Micro-etching cleaning process for preparing TOPCon battery, preparation method and TOPCon battery

Abstract

The invention discloses a micro-etching cleaning process for preparing a TOPCon cell, a preparation method and the TOPCon cell, and relates to the technical field of production and manufacturing of photovoltaic cells, and the cleaning process comprises the following steps: carrying out the first pickling of a silicon wafer after the growth of a back tunneling oxide layer and the deposition of an intrinsic amorphous silicon layer are completed through PVD (Physical Vapor Deposition); performing primary pure water cleaning on the pickled silicon wafer; pickling the silicon wafer for the second time; cleaning the silicon wafer with pure water for the second time; carrying out slow lifting dehydration on the silicon wafer; and drying the silicon wafer. The silicon wafer is subjected to micro-etching cleaning by using hydrofluoric acid, hydrochloric acid and hydrogen peroxide with a certain concentration, and meanwhile, a repeated cleaning mode is adopted, so that PSG, BSG and BPSG on the front surface of the silicon wafer and PSG on the back surface of the silicon wafer can be removed to achieve a good cleaning purpose, meanwhile, the A-grade product rate and the EL yield of the battery piece can be improved, the yield is improved, and the cleaning process is simple to operate and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of production and manufacturing of photovoltaic cells, and in particular to a micro-etching and cleaning process for preparing a TOPCon cell, a preparation method and a TOPCon cell. Background Art

[0002] Tunnel Oxide Passivated Contact solar cell (TOPcon) is a new type of passivated contact solar cell first proposed by the Fraunhofer Institute for Solar Energy Research in Germany at the 28th European PVSEC Photovoltaic Conference in 2013. First, a 1-2 nm tunnel oxide layer is prepared on the back of the cell, and then a layer of doped polysilicon is deposited. The two together form a passivated contact structure, providing good interface passivation for the back of the silicon wafer.

[0003] The current TOPcon solar cells use the LPCVD (low-pressure vapor deposition, which is chemical vapor deposition carried out under a reaction pressure of 27 to 270 Pa. It has the advantages of good film quality and uniformity, high yield, low cost, and easy automation) process to deposit tunneling oxide layers and polysilicon on the back of silicon wafers. The tunneling oxide layer uses the quantum tunneling effect to allow electrons to pass smoothly and prevent the recombination of holes, forming a back passivation contact effect together with doped polysilicon.

[0004] The PVD route does not have the problem of plating around, so the conventional method is to pickle the silicon wafer, using a certain concentration of HF and HCl to clean the silicon wafer, which can remove PSG, BSG, BPSG on the front of the silicon wafer and PSG on the back of the silicon wafer. However, there is a certain proportion of unique EL defects in the preparation of TOPCon cells by the PVD route, and conventional pickling cannot solve the EL problem. Summary of the invention

[0005] Based on the fact that a certain proportion of unique EL defects exist in the TOPCon cells currently prepared by the PVD route, and conventional acid pickling cannot solve the EL problem, the purpose of the present invention is to provide a micro-etching cleaning process for preparing TOPCon cells, a preparation method and a TOPCon cell. The cleaning process adopts a micro-etching process in the acid pickling, which can not only realize the cleaning of the TOPCon cell, but also improve the A-level product rate of the cell and reduce the EL defects.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present application provides a micro-etching and cleaning process for preparing a TOPCon cell, comprising the following steps:

[0008] Performing the first acid wash on the silicon wafer after the back tunneling oxide layer growth and the intrinsic amorphous silicon layer deposition are completed by PVD;

[0009] Perform the first pure water cleaning on the pickled silicon wafer;

[0010] Performing a second pickling on the silicon wafer;

[0011] The silicon wafer is cleaned with pure water for the second time;

[0012] Slowly pull and dehydrate the silicon wafer;

[0013] Dry the silicon wafer.

[0014] When the silicon wafer is dried, hot air drying at room temperature (25° C.) to 100° C. is used, and the drying gas is nitrogen or clean air.

[0015] As a preferred embodiment of the present application, the first pickling is performed using a mixed solution formed by hydrofluoric acid, hydrochloric acid, and hydrogen peroxide.

[0016] As a preferred embodiment of the present application, the concentration of the hydrofluoric acid is 0.5% to 5%; the concentration of the hydrochloric acid is 0.2% to 2%; and the concentration of the hydrogen peroxide is 2% to 15%.

