Preparation method of large tower footing silicon wafer of TOPCon battery

Abstract

The invention relates to a preparation method of a large tower footing silicon wafer of a TOPCon battery, and belongs to the technical field of solar battery preparation. Comprising the following steps: pre-cleaning; washing with water; alkali polishing: cleaning the silicon wafer by using an alkali polishing cleaning solution obtained by mixing DI, NaOH and an alkali polishing additive, wherein the mass ratio of the alkali polishing additive in the alkali polishing cleaning solution is 1-2%; washing with water; performing post-cleaning; washing with water; acid cleaning; washing with water; slowly lifting; and drying. By setting the mass ratio of the alkali polishing additive in the alkali polishing cleaning solution to be 1-2%, compared with the mass ratio of the alkali polishing additive in a traditional process to be 2-2.5%, the mass ratio of the alkali polishing additive is reduced, the use cost of the alkali polishing additive can be reduced, a large tower footing silicon wafer can be obtained, the specific surface area of the back face of the silicon wafer is smaller, the flatness is high, and the service life of the silicon wafer is prolonged. The natural oxide layer on the back surface is more uniform due to high flatness, deposition of the tunneling layer and the polycrystalline silicon thin film layer can be improved, and the back surface passivation effect is better.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell preparation, and in particular to a method for preparing a TOPCon cell large tower base silicon wafer. Background Art

[0002] With the continuous development of the energy industry, solar energy technology has rapidly emerged as a new type of energy and has gradually covered all aspects of the energy field. Solar photovoltaic cells can generate current when there is sunlight, so the scope of use of photovoltaic power generation is very wide. But at the same time, this emerging industry has also made the market competition increasingly fierce with the continuous advancement of technology. High-efficiency, low-cost, and high-reliability photovoltaic cells are the core competitiveness of market competition. TOPCon cells are a type of photovoltaic crystalline silicon cells. In recent years, due to its obvious advantages such as high conversion efficiency, low attenuation performance, and high mass production cost performance, they have gradually been adopted by companies in the industry.

[0003] The core structure of TOPCon cells is a tunneling oxide layer and polysilicon thin film layer prepared on the back of the silicon wafer to passivate the back surface and improve the long-wave response, thereby improving the conversion efficiency of the cell. However, the traditional small tower-based silicon wafer has a large and uneven back surface area, which leads to uneven growth of the natural oxide layer, resulting in poor preparation of the tunneling oxide layer and polysilicon thin film layer, which in turn affects the efficiency of the TOPCon cell. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a TOPCon battery large tower base silicon wafer. The technical solution of the present invention is as follows:

[0005] A method for preparing a TOPCon battery large tower base silicon wafer, comprising:

[0006] S1, pre-cleaning: using a cleaning solution obtained by mixing DI, NaOH and H2O2 to clean the base silicon wafer, and obtaining a first base silicon wafer after cleaning;

[0007] S2, water washing: washing the first base silicon wafer with DI to obtain a second base silicon wafer;

[0008] S3, alkali polishing: using an alkali polishing cleaning solution obtained by mixing DI, NaOH and an alkali polishing additive to clean the second substrate silicon wafer, and obtaining a third substrate silicon wafer after cleaning, wherein the mass proportion of DI in the alkali polishing cleaning solution is 93-95%, the mass proportion of NaOH is 3-5%, and the mass proportion of the alkali polishing additive is 1-2%;

[0009] S4, water washing: washing the third base silicon wafer with DI to obtain a fourth base silicon wafer;

[0010] S5, post-cleaning: using a cleaning solution obtained by mixing DI, NaOH and H2O2 to clean the fourth base silicon wafer, and obtaining a fifth base silicon wafer after cleaning;

[0011] S6, water washing: washing the fifth base silicon wafer with DI to obtain a sixth base silicon wafer;

[0012] S7, acid cleaning: using an acid cleaning solution obtained by mixing DI, HF and HCl to clean the sixth base silicon wafer, and obtaining a seventh base silicon wafer after cleaning;

[0013] S8, water washing: washing the seventh base silicon wafer with DI to obtain an eighth base silicon wafer;

[0014] S9, slow pulling: placing the eighth base silicon wafer into a slow pulling tank, wherein a mechanical arm is provided on the slow pulling tank, and the mechanical arm and the slow pulling tank cooperate to clean water stains on the surface of the eighth base silicon wafer, and obtain a ninth base silicon wafer after dehydration;

[0015] S10, drying: placing the ninth base silicon wafer into a drying tank for drying, so as to dry water stains on the surface of the ninth base silicon wafer.

