Crystalline silicon solar cell and preparation method thereof

Abstract

The invention provides a crystalline silicon solar cell and a preparation method thereof. The preparation method comprises the following steps: carrying out anisotropic corrosion treatment on a silicon wafer, and carrying out first texturing; carrying out isotropic corrosion treatment on the silicon wafer; and carrying out anisotropic corrosion treatment on the silicon wafer, and carrying out second texturing. According to the invention, after the first time of texturing, the silicon wafer is subjected to isotropic corrosion treatment, and the bottom of the textured pyramid is corroded, so that the small pyramid at the tower bottom is removed, and finally, the textured pyramid tower bottom is modified through the second time of texturing, so that the textured uniformity is improved, the reflectivity is reduced, and the photoelectric conversion efficiency of the solar cell is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of solar cells, and more specifically, to a crystalline silicon solar cell and a method for preparing the same. Background Art

[0002] In the field of solar cells, the conventional one-step texturing and cleaning method is currently widely used, which uses a mixed solution of alkali, texturing additives and pure water to anisotropically etch the surface of the silicon wafer to form a random pyramid light-trapping structure.

[0003] However, the current model has certain shortcomings, mainly the poor uniformity of the pyramid velvet structure and the presence of a large number of random pyramids of different sizes and unevenness, which have an adverse effect on subsequent passivation, metallization and other processes, resulting in reduced efficiency. Summary of the invention

[0004] In order to solve the above technical problems, the present disclosure provides a crystalline silicon solar cell and a preparation method thereof. The present disclosure provides a secondary texturing and cleaning method, which can improve the uniformity of the texturing structure and thereby improve the photoelectric conversion efficiency of the solar cell.

[0005] The present disclosure provides a method for preparing a textured structure of a crystalline silicon solar cell, comprising: performing anisotropic etching on a silicon wafer to perform a first texture making process; performing isotropic etching on the silicon wafer; performing anisotropic etching on the silicon wafer to perform a second texture making process.

[0006] In some embodiments, the silicon wafer is subjected to anisotropic etching for a first texturing, including: performing anisotropic etching on the silicon wafer at a first temperature for a first texturing; performing anisotropic etching on the silicon wafer for a second texturing, including: performing anisotropic etching on the silicon wafer at a second temperature for a second texturing; wherein the first temperature is greater than the second temperature.

[0007] In some embodiments, at a first temperature, the silicon wafer is subjected to an anisotropic etching treatment, including: using a second mixed solution of alkali and a first texturing additive to react with the silicon wafer at the first temperature; at a second temperature, the silicon wafer is subjected to an anisotropic etching treatment, including: using a third mixed solution of alkali and a second texturing additive to react with the silicon wafer at the second temperature.

[0008] In some embodiments, in the second mixed solution, the concentration of the alkali is 0.4 to 2.0 wt%, and the concentration of the first texturing additive is 0.3 to 1.0 wt%; using the second mixed solution of alkali and the first texturing additive to react with the silicon wafer at a first temperature includes: reacting with the silicon wafer at 78 to 85°C for 400 to 600 seconds.

[0009] In some embodiments, in the third mixed solution, the concentration of the alkali is 0.4 to 2.0 wt%, and the concentration of the second texturing additive is 0.3 to 1.0 wt%; using the third mixed solution of the alkali and the second texturing additive to react with the silicon wafer at the second temperature includes: reacting with the silicon wafer at 65 to 75°C for 100 to 400 seconds.

[0010] In some embodiments, performing an isotropic etching treatment on the silicon wafer includes: using a first mixed acid solution of nitric acid and hydrofluoric acid to react with the silicon wafer to perform an isotropic etching treatment on the silicon wafer.

[0011] In some embodiments, in the first mixed acid solution, the concentration of nitric acid is 60.0 to 70.0 wt %, and the concentration of hydrofluoric acid is 0.3 to 1.5 wt %, and reacting the silicon wafer with the first mixed acid solution of nitric acid and hydrofluoric acid includes: reacting with the silicon wafer at 20 to 25° C. for 60 to 200 seconds.

[0012] In some embodiments, the silicon wafer is subjected to anisotropic etching treatment, and after the second texturing, it also includes: cleaning the silicon wafer with a fourth mixed solution of alkali and hydrogen peroxide; soaking the silicon wafer with a second mixed acid solution of hydrofluoric acid and hydrochloric acid; and pre-dehydrating and drying the silicon wafer.

[0013] In some embodiments, in the fourth mixed solution, the concentration of alkali is 0.4 to 3.0 wt %, the concentration of hydrogen peroxide is 2.0 to 5.0 wt %, and cleaning the silicon wafer using the fourth mixed solution of alkali and hydrogen peroxide includes: cleaning the silicon wafer at 60 to 70° C. for 150 to 250 seconds.

[0014] In some embodiments, in the second mixed acid solution, the concentration of hydrofluoric acid is 3.0 to 6.0 wt%, and the concentration of hydrochloric acid is 2.0 to 5.0 wt%, and soaking the silicon wafer in the second mixed acid solution of hydrofluoric acid and hydrochloric acid includes: soaking the silicon wafer at 20 to 25° C. for 120 to 250 seconds.

[0015] In some embodiments, the pre-dehydration includes using water at 25 to 60° C. to pre-dehydrate the silicon wafer for 60 to 120 seconds; and the drying includes using a circulating hot air flow at 80 to 100° C. to dry the silicon wafer for 500 to 1000 seconds.

[0016] In some embodiments, the anisotropic etching treatment of the silicon wafer before the first texturing also includes: polishing the silicon wafer with an alkali solution; and pre-cleaning the silicon wafer with a first mixed solution of alkali and hydrogen peroxide.

[0017] In some embodiments, the concentration of the alkaline solution is 3.0 to 8.0 wt %, and polishing the silicon wafer using the alkaline solution includes: polishing the silicon wafer at 65 to 85° C. for 20 to 100 seconds.

[0018] In some embodiments, in the first mixed solution, the concentration of alkali is 0.5 to 3.0 wt %, the concentration of hydrogen peroxide is 2.0 to 5.0 wt %, and pre-cleaning the silicon wafer using the first mixed solution of alkali and hydrogen peroxide includes: pre-cleaning the silicon wafer at 60 to 70° C. for 100 to 240 seconds.

[0019] The present disclosure also provides a solar cell, which is a crystalline silicon solar cell prepared by the above preparation method.

