A single crystal silicon wafer texturing additive and a single crystal silicon wafer texturing method

Abstract

The application provides a single crystal silicon wafer texturing additive with better morphology and a single crystal silicon wafer texturing method, characterized in that the composition and content of the single crystal silicon wafer texturing additive are as follows: 0.001-0.1wt% of nucleating agent, 0.01-1wt% of main dispersing agent, 0.01-2wt% of auxiliary dispersing agent, 5-50wt% of defoaming agent, and the rest is deionized water; the additive can be added in the process of single crystal silicon wafer texturing, so that the morphology characteristics of the pyramid can be deeply studied, the requirement and direction of better morphology are firstly proposed, and the morphology is obtained; the morphology includes: the size of the pyramid can be adjusted, the size is similar and uniform, the height-width ratio is larger, and the specific surface area is larger.

Description

Technical Field

[0001] This invention relates to the photovoltaic field, specifically to a texturing additive for monocrystalline silicon wafers with superior morphology and a method for texturing monocrystalline silicon wafers. Background Technology

[0002] The urgent need for energy transition has spurred the rapid development of the new energy industry, and photovoltaics has ushered in an even greater boom. Opportunities and challenges often coexist, and higher photoelectric conversion efficiency has become the industry's primary focus. Further improvements in battery efficiency require more advanced technologies; these technologies are reflected in every stage of photovoltaic cell manufacturing, demanding that each technological aspect be optimized to the highest level.

[0003] Whether it's PERC cells, TOPcon, HJT, or IBC cells, texturing is an indispensable step, and the resulting pyramid shape is directly related to the efficiency of various photovoltaic cells. Further development of battery technology will inevitably lead to higher requirements for the pyramid shape.

[0004] The morphological characteristics of the pyramid primarily include: size, uniformity, aspect ratio, specific surface area, and microstructure. The role of microstructure is to further reduce the reflectivity of the silicon wafer surface after texturing; however, excessive microstructure can become recombination centers, leading to reduced efficiency. Therefore, microstructure is necessary, but must be moderate. The size of the pyramid needs to be matched with the battery structure. Once the size is determined, achieving better uniformity, a larger aspect ratio, and a larger specific surface area while maintaining similar sizes can improve light-trapping ability, increase current, and thus improve efficiency. The aspect ratio and specific surface area of ​​the pyramid should be compared within similar size ranges. Comparing aspect ratio and specific surface area outside the pyramid's size range is meaningless.

[0005] Currently, existing technologies mainly employ two approaches to obtain better morphology: (1) Optimization process: Chinese patent application No. 202210291697.7 states that adding a polishing process before texturing can improve the uniformity of the morphology after texturing. However, in order to save costs, the silicon wafer industry has developed towards thinner wafers, making this method even more difficult to apply in the future.

[0006] (2) Optimization of fabrication additives: Chinese patent application No. 201910819928.5 states that the method can obtain a more uniform pyramid shape, but the patent only obtained a set of larger pyramids and did not mention the uniformity when preparing small pyramids; moreover, the uniformity shown in the attached drawings of the specification of the application is not very good, and there is room for further optimization.

[0007] The aforementioned prior art solutions for obtaining better morphology still suffer from high costs, can only produce a set of larger pyramids, do not address the uniformity issues when preparing small pyramids, and exhibit poor uniformity as shown in the accompanying drawings of this application, which need to be addressed. Summary of the Invention

[0008] The purpose of this invention is to meet the higher requirements of the photovoltaic industry for the pyramid morphology after texturing. It proposes a texturing additive and method for monocrystalline silicon wafers with superior morphology. This additive, while ensuring alcohol-free, environmentally friendly, and rapid texturing, prioritizes and sets higher requirements for the pyramid morphology, achieving the following characteristics: adjustable pyramid size, similar and uniform size, larger aspect ratio, and larger specific surface area. This addresses the problems of existing technologies that, while achieving superior morphology, are costly, only produce a set of larger pyramids, fail to address the uniformity issues when preparing smaller pyramids, and exhibit poor uniformity.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A texturing additive for monocrystalline silicon wafers with superior morphology, wherein the additive components and their mass percentage content are as follows: nucleating agent 0.001~0.1wt%, main dispersant 0.01~1wt%, auxiliary dispersant 0.01~2wt%, defoamer 5~50wt%, and the balance being deionized water.

