A back-contact solar cell and its fabrication method

Abstract

This disclosure relates to the field of solar cell technology, and discloses a back-contact solar cell and its fabrication method. The cell includes: a substrate layer; a first doped region and a second doped region, alternately disposed on the back surface side of the substrate layer; an isolation groove located between adjacent first and second doped regions and extending into the substrate layer; at least one sidewall of the isolation groove includes a first cross-section, a second cross-section, and a third cross-section, the first and second cross-sections being formed within the first or second doped region, the first cross-section extending from the surface of the first or second doped region to its interior, the second cross-section connecting the first and third cross-sections, and the third cross-section being formed at least within the substrate layer and connected to the bottom of the isolation groove; the third cross-section includes a textured slope region and a smooth slope region. This disclosure can improve the optical utilization of the cell's back surface, thereby increasing the module's bifaciality, while also enhancing the cell's electrical performance.

Description

Technical Field

[0001] This disclosure relates to the field of solar cell technology, specifically to a back-contact solar cell and its fabrication method. Background Technology

[0002] Fully passivated back-contact solar cells are an innovative technology in the photovoltaic field. By combining TOPCon's tunneling oxide layer technology with the electrode design of classic back-contact solar cells, it retains TOPCon's excellent passivation performance while inheriting the characteristics of unobstructed high light-receiving area on the front side of back-contact solar cells. This combination significantly improves the cell's open-circuit voltage and conversion efficiency, while also ensuring mass production economics, making it a strong contender for next-generation high-efficiency battery technology.

[0003] The key issue currently hindering the further mass production and application of fully passivated back contact batteries is their low bifaciality and low optical utilization on the back side, making it difficult to achieve a higher overall power generation than mainstream TOPCon batteries in centralized power plants, thus limiting their application to some distributed scenarios.

[0004] Therefore, a solution is needed to improve the optical utilization rate of the back side of the fully passivated back contact cell and increase the bifaciality of the module. Summary of the Invention

[0005] In view of this, the present disclosure provides a back-contact solar cell and a method for its fabrication, in order to solve the problems of low bifaciality and low optical utilization of the back side of existing back-contact solar cells, which in turn affect the performance of the cells.

[0006] In a first aspect, this disclosure provides a back-contact solar cell, comprising: a substrate layer including a light-receiving surface and a back-lighting surface disposed opposite to each other; a first doped region and a second doped region alternately disposed on one side of the back-lighting surface of the substrate layer; an isolation groove located between adjacent first doped regions and second doped regions, the isolation groove extending into the substrate layer; at least one sidewall of the isolation groove includes a first cross-section, a second cross-section and a third cross-section, the first cross-section and the second cross-section being formed within the first doped region or the second doped region, the first cross-section extending from the surface of the first doped region or the second doped region to the interior of the first doped region or the second doped region, the second cross-section connecting the first cross-section and the third cross-section, the third cross-section being formed at least within the substrate layer and connected to the bottom of the isolation groove;

[0007] The third section is inclined relative to the backlight surface; the third section includes a velvety slope area and a smooth slope area; the velvety slope area is relatively close to the bottom of the isolation groove and is connected to the bottom of the isolation groove; the smooth slope area is connected to the second section.

[0008] Beneficial effects: The back-contact solar cell provided in this disclosure has at least one sidewall of the isolation groove that sequentially includes a first cross-section, a second cross-section, and a third cross-section from the groove opening to the bottom of the groove. The first and second cross-sections are formed within a first doped region or a second doped region. That is, the fault-depression structure formed by the first and second cross-sections penetrates at least part of the first doped region or part of the second doped region. On the one hand, incident light can undergo multiple refractions and reflections at the first and second cross-sections, improving the optical utilization of the back surface of the cell and thus improving the bifaciality of the module. On the other hand, the first and second cross-sections can increase the coverage area of ​​the passivation layer, improve the passivation performance of the side of the first doped region or the side of the second doped region (i.e., the first cross-section), reduce space charge recombination, and improve cell performance. In addition, the fault-depression structure can reduce the area of ​​part of the first doped region and part of the second doped region, which can reduce the coverage area of ​​polysilicon (polycrystalline silicon) on the back surface, reduce the parasitic absorption effect of polysilicon, and improve the optical performance of the cell.

[0009] The back-contact solar cell disclosed herein includes a textured slope region near the bottom of the isolation groove and a smooth slope region connected to the second section in its third section. The textured slope region can improve the optical utilization of light incident on the back of the cell at all angles, further enhancing the bifaciality of the corresponding module and increasing the all-weather module power, thereby improving the optical performance of the back-contact cell. The smooth slope region allows the passivation layer to uniformly cover the sidewalls of the isolation groove, improving the uniformity of sidewall passivation and enhancing the surface passivation performance of the cell, thus improving the electrical performance of the back-contact cell. Furthermore, since the pn junction of the back-contact solar cell is located at the top of the slope (i.e., the part of the third section near the second section), and the effective passivation of the pn junction region is crucial to the electrical performance of the cell, making the part of the third section near the second section a smooth structure is more conducive to the uniform coverage of the subsequent passivation layer, and the resulting electrical performance gain is higher than the optical gain brought by the textured structure in this area.

[0010] In one optional embodiment, the isolation groove near the sidewall of the first doped region and the isolation groove near the sidewall of the second doped region both include a first cross-section, a second cross-section, and a third cross-section.

[0011] In the isolation groove near the sidewall of the first doped region, a first cross-section and a second cross-section are formed in the first doped region. The first cross-section extends from the surface of the first doped region to the interior of the first doped region. The second cross-section connects the first cross-section and the third cross-section. The third cross-section is formed at least in the substrate layer and is connected to the bottom of the isolation groove.

