Method for preparing solar cell and solar cell

Abstract

The present invention discloses a method for preparing a solar cell and a solar cell. The method comprises removing the second mask layer on the first surface and side surfaces of a silicon substrate using a chain acid etching process; removing the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate using a chain alkaline etching process; removing the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate using a groove etching process, forming a suede light-trapping structure in the third region of the second surface of the silicon substrate and on the first surface, and removing the first mask layer in the first region and the second mask layer in the second region of the second surface of the silicon substrate. The method for preparing a solar cell and the solar cell of the present invention can optimize the cell preparation process, protect the environment, improve the suede quality, and increase cell efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cell preparation, and in particular relates to a method for preparing a solar cell and the solar cell. Background Art

[0002] In solar cells, due to the special structure of BC cells (back contact cells), it is usually necessary to protect the N-type doped salt-silica glass on the back when texturing the front side, so the manufacturing process is relatively complicated.

[0003] The conventional process in the existing technology is that in the pre-treatment process of texturing the front of the BC battery, under environmental protection conditions, the hydrofluoric acid and nitric acid method is used to remove the N-type doped salt silica glass and the winding coating on the front at the same time, and then texturing is carried out with an alkaline solution. This production process is relatively cumbersome and easily affects the texturing effect of the battery, and is also likely to have a certain impact on the environment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a solar cell and a solar cell, so as to optimize the cell preparation process, protect the environment, improve the velvet quality, and improve the cell efficiency.

[0005] In order to achieve the above object, a specific embodiment of the present invention provides the following technical solutions:

[0006] A method for preparing a solar cell, comprising:

[0007] A silicon substrate is provided, comprising a first surface and a second surface and a side surface disposed opposite to each other, the second surface comprising a first region and a second region spaced apart from each other, and a third region located between the first region and the second region, a first tunneling passivation structure, a first mask layer, and a second tunneling passivation structure being sequentially formed in the first region of the second surface of the silicon substrate, a second tunneling passivation structure and a second mask layer being sequentially formed in the second region of the second surface of the silicon substrate, a second tunneling passivation structure being formed in the third region of the second surface of the silicon substrate, and a second tunneling passivation structure and a second mask layer being sequentially formed on the first surface and the side surface of the silicon substrate;

[0008] Removing the second mask layer on the first surface and side surfaces of the silicon substrate using a chain acid etching process;

[0009] removing the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate by using a chain alkali etching process;

[0010] A groove etching process is used to remove the second tunneling passivation structure in the first area and the third area of ​​the second surface of the silicon substrate, a suede light trapping structure is formed on the third area and the first surface of the second surface of the silicon substrate, and the first mask layer in the first area and the second mask layer in the second area of ​​the second surface of the silicon substrate are removed.

[0011] In one or more embodiments of the present invention, chain acid etching is performed using a first etching solution to remove the second mask layer on the first surface and side surfaces of the silicon substrate;

[0012] The first etching solution includes an acid solution with a mass fraction of 5%-15%, and / or the first etching solution includes an HF solution.

[0013] In one or more embodiments of the present invention, a chain acid etching process is used to remove the second mask layer on the first surface and side surfaces of the silicon substrate, including:

[0014] Adjusting the height of the first etching solution in the solution tank of the chain machine so that the capillary roller in the solution tank is partially immersed in the first etching solution;

[0015] The first surface of the silicon substrate is placed on the capillary roller, and the first etching liquid is transferred to the first surface and side of the silicon substrate by the capillary phenomenon of the capillary roller during rolling, so as to etch the second mask layer on the first surface and side of the silicon substrate.

[0016] In one or more embodiments of the present invention, chain alkaline etching is performed using a second etching solution to remove the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate;

[0017] The second etching solution includes an alkaline solution with a mass fraction of 10%-20%, and / or the second etching solution includes a KOH solution, and / or the etching temperature for removing the second tunneling passivation structure using the second etching solution is 50° C.-70° C.

[0018] In one or more embodiments of the present invention, a chain alkali etching process is used to remove the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate, including:

[0019] Adjusting the height of the second etching solution in the chain machine solution tank so that the second etching solution is flush with the top surface of the capillary roller in the solution tank;

[0020] placing the first surface of the silicon substrate on the capillary roller so that the first surface of the silicon substrate contacts the second etching solution;

[0021] The second etching solution is assisted by the rolling of the capillary roller to etch the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate.

[0022] In one or more embodiments of the present invention, while a chain acid etching process is used to remove the second mask layer on the first surface and side surfaces of the silicon substrate, a liquid protective film is covered on the second surface of the silicon substrate.

[0023] In one or more embodiments of the present invention, a chain alkali etching process is used to remove the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate, while covering the second surface of the silicon substrate with a liquid protective film.

[0024] In one or more embodiments of the present invention, a trench alkali etching process is used to remove the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate, and a textured light trapping structure is formed in the third region of the second surface of the silicon substrate and on the first surface.

