Preparation method of bendable flexible single crystal textured silicon wafer, bendable single crystal textured silicon wafer and bendable solar cell

Abstract

The invention discloses a preparation method of a bendable flexible single crystal textured silicon wafer, the bendable single crystal textured silicon wafer and a bendable solar cell, and the method comprises the steps: carrying out the primary polishing of an original silicon wafer through an alkali solution, carrying out the secondary fine polishing through an acid solution, and polishing the edge of the silicon wafer into a smooth surface; the polished edge is protected by a mask for texturing, so that the single crystal textured silicon wafer with the polished edge is prepared, and the single crystal textured silicon wafer has excellent bendable and flexible performance and can be used for manufacturing flexible solar cells and assemblies capable of being wound; the method can be widely applied to silicon heterojunction (SHJ) solar cells, passivated emitter and back (PERC) solar cells, tunneling oxide passivation contact (TOPCon) solar cells, interdigital back contact (IBC) solar cells and the like, the process is simple, and the method has wide application prospects and practical value.

Description

Technical Field

[0001] The present invention relates to the field of texturing technology for single crystal silicon wafers, and in particular to a method for preparing a bendable flexible single crystal texturing silicon wafer. The present invention also relates to a bendable single crystal texturing silicon wafer and a bendable solar cell prepared by the texturing method. Background Art

[0002] Monocrystalline silicon solar cells account for a large proportion of the current photovoltaic market (approximately more than 95%), and have many advantages such as high conversion efficiency, good stability, and low cost. Since monocrystalline silicon is a brittle material and is very fragile, it is usually encapsulated with rigid glass to make photovoltaic modules, which do not have the characteristics of bendability and flexibility. With the development of photovoltaic application technology, more and more scenarios require lightweight and flexible photovoltaic modules, such as roofs, car roofs, portable power supplies, wearable electronic devices, etc. Therefore, there is an urgent practical application demand to improve the bendability and flexibility of monocrystalline silicon solar cells.

[0003] Relevant research has confirmed that the fragility of monocrystalline silicon solar cells is closely related to the line marks left on the edge when the silicon wafer is sliced ​​and the velvet structure on the surface. The velvet structure is prepared by the anisotropic reaction of the monocrystalline silicon wafer in an alkaline solution. It is a pyramid-shaped light-trapping structure that captures more sunlight. However, the line marks and pyramid structures left on the edge will reduce the mechanical strength of the silicon wafer, because the concave valleys of the line marks and the valleys of the adjacent pyramids form a relatively sharp angle, which is similar to forming many microscopic "notches" on the silicon wafer. When the silicon wafer is bent, vibrated, or subjected to thermal shock (dramatic temperature changes), stress concentration will occur at the notch position, causing the silicon wafer to easily break. Silicon wafer breakage may occur during the production of cells, the production of battery modules, and the use of photovoltaic products.

[0004] Further, for example, the invention patent application with application number CN202211090758X discloses a method and structure for rounding the edge of a silicon wafer to make the silicon wafer soft; another example is the invention patent application with application number CN2023101757573, which discloses a method for edge processing using plasma etching; and another example is the invention patent application with application number CN2023101363247, which discloses an edge-polished single-crystal texturing silicon wafer and a preparation method, in which the area with a width of 0.1 to 5 mm on the edge of the silicon wafer is prepared into a smooth surface without a pyramid structure, which can effectively reduce the stress concentration generated at the pyramid angle and improve the bendability and flexibility of the silicon wafer. The silicon wafer polishing method adopted in this patented technology is to corrode the silicon wafer in a relatively high concentration of alkaline solution for polishing. This polishing method has a certain degree of anisotropic reaction. These are previously disclosed. From the SEM photos provided in the patent text, it can be seen that although there is no pyramid structure at the edge of the silicon wafer, there are still some gaps, which affect the bending performance of the silicon wafer, and the smoothness of the edge can be further improved.

[0005] To this end, the applicant hopes to seek technical solutions to solve the above technical problems. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for texturing a single crystal silicon wafer, a bendable single crystal texturized silicon wafer and a bendable solar cell, which combines the two methods of alkaline solution polishing and acid solution polishing to polish the edge of the silicon wafer into a smoother surface. When the silicon wafer is subjected to external force, the internal stress can be evenly distributed to avoid stress concentration, and it is not easy to form a fracture starting point at the edge. The single crystal texturized silicon wafer and its solar cell prepared by this method have outstanding bendable and flexible performance.