[0012] In the isolation groove near the sidewall of the second doped region, a first cross-section and a second cross-section are formed in the second doped region. The first cross-section extends from the surface of the second doped region to the interior of the second doped region. The second cross-section connects the first cross-section and the third cross-section. The third cross-section is formed at least in the substrate layer and is connected to the bottom of the isolation groove.

[0013] In one alternative embodiment, the back-contact solar cell further includes:

[0014] A passivation layer is located on the surface of the first doped region and the second doped region, and covers the first cross-section and the second cross-section.

[0015] In one optional embodiment, the first doped region includes: a first tunneling oxide layer and a first doped layer stacked sequentially, wherein the first tunneling oxide layer is relatively close to the backlight surface;

[0016] The second doped region includes a second tunneling oxide layer and a second doped layer stacked sequentially, the second tunneling oxide layer being relatively close to the backlight surface, and the second doped layer having the opposite conductivity type to the first doped layer.

[0017] In one alternative embodiment, the second cross-section is formed within the first doped layer or the second doped layer; the first cross-section extends from the surface of the first doped layer or the second doped layer into the interior of the first doped layer or the second doped layer.

[0018] In one alternative embodiment, the second cross-section is formed within the first tunneling oxide layer or the second tunneling oxide layer; the first cross-section extends from the surface of the first doped layer or the second doped layer into the interior of the first tunneling oxide layer or the second tunneling oxide layer.

[0019] In one optional embodiment, the first doped region further includes a first inner extension layer located between the substrate layer and the first tunneling oxide layer, wherein the first inner extension layer has the same conductivity type as the first doped layer.

[0020] The second doped region also includes a second inner extension layer located between the substrate layer and the second tunneling oxide layer, the second inner extension layer having the same conductivity type as the second doped layer.

[0021] In one alternative embodiment, the second cross-section is formed within the first inner expansion layer or the second inner expansion layer; the first cross-section extends from the surface of the first doped layer or the second doped layer to the interior of the first inner expansion layer or the second inner expansion layer.

[0022] In one optional embodiment, the included angle between the first cross-section and the second cross-section is 30~90°;

[0023] The width of the second section is 0.5~10 μm; the distance between the second section and the backlight surface is 0.1~2.0 μm;

[0024] The first cross-section is a plane or a curved surface; the second cross-section is a plane or a curved surface.

[0025] Beneficial Effects: The back-contact solar cell provided in this disclosure has an angle of 30° to 90° between the first and second cross-sections. This causes the fracture-shaped recessed structure formed by the first and second cross-sections to recess inward towards the first or second doped region. This increases the coverage area of ​​the subsequent passivation layer, thereby increasing the mobile hydrogen content in the passivation layer of the upper local area of ​​the space charge region. This enhances hydrogen passivation in this region, reduces recombination in the space charge region, and further improves the cell's performance. Furthermore, it can further increase the number of refractions and reflections of incident light at the first and second cross-sections, improving the optical utilization of the cell's back surface and thus increasing the module's bifaciality.

[0026] In one alternative embodiment, the length of the velvet slope region is 1 / 5 to 4 / 5 of the length of the third cross section.

[0027] Beneficial effects: The back-contact solar cell provided by this disclosure has a textured slope region whose length accounts for 1 / 5 to 4 / 5 of the length of the third section. This allows the passivation layer to be uniformly covered on the sidewall of the isolation groove. The third section is close to the second section, completely covering the pn junction position, improving the uniformity of the passivation layer at the pn junction position, which can further improve the surface passivation performance of the cell, thereby improving the electrical performance of the back-contact solar cell.

[0028] Secondly, this disclosure also provides a method for preparing a back-contact solar cell, comprising:

[0029] Provide a base layer, including a light-receiving surface and a backlighting surface that are positioned opposite each other;

[0030] A first doped region and a second doped region are formed on the back side of the substrate layer, and the first doped region and the second doped region are alternately arranged.

[0031] An isolation groove is formed between adjacent first and second doped regions, the isolation groove extending into the substrate layer; at least one sidewall of the isolation groove includes a first cross-section, a second cross-section and a third cross-section, the first cross-section and the second cross-section are formed in the first doped region or the second doped region, the first cross-section extends from the surface of the first doped region or the second doped region to the interior of the first doped region or the second doped region, the second cross-section connects the first cross-section and the third cross-section, the third cross-section is formed at least in the substrate layer and is connected to the bottom of the isolation groove;

[0032] The third section is inclined relative to the backlight surface; the third section includes a velvety slope area and a smooth slope area; the velvety slope area is relatively close to the bottom of the isolation groove and is connected to the bottom of the isolation groove; the smooth slope area is connected to the second section. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of a back-contact solar cell according to an embodiment of the present disclosure.

[0035] Figure 2 This is a schematic diagram of another back-contact solar cell according to an embodiment of the present disclosure.

[0036] Figure 3 This is a schematic diagram of the structure of the isolation groove near the sidewall of the first doped region in a back-contact solar cell according to an embodiment of the present disclosure.

[0037] Figure 4 This is a schematic diagram of the structure of a back-contact solar cell in an embodiment of the present disclosure, in which the second cross-section is formed within the first doped layer.

[0038] Figure 5 This is a schematic diagram of the structure of a back-contact solar cell in an embodiment of the present disclosure, in which the second cross section is formed at the interface between the first doped layer and the first tunneling oxide layer.

[0039] Figure 6 This is a schematic diagram of the structure of a back-contact solar cell in an embodiment of the present disclosure, showing that the second cross section is formed at the interface between the first tunneling oxide layer and the first inner expansion layer.

[0040] Figure 7 This is a schematic diagram of the structure in which the second cross-section of a back-contact solar cell in an embodiment of the present disclosure is formed within the first inner expansion layer.

