CN111834211A - Pretreatment method of silicon wafer and preparation method of stitched solar module - Google Patents

Abstract

The invention belongs to the technical field of photovoltaics, and provides a silicon wafer pretreatment method and a stitch welding solar module preparation method, which comprise the following steps: the laser beam is adopted to rapidly heat the interior of the part of the silicon wafer to be cracked, and the fluid beam is adopted to rapidly cool the surface of the part of the silicon wafer to be cracked, so that the silicon wafer is cracked under the action of compressive stress and tensile stress, and plasma etching is carried out on at least one part of the surface of the silicon wafer. The method combines stress cracking and plasma etching to be applied to the pretreatment of the silicon wafer, can obviously improve the cutting damage to the silicon wafer, ensures that the section of the silicon wafer is uniform, has no burr or crack, obviously reduces the fragment rate of the silicon wafer, and obviously reduces the hidden crack number of the grains of the stitch-welded solar module.

Description

Pretreatment method of silicon wafer and preparation method of stitched solar module

technical field

The invention belongs to the field of photovoltaic technology, and particularly relates to a method for pretreatment of silicon wafers and a method for preparing stitched solar modules.

Background technique

As a new battery welding process, stitch welding technology realizes the superposition of battery cells on the basis of the traditional ribbon welding process, reduces the spacing between cells, maximizes the utilization area, and achieves high energy density.

During the preparation of stitch-bonded solar modules, after the silicon wafers are sorted, the silicon wafers need to be cut and pretreated, and then the silicon wafers are lapped and welded based on the welding technology using flexible welding tapes and custom tooling. Among them, the traditional silicon wafer cutting method is to use a pulsed laser with high energy density to draw a groove on the silicon wafer, and then mechanically break it apart. The section of the silicon wafer cut by the traditional method was observed by scanning electron microscope, and it was found that the section was extremely uneven, with obvious wavy shape and many burrs and cracks. This is because the laser heat caused chemical changes in the cut section of the battery, and the The melting phenomenon caused serious cutting damage to the silicon wafer. Due to the stress at the junction point of laser cutting and mechanical breaking, and the cutting part of the silicon wafer is located at the calendering position of the welding tape, the damage of the silicon wafer caused by the cutting process will ultimately affect the quality of the stitched solar modules. After pressing, more lines and cracks appear.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for pretreatment of silicon wafers and a method for preparing stitched solar modules in view of the above-mentioned deficiencies of the prior art.

In order to solve the above-mentioned technical problems, a first aspect of the present invention provides a method for preprocessing a silicon wafer, which sequentially includes: using a laser beam to rapidly heat the interior of the portion of the silicon wafer to be split, so that the portion of the silicon wafer to be split is rapidly heated. The internal expansion forms compressive stress; the surface of the part to be split of the silicon wafer is rapidly cooled by the fluid beam, so that the surface of the part to be split of the silicon wafer shrinks to form tensile stress; the silicon wafer is under the compressive stress and the tensile stress Splitting occurs under the action of the silicon wafer; at least a part of the surface of the silicon wafer is exposed to plasma, and plasma etching is performed on at least a part of the surface of the silicon wafer, wherein at least a part of the surface of the silicon wafer includes the part where the splitting occurs in the silicon wafer s surface.

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

The present invention combines stress slicing and plasma etching in the pretreatment of silicon wafers. First, a laser beam is used to rapidly heat the interior of the silicon wafer to be split, so that the internal expansion of the silicon wafer to be split forms compressive stress; a fluid beam is used to rapidly cool the surface of the silicon wafer to be split, so that the silicon wafer is to be split. The surface shrinks to form tensile stress; since the compressive stiffness of the brittle material is much greater than the tensile strength, when the tensile stress reaches the breaking strength of the silicon wafer, the silicon wafer will fracture naturally, and the crack will expand steadily with the laser and the cooling moving track. The method of the invention avoids the thermal damage and mechanical damage to the silicon wafer in the traditional process of "laser cutting combined with mechanical cracking", effectively improves the quality of the section of the silicon wafer, and also reduces the fragmentation rate during the splitting process. Secondly, after the silicon wafer is subjected to stress splits, plasma etching is performed on the silicon wafer to remove the diffusion layer on the surface of the silicon wafer and the slight cracks or dust on the surface of the split part, thereby further improving the surface properties of the silicon wafer.

