Method for improving smudginess of texturing blanking appearance

Abstract

The invention discloses a method for improving appearance smudginess of texturing blanking, and belongs to a texturing cleaning method in the technical field of solar photovoltaic power generation, and the technical scheme is as follows: feeding, placing a silicon wafer in texturing equipment for texturing preparation; pre-cleaning is conducted; washing for the first time: washing the silicon wafer which is pre-cleaned in the step S2 for 115-130 seconds; texturing is carried out; washing for the second time: washing the textured silicon wafer with water for 115-130 seconds; the washing time of the third time of washing is 115-130 seconds; pickling; washing for the fourth time; slowly lifting; performing drying; the invention provides the method for improving the appearance smudginess of the texturing blanking, and after the smudginess is improved, the electrical properties (such as conversion efficiency, open-circuit voltage and fill factor) and EL yield of the TOPCon battery piece are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of solar photovoltaic power generation, and in particular relates to a method for improving the dirty appearance of velveting blanks. Background Art

[0002] Solar photovoltaic power generation has become the most important area of solar energy utilization and has also seen rapid growth in recent years. Crystalline silicon cells are the primary source of photovoltaic power generation. However, surface defects and internal impurities in crystalline silicon cells limit further efficiency improvements. To improve the photoelectric conversion efficiency of solar cells, scholars and experts from around the world have designed various anti-reflection coatings to mitigate the impact of surface defects and internal impurities on solar cell efficiency.

[0003] OPCon (Tunnel Oxide Passivated Contact) cells are high-efficiency crystalline silicon solar cells based on passivated contact technology. Their core advantage lies in the tunneling passivation effect of the back oxide layer, which significantly reduces carrier recombination and improves conversion efficiency. The texturing process is a key step in TOPCon cell manufacturing. By forming a micron-scale textured structure on the silicon wafer surface, it reduces light reflection and enhances light absorption.

[0004] During the unloading process (i.e. when the silicon wafer is taken out of the texturing tank and transferred to the next process), the silicon wafer may introduce dirt (such as chemical residues, particulate matter, metal ions, etc.) due to improper process control or environmental factors, resulting in local passivation failure, leakage or efficiency reduction. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for improving the appearance of dirty texturing materials. After the dirt is improved, the electrical performance (such as conversion efficiency, Voc, FF) and EL yield of TOPCon cells are significantly improved. The core reasons are reduced surface recombination, enhanced passivation effect and reduced defects.

[0006] The object of the present invention is achieved by a method for improving the appearance of dirty velveting blanks, comprising the following steps:

[0007] S1, loading, placing the silicon wafer into the texturing equipment and preparing for texturing;

[0008] S2, pre-cleaning, placing the silicon wafer in multiple cleaning tanks in the texturing equipment for pre-cleaning treatment, the cleaning time is 210-230 seconds, and the cleaning temperature is 65-72°C;

[0009] S3, the first water washing, washing the silicon wafer after the pre-cleaning in S2 with water, the washing time is 115-130s;

[0010] S4, texturing, placing the silicon wafers washed in S3 into a texturing tank of a texturing equipment, wherein there is more than one texturing tank, and the silicon wafers are evenly placed in the more than one texturing tank;

[0011] S5, second water washing, washing the silicon wafer after texturing in S4, the washing time is 115-130s;

[0012] S6, post-alkali washing, placing the silicon wafer after water washing in S5 in an alkali washing tank, using an alkaline solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 110-130s, and the cleaning temperature is 65-70°C;

[0013] S7, the third water washing, the silicon wafer after the alkali washing in S6 is washed with water, the washing time is 115-130s;

[0014] S8, pickling, placing the silicon wafer after water washing in S7 in a pickling tank, using an acidic solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 110-130 seconds, the cleaning temperature is 65-70°C, and the acidic solution is a mixed solution of HF and HCl;

[0015] S9, the fourth water washing, washing the silicon wafer after the acid washing in S8 with water, the washing time is 115-130s;

[0016] S10, slow pulling, placing the silicon wafer washed in S9 into the slow pulling tank in the texturing equipment, the slow pulling time is 10-20 seconds, and the temperature is 60-80°C;

[0017] S11, drying, drying the silicon wafer after being pulled in S10, dividing the silicon wafer into multiple portions, and placing the multiple portions of silicon wafers in different drying tanks for drying after placement;

[0018] S12, unloading, unloading and placing the dried silicon wafers.

