Winding plating removing method, TOPCon battery and preparation method of TOPCon battery
By adopting a dewounding method during the preparation of TOPCon batteries, including the use of specific mixed solutions and RCA cleaning, the problem of incomplete winding is solved, and the battery is efficiently converted and low leakage rate is achieved.
Patent Information
- Application Number
- CN202311085453.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-25
- Publication Date
- 2025-02-28
AI Technical Summary
The winding problems caused by TOPCon batteries during the deposition and preparation process lead to incomplete dewounding, resulting in uneven composite centers on the front of the silicon wafer, resulting in low battery leakage and conversion efficiency.
A dewounding method is adopted, including removing the phosphosilicon glass layer of the wound plating, treating the silicon wafer using the first mixed solution and the second mixed solution, containing alkali, H2O2 and silicon wafer cleaning additives, as well as depolysilicon plating additives and alkalis, and finally RCA cleaning is performed to achieve completeness of the dewounding plating.
Through this method, the completeness of dewounding is achieved, the leakage rate of the TOPCon battery is reduced, and the conversion efficiency and contact isolation performance of the battery are improved.
Smart Images
Figure CN119545945A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of solar cells, and in particular to a de-wrap method, a TOPCon cell and a preparation method thereof. Background Art
[0002] During the deposition process of the tunneling silicon oxide layer and the phosphorus-doped polysilicon layer, TOPCon cells will have the problem of wrap-around plating, which requires subsequent de-wrapping. In order to ensure that TOPCon cells can achieve excellent contact isolation, the completeness of the de-wrapping plating needs to be guaranteed.
[0003] At present, the de-coating process of TOPCon cells is to first remove the phosphorus silicon glass layer by chain etching, then directly send it to the slot etching to clean the phosphorus expansion layer and polysilicon coating layer, and finally remove the borosilicate glass layer on the front. This de-coating process has the problem of incomplete de-coating, which causes the recombination center on the front of the silicon wafer, resulting in battery leakage and affecting the conversion efficiency of the battery. Summary of the invention
[0004] Based on this, it is necessary to provide a de-winding method, a TOPCon battery and a preparation method thereof to address the above problems. The de-winding method can achieve complete de-winding, so that the prepared TOPCon battery has excellent conversion efficiency and effectively reduces the leakage rate of the TOPCon battery.
[0005] A de-coating method comprises the following steps:
[0006] Obtaining a silicon wafer with wrap-around plating;
[0007] Removing the phosphosilicate glass layer;
[0008] The silicon wafer is treated with a first mixed solution, wherein the first mixed solution comprises, by volume fraction, 0.3% to 5% of alkali, 2% to 10% of H2O2, and 0.2% to 0.7% of a silicon wafer cleaning additive;
[0009] The silicon wafer is treated with a second mixed solution, wherein the second mixed solution comprises, by volume fraction, 0.2% to 1% of a polysilicon removal wrap-around additive and 2.5% to 10% of an alkali;
[0010] The silicon wafer is subjected to RCA cleaning to obtain a de-coated silicon wafer.
[0011] In one of the embodiments, a water film is formed on the back side of the silicon wafer with the coating, and an HF solution is used to remove the phosphosilicate glass layer coated on the front and side surfaces. The volume fraction of the HF solution is 50% to 90%, and the processing time is 1 min to 2.5 min.
[0012] In one embodiment, the volume ratio of the alkali to the H2O2 in the first mixed solution is 1:2 to 1:6, the volume ratio of the silicon wafer cleaning additive to the H2O2 is 1:25 to 1:35, the silicon wafer cleaning additive is selected from SC110 silicon wafer cleaning additive, and the alkali is selected from KOH and / or NaOH.
[0013] In one embodiment, in the step of treating the silicon wafer with the first mixed solution, the temperature is 55° C. to 70° C. and the time is 1 min to 3 min.
[0014] In one embodiment, in the step of treating the silicon wafer with the second mixed solution, the temperature is 65° C. to 75° C. and the time is 4 min to 7 min.
[0015] In one embodiment, the alkali in the second mixed solution is selected from KOH and / or NaOH, and the volume fraction of the alkali is 2.5% to 5%.
