Reworked silicon wafer texturing method, reworked silicon wafer and solar cell

Abstract

The invention provides a texturing method for a reworked silicon wafer, the reworked silicon wafer and a solar cell, and the method comprises the steps: S100, immersing the reworked silicon wafer in a first reaction solution containing deionized water, an alkaline reagent and a texturing additive, and carrying out the first texturing, so as to enable the surface of the reworked silicon wafer to form a pyramid structure, and to form a first reworked silicon wafer; and S200, the first reworked silicon wafer is immersed in a second reaction solution containing an alkaline reagent and deionized water for second-step texturing, and the amount of the alkaline reagent in the second reaction solution is lower than that of the alkaline reagent in the first reaction solution. And by removing the additive in the second step of texturing process, the generation of broken textures on the textured surface is reduced, and the high-plasticity and high-texturing-rate pyramid textured surface is prepared.

Description

Technical Field

[0001] The invention relates to the field of solar cells, and in particular to a reworked silicon wafer texturing method, a reworked silicon wafer and a solar cell. Background Art

[0002] Crystalline silicon solar cells have a large market share in the photovoltaic field due to their excellent efficiency, batch preparation and high stability. The mainstream PERC and TOPCON cell efficiencies have reached 24% and 26.5% in mass production, but various undesirable phenomena are inevitable in the production process, such as flower basket marks and boat marks caused by unsaturated flower baskets, which affect the defective rate of products. After the reworked silicon wafers are cleaned with HCl+HF and then subjected to processes such as texturing and diffusion, the efficiency of the cells will be affected to a certain extent. For example, the micro-surface texture changes slightly after texturing. <100> and <111> The difference in crystal surface reaction rate is narrowed; the diffusion square resistance is out of the monitoring water level during doping due to the change of the velvet surface; and the flatness and uniformity of the front and back films, etc. The conventional velvet making method used in the reworked sheet will cause a higher reflectivity, increase the probability of velvet fragmentation, reduce the uniformity of the velvet surface, and have an adverse effect on the subsequent diffusion, front and back film and other processes, thereby reducing the efficiency of the battery.

[0003] Therefore, it is necessary to develop a new process to optimize and improve the suede surface of the reworked sheet. Summary of the invention

[0004] In view of the above problems, in a first aspect, the present invention provides a method for texturing a reworked silicon wafer, the texturing method comprising the steps of:

[0005] S100, immersing the reworked silicon wafer in a first reaction solution containing deionized water, an alkaline reagent and a texturing additive to perform a first texturing step, so that a pyramid structure is formed on the surface of the reworked silicon wafer, thereby forming a first reworked silicon wafer;

[0006] S200, immersing the first reworked silicon wafer in a second reaction solution containing the alkaline reagent and deionized water to perform a second step of texturing, wherein the amount of the alkaline reagent in the second reaction solution is lower than the amount of the alkaline reagent in the first reaction solution.

[0007] Furthermore, the content of deionized water in the first reaction solution is 97.8-99%, the content of alkaline reagent is 0.8-1.7%, and the content of texturing additive is 0.23-0.56%.

[0008] Furthermore, the content of the alkaline agent in the second reaction solution is 0.06-0.14%, and the content of deionized water is 99.8-99.9%.

[0009] Furthermore, in the steps S100 and S200, the temperature of the first step of texturing is 70° C.-90° C.; the time of the first step of texturing is 250s-350s.

[0010] Furthermore, the temperature of the second step of texturing is 60°C-70°C; the time of the second step of texturing is 100s-150s.

[0011] Furthermore, the alkaline agent includes sodium hydroxide or potassium hydroxide.

[0012] Furthermore, before performing step S100, the following steps are also included:

[0013] Cleaning the reworked silicon wafer in an acidic reagent;

[0014] The texturing tank is cleaned twice using the alkaline reagent.

[0015] Furthermore, the acidic reagent includes hydrochloric acid and hydrofluoric acid.

[0016] Furthermore, the step S100 further includes automatically replenishing the alkaline solution and the texturing additive in steps, wherein the alkaline solution is replenished in steps for 3-5 times, and the texturing additive is replenished in steps for 2-4 times;

[0017] The step S200 also includes automatically replenishing the alkaline solution in steps, and the alkaline solution is replenished in steps for 3-5 times.

[0018] Furthermore, in the step 100, the deionized water is replenished with 6000mL to 8000mL at one time, the initial replenishment volume of the alkaline solution is 400mL to 500mL, and the initial replenishment volume of the texturing additive is 100mL to 150mL;

[0019] In the step 200, the deionized water is replenished in a one-time amount of 6000 mL to 8000 mL, and the initial replenishment volume of the alkaline solution is 300 to 500 mL.

