Texturing-positive plating synergistic process of low-reflectivity TOPCon solar cell

Abstract

The invention discloses a texturing-positive plating collaborative process for a low-reflectivity TOPCon solar cell, and relates to the field of solar cells. The process sequentially comprises the steps of primary texturing, water washing, secondary texturing and positive plating. Wherein the content of NaOH in a primary texturing tank solution of the primary texturing is greater than the content of NaOH in a secondary texturing tank solution of the secondary texturing; the reaction temperature of the primary texturing is higher than that of the secondary texturing, and the reaction time of the primary texturing is longer than that of the secondary texturing. Compared with a conventional single-time texturing process, through the modification effect of secondary texturing, the reflectivity of the silicon wafer can be remarkably reduced, and the textured surface quality and uniformity are improved. The design of'high alkali concentration + short time 'is adopted for primary texturing, the situation that the overall process time is too long due to the fact that a secondary texturing step is added is avoided while formation of a basic textured surface is guaranteed, and the quality and the efficiency are both considered. And the process parameters can be flexibly adjusted through tests, the adaptability is high, and the texturing requirements of different types of silicon wafers are met.

Description

Technical Field

[0001] This invention relates to the field of solar cells, and more specifically to a texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells. Background Technology

[0002] In the manufacturing of solar cells, texturing is a crucial step. Its main purpose is to construct specific microstructures on the surface of the silicon wafer to enhance the absorption of sunlight, reduce light reflection loss, and thus improve the photoelectric conversion efficiency of the solar cell. Currently, while the texturing process is relatively mature and widely used in the industry, its limitations are becoming increasingly apparent with technological advancements and the pursuit of higher conversion efficiencies. The core of a solar cell is absorbing sunlight and converting it into electrical energy; therefore, reducing the reflectivity of the cell's front surface is beneficial for improving conversion efficiency.

[0003] Currently widely used primary texturing methods have shortcomings in terms of surface uniformity and reflectivity. Poor surface uniformity results in variations in light absorption and conversion capabilities across different areas of the silicon wafer, affecting the overall consistency of battery performance. High reflectivity leads to lower battery conversion efficiency. High reflectivity means more sunlight is reflected away from the surface and cannot be effectively utilized by the light-absorbing layer inside the battery, directly reducing the number of photons that can be converted into electrical energy, resulting in lower conversion efficiency.

[0004] Furthermore, traditional texturing methods focus only on the textured surface structure itself, neglecting the compatibility between the subsequent positive plating process (anti-reflective film deposition) and the textured surface. Even with optimal textured surface design, mismatched positive plating process parameters (such as time) can lead to problems such as abnormal film color, increased reflectivity, and decreased battery efficiency. Therefore, the synergistic optimization of positive plating and texturing is crucial.

[0005] Based on this, in order to reduce the surface reflectivity of silicon wafers, increase the specific surface area of ​​the textured surface, and effectively improve the photoelectric conversion efficiency of the cells, a texturing-positive plating synergistic process for low-reflectivity solar cells was explored. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells, solving at least one technical problem mentioned in the background art.

[0007] (II) Technical Solution The technical solution adopted in this invention provides a texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells, wherein the process sequentially includes primary texturing, water washing, secondary texturing, and positive plating; The NaOH content in the primary texturing bath solution is greater than the NaOH content in the secondary texturing bath solution; and the reaction temperature of the primary texturing is higher than the reaction temperature of the secondary texturing, and the reaction time of the primary texturing is longer than the reaction time of the secondary texturing.

[0008] Preferably, the primary texturing bath solution comprises, by weight percentage: 2.0%-3.5% NaOH, 0.2%-0.6% primary texturing additive, and the remainder being water.

[0009] Preferably, the secondary texturing bath solution comprises, by weight percentage: 0.1%-0.3% NaOH, 0.2%-0.7% secondary texturing additive, and the remainder being water.

