Alkali polishing method of crystalline silicon battery piece, single-face polished crystalline silicon battery piece and battery

Abstract

The invention provides an alkali polishing method of a crystalline silicon cell, a single-side polished crystalline silicon cell and a battery, the alkali polishing method comprises the following steps: protecting one side of the crystalline silicon cell, soaking the crystalline silicon cell in an alkali solution with nano bubbles to obtain the single-side polished crystalline silicon cell, and the average size of the nano bubbles is 0.1-45nm. According to the alkali polishing method provided by the invention, the nano-bubbles are introduced into the alkali solution, pollution to the surfaces of chemicals and batteries is avoided, and the nano-bubbles have very high oxidation performance and surface potential and can have a relatively good etching effect on silicon and silicon oxide, so that the alkali concentration in the polishing process can be greatly reduced; therefore, the use amount of alkali is reduced, and the use amount of additives can be greatly reduced; besides, in the alkali polishing method, the alkali solution contains nano bubbles, so that the consumption of chemicals in the subsequent process can be further reduced, and the waste liquid treatment cost is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells and relates to an alkali polishing method for a crystalline silicon cell, in particular to an alkali polishing method for a crystalline silicon cell, a single-sided polished crystalline silicon cell and a battery. Background Art

[0002] During the manufacturing process of solar cells, the front side of the cell usually needs to be processed into a light-trapping velvet surface, so that it can absorb more sunlight to improve conversion efficiency; the back side of the cell usually needs to be processed into a flat surface so that the sunlight that hits the ground can be reflected and pass through the surface passivation material, be absorbed by silicon, and stimulate current, thereby contributing to the photocurrent and efficiency of the cell.

[0003] The industrial cell preparation method uses immersion to obtain a velvet surface on both sides; then after a boron diffusion process, the velvet surface on the front is protected, and the back of the cell is chemically polished with an alkaline solution. Chemical polishing has the function of removing oxides and impurities, reducing defects on the surface of the battery. Sodium hydroxide or potassium hydroxide is usually used as the main etchant, and additives are used to achieve the flatness requirement. In addition, after the cell is doped with phosphorus, the doped polysilicon that is plated also needs to be polished after the oxide layer and the intrinsic amorphous silicon layer are deposited.

[0004] The prior art uses alkali and additives to etch unwanted silicon oxide and doped silicon to obtain the desired structure. In order to obtain a stable etching rate during the process, a high alkali concentration needs to be maintained, so a large amount of alkali and additives will be consumed in the process.

[0005] CN117736736A discloses an alkaline etching additive for texturing the surface of monocrystalline silicon cells. The technical solution includes the following raw materials: 3-5% nucleating agent, 1-2% velvet regulator, 0.1-0.3% defoamer, 0.5-2% pH regulator, 5-8% toughening agent, and the balance of deionized water. The alkaline solution prepared in the document has uniform etching and long service life. At the same time, it reduces the reflectivity of the monocrystalline silicon cell and improves the light absorption of the monocrystalline silicon cell, so that the cell surface can still maintain good toughness when the roughness increases, avoids cracks caused by etching, increases the toughness of the cell, and ensures the performance and service life of the cell.

[0006] CN109285772A discloses a chain back-polishing method for polycrystalline silicon cells, which comprises spraying water on the front side of the diffused polycrystalline silicon cell to form a uniform water film protective layer, contacting the polycrystalline silicon cell with a mixture of hydrofluoric acid and nitric acid to remove the oxide layer around and on the back side of the polycrystalline silicon, contacting the polycrystalline silicon cell after the above treatment with an alkaline solution for corrosion polishing, washing the treated polycrystalline silicon cell with water, and washing the polycrystalline silicon cell after washing with water with an alkali and an acid in turn and drying.

