A secondary texturing modification additive for preparing a uniform deep-trap type textured surface of monocrystalline silicon, and a preparation method and application thereof

Abstract

The application discloses a single crystal silicon secondary texturing modification additive suitable for preparing a uniform deep-well type textured surface, and a preparation method and application thereof, and relates to the technical field of photovoltaic cell manufacturing. The additive comprises the following components in percentage by mass: a dendritic macromolecule nucleating agent 0.01%-0.5%, an ionic liquid modifier 0.5%-5.0%, an alkyne diol surfactant 0.05%-1.0%, an inorganic oxygen-containing acid salt 10%-20%, a functional synergistic component 0.1%-2.0%, and deionized water as the balance; the functional synergistic component is a compound of hydroxypropyl-beta-cyclodextrin, water-soluble imidazoline oleic acid and myo-inositol in a mass ratio of 1:(0.8-1.2):(1-2). The additive can significantly reduce the reflectivity of a silicon wafer surface and effectively improve the photoelectric conversion efficiency of a TOPCon cell.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell manufacturing technology, and in particular to a monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, its preparation method, and its application. Background Technology

[0002] With the rapid iteration and upgrading of crystalline silicon photovoltaic cell technology, high-efficiency cell technologies such as TOPCon tunneling oxide passivation contact, HJT heterojunction, and BC back contact have gradually become the mainstream development direction of the industry. High-efficiency cells place more stringent comprehensive requirements on the light-trapping textured surface of silicon wafers: on the one hand, the textured structure needs to have excellent light-trapping capabilities to minimize solar reflection loss; on the other hand, it also needs to ensure the overall uniformity of the microstructure to ensure that the subsequent passivation film can achieve good conformal coverage, reduce carrier recombination on the silicon wafer surface, and ultimately achieve a synergistic improvement in short-circuit current Isc and fill factor FF. In industrial production, monocrystalline silicon is generally anisotropically etched using alkaline solutions and texturing additives to prepare a micron-sized pyramid textured surface, thereby achieving the basic light-trapping effect.

[0003] To further reduce light reflection loss on silicon wafer surfaces, the industry has developed a secondary texturing process. This process first uses alkaline texturing to obtain a basic pyramidal texture, then uses a secondary texturing and modification solution to perform secondary etching on the pyramidal morphology, constructing secondary micro / nano structures in the gaps between the pyramids to further enhance the light-harvesting performance of the silicon wafer. Currently, commercially available secondary texturing additives mostly use linear polymers as etching inhibitors, relying on the polymer chains to spread and adsorb on the silicon surface, inhibiting etching of some crystal planes. However, this type of linear polymer adsorption mechanism has inherent limitations: molecular adsorption coverage is highly random, easily leading to localized over-etching or insufficient etching, causing deterioration of the texture uniformity, and resulting in production defects such as whitening of the texture, surface spots, and inter-wafer color differences.

[0004] Existing secondary texturing technology systems struggle to simultaneously balance the three core technical indicators of microstructure uniformity, light-trapping capability, and battery electrical performance, presenting irreconcilable contradictions. Pursuing deeper etched trenches to enhance light-trapping often results in a rough and disordered textured surface, defects in the passivation film coating, and increased carrier surface recombination rates, leading to losses in open-circuit voltage (Voc) and fill factor (FF). Conversely, prioritizing surface recombination levels only generates shallow hierarchical structures, resulting in significant light escape issues, limited room for reflectivity improvement, and only a slight increase in short-circuit current, hindering substantial breakthroughs in battery photoelectric conversion efficiency.

[0005] The existing technology lacks a texturing additive system that can achieve controllable and uniform longitudinal depth etching. Traditional linear polymer inhibitors cannot induce longitudinal corrosion of silicon materials at specific points. Furthermore, during the secondary texturing reaction, hydrogen bubbles generated by corrosion are easily trapped inside the newly formed microgrooves, isolating the corrosion solution and causing local corrosion termination, which further amplifies the problem of uneven texturing surface morphology.

[0006] Therefore, developing a secondary texturing additive for monocrystalline silicon suitable for preparing uniform deep-well textured surfaces, as well as its preparation method and application, is a technical challenge that urgently needs to be overcome for the industrialization of high-efficiency monocrystalline silicon solar cells. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a secondary texturing additive for monocrystalline silicon suitable for preparing uniform deep-trap textured surfaces, along with its preparation method and applications. This additive utilizes the synergistic effect of dendritic macromolecules and ionic liquids, particularly through the supramolecular pre-assembly of amino-functionalized ionic liquids and dendritic macromolecules to construct core-shell assemblies, the in-situ etching-passivation dynamic balance of fluorinated complex anions, the multidimensional supramolecular regulation of functional synergistic components (cyclodextrin / imidazoline / inositol), and a three-stage gradient temperature secondary texturing process. This selectively induces longitudinal depth etching on the pyramidal surface, forming a uniformly distributed and structurally stable deep-trap light-trapping structure. While significantly reducing reflectivity across the entire wavelength range, it maintains excellent electrical performance, achieving a substantial improvement in photoelectric conversion efficiency.

