Solar cell and method for manufacturing same

Abstract

The present application discloses a solar cell and a method for manufacturing same. The method for manufacturing the solar cell comprises: texturing an N-type silicon wafer (100); forming a front amorphous silicon layer (210) and a back amorphous silicon layer (220), the front amorphous silicon layer (210) comprising an N-type doped layer (212), and the back amorphous silicon layer (220) comprising a P-type doped layer (222); forming a first transparent conductive film (310) and a second transparent conductive film (320) to obtain a blue wafer; and performing a first light injection process on the blue wafer.

Description

Solar cell and preparation method thereof

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 6, 2023, with application number 202311148173.3 and invention name “Solar Cell and Its Preparation Method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of solar cell technology, and in particular, to solar cells and methods for preparing the same. Background Art

[0003] At present, the static attenuation of copper interconnection process cells is relatively large. The large attenuation will lead to problems such as cell failure and reduced power, which is not conducive to warehouse storage and shipment.

[0004] Therefore, current solar cells and their preparation methods still need to be improved.

[0005] Summary of the Invention

[0006] This application is based on the inventor's discovery and understanding of the following facts and problems:

[0007] In the related art, the steps for preparing copper electroplated heterojunction cells are as follows: first, the N-type monocrystalline silicon wafer is subjected to a texturing and cleaning treatment, and then, intrinsic amorphous silicon and N-type amorphous silicon thin films are deposited on the front of the silicon wafer, and intrinsic amorphous silicon and P-type amorphous silicon thin films are deposited on the back of the silicon wafer; a transparent conductive film (TCO conductive layer) is formed on the amorphous silicon, and then, a copper seed layer is formed on the transparent conductive film (the semi-finished product after the seed layer deposition is called a yellow film, and the surface of the transparent conductive film and the side of the battery body will be covered with a copper layer during the sputtering process), after photosensitive adhesive coating, pattern transfer, and development, the copper seed layer is used to grow copper grid lines in the electroplating solution due to its good conductive effect, and then the adhesive film and the remaining copper layer are removed, and a metal tin layer is chemically plated on the copper grid lines to protect the copper grid lines and serve as a welding metal for component welding; finally, after light injection treatment, a copper interconnected solar cell panel can be obtained. After the above process, the copper interconnect solar cell will have a large static attenuation, and the large dark decay will cause the cell to drop out of gear and the power to decrease, which is not conducive to storage and warehouse shipment.

[0008] The inventors discovered that the preparation process of copper electroplated heterojunction cells involves repeated use of corrosive liquids, such as plating solutions. These corrosive liquids can damage the transparent conductive film, leading to significant battery degradation. Through extensive experimental verification, the inventors discovered that after forming the transparent conductive film, the blue film can be treated with light injection. This stimulates the recombination of electrons and holes, increasing their concentration and improving the battery's conversion efficiency. During this light injection process, the oxide ions in the transparent conductive film's crystal structure rearrange, forming a more ordered structure, which helps improve its conductivity. Furthermore, light injection treatment of the blue film helps improve the degradation of solar cells.

[0009] In view of this, the present application aims to alleviate or solve at least one of the above-mentioned problems to at least some extent.

[0010] In one aspect of the present application, a method for preparing a solar cell is proposed. In some embodiments of the present application, the method for preparing a solar cell includes: performing a texturing treatment on an N-type silicon wafer to form a pyramid structure on both the front and back sides of the N-type silicon wafer; forming a front amorphous silicon layer and a back amorphous silicon layer, wherein the front amorphous silicon layer includes a front intrinsic amorphous silicon layer and an N-type doped layer located on the side of the front intrinsic amorphous silicon layer away from the N-type silicon wafer, and the back amorphous silicon layer includes a back intrinsic amorphous silicon layer and a P-type doped layer located on the side of the back intrinsic amorphous silicon layer away from the N-type silicon wafer; forming a first transparent conductive film on the side of the N-type doped layer away from the N-type silicon wafer, and forming a second transparent conductive film on the side of the P-type doped layer away from the N-type silicon wafer to obtain a blue film; and performing a first light injection treatment on the blue film. The first light injection treatment can improve the conductive properties of the transparent conductive film and help improve the static attenuation of the solar cell.

[0011] In some embodiments of the present application, the temperature of the first light injection treatment is 208°C to 215°C, and / or the duration of the first light injection treatment is 38s to 45s, and / or the wavelength of the light used in the first light injection treatment is 800nm ​​to 1000nm. When the temperature, duration, or wavelength of the first light injection treatment are within an appropriate range, the static degradation of the solar cell can be further improved, thereby improving the stability of the solar cell.