[0010] Preferably, the nucleating agent is a linear phenolic resin.

[0011] More preferably, the linear phenolic resin is selected from one or more of methyl phenolic resin, tert-butyl phenolic resin, and octyl phenolic resin; the molecular weight Mw of the linear phenolic resin is 2000~5000. More preferably, the linear phenolic resin needs to be prepared as a 0.1% wt aqueous solution, with 1~3 wt% sodium hydroxide added to enhance dissolution.

[0012] Preferably, the main dispersant is selected from one or more of sodium polystyrene sulfonate, sodium poly(4-styrene sulfonate-copolymer-acrylic acid), and sodium poly(4-styrene sulfonate-copolymer-maleic acid); the polymer has a molecular weight of 2000~8000.

[0013] Preferably, the auxiliary dispersant is a carbon chain surfactant selected from one or more of sodium secondary alkyl sulfonate, C8-12 alkyl glycoside, and C6-8 fluorocarbon surfactant.

[0014] Preferably, the defoaming agent is a microcrystalline cellulose whisker solution.

[0015] A further preferred embodiment is the treatment process for the microcrystalline cellulose whisker solution as follows: (1) Prepare the following solution according to the mass fraction: 5 wt% microcrystalline cellulose, 2 wt% sodium hydroxide, and 93 wt% water to obtain solution 1; (2) Solution 1 was emulsified and dispersed for 30 min using a high-speed dispersing emulsifier to obtain solution 2; (3) The solution 2 was circulated and ground using a bedroom sand mill. First, it was coarsely ground for 1 hour with 1.2-1.4 mm zirconium beads; then it was finely ground for 2 hours with 0.6-0.8 mm zirconium beads; to obtain a microcrystalline cellulose whisker solution. After treatment, the microcrystalline cellulose whisker solution can be well dissolved in water, with a length of 100-800 nm.

[0016] The present invention also provides a texturing solution for single crystal texturing, comprising the above-mentioned texturing additive and alkaline solution, wherein the mass ratio of the texturing additive to the alkaline solution is 0.2 to 2:100.

[0017] Preferably, the alkaline solution is a 0.4-1.2 wt% aqueous solution of sodium hydroxide or potassium hydroxide.

[0018] This invention also provides a texturing method for single-crystal silicon wafers with superior morphology, specifically including the following steps: S1. According to the following proportions: nucleating agent 0.001~0.1wt%, main dispersant 0.01~1wt%, auxiliary dispersant 0.01~2wt%, defoaming agent 5~50wt%, and the balance being deionized water, mix them evenly to prepare a flocking additive. S2. Add the texturing additive prepared in step S1 to the alkaline solution in a certain proportion and mix them evenly to prepare a texturing solution; wherein the mass ratio of the texturing additive to the alkaline solution is 0.2~2:100. S3. Immerse the clean monocrystalline silicon wafer in the texturing solution prepared in step S2 to perform surface texturing. The texturing temperature is 80~85℃ and the time is 7~9min.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: In the texturing additive of this invention, the nucleating agent is a linear phenolic resin, which needs to be prepared into a 0.1% wt aqueous solution, and 1-3 wt% sodium hydroxide is added to enhance dissolution. After adding sodium hydroxide, the phenolic hydroxyl groups react with the alkali to form sodium phenolate, which dissolves in water. After being dissolved in water, the phenolic resin, upon contact with the silicon wafer surface, can adsorb onto the silicon wafer surface as nucleation sites by forming aromatic hydrogen bonds between the benzene ring and the Si-H bonds on the silicon wafer surface. The hydrophobic short carbon chains on the benzene ring, such as methyl, tert-butyl, or octyl, can further enhance the hydrophobicity of the benzene ring and enhance the nucleation ability. At the same time, the corrosion-inhibiting properties of the hydrophobic short carbon chains can also obtain a certain microstructure and reduce reflectivity during pyramid formation. The amount of nucleating agent can control the size of the pyramid. Since the nucleating agent consists of chain segments with relatively similar molecular weights, as long as it can be uniformly dispersed in the texturing solution, a uniform texturing surface can be obtained.