[0017] As a preferred embodiment of the present application, the cleaning time of the first pickling is 150s to 600s, and the temperature is 20°C to 40°C.

[0018] As a preferred embodiment of the present application, the time for the first pure water cleaning is 50s to 150s.

[0019] As a preferred embodiment of the present application, the second pickling is performed using a hydrofluoric acid solution with a concentration of 5% to 20%.

[0020] As a preferred embodiment of the present application, the cleaning time of the second pickling is 100s to 600s, and the temperature is 20°C to 40°C.

[0021] As a preferred embodiment of the present application, the cleaning time of the silicon wafer during slow pulling and dehydration is 5s to 30s and the temperature is 20°C to 60°C.

[0022] In a second aspect, the present application provides a method for preparing a TOPCon battery, comprising the following steps:

[0023] The N-type single crystal silicon wafer is placed in an alkaline solution and an additive for double-sided texturing;

[0024] The textured silicon wafer obtained after texturing is subjected to tubular low-pressure boron diffusion to complete the production of PN junction;

[0025] The boron-diffused silicon wafer is etched with HF solution to the back surface borosilicate glass, and then an alkaline solution and an additive are used to polish the back side;

[0026] Using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the obtained silicon wafer;

[0027] The deposited silicon wafer is placed in a quartz tube for activation to complete the transformation from amorphous to polycrystalline;

[0028] Perform the first pure water cleaning on the pickled silicon wafer;

[0029] Performing a second pickling on the silicon wafer;

[0030] The silicon wafer is cleaned with pure water for the second time;

[0031] Slowly pull and dehydrate the silicon wafer;

[0032] Drying the silicon wafer;

[0033] The cleaned silicon wafer is subjected to atomic deposition method to deposit Al2O3 on the front surface;

[0034] The deposited silicon wafer is deposited by PECVD to form a SiNx:H solid film on the front surface to complete the production of the front surface anti-reflection layer;

[0035] A SiNx:H solid film is formed on the back surface by PECVD deposition to complete the production of the back surface anti-reflection layer;

[0036] The silicon wafers with double-sided SiNx:H coating are printed with metal paste by screen printing and sintered. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0037] Among them, the method of silicon wafer texturing is:

[0038] 1) Etching and removing the damaged layer on the surface of the single crystal silicon wafer;

[0039] 2) Cleaning the single crystal silicon wafer with deionized water;

[0040] 3) Use a texturing solution containing sodium hydroxide, isopropyl alcohol and sodium silicate for texturing.

[0041] The dosage ratio of sodium hydroxide, isopropyl alcohol and sodium silicate is (3-3.5):(18-21):1.

[0042] Isopropyl alcohol can speed up the reaction and eliminate bubbles; using a small amount of sodium silicate mixed with sodium hydroxide and isopropyl alcohol to make the suede surface can obtain a more uniform surface structure with lower reflectivity.

[0043] In a third aspect, the present application provides a TOPCon battery prepared using the above-mentioned preparation method.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] The present invention uses hydrofluoric acid, hydrochloric acid and hydrogen peroxide of a certain concentration to perform micro-etching cleaning on the silicon wafer, and adopts a multiple cleaning method at the same time, which can not only remove PSG, BSG, BPSG on the front side of the silicon wafer and PSG on the back side of the silicon wafer, achieving a good cleaning purpose, but also improve the A-level product rate of the battery cell and reduce EL defects, thereby improving the yield rate, and the cleaning process is simple to operate and low in cost. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0047] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for preparing a high-efficiency TOPCon battery based on a PVD route, and the specific preparation steps are:

[0050] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0051] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0052] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0053] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0054] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0055] S6. The activated silicon wafer is subjected to the first pickling with a mixed solution of 3% hydrofluoric acid, 1% hydrochloric acid and 9% hydrogen peroxide; the cleaning time is 350s and the temperature is set to 30°C. After the first pickling, a small amount of polysilicon on the poly layer on the back of the silicon wafer can be removed, achieving a micro-etching effect similar to alkali texturing, while removing metal ions and organic dirt introduced in the large process on the front.

[0056] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0057] S8. The silicon wafer is pickled for the second time using a hydrofluoric acid solution with a concentration of 10%, the cleaning time is 300 seconds, and the temperature is set to 30° C. The second pickling using a higher concentration of hydrofluoric acid solution can completely remove the BSG layer on the front side and part of the wet oxygen oxide layer formed by hydrogen peroxide, thereby achieving a hydrophobic effect.

