A method for preparing a pyramid bottom rounded structure on the surface of single crystal silicon

Abstract

The invention discloses a method for preparing a pyramid bottom rounded structure on the surface of monocrystalline silicon, and relates to the field of production of monocrystalline silicon solar cell wafers, comprising the following steps: (1) texturing: adding alkali solution, texturing additive and water into a texturing tank in a certain proportion, heating to a certain temperature, placing a silicon wafer into the texturing tank for reaction for a certain period of time, and then taking it out and washing it with pure water; (2) bottom rounding treatment: adding alkali solution, bottom rounding liquid and water into a rounding tank in a certain proportion, heating to a certain temperature, and then placing the silicon wafer into the rounding tank for reaction for a certain period of time to obtain a monocrystalline silicon wafer with a pyramid bottom rounded structure; (3) washing: washing the silicon wafer with pure water; (4) drying: drying the silicon wafer with hot clean air with nitrogen; the invention adopts a combination of alkali solution and bottom rounding liquid to replace the existing nitric acid hydrofluoric acid CP and ozone hydrofluoric acid CP, which is safer, more environmentally friendly and has lower cost.

Description

Technical Field

[0001] The present invention relates to the field of production of monocrystalline silicon solar cells, and in particular to a method for preparing a monocrystalline silicon surface pyramid bottom rounded structure. Background Art

[0002] In the production process of traditional monocrystalline silicon solar cells, the first step is texturing and cleaning, that is, the surface of the silicon wafer is etched by wet chemical etching to form a velvet structure with a pyramid structure, and the sunlight is reflected multiple times on the surface of the pyramid structure, thereby reducing the escape of light and increasing the absorption rate of sunlight, thereby increasing the current density of the solar cell and ultimately improving the photoelectric conversion efficiency of the solar cell; this structure is mainly formed by the principle of anisotropic corrosion of silicon by alkali.

[0003] However, for the new heterojunction (HJT) solar cells, due to their unique cell structure, a certain thickness of hydrogenated intrinsic amorphous silicon layer needs to be symmetrically deposited on the velvet surface on both sides of the silicon wafer. a-Si:H", this thin film layer can effectively passivate the silicon wafer and greatly reduce the carrier recombination rate. Therefore, for the manufacture of HJT cells, not only is it required that the pyramid velvet surface generated by the silicon wafer has a low reflectivity, but there are also special requirements for the microstructure of the pyramid surface; if the bottom of the pyramid between the pyramids is too sharp, it will lead to a-Si:H grows unevenly, and at these locations a-Si:H is prone to produce defective states during the growth process, or uneven deposition at the sharp end of the tower bottom, which affects the coating quality and leads to The passivation quality of a-Si:H is reduced, the carrier lifetime is reduced, and the battery efficiency is also reduced accordingly. Therefore, before the amorphous silicon deposition, the bottom of the pyramid needs to be rounded to facilitate the deposition of amorphous silicon film and improve the passivation quality.

[0004] In the process of texturing heterojunction solar cells, the pyramid morphology is processed by chemical polishing (CP), which includes nitric acid CP and ozone CP. The basic principle of both methods is "oxidation before etching". Nitric acid CP uses a mixed solution of nitric acid and hydrofluoric acid to etch the texturing silicon wafer. The strong oxidizing nitric acid oxidizes silicon into silicon oxide SiOx, and hydrofluoric acid dissolves it. The oxidation and dissolution process is repeated, thereby gradually etching the silicon wafer and the pyramid is gradually smoothed. The etching principle of ozone CP is similar to that of nitric acid CP, except that ozone is used instead of nitric acid as the oxidant.

