Method for removing winding plating of back contact battery and manufacturing process of back contact battery

Abstract

The invention provides a method for removing winding plating of a back contact cell and a manufacturing process of the back contact cell, and particularly relates to the technical field of solar cell preparation. The winding plating is positioned on the front surface and the edge of the back contact battery; the removing method comprises the following steps that the edge is cut through the SE technology to remove the edge winding plating layer; and then the winding plating layer on the front face is removed through laser. According to the removal method provided by the invention, the generation of the N-containing wastewater is effectively reduced, so that the pollution to the environment is reduced. And due to the high-precision characteristic of laser processing, the removal process of the coating is more accurate, the performance and quality of the battery piece can be maintained, and meanwhile errors and inconsistency possibly occurring in the processing process are reduced. In addition, due to the rapidity of laser processing, the production efficiency is remarkably improved, the production cycle is shortened, the product marketing time is shortened, and higher production flexibility and market response speed are brought to enterprises.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell preparation, and in particular to a method for removing wrap-around plating of a back contact cell and a manufacturing process of a back contact cell. Background Art

[0002] BC cell, full name Back Contact Cell, is a solar cell technology that designs all electrode contacts on the back of the cell. This design makes the front of the cell unobstructed, which can maximize the use of incident light and reduce optical losses, thereby improving the photoelectric conversion efficiency of the cell. BC cell technology is not only beautiful in appearance, but also has significant advantages in fields such as distributed photovoltaics because it has no grid lines blocking the front.

[0003] The wrap-around plating phenomenon of BC cells is mainly formed during the LPCVD (low-pressure chemical vapor deposition) process. In the LPCVD process, since the deposited film is not directional, when the cell is placed on a quartz boat, the oxide layer and the intrinsic polysilicon layer will not only be formed on the back of the cell, but will also be attached to the side and front of the cell, forming a wrap, which is the "wrap-around" phenomenon. This phenomenon will cause the excess tunneling layer and doped polysilicon layer to be removed, so the "de-wrap-around" process needs to be introduced later. However, the fundamental reason why LPCVD wrap-around plating has become a pain point is that de-wrap-around plating is difficult to control and affects the battery yield. Cleaning the wrap-around plating may result in incomplete removal or etching of the doped polysilicon layer, affecting battery efficiency. The LPCVD method is used to prepare tunneling oxide layers and doped polysilicon layers, which are generally cleaned and wrapped after phosphorus doping. The typical process flow of de-coating includes single-sided cleaning with HF acid to remove the phosphosilicate glass PSG (i.e., front and side) in the de-coating area; then double-sided cleaning with KOH alkali solution to remove the doped polysilicon (i.e., front and side) in the de-coating area. The back PSG layer protects the tunneling oxide layer and the doped polysilicon layer; finally, double-sided cleaning with HF acid is used to remove SiO2 (i.e., front and side) and back PSG in the de-coating area. The difficulty in the de-coating process is that the KOH alkali solution etches the doped polysilicon faster than the phosphosilicate glass PSG, and the reaction time difference between the two is difficult to effectively control, which may lead to incomplete removal of the doped polysilicon layer, or the protective phosphosilicate glass on the back is removed, resulting in the erosion of the back doped polysilicon layer, affecting the battery efficiency. At the same time, the solution used in the cleaning process will produce nitrogen (N)-containing wastes in the process of removing the de-coating. If these wastes are not handled properly, they will cause great pressure on the environment.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for removing the plating around the back contact battery, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0006] A second object of the present invention is to provide a manufacturing process for a back-contact battery.

[0007] A third object of the present invention is to provide a back contact battery.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] A first aspect of the present invention provides a method for removing wrap-around plating of a back contact battery, wherein the wrap-around plating is located on the front and edge of the back contact battery;

[0010] The removal method comprises the following steps:

[0011] The SE process is used to cut the edge and remove the edge coating; then the laser is used to remove the coating on the front side.

