Novel low-reflectivity suede, texturing additive and use method of texturing additive

Abstract

The invention discloses a novel low-reflectivity suede, a texturing additive and a using method thereof, and relates to the technical field of efficient crystalline silicon solar cell manufacturing, the novel low-reflectivity suede comprises a pyramid structure, the surface of the pyramid is provided with a wrinkle-shaped microstructure, and the side edges and the bottom of the pyramid are provided with concave structures; the average reflectivity of the suede surface in the wavelength range of 350 to 1,050 nm is 6 percent to 8.5 percent; according to the novel low-reflectivity suede, the texturing additive and the use method thereof, a second-step texturing process is adopted, and the additive of a specific formula is used in the second step, so that the surface of a conventional pyramid structure formed in the first step is further subjected to micro-etching; the composite textured surface with the wrinkle-shaped microstructure on the surface and the sunken structures on the side edges and the bottom is formed, so that multiple times of refraction and scattering of light in the textured surface are realized, and the average reflectivity of the monocrystalline silicon wafer in the wavelength range of 350-1050nm is remarkably reduced to 6-8.5% which is far lower than 10-11% of that of a conventional process.

Description

Technical Field

[0001] This invention relates to the field of high-efficiency crystalline silicon solar cell manufacturing technology, specifically to a novel low-reflectivity textured surface, texturing additives, and their application methods. Background Technology

[0002] In recent years, the photovoltaic industry, as a core force in global energy transition and green, low-carbon development, has experienced rapid technological innovation and market expansion. Especially between 2022 and 2025, with the in-depth implementation of the "dual carbon" goals, the market has placed higher demands on the photoelectric conversion efficiency of solar cells. As a mainstream product, the performance optimization of crystalline silicon solar cells directly relates to the reduction of photovoltaic power generation costs and the expansion of their application scope. Currently, solar cells convert light energy into electrical energy through the photoelectric effect or photochemical effect, and the cell's ability to absorb sunlight is a key factor determining photoelectric conversion efficiency. The high reflectivity of raw silicon wafers (typically above 30%) leads to a significant loss of light energy. Even after conventional wet etching processes, the reflectivity of monocrystalline silicon wafers can only be reduced to around 10%–11%, which has become a major bottleneck restricting further improvements in photoelectric conversion efficiency.

[0003] While existing technologies have attempted to further reduce reflectivity through methods such as inverted pyramid textured surfaces, these methods often require complex processes or specific equipment, increasing production costs and the difficulty of implementation. Especially given the current trend in the photovoltaic industry towards high efficiency, low cost, and large-scale production, a key technical problem urgently needs to be solved: how to effectively reduce the average reflectivity of monocrystalline silicon wafers in the 350-1050nm wavelength range to 6%–8.5% using the widely adopted and mature conventional alkaline texturing process without significantly increasing process complexity and cost. Existing technologies, when using conventional alkaline texturing to prepare low-reflectivity textured surfaces, struggle to simultaneously meet the multiple requirements of process simplicity, cost control, and significant reflectivity reduction, limiting the potential for further improvement in the photoelectric conversion efficiency of solar cells. Therefore, improvements are needed. Summary of the Invention

[0004] The purpose of this invention is to provide a novel low-reflectivity textured surface, textured additive, and method of application thereof, in order to solve the problem that conventional alkaline textured processes in the prior art are unable to effectively reduce the average reflectivity of monocrystalline silicon wafers in the 350-1050nm wavelength range to 6% to 8.5% while maintaining process simplicity and cost control.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a novel low-reflectivity velvet surface, comprising a pyramid structure, wherein the surface of the pyramid has a wrinkled microstructure, and the sides and bottom of the pyramid have a recessed structure; the average reflectivity of the velvet surface in the wavelength range of 350-1050nm is 6% to 8.5%.

[0006] A novel low-reflectivity suede additive, wherein the additive is a secondary suede additive and comprises the following components in weight percentage:

[0007] Defoamer: 1% to 4%, structure modifier: 0.2% to 2%, accelerator: 0.2% to 5%, solvent: 0.4% to 3%, balance: deionized water;

[0008] The total content of all the above components is 100%;

[0009] The defoaming agent is one or more of gelatin, sodium carboxymethyl cellulose, pectin, gum arabic, and sucrose.

