A method for modifying a silicon wafer pyramid velvet, a solar cell

Abstract

The application discloses a silicon wafer pyramid suede modification method and a solar cell, and belongs to the technical field of solar cell manufacturing. The silicon wafer pyramid suede modification method comprises the following steps: pretreatment; first step of texturing: the silicon wafer is placed in an alkali solution containing additive A, and a basic pyramid suede is formed through reaction; water washing; second step of modification: the silicon wafer is placed in an alkali solution containing additive B, and a tower body step structure and a nano pit are formed through reaction; post-treatment; the additive A and the additive B are different chemical system heterologous additives; and the temperature of the first step of texturing is higher than the temperature of the second step of modification. The application first constructs a high-density basic pyramid suede, then performs directional etching on the tower body, and simultaneously forms a step-shaped laminated surface and a surface nano pit array, so that the comprehensive performance of the solar cell is improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a method for modifying the pyramidal textured surface of a silicon wafer and a solar cell. Background Technology

[0002] In the manufacturing of crystalline silicon solar cells, texturing is a crucial step in reducing light reflectivity by etching a pyramidal array structure onto the silicon wafer surface, thus improving photoelectric conversion efficiency. However, current technologies face several bottlenecks: while the resulting pyramidal structure possesses basic light-trapping capabilities, its surface, due to insufficient etching, exhibits high flatness and smoothness, causing incident light to be reflected only once on a single sloping surface, resulting in low light-trapping efficiency. Current research attempts to improve light-trapping capabilities by constructing pyramidal structures in stages using a two-step texturing technique, but this remains hampered by two issues: the additives have limited chemical functions, making it impossible to controllably construct nanoscale pit arrays on the stepped surface, resulting in limited reflectivity reduction; to maintain the reactivity of the additives, the second-step process temperature is forced to increase, potentially inducing a surge in the lateral etching rate of the silicon material. This process causes mechanical instability and fracture at the pyramid tip, and non-uniform collapse in the base region, ultimately leading to deterioration of the textured surface structure and electrode contact interface, impairing electrical properties such as the cell fill factor. Existing processes struggle to achieve the synergistic construction of the pyramidal structure at the nanoscale and the micrometer-scale steps while suppressing high-temperature damage. Therefore, an innovative process is needed that can precisely control the etching direction at low temperatures, simultaneously achieving nanostructuring of the tower body while maintaining the integrity of the textured surface. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for modifying a silicon wafer pyramid textured surface and a solar cell. The method involves first constructing a high-density basic pyramid textured surface, then directionally etching the pyramid body to simultaneously form a stepped layered surface and a surface nano-pit array.

[0004] The present invention adopts the following technical solution: In a first aspect, the present invention discloses a method for modifying the pyramidal textured surface of a silicon wafer, comprising the following steps: S1 Pre-treatment: The silicon wafer is pre-cleaned and washed with water; S2 Step 1 Texturing: The silicon wafer is placed in an alkaline solution containing additive A, and the reaction forms a basic pyramid textured surface; S3 Water Wash: The silicon wafer is rinsed with deionized water; S4 Second step modification: The silicon wafer is placed in an alkaline solution containing additive B, and the reaction forms a tower-like stepped structure and nano-pits; S5 post-treatment: sequentially perform water washing, acid washing, slow lifting and drying; Additive A and Additive B are heterogeneous additives with different chemical systems. Additive A contains polysulfonate compounds and alkyl sulfonate compounds, while Additive B contains carboxylic acid polymers and nitrogen heterocyclic compounds. The temperature of the first step of texturing is higher than the temperature of the second step of finishing.

[0005] Furthermore, the concentration of polysulfonate compounds in additive A is 5-8 wt%, and the concentration of alkylsulfonate compounds is 2.5-3.5 wt%; the concentration of carboxylic acid polymers in additive B is 1.5-2.0 wt%, and the concentration of nitrogen heterocyclic compounds is 0.1-0.3 wt%.