[0025] In one or more embodiments of the present invention, a third etching solution is used to perform trench alkaline etching to remove the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate, and to form a textured light trapping structure in the third region of the second surface of the silicon substrate and on the first surface;

[0026] The third etching solution includes an alkaline solution with a mass fraction of 0.5%-1.5%, and / or,

[0027] The third etching solution includes KOH solution, and / or,

[0028] The texturing temperature for forming the textured light-trapping structure using the third etching solution is 70° C.-80° C., and the texturing time is 650s-950s.

[0029] In one or more embodiments of the present invention, a trench acid etching process is used to remove the first mask layer in the first region and the second mask layer in the second region of the second surface of the silicon substrate.

[0030] In one or more embodiments of the present invention, a fourth etching solution is used to perform a tank acid etching to remove the first mask layer and the second mask layer;

[0031] The fourth etching solution includes an acid solution with a mass fraction of 5%-10%, and / or,

[0032] The fourth etching solution includes HF solution, and / or,

[0033] The fourth etching solution is used to remove the first mask layer and the second mask layer at an etching temperature of 15° C.-25° C. and an etching time of 100 s-200 s.

[0034] In one or more embodiments of the present invention, after the step of removing the second mask layer by using a chain acid etching process, the method further includes cleaning the silicon substrate; and / or,

[0035] After the step of removing the second tunnel passivation structure on the first surface and side surfaces of the silicon substrate by using a chain alkali etching process, the method further includes cleaning the silicon substrate; and / or,

[0036] The method further includes cleaning the silicon substrate before and after the step of removing the second tunneling passivation structure in the first area and the third area of ​​the second surface of the silicon substrate by a groove etching process, and forming a velvet light trapping structure in the third area of ​​the second surface of the silicon substrate and the first surface, and after the step of removing the first mask layer and the second mask layer by a groove etching process.

[0037] In one or more embodiments of the present invention, a silicon substrate is provided, the silicon substrate including a first surface, a second surface, and a side surface arranged opposite to each other, the second surface including a first region and a second region spaced apart, and a third region located between the first region and the second region, the first region of the second surface of the silicon substrate sequentially forming a first tunneling passivation structure, a first mask layer, and a second tunneling passivation structure, the second region of the second surface of the silicon substrate sequentially forming a second tunneling passivation structure and a second mask layer, the third region of the second surface of the silicon substrate forming a second tunneling passivation structure, and the second tunneling passivation structure and the second mask layer sequentially formed on the first surface and the side surface of the silicon substrate, comprising:

[0038] forming a first tunneling passivation structure and a first mask layer in sequence on the first surface, the second surface and the side surface of the silicon substrate;

[0039] Using a laser process to remove the first mask layer in the second area and the third area of ​​the second surface of the silicon substrate;

[0040] removing the first mask layer on the first surface and side surfaces of the silicon substrate by pickling;

[0041] Alkaline washing is performed to remove the second region and the third region of the second surface of the silicon substrate, the first surface, and the first tunneling passivation structure on the side surface;

[0042] forming a second tunneling passivation structure and a second mask layer in sequence on the first surface, the second surface and the side surface of the silicon substrate;

[0043] The second mask layer in the first area and the third area of ​​the second surface of the silicon substrate is removed by using a laser process.

[0044] In one or more embodiments of the present invention, the first tunneling passivation structure includes a first tunneling layer and a first doping layer formed sequentially;

[0045] The second tunneling passivation structure includes a second tunneling layer and a second doping layer formed in sequence.

[0046] In one or more embodiments of the present invention, the first doped layer is a P-type doped layer, and the first mask layer is a P-type doped salt-silica glass;

[0047] The second doping layer is an N-type doping layer, and the second mask layer is N-type doped salt-silica glass.

[0048] A solar cell is prepared by the above-mentioned solar cell preparation method.

[0049] Compared with the prior art, the preparation method and solar cell of the present invention, in the pre-treatment process of texturing, remove the second mask layer on the first surface and the side through a chain acid etching process; then remove the second tunnel passivation structure on the first surface and the side through a chain alkaline etching process, and then perform a groove etching process to complete the texturing step, thereby reducing nitrogen emissions during the etching process and being beneficial to environmental protection. At the same time, it can maximize the protection time of the mask layer (first mask layer and second mask layer) on the second surface in the texturing liquid (third etching liquid) during the texturing process for the P-type region and the N-type region on the second surface, thereby widening the process window; optimize the battery preparation process, and can increase the texturing time to a certain extent, so that the reflectivity and uniformity of the prepared texturing surface are more uniform, thereby improving the texturing quality and improving the battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0051] Figure 1 is a process flow chart of a method for preparing a solar cell of the present invention;

[0052] Figure 2 FIG1 is a structural diagram of the first step of a method for preparing a solar cell according to an embodiment of the present invention;

[0053] Figure 3 FIG2 is a structural diagram of the second step of the method for preparing a solar cell according to an embodiment of the present invention;