[0012] Furthermore, the wrap-around plating includes a first tunnel oxide layer, a P-type polysilicon layer, a BSG layer, a second tunnel oxide layer, an N-type polysilicon layer and a PSG layer from the silicon substrate to a region away from the silicon substrate.

[0013] Furthermore, in the SE process, the output power of the laser is 80-120W.

[0014] Preferably, the frequency of the laser is 80-110 kHz.

[0015] Preferably, the moving speed of the laser is 1000-8000 mm / s.

[0016] Furthermore, in the SE process, the spot size of the laser is 0.75-1 μm.

[0017] Preferably, the laser engraving times are 1 to 6 times.

[0018] Furthermore, in the SE process, the pulse width of the laser is 1.0 to 2.0 fs, preferably 1.6 fs.

[0019] Furthermore, during the removal of the coating on the front side, the output power of the laser is 40 to 80 W.

[0020] Preferably, the frequency of the laser is 80-110 kHz.

[0021] Preferably, the moving speed of the laser is 1000-8000 mm / s.

[0022] Furthermore, during the removal of the front coating, the laser spot size is 5 to 35 μm.

[0023] Preferably, the laser engraving times are 2 to 10 times.

[0024] Furthermore, during the removal of the coating on the front side, the pulse width of the laser is 2.0 to 2.5 fs, preferably 2.1 fs.

[0025] The second aspect of the present invention provides a manufacturing process for a back contact cell, wherein a back structure is manufactured on a silicon substrate, and then the plating on the front and edge of the silicon substrate is removed, and finally the front of the silicon substrate is textured, and a passivation layer and an anti-reflection layer are deposited on both sides to obtain the back contact cell;

[0026] The removal of the wrap-around plating on the front side and edge of the silicon substrate is carried out by the removal method described in the first aspect.

[0027] The third aspect of the present invention provides a back-contact battery, which is prepared using the manufacturing process described in the second aspect.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The removal method provided by the present invention effectively reduces the generation of N-containing wastewater by avoiding the use of HNO3, thereby reducing pollution to the environment and meeting the current strict requirements for environmentally friendly production. In addition, the method does not rely on the use of chemicals, thereby reducing the use and consumption of chemicals, which not only reduces the potential impact on the environment, but also significantly reduces the manufacturing cost and enhances the economy of the production process. During the processing, the high energy density of the laser scribing beam and the non-contact processing method ensure the gentle treatment of the silicon wafer, reduce the damage and breakage of the silicon wafer during the processing, thereby improving the yield rate of the product. The high-precision characteristics of laser processing make the removal process of the coating more accurate, help maintain the performance and quality of the battery cell, and reduce the errors and inconsistencies that may occur during the processing. In addition, the rapidity of laser processing significantly improves production efficiency, shortens the production cycle, speeds up the time to market, and brings higher production flexibility and market response speed to enterprises. In general, the removal method of the present invention shows significant advantages in terms of environmental protection, economy, processing accuracy and production efficiency.

[0030] The manufacturing process provided by the present invention reduces damage to battery cells caused by incomplete removal of the plating layer or improper operation through effective removal of the front side plating and the edge side plating, thereby improving the yield rate in the production process, while also improving the degree of automation and production efficiency of the production line, reducing the uneven product quality caused by unstable chemical removal, and improving the stability and reliability of the manufacturing process.

[0031] The back-contact battery provided by the present invention, in view of the technical advantages brought by the above-mentioned manufacturing process, improves the yield, long-term durability and reliability of the prepared back-contact battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic diagram of the structure of a wrap-around plating distribution provided by the present invention.

[0034] Description of the main component symbols: 100 - N-type silicon substrate; 200 - front side; 210 - PSG layer; 220 - N-type polysilicon layer; 230 - second tunneling oxide layer; 240 - BSG layer; 250 - P-type polysilicon layer; 260 - first tunneling oxide layer. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0037] A first aspect of the present invention provides a method for removing wrap-around plating of a back contact cell, wherein the wrap-around plating is located on the front side 200 and the edge of the back contact cell;

[0038] The removal method comprises the following steps:

[0039] The SE process is used to cut the edge and remove the edge coating; then the laser is used to remove the coating on the front side.