[0020] The method for preparing a crystalline silicon solar cell provided by the present invention is to perform an isotropic etching treatment on a silicon wafer after the first texturing, and to etch the bottom of a velvet pyramid, thereby removing a small pyramid at the bottom of the pyramid, and finally to modify the bottom of the velvet pyramid through a second texturing, so that the uniformity of the velvet surface is improved and the reflectivity is reduced, thereby improving the photoelectric conversion efficiency of the solar cell.

[0021] The process disclosed in the present invention is simple in process flow and has a high process tolerance. It can be adapted to a variety of solar cell silicon wafers, for example, a variety of single crystal silicon wafers, and can be applied to various solar cell process technologies such as emitter and back passivated cells (PERC), oxide passivated contact (TOPCON), and heterojunction (HJT), and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for preparing a crystalline silicon solar cell according to some embodiments of the present disclosure is shown.

[0023] Figure 2 A schematic flow chart of a method for preparing a crystalline silicon solar cell according to some embodiments of the present disclosure is shown.

[0024] Figure 3 A schematic diagram of the texture structure of a silicon wafer after the first texturing according to some embodiments of the present disclosure is shown.

[0025] Figure 4 A schematic diagram of the texture structure of a silicon wafer before the second texturing according to some embodiments of the present disclosure is shown.

[0026] Figure 5 A schematic diagram of the texture structure of a silicon wafer after the second texturing according to some embodiments of the present disclosure is shown.

[0027] Figure 6 A schematic diagram showing the reflectivity of the velvet structure of the crystalline silicon solar cell according to the embodiment of the present disclosure and the comparative example is shown. DETAILED DESCRIPTION

[0028] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0029] refer to Figure 1 and Figure 2 The present disclosure provides a method for preparing a crystalline silicon solar cell, including step S101, performing anisotropic etching on a silicon wafer to perform a first texturing. In some embodiments, the first texturing can be performed by performing anisotropic etching on the silicon wafer in a conventional constant temperature texturing manner.

[0030] In some embodiments, the preparation method of the present disclosure further includes step S102: performing isotropic etching on the silicon wafer to achieve a suede modification effect. In some embodiments, the isotropic etching process is performed to erode the base of the suede pyramid of the silicon wafer to remove the small pyramid at the base, eliminate the adverse effects of the small pyramid, and improve the uniformity of the suede structure.

[0031] In some embodiments, the preparation method disclosed herein further comprises step S103: performing anisotropic etching on the silicon wafer and performing a second texturing. In some embodiments, the second texturing modifies the base of the velvet pyramid, and modifies the arc-shaped base formed by the isotropic etching into a pointed pyramid base to reduce the reflection of light by the velvet structure.

[0032] Therefore, after the first texturing, the present invention performs an isotropic etching treatment on the silicon wafer to etch the bottom of the velvet pyramid, thereby removing the small pyramid at the bottom of the pyramid, and finally modifies the bottom of the velvet pyramid through a second texturing to improve the uniformity of the velvet surface and reduce the reflectivity, thereby improving the photoelectric conversion efficiency of the solar cell.

[0033] In some embodiments, anisotropic etching is performed on a silicon wafer, and the first texturing includes: performing anisotropic etching on the silicon wafer at a first temperature, and performing the first texturing. In some embodiments, anisotropic etching is performed on a silicon wafer, and the second texturing includes: performing anisotropic etching on the silicon wafer at a second temperature, and performing the second texturing. In some embodiments, the first temperature is greater than the second temperature. The reaction between alkali and silicon wafer is more violent at high temperature, and the texturing surface control is more difficult. At low temperature, the reaction is relatively gentle, and the pyramid texturing cycle is extended. Specifically, for every 10°C decrease in reaction temperature, the etching rate of the alkali decreases by 1 to 2 times. The lower second temperature is conducive to gently modifying the bottom structure of the tower. If the second temperature is too high, it is easy to damage the pyramid structure formed by the previous first texturing. Therefore, the second temperature used for the second texturing is lower than the first temperature used for the first texturing. While achieving the modification of the bottom structure of the tower, it avoids damaging the pyramid structure formed by the previous first texturing.

[0034] In some embodiments, anisotropic etching of a silicon wafer at a first temperature includes: using a second mixed solution of alkali and a first texturing additive to react with the silicon wafer at the first temperature. In some embodiments, the second mixed solution remaining on the surface of the silicon wafer can then be removed with pure water. In some embodiments, the use of the first texturing additive in the second mixed solution can promote the formation of a velvet structure and reduce the weight loss of the silicon wafer. The first texturing additive disclosed in the present invention can be any suitable texturing additive for texturing, for example, the texturing additive HJ21 (V01). Figure 3 As shown, generally, the first texturing forms a pyramid structure on the surface of the silicon wafer, and small pyramids 31 exist between relatively large pyramids, which increases the non-uniformity of the texture structure and thus increases the light reflection of the texture structure.

[0035] In some embodiments, at a second temperature, anisotropic etching treatment of a silicon wafer comprises: using a third mixed solution of an alkali and a second texturing additive to react with the silicon wafer at the second temperature. In some embodiments, thereafter, the third mixed solution remaining on the surface of the silicon wafer can be removed with pure water. In some embodiments, the use of the second texturing additive in the third mixed solution can promote the formation of a velvet structure and reduce the weight loss of the silicon wafer. The second texturing additive disclosed in the present invention can adopt any suitable texturing additive for texturing, for example, the texturing additive HJ21 (V01). In some embodiments, the second texturing additive can be the same as or different from the first texturing additive, and both can be commonly used alcohol-free single crystal silicon texturing additives. In some embodiments, such as Figure 5 As shown, the second velvet making modifies the velvet pyramid bottom, and modifies the arc-shaped tower bottom 41 into a pointed pyramid tower bottom 51 to reduce the reflection of light by the velvet structure.

[0036] In some embodiments, in the second mixed solution, the concentration of the alkali is 0.4 to 2.0wt%, and the concentration of the first texturing additive is 0.3 to 1.0wt%. In some embodiments, the concentration of the alkali in the second mixed solution affects the corrosion rate or etching rate of the silicon wafer. The higher the concentration of the alkali, the faster the corrosion rate, but too high a corrosion rate may cause defects on the surface of the silicon wafer, such as holes; too low a concentration of the alkali may cause the corrosion rate to be too slow, prolonging the texturing time and affecting production efficiency. In some embodiments, the concentration of the alkali in the second mixed solution can be 0.4wt%, 0.8wt%, 1.2wt%, 1.6wt%, 2wt% or any suitable value therebetween. In some embodiments, if the concentration of the first texturing additive is too low, its effect of promoting the formation of the velvet structure is relatively limited; if the concentration of the first texturing additive is too high, its effect of promoting the formation of the velvet structure is no longer significantly increased, and excessive organic matter and metal ion residues may be introduced. In some embodiments, the concentration of the first texturing additive in the second mixed solution may be 0.3 wt %, 0.5 wt %, 0.8 wt %, 1 wt % or any suitable value therebetween.

