Back contact solar cell and method for manufacturing the same, photovoltaic module

Abstract

This application provides a back-contact solar cell and its fabrication method, as well as a photovoltaic module. The solar cell includes a silicon substrate, and the back side of the silicon substrate includes alternating first and second regions. Along a first direction, the first region includes a first surface, a first inclined surface, and a second surface that are sequentially connected. The angle between the first inclined surface and the second surface is α, where 50°≤α≤150°. This application avoids the increased leakage risk in the N-type and P-type regions due to the excessively thin passivation layer at the second interface on the first inclined surface, thereby improving the photoelectric conversion efficiency of the back-contact solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cells, and more particularly to a back-contact solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] HTBC (Heterojunction Tunnel Oxide Back Contact) solar cell technology is a high-efficiency crystalline silicon solar cell technology that combines the technical features of TBC (Tunnel Oxide Back Contact) cells and heterojunction cells. It is a highly promising high-performance crystalline silicon solar cell.

[0003] HTBC cells, as high-efficiency crystalline silicon-based single-junction solar cells, have broad market application prospects, but they still need continuous improvement to further enhance their photoelectric conversion efficiency. Summary of the Invention

[0004] To address the aforementioned technical issues, this application discloses a back-contact solar cell, its fabrication method, and a photovoltaic module, in order to further improve the photoelectric conversion efficiency of the back-contact solar cell.

[0005] In a first aspect, this application provides a back-contact solar cell, comprising: A silicon substrate, the back side of which includes alternating first and second regions; Along a first direction, the first region includes a first surface, a first inclined surface, and a second surface that are sequentially connected; The angle between the first inclined plane and the second surface is α, where 50°≤α≤150°; The first direction is the direction in which the width of the first region extends.

[0006] In some embodiments of this application, 80°≤α≤120°.

[0007] In some embodiments of this application, along a second direction, the second surface is lower than the first surface, the height difference between the first surface and the second surface is Δh, 50nm≤Δh≤300nm, and the second direction is the direction from the front side to the back side of the silicon substrate.

[0008] In some embodiments of this application, along the second direction, the silicon substrate to the first surface includes a doped inner extension layer, a first interface passivation layer, and an N-type doped layer.

[0009] In some embodiments of this application, the first surface is the side of the N-type doped layer that faces away from the silicon substrate.

[0010] In some embodiments of this application, the first slope includes at least an N-type doped layer.

[0011] In some embodiments of this application, a second interface passivation layer and a P-type doped layer are present on the first inclined surface.

[0012] In some embodiments of this application, the second surface is located on the back side of the silicon substrate, and the area to which the second surface belongs is a planar region.

[0013] In some embodiments of this application, a second interface passivation layer, a P-type doped layer, and a transparent conductive oxide layer are sequentially stacked on the second surface.

[0014] In some embodiments of this application, the first surface and the second surface are parallel to each other.

[0015] In some embodiments of this application, the first region further includes a second inclined surface, one side of which is in contact with the second surface, and the other side of which is in contact with the second region.

[0016] Secondly, this application provides a method for fabricating a back-contact solar cell as described in the first aspect, comprising the following steps: An initial structure for a back-contact solar cell is prepared, the initial structure of which includes a silicon substrate, the back side of which includes a doped inner extension layer, a first interface passivation layer, and an N-type doped layer. A mask layer is prepared on the surface of the N-type doped layer; Alternating first and second regions are formed on the back side of the silicon substrate by laser lift-off and wet texturing, and the included angle is formed between the first bevel and the second surface. Wherein, the thickness of the mask layer is H, in nm, and the included angle is α, in degrees, satisfying: α=380×e^(-0.025H)+10, 30 nm≤H≤80 nm.

[0017] In some embodiments of this application, the preparation method further includes: Other functional films and electrodes are formed in the first and second regions. The other functional films include a second interface passivation layer, a P-type doped layer, and a transparent conductive oxide layer.

[0018] Thirdly, this application provides a photovoltaic module, which includes a back-contact solar cell as described in the first aspect.

