An additive and cleaning process for solving the problem of double-insert front side wrap-around printing in TOPCon cells

Abstract

The present invention discloses an additive and a cleaning process for solving the problem of double-insert front-side circumferential plating and printing in TOPCon cells, which relates to the technical field of solar cell production and manufacturing. The additive comprises the following components: an alkali corrosion catalyst, a polycarboxyl polymer, an organic acid, a chelating agent, a surfactant, lactic acid, tetramethylol glycoluril, hydroxypropyl-β-cyclodextrin, hyperbranched polytriazole hb-PTA-OEG, and water. The additive and the cleaning process can selectively etch polysilicon and adsorb on the surface of BPSG to protect it from alkali corrosion during the removal of circumferential plating. At the same time, the corrosion rate of circumferential plating in the alkali solution can be increased, so that the front-side polysilicon can be removed more quickly and thoroughly, and the gain effect on the battery efficiency is obvious.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell production and manufacturing, and particularly relates to an additive and a cleaning process for solving the problem of LPCVD double-insert front-side wrap-around and overprinting of TOPCon cells. Background Art

[0002] A solar cell is a device that directly converts light energy into electrical energy through the photovoltaic effect or the photochemical effect. As a type of solar cell, the TOPCON (Thin Oxide Passivated Contact) cell is widely used because of its high photovoltaic conversion efficiency, relatively mature equipment and processes, and high mass-production cost performance.

[0003] During the production process of TOPCon cells, it is necessary to grow polysilicon on one side of the silicon wafer by LPCVD. When coating the target growth surface through the current polysilicon growth method, it is inevitable that polysilicon will also grow on the edge of the other side, which we call wrap-around plating. If this part of the wrap-around plated polysilicon is not removed, it will significantly reduce the efficiency of the solar cell and at the same time cause serious appearance defects. Therefore, usually an additional process is required to remove the wrap-around plating. After the TOPCon cell process, a layer of borosilicate glass, i.e., BSG, will be formed on the front side of the silicon wafer, and at the same time, the PSG and polysilicon layers wrap-around and overprint on the front side also cover it, and the junction is BPSG. Polysilicon is very easy to be removed in a hot alkali solution, so only by immersing the silicon wafer in the hot alkali solution for a period of time can the polysilicon in the wrap-around plating part be removed. However, the reaction rates of the alkali solution with different substances are different. During the process of removing the wrap-around plating, if no protective measures are taken, the reaction rate of BPSG is the fastest. Therefore, the pyramids in this part are very easy to be corroded, and appearance defects such as wrap-around and overprinting will be formed after the oxide layer is removed; when cleaning the wrap-around plating, it may lead to incomplete removal or etching of the doped polysilicon layer, affecting the cell efficiency. It is precisely under this situation that the additive and the cleaning process for solving the LPCVD double-insert front-side wrap-around and overprinting of TOPCon cells emerge as the times require, and its appearance has attracted great attention in the industry.

[0004] Existing additives and cleaning processes for solving the problem of LPCVD double-insert front-side wrap-around printing in TOPCon cells more or less have technical defects such as slow and incomplete removal of wrap-around, etching of doped polysilicon layers, and limited gain effect on cell efficiency. To solve the above problems, a Chinese invention patent with the application publication number CN116808881A discloses an alkali polishing additive for the LPCVD double-insert process of TOPCON cells. The contents of its various components are: 0.01 - 0.1 parts by mass of a nanomaterial catalyst treated by a nano-homogenizer, 3 - 8 parts by mass of a complexing dispersant, 1 - 5 parts by mass of an inorganic salt, 5 - 8 parts by mass of a surfactant, and 78.9 - 90.99 parts by mass of deionized water. The TOPCON cells polished with the above additive can clean the wrap-around polySi and a small amount of BPSG, selectively protect BSG, control the alkali corrosion rate, uniformly clean and corrode the wrap-around, and there are no problems such as poor appearance with color difference. It realizes the same cell efficiency as the single-insert process in the double-insert process, doubles the production capacity, reduces the cost, and the key of this invention is the effect of selectively protecting BSG, thus solving the double-insert process and appearance problems. However, its gain effect on cell efficiency needs to be further improved, and it depends on specific processing equipment with a large capital investment.