[0037] In some embodiments, using a second mixed solution of alkali and a first texturing additive to react with a silicon wafer at a first temperature includes: reacting with the silicon wafer at 78 to 85°C for 400 to 600 seconds. In some embodiments, if the first temperature of the first texturing is too high, the reaction of the alkali with the silicon wafer is more violent, the velvet control is more difficult, and excessive etching of the silicon wafer and uneven formation of the velvet structure are prone to occur; if the first temperature of the first texturing is too low, the pyramid texturing cycle is extended, affecting the texturing efficiency of the silicon wafer. Specifically, for every 10°C decrease in temperature, the etching rate of the alkali decreases by 1 to 2 times. In some embodiments, the first temperature of the first texturing can be 78°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C or any suitable value therebetween. In some embodiments, if the reaction time of the first texturing is too long, it is easy to cause excessive etching of the silicon wafer and uneven formation of the velvet structure; if the reaction time of the first texturing is too short, insufficient formation of the velvet structure is prone to occur. In some embodiments, the time of the first texturing can be 400 seconds, 450 seconds, 500 seconds, 550 seconds, 600 seconds, or any suitable value therebetween.

[0038] In some embodiments, in the third mixed solution, the concentration of the alkali is 0.4 to 2.0wt%, and the concentration of the second texturing additive is 0.3 to 1.0wt%. In some embodiments, the concentration of the alkali in the third mixed solution affects the corrosion rate or etching rate of the silicon wafer. The higher the concentration of the alkali, the faster the corrosion rate, but too high a corrosion rate may cause defects on the surface of the silicon wafer, such as holes; too low a concentration of the alkali may cause the corrosion rate to be too slow, prolonging the texturing time and affecting production efficiency. In some embodiments, the concentration of the alkali in the third mixed solution may be 0.4wt%, 0.8wt%, 1.2wt%, 1.6wt%, 2wt% or any suitable value therebetween. In some embodiments, if the concentration of the second texturing additive is too low, its effect in promoting the formation of the velvet structure is relatively limited; if the concentration of the second texturing additive is too high, its effect in promoting the formation of the velvet structure is no longer significantly increased, and excessive organic matter and metal ion residues may be introduced. In some embodiments, the concentration of the second texturing additive in the third mixed solution may be 0.3 wt %, 0.5 wt %, 0.8 wt %, 1 wt % or any suitable value therebetween.

[0039] In some embodiments, using a third mixed solution of an alkali and a second texturing additive to react with a silicon wafer at a second temperature includes: reacting with the silicon wafer at 65 to 75°C for 100 to 400 seconds. In some embodiments, if the second temperature of the second texturing is too high, the velvet control is more difficult, affecting the modification effect of the velvet structure, and may damage the pyramid structure obtained by the first texturing; if the second temperature of the second texturing is too low, it is necessary to extend the time of velvet modification, affecting the texturing efficiency of the silicon wafer. In some embodiments, the second temperature of the second texturing can be 65°C, 67°C, 69°C, 71°C, 73°C, 75°C or any suitable value therebetween. In some embodiments, if the time of the second texturing is too long, the modification effect of the velvet structure is no longer significantly increased, and the texturing efficiency is affected; if the time of the second texturing is too short, it may result in insufficient modification of the velvet structure, for example, the arc-shaped tower bottom 41 is not modified to a pointed tower bottom 51. In some embodiments, the second texturing time can be 100 seconds, 120 seconds, 160 seconds, 200 seconds, 240 seconds, 280 seconds, 320 seconds, 360 seconds, 400 seconds or any suitable value therebetween.

[0040] In some embodiments, isotropically etching the silicon wafer includes: using a first mixed acid solution of nitric acid and hydrofluoric acid to react with the silicon wafer to isotropically etching the silicon wafer to achieve a suede modification. In some embodiments, pure water can then be used to remove the first mixed acid solution remaining on the surface of the silicon wafer. In some embodiments, the first mixed acid solution corrodes the bottom of the suede pyramid to remove the small pyramid 31 at the bottom, eliminate the adverse effects of the small pyramid 31, and improve the uniformity of the suede structure. Figure 4 As shown, after the acid etching by the first mixed acid solution, a circular arc-shaped tower bottom 41 is formed.

[0041] In some embodiments, in the first mixed acid solution, the concentration of nitric acid is 60.0 to 70.0 wt%, and the concentration of hydrofluoric acid is 0.3 to 1.5 wt%. In some embodiments, the concentration of hydrofluoric acid in the first mixed acid solution affects the corrosion rate, and a lower hydrofluoric acid concentration will result in a slower corrosion rate, which may extend the processing time; while a higher hydrofluoric acid concentration may cause a faster corrosion rate, but also increase the potential risk of damage to the surface structure of the silicon wafer. In some embodiments, the concentration of hydrofluoric acid in the mixed acid solution may be 0.3 wt%, 0.6 wt%, 0.9 wt%, 1.2 wt%, 1.5 wt%, or any suitable value therebetween. In some embodiments, a too low concentration of nitric acid in the first mixed acid solution means a slower processing speed, and may not be able to fully remove all small pyramids, while a too high concentration of nitric acid may cause unnecessary excessive corrosion or increase the difficulty of subsequent cleaning. In some embodiments, the concentration of nitric acid in the first mixed acid solution may be 60 wt%, 62 wt%, 64 wt%, 66 wt%, 68 wt%, 70 wt%, or any suitable value therebetween.

[0042] In some embodiments, the first mixed acid solution of nitric acid and hydrofluoric acid is reacted with the silicon wafer, including: reacting with the silicon wafer at 20 to 25°C for 60 to 200 seconds. In some embodiments, the increase in the reaction temperature can accelerate the chemical reaction rate, thereby improving the removal efficiency of the small pyramids, but too high a temperature may cause excessive etching of the surface of the silicon wafer or other adverse effects. In addition, too high a temperature of the first mixed acid solution may also affect the stability of the mixed acid solution, especially for volatile nitric acid and hydrofluoric acid. In some embodiments, the temperature of the first mixed acid solution may be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C or any suitable temperature therebetween. In some embodiments, too long a reaction time with the first mixed acid solution may cause excessive etching of the silicon wafer surface and affect the velvet modification efficiency; too short a reaction time with the first mixed acid solution may fail to completely remove the small pyramids. In some embodiments, the reaction time with the first mixed acid solution may be 60 seconds, 90 seconds, 120 seconds, 150 seconds, 180 seconds, 200 seconds or any suitable value therebetween.

