Preparation method of solar cell and solar cell

Abstract

The invention discloses a preparation method of a solar cell and the solar cell. The preparation method comprises the following steps: removing a second mask layer on a first surface and a side surface of a silicon substrate by adopting a chained acid etching process; removing the second tunneling passivation structures on the first surface and the side surface of the silicon substrate and the second tunneling passivation structures in the first region and the third region of the second surface by adopting a groove type alkali etching process; forming a textured light trapping structure on a third region of the second surface of the silicon substrate and the first surface by adopting a texturing process; 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 by adopting a groove type acid etching process. According to the preparation method of the solar cell, in the texturing pretreatment process, part of the mask layer on the second surface is reserved through the chain type etching process, two-step texturing is achieved through the groove type etching process, and the mask layer is used for protecting the P-type region and the N-type region on the second surface in the texturing process.

Description

Technical Field

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

[0002] In a solar cell, due to the special structure of a BC cell (back contact cell), during front surface texturing, it is usually necessary to protect the back surface N-type doped salt silicon glass, so the manufacturing process is relatively complex.

[0003] The conventional process in the prior art is that in the pre-treatment process of front surface texturing of a BC cell, under the condition permitted by environmental protection, the method of using hydrofluoric acid plus nitric acid is adopted to remove both the front surface N-type doped salt silicon glass and the wrap plating layer at the same time, and then texturing is carried out through an alkaline solution. This manufacturing process is rather cumbersome and is likely to affect the back surface N-type doped salt silicon glass of the cell.

[0004] The information disclosed in this background art section is only intended to enhance the understanding of the overall background of the present invention, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] 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 and improve the cell efficiency.

[0006] In order to achieve the above purpose, the technical solution provided by a specific embodiment of the present invention is as follows: A method for preparing a solar cell, characterized by comprising: Providing a silicon substrate, the silicon substrate includes a first surface, a second surface and a side surface which are oppositely arranged, the second surface includes a first region and a second region which are spaced apart, 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 are sequentially formed on the first region of the second surface of the silicon substrate, a second tunneling passivation structure and a second mask layer are sequentially formed on the second region of the second surface of the silicon substrate, a second tunneling passivation structure is formed on the third region of the second surface of the silicon substrate, and a second tunneling passivation structure and a second mask layer are sequentially formed on the first surface and the side surface of the silicon substrate; Removing the second mask layer on the first surface and the side surface of the silicon substrate by using a chain acid etching process; Removing the second tunneling passivation structure on the first surface and the side surface of the silicon substrate and the second tunneling passivation structure on the first region and the third region of the second surface by using a tank alkaline etching process; Forming a textured light trapping structure on the third region of the second surface and the first surface of the silicon substrate by using a texturing process; The first mask layer in the first region and the second mask layer in the second region on the second surface of the silicon substrate are removed by using a slot-type acid etching process.

[0007] In one or more embodiments of the present invention, while removing the second mask layer on the first surface and the side surface of the silicon substrate by using a chain-type acid etching process, a liquid protective film is covered on the second surface of the silicon substrate.

[0008] In one or more embodiments of the present invention, the liquid protective film is a water film.

[0009] In one or more embodiments of the present invention, a chain-type acid etching is performed by using a first etching solution to remove the second mask layer on the first surface and the side surface of the silicon substrate.

[0010] In one or more embodiments of the present invention, 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.

[0011] In one or more embodiments of the present invention, a slot-type alkali etching is performed by using a second etching solution to remove the second tunneling passivation structure.

[0012] In one or more embodiments of the present invention, the second etching solution includes an alkali solution with a mass fraction of 2.5% - 3.5%; and / or, the second etching solution includes a KOH solution; and / or, The etching temperature for removing the second tunneling passivation structure by using the second etching solution is 60°C - 70°C, and the etching time is 50s - 80s.

[0013] In one or more embodiments of the present invention, a texturing is performed by using a texturing solution to form a texturing light-trapping structure.