[0010] Preferably, the reaction temperature for the primary texturing process is 81-83℃, and the reaction time is 250-300s.

[0011] Preferably, the reaction temperature for the secondary texturing is 60-70℃, and the reaction time is 80-120s.

[0012] Preferably, the positive plating is performed using plasma-enhanced chemical vapor deposition equipment to deposit a silicon nitride antireflective film, with ammonia and silane as the reaction gases, and the reaction pressure controlled at 200-250 Pa, the radio frequency power at 300-350 W, and the positive plating process time at 2450-2550 s.

[0013] Preferably, the process parameters for the water washing are as follows: the water washing time is controlled at 90-120s; the water washing temperature is controlled at 25℃; the bubbling mode is controlled to maintain continuous bubbling throughout the process; and the overflow size is controlled at 700-1000L / h, with continuous overflow throughout the process.

[0014] Preferably, the primary texturing additive comprises, by mass percentage: 0.1%~3% sodium hydroxide, 2%~10% isopropanol, 0.1-0.5% weak acid salt, 1%~2% surfactant, and the remainder is water.

[0015] Preferably, the secondary texturing additive comprises, by weight percentage: 0.02%~1.0% surfactant, 0.1%~0.8% chelating agent, 0.02%~1.0% defoamer, 0.03%~2.0% nucleating promoter, 0.5%~2.0% film-forming agent, and the remainder is water.

[0016] (III) Beneficial Effects This invention provides a texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells, which has the following advantages compared with the prior art: Primary texturing, through a combination of "high alkali concentration + normal temperature + short time," rapidly builds a basic textured surface while shortening the single-step time, avoiding excessively prolonged overall process time due to the addition of secondary texturing. Secondary texturing, through a combination of "low alkali concentration + low temperature + short time," gently corrects defects in the primary texturing surface (such as sharp edges and uneven areas), ultimately achieving the goal of low reflectivity. Compared to conventional single-step texturing processes, the corrective effect of secondary texturing can significantly reduce silicon wafer reflectivity and improve texture quality and uniformity. The primary texturing design, employing "high alkali concentration + short time," ensures the formation of a basic textured surface while avoiding excessively long overall process time due to the addition of secondary texturing steps, balancing quality and efficiency. Furthermore, the process parameters can be flexibly adjusted through experimentation, making it highly adaptable and suitable for the texturing needs of different types of silicon wafers.

[0017] The positive plating process time was adjusted to match the optimized textured surface, and the thickness of the controllable silicon nitride film was optimized to avoid abnormal light interference color (reddish tint) caused by an excessively thin film. At the same time, the film was ensured to be tightly bonded to the textured pyramidal surface, forming a dual low-reflection structure of "textured surface + anti-reflection film". This achieves the effects of reducing the reflectivity of the silicon wafer surface, increasing the light utilization rate, increasing the specific surface area of ​​the textured surface, and increasing the contact area with the paste, thereby improving the conversion efficiency of the solar cell. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 A schematic diagram illustrating the microscopic mechanism of action of secondary texturing additive B; Specific implementation methods To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, 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 scope of protection of the present invention. To address the problems raised in the background art, this invention adds a secondary texturing step. With a smaller amount of corrosion, this effectively reduces the amount of fine fibers on the surface of the texturized surface obtained from the first texturing step, resulting in a smoother and more even surface, enhanced uniformity, and thus reduced light scattering and loss on the surface. Secondly, the secondary texturing increases the specific surface area. A larger specific surface area facilitates more contact points with the slurry and also promotes slurry penetration. Most importantly, the secondary texturing significantly reduces the reflectivity of the solar cell surface by refining the structure, eliminating specular areas, optimizing the interface, and adapting to multiple wavelengths, thereby improving light absorption efficiency and ultimately enhancing the photoelectric conversion performance of the cell.

