Solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, particularly provides a solar cell and a preparation method of the solar cell, and aims to solve the problem that the conversion efficiency of the solar cell is affected by parasitic absorption of polycrystalline silicon. To this end, the solar cell provided by the present application comprises: a substrate; the first silicon oxide layer is arranged on the first surface of the substrate; and the plurality of first polycrystalline silicon regions are arranged on one surface, far away from the substrate, of the first silicon oxide layer. According to a conventional passivation contact cell, silicon oxide and polycrystalline silicon are generally laid on the whole layer of the back face of the cell, the first silicon oxide layer is arranged on the back face of the substrate, and the multiple first polycrystalline silicon regions which are arranged at intervals are arranged on the first silicon oxide layer, so that the effect of reducing the area of the polycrystalline silicon regions in a conventional passivation contact structure is achieved; therefore, parasitic absorption caused by light absorption of the polycrystalline silicon is reduced, the purpose of improving the photocurrent density and the conversion efficiency of the cell is achieved, and the problem that the conversion efficiency of the solar cell is affected by the parasitic absorption of the polycrystalline silicon is solved.

Description

Technical Field

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

[0002] Against the backdrop of rising energy demand and the increasing scarcity of traditional fossil fuels, people are increasingly placing greater emphasis on renewable energy sources such as solar and wind power. Solar energy, due to its clean, sustainable, and safe characteristics, is rapidly becoming one of the fastest-growing sectors in the renewable energy sector. TOPCon (Tunnel Oxide Passivated Contact) solar cells are experiencing rapid development due to their superior power conversion efficiency and cost-effectiveness. The silicon oxide and polysilicon on the back of TOPCon cells are crucial for cell passivation and also affect the conversion efficiency of solar cells. The numerous grain boundaries and defects on the polysilicon surface cause parasitic absorption, which reduces the efficiency of solar cells.

[0003] Accordingly, the art needs a new solar cell to solve the above problems. Summary of the Invention

[0004] In order to overcome the above-mentioned defects, the present application is proposed to solve or at least partially solve the technical problem that polysilicon parasitic absorption affects the conversion efficiency of solar cells.

[0005] In a first aspect, a solar cell is provided, comprising: a substrate; a first silicon oxide layer disposed on a first surface of the substrate; and a plurality of first polysilicon regions spaced apart from each other and disposed on a side of the first silicon oxide layer away from the substrate.

[0006] In one technical solution of the above-mentioned solar cell, it also includes: a second silicon oxide region and a second polysilicon region stacked in sequence on a side of the first polysilicon region away from the substrate, wherein the projections of the first polysilicon region, the second silicon oxide region and the second polysilicon region on the substrate overlap.

[0007] In one technical solution of the above-mentioned solar cell, it also includes: a first anti-reflection layer, located on the first silicon oxide layer exposed between the second polysilicon region and the multiple first polysilicon regions spaced apart from each other; and a first metal electrode, passing through the first anti-reflection layer and electrically contacting the second polysilicon region.

[0008] In one technical solution of the above solar cell, the thickness of the first polysilicon region is less than or equal to the thickness of the second polysilicon region.

[0009] In one technical solution of the above solar cell, the thickness of the second polysilicon region is 30 nm to 50 nm.

[0010] In one technical solution of the above solar cell, it further includes: a doping layer located on a second surface of the substrate opposite to the first surface; and a second anti-reflection layer located on a side of the doping layer away from the substrate.

[0011] In a second aspect, a method for preparing a solar cell is provided, the method comprising: depositing a first silicon oxide layer and a first polysilicon layer in sequence on a first surface of a substrate; and patterning the first polysilicon layer to obtain a plurality of first polysilicon regions spaced apart from each other.

[0012] In a technical solution of the above-mentioned method for preparing a solar cell, the method further includes: sequentially stacking a second silicon oxide region and a second polycrystalline silicon region on a side of the first polycrystalline silicon region away from the substrate, wherein the projections of the first polycrystalline silicon region, the second silicon oxide region and the second polycrystalline silicon region on the substrate overlap.