[0054] Figure 4 FIG3 is a structural diagram of the third step of the method for preparing a solar cell according to an embodiment of the present invention;

[0055] Figure 5 FIG4 is a structural diagram of the fourth step of the method for preparing a solar cell according to an embodiment of the present invention;

[0056] Figure 6FIG4 is a structural diagram of the fifth step of the method for preparing a solar cell according to an embodiment of the present invention;

[0057] Figure 7 FIG1 is a structural diagram of the sixth step of the method for preparing a solar cell according to an embodiment of the present invention;

[0058] Figure 8 FIG1 is a structural diagram of the seventh step of the method for preparing a solar cell according to an embodiment of the present invention;

[0059] Figure 9 FIG1 is a structural diagram of the eighth step of the method for preparing a solar cell according to an embodiment of the present invention;

[0060] Figure 10 FIG1 is a structural diagram of the ninth step of the method for preparing a solar cell according to an embodiment of the present invention;

[0061] Figure 11 FIG1 is a structural diagram of the tenth step of the method for preparing a solar cell according to an embodiment of the present invention;

[0062] Figure 12 This is a structural diagram of the eleventh step of the method for preparing a solar cell in one embodiment of the present invention.

[0063] Reference numerals:

[0064] 10-silicon substrate; S1-first surface; S2-second surface; S21-first region; S22-second region; S23-third region; S3-side; 21-first tunneling layer; 22-first doping layer; 30-first mask layer; 41-second tunneling layer; 42-second doping layer; 43-second mask layer; 50-texture light trapping structure. DETAILED DESCRIPTION

[0065] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0066] The present invention provides a preparation method of a solar cell and a solar cell. In a pre-treatment process for texturing, a chain acid etching process is used to remove the second mask layer on the first surface and the side surface; a chain alkali etching process is then used to remove the second tunnel passivation structure on the first surface and the side surface; and a groove etching process is then performed to complete the texturing step. This reduces nitrogen emissions during the etching process and is beneficial to environmental protection. At the same time, it can maximize the protection time of the mask layer (first mask layer and second mask layer) on the second surface in the texturing liquid (third etching liquid) for the P-type region and the N-type region on the second surface during the texturing process, thereby widening the process window. The battery preparation process is optimized, and the texturing time can be increased to a certain extent. The reflectivity and uniformity of the prepared texturing surface are more uniform, thereby improving the texturing surface quality and improving the battery efficiency.

[0067] refer to Figure 1 As shown, the present invention discloses a method for preparing a solar cell, which specifically includes the following steps:

[0068] S10, providing a silicon substrate, the silicon substrate comprising a first surface and a second surface and a side surface disposed opposite to each other, the second surface comprising a first region and a second region spaced apart from each other, and a third region located between the first region and the second region, a first tunneling passivation structure, a first mask layer, and a second tunneling passivation structure being sequentially formed in the first region of the second surface of the silicon substrate, a second tunneling passivation structure and a second mask layer being sequentially formed in the second region of the second surface of the silicon substrate, a second tunneling passivation structure being formed in the third region of the second surface of the silicon substrate, and a second tunneling passivation structure and a second mask layer being sequentially formed on the first surface and the side surface of the silicon substrate;

[0069] S20, removing the second mask layer on the first surface and side surfaces of the silicon substrate using a chain acid etching process;

[0070] S30, removing the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate using a chain alkali etching process;

[0071] S40, using a groove etching process to remove the second tunneling passivation structure in the first area and the third area of ​​the second surface of the silicon substrate, forming a suede light trapping structure on the third area and the first surface of the second surface of the silicon substrate, and removing the first mask layer in the first area and the second mask layer in the second area of ​​the second surface of the silicon substrate.

[0072] In step S10, the specific method for preparing the silicon substrate includes:

[0073] S101 , providing a silicon substrate, the silicon substrate comprising a first surface, a second surface and a side surface arranged opposite to each other, the second surface comprising a first region and a second region spaced apart from each other, and a third region located between the first region and the second region.

[0074] S102 , sequentially forming a first tunneling passivation structure and a first mask layer on the first surface, the second surface, and the side surface of the silicon substrate.

[0075] S103 , removing the first mask layer in the second area and the third area of ​​the second surface of the silicon substrate by using a laser process.

[0076] S104 , removing the first mask layer on the first surface and side surfaces of the silicon substrate by pickling.

[0077] S105 , removing the second region and the third region of the second surface of the silicon substrate, the first surface, and the first tunneling passivation structure on the side surface by alkali washing.

[0078] S106 , forming a second tunneling passivation structure and a second mask layer in sequence on the first surface, the second surface and the side surface of the silicon substrate.

[0079] S107 , removing the second mask layer in the first area and the third area of ​​the second surface of the silicon substrate by using a laser process.

[0080] The first tunneling passivation structure in step S10 includes a first tunneling layer and a first doped layer formed sequentially; the first doped layer is a P-type doped layer, and the first mask layer is a P-type doped salt-silicate glass. The second tunneling passivation structure includes a second tunneling layer and a second doped layer formed sequentially; the second doped layer is an N-type doped layer, and the second mask layer is an N-type doped salt-silicate glass.