[0020] The primary dispersant is one or more of sodium polystyrene sulfonate, sodium poly(4-styrene sulfonate-copolymer-acrylic acid), and sodium poly(4-styrene sulfonate-copolymer-maleic acid). Its structure is similar to that of the nucleating agent, both being block copolymers of benzene rings and benzene rings / carbon chains. The sulfonation of the benzene rings and the carboxyl groups on the carbon chains in the dispersant enhance its water solubility, allowing it to dissolve more uniformly in water. The block structure and chain length, similar to those of the nucleating agent, facilitate its binding with the nucleating agent, helping to ensure uniform dispersion of the nucleating agent in aqueous solution.

[0021] The auxiliary dispersant is a carbon-chain surfactant. It is selected from: sodium secondary alkyl sulfonate, C8-12 alkyl glycosides, and C6-8 fluorocarbon surfactants. Carbon-chain surfactants have short carbon chains and can only be adsorbed onto the silicon wafer surface by van der Waals forces. Their adsorption force is weak, making them difficult to adsorb and having little impact on the texturing reaction. Therefore, they can be used in large quantities. A large amount of surfactant can significantly reduce the surface tension of water, resulting in uniform dispersion of the nucleating agent.

[0022] The defoaming agent is a microcrystalline cellulose whisker solution. Under alkaline conditions, the microcrystalline cellulose is mechanically ground, further enhancing its water solubility; this allows it to dissolve in aqueous solution and adsorb onto the silicon wafer surface, acting as a defoaming agent. Compared to commonly chemically modified cellulose, the microcrystalline cellulose whisker solution has longer chain segments, which are more easily combined, forming a surface from lines. After entanglement with the nucleating agent, it forms a "surface" adsorption on the silicon wafer surface; simultaneously, the nucleating agent also has a certain chain length, enhancing the toughness of the "surface." As etching progresses, the entire surface is advanced, protecting the crystal face and forming a pyramid. This whole-surface etching method can quickly form a relatively complete crystal face; with continued etching, the pyramid base decreases while the height increases. Whole-surface etching also reduces the formation of fragmented fibers due to dislocations, making the surface more uniform and increasing the specific surface area. Attached Figure Description

[0023] Figure 1The textured surface morphology of the silicon wafer obtained in Example 1 of this invention; Figure 2 The textured surface morphology of the silicon wafer obtained in Example 2 of this invention; Figure 3 This is the textured surface morphology of the silicon wafer obtained in the comparative example of this invention. Detailed Implementation

[0024] To clarify the technical problems, technical solutions, implementation processes, and performance demonstrations, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative. The present invention is not intended to limit the scope of the invention. Various exemplary embodiments, features, and aspects of this disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the drawings denote elements with the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0025] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0026] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0027] Example 1 like Figure 1 The texturing process employs a texturing additive for monocrystalline silicon wafers with superior morphology, as described in this invention. The specific steps include: (1) Preparation of texturing additive: The texturing additive is prepared by mass percentage by adding 0.005% tert-butylphenol resin, 0.025% sodium polystyrene sulfonate, 0.04% C8~12 alkyl glycoside, and 12% microcrystalline cellulose whisker solution to 87.93% deionized water and mixing them evenly. (2) Preparation of texturing solution: Prepare a 1wt% NaOH solution in the texturing tank, and add the texturing additives from step (1) to the alkaline solution at a mass ratio of 0.5:100 and mix them evenly to obtain the texturing solution; (3) Texturing: The clean single crystal silicon wafer is immersed in the texturing solution in step (2) for surface texturing. After texturing at 83°C for 7 minutes, the silicon wafer is taken out, dried, and then subjected to reflectance and ZETA tests. The average reflectance is 9.8%.