[0016] In one embodiment, the step of performing RCA cleaning on the silicon wafer includes: using a mixed solution of 0.3% to 5% alkali and 2% to 15% H2O2 for the first cleaning, using a 40% to 50% HF solution for the second cleaning, using a mixed solution of 0.3% to 3% alkali and 1% to 15% H2O2 for the third cleaning, and using a 13% to 20% HF solution for the fourth cleaning.
[0017] In one embodiment, the temperature of the first cleaning is 50°C to 70°C, and the time is 1.5min to 2.5min;
[0018] And / or, the second cleaning time is 2 min to 3.5 min;
[0019] And / or, the temperature of the third washing is 55°C to 68°C, and the time is 1min to 2.5min;
[0020] And / or, the fourth cleaning time is 2 minutes to 3 minutes.
[0021] A method for preparing a TOPCon battery comprises the above-mentioned de-wrap plating method.
[0022] A TOPCon battery prepared by the TOPCon battery preparation method.
[0023] The de-coating method provided by the present invention first removes the de-coated phosphorus-silicon glass layer, then treats it with a first mixed solution, then treats it with a second mixed solution, and finally performs RCA cleaning, so that the de-coating can be completely achieved through the overall process and the coordination between the steps, and a silicon wafer with complete de-coating can be obtained. The silicon wafer is subsequently processed to obtain a TOPCon battery, which has excellent contact isolation, effectively reduces the leakage rate of the battery, and can provide high conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a schematic diagram of the process of the de-coating method of the present invention. DETAILED DESCRIPTION
[0025] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.
[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.
[0027] Reference Figure 1 , Figure 1 A schematic flow chart of a de-wrapping method provided by the present invention is shown, and the method comprises the following steps:
[0028] S1, obtaining a silicon wafer with winding plating;
[0029] S2, removing the phosphosilicon glass layer;
[0030] S3, treating the silicon wafer with a first mixed solution, wherein the first mixed solution comprises, by volume fraction, 0.3% to 5% of alkali, 2% to 10% of H2O2 and 0.2% to 0.7% of a silicon wafer cleaning additive.
[0031] S4, treating the silicon wafer with a second mixed solution, wherein the second mixed solution comprises, by volume fraction, 0.2% to 1% of a polysilicon removal wrap-around additive and 2.5% to 10% of an alkali;
[0032] S5, performing RCA cleaning on the silicon wafer to obtain a de-coated silicon wafer.
[0033] In the process of preparing TOPCon cells, the silicon wafer is first textured, and then any texture surface is diffused to prepare the emitter. This surface is used as the front side of the silicon wafer, and the other side is used as the back side of the silicon wafer. After polishing the back side, a tunneling oxide layer and a polysilicon layer are deposited, and then phosphorus is doped to form a passivation contact layer. In this process, the problem of wrapping plating will occur, resulting in a silicon wafer with wrapping plating in step S1, which needs to be de-wrapped.
[0034] Optionally, the silicon wafer is preferably an N-type single crystal silicon wafer, and the diffusion is preferably boron diffusion.
[0035] The process of boron diffusion and preparation of the tunnel oxide layer and the phosphorus-doped polysilicon layer is not specifically limited, wherein the tunnel oxide layer and the polysilicon layer are preferably prepared by LPCVD deposition, and then phosphorus diffusion is performed on the polysilicon layer to form a phosphorus-doped polysilicon layer. Preferably, the thickness of the prepared tunnel oxide layer is 1nm to 2nm, and the thickness of the phosphorus-doped polysilicon layer is 100nm to 210nm.
[0036] In order to achieve complete de-coating, in step S2 of the present invention, the phosphosilicate glass layer coated on the front and side surfaces of the silicon wafer is first removed.
[0037] Optionally, in an actual production line, the front side of the silicon wafer can be placed face down and controlled to float in an acidic solution, so that the front and side of the silicon wafer are in contact with the acidic solution, and the back of the silicon wafer is not in contact with the acidic solution, and the phosphorus silicon glass layer coated is removed after soaking for a period of time. The acidic solution is preferably an HF solution, the volume fraction of the HF solution is 50% to 90%, and the processing time is 1 min to 2.5 min.
