A method for preparing a double-sided multilayer passivation film of crystalline silicon

Abstract

The present invention relates to the technical field of photovoltaic equipment, and in particular to a method for preparing a double-sided multilayer passivation film of crystalline silicon. The preparation method comprises the following steps: pre-treating a base stainless steel sheet; preparing a multilayer composite film; treating the multilayer composite film; preparing a phosphate soft glass liquid; and preparing a double-sided multilayer passivation film of crystalline silicon. The present invention improves the crack resistance of the multilayer composite film with silicon nitride as the main component by coating the phosphate soft glass liquid on the surface of the multilayer composite film. During the high-temperature treatment process, the phosphate component can help promote grain boundary movement, which is very beneficial for improving the quality and passivation effect of the silicon nitride / silicon interface. In addition, the elastic modulus of the phosphate soft glass is relatively low, and it can act as a buffer layer between the silicon nitride film and the substrate, which helps to reduce or balance the deformation or cracking of the substrate that may be caused by the high stress of the silicon nitride.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic equipment, and in particular to a method for preparing a double-sided multilayer passivation film of crystalline silicon. Background Art

[0002] Crystalline silicon double-sided multilayer passivation film is an advanced surface treatment technology used on crystalline silicon solar cells. This technology achieves fine passivation of the silicon wafer surface by depositing multiple layers of thin films made of different materials on the front and back of the crystalline silicon wafer, thereby reducing charge carrier recombination losses and improving the cell's energy conversion efficiency and long-term stability. These thin film layers typically include intrinsic amorphous silicon (ia-Si:H), doped amorphous silicon (n / a-Si:H or p / a-Si:H), silicon nitride (SiNx), silicon oxide (SiOx), etc. Each layer has its own specific function, working together to passivate surface defects, optimize interface properties, and protect the silicon wafer from environmental influences. Double-sided passivation is particularly suitable for crystalline silicon solar cells that generate electricity on both sides, effectively utilizing back-incident light to increase power generation.

[0003] Existing crystalline silicon double-sided multilayer passivation films are primarily made of silicon nitride. When using plasma-enhanced chemical vapor deposition (PECVD) to prepare silicon nitride films, high-speed ion bombardment can cause compressive stress within the film. This is because the ions impacting the film surface cause silicon atoms to form a dense arrangement, reducing their volume and generating compressive stress. This can cause deformation or even cracks in the crystalline silicon double-sided multilayer passivation film, which is primarily composed of silicon nitride, leading to battery degradation. Therefore, the present invention provides a method for preparing a crystalline silicon double-sided multilayer passivation film to address the above-mentioned problems in the prior art. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a double-sided multilayer passivation film of crystalline silicon.

[0005] A method for preparing a double-sided multilayer passivation film of crystalline silicon comprises the following steps:

[0006] S1: Pretreatment of base stainless steel sheet

[0007] Prepare a stainless steel sheet, mechanically grind it, and then polish it to a mirror surface. Then, ultrasonically clean it in acetone and anhydrous ethanol, and finally dry it with a hair dryer. Place it in a drying oven for use. Then, coat the stainless steel sheet with PECVD technology. The coating reaction uses NH3 and SiH4 as the gas to obtain a silicon nitride coating on the stainless steel sheet.

[0008] S2: Preparation of multilayer composite membrane

[0009] The surface of the silicon nitride coating is hydrophilized using plasma surface treatment technology. The silicon nitride coating is placed in a plasma treatment machine, and ethylene-tetrafluoroethylene copolymer (ETFE) is introduced. After arcing, plasma grafting treatment is performed to obtain a double-layer composite film. The double-layer composite film is placed between two electrode plates in a plasma-enhanced chemical vapor deposition system chamber, and then hexamethyldisiloxane monomer and reactive gas oxygen are introduced to perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multi-layer composite film.

[0010] S3: Processing of multilayer composite films

[0011] Butyl acetate and EtOH are mixed to prepare a mixed solvent, ethylenediaminetetraacetic acid, azobisisobutylcyanide and a cross-linking agent diaminohydroquinone are mixed and added to the mixed solvent to obtain a treatment solution, and the multilayer composite membrane is heated under nitrogen protection, immersed in the treatment solution, and then reacted at a constant temperature to obtain a modified multilayer composite membrane.