[0007] The technical solution adopted by the present invention is as follows: A method for texturing a single crystal silicon wafer comprises at least the following steps: S1). Performing primary polishing on the single crystal silicon wafer in an alkaline solution; removing the cutting damage layer on the surface of the single crystal silicon wafer by alkaline etching polishing, reducing the surface roughness of the single crystal silicon wafer, and then cleaning the single crystal silicon wafer after alkaline etching polishing; S2). The silicon wafer is finely polished for a second time in an acid solution containing an oxidant and HF to obtain a polished single crystal silicon wafer; the pits and grooves formed by the single crystal silicon wafer being etched with alkaline solution in step S1) are removed by acid etching polishing to further improve the smoothness of the single crystal silicon wafer. Specifically, the surface roughness of the single crystal silicon wafer is reduced to Ra Less than 0.1 μm; S3). Cleaning the polished single crystal silicon wafer obtained in step S2), for removing the surface oxide layer of the polished single crystal silicon wafer, and then cleaning and drying in pure water, wherein preferably, cleaning is performed in an HF solution; S4). After completing step S3), a mask is set on the surface edge and side of the polished single crystal silicon wafer after cleaning; S5). In an alkaline solution containing a texturing additive, texturing is performed on the polished single crystal silicon wafer on which the mask is set in step S4); wherein a pyramid-shaped velvet surface is formed in the mask-free area of ​​the silicon wafer after texturing, and the mask area of ​​the silicon wafer after texturing remains a polished surface because it does not react with the alkali solution; S6). Clean and remove the mask on the polished single crystal silicon wafer after texturing in step S5).

[0008] Preferably, in step S1), the alkaline solution comprises at least one of NaOH and KOH, and / or the mass fraction of alkali in the alkaline solution is 1%-25%, and / or the temperature of the alkaline solution is 60°C-90°C, and / or the treatment time of the alkaline corrosion polishing is 0.5min-10min.

[0009] Preferably, in step S2), the acidic solution contains an oxidant and HF; the mass fraction of HF in the acidic solution is 0.5%-15%, and / or the temperature of the acidic solution is 15°C-40°C, and / or the treatment time of the acidic etching polishing is 3min-60min; the oxidant is preferably HNO3 or ozone; wherein the mass fraction of HNO3 in the acidic solution is 30%-60%; the mass fraction of ozone in the acidic solution is 20ppm-200ppm; further preferably, when the oxidant is HNO3, H The mass fraction of NO3 in the acidic solution is 30%-60%, the mass fraction of HF in the acidic solution is 0.5%-15%, the solution temperature of the acidic solution is 15°C-40°C, and the treatment time of acid corrosion polishing is 3min-30min; more preferably, when the oxidant is ozone, the mass fraction of ozone in the acidic solution is 20ppm-200ppm, the mass fraction of HF in the acidic solution is 0.5%-10%, the solution temperature of the acidic solution is 15°C-40°C, and the treatment time of acid corrosion polishing is 3min-60min.

[0010] Preferably, in step S3), the mass fraction of HF in the HF solution is 1%-5%, the temperature of the HF solution is room temperature, and the cleaning time is 2 min-10 min.

[0011] Preferably, in the step S4), the mask is formed by applying an adhesive on the edge of the silicon wafer and drying it, wherein the edge of the silicon wafer includes the front edge of the silicon wafer, the back edge of the silicon wafer and the side of the silicon wafer, and the width of the edge area of ​​the silicon wafer surface covered by the mask is 0.1mm-5mm; the adhesive is preferably a viscous solution obtained by dissolving solid organic matter in an organic solvent, wherein the solid organic matter preferably includes at least one of ethyl cellulose, polyvinyl chloride, polystyrene, styrene-butadiene rubber, and polyvinyl butyral, or a mixture of several thereof, and the mass fraction of the solid organic matter in the adhesive is preferably 5%-50%; the organic solvent preferably includes at least one of ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and isopropyl acetate, or a mixture of several thereof.

[0012] Preferably, in the step S5), the alkaline solution includes at least one of NaOH and KOH, and / or the mass fraction of alkali in the alkaline solution is 0.5%-10%, and / or the mass fraction of the texturing additive in the alkaline solution is 0.1%-2%; and / or the texturing temperature is 65°C-85°C, and / or the texturing time is 3min-15min; in the step S6), the mask on the polished single crystal silicon wafer after texturing in step S5) is removed by cleaning with an organic solvent, wherein the organic solvent preferably includes at least one of ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, isopropyl acetate or a mixture of several thereof, and / or the cleaning temperature is 20°C-60°C, and / or the cleaning time is 0.5min-10min.

[0013] Preferably, in the step S1), a texturing basket is used to load the single crystal silicon wafer; in the step S2), the single crystal silicon wafer after the alkaline etching polishing in the step S1) is taken out from the texturing basket and placed in an overlapping manner, wherein the edges of the overlapping single crystal silicon wafers are aligned and the upper and lower ends are fixed with clamps, and then placed in the acidic solution for acid etching polishing, so that only the edge area of ​​the silicon wafer is subjected to acid etching polishing, and after the acid etching polishing is completed, the silicon wafer that has completed the acid etching polishing is reloaded into the texturing basket.