[0020] Furthermore, the additives include: water, an etchant, a buffer, a defoaming agent and a surfactant.

[0021] In a second aspect, the present invention further provides a reworked silicon wafer with texturing, wherein the texturing silicon wafer is prepared by the reworked silicon wafer texturing method as described in any one of the above items.

[0022] In a third aspect, the present invention provides a solar cell, comprising a textured silicon wafer, wherein the textured silicon wafer is prepared by the reworked silicon wafer texture making method as described in any one of the above items.

[0023] Compared with the prior art, the present invention includes at least the following beneficial effects: a special two-step velvet making method is adopted to optimize the velvet surface of the reworked sheet, reduce the generation of velvet fragments, prepare a pyramid velvet surface with high plasticity and high velvet yield, provide good contact, increase the velvet reflectivity, and enhance the photovoltaic performance of the battery device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 A flow chart of a two-step texturing method for a reworked sheet provided by the present invention;

[0026] Figure 2 A schematic diagram of the velvet-like appearance of a reworked silicon wafer in one embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the velvet-like appearance of a reworked silicon wafer in another embodiment of the present invention;

[0028] Figure 4 FIG. 1 is a schematic diagram of the velvet-like appearance of a reworked silicon wafer in another embodiment of the present invention. DETAILED DESCRIPTION

[0029] A more detailed description of a reworked silicon wafer texturing method, a reworked silicon wafer and a solar cell of the present invention will be given below in conjunction with schematic diagrams, wherein preferred embodiments of the present invention are shown, and it should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0030] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0031] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in very simplified form and are not in exact proportions, and are only used to facilitate and clearly assist in illustrating the purpose of the embodiments of the present invention.

[0032] The present invention provides a method for reworking silicon wafers. Figure 1 The texturing method comprises the following steps:

[0033] S100, immersing the reworked silicon wafer in a first reaction solution containing deionized water, an alkaline reagent and a texturing additive to perform a first texturing step, so that a pyramid structure is formed on the surface of the reworked silicon wafer, thereby forming a first reworked silicon wafer;

[0034] S200, immersing the first reworked silicon wafer in a second reaction solution containing deionized water and an alkaline reagent to perform a second step of texturing, wherein the amount of the alkaline reagent in the second reaction solution is lower than the amount of the alkaline reagent in the first reaction solution.

[0035] Specifically, the reworked silicon wafer is first immersed in a first reaction solution containing an alkaline reagent and a texturing additive. The purpose of this stage is to form a pyramid structure on the surface of the silicon wafer, which helps to improve the silicon wafer's ability to absorb light. The alkaline reagent is used to corrode the surface of the silicon wafer to form a pyramid-shaped structure. The texturing additive includes chemicals used to control the corrosion rate and optimize the pyramid structure.

[0036] After the first step of texturing, the first reworked silicon wafer is then immersed in a second reaction solution containing the alkaline reagent. The purpose of this step is to further optimize the texture of the pyramid structure to reduce its reflectivity. The amount of alkaline reagent in the second reaction solution is lower than the amount of alkaline reagent in the first reaction solution. This reduction in dosage is to control the corrosion process, avoid excessive corrosion, and ensure the uniformity and quality of the pyramid structure.

[0037] Furthermore, the content of deionized water in the first reaction solution is 97.8-99%, the content of the alkaline agent is 0.8-1.7%, and the content of the texturing additive is 0.23-0.56%.

[0038] Furthermore, the content of the alkaline agent in the second reaction solution is 0.06-0.14%, and the content of deionized water is 99.8-99.9%.

[0039] Preferably, in the present invention, the deionized water content in the first reaction liquid is 439000 mL (98.5%), the alkaline agent content is 5100 mL (1.14%), and the texturing additive content is 1600 mL (0.36%). The deionized water content in the second reaction liquid is 439000 mL (99.9%), and the alkaline agent content is 400 mL (0.1%).

[0040] Furthermore, in steps S100 and S200, the temperature of the first step of texturing is 70°C-90°C; the time of the first step of texturing is 250s-350s; the temperature of the second step of texturing is 60°C-70°C; the time of the second step of texturing is 100s-150s.

[0041] In this embodiment, the total duration of the two-step texturing should not exceed the reaction time of conventional texturing.