[0019] This invention discloses a texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells. By adding a texturing step, the silicon wafer is texturized in stages to solve problems such as uneven texturing and high surface reflectivity of silicon wafers in the prior art. By specifically adjusting the positive plating process parameters, problems such as abnormal film color are avoided, thus ensuring the product quality of low-reflectivity solar cells.

[0020] Specifically, the process sequentially includes primary texturing, water washing, secondary texturing, and positive plating; wherein the NaOH content in the primary texturing bath solution is greater than the NaOH content in the secondary texturing bath solution; and the reaction temperature of the primary texturing is higher than the reaction temperature of the secondary texturing, and the reaction time of the primary texturing is longer than the reaction time of the secondary texturing.

[0021] The low-reflectivity texturing method proposed in this invention adds a second texturing step to the existing texturing process. This second etching process optimizes the formed texturized structure, further reducing reflectivity. The core principles include: refining the texturized structure to increase multiple reflections of light; the surface of large structures (such as large pyramids or deep corrosion pits) formed in the first texturing step may still have smooth areas. The second etching selectively etches the "edges" and "tops" of these structures, refining the large structure into smaller substructures (e.g., forming smaller pyramids on the surface of a pyramid, or creating finer pits at the edges of corrosion pits). The refined texturized surface causes more diffuse reflections after light incident, lengthening the light propagation path on the battery surface, increasing the probability of light absorption, and reducing direct reflection.

[0022] Filling structural gaps and reducing "specular reflection areas": After the first texturing process, gaps or flat areas may exist between the texturing structures, and these areas are prone to specular reflection. Through a second etching process, these gaps can be filled or covered, making the surface "rougher" and more uniform, eliminating localized high-reflectivity "specular areas," and allowing reflected light to be more dispersed in all directions, thereby reducing the overall reflectivity.

[0023] By optimizing the surface chemical state and reducing reflective interfaces, the etching solution further removes damaged layers, impurities, or oxide layers from the silicon wafer surface during the second etching process, resulting in a more uniform chemical state on the silicon surface. Simultaneously, the second etching process adjusts the "duty cycle" (the ratio of structure to gaps) of the textured surface, making the light reflection interface on the silicon surface more complex. This reduces reflectivity through the "light trapping" effect (light is absorbed after multiple reflections within the structure, rather than escaping).

[0024] To adapt to the absorption of different wavelengths of light, sunlight contains different wavelengths (visible light, infrared, ultraviolet), and different sizes of textured structures have different effects on suppressing the reflection of different wavelengths of light. A single structure formed by a single texturing process may be more effective for a certain wavelength band, while a "multi-level structure" formed by a second etching process (such as a large pyramid covered with a small pyramid) can adapt to a wider range of wavelengths, suppressing the reflection of both short and long wavelengths, thereby reducing the overall reflectivity.

[0025] The microscopic mechanism of action of the secondary flocking additive B used in the embodiments of the present invention (e.g.) Figure 1 This method utilizes the fact that Si atoms at the pyramid's apex have more exposed coordination sites on their surface compared to Si atoms at the base and body. Therefore, selective coordination protecting groups are introduced to selectively protect the pyramid's apex, enabling selective etching of the pyramid's base downwards. This results in a high aspect ratio pagoda-shaped pyramid structure, increasing light trapping and reducing reflectivity.

[0026] Specifically, the concentration of the chemical solution and reaction conditions in the texturing tank of the above-mentioned low-reflectivity texturing method. The specific process parameters of the primary fabrication tank in the above-mentioned primary fabrication process are as follows: Its core function is to rapidly form a basic nap using a high-concentration alkaline solution, laying the foundation for subsequent finishing and optimization processes.

[0027] The solution in the primary texturing tank consists of the following raw materials by weight percentage: NaOH 2.0%-3.5%, primary texturing additive A 0.2%-0.6%, and the remainder is pure water solvent. The reaction temperature is 81-83℃, and the reaction time is 400-450s.