[0014] Preferably, the step S6) further includes the following steps: S7). Cleaning and drying the polished single crystal silicon wafer after the mask is removed in step S6), wherein the cleaning and drying can respectively adopt the known cleaning and known drying processes, which are not the only limiting schemes of the present application; further preferably, in order to obtain a better cleaning effect, step S7) specifically includes the following operation steps, which are performed in sequence: S71). The polished single crystal silicon wafer after the texturing with the mask removed in step S6) is cleaned in SC1 solution (the subsequent steps in this step S7 are referred to as "texturing silicon wafer"); the SC1 solution is a mixed solution of alkali and H2O2; the alkali includes at least one of NaOH, KOH and ammonia water; in the SC1 solution, the mass fraction of the alkali is 0.2%-2%, the mass fraction of H2O2 is 0.4%-4%, the temperature of the SC1 solution is 50℃-80℃, and the cleaning time is 2min-10min; then the texturing silicon wafer is cleaned in pure water; S72). Cleaning the textured silicon wafer in an ozone solution, wherein the ozone solution is a solution containing ozone and HF, wherein the mass fraction of ozone in the ozone solution is 5ppm-50ppm, the mass fraction of HF in the ozone solution is 0.1%-3%, the solution temperature is 15°C-40°C, and the cleaning time is 2min-10min, and then cleaning the textured silicon wafer in pure water; S73). Cleaning the textured silicon wafer in an HF solution, wherein the mass fraction of HF in the HF solution is 1%-5%, the solution temperature is room temperature, the cleaning time is 2min-10min, and then cleaning the textured silicon wafer in pure water; S74). Drying the textured silicon wafer in hot air or hot nitrogen.

[0015] Preferably, a bendable single crystal textured silicon wafer is made by the textured method of the single crystal silicon wafer described above. The method is used to prepare the silicon wafer; preferably, the bending radius of curvature of the bendable single crystal textured silicon wafer is less than 15 mm.

[0016] Preferably, a bendable solar cell comprises a bendable single crystal textured silicon wafer, and the bendable single crystal textured silicon wafer comprises the bendable single crystal textured silicon wafer described above; wherein, the bendable solar cell preferably comprises any one of a silicon heterojunction solar cell, a passivated emitter and back solar cell, a tunneling oxide layer passivated contact solar cell, and an interdigitated back contact solar cell.

[0017] The texturing method for a single crystal silicon wafer provided by the present invention combines the two methods of alkaline solution polishing and acid solution polishing. The first step of alkaline solution polishing has a faster corrosion rate and removes the mechanical damage layer generated when the silicon wafer is cut. The second step of acid solution polishing has a slower corrosion rate. The surface obtained by the first step of polishing is finely polished to further improve the smoothness of the silicon wafer. The edge of the silicon wafer is polished into a smooth surface by a two-step polishing method. When the silicon wafer is subjected to external force, the internal stress can be evenly distributed to avoid stress concentration, and it is not easy to form a fracture starting point at the edge. The single crystal texturing silicon wafer and the solar cell prepared by this method have outstanding and superior bendable flexibility. The method of two-step polishing using alkaline solution and acid solution is better than using alkaline solution polishing alone or acid solution polishing alone, and a larger bending deformation amount can be obtained.

[0018] In addition, the present invention further provides a method for overlapping silicon wafers for polishing with an acidic solution, thereby reducing the contact area between the silicon wafer and the solution and performing etching and polishing only on the edge area of ​​the silicon wafer, which can significantly reduce the consumption of chemicals while improving production capacity. Moreover, since etching and polishing only on the edge area of ​​the silicon wafer can increase the etching amount without affecting the thickness of the silicon wafer, the rounding effect of the silicon wafer edges is more obvious, and the edges of the silicon wafer are changed from right angles to arcs, so that the bending performance of the silicon wafer is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the bendable single crystal textured silicon wafer obtained in Example 1 of the present invention. Figure 1 In the reference numerals, 002 is the front and back edge regions of the silicon wafer without the pyramid velvet structure, 003 is the side regions of the silicon wafer without the pyramid velvet structure, and 001 is the other regions of the silicon wafer covered with the pyramid velvet structure; Figure 2 The SEM microscopic image (left) and the laser 3D microscopic image (right) of the edge of the original single crystal silicon wafer selected in the specific embodiment of the present invention; Figure 3 The SEM microscopic image (left) and the laser 3D microscopic image (right) of the edge of the silicon wafer (polished by alkaline solution polishing) obtained in step (2) of Example 1 of the present invention; Figure 4 The SEM microscopic image (left) and the laser 3D microscopic image (right) of the edge of the silicon wafer (polished by two-step method) obtained in step (3) of Example 1 of the present invention; Figure 5 It is a comparison diagram of the surface contour lines of the edge of the silicon wafer obtained in step (2) of Example 1 of the present invention (marked as "alkaline solution polishing" in the figure) and the edge of the silicon wafer obtained in step (3) (marked as "two-step polishing" in the figure); Figure 6 A photo of a cell made using the bendable single crystal textured silicon wafer provided in Example 1 of the present invention (left) and a photo of a flexible component made using the cell (right); Figure 7 is a cross-sectional microscopic image of the silicon wafer obtained by completing step (3) in Example 1 of the present invention; Figure 8 is a cross-sectional microscopic image of the silicon wafer obtained by completing step (3) in Example 3 of the present invention; Fig. 9 The photographs are of the three-point bending test process of the single crystal textured silicon wafers provided in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5 respectively; Fig.10It is a comparison chart of the results of three-point bending tests on the single crystal textured silicon wafers provided in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5, respectively. DETAILED DESCRIPTION