[0019] Compared with the prior art, this application has at least the following beneficial effects: This application provides a back-contact solar cell and its fabrication method, as well as a photovoltaic module. The back-contact solar cell includes a silicon substrate. The back side of the silicon substrate includes alternating first and second regions. Along a first direction, i.e., the width extension direction of the first region, the first region includes a first surface, a first inclined surface, and a second surface that are sequentially connected. The angle between the first inclined surface and the second surface is α, where 50°≤α≤150°. By adjusting the angle α between the first inclined surface and the second surface within the scope of this application, the second interface passivation layer at the first inclined surface can be made to have a thicker thickness. This avoids increasing the leakage risk in the N-type and P-type regions due to the second interface passivation layer at the first inclined surface being too thin, thereby improving the open-circuit voltage and fill factor of the back-contact solar cell and thus improving the photoelectric conversion efficiency of the back-contact solar cell. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a back-contact solar cell in one embodiment of this application; Figure 2a This is a partial structural diagram of a back-contact solar cell in one embodiment of this application; Figure 2b This is a partial structural diagram of a back-contact solar cell according to another embodiment of this application; Figure 2c This is a partial structural diagram of a back-contact solar cell in another embodiment of this application; Figure 3 This is a schematic diagram of a silicon substrate in one embodiment of this application; Figure 4 This is a schematic diagram of the deposition of an intrinsic polysilicon layer and a first interface passivation layer in one embodiment of this application; Figure 5 This is a schematic diagram of the doped inner extension layer and the PSG layer in one embodiment of this application; Figure 6 This is a schematic diagram illustrating the removal of the PSG layer in one embodiment of this application; Figure 7 This is a schematic diagram of the formation of a mask layer in one embodiment of this application; Figure 8 This is a schematic diagram illustrating the formation of a side erosion angle in one embodiment of this application; Figure 9This is a scanning electron microscope image of Embodiment 1 of this application taken after the formation of the lateral etching angle; Figure 10 This is a scanning electron microscope image of Embodiment 6 of this application taken after the formation of the lateral etching angle.

[0022] Explanation of reference numerals in the attached figures: 1-Silicon substrate, 2-First region, 3-Second region, 4-Doped inner layer, 5-First interface passivation layer, 6-N-type doped layer, 7-Second interface passivation layer, 8-P-type doped layer, 9-Transparent conductive oxide layer, 10-Electrode, 11-Front-side passivation layer, 12-Antireflection layer, 21-First surface, 22-Second surface, 23-First slope, 24-Second slope, 100-Intrinsic polysilicon layer, 101-PSG layer, 102-Mask layer. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0025] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0026] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0027] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0028] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0029] Firstly, this application provides a back-contact solar cell, with reference to... Figure 1 The back-contact solar cell includes a silicon substrate 1. The back side of the silicon substrate 1 includes alternating first regions 2 and second regions 3. The first region 2 includes a planar region and a sloped region, with the sloped region adjacent to the second region 3. The second region 3 is a textured region. Along a first direction, the first region 2 includes a first surface 21, a first slope 23, and a second surface 22 that are sequentially connected. The first surface 21 is located on the back side of the N-type doped layer. The top side of the first slope 23 is connected to the first surface 21, and the bottom side of the first slope 23 is connected to the second surface 22. An angle, also known as a side etching angle, is formed during the wet texturing process. The angle is α, 50°≤α≤150°, preferably 80°≤α≤120°. For example, α is 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, or 150°.

[0030] In this application, references Figure 1 The first direction is the direction in which the width of the first region 2 extends.

[0031] When the included angle α is too small, during the deposition of the second interface passivation layer, since the growth mode of the second interface passivation layer is perpendicular to the first surface, the thickness of the second interface passivation layer grown at the first slope of the N-type doped layer is relatively thin, which leads to a decrease in the insulation performance of the second interface passivation layer at the first slope, thereby increasing the leakage risk in the N-type and P-type regions. When the included angle α is too large, it means that a relatively large included angle α needs to be prepared by reducing the thickness of the mask layer and / or reducing the thickness of the N-type region, which will make the thickness of the N-type region too thin, thereby reducing the generation of photogenerated carriers and affecting the short-circuit current of the back contact solar cell. Based on this, the back-contact solar cell provided in this application, by adjusting the angle α between the first inclined surface and the second surface within the above-mentioned range, makes it easier for the second interface passivation layer to grow at the first inclined surface during the deposition process. This allows the second interface passivation layer at the first inclined surface to have a thicker thickness, thereby avoiding the risk of leakage in the N-type and P-type regions due to the second interface passivation layer at the first inclined surface being too thin. This improves the open-circuit voltage and fill factor of the back-contact solar cell, thereby improving the photoelectric conversion efficiency of the back-contact solar cell.