The second aspect of the present invention also provides a method for preparing a stitch-bonded solar module, the method comprising: pre-processing a silicon wafer according to the method described in the first aspect of the present invention, and stitch-bonding the pre-treated silicon wafer technology to prepare solar modules. With the solar module prepared by the method provided in the second aspect of the present invention, the problem of cracking of lines is significantly improved.

Preferably, in the pretreatment method for silicon wafers provided by the present invention, the step of rapidly heating the interior of the silicon wafer to be split by a laser beam sequentially includes: using a laser beam with a wavelength of 320-400 nm and a power of 3-5W The ultraviolet laser beam rapidly heats the interior of the silicon wafer to be split; the infrared laser beam with a wavelength of 1060-1100 nm and a power of 100 to 150 W is used to rapidly heat the interior of the silicon wafer to be split.

Preferably, in the pretreatment method of the silicon wafer provided by the present invention, the distance between the interior of the portion of the silicon wafer to be split and the surface of the portion to be split of the silicon wafer is 1˜3 mm. In this distance range, the success rate of stress cleavage and the cleaving effect are the best.

Preferably, in the pretreatment method for silicon wafers provided by the present invention, in the step of rapidly cooling the surface of the silicon wafer to be split by a fluid beam, the fluid beam is selected from liquid water, liquid carbon dioxide, liquid hydrogen , at least one of liquid nitrogen, low temperature inert gas, low temperature carbon dioxide gas, low temperature hydrogen gas, and low temperature nitrogen gas.

Preferably, in the pretreatment method for silicon wafers provided by the present invention, the temperature of the fluid beam is 20-30°C. In the method of the present invention, the laser beam can make the internal temperature of the part of the silicon wafer to be split to reach 150-200° C. At the same time, according to the laser parameters and the heating position of the present invention, it is only necessary to apply 20 to 20 to the surface of the part of the silicon wafer to be split. Stress splitting can be achieved by rapid cooling of the fluid beam at 30°C. The fluid beam at 20-30° C. is easy to obtain and easy to use, so that the method of the present invention has good operability and easy industrial application.

Preferably, in the method for pretreatment of silicon wafers provided by the present invention, the plasma etching step is performed in a plasma etcher.

Preferably, in the pretreatment method for silicon wafers provided by the present invention, the gas for forming the plasma contains at least CF ₄ and O ₂ , the flow rate of the CF ₄ is 100-120 sccm/min, and the flow rate of the O ₂ is 100-120 sccm/min. The flow rate is 10～15sccm/min.

Preferably, in the pretreatment method for silicon wafers provided by the present invention, the pressure of the high-frequency glow that excites the plasma is 300-350 Pa, and the power is 100-120 W.

Preferably, in the pretreatment method for silicon wafers provided by the present invention, the time for turning on the high-frequency glow is 10-18 minutes, preferably 14 minutes.

Under the above-mentioned plasma gas flow rate range and the pressure and power conditions of the high-pressure glow provided by the present invention, when the high-frequency glow is turned on and the plasma etching time on the surface of the silicon wafer is 14 minutes, the stitched solar modules can be welded. The improvement effect of cracks is the best, and the number of cracks in the whole assembly can be controlled within 4 places.

Description of drawings

1 is a scanning electron microscope image of the edge of a silicon wafer lobe pretreated according to the method of the present invention in Example 3;

Fig. 2 is the scanning electron microscope picture of the silicon wafer cutting edge after traditional laser slicing and plasma etching treatment in Comparative Example 1;

Fig. 3 is the scanning electron microscope image of the sliced section of the silicon wafer after pretreatment according to the method of the present invention in Example 3;

Fig. 4 is the scanning electron microscope picture of the silicon wafer cut section after traditional laser slicing and plasma etching treatment in Comparative Example 1;

FIG. 5 is a schematic structural diagram of two adjacent silicon wafers connected in series in a stitch-bonded solar module according to an embodiment.

Detailed ways

In order to understand the objects, features and advantages of the present invention more clearly, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The materials used without specifying the manufacturer are conventional products that can be purchased from the market. The description of the exemplary embodiments is for illustrative purposes only, and not for the purpose of limiting the invention and its applications.