[0012] S4: Preparation of phosphate soft glass liquid

[0013] Tetraethyl orthophosphate is added to an alcohol solution of phosphorus pentoxide, and then a hydrochloric acid solution is added to obtain a phosphate solution, the phosphate solution is fractionated to obtain a sol, and then the sol is added to an alcohol solution of tetraethyl orthophosphate and aluminum nitrate to obtain a phosphate soft glass liquid;

[0014] S5: Preparation of double-sided multilayer passivation film on crystalline silicon

[0015] In a fume hood, immerse the modified multilayer composite film into a phosphate soft glass solution, wait for 5-10 seconds to allow the substrate surface to be completely wetted, then pull it out and dry it to obtain a crystalline silicon double-sided multilayer passivation film.

[0016] Furthermore, step S1 of pre-treating the base stainless steel sheet comprises the following steps:

[0017] S1.1: Prepare a 1.5 cm × 1.5 cm stainless steel sheet and mechanically grind it with 400, 600, 800, and 1000 grit sandpaper in sequence, then polish it to a mirror finish.

[0018] S1.2: Perform ultrasonic cleaning in acetone and then anhydrous ethanol, then dry with a hair dryer and place in a drying oven until ready for use. Perform ultrasonic cleaning again with anhydrous ethanol before each use to ensure the stainless steel surface is clean.

[0019] S1.3: Then, a film is coated on the stainless steel sheet using PECVD technology. The gases used in the coating reaction are NH3 and SiH4, and a silicon nitride coating is obtained on the stainless steel sheet.

[0020] Furthermore, step S2 of preparing a multilayer composite film comprises the following steps:

[0021] S2.1: Use plasma surface treatment technology to hydrophilize the surface of the silicon nitride coating. Place the silicon nitride coating in a plasma treatment machine, evacuate to 0.3 mbar, and then introduce ethylene-tetrafluoroethylene copolymer (ETFE) at a rate of 0.4 ml / min. Simultaneously, adjust the power of the plasma treatment machine to 50 W. After arcing, perform plasma grafting treatment for 10-15 minutes to obtain a double-layer composite film.

[0022] S2.2: Place the double-layer composite film between the two electrode plates of the plasma enhanced chemical vapor deposition system chamber, evacuate to 102-104Pa, control the temperature of the double-layer composite film to 60-65℃, and the deposition time to 20-30min. Then, introduce hexamethyldisiloxane monomer and reaction gas oxygen at a rate of 300mL / min, adjust the plasma discharge power to 300w, generate plasma, and perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multi-layer composite film.

[0023] Furthermore, step S3 of processing the multilayer composite film comprises the following steps:

[0024] S3.1: Butyl acetate and EtOH are mixed in a mass ratio of 1:4 to prepare a mixed solvent. Ethylenediaminetetraacetic acid, azobisisobutylcyanide, and a cross-linker, diaminohydroquinone, are mixed in a mass ratio of 1:1:2 and added to the mixed solvent in an amount equal to 20% of the total mass of the system to obtain a treatment solution.

[0025] S3.2: Under nitrogen protection, the multilayer composite membrane is heated to 74-76° C., immersed in the treatment solution, and then reacted at a constant temperature for 5-5.5 hours to obtain a modified multilayer composite membrane.

[0026] Furthermore, step S4 of preparing phosphate soft glass liquid includes the following steps:

[0027] S4.1: Add tetraethyl orthophosphate to an alcoholic solution of phosphorus pentoxide, and then add hydrochloric acid solution, wherein the mass ratio of tetraethyl orthophosphate, hydrochloric acid solution, and alcoholic solution of phosphorus pentoxide is (1-2):(3-4):(3-5), to obtain a phosphate solution;

[0028] S4.2: Fractionally distilling the phosphate solution to obtain a sol, and then adding the sol to an alcoholic solution of tetraethyl orthophosphate and aluminum nitrate, wherein the mass ratio of the sol, tetraethyl orthophosphate, and the alcoholic solution of aluminum nitrate is (1-2):(0.5-1):(5-6), to obtain a phosphate soft glass liquid;

[0029] Furthermore, step S5 of preparing a double-sided multilayer passivation film on crystalline silicon comprises the following steps:

[0030] S5.1: Immerse the modified multilayer composite film in a phosphate soft glass solution in a fume hood for 5-10 seconds to allow the substrate surface to be completely wetted to avoid gaps.

[0031] S5.2: Then pull it upward at 60° at a speed of 6-8 cm / min and dry it at 60-80°C for 5-6 hours to obtain a double-sided multi-layer passivation film on the crystalline silicon.