[0005] Therefore, developing an additive and cleaning process for solving the LPCVD double-insert front-side wrap-around printing in TOPCon cells, which can selectively etch polysilicon and adsorb on the surface of BPSG to protect it from alkali corrosion during the removal of wrap-around, and at the same time can increase the corrosion rate of wrap-around in the alkali solution, making the removal of front-side polysilicon faster and more thorough, and having an obvious gain effect on cell efficiency, meets the market demand, has broad market value and application prospects, and is of great significance for promoting the further development of the TOPCon cell field. Summary of the Invention

[0006] The main purpose of the present invention is to provide an additive and cleaning process for solving the LPCVD double-insert front-side wrap-around printing in TOPCon cells, which can selectively etch polysilicon and adsorb on the surface of BPSG to protect it from alkali corrosion during the removal of wrap-around, and at the same time can increase the corrosion rate of wrap-around in the alkali solution, making the removal of front-side polysilicon faster and more thorough, and having an obvious gain effect on cell efficiency.

[0007] To achieve the above object, the present invention provides an additive for solving the problem of double-insert front-side circumferential overprinting in TOPCon cells, comprising the following components by mass percentage: an alkali corrosion catalyst 0.8wt%-1.5wt%, a polycarboxyl polymer 0.5wt%-1wt%, an organic acid 0.1wt%-0.6wt%, a chelating agent 0.3wt%-0.8wt%, a surfactant 0.8wt%-2wt%, lactic acid 0.3wt%-1wt%, tetramethylol glycoluril 0.05wt%-0.12wt%, hydroxypropyl-β-cyclodextrin 0.03wt%-0.1wt%, hyperbranched polytriazole hb-PTA-OEG 0.03wt%-0.08wt%, and the balance is water.

[0008] Preferably, the alkali corrosion catalyst is one or a combination of two or more of ammonium persulfate, m-chloroperbenzoic acid, and urea peroxide.

[0009] Preferably, the polycarboxyl polymer is one or a combination of two or more of polyaspartic acid, sodium polyacrylate, and polycarboxylate dispersant 5040.

[0010] Preferably, the organic acid is one or a combination of formic acid, acetic acid, citraconic acid, sulfamic acid, and methanesulfonic acid.

[0011] Preferably, the chelating agent is one or a combination of two or more of citric acid, tartaric acid, malic acid, EDTA, and sodium gluconate.

[0012] Preferably, the surfactant is one or a combination of two or more of span 80, tween 20, sodium dodecylbenzenesulfonate, and lauramidopropyl betaine.

[0013] Preferably, there are special requirements for the source of the hyperbranched polytriazole hb-PTA-OEG. In one embodiment of the present invention, the hyperbranched polytriazole hb-PTA-OEG is prepared by the method of Example 1 of the Chinese invention patent with the authorization announcement number CN104403103B.

[0014] Another object of the present invention is to provide a cleaning process for removing the circumferential degree by using the additive for solving the double-insert front-side circumferential overprinting in TOPCon cells, comprising the following steps:

[0015] Step S1: After mixing the components of the additive for solving the double-insert front-side circumferential overprinting in TOPCon cells evenly, an additive for solving the double-insert front-side circumferential overprinting in TOPCon cells is obtained;

[0016] Step S2: The silicon wafer is etched with hydrofluoric acid to remove the phosphosilicate glass on the front side;

[0017] Step S3: Add the additive prepared in Step S1 for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells into the alkali solution and stir well. Etch the silicon wafer treated in Step S2 with the alkali solution, and then successively perform deionized water cleaning, post-cleaning, deionized water washing, pickling, deionized water cleaning, slow lifting, and then drying.

[0018] Preferably, the mass percentage concentration of the hydrofluoric acid in Step S2 is 45 - 55 wt%. During acid etching, the silicon wafer is etched with the front side facing down in the PSG removal tank to protect the back PSG, and the acid etching time is ≥ 10 s.

[0019] Preferably, the alkali solution in Step S3 is a sodium hydroxide solution or a potassium hydroxide solution; the mass percentage concentration of the alkali solution is 1 - 2 wt%.

[0020] Preferably, the volume ratio of the additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells to the alkali solution in Step S3 is (0.5 - 1.5):100.

[0021] Preferably, the temperature of the alkali etching in Step S3 is 60 - 75 °C, and the time is 300 - 500 s.

[0022] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0023] (1) The cleaning process for de-winding and cleaning using the additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells disclosed in the present invention is simple and easy to implement, convenient for operation and control, has low dependence on equipment, consumes less energy, has little impact on the environment, has good appearance after cleaning, high alkali etching efficiency and good effect, is suitable for industrial production, and has high popularization and application value.