[0007] CN118053934A discloses an alkali polishing process for improving the open voltage of Topcon cells, including pre-cleaning: pre-cleaning the silicon wafer; alkali polishing: polishing the back of the silicon wafer using a mixture of potassium hydroxide and alkali polishing additives; post-cleaning: washing the alkali-polished silicon wafer in a mixed solution of 0.98±0.01wt% hydrogen peroxide, 0.3±0.01wt% sodium hydroxide and pure water; acid washing: acid washing the silicon wafer using a mixed solution of 0.97±0.01wt% hydrochloric acid and pure water. The alkali polishing process improves the post-cleaning and acid washing steps of the existing Topcon cells in the alkali polishing process. The process of the document can improve the back passivation performance of the Topcon cells, thereby achieving the effect of improving the open circuit voltage of the Topcon cells and improving the photoelectric conversion efficiency.

[0008] The alkali polishing methods for crystalline silicon cells disclosed in the prior art all have certain defects, such as high consumption of alkali, high usage of additives, and high consumption of HF required in the subsequent cleaning process. Therefore, it is very important to develop and design a new alkali polishing method for crystalline silicon cells, single-sided polished crystalline silicon cells and batteries. Summary of the invention

[0009] In view of the deficiencies in the prior art, the purpose of the present invention is to provide an alkali polishing method for crystalline silicon cell wafers, a single-sided polished crystalline silicon cell wafer and a battery. In the alkali polishing method provided by the present invention, nanobubbles are introduced into the alkali solution, which will not pollute the chemicals and the battery surface. Since the nano-scale bubbles have very high oxidation performance and surface potential, they can have a good etching effect on silicon and silicon oxide, so that the alkali concentration in the polishing process can be greatly reduced, thereby reducing the amount of alkali used, and the use of additives can also be greatly reduced. In addition, since the alkali solution in the alkali polishing method contains nanobubbles, the chemical consumption of subsequent processes can be further reduced, thereby greatly reducing the cost of waste liquid treatment.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides an alkali polishing method for a crystalline silicon cell, the alkali polishing method comprising:

[0012] One side of the crystalline silicon cell is protected and then immersed in an alkaline solution with nano bubbles to obtain a single-side polished crystalline silicon cell, wherein the average size of the nano bubbles is 0.1-45 nm.

[0013] The average size of the nanobubbles in the present invention is 0.1-45 nm, that is, the average diameter of the nanobubbles is 0.1-45 nm, for example, 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 2 nm, 3 nm, 5 nm, 6 nm, 7 nm, 8 nm, 10 nm, 12 nm, 13 nm, 15 nm, 17 nm, 20 nm, 22 nm, 23 nm, 25 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm , 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm or 45nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; when the average size of the nanobubbles introduced into the sodium hydroxide solution is 0.1-45nm, when the same alkaline polishing state is reached, the required working concentration of the alkali is smaller, the required working concentration of the additive is smaller, and the working concentration of HF is even lower; this is because the size of the nanobubbles is too small, it is more difficult to prepare, the concentration of the formed nanobubble solution is not enough, and the expected effect cannot be achieved; when the size of the nanobubbles is too large, the nanobubbles are easily aggregated to form large bubbles, thereby affecting the process effect.

[0014] A pure aqueous solution is composed of water molecules and a small amount of H + and OH - The gas-liquid interface formed by bubbles in water has the property of being easy to accept H + and OH - The characteristics of the nanobubble are that cations are usually easier to leave the gas-liquid interface than anions, and the interface is often negatively charged; the surface that has been charged generally tends to adsorb counterions in the medium, especially high-valent counterions, thereby forming a stable double layer; the potential difference generated by the surface charge of the nanobubble is often characterized by the zeta potential, which is an important factor in determining the adsorption performance of the bubble interface; when the nanobubble shrinks in water, the charged ions are rapidly concentrated and enriched on the very narrow bubble interface, which is manifested as a significant increase in the zeta potential, and a very high zeta potential value can be formed at the interface before the bubble bursts; in addition, at the moment when the nanobubble bursts in the solution, due to the drastic change of the disappearance of the gas-liquid interface, the high-concentration ions gathered on the interface release the accumulated chemical energy all at once, and at this time a large number of hydroxyl radicals can be stimulated; hydroxyl radicals have an ultra-high redox potential and will produce an extremely strong oxidizing effect; therefore, the nanobubble has a very high oxidizing performance and surface potential in the solution.