[0043] like Figure 2 As shown, in some embodiments, the preparation method of the present disclosure further includes: using a fourth mixed solution of alkali and hydrogen peroxide to clean the silicon wafer to remove organic residues on the surface of the silicon wafer. Generally, the organic residues mainly come from the first and second texturing additives. In some embodiments, the presence of hydrogen peroxide in the fourth mixed solution is beneficial to enhance the cleaning effect. Then, the fourth mixed solution remaining on the surface of the silicon wafer can be removed with pure water.

[0044] like Figure 2 As shown, in some embodiments, the preparation method of the present disclosure further includes: soaking the silicon wafer in a second mixed acid solution of hydrofluoric acid and hydrochloric acid to remove metal ions on the surface of the silicon wafer. In some embodiments, the metal ions on the surface of the silicon wafer mainly come from the alkali and the first and second texturing additives. Then, pure water can be used to remove the second mixed acid solution remaining on the surface of the silicon wafer. Figure 2 As shown, in some embodiments, the preparation method of the present disclosure further includes: pre-dehydrating and drying the silicon wafer for further processing in the preparation of crystalline silicon solar cells.

[0045] In some embodiments, in the fourth mixed solution, the concentration of the alkali is 0.4 to 3.0 wt%, and the concentration of the hydrogen peroxide is 2.0 to 5.0 wt%. In some embodiments, the fourth mixed solution can remove organic matter on the surface of the silicon wafer. The higher the concentration of the alkali in the fourth mixed solution, the stronger the ability to remove organic matter. Therefore, when the concentration of the alkali is too low, it may not be able to effectively remove all organic matter; when the concentration of the alkali is too high, it may cause excessive corrosion of the surface of the silicon wafer and produce microscopic defects. In some embodiments, the concentration of the alkali in the fourth mixed solution can be 0.4 wt%, 0.8 wt%, 1.2 wt%, 1.6 wt%, 2 wt%, 2.5 wt%, 3 wt% or any suitable value therebetween. Hydrogen peroxide is a strong oxidant that can oxidize organic matter on the surface of the silicon wafer in an alkaline environment. The presence of hydrogen peroxide can accelerate the decomposition of organic matter and improve the cleaning efficiency. When the concentration of hydrogen peroxide is too low, the oxidation effect is weak and the organic matter on the surface may not be fully oxidized; when the concentration of hydrogen peroxide is too high, it can cause excessive bubbles to form on the surface of the silicon wafer, affecting the cleaning effect. When hydrogen peroxide and alkali are used together, a synergistic effect can be produced to enhance the cleaning effect; the oxidizing effect of hydrogen peroxide combined with the dissolving effect of alkali can more effectively remove organic matter on the surface of the silicon wafer. In some embodiments, the concentration of hydrogen peroxide in the fourth mixed solution is 2wt%, 3wt%, 4wt%, 5wt% or any suitable value therebetween.

[0046] In some embodiments, cleaning the silicon wafer using a fourth mixed solution of alkali and hydrogen peroxide includes: cleaning the silicon wafer at 60 to 70°C for 150 to 250 seconds to remove organic residues on the surface of the silicon wafer. In some embodiments, increasing the cleaning temperature can accelerate the speed of the chemical reaction, thereby improving the cleaning efficiency and removing organic matter faster; however, too high a temperature may affect the stability of hydrogen peroxide, which is easily decomposed at high temperatures, thereby affecting the cleaning effect; in addition, too high a temperature may cause changes on the surface of the silicon wafer, such as microcracks or changes in the surface structure. In some embodiments, the cleaning temperature may be 60°C, 62°C, 65°C, 68°C, 70°C, or any suitable temperature therebetween. In some embodiments, a long cleaning time may affect the cleaning efficiency, and an excessively extended cleaning time has limited effect on improving the cleaning effect; while a short cleaning time may result in the inability to completely remove organic matter on the surface of the silicon wafer. In some embodiments, the cleaning time may be 150 seconds, 170 seconds, 190 seconds, 210 seconds, 230 seconds, 250 seconds, or any suitable value therebetween.

[0047] In some embodiments, in the second mixed acid solution, the concentration of hydrofluoric acid is 3.0 to 6.0wt%, and the concentration of hydrochloric acid is 2.0 to 5.0wt%. In some embodiments, the main function of hydrofluoric acid is to remove the oxide layer on the surface of the silicon wafer. The concentration of hydrofluoric acid in the mixed acid solution affects the corrosion rate. A lower hydrofluoric acid concentration will result in a slower corrosion rate, which may extend the processing time; while a higher hydrofluoric acid concentration may cause a faster corrosion rate, but it also increases the potential risk of damage to the surface structure of the silicon wafer. In some embodiments, the concentration of hydrofluoric acid in the mixed acid solution can be 3wt%, 4wt%, 5wt%, 6wt% or any suitable value therebetween. In some embodiments, the hydrochloric acid in the mixed acid solution has the dual effects of acidity and complexation. It can form water-soluble complexes with a variety of metal ions, thereby effectively removing metal ions on the surface of the silicon wafer. In some embodiments, a too low concentration of hydrochloric acid in the mixed acid solution may not be able to fully remove all metal ions, while a too high concentration of hydrochloric acid may cause unnecessary corrosion or increase the difficulty of subsequent cleaning. In addition, the concentration of hydrochloric acid also affects the corrosion rate. A lower concentration may mean a slower processing speed, while a higher concentration may bring a faster corrosion rate, but care should also be taken to avoid excessive corrosion of the silicon wafer. In some embodiments, the concentration of the hydrochloric acid in the second mixed acid solution may be 2wt%, 3wt%, 4wt%, 5wt% or any suitable value therebetween.

[0048] In some embodiments, soaking the silicon wafer in a mixed acid solution of hydrofluoric acid and hydrochloric acid includes: soaking the silicon wafer at 20 to 25°C for 120 to 250 seconds to remove metal ions on the surface of the silicon wafer. In some embodiments, increasing the temperature of the acid soaking can accelerate the chemical reaction rate, thereby improving the removal efficiency of metal ions, but too high a temperature may cause excessive etching of the surface of the silicon wafer or produce other adverse effects. In addition, too high a temperature of the acid soaking will also affect the stability of the mixed acid solution, especially for volatile hydrochloric acid and hydrofluoric acid. In some embodiments, the temperature of the acid soaking can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C or any suitable temperature therebetween. In some embodiments, if the acid soaking time is too long, it may cause excessive etching of the surface of the silicon wafer and affect the pickling efficiency; if the acid soaking time is too short, all metal ions may not be completely removed. In some embodiments, the acid soaking time can be 120 seconds, 150 seconds, 170 seconds, 190 seconds, 210 seconds, 230 seconds, 250 seconds or any suitable value therebetween.