[0012] In some embodiments of the present application, after the blue film is subjected to the first light injection treatment, the method for preparing a solar cell further includes: forming a copper seed layer on the side of the first transparent conductive film away from the N-type silicon wafer and the side of the second transparent conductive film away from the N-type silicon wafer to obtain a yellow film; forming a photosensitive adhesive on the surface of the copper seed layer away from the N-type silicon wafer, and removing the photosensitive adhesive at the grid line position; wrapping the four sides and corner positions of the yellow film with adhesive; forming a first copper grid line on the copper seed layer on the front side of the N-type silicon wafer, and forming a second copper grid line on the copper seed layer on the back side of the N-type silicon wafer; performing a film removal process and a back etching process to remove the adhesive The first copper seed layer is located between the first copper grid line and the first transparent conductive film, and the second copper seed layer is located between the second copper grid line and the second transparent conductive film; and a first metal tin layer and a second metal tin layer are formed, the first metal tin layer covers the surface of the first copper grid line away from the N-type silicon wafer and at least part of the side surface of the first copper grid line, and the second metal tin layer covers the surface of the second copper grid line away from the N-type silicon wafer and at least part of the side surface of the second copper grid line.

[0013] In some embodiments of the present application, after forming the first metal tin layer and the second metal tin layer, the method further includes: performing a second light injection process. The second light injection process can further improve the performance of the solar cell and help further increase the conversion efficiency of the solar cell.

[0014] In some embodiments of the present application, the temperature of the second light injection treatment is 200°C to 220°C, and / or the duration of the second light injection treatment is 60s to 120s. Setting the temperature and / or duration of the second light injection treatment within the above ranges is beneficial to further improving the conversion efficiency of the solar cell.

[0015] In some embodiments of the present application, the method for preparing a solar cell satisfies at least one of the following conditions: the thickness of the front intrinsic amorphous silicon layer is 3nm to 6nm; the thickness of the back intrinsic amorphous silicon layer is 3nm to 9nm; the front amorphous silicon layer is formed by plasma-enhanced chemical vapor deposition; the back amorphous silicon layer is formed by plasma-enhanced chemical vapor deposition; the thickness of the N-type doped layer is 5nm to 10nm; the thickness of the P-type doped layer is 5nm to 15nm; the N-type doped layer is a phosphorus-doped amorphous silicon layer; and the P-type doped layer is a boron-doped amorphous silicon layer. This helps further improve the overall performance of the solar cell.

[0016] In some embodiments of the present application, the method for preparing a solar cell satisfies at least one of the following conditions: the thickness of the first transparent conductive film is 90nm to 110nm; the thickness of the second transparent conductive film is 90nm to 110nm; the material of the first transparent conductive film is ITO; the material of the second transparent conductive film is ITO; the first transparent conductive film is formed by a physical vapor deposition method; the second transparent conductive film is formed by a physical vapor deposition method.

[0017] In some embodiments of the present application, the method for preparing a solar cell satisfies at least one of the following conditions: the copper seed layer is formed by physical vapor deposition; the thickness of the photosensitive resin is 10 μm to 14 μm; and a sodium hydroxide solution with a concentration of 10 g / L to 20 g / L is used for film removal.

[0018] In some embodiments of the present application, the method for preparing a solar cell satisfies at least one of the following conditions: the thickness of the first copper grid line is 8 μm to 10 μm; the thickness of the second copper grid line is 8 μm to 10 μm; the thickness of the first metal tin layer is 2 μm to 6 μm; the thickness of the second metal tin layer is 2 μm to 6 μm.

[0019] In another aspect, the present application provides a solar cell. In some embodiments of the present application, the solar cell is prepared using the aforementioned method. As a result, the solar cell has good stability and low static decay. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] FIG1 shows a flow chart of a method for preparing a solar cell according to one embodiment of the present application;

[0022] FIG2 shows a flow chart of a method for preparing a solar cell according to another embodiment of the present application;

[0023] FIG3 shows a schematic structural diagram of a solar cell according to an embodiment of the present application;

[0024] FIG4 shows a schematic diagram of a partial structure of a solar cell according to an embodiment of the present application;

[0025] Figure 5 shows a comparison of the conversion efficiency attenuation of the experimental group, baseline group, and HJT group battery samples.

[0026] 100: N-type silicon wafer; 110: front side; 120: back side; 130: pyramid structure; 210: front amorphous silicon layer; 211: front intrinsic amorphous silicon layer; 212: N-type doped layer; 220: back side amorphous silicon layer; 221: back side intrinsic amorphous silicon layer; 222: P-type doped layer; 310: first transparent conductive film; 320: second transparent conductive film; 410: first copper seed layer; 420: second copper seed layer; 510: first copper grid line; 520: second copper grid line; 610: first metal tin layer; 620: second metal tin layer. DETAILED DESCRIPTION

[0027] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0028] In one aspect of the present application, a method for preparing a solar cell is provided. In some embodiments of the present application, referring to FIG1 and FIG2 , the method for preparing a solar cell may include the following steps:

[0029] S100: performing texturing treatment on the N-type silicon wafer.