[0041] Figure 8 This is a schematic diagram of the structure of a back-contact solar cell in an embodiment of the present disclosure, showing the second cross-section formed at the interface between the first inner expansion layer and the substrate layer.

[0042] Figure 9 This is a schematic diagram of the structure of a back-contact solar cell in an embodiment of the present disclosure, in which the second cross-section is formed within the second doped layer.

[0043] Figure 10 This is a schematic diagram of the structure in which the second cross-section of a back-contact solar cell in an embodiment of the present disclosure is formed within the second inner expansion layer.

[0044] Figure 11This is a schematic diagram of the structure of a back-contact solar cell in an embodiment of the present disclosure, showing the second cross-section formed at the interface between the second inner expansion layer and the substrate layer.

[0045] Figure 12A This is a schematic diagram of the structure of the first and second cross sections in Example 1 of the back-contact solar cell of this disclosure.

[0046] Figure 12B This is a schematic diagram of the structure of the first and second cross sections in Example 2 of the back-contact solar cell of this disclosure.

[0047] Figure 12C This is a schematic diagram of the structure of the first and second cross sections in Example 3 of the back-contact solar cell of this disclosure.

[0048] Figure 12D This is a schematic diagram of the structure of the first and second cross sections in Example 4 of the back-contact solar cell of this disclosure.

[0049] Figure 12E This is a schematic diagram of the structure of the first and second cross sections in Example 5 of the back-contact solar cell of this disclosure.

[0050] Figure 12F This is a schematic diagram of the structure of the first and second cross sections in Example 6 of the back-contact solar cell of this disclosure.

[0051] Figure 13 This is a cross-sectional scanning electron microscope schematic diagram of the sidewall morphology of the isolation groove near the first doped region in an embodiment of the back-contact solar cell of this disclosure.

[0052] Figure 14 This is a top-view scanning electron microscope schematic diagram of the sidewall morphology of the isolation groove near the first doped region of the back contact solar cell according to an embodiment of the present disclosure.

[0053] Figure 15 This is a 45° cross-sectional scanning electron microscope schematic diagram of the sidewall morphology of the isolation groove near the first doped region of the back contact solar cell according to an embodiment of the present disclosure.

[0054] Figure 16 This is a schematic flowchart of a method for fabricating a back-contact solar cell according to an embodiment of the present disclosure.

[0055] Explanation of reference numerals in the attached figures:

[0056] 10. Substrate layer; 20. First doped region; 21. First tunneling oxide layer; 22. First doped layer; 23. First inner expansion layer; 30. Second doped region; 31. Second tunneling oxide layer; 32. Second doped layer; 33. Second inner expansion layer; 40. Isolation groove; 41. Textured structure; 51. First cross-section; 52. Second cross-section; 53. Third cross-section; 531. Textured slope region; 532. Smooth slope region; 60. Fault depression structure; 70. Passivation layer. Detailed Implementation

[0057] The present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the present disclosure and not intended to limit it. It should also be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the drawings, not all structures. In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present disclosure. The accompanying drawings show various structural schematic diagrams according to embodiments of the present disclosure. These drawings are not drawn to scale, and some details are enlarged for clarity and may be omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. In the context of this disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Additionally, if one layer / component is "above" another layer / component in one orientation, then when the orientation is reversed, that layer / component can be "below" that other layer / component.

[0058] Fully passivated back-contact solar cells are an innovative technology in the photovoltaic field. By combining TOPCon's tunneling oxide layer technology with the electrode design of classic back-contact solar cells, it retains TOPCon's excellent passivation performance while inheriting the characteristics of unobstructed high light-receiving area on the front side of back-contact solar cells. This combination significantly improves the cell's open-circuit voltage and conversion efficiency, while also ensuring mass production economics, making it a strong contender for next-generation high-efficiency battery technology.

[0059] The key issue currently hindering the further mass production and application of fully passivated back contact batteries is their low bifaciality and low optical utilization on the back side, making it difficult to achieve a higher overall power generation than mainstream TOPCon batteries in centralized power plants, thus limiting their application to some distributed scenarios.

[0060] Therefore, a solution is needed to improve the optical utilization rate of the back side of the fully passivated back contact cell and increase the bifaciality of the module.

[0061] refer to Figures 1 to 2 This embodiment provides a back-contact solar cell, comprising: a substrate layer 10, including a light-receiving surface and a back-lighting surface disposed opposite to each other; a first doped region 20 and a second doped region 30, alternately disposed on the back-lighting side of the substrate layer 10; an isolation groove 40 located between adjacent first doped regions 20 and second doped regions 30, the isolation groove 40 penetrating the first doped region 20 and the second doped region 30 and extending into the substrate layer 10; at least one sidewall of the isolation groove 40 includes a first cross-section 51, a second cross-section 52 and a third cross-section 53, the first cross-section 51 and the second cross-section 52 being formed in the first doped region 20 or the second doped region 30. Inside, the first cross-section 51 extends from the surface of the first doped region 20 or the second doped region 30 to the interior of the first doped region 20 or the second doped region 30. The second cross-section 52 connects the first cross-section 51 and the third cross-section 53. The third cross-section 53 is formed at least in the substrate layer 10 and is connected to the bottom of the isolation groove 40. The third cross-section 53 is inclined relative to the backlight surface. The third cross-section 53 includes a textured slope region 531 and a smooth slope region 532. The textured slope region 531 is relatively close to the bottom of the isolation groove 40 and is connected to the bottom of the isolation groove. The smooth slope region 532 is connected to the second cross-section 52.

[0062] It should be noted that the isolation groove 40 penetrates the first doped region 20 and the second doped region 30, meaning that the isolation groove 40 extends from the surface of the first doped region 20 and the surface of the second doped region 30 toward the substrate layer 10, penetrating the first doped region 20 and the second doped region 30. Figure 1 and Figure 2 The isolation groove extends downwards.