[0040] The removal method provided by the present invention effectively reduces the generation of N-containing wastewater by avoiding the use of HNO3, thereby reducing pollution to the environment and meeting the current strict requirements for environmentally friendly production. In addition, the method does not rely on the use of chemicals, thereby reducing the use and consumption of chemicals, which not only reduces the potential impact on the environment, but also significantly reduces the manufacturing cost and enhances the economy of the production process. During the processing, the high energy density of the laser scribing beam and the non-contact processing method ensure the gentle treatment of the silicon wafer, reduce the damage and breakage of the silicon wafer during the processing, thereby improving the yield rate of the product. The high-precision characteristics of laser processing make the removal process of the coating more accurate, help maintain the performance and quality of the battery cell, and reduce the errors and inconsistencies that may occur during the processing. In addition, the rapidity of laser processing significantly improves production efficiency, shortens the production cycle, speeds up the time to market, and brings higher production flexibility and market response speed to enterprises. In general, the removal method of the present invention shows significant advantages in terms of environmental protection, economy, processing accuracy and production efficiency.

[0041] In some embodiments of the present invention, Figure 1 As shown, when preparing the back structure of the back contact cell, the first tunnel oxide layer 260, the P-type polysilicon layer 250, the BSG layer 240, the second tunnel oxide layer 230, the N-type polysilicon layer 220 and the PSG layer 210 are generally deposited. Since the deposited film has no directionality, these layered structures will not only be formed on the back of the cell, but also attached to the side and front 200 of the cell to form a wrap. Therefore, wrap-around plating is formed, and the wrap-around plating structure includes the first tunnel oxide layer 260, the P-type polysilicon layer 250, the BSG layer 240, the second tunnel oxide layer 230, the N-type polysilicon layer 220 and the PSG layer 210 from the silicon substrate to the silicon substrate away from the silicon substrate.

[0042] Furthermore, in the SE process, the output power of the laser is 80-120W, which ensures sufficient energy to remove the coating while avoiding excessive damage to the silicon wafer.

[0043] Typically but not limiting, the output power of the laser may be, for example, 80 W, 85 W, 90 W, 95 W, 100 W, 105 W, 110 W, 115 W or 120 W, or any value within the range of 80 W to 120 W;

[0044] Preferably, the frequency of the laser is 80 to 110 kHz, which provides an appropriate pulse frequency to achieve efficient and uniform processing effects, and helps to improve the overall quality and performance of the battery cell.

[0045] Typically but not limiting, the frequency of the laser can be, for example, 80kHz, 82kHz, 84kHz, 86kHz, 88kHz, 90kHz, 92kHz, 94kHz, 96kHz, 98kHz, 100kHz, 102kHz, 104kHz, 106kHz, 108kHz, 110kHz, or any value within the range of 80kHz to 110kHz.

[0046] Preferably, the moving speed of the laser is 1000-8000 mm / s, which can improve production efficiency while maintaining processing quality.

[0047] Typically but not restrictively, the moving speed of the laser can be, for example, 1000 mm / s, 2000 mm / s, 3000 mm / s, 4000 mm / s, 5000 mm / s, 6000 mm / s, 7000 mm / s, 8000 mm / s, or any value within the range of 1000 mm / s to 8000 mm / s.

[0048] Furthermore, in the SE process, the spot size of the laser is 0.75-1 μm. Such a small spot size helps to achieve high-precision processing, ensure the accuracy of removing the coating, and avoid unnecessary damage to the battery cell.

[0049] Typically but not restrictively, in the SE process, the spot size of the laser may be, for example, 0.75 μm, 0.8 μm, 0.9 μm, 1.0 μm, or any value within the range of 0.75 μm to 1 μm.

