Comparative Example 1

[0068] This comparative example uses a commercially available silver paste product from Ruxing, model number RX62604 series.

[0069] Performance Evaluation

[0070] The back silver paste from the examples and comparative examples was printed onto PERC crystalline silicon solar cells. The cells were then dried and sintered at peak temperatures of 750°C and 790°C to obtain the final cells. A photoluminescence (PL) analyzer was used to detect the corrosion of the passivation layer by the back silver paste. A HALM analyzer was used to test the electrical performance of the cells. A peel strength tester was used to test the pull-out force of the electrodes. Ten parallel samples were tested for each example and comparative example, and the average value was taken. The results are shown in Table 1.

[0071] Table 1

[0072]

[0073] Compared to the comparative example, in Examples 1-6 of this application, the conversion efficiency (Eta) was improved under both firing temperatures, mainly reflected in increased Uoc and FF, and the tensile strength was also better than that of the comparative example. Meanwhile, from... Figures 1-4It can be seen that the blackening of the back electrode position is brighter than that of the comparative example at both firing temperatures, indicating that its corrosion is weaker than that of the comparative example. This further demonstrates that the glass powder of the present invention can reduce the corrosion of the back passivation layer, thereby enabling the PERC back silver paste to have better tensile strength and weak corrosion resistance over a wider sintering range. While ensuring tensile strength, it promotes the improvement of Uoc and FF, thus improving the battery efficiency.

Claims

1. A glass powder for PERC back-side silver paste, characterized in that: The glass powder is a two-component glass powder comprising glass powder A and glass powder B. By weight percentage, glass powder A contains: CuO 20.5%, MnO2 10.5%, TiO2 5%, Bi2O3 18%, TeO2 4%, B2O3 3.5%, Sb2O3 1%, WO3 1%, Y2O3 1%, Cr2O3 0.5%, with SiO2 as the balance; glass powder B contains: CuO 20%, MnO2 10.5%, PbO 17%, TiO2 10%, TeO2 3.5%, B2O3 2.5%, BaCO3 2%, PbF2 1%, AlF3 1.5%, with SiO2 as the balance.

2. A method for preparing glass powder for PERC back-side silver paste according to claim 1, characterized in that: The steps include the following: S1: The raw material for preparing glass powder A is melted at high temperature, quenched in water, ball-milled, dried, and sieved to obtain glass powder A; S2: The raw material for preparing glass powder B is melted at high temperature, quenched in water, ball-milled, dried, and sieved to obtain glass powder B; S3: Glass powder A and glass powder B are mixed in a certain proportion to obtain the final product.

3. The application of the glass powder for PERC back-side silver paste according to claim 1, characterized in that: This includes the application of this glass powder in silver paste for solar cells.

4. The application of the glass powder for PERC back-side silver paste according to claim 3, characterized in that: The composition of the silver paste for solar cells, by mass percentage, includes at least: 0.5~1% glass powder A, 0.5~1% glass powder A, 50~65% silver powder, 1~5% organic solvent, and the balance being organic carrier.

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