According to the first aspect of the present invention, an embodiment of the present invention provides a method for preprocessing a silicon wafer, which sequentially includes: using a laser beam to rapidly heat the interior of the portion of the silicon wafer to be split, so that the portion of the silicon wafer to be split is rapidly heated. The internal expansion of the silicon wafer forms compressive stress; the surface of the silicon wafer to be split is rapidly cooled by a fluid beam, so that the surface of the silicon wafer to be split is contracted to form tensile stress; the silicon wafer is under the compressive stress and the tensile stress. Splitting occurs under the action of stress; at least a part of the surface of the silicon wafer is exposed to plasma, and at least a part of the surface of the silicon wafer is subjected to plasma etching, wherein at least a part of the surface of the silicon wafer includes the splitting of the silicon wafer surface of the part.

In some embodiments of the present invention, the step of rapidly heating the interior of the silicon wafer to be split by a laser beam sequentially includes: firstly using an ultraviolet laser beam with a wavelength of 320-400 nm and a power of 3-5W to heat the silicon wafer The interior of the part to be split is rapidly heated; and then an infrared laser beam with a wavelength of 1060-1100 nm and a power of 100-150 W is used to rapidly heat the interior of the part to be split of the silicon wafer. As an example of some embodiments, an ultraviolet laser beam with a wavelength of 320nm and a power of 3W can be used; an ultraviolet laser beam with a wavelength of 350nm and a power of 5W; an ultraviolet laser beam with a wavelength of 380nm and a power of 4W; 4.5W UV laser beam, etc. Similarly, as an example of some embodiments, an infrared laser beam with a wavelength of 1060nm and a power of 100W can be used; an infrared laser beam with a wavelength of 1070nm and a power of 110W; an infrared laser beam with a wavelength of 1080nm and a power of 120W; the wavelength is Infrared laser beam with 1090nm and power of 130W; infrared laser beam with wavelength of 1100nm and power of 150W, etc.

In some embodiments of the present invention, the distance between the interior of the portion to be split of the silicon wafer and the surface of the portion to be split of the silicon wafer is 1˜3 mm. As an example of some embodiments, the distance between the interior of the portion to be split of the silicon wafer and the surface of the portion to be split of the silicon wafer may be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, or the like.

In some embodiments of the present invention, in the step of using a fluid beam to rapidly cool the surface of the silicon wafer to be split, the fluid beam is selected from liquid water, liquid carbon dioxide, liquid hydrogen, liquid nitrogen, low temperature inert gas, low temperature At least one of carbon dioxide gas, low temperature hydrogen gas, and low temperature nitrogen gas.

In some embodiments of the present invention, the temperature of the fluid beam is 20-30°C. As an example of some embodiments, the temperature of the fluid beam may be 20°C, 24°C, 26°C, 28°C, or 30°C, and the like.

In some embodiments of the present invention, the plasma etching step is performed in a plasma etcher. The embodiment of the present invention has no special requirements on the brand and model of the plasma etching machine, as long as the plasma etching machine that can complete the following plasma etching process is applicable: under low pressure, the reaction gas is Under excitation, ionization is generated and a plasma is formed. The plasma is composed of charged electrons and ions. Under the impact of the electrons, the gas in the reaction chamber can absorb energy and form a large number of active reactive radicals in addition to being converted into ions. The active reactive group reacts chemically with the surface of the material to be etched and forms a volatile reaction product; the reaction product separates from the surface of the material to be etched and is drawn out of the cavity by the vacuum system.

In some embodiments of the present invention, the gas forming the plasma contains at least CF ₄ and O ₂ , the flow rate of the CF ₄ is 100-120 sccm/min, and the flow rate of the O ₂ is 10-15 sccm/min. As an example of some embodiments, the flow rate of CF ₄ may be 100sccm/min, 105sccm/min, 110sccm/min, 115sccm/min, 120sccm/min, etc.; the flow rate of O ₂ may be 10sccm/min, 11sccm/min, 12sccm/min min, 13sccm/min, 14sccm/min, 15sccm/min, etc.

In some embodiments of the present invention, the pressure of the high-frequency glow for exciting the plasma is 300-350 Pa, and the power is 100-120 W. As an example of some embodiments, the pressure to excite the high-frequency glow of the plasma may be 300Pa, 310Pa, 320Pa, 340Pa, 350Pa, etc.; the power may be 100W, 105W, 110W, 115W, 120W, etc.

In some embodiments of the present invention, the high-frequency glow is turned on for 10-18 minutes. For example, the time for turning on the high-frequency glow may be 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, and the like.