[0020] This embodiment provides a texturing method for a single crystal silicon wafer, which at least includes the following steps: S1). In alkaline solution, single crystal silicon wafer (can be combined with Figure 2 As shown in the figure, the edge surface of the original single crystal silicon wafer is covered with line marks and notches caused by mechanical cutting) and alkaline etching polishing is performed; the cutting damage layer on the surface of the single crystal silicon wafer is removed by alkaline etching polishing to reduce the surface roughness of the single crystal silicon wafer, and then the single crystal silicon wafer after alkaline etching polishing is cleaned; S2). In an acidic solution, the single crystal silicon wafer after the alkaline etching polishing in step S1) is subjected to acid etching polishing to obtain a polished single crystal silicon wafer; the pits and grooves formed by the alkaline etching of the single crystal silicon wafer in step S1) are removed by acid etching polishing to further improve the smoothness of the single crystal silicon wafer; S3). Cleaning the polished single crystal silicon wafer obtained in step S2), for removing the surface oxide layer of the polished single crystal silicon wafer, and then cleaning and drying in pure water, wherein preferably, cleaning is performed in an HF solution; S4). After completing step S3), a mask is set on the surface edge and side of the polished single crystal silicon wafer after cleaning; S5). In an alkaline solution containing a texturing additive, texturing is performed on the polished single crystal silicon wafer on which the mask is set in step S4); wherein a pyramid-shaped velvet surface is formed in the mask-free area of ​​the silicon wafer after texturing, and the mask area of ​​the silicon wafer after texturing remains a polished surface because it does not react with the alkali solution; S6). Clean and remove the mask on the polished single crystal silicon wafer after texturing in step S5), see the figure.

[0021] Please refer to Figure 1 As shown, the embodiment of the present invention also provides a bendable single crystal textured silicon wafer, It is prepared by the texturing method of the single crystal silicon wafer described above.

[0022] An embodiment of the present invention further provides a bendable solar cell, comprising the bendable single crystal textured silicon wafer described above; wherein the bendable solar cell preferably comprises any one of a silicon heterojunction solar cell (such as an HJT solar cell, an SHJ solar cell, a HIT solar cell), a passivated emitter and back (PERC) solar cell, a tunneling oxide passivated contact (TOPCon) solar cell, and an interdigitated back contact (IBC) solar cell. Of course, other types of bendable solar cells can also be further manufactured according to actual needs, and this embodiment does not impose any particular restrictions on this.

[0023] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0024] In order to further illustrate the implementation process and implementation effect of the present application, based on the above implementation scheme, the present application further proposes the following examples and comparative examples: Example 1