[0015] In the alkali polishing method provided by the present invention, nanobubbles are introduced into the alkali solution, which will not pollute the chemicals and the battery surface. Since the nano-scale bubbles have very high oxidation performance and surface potential, they can have a good etching effect on silicon and silicon oxide, so the alkali concentration in the polishing process can be greatly reduced, thereby reducing the amount of alkali used, and the use of additives can also be greatly reduced. In addition, since the alkali solution in the alkali polishing method contains nanobubbles, the chemical consumption of subsequent processes can be further reduced, thereby greatly reducing the waste liquid treatment cost.

[0016] Preferably, the flow rate of the nanobubbles into the alkaline solution is 0.01 to 1 L / min, for example, 0.01 L / min, 0.02 L / min, 0.05 L / min, 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min or 1 L / min, 0.01 L / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also acceptable. The same value applies; when the inlet flow rate of nanobubbles in the sodium hydroxide solution is 0.01-1L / min, when the same alkaline state is reached, the required working concentration of alkali is smaller, the required working concentration of additives is smaller, and the required working concentration of HF is smaller. This is because when the gas volume is too low, the concentration of the generated nanobubbles in the aqueous solution is not enough to achieve the ideal effect; when the gas volume is too high, the generated nanobubbles are normally distributed, the distribution is wider, the amount of large bubbles generated increases, and a bubbling-like effect is formed. Since HF is more volatile, bubbling is more likely to promote its volatilization, resulting in increased consumption.

[0017] Preferably, the nanobubble generation method includes any one of a cyclotron shear method, a pressurized dissolved gas method or a mixed jet method, or a combination of at least two of them. Typical but non-limiting combinations include a combination of a cyclotron shear method and a pressurized dissolved gas method, a combination of a pressurized dissolved gas method and a mixed jet method, or a combination of a cyclotron shear method, a pressurized dissolved gas method and a mixed jet method.

[0018] Preferably, the alkaline solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0019] Preferably, the mass concentration of the alkali in the alkaline solution is 3 to 7 wt%, for example, it can be 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt% or 7wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the alkaline solution further comprises an additive.

[0021] The additives described in the present invention are commercially available mature additives, such as AT-29 (produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd.), PS-42 (produced by Changzhou Shichuang Energy Technology Co., Ltd.) or BP-21 (produced by Shaoxing Tuobang New Energy Co., Ltd.).

[0022] The additive in the alkaline solution of the present invention mainly has the following functions: improving the polishing effect, protecting the non-processing surface of the silicon wafer, improving the reflectivity, increasing the stability of the polishing solution and reducing the dependence on hydrofluoric acid, thereby reducing the cost of wastewater treatment.

[0023] Preferably, the mass concentration of the additive in the additive is 0.5-1.5wt%, for example, it can be 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt% or 1.5wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the soaking time is 155-300 seconds, and the soaking temperature is 60-70°C.

[0025] The soaking time described in the present invention is 155 to 300 seconds, for example, it can be 155 seconds, 165 seconds, 175 seconds, 185 seconds, 195 seconds, 205 seconds, 215 seconds, 225 seconds, 235 seconds, 245 seconds, 255 seconds, 265 seconds, 275 seconds, 285 seconds, 295 seconds or 300 seconds, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] The soaking temperature in the present invention is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; when the soaking temperature in the sodium hydroxide solution is 60-70°C, when the same alkaline polishing state is reached, the required working concentration of the alkali is small, the required working concentration of the additive is small, and the required working concentration of HF is small. This is because when the temperature is too low, the reaction speed is slow, and a higher alkali concentration is required to achieve the effect; when the temperature is too high, water is easy to volatilize, and the volatilization of water will also bring out chemicals, so it is not conducive to reducing the consumption of chemicals.

[0027] Preferably, the crystalline silicon cell comprises a boron-diffused crystalline silicon cell or a phosphorus-doped crystalline silicon cell.