[0024] (2)The additive for solving the problem of LPCVD double-insert front side wrap-around and overprinting in TOPCon cells disclosed by the present invention comprises the following components calculated by mass percentage: an alkali corrosion catalyst of 0.8 wt% - 1.5 wt%, a polycarboxyl polymer of 0.5 wt% - 1 wt%, an organic acid of 0.1 wt% - 0.6 wt%, a chelating agent of 0.3 wt% - 0.8 wt%, a surfactant of 0.8 wt% - 2 wt%, lactic acid of 0.3 wt% - 1 wt%, tetramethylol glycoluril of 0.05 wt% - 0.12 wt%, hydroxypropyl β-cyclodextrin of 0.03 wt% - 0.1 wt%, and hyperbranched polytriazole hb-PTA-OEG of 0.03 wt% - 0.08 wt%, with the balance being water. Through the mutual cooperation and joint action of each component, the prepared additive can selectively etch polysilicon and adsorb on the BPSG surface, protecting it from alkali corrosion during the stripping process. At the same time, it can increase the corrosion rate of the wrap-around plating in the alkali solution, making the removal of the front-side polysilicon faster and more thorough. At the same time, it can protect the PN junction on the front side of the silicon wafer from being damaged, and has an obvious effect on increasing the battery efficiency.

[0025] (3)The alkali corrosion catalyst in the additive for solving the problem of LPCVD double-insert front side wrap-around and overprinting in TOPCon cells disclosed by the present invention can, to a certain extent, accelerate the oxidation step and thus enhance the decomposition effect of polysilicon; the polycarboxyl polymer has hydrophilic carboxyl groups, and has dipole-dipole interactions, hydrophilic-hydrophobic interactions, and hydrogen bond interactions with BPSG on the front side of the cell wafer, and is easy to adsorb at the BPSG position, forming a film by adsorption, preventing hydroxide from contacting BPSG, and realizing the selective corrosion of BPSG and polysilicon, so that the pyramids on the front side of the cell are not damaged during the stripping process; organic acid substances can further protect BPSG from being corroded. The selected organic acid substances selectively corrode polysilicon but do not react with single-crystalline silicon and silicon oxide, and due to their electrostatic interactions, they can be well adsorbed on the surface of the oxide layer, temporarily preventing the corrosion and damage of the adsorption sites, so as to better protect BPSG further; the chelating agent can effectively chelate metal ions, further enhance the cleaning effect, and prevent the silicon wafer from adsorbing metal ions and causing a reduction in the conversion efficiency; the surfactant, lactic acid, tetramethylol glycoluril, hydroxypropyl β-cyclodextrin, and hyperbranched polytriazole hb-PTA-OEG, through their mutual cooperation with other components, can further improve the effect and efficiency of selective etching, enabling the product to adapt to selectively etching polysilicon while protecting the front-side oxide layer and pyramids from being damaged. This additive product can completely protect the oxide layer and pyramids on the premise of promoting the cleaning of polysilicon during the alkali etching process, improve the cleaning effect of the silicon wafer, and at the same time protect the PN junction on the front side of the silicon wafer from being damaged. Description of the Drawings

[0026] Figure 1 It is the surface morphology diagram of the silicon wafer before stripping in Example 1 of the present invention;

[0027] Figure 2 This is the surface morphology diagram after de-winding plating in Embodiment 1 of the present invention;

[0028] Figure 3 This is the scanning electron microscope image of the pyramid at the BPSG part in Embodiment 1 of the present invention;

[0029] Figure 4 This is the scanning electron microscope image of the pyramid at the BPSG part in Comparative Example 1 of the present invention. Detailed implementation manners

[0030] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious variations.

[0031] Embodiment 1, An additive for solving the problem of double-insert front-side winding and overprinting in TOPCon cells, comprising the following components calculated by mass percentage: alkali corrosion catalyst 0.8wt%, polycarboxyl polymer 0.5wt%, organic acid 0.1wt%, chelating agent 0.3wt%, surfactant 0.8wt%, lactic acid 0.3wt%, tetramethylol glycoluril 0.05wt%, hydroxypropyl β-cyclodextrin 0.03wt%, hyperbranched polytriazole hb-PTA-OEG 0.03wt%, and the balance is water.