[0042] Specifically, in the first step of the texturing process, the temperature is controlled between 70°C and 90°C. This temperature range is to promote chemical reactions and accelerate the formation of the pyramid structure on the surface of the silicon wafer. The immersion time is 250s-350s. This period of time allows sufficient corrosion to occur to form the desired pyramid structure. Preferably, in this embodiment, the temperature of the first step of the texturing process is maintained at 83°C and the immersion time is 320s.

[0043] During the second step of the texturing process, the temperature is controlled between 60°C and 70°C. The temperature of this step is lower in order to more finely adjust the pyramid structure and reduce the reflectivity. The immersion time is 100s-150s. A shorter time may be used to control the degree of corrosion and avoid excessive corrosion. Preferably, in this embodiment, the temperature of the second step of the texturing process is maintained at 65°C and the immersion time is 120s. The total duration of the two-step texturing should not exceed the reaction time of conventional texturing, in order to ensure that the texturing process of the reworked sheet does not take longer than the conventional texturing step, thereby maintaining production efficiency and cost-effectiveness.

[0044] Furthermore, the alkaline agent includes sodium hydroxide or potassium hydroxide. Preferably, in this embodiment, sodium hydroxide is used as the alkaline agent.

[0045] Furthermore, before performing step S100, the following steps are also included:

[0046] Cleaning the reworked silicon wafer in an acidic reagent;

[0047] The texturing tank is cleaned twice using the alkaline reagent.

[0048] Furthermore, the acidic reagent includes hydrochloric acid and hydrofluoric acid.

[0049] Specifically, in order to ensure that the surface of the reworked silicon wafer is clean and free of impurities before texturing, and to ensure the cleanliness of the texturing tank, thereby improving the quality and efficiency of the texturing process, the reworked silicon wafer is cleaned in an acidic reagent. The purpose of this step is to remove the natural oxide layer, grease, dust and other contaminants on the surface of the silicon wafer. The acidic reagent can be hydrochloric acid, hydrofluoric acid or other suitable acids, which can effectively remove impurities on the surface of the silicon wafer and prepare a clean surface for the subsequent texturing step. Hydrochloric acid and hydrofluoric acid are selected in this embodiment.

[0050] Use alkaline reagent to clean the texturing tank twice: It is very important to clean the texturing tank before texturing, because there may be impurities left in the tank from the previous texturing process, such as unreacted reagents, silicon wafer surface debris or other solid particles. Using alkaline reagent to clean the tank can ensure the cleanliness of the tank and prevent these impurities from affecting the texturing quality. Cleaning twice can better ensure the cleanliness of the tank and reduce potential contamination risks.

[0051] Furthermore, the step S100 further includes automatically replenishing the alkaline solution and the texturing additive in steps, wherein the alkaline solution is replenished 3-5 times in steps, and the texturing additive is replenished 2-4 times in steps;

[0052] The step S200 also includes automatically replenishing the alkaline solution in steps, and the alkaline solution is replenished in steps for 3-5 times.

[0053] Furthermore, in the step 100, the deionized water is replenished in a one-time amount of 6000mL-8000mL, the initial replenishment amount of the alkaline solution is 440mL-480mL, and the initial replenishment amount of the texturing additive is 100mL-140mL;

[0054] In the step 200, the deionized water is replenished with 6000mL-8000mL at one time, and the initial replenishment volume of the alkaline solution is 30mL-80mL.

[0055] Preferably, in the first step of texturing, 7000 mL of deionized water is replenished at one time, the initial replenishment volume of the alkaline solution is 460 mL, the replenishment frequency is 4 times, and the initial replenishment volume of the texturing additive is 120 mL, the replenishment frequency is 4 times; in the second step of texturing, 7000 mL of deionized water is replenished at one time, the initial replenishment volume of the alkaline solution is 40 mL, and the replenishment frequency is 4 times.

[0056] Further, the additives include: water, an etchant, a buffer, a defoamer and a surfactant. In a possible embodiment of the present invention, the etchant is potassium sorbate and the buffer is sodium acetate. Those skilled in the art can also replace the selected reagents as needed.

[0057] Embodiment 1:

[0058] The present application is further explained below with specific embodiments:

[0059] S1: The oxide layer on the surface of the reworked wafer is cleaned by hydrochloric acid and hydrofluoric acid.

[0060] S2: Change the tank liquid, wash and lubricate the tank twice with sodium hydroxide, and prepare the liquid.

[0061] S3: Immersing the reworked silicon wafer in a first reaction solution containing sodium hydroxide and a texturing additive to perform a first texturing step, so that a pyramid structure is formed on the surface of the single crystal silicon wafer to form a first reworked silicon wafer.