[0063] In one embodiment, the first doped region 20 includes a first tunneling oxide layer 21 and a first doped layer 22 stacked sequentially, with the first tunneling oxide layer 21 being relatively close to the backlight surface; the second doped region 30 includes a second tunneling oxide layer 31 and a second doped layer 32 stacked sequentially, with the second tunneling oxide layer 31 being relatively close to the backlight surface, and the second doped layer 32 having the opposite conductivity type to the first doped layer 22.

[0064] In one embodiment, the first doped region 20 further includes a first inner expansion layer 23 located between the substrate layer 10 and the first tunneling oxide layer 21, the first inner expansion layer 23 having the same conductivity type as the first doped layer 22; the second doped region 30 further includes a second inner expansion layer 33 located between the substrate layer 10 and the second tunneling oxide layer 31, the second inner expansion layer 33 having the same conductivity type as the second doped layer 32.

[0065] Specifically, the substrate 10 is a silicon substrate. The doping type of the first doped region 20 is the same as that of the first doped layer 22, and the doping type of the second doped region 30 is the same as that of the second doped layer 32. The doping types of the first doped region 20 and the second doped region 30 are opposite. The doping type of the first doped region 20 is the same as or opposite to that of the substrate 10. The first doped region 20 and the second doped region 30 are respectively included in the structural layers diffused on the backlight side of the substrate 10. In some embodiments, the first doped region 20 is a P-type doped region and the second doped region 30 is an N-type doped region. In other embodiments, the first doped region 20 is an N-type doped region and the second doped region 30 is a P-type doped region. The isolation groove 40 includes two sidewalls, one sidewall located near the first doped region 20 and the other sidewall located near the second doped region 30.

[0066] The isolation groove 40 can be a trench structure that is relatively recessed into the surface of the first doped region 20 and the second doped region 30, obtained by laser etching and wet cleaning. In this embodiment, the isolation trench extends a certain distance into the substrate layer 10. The bottom of the isolation groove 40 is a textured structure 41. In some examples, the textured structure 41 is a pyramid textured surface. At least one sidewall of the isolation groove 40 includes a first cross-section 51, a second cross-section 52, and a third cross-section 53. Specifically, at least one sidewall of the isolation groove 40 includes a first cross-section 51, a second cross-section 52, and a third cross-section 53 sequentially from the groove opening to the bottom of the groove.

[0067] In some alternative implementations, such as Figure 1 and Figure 2 As shown, the first cross-section 51 and the second cross-section 52 constitute a fracture recess structure 60; the fracture recess structure 60 is recessed on the surface of the first doped region 20 or the surface of the second doped region 30, and is recessed in the sidewall of the isolation groove 40. The fracture recess structure 60 penetrates at least a portion of the first doped region 20 or a portion of the second doped region 30.

[0068] In some embodiments, the fracture recess structure 60 is located only on one sidewall of the isolation groove 40 near the first doped region 20 or the second doped region 30, such as Figure 1 As shown, the fracture recess structure 60 penetrates at least a portion of the first doped region 20 or a portion of the second doped region 30. In other embodiments, both sidewalls of the isolation groove 40 include a first cross-section 51, a second cross-section 52, and a third cross-section 53, and each sidewall of the isolation groove 40 includes a fracture recess structure 60 formed by the first cross-section 51 and the second cross-section 52, as shown. Figure 2 As shown. The fault depression structures 60 located on the two sidewalls may be the same or different. Each fault depression structure 60 penetrates at least a portion of the first doped region 20 or a portion of the second doped region 30.

[0069] Beneficial effects: The back-contact solar cell provided in this embodiment has at least one sidewall of the isolation groove that sequentially includes a first cross-section, a second cross-section, and a third cross-section from the groove opening to the bottom of the groove. The first and second cross-sections are formed within the first or second doped region, meaning that the fractured recess structure formed by the first and second cross-sections penetrates at least part of the first or second doped region. On the one hand, this allows incident light to undergo multiple refractions and reflections at the first and second cross-sections, improving the optical utilization of the back surface of the cell and thus increasing the bifaciality of the module. On the other hand, the first and second cross-sections can increase the coverage area of ​​the passivation layer, improve the passivation performance of the side of the first or second doped region (i.e., the first cross-section), reduce space charge recombination, and improve cell performance. In addition, the fractured recess structure can reduce the area of ​​part of the first and second doped regions, thereby reducing the coverage area of ​​the polysilicon (polycrystalline silicon) on the back surface, reducing the parasitic absorption effect of polysilicon, and improving the optical performance of the cell.

[0070] In some alternative implementations, such as Figure 2 As shown, the isolation groove 40 near the sidewall of the first doped region 20 and the isolation groove 40 near the sidewall of the second doped region 30 both include a first cross-section 51, a second cross-section 52 and a third cross-section 53;

[0071] In the isolation groove 40 near the sidewall of the first doped region 20, a first cross-section 51 and a second cross-section 52 are formed in the first doped region 20. The first cross-section 51 extends from the surface of the first doped region 20 to the interior of the first doped region 20. The second cross-section 52 connects the first cross-section 51 and the third cross-section 53. The third cross-section 53 is formed at least in the substrate layer 10 and is connected to the bottom of the isolation groove 40.

[0072] In the isolation groove 40 near the sidewall of the second doped region 30, a first cross-section 51 and a second cross-section 52 are formed in the second doped region 30. The first cross-section 51 extends from the surface of the second doped region 30 to the interior of the second doped region 30. The second cross-section 52 connects the first cross-section 51 and the third cross-section 53. The third cross-section 53 is formed at least in the substrate layer 10 and is connected to the bottom of the isolation groove 40.

