Preparation method of photovoltaic cell for improving ALD passivation and photovoltaic cell

Abstract

The invention discloses a photovoltaic cell preparation method for improving ALD passivation and a photovoltaic cell, and belongs to the technical field of photovoltaic cells. The preparation method comprises the following steps: performing texturing, front boron diffusion, oxidation, back etching and polishing on a silicon wafer, preparing a back tunneling oxide layer and an amorphous silicon layer, performing acid pickling, removing the tunneling oxide layers on the back and the side surfaces through cleaning, preparing front and back passivation films, printing electrodes and the like, washing with water: washing with a cleaning solution containing potassium hydroxide and hydrogen peroxide, washing with water, pickling, and washing with water; repeating the steps; and cleaning with the oxidizing liquid again, and washing with water. According to the invention, through the improvement of the processing technology of the tunneling oxide layer and the amorphous silicon back winding plating, the yield of the battery production line is improved, the control of the production line is simpler and more convenient, the promotion of the passivation of the oxide layer before ALD is more stable, and the battery conversion efficiency of the production line is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a preparation method of a photovoltaic cell for improving ALD passivation and a photovoltaic cell. Background Art

[0002] Nowadays, the preparation method of TOPCon cells is relatively mature. The current mainstream preparation process includes (see CN110299422B, CN112599615B): double-sided texturing of N-type Cz-Si, front boron diffusion, back BSG etching + alkali polishing, preparation of tunneling oxide layer and doped amorphous silicon (a-Si:H) on the back, high-temperature annealing, de-plating, front aluminum oxide, front silicon nitride / silicon oxynitride stacking structure, back silicon nitride, screen printing of front and back metal electrodes, sintering light injection, laser assisted sintering (LECO). The traditional ALD (atomic layer deposition) process uses water or ozone as the oxygen source precursor and trimethylaluminum as the aluminum source precursor to react. The resulting aluminum oxide film has poor density or low efficiency.

[0003] At present, ALD mainly achieves the effect of passivation improvement by growing an oxide layer before preparing an aluminum oxide film layer through pre-ozone treatment / pre-water treatment. However, after long-term use of the ALD machine, dust will accumulate inside, affecting the passivation effect of the oxide layer. In addition, in the production process, after long-term use of the RCA process machine, metal ions are not easily removed cleanly. Metal ions are deep-level impurities for photovoltaic cells, and have strong recombination ability for carriers, and will become recombination centers. Reaction byproducts, additives and other organic matter will accumulate in the tank. After the silicon wafer passes through the tank, organic matter is easy to adhere to the silicon wafer, affecting the battery conversion efficiency. Therefore, solutions to the above technical problems are urgently needed. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a photovoltaic cell and a photovoltaic cell for improving ALD passivation. The present invention focuses on improving the processing technology of preparing a tunneling oxide layer and amorphous silicon post-plating, thereby improving the yield of the battery mass production line, making the control of the production line simpler, and promoting the passivation of the ALD front oxide layer more stable, thereby improving the conversion efficiency of the production line battery.

[0005] The technical solution of the present invention is as follows:

[0006] A first aspect of the present invention provides a method for preparing a photovoltaic cell for improving ALD passivation, the method comprising the following steps:

[0007] S1: Silicon wafer texturing treatment to form a pyramid morphology on both sides of the silicon wafer.

[0008] S2: Boron diffusion doping is performed on the front side of the silicon wafer, and oxidation treatment is performed, and a borosilicate glass layer is grown on the front side of the silicon wafer.

[0009] S3: Etching and polishing the back of the silicon wafer to remove the borosilicate glass on the back and sides.

[0010] S4: Prepare a tunnel oxide layer and an amorphous silicon layer on the back side of the silicon wafer.

[0011] S5: Pickling to remove the phosphosilicate glass on the front and sides of the silicon wafer.

[0012] S6: The silicon wafer is cleaned again to remove the tunneling oxide layer on the front and side surfaces.

[0013] S7: After step S6, aluminum oxide and silicon nitride / silicon oxynitride passivation films are sequentially prepared on the front side of the silicon wafer cleaned; and a silicon nitride passivation film is prepared on the back side of the silicon wafer.

[0014] S8: Graphic electrodes are printed on the front and back sides of the silicon wafer, sintered, and treated with light injection, followed by laser-induced sintering.

[0015] Step S6 includes:

[0016] S6-1: The silicon wafer is first cleaned with alkaline solution and then washed with water.

[0017] S6-2: After cleaning with the first cleaning solution, rinse with water.

[0018] S6-3: After pickling, wash with water.

[0019] S6-4: Repeat the above steps S6-2 and S6-3.

[0020] S6-5: After cleaning again with the second cleaning solution, rinse with water.

[0021] S6-6: After slowly pulling and lifting through the water washing tank, it is dried.

[0022] The first cleaning solution includes potassium hydroxide and hydrogen peroxide.

[0023] The second cleaning solution includes an oxidant.

[0024] Preferably, in step S6-1, the alkali solution includes a potassium hydroxide solution; the mass fraction of the potassium hydroxide solution is 40-50%; it also includes an additive and water; the additive is an additive for protecting the borosilicate glass layer; the temperature of the alkali solution cleaning is 65-75°C, and the time is 200-300s; the water washing time is 100-200s.

[0025] Preferably, in the alkali solution, the volume ratio of the potassium hydroxide solution, the additive and the water is 30-50:8-10:582-690.

[0026] Preferably, in step S6-2, the first cleaning solution includes a hydrogen peroxide solution, a potassium hydroxide solution and water.

[0027] Preferably, the concentration of the hydrogen peroxide solution is 30-35wt%, and the concentration of the potassium hydroxide solution is 40-50wt%; the volume ratio of the hydrogen peroxide solution, the potassium hydroxide solution, and the water is 10-30:5-10:605-710.

[0028] Preferably, in step S6-2, the cleaning temperature is 55-65°C and the time is 150-250s; the water washing time is 100-200s.

[0029] Preferably, in step S6-3, the pickling cleaning solution includes hydrofluoric acid solution and water; the concentration of the hydrofluoric acid solution is 35-40wt%; the volume ratio of the hydrofluoric acid solution to water is 3-10:617-740; the pickling time is 180-250s, the temperature is 60-70°C; the water washing time is 100-200s.

[0030] Preferably, the oxidant includes at least one of ozone, concentrated nitric acid, hydrogen peroxide, persulfate, and peroxide; preferably, the oxidant is ozone; in step S6-5, the second cleaning liquid also includes a chlorine source solution and water; the chlorine source solution includes at least one of chlorine water, hydrochloric acid, NH4Cl solution, and HClO solution.

[0031] Preferably, in step S6-5, the concentration of the chlorine source solution is 35-40wt%; in the second cleaning solution, the mass fraction of the oxidant is 3-8‰; the volume ratio of the chlorine source solution to the water is 15-30:605-720; the cleaning time of the second cleaning solution is 180-250s; and the water washing time is 100-200s.

[0032] Preferably, in step S6-6, the treatment temperature of the slow-pulling and lifting water washing tank is 60-80°C, and the time is 60-120s; the temperature of the drying is 80-100°C, and the time is 720-900s.