[0014] In one or more embodiments of the present invention, the texturing solution includes an alkali solution with a mass fraction of 0.5% - 1.5%; and / or, the texturing solution includes a KOH solution; and / or, The texturing temperature for forming the texturing light-trapping structure by using the texturing solution is 70°C - 80°C, and the texturing time is 500s - 750s.

[0015] In one or more embodiments of the present invention, a slot-type acid etching is performed by using a third etching solution to remove the first mask layer and the second mask layer.

[0016] In one or more embodiments of the present invention, the third etching solution includes an acid solution with a mass fraction of 5% - 10%; and / or, the third etching solution includes an HF solution; and / or, The etching temperature for removing the first mask layer and the second mask layer using the third etching solution is 15°C - 25°C, and the etching time is 100s - 200s.

[0017] In one or more embodiments of the present invention, after the step of removing the second mask layer using a chain acid etching process, it further includes cleaning the silicon substrate; and / or, After the step of removing the second tunneling passivation structure using a tank alkali etching process, it further includes cleaning the silicon substrate; and / or, After the step of forming a textured light-trapping structure using a texturing process, it further includes cleaning the silicon substrate; and / or, After the step of removing the first mask layer and the second mask layer using a tank acid etching process, it further includes cleaning the silicon substrate.

[0018] In one or more embodiments of the present invention, the preparation method further includes: Forming a first tunneling passivation structure and a first mask layer on the first surface, second surface, and side surface of the silicon substrate in sequence; Removing the first mask layer in the second region and the third region of the second surface of the silicon substrate using a laser process; Removing the first mask layer on the first surface and the side surface of the silicon substrate by pickling; Removing the first tunneling passivation structure on the second region and the third region of the second surface, the first surface, and the side surface of the silicon substrate by alkali washing; Forming a second tunneling passivation structure and a second mask layer on the first surface, second surface, and side surface of the silicon substrate in sequence; Removing the second mask layer in the first region and the third region of the second surface of the silicon substrate using a laser process.

[0019] 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 in sequence; The second tunneling passivation structure includes a second tunneling layer and a second doping layer formed in sequence.

[0020] In one or more embodiments of the present invention, the first doping layer is a P-type doping layer, and the first mask layer is P-type doped salt silicon glass; The second doping layer is an N-type doping layer, and the second mask layer is N-type doped salt silicon glass.

[0021] A solar cell is prepared by the preparation method of the above-mentioned solar cell.

[0022] Compared with the prior art, in the method for preparing a solar cell and the solar cell of the present invention, without using nitric acid, in the pretreatment process of texturing, part of the mask layer (the first mask layer and the second mask layer) on the second surface is retained through a chain etching process, and the steps of removing the bypass plating and texturing are completed through a tank etching process, realizing two-step texturing of the solar cell, and protecting the P-type region and the N-type region on the second surface by using the mask layer during the texturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a process flow chart of the method for preparing a solar cell of the present invention; Figures 2a - 2k It is a step structure diagram of the method for preparing a solar cell in an embodiment of the present invention.

[0025] Reference numerals: 10 - silicon substrate; S1 - first surface; S2 - second surface; S21 - first region; S22 - second region; S23 - third region; S3 - side surface; 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 - surface texture light trapping structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] As mentioned in the background art, in the prior art for BC cells in solar cells, the texturing method is too complicated and the salt silicon glass mask layer on the back of the cell is easily affected during the texturing process.

[0028] Based on this, the present invention provides a method for preparing a solar cell and a solar cell. By using a chain etching process to first remove the salt silicon glass mask layer on the first surface and the side surface of the silicon substrate, then using a trough etching process to remove the wrap plating layer, and finally using a trough etching process to perform texturing, the entire process can simultaneously satisfy the good protection of the salt silicon glass mask layer on the second surface of the solar cell, thereby achieving good protection of the P-type region (the first tunneling passivation structure) and the N-type region (the second tunneling passivation structure) on the second surface, optimizing the battery preparation process and improving the battery efficiency.