[0019] Furthermore, the texturing equipment is placed in an environment with an FFU filtration system for use.

[0020] Furthermore, deionized water is used in the pre-cleaning, and the deionized water includes 3-5% NAOH and 10-15% hydrogen peroxide.

[0021] Furthermore, the texturing equipment is provided with a plurality of ultrasonic oscillating devices, which are respectively arranged in the cleaning tank, the texturing tank, the alkaline washing tank and the acid washing tank, with an ultrasonic power of 100-120W and a frequency of 40-65kHZ.

[0022] Furthermore, the alkali washing solution in the post-alkali washing is sodium hydroxide or potassium hydroxide (KOH) mixed with isopropyl alcohol (IPA) and additives (such as NaClO3).

[0023] Furthermore, in the third water washing, the surface of the silicon wafer is rounded by an acid solution containing ozone after water washing.

[0024] Furthermore, the acid solution has an ozone concentration of 50 PPM-90 PPM, a hydrofluoric acid concentration of 2%-5%, a hydrochloric acid concentration of 0.05%-0.45%, and the balance is deionized water. The temperature of the mixed solution is 66° C.-68° C., and the reaction time is 100 s-120 s.

[0025] Furthermore, the texturing solvent used in the texturing operation of S4 is water, alkali and a texturing additive, and the volume ratio of the water, the alkali and the texturing additive is 3600:(40-45):(18-20).

[0026] Furthermore, a stirring device or a bubbling device is provided in the texturing tank.

[0027] Furthermore, the texturing additive is a mixed solvent of sodium silicate and isopropyl alcohol.

[0028] The beneficial effects of the present invention are embodied in:

[0029] In the present invention, the multi-stage deionized water washing method provided can effectively dilute the chemical residues in the texturing solution and reduce the surface pollution concentration. The standardized process can ensure the process stability and reduce human operation errors. The cost is low, the deionized water system technology is mature, the equipment maintenance is simple, and it is suitable for large-scale mass production. The FFU system can remove 99.99% of particles ≥0.3μm in the air through high-efficiency filtration (HEPA / ULPA), meeting the cleanliness requirements of ISO Class 5 and above. The temperature and humidity are stably controlled to avoid condensation or electrostatic adsorption on the silicon wafer surface due to environmental fluctuations. The electrical performance (such as conversion efficiency, Voc, FF) and EL yield of the TOPCon cell are significantly improved. The core reason is the reduced surface recombination, enhanced passivation effect and reduced defects. DETAILED DESCRIPTION

[0030] The following embodiments of the technical solution of the present invention are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only used as examples and are not intended to limit the scope of protection of the present invention.

[0031] It should be noted that, unless otherwise specified, the technical or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0032] A method for improving the dirty appearance of velveting blanks, comprising the following steps:

[0033] S1, loading, placing the silicon wafer into the texturing equipment and preparing for texturing;

[0034] S2. Pre-cleaning: Place the silicon wafer in multiple cleaning tanks in the texturing equipment for pre-cleaning. The cleaning time is 210-230 seconds and the cleaning temperature is 65-72°C. The purpose of silicon wafer pre-treatment is to remove mechanical damage layers, oxides, and contaminants (such as grease and metal ions) on the silicon wafer surface. Key parameters include temperature (62-65°C), alkali concentration (3-5% NaOH), and hydrogen peroxide concentration (10-15%).

[0035] S3, the first water washing, washing the silicon wafer after the pre-cleaning in S2 with water, the washing time is 115-130s;

[0036] S4, texturing, placing the silicon wafers that have completed water washing in S3 into the texturing tank of the texturing equipment, wherein there is more than one texturing tank, and the silicon wafers are evenly placed in the more than one texturing tank; purpose of texturing: to form a uniform velvet structure (pyramid or hole morphology) on the surface of the silicon wafer and reduce the light reflectivity; process type: alkaline texturing (single crystal silicon), solution: sodium hydroxide (NaOH) or potassium hydroxide (KOH) mixed with isopropyl alcohol (IPA) and additives.