[0016] Optionally, the cleaning liquid in S1 and S5 cleans the silicon wafer for 100 to 120 seconds, and the temperature of the cleaning liquid is 60 to 70° C.; the mass proportion of DI in the cleaning liquid is 93 to 95%, the mass proportion of NaOH is 2 to 3%, and the mass proportion of H2O2 is 4 to 5%.

[0017] Optionally, in S2, S4, S6 and S8, the time for washing the silicon wafer with water is 80 to 120 seconds, and the temperature of the water washing is room temperature.

[0018] Optionally, the time for cleaning the silicon wafer with the alkaline polishing cleaning solution in S3 is 190 to 230 seconds, and the temperature of the alkaline polishing cleaning solution is 60 to 70°C.

[0019] Optionally, the time for the slow extraction tank and the robotic arm to clean the eighth base silicon wafer in S9 is 0s to 20s.

[0020] Optionally, in S10, the ninth texturing substrate is dried at a temperature of 87-107° C. for a time of 800-900 seconds.

[0021] Optionally, the acid cleaning solution used for acid cleaning in S7 contains 96-98% by mass of DI, 1-2% by mass of HF, and 1-2% by mass of HCl; the acid cleaning solution cleans the silicon wafer for 100-120 seconds at room temperature.

[0022] All the above optional technical solutions can be combined arbitrarily, and the present invention does not provide detailed descriptions of the structures after the combinations.

[0023] By means of the above scheme, the beneficial effects of the present invention are as follows:

[0024] By setting the mass proportion of alkali polishing additives in the alkali polishing cleaning solution to 1-2%, compared with the mass proportion of alkali polishing additives in the traditional process of 2-2.5%, the mass proportion of alkali polishing additives is reduced, which not only reduces the cost of using alkali polishing additives, but also enables the acquisition of large tower base silicon wafers, so that the back surface area of ​​the silicon wafer is smaller and the flatness is high. The natural oxide layer on the back is more uniform due to the high flatness, which can improve the deposition of the tunneling layer and the polysilicon thin film layer, better passivate the back surface of the silicon wafer, and have a higher reflectivity in the long wave band.

[0025] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the method for preparing the TOPCon battery large tower base silicon wafer provided in an embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram of the structure of the large tower base silicon wafer prepared in an embodiment of the present invention.

[0028] Figure 3 It is a schematic diagram of the structure of a small tower base silicon wafer prepared by traditional technology. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0030] like Figure 1 As shown, the method for preparing a TOPCon battery large tower base silicon wafer provided in an embodiment of the present invention comprises:

[0031] S1, pre-cleaning: using a cleaning solution obtained by mixing DI, NaOH and H2O2 to clean the base silicon wafer, and obtaining a first base silicon wafer after cleaning.

[0032] Among them, pre-cleaning is used to deal with poor appearance conditions such as damaged layers and surface conditions on the silicon wafer surface. Chemical substances (NaOH and H2O2) in the cleaning liquid are used to clean organic matter contaminated on the surface of the silicon wafer to prevent it from affecting subsequent reactions.

[0033] Specifically, the cleaning liquid takes 100 to 120 seconds to clean the silicon wafer, and the temperature of the cleaning liquid is 60 to 70° C.; the mass proportion of DI (deionized water) in the cleaning liquid is 93 to 95%, the mass proportion of NaOH is 2 to 3%, and the mass proportion of H2O2 is 4 to 5%.

[0034] S2, water washing: using DI to wash the first base silicon wafer with water, and obtaining a second base silicon wafer after washing with water.

[0035] The purpose of water cleaning is to clean the cleaning liquid remaining on the surface of the silicon wafer after the pre-cleaning.

[0036] Specifically, the time for washing the silicon wafer with water is 80 to 120 seconds, and the temperature of the water washing is room temperature.

[0037] S3, alkali polishing: use an alkali polishing cleaning solution obtained by mixing DI, NaOH and an alkali polishing additive to clean the second base silicon wafer, and obtain a third base silicon wafer after cleaning, wherein the mass proportion of DI in the alkali polishing cleaning solution is 93-95%, the mass proportion of NaOH is 3-5%, and the mass proportion of the alkali polishing additive is 1-2%.