[0005] The existing CP treatment method in the texturing process of heterojunction solar cells has the following disadvantages: nitric acid CP requires a large amount of nitric acid and hydrofluoric acid, and the reaction conditions are harsh and need to be kept at a low temperature (below 10°C) to achieve a good effect. At the same time, the use of a large amount of strong oxidizing acid and strong corrosive acid greatly increases the danger of the process and increases the cost of wastewater treatment; therefore, both in terms of safety and environmental protection, nitric acid CP is in urgent need of replacement. Ozone CP requires ozone and hydrofluoric acid. The use of ozone will affect the environment of the entire tank texturing machine. Ozone overflow will increase the ozone concentration in the texturing machine, which will seriously affect the texturing effect of the entire texturing machine, resulting in an abnormal increase in the reflectivity of the silicon wafer after texturing and unstable process. At the same time, the use of ozone requires an ozone machine, which requires high-frequency and high-voltage discharge to work, requires a large amount of electricity and is very dangerous, so it is not an ideal process. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a rounded structure of the bottom of a pyramid on the surface of a single crystal silicon wafer, so that the bottom of the velvet pyramid formed on the single crystal silicon wafer is more rounded while the top of the pyramid remains unchanged, and the passivation quality of the amorphous silicon film layer of the heterojunction battery is improved without greatly affecting the reflectivity, thereby improving the current density and battery efficiency of the battery.

[0007] To achieve the purpose of the present invention, the present invention is implemented by the following technical solutions:

[0008] A method for preparing a monocrystalline silicon surface pyramid bottom rounded structure comprises the following steps:

[0009] (1) Velvet making

[0010] Alkaline solution, texturing additives and water are added into the texturing tank in a certain proportion, heated to a certain temperature, and then the silicon wafer is placed into the texturing tank for a certain reaction time, and then taken out and washed with pure water;

[0011] (2) Rounding treatment of the bottom of the tower

[0012] Alkaline solution, bottom rounding liquid and water are added into the rounding tank in proportion, and after heating to a certain temperature, the silicon wafer treated in step (1) is placed into the rounding tank for reaction for a certain period of time to obtain a single crystal silicon wafer with a pyramid bottom rounding structure;

[0013] (3) Washing

[0014] Wash the silicon wafer after the treatment in step (2) with pure water;

[0015] (4) Drying

[0016] The silicon wafer treated in step (3) is dried using hot clean air with nitrogen.

[0017] Further settings are as follows:

[0018] Preferably, in steps (1) and (2), the alkali solution is one or more of sodium hydroxide, potassium hydroxide, ammonia water, and TMAH.

[0019] Preferably, in step (1), the texturing tank needs to be heated to 70-90°C and maintained at this temperature; the silicon wafer reacts in the texturing tank for 5-8 minutes and is washed with pure water for 2-5 minutes after texturing.

[0020] Preferably, in the texturing tank of step (1), the content of the texturing additive is 0.3-0.6% and the content of the alkali solution is 0.5-5% based on the total volume of the solution.

[0021] Preferably, in step (2), the bottom rounding liquid of the tower is a combination of one or more cationic surfactants such as polyquaternium-16, cationic guar gum, and sorbic acid.

[0022] Particularly preferably, the bottom rounded liquid is configured according to the following composition in weight percentage: 0.01-0.15% of polyquaternium-16, 0.1-2.0% of cationic guar gum, 0.5-3.0% of sorbic acid, and the balance is water.

[0023] Preferably, in the rounding tank of step (2), the content of the alkali solution is 0.2-2.5% based on the total volume of the solution; and the content of the rounding liquid at the bottom of the tower is 0.1-0.5%.

[0024] Preferably, in the rounding treatment of the bottom of the tower in step (2), the reaction temperature of the silicon wafer in the rounding tank is 10-60° C. and the reaction time is 1-6 min.

[0025] Preferably, the washing time with pure water in step (3) is 2-6 minutes, and the circulating bubbling is turned on at the same time.

[0026] Preferably, nitrogen must be introduced during the drying process in step (4) to ensure that the silicon wafer will not be oxidized by hot air and to ensure effective passivation of the subsequently deposited hydrogenated amorphous silicon thin film layer.