According to the second aspect of the present invention, an embodiment of the present invention further provides a method for preparing a stitch-bonded solar module, comprising: pre-processing a silicon wafer according to the method described in the first aspect of the present invention, Silicon wafers are fabricated into solar modules by stitch welding technology.

The embodiments of the present invention do not have special limitations on the specific process steps for preparing a solar module by using the stitch welding technology, which can be performed according to the conventional preparation method of a stitch welding solar module in the art.

In the stitch welding solar module provided by the embodiment of the present invention, a plurality of pretreated silicon wafers are overlapped and connected in series with each other, and a welding tape is provided between two adjacent silicon wafers. In the preparation process of the stitched solar module, the welding tape can be positioned between two adjacent silicon wafers and welded to obtain a battery string that is overlapped and connected in series by several silicon wafers; The substrate, EVA film layer, battery string and backplane are heated and cured into a rigid whole. Since the split part of the silicon wafer in the pretreatment process is in a position that coincides with the welding tape, the surface properties and stress resistance of the split part of the silicon wafer have higher requirements during the welding and lamination process. If it is thermally affected or mechanically damaged during the process, or there are many microcracks or burrs on the surface of the split part, it is easy to cause cracks in the laminated components.

The advantages of the present application are further described below with reference to specific embodiments. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. Unless otherwise specified, various parameters involved in this specification have general meanings known in the art, and can be measured according to methods known in the art. For example, the tests can be performed according to the methods given in the examples of the present application. In addition, the preferred ranges and options of various parameters given in various preferred embodiments can be combined arbitrarily, and various combinations obtained thereby are considered to be within the scope of the disclosure of the present application.

Examples 1 to 12

1. Pretreatment of silicon wafers

After the silicon wafer is sorted, the ultraviolet laser beam (continuous laser) is used to rapidly heat the interior of the silicon wafer to be split for 1-2 seconds; then the infrared laser beam (continuous laser) is used to rapidly heat the interior of the silicon wafer to be split for 1. ~2 seconds, so that the internal expansion of the silicon wafer to be split to form a compressive stress. A fluid beam is used to rapidly cool the surface of the silicon wafer to be split, and the cooling time is 1-2 seconds, so that the surface of the silicon wafer to be split is contracted to form tensile stress. The silicon wafer breaks under the action of compressive stress and tensile stress, and the crack expands stably with the moving track of the laser beam and the fluid beam.

The silicon wafer is placed in a plasma etching machine for plasma etching, the gas for forming the plasma contains CF ₄ and O ₂ , and the flow rate of CF ₄ is controlled to be 100-120 sccm/min, and the flow rate of O ₂ is 10- 15sccm/min. The specific process flow of plasma etching is briefly described as follows: turn on the gas, power on the whole machine, high-frequency preheating, turn on the pump, pre-pump the tail gas, turn off the pre-pump and open the main pump, and send the process gas (CF ₄ and O ₂ ) And diluted, when the pressure is stable at the set value, turn on the high-frequency glow discharge, turn off the high-frequency glow, turn off the process gas, send nitrogen, inflate the lid, and remove the silicon wafer.

2. Preparation of stitch welding solar modules

Using conventional stitch welding technology to prepare solar modules, the specific process steps are briefly described as follows: take a number of pretreated silicon wafers, position the welding strips between two adjacent pretreated silicon wafers, and weld them to obtain a A number of pretreated silicon wafers are overlapped with each other in series with battery strings; then laminated; and the glass substrate, EVA film layer, battery string and backplane are heated and cured into a rigid whole to obtain a stitched solar module.

The specific process parameters of Examples 1-12 are shown in Table 1.

Comparative Example 1

The difference between Comparative Example 1 and Example 3 is that a conventional laser slicer is used to perform laser grooving on a silicon wafer with a 100W ultraviolet laser, and then mechanically break it apart. Subsequent preparation steps for plasma etching of silicon wafers and stitch welding of solar modules are the same as in Example 3, and the specific process parameters are shown in Table 1.

Comparative Example 2

The difference between Comparative Example 1 and Example 3 is that: first, an infrared laser beam (continuous laser) is used to rapidly heat the interior of the silicon wafer to be split for 1 to 2 seconds; then an ultraviolet laser beam (continuous laser) is used to heat the silicon wafer to be split. The interior of the silicon wafer is rapidly heated for 1 to 2 seconds; then the surface of the silicon wafer to be split is rapidly cooled by a fluid beam, the silicon wafer cannot achieve natural stress splitting, and the splitting is mechanically matched. Subsequent preparation steps for plasma etching of silicon wafers and stitch welding of solar modules are the same as in Example 3, and the specific process parameters are shown in Table 1.