[0006] Furthermore, the polysulfonate compound in additive A is sodium polystyrene sulfonate, and the alkyl sulfonate compound is sodium dodecyl sulfonate; the carboxylic acid polymer in additive B is hydrolyzed polymaleic anhydride, and the nitrogen heterocyclic compound is 2-amino-5-nitropyrimidine.

[0007] Furthermore, additive A also includes sodium benzoate and deionized water; additive B also includes surfactant, sodium benzoate, sodium chloride, water and a protective agent.

[0008] Further, the amount of additive A is 0.50-0.80 wt%, and the amount of additive B is 0.30-0.60 wt%. Preferably, the amount of additive A is 0.50 wt%, 0.53 wt%, 0.55 wt%, 0.60 wt%, 0.62 wt%, 0.64 wt%, 0.65 wt%, 0.68 wt%, 0.70 wt%, 0.72 wt%, 0.75 wt%, 0.78 wt%, 0.80 wt%, or any combination thereof. The amount of additive B is 0.30 wt%, 0.33 wt%, 0.35 wt%, 0.40 wt%, 0.42 wt%, 0.43 wt%, 0.45 wt%, 0.48 wt%, 0.50 wt%, 0.52 wt%, 0.55 wt%, 0.58 wt%, 0.60 wt%, or any combination thereof.

[0009] Furthermore, the amount of additive A added is 0.60 wt%, and the amount of additive B added is 0.43 wt%.

[0010] Additive A forms an electrostatic steric hindrance layer on the silicon crystal surface using sodium polystyrene sulfonate in a high-temperature (80-90℃) alkaline environment, synergistically reducing surface tension with sodium dodecyl sulfonate to achieve high-density vertical pyramidal growth. Additive B, in a lower-temperature environment (60-70℃), utilizes hydrolyzed polymaleic anhydride for selective adsorption at the step edges, triggering localized electrochemical corrosion to generate pits. This, in conjunction with the photolysis of 2-amino-5-nitropyrimidine, generates nitrogen free radicals to passivate the inner walls of the pits. This heterogeneous additive system achieves high-temperature nucleation and low-temperature precise etching, improving the overall performance of solar cells.

[0011] Further, the alkaline solution is NaOH or KOH, the concentration of the alkaline solution in the first step of texturing is 1.0-2.0 wt%, and the concentration of the alkaline solution in the second step of modification is 0.050-0.080 wt%. Preferably, the concentration of the alkaline solution in the first step of texturing is 1.0 wt%, 1.3 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, or any combination thereof. The concentration of the alkaline solution in the second step of modification is 0.050 wt%, 0.053 wt%, 0.055 wt%, 0.060 wt%, 0.062 wt%, 0.064 wt%, 0.065 wt%, 0.068 wt%, 0.070 wt%, 0.072 wt%, 0.075 wt%, 0.078 wt%, 0.080 wt%, or any combination thereof.

[0012] Furthermore, the concentration of the alkali solution used in the first step of texturing is 1.32 wt%, and the concentration of the alkali solution used in the second step of modification is 0.060 wt%.

[0013] Furthermore, the first step of the flocking process is carried out at a temperature of 80-90℃, and the second step of the finishing process is carried out at a temperature of 60-70℃.

[0014] Furthermore, the first step of the flocking process takes 260-280 seconds, and the second step of the finishing process takes 80-140 seconds.

[0015] Secondly, the present invention provides a solar cell using the above-described silicon wafer pyramid textured surface decoration method.

[0016] Furthermore, the solar cell is any one of TOPCON, PERC, or BC cells.