[0032] The alkali corrosion catalyst is ammonium persulfate; the polycarboxyl polymer is polyaspartic acid; the organic acid is formic acid; the chelating agent is citric acid; the surfactant is Span 80; the hyperbranched polytriazole hb-PTA-OEG is prepared by the method of Embodiment 1 of the Chinese invention patent with the authorization announcement number CN104403103B.

[0033] A cleaning process for de-winding cleaning using the additive for solving the double-insert front-side winding and overprinting in TOPCon cells, comprising the following steps:

[0034] Step S1, After mixing the components of the additive for solving the double-insert front-side winding and overprinting in TOPCon cells evenly, an additive for solving the double-insert front-side winding and overprinting in TOPCon cells is obtained;

[0035] Step S2, The silicon wafer is etched with hydrofluoric acid and then the phosphorus-silicate glass on the front side is removed;

[0036] Step S3: Add the additive prepared in Step S1 for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells into the lye and stir well. Etch the silicon wafer treated in Step S2 with the lye, and then successively wash it with deionized water, perform post-washing, wash with deionized water again, pickle, wash with deionized water again, slowly lift it, and then dry it.

[0037] In Step S2, the mass percentage concentration of the hydrofluoric acid is 45 wt%. During acid etching, the silicon wafer is etched with the front side facing down in the PSG removal tank to protect the back-side PSG, and the acid etching time is ≥ 10 s.

[0038] In Step S3, the lye is a sodium hydroxide solution; the mass percentage concentration of the lye is 1 wt%. In Step S3, the volume ratio of the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells to the lye is 0.5:100; in Step S3, the temperature of the alkali etching is 60 °C and the time is 300 s.

[0039] Example 2: An additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells, including the following components calculated by mass percentage: 1 wt% of alkali corrosion catalyst, 0.6 wt% of polycarboxyl polymer, 0.2 wt% of organic acid, 0.4 wt% of chelating agent, 1 wt% of surfactant, 0.5 wt% of lactic acid, 0.07 wt% of tetramethylol glycoluril, 0.05 wt% of hydroxypropyl β-cyclodextrin, 0.04 wt% of hyperbranched polytriazole hb-PTA-OEG, and the balance is water.

[0040] The alkali corrosion catalyst is m-chloroperbenzoic acid; the polycarboxyl polymer is sodium polyacrylate; the organic acid is acetic acid; the chelating agent is tartaric acid; the surfactant is Tween 20; the hyperbranched polytriazole hb-PTA-OEG is prepared by the method of Example 1 of the Chinese invention patent with the authorization announcement number CN104403103B.

[0041] A cleaning process for removing circumferential degree using the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells includes the following steps:

[0042] Step S1: After mixing the components of the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells evenly, obtain the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells.

[0043] Step S2: After acid etching the silicon wafer with hydrofluoric acid, remove the phosphorus-silicon glass on the front side.

[0044] Step S3: Add the additive prepared in Step S1 for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells into the lye and stir evenly. Etch the silicon wafers treated in Step S2 with the lye, and then successively wash them with deionized water, post-wash, deionized water wash, pickling, deionized water wash, slowly lift and then dry.

[0045] In Step S2, the mass percentage concentration of the hydrofluoric acid is 48 wt%; during acid etching, the silicon wafers are etched in the PSG removal tank with the front side facing down to protect the back-side PSG, and the acid etching time is ≥10 s; in Step S3, the lye is a potassium hydroxide solution; the mass percentage concentration of the lye is 1.2 wt%.

[0046] In Step S3, the volume ratio of the additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells to the lye is 0.8:100; in Step S3, the temperature of the lye etching is 65 °C and the time is 350 s.

[0047] Example 3: An additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells, comprising the following components by mass percentage: alkali corrosion catalyst 1.2 wt%, polycarboxyl polymer 0.7 wt%, organic acid 0.35 wt%, chelating agent 0.5 wt%, surfactant 1.3 wt%, lactic acid 0.6 wt%, tetramethylol glycoluril 0.09 wt%, hydroxypropyl β-cyclodextrin 0.07 wt%, hyperbranched polytriazole hb-PTA-OEG 0.06 wt%, and the balance is water.

[0048] The alkali corrosion catalyst is urea peroxide; the polycarboxyl polymer is polycarboxylate dispersant 5040; the organic acid is citraconic acid; the chelating agent is malic acid; the surfactant is sodium dodecylbenzenesulfonate; the hyperbranched polytriazole hb-PTA-OEG is prepared by the method of Example 1 of the Chinese invention patent with the authorization announcement number CN104403103B.