[0030] 1 to 4 , an N-type silicon wafer 100 is subjected to a texturing process, forming pyramid structures 130 on both the front side 110 and the back side 120 of the N-type silicon wafer. The texturing process forms a velvet surface on the surface of the N-type silicon wafer, forming pyramid structures 130 on both the front side 110 and the back side 120 of the N-type silicon wafer, as shown in FIG3 and FIG4 . This reduces the reflectivity of the silicon wafer surface to light, increases the silicon wafer's absorption rate of photons, and contributes to increasing the photogenerated current.

[0031] In some embodiments of the present application, referring to FIG4 , the height d of the pyramid structure 130 can be 2 μm to 8 μm. For example, the height d of the pyramid structure 130 can be 2 μm, 3 μm, 5 μm, 6 μm, 8 μm, etc. Thus, pyramid structures of the above dimensions are more conducive to reducing the reflectivity of light on the silicon wafer surface and promoting the absorption of photons by the silicon wafer. It should be noted that the multiple pyramid structures can have different heights.

[0032] In some embodiments of the present application, the N-type silicon wafer may be an N-type single crystal silicon wafer.

[0033] S200: forming a front amorphous silicon layer and a back amorphous silicon layer.

[0034] 1 to 4 , after the texturing process, a front amorphous silicon layer 210 is formed on the front surface 110 of the N-type silicon wafer 100, and a back amorphous silicon layer 220 is formed on the back surface 120 of the N-type silicon wafer 100. Referring to FIG3 , the front amorphous silicon layer 210 includes a front intrinsic amorphous silicon layer 211 and an N-type doped layer 212 located on a side of the front intrinsic amorphous silicon layer 211 away from the N-type silicon wafer 100. The back amorphous silicon layer 220 includes a back intrinsic amorphous silicon layer 221 and a P-type doped layer 222 located on a side of the back intrinsic amorphous silicon layer 221 away from the N-type silicon wafer 100.

[0035] In some embodiments of the present application, the front amorphous silicon layer 210 may be formed using a plasma enhanced chemical vapor deposition (PECVD) method. Thus, the thickness and composition of each layer in the front amorphous silicon layer are uniform, which is beneficial for further improving the overall performance of the solar cell.

[0036] In some embodiments of the present application, the back amorphous silicon layer 220 may be formed by plasma enhanced chemical vapor deposition, thereby ensuring uniform thickness and composition of each layer in the back amorphous silicon layer, thereby further improving the overall performance of the solar cell.

[0037] In some embodiments of the present application, the thickness of the front intrinsic amorphous silicon layer 211 can be 3nm to 6nm. For example, the thickness of the front intrinsic amorphous silicon layer 211 can be 3nm, 4nm, 4.5nm, 5nm, 6nm, etc. Therefore, the front intrinsic amorphous silicon layer has good passivation performance, which is beneficial to improving the overall performance of the solar cell.

[0038] In some embodiments of the present application, the thickness of the back intrinsic amorphous silicon layer 221 can be 3nm to 9nm. For example, the thickness of the back intrinsic amorphous silicon layer 221 can be 3nm, 5nm, 7nm, 9nm, etc. Therefore, the back intrinsic amorphous silicon layer has good passivation performance, which is beneficial to improving the overall performance of the solar cell.

[0039] In some embodiments of the present application, the thickness of the N-type doping layer 212 may be 5 nm to 10 nm. For example, the thickness of the N-type doping layer 212 may be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc.

[0040] In some embodiments of the present application, the N-type doped layer 212 may be a phosphorus-doped amorphous silicon layer.

[0041] In some embodiments of the present application, the thickness of the P-type doping layer 222 may be 5 nm to 15 nm. For example, the thickness of the P-type doping layer 222 may be 5 nm, 8 nm, 10 nm, 13 nm, 15 nm, etc.

[0042] In some embodiments of the present application, the P-type doped layer 222 may be a boron-doped amorphous silicon layer.

[0043] S300: forming a first transparent conductive film and a second transparent conductive film to obtain a blue film.

[0044] According to some embodiments of the present application, referring to Figures 1 to 3, a first transparent conductive film 310 is formed on a side of the N-type doped layer 212 away from the N-type silicon wafer 100, and a second transparent conductive film 320 is formed on a side of the P-type doped layer 222 away from the N-type silicon wafer 100, thereby obtaining a blue film.

[0045] In some embodiments of the present application, the first transparent conductive film 310 may be formed using physical vapor deposition (PVD), and the second transparent conductive film 320 may be formed using physical vapor deposition (PVD). The use of physical vapor deposition to form the first and second transparent conductive film layers is a mature process that is beneficial for improving the film quality of the conductive film layers, thereby further enhancing the performance of the solar cell.

[0046] In some embodiments of the present application, the thickness of the first transparent conductive film 310 can be 90nm to 110nm. For example, the thickness of the first transparent conductive film 310 can be 90nm, 95nm, 100nm, 105nm, 110nm, etc. When the thickness of the first transparent conductive film is within the above range, the film layer has good light transmittance, which is beneficial to the absorption of light by the solar cell.