[0008] To achieve the above objectives, the present invention provides a monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, comprising the following components by mass percentage: 0.01%~0.5% dendritic macromolecular nucleating agent, 0.5%~5.0% ionic liquid modifier, 0.05%~1.0% acetylenic diol surfactant, 10%~20% inorganic oxyacid salt, 0.1%~2.0% functional synergistic component, and the balance being deionized water; wherein the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:(0.8-1.2):(1-2).

[0009] Preferably, the dendritic macromolecular nucleating agent is a polyamide-amine dendritic macromolecular (PAMAM) or polypropylene imine dendritic macromolecular (PPI) with a molecular generation of G1.0 to G2.0.

[0010] Preferably, the polyamide-amine dendritic macromolecule is of type CYD-110A, molecular generation number G1.0, terminal group is amino, number of terminal groups is 8, molecular weight is 1430, and is provided by Weihai Chenyuan Molecular New Materials Co., Ltd.

[0011] Preferably, the polypropylene imine dendritic macromolecule is a polypropylene imine tetraamine dendritic polymer DAB-AM-4 with a molecular generation of G1.0.

[0012] Preferably, the ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate.

[0013] Preferably, the acetylenic diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol.

[0014] Preferably, the inorganic oxyacid salt is one or a combination of two or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, or sodium pyrophosphate.

[0015] Preferably, the hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5, is of industrial grade, and is provided by Shandong Zhonghuan Zhongjie Biotechnology Co., Ltd.

[0016] Another object of the present invention is to provide a method for preparing a secondary texturing modification additive for monocrystalline silicon suitable for preparing a uniform deep-well textured surface, comprising the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:(5~20) and stirred at 300rpm~500rpm for 30min~60min at 40℃~60℃ to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 25℃~40℃ for 20min~40min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 300 rpm to 600 rpm for 20 min to 40 min at 25℃ to 40℃ until the solution is uniform and transparent, thus obtaining the monocrystalline silicon secondary texturing modification additive.

[0017] Another object of the present invention is to provide the application of the aforementioned monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces in the monocrystalline silicon secondary texturing process, comprising the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a temperature of 50℃~60℃ for 38~42s. Step D2: Remove the silicon wafer after completing step D1, rinse it with deionized water, and then place it in a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 70℃~90℃ and the texturing time is 300s~500s to form a basic pyramid textured surface on the silicon wafer. Then remove the silicon wafer and rinse it with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.1% to 0.5% at a mass fraction of 0.5% to 2.0% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a temperature of 50℃~60℃ for 40s; then place it into an acidic solution for cleaning at a temperature of 20℃~30℃ for 100s; after removing the silicon wafer, rinse it with deionized water and dry it at 60℃~80℃.

[0018] Preferably, the alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 0.5% to 1% potassium hydroxide or sodium hydroxide, 3% to 5% hydrogen peroxide, and the balance being deionized water.

[0019] Preferably, the primary texturing solution in step D2 comprises the following components by weight percentage: 1%~2% KOH or NaOH, 0.5%~2% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40.

[0020] Preferably, the alkaline post-cleaning solution comprises the following components by mass fraction: 0.5%~1% KOH or NaOH, 3%~5% hydrogen peroxide, and the balance being deionized water.

[0021] Preferably, the secondary texturing in step D3 adopts a three-stage gradient heating program: the first stage is the nucleation period, with a temperature of 50℃~58℃ and a time of 20s~40s; the second stage is the longitudinal etching period, with a temperature of 62℃~70℃ and a time of 50s~90s; and the third stage is the trimming period, with a temperature of 50℃~58℃ and a time of 20s~40s.

[0022] Preferably, the depth of the uniform deep-well textured surface deep-well structure described in step D3 is 0.8 μm to 1.5 μm, the width-to-depth ratio is 1:(1.5~3), and the deep-well distribution density is 5×10⁻⁶. 6 pcs / cm 2 ~2×10 7 pcs / cm 2 .

[0023] Preferably, the acidic solution in step D4 is a hydrochloric acid aqueous solution with a mass fraction of 5% to 10% or a hydrofluoric acid aqueous solution with a mass fraction of 2% to 5%.

[0024] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) A core-shell assembly is constructed by supramolecular pre-assembly of dendritic macromolecules and amino-functionalized ionic liquids. Combined with the dynamic balance control mechanism of in-situ etching-passivation of fluorine complex anions, a multidimensional supramolecular control system of functional synergistic components with exclusive compounding is adopted. This effectively solves the industry pain points of disordered etching, easy structural collapse and uneven texture distribution in traditional secondary texturing. It achieves the technical effect of accurately inducing longitudinal depth etching on the textured surface of silicon wafer pyramid, and can stably form a deep trap light trap structure with controllable size and uniform arrangement.