[0032] Furthermore, the thickness of the double-layer composite film is 100 nm.

[0033] Furthermore, during the entire grafting process, the vacuum pressure in the plasma treatment machine is maintained within 0.9 mbar during plasma grafting.

[0034] Furthermore, the thickness of the multilayer composite film is 200 nm.

[0035] Furthermore, the coating thickness of the crystalline silicon double-sided multilayer passivation film is 200-300 nm.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] 1. The present invention improves the crack resistance of the modified multilayer composite film with silicon nitride as the main component by coating the surface of the modified multilayer composite film with phosphate soft glass liquid. During the high-temperature treatment process, the phosphate component can help promote grain boundary movement, which is very beneficial for improving the quality of the silicon nitride / silicon interface and the passivation effect. In addition, the elastic modulus of phosphate soft glass is relatively low, and it can act as a buffer layer between the silicon nitride film and the substrate, which helps to alleviate the overall deformation and cracking problems of the crystalline silicon double-sided multilayer passivation film caused by the high stress of silicon nitride.

[0038] 2. The present invention places the multilayer composite film in a treatment solution prepared with ethylenediaminetetraacetic acid, azobisisobutyl cyanide and a cross-linking agent diaminohydroquinone as main components. The cross-linking agent diaminohydroquinone can react with the active points on the surface of the multilayer composite film to form covalent bonds, thereby realizing cross-linking modification between the film layers, thereby improving the adhesion between the multilayer composite film and the phosphate soft glass liquid, so that the prepared modified multilayer composite film has a slight cross-linking ability, so that when the phosphate soft glass film is subsequently coated, the phosphate soft glass liquid can be better wrapped on the surface of the modified multilayer composite film, thereby improving the bonding ability between the phosphate soft glass and the modified multilayer composite film, and reducing the possibility of deformation of the crystalline silicon double-sided multilayer passivation film.

[0039] 3. The present invention vapor-deposits a silicon dioxide film on the surface of a silicon nitride film. Since silicon dioxide itself has good insulating properties, it can enhance the dielectric strength and insulating properties after combining with the silicon nitride film. In addition, the vapor deposition technology can control the growth of the film at the atomic level, forming silicon dioxide nucleation points on the silicon nitride surface and gradually expanding outward to form a continuous film, so that a high-quality interface directly connected by covalent bonds is formed between the silicon dioxide and the silicon nitride, thereby improving the adhesion and electrical properties between the silicon dioxide film layer and the silicon nitride film layer, thereby improving the physical and electrical properties of the crystalline silicon double-sided multilayer passivation film. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable one skilled in the relevant art to make and use the present disclosure.

[0041] Figure 1 This is a flow chart of a method for preparing a crystalline silicon double-sided multilayer passivation film used in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following describes in detail a method for preparing a double-sided multilayer passivation film for crystalline silicon provided by the present invention, with reference to the accompanying drawings and specific embodiments. It is also noted that, to provide a more detailed description, the following embodiments are best and preferred embodiments, and those skilled in the art may employ alternative methods for implementing certain known technologies. Furthermore, the accompanying drawings are intended only to provide a more detailed description of the embodiments and are not intended to limit the present invention.

[0043] Example 1:

[0044] A method for preparing a double-sided multilayer passivation film of crystalline silicon, such as Figure 1 As shown, the following steps are included:

[0045] S1: Pretreatment of base stainless steel sheet

[0046] S1.1: Prepare a 1.5 cm × 1.5 cm stainless steel sheet and mechanically grind it with 400, 600, 800, and 1000 grit sandpaper in sequence, then polish it to a mirror finish.

[0047] S1.2: Perform ultrasonic cleaning in acetone and then anhydrous ethanol, then dry with a hair dryer and place in a drying oven until ready for use. Perform ultrasonic cleaning again with anhydrous ethanol before each use to ensure the stainless steel surface is clean.

[0048] S1.3: Then, a film is coated on the stainless steel sheet using PECVD technology. The gases used in the coating reaction are NH3 and SiH4, and a silicon nitride coating is obtained on the stainless steel sheet.

[0049] S2: Preparation of multilayer composite membranes

[0050] S2.1: The surface of the silicon nitride film was hydrophilized using plasma surface treatment technology. The silicon nitride film was placed in a plasma treatment chamber and evacuated to 0.3 mbar. Ethylene tetrafluoroethylene copolymer (ETFE) was then introduced at a rate of 0.4 ml / min. The power of the plasma treatment chamber was adjusted to 50 W. After arcing, plasma grafting was performed for 10 minutes. During the entire grafting process, the vacuum pressure in the plasma treatment chamber was maintained within 0.9 mbar, resulting in a double-layer composite film having a thickness of 100 nm.