[0033] A second aspect of the present invention provides a photovoltaic cell prepared by the preparation method described in the first aspect.

[0034] The beneficial technical effects of the present invention are:

[0035] The present invention improves the silicon wafer de-plating process, especially by adding a strong oxidant and / or chlorine source hydrochloric acid cleaning process, and utilizes the ability of chlorine to remove metal ions in coordination with the strong oxidizing property of the strong oxidant and the effect of oxygen molecules, so that metal ions such as potassium ions and sodium ions can be effectively removed while preparing a high-quality silicon oxide film layer. At the same time, the strong oxidant has a good cleaning effect on organic matter, and can effectively remove organic pollution such as additives and by-products on the surface of the silicon wafer, increase the hydrogen content of the front silicon oxide layer, improve hydrogen passivation, stabilize the passivation improvement of the aluminum oxide front oxide layer, simplify the control of the production line, improve the yield rate of the production line, and thus improve the production efficiency of the production line. The yield rate of the production line is increased by 0.5%-2%, and the battery conversion efficiency is increased by 0.03%-0.08%. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the silicon wafer of the present invention.

[0037] In the figure: 1. Aluminum oxide layer; 2. P layer; 3. Tunneling oxide layer; 4. Silicon nitride; 5. Silicon nitride + silicon oxynitride layer; 6. Front oxide layer; 7. n-poly layer. DETAILED DESCRIPTION

[0038] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0039] A first aspect of the present invention provides a method for preparing a photovoltaic cell for improving ALD passivation, the method comprising the following steps:

[0040] S1: Silicon wafer texturing treatment to form a pyramid morphology on both sides of the silicon wafer.

[0041] S2: Boron diffusion doping is performed on the front side of the silicon wafer, and oxidation treatment is performed, and a borosilicate glass layer (BSG) is grown on the front side of the silicon wafer.

[0042] S3: Etching and polishing the back of the silicon wafer to remove the borosilicate glass on the back and sides.

[0043] S4: Prepare a tunnel oxide layer and an amorphous silicon layer on the back side of the silicon wafer.

[0044] S5: Pickling to remove the phosphosilicate glass on the front and sides of the silicon wafer.

[0045] S6: The silicon wafer is cleaned again to remove the tunneling oxide layer on the front and side surfaces.

[0046] S7: After step S6, aluminum oxide and silicon nitride / silicon oxynitride passivation films are sequentially prepared on the front side of the silicon wafer cleaned; and a silicon nitride passivation film is prepared on the back side of the silicon wafer.

[0047] S8: Graphic electrodes are printed on the front and back of the silicon wafer, sintered, and light injected, and then laser-induced sintered to obtain photovoltaic cells. The structure of the photovoltaic cell is as follows: Figure 1 shown.

[0048] In some embodiments of the present invention, step S6 includes:

[0049] S6-1: The silicon wafer is first cleaned with alkaline solution and then washed with water.

[0050] S6-2: After cleaning with the first cleaning solution, rinse with water.

[0051] S6-3: After pickling, wash with water.

[0052] S6-4: Repeat the above steps S6-2 and S6-3.

[0053] S6-5: After cleaning again with the second cleaning solution, rinse with water.

[0054] S6-6: After slowly pulling and lifting through the water washing tank, it is dried.

[0055] The first cleaning solution includes potassium hydroxide and hydrogen peroxide; the second cleaning solution includes an oxidant.

[0056] In some embodiments, in step S3, after the boron diffusion on the front side, the back side of the silicon wafer is subjected to doped silicon glass etching and polishing, so as to remove the doped silicon glass formed on the back side and the periphery of the silicon wafer due to the doping diffusion, form a smooth and flat morphology on the back side of the silicon wafer, and increase the back side reflectivity.

[0057] In some embodiments, in step S4, the amorphous silicon is intrinsic amorphous silicon or doped amorphous silicon. When it is intrinsic amorphous silicon, it needs to be doped. When it is doped amorphous silicon, it needs to be annealed.

[0058] In some embodiments, step S5 is performed in a chain cleaning machine. Specifically, in the chain cleaning machine, the phosphosilicate glass layer on the front and side surfaces of the N-type silicon wafer is removed by using a hydrofluoric acid solution (for removing phosphosilicate glass) with a roller belt speed of 2-4 m / min. The hydrofluoric acid solution used can react with silicon dioxide in the phosphosilicate glass to generate volatile silicon tetrafluoride gas, thereby achieving the removal of the phosphosilicate glass.

[0059] In some embodiments of the present invention, step S6 is implemented by a tank cleaning machine, a cleaning tank, etc., and specifically includes the following steps: the silicon wafer after the front and side phosphosilicate glass (PSG) etching enters the tank cleaning machine, and passes through the first cleaning tank, the water washing tank, the second cleaning tank, the water washing tank, the third cleaning tank, the water washing tank, the fourth cleaning tank, the water washing tank, the fifth cleaning tank, the water washing tank, the sixth cleaning tank, the water washing tank, the slow pulling tank, and the drying tank in sequence. Among them, the first cleaning tank and the water washing tank correspond to step S6-1, that is, after adding alkaline solution for cleaning, water washing. The second cleaning tank and the water washing tank correspond to step S6-2; the third cleaning tank and the water washing tank correspond to step S6-3; the fourth cleaning tank and the water washing tank correspond to the repetition of step S6-2 in step S6-4, that is, the liquid and treatment conditions of the fourth cleaning tank and the water washing tank are the same as those of the second cleaning tank and the water washing tank. The fifth cleaning tank and water washing tank correspond to the repetition of step S6-3 in step S6-4, that is, the liquid and treatment conditions of the fifth cleaning tank and water washing tank are the same as those of the third cleaning tank and water washing tank. The sixth cleaning tank and water washing tank correspond to step S6-5. The slow pull lifting tank and drying tank correspond to step S6-6.

[0060] Step S6-1 is to remove the phosphorus-doped polysilicon layer on the front and side of the N-type silicon wafer by using alkaline solution in a de-coating tank cleaning machine. Specifically: the silicon wafer is placed in a first cleaning tank containing alkaline solution, and after cleaning at a certain temperature, the robot grabs it and sends it to the water tank. After entering the water washing tank, the silicon wafer is placed in the water washing tank for water washing, and then the robot grabs it and sends it to the second cleaning tank.

[0061] In some embodiments, in step S6-1, the alkali solution includes a potassium hydroxide solution; the mass fraction of the potassium hydroxide solution is 40-50%.

[0062] In some embodiments, in step S1, the silicon wafer is N-type Cz-Si.

[0063] In some embodiments, the alkali solution further includes additives and water.

[0064] The additive is an additive for protecting the borosilicate glass layer. The present invention does not limit the additive. Any additive that can achieve the effect of the present invention is within the protection scope of the present invention. Preferably, the additive is Topband N-type TOPCon winding Poly layer cleaning additive, model: PR21V12.

[0065] In some embodiments, in the alkali solution, the volume ratio of the potassium hydroxide solution, the additive and the water is 30-50:8-10:582-690.

[0066] In some embodiments, the temperature of the alkaline solution cleaning is 65-75° C., and the time is 200-300 seconds; the time of the water washing is 100-200 seconds.