[0073] The first doped region 20 and the second doped region 30 are alternately arranged in the first direction. Figures 1-11 All are cross-sectional views parallel to the first direction and perpendicular to the backlight surface. For ease of explanation, Figures 3-8 The following explanation uses the sidewall of the isolation groove 40 near the first doped region 20 as an example. In practice, the sidewall of the isolation groove 40 near the second doped region 30 can also include a first cross-section 51, a second cross-section 52, and a third cross-section 53, such as... Figures 9-11 As shown. Figures 3-8The structures shown can all be implemented in the same way on the sidewall of the isolation groove 40 near the second doped region 30.

[0074] Figure 13 , Figure 14 , Figure 15 The following are electron microscope schematic diagrams showing the sidewall of the isolation groove 40 near the first doped region scanned from different directions. It can be seen that the sidewall has a first cross-section 51, a second cross-section 52, and a third cross-section 53.

[0075] In some alternative embodiments, the back-contact solar cell further includes:

[0076] The passivation layer 70 is located on the surface of the first doped region 20 and the surface of the second doped region 30, and covers the first cross section 51 and the second cross section 52.

[0077] In specific implementations, the passivation layer 70 may include one or more of a silicon oxide layer and an aluminum oxide layer; in other embodiments, the passivation layer may also include other passivation film layers.

[0078] In some alternative implementations, such as Figure 3 As shown, the passivation layer 70 also covers the third cross section 53.

[0079] In some alternative implementations, such as Figure 3 As shown, the passivation layer 70 also covers the bottom of the isolation groove.

[0080] In some alternative implementations, the passivation layer 70 also covers the light-receiving surface and sides of the substrate.

[0081] Beneficial effects: The back-contact solar cell provided in this embodiment can improve the passivation effect of the first and second doped regions on the back surface by setting passivation layers on the surfaces of the first and second doped regions. The passivation layer covers the first and second cross sections, which can increase the coverage area of ​​the passivation layer, increase the mobile hydrogen content of the passivation layer in the upper local area of ​​the space charge region, realize hydrogen passivation enhancement in this region, improve the passivation performance of the side of the first or second doped region (i.e., the first cross section), reduce recombination in the space charge region, and improve the battery performance.

[0082] In some optional embodiments, the first doped region 20 includes a first tunneling oxide layer 21 and a first doped layer 22 stacked sequentially, with the first tunneling oxide layer 21 relatively close to the backlight surface;

[0083] The second doped region 30 includes a second tunneling oxide layer 31 and a second doped layer 32 stacked sequentially. The second tunneling oxide layer 31 is relatively close to the backlight surface, and the second doped layer 32 has the opposite conductivity type to the first doped layer 22.

[0084] In some alternative embodiments, the second cross section 52 is formed within the first doped layer 22 or the second doped layer 32; the first cross section 51 extends from the surface of the first doped layer 22 or the second doped layer 32 into the interior of the first doped layer 22 or the second doped layer 32.

[0085] In specific implementation, the fracture recess structure 60 formed by the first cross-section 51 and the second cross-section 52 is recessed on the surface of the first doped layer 22 or the surface of the second doped layer 32, and is recessed on the side of the first doped layer 22 or the second doped layer 32. The fracture recess structure 60 penetrates a portion of the first doped layer 22 or a portion of the second doped layer 32. In one example, such as Figure 4 As shown, the fault depression structure 60 penetrates a portion of the first doped layer 22. In another example, as... Figure 9 As shown, the fault depression structure 60 penetrates the second doped layer 32.

[0086] In some alternative embodiments, the second cross-section 52 is formed at the interface between the first doped layer 22 and the first tunneling oxide layer 21, or at the interface between the second doped layer 32 and the second tunneling oxide layer 31; the first cross-section 51 extends from the surface of the first doped layer 22 or the second doped layer 32 to the interface between the first doped layer 22 and the first tunneling oxide layer 21, or the second doped layer 32 and the second tunneling oxide layer 31. The fracture recess structure 60 penetrates the first doped layer 22 or the second doped layer 32. The fracture recess structure 60 is located on the side of the first doped layer 22 or the side of the second doped layer 32. In one example, such as Figure 5 As shown, the second cross-section 52 is formed at the interface between the first doped layer 22 and the first tunneling oxide layer 21. The fault depression structure 60 penetrates the first doped layer 22 completely and is located on the side of the first doped layer 22.

[0087] In some alternative embodiments, the second cross section 52 is formed within the first tunneling oxide layer 21 or the second tunneling oxide layer 31; the first cross section 51 extends from the surface of the first doped layer 22 or the second doped layer 32 into the interior of the first tunneling oxide layer 21 or the second tunneling oxide layer 31.

[0088] In practice, the thickness of the first tunneling oxide layer 21 or the second tunneling oxide layer 31 is relatively thin. Therefore, the second cross section 52 is located within the first tunneling oxide layer 21 or the second tunneling oxide layer 31, and has little impact on the area of ​​the passivation layer 70.

[0089] In some alternative embodiments, the first doped region 20 further includes a first inner expansion layer 23 located between the substrate layer 10 and the first tunneling oxide layer 21, wherein the first inner expansion layer 23 has the same conductivity type as the first doped layer 22.

[0090] The second doped region 30 also includes a second inner expansion layer 33 located between the substrate layer 10 and the second tunneling oxide layer 31, wherein the second inner expansion layer 33 has the same conductivity type as the second doped layer 32.