[0051] S2.2: Place the double-layer composite film between the two electrode plates of the plasma enhanced chemical vapor deposition system chamber, evacuate to 102Pa, control the temperature of the double-layer composite film to 60°C, and the deposition time to 20min. Then, introduce hexamethyldisiloxane monomer and reaction gas oxygen at a rate of 300mL / min, adjust the plasma discharge power to 300w, generate plasma, and perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multilayer composite film. The thickness of the multilayer composite film is 200nm.

[0052] S3: Processing of multilayer composite films

[0053] S3.1: Butyl acetate and EtOH are mixed in a mass ratio of 1:4 to prepare a mixed solvent. Ethylenediaminetetraacetic acid, azobisisobutylcyanide, and a cross-linker, diaminohydroquinone, are mixed in a mass ratio of 1:1:2 and added to the mixed solvent in an amount equal to 20% of the total mass of the system to obtain a treatment solution.

[0054] S3.2: Under nitrogen protection, the multilayer composite membrane is heated to 74° C., immersed in the treatment solution, and then reacted at a constant temperature for 5 hours, thereby obtaining a modified multilayer composite membrane.

[0055] S4: Preparation of phosphate soft glass liquid

[0056] S4.1: Add tetraethyl orthophosphate to an alcoholic solution of phosphorus pentoxide, and then add hydrochloric acid solution, wherein the mass ratio of tetraethyl orthophosphate, hydrochloric acid solution, and alcoholic solution of phosphorus pentoxide is 2:3:5, to obtain a phosphate solution;

[0057] S4.2: Fractionally distilling the phosphate solution to obtain a sol, and then adding the sol to an alcoholic solution of tetraethyl orthophosphate and aluminum nitrate, wherein the mass ratio of the sol, tetraethyl orthophosphate, and the alcoholic solution of aluminum nitrate is 2:1:6, to obtain a phosphate soft glass liquid;

[0058] S5: Preparation of double-sided multilayer passivation film on crystalline silicon

[0059] S5.1: Immerse the modified multilayer composite film in a phosphate soft glass solution in a fume hood for 10 seconds to allow the substrate surface to be completely wetted to avoid gaps.

[0060] S5.2: Then pull it upward at a speed of 6 cm / min and 60°, and dry it at 60°C for 5 hours to obtain a crystalline silicon double-sided multilayer passivation film. The coating thickness of the crystalline silicon double-sided multilayer passivation film is 300 nm.

[0061] Example 2:

[0062] A method for preparing a double-sided multilayer passivation film of crystalline silicon, such as Figure 1 As shown, the following steps are included:

[0063] S1: Pretreatment of base stainless steel sheet

[0064] S1.1: Prepare a 1.5 cm × 1.5 cm stainless steel sheet and mechanically grind it with 400, 600, 800, and 1000 grit sandpaper in sequence, then polish it to a mirror finish.

[0065] S1.2: Perform ultrasonic cleaning in acetone and then anhydrous ethanol, then dry with a hair dryer and place in a drying oven until ready for use. Perform ultrasonic cleaning again with anhydrous ethanol before each use to ensure the stainless steel surface is clean.

[0066] S1.3: Then, a film is coated on the stainless steel sheet using PECVD technology. The gases used in the coating reaction are NH3 and SiH4, and a silicon nitride coating is obtained on the stainless steel sheet.

[0067] S2: Preparation of multilayer composite membranes

[0068] S2.1: The surface of the silicon nitride film was hydrophilized using plasma surface treatment technology. The silicon nitride film was placed in a plasma treatment chamber and evacuated to 0.3 mbar. Ethylene tetrafluoroethylene copolymer (ETFE) was then introduced at a rate of 0.4 ml / min. The power of the plasma treatment chamber was adjusted to 50 W. After arcing, plasma grafting was performed for 10 minutes. During the entire grafting process, the vacuum pressure in the plasma treatment chamber was maintained within 0.9 mbar, resulting in a double-layer composite film having a thickness of 100 nm.