[0013] In one technical solution of the above-mentioned method for preparing a solar cell, the second silicon oxide region and the second polysilicon region are sequentially stacked on a side of the first polysilicon region away from the substrate, including: forming the second silicon oxide region by laser irradiation of the first polysilicon region; forming a second polysilicon layer on the first silicon oxide layer exposed in the second silicon oxide region and the multiple first polysilicon regions spaced apart from each other; and patterning the second polysilicon layer to remove the second polysilicon layer on the first silicon oxide layer, thereby forming a second polysilicon region only in the second silicon oxide region.

[0014] In one technical solution of the above-mentioned method for preparing a solar cell, the method further includes: forming a first anti-reflection layer on the exposed first silicon oxide layer and the second polysilicon region; and forming a first metal electrode through the first anti-reflection layer to electrically contact the second polysilicon region.

[0015] In one technical solution of the above-mentioned method for preparing a solar cell, the thickness of the second polysilicon region is 30 nm to 50 nm.

[0016] In one technical solution of the above-mentioned method for preparing a solar cell, the method further includes: forming a doping layer on a second surface of the substrate opposite to the first surface; and forming a second anti-reflection layer on a surface of the doping layer away from the substrate.

[0017] The above one or more technical solutions of this application have at least one or more of the following beneficial effects:

[0018] In the technical solution for implementing the present application, by setting a first silicon oxide layer on the back side of the substrate and setting a patterned first polysilicon region on the first silicon oxide layer, the effect of reducing the area of ​​the polysilicon region in the conventional passivation contact structure is achieved, thereby reducing the parasitic absorption caused by polysilicon light absorption, and achieving the purpose of improving the photocurrent density and conversion efficiency of the battery.

[0019] In implementing the technical solution of the present application, by superimposing a second silicon oxide region and a second polysilicon region on the first polysilicon region, the passivation effect of the solar cell is further enhanced, the recombination loss is reduced, and the short-circuit current density, open-circuit voltage and fill factor of the solar cell are increased, thereby improving the overall photoelectric conversion efficiency of the cell.

[0020] In the technical solution for implementing the present application, since polysilicon is included only in the area where the metal electrode is set, and the metal electrode reduces surface recombination and metal contact recombination through two layers of passivation contact structure (tunneling layer), the purpose of improving the battery passivation effect while reducing parasitic absorption is achieved.

[0021] In implementing the technical solution of the present application, by arranging a metal electrode on the second silicon oxide region, the purpose of preventing the silver paste from penetrating the tunneling layer and affecting the battery performance is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The disclosure of this application will become more easily understood with reference to the accompanying drawings. Those skilled in the art will readily appreciate that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application. Among them:

[0023] Figure 1 is a schematic diagram of the main structure of a solar cell according to an embodiment of the present application;

[0024] Figure 2 is a schematic diagram of the main structure of a solar cell according to another embodiment of the present application;

[0025] Figure 3 is a schematic diagram of the main structure of a solar cell according to another embodiment of the present application;

[0026] Figure 4 is a schematic diagram of the main structure of a solar cell according to another embodiment of the present application;

[0027] Figure 5 This is a schematic flow chart of the main steps of a method for preparing a solar cell according to one embodiment of the present application;

[0028] Figure 6 is an intermediate schematic diagram of a solar cell preparation process according to one embodiment of the present application;

[0029] Figure 7 is a schematic diagram of a first mask according to an embodiment of the present application;

[0030] Figure 8 is an intermediate schematic diagram of a solar cell preparation process according to another embodiment of the present application;

[0031] Figure 9 is a schematic diagram of a second mask according to an embodiment of the present application.

[0032] Reference numerals:

[0033] 1: substrate; 2: first silicon oxide layer; 3: first polysilicon region; 4: second silicon oxide region; 5: second polysilicon region; 6: doping layer; 7: second anti-reflection layer; 8: first anti-reflection layer; 9: first metal electrode; 31: first polysilicon layer; 10: first mask; 11: second mask; 51: second polysilicon layer; 52: third silicon oxide region. DETAILED DESCRIPTION

[0034] Some embodiments of the present application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application and are not intended to limit the scope of protection of the present application.

[0035] In the description of this application, the terms "first", "second", etc. are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way are interchangeable where appropriate so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or a communication between two elements, a wireless connection, or a wired connection.

[0036] In addition, if the meaning of "and / or" appears in this application, it includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application. The term "at least one A or B" or "at least one of A and B" has a similar meaning to "A and / or B" and can include only A, only B, or A and B. The singular terms "one" and "this" can also include plural forms.