[0049] In some embodiments, pre-dehydration includes using water at 25 to 60°C to pre-dehydrate the silicon wafer for 60 to 120 seconds, for example, using a slow pull method. Slow pull is a pretreatment process for drying, and its working principle is to use the surface tension of water to allow the cleaned workpiece to slowly remove water from the surface of the workpiece during the process of slowly withdrawing the water surface, thereby obtaining a relatively dry workpiece and preparing for the subsequent drying step. In some embodiments, the higher the pre-dehydration temperature, the faster the water evaporates; the lower the temperature, the longer it takes to complete the pre-dehydration, thereby affecting the pre-dehydration efficiency; however, if the temperature is too high, it may cause the water on the surface of the silicon wafer to evaporate too quickly, leaving water marks or affecting the uniformity of the surface. In some embodiments, the pre-dehydration temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or any suitable temperature therebetween. In some embodiments, a pre-dehydration time that is too long will affect the efficiency of the pre-dehydration, while a pre-dehydration time that is too short may result in incomplete water removal, affecting the execution of subsequent processes. In some embodiments, the pre-dehydration time can be 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds, or any suitable value therebetween.

[0050] In some embodiments, drying includes drying the silicon wafer for 500 to 1000 seconds using a circulating hot air flow at 80 to 100°C. In some embodiments, the higher the drying temperature, the faster the water evaporates, shortening the drying time; the lower the temperature, the longer it takes to complete the drying, thereby affecting the drying efficiency; however, if the temperature is too high, it may cause thermal damage to the surface of the silicon wafer, such as changes in the surface structure, the generation of microcracks, etc. In addition, if the drying temperature is too low, the water may not evaporate completely, thereby affecting the execution of subsequent processes. In some embodiments, the drying temperature may be 80°C, 85°C, 90°C, 95°C, 100°C, or any suitable temperature therebetween. In some embodiments, a drying time that is too long may affect the drying efficiency, while a drying time that is too short may result in incomplete water removal, affecting the execution of subsequent processes. In some embodiments, the drying time may be 500 seconds, 600 seconds, 700 seconds, 800 seconds, 900 seconds, 1000 seconds, or any suitable value therebetween.

[0051] In some embodiments, the silicon wafer is subjected to anisotropic etching treatment, and before the first texturing, the preparation method further includes: polishing the silicon wafer with an alkaline solution; pre-cleaning the silicon wafer with a first mixed solution of alkali and hydrogen peroxide to remove impurities on the surface of the silicon wafer to eliminate the influence of impurities on the subsequent texturing process. In some embodiments, by polishing the silicon wafer, the cutting line marks and other defects or damages on the surface of the silicon wafer can be removed, making the surface of the silicon wafer smoother, thereby facilitating the uniform formation of the subsequent velvet structure. Then, pure water can be used to remove the residual liquid on the surface of the silicon wafer. In some embodiments, the presence of hydrogen peroxide in the first mixed solution is conducive to enhancing the cleaning effect. Then, pure water can be used to remove the first mixed solution remaining on the surface of the silicon wafer.

[0052] In some embodiments, the concentration of the alkaline solution is 3.0 to 8.0 wt%. In some embodiments, the higher the concentration of the alkaline solution, the faster the corrosion rate; otherwise, the slower. If the concentration of the alkaline solution is too high, the corrosion rate will be too high, and too high a corrosion rate may cause surface defects of the silicon wafer; if the concentration of the alkaline solution is too low, the corrosion rate will be too low, and too low a corrosion rate will affect the polishing efficiency. In some embodiments, the concentration of the alkaline solution can be 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt% or any suitable value therebetween.

[0053] In some embodiments, polishing the silicon wafer with an alkaline solution includes: polishing the silicon wafer at 65 to 85°C for 20 to 100 seconds to remove the cutting line marks and other defects or damage on the surface of the silicon wafer. In some embodiments, if the polishing temperature is too high, the reaction between the alkali and the silicon wafer is too violent, which is easy to cause surface defects of the silicon wafer; if the polishing temperature is too low, the corrosion rate of the alkali is slow, which will affect the polishing efficiency. In some embodiments, the temperature used for polishing can be 65°C, 70°C, 75°C, 80°C, 85°C or any suitable temperature therebetween. Similarly, if the polishing time is too long, it is easy to cause excessive etching of the silicon wafer; if the polishing time is too short, it may result in insufficient polishing, and the damage on the surface of the silicon wafer is not fully removed. In some embodiments, the polishing time can be 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds or any suitable value therebetween.

[0054] In some embodiments, in the first mixed solution, the concentration of the alkali is 0.5 to 3.0 wt%, and the concentration of the hydrogen peroxide is 2.0 to 5.0 wt%. In some embodiments, the first mixed solution can remove pollutants and oxide layers on the surface of the silicon wafer, providing a clean foundation for the subsequent texturing step. In some embodiments, the alkali in the first mixed solution is mainly used to remove impurities on the surface of the silicon wafer, such as oil and wax. When the concentration of the alkali is too low, it may not be able to effectively remove all impurities; when the concentration of the alkali is too high, it may cause damage to the surface of the silicon wafer or even change the surface morphology. In some embodiments, the concentration of the alkali in the first mixed solution can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt% or any suitable value therebetween. Hydrogen peroxide is a strong oxidant that can accelerate the oxidation process and help remove organic matter and some inorganic impurities on the surface. When the concentration of hydrogen peroxide is too low, the oxidation effect is weak and the pollutants on the surface may not be fully oxidized; when the concentration of hydrogen peroxide is too high, it may cause an additional oxide layer on the surface of the silicon wafer, affecting the subsequent texturing effect. When hydrogen peroxide and alkali are used together, a synergistic effect can be produced to enhance the cleaning effect; the oxidation effect of hydrogen peroxide combined with the dissolution effect of alkali can more effectively remove impurities on the surface of the silicon wafer. In some embodiments, the concentration of hydrogen peroxide in the first mixed solution is 2wt%, 3wt%, 4wt%, 5wt% or any suitable value therebetween.