[0047] In some embodiments of the present application, the material of the first transparent conductive film 310 may be ITO (indium tin oxide). Thus, the film layer has good conductivity, which is beneficial to further improve the performance of the solar cell.

[0048] In some embodiments of the present application, the thickness of the second transparent conductive film 320 can be 90nm to 110nm. For example, the thickness of the second transparent conductive film 320 can be 90nm, 95nm, 100nm, 105nm, 110nm, etc. When the thickness of the second transparent conductive film is within the above range, the film layer has good light transmittance, which is beneficial to the absorption of light by the solar cell.

[0049] In some embodiments of the present application, the second transparent conductive film 320 may be made of ITO, so that the film layer has good conductivity, which is beneficial to further improve the performance of the solar cell.

[0050] S400: performing a first light injection process on the blue diaphragm.

[0051] After the blue film is formed, the blue film is subjected to a first light injection treatment. The first light injection treatment has the following beneficial technical effects: on the one hand, the first light injection treatment process can increase the concentration of electrons and holes by stimulating the recombination of electrons and holes, thereby improving the conversion efficiency of the battery. On the other hand, the first light injection treatment can improve the spectral response of the solar cell, so that it can generate electrical energy under light of different wavelengths. On the other hand, the oxide ions in the crystal structure of the first transparent conductive film and the second transparent conductive film are rearranged to form a more ordered structure, which is conducive to improving its conductive performance. Experimental verification shows that after the blue film is subjected to the first light treatment, the electrical performance of the solar cell is improved and the static attenuation of the solar cell is improved.

[0052] In some embodiments of the present application, the temperature of the first light injection treatment can be 208°C to 215°C. For example, the temperature of the first light injection treatment can be 208°C, 209°C, 210°C, 212°C, 213°C, 215°C, etc. The temperature of the first light injection treatment is within the above range, which is conducive to the transparent conductive film forming a more ordered structure, thereby helping to improve its conductive performance; and, it can at least to a certain extent alleviate or even avoid the technical problem of corrosive liquids causing damage to the transparent conductive film layer in the subsequent preparation process, thereby helping to improve the conversion efficiency and stability of the solar cell.

[0053] In some embodiments of the present application, the duration of the first light injection treatment can be 38 seconds to 45 seconds. For example, the duration of the first light injection treatment can be 38 seconds, 39 seconds, 40 seconds, 41 seconds, 43 seconds, 45 seconds, etc. The duration of the first light injection treatment within the above range is beneficial for repairing the transparent conductive film layer, improving the conductivity of the transparent conductive film layer, and improving the static degradation problem of the solar cell, thereby improving the stability of the solar cell.

[0054] In some embodiments of the present application, the wavelength of light for the first light injection treatment can be 800nm ​​to 1000nm. For example, the wavelength of light for the first light injection treatment can be 800nm, 850nm, 900nm, 950nm, 1000nm, etc. The light of the above wavelengths can effectively repair the structure of the transparent conductive film layer, improve the conductivity of the transparent conductive film layer, and prevent corrosive liquids from damaging the transparent conductive film layer, which is beneficial to improving the stability of the solar cell and improving the static attenuation of the solar cell.

[0055] In some embodiments of the present application, referring to FIG2 , after the blue film is subjected to the first light injection treatment, the method for preparing a solar cell may further include the following steps:

[0056] S500: forming a copper seed layer to obtain a yellow film.

[0057] Referring to Figures 2 and 3 , a copper seed layer is formed on the side of the first transparent conductive film 310 facing away from the N-type silicon wafer 100 and on the side of the second transparent conductive film 320 facing away from the N-type silicon wafer 100, respectively, to form a yellow film. The copper seed layer provides good bonding strength for the subsequent formation of copper grid lines, facilitating the subsequent fabrication of the copper grid lines.

[0058] In some embodiments of the present application, the copper seed layer may be formed by physical vapor deposition, which is a mature process and is beneficial for improving the yield rate of solar cells.

[0059] In some embodiments of the present application, the thickness of the copper seed layer can be 150nm to 250nm. For example, the thickness of the copper seed layer can be 150nm, 180nm, 200nm, 230nm, 250nm, etc. The copper seed layer of the above thickness can provide a stronger bonding force for the copper grid line, and the thickness of the copper seed layer is relatively thin, which has no adverse effect on the overall thickness of the solar cell.

[0060] S600: forming a photosensitive adhesive on the surface of the copper seed layer and removing the photosensitive adhesive at the gate line position.

[0061] In some embodiments of the present application, after the copper seed layer is formed, a photosensitive resin is formed on the surface of the copper seed layer away from the N-type silicon wafer 100, a grid line pattern is printed by laser and a development process is performed, and the photosensitive resin at the grid line position is removed. The grid line position refers to the position where the grid line is to be formed subsequently. Printing the grid line pattern refers to printing on the photosensitive resin using a laser according to a specific pattern, and the laser energy can be 170mJ. After the development process is performed, the photosensitive resin at the grid line position is removed, thereby exposing part of the copper seed layer, and copper grid lines can be formed on the exposed copper seed layer subsequently by an electroplating method.