[0032] In some embodiments of this application, reference is made to Figure 2a and Figure 2b Along the second direction, the second surface 22 is lower than the first surface 21, and the height difference between the first surface 21 and the second surface 22 is Δh, where 50nm ≤ Δh ≤ 300nm. For example, Δh can be 50nm, 80nm, 100nm, 150nm, 180nm, 200nm, 220nm, 250nm, or 300nm. Within this range, Δh can balance the diffusion length of photogenerated carriers with the photoelectric conversion efficiency of the back-contact solar cell, while also ensuring uniform growth of the second interface passivation layer.

[0033] In this application, the second direction is the direction from the front side to the back side of the silicon substrate.

[0034] In some embodiments of this application, reference is made to Figure 1 and Figure 2a Along the second direction, the silicon substrate 1 includes a doped inner extension layer 4, a first interface passivation layer 5, and an N-type doped layer 6 between it and the first surface. The total thickness of the doped inner extension layer 4, the first interface passivation layer 5, and the N-type doped layer 6 is Δh. The total thickness of the doped inner extension layer, the first interface passivation layer, and the N-type doped layer is within the aforementioned range, which can simultaneously balance the carrier diffusion length and the photoelectric conversion efficiency of the back-contact solar cell.

[0035] In some embodiments of this application, reference is made to Figure 1 and Figure 2aThe first surface 21 is the side of the N-type doped layer 6 that faces away from the silicon substrate 1. Thus, the sidewall of the N-type doped layer forms part of the first inclined surface, and the first surface is in contact with the first inclined surface.

[0036] In some embodiments of this application, the first slope includes at least an N-type doped layer. In one example, reference... Figure 2a The first inclined surface 23 can be a slope formed by the sidewalls of the doped inner layer 4, the sidewalls of the first interface passivation layer 5, and the sidewalls of the N-type doped layer 6. The side of the doped inner layer 4 facing away from the first interface passivation layer 5 contacts the silicon substrate 1, thereby making the first inclined surface contact the second surface; in another example, refer to Figure 2b The first inclined surface 23 can be an inclined surface formed by the sidewall of the doped inner expansion layer 4.

[0037] In some embodiments of this application, reference is made to Figure 2c The first inclined surface 23 has a second interface passivation layer 7 and a P-type doped layer 8.

[0038] In some embodiments of this application, reference is made to Figure 2a The second surface 22 is located on the back side of the silicon substrate 1, and the area to which the second surface 22 belongs is a planar region. On the one hand, the second surface is in contact with the first inclined surface and forms an angle; on the other hand, since the area to which the second surface belongs is a planar region, it is easier to deposit and grow a functional film layer of uniform thickness on the second surface, which is beneficial to improving the performance of the back contact solar cell.

[0039] In some embodiments of this application, reference is made to Figure 1 The second surface 22 is provided with a second interface passivation layer 7, a P-type doped layer 8 and a transparent conductive oxide layer 9 stacked sequentially. The deposition thickness of these functional films on the second surface is more uniform, which is beneficial to improving the performance of the back contact solar cell.

[0040] In some embodiments of this application, reference is made to Figure 2a The first surface 21 and the second surface 22 are parallel to each other. The area to which the first surface belongs is a planar region, and the first surface is more likely to deposit and grow a functional film layer of uniform thickness, which is beneficial to improving the performance of the back contact solar cell.

[0041] In some embodiments of this application, reference is made to Figure 1 The first region 2 further includes a second inclined surface 24, one side of which is connected to the second surface 22, and the other side of which is connected to the second region 3.

[0042] In some embodiments of this application, reference is made to Figure 1A passivation layer 11 and an antireflection layer 12 are sequentially disposed on the front side of the silicon substrate 1, and the front side of the silicon substrate 1 has a textured surface structure, which can passivate the front side of the silicon substrate 1, reduce light reflection, and improve the utilization rate of light.

[0043] In some embodiments of this application, reference is made to Figure 1 Electrodes 10 are also provided in the first region 2 and the second region 3.