[0027] Preferably, in step (4), the drying temperature is 50-80° C. and the drying time is 6-15 min.

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

[0029] The present invention adopts a combination of alkaline solution and bottom rounding liquid to replace the existing nitric acid hydrofluoric acid CP and ozone hydrofluoric acid CP, and obtains a single crystal silicon wafer with a surface pyramid bottom rounding structure. The method has simple process control, is safer, and is more environmentally friendly. At the same time, because the rounding liquid is highly hydrophilic and easy to clean, the traditional pickling process can be omitted, and it has great compatibility with the existing machine tank body, does not need to be modified, and has lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an SEM image of the pyramid structure of the single crystal silicon wafer prepared in Example 1 after normal alkali texturing.

[0031] Figure 2 This is an SEM image of the pyramid bottom rounded structure after the normal bottom rounded treatment prepared in Example 2.

[0032] Figure 3 This is an SEM picture of the rounded structure of the pyramid base after the rounding treatment in Example 9 after increasing the alkali solution concentration, temperature and time.

[0033] Figure 4 This is an SEM image of the rounded structure at the bottom of the pyramid after increasing the rounding treatment time in Example 10. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings and preferred embodiments of the specification. Of course, the embodiments of the present invention involved in the following description are usually only part of the embodiments of the present invention, rather than all of the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] In the following examples, unless otherwise defined, all materials are known or commercially available.

[0036] In the embodiment of the present invention, the silicon wafer used is an externally purchased A-grade M10-sized gallium-doped P-type silicon wafer with a thickness of 150-10+20 μm.

[0037] In the embodiment of the present invention, the alkali solution is commercially available KOH with a concentration of 45%.

[0038] In the embodiment of the present invention, the texturing additive is not particularly limited, and a texturing additive with an existing typical formula may be used, or any existing commercially available texturing additive may be purchased, for example, the texturing additive produced by Shaoxing Guizhang New Energy Technology Co., Ltd.

[0039] In the embodiment of the present invention, the bottom rounding liquid is configured according to the following composition in weight percentage: 0.1% of polyquaternium-16, 1% of cationic guar gum, 2% of sorbic acid, and the balance is pure water.

[0040] In the embodiment of the present invention, the formula of the texturing solution and the rounding bath solution has the following content percentage of each component: mass of component g / total volume of solution ml×100%.

[0041] Example 1

[0042] Step 1: Velveting

[0043] In a 45L texturing tank, prepare 40L of texturing liquid, heat the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes before taking it out.

[0044] The formula of the velvet liquid is as follows:

[0045] Lye 2.5%

[0046] Texturing additive 0.5%

[0047] The balance is pure water.

[0048] Step 2: Wash

[0049] The silicon wafer was washed with pure water for 2 minutes.

[0050] Step 3: Drying

[0051] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0052] The dried silicon wafer was taken out for SEM testing, and the SEM images were as follows Figure 1 shown.

[0053] Example 2

[0054] Step 1: Velveting

[0055] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0056] The formula of the velvet liquid is as follows:

[0057] Lye 2.5%

[0058] Texturing additive 0.5%

[0059] The balance is pure water.

[0060] Step 2: Rounding the bottom of the tower

[0061] Prepare 40L of rounding tank solution, heat the tank solution to 30°C, and place the silicon wafer treated in step 1 into the rounding tank to react for 60 seconds.

[0062] The formula of rounding tank liquid is as follows:

[0063] Lye 0.25%

[0064] 0.25% of the rounded liquid at the bottom of the tower

[0065] The balance is pure water.

[0066] Step 3: Wash

[0067] Take out the silicon wafer treated in step 2, and wash the silicon wafer with pure water for 2 minutes;

[0068] Step 4: Drying

[0069] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0070] The dried silicon wafer was taken out for SEM testing, and the SEM images were as follows Figure 2 shown.