[0058] S9. Rinse the silicon wafer with pure water for a second time, with the cleaning time being 100 seconds.

[0059] S10, slowly pull and dehydrate the silicon wafer, the cleaning time is 20s, and the temperature is set to 40°C.

[0060] S11, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0061] S12, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0062] S13, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition, thereby completing the production of the front surface anti-reflection layer.

[0063] S14, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0064] S15. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0065] Example 2

[0066] This embodiment provides a method for preparing a high-efficiency TOPCon battery based on a PVD route. The difference from Example 1 is that the pickling mixed solution used in step S6 of this embodiment is: a mixed solution of hydrofluoric acid with a concentration of 0.5%, hydrochloric acid with a concentration of 0.2% and hydrogen peroxide with a concentration of 2%. The other technical features are the same as those of Example 1.

[0067] The specific preparation steps are:

[0068] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0069] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0070] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0071] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0072] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0073] S6. The activated silicon wafer is subjected to the first pickling with a mixed solution of 0.5% hydrofluoric acid, 0.2% hydrochloric acid and 2% hydrogen peroxide; the cleaning time is 350s and the temperature is set to 30°C. After the first pickling, a small amount of polysilicon on the poly layer on the back of the silicon wafer can be removed, achieving a micro-etching effect similar to alkali texturing, while removing the metal ions and organic dirt introduced in the large process on the front.

[0074] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0075] S8. The silicon wafer is pickled for the second time using a hydrofluoric acid solution with a concentration of 10%, the cleaning time is 300 seconds, and the temperature is set to 30° C. The second pickling using a higher concentration of hydrofluoric acid solution can completely remove the BSG layer on the front side and part of the wet oxygen oxide layer formed by hydrogen peroxide, thereby achieving a hydrophobic effect.

[0076] S9. Rinse the silicon wafer with pure water for a second time, with the cleaning time being 100 seconds.

[0077] S10, slowly pull and dehydrate the silicon wafer, the cleaning time is 20s, and the temperature is set to 40°C.

[0078] S11, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0079] S12, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0080] S13, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition, thereby completing the production of the front surface anti-reflection layer.

[0081] S14, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0082] S15. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0083] Example 3

[0084] This embodiment provides a method for preparing a high-efficiency TOPCon battery based on a PVD route. The difference from Example 1 is that the pickling mixed solution used in step S6 of this embodiment is: a mixed solution of hydrofluoric acid with a concentration of 5%, hydrochloric acid with a concentration of 2% and hydrogen peroxide with a concentration of 15%. Other technical features are the same as those of Example 1.

[0085] The specific preparation steps are:

[0086] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0087] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0088] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0089] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0090] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0091] S6. The activated silicon wafer is subjected to the first pickling with a mixed solution of 5% hydrofluoric acid, 2% hydrochloric acid and 15% hydrogen peroxide; the cleaning time is 350s and the temperature is set to 30°C. After the first pickling, a small amount of polysilicon on the poly layer on the back of the silicon wafer can be removed, achieving a micro-etching effect similar to alkali texturing, while removing the metal ions and organic dirt introduced in the large process on the front.

[0092] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0093] S8. The silicon wafer is pickled for the second time using a hydrofluoric acid solution with a concentration of 10%, the cleaning time is 300 seconds, and the temperature is set to 30° C. The second pickling using a higher concentration of hydrofluoric acid solution can completely remove the BSG layer on the front side and part of the wet oxygen oxide layer formed by hydrogen peroxide, thereby achieving a hydrophobic effect.

[0094] S9. Rinse the silicon wafer with pure water for a second time, with the cleaning time being 100 seconds.

[0095] S10, slowly pull and dehydrate the silicon wafer, the cleaning time is 20s, and the temperature is set to 40°C.

[0096] S11, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0097] S12, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0098] S13, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition, thereby completing the production of the front surface anti-reflection layer.

[0099] S14, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0100] S15. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0101] Comparative Example 1

[0102] This comparative example provides a method for preparing a high-efficiency TOPCon battery based on a PVD route. Unlike Example 1, this comparative example does not perform a second acid wash and a second pure water wash, and other technical features are the same as those of Example 1.