[0037] Reaction principle: anisotropic corrosion, forming a pyramid structure (typical size 1-3μm), key equipment: constant temperature texturing tank (with stirring or bubbling device), acid and alkali resistant materials (such as PVDF or PTFE),

[0038] S5, the second water washing, washing the silicon wafer after the texturing in S4 with water, the washing time is 115-130 seconds, to ensure that there is no residue on the surface;

[0039] S6, post-alkali washing, placing the silicon wafer after water washing in S5 in an alkali washing tank, using an alkaline solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 110-130s, and the cleaning temperature is 65-70°C;

[0040] S7, the third water washing, the silicon wafer after the alkali washing in S6 is washed with water, the washing time is 115-130s;

[0041] S8, pickling, placing the silicon wafer after water washing in S7 in a pickling tank, using an acidic solution to clean the residual organic matter of additives on the silicon surface, the cleaning time is 110-130s, the cleaning temperature is 65-70°C, the acidic solution is a mixed solution of HF and HCl; the purpose of pickling: to neutralize the alkali residue and increase the dehydration effect; HCl: neutralizes the alkali residue; removes surface metal ions and forms a water-soluble complex; HF: removes the surface SiO2 layer and forms Si-H passivation bonds, which has a good hydrophobic effect; (the amount of HCl added to the self-replenishing solution cannot be greater than the amount of HF, otherwise the effect will be reversed).

[0042] S9, the fourth water washing, washing the silicon wafer after the acid washing in S8 with water, the washing time is 115-130s;

[0043] S10, slow pulling, placing the silicon wafer washed in S9 into the slow pulling tank in the texturing equipment, the slow pulling time is 10-20 seconds, and the temperature is 60-80°C;

[0044] S11, drying, drying the silicon wafer after being pulled in S10, dividing the silicon wafer into multiple portions, and placing the multiple portions of silicon wafers in different drying tanks for drying after placement;

[0045] S12, unloading, unloading and placing the dried silicon wafers.

[0046] Preferably, the texturing equipment is placed in an environment with an FFU filtration system for use.

[0047] Preferably, deionized water is used in the pre-cleaning, wherein the deionized water comprises 3-5% NAOH and 10-15% hydrogen peroxide.

[0048] Preferably, a plurality of ultrasonic oscillating devices are provided in the texturing equipment, and the plurality of ultrasonic oscillating devices are respectively arranged in the cleaning tank, the texturing tank, the alkaline washing tank and the acid washing tank, with an ultrasonic power of 100-120W and a frequency of 40-65kHZ.

[0049] Preferably, the alkali washing solution in the post-alkali washing is sodium hydroxide or potassium hydroxide (KOH) mixed with isopropyl alcohol (IPA) and an additive, and the additive can be NaClO3.

[0050] Preferably, in the third water washing, the surface of the silicon wafer is rounded by an acid solution containing ozone after water washing.

[0051] Preferably, the ozone concentration in the acid solution is 50 PPM-90 PPM, the hydrofluoric acid concentration is 2%-5%, the hydrochloric acid concentration is 0.05%-0.45%, and the balance is deionized water. The temperature of the mixed solution is 66° C.-68° C., and the reaction time is 100s-120s.

[0052] Preferably, the texturing solvent used in the texturing operation of S4 is water, alkali and a texturing additive, and the volume ratio of the water, the alkali and the texturing additive is 3600:(40-45):(18-20).

[0053] Preferably, a stirring device or a bubbling device is provided in the texturing tank.

[0054] Preferably, the texturing additive is a mixed solvent of sodium silicate and isopropyl alcohol.