[0091] In some alternative embodiments, the second cross-section 52 is formed at the interface between the first tunneling oxide layer 21 and the first inner expansion layer 23, or at the interface between the second tunneling oxide layer 31 and the second inner expansion layer 33; the first cross-section 51 extends from the surface of the first doped layer 22 or the second doped layer 32 to the interface between the first tunneling oxide layer 21 and the first inner expansion layer 23, or the interface between the second tunneling oxide layer 31 and the second inner expansion layer 33. The fracture recess structure 60 penetrates the first tunneling oxide layer 21 or the second tunneling oxide layer 31. In one example, such as Figure 6 As shown, the fault depression structure 60 sequentially penetrates the first doped layer 22 and the first tunneling oxide layer 21; the fault depression structure 60 is located on the side of the first doped layer 22 and the side of the second tunneling oxide layer 31.

[0092] In some alternative embodiments, the second cross section 52 is formed within the first inner expansion layer 23 or the second inner expansion layer 33; the first cross section 51 extends from the surface of the first doped layer 22 or the second doped layer 32 into the interior of the first inner expansion layer 23 or the second inner expansion layer 33.

[0093] In specific implementation, the fracture recess structure 60 formed by the first cross-section 51 and the second cross-section 52 is recessed on the surface of the first doped layer 22 and also recessed on the side of the first inner layer 23 or the second inner layer 33. The fracture recess structure 60 penetrates a portion of the first inner layer 23 or a portion of the second inner layer 33. In one example, such as Figure 7 As shown, the second cross-section 52 is formed within the first inner expansion layer 23, and the fracture depression structure 60 sequentially penetrates the first doped layer 22, the first tunneling oxide layer 21, and part of the first inner expansion layer 23. In another example, as... Figure 10 As shown, the second cross-section 52 is formed within the second inner expansion layer 33, and the fault depression structure 60 sequentially penetrates the second doped layer 32, the second tunneling oxide layer 31, and part of the second inner expansion layer 33.

[0094] In some alternative embodiments, the second cross-section 52 is formed at the interface between the first inner expansion layer 23 and the substrate layer 10 or the interface between the second inner expansion layer 33 and the substrate layer 10; the first cross-section 51 extends from the surface of the first doped layer 22 or the second doped layer 32 to the interface between the first inner expansion layer 23 and the substrate layer 10 or the interface between the second inner expansion layer 33 and the substrate layer 10. The fracture recess structure 60 penetrates the first inner expansion layer 23 or the second inner expansion layer 33. In one example, such as Figure 8As shown, the fault depression structure 60 sequentially penetrates the first doped layer 22, the first tunneling oxide layer 21, and the first inner expansion layer 23; the fault depression structure 60 is located on the side of the first doped layer 22, the side of the first tunneling oxide layer 21, and the side of the first inner expansion layer 23. In another example, as... Figure 11 As shown, the fault depression structure 60 sequentially penetrates the second doped layer 32, the second tunneling oxide layer 31, and the second inner expansion layer 33; the fault depression structure 60 is located on the side of the second doped layer 32, the side of the second tunneling oxide layer 31, and the side of the second inner expansion layer 33.

[0095] In some alternative embodiments, the included angle between the first section 51 and the second section 52 is 30° to 90°.

[0096] The width of the second section 52 is 0.5~10 μm, for example 0.5 μm, 3 μm, 5 μm, 8 μm or 10 μm;

[0097] The distance between the second section 52 and the backlight surface is 0.1~2.0 μm, for example 0.1 μm, 0.5 μm, 1 μm, 1.5 μm or 2 μm.

[0098] Beneficial Effects: The back-contact solar cell provided in this embodiment has an angle of 30° to 90° between the first and second cross-sections. This causes the fracture-shaped recessed structure formed by the first and second cross-sections to recess inward towards the first or second doped region. This increases the coverage area of ​​the subsequent passivation layer, thereby increasing the mobile hydrogen content in the passivation layer of the upper region of the space charge region. This enhances hydrogen passivation in this region, reduces recombination in the space charge region, and further improves the performance of the cell. Furthermore, it can further increase the number of refractions and reflections of incident light at the first and second cross-sections, improving the optical utilization of the cell's back surface and thus increasing the bifaciality of the module.

[0099] In some alternative embodiments, the first cross-section 51 is a plane or a curved surface; the second cross-section 52 is a plane or a curved surface. The second cross-section 52 may be parallel to or not parallel to the backlit surface.

[0100] Specifically, the fault depression structure 60 formed by the first cross-section 51 and the second cross-section 52 has a variety of cross-sectional shapes. Figures 12A-12F All are cross-sectional views of the fault depression structure 60, which is parallel to the first direction and perpendicular to the backlight surface.

[0101] In Example 1, such as Figure 12A As shown, both the first section 51 and the second section 52 are planes with an included angle of 90°, and the second section 52 is parallel to the backlight surface.

[0102] In Example 2, such as Figure 12BAs shown, both the first section 51 and the second section 52 are planes with an included angle of less than 90°, and the second section 52 is parallel to the backlight surface.

[0103] In Example 3, such as Figure 12C As shown, the first cross-section 51 is an outwardly convex curved surface, and the second cross-section 52 is a plane with an included angle of less than 90°.

[0104] In Example 4, such as Figure 12D As shown, the first cross-section 51 is an inwardly concave curved surface, and the second cross-section 52 is a plane with an included angle of less than 90°.

[0105] In Example 5, such as Figure 12E As shown, both the first section 51 and the second section 52 are curved surfaces, and the included angle is less than 90°.

[0106] In Example 6, such as Figure 12F As shown, the second section 52 is a plane, and the second section 52 is not parallel to the backlight surface. The angle between the first section 51 and the second section 52 is less than 90°.

[0107] In other examples, the fault depression structure 60 formed by the first cross-section 51 and the second cross-section 52 may also have other cross-sectional shapes.

[0108] In some alternative implementations, the second section 52 is parallel to the backlight surface.