[0010] Furthermore, the structure modifier is one or more of sodium styrene sulfonate, polyacrylamide, sodium polyacrylate, and calcium polyacrylate.

[0011] Furthermore, the promoter is one or more of triethylamine, 8-hydroxyquinoline, and saccharin.

[0012] Furthermore, the solvent is one or both of hexanediol and glycerol.

[0013] A novel method for using low-reflectivity suede and suede additives includes the following steps:

[0014] S1. One-step alkaline texturing: The monocrystalline silicon wafer is placed in the first alkaline texturing solution and reacted at 70-90℃ for 200-500 seconds to form a pyramid structure on the surface of the silicon wafer; the first alkaline texturing solution is composed of a first-step texturing additive, alkali and deionized water, wherein the mass percentage of the first-step texturing additive is 0.1%-2% and the mass percentage of the alkali is 0.5%-3%, and the alkali is one or both of sodium hydroxide and potassium hydroxide;

[0015] S2. Water washing: Wash the texturized silicon wafer in step S1 with deionized water at 20-30℃ for 2-3 minutes.

[0016] S3, Two-step alkaline texturing: The silicon wafer cleaned in step S2 is placed in a second alkaline texturing solution and reacted at 50-80°C for 50-400 seconds; the second alkaline texturing solution is composed of the texturing additive described in claim 2, alkali, and deionized water, wherein the mass percentage of the texturing additive is 0.1%-2%, the mass percentage of the alkali is 0.1%-2%, and the alkali is one or both of sodium hydroxide and potassium hydroxide;

[0017] S4. Post-processing: Wash and dry the silicon wafer after texturing in step S3.

[0018] Furthermore, in step S1, the first-step fabrication additive is a conventional alkaline fabrication additive.

[0019] Furthermore, in step S4, the drying temperature is 70-100℃ and the drying time is 500-600 seconds.

[0020] Furthermore, in step S3, the temperature of the second alkaline texturing solution is 60-69°C.

[0021] Furthermore, in step S3, the reaction time for the two-step alkaline texturing is 100-130 seconds.

[0022] Compared with existing technologies, the present invention provides a novel low-reflectivity textured surface, textured additive, and method of application. By employing a two-step textured process and using a specific formulation additive in the second step, the conventional pyramid structure surface formed in the first step is further micro-etched, forming a composite textured surface with a wrinkled microstructure on the surface and concave structures on the sides and bottom. This achieves multiple refractions and scattering of light within the textured surface, significantly reducing the average reflectivity of single-crystal silicon wafers in the 350-1050nm wavelength range to 6%-8.5%, far lower than the 10%-11% of conventional processes.

[0023] By setting up a synergistic system containing defoaming agents, structure modifiers, accelerators, and solvents in the second-step texturing additive, the defoaming agents can quickly remove reaction gases to make the reaction uniform, the structure modifiers can selectively adsorb and inhibit the corrosion of the pyramid tip, the accelerators can accelerate the etching of the bottom of the pyramid to form a depression, and the solvents can enhance the permeability of the texturing solution. Thus, the direction and rate of micro-etching can be precisely controlled together, ensuring the efficient and stable preparation of the new low-reflectivity texturing structure.

[0024] By setting the process parameters of the two-step texturing process (such as reaction temperature 50-80℃, reaction time 50-400s) and the content of each component in the additives to a specific range and connecting them with the first-step texturing process, this new texturing method is fully compatible with the conventional alkaline texturing equipment on the existing production line. This achieves the effect of putting it into application without major modifications to the existing production line, greatly reducing the cost and threshold of process upgrades. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0026] Figure 1 This is a top-view SEM image of the pyramid-shaped surface of a texturized silicon wafer provided in an embodiment of the present invention.

[0027] Figure 2 This is a SEM side-top view of the pyramid on the surface of a texturized silicon wafer provided in an embodiment of the present invention;

[0028] Figure 3 This is a SEM cross-sectional view of the pyramid on the surface of a texturized silicon wafer provided in an embodiment of the present invention;

[0029] Figure 4 The images show the D8 reflectance of silicon wafers after texturing in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] As attached Figure 1 To be continued Figure 4 As shown:

[0032] Example 1:

[0033] This invention provides a novel low-reflectivity textured surface, a textured additive, and a method for using the same. The textured surface is characterized by a pyramidal textured structure forming on the surface of the prepared single-crystal silicon wafer. Scanning electron microscopy (SEM) reveals a clear, wrinkled microstructure on the surface of this pyramidal structure, with distinct depressions visible on the sides and bottom. This microstructure significantly reduces reflectivity by inducing multiple refractions and scatterings of light.