[0037] TOPCon cells are experiencing rapid growth due to their superior power conversion efficiency and cost-effectiveness. The passivation contact structure composed of silicon oxide and polysilicon on the back of TOPCon cells is crucial for cell passivation and also affects the conversion efficiency of solar cells. Therefore, efficient design of the polysilicon / silicon oxide layer on the back of TOPCon cells is a key research focus for improving solar cell conversion efficiency. Currently, the polysilicon / silicon oxide layer on the back of TOPCon cells has the following problems: The large thickness of the polysilicon leads to high parasitic absorption, which affects the cell conversion efficiency; the passivation properties of the single-layer polysilicon and silicon oxide need to be further improved to increase the cell's open-circuit voltage; and reducing the thickness of the polysilicon layer may cause some silver paste to penetrate the tunneling layer after sintering, thereby affecting the cell's electrical performance.

[0038] In view of the above problems, this embodiment provides a solar cell. Figure 1 , Figure 1 FIG. 1 is a schematic diagram of the main structure of a solar cell according to an embodiment of the present application. Figure 1 As shown, the solar cell in the embodiment of the present application mainly includes: a substrate 1; a first silicon oxide layer 2; and multiple spaced-apart first polysilicon regions 3. The first silicon oxide layer 2 is disposed on the first surface of the substrate, and the multiple spaced-apart first polysilicon regions 3 are disposed on the side of the first silicon oxide layer 2 facing away from the substrate. This embodiment is described using the example of the first silicon oxide layer 2 disposed on the back side of the substrate; the same applies when the first silicon oxide layer 2 is disposed on the front side.

[0039] Currently, conventional TOPCon cells usually have a whole layer of silicon oxide and polysilicon laid on the back of the substrate. This embodiment reduces the coverage area of ​​polysilicon on the substrate by providing a patterned first polysilicon region on the first silicon oxide layer, thereby reducing parasitic absorption of sunlight and improving the photocurrent density of the solar cell.

[0040] In an optional embodiment, as Figure 2As shown, a second silicon oxide region 4 and a second polysilicon region 5 are sequentially stacked on a side of the first polysilicon region 3 away from the substrate. The projections of the first polysilicon region 3, the second silicon oxide region 4 and the second polysilicon region 5 on the substrate overlap.

[0041] In this embodiment, by superimposing the second silicon oxide region and the second polysilicon region on the first polysilicon region to form a double-layer passivation contact structure, the passivation effect of the solar cell is further improved, the recombination loss is reduced, and the short-circuit current density, open-circuit voltage and fill factor of the solar cell are increased, thereby improving the overall photoelectric conversion efficiency of the cell.

[0042] In an optional embodiment, as Figure 3 As shown, the solar cell further includes a first anti-reflection layer 8 located on the first silicon oxide layer 2 exposed between the second polysilicon region 5 and the plurality of first polysilicon regions 3 spaced apart from each other.

[0043] In an optional embodiment, as Figure 4 As shown, the solar cell further includes a first metal electrode 9 , which passes through the first anti-reflection layer 8 and is in electrical contact with the second polysilicon region 5 .

[0044] In an optional embodiment, as Figure 3 As shown, the solar cell further includes: a doping layer 6 and a second anti-reflection layer 7. The doping layer 6 is located on the front side of the substrate, and the second anti-reflection layer 7 is located on the side of the doping layer 6 away from the substrate.

[0045] This embodiment achieves the effect of reducing light reflection on the surface of the solar cell and improving light energy utilization efficiency through the first anti-reflection layer and the second anti-reflection layer.

[0046] In one embodiment, taking an N-type substrate as an example, the doping layer may be a P+ layer obtained by boron diffusion, and the anti-reflection layer may be Al2O3 or SiN x The first polysilicon region and the second polysilicon region can be n+-poly doped polysilicon with a high electron concentration of phosphorus-doped elements.

[0047] In one embodiment, the solar cell further includes a second metal electrode, which passes through the second anti-reflection layer and is in electrical contact with the doping layer.

[0048] In an optional embodiment, the thickness of the first polysilicon region is less than or equal to the thickness of the second polysilicon region, and the thickness of the second polysilicon region is 30nm to 50nm. Exemplarily, the thickness of the second polysilicon region can be 30nm, 35nm, 40nm, 45nm, or 50nm.