[0025] (2) By precisely defining the proportion, molecular size and compounding ratio of each functional component, and adopting the additive preparation process of step assembly, ultrasonic dispersion and uniform stirring, the synergistic stability and uniformity of each component of the additive are ensured, avoiding the defects of traditional texturing additives such as single function, poor component compatibility and unstable effect. The technical effect of precise control of deep well structure depth, width-to-depth ratio and distribution density is achieved, which greatly improves the regularity and stability of single crystal silicon texturing structure.

[0026] (3) By adapting the three-stage gradient heating secondary texturing process and the graded acid and alkali cleaning process, a refined and segmented texturing and modification process is adopted to achieve precise step-by-step control of texturing nucleation, deep etching and structural repair. This results in a significant reduction in the reflectivity of the silicon wafer across the entire wavelength range, while ensuring the excellent electrical performance of the monocrystalline silicon substrate throughout the process. Ultimately, this leads to a substantial improvement in the photoelectric conversion efficiency of monocrystalline silicon photovoltaic cells, which is significantly better than the comprehensive application effect of traditional texturing technology. Attached Figure Description

[0027] Figure 1 This is a SEM image of the textured surface of a silicon wafer obtained using a traditional one-step texturing process in Comparative Example 1 of this invention. Figure 2 This is a SEM image of the textured surface of the silicon wafer obtained after secondary texturing in Example 1 of the present invention; Figure 3 This is a SEM image of the textured surface of the silicon wafer obtained after secondary texturing in Example 2 of the present invention. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0029] Example 1: As Figure 2A monocrystalline silicon secondary texturing and modification additive suitable for preparing uniform deep-well textured surfaces comprises the following components by mass percentage: 0.01% dendritic macromolecular nucleating agent, 0.5% ionic liquid modifier, 0.05% acetylenic diol surfactant, 10% inorganic oxyacid salt, 0.1% functional synergistic component, and the balance being deionized water; wherein the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:0.8:1.

[0030] The dendritic macromolecular nucleating agent is a polyamide-amine dendritic macromolecular (PAMAM); the polyamide-amine dendritic macromole is model CYD-110A, molecular generation G1.0, terminal group is amino, number of terminal groups is 8, molecular weight is 1430, and it is provided by Weihai Chenyuan Molecular New Materials Co., Ltd.; this type of dendritic molecule has a highly branched spherical three-dimensional structure and a large number of terminal amino functional groups, which can be enriched on specific crystal faces of the pyramid through electrostatic adsorption, and form a local "micromask" by means of the steric hindrance effect of its spherical molecules, selectively protecting the adsorbed area from alkaline corrosion, thereby inducing differential deep corrosion in adjacent unprotected areas, forming a longitudinally extending "deep valley" structure at the bottom and sidewalls between the pyramids.

[0031] The ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate. In aqueous solution, the ionic liquid dissociates into organic cations and inorganic anions. The organic cations can be adsorbed onto the negatively charged silicon surface via electrostatic interactions, regulating the double-layer capacitance and charge distribution at the silicon / solution interface and promoting the deepening of localized pitting corrosion. The imidazole rings adsorb onto the silicon surface via electrostatic interactions to regulate the double layer, while the terminal amino groups interact with the internal amide groups and terminal amino groups of the dendritic macromolecules (PAMAM / PPI) through hydrogen bonding, causing the ionic liquid to accumulate directionally around the dendritic macromolecules, forming a core-shell supramolecular assembly with the dendritic macromolecules as the core and the ionic liquid as the shell. The adsorption of this supramolecular assembly on the silicon surface transforms from "random adsorption" in traditional simple mixed systems to "directional adsorption," significantly improving the spatial positioning accuracy and coverage uniformity of the micromask.

[0032] The acetylenic diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol; this type of surfactant has extremely low dynamic surface tension, enabling it to rapidly penetrate into the etched deep valley during the formation of the deep trap structure, promptly expelling hydrogen bubbles generated by the corrosion reaction and preventing blockage of the valley openings by bubbles, thus avoiding corrosion interruption or unevenness; the inorganic oxyacid salt is disodium hydrogen phosphate; this type of phosphate forms HPO4 in aqueous solution. 2- / H2PO 4- The buffer pair can maintain the stability of the solution pH during the secondary texturing process.