[0062] In some embodiments of the present application, the thickness of the photosensitive adhesive can be 10μm to 14μm. For example, the thickness of the photosensitive adhesive can be 10μm, 11μm, 12μm, 13μm, 14μm, etc. The photosensitive adhesive can be used as a mask, and during the electroplating process, copper grid lines will not be deposited on the surface of the photosensitive adhesive.

[0063] S700: Wrap the four sides and corners of the yellow film with adhesive.

[0064] After removing the photosensitive resin at the grid line position, the four sides and corners of the yellow film are wrapped with adhesive to prevent copper from being deposited on the four sides and corners of the yellow film during the subsequent electroplating process.

[0065] S800: forming a first copper grid line and a second copper grid line.

[0066] 2 and 3 , a first copper gate line 510 is formed on the copper seed layer on the front side of the N-type silicon wafer 100 , and a second copper gate line 520 is formed on the copper seed layer on the back side of the N-type silicon wafer 100 .

[0067] In this step, the first copper grid line and the second copper grid line can be formed by electroplating (chemical plating). According to some embodiments of the present application, in the electroplating solution for forming the copper grid line, Cu 2+ The concentration of can be 20g / L~100g / L, the concentration of H2SO4 can be 20g / L~100g / L, for example, Cu 2+ The concentration of H2SO4 can be 20g / L, 30g / L, 50g / L, 70g / L, 100g / L, etc., and the concentration of H2SO4 can be 20g / L, 30g / L, 50g / L, 70g / L, 100g / L, etc. According to some embodiments of the present application, the electroplating solution for forming the copper grid line can also contain a certain amount of additives.

[0068] In some embodiments of the present application, the thickness of the first copper grid line 510 may be 8 μm to 10 μm. For example, the thickness of the first copper grid line 510 may be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, etc.

[0069] In some embodiments of the present application, the thickness of the second copper grid line 520 may be 8 μm to 10 μm. For example, the thickness of the second copper grid line 520 may be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, etc.

[0070] S900: performing film stripping and back etching.

[0071] In some embodiments of the present application, referring to Figures 2 and 3, after the first copper grid lines 510 and the second copper grid lines 520 are formed, a stripping process and an etch-back process are performed to remove the adhesive material and the remaining photosensitive adhesive, the copper seed layer not covered by the first copper grid lines 510, and the copper seed layer not covered by the second copper grid lines 520, to form a first copper seed layer 410 and a second copper seed layer 420. The first copper seed layer 410 is located between the first copper grid lines 510 and the first transparent conductive film 310, and the second copper seed layer 420 is located between the second copper grid lines 520 and the second transparent conductive film 320.

[0072] In some embodiments of the present application, a sodium hydroxide (NaOH) solution with a concentration of 10 g / L to 20 g / L may be used for the film removal process. The sodium hydroxide solution with the above concentration can remove the adhesive material and the remaining photosensitive adhesive.

[0073] In some embodiments of the present application, a back-etching liquid can be used for back-etching. In the back-etching liquid, the concentration of H2SO4 can be 10g / L, and the concentration of H2O2 can be 10g / L. The battery is soaked in the back-etching liquid to remove the copper seed layer on the surface where no copper grid line is formed.

[0074] S1000: forming a first metal tin layer and a second metal tin layer.

[0075] 2 and 3 , after the film stripping and etching back processes, a first metal tin layer 610 and a second metal tin layer 620 are formed. The first metal tin layer 610 can cover the surface of the first copper grid line 510 away from the N-type silicon wafer 100 and at least a portion of the side surface of the first copper grid line 510. The second metal tin layer 620 can cover the surface of the second copper grid line 520 away from the N-type silicon wafer 100 and at least a portion of the side surface of the second copper grid line 520. Thus, the first metal tin layer and the second metal tin layer can respectively protect the first and second copper grid lines and can also serve as solder metal for component soldering.

[0076] In some embodiments of the present application, referring to Figure 3, the first metal tin layer 610 can cover the surface of the first copper grid line 510 away from the N-type silicon wafer 100, the side of the first copper grid line 510, and at least a portion of the side of the first copper seed layer 410, and the second metal tin layer 620 can cover the surface of the second copper grid line 520 away from the N-type silicon wafer 100, the side of the second copper grid line 520, and at least a portion of the side of the second copper seed layer 420.

[0077] According to some embodiments of the present application, the first metal tin layer 610 and the second metal tin layer 620 can be formed by electroplating (chemical plating). According to some embodiments of the present application, in the electroplating solution for forming the metal tin layer, Sn 2+ The concentration of Sn can be 10g / L to 60g / L, and the concentration of MSA (Methyl sulfonic acid) can be 100g / L to 300g / L. For example, Sn 2+ The concentration of can be 10g / L, 20g / L, 30g / L, 40g / L, 50g / L, 60g / L, etc., and the concentration of MSA can be 100g / L, 150g / L, 200g / L, 250g / L, 300g / L, etc. According to some embodiments of the present application, the electroplating solution for forming the metal tin layer may further contain a certain amount of additives.