[0055] Example 1

[0056] A method for improving the dirty appearance of velveting blanks, comprising the following steps:

[0057] S1, loading, placing the silicon wafer into the texturing equipment and preparing for texturing;

[0058] S2. Pre-cleaning: Place the silicon wafer in multiple cleaning tanks in the texturing equipment for pre-cleaning. The texturing equipment is placed in an environment with an FFU filtration system. The cleaning time is 120 seconds and the cleaning temperature is 68°C. The texturing equipment is equipped with multiple ultrasonic oscillators, which are respectively arranged in the cleaning tank, texturing tank, alkaline cleaning tank and acid cleaning tank. The ultrasonic power is 110W and the frequency is 60kHZ. The purpose of silicon wafer pretreatment is to remove the mechanical damage layer, oxides and pollutants (such as grease and metal ions) on the surface of the silicon wafer. Key parameters include temperature (62-65°C), alkali concentration (5%) and hydrogen peroxide concentration (15%).

[0059] S3, the first water washing, using deionized water containing 3% NAOH and 10% hydrogen peroxide to wash the silicon wafers after the pre-cleaning in S2, the washing time is 120s;

[0060] S4, texturing, placing the silicon wafers that have completed water washing in S3 into the texturing tank of the texturing equipment, wherein there is more than one texturing tank, and the silicon wafers are evenly placed in the more than one texturing tank; purpose of texturing: to form a uniform velvet structure (pyramid or hole morphology) on the surface of the silicon wafer to reduce the light reflectivity; process type: alkaline texturing (single crystal silicon), solution: sodium hydroxide (NaOH) or potassium hydroxide (KOH) mixed with isopropyl alcohol (IPA) and additives (such as NaClO3).

[0061] Reaction principle: anisotropic corrosion, forming a pyramid structure (typical size 1-3μm), key equipment: constant temperature texturing tank (with stirring or bubbling device), acid and alkali resistant materials (such as PVDF or PTFE),

[0062] S5, the second water washing, washing the silicon wafer after the texturing in S4 with water, the washing time is 120 seconds, to ensure that there is no residue on the surface;

[0063] S6, post-alkali washing, placing the silicon wafer after water washing in S5 in an alkali washing tank, using an alkaline solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 120s, and the cleaning temperature is 68°C;

[0064] S7, a third water wash, washing the silicon wafer after the alkali wash in S6 with water for 120 seconds, and then performing a rounding treatment on the surface of the silicon wafer with an acid solution containing ozone;

[0065] S8, pickling, placing the silicon wafer after water washing in S7 in a pickling tank, using an acidic solution to clean the residual organic matter of additives on the silicon surface, the cleaning time is 120s, the cleaning temperature is 68°C, and the acidic solution is a mixed solution of HF and HCl; the purpose of pickling is to neutralize the alkali residue and increase the dehydration effect; HCl: neutralizes the alkali residue; removes the surface metal ions and forms a water-soluble complex; HF: removes the surface SiO2 layer and forms Si-H passivation bonds, which has a good hydrophobic effect; (the amount of HCl in the self-replenishing solution cannot be greater than the amount of HF, otherwise the effect will be reversed).

[0066] S9, the fourth water washing, washing the silicon wafer after the acid washing in S8 with water, the washing time is 120s;

[0067] S10, slow pulling, placing the silicon wafer washed in S9 into the slow pulling tank in the texturing equipment, the slow pulling time is 10 seconds, and the temperature is 68°C;

[0068] S11, drying, drying the silicon wafer after being pulled in S10, dividing the silicon wafer into multiple portions, and placing the multiple portions of silicon wafers in different drying tanks for drying after placement;

[0069] S12, unloading, unloading and placing the dried silicon wafers.

[0070] Example 2

[0071] A method for improving the dirty appearance of velveting blanks, comprising the following steps:

[0072] S1, loading, placing the silicon wafer into the texturing equipment and preparing for texturing;

[0073] S2. Pre-cleaning: Place the silicon wafer in multiple cleaning tanks in the texturing equipment for pre-cleaning. The texturing equipment is placed in an environment with an FFU filtration system. The cleaning time is 120 seconds and the cleaning temperature is 68°C. The texturing equipment is equipped with multiple ultrasonic oscillators, which are respectively arranged in the cleaning tank, texturing tank, alkaline cleaning tank and acid cleaning tank. The ultrasonic power is 110W and the frequency is 60kHZ. The purpose of silicon wafer pretreatment is to remove the mechanical damage layer, oxides and pollutants (such as grease and metal ions) on the surface of the silicon wafer. The key parameters are: temperature (62°C), alkali concentration (5%), and hydrogen peroxide concentration (15%).