[0081] In step S20, a first etching solution is used to perform chain acid etching to remove the second mask layer on the first surface and side surfaces of the silicon substrate. The first etching solution includes an acid solution with a mass fraction of 5% to 15%, and / or the first etching solution includes an HF solution. Specifically, the height of the first etching solution in the solution tank of the chain etching machine is adjusted so that the capillary roller in the solution tank is partially immersed in the first etching solution. The first surface of the silicon substrate is placed on the capillary roller, and the capillary phenomenon of the capillary roller during the rolling process transfers the first etching solution to the first surface and side surfaces of the silicon substrate, thereby etching the second mask layer on the first surface and side surfaces of the silicon substrate.

[0082] In step S20, while removing the second mask layer on the first surface and side surfaces of the silicon substrate using a chain acid etching process, the second surface of the silicon substrate is covered with a liquid protective film to protect the second mask layer on the second surface. The liquid protective film is preferably a water film.

[0083] In step S30, a second etchant is used to perform chain alkaline etching to remove the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate. The second etchant comprises an alkaline solution having a mass fraction of 10% to 20%, and / or comprises a KOH solution, and / or the etching temperature for removing the second tunneling passivation structure using the second etchant is 50°C to 70°C. Specifically, the height of the second etchant in the solution tank of the chain machine is adjusted so that the second etchant is flush with the top surface of the capillary roller in the solution tank. The first surface of the silicon substrate is placed on the capillary roller so that the second tunneling passivation structure on the first surface of the silicon substrate contacts the second etchant. The rolling of the capillary roller assists the second etchant in etching the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate.

[0084] In step S30, while the second tunnel passivation structure on the first surface and side surfaces of the silicon substrate is removed by a chain alkali etching process, the second surface of the silicon substrate is also covered with a liquid protective film to protect the second mask layer on the second surface.

[0085] In step S40, a trench alkaline etching process is first used to remove the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate, followed by texturing to form a textured light-trapping structure. During the texturing process, additives are added to protect the first and second mask layers on the second surface, further extending the texturing time. Subsequently, a trench acid etching process is used to remove the first mask layer in the first region and the second mask layer in the second region of the second surface of the silicon substrate, completing the texturing process.

[0086] In the above-mentioned multiple process steps, after the step of removing the second mask layer by a chain acid etching process, the step of cleaning the silicon substrate is also included. After the step of removing the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate by a chain alkali etching process, the step of cleaning the silicon substrate is also included. Before or after the step of removing the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate by a trench alkali etching process and forming a textured light-trapping structure, the step of cleaning the silicon substrate is also included. After the step of removing the first and second mask layers by a trench acid etching process, the step of cleaning the silicon substrate is also included.

[0087] The preparation method of the solar cell of the present invention first removes the salt-silica glass mask layer on the first surface and the side surface through a chain acid etching process, then removes the second tunnel passivation structure on the first surface and the side surface through a chain alkali etching process, and finally performs texturing through a groove etching process, thereby reducing nitrogen emissions during the etching process and being beneficial to environmental protection. At the same time, it can maximize the protection time of the mask layer (first mask layer and second mask layer) on the second surface in the texturing liquid (third etching liquid) during the texturing process for the P-type region and the N-type region on the second surface, thereby widening the process window; it optimizes the battery preparation process, can increase the texturing time to a certain extent, and the reflectivity and uniformity of the prepared velvet surface are more improved, thereby improving the velvet quality and improving the battery efficiency.

[0088] The present invention will be further described below with reference to specific embodiments.

[0089] Example 1:

[0090] Ginseng Figure 2 As shown, a silicon substrate 10 is provided. The silicon substrate 10 includes a first surface S1 and a second surface S2 disposed opposite each other, and a side surface S3 located between the first surface S1 and the second surface S2. The second surface S2 includes a first region S21 and a second region S22 spaced apart from each other, and a third region S23 located between the first region S21 and the second region S22. The first surface S1 is the front surface (i.e., the light-receiving surface) of the silicon substrate 10, the second surface S2 is the back surface (i.e., the backlight surface) of the silicon substrate 10, the first region S21 is a first doped region, the second region S22 is a second doped region, and the third region S23 is an isolation region.

[0091] The silicon substrate 10 in this embodiment is an N-type silicon substrate.

[0092] Ginseng Figure 3 As shown, a first tunneling passivation structure and a first mask layer 30 are sequentially formed on the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10. The first tunneling passivation structure includes a first tunneling layer 21 and a first doping layer 22. The first doping layer 22 is a P-type doped layer, and the first mask layer 30 is a P-type doped salt-silica glass.

[0093] It is understandable that the first tunneling passivation structure and the first mask layer 30 formed on the first surface S1 of the silicon substrate 10 and the bypass coating layer (the first tunneling passivation structure and the first mask layer 30 ) on the side surface S3 all need to be removed in subsequent processes.