[0038] Furthermore, when de-coating the phosphosilicate glass layer, a water film can be formed on the back of the silicon wafer to better protect the passivation contact layer on the back of the silicon wafer. The method of forming the water film is not limited. Preferably, a spraying method is used to form a water film on the back of the silicon wafer.
[0039] In step S3, the silicon wafer is treated with a first mixed solution including alkali, H2O2 and a silicon wafer cleaning additive. Specifically, the silicon wafer is soaked in the first mixed solution for a period of time, then taken out and rinsed with water. Preferably, the treatment temperature is 55°C to 70°C and the treatment time is 1 min to 3 min.
[0040] Optionally, in the first mixed solution, the silicon wafer cleaning additive is selected from SC110 silicon wafer cleaning additive, the alkali is selected from KOH and / or NaOH, the volume ratio of the alkali to the H2O2 is preferably 1:2 to 1:6, and the volume ratio of the silicon wafer cleaning additive to the H2O2 is preferably 1:25 to 1:35, which can further enhance the cleaning effect of the first mixed solution.
[0041] In step S4, the silicon wafer is treated with a second mixed solution including a polysilicon removal wrapping additive and an alkali. Preferably, the alkali in the second mixed solution is preferably KOH and / or NaOH, the volume fraction of the alkali is preferably 2.5% to 5%, and / or the treatment temperature is 65°C to 75°C, and the treatment time is 4 minutes to 7 minutes, so as to further enhance the completeness of the cleaning wrapping.
[0042] In step S5, the step of performing RCA cleaning on the silicon wafer includes: in terms of volume fraction, using a mixed solution of 0.3% to 5% alkali and 2% to 15% H2O2 for the first cleaning, using a 40% to 50% HF solution for the second cleaning, using a mixed solution of 0.3% to 3% alkali and 1% to 15% H2O2 for the third cleaning, and using a 13% to 20% HF solution for the fourth cleaning. Preferably, a silicon wafer cleaning additive can be added to the mixed solution for the first cleaning, and the silicon wafer cleaning additive is preferably an SC110 silicon wafer cleaning additive, and the silicon wafer cleaning additive concentration is preferably 0.2% to 2%; a silicon wafer cleaning additive can be added to the mixed solution for the fourth cleaning, and the silicon wafer cleaning additive is preferably an SC110 silicon wafer cleaning additive, and the silicon wafer cleaning additive concentration is preferably 0.2% to 2%. Preferably, in the first cleaning to the fourth cleaning, the alkali is selected from KOH and / or NaOH.
[0043] Among them, the temperature of the first cleaning is 50℃~70℃, and the time is 1.5min~2.5min; the time of the second cleaning is 2min~3.5min; the temperature of the third cleaning is 55℃~68℃, and the time is 1min~2.5min; the time of the fourth cleaning is 2min~3min.
[0044] Therefore, by coordinating steps S1 to S5 and regulating the process parameters of each step, the completeness of the de-coating can be achieved, and a silicon wafer with complete de-coating can be obtained.
[0045] The present invention also provides a method for preparing a TOPCon battery, comprising adopting the above-mentioned de-winding plating method.
[0046] The present invention also provides a TOPCon battery, which can effectively reduce the leakage rate and has excellent contact isolation, providing high conversion efficiency.
[0047] Hereinafter, the de-wrap method, TOPCon cell and preparation method thereof will be further described through the following specific examples.
[0048] Example 1
[0049] The N-type single crystal silicon wafer is textured, and one of the textured surfaces is expanded with boron using the boron diffusion process as the front side, and the other side is used as the back side. After the back side is polished, a 1.2nm tunneling oxide layer is deposited using LPCVD. After the polysilicon layer is deposited using LPCVD, phosphorus is doped to form a 150nm phosphorus-doped polysilicon layer, and finally a passivation contact layer is formed.
[0050] Then, the silicon wafer after the passivation contact layer is formed is subjected to a de-plating process, and the specific steps include:
[0051] A water film was sprayed on the back of the silicon wafer, and then the silicon wafer was placed face down in a hydrofluoric acid solution with a volume fraction of 80% for cleaning for 1.3 minutes to remove the phosphorus silicon glass layer coated on the front and side surfaces.