[0067] Preferably, the tank volume of the first cleaning tank and the water washing tank is 720L. The first cleaning tank contains 40L of 48wt% potassium hydroxide aqueous solution, 9L of additives and 671L of pure water. Step S6-1 is to place the silicon wafer in the first cleaning tank, treat it at 68°C for 270s, and then grab it by a robot and send it to the water tank. After entering the water washing tank, place the silicon wafer in the water washing tank for treatment for 130s, and then grab it by a robot and send it to the second cleaning tank.

[0068] In some embodiments, step S6-2 is to use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-winding plating tank cleaning machine to remove additives and chemical components remaining on the surface of the N-type silicon wafer. Specifically: after the silicon wafer is placed in the second cleaning tank for cleaning, the robot grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for water washing, and then the robot grabs it and sends it to the third cleaning tank.

[0069] In some embodiments, in step S6-2, the first cleaning solution includes a hydrogen peroxide solution, a potassium hydroxide solution and water.

[0070] Preferably, the concentration of the hydrogen peroxide solution is 30-35 wt %, and the concentration of the potassium hydroxide solution is 40-50 wt %.

[0071] In some embodiments, the volume ratio of the hydrogen peroxide solution, the potassium hydroxide solution, and the water is 10-30:5-10:605-710.

[0072] In some embodiments, in step S6-2, the cleaning temperature is 55-65°C and the time is 150-250s; the water washing time is 100-200s.

[0073] Preferably, the second cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 180s, then the robot grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130s, then the robot grabs it and sends it to the third cleaning tank.

[0074] In some embodiments, step S6-3 is to use a hydrofluoric acid solution in a de-coating tank cleaning machine to remove the borosilicate glass layer on the front side of the N-type silicon wafer, the tunneling oxide layer on the front side and the side, and the phosphorus silicon glass layer on the back side. Specifically: after the silicon wafer is placed in the tank for cleaning, the robot grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for water washing, and then the robot grabs it and sends it to the fourth cleaning tank.

[0075] In some embodiments, in step S6-3, the pickling cleaning solution includes hydrofluoric acid solution and water.

[0076] In some embodiments, the concentration of the hydrofluoric acid solution is 35-40 wt %; the volume ratio of the hydrofluoric acid solution to water is 3-10:617-740.

[0077] In some embodiments, the acid washing time is 180-250 seconds at a temperature of 60-70° C.; the water washing time is 100-200 seconds.

[0078] In some embodiments, the oxidant includes at least one of ozone, concentrated nitric acid, hydrogen peroxide, persulfate, and peroxide; preferably, the oxidant is ozone.

[0079] Preferably, the third cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. The silicon wafer is placed in the tank for treatment for 220 seconds and then grabbed by a robot and sent to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for treatment for 130 seconds and then grabbed by a robot and sent to the fourth cleaning tank.

[0080] In some embodiments, step S6-4 is to repeat step S6-2 and step S6-3. The repetitive process is carried out in the fourth cleaning tank, its corresponding water washing tank, the fifth cleaning tank, and its corresponding water washing tank, respectively. Repeat step S6-2, use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in the de-coating tank cleaning machine to remove the residual additives and acidic chemical components that have not been removed from the surface of the N-type silicon wafer; then repeat step S6-3, use hydrofluoric acid solution to pickle the N-type silicon wafer in the de-coating tank cleaning machine. Use hydrofluoric acid solution to pickle the N-type silicon wafer in the de-coating tank cleaning machine. Specifically, after the silicon wafer is placed in the fourth cleaning tank for cleaning, the robot arm grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for cleaning, and the robot arm grabs it and sends it to the fifth cleaning tank; after the silicon wafer is placed in the fifth tank for cleaning, the robot arm grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for cleaning, and the robot arm grabs it and sends it to the sixth cleaning tank.

[0081] Preferably, the fourth cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. After the silicon wafer is placed in the tank and treated at 60°C for 150-250s, the robot grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for 130s and then the robot grabs it and sends it to the fifth cleaning tank. The fifth cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. After the silicon wafer is placed in the tank for 220s, the robot grabs it and sends it to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for 130s and then the robot grabs it and sends it to the sixth cleaning tank.

[0082] In some embodiments, step S6-5 is a preparation method using doped oxidation, and the N-type silicon wafer is cleaned using a strong oxidant ozone and a chlorine source-hydrochloric acid mixed solution in a de-coating tank cleaning machine.

[0083] In some embodiments, in step S6-5, the second cleaning solution further includes a chlorine source solution and water;

[0084] The chlorine source solution includes at least one of chlorine water, hydrochloric acid, NH4Cl solution, and HClO solution.

[0085] In some embodiments, in step S6-5, the concentration of the chlorine source solution is 35-40 wt%.

[0086] In some embodiments, in the second cleaning solution, the mass fraction of the oxidant is 3-8‰; the volume ratio of the chlorine source solution to the water is 15-30:605-720; the cleaning time of the second cleaning solution is 180-250s; and the water washing time is 100-200s.

[0087] Preferably, the sixth cleaning tank includes ozone, 20 liters of 38 wt% hydrochloric acid aqueous solution and 700 liters of pure water. The silicon wafer is placed in the tank for treatment for 200 seconds and then grabbed by a robot and sent to the water tank; after entering the water washing tank, the silicon wafer is placed in the water washing tank for treatment for 130 seconds and then grabbed by a robot and sent to the slow pulling tank.

[0088] It can be understood that the present invention improves the preparation method of the silicon oxide layer before ALD. The preparation method of the silicon oxide layer before ALD adopts a chlorine-doped oxidation method, so that the oxidation rate and the quality of the oxide layer are improved. During chlorine-doped oxidation, not only does the reactant contain water vapor that can accelerate oxidation, but chlorine accumulates near the interface between Si and SiO2. In the presence of oxygen, chlorosilicon compounds are easily converted into silicon oxide, which can catalyze oxidation. The chlorine atoms in the oxide layer can purify the activity of sodium ions, thereby reducing oxidation defects introduced by sodium ion contamination of equipment, process raw materials, etc.

[0089] In some embodiments, in step S6-6, the treatment temperature of the slow pull and lift water washing tank is 60-80°C, and the time is 60-120s; the temperature of the drying is 80-100°C, and the time is 720-900s.

[0090] Preferably, after entering the slow pulling water tank, the temperature of the slow pulling water tank is 75°C, and the silicon wafer is placed in the slow pulling water tank for treatment for 90 seconds before being grabbed by a robot and sent to a drying tank; after entering the drying tank, the temperature of the drying tank is 90°C, and the silicon wafer is placed in the drying tank for treatment for 780 seconds before being grabbed by a robot to complete the cleaning process.

[0091] In some embodiments, in step S7, the thickness of the aluminum oxide is 3-4 nm, the thickness of the silicon nitride / silicon oxynitride stacked structure is 70-80 nm, and the thickness of the back film layer, ie, the silicon nitride passivation film, is 70-90 nm.