[0103] The specific preparation steps are:

[0104] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0105] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0106] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0107] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0108] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0109] S6. The activated silicon wafer is pickled with a mixed solution of 3% hydrofluoric acid, 1% hydrochloric acid and 9% hydrogen peroxide; the cleaning time is 350s and the temperature is set to 30°C. After one pickling, a small amount of polysilicon on the poly layer on the back of the silicon wafer can be removed, and the micro-etching effect similar to alkali texturing can be basically achieved. At the same time, the metal ions and organic dirt introduced in the large process on the front are removed, but the BSG layer on the front and the wet oxygen oxide layer formed by part of hydrogen peroxide cannot be completely removed.

[0110] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0111] S8. Slowly pull and dehydrate the silicon wafer, the cleaning time is 20 seconds, and the temperature is set to 40°C.

[0112] S9, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0113] S10, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0114] S11, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition to complete the production of the front surface anti-reflection layer.

[0115] S12, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0116] S13. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0117] Comparative Example 2

[0118] This comparative example provides a method for preparing a high-efficiency TOPCon battery based on a PVD route. Unlike Example 1, the mixed solution used in the first pickling in this comparative example is 3% hydrofluoric acid and 1% hydrochloric acid, and no hydrogen peroxide is added. Other technical features are the same as those in Example 1.

[0119] The specific preparation steps are:

[0120] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0121] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0122] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0123] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0124] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0125] S6. The activated silicon wafer is pickled for the first time using a mixed solution of 3% hydrofluoric acid and 1% hydrochloric acid; the cleaning time is 350s and the temperature is set to 30°C. After the first pickling, a small amount of polysilicon on the poly layer on the back of the silicon wafer can be removed, and the micro-etching effect similar to alkali texturing can not be achieved. At the same time, the metal ions and organic dirt introduced in the large process on the front side can be removed.

[0126] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0127] S8. The silicon wafer is pickled for the second time using a hydrofluoric acid solution with a concentration of 10%, the cleaning time is 300 seconds, and the temperature is set to 30° C. The second pickling using a higher concentration of hydrofluoric acid solution can completely remove the BSG layer on the front side and part of the wet oxygen oxide layer formed by hydrogen peroxide, thereby achieving a hydrophobic effect.

[0128] S9. Rinse the silicon wafer with pure water for a second time, with the cleaning time being 100 seconds.

[0129] S10, slowly pull and dehydrate the silicon wafer, the cleaning time is 20s, and the temperature is set to 40°C.

[0130] S11, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0131] S12, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0132] S13, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition, thereby completing the production of the front surface anti-reflection layer.

[0133] S14, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0134] S15. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0135] Comparative Example 3

[0136] This comparative example provides a method for preparing a high-efficiency TOPCon battery based on a PVD route. Unlike Example 1, the mixed solution used in the first pickling in this comparative example is a mixed solution of 1% hydrochloric acid and 9% hydrogen peroxide, and no hydrofluoric acid is added. Other technical features are the same as those in Example 1.

[0137] The specific preparation steps are:

[0138] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0139] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0140] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0141] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0142] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0143] S6. The activated silicon wafer is subjected to the first pickling with a mixed solution of 9% hydrogen peroxide and 1% hydrochloric acid; the cleaning time is 350s and the temperature is set to 30°C. After the first pickling, since the front oxide layer and BSG layer cannot be removed, the small amount of polysilicon on the poly layer on the back of the silicon wafer cannot be removed, and the micro-etching effect similar to alkali texturing cannot be achieved, but the metal ions and organic dirt introduced in the large process on the front can be removed.

[0144] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0145] S8. The silicon wafer is pickled for the second time using a hydrofluoric acid solution with a concentration of 10%, the cleaning time is 300 seconds, and the temperature is set to 30° C. The second pickling using a higher concentration of hydrofluoric acid solution can completely remove the BSG layer on the front side and part of the wet oxygen oxide layer formed by hydrogen peroxide, thereby achieving a hydrophobic effect.

[0146] S9. Rinse the silicon wafer with pure water for a second time, with the cleaning time being 100 seconds.

[0147] S10, slowly pull and dehydrate the silicon wafer, the cleaning time is 20s, and the temperature is set to 40°C.

[0148] S11, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0149] S12, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0150] S13, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition, thereby completing the production of the front surface anti-reflection layer.

[0151] S14, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0152] S15. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0153] Comparative Example 4

[0154] This comparative example provides a method for preparing a high-efficiency TOPCon battery based on a PVD route. Unlike Example 1, the mixed solution used in the first pickling in this comparative example is a mixed solution of 3% hydrofluoric acid and 9% hydrogen peroxide, and no hydrochloric acid is added. Other technical features are the same as those in Example 1.