[0094] Exemplarily, a first tunneling layer 21, such as a SiO2 layer, is grown on the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10. Then, an intrinsic polysilicon layer is grown on the surface of the first tunneling layer 21. The SiO2 layer and the intrinsic polysilicon layer are grown to cover the entire surface of the silicon substrate 10. Boron is then deposited on the intrinsic polysilicon layer and then diffused at high temperature to form a P-type doped first doped layer 22 (boron-doped polysilicon layer), and a first mask layer 30 (BSG layer) is simultaneously formed.

[0095] Ginseng Figure 4 As shown, the first mask layer 30 on the second region S22 and the third region S23 of the second surface S2 of the silicon substrate 10 is removed by a laser process to expose the first tunneling passivation structure below the second region S22 and the third region S23 of the second surface S2.

[0096] Ginseng Figure 5 As shown, a chain acid etching process is used to remove the first mask layer 30 on the first surface S1 and the side surface S3 of the silicon substrate 10. The acid solution in the chain acid etching process is preferably HF solution (hydrofluoric acid solution). After the etching is completed, the silicon substrate 10 is cleaned.

[0097] Ginseng Figure 6 As shown, a trench alkali etching process is used to remove the first tunneling passivation structure on the second region S22 and third region S23 of the second surface S2 of the silicon substrate 10, the first surface S1, and the side surface S3. The alkaline solution in the trench alkali etching process is preferably a KOH solution (potassium hydroxide solution). After etching is completed, the silicon substrate 10 is cleaned.

[0098] Ginseng Figure 7 As shown, a second tunneling passivation structure and a second mask layer 43 are sequentially formed on the first surface, the second surface S2, and the side surface S3 of the silicon substrate 10. The second tunneling passivation structure includes a second tunneling layer 41 and a second doping layer 42 formed sequentially. The second doping layer 42 is an N-type doped layer, and the second mask layer 43 is an N-type doped salt silicate glass.

[0099] It is understandable that the second tunneling passivation structure and the second mask layer 43 formed on the first surface S1 of the silicon substrate 10 and the plating layer (the second tunneling passivation structure and the second mask layer 43) on the side surface S3 need to be removed in subsequent processes.

[0100] Exemplarily, a second tunneling layer 41, such as a SiO2 layer, is grown on the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10. Furthermore, an intrinsic polysilicon layer is grown on the surface of the second tunneling layer 41. The SiO2 layer and the intrinsic polysilicon layer are grown to cover the entire surface of the silicon substrate 10. Then, phosphorus is deposited and high-temperature diffused on the intrinsic polysilicon layer to form an N-type doped second doped layer 42 (phosphorus-doped polysilicon layer), and a second mask layer 43 (PSG layer) is simultaneously formed.

[0101] Ginseng Figure 8 As shown, the second mask layer 43 on the first region S21 and the third region S23 of the second surface S2 of the silicon substrate 10 is removed by a laser process to expose the second tunneling passivation structure below the first region S21 and the third region S23 of the second surface S2.

[0102] Ginseng Figure 9 As shown, a chain acid etching process is used to remove the second mask layer 43 on the first surface S1 and side surface S3 of the silicon substrate 10. While the chain acid etching process is being used to remove the second mask layer on the first surface S1 and side surface S3, a liquid protective film (not shown) is applied to the second surface S2 of the silicon substrate 10. The liquid protective film is preferably a water film that protects the second mask layer 43 on the second surface S2 of the silicon substrate 10.

[0103] The first etching solution is used for chain acid etching to remove the second mask layer 43 on the first surface S1 and the side surface S3 of the silicon substrate 10. The first etching solution comprises an acid solution with a mass fraction of 5% to 15%. The first etching solution is preferably an HF solution.

[0104] For example, a room-temperature HF (hydrofluoric acid) solution with a mass fraction of 10% is prepared and placed in the solution tank of a chain machine. The height of the HF (hydrofluoric acid) solution in the solution tank is adjusted so that the capillary roller in the solution tank is partially immersed in the HF (hydrofluoric acid) solution. The capillary roller speed in the solution tank is adjusted to 2m / s to 4m / s, preferably 2m / s. With the second surface S2 of the silicon substrate 10 facing upward, while or after the second surface S2 is protected by a water spray film, the first surface S1 of the silicon substrate 10 is placed on the capillary roller. The capillary roller evenly moves through the solution tank of the chain machine under the action of the capillary roller. The capillary phenomenon during the rolling process transfers the HF (hydrofluoric acid) solution to the first surface S1 and side surface S3 of the silicon substrate 10, removing the second mask layer 43 on the first surface S1 and side surface S3. After etching is completed, the silicon substrate 10 is cleaned.