[0025] Prepare a bendable single crystal textured silicon wafer as follows: (1) Clean the original single crystal silicon wafer in SC1 solution containing KOH and H2O2 (see Figure 2 As shown in the figure), the pollutants on the surface of the silicon wafer are removed; wherein the mass fraction of KOH in the SC1 solution is 1%, the mass fraction of H2O2 is 1%, the temperature of the SC1 solution is 65°C, the cleaning time is 3 minutes, and then the silicon wafer is cleaned in pure water for 2 minutes; (2) etching and polishing the silicon wafer obtained in the above step (1) in a KOH solution with a mass fraction of 10%, the KOH solution temperature is 80° C., the etching and polishing time is 3 min, and then the silicon wafer is washed in pure water for 2 min; (3) The silicon wafer obtained in step (2) above (see Figure 3 As shown, it can be seen that the silicon wafer obtained in step (2) has removed the mechanical damage layer and improved the smoothness, but still has shallow pits and grooves) for corrosion polishing; in the mixed solution, the mass fraction of HNO3 is 50%, the mass fraction of HF is 2%, the temperature of the mixed solution is 20°C, the corrosion polishing time is 10 minutes, and then the silicon wafer is washed in pure water for 2 minutes; (4) The silicon wafer obtained in step (3) above was cleaned in a 3% by mass HF solution (see Figure 4 and Figure 7 As shown, through Figure 4 It can be seen that the silicon wafer obtained in step (3) has removed the pits and grooves formed by alkaline solution polishing, and the smoothness is further improved, with a significantly smoother surface). The temperature is room temperature, the cleaning time is 3 minutes, and then the silicon wafer is washed in pure water for 2 minutes, and then the silicon wafer is dried in hot air at a temperature of 60°C for 10 minutes; see further Figure 5 It can be seen from the content that the maximum height of the edge surface profile of the silicon wafer polished with alkaline solution (i.e., the silicon wafer obtained in step (2)) is about 3.5 μm, and the surface roughness is Ra The maximum height of the edge surface profile fluctuation of the silicon wafer after two-step polishing (i.e., the silicon wafer obtained in step (3)) is about 0.2 μm, and the surface roughness is about 0.8 μm. Ra Reduced to about 0.05μm; Ra It refers to the "arithmetic mean deviation of the height of the surface profile"; (5) applying adhesive to the edge of the silicon wafer obtained in the above step (4) so ​​that the front edge, the back edge and the side of the silicon wafer are all covered by the adhesive, wherein the width of the front and back edge coverage areas of the silicon wafer is 0.5 mm, and the adhesive is a mixture of polyvinyl butyral and tetrahydrofuran, wherein the mass fraction of polyvinyl butyral is 25%; then drying the adhesive with hot air at a temperature of 120° C. for 10 min to obtain a polished silicon wafer with the edge covered by polyvinyl butyral; (6) Placing the silicon wafer obtained in the above step (5) in a mixed solution of KOH and a texturing additive for texturing, wherein the brand of the texturing additive is TS53V01 produced by Changzhou Shichuang Energy Co., Ltd.; in the mixed solution, the mass fraction of KOH is 1%, the mass fraction of the texturing additive is 0.7%, the texturing temperature is 70°C, the texturing time is 6 minutes, and then the silicon wafer is washed in pure water for 2 minutes; (7) washing the silicon wafer obtained in step (6) above in tetrahydrofuran to remove the polyvinyl butyral mask at room temperature for 5 minutes, and then washing the silicon wafer in pure water for 2 minutes; (8) Cleaning the silicon wafer obtained in step (7) in a SC1 solution containing KOH and H2O2; in the SC1 solution, the mass fraction of KOH is 1%, the mass fraction of H2O2 is 1%, the temperature is 65°C, the cleaning time is 5 minutes, and then the silicon wafer is cleaned in pure water for 2 minutes; (9) Cleaning the silicon wafer obtained in step (8) in a solution containing ozone and HF; in the solution, the mass fraction of ozone is 30 ppm, the mass fraction of HF is 0.5%, the temperature is 25° C., and the cleaning time is 3 min. Then, the silicon wafer is cleaned in pure water for 2 min. (10) Cleaning the silicon wafer obtained in step (9) in an HF solution; in the HF solution, the mass fraction of HF is 5%, the temperature is room temperature, and the cleaning time is 3 minutes, and then cleaning the silicon wafer in pure water for 2 minutes; (11) Dry the silicon wafer obtained in step (10) in hot air at 60°C for 10 min to obtain Figure 1 The bendable single crystal textured silicon wafer shown.

[0026] It should be noted that in the above-mentioned preparation process of Example 1, a velvet basket is used to load the single crystal silicon wafer.

[0027] The bendable single crystal textured silicon wafer provided in Example 1 can be used to further manufacture silicon heterojunction solar cells (such as HJT solar cells, SHJ solar cells, HIT solar cells) passivated emitter and back (PERC) solar cells, tunneling oxide passivated contact (TOPCon) solar cells or interdigitated back contact (IBC) solar cells.

[0028] For more details, please refer to Figure 6 As shown, a cell is made using the bendable single crystal textured silicon wafer provided in Example 1 of the present invention, and a flexible component is further made using the cell; the bendable solar cell silicon wafer provided in this embodiment and the flexible component made based on the bendable solar cell silicon wafer have outstanding bendable flexibility, with a bending radius of curvature less than 15mm, and can be used to make a lightweight flexible solar cell component that can be rolled up, with a winding diameter of less than 40mm. Example 2