[0028] The specific process parameters for the secondary flocking tank are as follows: Core function: To modify and optimize the pile surface after the first pile forming process, reduce surface defects, lower reflectivity, and improve the uniformity of the pile surface.

[0029] The solution in the secondary texturing tank consists of the following raw materials by weight percentage: NaOH 0.1%-0.3%, secondary texturing additive B 0.2%-0.7%, and the remainder is pure water solvent. The reaction temperature is 60-70℃, and the reaction time is 80-120s.

[0030] The above-mentioned process, by adjusting the parameters of the primary texturing bath, rapidly forms a basic texturing surface using a high-concentration alkaline solution, laying the foundation for subsequent secondary texturing and optimization. The alkaline concentration is higher than that of a conventional single-pass texturing process; the reaction temperature is consistent with that of a conventional single-pass texturing process (e.g., within the conventional temperature range, with specific values ​​determined based on the silicon wafer type and conventional process parameters). The reaction time is shorter than that of a conventional single-pass texturing process, aiming to form a uniform, non-over-corroded basic texturing surface under high alkaline concentration.

[0031] The secondary pile forming process modifies and optimizes the pile surface after the primary pile forming, reducing surface defects, lowering reflectivity, and improving pile surface uniformity.

[0032] The alkali concentration is lower than that of the primary texturing bath (it does not need to be too high, the aim is to gently modify the texturing surface). The reaction temperature is lower than that of the primary texturing bath (by lowering the temperature, the reaction rate is slowed down to avoid over-modification that could damage the texturing surface). The reaction time is shorter than that of the primary texturing bath to achieve a smooth texturing surface and reduce reflectivity.

[0033] The primary texturing process uses a combination of "high alkali concentration + normal temperature + short time" to quickly build a basic texturing surface while shortening the single-step time, avoiding excessively prolonged overall process time due to the addition of secondary texturing. The secondary texturing process uses a combination of "low alkali concentration + low temperature + short time" to gently correct defects in the primary texturing surface (such as sharp edges and uneven areas), ultimately achieving the goal of low reflectivity.

[0034] Compared to conventional single-step texturing processes, the secondary texturing step significantly reduces silicon wafer reflectivity and improves the quality and uniformity of the textured surface. The primary texturing process employs a "high alkali concentration + short time" design, ensuring the formation of a basic textured surface while avoiding excessively long overall process times caused by adding a secondary texturing step, thus balancing quality and efficiency. Furthermore, the process parameters can be flexibly adjusted through experimentation, making it highly adaptable and suitable for the texturing needs of different types of silicon wafers.

[0035] Given the different core functions of primary and secondary texturing tanks (primary texturing aims to quickly form a basic textured surface, while secondary texturing aims to refine and optimize the textured surface and reduce reflectivity), the types of additives used in the two processes differ. In this scheme, additive A in the primary texturing tank mainly works with a high-alkaline concentration solution to assist in achieving rapid and uniform etching of the silicon wafer surface, providing support for the formation of the basic textured surface; additive B in the secondary texturing tank mainly works with a low-alkaline concentration solution to assist in finely refining the textured surface after primary texturing, reducing surface defects, and further optimizing the textured surface morphology.

[0036] Primary texturing additive A is typically alkaline and mainly consists of water, isopropanol (IPA), sodium hydroxide (NaOH), weak acid salts (such as sodium carbonate, sulfites, etc.), and surfactants (such as any or a combination of fatty alcohol polyoxyethylene ether AEO-7, fatty alcohol polyoxyethylene ether AEO-9, alkylphenol polyoxyethylene ether OP-10, etc.). The mass ratio is 0.1%~3% sodium hydroxide, 2%~10% isopropanol, 0.1-0.5% weak acid salt, 1%~2% surfactant, and the remainder is water. Composition characteristics: Primary texturing requires the formation of a pyramid-like structure on the silicon wafer surface. Primary texturing additive A usually contains a relatively high amount of strong alkaline components such as sodium hydroxide to ensure strong corrosion resistance, while also using appropriate amounts of organic solvents such as isopropanol to control the reaction rate and allow the initial texturing surface to form.