[0092] The present invention adds a strong oxidant and a chlorine-source hydrochloric acid mixed solution for cleaning in the silicon wafer de-plating process, utilizes the ability of chlorine to remove metal ions, the strong oxidizing property of ozone and oxygen molecules, etc., and can effectively remove metal ions such as potassium and sodium while preparing a high-quality silicon oxide film layer. Ozone also has a good cleaning effect on organic matter, and can effectively remove organic contamination such as additives and reaction byproducts on the surface of the silicon wafer, increase the hydrogen content of the front silicon oxide layer, and improve hydrogen passivation. At the same time, it avoids the influence of dust remaining in the chamber after long-term use of ALD on the front oxide layer of aluminum oxide, stabilizes the passivation improvement of the front oxide layer of aluminum oxide, makes the control of the production line simpler, improves the yield rate of the production line, and then improves the conversion efficiency of the production line battery, the yield rate of the production line is increased by 0.5%-2%, and the battery conversion efficiency is increased by 0.03%-0.08%.

[0093] The second aspect of the present invention provides a photovoltaic cell prepared by the preparation method of the first aspect.

[0094] The present invention is further described below by way of examples, etc. It is to be understood that the process equipment or devices not specifically noted in the examples of the present invention are all conventional equipment or devices in the art.

[0095] Example 1

[0096] A method for preparing a photovoltaic cell for improving ALD passivation comprises the following steps:

[0097] Step (1): The silicon wafer is subjected to texturing treatment to form a pyramid-shaped structure on both sides of the single crystal silicon.

[0098] Step (2): Perform single-sided diffusion doping and oxidation treatment on the front side of the silicon wafer after texturing, and grow doped silicon glass, such as borosilicate glass (BSG), on the surface of the silicon wafer.

[0099] Step (3): Etch and polish the doped silicon glass on the back of the silicon wafer to remove the doped silicon glass formed on the back and periphery of the silicon wafer due to doping diffusion, form a smooth and flat morphology on the back of the silicon wafer, increase the back reflectivity, and at the same time repair some of the damage caused by laser grooving to the silicon wafer, thereby increasing the minority carrier lifetime.

[0100] Step (4): preparing a tunnel oxide layer and doped amorphous silicon on the back of the cleaned silicon wafer in sequence, and performing annealing treatment.

[0101] Step (5): In a chain cleaning machine, the roller belt speed is 3 m / min, and a hydrofluoric acid solution with a mass fraction of 5% is used to remove the phosphosilicate glass layer on the front and side surfaces of the N-type silicon wafer.

[0102] Step (6): After the front phosphosilicate glass (PSG) is etched, the silicon wafer enters the tank cleaning machine and needs to pass through the first cleaning tank, water washing tank, second cleaning tank, water washing tank, third cleaning tank, water washing tank, fourth cleaning tank, water washing tank, fifth cleaning tank, water washing tank, sixth cleaning tank, water washing tank, slow pulling tank, and drying tank in sequence. In the de-coating tank cleaning machine, potassium hydroxide solution is used to remove the phosphorus-doped polysilicon layer coated on the front and side of the N-type silicon wafer. Among them, the volume of each tank body is 720L, and the first cleaning tank contains 40L of 48wt% potassium hydroxide aqueous solution, 9L of additives and 671L of pure water. The silicon wafer is placed in the tank and treated at 68°C for 270s, and then the robot grabs it and sends it to the water tank. Among them, the additive is TopBang N-type TOPCon coating Poly layer cleaning additive, model: PR21V12.

[0103] Step (7): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the second cleaning tank.

[0104] Step (8): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove additives and chemical components remaining on the surface of the N-type silicon wafer, wherein the second cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 180s, then the robot grabs it and sends it to the water tank.

[0105] Step (9): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs the wafer and sends it to the third cleaning tank.

[0106] Step (10): Use hydrofluoric acid solution in a de-coating tank cleaning machine to remove the borosilicate glass layer on the front side of the N-type silicon wafer, the tunneling oxide layer on the front and side, and the phosphosilicate glass layer on the back side, wherein the third cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for treatment for 220 seconds and then grab it with a robot and send it to the water tank.

[0107] Step (11): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The wafer is then grabbed by a robot and sent to the fourth cleaning tank.

[0108] Step (12): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove residual additives and acidic chemical components that have not been removed from the surface of the N-type silicon wafer. The fourth cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 150-250s. The robot arm grabs it and sends it to the water tank.

[0109] Step (13): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the fifth cleaning tank.

[0110] Step (14): Use hydrofluoric acid solution to pickle the N-type silicon wafer in a de-coating tank cleaning machine, wherein the fifth cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for 220 seconds and then grab it with a robot and send it to the water tank.

[0111] Step (15): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the sixth cleaning tank.

[0112] Step (16): Using the chlorine-doped oxidation preparation method, the N-type silicon wafer is cleaned in a de-coating tank-type cleaning machine using a strong oxidant ozone and a chlorine source hydrochloric acid mixed solution, wherein the sixth cleaning tank, taking ozone as an example, includes an ozone mass fraction of 5‰, 20 liters of 38wt% hydrochloric acid aqueous solution and 700 liters of pure water. The silicon wafer is placed in the tank for treatment for 200s and then grabbed by a robot and sent to the water tank.

[0113] Step (17): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs it and sends it to the slow pulling tank.

[0114] Step (18): After entering the slow pull water tank, the temperature of the slow pull water tank is 75°C. The silicon wafer is placed in the slow pull water tank for 90 seconds and then grabbed by a robot and sent to a drying tank.

[0115] Step (19): After entering the drying tank, the temperature of the drying tank is 90°C. The silicon wafer is placed in the drying tank for 780 seconds, and then the robot grabs and unloads the wafer to complete the cleaning process.

[0116] Step (20): Prepare an aluminum oxide + silicon nitride / silicon nitride oxide passivation film on the front side of the silicon wafer, and prepare a silicon nitride passivation film on the back side of the silicon wafer.

[0117] Step (21): Patterned electrodes are printed on the front and back of the silicon wafer respectively, followed by electrode sintering and subsequent light injection treatment, laser induced sintering technology, to obtain the photovoltaic cell described in this patent.

[0118] Example 2

[0119] A method for preparing a photovoltaic cell for improving ALD passivation comprises the following steps:

[0120] Step (1): The silicon wafer is subjected to texturing treatment to form a pyramid-shaped structure on both sides of the single crystal silicon.

[0121] Step (2): Perform single-sided diffusion doping and oxidation treatment on the front side of the silicon wafer after texturing, and grow doped silicon glass, such as borosilicate glass (BSG), on the surface of the silicon wafer.

[0122] Step (3): Etch and polish the doped silicon glass on the back of the silicon wafer to remove the doped silicon glass formed on the back and periphery of the silicon wafer due to doping diffusion, form a smooth and flat morphology on the back of the silicon wafer, increase the back reflectivity, and at the same time repair some of the damage caused by laser grooving to the silicon wafer, thereby increasing the minority carrier lifetime.

[0123] Step (4): preparing a tunnel oxide layer and doped amorphous silicon on the back of the cleaned silicon wafer in sequence, and performing annealing treatment.

[0124] Step (5): In the chain cleaning machine, the roller belt speed is 3m / min, and a hydrofluoric acid solution with a mass fraction of 5% is used.

[0125] Remove the phosphosilicate glass layer on the front and side of the N-type silicon wafer.