The pretreated silicon wafers and the prepared stitch-bonded solar modules in Examples 1-12 and Comparative Examples 1-2 were respectively observed and detected for the cross-sectional quality of silicon wafers, the fragmentation rate of silicon wafers, and the cracks in the lines of the modules.

Among them, the detection of cracks in the module is carried out using an EL tester (automatic tester for defect detection of solar cell modules), which uses the electroluminescence principle of crystalline silicon and uses a high-resolution CCD camera to capture the close-up of the module. Infrared images to obtain and determine the cracking defects of the components.

Fig. 1 is the scanning electron microscope image of the edge of the silicon wafer after pretreatment according to the method of the present invention in Example 3; Fig. 2 is the scanning of the cutting edge of the silicon wafer after conventional laser slicing and plasma etching treatment in Comparative Example 1 Electron microscope image.

Fig. 3 is the scanning electron microscope image of the sliced section of the silicon wafer after pretreatment according to the method of the present invention in Example 3; Fig. 4 is the scanning of the cut section of the silicon wafer after conventional laser sectioning and plasma etching treatment in Comparative Example 1 Electron microscope image.

According to the comparison of Figures 1 to 4, it can be seen that the edge of the silicon wafer in Example 3 of the present invention does not have any heat-affected zone. With very little material removed, dust generation can be greatly reduced. This shows that the pretreatment method provided by the present invention can effectively reduce the cutting damage of the cell, improve the mechanical strength of the silicon wafer, and make the silicon wafer have better electrical performance. In contrast, the conventional laser slicing technology used in Comparative Example 1 will leave an obvious heat-affected zone on the edge of the silicon wafer, the laser damage depth to the section of the silicon wafer is almost 50% of the material thickness, and there are many micro-cracks on the section of the silicon wafer. , which can reduce the mechanical strength of the silicon wafer, and must be accompanied by a large amount of dust during the processing.

FIG. 5 is a schematic structural diagram of two adjacent silicon wafers connected in series in a stitch-bonded solar module according to an embodiment of the present invention. As shown in FIG. 5 , the two silicon wafers 1 pretreated by the method of the present invention are overlapped and connected in series, and the welding tape 2 is connected to the lower surface of the first silicon wafer and the second silicon wafer among the two adjacent silicon wafers. On the upper surface of the silicon wafer 1, the edge 3 of the silicon wafer 1 coincides with the welding strip 2, wherein the edge 3 of the silicon wafer 1 is the part of the silicon wafer split during the pretreatment process. Because the silicon wafer pretreated by the method provided by the present invention is not affected by obvious heat and mechanical damage, and has better surface properties and higher mechanical strength, it is not easy to be welded and laminated during the process of lamination. Create cracks in the texture.

The rest of the test results are shown in Table 1.

Table 1

In Examples 1 to 12, the method provided by the present invention was used to pretreat the silicon wafer, and the pretreated silicon wafer was prepared into a stitch welding solar module. In Comparative Example 1, a conventional laser slicer cutting method combined with mechanical breaking is used to cut a silicon wafer, and then plasma etching is performed on the cut silicon wafer, and a stitch welding solar module is further prepared. From the test results in Table 1, it can be seen that the sections of the silicon wafers in Examples 1 to 12 are uniform and free of burrs and cracks, while the sections of the silicon wafers in Comparative Example 1 are uneven and have many burrs and cracks. At the same time, compared with Comparative Example 1, the silicon wafer fragmentation rate and the number of cracks in the component lines of Examples 1 to 12 were significantly decreased. This shows that the silicon wafer pretreatment method provided by the present invention can significantly reduce the laser cutting damage to the silicon wafer, make the material of the silicon wafer split part more smooth and uniform, without burrs or cracks, and significantly improve the cracking problem of the components. It has a very low fragmentation rate, which is beneficial to the improvement of production capacity.

In Comparative Example 2, although the laser beam is also used to heat the inside of the silicon wafer and the fluid beam to cool the surface of the silicon wafer, it first uses an infrared laser beam for heating, and then uses an ultraviolet laser beam for heating. After the two-step laser internal heating, combined with the surface cooling of the fluid beam, the silicon wafer cannot achieve natural stress splitting, and mechanical force is required to cooperate with the splitting. From the test results in Table 1, it can be seen that Comparative Example 2 does not significantly improve the silicon chip section quality, fragmentation rate and component cracks.