[0078] In some embodiments of the present application, the thickness of the first metal tin layer 610 may be 2 μm to 6 μm. For example, the thickness of the first metal tin layer 610 may be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, etc.

[0079] In some embodiments of the present application, the thickness of the second metal tin layer 620 may be 2 μm to 6 μm. For example, the thickness of the second metal tin layer 620 may be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, etc. It should be noted that the thickness of the first metal tin layer refers to the distance between the surface of the first metal tin layer away from the first copper grid line and the surface of the first metal tin layer in contact with the first copper grid line. The above two surfaces refer to two substantially parallel surfaces of the first metal tin layer. Similarly, the thickness of the second metal tin layer refers to the distance between the surface of the second metal tin layer away from the second copper grid line and the surface of the first metal tin layer in contact with the second copper grid line.

[0080] The metal tin layer of the above thickness can play a better role in protecting the copper grid line, and can be used as a welding metal for component welding.

[0081] In some embodiments of the present application, referring to FIG. 2 , after forming the first metal tin layer 610 and the second metal tin layer 620, the method for preparing a solar cell may further include the following steps:

[0082] S1100: Perform a second light injection process.

[0083] In some embodiments of the present application, the temperature of the second light injection treatment can be 200℃~220℃. For example, the temperature of the second light injection treatment can be 200℃, 205℃, 210℃, 215℃, 220℃, etc., which is beneficial to repair the solar cells and improve the conversion efficiency of the cells.

[0084] In some embodiments of the present application, the time of the second light injection treatment can be 60s to 120s. For example, the time of the second light injection treatment can be 60s, 80s, 100s, 110s, 120s, etc., which is beneficial to further improve the repair effect of the solar cell and further improve the conversion efficiency of the cell.

[0085] In another aspect, this application provides a solar cell. In some embodiments of this application, the solar cell is prepared using the aforementioned method. As a result, the solar cell has high conversion efficiency; good spectral response, capable of generating electricity under illumination of different wavelengths; and good stability, with slow static decay and slow power decay in gears. Its electrical performance is stable, allowing for extended storage.

[0086] The present application will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are merely for illustrative purposes and are not intended to limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment employed are all commercially available. If, in the following examples, specific processing conditions and treatment methods are not clearly described, then conditions and methods well known in the art may be used to process.

[0087] Experimental group

[0088] The N-type silicon wafer is texturized, and a front amorphous silicon layer is formed on the front side of the N-type silicon wafer and a back amorphous silicon layer is formed on the back side of the N-type silicon wafer by a PECVD method. The front amorphous silicon layer includes a front intrinsic amorphous silicon layer (with a thickness of 3nm to 6nm) and an N-type doped layer (phosphorus-doped amorphous silicon layer with a thickness of 5nm to 10nm) located on the side of the front amorphous silicon layer away from the N-type silicon wafer. The back amorphous silicon layer includes a back intrinsic amorphous silicon layer (with a thickness of 3nm to 9nm) and a P-type doped layer (boron-doped amorphous silicon layer with a thickness of 5nm to 15nm) located on the side of the back amorphous silicon layer away from the N-type silicon wafer.

[0089] A PVD method is used to form a first transparent conductive film (made of ITO with a thickness of 90nm to 110nm) on the side of the N-type doped layer away from the N-type silicon wafer, and a second transparent conductive film (made of ITO with a thickness of 90nm to 110nm) is formed on the side of the P-type doped layer away from the N-type silicon wafer to obtain a blue film.

[0090] The blue film is subjected to a first light injection treatment at a temperature of 210° C., a time of 38 seconds, and a light wavelength of 800 nm to 1000 nm.

[0091] A copper seed layer is formed on the side of the first transparent conductive film away from the N-type silicon wafer and the side of the second transparent conductive film away from the N-type silicon wafer by PVD method to obtain a yellow film. The thickness of the copper seed layer is 150nm to 250nm.

[0092] A photosensitive adhesive is formed on the surface of the copper seed layer, a grid line pattern is laser printed and developed, and the photosensitive adhesive at the grid line position is removed; the four sides and corner positions of the yellow film are wrapped with adhesive; a first copper grid line is formed on the copper seed layer on the front side of the N-type silicon wafer and a second copper grid line is formed on the copper seed layer on the back side of the N-type silicon wafer by electroplating; a film stripping process and a back etching process are performed to remove the adhesive and the remaining photosensitive adhesive, and remove the copper seed layer on the surface of which the copper grid line is not formed; a first metal tin layer and a second metal tin layer are formed by electroplating, the first metal tin layer covering the surface of the first copper grid line away from the N-type silicon wafer and at least a portion of the side surface of the first copper grid line, and the second metal tin layer covering the surface of the second copper grid line away from the N-type silicon wafer and at least a portion of the side surface of the second copper grid line.