[0017] The present invention has the following beneficial effects: This invention discloses a method for texturing a pyramidal surface on silicon wafers and a solar cell. Through stepwise control and temperature adaptation of a heterogeneous additive system, a one-step texturing and two-step modification process is employed, controlling the additive type and reaction temperature to achieve nanostructural etching of the stepped pyramidal body. Additive A primarily constructs a high-density basic pyramidal step structure, while additive B precisely controls the formation of nano-pits on the step surface and simultaneously completes surface passivation. The step structure extends the incident light propagation path, and the nano-pits enhance broadband absorption and reduce reflectivity through multiple scattering effects. Simultaneously, the pits significantly increase the contact area with the metal paste. The heterogeneous additive combination achieves nucleation control and etching orientation, while the low-temperature process effectively avoids the risk of over-etching, ensuring the integrity of the texturized structure and improving the overall performance of the solar cell. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The image shows a scanning electron microscope image of the textured surface of a silicon wafer prepared in Example 1 of this invention. (A) Top view of the textured surface, magnification 60000× (B) Side cross-sectional view, magnification 30000×. Figure 2 The image shows a scanning electron microscope (SEM) image of the textured silicon wafer prepared in Comparative Example 1 of this invention. (A) Top view of the textured surface, magnification 60000× (B) Side cross-sectional view, magnification 30000×. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0021] It should be noted that the embodiments of the present invention use TOPCon cells as an example to illustrate in detail the method of silicon wafer pyramid textured surface modification in solar cells. However, based on the same technical principles, those skilled in the art will understand that this technical solution is equally applicable to other types of solar cells, including but not limited to: TOPCon cells, PERC cells, and BC cells. By making conventional adaptive adjustments to the parameters of the silicon wafer pyramid textured surface modification method in the present invention according to the process characteristics of the specific cell type, equivalent technical effects can be achieved. Such adjustments fall within the scope of protection of those skilled in the art without creative effort, and therefore are all within the scope of protection of the present invention.

[0022] Example 1 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: The silicon wafer is rinsed with deionized water for 40 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 65°C for 100 seconds to form a tower-shaped stepped structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0023] Example 2 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.00wt% alkaline solution, and 0.5wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 70°C for 260 seconds to form a basic pyramid textured surface. S3. Water washing: Rinse the silicon wafer with deionized water for 30 seconds; S4. Second modification step: The above silicon wafer is placed in a 0.05wt% alkaline solution, and 0.30wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 60°C for 80 seconds to form a tower body step structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0024] Example 3 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 2.00wt% alkaline solution, and 0.80wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 90°C for 280 seconds to form a basic pyramid textured surface. S3. Water washing: The silicon wafer is rinsed with deionized water for 60 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.08wt% alkaline solution, and 0.60wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 70°C for 120 seconds to form a tower body step structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0025] Example 4 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: Rinse the silicon wafer with deionized water for 30-60 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 80°C for 100 seconds to form a tower-shaped stepped structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0026] Example 5 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: Rinse the silicon wafer with deionized water for 30-60 seconds; S4. Second modification step: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 50°C for 100 seconds to form a tower-shaped stepped structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0027] Example 6 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: Rinse the silicon wafer with deionized water for 30-60 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.5wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 50°C for 100 seconds to form a tower body step structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0028] Example 7 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: Rinse the silicon wafer with deionized water for 30-60 seconds; S4. Second modification step: The above silicon wafer is placed in a 0.03wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 50°C for 100 seconds to form a tower body step structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0029] Example 8 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 2.00wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82°C for 270 seconds to form a basic pyramid textured surface. S3. Water washing: The silicon wafer is rinsed with deionized water for 40 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 65°C for 100 seconds to form a tower-shaped stepped structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0030] Example 9 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.30% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82°C for 270 seconds to form a basic pyramid textured surface. S3. Water washing: The silicon wafer is rinsed with deionized water for 40 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 0.43wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 65°C for 100 seconds to form a tower-shaped stepped structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0031] Example 10 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: The silicon wafer is rinsed with deionized water for 40 seconds; S4. Second modification step: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 1.00wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 65°C for 100 seconds to form a tower body step structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0032] Example 11 This embodiment provides a method for modifying the pyramidal textured surface of a silicon wafer, which includes the following steps: S1. Pre-treatment: Pre-cleaning and washing of silicon wafers; S2. First step texturing: The silicon wafer is placed in a 1.32wt% alkaline solution, and 0.60wt% of additive A is added. Additive A contains 3% sodium dodecyl sulfonate, 7% sodium polystyrene sulfonate, 1% sodium benzoate, and 89% deionized water. The reaction is carried out at 82℃ for 270 seconds to form a basic pyramid textured surface. S3. Water washing: The silicon wafer is rinsed with deionized water for 40 seconds; S4. Second step modification: The above silicon wafer is placed in a 0.060wt% alkaline solution, and 0.20wt% of additive B is added. Additive B contains 1.8% of hydrolyzed polymaleic anhydride of carboxylic acid polymer, 0.52% of nitrogen heterocyclic compound 2-amino-5-nitropyrimidine, 3.05% of surfactant, 0.50% of sodium benzoate, 0.32% of sodium chloride, 92.16% of water and 1.65% of protective agent. The reaction is carried out at 65°C for 100 seconds to form a tower body step structure and nano-pits. S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 is that steps S3 and S4 are removed, while the remaining preparation methods and parameters are consistent with those of Example 1.