[0044] The material of the first interface passivation layer can include at least one of various dielectric materials, such as silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the first interface passivation layer can be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation performance, can minimize the recombination loss of minority carriers on the semiconductor substrate surface, and is a thin film with excellent durability for subsequent high-temperature processes. To better provide interface passivation for the substrate, the thickness of the first interface passivation layer can be 0.1 nm to 5 nm. For example, the thickness of the first interface passivation layer can be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, etc.; however, this application is not limited to these values, and the thickness of the first interface passivation layer can have various values. The first interface passivation layer acts as a barrier for electrons and holes and can combine with the polycrystalline silicon layer to prevent minority carriers from passing through. The first interface passivation layer can also act as a pinhole channel, allowing charge carriers within the crystalline silicon solar cell to move freely. The selective passage of majority carriers through heavily doped polycrystalline silicon helps reduce recombination losses of minority carriers. Additionally, the first interface passivation layer can serve as a diffusion barrier to prevent dopants from the doped polycrystalline silicon layer from diffusing into the semiconductor substrate.

[0045] This application does not impose any particular limitation on the thickness of each functional film layer, as long as it can achieve the purpose of this invention. For example, the thickness of the N-type doped layer is 30 nm to 500 nm; the thickness of the second interface passivation layer is 0.1 nm to 20 nm, and the main component of the second interface passivation layer is intrinsic amorphous silicon; the thickness of the P-type doped layer is 5 nm to 100 nm; the material of the transparent conductive oxide layer includes indium tin oxide (ITO), and the thickness is 20 nm to 150 nm; the material of the electrode includes silver; the material of the front passivation layer includes aluminum oxide; the material of the antireflection layer includes, but is not limited to, silicon nitride layer, silicon oxynitride layer, silicon oxide, etc., and the thickness is 30 nm to 180 nm.

[0046] Secondly, this application provides a method for fabricating a back-contact solar cell as described in the first aspect, comprising the following steps: Step A: Prepare the initial structure of the back contact solar cell. The initial structure of the back contact solar cell includes a silicon substrate. The back side of the silicon substrate includes a doped inner extension layer, a first interface passivation layer, and an N-type doped layer. Step B: Prepare a mask layer on the surface of the N-type doped layer; Step C: By laser lift-off and wet texturing, alternating first and second regions are formed on the back side of the silicon substrate, and the included angle is formed between the first bevel and the second surface; The thickness of the mask layer is H, in nm, and the included angle is α, in degrees, satisfying: α = 380 × e^(-0.025H) + 10, 30 nm ≤ H ≤ 80 nm.

[0047] In this application, an ellipsometer can be used to measure the thickness of the mask layer in the semi-finished solar cell after the mask layer is formed; a scanning electron microscope can be used to take a SEM image of the back contact solar cell, and then a protractor can be used to measure the size of the lateral erosion angle in the SEM image.

[0048] The specific steps of step A include: Step a, Reference Figure 3 A silicon substrate 1 is provided, which can be an N-type silicon substrate with a thickness of 100μm~220μm; Step b, Reference Figure 4 A first interface passivation layer 5 and an intrinsic polycrystalline silicon layer 100 are deposited on the back side of the silicon substrate 1. Step c, Reference Figure 5 Phosphorus doping is performed on the intrinsic polycrystalline silicon layer 100 to form an N-type doped layer 6. Phosphorus atoms diffuse toward the silicon substrate 1 during high-temperature annealing to form an inner doped layer 4 between the silicon substrate 1 and the first interface passivation layer 5. At the same time, a phosphosilicate glass (PSG) layer 101 is formed on the back side of the N-type doped layer 6. Step d: Wash away PSG layer 101 with HF aqueous solution to form Figure 6 The battery structure shown; In step B, refer to Figure 7 A silicon nitride (SiN) layer was deposited on the back side of the N-type doped layer 6 using a PECVD process. x The mask layer 102 is used as a mask layer. The thickness H of the mask layer has the following relationship with the lateral etching angle α formed after the subsequent wet texturing process: α = 380 × e^(-0.025H) + 10. Since the thickness H of the mask layer affects the lateral etching angle α formed after the subsequent wet texturing process, and since the included angle α affects the thickness of the second interface passivation layer deposited at the first slope, when 30 nm ≤ H ≤ 80 nm, the included angle α can be adjusted within the range of this application, so that the second interface passivation layer deposited at the first slope is not too thin.

[0049] Step C includes the following specific steps: Laser ablation is performed on the area to be texturized to remove the mask layer, followed by wet texturizing. (Refer to...) Figure 8 A first region 2 and a second region 3 are formed on the back side of the silicon substrate 1, and a side etching angle α is formed in the first region 2. The silicon nitride in the mask layer 102 undergoes a wet texturing process, and after treatment with alkaline solution and hydrofluoric acid solution, this mask layer is finally removed.