[0093] A second light injection treatment is performed to obtain a solar cell. The temperature of the second light injection treatment is 200° C. to 220° C., and the time is 60s to 120s.

[0094] Benchmark Group

[0095] Unlike the experimental group, the baseline group did not undergo the first light injection process on the blue film during the solar cell preparation process. The remaining steps and parameters were the same as those of the experimental group.

[0096] HJT group

[0097] Unlike the experimental group, the HJT group did not perform the first light injection treatment on the blue film during the solar cell fabrication process. Instead, the HJT group used silver paste to print grid lines on the surfaces of the first and second transparent conductive films facing away from the N-type silicon wafer. This was followed by the light injection treatment to produce the solar cell. The remaining steps and parameters were the same as those for the experimental group.

[0098] Attenuation tests were performed on the solar cell samples in the experimental group, the reference group, and the HJT group. The cells were stored in normal plastic packaging (temperature 20°C, humidity 62%). The test results can be found in Table 1 and Figure 5 below.

[0099] Table 1 Test data of different gears of experimental group and benchmark group

[0100] In Table 1, Eta is the conversion efficiency (the average conversion efficiency of multiple battery cells), Uoc is the open circuit voltage, Isc is the short circuit current, FF is the fill factor, Eta standard deviation is the standard deviation of the conversion efficiency of multiple battery cells, and Eta maximum is the maximum value of the conversion efficiency of multiple battery samples. The more stable the conversion efficiency, the more stable the power of the battery. "Initial" means that the battery has been stored for 0 days, and "40 days" means that the battery has been stored for 40 days. It should be noted that when the battery is automatically run, the battery cell samples may be broken due to various reasons. Therefore, the number of battery cells stored for 40 days may be less than the initial number of battery cells.

[0101] The experimental group -24.5% and the experimental group -24.6% refer to the experimental group solar cell samples being tested at the conversion efficiency of 24.5% and the conversion efficiency of 24.6% respectively; the benchmark group -24.5% and the benchmark group -24.6% refer to the benchmark group solar cell samples being tested at the conversion efficiency of 24.5% and the conversion efficiency of 24.6% respectively.

[0102] As shown in Figure 5 and Table 1, the solar cells of the HJT group were tested at a conversion efficiency of 24.5%. The conversion efficiency of the cells after 40 days of storage was attenuated by 0.31% compared with the initial conversion efficiency. The solar cells of the HJT group were tested at a conversion efficiency of 24.6%. The conversion efficiency of the cells after 40 days of storage was attenuated by 0.32% compared with the initial conversion efficiency. The solar cells of the reference group were tested at a conversion efficiency of 24.5%. The conversion efficiency of the cells after 40 days of storage was attenuated by 0. The solar cells in the benchmark group were tested at a conversion efficiency of 24.6%. The conversion efficiency of the batteries after 40 days of storage was attenuated by 0.38% compared with the initial conversion efficiency. The solar cells in the experimental group were tested at a conversion efficiency of 24.5%. The conversion efficiency of the batteries after 40 days of storage was attenuated by 0.27%. The solar cells in the experimental group were tested at a conversion efficiency of 24.6%. The conversion efficiency of the batteries after 40 days of storage was attenuated by 0.25%.

[0103] By comparison, it can be seen that compared with the solar cell samples in the benchmark group, the solar cell samples in the experimental group significantly reduced the static attenuation of the conversion efficiency of the copper interconnected solar cells by performing the first light injection treatment on the blue film, thereby effectively improving the stability of the solar cells; compared with the solar cells with grid lines formed by silver paste printing, the solar cell samples in the experimental group of this application still have better stability and smaller static attenuation.

[0104] In general, the solar cell samples prepared using the method proposed in this application have less static attenuation and more stable battery performance, which is conducive to long-term storage of the battery.

[0105] In the description of this application, the terms "front", "back", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and do not require that this application must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0106] In the description of this specification, the descriptions with reference to the terms "one embodiment", "another embodiment", "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory. In addition, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0107] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for preparing a solar cell, comprising: Performing a texturing process on an N-type silicon wafer so that both the front and back sides of the N-type silicon wafer form a pyramid structure; Forming a front amorphous silicon layer and a back amorphous silicon layer, wherein the front amorphous silicon layer includes a front intrinsic amorphous silicon layer and an N-type doped layer located on a side of the front intrinsic amorphous silicon layer away from the N-type silicon wafer, and the back amorphous silicon layer includes a back intrinsic amorphous silicon layer and a P-type doped layer located on a side of the back intrinsic amorphous silicon layer away from the N-type silicon wafer; Forming a first transparent conductive film on a side of the N-type doped layer away from the N-type silicon wafer, and forming a second transparent conductive film on a side of the P-type doped layer away from the N-type silicon wafer, to obtain a blue film; A first light injection process is performed on the blue film.