[0049] A cleaning process for de-winding and cleaning using the additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells includes the following steps:

[0050] Step S1: After mixing the components of the additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells evenly, obtain the additive for solving the problem of LPCVD double-insert front-side circumferential overprinting of TOPCon cells;

[0051] Step S2: After acid etching the silicon wafers with hydrofluoric acid, remove the phosphorus-silicon glass on the front side;

[0052] Step S3: Add the additive formulated in Step S1 for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells into the lye and stir evenly. Etch the silicon wafers treated in Step S2 with the lye, and then successively wash with deionized water, post-wash, wash with deionized water, pickling, wash with deionized water, slowly lift, and then dry.

[0053] In Step S2, the mass percentage concentration of the hydrofluoric acid is 50 wt%. During acid etching, the front side of the silicon wafer is facing down and etched in the PSG removal tank to protect the back PSG, and the acid etching time is ≥ 10 s. In Step S3, the lye is a sodium hydroxide solution; the mass percentage concentration of the lye is 1.5 wt%.

[0054] In Step S3, the volume ratio of the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells to the lye is 1:100; in Step S3, the temperature of the lye etching is 68 °C and the time is 400 s.

[0055] Example 4: An additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells, comprising the following components by mass percentage: alkali corrosion catalyst 1.4 wt%, polycarboxyl polymer 0.9 wt%, organic acid 0.5 wt%, chelating agent 0.7 wt%, surfactant 1.8 wt%, lactic acid 0.9 wt%, tetramethylol glycoluril 0.11 wt%, hydroxypropyl β-cyclodextrin 0.09 wt%, hyperbranched polytriazole hb-PTA-OEG 0.07 wt%, and the balance is water.

[0056] The alkali corrosion catalyst is composed of ammonium persulfate, m-chloroperoxybenzoic acid, and urea peroxide mixed in a mass ratio of 1:2:3; the polycarboxyl polymer is composed of polyaspartic acid, sodium polyacrylate, and polycarboxylate dispersant 5040 mixed in a mass ratio of 1:3:5; the organic acid is composed of formic acid, acetic acid, citraconic acid, sulfamic acid, and methanesulfonic acid mixed in a mass ratio of 1:1:2:1:3; the chelating agent is composed of citric acid, tartaric acid, malic acid, EDTA, and sodium gluconate mixed in a mass ratio of 2:1:3:2:5; the surfactant is composed of Span 80, Tween 20, sodium dodecylbenzenesulfonate, and lauramidopropyl betaine mixed in a mass ratio of 1:3:4:2; the hyperbranched polytriazole hb-PTA-OEG is prepared by the method of Example 1 of the Chinese invention patent with the authorization announcement number CN104403103B.

[0057] A cleaning process for de-winding and cleaning using the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells includes the following steps:

[0058] Step S1: After uniformly mixing each component of the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells, an additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells is obtained.

[0059] Step S2: The silicon wafer is etched with hydrofluoric acid and then the phosphorus-silicate glass on the front side is removed.

[0060] Step S3: The additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells prepared in Step S1 is added to the alkali solution and stirred evenly. The silicon wafer treated in Step S2 is alkali-etched, and then successively undergoes deionized water washing, post-washing, deionized water washing, acid washing, deionized water washing, slow lifting, and then drying.

[0061] In Step S2, the mass percentage concentration of the hydrofluoric acid is 53 wt%. During acid etching, the silicon wafer is placed face-down in the PSG removal tank for etching to protect the back-side PSG, and the acid etching time is ≥10 s. In Step S3, the alkali solution is a sodium hydroxide solution; the mass percentage concentration of the alkali solution is 1.8 wt%.

[0062] In Step S3, the volume ratio of the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells to the alkali solution is 1.3:100; the temperature of the alkali etching in Step S3 is 73 °C, and the time is 450 s.

[0063] Example 5: An additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells, including the following components by mass percentage: alkali corrosion catalyst 1.5 wt%, polycarboxyl polymer 1 wt%, organic acid 0.6 wt%, chelating agent 0.8 wt%, surfactant 2 wt%, lactic acid 1 wt%, tetramethylol glycoluril 0.12 wt%, hydroxypropyl β-cyclodextrin 0.1 wt%, hyperbranched polytriazole hb-PTA-OEG 0.08 wt%, and the balance is water.