[0029] The main difference between Example 2 and Example 1 is that: in Example 2, step (1) uses ozone cleaning instead of SC1 cleaning; NaOH is used instead of KOH; step (3) uses ozone polishing instead of nitric acid polishing; the adhesive uses a mixture of ethyl cellulose and ethanol; the texturing additive in step (6) uses MQT-709H produced by Huzhou Sanfeng Energy Technology Co., Ltd.; step (7) uses ethanol instead of tetrahydrofuran; this Example 2 specifically prepares the bendable single crystal texturing silicon wafer according to the following steps: (1) Cleaning the original single crystal silicon wafer in a solution containing ozone and HF; in the solution, the mass fraction of ozone is 30 ppm, the mass fraction of HF is 0.5%, the solution temperature is 25°C, the cleaning time is 3 minutes, and then the silicon wafer is cleaned in pure water for 2 minutes; (2) etching and polishing the silicon wafer obtained in the above step (1) in a 7% by mass NaOH solution at a temperature of 80° C. for 3 min, and then washing the silicon wafer in pure water for 2 min; (3) etching and polishing the silicon wafer obtained in the above step (2) in a mixed solution containing ozone and HF; in the mixed solution, the mass fraction of ozone is 80 ppm, the mass fraction of HF is 5%, the temperature of the mixed solution is 25° C., the etching and polishing time is 30 min, and then the silicon wafer is washed in pure water for 2 min; (4) washing the silicon wafer obtained in step (3) above in a 3% by mass HF solution at room temperature for 3 minutes, then washing the silicon wafer in pure water for 2 minutes, and then drying the silicon wafer in hot air at 60°C for 10 minutes; (5) applying adhesive to the edge of the silicon wafer obtained in the above step (4) so ​​that the front edge, the back edge and the side of the silicon wafer are all covered by the adhesive, wherein the width of the front and back edge coverage areas of the silicon wafer is 0.5 mm, and the adhesive is a mixture of ethyl cellulose and ethanol, wherein the mass fraction of ethyl cellulose is 25%; then drying the adhesive with hot air at a temperature of 150° C. for 10 min to obtain a polished silicon wafer with the edge covered by ethyl cellulose; (6) Placing the silicon wafer obtained in the above step (5) in a mixed solution of NaOH and a texturing additive for texturing, wherein the texturing additive model is MQT-709H produced by Huzhou Sanfeng Energy Technology Co., Ltd.; in the mixed solution, the mass fraction of NaOH is 0.6%, the mass fraction of the texturing additive is 0.5%, the texturing temperature is 70°C, the texturing time is 6 minutes, and then the silicon wafer is washed in pure water for 2 minutes; (7) Washing the silicon wafer obtained in step (6) above in ethanol to remove the ethyl cellulose mask at room temperature for 5 minutes, and then washing the silicon wafer in pure water for 2 minutes; (8) Cleaning the silicon wafer obtained in step (7) in a SC1 solution containing NaOH and H2O2; in the SC1 solution, the mass fraction of NaOH is 0.6%, the mass fraction of H2O2 is 1%, the temperature is 65°C, the cleaning time is 5 minutes, and then the silicon wafer is cleaned in pure water for 2 minutes; (9) Cleaning the silicon wafer obtained in step (8) in a solution containing ozone and HF; in the solution, the mass fraction of ozone is 30 ppm, the mass fraction of HF is 0.5%, the temperature is 25° C., and the cleaning time is 3 min. Then, the silicon wafer is cleaned in pure water for 2 min. (10) Cleaning the silicon wafer obtained in step (9) in an HF solution; in the HF solution, the mass fraction of HF is 5%, the temperature is room temperature, and the cleaning time is 3 minutes, and then cleaning the silicon wafer in pure water for 2 minutes; (11) Dry the textured silicon wafer obtained in step (10) in hot air at a temperature of 60° C. for 10 min to obtain a bendable single crystal textured silicon wafer. Example 3

[0030] The main difference between Example 3 and Example 1 is that in step 3, the silicon wafers are overlapped and polished. In Example 3, the bendable single crystal textured silicon wafer is prepared according to the following steps: (1) Clean the original single crystal silicon wafer in a SC1 solution containing KOH and H2O2 to remove pollutants on the surface of the silicon wafer; the mass fraction of KOH in the SC1 solution is 1%, the mass fraction of H2O2 is 1%, the temperature of the SC1 solution is 65°C, the cleaning time is 3 minutes, and then the silicon wafer is cleaned in pure water for 2 minutes; (2) etching and polishing the silicon wafer obtained in the above step (1) in a KOH solution with a mass fraction of 10%, the KOH solution temperature is 80° C., the etching and polishing time is 3 min, and then the silicon wafer is washed in pure water for 2 min; (3) The silicon wafers obtained in the above step (2) are taken out from the velvet basket and overlapped, wherein the edges of the overlapped single crystal silicon wafers are aligned and the upper and lower ends are fixed by clamps, and then the overlapped silicon wafers are corroded and polished in a mixed solution of HNO3 and HF; in the mixed solution, the mass fraction of HNO3 is 50%, the mass fraction of HF is 3%, the temperature of the mixed solution is 20°C, the corroded and polished time is 15 minutes, and after the acid corroded and polished silicon wafers are completed (see Figure 8 As shown) reload the velvet basket, and then wash the silicon wafer in pure water for 2 minutes; (4) washing the silicon wafer obtained in step (3) above in a 3% by mass HF solution at room temperature for 3 minutes, then washing the silicon wafer in pure water for 2 minutes, and then drying the silicon wafer in hot air at 60°C for 10 minutes; (5) applying adhesive to the edge of the silicon wafer obtained in the above step (4) so ​​that the front edge, the back edge and the side of the silicon wafer are all covered by the adhesive, wherein the width of the front and back edge coverage areas of the silicon wafer is 0.5 mm, and the adhesive is a mixture of polyvinyl butyral and tetrahydrofuran, wherein the mass fraction of polyvinyl butyral is 25%; then drying the adhesive with hot air at a temperature of 120° C. for 10 min to obtain a polished silicon wafer with the edge covered by polyvinyl butyral; (6) Placing the silicon wafer obtained in the above step (5) in a mixed solution of KOH and a texturing additive for texturing, wherein the brand of the texturing additive is TS53V01 produced by Changzhou Shichuang Energy Co., Ltd.; in the mixed solution, the mass fraction of KOH is 1%, the mass fraction of the texturing additive is 0.7%, the texturing temperature is 70°C, the texturing time is 6 minutes, and then the silicon wafer is washed in pure water for 2 minutes; (7) washing the silicon wafer obtained in step (6) above in tetrahydrofuran to remove the polyvinyl butyral mask at room temperature for 5 minutes, and then washing the silicon wafer in pure water for 2 minutes; (8) Cleaning the silicon wafer obtained in step (7) in a SC1 solution containing KOH and H2O2; in the SC1 solution, the mass fraction of KOH is 1%, the mass fraction of H2O2 is 1%, the temperature is 65°C, the cleaning time is 5 minutes, and then the silicon wafer is cleaned in pure water for 2 minutes; (9) Cleaning the silicon wafer obtained in step (8) in a solution containing ozone and HF; in the solution, the mass fraction of ozone is 30 ppm, the mass fraction of HF is 0.5%, the temperature is 25° C., and the cleaning time is 3 min. Then, the silicon wafer is cleaned in pure water for 2 min. (10) Cleaning the silicon wafer obtained in step (9) in an HF solution; in the HF solution, the mass fraction of HF is 5%, the temperature is room temperature, and the cleaning time is 3 minutes, and then cleaning the silicon wafer in pure water for 2 minutes; (11) Dry the silicon wafer obtained in the above step (10) in hot air at a temperature of 60° C. for 10 minutes to obtain a bendable single crystal textured silicon wafer.