[0069] S2.2: Place the double-layer composite film between the two electrode plates of the plasma enhanced chemical vapor deposition system chamber, evacuate to 102Pa, control the temperature of the double-layer composite film to 60°C, and the deposition time to 20min. Then, introduce hexamethyldisiloxane monomer and reaction gas oxygen at a rate of 300mL / min, adjust the plasma discharge power to 300w, generate plasma, and perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multilayer composite film. The thickness of the multilayer composite film is 200nm.

[0070] S3: Processing of multilayer composite films

[0071] S3.1: Butyl acetate and EtOH are mixed in a mass ratio of 1:4 to prepare a mixed solvent. Ethylenediaminetetraacetic acid, azobisisobutylcyanide, and a cross-linker, diaminohydroquinone, are mixed in a mass ratio of 1:1:2 and added to the mixed solvent in an amount equal to 20% of the total mass of the system to obtain a treatment solution.

[0072] S3.2: Under nitrogen protection, the multilayer composite membrane is heated to 74° C., immersed in the treatment solution, and then reacted at a constant temperature for 5 hours, thereby obtaining a modified multilayer composite membrane.

[0073] S4: Preparation of phosphate soft glass liquid

[0074] S4.1: Add tetraethyl orthophosphate to an alcoholic solution of phosphorus pentoxide, and then add hydrochloric acid solution, wherein the mass ratio of tetraethyl orthophosphate, hydrochloric acid solution, and alcoholic solution of phosphorus pentoxide is 1:4:3, to obtain a phosphate solution;

[0075] S4.2: Fractionally distilling the phosphate solution to obtain a sol, and then adding the sol to an alcoholic solution of tetraethyl orthophosphate and aluminum nitrate, wherein the mass ratio of the sol, tetraethyl orthophosphate, and the alcoholic solution of aluminum nitrate is 1:0.5:5, to obtain a phosphate soft glass liquid;

[0076] S5: Preparation of double-sided multilayer passivation film on crystalline silicon

[0077] S5.1: Immerse the modified multilayer composite film in a phosphate soft glass solution in a fume hood for 10 seconds to allow the substrate surface to be completely wetted to avoid gaps.

[0078] S5.2: Then pull it upward at a speed of 6 cm / min and 60°, and dry it at 60°C for 5 hours to obtain a crystalline silicon double-sided multilayer passivation film. The coating thickness of the crystalline silicon double-sided multilayer passivation film is 300 nm.

[0079] Example 3:

[0080] A method for preparing a double-sided multilayer passivation film of crystalline silicon, such as Figure 1 As shown, the following steps are included:

[0081] S1: Pretreatment of base stainless steel sheet

[0082] S1.1: Prepare a 1.5 cm × 1.5 cm stainless steel sheet and mechanically grind it with 400, 600, 800, and 1000 grit sandpaper in sequence, then polish it to a mirror finish.

[0083] S1.2: Perform ultrasonic cleaning in acetone and then anhydrous ethanol, then dry with a hair dryer and place in a drying oven until ready for use. Perform ultrasonic cleaning again with anhydrous ethanol before each use to ensure the stainless steel surface is clean.

[0084] S1.3: Then, a film is coated on the stainless steel sheet using PECVD technology. The gases used in the coating reaction are NH3 and SiH4, and a silicon nitride coating is obtained on the stainless steel sheet.

[0085] S2: Preparation of multilayer composite membranes

[0086] S2.1: The surface of the silicon nitride film was hydrophilized using plasma surface treatment technology. The silicon nitride film was placed in a plasma treatment chamber and evacuated to 0.3 mbar. Ethylene tetrafluoroethylene (ETFE) was then introduced at a rate of 0.4 ml / min. The power of the plasma treatment chamber was adjusted to 50 W. After arcing, plasma grafting was performed for 15 minutes. During the entire grafting process, the vacuum pressure in the plasma treatment chamber was maintained within 0.9 mbar, resulting in a double-layer composite film having a thickness of 100 nm.

[0087] S2.2: Place the double-layer composite film between the two electrode plates of the plasma enhanced chemical vapor deposition system chamber, evacuate to 104Pa, control the temperature of the double-layer composite film to 65°C, and the deposition time to 30min. Then, introduce hexamethyldisiloxane monomer and reaction gas oxygen at a rate of 300mL / min, adjust the plasma discharge power to 300w, generate plasma, and perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multilayer composite film. The thickness of the multilayer composite film is 200nm.