[0049] At present, the thickness of the polysilicon layer is usually between 120nm and 150nm. In theory, the thicker the polysilicon layer, the less likely it is to burn through, and the wider the metallization sintering window, but the parasitic absorption will also be greater, resulting in short-circuit current loss. In this embodiment, polysilicon is only arranged in the area where the metal electrode is arranged, and the metal electrode reduces surface recombination and metal contact recombination through a two-layer passivation contact structure (tunneling layer), thereby achieving the purpose of improving the battery passivation effect while reducing parasitic absorption. At the same time, silicon oxide is used to inhibit the penetration of silver paste, thereby avoiding the problem of silver paste penetrating the tunneling layer and affecting battery performance after reducing the thickness of polysilicon.

[0050] Another aspect of the present application provides a method for preparing a solar cell. Figure 5 FIG. 1 is a flow chart of the main steps of a method for preparing a solar cell according to an embodiment of the present application. Figure 5 As shown, the method for preparing the solar cell in the embodiment of the present application mainly includes the following steps:

[0051] Step S501 : depositing a first silicon oxide layer and a first polysilicon layer in sequence on a first surface of a substrate.

[0052] In this embodiment, the first surface is explained as the back side of the substrate. When the first surface is the front side of the substrate, the method is similar. Figure 6 As shown, a first silicon oxide layer 2 and a first polysilicon layer 31 are sequentially deposited on the back side of the substrate 1 .

[0053] Step S502 : patterning the first polysilicon layer to obtain a plurality of first polysilicon regions spaced apart from each other.

[0054] In this embodiment, the first polysilicon layer is patterned to obtain a plurality of first polysilicon regions spaced apart from each other. It should be noted that this embodiment does not impose a specific limit on the number of first polysilicon regions, which can be set according to specific needs.

[0055] In one embodiment, Figure 7 As shown, the deposited first polysilicon layer 31 is etched using a mask 11 and an etching solution to obtain a patterned first polysilicon region 3. The obtained first polysilicon region 3 can be referred to Figure 1 There are multiple first polysilicon regions 3 spaced apart from each other.

[0056] In one embodiment, a pulsed ultraviolet nanosecond laser can be used to form a patterned second silicon oxide region on the first polysilicon layer as a first mask, and then the exposed first polysilicon layer not covered by the first mask is etched away to obtain multiple first polysilicon regions spaced apart from each other.

[0057] In one embodiment, an etching solution such as potassium hydroxide (KOH) solution may be used to etch away the first polysilicon layer not covered by the second silicon oxide region, thereby obtaining a plurality of first polysilicon regions spaced apart from each other.

[0058] In an optional implementation, after the above step S502, the following step S503 is further included:

[0059] Step S503 , sequentially stacking a second silicon oxide region and a second polysilicon region on a side of the first polysilicon region away from the substrate, wherein the projections of the first polysilicon region, the second silicon oxide region, and the second polysilicon region on the substrate overlap.

[0060] In an optional implementation, the above step S503 may further include the following steps S5031 to S5033:

[0061] In step S5031 , a second silicon oxide region is formed by irradiating the first polysilicon region with a laser.

[0062] In step S5032 , a second polysilicon layer is formed on the first silicon oxide layer exposed in the second silicon oxide region and the plurality of first polysilicon regions spaced apart from each other.

[0063] In step S5033 , the second polysilicon layer is patterned to remove the second polysilicon layer on the first silicon oxide layer, and a second polysilicon region is formed only in the second silicon oxide region.

[0064] As an example, assume that the second silicon oxide region is used as the first mask, such as Figure 8 As shown, a second polysilicon layer 51 is formed on the first silicon oxide layer 2 exposed between the second silicon oxide region 4 and the plurality of first polysilicon regions 3 spaced apart from each other. Figure 9 As shown, a patterned third silicon oxide region 52 is formed on the second polysilicon layer 51 as a second mask. Then, the second polysilicon layer 51 not covered by the second mask 52 is etched away, forming a second polysilicon region only on the second silicon oxide region 4. Finally, the second mask 52 is cleaned.

[0065] In one embodiment, the second mask may be removed using a standard cleaning method using a hydrofluoric acid solution.

[0066] In one embodiment, the thickness of the second polysilicon region is 30 nm to 50 nm, such as 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm, and the thickness of the first polysilicon region is less than or equal to the thickness of the second polysilicon region.