[0109] In some alternative embodiments, the included angle between the first section 51 and the second section 52 is less than 90°, such as... Figures 12B-12D As shown.

[0110] In some alternative embodiments, the included angle between the first section 51 and the second section 52 is 30 to 80°.

[0111] Beneficial effects: The back-contact solar cell provided in this embodiment has an angle of 30~80° between the first and second cross sections. This allows the fractured depression structure formed by the first and second cross sections to have a larger depression towards the inside of the first or second doped region. This can further increase the coverage area of ​​the subsequent passivation layer, increase the mobile hydrogen content of the passivation layer in the upper local area of ​​the space charge region, achieve hydrogen passivation enhancement in this region, reduce space charge recombination, improve the passivation performance of the surface and sides of the first and second doped regions, reduce the carrier recombination rate, and help improve the photoelectric conversion efficiency of the back-contact solar cell.

[0112] In other embodiments, the second section 52 may also be non-parallel to the backlight surface, with a certain angle between them.

[0113] In some alternative implementations, such as Figures 1-7 As shown, the third section 53 is inclined relative to the backlight surface;

[0114] The third section 53 includes a velvety slope region 531 and a smooth slope region 532; the velvety slope region 531 is relatively close to the bottom of the isolation groove 40 and is connected to the bottom of the isolation groove 40; the smooth slope region 532 is connected to the second section 52.

[0115] In practice, the first doped region 20 and the second doped region 30 are alternately arranged in the first direction. Figures 1-8 All cross-sectional views are parallel to the first direction and perpendicular to the backlight surface. It can be seen that the textured slope region 531 is relatively close to the bottom of the isolation groove 40 and is connected to the bottom of the isolation groove 40. The textured slope region 531 extends from bottom to top; the smooth slope region 532 is connected to the second cross-section 52. If the third cross-section 53 is entirely textured, the passivation layer 70 cannot be uniformly covered, which will reduce the surface passivation performance. If the third cross-section 53 is entirely polished, the reflectivity of the back incident light on the third cross-section 53 will be too high, resulting in low optical utilization and reduced double-sidedness.

[0116] In some embodiments, the surface of the velvet slope region 531 has a pyramidal velvet surface, and the smooth slope region 532 is smooth relative to the velvet slope region 531.

[0117] Beneficial Effects: The back-contact solar cell provided in this embodiment has a third cross-section comprising a textured slope region near the bottom of the isolation groove and a smooth slope region connected to the second cross-section. The textured slope region can improve the optical utilization rate of light incident on the back of the cell at all angles, further improving the bifaciality of the corresponding module and increasing the all-weather module power, thus improving the optical performance of the back-contact cell. The smooth slope region can uniformly cover the passivation layer on the sidewall of the isolation groove, improving the uniformity of sidewall passivation and the surface passivation performance of the cell, thereby improving the electrical performance of the back-contact cell. In addition, since the pn junction of the back-contact solar cell is located at the top of the slope (i.e., the part of the third cross-section near the second cross-section), and the effective passivation of the pn junction region is crucial to the electrical performance of the cell, making the part of the third cross-section near the second cross-section a smooth structure is more conducive to the uniform coverage of the subsequent passivation layer, and the resulting electrical performance gain is higher than the optical gain brought by the textured structure.

[0118] In some alternative embodiments, the length of the velvet slope region 531 is 1 / 5 to 4 / 5 of the length of the third section 53.

[0119] In practice, the length of the velvet-surface slope region 531 accounts for 1 / 5 to 4 / 5 of the length of the third section 53.

[0120] like Figure 1As shown, the length of the third section 53 refers to the distance the sidewall of the isolation groove 40 extends from the bottom along the third section 53 from bottom to top, that is... Figure 1 In this context, L; the length of the velvet slope region 531 refers to the distance that the velvet slope region 531 extends along the sidewall of the isolation groove 40, that is... Figure 1 L1 in the middle.

[0121] Beneficial effects: In the back-contact solar cell provided in this embodiment, the length of the textured slope region accounts for 1 / 5 to 4 / 5 of the length of the third section. This allows the passivation layer to be uniformly covered on the sidewall of the isolation groove. The third section is close to the second section, completely covering the pn junction position, which improves the uniformity of the passivation layer at the pn junction position. This can further improve the surface passivation performance of the cell, thereby improving the electrical performance of the back-contact cell.

[0122] refer to Figure 16 This disclosure also provides a method for fabricating a back-contact solar cell, comprising:

[0123] Step S101: Provide a substrate layer 10, including a light-receiving surface and a backlight surface disposed opposite to each other.

[0124] In practice, the substrate 10 is a silicon substrate. In one example, the substrate 10 is an n-type silicon wafer.

[0125] In step S102, a first doped region 20 and a second doped region 30 are formed on the back side of the substrate 10, with the first doped region 20 and the second doped region 30 being alternately arranged.

[0126] In specific implementation, an initial first doped region may first be deposited on the substrate layer 10 using LPCVD technology. Then, a trenching process is performed on the backlight side of the initial first doped region using methods such as laser etching. This trenching process removes a portion of the substrate layer 10, followed by alkaline cleaning to remove impurities. Next, an initial second doped region is deposited on the trenched substrate layer 10 again using LPCVD technology. This initial second doped region covers the remaining initial first doped region, as well as the sidewalls and bottom of the trenched area of ​​the substrate layer 10. Then, in the area adjacent to the initial second doped region deposited in the trenched area, the initial second doped region located on the initial first doped region is removed using methods such as laser etching, forming alternating first doped regions 20 and second doped regions 30. In actual processes, the initial first and second doped regions are deposited omnidirectionally on the light-receiving surface, backlight surface, and sidewalls of the substrate layer 10. Therefore, after removing the initial second doped region located on the initial first doped region, a chain-like method is also used to remove the deposited material on the light-receiving side and sidewalls of the battery. In one example, the first doped region 20 is an N-type doped region, and the second doped region 30 is a P-type doped region.