[0071] Example 3

[0072] Step 1: Velveting

[0073] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0074] The formula of the velvet liquid is as follows:

[0075] Lye 2.5%

[0076] Texturing additive 0.5%

[0077] The balance is pure water.

[0078] Step 2: Rounding the bottom of the tower

[0079] Prepare 40L of rounding tank solution, heat the tank solution to 45°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 90 seconds.

[0080] The formula of rounding tank liquid is as follows:

[0081] Lye 0.25%

[0082] 0.25% of the rounded liquid at the bottom of the tower

[0083] The balance is pure water.

[0084] Step 3: Wash

[0085] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0086] Step 4: Drying

[0087] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes;

[0088] Example 4

[0089] Step 1: Velveting

[0090] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0091] The formula of the velvet liquid is as follows:

[0092] Lye 2.5%

[0093] Texturing additive 0.5%

[0094] The balance is pure water.

[0095] Step 2: Rounding the bottom of the tower

[0096] Prepare 40L of rounding tank liquid, heat the tank liquid to 60°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 120 seconds.

[0097] The formula of rounding tank liquid is as follows:

[0098] Lye 0.25%

[0099] 0.25% of the rounded liquid at the bottom of the tower

[0100] The balance is pure water.

[0101] Step 3: Wash

[0102] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0103] Step 4: Drying

[0104] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0105] Example 5

[0106] Step 1: Velveting

[0107] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0108] The formula of the velvet liquid is as follows:

[0109] Lye 2.5%

[0110] Texturing additive 0.5%

[0111] The balance is pure water.

[0112] Step 2: Rounding the bottom of the tower

[0113] Prepare 40L of rounding tank solution, heat the tank solution to 30°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 90 seconds.

[0114] The formula of rounding tank liquid is as follows:

[0115] Lye 0.35%

[0116] 0.25% of the rounded liquid at the bottom of the tower

[0117] The balance is pure water.

[0118] Step 3: Wash

[0119] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0120] Step 4: Drying

[0121] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0122] Example 6

[0123] Step 1: Velveting

[0124] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0125] The formula of the velvet liquid is as follows:

[0126] Lye 2.5%

[0127] Texturing additive 0.5%

[0128] The balance is pure water.

[0129] Step 2: Rounding the bottom of the tower

[0130] Prepare 40L of rounding tank solution, heat the tank solution to 45°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 120 seconds;

[0131] The formula of rounding tank liquid is as follows:

[0132] Lye 0.35%

[0133] 0.25% of the rounded liquid at the bottom of the tower

[0134] The balance is pure water.

[0135] Step 3: Wash

[0136] Take out the silicon wafer treated in the previous step and wash it with pure water for 2 minutes;

[0137] Step 4: Drying: Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0138] Example 7

[0139] Step 1: Velveting

[0140] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0141] The formula of the velvet liquid is as follows:

[0142] Lye 2.5%

[0143] Texturing additive 0.5%

[0144] The balance is pure water.

[0145] Step 2: Rounding the bottom of the tower

[0146] Prepare 40L of rounding tank liquid, heat the tank liquid to 60°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 60 seconds.

[0147] The formula of rounding tank liquid is as follows:

[0148] Lye 0.35%

[0149] 0.25% of the rounded liquid at the bottom of the tower

[0150] The balance is pure water.

[0151] Step 3: Wash

[0152] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0153] Step 4: Drying

[0154] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0155] Example 8

[0156] Step 1: Velveting

[0157] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0158] The formula of the velvet liquid is as follows:

[0159] Lye 2.5%

[0160] Texturing additive 0.5%

[0161] The balance is pure water.

[0162] Step 2: Rounding the bottom of the tower

[0163] Prepare 40L of rounding tank solution, heat the tank solution to 30°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 120 seconds.

[0164] The formula of rounding tank liquid is as follows:

[0165] Lye 0.45%

[0166] 0.25% of the rounded liquid at the bottom of the tower

[0167] The balance is pure water.