[0038] The purpose of alkali polishing is to etch and polish the back and edge of the silicon wafer using a mixture of NaOH and an alkali polishing additive (ADDI). The alkali polishing additive can be a product available on the market.

[0039] Specifically, the time for cleaning the silicon wafer with the alkaline polishing cleaning solution in S3 is 190 to 230 seconds, and the temperature of the alkaline polishing cleaning solution is 60 to 70°C.

[0040] In the embodiment of the present invention, the mass proportion of the alkali polishing additive in the alkali polishing cleaning solution is set to 1-2%, which is lower than the mass proportion of the alkali polishing additive in the traditional process of 2-2.5.

[0041] S4, water washing: washing the third base silicon wafer with DI to obtain a fourth base silicon wafer.

[0042] Among them, the purpose of water cleaning after alkali polishing is to clean the chemical substances remaining on the surface of the silicon wafer during the alkali polishing process by flowing pure water.

[0043] Specifically, the time for washing the silicon wafer with water is 80 to 120 seconds, and the temperature of the water washing is room temperature.

[0044] S5, post-cleaning: using a cleaning solution obtained by mixing DI, NaOH and H2O2 to clean the fourth base silicon wafer, and obtaining a fifth base silicon wafer after cleaning.

[0045] Among them, the purpose of post-cleaning is to clean the organic matter in the alkaline polishing process by a mixture of NaOH and H2O2.

[0046] Specifically, the cleaning liquid cleans the silicon wafer for 100 to 120 seconds, and the temperature of the cleaning liquid is 60 to 70° C.; the mass proportion of DI in the cleaning liquid is 93 to 95%, the mass proportion of NaOH is 2 to 3%, and the mass proportion of H2O2 is 4 to 5%.

[0047] S6, water washing: washing the fifth base silicon wafer with DI to obtain a sixth base silicon wafer.

[0048] Among them, the purpose of post-cleaning and post-water cleaning is to clean the chemicals remaining on the surface of the silicon wafer during the post-cleaning process by flowing pure water.

[0049] Specifically, the time for washing the silicon wafer with water is 80 to 120 seconds, and the temperature of the water washing is room temperature.

[0050] S7, acid cleaning: using an acid cleaning solution obtained by mixing DI, HF and HCl to clean the sixth base silicon wafer, and obtaining a seventh base silicon wafer after cleaning.

[0051] Among them, acid cleaning is to use a mixture of HF and HCL to clean the silicon dioxide layer on the surface of the silicon wafer to improve the hydrophobicity of the silicon wafer surface.

[0052] Specifically, the time for cleaning the silicon wafer with the acid cleaning solution is 100 to 120 seconds, and the acid cleaning temperature is room temperature; wherein, the mass proportion of DI in the acid cleaning solution used for acid cleaning in S7 is 96 to 98%, the mass proportion of HF is 1 to 2%, and the mass proportion of HCl is 1 to 2%.

[0053] S8, water washing: washing the seventh base silicon wafer with DI to obtain an eighth base silicon wafer.

[0054] Among them, the purpose of water washing after acid cleaning is to use flowing pure water to clean the chemical substances remaining on the surface of the silicon wafer during the previous acid cleaning process.

[0055] Specifically, the time for washing the silicon wafer with water is 80 to 120 seconds, and the temperature of the water washing is room temperature.

[0056] S9, slow pulling: placing the eighth base silicon wafer into a slow pulling tank, on which a mechanical arm is provided, and the mechanical arm and the slow pulling tank cooperate to clean water stains on the surface of the eighth base silicon wafer, and obtain a ninth base silicon wafer after dehydration.

[0057] The purpose of slow pulling is to clean the water on the surface of the silicon wafer after cleaning in the water tank, and to prevent water stains on the surface of the silicon wafer after drying.

[0058] Specifically, the time for the slow extraction tank and the robotic arm to clean the eighth substrate silicon wafer in S9 is 0 to 20 seconds.

[0059] S10, thermal drying: placing the ninth base silicon wafer into a drying tank for drying, so as to dry water stains on the surface of the ninth base silicon wafer.

[0060] The purpose of thermal drying is to dry the surface of the silicon wafer with hot air.

[0061] Specifically, the ninth texturing substrate is dried at a temperature of 87-107° C. for 800-900 seconds in S10 .