[0050] In laser film-opening processing, the laser can be at least one of nanosecond, picosecond, or femtosecond lasers, and the wavelength can be any of infrared, visible, or ultraviolet lasers.

[0051] In some embodiments of this application, the preparation method further includes: Other functional films and electrodes are formed in the first and second regions, the other functional films including a second interface passivation layer, a P-type doped layer, and a transparent conductive oxide layer; and a front passivation layer and an anti-reflection layer are formed on the front side of the silicon substrate, as shown in the reference. Figure 1 This ultimately forms the back-contact solar cell structure of this application.

[0052] This application provides a method for fabricating a back-contact solar cell. Based on the relationship between the thickness H of the mask layer and the included angle α: α = 380 × e^(-0.025H) + 10, by adjusting the thickness H of the mask layer, the included angle α is controlled within the range of this application. As a result, during the subsequent deposition of the second interface passivation layer, the second interface passivation layer is more likely to grow at the first slope, enabling the second interface passivation layer at the first slope to have a thicker thickness. This avoids the increased leakage risk in the N-type and P-type regions due to the second interface passivation layer at the first slope being too thin, thereby improving the open-circuit voltage and fill factor of the back-contact solar cell and thus improving the photoelectric conversion efficiency of the back-contact solar cell.

[0053] Thirdly, this application provides a photovoltaic module, which includes a back-contact solar cell as described in the first aspect, or the photovoltaic module includes a back-contact solar cell prepared by the preparation method described in the second aspect.

[0054] This application also provides a photovoltaic module for converting received light energy into electrical energy and transmitting it to an external load. The photovoltaic module includes: at least one cell string, which is formed by connecting multiple back-contact solar cells as described above; an encapsulating film for covering the surface of the cell string; and a cover plate for covering the surface of the encapsulating film facing away from the cell string.

[0055] Example The back-contact solar cell, its preparation method, and photovoltaic module of this application will be further described below with reference to more specific embodiments.

[0056] Example 1 An N-type silicon substrate is provided. A first interface passivation layer and an intrinsic polysilicon layer are deposited on the back side of the silicon substrate. The intrinsic polysilicon layer is then phosphorus-doped to form an N-type doped layer. Phosphorus atoms diffuse toward the silicon substrate during high-temperature annealing, forming a doped inner diffusion layer between the silicon substrate and the first interface passivation layer. Simultaneously, a phosphorus-doped phosphorus (PSG) layer is formed on the back side of the N-type doped layer. The PSG layer is removed by washing with an HF aqueous solution. Finally, a silicon nitride (SiN) layer is deposited on the back side of the N-type doped layer using a PECVD process. x As a mask layer, the thickness H of the mask layer is 50 nm; then, through laser lift-off and wet texturing, alternating first and second regions are formed on the back side of the silicon substrate, and the included angle α between the first inclined surface and the second surface is formed, with the included angle α being 115°; then, a second interface passivation layer, a P-type doped layer, a transparent conductive oxide layer, and electrodes are fabricated in the first and second regions to obtain a back contact solar cell, the cell structure of which is as follows. Figure 1 As shown.

[0057] Examples 2 to 7 Except for adjusting the thickness of the mask layer according to Table 1 during mask layer preparation, and changing the included angle α accordingly, everything else is the same as in Example 1.

[0058] Comparative Example 1 Except for adjusting the thickness of the mask layer to 200 nm during mask layer preparation, and changing the included angle α accordingly, everything else is the same as in Example 1.

[0059] Comparative Example 2 Except for adjusting the thickness of the mask layer to 20 nm during mask layer preparation, and changing the included angle α accordingly, everything else is the same as in Example 1.

[0060] Table 1: Mask layer thickness and angle α for each embodiment and comparative example

[0061] Test methods and equipment: Open circuit voltage, short circuit current, and fill factor tests: The current (I)-voltage (V) of the solar cells in each embodiment and comparative example were measured using an IV tester (model: MX-MPVC-A20, manufacturer: Suzhou Maiwei Technology Co., Ltd.) to obtain the open-circuit voltage (iVoc), fill factor (iFF) and photoelectric conversion efficiency (PCE) of the solar cells.