[0050] Preferably, the laser engraving times are 1 to 6 times. Multiple engravings can more finely control the processing process and improve the thoroughness and uniformity of removing the coating.

[0051] The number of times of laser engraving may be, for example, 1 time, 2 times, 3 times, 4 times, 5 times, 6 times, or any value within the range of 1 to 6 times.

[0052] Furthermore, in the SE process, the pulse width of the laser is 1.0 to 2.0 fs, preferably 1.6 fs. Such a pulse width helps to achieve ultra-fine processing effects, reduce heat-affected zones, and maintain the integrity and performance of silicon wafers.

[0053] Typically but not limiting, the pulse width of the laser may be, for example, 1.0 fs, 1.2 fs, 1.4 fs, 1.6 fs, 1.8 fs, or 2.0 fs, preferably 1.6 fs, and may be any value within the range of 1.0 fs to 2.0 fs.

[0054] Furthermore, during the removal of the coating on the front side, the output power of the laser is 40 to 80 W. The power within this range can ensure the effective removal of the coating on the silicon wafer during the laser processing, while avoiding excessive thermal impact or damage to the silicon wafer, thereby ensuring the accuracy of the processing and the integrity of the silicon wafer.

[0055] Typically but not limiting, during the front-side coating removal process, the output power of the laser can be, for example, 40W, 45W, 50W, 55W, 60W, 65W, 70W, 75W or 80W, or any value within the range of 40W to 80W.

[0056] Preferably, the frequency of the laser is 80 to 110 kHz, which ensures the repeatability and uniformity of the laser processing and helps to improve the processing efficiency.

[0057] Typically but not limiting, the frequency of the laser can be, for example, 80kHz, 82kHz, 84kHz, 86kHz, 88kHz, 90kHz, 92kHz, 94kHz, 96kHz, 98kHz, 100kHz, 102kHz, 104kHz, 106kHz, 108kHz, 110kHz, or any value within the range of 80kHz to 110kHz.

[0058] Preferably, the moving speed of the laser is 1000-8000 mm / s. Such a speed range enables the laser processing to be completed in a shorter time, thereby improving production efficiency.

[0059] Typically but not restrictively, the moving speed of the laser can be, for example, 1000 mm / s, 2000 mm / s, 3000 mm / s, 4000 mm / s, 5000 mm / s, 6000 mm / s, 7000 mm / s, 8000 mm / s, or any value within the range of 1000 mm / s to 8000 mm / s.

[0060] Furthermore, during the removal of the front coating, the laser spot size is 5 to 35 μm. The small spot size helps to achieve high-precision processing, making the removal of the coating more precise and accurate, which helps to improve the performance of the battery cell.

[0061] Typically but not restrictively, during the removal of the front coating, the laser spot size can be, for example, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, or any value within the range of 5μm to 35μm.

[0062] Preferably, the laser engraving times are 2 to 10 times. Through multiple engravings, the processing process can be more finely controlled, the thoroughness and uniformity of removing the coating can be improved, and different processing requirements can be met.

[0063] Typically but not limiting, the number of laser engravings may be, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times, or any value within the range of 2 to 10 times.

[0064] Furthermore, during the removal of the coating on the front side, the pulse width of the laser is 2.0 to 2.5 fs, preferably 2.1 fs. Such an ultra-short pulse width helps to achieve ultra-fine processing effects, reduce the heat-affected zone, and maintain the integrity and performance of the silicon wafer.

[0065] Typically but not limiting, the pulse width of the laser may be, for example, 2.0 fs, 2.1 fs, 2.2 fs, 2.3 fs, 2.4 fs, or 2.5 fs, preferably 2.1 fs, and may be any value within the range of 2.0 fs to 2.5 fs.

[0066] The second aspect of the present invention provides a manufacturing process for a back contact cell, wherein a back structure is manufactured on a silicon substrate, and then the plating on the front side 200 and the edge of the silicon substrate is removed, and finally the front side 200 of the silicon substrate is textured, and a passivation layer and an anti-reflection layer are deposited on both sides to obtain the back contact cell;

[0067] The removal of the front side 200 and the edge of the silicon substrate is performed by the removal method described in the first aspect.