[0037] The main components of secondary texturing additive B generally include surfactants (such as any or a combination of fatty alcohol polyoxyethylene ether AEO-7, fatty alcohol polyoxyethylene ether AEO-9, alkylphenol polyoxyethylene ether OP-10, etc.), chelating agents (such as any or a combination of fatty alcohol polyoxyethylene ether AEO-7, fatty alcohol polyoxyethylene ether AEO-9, alkylphenol polyoxyethylene ether OP-10, etc.), defoaming agents (such as any or a combination of diethylene glycol monobutyl ether, methanol, modified silicone oil ether, cellulose ether, etc.), nucleating promoters (such as any or a combination of petroleum ether, nonionic fluorocarbon polymer, cetearyl alcohol polyether-25, etc.), film-forming agents (such as any or a combination of polyethylene glycol-400, polyethylene glycol-600, polyvinyl alcohol, polyethylene oxide, etc.), and water. By weight percentage, it contains 0.02%~1.0% surfactant, 0.1%~0.8% chelating agent, 0.02%~1.0% defoamer, 0.03%~2.0% nucleating accelerator, and 0.5%~2.0% film-forming agent, with the balance being water. Composition characteristics: Secondary texturing aims to refine the texture of the textured surface after primary texturing, forming a finer nanostructure. Therefore, the secondary texturing additive B contains relatively less strong alkaline components and increases the amount of nucleating accelerators, such as cocoa pigments and hesperidin, to further refine and optimize the textured surface. Simultaneously, chelating agents and cleaning agents remove any impurities that may remain from the primary texturing process, ensuring the quality of the textured surface.

[0038] Furthermore, given that the working principles and proportions of primary texturing additive A and secondary texturing additive B are different, mixing the two will severely interfere with the secondary texturing effect. Therefore, after the primary texturing is completed and before the secondary texturing begins, the battery cells need to undergo a targeted water washing treatment. The specific process parameters are as follows: Washing time: 90-120 seconds, to ensure that additives and other organic matter remaining from the first velvet process are fully dissolved and removed; Washing temperature: controlled at 25℃, matching the solubility characteristics of additives to ensure cleaning efficiency; Bubbling mode: Maintains continuous bubbling throughout the process, enhancing the removal of organic matter through the agitation of the cleaning solution and avoiding localized residue; Overflow mode and size: The overflow is continuous throughout the process, and the overflow size is controlled at 700-1000L / h to promptly discharge the cleaning fluid containing residual organic matter and prevent it from re-adhering to the surface of the battery cells.

[0039] By precisely controlling the above-mentioned washing process parameters, residual substances from the primary fleece lining process can be removed, effectively preventing them from mixing with secondary fleece lining additives, thus ensuring the stable progress of the secondary fleece lining process and subsequent optimization of fleece surface performance.

[0040] Furthermore, to improve the quality of the textured surface, this invention proposes optimizing the compatibility between the subsequent positive plating process (anti-reflective film deposition) and the textured surface. Even with an optimal textured surface design, mismatched positive plating process parameters (such as time) can lead to problems such as abnormal film color, increased reflectivity, and decreased battery efficiency. Therefore, the synergistic optimization of positive plating and textured surface preparation is crucial.

[0041] Specifically, to match the low reflectivity and high specific surface area textured surface after texturing, the process time of the positive plating step needs to be adjusted. Plasma-enhanced chemical vapor deposition (PECVD) is used for positive plating to deposit a silicon nitride antireflective film, using ammonia and silane as reactant gases, controlling the reaction pressure at 200-250 Pa and the RF power at 300-350 W. To address the issue of a reddish film color caused by the traditionally short positive plating process time, the positive plating process time is optimized and adjusted from the original 2400-2500 s to 2450-2550 s.