[0034] Preparation of the flocking additive (secondary flocking additive):

[0035] This step involves preparing the key additive for the second step of flocking, and its composition by mass percentage is as follows:

[0036] Defoaming agent: Sodium carboxymethyl cellulose, 2%;

[0037] Structure modifier: Sodium styrene sulfonate, 0.2%;

[0038] Accelerator: Triethylamine, 0.4%;

[0039] Solvent: Hexanediol, 0.4%;

[0040] Deionized water: balance; the total content of all the above components is 100%.

[0041] Place all the above components in a mixing container at room temperature and pressure, and stir at a mechanical stirring speed of 200 revolutions per minute for 30 minutes until they are completely mixed and homogeneous, forming a clear and transparent secondary texturing additive B solution for later use.

[0042] Preparation method steps

[0043] The preparation of low-reflectivity velvet surface is carried out in the following steps:

[0044] S1. Preparation and reaction of one-step alkaline texturing solution:

[0045] Preparation of the first alkaline texturing solution: In the texturing tank, add deionized water, 2% sodium hydroxide (NaOH) by mass, and 0.1% commercially available texturing additive A by mass in sequence. Mix at 70°C and a stirring speed of 150 rpm for 15 minutes to ensure the solution is homogeneous.

[0046] One-step fleece processing: This process involves processing materials in specifications M2, P type, ... <100> A single-crystal silicon wafer with the desired crystal orientation is immersed in the texturing solution described above. The temperature of the texturing bath is raised to and maintained at 80°C, and the reaction time is 300 seconds. Hydrogen gas is generated during the reaction. After the reaction, a uniform, conventional pyramidal morphology is formed on the surface of the silicon wafer.

[0047] S2, Intermediate Wash:

[0048] After texturing, the silicon wafer is removed from the texturing solution and immediately transferred to a flowing deionized water bath at 20°C for immersion and cleaning for 2 minutes to thoroughly remove residual alkali and reaction products from the silicon wafer surface.

[0049] S3. Two-step preparation and reaction of alkaline texturing solution:

[0050] Preparation of the second alkaline texturing solution: In another texturing tank, add deionized water, 0.1% sodium hydroxide (NaOH) by mass, and 0.1% secondary texturing additive B solution prepared in step 2 of this embodiment by mass. Mix at 30°C and a stirring speed of 100 rpm for 10 minutes to ensure the solution is homogeneous.

[0051] Two-step texturing: The silicon wafer cleaned in step S2 is immersed in the second alkaline texturing solution. The temperature of the texturing bath is raised to and maintained at 60°C, and the reaction time is 100 seconds. This step is a micro-etching process, which selectively etches the pyramid surface formed in the one-step texturing, forming a wrinkled microstructure and a recessed structure on the sides and bottom.

[0052] S4. Post-processing:

[0053] Water washing: Take out the silicon wafer after the two-step texturing and immediately put it into a flowing deionized water bath at a temperature of 20°C for immersion and cleaning for 2 minutes.

[0054] Drying: Place the cleaned silicon wafers in a clean oven and dry them at a constant temperature of 100°C for 500 seconds. After removal, you will obtain finished silicon wafers with a novel low-reflectivity textured surface.

[0055] Performance Tests and Results:

[0056] Reflectivity test: The average reflectivity of the dried silicon wafer was measured within the wavelength range of 350-1050nm. The test result was 6.33%.

[0057] Morphological characteristics: The specific surface area of ​​the pyramid is 1.31.

[0058] Example 2:

[0059] This embodiment is basically the same as the previous embodiment, except that the textured structure is characterized by a pyramidal textured structure on the surface of the prepared single-crystal silicon wafer. Scanning electron microscopy (SEM) reveals that the surface of this pyramidal structure also exhibits a wrinkled microstructure, and there are depressions on the sides and bottom of the pyramid. Its morphology is similar to that of Embodiment 1, and both belong to the low-reflectivity textured structure protected by this invention.