[0068] The manufacturing process provided by the present invention reduces damage to the battery cells caused by incomplete removal of the plating layer or improper operation through the effective removal of the front side 200 and the edge plating, improves the yield rate in the production process, and at the same time improves the automation level and production efficiency of the production line, reduces the uneven product quality caused by unstable chemical removal, and improves the stability and reliability of the manufacturing process.

[0069] The third aspect of the present invention provides a back-contact battery, which is prepared using the manufacturing process described in the second aspect.

[0070] The back-contact battery provided by the present invention has the technical advantages brought by the above-mentioned manufacturing process, so that the yield, long-term durability and reliability of the prepared back-contact battery are improved. The present invention is further illustrated by specific examples and comparative examples below, but it should be understood that these examples are only used for more detailed explanations and should not be understood as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, if no specific conditions are specified, are carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0071] Preparation Example

[0072] In this preparation example, the back structure of the back contact battery is manufactured, and the preparation process is as follows: the N-type silicon substrate 100 is double-sided polished, and then a first tunneling oxide layer 260, a P-type amorphous silicon layer 250, a BSG layer 240, a second tunneling oxide layer 230, an N-type amorphous silicon layer 220 and a PSG layer 210 are deposited on the back side, and at the same time, the front and side surfaces of the back contact battery have the above-mentioned layered structure.

[0073] The battery cell obtained in the preparation example was used to carry out the process of the embodiment and the comparative example.

[0074] Example 1

[0075] This embodiment provides a method for removing wrap-around plating, and the process is as follows:

[0076] 1. Place the cell on a laser machine and use the SE process to cut the edge of the silicon wafer until the silicon substrate is exposed on the side to obtain a cell with the edge coating removed.

[0077] Among them, in the SE process, the output power of the laser is 80w, the frequency is 80kHz, the pulse width is set to 1.6fs, the moving speed is 1000mm / s, the spot size is controlled to 0.75μm, and the number of engraving times is controlled to 2 times.

[0078] 2. For the front side of the cell where the edge coating is to be removed, local vaporization is performed in the laser irradiation area to remove the front side coating.

[0079] Among them, the output power of the laser is 40w, the frequency is 80kHz, the pulse width is set to 2.1fs, the moving speed is 1000mm / s, the spot size is controlled to 5μm, and the number of engraving times is controlled to 3 times.

[0080] Example 2

[0081] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 1 is that in the SE process, the output power of the laser is 90w. The remaining steps and parameters are the same as those in Embodiment 1 and will not be repeated here.

[0082] Example 3

[0083] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 2 is that in the SE process, the output frequency of the laser is 90 kHz, the number of engraving times is 3 times, and the remaining steps and parameters are the same as those in Embodiment 2, which will not be repeated here.

[0084] Example 4

[0085] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 3 is that during the front-side de-wrapping process, the output power of the laser is 50W. The remaining steps and parameters are the same as those in Embodiment 3 and will not be repeated here.

[0086] Example 5

[0087] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 3 is that during the front-side de-wrapping process, the output power of the laser is 60W. The remaining steps and parameters are the same as those in Embodiment 3 and will not be repeated here.

[0088] Example 6

[0089] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 4 is that during the front-side de-coating process, the moving speed of the laser is 2000 mm / s, the spot size is controlled to be 6 μm, and the remaining steps and parameters are the same as Embodiment 4 and will not be repeated here.

[0090] Example 7

[0091] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 6 is that during the front-side de-coating process, the output power of the laser is 40w, the spot size is controlled to 8μm, the number of engraving times is controlled to 4 times, and the remaining steps and parameters are the same as Embodiment 6 and will not be repeated here.