[0155] The specific preparation steps are:

[0156] S1. Place an N-type single crystal silicon wafer in a KOH solution with a mass fraction of 2% (wherein the KOH solution can be replaced by a NaOH solution) and a texturing additive with a volume fraction of 0.6% for double-sided texturing; wherein the texturing additive is a conventional texturing additive.

[0157] S2. Perform tubular low-pressure boron diffusion on the textured silicon wafer obtained after texturing to complete the production of the PN junction.

[0158] S3. Use HF solution to remove BSG formed during the back boron diffusion process on the boron-diffused silicon wafer, and then use a KOH solution with a mass fraction of 7% (the KOH solution can be replaced by a NaOH solution) and an alkali polishing additive with a volume fraction of 0.6% to perform back polishing and edge etching; the alkali polishing additive is a conventional alkali polishing additive.

[0159] S4, using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the silicon wafer obtained in step S3.

[0160] S5. Place the deposited silicon wafer into a quartz tube and activate it at 850°C to complete the transformation from amorphous to polycrystalline.

[0161] S6. The activated silicon wafer is subjected to the first pickling with a mixed solution of 9% hydrogen peroxide and 3% hydrofluoric acid; the cleaning time is 350s and the temperature is set to 30°C. After the first pickling, a small amount of polysilicon on the poly layer on the back of the silicon wafer can be removed, achieving a micro-etching effect similar to alkaline texturing, but it will weaken the effect of removing metal ions and organic dirt introduced in the large process on the front side.

[0162] S7. The silicon wafer after the acid washing is cleaned with pure water for the first time, and the cleaning time is 100 seconds.

[0163] S8. The silicon wafer is pickled for the second time using a hydrofluoric acid solution with a concentration of 10%, the cleaning time is 300 seconds, and the temperature is set to 30° C. The second pickling using a higher concentration of hydrofluoric acid solution can completely remove the BSG layer on the front side and part of the wet oxygen oxide layer formed by hydrogen peroxide, thereby achieving a hydrophobic effect.

[0164] S9. Rinse the silicon wafer with pure water for a second time, with the cleaning time being 100 seconds.

[0165] S10, slowly pull and dehydrate the silicon wafer, the cleaning time is 20s, and the temperature is set to 40°C.

[0166] S11, drying the silicon wafer, the drying method is: using hot air drying at a temperature of 60°C, wherein the gas is nitrogen or clean air. After this step is completed, PSG, BSG, BPSG on the front side of the silicon wafer and PSG and some dirt on the back side of the silicon wafer can be effectively removed.

[0167] S12, depositing an Al2O3 film layer on the front surface of the cleaned silicon wafer using an atomic deposition method.

[0168] S13, forming a SiNx:H solid film on the front surface of the deposited silicon wafer by PECVD deposition, thereby completing the production of the front surface anti-reflection layer.

[0169] S14, forming a SiNx:H solid film on the back side by PECVD deposition to complete the production of the back surface anti-reflection layer.

[0170] S15. Print metal paste on the double-sided SiNx:H coated silicon wafer by screen printing and perform high-temperature sintering. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

[0171] Compared with the comparative example, the advantages of Examples 1 to 3 of the present application are:

[0172] 1. Two acid washes are required. After the first acid wash, in addition to removing the BSG layer on the front and the oxide layer on the back, a small amount of polysilicon on the poly layer on the back of the silicon wafer can also be removed, thereby achieving a micro-etching effect similar to alkaline texturing, while removing metal ions and organic dirt introduced in the large process on the front.

[0173] 2. Secondary pickling enhances the cleaning effect: The second pickling can completely remove the front BSG layer that is not needed by the terminal battery and the wet oxygen oxide layer formed by part of the hydrogen peroxide, achieving the hydrophobic effect on the surface of the silicon wafer and ensuring the appearance and quality of the product.