[0029] Reference Figure 1 As shown, the present invention discloses a method for preparing a solar cell, which specifically includes the following steps: S10, Provide a silicon substrate, the silicon substrate includes a first surface and a second surface arranged oppositely, the second surface includes a first region and a second region distributed at intervals, and a third region located between the first region and the second region. The first region of the second surface of the silicon substrate is successively formed with 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 is successively formed with a second tunneling passivation structure and a second mask layer. The third region of the second surface of the silicon substrate is formed with a second tunneling passivation structure. The second tunneling passivation structure and the second mask layer are successively formed on the first surface and the side surface of the silicon substrate.

[0030] S20, Use a chain acid etching process to remove the second mask layer on the first surface and the side surface of the silicon substrate.

[0031] S30, Use a trough alkaline etching process to remove the second tunneling passivation structure on the first surface and the side surface of the silicon substrate and the second tunneling passivation structure in the first region and the third region of the second surface.

[0032] S40, Use a texturing process to form a textured light-trapping structure on the third region of the second surface and the first surface of the silicon substrate.

[0033] S50, Use a trough acid etching process 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.

[0034] Among them, in step S10, the specific preparation method includes: S101, Provide a silicon substrate, the silicon substrate includes a first surface, a second surface arranged oppositely, and a side surface. The second surface includes a first region and a second region distributed at intervals, and a third region located between the first region and the second region.

[0035] S102, Successively form 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.

[0036] S103, remove the first mask layer in the second region and the third region on the second surface of the silicon substrate by using a laser process.

[0037] S104, remove the first mask layer on the first surface and the side surface of the silicon substrate by pickling.

[0038] S105, remove the first tunneling passivation structure on the second region and the third region of the second surface, the first surface, and the side surface of the silicon substrate by alkali cleaning.

[0039] S106, sequentially form a second tunneling passivation structure and a second mask layer on the first surface, the second surface, and the side surface of the silicon substrate.

[0040] S107, remove the second mask layer in the first region and the third region on the second surface of the silicon substrate by using a laser process.

[0041] The first tunneling passivation structure in step S10 includes a first tunneling layer and a first doping layer formed in sequence; the first doping layer is a P-type doping layer, and the first mask layer is a P-type doped salt silicon glass. The second tunneling passivation structure includes a second tunneling layer and a second doping layer formed in sequence; the second doping layer is an N-type doping layer, and the second mask layer is an N-type doped salt silicon glass.

[0042] In step S20, while removing the second mask layer on the first surface and the side surface of the silicon substrate by using a chain acid etching process, a liquid protective film is covered on the second surface of the silicon substrate to protect the second mask layer on the second surface. The liquid protective film is preferably a water film.

[0043] In step S30, when performing a tank alkali etching with a second etching solution to remove the second tunneling passivation structure, an additive is also added to protect the first mask layer and the second mask layer on the second surface.

[0044] In step S40, when performing texturing with a texturing solution to form a textured light-trapping structure, an additive is also added to protect the first mask layer and the second mask layer on the second surface.

[0045] In the above process steps, after the step of removing the second mask layer by using a chain acid etching process, it further includes a step of cleaning the silicon substrate. After the step of removing the second tunneling passivation structure by using a tank alkali etching process, it further includes a step of cleaning the silicon substrate. After the step of forming a textured light-trapping structure by using a texturing process, it further includes a step of cleaning the silicon substrate. After the step of removing the first mask layer and the second mask layer by using a tank acid etching process, it further includes a step of cleaning the silicon substrate.

[0046] The preparation method of the solar cell of the present invention, after removing the salt silicon glass mask layer on the first surface and the side surface through the chain etching process, first removes the wrap-around plating layer through the trough etching process, and then performs texturing through the trough etching process, realizing two-step texturing of the solar cell. During the whole process, good protection of the salt silicon glass mask layer on the second surface of the solar cell is satisfied at the same time, thereby realizing good protection of the P-type region (the first tunneling passivation structure) and the N-type region (the second tunneling passivation structure) on the second surface, optimizing the battery preparation process and improving the battery efficiency.

[0047] The present invention will be further described below in conjunction with specific embodiments.