[0028] The morphology of the textured surface of the silicon wafer was observed, and the results are as follows: Figure 1As shown, the silicon wafer surface is uniformly covered with large-sized pyramids, for example, the base size of the pyramids is between 1.7-1.8μm. These pyramids are basically the same size and are arranged neatly and uniformly.

[0029] Example 2 like Figure 2 The texturing process employs a texturing additive for monocrystalline silicon wafers with superior morphology, as described in this invention. The specific steps include: (1) Preparation of texturing additive: Prepare by mass percentage by adding 0.01% octylphenol resin, 0.05% sodium poly(4-styrene sulfonate-copolymer-acrylic acid), 0.07% sodium secondary alkyl sulfonate, and 20% microcrystalline cellulose whisker solution to 79.87% deionized water and mixing evenly to obtain texturing additive. (2) Preparation of texturing solution: Prepare a 0.7wt% NaOH solution in the texturing tank, and add the texturing additives from step (1) to the alkaline solution at a mass ratio of 0.8:100 and mix them evenly to obtain the texturing solution; (3) Texturing: The clean single crystal silicon wafer is immersed in the texturing solution in step (2) for surface texturing. After texturing at 83°C for 7 minutes, the silicon wafer is taken out, dried, and then subjected to reflectance and ZETA tests. The average reflectance is 10.0%.

[0030] The morphology of the textured surface of the silicon wafer was observed, and the results are as follows: Figure 2 As shown, small pyramids are evenly distributed on the surface of the silicon wafer. For example, the base size of the pyramid is between 1.55 and 1.7 μm. These pyramids are basically the same size and are arranged neatly and evenly.

[0031] Comparative Example Texturing: Prepare a 1wt% sodium hydroxide alkaline solution. Add a texturing additive (produced by Changzhou Shichuang Energy Co., Ltd., product model: TS55) to the alkaline solution at a mass ratio of 0.7:100 and stir evenly to form a texturing solution. Immerse the monocrystalline silicon wafer in the texturing solution for surface texturing. After texturing at 83℃ for 7 minutes, remove the silicon wafer, dry it, and perform reflectivity and ZETA tests. The average reflectivity is 9.6%.

[0032] The morphology of the textured surface of the silicon wafer was observed, and the results are as follows: Figure 3 As shown, the pyramids on the silicon wafer surface are not very uniform, with large differences in size, some larger and some smaller, and unevenly distributed. Furthermore, there are many fragments of pyramids due to the misalignment of pyramids of different sizes.

[0033] The textured wafers obtained in the above embodiments and comparative examples were tested using an NXT Helios-rc reflectance meter. The front and back sides of the silicon wafers were tested separately, and the average reflectance of both sides was calculated. A KLA Tencor ZETA INSTRUMENTS instrument in Pyramid-100X mode was used to scan the silicon wafer surface, obtaining data on the base, height, number, and specific surface area of ​​the pyramidal morphology within the scanned area. The reflectance and textured ZETA data for the specific embodiments and comparative examples are shown in the table below: Table 1. Data on the suede surface of the examples and comparative examples Example 1 9.8% 1.740 1.381 20.09 1.404 1.7~1.8 Example 2 10.0% 1.601 1.071 22.96 1.273 1.55~1.7 Comparative Example 9.6% 1.745 1.206 18.59 1.334 1.7~1.8 By comparing the examples and comparative examples in Table 1, we can obtain the following: (1) The pile surface of Example 1 is larger and the pile surface of Example 2 is smaller, indicating that the patent can obtain uniform pile surfaces of different sizes; (2) The reflectance of Example 1 is close to that of the comparative example, and the velvet surface is significantly more uniform than that of the comparative example, with fewer small towers and broken velvet. When the tower base is similar, Example 1 has a higher tower height (1.3-1.4μm), more towers (200,000-210,000), and a larger specific surface area (1.35-1.45), indicating that the invention can obtain a better pyramid velvet surface.