[0105] Ginseng Figure 10As shown, a chain alkali etching process is used to remove the second tunneling passivation structure on the first surface S1 and side surface S3 of the silicon substrate 10. While the chain alkali etching process is used to remove the second tunneling passivation structure on the first surface S1 and side surface S3, a liquid protective film (not shown) is also applied to the second surface S2 of the silicon substrate 10. The liquid protective film is preferably a water film, which also protects the second mask layer 43 located on the second surface S2 of the silicon substrate 10.

[0106] A second etchant is used to perform chain alkaline etching to remove the second tunneling passivation structure on the first surface S1 and side surface S3 of the silicon substrate 10. The second etchant comprises an alkaline solution having a mass fraction of 10% to 20%. The second etchant is preferably a KOH solution. The etching temperature for removing the second tunneling passivation structure using the second etchant is 50° C. to 70° C.

[0107] Exemplarily, a KOH (potassium hydroxide) solution with a mass fraction of 15% is prepared and placed in the solution tank of the chain machine, and the height of the KOH (potassium hydroxide) solution in the solution tank of the chain machine is adjusted so that the KOH (potassium hydroxide) solution is flush with the top surface of the capillary roller in the solution tank, or the KOH (potassium hydroxide) solution in the solution tank is slightly higher than the top surface of the capillary roller; the speed of the capillary roller in the solution tank of the chain machine is adjusted to 2m / s to 4m / s, preferably 2m / s, and the temperature of the KOH (potassium hydroxide) solution is adjusted to 60°C. With the second surface S2 of the silicon substrate 10 facing upward, the first surface S1 of the silicon substrate 10 is placed on a capillary roller while or after the second surface S2 is protected by a water spray. The second tunneling passivation structure on the first surface S1 of the silicon substrate 10 is kept in contact with a KOH (potassium hydroxide) solution. The second tunneling passivation structure on the first surface S1 is removed uniformly by the capillary roller through a chain conveyor. Furthermore, the second tunneling passivation structure on the side surface S3 is removed by the capillary roller's subtle capillary action on the KOH (potassium hydroxide) solution (alkaline solution). After etching, the silicon substrate 10 is cleaned and dried using the chain conveyor's air knife.

[0108] Ginseng Figure 11 As shown, the second tunnel passivation structure in the first area S21 and the third area S23 of the second surface S2 of the silicon substrate 10 is removed by a trench alkaline etching process, and a textured light trapping structure 50 is formed on the third area S23 of the second surface S2 of the silicon substrate 10 and the first surface S1.

[0109] A third etchant is used for trench alkaline etching to remove the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate, and to form a textured light-trapping structure in the third region of the second surface and the first surface of the silicon substrate. The third etchant comprises an alkaline solution with a mass fraction of 0.5% to 1.5%; the third etchant comprises a KOH solution. The texturing temperature for forming the textured light-trapping structure using the third etchant is 70°C to 80°C, and the texturing time is 650s to 950s.

[0110] It can be understood that while the velvet light-trapping structure 50 is formed on the first surface S1 of the silicon substrate 10, the velvet light-trapping structure 50 is also formed on the third area S23 of the second surface S2 of the silicon substrate 10, which can form a good isolation effect on the P-type region (first tunneling passivation structure) and the N-type region (second tunneling passivation structure) on the second surface.

[0111] For example, a 0.5% KOH (potassium hydroxide) alkaline solution is prepared in one of the slots of the slot machine, and a 1% additive is added to form a mixed solution. The additives are commonly used in the prior art to protect the mask layers (first and second mask layers) during the texturing process, and are not elaborated in detail in this application. The silicon substrate 10 is immersed in the mixed solution at a temperature of 70°C for 700 seconds, forming a textured light-trapping structure 50 on the third region S23 of the first surface S1 and the second surface S2 of the silicon substrate 10.

[0112] It is understood that before using a trench-type alkaline etching process to remove the second tunneling passivation structure and form the textured light-trapping structure, the silicon substrate 10 can be pre-cleaned using a KOH solution having a mass fraction of 0.3% to 0.5%, preferably 0.3%, mixed with a H2O2 solution having a mass fraction of 1% to 2%, preferably 1%, at a temperature of 60°C to 70°C for 100 to 200 seconds. Finally, the substrate is rinsed with deionized water. After using a trench-type alkaline etching process to remove the second tunneling passivation structure and form the textured light-trapping structure, the silicon substrate 10 needs to be cleaned again using a KOH solution having a mass fraction of 0.3% to 0.5%, preferably 0.3%, mixed with a H2O2 solution having a mass fraction of 1% to 2%, preferably 1%, at a temperature of 70°C to 80°C for 100 to 200 seconds. Finally, the substrate is rinsed with deionized water.

[0113] Ginseng Figure 12 As shown, a trench acid etching process is used to remove the first mask layer 30 on the first region S21 and the second mask layer 43 on the second region S22 of the second surface S2 of the silicon substrate 10 .

[0114] A fourth etching solution is used for tank acid etching to remove the first mask layer 30 and the second mask layer 43. The fourth etching solution comprises an acid solution with a mass fraction of 5%-10%. The fourth etching solution is preferably an HF solution, the etching temperature is 15°C-25°C, and the etching time is 100s-200s.