[0033] The hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5, is of industrial grade, and is provided by Shandong Zhonghuan Zhongjie Biotechnology Co., Ltd. The hydroxypropyl-β-cyclodextrin has a barrel-shaped structure with a hydrophobic inner cavity and a hydrophilic outer cavity, and can form inclusion complexes with the imidazolium cations of ionic liquids through host-guest inclusion interactions. This inclusion interaction has a triple synergistic effect: the inclusion of ionic liquid cations in the cyclodextrin inner cavity can delay their rapid adsorption in the early stages of texturing, avoiding uneven local corrosion and achieving uniform release of the ionic liquid throughout the texturing process; the cyclodextrin directionally enriches the ionic liquid cations around dendritic macromolecules through host-guest recognition, enhancing the structural stability of the core-shell supramolecular assembly; and the numerous hydroxyl groups in the hydrophilic outer cavity of the cyclodextrin can form weak hydrogen bonds with the silicon surface, assisting in the uniform nucleation of micromasks at the valley floor of the pyramid.

[0034] The water-soluble oleic acid imidazoline has a molecular structure comprising a five-membered imidazoline ring and a long oleic acid chain. The two nitrogen atoms in the five-membered imidazoline ring possess lone pairs of electrons, allowing them to adsorb onto the silicon surface through coordination. The long oleic acid chain provides steric hindrance. Inositol has a cyclohexane stereostructure with six hydroxyl groups. These six hydroxyl groups can form a multidimensional hydrogen bond network with the amide groups of dendritic macromolecules, the anions of ionic liquids, the luminal hydroxyl groups of cyclodextrins, and the silanol groups on the silicon surface through hydrogen bonding, enhancing the structural integrity and stability of the entire supramolecular assembly system. Simultaneously, the multi-hydroxyl structure of inositol can form a weak adsorption layer on the silicon surface, helping to regulate the uniformity of the etching rate and preventing pyramid collapse caused by localized over-etching.

[0035] When the three functional synergistic components are used in combination, the host-guest controlled release of hydroxypropyl-β-cyclodextrin, the synergistic adsorption of water-soluble oleic acid imidazoline, and the hydrogen bond network stabilization of inositol form a three-dimensional synergistic regulatory system of "controlled release-adsorption-stabilization", which achieves the optimal balance of depth, uniformity and electrical performance of the deep trap structure.

[0036] A method for preparing a secondary texturing additive for monocrystalline silicon suitable for preparing a uniform deep-well textured surface includes the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:5 and stirred at 300 rpm for 30 min at 40 °C to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 25 °C for 20 min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 300 rpm for 20 minutes at 25°C until the solution is uniform and transparent to obtain the monocrystalline silicon secondary texturing modification additive.

[0037] The application of the aforementioned monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces in the monocrystalline silicon secondary texturing process includes the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a temperature of 50°C for 38 seconds. Step D2: Remove the silicon wafer after completing step D1, rinse it with deionized water, and then place it in a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 70℃ and the texturing time is 300s to form a basic pyramid texture on the surface of the silicon wafer. Then remove the silicon wafer and rinse it with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.1% at a mass fraction of 0.5% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a cleaning temperature of 50°C for 40 seconds; then place it into an acidic solution for cleaning at a cleaning temperature of 20°C for 100 seconds; after removing the silicon wafer, rinse it with deionized water and dry it at 60°C.

[0038] The alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 0.5% potassium hydroxide, 3% hydrogen peroxide, and the balance being deionized water; the primary texturing solution in step D2 comprises the following components by weight percentage: 1% KOH, 0.5% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40; the alkaline post-cleaning solution comprises the following components by mass fraction: 0.5% KOH, 3% hydrogen peroxide, and the balance being deionized water.

[0039] The secondary texturing process described in step D3 adopts a three-stage gradient heating program: the first stage is the nucleation period, with a temperature of 50℃ and a time of 20s; the second stage is the deep etching period, with a temperature of 62℃ and a time of 50s; the third stage is the trimming period, with a temperature of 50℃ and a time of 20s; the acidic solution described in step D4 is a 5% hydrochloric acid aqueous solution.

[0040] Example 2: As Figure 3A secondary texturing additive for monocrystalline silicon suitable for preparing uniform deep-well textured surfaces comprises the following components by mass percentage: 0.15% dendritic macromolecular nucleating agent, 2.0% ionic liquid modifier, 0.3% acetylenic diol surfactant, 13% inorganic oxyacid salt, 0.7% functional synergistic component, and the balance being deionized water; wherein the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:0.9:1.2.

[0041] The dendritic macromolecular nucleating agent is polypropylene imine dendritic macromolecule (PPI); the polypropylene imine dendritic macromolecule is polypropylene imine tetraamine dendritic polymer DAB-AM-4, with a molecular generation of G1.0; the ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate; the acetylenic diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol; the inorganic oxyacid salt is sodium dihydrogen phosphate; the hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5, is industrial grade, and is provided by Shandong Zhonghuan Zhongjie Biotechnology Co., Ltd.

[0042] A method for preparing a secondary texturing additive for monocrystalline silicon suitable for preparing a uniform deep-well textured surface includes the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:9 and stirred at 350 rpm for 40 min at 45 °C to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 30 °C for 25 min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 350 rpm for 25 minutes at 29°C until the solution is uniform and transparent to obtain the monocrystalline silicon secondary texturing modification additive.