[0126] Step (6): After the front phosphosilicate glass (PSG) is etched, the silicon wafer enters the tank cleaning machine and needs to pass through the first cleaning tank, water washing tank, second cleaning tank, water washing tank, third cleaning tank, water washing tank, fourth cleaning tank, water washing tank, fifth cleaning tank, water washing tank, sixth cleaning tank, water washing tank, slow pulling tank, and drying tank in sequence. In the de-coating tank cleaning machine, potassium hydroxide solution is used to remove the phosphorus-doped polysilicon layer coated on the front and side of the N-type silicon wafer. Among them, the volume of each tank body is 720L, and the first cleaning tank contains 40L of 48wt% potassium hydroxide aqueous solution, 9L of additives and 671L of pure water. The silicon wafer is placed in the tank and treated at 68°C for 270s, and then the robot grabs it and sends it to the water tank. Among them, the additive is TopBang N-type TOPCon coating Poly layer cleaning additive, model: PR21V12.

[0127] Step (7): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the second cleaning tank.

[0128] Step (8): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove additives and chemical components remaining on the surface of the N-type silicon wafer, wherein the second cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 180s, then the robot grabs it and sends it to the water tank.

[0129] Step (9): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs the wafer and sends it to the third cleaning tank.

[0130] Step (10): Use hydrofluoric acid solution in a de-coating tank cleaning machine to remove the borosilicate glass layer on the front side of the N-type silicon wafer, the tunneling oxide layer on the front and side, and the phosphosilicate glass layer on the back side, wherein the third cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for treatment for 220 seconds and then grab it with a robot and send it to the water tank.

[0131] Step (11): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The wafer is then grabbed by a robot and sent to the fourth cleaning tank.

[0132] Step (12): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove residual additives and acidic chemical components that have not been removed from the surface of the N-type silicon wafer. The fourth cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 150-250s. The robot arm grabs the wafer and sends it to the water tank.

[0133] Step (13): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the fifth cleaning tank.

[0134] Step (14): Use hydrofluoric acid solution to pickle the N-type silicon wafer in a de-coating tank cleaning machine, wherein the fifth cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for 220 seconds and then grab it with a robot and send it to the water tank.

[0135] Step (15): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the sixth cleaning tank.

[0136] Step (16): Using the preparation method of doped oxidation, the N-type silicon wafer is cleaned in a de-coating tank-type cleaning machine using a strong oxidant ozone and a chlorine source hydrochloric acid mixed solution, wherein the sixth cleaning tank, taking ozone as an example, includes an ozone mass fraction of 1‰, 20 liters of 38wt% hydrochloric acid aqueous solution and 700 liters of pure water. The silicon wafer is placed in the tank for treatment for 200s and then grabbed by a robot and sent to the water tank.

[0137] Step (17): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs it and sends it to the slow pulling tank.

[0138] Step (18): After entering the slow pull water tank, the temperature of the slow pull water tank is 75°C. The silicon wafer is placed in the slow pull water tank for 90 seconds and then grabbed by a robot and sent to a drying tank.

[0139] Step (19): After entering the drying tank, the temperature of the drying tank is 90°C. The silicon wafer is placed in the drying tank for 780 seconds, and then the robot grabs and unloads the wafer to complete the cleaning process.

[0140] Step (20): Prepare an aluminum oxide + silicon nitride / silicon nitride oxide passivation film on the front side of the silicon wafer, and prepare a silicon nitride passivation film on the back side of the silicon wafer.

[0141] Step (21): Patterned electrodes are printed on the front and back of the silicon wafer respectively, followed by electrode sintering and subsequent light injection treatment, laser induced sintering technology, to obtain the photovoltaic cell described in this patent.

[0142] Example 3

[0143] A method for preparing a photovoltaic cell for improving ALD passivation comprises the following steps:

[0144] Step (1): The silicon wafer is subjected to texturing treatment to form a pyramid-shaped structure on both sides of the single crystal silicon.

[0145] Step (2): Perform single-sided diffusion doping and oxidation treatment on the front side of the silicon wafer after texturing, and grow doped silicon glass, such as borosilicate glass (BSG), on the surface of the silicon wafer.

[0146] Step (3): Etch and polish the doped silicon glass on the back of the silicon wafer to remove the doped silicon glass formed on the back and periphery of the silicon wafer due to doping diffusion, form a smooth and flat morphology on the back of the silicon wafer, increase the back reflectivity, and at the same time repair some of the damage caused by laser grooving to the silicon wafer, thereby increasing the minority carrier lifetime.

[0147] Step (4): sequentially preparing a tunneling oxide layer and doped amorphous silicon on the back side of the cleaned silicon wafer and performing annealing treatment.

[0148] Step (5): In the chain cleaning machine, the roller belt speed is 3m / min, and a hydrofluoric acid solution with a mass fraction of 5% is used.

[0149] Remove the phosphosilicate glass layer on the front and side of the N-type silicon wafer.

[0150] Step (6): After the front phosphosilicate glass (PSG) is etched, the silicon wafer enters the tank cleaning machine and needs to pass through the first cleaning tank, water washing tank, second cleaning tank, water washing tank, third cleaning tank, water washing tank, fourth cleaning tank, water washing tank, fifth cleaning tank, water washing tank, sixth cleaning tank, water washing tank, slow pulling tank, and drying tank in sequence. In the de-coating tank cleaning machine, potassium hydroxide solution is used to remove the phosphorus-doped polysilicon layer coated on the front and side of the N-type silicon wafer. Among them, the volume of each tank body is 720L, and the first cleaning tank contains 40L of 48wt% potassium hydroxide aqueous solution, 9L of additives and 671L of pure water. The silicon wafer is placed in the tank and treated at 68°C for 270s, and then the robot grabs it and sends it to the water tank. Among them, the additive is TopBang N-type TOPCon coating Poly layer cleaning additive, model: PR21V12.

[0151] Step (7): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the second cleaning tank.

[0152] Step (8): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove additives and chemical components remaining on the surface of the N-type silicon wafer, wherein the second cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 180s, then the robot grabs it and sends it to the water tank.

[0153] Step (9): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs the wafer and sends it to the third cleaning tank.

[0154] Step (10): Use hydrofluoric acid solution in a de-coating tank cleaning machine to remove the borosilicate glass layer on the front side of the N-type silicon wafer, the tunneling oxide layer on the front and side, and the phosphosilicate glass layer on the back side, wherein the third cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for treatment for 220 seconds and then grab it with a robot and send it to the water tank.

[0155] Step (11): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The wafer is then grabbed by a robot and sent to the fourth cleaning tank.

[0156] Step (12): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove residual additives and acidic chemical components that have not been removed from the surface of the N-type silicon wafer. The fourth cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 150-250s. The robot arm grabs the wafer and sends it to the water tank.

[0157] Step (13): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the fifth cleaning tank.

[0158] Step (14): Use hydrofluoric acid solution to pickle the N-type silicon wafer in a de-coating tank cleaning machine, wherein the fifth cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for 220 seconds and then grab it with a robot and send it to the water tank.

[0159] Step (15): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the sixth cleaning tank.