[0168] Step 3: Wash

[0169] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0170] Step 4: Drying

[0171] The silicon wafer was placed in a hot clean air (65°C) drying tank filled with nitrogen and dried for 12 minutes.

[0172] Example 9

[0173] Step 1: Velveting

[0174] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0175] The formula of the velvet liquid is as follows:

[0176] Lye 2.5%

[0177] Texturing additive 0.5%

[0178] The balance is pure water.

[0179] Step 2: Rounding the bottom of the tower

[0180] Prepare 40L of rounding tank liquid, heat the tank liquid to 45°C, and then put the silicon wafer treated in the previous step into the rounding tank to react for 60 seconds.

[0181] The formula of rounding tank liquid is as follows:

[0182] Lye 0.45%

[0183] 0.25% of the rounded liquid at the bottom of the tower

[0184] The balance is pure water.

[0185] Step 3: Wash

[0186] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0187] Step 4: Drying

[0188] Place the silicon wafer in a hot clean air (65°C) drying tank filled with nitrogen and dry it for 12 minutes.

[0189] The dried silicon wafer was taken out for SEM testing, and the SEM images were as follows Figure 3 shown.

[0190] Example 10

[0191] Step 1: Velveting

[0192] In a 45L texturing tank, prepare 40L of texturing liquid. After heating the texturing liquid to 82°C, put the silicon wafer into the texturing tank and react for 6 minutes, then take it out and wash the silicon wafer with pure water for 2 minutes.

[0193] The formula of the velvet liquid is as follows:

[0194] Lye 2.5%

[0195] Texturing additive 0.5%

[0196] The balance is pure water.

[0197] Step 2: Rounding the bottom of the tower

[0198] Prepare 40L of rounding tank liquid, heat the tank liquid to 60°C, and place the silicon wafer treated in the previous step into the rounding tank to react for 90 seconds.

[0199] The formula of rounding tank liquid is as follows:

[0200] Lye 0.45%

[0201] 0.25% of the rounded liquid at the bottom of the tower

[0202] The balance is pure water.

[0203] Step 3: Wash

[0204] After taking out the silicon wafer processed in the previous step, wash the silicon wafer with pure water for 2 minutes.

[0205] Step 4: Drying

[0206] The silicon wafer was placed in a hot clean air (65°C) drying tank filled with nitrogen and dried for 12 minutes.

[0207] The dried silicon wafer was taken out for SEM testing, and the SEM images were as follows Figure 4 shown.

[0208] Structure confirmation:

[0209] like Figure 1 to Figure 4 As shown, Figure 1 This is a SEM picture of the pyramid structure of the single crystal silicon wafer prepared in Example 1 after normal alkali texturing. Figure 2 This is a SEM image of the pyramid bottom rounded structure after normal bottom rounding treatment prepared in Example 2. Figure 3 This is a SEM picture of the rounded structure of the pyramid bottom after the alkali solution concentration and temperature were increased in Example 9; Figure 4 This is an SEM image of the rounded structure of the pyramid base after increasing the alkali solution concentration, temperature and rounding treatment time in Example 10.

[0210] First, compare Figure 1 and Figure 2 It can be seen that after the rounding treatment in step (2) of the present invention, the bottom part of the pyramid has a rounded structure. Figure 2 and Figure 3 , after increasing the alkali concentration and reaction temperature, it is obvious that the roundness of the bottom of the tower is greater; Figure 3 and Figure 4 , further increasing the alkali solution concentration, reaction temperature and reaction time, the roundness of the tower bottom is further enhanced; it can be seen from the above figure that the method of the present invention can achieve different degrees of roundness of the tower bottom.

[0211] Performance Testing:

[0212] The silicon wafers prepared in Examples 1-10 were subjected to weight loss and reflectivity tests, wherein: the weight loss was measured using an electronic analytical balance, and the reflectivity was measured using a D8 reflectivity meter. The test results are shown in Table 1.