[0052] The silicon wafer after de-coating the phosphorus silicon glass layer is placed in a first mixed solution at a temperature of 65°C for immersion and cleaning for 120 seconds, and then taken out and rinsed with water, wherein the first mixed solution includes 6% by volume of hydrogen peroxide, 1.4% of NaOH and 0.2% of SC110 silicon wafer cleaning additive. Then the cleaned silicon wafer is placed in a second mixed solution at a temperature of 72°C for immersion and cleaning for 320 seconds, wherein the second mixed solution includes 0.35% by volume of PR21 de-coating additive and 4.7% of NaOH.
[0053] Then, the silicon wafer is immersed in a mixed solution at a temperature of 65°C for cleaning for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 1.4% by volume of NaOH and 0.2% by volume of SC110 silicon wafer cleaning additive; the cleaned silicon wafer is immersed in a 40% by volume HF solution for 180 seconds, and then rinsed with water after being taken out; the silicon wafer is immersed in a mixed solution at a temperature of 63°C for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 0.7% by volume of NaOH and 0.2% by volume of SC110 silicon wafer cleaning additive; the silicon wafer is immersed in a 14% by volume HF solution for 180 seconds, slowly pulled up for pre-dehydration and then dried to obtain the de-wrapped silicon wafer.
[0054] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0055] The electrical performance values of the TOPCon battery of this embodiment are shown in Table 1.
[0056] Embodiment 2:
[0057] The N-type single crystal silicon wafer is textured, and one of the textured surfaces is expanded with boron using the boron diffusion process as the front side, and the other side is used as the back side. After the back side is polished, a 1.2nm tunneling oxide layer is deposited using LPCVD. After the polysilicon layer is deposited using LPCVD, phosphorus is doped to form a 150nm phosphorus-doped polysilicon layer, and finally a passivation contact layer is formed.
[0058] Then, the silicon wafer after the passivation contact layer is formed is subjected to a de-plating process, and the specific steps include:
[0059] A water film was sprayed on the back of the silicon wafer, and then the silicon wafer was placed face down in a 70% by volume hydrofluoric acid solution for cleaning for 1.6 minutes to remove the phosphosilicate glass layer coated on the front and side surfaces.
[0060] The silicon wafer after de-coating the phosphorus silicon glass layer is placed in a first mixed solution at a temperature of 64°C for immersion and cleaning for 120 seconds, and then rinsed with water after being taken out, wherein the first mixed solution includes 6% by volume of hydrogen peroxide, 1.5% of NaOH and 0.2% of SC110 silicon wafer cleaning additive. Then the cleaned silicon wafer is placed in a second mixed solution at a temperature of 72°C for immersion and cleaning for 350 seconds, wherein the second mixed solution includes 0.35% by volume of PR21 de-coating additive and 4.5% of NaOH.
[0061] Then, the silicon wafer is immersed in a mixed solution at a temperature of 65°C for cleaning for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 1.5% by volume of NaOH and 0.5% by volume of SC110 silicon wafer cleaning additive; the cleaned silicon wafer is immersed in a 45% by volume HF solution for 180 seconds, and then rinsed with water after being taken out; the silicon wafer is immersed in a mixed solution at a temperature of 62°C for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 0.7% by volume of NaOH and 0.5% by volume of SC110 silicon wafer cleaning additive; the silicon wafer is immersed in a 15% by volume HF solution for 180 seconds, slowly pulled up for pre-dehydration and then dried to obtain the de-wrapped silicon wafer.
[0062] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0063] The electrical performance values of the TOPCon battery of this embodiment are shown in Table 1.
[0064] Embodiment 3:
[0065] The N-type single crystal silicon wafer is textured, and one of the textured surfaces is expanded with boron using the boron diffusion process as the front side, and the other side is used as the back side. After the back side is polished, a 1.2nm tunneling oxide layer is deposited using LPCVD. After the polysilicon layer is deposited using LPCVD, phosphorus is doped to form a 150nm phosphorus-doped polysilicon layer, and finally a passivation contact layer is formed.