[0055] In some embodiments, pre-cleaning the silicon wafer using a first mixed solution of alkali and hydrogen peroxide includes: pre-cleaning the silicon wafer at 60 to 70°C for 100 to 240 seconds to remove impurities on the surface of the silicon wafer. In some embodiments, increasing the temperature of the pre-cleaning can speed up the chemical reaction, thereby improving the cleaning efficiency and removing impurities faster; however, too high a temperature may affect the stability of hydrogen peroxide, which is easily decomposed at high temperatures, thereby affecting the cleaning effect; in addition, too high a temperature may cause changes on the surface of the silicon wafer, such as microcracks or changes in the surface structure. In some embodiments, the pre-cleaning temperature can be 60°C, 62°C, 65°C, 68°C, 70°C or any suitable temperature therebetween. In some embodiments, too long a pre-cleaning time will affect the efficiency of the pre-cleaning, and too long a pre-cleaning time will have limited effect on improving the pre-cleaning effect; while too short a pre-cleaning time may result in the inability to completely remove impurities on the surface of the silicon wafer. In some embodiments, the pre-cleaning time can be 100 seconds, 120 seconds, 140 seconds, 160 seconds, 180 seconds, 200 seconds, 220 seconds, 240 seconds, or any suitable value therebetween.

[0056] In some embodiments, the alkali in the alkaline solution, the first mixed solution, the second mixed solution, the third mixed solution and the second mixed solution independently includes potassium hydroxide and / or sodium hydroxide. The atomic radius of other elements in the I group elements is larger, and the barrier effect of the formed alkali on the reaction is also larger, the corresponding reaction etching rate will decrease, and the cost will increase. Therefore, in the present disclosure, by using potassium hydroxide and / or sodium hydroxide, both corrosion efficiency and cost can be benefited. In some embodiments, potassium hydroxide and sodium hydroxide can be replaced with each other in a mass ratio of 1:1.6, which has little effect on various reactions in the process.

[0057] In some embodiments, the silicon wafer of the present disclosure includes single crystal silicon. Due to the anisotropy of single crystal silicon, that is, different crystal directions have different corrosion rates, corrosion in an alkaline solution will cause a pyramid-shaped structure to form on the surface, which can effectively reduce reflection and increase light absorption, helping to improve the photoelectric conversion efficiency of solar cells.

[0058] In some embodiments, the present disclosure also provides a crystalline silicon solar cell prepared by the above preparation method. By adopting the secondary texturing method of the present disclosure, the texture structure of the prepared crystalline silicon solar cell is made more uniform, thereby reducing the reflectivity of the texture structure and improving the photoelectric conversion efficiency of the solar cell.

[0059] The following is a description with reference to specific embodiments to provide a better understanding of the technical solution of the present disclosure.

[0060] Example 1

[0061] A method for preparing a crystalline silicon solar cell, the method comprising the following steps:

[0062] S1, polishing: polishing the silicon wafer for 80 seconds at 82° C. using a 5.50 wt % potassium hydroxide solution to remove cutting line marks and other defects on the surface of the silicon wafer; and then washing with water for 120 seconds to remove residual liquid on the surface of the silicon wafer;

[0063] S2, pre-cleaning: at 65° C., using a mixture of 1.25 wt % potassium hydroxide and 3.50 wt % hydrogen peroxide to clean for 120 seconds to remove impurities on the surface of the silicon wafer; and then washing with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0064] S3, primary texturing: at 85°C, the silicon wafer is first texturized for 400 seconds using a mixture of 0.90wt% potassium hydroxide and 0.60wt% HJ21 (V01) texturing additives to form a pyramid structure on the surface of the silicon wafer; then the mixture is washed with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer; the pyramid velvet structure on the surface of the silicon wafer after the primary texturing is as follows Figure 3 As shown;

[0065] S4, velvet modification: At 25°C, use a mixed acid of 68.00wt% nitric acid and 1.40wt% hydrofluoric acid to corrode the bottom of the velvet pyramid for 80 seconds to remove the small pyramid at the bottom of the tower; then wash with water for 120 seconds to remove the residual mixed solution on the surface of the silicon wafer; the pyramid velvet structure on the surface of the silicon wafer after velvet modification is as follows Figure 4 As shown;

[0066] S5. Secondary texturing: At 75°C, the silicon wafer is secondarily texturized for 240 seconds using a mixture of 0.90wt% potassium hydroxide and 0.60wt% HJ21 (V01) texturing additives to modify the bottom of the velvet pyramid. The silicon wafer is then washed with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer. The pyramid velvet structure on the surface of the silicon wafer after the secondary texturing is as follows: Figure 5 As shown;

[0067] S6, alkali washing: at 65°C, use a mixture of 1.25wt% potassium hydroxide and 3.50wt% hydrogen peroxide to wash for 240s to remove organic residues on the surface of the silicon wafer; then wash with water for 120s to remove the residual mixture on the surface of the silicon wafer;

[0068] S7, pickling: at 25°C, use a mixture of 5.00% hydrofluoric acid and 3.20% hydrochloric acid to soak for 120 seconds to remove metal ions on the surface of the silicon wafer; then rinse with water for 120 seconds to remove the residual mixed solution on the surface of the silicon wafer;

[0069] S8, slow pulling: pre-dehydrating the silicon wafer by slow pulling for 120 seconds at 55°C;

[0070] S9, drying: use 90°C circulating hot air to dry the silicon wafer for 800 seconds to complete the texturing process.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that steps S4 and S5 in Example 1 are removed, and the texturing process is used as a one-time comparison, and other process parameters are the same as those in Example 1.