[0213] Table 1

[0214]

[0215] analyze:

[0216] (1) It can be seen from the above examples that the method of the present invention has a larger process adjustment window than the existing CP process, and the desired structure can be obtained under relatively mild reaction conditions, such as Example 2; the reason for this is that the rounding liquid at the bottom of the pyramid is selectively adsorbed on the top of the pyramid, and at the same time greatly weakens the reaction rate of the alkali and silicon, so that the etching of silicon by the alkali is transformed from anisotropic etching to isotropic etching, so that the bottom of the pyramid can react slowly with the alkali solution, and finally a rounded structure of the bottom of the pyramid is formed.

[0217] (2) It is not difficult to see from the above table that the reflectivity of a silicon wafer with a pyramid bottom rounded structure on the surface of a single crystal silicon obtained by the process of the present invention is positively correlated with the alkali concentration, reaction temperature and reaction time. Specifically: By comparing Example 4, Example 6 and Example 8, it can be seen that the effect of temperature on the rounded degree of the pyramid bottom in step 2 is greater than the effect of alkali concentration on the rounded degree of the pyramid bottom; By comparing Example 4, Example 7 and Example 10, it can be seen that the effect of alkali concentration on the rounded degree of the pyramid bottom in step 2 is greater than the effect of reaction time on the rounded degree of the pyramid bottom; In summary, in the reaction conditions of step 2, the degree of influence on the rounded structure of the pyramid bottom is temperature>alkali concentration>reaction time from strong to weak.

Claims

1. A method for preparing a pyramid bottom rounded structure on the surface of single crystal silicon, characterized in that: The steps include: (1) Velvet making Alkaline solution, texturing additives and water are added into the texturing tank in a certain proportion, heated to a certain temperature, and then the silicon wafer is placed into the texturing tank for a certain reaction time, and then taken out and washed with pure water; (2) Rounding of the bottom of the tower Alkaline solution, bottom rounding liquid and water are added into the rounding tank in proportion, and after heating to a certain temperature, the silicon wafer treated in step (1) is placed into the rounding tank for reaction for a certain period of time to obtain a single crystal silicon wafer with a pyramid bottom rounding structure; (3) Washing Wash the silicon wafer after the treatment in step (2) with pure water; (4) Drying The silicon wafer treated in step (3) is dried using hot clean air with nitrogen.

2. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: The alkali solution in steps (1) and (2) is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water and TMAH.

3. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: In step (1), the texturing tank is heated to 70-90°C, the silicon wafer reacts in the texturing tank for 5-8 minutes, and is washed with pure water for 2-5 minutes after texturing.

4. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: In the texturing tank of step (1), the content of the texturing additive is 0.3-0.6% and the content of the alkali solution is 0.5-5% based on the total volume of the solution.

5. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: In the tower bottom rounding treatment in step (2), the tower bottom rounding liquid is selected from one or more combinations of polyquaternium salt-16, cationic guar gum, and sorbic acid.

6. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: The bottom rounded liquid in step (2) is composed of the following components in weight percentage: 0.01-0.15% of polyquaternium-16, 0.1-2.0% of cationic guar gum, 0.5-3.0% of sorbic acid, and the balance is water.

7. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: In the rounding tank of step (2), the content of the alkali solution is 0.2-2.5% based on the total volume of the solution; the content of the rounding liquid at the bottom of the tower is 0.1-0.5%.

8. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: In step (2), the bottom of the tower is subjected to rounding treatment, and the reaction temperature of the silicon wafer in the rounding tank is 10-60° C. and the reaction time is 1-6 min.

9. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: The washing time with pure water in step (3) is 2-6 minutes.

10. The method for preparing a monocrystalline silicon surface pyramid bottom rounded structure according to claim 1, characterized in that: In step (4), the drying temperature is 50-80° C. and the drying time is 6-15 min.

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