[0088] S3: Processing of multilayer composite films

[0089] S3.1: Butyl acetate and EtOH are mixed in a mass ratio of 1:4 to prepare a mixed solvent. Ethylenediaminetetraacetic acid, azobisisobutylcyanide, and a cross-linker, diaminohydroquinone, are mixed in a mass ratio of 1:1:2 and added to the mixed solvent in an amount equal to 20% of the total mass of the system to obtain a treatment solution.

[0090] S3.2: Under nitrogen protection, the multilayer composite membrane is heated to 76° C., immersed in the treatment solution, and then reacted at a constant temperature for 5.5 hours to obtain a modified multilayer composite membrane.

[0091] S4: Preparation of phosphate soft glass liquid

[0092] S4.1: Add tetraethyl orthophosphate to an alcoholic solution of phosphorus pentoxide, and then add hydrochloric acid solution, wherein the mass ratio of tetraethyl orthophosphate, hydrochloric acid solution, and alcoholic solution of phosphorus pentoxide is 2:3:5, to obtain a phosphate solution;

[0093] S4.2: Fractionally distilling the phosphate solution to obtain a sol, and then adding the sol to an alcoholic solution of tetraethyl orthophosphate and aluminum nitrate, wherein the mass ratio of the sol, tetraethyl orthophosphate, and the alcoholic solution of aluminum nitrate is 2:1:6, to obtain a phosphate soft glass liquid;

[0094] S5: Preparation of double-sided multilayer passivation film on crystalline silicon

[0095] S5.1: Immerse the modified multilayer composite film in a phosphate soft glass solution in a fume hood for 5 seconds to allow the substrate surface to be completely wetted to avoid gaps.

[0096] S5.2: Then pull it upward at a speed of 6 cm / min and 60°, and dry it at 80°C for 6 hours to obtain a crystalline silicon double-sided multilayer passivation film. The coating thickness of the crystalline silicon double-sided multilayer passivation film is 300 nm.

[0097] Comparative Example 1:

[0098] Compared with Example 1, the difference of Comparative Example 1 is that in step S5, instead of immersing the modified multilayer composite film in the phosphate soft glass liquid, a layer of silicon carbide film is plated on the surface of the modified multilayer composite film, specifically: "S5: Preparation of crystalline silicon double-sided multilayer passivation film

[0099] A SiC film was deposited on the modified multilayer composite film using an ion beam multifunctional sputtering coating device to obtain a crystalline silicon double-sided multilayer passivation film. The thickness of the crystalline silicon double-sided multilayer passivation film was 300 nm. The crystalline silicon double-sided multilayer passivation film prepared in step S5 was recorded as Comparative Example 1.

[0100] Comparative Example 2:

[0101] Compared with Example 1, the difference of Comparative Example 2 is that step S3 is not performed, and the multilayer composite film is directly used in step S5 to prepare a crystalline silicon double-sided multilayer passivation film, specifically: "S5: Preparation of crystalline silicon double-sided multilayer passivation film

[0102] S5.1: In a fume hood, immerse the multilayer composite film in a phosphate soft glass solution for 10 seconds to allow the substrate surface to be completely wetted, avoiding any gaps.

[0103] S5.2: The film was then pulled upward at a speed of 6 cm / min at an angle of 60° and dried at 60°C for 5 h to obtain a crystalline silicon double-sided multilayer passivation film. The coating thickness of the crystalline silicon double-sided multilayer passivation film was 300 nm. The crystalline silicon double-sided multilayer passivation film prepared in step S5 is referred to as Comparative Example 2.

[0104] Comparative Example 3:

[0105] Compared with Example 1, the difference of Comparative Example 3 is that step S2.2 is not performed in step S2, specifically: "S2: Preparation of multilayer composite film

[0106] S2.1: The surface of the silicon nitride film was hydrophilized using plasma surface treatment technology. The silicon nitride film was placed in a plasma treatment chamber and evacuated to 0.3 mbar. Ethylene tetrafluoroethylene copolymer (ETFE) was then introduced at a rate of 0.4 ml / min. The power of the plasma treatment chamber was adjusted to 50 W. After arcing, plasma grafting was performed for 10 minutes. During the entire grafting process, the vacuum pressure in the plasma treatment chamber was maintained within 0.9 mbar, resulting in a double-layer composite film having a thickness of 100 nm.

[0107] S3: Processing of multilayer composite films

[0108] S3.1: Butyl acetate and EtOH are mixed in a mass ratio of 1:4 to prepare a mixed solvent. Ethylenediaminetetraacetic acid, azobisisobutylcyanide, and a cross-linker, diaminohydroquinone, are mixed in a mass ratio of 1:1:2 and added to the mixed solvent in an amount equal to 20% of the total mass of the system to obtain a treatment solution.