[0060] Preparation of the flocking additive (secondary flocking additive):

[0061] This step involves preparing the additive for the second step of flocking. Its composition is a key variation of Example 2, and its composition by mass percentage is as follows:

[0062] Defoaming agent: Gelatin, 1%;

[0063] Structure modifier: Sodium styrene sulfonate, 0.5%;

[0064] Accelerator: Triethylamine, 0.4%;

[0065] Solvent: Glycerol, 0.4%;

[0066] Deionized water: balance; the total content of all the above components is 100%.

[0067] Place all the above components in a mixing container at room temperature and pressure. Since gelatin is solid, first pre-swell it with a portion of deionized water preheated to 40°C for 10 minutes, then add the remaining components and stir at a mechanical stirring speed of 250 rpm for 40 minutes until a homogeneous solution without visible particles is formed, which is the secondary texturing additive B solution, for later use.

[0068] Preparation method steps:

[0069] The preparation of low-reflectivity velvet surface is carried out in the following steps:

[0070] S1. Preparation and reaction of one-step alkaline texturing solution:

[0071] Preparation of the first alkaline texturing solution: In the texturing tank, add deionized water, 2% sodium hydroxide (NaOH) by mass, and 0.5% commercially available texturing additive A by mass in sequence. Mix at 75°C and a stirring speed of 150 rpm for 15 minutes to ensure the solution is homogeneous.

[0072] One-step fleece processing: This process involves processing materials in specifications M2, P type, ... <100> A single-crystal silicon wafer with the desired crystal orientation is immersed in the texturing solution described above. The temperature of the texturing bath is raised to and maintained at 81°C, and the reaction time is 330 seconds. After the reaction is complete, a uniform, conventional pyramidal morphology is formed on the surface of the silicon wafer.

[0073] S2, Intermediate Water Wash: Remove the silicon wafer after texturing in one step from the texturing solution and immediately transfer it to a flowing deionized water bath at a temperature of 20°C for immersion and washing for 3 minutes.

[0074] S3. Two-step preparation and reaction of alkaline texturing solution:

[0075] Preparation of the second alkaline texturing solution: In another texturing tank, add deionized water, 0.9% sodium hydroxide (NaOH) by mass, and 0.5% secondary texturing additive B solution prepared in step 2 of this embodiment by mass. Mix at 35°C and a stirring speed of 120 rpm for 12 minutes to ensure the solution is homogeneous.

[0076] Two-step texturing: The silicon wafer, cleaned in step S2, is immersed in the second alkaline texturing solution. The temperature of the texturing bath is raised to and maintained at 65°C, and the reaction time is 100 seconds. This step micro-etches the pyramid formed in the first-step texturing to create the target textured surface structure.

[0077] S4. Post-processing:

[0078] Water washing: Take out the silicon wafer after the two-step texturing and immediately put it into a flowing deionized water bath at a temperature of 20°C for immersion and cleaning for 2 minutes.

[0079] Drying: Place the cleaned silicon wafers in a clean oven and dry them at a constant temperature of 100°C for 600 seconds. After removal, you will obtain finished silicon wafers with a novel low-reflectivity textured surface.

[0080] Performance Tests and Results:

[0081] Reflectivity test: The average reflectivity of the dried silicon wafer was measured within the wavelength range of 350-1050nm. The test result was 6.34%.

[0082] Morphological characterization: The specific surface area of ​​the pyramid is 1.35.

[0083] Example 3:

[0084] This embodiment is basically the same as the previous embodiment, except that the textured structure is characterized by a pyramidal textured structure on the surface of the prepared single-crystal silicon wafer. Scanning electron microscopy (SEM) reveals a distinct wrinkled microstructure on the surface of this pyramidal structure, with clear depressions on the sides and bottom. Its morphological characteristics are similar to those of Embodiments 1 and 2, and all belong to the low-reflectivity textured structure protected by this invention.

[0085] Preparation of the flocking additive (secondary flocking additive):

[0086] This step involves preparing the additive for the second step of flocking. Its composition is a key variation of Example 3, and its composition by mass percentage is as follows:

[0087] Defoaming agent: Gum arabic, 3%;

[0088] Structure modifier: Sodium polyacrylate, 0.8%;

[0089] Accelerator: 8-hydroxyquinoline, 0.4%;

[0090] Solvent: Glycerol, 0.6%;

[0091] Deionized water: balance; the total content of all the above components is 100%.