[0043] The application of the aforementioned monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces in the monocrystalline silicon secondary texturing process includes the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a cleaning temperature of 53°C for 39 seconds. Step D2: Remove the silicon wafer after completing step D1, rinse it with deionized water, and then place it in a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 75℃ and the texturing time is 350s to form a basic pyramid texture on the surface of the silicon wafer. Then remove the silicon wafer and rinse it with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.2% at a mass fraction of 0.9% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a cleaning temperature of 53°C for 40 seconds; then place it into an acidic solution for cleaning at a cleaning temperature of 22°C for 100 seconds; after removing the silicon wafer, rinse it with deionized water and dry it at 65°C.

[0044] The alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 0.7% sodium hydroxide, 3.5% hydrogen peroxide, and the balance being deionized water; the primary texturing solution in step D2 comprises the following components by weight percentage: 1.2% NaOH, 0.9% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40; the alkaline post-cleaning solution comprises the following components by mass fraction: 0.6% NaOH, 3.5% hydrogen peroxide, and the balance being deionized water.

[0045] The secondary texturing process described in step D3 adopts a three-stage gradient heating program: the first stage is the nucleation period, with a temperature of 52℃ and a time of 25s; the second stage is the deep etching period, with a temperature of 64℃ and a time of 60s; the third stage is the trimming period, with a temperature of 52℃ and a time of 25s; the acidic solution described in step D4 is a 2% hydrofluoric acid aqueous solution.

[0046] Example 3: A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, comprising the following components by mass percentage: 0.3% dendritic macromolecular nucleating agent, 3.0% ionic liquid modifier, 0.5% acetylenic diol surfactant, 15% inorganic oxyacid salt, 1.1% functional synergistic component, and the balance being deionized water; the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:1:1.5; the dendritic macromolecular nucleating agent is a polyamide-amine type dendritic macromolecular (PAMAM); the polyamide... The amine-type dendritic macromolecule, model number CYD-110A, molecular generation G1.0, terminal group is amino, number of terminal groups is 8, molecular weight is 1430, and it is provided by Weihai Chenyuan Molecular New Materials Co., Ltd.; the ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate; the acetylenol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol; the inorganic oxyacid salt is sodium pyrophosphate; the hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5, is industrial grade, and is provided by Shandong Zhonghuan Zhongjie Biotechnology Co., Ltd.

[0047] A method for preparing a secondary texturing additive for monocrystalline silicon suitable for preparing a uniform deep-well textured surface includes the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:13 and stirred at 400 rpm for 45 min at 50 °C to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 32 °C for 30 min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 450 rpm for 30 minutes at 33°C until the solution is uniform and transparent to obtain the monocrystalline silicon secondary texturing modification additive.

[0048] The application of the aforementioned monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces in the monocrystalline silicon secondary texturing process includes the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a temperature of 55°C for 40 seconds. Step D2: Remove the silicon wafer after completing step D1, rinse it with deionized water, and then place it in a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 80℃ and the texturing time is 400s to form a basic pyramid texture on the surface of the silicon wafer. Then remove the silicon wafer and rinse it with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.3% at a mass fraction of 1.2% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a cleaning temperature of 55°C for 40 seconds; then place it into an acidic solution for cleaning at a cleaning temperature of 25°C for 100 seconds; after removing the silicon wafer, rinse it with deionized water and dry it at 70°C.

[0049] The alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 0.7% potassium hydroxide, 4% hydrogen peroxide, and the balance being deionized water; the primary texturing solution in step D2 comprises the following components by weight percentage: 1.5% KOH, 1.2% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40; the alkaline post-cleaning solution comprises the following components by mass fraction: 0.7% KOH, 4% hydrogen peroxide, and the balance being deionized water.

[0050] The secondary texturing process described in step D3 adopts a three-stage gradient heating program: the first stage is the nucleation period, with a temperature of 55℃ and a time of 30s; the second stage is the deep etching period, with a temperature of 67℃ and a time of 70s; the third stage is the trimming period, with a temperature of 55℃ and a time of 30s; the acidic solution described in step D4 is a 7% hydrochloric acid aqueous solution.

[0051] Example 4: A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, comprising the following components by mass percentage: 0.4% dendritic macromolecular nucleating agent, 4.0% ionic liquid modifier, 0.9% acetylenic diol surfactant, 18% inorganic oxyacid salt, 1.8% functional synergistic component, and the balance being deionized water; the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:1.1:1.8.

[0052] The dendritic macromolecular nucleating agent is polypropylene imine dendritic macromolecule (PPI); the polypropylene imine dendritic macromolecule is polypropylene imine tetraamine dendritic polymer DAB-AM-4, with a molecular generation of G1.0; the ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate; the acetylenic diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol; the inorganic oxyacid salt is sodium pyrophosphate; the hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5, is industrial grade, and is provided by Shandong Zhonghuan Zhongjie Biotechnology Co., Ltd.