[0160] Step (16): Using the preparation method of doped oxidation, the N-type silicon wafer is cleaned in a de-coating tank-type cleaning machine using a strong oxidant ozone and a chlorine source hydrochloric acid mixed solution, wherein the sixth cleaning tank, taking ozone as an example, includes an ozone mass fraction of 15‰, 20 liters of 38wt% hydrochloric acid aqueous solution and 700 liters of pure water. The silicon wafer is placed in the tank for treatment for 200s and then grabbed by a robot and sent to the water tank.

[0161] Step (17): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs it and sends it to the slow pulling tank.

[0162] Step (18): After entering the slow pull water tank, the temperature of the slow pull water tank is 75°C. The silicon wafer is placed in the slow pull water tank for 90 seconds and then grabbed by a robot and sent to a drying tank.

[0163] Step (19): After entering the drying tank, the temperature of the drying tank is 90°C. The silicon wafer is placed in the drying tank for 780 seconds, and then the robot grabs and unloads the wafer to complete the cleaning process.

[0164] Step (20): Prepare an aluminum oxide + silicon nitride / silicon nitride oxide passivation film on the front side of the silicon wafer, and prepare a silicon nitride passivation film on the back side of the silicon wafer.

[0165] Step (21): Patterned electrodes are printed on the front and back of the silicon wafer respectively, followed by electrode sintering and subsequent light injection treatment, laser induced sintering technology, to obtain the photovoltaic cell described in this patent.

[0166] Example 4

[0167] A method for preparing a photovoltaic cell for improving ALD passivation comprises the following steps:

[0168] Step (1): The silicon wafer is subjected to texturing treatment to form a pyramid-shaped structure on both sides of the single crystal silicon.

[0169] Step (2): Perform single-sided diffusion doping and oxidation treatment on the front side of the silicon wafer after texturing, and grow doped silicon glass, such as borosilicate glass (BSG), on the surface of the silicon wafer.

[0170] Step (3): Etch and polish the doped silicon glass on the back of the silicon wafer to remove the doped silicon glass formed on the back and periphery of the silicon wafer due to doping diffusion, form a smooth and flat morphology on the back of the silicon wafer, increase the back reflectivity, and at the same time repair some of the damage caused by laser grooving to the silicon wafer, thereby increasing the minority carrier lifetime.

[0171] Step (4): sequentially preparing a tunneling oxide layer and doped amorphous silicon on the back side of the cleaned silicon wafer and performing annealing treatment.

[0172] Step (5): In a chain cleaning machine, the roller belt speed is 3 m / min, and a hydrofluoric acid solution with a mass fraction of 5% is used to remove the phosphosilicate glass layer on the front and side surfaces of the N-type silicon wafer.

[0173] Step (6): After the front phosphosilicate glass (PSG) is etched, the silicon wafer enters the tank cleaning machine and needs to pass through the first cleaning tank, water washing tank, second cleaning tank, water washing tank, third cleaning tank, water washing tank, fourth cleaning tank, water washing tank, fifth cleaning tank, water washing tank, sixth cleaning tank, water washing tank, slow pulling tank, and drying tank in sequence. In the de-coating tank cleaning machine, potassium hydroxide solution is used to remove the phosphorus-doped polysilicon layer coated on the front and side of the N-type silicon wafer. Among them, the volume of each tank body is 720L, and the first cleaning tank contains 40L of 48wt% potassium hydroxide aqueous solution, 9L of additives and 671L of pure water. The silicon wafer is placed in the tank and treated at 68°C for 270s, and then the robot grabs it and sends it to the water tank. Among them, the additive is TopBang N-type TOPCon coating Poly layer cleaning additive, model: PR21V12.

[0174] Step (7): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the second cleaning tank.

[0175] Step (8): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove additives and chemical components remaining on the surface of the N-type silicon wafer, wherein the second cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 180s, then the robot grabs it and sends it to the water tank.

[0176] Step (9): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs the wafer and sends it to the third cleaning tank.

[0177] Step (10): Use hydrofluoric acid solution in a de-coating tank cleaning machine to remove the borosilicate glass layer on the front side of the N-type silicon wafer, the tunneling oxide layer on the front and side, and the phosphosilicate glass layer on the back side, wherein the third cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for treatment for 220 seconds and then grab it with a robot and send it to the water tank.

[0178] Step (11): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The wafer is then grabbed by a robot and sent to the fourth cleaning tank.

[0179] Step (12): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove residual additives and acidic chemical components that have not been removed from the surface of the N-type silicon wafer. The fourth cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 150-250s. The robot arm grabs it and sends it to the water tank.

[0180] Step (13): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the fifth cleaning tank.

[0181] Step (14): Use hydrofluoric acid solution to pickle the N-type silicon wafer in a de-coating tank cleaning machine, wherein the fifth cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for 220 seconds and then grab it with a robot and send it to the water tank.

[0182] Step (15): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the sixth cleaning tank.

[0183] Step (16): Using the preparation method of doped oxidation, the N-type silicon wafer is cleaned in a de-coating tank-type cleaning machine using a strong oxidant ozone and a chlorine source hydrochloric acid mixed solution, wherein the sixth cleaning tank, taking ozone as an example, includes an ozone mass fraction of 5‰, 50 liters of 38wt% hydrochloric acid aqueous solution and 700 liters of pure water. The silicon wafer is placed in the tank for treatment for 200s and then grabbed by a robot and sent to the water tank.

[0184] Step (17): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs it and sends it to the slow pulling tank.

[0185] Step (18): After entering the slow pull water tank, the temperature of the slow pull water tank is 75°C. The silicon wafer is placed in the slow pull water tank for 90 seconds and then grabbed by a robot and sent to a drying tank.

[0186] Step (19): After entering the drying tank, the temperature of the drying tank is 90°C. The silicon wafer is placed in the drying tank for 780 seconds, and then the robot grabs and unloads the wafer to complete the cleaning process.

[0187] Step (20): Prepare an aluminum oxide + silicon nitride / silicon nitride oxide passivation film on the front side of the silicon wafer, and prepare a silicon nitride passivation film on the back side of the silicon wafer.

[0188] Step (21): Patterned electrodes are printed on the front and back of the silicon wafer respectively, followed by electrode sintering and subsequent light injection treatment, laser induced sintering technology, to obtain the photovoltaic cell described in this patent.

[0189] Example 5

[0190] A method for preparing a photovoltaic cell for improving ALD passivation comprises the following steps:

[0191] Step (1): The silicon wafer is subjected to texturing treatment to form a pyramid-shaped structure on both sides of the single crystal silicon.

[0192] Step (2): Perform single-sided diffusion doping and oxidation treatment on the front side of the silicon wafer after texturing, and grow doped silicon glass, such as borosilicate glass (BSG), on the surface of the silicon wafer.

[0193] Step (3): Etch and polish the doped silicon glass on the back of the silicon wafer to remove the doped silicon glass formed on the back and periphery of the silicon wafer due to doping diffusion, form a smooth and flat morphology on the back of the silicon wafer, increase the back reflectivity, and at the same time repair some of the damage caused by laser grooving to the silicon wafer, thereby increasing the minority carrier lifetime.

[0194] Step (4): sequentially preparing a tunneling oxide layer and doped amorphous silicon on the back side of the cleaned silicon wafer and performing annealing treatment.

[0195] Step (5): In the chain cleaning machine, the roller belt speed is 3m / min, and a hydrofluoric acid solution with a mass fraction of 5% is used.