[0073] Example 2

[0074] A method for preparing a crystalline silicon solar cell, the method comprising the following steps:

[0075] S1, polishing: polishing the silicon wafer for 100 seconds using a 6.50wt% potassium hydroxide solution at 80°C to remove cutting line marks and other defects on the surface of the silicon wafer; and then washing with water for 120 seconds to remove residual liquid on the surface of the silicon wafer;

[0076] S2, pre-cleaning: at 63° C., using a mixture of 1.50 wt % potassium hydroxide and 3.25 wt % hydrogen peroxide to clean for 120 seconds to remove impurities on the surface of the silicon wafer; and then washing with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0077] S3, primary texturing: at 82° C., the silicon wafer is firstly texturized for 480 seconds using a mixture of 0.80 wt % potassium hydroxide and 0.50 wt % HJ21 (V01) texturing additive to form a pyramid structure on the surface of the silicon wafer; and then the mixture is washed with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0078] S4, suede modification: at 22° C., use a mixed acid of 65.00 wt % nitric acid and 0.80 wt % hydrofluoric acid to etch the bottom of the suede pyramid for 120 seconds to remove the small pyramid at the bottom; then wash with water for 120 seconds to remove the residual mixed solution on the surface of the silicon wafer;

[0079] S5. Secondary texturing: At 68°C, the silicon wafer is secondarily texturized for 300 seconds using a mixture of 0.80wt% potassium hydroxide and 0.50wt% HJ21 (V01) texturing additives to modify the bottom of the velvet pyramid; then the mixture is washed with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0080] S6, alkali washing: at 68°C, use a mixture of 1.50wt% potassium hydroxide and 3.25wt% hydrogen peroxide to wash for 240s to remove organic residues on the surface of the silicon wafer; then wash with water for 120s to remove the residual mixture on the surface of the silicon wafer;

[0081] S7, pickling: at 25°C, use a mixture of 4.40% hydrofluoric acid and 3.00% hydrochloric acid to soak for 150 seconds to remove metal ions on the surface of the silicon wafer; then rinse with water for 120 seconds to remove the residual mixed solution on the surface of the silicon wafer;

[0082] S8, slow pulling: pre-dehydrate the silicon wafer using a slow pulling method at 25°C for 120 seconds;

[0083] S9, drying: use 85°C circulating hot air to dry the silicon wafer for 800 seconds to complete the texturing process.

[0084] Comparative Example 2

[0085] The difference from Example 2 is that steps S4 and S5 in Example 2 are removed, and the texturing process is compared in one step, and other process parameters are the same as those in Example 2.

[0086] Example 3

[0087] A method for preparing a crystalline silicon solar cell, the method comprising the following steps:

[0088] S1, polishing: polishing the silicon wafer for 100 seconds using a 7.50wt% potassium hydroxide solution at 75°C to remove cutting line marks and other defects on the surface of the silicon wafer; then washing with water for 120 seconds to remove residual liquid on the surface of the silicon wafer;

[0089] S2, pre-cleaning: at 68° C., using a mixture of 0.90 wt % potassium hydroxide and 4.00 wt % hydrogen peroxide to clean for 150 seconds to remove impurities on the surface of the silicon wafer; and then washing with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0090] S3, primary texturing: at 80° C., the silicon wafer is firstly texturized for 600 seconds using a mixture of 0.63 wt % potassium hydroxide and 0.40 wt % HJ21 (V01) texturing additive to form a pyramid structure on the surface of the silicon wafer; and then the mixture is washed with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0091] S4, suede modification: at 20°C, use a mixed acid of 61.00wt% nitric acid and 0.40wt% hydrofluoric acid to etch the bottom of the suede pyramid for 180 seconds to remove the small pyramid at the bottom; then wash with water for 120 seconds to remove the residual mixed solution on the surface of the silicon wafer;

[0092] S5, secondary texturing: at 65°C, the silicon wafer is secondarily texturized for 320 seconds using a mixture of 0.63wt% potassium hydroxide and 0.40wt% HJ21 (V01) texturing additive to modify the bottom of the velvet pyramid; then the mixture is washed with water for 120 seconds to remove the residual mixture on the surface of the silicon wafer;

[0093] S6, alkali washing: at 65°C, use a mixture of 1.00wt% potassium hydroxide and 3.00wt% hydrogen peroxide to wash for 240s to remove organic residues on the surface of the silicon wafer; then wash with water for 120s to remove the residual mixture on the surface of the silicon wafer;

[0094] S7, pickling: at 25°C, use a mixture of 4.00% hydrofluoric acid and 2.00% hydrochloric acid to soak for 200 seconds to remove metal ions on the surface of the silicon wafer; then wash with water for 120 seconds to remove the residual mixed solution on the surface of the silicon wafer;

[0095] S8, slow pulling: pre-dehydrate the silicon wafer using a slow pulling method at 30°C for 100 seconds;

[0096] S9, drying: use 80°C circulating hot air to dry the silicon wafer for 1000 seconds to complete the texturing process.

[0097] Comparative Example 3

[0098] The difference from Example 3 is that steps S4 and S5 in Example 3 are removed, and the texturing process is compared in one step, and other process parameters are the same as those in Example 3.

[0099] In order to verify the advantages of the velvet surface compared with the traditional one-time velvet process, the reflectivity of the velvet surface of the silicon wafer and the electrical performance of the solar cell obtained by the velvet process of each embodiment and the comparative example are compared.

[0100] like Figure 6 As shown in the figure, it is a comparison chart of the velvet reflectivity of silicon wafers prepared by the preparation methods of various embodiments and comparative examples. The D8 velvet reflectometer of Zhidong Optoelectronics is used to test the light reflectivity intensity of the velvet structure of the silicon wafer in the wavelength range of 360 to 1050nm. 25 sample silicon wafers are taken for each group of embodiments and comparative examples for measurement, and 9 points are taken from the center and edge of each silicon wafer for multi-point automatic measurement and the average value is taken.

[0101] Depend on Figure 6 It can be seen that the reflectivity of each embodiment is lower than that of the corresponding control example, with an average decrease ranging from about 0.20% to 0.33%. This shows that the secondary velvet surface prepared by the embodiment has a more uniform morphology, a reduced number of tiny pyramids in the velvet surface, and better light absorption.

[0102] As shown in Table 1, it is a comparison table of the electrical properties of solar cells prepared by the preparation methods of various embodiments and comparative examples, and Table 1 is based on the electrical properties of each group of comparative examples as a reference. In this experiment, an n-type single crystal silicon wafer is used as a substrate, the silicon wafer size is 210.1 mm×105.05 mm, the silicon wafer thickness is 110-130 μm, and the silicon wafer resistivity is 0.3-2.1 Ω·cm. The overall solution for manufacturing a Maiwei HJT heterojunction high-efficiency battery is firstly carried out through the texturing and cleaning steps described in the embodiments / comparative examples of the present invention, and then an intrinsic amorphous silicon layer and an n-type doped amorphous silicon layer are sequentially deposited on the front side of an n-type silicon wafer substrate, and an intrinsic amorphous silicon layer and a p-type doped amorphous silicon layer are sequentially deposited on the back side of the n-type silicon wafer substrate; then an indium tin oxide (ITO) transparent conductive film is deposited on the amorphous silicon layer on both the front and back sides; finally, silver grid lines are printed on the surfaces of the double-sided ITO transparent conductive films by screen printing technology, and metal silver electrodes with good ohmic contact are formed after drying and curing, and finally an HJT solar cell is prepared, and a Maiwei electrical performance tester (in compliance with the IEC60904 series industry standards) is used to test the HJT solar cell under standard test conditions (STC) (i.e., the light intensity is 1000W / m 2 , spectrum is AM1.5, temperature is 25°C), the difference in photoelectric conversion efficiency (including Eta, Uoc, Isc, FF parameters) of the HJT solar cells of the embodiment and the comparative example is tested.