[0062] The embodiment of the present invention reduces the mass proportion of the alkali polishing additive in the alkali polishing cleaning solution by setting the mass proportion of the alkali polishing additive to 1-2%, compared with the mass proportion of the alkali polishing additive in the traditional process of 2-2.5%, so that the prepared TOPCon battery is a large tower base silicon wafer, while the TOPCon battery prepared by the traditional process is a small tower base silicon wafer. The electrical properties of the TOPCon battery prepared by the method provided by the embodiment of the present invention and the traditional process are tested, and the test results are shown in Table 1.

[0063] Table 1

[0064]

[0065] It can be seen from Table 1 that the efficiency Eta of the TOPCon battery prepared by the method provided in the embodiment of the present invention is improved by 0.048, which is mainly reflected in the increase of current Isc by 3mA and FF by 0.21.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a TOPCon battery large tower base silicon wafer, characterized in that: include: S1, pre-cleaning: using a cleaning solution obtained by mixing DI, NaOH and H2O2 to clean the base silicon wafer, and obtaining a first base silicon wafer after cleaning; S2, water washing: washing the first base silicon wafer with DI to obtain a second base silicon wafer; S3, alkali polishing: using an alkali polishing cleaning solution obtained by mixing DI, NaOH and an alkali polishing additive to clean the second substrate silicon wafer, and obtaining a third substrate silicon wafer after cleaning, wherein the mass proportion of DI in the alkali polishing cleaning solution is 93-95%, the mass proportion of NaOH is 3-5%, and the mass proportion of the alkali polishing additive is 1-2%; S4, water washing: washing the third base silicon wafer with DI to obtain a fourth base silicon wafer; S5, post-cleaning: using a cleaning solution obtained by mixing DI, NaOH and H2O2 to clean the fourth base silicon wafer, and obtaining a fifth base silicon wafer after cleaning; S6, water washing: washing the fifth base silicon wafer with DI to obtain a sixth base silicon wafer; S7, acid cleaning: using an acid cleaning solution obtained by mixing DI, HF and HCl to clean the sixth base silicon wafer, and obtaining a seventh base silicon wafer after cleaning; S8, water washing: washing the seventh base silicon wafer with DI to obtain an eighth base silicon wafer; S9, slow pulling: placing the eighth base silicon wafer into a slow pulling tank, wherein a mechanical arm is provided on the slow pulling tank, and the mechanical arm and the slow pulling tank cooperate to clean water stains on the surface of the eighth base silicon wafer, and obtain a ninth base silicon wafer after dehydration; S10, drying: placing the ninth base silicon wafer into a drying tank for drying, so as to dry water stains on the surface of the ninth base silicon wafer.

2. The method for preparing the TOPCon battery large tower base silicon wafer according to claim 1, characterized in that: The cleaning liquid in S1 and S5 cleans the silicon wafer for 100 to 120 seconds, and the temperature of the cleaning liquid is 60 to 70° C.; the mass proportion of DI in the cleaning liquid is 93 to 95%, the mass proportion of NaOH is 2 to 3%, and the mass proportion of H2O2 is 4 to 5%.

3. The method for preparing the TOPCon battery large tower base silicon wafer according to claim 1, characterized in that: In S2, S4, S6 and S8, the time for washing the silicon wafer is 80 to 120 seconds, and the washing temperature is room temperature.

4. The method for preparing the TOPCon battery large tower base silicon wafer according to claim 1, characterized in that: The time for cleaning the silicon wafer with the alkaline cleaning solution in S3 is 190 to 230 seconds, and the temperature of the alkaline cleaning solution is 60 to 70°C.

5. The method for preparing the TOPCon battery large tower base silicon wafer according to claim 1, characterized in that: The time for the slow extraction tank and the robotic arm to clean the eighth substrate silicon wafer in S9 is 0s to 20s.

6. The method for preparing the TOPCon battery large tower base silicon wafer according to claim 1, characterized in that: In the step S10 , the ninth texturing substrate is dried at a temperature of 87 to 107° C. for a time of 800 to 900 seconds.

7. The method for preparing the TOPCon battery large tower base silicon wafer according to claim 1, characterized in that: In the acid cleaning solution used for the acid cleaning in S7, the mass proportion of DI is 96-98%, the mass proportion of HF is 1-2%, and the mass proportion of HCl is 1-2%; the time for cleaning the silicon wafer with the acid cleaning solution is 100-120s, and the temperature is room temperature.

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