[0042] The above optimization can control the thickness of the silicon nitride film, avoid abnormal light interference color (reddish) caused by the film being too thin, and ensure that the film is tightly bonded to the textured pyramid surface after texturing, forming a dual low-reflection structure of "textured surface + anti-reflection film", further reducing the surface reflectivity of the battery, and the film has a uniform light blue appearance without quality defects such as reddish spots.

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail.

[0044] Example 1 The texturing-positive plating synergistic process method for low-reflectivity solar cells proposed in this embodiment can achieve optimal results under the following process parameters, which are as follows: Preparation of primary texturing tank solution (by weight percentage) NaOH: 2.28%; Primary flocking additive A: 0.35%; Balance: Pure water; Time: 270s; Temperature: 82℃; At this ratio, high-concentration NaOH can quickly form a basic texturing surface in a short time. Combined with primary texturing additives, it can effectively ensure the uniformity of etching and lay a good foundation for subsequent secondary texturing.

[0045] Parameters of the velvet washing tank Time: 100s; Temperature: 25℃; Bubble mode: Bubbles continuously; Overflow mode: Always overflowing; Overflow capacity: 800L / h; Preparation of secondary texturing tank solution (by weight percentage) NaOH: 0.15%; Secondary flocking additive B: 0.46%; Balance: Pure water; Time: 100s; Temperature: 65℃; Low concentrations of NaOH can achieve gentle modification of the pile surface after primary pile forming. Combined with secondary pile forming additives, it can further optimize the pile surface morphology, reduce surface defects, and ultimately achieve the goal of low reflectivity.

[0046] Positive plating process parameters Reaction pressure: 250 Pa; RF power: 320W; Time: 2460s A reasonable processing time can match the low-reflectivity textured surface and avoid abnormal light interference color (reddish tint) caused by an excessively thin film layer.

[0047] Comparative Example 1 This comparative example provides a conventional primary texturing process in the texturing process of solar cells: Texturing tank solution preparation NaOH: 1.9%; Down-making additive: 0.38%; Balance: Pure water; Time: 420s; Temperature: 82℃; This ratio allows the surface of solar cells to be etched, thereby forming a pyramid-shaped surface morphology.

[0048] Positive plating process parameters Reaction pressure: 250 Pa; RF power: 320W; Time: 2400s; Comparative Example 2 This comparative example provides a secondary texturing process for solar cells, as detailed below: Preparation of primary texturing tank solution (by weight percentage) NaOH: 2.28%; Primary flocking additive A: 0.35%; Balance: Pure water; Time: 350s; Temperature: 82℃; Parameters of the velvet washing tank Time: 100s; Temperature: 25℃; Bubble mode: Bubbles continuously; Overflow mode: Always overflowing; Overflow capacity: 800L / h; Preparation of secondary texturing tank solution (by weight percentage) NaOH: 0.15%; Secondary flocking additive B: 0.46%; Balance: Pure water; Time: 100s; Temperature: 60℃; Positive plating process parameters Reaction pressure: 250 Pa; RF power: 320W; Time: 2460s. Comparative Example 3 This comparative example provides a secondary texturing process for solar cells (one-step and two-step texturing use the same type of additive), as detailed below. Preparation of primary texturing tank solution (by weight percentage) NaOH: 2.28%; Primary flocking additive A: 0.35%; Balance: Pure water; Time: 270s; Temperature: 82℃; Parameters of the velvet washing tank Time: 100s; Temperature: 25℃; Bubble mode: Bubbles continuously; Overflow mode: Always overflowing; Overflow capacity: 800L / h; Preparation of secondary texturing tank solution (by weight percentage) NaOH: 0.15%; Secondary flocking additive A: 0.46%; Balance: Pure water; Time: 100s; Temperature: 65℃; Positive plating process parameters Reaction pressure: 250 Pa; RF power: 320W; Time: 2460s; Comparative Example 4 This comparative example provides a secondary texturing process for solar cells (the positive plating process time is not matched to the low-reflectivity texturized surface), as detailed below. Preparation of primary texturing tank solution (by weight percentage) NaOH: 2.28%; Primary flocking additive A: 0.35%; Balance: Pure water; Time: 270s; Temperature: 82℃; Parameters of the velvet washing tank Time: 100s; Temperature: 25℃; Bubble mode: Bubbles continuously; Overflow mode: Always overflowing; Overflow capacity: 800L / h; Preparation of secondary texturing tank solution (by weight percentage) NaOH: 0.15%; Secondary flocking additive B: 0.46%; Balance: Pure water; Time: 100s; Temperature: 65℃; Positive plating process parameters Reaction pressure: 250 Pa; RF power: 320W; Time: 2400s; The same monocrystalline silicon wafer from the same source and production line as in Example 1 was processed using the above-described process. The textured surface of the solar cells after the reactions in the examples and comparative examples is shown in Table 1.