[0066] Then, the silicon wafer after the passivation contact layer is formed is subjected to a de-plating process, and the specific steps include:
[0067] A water film was sprayed on the back of the silicon wafer, and then the silicon wafer was placed face down in a 60% by volume hydrofluoric acid solution for cleaning for 1.3 minutes to remove the phosphosilicate glass layer coated on the front and side surfaces.
[0068] The silicon wafer after de-coating the phosphorus silicon glass layer is placed in a first mixed solution at a temperature of 65°C and soaked for 120 seconds, and then rinsed with water. The first mixed solution includes 6% hydrogen peroxide, 1.5% NaOH and 0.6% SC110 silicon wafer cleaning additive. Then the cleaned silicon wafer is placed in a second mixed solution at a temperature of 72°C and soaked for 320 seconds. The second mixed solution includes 0.35% PR21 de-coating additive and 4.5% NaOH.
[0069] Then, the silicon wafer is immersed in a mixed solution at a temperature of 65°C for cleaning for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 1.5% by volume of NaOH and 0.2% by volume of SC110 silicon wafer cleaning additive; the cleaned silicon wafer is immersed in a 42% by volume of HF solution for 180 seconds, and then rinsed with water after being taken out; the silicon wafer is immersed in a mixed solution at a temperature of 62°C for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 0.7% by volume of NaOH and 0.2% by volume of SC110 silicon wafer cleaning additive; the silicon wafer is immersed in a 15% by volume of HF solution for 180 seconds, slowly pulled up for pre-dehydration and then dried to obtain the de-wrapped silicon wafer.
[0070] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0071] The electrical performance values of the TOPCon battery of this embodiment are shown in Table 1.
[0072] Example 4
[0073] The N-type single crystal silicon wafer is textured, and one of the textured surfaces is expanded with boron using the boron diffusion process as the front side, and the other side is used as the back side. After the back side is polished, a 1.2nm tunneling oxide layer is deposited using LPCVD. After the polysilicon layer is deposited using LPCVD, phosphorus is doped to form a 150nm phosphorus-doped polysilicon layer, and finally a passivation contact layer is formed.
[0074] Then, the silicon wafer after the passivation contact layer is formed is subjected to a de-plating process, and the specific steps include:
[0075] A water film was sprayed on the back of the silicon wafer, and then the silicon wafer was placed face down in a 50% by volume hydrofluoric acid solution for cleaning for 2.5 minutes to remove the phosphosilicate glass layer coated on the front and side surfaces.
[0076] The silicon wafer after de-coating the phosphorus silicon glass layer is placed in a first mixed solution at a temperature of 65°C for immersion and cleaning for 120 seconds, and then taken out and rinsed with water, wherein the first mixed solution includes 6% hydrogen peroxide, 1% NaOH and 0.2% SC110 silicon wafer cleaning additive by volume. Then the cleaned silicon wafer is placed in a second mixed solution at a temperature of 70°C for immersion and cleaning for 380 seconds, wherein the second mixed solution includes 0.85% PR21 de-coating additive by volume and 5% NaOH.
[0077] Then, the silicon wafer is immersed in a mixed solution at a temperature of 65°C for cleaning for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 1% of NaOH and 1% of SC110 silicon wafer cleaning additive; the cleaned silicon wafer is immersed in a 50% by volume HF solution for 180 seconds, and then rinsed with water after being taken out; the silicon wafer is immersed in a mixed solution at a temperature of 63°C for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 0.8% of NaOH and 0.2% of SC110 silicon wafer cleaning additive; the silicon wafer is immersed in a 18% by volume HF solution for 180 seconds, slowly pulled up for pre-dehydration and then dried to obtain the de-wrapped silicon wafer.
[0078] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0079] The electrical performance values of the TOPCon battery of this embodiment are shown in Table 1.
[0080] Comparative Example 1:
[0081] The N-type single crystal silicon wafer is textured, and one of the textured surfaces is expanded with boron using the boron diffusion process as the front side, and the other side is used as the back side. After the back side is polished, a 1.2nm tunneling oxide layer is deposited using LPCVD. After the polysilicon layer is deposited using LPCVD, phosphorus is doped to form a 150nm phosphorus-doped polysilicon layer, and finally a passivation contact layer is formed.