[0031] It should be noted that this embodiment 3 further proposes a method of setting the silicon wafers to be placed in an overlapping state for acid solution polishing, which reduces the contact area between the silicon wafers and the solution, and only performs corrosion polishing on the edge area of ​​the silicon wafer, which can greatly reduce the consumption of chemicals and improve production capacity at the same time; specifically, when the silicon wafers are loaded in a basket in Embodiment 1-2, the distance between the silicon wafers is usually more than 5mm, and a basket with a length of 500mm can load a maximum of 100 wafers; while this embodiment proposes to place the silicon wafers in an overlapping manner, for a silicon wafer with a thickness of 100μm, a distance of 500mm can be placed 5000 silicon wafers, and the loading capacity is increased by 50 times, so the production capacity is greatly improved; more importantly, after the silicon wafers are loaded in a basket for acid solution polishing in Embodiment 1, the microscopic image of the cross section of the silicon wafer is shown in FIG. Figure 7 As shown, it can be seen that the edges and corners of the silicon wafer have a certain rounding effect; in this embodiment 3, when the silicon wafers are overlapped and polished with an acid solution, since only the edge area of ​​the silicon wafer is etched and polished, the etching amount can be increased without affecting the thickness of the silicon wafer, so that the rounding effect of the edges and corners of the silicon wafer is more obvious, and the edges of the silicon wafer are changed from right angles to arcs. See the microscopic image of the cross section of the silicon wafer. Figure 8 As shown, the curved edge of the silicon wafer can further improve the bending performance. Comparative Example 1:

[0032] The only difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, step (3), step (4), step (5) and step (7) in Example 1 are omitted; the silicon wafer prepared in Comparative Example 1 is completely covered with a pyramid-shaped velvet structure and has no polished edge. The pyramid structure at the edge of the silicon wafer forms a relatively sharp notch, which is prone to stress concentration and reduces the bendability and flexibility of the silicon wafer. Comparative Example 2:

[0033] Comparative Example 2 adopts the method disclosed in Example 1 of CN116230787A. The prepared texturing silicon wafer has a polished edge, but the surface roughness of the edge is much higher than that of Example 1. Fig.10 It can be seen that the bendability and flexibility of the silicon wafer obtained is obviously inferior to that of Example 1. Comparative Example 3:

[0034] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, step (2) in Example 1 is omitted. Comparative Example 4:

[0035] The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, step (3) in Example 1 is omitted. Comparative Example 5:

[0036] The difference between Comparative Example 5 and Example 1 is that in Comparative Example 5, step (5) and step (7) in Example 1 are omitted.

[0037] The bendability of the single crystal textured silicon wafers obtained in Examples 1-3 and Comparative Examples 1-5 was evaluated by a three-point bending test. The test method refers to the national standard GB / T 34171-2017 "Three-point bending method for testing the bending performance of thin and ultra-thin glass". The thickness of the single crystal textured silicon wafer in Examples 1-3 and Comparative Examples 1-5 is 100±3μm, the length × width of the single crystal textured silicon wafer is 156.8mm × 156.8mm, and the span of the lower pressure rod in the three-point bending test is 30mm. The test process can be seen in Fig. 9 The three-point bending test results of Examples 1-3 and Comparative Examples 1-2 are shown in Fig.10 As shown; Five groups of samples were taken from each of Examples 1-3 and Comparative Examples 1-5 to test the compression deformation during crushing (referred to as “crushing deformation” for short). The average values ​​of the crushing deformation are shown in Table 1 below.