[0028] The alkali polishing method described in the present invention is applied to back polishing after boron diffusion or front polishing after phosphorus doping; the purpose of back polishing after boron diffusion is to remove the damaged layer and impurities on the back of the silicon wafer, as well as the uneven area that may be formed during the boron diffusion process. Back polishing can improve the surface quality of the battery cell, reduce surface recombination, and thus improve the photoelectric conversion efficiency of the battery; front polishing after phosphorus doping refers to the chemical etching process performed on the front side of the silicon wafer after phosphorus doping, the purpose of which is to remove the damaged layer, improve the surface quality and reduce surface recombination.

[0029] In a second aspect, the present invention provides a single-side polished crystalline silicon cell wafer, wherein the single-side polished crystalline silicon cell wafer is obtained by the alkaline polishing method described in the first aspect.

[0030] In a third aspect, the present invention provides a solar cell, comprising the single-sided polished crystalline silicon cell described in the second aspect.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] In the alkali polishing method provided by the present invention, nanobubbles are introduced into the alkali solution, which will not pollute the chemicals and the battery surface. Since the nano-scale bubbles have very high oxidation performance and surface potential, they can have a good etching effect on silicon and silicon oxide, so the alkali concentration in the polishing process can be greatly reduced, thereby reducing the amount of alkali used, and the use of additives can also be greatly reduced. In addition, since the alkali solution in the alkali polishing method contains nanobubbles, the chemical consumption of subsequent processes can be further reduced, thereby greatly reducing the cost of waste liquid treatment. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0034] Example 1

[0035] This embodiment provides an alkali polishing method for a crystalline silicon cell, the alkali polishing method comprising:

[0036] One side of the crystalline silicon cell was protected, and then immersed in a sodium hydroxide solution into which nanobubbles with an average size of 20 nm were introduced at a flow rate of 0.3 L / min at 65° C. for 220 seconds to obtain a single-sided polished crystalline silicon cell;

[0037] The mass concentration of sodium hydroxide in the sodium hydroxide solution is 5wt%, and the sodium hydroxide solution also includes AT-29 (produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd.) with a mass concentration of 1wt%. The nanobubbles are generated by cyclotron shearing method.

[0038] Example 2

[0039] This embodiment provides an alkali polishing method for a crystalline silicon cell, the alkali polishing method comprising:

[0040] One side of the crystalline silicon cell was protected, and then immersed in a potassium hydroxide solution into which nanobubbles with an average size of 10 nm were introduced at a flow rate of 0.6 L / min at 62° C. for 180 s to obtain a single-sided polished crystalline silicon cell;

[0041] The mass concentration of potassium hydroxide in the potassium hydroxide solution is 4wt%, and the potassium hydroxide solution also includes PS-42 (produced by Changzhou Shichuang Energy Technology Co., Ltd.) with a mass concentration of 1.2wt%. The nanobubbles are generated by a pressurized dissolved gas method.

[0042] Example 3

[0043] This embodiment provides an alkali polishing method for a crystalline silicon cell, the alkali polishing method comprising:

[0044] One side of the crystalline silicon cell was protected, and then immersed in a sodium hydroxide solution into which nanobubbles with an average size of 30 nm were introduced at a flow rate of 0.1 L / min at 68° C. for 260 seconds to obtain a single-sided polished crystalline silicon cell;

[0045] The mass concentration of sodium hydroxide in the sodium hydroxide solution is 6wt%, and the sodium hydroxide solution also includes BP-21 (produced by Shaoxing Tuobang New Energy Co., Ltd.) with a mass concentration of 0.8wt%. The nanobubbles are generated by a mixed jet method.

[0046] Example 4

[0047] This embodiment provides an alkali polishing method for a crystalline silicon cell, the alkali polishing method comprising:

[0048] One side of the crystalline silicon cell was protected, and then immersed in a potassium hydroxide solution into which nanobubbles with an average size of 45 nm were introduced at a flow rate of 1 L / min at 60° C. for 155 seconds to obtain a single-sided polished crystalline silicon cell;

[0049] The mass concentration of potassium hydroxide in the potassium hydroxide solution is 3wt%, and the potassium hydroxide solution also includes AT-29 (produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd.) with a mass concentration of 1.5wt%. The nanobubbles are generated by cyclotron shearing method.