[0092] Place all the above components in a mixing container at room temperature and pressure. Since gum arabic is a solid powder, premix it with some deionized water and stir for 15 minutes to ensure it is fully dispersed. Then add the remaining components and stir at a mechanical stirring speed of 280 rpm for 35 minutes until a homogeneous and stable viscous liquid is formed, which is the secondary texturing additive B solution, for later use.

[0093] Preparation method steps:

[0094] The preparation of low-reflectivity velvet surface is carried out in the following steps:

[0095] S1. Preparation and reaction of one-step alkaline texturing solution:

[0096] Preparation of the first alkaline texturing solution: In the texturing tank, add deionized water, 3% sodium hydroxide (NaOH) by mass, and 0.5% commercially available texturing additive A by mass in sequence. Mix at 78°C and a stirring speed of 160 rpm for 18 minutes to ensure the solution is homogeneous.

[0097] One-step fleece processing: This process involves processing materials in specifications M2, P type, ... <100> A single-crystal silicon wafer with the desired crystal orientation is immersed in the texturing solution described above. The temperature of the texturing bath is raised to and maintained at 83°C, and the reaction time is 350 seconds. After the reaction, a uniform and dense conventional pyramidal morphology is formed on the surface of the silicon wafer.

[0098] S2, Intermediate Water Wash: Remove the silicon wafer after texturing in one step from the texturing solution and immediately transfer it to a flowing deionized water bath at a temperature of 20°C for immersion and washing for 3 minutes.

[0099] S3. Two-step preparation and reaction of alkaline texturing solution:

[0100] Preparation of the second alkaline texturing solution: In another texturing tank, add deionized water, 2% sodium hydroxide (NaOH) by mass, and 0.4% secondary texturing additive B solution prepared in step 2 of this embodiment by mass. Mix at 40°C and a stirring speed of 130 rpm for 15 minutes to ensure the solution is homogeneous.

[0101] Two-step texturing: The silicon wafer, cleaned in step S2, is immersed in the second alkaline texturing solution. The temperature of the texturing bath is raised to and maintained at 69°C, and the reaction time is 130 seconds. This step selectively micro-etches the pyramid formed in the first-step texturing, effectively creating surface wrinkles and side-bottom recessed structures.

[0102] S4. Post-processing:

[0103] Water washing: Take out the silicon wafer after the two-step texturing and immediately put it into a flowing deionized water bath at a temperature of 20°C for immersion and cleaning for 2 minutes.

[0104] Drying: Place the cleaned silicon wafers in a clean oven and dry them at a constant temperature of 100°C for 600 seconds. After removal, you will obtain finished silicon wafers with a novel low-reflectivity textured surface.

[0105] Performance Tests and Results:

[0106] Reflectivity test: The average reflectivity of the dried silicon wafer was measured within the wavelength range of 350-1050nm. The test result was 6.50%.

[0107] Morphological characteristics: The specific surface area of ​​the pyramid is 1.33.

[0108] Example 4:

[0109] This embodiment is essentially the same as the previous embodiment, except for the textured surface: a pyramidal textured structure is formed on the surface of the prepared single-crystal silicon wafer. Scanning electron microscopy (SEM) revealed that, compared to Embodiment 1, due to the extended two-step texturing time, the wrinkled microstructure on the pyramidal surface is more pronounced, and the recessed structures on the sides and bottom of the pyramid are also deeper. This structural change demonstrates the controllability of process parameters on the final textured surface morphology.

[0110] Preparation of the flocking additive (secondary flocking additive):

[0111] The secondary flocking additive formula used in this embodiment is exactly the same as that in Example 1, in order to eliminate the interference of formula variables on the experimental results:

[0112] Defoaming agent: Sodium carboxymethyl cellulose, 2%;

[0113] Structure modifier: Sodium styrene sulfonate, 0.2%;

[0114] Accelerator: Triethylamine, 0.4%;

[0115] Solvent: Hexanediol, 0.4%;

[0116] Deionized water: balance; the total content of all the above components is 100%.