[0109] S3.2: Under nitrogen protection, the double-layer composite film is heated to 74°C, immersed in the treatment solution, and then reacted at a constant temperature for 5 hours to obtain a modified multilayer composite film. The crystalline silicon double-sided multilayer passivation film prepared in step S5 is recorded as Comparative Example 3.

[0110] The crystalline silicon double-sided multilayer passivation films of Examples 1-3 and Comparative Examples 1-3 were placed in an accelerated UV aging device, with a cumulative irradiation of 200 kWh / m 2 , and then refer to GB / T31034-2014 to test the elongation at break of the test specimens before and after aging.

[0111] Table 1: Elongation at break

[0112] Elongation at break (%) Example 1 157 Example 2 155 Example 3 154 Comparative Example 1 106 Comparative Example 2 119 Comparative Example 3 128

[0113] In the table, the elongations at break of Examples 1-3 are 157%, 155% and 154% respectively. The elongation at break can reflect the crack resistance of the tested sample. The higher the elongation at break, the less likely the tested sample is to break and the better the crack resistance.

[0114] The elongation at break of Comparative Example 1 is only 106%. This shows that when a crystalline silicon double-sided multilayer passivation film with silicon nitride film as the main material is prepared by plasma enhanced chemical vapor deposition, high-speed ion bombardment will cause compressive stress inside the film, resulting in a large internal stress of the silicon nitride film. As a result, it is easy to deform and crack when exposed to the external environment for a long time, and finally lead to fracture.

[0115] The elongation at break of Comparative Example 2 is 119%, which shows that the presence of phosphate soft glass improves the crack resistance of the crystalline silicon double-sided multilayer passivation film. However, due to the lack of treatment, the adhesion between the phosphate soft glass and the multilayer composite film is insufficient, and the performance improvement is limited.

[0116] The elongation at break of Comparative Example 3 is 128%. It can be seen that the vapor-deposited silicon dioxide film on the surface of the silicon nitride film also has the effect of improving the physical properties of the crystalline silicon double-sided multilayer passivation film, and the phosphate soft glass has a greater improvement on the crack resistance of the crystalline silicon double-sided multilayer passivation film.

[0117] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing a double-sided multilayer passivation film of crystalline silicon, characterized in that: The steps include: S1: Pretreatment of base stainless steel sheet Prepare stainless steel sheets, grind them mechanically, and then polish them to a mirror surface. Then, clean them ultrasonically in acetone and anhydrous ethanol, dry them with a hair dryer, and place them in a drying oven for later use. Then, coat the stainless steel sheets with PECVD technology. The gases used in the coating reaction are NH3 and SiH4, to obtain silicon nitride coating on stainless steel sheet; S2: Preparation of multilayer composite membranes The surface of the silicon nitride coating is hydrophilized using plasma surface treatment technology. The silicon nitride coating is placed in a plasma treatment machine, and ethylene-tetrafluoroethylene copolymer (ETFE) is introduced. After arcing, plasma grafting treatment is performed to obtain a double-layer composite film. The double-layer composite film is placed between two electrode plates in a plasma-enhanced chemical vapor deposition system chamber, and then hexamethyldisiloxane monomer and reactive gas oxygen are introduced to perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multi-layer composite film. S3: Processing of multilayer composite films Butyl acetate and EtOH are mixed to prepare a mixed solvent, ethylenediaminetetraacetic acid, azobisisobutylcyanide and a cross-linking agent diaminohydroquinone are mixed and added to the mixed solvent to obtain a treatment solution, and the multilayer composite membrane is heated under nitrogen protection, immersed in the treatment solution, and then reacted at a constant temperature to obtain a modified multilayer composite membrane. S4: Preparation of phosphate soft glass liquid Tetraethyl orthophosphate is added to an alcohol solution of phosphorus pentoxide, and then a hydrochloric acid solution is added to obtain a phosphate solution, the phosphate solution is fractionated to obtain a sol, and then the sol is added to an alcohol solution of tetraethyl orthophosphate and aluminum nitrate to obtain a phosphate soft glass liquid; S5: Preparation of double-sided multilayer passivation film on crystalline silicon In a fume hood, immerse the modified multilayer composite film into a phosphate soft glass solution, wait for 5-10 seconds to allow the substrate surface to be completely wetted, then pull it out and dry it to obtain a crystalline silicon double-sided multilayer passivation film.

2. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 1, characterized in that: Step S1: pre-treating the base stainless steel sheet, including the following steps: S1.1: Prepare a 1.5 cm × 1.5 cm stainless steel sheet and mechanically grind it with 400, 600, 800, and 1000 grit sandpaper in sequence, then polish it to a mirror finish. S1.2: Perform ultrasonic cleaning in acetone and then anhydrous ethanol, then dry with a hair dryer and place in a drying oven until ready for use. Perform ultrasonic cleaning again with anhydrous ethanol before each use to ensure the stainless steel surface is clean. S1.3: Then, a film is coated on the stainless steel sheet using PECVD technology. The gases used in the coating reaction are NH3 and SiH4, and a silicon nitride coating is obtained on the stainless steel sheet.

3. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 2, characterized in that: Step S2 is to prepare a multilayer composite film, comprising the following steps: S2.1: Use plasma surface treatment technology to hydrophilize the surface of the silicon nitride coating. Place the silicon nitride coating in a plasma treatment machine, evacuate to 0.3 mbar, and then introduce ethylene-tetrafluoroethylene copolymer (ETFE) at a rate of 0.4 ml / min. Simultaneously, adjust the power of the plasma treatment machine to 50 W. After arcing, perform plasma grafting treatment for 10-15 minutes to obtain a double-layer composite film. S2.2: Place the double-layer composite film between the two electrode plates of the plasma enhanced chemical vapor deposition system chamber, evacuate to 102-104Pa, control the temperature of the double-layer composite film to 60-65℃, and the deposition time to 20-30min. Then, introduce hexamethyldisiloxane monomer and reaction gas oxygen at a rate of 300mL / min, adjust the plasma discharge power to 300w, generate plasma, and perform plasma-assisted chemical vapor deposition of silicon dioxide to obtain a multi-layer composite film.

4. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 3, characterized in that: Step S3 processes the multilayer composite film, comprising the following steps: S3.1: Butyl acetate and EtOH are mixed in a mass ratio of 1:4 to prepare a mixed solvent. Ethylenediaminetetraacetic acid, azobisisobutylcyanide, and a cross-linker, diaminohydroquinone, are mixed in a mass ratio of 1:1:2 and added to the mixed solvent in an amount equal to 20% of the total mass of the system to obtain a treatment solution. S3.2: Under nitrogen protection, the multilayer composite membrane is heated to 74-76° C., immersed in the treatment solution, and then reacted at a constant temperature for 5-5.5 hours to obtain a modified multilayer composite membrane.

5. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 4, characterized in that: Step S4 is to prepare phosphate soft glass liquid, comprising the following steps: S4.1: Add tetraethyl orthophosphate to an alcoholic solution of phosphorus pentoxide, and then add hydrochloric acid solution, wherein the mass ratio of tetraethyl orthophosphate, hydrochloric acid solution, and alcoholic solution of phosphorus pentoxide is (1-2):(3-4):(3-5), to obtain a phosphate solution; S4.2: Fractionally distill the phosphate solution to obtain a sol, and then add the sol to an alcohol solution of tetraethyl orthophosphate and aluminum nitrate, wherein the mass ratio of the sol, tetraethyl orthophosphate and the alcohol solution of aluminum nitrate is (1-2):(0.5-1):(5-6) to obtain a phosphate soft glass liquid.

6. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 5, characterized in that: Step S5 is to prepare a double-sided multilayer passivation film of crystalline silicon, comprising the following steps: S5.1: Immerse the modified multilayer composite film in a phosphate soft glass solution in a fume hood for 5-10 seconds to allow the substrate surface to be completely wetted to avoid gaps. S5.2: Then pull it upward at 60° at a speed of 6-8 cm / min and dry it at 60-80°C for 5-6 hours to obtain a double-sided multi-layer passivation film on the crystalline silicon.

7. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 6, characterized in that: The thickness of the double-layer composite film is 100 nm.

8. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 7, characterized in that: During the entire grafting process, the vacuum pressure in the plasma treatment machine is maintained within 0.9 mbar when the plasma treatment machine is performing plasma grafting.

9. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 8, characterized in that: The thickness of the multilayer composite film is 200 nm.

10. The method for preparing a double-sided multilayer passivation film of crystalline silicon according to claim 9, characterized in that: The coating thickness of the double-sided multilayer passivation film of crystalline silicon is 200-300nm.

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