[0103] Table 1

[0104]

[0105] As shown in Table 1, the efficiency of each embodiment is significantly improved compared with the comparative example, and the improvement range is about 0.08% to 0.14%. Among them, the open circuit voltage and short circuit current are significantly improved. Figure 6 This corresponds to the reflectivity data, which shows that the embodiment has better light absorption rate and suede uniformity, so that its PN junction photoelectric conversion efficiency and passivation effect are better in the subsequent solar cell preparation process.

[0106] It should be understood by those skilled in the art that the above embodiments are merely exemplary embodiments and that various changes, substitutions and alterations may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a crystalline silicon solar cell, characterized in that: include: Anisotropic etching is performed on the silicon wafer to perform the first texturing; performing isotropic etching on the silicon wafer; The silicon wafer is subjected to anisotropic etching treatment and a second texturing process is performed.

2. The method for preparing a crystalline silicon solar cell according to claim 1, characterized in that: The silicon wafer is subjected to anisotropic etching treatment to perform a first texturing process, including: At a first temperature, anisotropically etching the silicon wafer to perform a first texturing process; The silicon wafer is subjected to anisotropic etching treatment and a second texturing process, including: At a second temperature, anisotropically etching the silicon wafer to perform a second texturing process; Wherein, the first temperature is greater than the second temperature.

3. The method for preparing a crystalline silicon solar cell according to claim 2, characterized in that: At a first temperature, anisotropically etching the silicon wafer, including: using a second mixed solution of alkali and a first texturing additive to react with the silicon wafer at the first temperature; Anisotropically etching the silicon wafer at a second temperature includes: using a third mixed solution of alkali and a second texturing additive to react with the silicon wafer at the second temperature.

4. The method for preparing a crystalline silicon solar cell according to claim 3, characterized in that: In the second mixed solution, the concentration of the alkali is 0.4 to 2.0 wt %, and the concentration of the first texturing additive is 0.3 to 1.0 wt %; Using the second mixed solution of alkali and the first texturing additive to react with the silicon wafer at the first temperature includes: reacting with the silicon wafer at 78 to 85° C. for 400 to 600 seconds.

5. The method for preparing a crystalline silicon solar cell according to claim 4, characterized in that: In the third mixed solution, the concentration of the alkali is 0.4 to 2.0 wt %, and the concentration of the second texturing additive is 0.3 to 1.0 wt %; Using the third mixed solution of the alkali and the second texturing additive to react with the silicon wafer at the second temperature includes: reacting with the silicon wafer at 65 to 75° C. for 100 to 400 seconds.

6. The method for preparing a crystalline silicon solar cell according to any one of claims 1 to 5, characterized in that: The silicon wafer is subjected to isotropic etching treatment, comprising: A first mixed acid solution of nitric acid and hydrofluoric acid is used to react with the silicon wafer to perform an isotropic etching process on the silicon wafer.

7. The method for preparing a crystalline silicon solar cell according to claim 6, characterized in that: In the first mixed acid solution, the concentration of nitric acid is 60.0 to 70.0 wt %, and the concentration of hydrofluoric acid is 0.3 to 1.5 wt %. Using the first mixed acid solution of nitric acid and hydrofluoric acid to react with the silicon wafer includes: reacting with the silicon wafer at 20 to 25° C. for 60 to 200 seconds.

8. The method for preparing a crystalline silicon solar cell according to any one of claims 1 to 5, characterized in that: After the silicon wafer is subjected to anisotropic etching and second texturing, the method further comprises: Cleaning the silicon wafer using a fourth mixed solution of alkali and hydrogen peroxide; Soaking the silicon wafer in a second mixed acid solution of hydrofluoric acid and hydrochloric acid; The silicon wafer is pre-dehydrated and dried.

9. The method for preparing a crystalline silicon solar cell according to claim 8, characterized in that: In the fourth mixed solution, the concentration of alkali is 0.4 to 3.0 wt %, and the concentration of hydrogen peroxide is 2.0 to 5.0 wt %. Cleaning the silicon wafer using the fourth mixed solution of alkali and hydrogen peroxide includes: cleaning the silicon wafer at 60 to 70° C. for 150 to 250 seconds.

10. The method for preparing a crystalline silicon solar cell according to claim 8, characterized in that: In the second mixed acid solution, the concentration of hydrofluoric acid is 3.0 to 6.0 wt %, and the concentration of hydrochloric acid is 2.0 to 5.0 wt %. Soaking the silicon wafer in the second mixed acid solution of hydrofluoric acid and hydrochloric acid includes: soaking the silicon wafer at 20 to 25° C. for 120 to 250 seconds.

11. The method for preparing a crystalline silicon solar cell according to claim 8, characterized in that: The pre-dehydration includes using water at 25 to 60° C. to pre-dehydrate the silicon wafer for 60 to 120 seconds; the drying includes using a circulating hot air flow at 80 to 100° C. to dry the silicon wafer for 500 to 1000 seconds.

12. The method for preparing a crystalline silicon solar cell according to any one of claims 1 to 5, characterized in that: The anisotropic etching of silicon wafers, before the first texturing, also includes: Polishing silicon wafers using alkaline solutions; The silicon wafer is pre-cleaned using a first mixed solution of alkali and hydrogen peroxide.

13. The method for preparing a crystalline silicon solar cell according to claim 12, characterized in that: The concentration of the alkaline solution is 3.0 to 8.0 wt %. Polishing the silicon wafer using the alkaline solution includes: polishing the silicon wafer at 65 to 85° C. for 20 to 100 seconds.

14. The method for preparing a crystalline silicon solar cell according to claim 12, characterized in that: In the first mixed solution, the concentration of alkali is 0.5 to 3.0 wt %, and the concentration of hydrogen peroxide is 2.0 to 5.0 wt %. Pre-cleaning the silicon wafer using the first mixed solution of alkali and hydrogen peroxide includes: pre-cleaning the silicon wafer at 60 to 70° C. for 100 to 240 seconds.

15. A solar cell, characterized in that: The solar cell is a crystalline silicon solar cell prepared according to the method for preparing a crystalline silicon solar cell according to any one of claims 1 to 14.

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