[0064] The alkali corrosion catalyst is m-chloroperbenzoic acid; the polycarboxyl polymer is polycarboxylate dispersant 5040; the organic acid is sulfamic acid; the chelating agent is sodium gluconate; the surfactant is Span 80; the hyperbranched polytriazole hb-PTA-OEG is prepared according to the method of Example 1 of the Chinese invention patent with the authorization announcement number CN104403103B.

[0065] A cleaning process for removing the circumferential degree using the additive for solving the LPCVD double-insert front-side circumferential overprinting of TOPCon cells includes the following steps:

[0066] Step S1: After uniformly mixing each component of the additive for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells, an additive for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells is obtained.

[0067] Step S2: After the silicon wafers are etched with hydrofluoric acid, the phosphorus-silicate glass on the front side is removed.

[0068] Step S3: Add the additive for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells prepared in Step S1 to the alkaline solution and stir evenly. Then, etch the silicon wafers treated in Step S2 with the alkaline solution, and then sequentially perform deionized water cleaning, post-cleaning, deionized water washing, pickling, deionized water cleaning, slow lifting, and drying.

[0069] In Step S2, the mass percentage concentration of the hydrofluoric acid is 55 wt%. During the acid etching, the silicon wafers are placed face down in the PSG removal tank for etching to protect the PSG on the back side, and the acid etching time is ≥ 10 s.

[0070] In Step S3, the alkaline solution is sodium hydroxide solution or potassium hydroxide solution; the mass percentage concentration of the alkaline solution is 2 wt%; the volume ratio of the additive for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells to the alkaline solution in Step S3 is 1.5:100; the temperature of the alkaline etching in Step S3 is 75 °C, and the time is 500 s.

[0071] Comparative Example 1

[0072] The present invention provides an additive and a cleaning process for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells, which are similar to Example 1, except that hyperbranched polytriazole hb-PTA-OEG and lactobionic acid are not added.

[0073] Comparative Example 2

[0074] The present invention provides an additive and a cleaning process for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells, which are similar to Example 1, except that tetramethylol glycoluril and hydroxypropyl β-cyclodextrin are not added.

[0075] Perform relevant performance tests on the additives for solving the LPCVD double-insert front-end wrap-around printing of TOPCon cells involved in the above Examples 1-5 and Comparative Examples 1-2. The test results are shown in Table 1, and the test methods are as follows:

[0076] (1) Appearance: Observe the appearance changes of the silicon wafers after alkaline etching and cleaning. If the side etching is clean, the tower base size is normal, there is no residue in the front side cleaning of the wrap-around plating, the pyramid on the front surface of the silicon wafer is well protected, and the polysilicon layer on the back side is well protected, then the appearance passes; if any of the following situations occur: the pyramid texture on the front surface is damaged, there is an obvious wrap-around and overprint on the appearance, and the polysilicon layer on the back side is corroded, which damages the tunneling structure of the TOPCon battery, then the appearance fails.

[0077] (2) Electrical performance: After alkaline etching and cleaning of each silicon wafer, it enters the subsequent solar cell manufacturing process to make finished cell wafers. Use a dedicated test instrument for solar cell wafers, such as a single flash simulator, to test each made finished cell wafer; the test conditions are standard test conditions (STC): light intensity 1000W / m 2 ; spectral AM1.5; temperature 25°C; the test method is carried out in accordance with IEC904-1. The main electrical performance parameters of the cell wafers are: photoelectric conversion efficiency (Eta, unit: %), fill factor (FF, unit: %).

[0078] Table 1

[0079]

[0080] As can be seen from Table 1, the additive and cleaning process disclosed in the embodiments of the present invention for solving the wrap-around and overprint on the front side of TOPCon battery LPCVD double insertion has a more excellent alkaline etching and cleaning effect compared with the products of the comparative examples, and has a more obvious gain effect on the photoelectric conversion efficiency of solar cell wafers; the addition of hyperbranched polytriazole hb-PTA-OEG, lactobionic acid, tetramethylol glycoluril, and hydroxypropyl-β-cyclodextrin is beneficial to improving the above performance.