[0074] S3, the first water washing, using deionized water containing 3% NAOH and 10% hydrogen peroxide to wash the silicon wafers after the pre-cleaning in S2, the washing time is 120s;

[0075] S4, texturing, placing the silicon wafers that have completed water washing in S3 into the texturing tank of the texturing equipment, wherein there is more than one texturing tank, and the silicon wafers are evenly placed in the more than one texturing tank; purpose of texturing: to form a uniform velvet structure (pyramid or hole morphology) on the surface of the silicon wafer to reduce the light reflectivity; process type: alkaline texturing (single crystal silicon), solution: sodium hydroxide (NaOH) or potassium hydroxide (KOH) mixed with isopropyl alcohol (IPA) and additives (such as NaClO3).

[0076] Reaction principle: Anisotropic corrosion to form a pyramid structure (typical size 1-3μm). Key equipment: constant temperature texturing tank (with stirring or bubbling device), acid and alkali resistant materials (such as PVDF or PTFE). The texturing solvents used in the S4 texturing operation are water, alkali and texturing additives. The volume ratio of the water, the alkali and the texturing additive is 3600: (40-45): (18-20); the texturing additive is a mixed solvent of sodium silicate and isopropyl alcohol.

[0077] S5, the second water washing, washing the silicon wafer after the texturing in S4 with water, the washing time is 120 seconds, to ensure that there is no residue on the surface;

[0078] S6, post-alkali washing, placing the silicon wafer after water washing in S5 in an alkali washing tank, using an alkaline solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 120s, and the cleaning temperature is 68°C;

[0079] S7, a third water wash, washing the silicon wafer after the alkali wash in S6 with water for 120 seconds, and then performing a rounding treatment on the surface of the silicon wafer with an acid solution containing ozone;

[0080] S8, pickling, placing the silicon wafer after water washing in S7 in a pickling tank, using an acidic solution to clean the residual organic matter of additives on the silicon surface, the cleaning time is 120s, the cleaning temperature is 68°C, the acidic solution is a mixed solution of HF and HCl; the purpose of pickling: to neutralize alkali residues and increase the dehydration effect; HCl: neutralizes alkali residues; removes surface metal ions to form water-soluble complexes; HF: removes the surface SiO2 layer to form Si-H passivation bonds, which has a good hydrophobic effect; (the amount of HCl added cannot be greater than the amount of HF, otherwise the effect will be reversed), the ozone concentration in the acid solution is 50PPM, the hydrofluoric acid concentration is 2%, the hydrochloric acid concentration is 0.05%, and the balance is deionized water. The temperature of the mixed solution is 66°C, and the reaction time is 100s.

[0081] S9, the fourth water washing, washing the silicon wafer after the acid washing in S8 with water, the washing time is 120s;

[0082] S10, slow pulling, placing the silicon wafer washed in S9 into the slow pulling tank in the texturing equipment, the slow pulling time is 10 seconds, and the temperature is 68°C;

[0083] S11, drying, drying the silicon wafer after being pulled in S10, dividing the silicon wafer into multiple portions, and placing the multiple portions of silicon wafers in different drying tanks for drying after placement;

[0084] S12, unloading, unloading and placing the dried silicon wafers.

[0085] Example 3

[0086] A method for improving the dirty appearance of velveting blanks, comprising the following steps:

[0087] S1, loading, placing the silicon wafer into the texturing equipment and preparing for texturing;

[0088] S2. Pre-cleaning: Place the silicon wafer in multiple cleaning tanks in the texturing equipment for pre-cleaning. The texturing equipment is placed in an environment with an FFU filtration system. The cleaning time is 120 seconds and the cleaning temperature is 68°C. The texturing equipment is equipped with multiple ultrasonic oscillators, which are respectively arranged in the cleaning tank, texturing tank, alkaline cleaning tank and acid cleaning tank. The ultrasonic power is 110W and the frequency is 60kHZ. The purpose of silicon wafer pretreatment is to remove the mechanical damage layer, oxides and pollutants (such as grease and metal ions) on the surface of the silicon wafer. The key parameters are: temperature (72°C), alkali concentration (5%) and hydrogen peroxide concentration (12%).