[0115] For example, a 5% by mass HF (hydrofluoric acid) solution is prepared in one tank of a tank-type machine. The silicon substrate 10 is immersed in the HF solution at room temperature, for example, 15°C-25°C, for 100 seconds. The first mask layer 30 on the first region S21 and the second mask layer 43 on the second region S22 of the second surface S2 of the silicon substrate 10 are then removed. Finally, the substrate is rinsed with deionized water and dried.

[0116] At this point, the solar cell texturing step is complete. Subsequently, conventional techniques can be used to fabricate the front surface field on the first surface of the cell, a passivation layer on the first and / or second surface of the cell, and electrodes on the second surface. Since the fabrication of the front surface field, passivation layer, and electrodes can all be accomplished using existing techniques and are not the novelties of this invention, this invention will not elaborate on these techniques in detail.

[0117] The present invention also provides a solar cell prepared by the above method. The solar cell is a BC cell, comprising a silicon substrate 10. Figure 2 As shown, the silicon substrate 10 includes a first surface S1 and a second surface S2 disposed opposite each other, and a side surface S3 located between the first surface S1 and the second surface S2. The second surface S2 includes a first region S21 and a second region S22 spaced apart from each other, and a third region S23 located between the first region S21 and the second region S22. The first surface S1 is the front surface (i.e., the light-receiving surface) of the silicon substrate 10, the second surface S2 is the back surface (i.e., the backlight surface) of the silicon substrate 10, the first region S21 is a first doped region, the second region S22 is a second doped region, and the third region S23 is an isolation region.

[0118] The silicon substrate 10 in this embodiment is an N-type silicon substrate.

[0119] refer to Figure 12 As shown, a textured light-trapping structure 50 is formed on the first surface S1 of the silicon substrate 10. A textured light-trapping structure 50 is also formed on the third region S23 on the second surface S2 of the silicon substrate 10. Alkali texturing can form a pyramid textured structure on the third region S23 on the second surface S2 of the silicon substrate 10 and on the first surface S1.

[0120] A first tunneling layer 21 and a first doping layer 22 are stacked in sequence on the first region S21 on the second surface S2 of the silicon substrate 10. The first tunneling layer 21 can provide a good interface passivation effect, and the first doping layer 22 can provide a field passivation effect. At the same time, because the doping concentration of this layer is relatively high, it can improve contact and reduce resistance.

[0121] The first tunneling layer 21 is a silicon oxide layer, a silicon oxynitride layer, or a combination of the two, preferably a silicon oxide layer; and the first doping layer 22 is a boron-doped polysilicon layer.

[0122] A second tunneling layer 41 and a second doping layer 42 are stacked in sequence on the second region S22 on the second surface S2 of the silicon substrate 10. The second tunneling layer 41 can provide a good interface passivation effect, and the second doping layer 42 can provide a field passivation effect. At the same time, because the doping concentration of this layer is relatively high, it can improve contact and reduce resistance.

[0123] The second tunneling layer 41 is a silicon oxide layer, a silicon oxynitride layer, or a combination of the two, preferably a silicon oxide layer; and the second doping layer 42 is a phosphorus-doped polysilicon layer.

[0124] The solar cell of this embodiment may also include conventional structures such as a front surface field, a passivation layer, an anti-reflection layer, and electrodes (not shown). The passivation layer may be an aluminum oxide passivation layer. The anti-reflection layer may be a laminated film formed by one or more of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer.

[0125] Compared with the prior art, the preparation method and solar cell of the present invention, in the pre-treatment process of texturing, remove the second mask layer on the first surface and the side through a chain acid etching process; then remove the second tunnel passivation structure on the first surface and the side through a chain alkaline etching process, and then perform a groove etching process to complete the texturing step, thereby reducing nitrogen emissions during the etching process and being beneficial to environmental protection. At the same time, it can maximize the protection time of the mask layer (first mask layer and second mask layer) on the second surface in the texturing liquid (third etching liquid) for the P-type region and N-type region on the second surface during the texturing process, thereby widening the process window; optimize the battery preparation process, and can increase the texturing time to a certain extent, so that the reflectivity and texture of the prepared texture are more uniform, thereby improving the texture quality and improving the battery efficiency; it can achieve nitric acid-free polishing of the first surface of the battery, reduce nitrogen emissions, and be beneficial to environmental protection.