The difference between Examples 1 to 8 and Examples 9 and 10 is that in the step of rapidly heating the interior of the silicon wafer to be split by using a laser beam, the distance between the heating portion inside the silicon wafer and the surface of the silicon wafer is different. The distances in Examples 1 to 8 were 1 to 3 mm, while the distances in Examples 9 and 10 were 0.5 mm and 4 mm, respectively. From the test results in Table 1, it can be seen that in the step of rapidly heating the interior of the silicon wafer to be split by the laser beam, when the distance between the heating part inside the silicon wafer and the surface of the silicon wafer is within the range of 1 to 3 mm, the fragmentation rate of the silicon wafer will be reduced. Lowest, minimal dicing damage to the silicon wafer during the splitting process.

The difference between Examples 1 to 8 and Examples 11 to 12 is that in the step of plasma etching the silicon wafer, the time for turning on the high-frequency glow is different, that is, the time for plasma etching is different. The plasma etching time in Examples 1 to 8 is in the range of 10 to 18 min, while the plasma etching time in Examples 11 and 12 is 7 min and 23 min, respectively. From the test results in Table 1, it can be seen that the plasma etching time is in the range of 10 to 18 minutes, and the improvement effect on the cracks of the component lines is the most obvious.

The above examples are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with the technology to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention. All equivalent transformations or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. a pretreatment method of silicon wafer, is characterized in that, comprises successively: Using a laser beam to rapidly heat the inside of the part to be split of the silicon wafer, so that the inner part of the part to be split of the silicon wafer expands to form a compressive stress; Use a fluid beam to rapidly cool the surface of the part to be split of the silicon wafer, so that the surface of the part to be split of the silicon wafer shrinks to form tensile stress; The silicon wafer is split under the action of the compressive stress and the tensile stress; At least a part of the surface of the silicon wafer is exposed to plasma, and at least a part of the surface of the silicon wafer is subjected to plasma etching, wherein at least a part of the surface of the silicon wafer includes the surface of the part where the splinter of the silicon wafer occurs. 2 . The method for preprocessing a silicon wafer according to claim 1 , wherein the step of rapidly heating the interior of the silicon wafer to be split by a laser beam sequentially comprises: 2 . Use an ultraviolet laser beam with a wavelength of 320 to 400 nm and a power of 3 to 5 W to rapidly heat the interior of the silicon wafer to be split; An infrared laser beam with a wavelength of 1060-1100 nm and a power of 100-150 W is used to rapidly heat the inside of the silicon wafer to be split. 3 . The method for preprocessing a silicon wafer according to claim 1 , wherein the distance between the interior of the portion of the silicon wafer to be split and the surface of the portion to be split of the silicon wafer is 1-3 mm. 4 . 4 . The method for preprocessing silicon wafers according to claim 1 , wherein in the step of rapidly cooling the surface of the silicon wafer to be split by a fluid beam, the fluid beam is selected from liquid water, liquid carbon dioxide , at least one of liquid hydrogen, liquid nitrogen, low temperature inert gas, low temperature carbon dioxide gas, low temperature hydrogen gas, and low temperature nitrogen gas. 5 . The method for preprocessing silicon wafers according to claim 1 , wherein the temperature of the fluid beam is 20-30° C. 6 . 6 . The method for preprocessing a silicon wafer according to claim 1 , wherein the plasma etching step is performed in a plasma etcher. 7 . 7 . The method for preprocessing silicon wafers according to claim 6 , wherein the gas for forming the plasma contains at least CF ₄ and O ₂ , the flow rate of the CF ₄ is 100-120 sccm/min, and the The flow rate of O ₂ is 10-15 sccm/min. 8 . The method for preprocessing silicon wafers according to claim 7 , wherein the pressure of the high-frequency glow for exciting the plasma is 300-350 Pa, and the power is 100-120 W. 9 . 9 . The method for preprocessing silicon wafers according to claim 8 , wherein the time for turning on the high-frequency glow is 10-18 minutes, preferably 14 minutes. 10 . 10. A preparation method of a stitch welding solar module, characterized in that, comprising: According to the method according to any one of claims 1 to 9, the silicon wafer is pretreated, and the pretreated silicon wafer is prepared into a solar module by stitch welding technology.

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