[0048] Embodiment 1: Refer Figure 2a As shown, a silicon substrate 10 is provided. The silicon substrate 10 includes a first surface S1 and a second surface S2 which are oppositely arranged, 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 which are spaced apart, 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 the first doping region, the second region S22 is the second doping region, and the third region S23 is the isolation region.

[0049] The silicon substrate 10 in this embodiment is an N-type silicon substrate.

[0050] Refer Figure 2b 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 doping layer, and the first mask layer 30 is P-type doped salt silicon glass.

[0051] It can be understood that the first tunneling passivation structure and the first mask layer 30 formed on the first surface S1 and the side surface S3 of the silicon substrate 10 are wrap-around plating layers and need to be removed in subsequent processes.

[0052] Exemplarily, a first tunneling layer 21, such as a SiO 2 layer, is grown on the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10, and then an intrinsic polysilicon layer is grown on the surface of the first tunneling layer 21. The SiO 2 layer and the intrinsic polysilicon layer grow over the entire surface of the silicon substrate 10. Then, boron deposition and high-temperature diffusion are performed on the intrinsic polysilicon layer to form a P-type doped first doping layer 22 (boron-doped polysilicon layer), and at the same time, a first mask layer 30 (BSG layer) is formed.

[0053] As shown Figure 2c in FIG. 0, a 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, exposing a first tunneling passivation structure located below the second region S22 and the third region S23 of the second surface S2.

[0054] As shown Figure 2d in FIG. 1, the first mask layer 30 on the first surface S1 and the side surface S3 of the silicon substrate 10 is removed by a chain acid etching process. Among them, the acid solution in the chain acid etching process is preferably an HF solution (hydrofluoric acid solution). After etching, the silicon substrate 10 is cleaned.

[0055] As shown Figure 2e in FIG. 2, the first tunneling passivation structure on the second region S22 and the third region S23 of the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10 is removed by a tank alkaline etching process. Among them, the alkaline solution in the tank alkaline etching process is preferably a KOH solution (potassium hydroxide solution). After etching, the silicon substrate 10 is cleaned.

[0056] As shown Figure 2f in FIG. 3, 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 in sequence. The second doping layer 42 is an N-type doping layer, and the second mask layer 43 is an N-type doped salt silicon glass.

[0057] It can be understood that the second tunneling passivation structure and the second mask layer 43 formed on the first surface S1 and the side surface S3 of the silicon substrate 10 are wrap-around coatings and need to be removed in subsequent processes.

[0058] Exemplarily, a second tunneling layer 41, such as a SiO 2 layer, is continuously grown on the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10, and then an intrinsic polysilicon layer is grown on the surface of the second tunneling layer 41. The SiO 2 layer and the intrinsic polysilicon layer also grow over the entire surface of the silicon substrate 10. Then, phosphorus deposition and high-temperature diffusion are performed on the intrinsic polysilicon layer to form an N-type doped second doping layer 42 (phosphorus-doped polysilicon layer), and at the same time, a second mask layer 43 (PSG layer) is formed.

[0059] As shown Figure 2g in FIG. 4, 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, exposing the second tunneling passivation structure located below the first region S21 and the third region S23 of the second surface S2.

[0060] As shownFigure 2h As shown, a chain acid etching process is used to remove the second mask layer 43 on the first surface S1 and the side surface S3 of the silicon substrate 10. When the second mask layer is removed by the chain acid etching process, a liquid protective film (not shown in the figure) is covered on the second surface S2 of the silicon substrate 10. The liquid protective film is preferably a water film, which can protect the second mask layer 43 on the second surface S2 of the silicon substrate 10.

[0061] Among them, a chain acid etching is performed using a first etching solution 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 includes an acid solution with a mass fraction of 5% - 15%. The first etching solution is preferably an HF solution.