[0049] Table 1 As shown in Table 1, the velvet structure and reflectivity of the embodiments in this application are significantly different from those of Comparative Example 1 and Comparative Example 2. The specific analysis is as follows: Comparison of the Example and Comparative Example 1: Compared to Comparative Example 1, which only uses a single texturing process, Example 1 significantly increases the specific surface area of ​​the texturized surface by adding an additional texturing step. Correspondingly, the reflectivity of Example 1 is significantly lower than that of Comparative Example 1. This indicates that adding an additional texturing step in the texturing process can effectively optimize the microstructure of the texturized surface, improve the ability to capture incident light, reduce light reflection loss, and lay a structural foundation for improving the photoelectric conversion efficiency of solar cells.

[0050] Comparison of Example 1 and Comparative Example 2: Comparative Example 2 employs a two-stage texturing process, but extends the time of the first texturing step. Data shows that the excessively long first texturing time leads to excessive corrosion, resulting in a larger textural surface and a significantly reduced textural density. Simultaneously, Comparative Example 2 achieves a reflectivity of 10.37%, significantly higher than Example 1. Further analysis of process parameters reveals that the temperature of the second texturing step in Comparative Example 2 is lower. This indicates that not all two-stage texturing processes can achieve performance optimization. The two-stage texturing scheme that merely extends the single texturing time (Comparative Example 2) will cause excessive corrosion, disrupting the textural density balance and leading to increased reflectivity. In contrast, the two-stage texturing process of Example 1 (a reasonable first texturing time + second texturing temperature) can precisely control the textural structure within the two-stage texturing framework (balancing specific surface area and density), effectively reducing reflectivity. This verifies the rationality and innovation of the two-stage texturing process parameter design in this application, demonstrating superior technical performance compared to the two-stage texturing scheme of Comparative Example 2.

[0051] Comparison of Example 1 and Comparative Example 3: Compared with the "A+B" flocking scheme of the present invention, Comparative Example 3, which does not introduce additive B and only achieves flocking through two applications of additive A, has the following key problems: (1) Lack of fine finishing effect on the flock surface: The core function of additive B is to "repair the surface micro-defects after the first flocking" and "regulate the flock growth rate", while additive A only focuses on basic corrosion to form flock and has no fine finishing ability; therefore, in Comparative Example 3, the flock surface defects (such as micro-pinholes and irregular protrusions) formed after the first flocking cannot be repaired; (2) Causes the flock surface to be too large and the morphology to be out of control: In the second flocking stage, additive A continues to corrode the existing flock surface. Due to the lack of the "growth inhibition" effect of additive B, the size of the flock pyramid continues to increase (the final measured height reaches 1.325 μm, far exceeding the optimal range of 1.034 μm in the example); at the same time, the excessively large flock structure is prone to "pyramid stacking and local collapse", which destroys the overall uniformity of the flock surface.