2. The method according to claim 1, wherein: The temperature of the first light injection treatment is 208° C. to 215° C.

3. The method according to any one of claims 1 to 2, wherein: The first light injection process lasts for 38 seconds to 45 seconds.

4. The method according to any one of claims 1 to 3, wherein: The wavelength of light used in the first light injection treatment is 800nm ​​to 1000nm.

5. The method according to any one of claims 1 to 4, wherein: After performing the first light injection process on the blue film, the method further includes: forming a copper seed layer on a side of the first transparent conductive film away from the N-type silicon wafer and a side of the second transparent conductive film away from the N-type silicon wafer to obtain a yellow film; forming a photosensitive adhesive on a surface of the copper seed layer away from the N-type silicon wafer, and removing the photosensitive adhesive at the gate line position; Wrap the four sides and corners of the yellow film with adhesive material; Forming a first copper gate line on the copper seed layer on the front side of the N-type silicon wafer, and forming a second copper gate line on the copper seed layer on the back side of the N-type silicon wafer; Performing a film stripping process and a back etching process to remove the adhesive material and the remaining photosensitive adhesive, the copper seed layer not covered by the first copper grid line, and the copper seed layer not covered by the second copper grid line to form a first copper seed layer and a second copper seed layer, wherein the first copper seed layer is located between the first copper grid line and the first transparent conductive film, and the second copper seed layer is located between the second copper grid line and the second transparent conductive film; A first metal tin layer and a second metal tin layer are formed, wherein the first metal tin layer covers the surface of the first copper grid line away from the N-type silicon wafer and at least part of the side surface of the first copper grid line, and the second metal tin layer covers the surface of the second copper grid line away from the N-type silicon wafer and at least part of the side surface of the second copper grid line.

6. The method according to claim 5, wherein: After forming the first metal tin layer and the second metal tin layer, the method further includes: performing a second light injection process.

7. The method according to claim 6, wherein: The temperature of the second light injection treatment is 200° C. to 220° C.

8. The method according to any one of claims 6 to 7, wherein: The second light injection process lasts for 60s to 120s.

9. The method according to any one of claims 1 to 8, wherein: The thickness of the front intrinsic amorphous silicon layer is 3nm-6nm.

10. The method according to any one of claims 1 to 9, wherein: The thickness of the back intrinsic amorphous silicon layer is 3nm-9nm.

11. The method according to any one of claims 1 to 10, wherein: The front amorphous silicon layer is formed by plasma enhanced chemical vapor deposition method.

12. The method according to any one of claims 1 to 11, wherein: The back amorphous silicon layer is formed by plasma enhanced chemical vapor deposition.

13. The method according to any one of claims 1 to 12, wherein: The thickness of the N-type doping layer is 5nm-10nm.

14. The method according to any one of claims 1 to 13, wherein: The thickness of the P-type doping layer is 5nm-15nm.

15. The method according to any one of claims 1 to 14, wherein: The N-type doped layer is a phosphorus-doped amorphous silicon layer.

16. The method according to any one of claims 1 to 15, wherein: The P-type doped layer is a boron-doped amorphous silicon layer.

17. The method according to any one of claims 1 to 16, wherein: The thickness of the first transparent conductive film is 90 nm to 110 nm.

18. The method according to any one of claims 1 to 17, wherein: The thickness of the second transparent conductive film is 90 nm to 110 nm.

19. The method according to any one of claims 1 to 18, wherein: The material of the first transparent conductive film is ITO.

20. The method according to any one of claims 1 to 19, wherein: The material of the second transparent conductive film is ITO.

21. The method according to any one of claims 1 to 20, wherein: The first transparent conductive film is formed by a physical vapor deposition method.

22. The method according to any one of claims 1 to 21, wherein: The second transparent conductive film is formed by a physical vapor deposition method.

23. The method according to any one of claims 5 to 8, wherein: The copper seed layer is formed by physical vapor deposition.

24. The method according to any one of claims 5 to 8 and 23, wherein: The thickness of the photosensitive adhesive is 10 μm to 14 μm.

25. The method according to any one of claims 5 to 8, 23 to 24, wherein: Use a sodium hydroxide solution with a concentration of 10g / L to 20g / L for film removal.

26. The method according to any one of claims 5 to 8 and 23 to 25, wherein: The thickness of the first copper grid line is 8 μm to 10 μm.

27. The method according to any one of claims 5 to 8 and 23 to 26, wherein: The thickness of the second copper grid line is 8 μm to 10 μm.

28. The method according to any one of claims 5 to 8 and 23 to 27, wherein: The thickness of the first metal tin layer is 2 μm to 6 μm.

29. The method according to any one of claims 5 to 8, 23 to 28, wherein: The thickness of the second metal tin layer is 2 μm to 6 μm.

30. A solar cell, wherein the solar cell is prepared by the method according to any one of claims 1 to 29.

Images