[0067] In an optional implementation, the above step S503 further includes the following steps S504 to S507:

[0068] Step S504 , forming a first anti-reflection layer on the exposed first silicon oxide layer and the second polysilicon region.

[0069] In this embodiment, a first anti-reflection layer (Al2O3 / SiNx) is deposited on the exposed first silicon oxide layer and the second polysilicon region to reduce light reflection on the back side of the solar cell and improve light energy utilization.

[0070] Step S505 , forming a first metal electrode, passing through the first anti-reflection layer and electrically contacting the second polysilicon region.

[0071] In this embodiment, a first metal electrode (such as a silver electrode) is sintered on the first anti-reflection layer. The first metal electrode passes through the first anti-reflection layer and is in electrical contact with the second polysilicon region.

[0072] Step S506 , forming a doping layer on a second surface of the substrate opposite to the first surface.

[0073] In this embodiment, taking an N-type substrate as an example, a P+ doped layer can be obtained on the front side of the substrate by boron diffusion.

[0074] Step S507 , forming a second anti-reflection layer on a surface of the doped layer away from the substrate.

[0075] In this embodiment, a second anti-reflection layer (such as Al2O3 / SiN x ) to reduce the reflection of light on the front of the solar cell and improve the utilization rate of light energy.

[0076] In one embodiment, a second metal electrode (such as a silver electrode) is sintered on the second anti-reflection layer, and the second metal electrode passes through the second anti-reflection layer and is in electrical contact with the doping layer.

[0077] In one embodiment, a P+ doped layer may be obtained between the back surface of the substrate and the first silicon oxide layer by boron diffusion, thereby obtaining a back-contact type solar cell.

[0078] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art will understand that in order to achieve the effect of the present application, different steps do not have to be performed in such an order. They can be performed simultaneously (in parallel) or in other orders. These adjusted solutions are equivalent to the technical solutions described in this application, and therefore will also fall within the scope of protection of this application.

[0079] In an application scenario according to an embodiment of the present application, the following three specific embodiments of solar cell preparation are provided:

[0080] Example 1:

[0081] (1) A 1 nm thick first silicon oxide layer and a 30 nm thick first polysilicon layer are deposited on the back side of the substrate.

[0082] (2) A 1 nm patterned second silicon oxide region was grown using a 300 nm pulsed ultraviolet nanosecond laser at 300-400 mm / s and a laser power of 2 W to serve as an etching mask.

[0083] (3) Use KOH to etch away other areas not protected by the second silicon oxide area.

[0084] (4) Continue to deposit a second polysilicon layer of 30nm on the back side.

[0085] (5) A third silicon oxide region of 1 nm is again generated using laser light to serve as an etching mask.

[0086] (6) Use KOH to etch away other areas not protected by the third silicon oxide area.

[0087] (7) Use hydrofluoric acid solution to clean the third silicon oxide area.

[0088] Example 2:

[0089] (1) A 1 nm thick first silicon oxide layer and a 30 nm thick first polysilicon layer are deposited on the back side of the substrate.

[0090] (2) A 1 nm patterned second silicon oxide region was grown using a 300 nm pulsed ultraviolet nanosecond laser at 300-400 mm / s and a laser power of 2 W to serve as an etching mask.

[0091] (3) Use KOH to etch away other areas not protected by the second silicon oxide area.

[0092] (4) Continue to deposit a second polysilicon layer of 40nm on the back side.

[0093] (5) A third silicon oxide region of 1 nm is again generated using laser light to serve as an etching mask.

[0094] (6) Use KOH to etch away other areas not protected by the third silicon oxide area.

[0095] (7) Use hydrofluoric acid solution to clean the third silicon oxide area.

[0096] Example 3:

[0097] (1) A 1 nm thick first silicon oxide layer and a 30 nm thick first polysilicon layer are deposited on the back side of the substrate.

[0098] (2) A 1 nm patterned second silicon oxide region was grown using a 300 nm pulsed ultraviolet nanosecond laser at 300-400 mm / s and a laser power of 2 W to serve as an etching mask.

[0099] (3) Use KOH to etch away other areas not protected by the second silicon oxide area.

[0100] (4) Continue to deposit a second polysilicon layer of 50nm on the back side.

[0101] (5) A third silicon oxide region of 1 nm is again generated using laser light to serve as an etching mask.