[0117] The preparation method is exactly the same as in Example 1: Place the above components in a mixing container at room temperature and pressure, and stir at a mechanical stirring speed of 200 revolutions per minute for 30 minutes until they are completely mixed and a clear and transparent solution is formed for later use.

[0118] Preparation method steps:

[0119] The preparation of the low-reflectivity velvet surface is carried out in the following steps, wherein the two-step velvet preparation time is a key variation of this embodiment:

[0120] S1. Preparation and reaction of alkaline texturing solution in one step: This step is exactly the same as in Example 1: using 0.1% by mass of additive and 2% by mass of sodium hydroxide, reacting at 80°C for 300 seconds to form a uniform initial pyramid structure.

[0121] S2, Intermediate water wash: This step is exactly the same as in Example 1: wash in flowing deionized water at 20°C for 2 minutes.

[0122] S3. Two-step preparation and reaction of alkaline texturing solution:

[0123] Preparation of the second alkaline texturing solution: The formula is the same as in Example 1, that is, it contains 0.1% sodium hydroxide and 0.1% secondary texturing additive by mass.

[0124] Two-step texturing: The cleaned silicon wafer is immersed in the two-step texturing solution. The temperature of the texturing solution is maintained at 60°C, the same as in Example 1, but the reaction time is extended to 200 seconds (twice the reaction time of Example 1, within the range of 50-400 seconds as claimed in the claims).

[0125] S4. Post-processing:

[0126] Water washing: Take out the silicon wafer after the two-step texturing and immerse it in a flowing deionized water bath at 20°C for 2 minutes.

[0127] Drying: Dry the cleaned silicon wafers at 100°C for 500 seconds.

[0128] Performance Tests and Results:

[0129] Reflectivity test: The average reflectivity in the wavelength range of 350-1050nm is 6.8%.

[0130] Morphological characteristics: The specific surface area of ​​the pyramid is 1.38.

[0131] Example 5:

[0132] This embodiment is essentially the same as the previous embodiment, except for the textured surface: the prepared single-crystal silicon wafer has a pyramidal textured surface. Scanning electron microscopy (SEM) reveals obvious wrinkled microstructures on the pyramidal surface, with visible depressions on the sides and bottom of the pyramid. Compared to Embodiment 1, the development of the microstructure is relatively mild due to the reduced amount of additives.

[0133] Preparation of the flocking additive (secondary flocking additive):

[0134] The secondary texturing additive used in this embodiment has the same formulation as in Example 1, but the stock solution is prepared at a concentration 10 times that of the target working solution to ensure accurate dosing at low dosages.

[0135] Defoaming agent: Sodium carboxymethyl cellulose, 2%;

[0136] Structure modifier: Sodium styrene sulfonate, 0.2%;

[0137] Accelerator: Triethylamine, 0.4%;

[0138] Solvent: Hexanediol, 0.4%;

[0139] Deionized water: balance; the total content of all the above components is 100%.

[0140] The preparation method is the same as in Example 1, and a 10% mass fraction of additive mother liquor is obtained.

[0141] Preparation method steps:

[0142] The preparation of the low-reflectivity velvet surface is carried out in the following steps, wherein the final concentration of the secondary velvet additive is a key variation of this embodiment:

[0143] S1. Preparation and reaction of one-step alkaline texturing solution:

[0144] This step is exactly the same as in Example 1: using 0.1% by mass of additive and 2% by mass of sodium hydroxide, reacting at 80°C for 300 seconds.

[0145] S2, Intermediate water wash: This step is exactly the same as in Example 1: wash in flowing deionized water at 20°C for 2 minutes.

[0146] S3. Two-step preparation and reaction of alkaline texturing solution:

[0147] Preparation of the second alkaline texturing solution: In the texturing tank, deionized water, sodium hydroxide (NaOH) at a mass ratio of 0.1%, and the 10% additive stock solution prepared in the previous step at a mass ratio of 0.1% are added sequentially. This step ensures that the actual mass ratio of the secondary texturing additive in the final working solution is 0.01% (i.e., 0.1% × 10%), which is one-tenth of the lower limit of 0.1% in the claims, constituting a rigorous boundary condition test.

[0148] Two-step texturing: The cleaned silicon wafer is immersed in the second alkaline texturing solution described above. The temperature of the texturing tank is maintained at 60°C, and the reaction time is 150 seconds (50% longer than in Example 1 to compensate for the possible decrease in reaction rate due to low additive concentration).