[0062] Exemplarily, an HF (hydrofluoric acid) solution with a mass fraction of 5% is prepared and placed in the solution tank of the chain machine. The height of the HF (hydrofluoric acid) solution in the solution tank of the chain machine is adjusted so that the capillary roller in the solution tank is partially immersed in the HF (hydrofluoric acid) solution; the speed of the capillary roller in the solution tank of the chain machine is adjusted to 2 m / s - 4 m / s, preferably 2 m / s. The second surface S2 of the silicon substrate 10 faces upward. While or after spraying a water film to protect the second surface S2, the first surface S1 of the silicon substrate 10 is placed on the capillary roller, and the silicon substrate 10 uniformly passes through the solution tank of the chain machine under the rolling action of the capillary roller. The HF (hydrofluoric acid) solution is transferred to the first surface S1 and the side surface S3 of the silicon substrate 10 through the capillary phenomenon during the rolling of the capillary roller, and the second mask layer 43 on the first surface S1 and the side surface S3 is removed. After etching, the silicon substrate 10 is cleaned.

[0063] Refer Figure 2i As shown, a tank alkaline etching process is used to remove the second tunneling passivation structure on the first region S21 and the third region S23 of the second surface S2, the first surface S1, and the side surface S3 of the silicon substrate 10.

[0064] Among them, a tank alkaline etching is performed using a second etching solution to remove the second tunneling passivation structure. The second etching solution includes an alkaline solution with a mass fraction of 2.5% - 3.5%; the second etching solution includes a KOH solution, the etching temperature is 60°C - 70°C, and the etching time is 50 s - 80 s. After etching, the silicon substrate 10 is cleaned.

[0065] Exemplarily, a KOH (potassium hydroxide) alkali solution with a mass fraction of 2.5% is prepared in one of the slots of the trough machine, and 1% of the first additive is added to form a mixed solution. The first additive is a common additive used in the prior art to protect the mask layer (the first mask layer and the second mask layer), and this application does not elaborate on it in detail. The above-mentioned silicon substrate 10 is immersed in the mixed solution, the temperature is maintained at 60 °C, and the immersion time is 50 s to remove the second tunneling passivation structure on the first surface S1 and the side surface S3 of the silicon substrate 10 and the second tunneling passivation structure on the first region S21 and the third region S23 of the second surface S2. Then, a KOH solution with a mass fraction of 0.3% - 0.5%, preferably 0.3%, and H 2 O 2 , preferably 1%, are mixed, and the silicon substrate 10 is cleaned in an environment with a temperature of 60 °C - 70 °C for 100 s - 200 s. Finally, it is rinsed with deionized water.

[0066] As shown in Figure 2j , a surface texture light trapping structure 50 is formed on the third region S23 of the second surface S2 and the first surface S1 of the silicon substrate 10 by using a texturing process. Among them, the texturing solution used includes an alkali solution with a mass fraction of 0.5% - 1.5%; the texturing solution includes a KOH solution, the texturing temperature is 70 °C - 80 °C, and the texturing time is 500 s - 750 s.

[0067] It can be understood that while the surface texture light trapping structure 50 is formed on the first surface S1 of the silicon substrate 10, the surface texture light trapping structure 50 is also formed on the third region S23 of the second surface S2 of the silicon substrate 10, which can form a good isolation effect on the P-type region (the first tunneling passivation structure) and the N-type region (the second tunneling passivation structure) on the second surface.

[0068] Exemplarily, a KOH (potassium hydroxide) alkali solution with a mass fraction of 0.5% is prepared in one of the slots of the trough machine, and 1% of the second additive is added to form a mixed solution. The second additive is a common additive used in the prior art to protect the mask layer (the first mask layer and the second mask layer) during the texturing process, and this application does not elaborate on it in detail. The above-mentioned silicon substrate 10 is immersed in the mixed solution, the temperature is maintained at 70 °C, and the immersion time is 500 s to form a surface texture light trapping structure 50 on the first surface S1 and the third region S23 of the second surface S2 of the silicon substrate 10. Then, a KOH solution with a mass fraction of 0.3% - 0.5%, preferably 0.3%, and H 2 O 2 , preferably 1%, are mixed, and the silicon substrate 10 is cleaned in an environment with a temperature of 70 °C - 80 °C for 100 s - 200 s. Finally, it is rinsed with deionized water.