[0126] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a solar cell, characterized in that: include: A silicon substrate is provided, comprising a first surface and a second surface and a side surface disposed opposite to each other, the second surface comprising a first region and a second region spaced apart from each other, and a third region located between the first region and the second region, a first tunneling passivation structure, a first mask layer, and a second tunneling passivation structure being sequentially formed in the first region of the second surface of the silicon substrate, a second tunneling passivation structure and a second mask layer being sequentially formed in the second region of the second surface of the silicon substrate, a second tunneling passivation structure being formed in the third region of the second surface of the silicon substrate, and a second tunneling passivation structure and a second mask layer being sequentially formed on the first surface and the side surface of the silicon substrate; Removing the second mask layer on the first surface and side surfaces of the silicon substrate using a chain acid etching process; Using a second etching solution to perform a chain alkaline etching process to remove the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate, wherein the second etching solution includes an alkaline solution with a mass fraction of 10% to 20%; A third etching solution is used to perform a groove etching process to remove the second tunneling passivation structure in the first and third regions of the second surface of the silicon substrate, thereby forming a textured light-trapping structure on the third region of the second surface and the first surface of the silicon substrate. The third etching solution includes an alkaline solution with a mass fraction of 0.5% to 1.5%. The texture forming time for forming the textured light-trapping structure is 650 seconds to 950 seconds. A trench etching process is used to remove the first mask layer in the first area and the second mask layer in the second area of ​​the second surface of the silicon substrate.

2. The method for preparing a solar cell according to claim 1, wherein: Performing chain acid etching using a first etching solution to remove the second mask layer on the first surface and side surfaces of the silicon substrate; The first etching solution includes an acid solution with a mass fraction of 5%-15%, and / or the first etching solution includes an HF solution.

3. The method for preparing a solar cell according to claim 2, wherein: Removing the second mask layer on the first surface and side surfaces of the silicon substrate using a chain acid etching process, comprising: Adjusting the height of the first etching solution in the solution tank of the chain machine so that the capillary roller in the solution tank is partially immersed in the first etching solution; The first surface of the silicon substrate is placed on the capillary roller, and the first etching liquid is transferred to the first surface and side of the silicon substrate by the capillary phenomenon of the capillary roller during rolling, so as to etch the second mask layer on the first surface and side of the silicon substrate.

4. The method for preparing a solar cell according to claim 1, wherein: The second etching solution includes a KOH solution, and / or the etching temperature for removing the second tunnel passivation structure using the second etching solution is 50° C.-70° C.

5. The method for preparing a solar cell according to claim 1, wherein: Removing the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate using a chain alkali etching process, comprising: Adjusting the height of the second etching solution in the chain machine solution tank so that the second etching solution is flush with the top surface of the capillary roller in the solution tank; placing the first surface of the silicon substrate on the capillary roller so that the first surface of the silicon substrate contacts the second etching solution; The second etching solution is assisted by the rolling of the capillary roller to etch the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate.

6. The method for preparing a solar cell according to claim 1, wherein: While removing the second mask layer on the first surface and side surfaces of the silicon substrate by a chain acid etching process, the second surface of the silicon substrate is covered with a liquid protective film; and / or, A chain alkali etching process is adopted to remove the second tunnel passivation structure on the first surface and side surfaces of the silicon substrate, while covering the second surface of the silicon substrate with a liquid protective film.

7. The method for preparing a solar cell according to claim 1, wherein: The third etching solution includes a KOH solution, and / or the texturing temperature for forming the textured light-trapping structure using the third etching solution is 70° C.-80° C.

8. The method for preparing a solar cell according to claim 1, wherein: A trench acid etching process is used to remove the first mask layer in the first area and the second mask layer in the second area of ​​the second surface of the silicon substrate.

9. The method for preparing a solar cell according to claim 8, wherein: Performing trench acid etching using a fourth etching solution to remove the first mask layer and the second mask layer; The fourth etching solution includes an acid solution with a mass fraction of 5%-10%, and / or the fourth etching solution includes an HF solution, and / or the etching temperature for removing the first mask layer and the second mask layer using the fourth etching solution is 15°C-25°C, and the etching time is 100s-200s.

10. The method for preparing a solar cell according to claim 1, wherein: After the step of removing the second mask layer by using a chain acid etching process, the method further includes cleaning the silicon substrate; and / or, After the step of removing the second tunneling passivation structure on the first surface and side surfaces of the silicon substrate by using a chain alkali etching process, the method further includes cleaning the silicon substrate; and / or, The method further includes cleaning the silicon substrate before and after the step of removing the second tunneling passivation structure in the first area and the third area of ​​the second surface of the silicon substrate by a groove etching process, and forming a velvet light trapping structure in the third area of ​​the second surface of the silicon substrate and the first surface, and after the step of removing the first mask layer and the second mask layer by a groove etching process.

11. The method for preparing a solar cell according to claim 1, wherein: The first tunneling passivation structure includes a first tunneling layer and a first doping layer formed in sequence; The second tunneling passivation structure includes a second tunneling layer and a second doping layer formed in sequence.

12. The method for preparing a solar cell according to claim 11, wherein: The first doped layer is a P-type doped layer, and the first mask layer is a P-type doped salt-silica glass; The second doping layer is an N-type doping layer, and the second mask layer is N-type doped salt-silica glass.

13. A solar cell, characterized in that: The solar cell is prepared by the method for preparing the solar cell according to any one of claims 1 to 12.

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