[0050] Example 5

[0051] This embodiment provides an alkali polishing method for a crystalline silicon cell, the alkali polishing method comprising:

[0052] One side of the crystalline silicon cell was protected, and then immersed in a potassium hydroxide solution into which nanobubbles with an average size of 0.1 nm were introduced at a flow rate of 0.01 L / min for 300 seconds at 70° C. to obtain a single-sided polished crystalline silicon cell;

[0053] The mass concentration of potassium hydroxide in the potassium hydroxide solution is 7wt%, and the potassium hydroxide solution also includes AT-29 (produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd.) with a mass concentration of 0.5wt%. The generation method of the nanobubbles includes any one of a cyclotron shear method, a pressurized dissolved gas method or a mixed jet method, or a combination of at least two of them.

[0054] Example 6

[0055] This embodiment provides an alkaline polishing method for crystalline silicon solar cells, which is the same as that of Embodiment 1 except that the flow rate of nanobubbles in the sodium hydroxide solution is 0.005 L / min.

[0056] Example 7

[0057] This embodiment provides an alkaline polishing method for crystalline silicon solar cells, which is the same as that of Embodiment 1 except that the flow rate of nanobubbles in the sodium hydroxide solution is 1.5 L / min.

[0058] Example 8

[0059] This embodiment provides an alkaline polishing method for crystalline silicon solar cells, which is the same as that of Embodiment 1 except that the immersion temperature in the sodium hydroxide solution is 50°C.

[0060] Example 9

[0061] This embodiment provides an alkaline polishing method for crystalline silicon solar cells, which is the same as that of Embodiment 1 except that the temperature of the immersion in the sodium hydroxide solution is 80°C.

[0062] Comparative Example 1

[0063] This comparative example provides an alkaline polishing method for a crystalline silicon cell, which is the same as Example 1 except that the average size of the nanobubbles introduced into the sodium hydroxide solution is 0.05 nm.

[0064] Comparative Example 2

[0065] This comparative example provides an alkaline polishing method for a crystalline silicon cell, which is the same as Example 1 except that the average size of the nanobubbles introduced into the sodium hydroxide solution is 50 nm.

[0066] Comparative Example 3

[0067] This comparative example provides an alkaline polishing method for a crystalline silicon cell, which is the same as Example 1 except that nanobubbles are not introduced into the sodium hydroxide solution.

[0068] The crystalline silicon cell wafers after boron diffusion were back-polished by the alkaline polishing method provided in the above-mentioned embodiments and comparative examples until the unprotected side of the crystalline silicon cell wafer after boron diffusion was polished to a reflectivity of 50%; phosphorus doping was performed in the subsequent process, and the obtained phosphorus-doped crystalline silicon cell wafers were front-polished to remove the front protective layer until there was no obvious color difference on the polished surface of the crystalline silicon cell wafer during the front polishing, and the total consumption of alkali and the total consumption of additives in the alkaline solution used in the back-polishing and front-polishing processes of 10,000 crystalline silicon cell wafers were recorded as shown in Table 1; in addition, after the back-polishing and front-polishing, 10,000 obtained single-sided polished crystalline silicon cell wafers were cleaned with HF acid solution (HF mass concentration of 49wt%), and the total consumption of HF was recorded as shown in Table 1.

[0069] Table 1

[0070]

[0071] The mass concentration of the alkali is 45%; the mass concentration of the HF acid is 49%.

[0072] From Table 1, we can get:

[0073] (1) The alkaline polishing method for the crystalline silicon cell provided in Examples 1 to 5 is used for alkaline polishing. When the same alkaline polishing state is reached, the molar amount of the consumed alkali is smaller, the molar amount of the consumed additive is smaller, and the consumption of HF is smaller;

[0074] (2) By comparing Example 1 with Examples 6 and 7, it can be seen that the flow rate of nanobubbles in the sodium hydroxide solution of the present invention affects the consumption of chemicals; when the flow rate of nanobubbles in the sodium hydroxide solution is 0.01-1 L / min, when the same alkaline state is reached, the required working concentration of the alkali is smaller, the required working concentration of the additive is smaller, and the required working concentration of HF is smaller. This is because when the gas volume is too low, the concentration of the generated nanobubbles in the aqueous solution is not enough and the ideal effect cannot be achieved; when the gas volume is too high, the generated nanobubbles are normally distributed, the distribution is wider, the amount of large bubbles generated increases, and a bubbling-like effect is formed. Since HF is more volatile, bubbling is more likely to promote its volatilization, resulting in increased consumption;