[0034] Comparative Example 2 The difference between this comparative example and Example 1 is that step S4 is changed to repeat step S2, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0035] Comparative Example 3 The difference between this comparative example and Example 1 is that step S2 is changed to repeat step S4, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0036] The silicon wafers of Examples 1-11 and Comparative Examples 1-3, after texturing, were further subjected to subsequent battery fabrication processes, including: boron diffusion, removal and alkaline polishing of borosilicate glass layers, LPCVD deposition, phosphorus diffusion, removal of phosphorus silicate glass layers and RCA cleaning, ALD passivation, front and back antireflective film deposition, electrode screen printing and sintering.

[0037] The performance of the prepared TOPCon solar cells was tested, and the results are shown in Table 2.

[0038] Table 1. Test results of textured surface on silicon wafers Table 2 Battery performance test results Table 1 shows the silicon wafer textured surface test results, and Table 2 shows the battery performance test results. As can be seen from the test results of Examples 1-5 and Comparative Examples 1-3, the silicon wafer pyramid textured surface modification method provided by this invention, through the construction of a heterogeneous additive system, combined with a step-by-step control mechanism of one-step texturing and two-step modification, and with appropriate temperature control and alkaline solution concentration settings, achieves nanostructural etching of the pyramid body, effectively avoiding damage to the textured surface structure caused by over-etching, and ensuring the integrity and uniformity of the pyramid structure. This technology exhibits good adaptability in solar cell fabrication, not only improving the specific surface area and nucleation density of the silicon wafer surface, but also significantly improving the photoelectric conversion performance of the battery, resulting in a significant improvement in the overall performance of the solar cell, which is of great significance in the field of solar cell technology.

[0039] As can be seen from the test results of Example 1 and Comparative Examples 1-3, compared with the one-step texturing and two-step modification methods, the texturing effect and solar cell performance of the one-step texturing method and the two-step texturing method with the same additive are both inferior. Figure 1 As shown, Example 1 exhibits a moderate pyramid width, pyramid height, and a high number of nuclei in the textured surface of the silicon wafer. The pyramidal textured surface of the silicon wafer presents a stepped shape, and the sides display a nano-pit structure with a corresponding specific surface area of ​​1.375, indicating that its textured surface structure is uniform and reasonable. Figure 2 As shown, the silicon wafer pyramid texture prepared by the one-step texturing method in Comparative Example 1 is smooth and flat, with no pits on the sides. Regarding cell performance, Example 1 achieved a conversion efficiency of 26.365%, significantly higher than Comparative Example 1 (26.115%), Comparative Example 2 (26.085%), and Comparative Example 3 (26.027%). Furthermore, it exhibited superior fill factor, open-circuit voltage, and short-circuit current, with higher parallel resistance and lower series resistance, indicating lower edge leakage, fewer defects, and lower transmission loss. This demonstrates that the present invention, by constructing a heterogeneous additive system and combining a step-by-step control mechanism of one-step texturing and two-step modification, effectively improves the textured surface structure of the silicon wafer, thereby enhancing the overall performance of the solar cell.

[0040] As can be seen from the test results of Examples 1 and 4-5, the temperature of the second modification step affects the texturing effect. Temperatures that are too high or too low result in poor texturing and solar cell performance, with cell performance slightly lower than in Example 1, with conversion efficiencies of 26.138% and 26.236%, respectively. In contrast, Example 1 exhibits a suitable modification temperature and superior cell performance, indicating that a reasonable setting of the second modification temperature range has a significant impact on forming a superior texturized structure and improving photoelectric conversion efficiency.