[0062] S4: Immersing the first reworked silicon wafer in a second reaction solution containing sodium hydroxide to perform a second step of texturing.

[0063] In step S3 of the present embodiment, please refer to Table 1 for details. The initial sodium hydroxide content of the first tank is 5100mL, and the alkali solution is automatically replenished four times, which are 460mL, 460mL, 465mL, and 470mL respectively; the initial deionized water content is 439000mL, and the replenishment is 7000mL; the initial texturing additive content is 1600mL, and it is automatically replenished 4 times, which are 120mL, 120mL, 130mL, and 130mL respectively.

[0064] The second tank was initially prepared with 400mL of sodium hydroxide and 439,000mL of deionized water. The sodium hydroxide was automatically replenished four times, namely 40mL, 50mL, 60mL, and 70mL, and the deionized water was replenished to 7,000mL. In order to reduce the impact on production capacity, the total duration of the two-step texturing should not exceed the reaction time of conventional texturing, and the process should be circulated and bubbling. After unloading, a D8 reflectometer and a scanning electron microscope are used to monitor the reflectivity and velvet surface. The reflectivity should be lower than that of the production line, and the velvet yield should be higher. Table 2 shows the electrical performance characterization data of the silicon wafer obtained using the data of this embodiment. Figure 2 Schematic diagram of the velvet appearance of the reworked silicon wafer in this embodiment.

[0065] Table 1

[0066]

[0067] Table 2

[0068] Group Eta Isc Voc FF Rs R Conventional Velveting 23.543 0.6936 18.253 0.0013 372 82.01 Secondary Velveting 23.593 0.6942 18.266 0.0013 371 82.05 GAP 0.05％ 0.0006 0.013 0 -1 0.04

[0069] Embodiment 2:

[0070] In step S3 of the present embodiment, please refer to Table 3 for details. The initial sodium hydroxide content of the first tank is 5500mL, and the alkali solution is automatically replenished 4 times, which are 465mL, 465mL, 470mL, and 470mL respectively; the initial deionized water content is 440000mL, and the replenishment is 7000mL; the initial texturing additive content is 1500mL, and it is automatically replenished 4 times, which are 110mL, 110mL, 120mL, and 120mL respectively.

[0071] The second tank was initially prepared with 400mL of sodium hydroxide and 440,000mL of deionized water. The sodium hydroxide was automatically replenished 4 times, namely 45mL, 55mL, 65mL, and 75mL, and the deionized water was replenished with 8,000mL. In order to reduce the impact on production capacity, the total duration of the two-step texturing should not exceed the reaction time of conventional texturing, and the process should be circulated and bubbling. After unloading, a D8 reflectometer and a scanning electron microscope are used to monitor the reflectivity and velvet surface. The reflectivity should be lower than that of the production line, and the velvet yield should be higher. As shown in Table 4, the electrical performance characterization data of the silicon wafer obtained using the data of this embodiment is shown. Figure 3 Schematic diagram of the velvet appearance of the reworked silicon wafer in this embodiment.

[0072] Table 3

[0073]

[0074] Table 4

[0075] Group Eta Isc Voc FF Rs R Conventional Velveting 23.612 18.241 0.6956 82.05 1.2681 650 Secondary Velveting 23.590 18.233 0.6949 82.10 1.2505 646 GAP -0.021％ -0.008 -0.0007 0.05 -0.0176 -3

[0076] Embodiment three:

[0077] In step S3 of the present embodiment, please refer to Table 5 for details. The initial sodium hydroxide content of the first tank is 4800mL, and the alkali solution is automatically replenished 4 times, which are 455mL, 455mL, 460mL, and 460mL respectively; the initial deionized water content is 440000mL, and the replenishment is 7000mL; the initial texturing additive content is 1700mL, and it is automatically replenished 4 times, which are 125mL, 125mL, 130mL, and 130mL respectively.

[0078] The second tank was initially prepared with 400mL of sodium hydroxide and 440,000mL of deionized water. The sodium hydroxide was automatically replenished 4 times, namely 35mL, 45mL, 55mL, and 60mL, and the deionized water was replenished with 8,000mL. In order to reduce the impact on production capacity, the total duration of the two-step texturing should not exceed the reaction time of conventional texturing, and the process should be circulated and bubbling. After unloading, a D8 reflectometer and a scanning electron microscope are used to monitor the reflectivity and velvet surface. The reflectivity should be lower than that of the production line, and the velvet yield should be higher. Table 6 shows the electrical performance characterization data of the silicon wafer obtained using the data of this embodiment. Figure 4 Schematic diagram of the velvet appearance of the reworked silicon wafer in this embodiment.