[0196] Remove the phosphosilicate glass layer on the front and side of the N-type silicon wafer.

[0197] Step (6): After the front phosphosilicate glass (PSG) is etched, the silicon wafer enters the tank cleaning machine and needs to pass through the first cleaning tank, water washing tank, second cleaning tank, water washing tank, third cleaning tank, water washing tank, fourth cleaning tank, water washing tank, fifth cleaning tank, water washing tank, sixth cleaning tank, water washing tank, slow pulling tank, and drying tank in sequence. In the de-coating tank cleaning machine, potassium hydroxide solution is used to remove the phosphorus-doped polysilicon layer coated on the front and side of the N-type silicon wafer. Among them, the volume of each tank body is 720L, and the first cleaning tank contains 40L of 48wt% potassium hydroxide aqueous solution, 9L of additives and 671L of pure water. The silicon wafer is placed in the tank and treated at 68°C for 270s, and then the robot grabs it and sends it to the water tank. Among them, the additive is TopBang N-type TOPCon coating Poly layer cleaning additive, model: PR21V12.

[0198] Step (7): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the second cleaning tank.

[0199] Step (8): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove additives and chemical components remaining on the surface of the N-type silicon wafer, wherein the second cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 180s, then the robot grabs it and sends it to the water tank.

[0200] Step (9): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs the wafer and sends it to the third cleaning tank.

[0201] Step (10): Use hydrofluoric acid solution in a de-coating tank cleaning machine to remove the borosilicate glass layer on the front side of the N-type silicon wafer, the tunneling oxide layer on the front and side, and the phosphosilicate glass layer on the back side, wherein the third cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for treatment for 220 seconds and then grab it with a robot and send it to the water tank.

[0202] Step (11): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The wafer is then grabbed by a robot and sent to the fourth cleaning tank.

[0203] Step (12): Use potassium hydroxide and hydrogen peroxide to clean the N-type silicon wafer in a de-coating tank cleaning machine to remove residual additives and acidic chemical components that have not been removed from the surface of the N-type silicon wafer. The fourth cleaning tank includes 20 liters of 32wt% hydrogen peroxide aqueous solution, 6 liters of 48wt% potassium hydroxide aqueous solution and 694 liters of pure water. The silicon wafer is placed in the tank and treated at 60°C for 150-250s. The robot arm grabs the wafer and sends it to the water tank.

[0204] Step (13): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the fifth cleaning tank.

[0205] Step (14): Use hydrofluoric acid solution to pickle the N-type silicon wafer in a de-coating tank cleaning machine, wherein the fifth cleaning tank includes 5 liters of 38wt% hydrofluoric acid aqueous solution and 715 liters of pure water. Place the silicon wafer in the tank for 220 seconds and then grab it with a robot and send it to the water tank.

[0206] Step (15): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds before being grabbed by a robot and sent to the sixth cleaning tank.

[0207] Step (16): Using the preparation method of doped oxidation, the N-type silicon wafer is cleaned in a de-coating tank-type cleaning machine using a strong oxidant ozone and a chlorine source hydrochloric acid mixed solution, wherein the sixth cleaning tank, taking ozone as an example, includes an ozone mass fraction of 5‰, 5 liters of 38wt% hydrochloric acid aqueous solution and 700 liters of pure water. The silicon wafer is placed in the tank for treatment for 200s and then grabbed by a robot and sent to the water tank.

[0208] Step (17): After entering the water washing tank, the silicon wafer is placed in the water washing tank and treated for 130 seconds. The robot then grabs it and sends it to the slow pulling tank.

[0209] Step (18): After entering the slow pull water tank, the temperature of the slow pull water tank is 75°C. The silicon wafer is placed in the slow pull water tank for 90 seconds and then grabbed by a robot and sent to a drying tank.

[0210] Step (19): After entering the drying tank, the temperature of the drying tank is 90°C. The silicon wafer is placed in the drying tank for 780 seconds, and then the robot grabs and unloads the wafer to complete the cleaning process.

[0211] Step (20): Prepare an aluminum oxide + silicon nitride / silicon nitride oxide passivation film on the front side of the silicon wafer, and prepare a silicon nitride passivation film on the back side of the silicon wafer.

[0212] Step (21): Patterned electrodes are printed on the front and back of the silicon wafer respectively, followed by electrode sintering and subsequent light injection treatment, laser induced sintering technology, to obtain the photovoltaic cell described in this patent.

[0213] Comparative Example 1

[0214] Comparative Example 1 directly uses conventionally produced solar cells, that is, without step (16) and step (17), and the rest is the same as Example 1. Pre-water treatment is carried out before the preparation of the aluminum oxide film layer in the ALD process. The pre-water cycle number is 2 cycles, the oxidation time is 20 seconds, the nitrogen purge is 20 seconds, and the purge flow rate is 15000sccm to prepare the front oxide layer.

[0215] Comparative Example 2

[0216] Comparative Example 2 is substantially the same as Example 1, except that in step (16), 36 liters of 69 wt% concentrated nitric acid is used as the strong oxidant, and the rest of the process is exactly the same.

[0217] Test example:

[0218] The performance of the solar cells obtained in Examples 1 to 5 and Comparative Examples 1 to 2 was characterized by the following test method: using a Halm IV tester at 25 ± 2 °C and a light intensity of 1000 ± 50 W / m 2 The test results are shown in Table 1.

[0219] Table 1. Performance test results of solar cells obtained in Examples 1 to 5 and Comparative Examples 1 to 2

[0220] Performance Indicators Eff(%) Voc(V) Isc(A) FF(%) Yield rate (%) Example 1 25.51 0.7196 13.757 85.15 95.89 Example 2 25.43 0.7179 13.752 85.13 94.62 Example 3 25.41 0.7197 13.756 84.98 94.24 Example 4 25.40 0.7174 13.751 85.13 94.18 Example 5 25.48 0.7193 13.755 85.12 94.75 Comparative Example 1 25.45 0.7185 13.754 85.12 94.57 Comparative Example 2 25.49 0.7193 13.755 85.11 95.53

[0221] In Table 1, Eff refers to the battery conversion efficiency, Voc is the open circuit voltage of the battery cell, Isc is the short circuit current of the battery cell, and FF is the fill factor of the battery cell.