[0062] Table 2: Performance data of each embodiment and comparative example

[0063] As can be seen from Examples 1 to 7 and Comparative Examples 1 to 2, the included angle α gradually decreases as the mask layer thickness H increases. When the mask layer thickness is too thick (e.g., Comparative Example 1), the included angle α is less than 50°, resulting in a smaller open-circuit voltage and fill factor of the back-contact solar cell, leading to a lower photoelectric conversion efficiency. When the mask layer thickness is too thin (e.g., Comparative Example 2), the included angle α is greater than 150°, resulting in a thinner N-type region and a smaller number of photogenerated carriers, also leading to a lower photoelectric conversion efficiency. However, by adjusting the mask layer thickness H within the range of this application, and thus adjusting the included angle α within the range of this application, the open-circuit voltage and fill factor of the back-contact solar cell are improved, and the photoelectric conversion efficiency of the back-contact solar cell is improved.

[0064] Figure 9 This is a scanning electron microscope image of Embodiment 1 of this application after the formation of the lateral etching angle. As can be seen from the image, the size of the lateral etching angle is 115°.

[0065] Figure 10 This is a scanning electron microscope image of Embodiment 6 of this application after the formation of the lateral etching angle. As can be seen from the image, the size of the lateral etching angle is 60°.

[0066] The foregoing has provided a detailed description of a back-contact solar cell, its fabrication method, and a photovoltaic module disclosed in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A back-contact solar cell, characterized in that, include: A silicon substrate, the back side of which includes alternating first and second regions; Along a first direction, the first region includes a first surface, a first inclined surface, and a second surface that are sequentially connected; The angle between the first inclined plane and the second surface is α, where 50°≤α≤150°; The first direction is the direction in which the width of the first region extends.

2. The back-contact solar cell according to claim 1, characterized in that, 80°≤α≤120°。 3. The back-contact solar cell according to claim 1, characterized in that, Along the second direction, the second surface is lower than the first surface, and the height difference between the first surface and the second surface is Δh, where 50nm≤Δh≤300nm. The second direction is the direction from the front side to the back side of the silicon substrate.

4. The back-contact solar cell according to claim 3, characterized in that, Along the second direction, the silicon substrate to the first surface includes a doped inner extension layer, a first interface passivation layer, and an N-type doped layer.

5. The back-contact solar cell according to claim 4, characterized in that, The first surface is the side of the N-type doped layer that faces away from the silicon substrate.

6. The back-contact solar cell according to claim 4, characterized in that, The first slope contains at least an N-type doped layer.

7. The back-contact solar cell according to claim 4, characterized in that, The first inclined surface contains a second interface passivation layer and a P-type doped layer.

8. The back-contact solar cell according to claim 1, characterized in that, The second surface is located on the back side of the silicon substrate, and the area to which the second surface belongs is a planar region.

9. The back-contact solar cell according to claim 8, characterized in that, A second interface passivation layer, a P-type doped layer, and a transparent conductive oxide layer are sequentially stacked on the second surface.

10. The back-contact solar cell according to claim 1, characterized in that, The first surface and the second surface are parallel to each other.

11. The back-contact solar cell according to claim 1, characterized in that, The first region also includes a second inclined surface, one side of which is in contact with the second surface, and the other side of which is in contact with the second region.

12. A method for preparing a back-contact solar cell as described in any one of claims 1 to 11, characterized in that, Includes the following steps: An initial structure for a back-contact solar cell is prepared, the initial structure of which includes a silicon substrate, the back side of which includes a doped inner extension layer, a first interface passivation layer, and an N-type doped layer. A mask layer is prepared on the surface of the N-type doped layer; Alternating first and second regions are formed on the back side of the silicon substrate by laser lift-off and wet texturing, and the included angle is formed between the first bevel and the second surface. Wherein, the thickness of the mask layer is H, in nm, and the included angle is α, in degrees, satisfying: α=380×e^(-0.025H)+10, 30 nm≤H≤80 nm.

13. The method for preparing a back-contact solar cell according to claim 12, characterized in that, The preparation method further includes: Other functional films and electrodes are formed in the first and second regions. The other functional films include a second interface passivation layer, a P-type doped layer, and a transparent conductive oxide layer.

14. A photovoltaic module, characterized in that, The photovoltaic module includes the back-contact solar cell as described in any one of claims 1 to 11.

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