[0069] Reference Figure 2k As shown, a trench acid etching process is used to remove the first mask layer 30 on the first region S21 of the second surface S2 of the silicon substrate 10 and the second mask layer 43 on the second region S22.

[0070] Among them, a trench acid etching is carried out using a third etching solution to remove the first mask layer 30 and the second mask layer 43. The third etching solution includes an acid solution with a mass fraction of 5% - 10%; the third etching solution is preferably an HF solution, the etching temperature is 15°C - 25°C, and the etching time is 100s - 200s.

[0071] Exemplarily, a HF (hydrofluoric acid) solution with a mass fraction of 5% is prepared in one of the trenches of the trench machine, the above-mentioned silicon substrate 10 is immersed in the HF solution, the temperature is maintained at room temperature, such as 15°C - 25°C, and the immersion time is 100s to remove the first mask layer 30 on the first region S21 of the second surface S2 of the silicon substrate 10 and the second mask layer 43 on the second region S22. Finally, it is rinsed with deionized water and dried.

[0072] So far, the texturing step of the solar cell is completed. Subsequently, according to the traditional technology, a front surface field can be prepared on the first surface of the cell, a passivation layer can be prepared on the first surface and / or the second surface of the cell, and structures such as electrodes can be prepared on the second surface of the cell. Since the preparation of structures such as the front surface field, the passivation layer, and the electrodes can all adopt existing technologies and are not the innovation points of the present invention, the present invention will not elaborate on this in detail.

[0073] The present invention also provides a solar cell prepared by the above method. This solar cell is a BC cell and includes a silicon substrate 10. Referring to Figure 2a As shown, the silicon substrate 10 includes a first surface S1 and a second surface S2 which are oppositely arranged, 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 which are spaced apart, 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 light-shielding surface) of the silicon substrate 10, the first region S21 is a first doping region, the second region S22 is a second doping region, and the third region S23 is an isolation region.

[0074] The silicon substrate 10 in this embodiment is an N-type silicon substrate.

[0075] Reference Figure 2kAs shown, a texture light-trapping structure 50 is formed on the first surface S1 of the silicon substrate 10. A texture light-trapping structure 50 is also formed on the third region S23 of the second surface S2 of the silicon substrate 10. A pyramid texture structure can be formed on the third region S23 of the second surface S2 and the first surface S1 of the silicon substrate 10 by alkaline texturing.

[0076] On the first region S21 of the second surface S2 of the silicon substrate 10, a first tunneling layer 21 and a first doped layer 22 are sequentially stacked. The first tunneling layer 21 can provide a good interface passivation effect, and the first doped 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 the contact and reduce the resistance.

[0077] Among them, the first tunneling layer 21 is one or a combination of two of a silicon oxide layer and a silicon oxynitride layer, preferably a silicon oxide layer; the first doped layer 22 is a boron-doped polysilicon layer.

[0078] On the second region S22 of the second surface S2 of the silicon substrate 10, a second tunneling layer 41 and a second doped layer 42 are sequentially stacked. The second tunneling layer 41 can provide a good interface passivation effect, and the second doped 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 the contact and reduce the resistance.

[0079] Among them, the second tunneling layer 41 is one or a combination of two of a silicon oxide layer and a silicon oxynitride layer, preferably a silicon oxide layer; the second doped layer 42 is a phosphorus-doped polysilicon layer.

[0080] The solar cell of this embodiment may further include traditional structures such as a front surface field, a passivation layer, an antireflection layer, and electrodes (not shown in the figure). The passivation layer can be an aluminum oxide passivation layer. The antireflection layer can be a stacked film formed by any one or more of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer.

[0081] Compared with the prior art, in the pre-treatment process of texturing in the preparation method of the solar cell and the solar cell of the present invention, by means of a chain etching process, part of the mask layer (the first mask layer and the second mask layer) on the second surface is retained, and the steps of removing the plating and texturing are completed by means of a batch etching process, realizing two-step texturing of the solar cell, and protecting the P-type region and the N-type region on the second surface by using the mask layer during the texturing process; optimizing the battery preparation process and improving the battery efficiency.