[0081] At the same time, taking Example 1 as an example, the surface morphology diagrams of the silicon wafers before wrap-around removal cleaning using the additives and cleaning methods of each example are shown in Figure 1 , and the surface morphology diagrams after wrap-around plating removal are shown in Figure 2 , and the scanning electron microscope diagrams of the pyramid at the BPSG part are shown in Figure 3 ; from Figures 1-3 it can be seen that the side etching is clean, the tower base size is normal, there is no residue in the front side cleaning of the wrap-around plating, and the pyramid on the front surface of the silicon wafer is well protected.

[0082] At the same time, the scanning electron microscope diagrams of the pyramid at the BPSG part of Comparative Example 1 are shown in Figure 4 , and from Figure 4 it can be seen that the pyramid texture on the front surface of the silicon wafer is damaged after alkaline etching and cleaning, and there is an obvious wrap-around and overprint on the appearance.

[0083] The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, various changes and improvements will occur to the present invention, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. An additive for solving the problem of LPCVD double-insertion front-side expansion printing of TOPCon cells, characterized in that: The invention comprises the following components calculated by mass percentage: 0.8wt%-1.5wt% of alkaline corrosion catalyst, 0.5wt%-1wt% of polycarboxyl polymer, 0.1wt%-0.6wt% of organic acid, 0.3wt%-0.8wt% of chelating agent, 0.8wt%-2wt% of surfactant, 0.3wt%-1wt% of lactobionic acid, 0.05wt%-0.12wt% of tetrahydroxymethyl glycoluril, 0.03wt%-0.1wt% of hydroxypropyl beta-cyclodextrin, 0.03wt%-0.08wt% of hyperbranched polytriazole hb-PTA-OEG, and the balance is water; the alkaline corrosion catalyst is one or a combination of two or more of ammonium persulfate, meta-chloroperbenzoic acid, and urea peroxide; the polycarboxyl polymer is one or a combination of two or more of polyaspartic acid, sodium polyacrylate, and polycarboxylate dispersant 5040.

2. The additive for solving the problem of LPCVD double-insertion front-side winding and expansion printing of TOPCon cells according to claim 1, characterized in that: The organic acid is one or a combination of formic acid, acetic acid, citraconic acid, aminosulfonic acid and methanesulfonic acid.

3. The additive for solving the problem of LPCVD double-insertion front-side expansion printing of TOPCon cells according to claim 1, characterized in that: The chelating agent is one or a combination of two or more of citric acid, tartaric acid, malic acid, EDTA and sodium gluconate.

4. The additive for solving the problem of LPCVD double-insertion front-side winding and expansion printing of TOPCon cells according to claim 1, characterized in that: The surfactant is one or a combination of two or more of Span 80, Tween 20, sodium dodecylbenzene sulfonate, and lauroylamidopropyl betaine.

5. A cleaning process for removing winding and cleaning using the additive for solving the problem of LPCVD double-insertion front winding and expansion printing of TOPCon cells as described in any one of claims 1 to 4, characterized in that: The steps include: Step S1, after uniformly mixing the components of the additive for solving the problem of LPCVD double-insertion front-side winding and expansion of TOPCon batteries, the additive for solving the problem of LPCVD double-insertion front-side winding and expansion of TOPCon batteries is obtained; Step S2, etching the silicon wafer with hydrofluoric acid to remove the phosphosilicate glass on the front side; Step S3, add the additive for solving the TOPCon battery LPCVD dual-insertion front-side expansion printing prepared in step S1 into the alkaline solution and stir evenly, alkali-etch the silicon wafer treated in step S2, and then sequentially perform deionized water washing, post-washing, deionized water washing, acid washing, deionized water washing, slow pulling and drying.

6. The cleaning process according to claim 5, characterized in that: The mass percentage concentration of the hydrofluoric acid in step S2 is 45-55wt%; during the acid etching, the silicon wafer is etched in the PSG removal groove with the front side facing downward to protect the PSG on the back side, and the acid etching time is ≥10s.

7. The cleaning process according to claim 5, characterized in that: The alkali solution described in step S3 is sodium hydroxide solution or potassium hydroxide solution; the mass percentage concentration of the alkali solution is 1-2wt%; the volume ratio of the additive used to solve the LPCVD double-insertion front winding and expansion printing of the TOPCon battery described in step S3 and the alkali solution is (0.5-1.5):

100.

8. The cleaning process according to claim 5, characterized in that: The alkaline etching in step S3 is carried out at a temperature of 60-75° C. and for a time of 300-500 seconds.

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