[0149] S4. Post-processing:

[0150] Washing and drying: The steps and parameters are exactly the same as in Example 1, that is, washing in deionized water at 20°C for 2 minutes, and then drying at 100°C for 500 seconds.

[0151] Performance Tests and Results:

[0152] Reflectivity test: The average reflectivity in the wavelength range of 350-1050nm is 7.5%.

[0153] Morphological characteristics: The specific surface area of ​​the pyramid is 1.29.

[0154] Comparative example:

[0155] Comparison without secondary flocking additive: A comparative experiment clearly demonstrates that the secondary flocking additive is an indispensable key component in this invention. Without this additive, even using the same two-step flocking process, it is impossible to form a low-reflectivity flocked surface with wrinkles and depressions.

[0156] The comparative example maintained the same process flow, basic reagent (alkali) concentration, and main process parameters as Example 1, except that no secondary texturing additives were added to the texturing solution in the second step, in order to isolate and highlight the technical contribution of the secondary texturing additives.

[0157] Preparation method steps:

[0158] The preparation of the velvet surface is carried out in the following steps, the only difference from Example 1 is indicated in bold:

[0159] S1. Preparation and reaction of one-step alkaline texturing solution:

[0160] This step is exactly the same as in Example 1: In the texturing tank, deionized water, 2% sodium hydroxide (NaOH) by mass, and 0.1% commercially available texturing additive A by mass are added sequentially. The mixture is stirred at 150 rpm for 15 minutes at 80°C to ensure a homogeneous solution.

[0161] One-step fleece processing: This process involves processing materials in specifications M2, P type, ... <100> A single-crystal silicon wafer with the desired crystal orientation is immersed in the texturing solution described above. The temperature of the texturing bath is maintained at 80°C, and the reaction time is 300 seconds. After the reaction, a uniform, conventional pyramidal morphology is formed on the surface of the silicon wafer.

[0162] S2, Intermediate water wash: This step is exactly the same as in Example 1: Take out the silicon wafer after texturing in one step and immediately transfer it to a flowing deionized water bath at a temperature of 20°C for immersion and cleaning for 2 minutes.

[0163] S3. Two-step preparation and reaction of alkaline texturing solution (key difference steps):

[0164] Preparation of the second alkaline texturing solution: In another texturing tank, only deionized water and 0.1% sodium hydroxide (NaOH) by mass are added, without any secondary texturing additives. The mixture is stirred at 100 rpm for 10 minutes at 30°C to obtain the second-step treatment solution containing only dilute alkali.

[0165] Two-step processing: Immerse the silicon wafers cleaned in step S2 into the above-mentioned alkaline solution without additives. Maintain the temperature of the processing tank at 60°C and the reaction time is 100 seconds.

[0166] S4. Post-processing:

[0167] Water washing: Take out the silicon wafer after the second step of processing and immediately put it into a flowing deionized water bath at a temperature of 20°C for immersion and cleaning for 2 minutes.

[0168] Drying: Place the cleaned silicon wafers in a clean oven and dry them at a constant temperature of 100°C for 500 seconds. After removal, a comparative sample is obtained.

[0169] Performance Tests and Results:

[0170] Reflectivity test: The average reflectivity of the dried silicon wafer was measured within the wavelength range of 350-1050nm. The test result was 10.15%.

[0171] Morphological characterization: The specific surface area of ​​the pyramid was 1.25. SEM observation showed that its textured surface was typical of a pyramid, with a smooth surface and no wrinkled microstructures. No obvious depressions were observed on the sides or bottom of the pyramid.

[0172] Comparison table of reflectivity and pyramid size of texturized silicon wafers in Examples 1, 2, 3 and the comparative example:

[0173] Group reflectivity Pyramid surface area Example 1 6.33 1.31 Example 2 6.34 1.35 Example 3 6.50 1.33 Comparative Example 10.15 1.25

[0174] Comparative analysis and conclusions:

[0175] This comparative example is directly compared with Example 1:

[0176] The only process variable is that both are completely identical in the first step of flocking, washing, the second step of alkali concentration, temperature, time, and post-treatment steps. The only difference is that the flocking solution in Example 1 contains the secondary flocking additive of this invention, while the comparative example does not.