[0075] (3) By comparing Example 1 with Examples 8 and 9, it can be seen that the temperature of the immersion in the sodium hydroxide solution in the present invention affects the consumption of chemicals; when the immersion temperature in the sodium hydroxide solution is 60-70°C, when the same alkaline polishing state is achieved, the required working concentration of the alkali is smaller, the required working concentration of the additive is smaller, and the required working concentration of HF is smaller. This is because when the temperature is too low, the reaction speed is slower and a higher alkali concentration is required to achieve the effect; when the temperature is too high, water is easy to volatilize, and the volatilization of water will also bring out chemicals, which is not conducive to reducing the consumption of chemicals. ;

[0076] (4) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the average size of the nanobubbles introduced into the sodium hydroxide solution in the present invention affects the consumption of chemicals; when the average size of the nanobubbles introduced into the sodium hydroxide solution is 0.1-45 nm, when the same alkaline polishing state is achieved, the required working concentration of the alkali is smaller, the required working concentration of the additive is smaller, and the working concentration of HF is even lower; this is because the nanobubbles are too small and difficult to prepare, and the concentration of the formed nanobubble solution is not enough to achieve the expected effect; when the nanobubbles are too large, the nanobubbles are easily aggregated to form large bubbles, thereby affecting the process effect;

[0077] (5) By comparing Example 1 with Comparative Example 3, it can be seen that in the alkali polishing method provided by the present invention, nanobubbles are introduced into the alkali solution, which will not pollute the chemicals and the battery surface. In addition, since the nano-scale bubbles have very high oxidation performance and surface potential, they can have a good etching effect on silicon and silicon oxide. Therefore, the alkali concentration in the polishing process can be greatly reduced, thereby reducing the amount of alkali used, and the use of additives can also be greatly reduced. In addition, since the alkali solution in the alkali polishing method contains nanobubbles, the chemical consumption of the subsequent process can be further reduced, thereby greatly reducing the cost of waste liquid treatment.

[0078] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. An alkaline polishing method for crystalline silicon solar cells, It is characterized in that The alkali polishing method comprises: One side of the crystalline silicon cell is protected and then immersed in an alkaline solution with nano bubbles to obtain a single-side polished crystalline silicon cell, wherein the average size of the nano bubbles is 0.1-45 nm.

2. The alkali polishing method according to claim 1, It is characterized in that The flow rate of the nanobubbles passing into the alkaline solution is 0.01-1 L / min.

3. The alkali polishing method according to claim 1 or 2, It is characterized in that The nanobubble generation method includes any one of a cyclotron shearing method, a pressurized gas dissolution method or a mixed jet method, or a combination of at least two of them.

4. The alkali polishing method according to any one of claims 1 to 3, It is characterized in that The alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution; Preferably, the mass concentration of the alkali in the alkali solution is 3-7 wt %.

5. The alkali polishing method according to any one of claims 1 to 4, It is characterized in that The alkaline solution also includes additives.

6. The alkali polishing method according to claim 5, It is characterized in that The mass concentration of the additive in the additive is 0.5-1.5wt%.

7. The alkali polishing method according to any one of claims 1 to 6, It is characterized in that The soaking time is 155-300 seconds, and the soaking temperature is 60-70°C.

8. The alkali polishing method according to any one of claims 1 to 7, It is characterized in that The crystalline silicon cell sheet includes a boron-diffused crystalline silicon cell sheet or a phosphorus-doped crystalline silicon cell sheet.

9. A single-sided polished crystalline silicon cell, It is characterized in that The single-side polished crystalline silicon cell is obtained by the alkali polishing method described in any one of claims 1 to 8.

10. A solar cell, It is characterized in that The solar cell comprises the single-side polished crystalline silicon cell sheet as claimed in claim 9.

Images