[0052] Comparison of Example 1 and Comparative Example 4: Comparative Example 4, due to the failure to adjust the positive plating process time, directly resulted in two quality problems: "reddish film color" (normal film color is blue) and "abnormal film thickness (66nm)," which is far below the normal film thickness range of Example 1 (73.8nm). Compared with Example 1 of this invention, the ultra-thin 66nm positive plating layer directly leads to a comprehensive degradation of the product's core performance: optical performance failure, extremely poor film stability, and a sharp drop in core performance, completely failing to meet product performance standards.

[0053] The same monocrystalline silicon wafers from the same source and production line as in Example 1 were processed using the above-described process. They then underwent the same wet processing, diffusion, coating, and screen printing processes. Table 2 shows a comparison of the electrical performance of the solar cells after the reactions in Examples 1 and 2, and the electrical performance and efficiency were tested according to the national standard GB / T 6495.1.

[0054] Table 2 As shown in Table 2, the efficiency gain of the example (low-reflectivity texturing method) compared to the comparative example (conventional one-step texturing method) is 0.107%, with a relatively small overall change in open voltage. The main improvements are a 0.12 higher FF filling rate and a 58 mA higher short-circuit current. The increased efficiency is due to the high specific surface area of ​​the texturized surface creating numerous tiny gaps and channels, which facilitates slurry penetration and adhesion. The lower reflectivity also enhances light utilization.

[0055] This invention improves the conversion efficiency of solar cells by adding a texturing step, performing texturing on silicon wafers in stages, and adjusting the positive plating process time to match the optimized texturing surface. This achieves effects such as reducing the surface reflectivity of silicon wafers, increasing light utilization, increasing the specific surface area of ​​the texturing surface, and increasing the contact area with the paste.

[0056] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells, characterized in that, The process includes, in sequence, primary texturing, water washing, secondary texturing, and positive plating; The NaOH content in the primary texturing bath solution is greater than the NaOH content in the secondary texturing bath solution; and the reaction temperature of the primary texturing is higher than the reaction temperature of the secondary texturing, and the reaction time of the primary texturing is longer than the reaction time of the secondary texturing.

2. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 1, characterized in that, The primary texturing bath solution comprises, by weight percentage: 2.0%-3.5% NaOH, 0.2%-0.6% primary texturing additive, and the remainder being water.

3. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 1, characterized in that, The secondary texturing bath solution comprises, by weight percentage: 0.1%-0.3% NaOH, 0.2%-0.7% secondary texturing additive, and the remainder being water.

4. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 1, characterized in that, The reaction temperature for the primary texturing process is 81-83℃, and the reaction time is 250-300s.

5. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 1, characterized in that, The reaction temperature for the secondary texturing process is 60-70℃, and the reaction time is 80-120s.

6. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 1, characterized in that, The positive plating process involves depositing a silicon nitride antireflective film using plasma-enhanced chemical vapor deposition equipment. Ammonia and silane are used as the reaction gases, and the reaction pressure is controlled at 200-250 Pa, the radio frequency power at 300-350 W, and the positive plating process time at 2450-2550 s.

7. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 1, characterized in that... The process parameters for the water washing are as follows: the water washing time is controlled at 90-120s; the water washing temperature is controlled at 25℃; the bubbling mode is controlled to maintain continuous bubbling throughout the process; and the overflow size is controlled to be 700-1000L / h with continuous overflow throughout the process.

8. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 2, characterized in that... The primary flocking additive comprises, by weight percentage: Sodium hydroxide 0.1%~3%, isopropanol 2%~10%, weak acid salt 0.1-0.5%, surfactant 1%~2%, the remainder is water.

9. The texturing-positive plating synergistic process for low-reflectivity TOPCon solar cells according to claim 3, characterized in that... The secondary flocking additive, by mass percentage, comprises: Surfactant 0.02%~1.0%, chelating agent 0.1%~0.8%, defoamer 0.02%~1.0%, nucleation promoter 0.03%~2.0%, film-forming agent 0.5%~2.0%, the remainder is water.

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