[0222] It can be seen from Table 1 that by comparing the experimental data of Example 1 with that of Comparative Example 1, the yield rate of the solar cell prepared by the technical solution of the present application is improved by 1.32%, and the efficiency is improved by 0.06%, which is mainly reflected in the increase of Voc by 1.1mV; by comparing the experimental data of Example 2 with that of Comparative Example 1, it can be seen that the ozone mass fraction is too low, the yield rate is slightly improved, and the efficiency of the solar cell is reduced, which is mainly reflected in the reduction of Voc. This is because the thickness of the prepared front oxide layer is too thin and the passivation is improved less; by comparing the experimental data of Example 3 with that of Comparative Example 1, it can be seen that the ozone mass fraction is too high, the yield rate is reduced, and the efficiency of the solar cell is reduced, which is mainly reflected in the reduction of FF. This is because the thickness of the prepared front oxide layer is too thick, which affects the contact of the metal electrode, and the passivation has not been significantly improved; by comparing the experimental data of Example 4 with that of Comparative Example 1, it can be seen that the hydrochloric acid content is too high, the yield rate is reduced, and the solar cell The efficiency of the battery cell is reduced, mainly manifested in the reduction of Voc. This is because when the chlorine concentration is too high, metal ions such as sodium and potassium will be neutralized, and the prepared oxide film will produce negative bias instability, affecting the passivation effect. By comparing the experimental data of Example 5 with that of Comparative Example 1, it can be obtained that the hydrochloric acid content is too low, the yield rate is improved, and the efficiency of the solar cell is improved, which is mainly manifested in the improvement of Voc. This is because hydrochloric acid removes metal ions such as sodium and potassium, and ozone removes residual additives, reaction by-products and other organic matter, thereby improving the passivation effect of the front oxide layer. However, the hydrochloric acid concentration is too low, and the improvement effect is worse than that of Example 1. By comparing the experimental data of Comparative Example 2 with that of Comparative Example 1, it can be obtained that concentrated nitric acid is selected as a strong oxidant, the yield rate is improved, and the efficiency of the solar cell is improved, which is mainly manifested in the improvement of Voc. The improvement effect is slightly lower than that of Example 1, but the emission of concentrated nitric acid is a big problem. The state has strict control over nitrogen emissions, and the use of concentrated nitric acid will increase the cost of waste liquid discharge.

[0223] In summary, this patent improves the preparation method of the silicon oxide layer before ALD, adds a strong oxidant-ozone (or concentrated nitric acid, peroxide, persulfate, hydrogen peroxide, etc.) and a hydrogen-chlorine source-hydrochloric acid (or chlorine water, NH4CI, HCLO, etc.) mixed solution cleaning in the silicon wafer de-plating process, and utilizes the metal ion removal ability of chlorine and the strong oxidizing property of ozone. While preparing a high-quality silicon oxide film layer, metal ions such as potassium and sodium can be effectively removed. Ozone also has a good cleaning effect on organic matter, and can effectively remove organic contamination such as additives and reaction by-products on the surface of the silicon wafer. The preparation method of the silicon oxide layer before ALD adopts a chlorine-doped oxidation method to improve the oxidation rate and the quality of the oxide layer. When chlorine-doped oxidation is used, not only does the reactant contain water vapor that can accelerate oxidation, but chlorine accumulates near the interface between Si and SiO2. In the presence of oxygen, chlorine silicon compounds are easily converted into silicon oxide, which can catalyze oxidation. The chlorine atoms in the oxide layer can purify the activity of sodium ions, thereby reducing oxidation defects introduced by sodium ion contamination of equipment, process raw materials, etc. At the same time, it avoids the influence of residual dust in the chamber after long-term use of ALD on the front oxide layer of aluminum oxide, stabilizes the passivation of the front oxide layer of aluminum oxide, makes the control of the production line easier, improves the production line yield, and thus improves the battery conversion efficiency of the production line. The production line yield is increased by 0.5%-2%, and the battery conversion efficiency is increased by 0.03%-0.08%.

[0224] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A method for preparing a photovoltaic cell for improving ALD passivation, characterized in that: The preparation method comprises the following steps: S1: Silicon wafer texturing treatment, forming pyramid morphology on both sides of the silicon wafer; S2: Boron diffusion doping and oxidation treatment are performed on the front side of the silicon wafer, and a borosilicate glass layer is grown on the front side of the silicon wafer; S3: Etching and polishing the back of the silicon wafer to remove the borosilicate glass on the back and sides; S4: preparing a tunnel oxide layer and an amorphous silicon layer on the back side of the silicon wafer; S5: pickling to remove the phosphosilicate glass on the front and side of the silicon wafer; S6: The silicon wafer is cleaned again to remove the tunneling oxide layer on the front and side surfaces; S7: aluminum oxide and silicon nitride / silicon oxynitride passivation films are sequentially prepared on the front side of the silicon wafer cleaned in step S6; and a silicon nitride passivation film is prepared on the back side of the silicon wafer; S8: Patterned electrodes are printed on the front and back of the silicon wafer, sintered, and treated with light injection, followed by laser-induced sintering; Step S6 includes: S6-1: The silicon wafer is first cleaned with alkali solution and then washed with water; S6-2: After washing with the first cleaning solution, washing with water; S6-3: After pickling, wash with water; S6-4: Repeat the above steps S6-2 and S6-3; S6-5: washing again with the second cleaning solution, and then washing with water; S6-6: After slowly pulling and lifting through the water washing tank, drying; The first cleaning solution includes potassium hydroxide and hydrogen peroxide; The second cleaning solution includes an oxidant.

2. The preparation method according to claim 1, characterized in that: In step S6-1, the alkali solution includes a potassium hydroxide solution; the mass fraction of the potassium hydroxide solution is 40-50%; Also includes additives and water; The additive is an additive for protecting the borosilicate glass layer; The temperature of the alkaline solution cleaning is 65-75°C and the time is 200-300s; the time of the water washing is 100-200s.

3. The preparation method according to claim 2, characterized in that: In the alkali solution, the volume ratio of the potassium hydroxide solution, the additive and the water is 30-50:8-10:582-690.

4. The preparation method according to claim 1, characterized in that: In step S6-2, the first cleaning solution includes a hydrogen peroxide solution, a potassium hydroxide solution and water; Preferably, the concentration of the hydrogen peroxide solution is 30-35wt%, and the concentration of the potassium hydroxide solution is 40-50wt%; The volume ratio of the hydrogen peroxide solution, the potassium hydroxide solution and the water is 10-30:5-10:605-710.

5. The preparation method according to claim 1, characterized in that: In step S6-2, the cleaning temperature is 55-65°C and the time is 150-250s; the water washing time is 100-200s.

6. The preparation method according to claim 1, characterized in that: In step S6-3, the pickling cleaning solution includes hydrofluoric acid solution and water; The concentration of the hydrofluoric acid solution is 35-40wt%; The volume ratio of the hydrofluoric acid solution to water is 3-10:617-740; The acid washing time is 180-250s, the temperature is 60-70°C; the water washing time is 100-200s.

7. The preparation method according to claim 1, characterized in that: The oxidant includes at least one of ozone, concentrated nitric acid, hydrogen peroxide, persulfate, and peroxide; preferably, the oxidant is ozone; In step S6-5, the second cleaning solution also includes a chlorine source solution and water; The chlorine source solution includes at least one of chlorine water, hydrochloric acid, NH4Cl solution, and HClO solution.

8. The preparation method according to claim 7, characterized in that: In step S6-5, the concentration of the chlorine source solution is 35-40wt%; In the second cleaning solution, the mass fraction of the oxidant is 3-8‰; the volume ratio of the chlorine source solution to the water is 15-30:605-720; The cleaning time of the second cleaning solution is 180-250s; The washing time is 100-200s.

9. The preparation method according to claim 1, characterized in that: In step S6-6, the treatment temperature of the slow pull and lifting water washing tank is 60-80°C and the time is 60-120s; The drying temperature is 80-100° C., and the drying time is 720-900 seconds.

10. A photovoltaic cell prepared by the preparation method according to any one of claims 1 to 9.

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