[0053] A method for preparing a secondary texturing additive for monocrystalline silicon suitable for preparing a uniform deep-well textured surface includes the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:18 and stirred at 480 rpm for 55 min at 55 °C to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 38 °C for 35 min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 570 rpm for 35 minutes at 38°C until the solution is uniform and transparent to obtain the monocrystalline silicon secondary texturing modification additive.

[0054] The application of the aforementioned monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces in the monocrystalline silicon secondary texturing process includes the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a temperature of 58°C for 41 seconds. Step D2: Remove the silicon wafer after completing step D1, rinse it with deionized water, and then place it in a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 85℃ and the texturing time is 480s to form a basic pyramid texture on the surface of the silicon wafer. Then remove the silicon wafer and rinse it with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.4% at a mass fraction of 1.6% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a cleaning temperature of 58°C for 40 seconds; then place it into an acidic solution for cleaning at a cleaning temperature of 28°C for 100 seconds; after removing the silicon wafer, rinse it with deionized water and dry it at 75°C.

[0055] The alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 0.9% sodium hydroxide, 4.5% hydrogen peroxide, and the balance being deionized water; the primary texturing solution in step D2 comprises the following components by weight percentage: 1.8% KOH, 1.8% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40; the alkaline post-cleaning solution comprises the following components by mass fraction: 0.8% NaOH, 4.5% hydrogen peroxide, and the balance being deionized water.

[0056] The secondary texturing process described in step D3 adopts a three-stage gradient heating program: the first stage is the nucleation period, with a temperature of 57℃ and a time of 35s; the second stage is the deep etching period, with a temperature of 68℃ and a time of 85s; the third stage is the trimming period, with a temperature of 57℃ and a time of 35s; the acidic solution described in step D4 is a 4.5% hydrofluoric acid aqueous solution.

[0057] Example 5: A single-crystal silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, comprising the following components by mass percentage: 0.5% dendritic macromolecular nucleating agent, 5.0% ionic liquid modifier, 1.0% acetylenic diol surfactant, 20% inorganic oxyacid salt, 2.0% functional synergistic component, and the balance being deionized water; wherein the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:1.2:2.

[0058] The dendritic macromolecule nucleating agent is a polyamide-amine dendritic macromolecule (PAMAM); the polyamide-amine dendritic macromolecule is CYD-110A, with a molecular generation of G1.0, an amino terminal group, 8 terminal groups, and a molecular weight of 1430, and is provided by Weihai Chenyuan Molecular New Materials Co., Ltd.; the ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate; the acetylenol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol; the inorganic oxyacid salt is disodium hydrogen phosphate; the hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5, is industrial grade, and is provided by Shandong Zhonghuan Zhongjie Biotechnology Co., Ltd.

[0059] A method for preparing a secondary texturing additive for monocrystalline silicon suitable for preparing a uniform deep-well textured surface includes the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:20 and stirred at 500 rpm for 60 min at 60 °C to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 40 °C for 40 min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 600 rpm for 40 minutes at 40°C until the solution is uniform and transparent to obtain the monocrystalline silicon secondary texturing modification additive.

[0060] The application of the aforementioned monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces in the monocrystalline silicon secondary texturing process includes the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a temperature of 60°C for 42 seconds. Step D2: Remove the silicon wafer after completing step D1, rinse it with deionized water, and then place it in a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 90℃ and the texturing time is 500s to form a basic pyramid texture on the surface of the silicon wafer. Then remove the silicon wafer and rinse it with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.5% at a mass fraction of 2.0% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a cleaning temperature of 60°C for 40 seconds; then place it into an acidic solution for cleaning at a cleaning temperature of 30°C for 100 seconds; after removing the silicon wafer, rinse it with deionized water and dry it at 80°C.

[0061] The alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 1% sodium hydroxide, 5% hydrogen peroxide, and the balance being deionized water; the primary texturing solution in step D2 comprises the following components by weight percentage: 2% NaOH, 2% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40; the alkaline post-cleaning solution comprises the following components by mass fraction: 1% NaOH, 5% hydrogen peroxide, and the balance being deionized water.

[0062] The secondary texturing process described in step D3 adopts a three-stage gradient heating program: the first stage is the nucleation period, with a temperature of 58℃ and a time of 40s; the second stage is the deep etching period, with a temperature of 70℃ and a time of 90s; the third stage is the trimming period, with a temperature of 58℃ and a time of 40s; the acidic solution described in step D4 is a 10% hydrochloric acid aqueous solution.

[0063] Comparative Example 1 like Figure 1 The process involves only one-time flocking, without secondary flocking or finishing. The first flocking process is: 2% NaOH + 0.5% TS-40, 70℃, 300s. After flocking, the product is directly washed, acid-washed, and dried.