[0102] (6) Use KOH to etch away other areas not protected by the third silicon oxide area.

[0103] (7) Use hydrofluoric acid solution to clean the third silicon oxide area.

[0104] This embodiment reduces the thickness of the polysilicon region and reduces the metal contact recombination on the back side through the design of a two-layer tunneling layer and two thin polysilicon layers with selective contact, thereby improving the passivation performance of the battery. Compared with ordinary solar cells, it has the following beneficial effects: by reducing the recombination loss in the metallized area, the purpose of improving the photoelectric conversion efficiency is achieved, which helps to improve the short-circuit current density, open-circuit voltage and fill factor of the battery, thereby improving the overall photoelectric conversion efficiency of the solar cell. Since the passivation contact is only present in the metallized area and there is no passivation contact in the non-metallized area, the parasitic absorption of sunlight caused by the absorption of the polysilicon layer is reduced, thereby improving the photocurrent density of the battery. Through the protection of two layers of silicon oxide, the slurry is prevented from burning through the tunneling layer and affecting the battery performance, thereby improving the open-circuit voltage and short-circuit current of the battery.

[0105] Thus far, the technical solution of the present application has been described in conjunction with an embodiment shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A solar cell, characterized in that: include: substrate; A first silicon oxide layer is disposed on a first surface of the substrate; A plurality of first polysilicon regions spaced apart from each other are arranged on a side of the first silicon oxide layer away from the substrate.

2. The solar cell according to claim 1, characterized in that: Also includes: A second silicon oxide region and a second polysilicon region are sequentially stacked on a side of the first polysilicon region away from the substrate, wherein projections of the first polysilicon region, the second silicon oxide region and the second polysilicon region on the substrate overlap.

3. The solar cell according to claim 2, characterized in that: Also includes: A first anti-reflection layer is located on the first silicon oxide layer exposed between the second polysilicon region and the plurality of first polysilicon regions spaced apart from each other; A first metal electrode passes through the first anti-reflection layer and is in electrical contact with the second polysilicon region.

4. The solar cell according to claim 2, characterized in that: The thickness of the first polysilicon region is less than or equal to the thickness of the second polysilicon region.

5. The solar cell according to claim 2, characterized in that: The thickness of the second polysilicon region is 30 nm to 50 nm.

6. The solar cell according to any one of claims 1 to 5, characterized in that Also includes: a doping layer, located on a second surface of the substrate opposite to the first surface; The second anti-reflection layer is located on a side of the doped layer away from the substrate.

7. A method for preparing a solar cell, characterized in that: The method comprises: Depositing a first silicon oxide layer and a first polysilicon layer in sequence on a first surface of the substrate; The first polysilicon layer is patterned to obtain a plurality of first polysilicon regions spaced apart from each other.

8. The method for preparing a solar cell according to claim 7, characterized in that: The method further comprises: A second silicon oxide region and a second polysilicon region are sequentially stacked on a side of the first polysilicon region away from the substrate, wherein the projections of the first polysilicon region, the second silicon oxide region and the second polysilicon region on the substrate overlap.

9. The method for preparing a solar cell according to claim 8, characterized in that: The second silicon oxide region and the second polysilicon region are sequentially stacked on a side of the first polysilicon region away from the substrate, comprising: irradiating the first polysilicon region with laser to form a second silicon oxide region; forming a second polysilicon layer on the second silicon oxide region and the first silicon oxide layer exposed by the plurality of first polysilicon regions spaced apart from each other; The second polysilicon layer is patterned to remove the second polysilicon layer on the first silicon oxide layer, and a second polysilicon region is formed only in the second silicon oxide region.

10. The method for preparing a solar cell according to claim 9, characterized in that: The method further comprises: forming a first anti-reflection layer on the exposed first silicon oxide layer and second polysilicon region; A first metal electrode is formed to pass through the first anti-reflection layer and to be in electrical contact with the second polysilicon region.

11. The method for preparing a solar cell according to claim 8, characterized in that: The thickness of the second polysilicon region is 30 nm to 50 nm.

12. The method for preparing a solar cell according to any one of claims 7 to 11, characterized in that: The method further comprises: forming a doping layer on a second surface of the substrate opposite to the first surface; A second anti-reflection layer is formed on a surface of the doped layer away from the substrate.

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