[0034] In summary, the highlight of this invention is: the preparation of a pyramidal textured surface with superior morphology, comprising: 1) The pyramid size can be adjusted by modifying process parameters such as concentration, ratio, and reaction time; 2) Within a certain range of pyramid sizes, achieve better morphology: Pyramids are similar in size, more uniform, have a larger aspect ratio, and a larger specific surface area, thereby increasing short-circuit current and improving battery efficiency. The uniformity, aspect ratio, and specific surface area of ​​the pyramid are positively correlated with the short-circuit current of the battery.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A single crystal silicon wafer texturizing additive characterized by, The additive components and their percentage content are as follows: nucleating agent 0.001~0.1wt%, main dispersant 0.01~1wt%, auxiliary dispersant 0.01~2wt%, defoamer 5~50wt%, and the balance is deionized water; the nucleating agent is a linear phenolic resin; the linear phenolic resin needs to be prepared into a 0.1%wt aqueous solution, and 1~3wt% sodium hydroxide is added to enhance dissolution; the defoamer is a microcrystalline cellulose whisker solution; the treatment process of the microcrystalline cellulose whisker solution is as follows: (1) Prepare the following solution according to the mass fraction: 5 wt% microcrystalline cellulose, 2 wt% sodium hydroxide, and 93 wt% water to obtain solution 1; (2) Solution 1 was emulsified and dispersed for 30 min using a high-speed dispersing emulsifier to obtain solution 2; (3) The solution 2 was circulated and ground using a bedroom sand mill. First, it was coarsely ground with 1.2-1.4 mm zirconium beads for 0.5-1.5 h; then it was finely ground with 0.6-0.8 mm zirconium beads for 1-3 h; to obtain microcrystalline cellulose whisker solution. After treatment, the microcrystalline cellulose whisker solution can be well dissolved in water, with a length of 100-800 nm.

2. A single crystal silicon wafer texturizing additive according to claim 1, wherein The linear phenolic resin is selected from one or more of methyl phenolic resin, tert-butyl phenolic resin, and octyl phenolic resin; the molecular weight of the linear phenolic resin is Mw 2000~5000.

3. A single crystal silicon wafer texturizing additive according to claim 1, wherein The main dispersant is selected from one or more of sodium polystyrene sulfonate, sodium poly(4-styrene sulfonate-copolymer-acrylic acid), and sodium poly(4-styrene sulfonate-copolymer-maleic acid); the polymer has a molecular weight Mw of 2000~8000.

4. A single crystal silicon wafer texturizing additive according to claim 1 wherein, The auxiliary dispersant is a carbon chain surfactant, selected from one or more of sodium secondary alkyl sulfonate, C8-12 alkyl glycoside, and C6-8 fluorocarbon surfactant.

5. A single crystal etching solution for etching a single crystal, characterized by comprising: It includes the texturing additive and alkaline solution according to any one of claims 1-4, wherein the mass ratio of the texturing additive and alkaline solution is 0.2 to 2:

100.

6. The single crystal, according to claim 5, wherein the etching solution for etching is characterized by comprising the following components: a hydrofluoric acid, a nitric acid, a sulfuric acid, and a surfactant. The alkaline solution is a 0.4–1.2 wt% aqueous solution of sodium hydroxide or potassium hydroxide.

7. A method for texturing a single crystal silicon wafer using the texturing solution for single crystal texturing according to claim 5 or 6, characterized by, Specifically, the following steps are included: S1. According to the following proportions: nucleating agent 0.001~0.1wt%, main dispersant 0.01~1wt%, auxiliary dispersant 0.01~2wt%, defoaming agent 5~50wt%, and the balance being deionized water, mix them evenly to prepare a flocking additive. S2. Add the texturing additive prepared in step S1 to the alkaline solution in a certain proportion and mix them evenly to prepare a texturing solution; wherein the mass ratio of the texturing additive to the alkaline solution is 0.2~2:

100. S3. Immerse the clean monocrystalline silicon wafer in the texturing solution prepared in step S2 to perform surface texturing. The texturing temperature is 80~85℃ and the time is 7~9min.

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