[0064] Comparative Example 2 A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, its preparation method and application are basically the same as in Example 5, except that an equal amount of hydroxypropyl-β-cyclodextrin is used instead of water-soluble oleic acid imidazoline.

[0065] Comparative Example 3 A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, its preparation method and application are basically the same as in Example 5, except that an equal amount of water-soluble oleic acid imidazoline is used instead of hydroxypropyl-β-cyclodextrin.

[0066] Comparative Example 4 A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, its preparation method and application are basically the same as in Example 5, except that an equal amount of water-soluble oleic acid imidazoline is used instead of inositol.

[0067] Comparative Example 5 A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, its preparation method and application are basically the same as those in Example 5, except that an equal amount of inositol is used instead of water-soluble oleic acid imidazoline.

[0068] Comparative Example 6 A monocrystalline silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, its preparation method and application are basically the same as those in Example 5, except that the ionic liquid modifier is 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0069] Performance test examples Surface reflectance testing: A UV-Vis-NIR spectrophotometer (with integrating sphere attachment) was used, with a standard white board (PTFE, reflectance ≥99%) as a reference. The hemispherical reflectance of the silicon wafer surface was measured in 5nm increments within the wavelength range of 350nm~1050nm. The arithmetic mean of the reflectance at each wavelength point was taken as the average reflectance of the sample. Tests were conducted at 5 locations for each sample, including the center and four corners of the silicon wafer, and the average value was taken.

[0070] Battery electrical performance testing: Texturized silicon wafers were processed using the standard TOPCon battery manufacturing process (including boron diffusion, tunnel oxide deposition, polycrystalline silicon deposition, laser grooving, passivation deposition, screen printing, and sintering) to create complete 182mm × 182mm cells. A solar simulator paired with an IV tester was used, following IEC 60904-1:2006, under standard test conditions (STC: irradiance 1000W / m²). 2 The photoelectric conversion efficiency (Eta) of the battery was measured at a battery temperature of 25°C and under AM1.5G standard spectrum. Ten battery cells were tested for each example, and the average value was taken. The test results are shown in Table 1.

[0071] Table 1

[0072] Test data shows that, compared to Comparative Example 1 (average reflectance 10.36%, photoelectric conversion efficiency 25.403%), which uses only a conventional one-time texturing process as a mass production benchmark, the two-time texturing modification system of Example 5 of this invention can significantly optimize the textured surface structure of monocrystalline silicon, effectively reduce the average reflectance of the silicon wafer surface to 7.21%, and increase the photoelectric conversion efficiency of the battery to 25.972%, achieving the best overall performance. The performance of Comparative Examples 2-5, which lack or have replaced each functional component, is significantly worse than that of Example 5. Among them, Comparative Examples 2 and 3 have poorer textured surface uniformity due to the lack of a single synergistic functional component. The significant increase in reflectivity and the significant decrease in conversion efficiency in Comparative Examples 4 and 5, due to the replacement of component ratios, resulted in decreased etching stability and a slight performance degradation. This fully verifies the synergistic effect of the ternary compound system of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol. Compared to Example 5, Comparative Example 6, which replaced the specific ionic liquid modifier, showed a weakened supramolecular assembly and textured surface control effect, with increased reflectivity and decreased conversion efficiency. This demonstrates that the compatibility between 1-aminoethyl-3-methylimidazolium tetrafluoroborate and PAMAM dendrimers is key to achieving a high-quality deep-well textured surface in this system.

[0073] 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 principles of 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 claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A single-crystal silicon secondary texturing modification additive suitable for preparing uniform deep-well textured surfaces, characterized in that, The product comprises the following components by mass percentage: 0.01%~0.5% dendritic nucleating agent, 0.5%~5.0% ionic liquid modifier, 0.05%~1.0% acetylenic diol surfactant, 10%~20% inorganic oxyacid salt, 0.1%~2.0% functional synergistic component, and the balance being deionized water; the functional synergistic component is a compound of hydroxypropyl-β-cyclodextrin, water-soluble oleic acid imidazoline, and inositol in a mass ratio of 1:(0.8-1.2):(1-2); the ionic liquid modifier is 1-aminoethyl-3-methylimidazolium tetrafluoroborate; the dendritic nucleating agent is a polyamide-amine type dendritic macromolecule or a polypropylene imine dendritic macromolecule with a molecular generation of G1.0~G2.

0.

2. The single-crystal silicon secondary texturing modification additive according to claim 1, characterized in that, The polyamide-amine dendritic macromolecule is designated as CYD-110A, with a molecular generation of G1.0, an amino group at the end, 8 terminal groups, and a molecular weight of 1430.

3. The single-crystal silicon secondary texturing modification additive according to claim 1, characterized in that, The polypropylene imine dendritic macromolecule is a polypropylene imine tetraamine dendritic polymer DAB-AM-4 with a molecular generation of G1.