[0079] Table 5

[0080]

[0081] Table 6

[0082] Group Eta Isc Voc FF Rs R Conventional Velveting 23.599 0.694 18.237 0.0012 275 82.22 Secondary Velveting 23.631 0.6944 18.238 0.0012 270 82.28 GAP 0.031％ 0.0004 0.001 0 -5 0.06

[0083] In a second aspect, the present invention further provides a reworked silicon wafer with texturing, wherein the texturing silicon wafer is prepared by the reworked silicon wafer texturing method as described in any one of the above items.

[0084] In a third aspect, the present invention provides a solar cell, comprising a textured silicon wafer, wherein the textured silicon wafer is prepared by the reworked silicon wafer texture making method as described in any one of the above items.

[0085] In summary, the present invention reduces the generation of velvet fragments by removing the additives in the second step of the texturing process, and prepares a pyramid velvet with high plasticity and high velvet yield. If the consumption of alkali and additives is increased to reduce the corrosion depth, the velvet uniformity will deteriorate, and velvet fragments will be easily generated; conversely, the velvet yield is higher and the velvet is smaller. The total duration of the two-step texturing is controlled within the reaction time of conventional texturing to ensure that the texturing process of the reworked sheet does not extend the production cycle, thereby maintaining production efficiency and cost-effectiveness. During the texturing process, the alkaline solution and the texturing additives are automatically replenished in a gradient manner to maintain the stability and consistency of the reaction solution and ensure the texturing effect. At the same time, unqualified silicon wafers can be reused to reduce the waste of raw materials and reduce production costs.

[0086] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A method for texturing a reworked silicon wafer, characterized in that: The texturing method comprises the steps of: S100, immersing the reworked silicon wafer in a first reaction solution containing deionized water, an alkaline reagent and a texturing additive to perform a first texturing step, so that a pyramid structure is formed on the surface of the reworked silicon wafer, thereby forming a first reworked silicon wafer; S200, immersing the first reworked silicon wafer in a second reaction solution containing an alkaline reagent and deionized water to perform a second step of texturing, wherein the amount of the alkaline reagent in the second reaction solution is lower than the amount of the alkaline reagent in the first reaction solution.

2. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: The content of deionized water in the first reaction liquid is 97.8-99%, the content of alkaline reagent is 0.8-1.7%, and the content of texturing additive is 0.23-0.56%.

3. The method for texturing a reworked silicon wafer as claimed in claim 2, characterized in that: The content of the alkaline agent in the second reaction solution is 0.06-0.14%, and the content of the deionized water is 99.8-99.9%.

4. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: The temperature of the first step of texturing is 70° C.-90° C.; the time of the first step of texturing is 250s-350s.

5. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: The temperature of the second step of texturing is 60°C-70°C; the time of the second step of texturing is 100s-150s.

6. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: The alkaline agent includes sodium hydroxide or potassium hydroxide.

7. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: Before performing step S100, the following steps are also included: Cleaning the reworked silicon wafer in an acidic reagent; The texturing tank is cleaned twice using the alkaline reagent.

8. The method for texturing a reworked silicon wafer according to claim 7, characterized in that: The acidic reagent includes hydrochloric acid and hydrofluoric acid.

9. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: The step S100 also includes automatically replenishing the alkaline solution and the texturing additive in steps, wherein the alkaline solution is replenished 3-5 times in steps, and the texturing additive is replenished 2-4 times in steps; The step S200 also includes automatically replenishing the alkaline solution in steps, and the alkaline solution is replenished in steps for 3-5 times.

10. The method for texturing a reworked silicon wafer according to claim 9, characterized in that: In the step 100, the deionized water is replenished with 6000mL to 8000mL at one time, the initial replenishment volume of the alkaline solution is 400mL to 500mL, and the initial replenishment volume of the texturing additive is 100mL to 150mL; In the step 200, the deionized water is replenished in a one-time amount of 6000mL to 8000mL, and the initial replenishment volume of the alkaline solution is 30mL to 80mL.

11. The method for texturing a reworked silicon wafer according to claim 1, characterized in that: The additives include: water, an etchant, a buffer, a defoamer and a surfactant.

12. A reworked silicon wafer, characterized in that: The texturing silicon wafer is prepared by the texturing method for a reworked silicon wafer according to any one of claims 1-11.

13. A solar cell, characterized in that: It comprises a texturing silicon wafer, and the texturing silicon wafer is prepared by the texturing method for a reworked silicon wafer as described in any one of claims 1-11.

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