[0089] S3, the first water washing, using deionized water containing 3% NAOH and 10% hydrogen peroxide to wash the silicon wafers after the pre-cleaning in S2, the washing time is 120s;

[0090] S4, texturing, placing the silicon wafers that have completed water washing in S3 into the texturing tank of the texturing equipment, wherein there is more than one texturing tank, and the silicon wafers are evenly placed in the more than one texturing tank; purpose of texturing: to form a uniform velvet structure (pyramid or hole morphology) on the surface of the silicon wafer to reduce the light reflectivity; process type: alkaline texturing (single crystal silicon), solution: potassium hydroxide (KOH) mixed with isopropyl alcohol (IPA) and additives (such as NaClO3).

[0091] Reaction principle: Anisotropic corrosion to form a pyramid structure (typical size 1-3μm). Key equipment: constant temperature texturing tank (with stirring or bubbling device), acid and alkali resistant materials (such as PVDF or PTFE). The texturing solvent used in the S4 texturing operation is water, alkali and texturing additives. The volume ratio of water, alkali and texturing additives is 3600:42:19; the texturing additive is a mixed solvent of sodium silicate and isopropyl alcohol.

[0092] S5, the second water washing, washing the silicon wafer after the texturing in S4 with water, the washing time is 120 seconds, to ensure that there is no residue on the surface;

[0093] S6, post-alkali washing, placing the silicon wafer after water washing in S5 in an alkali washing tank, using an alkaline solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 120s, and the cleaning temperature is 68°C;

[0094] S7, a third water wash, washing the silicon wafer after the alkali wash in S6 with water for 120 seconds, and then performing a rounding treatment on the surface of the silicon wafer with an acid solution containing ozone;

[0095] S8, pickling, placing the silicon wafer after water washing in S7 in a pickling tank, using an acidic solution to clean the residual organic matter of additives on the silicon surface, the cleaning time is 120s, the cleaning temperature is 68°C, the acidic solution is a mixed solution of HF and HCl; the purpose of pickling: to neutralize alkali residues and increase the dehydration effect; HCl: neutralizes alkali residues; removes surface metal ions to form water-soluble complexes; HF: removes the surface SiO2 layer to form Si-H passivation bonds, which has a good hydrophobic effect; (the amount of HCl added cannot be greater than the amount of HF, otherwise the effect will be reversed), the ozone concentration in the acid solution is 90PPM, the hydrofluoric acid concentration is 5%, the hydrochloric acid concentration is 0.45%, and the balance is deionized water. The temperature of the mixed solution is 68°C, and the reaction time is 120s.

[0096] S9, the fourth water washing, washing the silicon wafer after the acid washing in S8 with water, the washing time is 120s;

[0097] S10, slow pulling, placing the silicon wafer washed in S9 into the slow pulling tank in the texturing equipment, the slow pulling time is 10 seconds, and the temperature is 68°C;

[0098] S11, drying, drying the silicon wafer after being pulled in S10, dividing the silicon wafer into multiple portions, and placing the multiple portions of silicon wafers in different drying tanks for drying after placement;

[0099] S12, unloading, unloading and placing the dried silicon wafers.

[0100] Comparative Example 1

[0101] A method for improving the dirty appearance of velveting blanks is provided. The method is different from Example 1 in that S5 is not included, and the rest is the same as Example 1.

[0102] Comparative Example 2

[0103] A method for improving the dirty appearance of velveting blanks is provided. The method is different from Example 1 in that S7 is not included, and the rest is the same as Example 1.

[0104] Comparative Example 3

[0105] A method for improving the dirty appearance of velveting blanks is provided. The method is different from Example 1 in that S9 is not included, and the rest is the same as Example 1.

[0106] Comparative Example 4

[0107] A method for improving the dirty appearance of texturing blanks is provided. The method is different from Example 1 in that the texturing equipment is not placed in an environment with an FFU filtration system, and the rest is the same as Example 1.