[0082] Then, the silicon wafer after the passivation contact layer is formed is subjected to a de-plating process, and the specific steps include:
[0083] A water film was sprayed on the back of the silicon wafer, and then the silicon wafer was placed face down in a hydrofluoric acid solution with a volume fraction of 80% for cleaning for 1.3 minutes to remove the phosphorus silicon glass layer coated on the front and side surfaces.
[0084] Then, the silicon wafer after de-coating the phosphosilicon glass layer is immersed and cleaned in a second mixed solution at a temperature of 72° C. for 320 seconds, wherein the second mixed solution includes 0.35% by volume of the polysilicon de-coating additive PR21 and 4.5% by volume of NaOH.
[0085] Then, the silicon wafer is immersed in a mixed solution at a temperature of 65°C for cleaning for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 1.5% by volume of NaOH and 0.2% by volume of SC110 silicon wafer cleaning additive; the cleaned silicon wafer is immersed in a 42% by volume of HF solution for 180 seconds, and then rinsed with water after being taken out; the silicon wafer is immersed in a mixed solution at a temperature of 62°C for 120 seconds, and then rinsed with water after being taken out, wherein the mixed solution includes 6% by volume of hydrogen peroxide, 0.7% by volume of NaOH and 0.2% by volume of SC110 silicon wafer cleaning additive; the silicon wafer is immersed in a 15% by volume of HF solution for 180 seconds, slowly pulled up for pre-dehydration and then dried to obtain the de-wrapped silicon wafer.
[0086] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0087] The electrical performance values of the TOPCon battery of this comparative example are shown in Table 1.
[0088] Comparative Example 2
[0089] The only difference between Comparative Example 2 and Example 1 is that the SC110 silicon wafer cleaning additive is not added to the first mixed solution.
[0090] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0091] The electrical performance values of the TOPCon battery of this comparative example are shown in Table 1.
[0092] Comparative Example 3
[0093] The difference between Comparative Example 3 and Example 1 is that in the first mixed solution, the volume fraction of hydrogen peroxide is 1.9%, NaOH is 0.28%, and SC110 silicon wafer cleaning additive is 0.74%.
[0094] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0095] The electrical performance values of the TOPCon battery of this comparative example are shown in Table 1.
[0096] Comparative Example 4
[0097] The difference between Comparative Example 4 and Example 1 is that in the second mixed solution, the volume fraction of the polysilicon removal plating additive PR21 is 1.4%, and the volume fraction of NaOH is 10.6%.
[0098] The silicon wafer after de-coating is subjected to sequential back-deposition of aluminum oxide, front-deposition of silicon nitride, back-deposition of silicon nitride, screen printing, sintering, and annealing to obtain a TOPCon cell.
[0099] The electrical performance values of the TOPCon battery of this comparative example are shown in Table 1.
[0100] Table 1
[0101]
[0102] In Table 1: Uoc represents open circuit voltage, Isc represents short circuit current, FF represents fill factor, Eta represents conversion efficiency, and IRev2 represents reverse leakage current.
[0103] From Examples 1-4 and Comparative Example 1 in Table 1, it can be seen that the reverse leakage current IRev2 of the TOPCon battery prepared in Comparative Example 1 is 0.3106A, which is about 0.06A higher than that of the example, and the conversion efficiency Eta is 24.82%, which is about 0.04% lower than that of the example, indicating that the leakage rate of the TOPCon battery in Comparative Example 1 is increased and the conversion efficiency is reduced compared with Examples 1-4, and the electrical performance of the TOPCon battery is poor. Therefore, it is shown that after the de-coating of the phosphorus silicon glass layer, the first mixed solution of alkali, H2O2 and SC110 silicon wafer cleaning additive is used to treat the silicon wafer, and then the second mixed solution of the polysilicon de-coating additive and alkali is used to treat the silicon wafer, and the RCA cleaning is recently performed. The coordination of the overall process can achieve the completeness of the de-coating, so that the completely de-coated silicon wafer is used to prepare the TOPCon battery, and the electrical performance of the TOPCon battery is significantly improved compared with Comparative Example 1.