[0177] Significant differences in results:

[0178] Reflectivity: The reflectivity of the comparative example (10.15%) was much higher than that of Example 1 (6.33%), with a difference of 3.82%.

[0179] Morphology: The comparative example only presents a typical pyramid structure, while Example 1 forms a composite structure with characteristic folds and depressions.

[0180] Specific surface area: The specific surface area of ​​the comparative example (1.25) is smaller than that of Example 1 (1.31), indicating that its surface microstructure is less complex.

[0181] Conclusion: This comparison irrefutably proves that the low reflectivity achieved by this invention does not originate from the simple "two-step alkali treatment" process itself, but is synergistically produced by the combined action of the "two-step alkali treatment" and "specific secondary flocking additives." These additives are essential for generating the characteristic flocked surface structure, thereby achieving ultra-low reflectivity.

[0182] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A novel low-reflectivity velvet surface, characterized in that, It includes a pyramid structure, the surface of which has a pleated microstructure, and the sides and bottom of which have a recessed structure; the velvet surface has an average reflectance of 6% to 8.5% in the wavelength range of 350-1050nm.

2. A novel low-reflectivity suede additive, applicable to the novel low-reflectivity suede described in claim 1, characterized in that, The additive is a secondary flocking additive, composed of the following components in weight percentage: Defoamer: 1% to 4%, structure modifier: 0.2% to 2%, accelerator: 0.2% to 5%, solvent: 0.4% to 3%, balance: deionized water; The total content of all the above components is 100%; The defoaming agent is one or more of gelatin, sodium carboxymethyl cellulose, pectin, gum arabic, and sucrose.

3. The novel low-reflectivity suede additive according to claim 2, characterized in that, The structure modifier is one or more of sodium styrene sulfonate, polyacrylamide, sodium polyacrylate, and calcium polyacrylate.

4. The novel low-reflectivity suede additive according to claim 2, characterized in that, The promoter is one or more of triethylamine, 8-hydroxyquinoline, and saccharin.

5. The novel low-reflectivity suede additive according to claim 2, characterized in that, The solvent is one or both of hexanediol and glycerol.

6. A method for using a novel low-reflectivity suede and a suede-making additive, applicable to the preparation of the novel low-reflectivity suede as described in claim 1, and using the suede-making additive as described in claim 2, characterized in that... Includes the following steps: S1. One-step alkaline texturing: The monocrystalline silicon wafer is placed in the first alkaline texturing solution and reacted at 70-90℃ for 200-500 seconds to form a pyramid structure on the surface of the silicon wafer; the first alkaline texturing solution is composed of a first-step texturing additive, alkali and deionized water, wherein the mass percentage of the first-step texturing additive is 0.1%-2% and the mass percentage of the alkali is 0.5%-3%, and the alkali is one or both of sodium hydroxide and potassium hydroxide; S2. Water washing: Wash the texturized silicon wafer in step S1 with deionized water at 20-30℃ for 2-3 minutes. S3, Two-step alkaline texturing: The silicon wafer cleaned in step S2 is placed in a second alkaline texturing solution and reacted at 50-80°C for 50-400 seconds; the second alkaline texturing solution is composed of the texturing additive described in claim 2, alkali, and deionized water, wherein the mass percentage of the texturing additive is 0.1%-2%, the mass percentage of the alkali is 0.1%-2%, and the alkali is one or both of sodium hydroxide and potassium hydroxide; S4. Post-processing: Wash and dry the silicon wafer after texturing in step S3.

7. The method of using a novel low-reflectivity suede surface and suede additive according to claim 6, characterized in that, In step S1, the first step of the texturing additive is a conventional alkaline texturing additive.

8. The method of using a novel low-reflectivity suede surface and suede additive according to claim 6, characterized in that, In step S4, the drying temperature is 70-100℃ and the drying time is 500-600 seconds.

9. The method of using a novel low-reflectivity suede surface and suede additive according to claim 6, characterized in that, In step S3, the temperature of the second alkaline texturing solution is 60-69°C.

10. The method of using a novel low-reflectivity suede and suede additive according to claim 6, characterized in that, In step S3, the reaction time for the two-step alkaline texturing is 100-130 seconds.

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