[0038] Fracture deformation (mm) Example 1 18.4 Example 2 17.7 Example 3 19.2 Comparative Example 1 5.9 Comparative Example 2 10.5 Comparative Example 3 7.7 Comparative Example 4 9.2 Comparative Example 5 6.2 It is particularly noted that the edge of the silicon wafer in comparative example 1 has a pyramid-shaped velvet structure, and the deformation during fragmentation is the smallest, with an average of 5.9 mm; the edge of the silicon wafer in comparative example 2 is polished with an alkaline solution, and the deformation during fragmentation is increased to 10.5 mm; the present invention adopts a two-step method of polishing with an alkaline solution and an acidic solution, and the deformation during fragmentation of Example 1 and Example 2 is increased to 18.4 mm and 17.7 mm, respectively. In Example 3, during polishing with an acidic solution, the silicon wafers are placed in an overlapping manner, and the corrosion amount of the edge is increased, so that the edge of the silicon wafer is changed from a right angle to an arc, and the deformation during fragmentation is increased. The amount was increased to 19.2mm, and the bendability was optimal; compared with Example 1, Comparative Examples 3 and 4 reduced the steps of alkaline solution polishing and acid solution polishing respectively, and the smoothness of the silicon wafer edge was not as good as the two-step polishing method in Example 1, and the amount of fragmentation and deformation was reduced to 7.7mm and 9.2mm respectively; compared with Example 1, Comparative Example 5 did not set a mask to protect the polished edge before texturing, and a pyramid structure was formed on the edge of the silicon wafer after texturing, so the amount of fragmentation and deformation was reduced to 6.2mm, which was equivalent to the amount of fragmentation and deformation of the conventional texturing process in Comparative Example 1.

[0039] The key technical means of this embodiment include processing the edge of the single crystal silicon wafer and polishing the edge of the silicon wafer into a very smooth surface. When the silicon wafer is bent, vibrated, or subjected to thermal shock, stress concentration is not easily generated on the edge of the silicon wafer, thereby reducing the probability of the silicon wafer breaking and improving its bendability and flexibility.

[0040] The bendable single crystal textured silicon wafer provided in this embodiment is suitable for manufacturing thin silicon heterojunction solar cells with a thickness of less than 120 μm, and further manufacturing bendable and windable flexible solar cell modules. It can also be widely used in PERC, TOPCon, IBC and other solar cells, and reduces the breakage rate of silicon wafers during the thinning process of silicon wafers. It has broad application prospects and practical value.

[0041] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0042] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a bendable flexible single crystal textured silicon wafer, characterized in that: At least the following steps are included: S1). Primary polishing of a single crystal silicon wafer in an alkaline solution; S2). Perform secondary fine polishing on the silicon wafer in an acidic solution containing an oxidant and HF; S3). Cleaning the polished single crystal silicon wafer obtained in step S2); S4). After completing step S3), a mask is set on the surface edge and side of the polished single crystal silicon wafer after cleaning; S5). In an alkaline solution containing a texturing additive, texturing is performed on the polished single crystal silicon wafer on which the mask is set in step S4); S6). Clean and remove the mask on the single crystal silicon wafer after the texturing in step S5).

2. The preparation method according to claim 1, characterized in that: In the step S1), the alkaline solution includes at least one of NaOH and KOH; in the step S2), the oxidant is HNO3 or ozone.

3. The preparation method according to claim 1, characterized in that: In the step S4), the mask is formed by applying an adhesive on the edge of the silicon wafer and drying it, wherein the edge of the silicon wafer includes the front edge of the silicon wafer, the back edge of the silicon wafer and the side of the silicon wafer; the adhesive is preferably a viscous solution obtained by dissolving solid organic matter in an organic solvent, wherein the solid organic matter preferably includes at least one of ethyl cellulose, polyvinyl chloride, polystyrene, styrene-butadiene rubber, and polyvinyl butyral, or a mixture of several of them; the organic solvent preferably includes at least one of ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and isopropyl acetate, or a mixture of several of them.

4. The preparation method according to claim 1, characterized in that: In the step S6), the mask on the single crystal silicon wafer after texturing in step S5) is removed by cleaning with an organic solvent, wherein the organic solvent preferably includes at least one of ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and isopropyl acetate, or a mixture of several thereof.

5. The preparation method according to claim 1, characterized in that: The step S6) further includes the following steps: S7). Clean and dry the polished single crystal silicon wafer after the mask is removed in step S6).

6. A bendable single crystal textured silicon wafer, characterized in that: The single crystal silicon wafer is prepared by the texturing method according to any one of claims 1 to 5.

7. A bendable solar cell, comprising a bendable single crystal textured silicon wafer, characterized in that: The bendable single crystal textured silicon wafer includes the bendable single crystal textured silicon wafer according to claim 6; wherein the bendable solar cell preferably includes any one of a silicon heterojunction solar cell, a passivated emitter and back solar cell, a tunneling oxide layer passivated contact solar cell, and an interdigitated back contact solar cell.

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