[0092] Example 8

[0093] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 7 is that during the front-side de-coating process, the laser spot size is controlled to be 10 μm, the number of engraving times is controlled to be 5 times, and the remaining steps and parameters are the same as Embodiment 7 and will not be repeated here.

[0094] Example 9

[0095] This embodiment provides a method for removing wrap-around plating. The difference from Embodiment 7 is that during the front-side de-wrapping process, the moving speed of the laser is 2500 mm / s. The remaining steps and parameters are the same as those in Embodiment 7 and will not be repeated here.

[0096] Comparative Example 1

[0097] This comparative example provides a method for removing the wrap-around plating, and the steps are as follows:

[0098] 1. Place the front side of the cell in contact with a mixed solution of nitric acid and hydrofluoric acid (wherein the mass concentration of nitric acid is 15% and the mass concentration of hydrofluoric acid is 20%) to remove the front side coating. Control the temperature of the nitric acid solution at 25°C and stop removing after observing that the silicon substrate is completely exposed.

[0099] 2. Then, remove the wrapping layer from one side of the cell in the same manner as in step 1, and stop when the silicon substrate is completely exposed; finally, remove the wrapping layer from the other side in the same manner as in step 1, to obtain a cell with all the wrapping layers removed.

[0100] Test Case

[0101] The back contact cells obtained in the examples and comparative examples were subjected to IV tests, and the obtained data are shown in Table 1 below.

[0102] Table 1

[0103] efficiency% Yield % efficiency% Yield % Example 1 25.55 90.26 Example 6 25.57 90.45 Example 2 25.53 90.05 Example 7 25.59 90.51 Example 3 25.55 90.21 Example 8 25.54 90.22 Example 4 25.56 90.33 Example 9 25.61 90.63 Example 5 25.54 90.28 Comparative Example 1 25.53 90.11

[0104] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for removing back contact cell wrap-around plating, characterized in that: The wrap-around plating is located on the front and edge of the back contact battery; The removal method comprises the following steps: The SE process is used to cut the edge and remove the edge coating; then the laser is used to remove the coating on the front side.

2. The removal method according to claim 1, characterized in that: The wrap-around plating includes a first tunnel oxide layer, a P-type polysilicon layer, a BSG layer, a second tunnel oxide layer, an N-type polysilicon layer and a PSG layer from the silicon substrate to a layer far away from the silicon substrate.

3. The removal method according to claim 1, characterized in that: In the SE process, the output power of the laser is 80-120w; Preferably, the frequency of the laser is 80 to 110 kHz; Preferably, the moving speed of the laser is 1000-8000 mm / s.

4. The removal method according to claim 1, characterized in that: In the SE process, the spot size of the laser is 0.75 to 1 μm; Preferably, the laser engraving times are 1 to 6 times.

5. The removal method according to claim 1, characterized in that: In the SE process, the pulse width of the laser is 1.0 to 2.0 fs, preferably 1.6 fs.

6. The removal method according to claim 1, characterized in that: During the removal of the coating on the front side, the output power of the laser is 40 to 80 W; Preferably, the frequency of the laser is 80 to 110 kHz; Preferably, the moving speed of the laser is 1000-8000 mm / s.

7. The removal method according to claim 1, characterized in that: During the removal of the coating on the front side, the laser spot size is 5 to 35 μm; Preferably, the laser engraving times are 2 to 10 times.

8. The removal method according to claim 1, characterized in that: During the removal of the coating on the front side, the pulse width of the laser is 2.0 to 2.5 fs, preferably 2.1 fs.

9. A process for manufacturing a back contact battery, characterized in that: The back structure is fabricated on the silicon substrate, and then the plating on the front and edge of the silicon substrate is removed, and finally the front of the silicon substrate is textured, and a passivation layer and an anti-reflection layer are deposited on both sides to obtain the back contact cell; The removal of the wrap-around plating on the front side and the edge of the silicon substrate is carried out by the removal method described in any one of claims 1 to 8.

10. A back contact battery, characterized in that: The method is prepared by the manufacturing process described in claim 9.

Images