[0108] Table 1 shows the performance test results of the solar cells obtained in Examples 1-3 and Comparative Examples 1-4

[0109]

[0110] In summary, after the contamination is improved, the electrical performance (such as conversion efficiency, open circuit voltage, fill factor) and EL yield of TOPCon cells are significantly improved. The core reasons are reduced surface recombination, enhanced passivation effect and reduced defects.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for improving the appearance of dirty velvet blanks, characterized in that: The steps include: S1, loading, placing the silicon wafer into the texturing equipment and preparing for texturing; S2, pre-cleaning, placing the silicon wafer in multiple cleaning tanks in the texturing equipment for pre-cleaning treatment, the cleaning time is 210-230 seconds, and the cleaning temperature is 65-72°C; S3, the first water washing, washing the silicon wafer after the pre-cleaning in S2 with water, the washing time is 115-130s; S4, texturing, placing the silicon wafers washed in S3 into a texturing tank of a texturing equipment, wherein there is more than one texturing tank, and the silicon wafers are evenly placed in the more than one texturing tank; S5, second water washing, washing the silicon wafer after texturing in S4, the washing time is 115-130s; S6, post-alkali washing, placing the silicon wafer after water washing in S5 in an alkali washing tank, using an alkaline solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 110-130s, and the cleaning temperature is 65-70°C; S7, the third water washing, the silicon wafer after the alkali washing in S6 is washed with water, the washing time is 115-130s; S8, pickling, placing the silicon wafer after water washing in S7 in a pickling tank, using an acidic solution to clean the additive residual organic matter on the silicon surface, the cleaning time is 110-130 seconds, the cleaning temperature is 65-70°C, and the acidic solution is a mixed solution of HF and HCl; S9, the fourth water washing, washing the silicon wafer after the acid washing in S8 with water, the washing time is 115-130s; S10, slow pulling, placing the silicon wafer washed in S9 into the slow pulling tank in the texturing equipment, the slow pulling time is 10-20 seconds, and the temperature is 60-80°C; S11, drying, drying the silicon wafer after being pulled in S10, dividing the silicon wafer into multiple portions, and placing the multiple portions of silicon wafers in different drying tanks for drying after placement; S12, unloading, unloading and placing the dried silicon wafers.

2. The method for improving the dirty appearance of velvet blanks according to claim 1, characterized in that: The texturing equipment is placed in an environment with an FFU filtering system for use.

3. The method for improving the appearance of dirty velvet blanks according to claim 1, characterized in that: Deionized water is used in the pre-cleaning, and the deionized water contains 3-5% NAOH and 10-15% hydrogen peroxide.

4. The method for improving the appearance of dirty velvet blanks according to claim 1, characterized in that: The texturing equipment is provided with a plurality of ultrasonic oscillating devices, which are respectively arranged in the cleaning tank, the texturing tank, the alkaline washing tank and the acid washing tank. The ultrasonic power is 100-120W and the frequency is 40-65kHZ.

5. The method for improving the appearance of dirty velvet blanks according to claim 1, characterized in that: The alkali washing solution in the post-alkali washing is sodium hydroxide or potassium hydroxide mixed with isopropyl alcohol and additives.

6. The method for improving the appearance of dirty velvet blanks according to claim 1, characterized in that: In the third water washing, after the water washing, the surface of the silicon wafer is rounded by an acid solution containing ozone.

7. The method for improving the appearance of dirty velvet blanks according to claim 6, characterized in that: The acid solution contains ozone at a concentration of 50 PPM to 90 PPM, hydrofluoric acid at a concentration of 2% to 5%, hydrochloric acid at a concentration of 0.05% to 0.45%, and deionized water as the balance. The temperature of the mixed solution is 66° C. to 68° C., and the reaction time is 100 s to 120 s.

8. The method for improving the dirty appearance of velvet blanks according to claim 1, characterized in that: The texturing solvents used in the texturing operation of S4 are water, alkali and a texturing additive, and the volume ratio of the water, the alkali and the texturing additive is 3600:(40-45):(18-20).

9. The method for improving the appearance of dirty velvet blanks according to claim 1, characterized in that: The texturing tank is provided with a stirring device or a bubbling device.

10. The method for improving the appearance of dirty velvet blanks according to claim 8, characterized in that: The texturing additive is a mixed solvent of sodium silicate and isopropyl alcohol.

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