[0174] The TOPCon cells prepared in the examples and comparative examples were tested for electrical performance parameters and A-grade yield under the same conditions. The electrical performance parameter test was conducted in accordance with the standard test conditions for photovoltaic cells established by the International Electrotechnical Commission (IEC), where the solar radiation intensity was 1000W / m2, the spectrum was AM1.5, and the temperature was 25°C; the A-grade yield test adopted the product appearance and EL test method of the "General N-type Battery Quality Inspection Standard" in the photovoltaic industry, that is, the battery surface had no obvious dirt, fingerprints, drug residues, dirt, watermarks, scratches and other appearance abnormalities, and the EL image had no black spots, black spots, black edges, dark pieces, clouds, concentric circles, hidden cracks, fixture marks and other black defects. The test data under the same conditions are shown in the following table:

[0175]

[0176]

[0177] The comparison results show that the appearance of the product prepared by the invention content of the embodiment of this application meets the industry's N-type battery quality standards, and the hydrophobicity meets the "Industry Silicon Wafer Surface Hydrophilicity Determination Standard". Compared with Comparative Examples 2 and 4, the TOPCon battery prepared in Example 1 has better efficiency, and the EL defect is reduced by more than 2%, which can greatly improve the product A-level rating rate. In addition, the entire process does not require additional cleaning equipment, and can be implemented on existing cleaning equipment. Only one chemical needs to be added. The process has strong compatibility and is easy to quickly promote the production line and convert into economic benefits.

[0178] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A micro-etching and cleaning process for preparing TOPCon cells, characterized in that: The following steps are involved: Performing the first acid wash on the silicon wafer after the back tunneling oxide layer growth and the intrinsic amorphous silicon layer deposition are completed by PVD; Perform the first pure water cleaning on the pickled silicon wafer; Performing a second pickling on the silicon wafer; The silicon wafer is cleaned with pure water for the second time; Slowly pull and dehydrate the silicon wafer; Dry the silicon wafer.

2. A micro-etching and cleaning process for preparing TOPCon cells according to claim 1, characterized in that: The first pickling is performed using a mixed solution of hydrofluoric acid, hydrochloric acid and hydrogen peroxide.

3. A micro-etching and cleaning process for preparing TOPCon cells according to claim 2, characterized in that: The concentration of the hydrofluoric acid is 0.5% to 5%; the concentration of the hydrochloric acid is 0.2% to 2%; and the concentration of the hydrogen peroxide is 2% to 15%.

4. A micro-etching and cleaning process for preparing TOPCon cells according to claim 1, characterized in that: The cleaning time of the first pickling is 150s to 600s, and the temperature is 20℃ to 40℃.

5. A micro-etching and cleaning process for preparing TOPCon cells according to claim 1, characterized in that: The first pure water cleaning time is 50s to 150s.

6. A micro-etching and cleaning process for preparing TOPCon cells according to claim 1, characterized in that: The second pickling is carried out using a hydrofluoric acid solution with a concentration of 5% to 20%.

7. A micro-etching and cleaning process for preparing TOPCon cells according to claim 1, characterized in that: The cleaning time of the second pickling is 100s to 600s, and the temperature is 20℃ to 40℃.

8. The micro-etching and cleaning process for preparing TOPCon cells according to claim 1, characterized in that: The cleaning time for slow pulling and dehydration of the silicon wafer is 5s to 30s, and the temperature is 20°C to 60°C.

9. A method for preparing a TOPCon battery, characterized in that: The following steps are involved: The N-type single crystal silicon wafer is placed in an alkaline solution and an additive for double-sided texturing; The textured silicon wafer obtained after texturing is subjected to tubular low-pressure boron diffusion to complete the production of PN junction; The boron-diffused silicon wafer is etched with HF solution to the back surface borosilicate glass, and then an alkaline solution and an additive are used to polish the back side; Using a plate-type PVD device to grow a back-side tunneling oxide layer and a phosphorus-containing poly layer on the obtained silicon wafer; The deposited silicon wafer is placed in a quartz tube for activation to complete the transformation from amorphous to polycrystalline; The silicon wafer is cleaned by using the micro-etching cleaning process described in any one of claims 1 to 8; The cleaned silicon wafer is subjected to atomic deposition method to deposit Al2O3 on the front surface; The deposited silicon wafer is deposited by PECVD to form a SiNx solid film on the front surface to complete the production of the front surface anti-reflection layer; A SiNx:H solid film is formed on the back surface by PECVD deposition to complete the production of the back surface anti-reflection layer; The silicon wafers with double-sided SiNx:H coating are printed with metal paste by screen printing and sintered. Electrodes are formed on the front and back sides to collect and transmit current, forming ohmic contacts and completing the preparation of TOPcon solar cells.

10. A TOPCon battery, characterized in that: The preparation method according to claim 9 is used for preparation.

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