0.

4. The single-crystal silicon secondary texturing modification additive according to claim 1, characterized in that, The acetylenic diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol.

5. The single-crystal silicon secondary texturing modification additive according to claim 1, characterized in that, The inorganic oxyacid salt is one or a combination of two or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, or sodium pyrophosphate; the hydroxypropyl-β-cyclodextrin has a molar substitution degree of 0.4-1.5 and is of industrial grade.

6. A method for preparing a single-crystal silicon secondary texturing modification additive suitable for preparing a uniform deep-well textured surface according to any one of claims 1-5, characterized in that, Includes the following steps: S1. The dendritic macromolecular nucleating agent and the ionic liquid modifier are mixed at a mass ratio of 1:(5~20) and stirred at 300rpm~500rpm for 30min~60min at 40℃~60℃ to allow the two to fully assemble into a core-shell supramolecular complex through hydrogen bonding and electrostatic interaction. The supramolecular complex, the functional synergistic component and the inorganic oxyacid salt are then added to deionized water and ultrasonically dispersed at 25℃~40℃ for 20min~40min until completely dissolved to obtain a homogeneous basic solution. S2. Add an acetylenic diol surfactant to the homogeneous base solution and stir at 300 rpm to 600 rpm for 20 min to 40 min at 25℃ to 40℃ until the solution is uniform and transparent, thus obtaining the monocrystalline silicon secondary texturing modification additive.

7. The application of a monocrystalline silicon secondary texturing modification additive according to any one of claims 1-5, suitable for preparing uniform deep-well textured surfaces, in the monocrystalline silicon secondary texturing process, characterized in that, Includes the following steps: Step D1: Place the monocrystalline silicon wafer into an alkaline pre-cleaning solution for pre-cleaning at a temperature of 50℃~60℃ for 38~42s. Step D2: Take out the silicon wafer after completing step D1, rinse it with deionized water, and put it into a primary texturing solution containing conventional texturing additives for primary texturing. The texturing temperature is 70℃~90℃ and the texturing time is 300s~500s to form a basic pyramid textured surface on the silicon wafer. The silicon wafer is then removed and rinsed with deionized water. Step D3: Add the above-mentioned monocrystalline silicon secondary texturing and modification additive to an alkaline solution with a mass fraction of 0.1% to 0.5% at a mass fraction of 0.5% to 2.0% to prepare a secondary texturing solution; place the silicon wafer that has completed step D2 into the secondary texturing solution for secondary texturing and modification to form a uniform deep-well textured surface on the silicon wafer; then remove the silicon wafer and rinse it with deionized water. Step D4: Place the silicon wafer that has completed step D3 into an alkaline cleaning solution for post-cleaning at a temperature of 50℃~60℃ for 40s; then place it into an acidic solution for cleaning at a temperature of 20℃~30℃ for 100s; after removing the silicon wafer, rinse it with deionized water and dry it at 60℃~80℃.

8. The application of the monocrystalline silicon secondary texturing modification additive according to claim 7, suitable for preparing uniform deep-well textured surfaces, in the monocrystalline silicon secondary texturing process, characterized in that, The alkaline pre-cleaning solution in step D1 comprises the following components by weight percentage: 0.5%–1% potassium hydroxide or sodium hydroxide, 3%–5% hydrogen peroxide, and the balance being deionized water; the primary texturing solution in step D2 comprises the following components by weight percentage: 1%–2% KOH or NaOH, 0.5%–2% conventional texturing additive, and the balance being deionized water; the conventional texturing additive is Changzhou Shichuang Energy TS-40; the alkaline post-cleaning solution comprises the following components by mass fraction: 0.5%–1% KOH or NaOH, 3%–5% hydrogen peroxide, and the balance being deionized water.

9. The application of the monocrystalline silicon secondary texturing modification additive according to claim 7, suitable for preparing uniform deep-well textured surfaces, in the monocrystalline silicon secondary texturing process, characterized in that, The secondary texturing process described in step D3 employs a three-stage gradient heating procedure: the first stage is the nucleation period, with a temperature of 50℃~58℃ and a time of 20s~40s; the second stage is the deep etching period, with a temperature of 62℃~70℃ and a time of 50s~90s; and the third stage is the finishing period, with a temperature of 50℃~58℃ and a time of 20s~40s. The depth of the uniform deep-well textured surface deep-well structure described in step D3 is 0.8μm~1.5μm, the width-to-depth ratio is 1:(1.5~3), and the deep-well distribution density is 5×10⁻⁶. 6 pcs / cm 2 ~2×10 7 pcs / cm 2 The acidic solution mentioned in step D4 is a hydrochloric acid aqueous solution with a mass fraction of 5% to 10% or a hydrofluoric acid aqueous solution with a mass fraction of 2% to 5%.

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