[0082] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0083] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments 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, the silicon substrate comprising a first surface and a second surface and a side surface which are arranged opposite to each other, the second surface comprising a first region and a second region which are spaced apart, and a third region between the first region and the second region, a first tunneling passivation structure, a first mask layer, and a second tunneling passivation structure are sequentially formed in the first region of the second surface of the silicon substrate, a second tunneling passivation structure and a second mask layer are sequentially formed in the second region of the second surface of the silicon substrate, a second tunneling passivation structure is formed in the third region of the second surface of the silicon substrate, and a second tunneling passivation structure and a second mask layer are sequentially formed on the first surface and the side surface of the silicon substrate; Using a chain acid etching process to remove the second mask layer on the first surface and side surfaces of the silicon substrate; Using a trench alkali etching process to remove the second tunneling passivation structure on the first surface and side surface of the silicon substrate and the second tunneling passivation structure in the first region and the third region of the second surface; A textured light trapping structure is formed on the third area of ​​the second surface of the silicon substrate and on the first surface by using a textured process; 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.

2. The method for preparing a solar cell according to claim 1, characterized in that: While the second mask layer on the first surface and the side surface of the silicon substrate is removed by a chain acid etching process, a liquid protective film is covered on the second surface of the silicon substrate.

3. The method for preparing a solar cell according to claim 1, characterized in that: 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.

4. The method for preparing a solar cell according to claim 3, characterized in that: The first etching solution comprises an acid solution with a mass fraction of 5%-15%; and / or, The first etching solution includes HF solution.

5. The method for preparing a solar cell according to claim 1, characterized in that: A second etching solution is used to perform trench alkaline etching to remove the second tunnel passivation structure.

6. The method for preparing a solar cell according to claim 5, characterized in that: The second etching solution comprises an alkaline solution with a mass fraction of 2.5%-3.5%; and / or, The second etching solution includes a KOH solution; and / or, The etching temperature for removing the second tunnel passivation structure by using the second etching solution is 60° C.-70° C., and the etching time is 50s-80s.

7. The method for preparing a solar cell according to claim 1, characterized in that: A texturing liquid is used for texturing to form a velvet surface light-trapping structure.

8. The method for preparing a solar cell according to claim 7, characterized in that: The texturing liquid comprises an alkali solution with a mass fraction of 0.5%-1.5%; and / or, The texturing solution includes a KOH solution; and / or, The texturing temperature for forming the velvet light-trapping structure with a texturing liquid is 70°C-80°C, and the texturing time is 500s-750s.

9. The method for preparing a solar cell according to claim 1, characterized in that: A third etching solution is used to perform trench acid etching to remove the first mask layer and the second mask layer.

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

11. The method for preparing a solar cell according to claim 1, characterized in that: After the step of removing the second mask layer by a chain acid etching process, the method further includes cleaning the silicon substrate; and / or, After the step of removing the second tunnel passivation structure by using a trench alkali etching process, the step further includes cleaning the silicon substrate; and / or, After the step of forming the textured light-trapping structure by a texture making process, the method further includes cleaning the silicon substrate; and / or, After the step of removing the first mask layer and the second mask layer by using a trench acid etching process, the method further includes cleaning the silicon substrate.

12. The method for preparing a solar cell according to claim 1, characterized in that: The preparation method further comprises: 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; 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; Acid washing is performed to remove the first mask layer on the first surface and side surfaces of the silicon substrate; Alkaline washing removes the second region and the third region of the second surface of the silicon substrate, the first surface and the first tunnel passivation structure on the side surface; Sequentially forming a second tunneling passivation structure and a second mask layer on the first surface, the second surface and the side surface of the silicon substrate; 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.

13. The method for preparing a solar cell according to claim 1, characterized in that: 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 which are formed in sequence.

14. The method for preparing a solar cell according to claim 13, characterized in that: The first doped layer is a P-type doped layer, and the first mask layer is a P-type doped salt-silicon glass; The second doping layer is an N-type doping layer, and the second mask layer is N-type doped salt-silicon glass.

15. 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 14.

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