[0104] It can be seen from Example 1 and Comparative Example 2 in Table 1 that when the first mixed solution is used to treat the silicon wafer, when the silicon wafer additive is not added to the first mixed solution, the reverse leakage current of the prepared cell increases and the conversion efficiency decreases. This indicates that the silicon wafer additive can further increase the cleaning strength of the silicon wafer, thereby improving the electrical performance of the cell.
[0105] It can be seen from Example 1 and Comparative Example 3 in Table 1 that, in the process of treating the silicon wafer with the first mixed solution, adding a relatively high concentration of silicon wafer cleaning agent and a relatively low concentration of hydrogen peroxide increases the reverse leakage current of the prepared battery cell and reduces the conversion efficiency. This indicates that in the first mixed solution, the concentration ratio of the silicon wafer additive to the hydrogen peroxide needs to be controlled within an appropriate range to effectively enhance the cleaning effect.
[0106] It can be seen from Example 1 and Comparative Example 4 in Table 1 that in the process of treating silicon wafers with the second mixed solution, when excessive amounts of polysilicon de-plating additives and alkali are added, excessive protection will cause the polysilicon plated on the front side to be unable to be cleaned cleanly, resulting in a high reverse leakage current of the prepared battery cell and a reduced conversion efficiency.
[0107] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0108] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A de-coating method, characterized in that: The following steps are involved: Obtaining a silicon wafer with wrap-around plating; Removing the phosphosilicate glass layer; The silicon wafer is treated with a first mixed solution, wherein the first mixed solution comprises, by volume fraction, 0.3% to 5% of alkali, 2% to 10% of H2O2, and 0.2% to 0.7% of a silicon wafer cleaning additive; The silicon wafer is treated with a second mixed solution, wherein the second mixed solution comprises, by volume fraction, 0.2% to 1% of a polysilicon removal wrap-around additive and 2.5% to 10% of an alkali; The silicon wafer is subjected to RCA cleaning to obtain a de-coated silicon wafer.
2. The de-coating method according to claim 1, characterized in that: A water film is formed on the back of the silicon wafer with wrap-around coating, and an HF solution is used to remove the phosphosilicate glass layer on the front and side wrap-around coatings. The volume fraction of the HF solution is 50% to 90%, and the processing time is 1 minute to 2.5 minutes.
3. The de-coating method according to claim 1, characterized in that: The volume ratio of the alkali to the H2O2 in the first mixed solution is 1:2 to 1:6, the volume ratio of the silicon wafer cleaning additive to the H2O2 is 1:25 to 1:35, the silicon wafer cleaning additive is selected from SC110 silicon wafer cleaning additive, and the alkali is selected from KOH and / or NaOH.
4. The de-coating method according to claim 1 or 3, characterized in that: In the step of treating the silicon wafer with the first mixed solution, the temperature is 55° C. to 70° C. and the time is 1 min to 3 min.
5. The de-coating method according to claim 1, characterized in that: In the step of treating the silicon wafer with the second mixed solution, the temperature is 65° C. to 75° C. and the time is 4 min to 7 min.
6. The de-coating method according to claim 1 or 5, characterized in that: The alkali in the second mixed solution is selected from KOH and / or NaOH, and the volume fraction of the alkali is 2.5% to 5%.
7. The de-coating method according to claim 1, characterized in that: The steps of performing RCA cleaning on the silicon wafer include: by volume fraction, using a mixed solution of 0.3% to 5% alkali and 2% to 15% H2O2 for the first cleaning, using a 40% to 50% HF solution for the second cleaning, using a mixed solution of 0.3% to 3% alkali and 1% to 15% H2O2 for the third cleaning, and using a 13% to 20% HF solution for the fourth cleaning.
8. The de-coating method according to claim 7, characterized in that: The first cleaning temperature is 50°C to 70°C and the time is 1.5min to 2.5min; And / or, the second cleaning time is 2 min to 3.5 min; And / or, the temperature of the third washing is 55°C to 68°C, and the time is 1min to 2.5min; And / or, the fourth cleaning time is 2 minutes to 3 minutes.
9. A method for preparing a TOPCon battery, characterized in that: The invention comprises a de-coating method as described in any one of claims 1 to 8.
10. A TOPCon battery prepared by the method for preparing a TOPCon battery according to claim 9.