[0041] As can be seen from the test results of Examples 1 and 6-7, the concentration of the alkaline solution in the second modification step affects the texturing effect. Both excessively high and low alkaline solution concentrations result in poor texturing performance and low solar cell performance. The battery conversion efficiencies of Examples 6 and 7 were 26.220% and 26.207%, respectively, both lower than that of Example 1. This indicates that both excessively high and excessively low alkali concentrations are not conducive to the formation of a good textured surface structure. Excessively high alkali concentrations will cause damage to the textured surface, while excessively low alkali concentrations will lead to a decrease in battery performance. This further verifies the rationality and necessity of the alkali concentration range set in the claims.

[0042] As can be seen from the test results of Examples 1 and Examples 8-11, when the amount of additive A or B exceeds the range defined in the claims (Examples 8-11), the battery performance decreases to varying degrees regardless of whether the amount is increased or decreased. In contrast, Example 1 is within the optimal range for dosage control, indicating that the present invention has a significant impact on the dosage of additives A and B, which can optimize the textured surface structure and improve battery performance.

[0043] In summary, by comparing the examples and comparative examples, it can be concluded that the present invention, by employing a one-step texturing and two-step modification process and setting reasonable texturing temperature, alkali concentration, additive system and dosage, can significantly improve the textured surface structure of silicon wafers, increase specific surface area and nucleation density, thereby effectively improving the conversion efficiency and overall performance of solar cells.

[0044] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for modifying the pyramidal textured surface of a silicon wafer, characterized in that, Includes the following steps: S1 Pre-treatment: The silicon wafer is pre-cleaned and washed with water; S2 Step 1 Texturing: The silicon wafer is placed in an alkaline solution containing additive A, and the reaction forms a basic pyramid textured surface; S3 Water Wash: The silicon wafer is rinsed with deionized water; S4 Second step modification: The silicon wafer is placed in an alkaline solution containing additive B, and the reaction forms a tower-like stepped structure and nano-pits; S5. Post-treatment: sequentially perform water washing, acid washing, slow lifting and drying; Additive A and Additive B are heterogeneous additives with different chemical systems. Additive A contains polysulfonate compounds and alkyl sulfonate compounds, while Additive B contains carboxylic acid polymers and nitrogen heterocyclic compounds. The polysulfonate compound in additive A is sodium polystyrene sulfonate, and the alkyl sulfonate compound is sodium dodecyl sulfonate; the carboxylic acid polymer in additive B is hydrolyzed polymaleic anhydride, and the nitrogen heterocyclic compound is 2-amino-5-nitropyrimidine. The temperature of the first step of texturing is higher than the temperature of the second step of finishing. In an environment of 60-70℃, the additive B utilizes the selective adsorption of hydrolyzed polymaleic anhydride at the edge of the step to trigger local electrochemical corrosion and generate pits. This, in conjunction with the photolysis of 2-amino-5-nitropyrimidine, generates nitrogen free radicals that passivate the inner wall of the pits.

2. The method according to claim 1, characterized in that: The amount of additive A is 0.50-0.80 wt%, and the amount of additive B is 0.30-0.60 wt%.

3. The method according to claim 1, characterized in that: The alkaline solution is NaOH or KOH. The concentration of the alkaline solution in the first step of texturing is 1.0-2.0 wt%, and the concentration of the alkaline solution in the second step of modification is 0.050-0.080 wt%.

4. The method according to claim 1, characterized in that: The first step of the flocking process is carried out at a temperature of 80-90℃, and the second step of the finishing process is carried out at a temperature of 60-70℃.

5. The method according to claim 1, characterized in that: The first step of the flocking process takes 260-280 seconds, and the second step of finishing takes 80-140 seconds.

6. A solar cell, characterized in that: The silicon wafers prepared by the silicon wafer pyramid textured surface finishing method according to any one of claims 1-5 are included.

7. The solar cell according to claim 6, characterized in that, The solar cell is any one of TOPCON, PERC, or BC cells.

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