[0127] In step S103, an isolation groove 40 is formed between adjacent first doped regions 20 and second doped regions 30. The isolation groove 40 penetrates the first doped region 20 and the second doped region 30 and extends into the substrate layer 10. At least one sidewall of the isolation groove 40 includes a first cross-section 51, a second cross-section 52 and a third cross-section 53. The first cross-section 51 and the second cross-section 52 are formed in the first doped region 20 or the second doped region 30. The first cross-section 51 extends from the surface of the first doped region 20 or the second doped region 30 to the interior of the first doped region 20 or the second doped region 30. The second cross-section 52 connects the first cross-section 51 and the third cross-section 53. The third cross-section 53 is formed at least in the substrate layer 10 and is connected to the bottom of the isolation groove 40.

[0128] The third section is inclined relative to the backlight surface; the third section includes a velvety slope area and a smooth slope area; the velvety slope area is relatively close to the bottom of the isolation groove and is connected to the bottom of the isolation groove; the smooth slope area is connected to the second section.

[0129] In specific implementation, an isolation groove 40 is formed between the first doped region 20 and the second doped region 30 through methods such as laser etching or wet etching. The bottom of the isolation groove 40 has a textured surface structure 41. Figure 1 and Figure 2 As shown, at least one sidewall of the isolation groove 40, from the groove opening to the bottom of the groove, sequentially includes a first cross-section 51, a second cross-section 52, and a third cross-section 53; the first cross-section 51 and the second cross-section 52 constitute a fracture recess structure 60; the fracture recess structure 60 is recessed into the surface of the first doped region 20 or the surface of the second doped region 30, and is recessed into the sidewall of the isolation groove 40. The fracture recess structure 60 at least penetrates a portion of the first doped region 20 or a portion of the second doped region 30.

[0130] In some alternative embodiments, the method for fabricating a back-contact solar cell further includes:

[0131] A passivation layer 70 is formed, which is located on the surface of the first doped region 20 and the surface of the second doped region 30, and covers the first cross section 51 and the second cross section 52.

[0132] In some alternative implementations, such as Figure 3 As shown, the passivation layer 70 also covers the third cross section 53.

[0133] In some alternative implementations, such as Figure 3 As shown, the passivation layer 70 also covers the bottom of the isolation groove.

[0134] In some alternative implementations, the passivation layer 70 also covers the light-receiving surface and sides of the substrate.

[0135] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0136] Although embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A back-contact solar cell, characterized in that, include: The base layer includes a light-receiving surface and a backlighting surface that are positioned opposite to each other; The first doped region and the second doped region are alternately disposed on the back side of the substrate layer; An isolation groove is located between adjacent first doped regions and second doped regions, and the isolation groove extends into the substrate layer; At least one sidewall of the isolation groove includes a first cross-section, a second cross-section, and a third cross-section. The first cross-section and the second cross-section are formed in the first doped region or the second doped region. The first cross-section extends from the surface of the first doped region or the second doped region to the interior of the first doped region or the second doped region. The second cross-section connects the first cross-section and the third cross-section. The third cross-section is formed at least in the substrate layer and is connected to the bottom of the isolation groove. The third cross-section is inclined relative to the backlight surface; the third cross-section includes a velvety slope area and a smooth slope area; the velvety slope area is relatively close to the bottom of the isolation groove and is connected to the bottom of the isolation groove; the smooth slope area is connected to the second cross-section.

2. The back-contact solar cell according to claim 1, characterized in that, The isolation groove near the sidewall of the first doped region and the isolation groove near the sidewall of the second doped region both include a first cross-section, a second cross-section, and a third cross-section; In the isolation groove near the sidewall of the first doped region, the first cross-section and the second cross-section are formed in the first doped region. The first cross-section extends from the surface of the first doped region to the interior of the first doped region. The second cross-section connects the first cross-section and the third cross-section. The third cross-section is formed at least in the substrate layer and is connected to the bottom of the isolation groove. Near the sidewall of the second doped region in the isolation groove, the first cross-section and the second cross-section are formed in the second doped region. The first cross-section extends from the surface of the second doped region to the interior of the second doped region. The second cross-section connects the first cross-section and the third cross-section. The third cross-section is formed at least in the substrate layer and is connected to the bottom of the isolation groove.

3. The back-contact solar cell according to claim 1, characterized in that, The back-contact solar cell also includes: A passivation layer is located on the surfaces of the first doped region and the second doped region, and covers the first cross-section and the second cross-section.

4. The back-contact solar cell according to claim 1, characterized in that, The first doped region includes: a first tunneling oxide layer and a first doped layer stacked sequentially, wherein the first tunneling oxide layer is relatively close to the backlight surface; The second doped region includes: a second tunneling oxide layer and a second doped layer stacked sequentially, the second tunneling oxide layer being relatively close to the backlight surface, and the second doped layer having the opposite conductivity type to the first doped layer.

5. The back-contact solar cell according to claim 4, characterized in that, The second cross-section is formed within the first doped layer or the second doped layer; the first cross-section extends from the surface of the first doped layer or the second doped layer to the interior of the first doped layer or the second doped layer.

6. The back-contact solar cell according to claim 4, characterized in that, The second cross-section is formed within the first tunneling oxide layer or the second tunneling oxide layer; the first cross-section extends from the surface of the first doped layer or the second doped layer into the interior of the first tunneling oxide layer or the second tunneling oxide layer.

7. The back-contact solar cell according to claim 4, characterized in that, The first doped region further includes a first inner extension layer located between the substrate layer and the first tunneling oxide layer, wherein the first inner extension layer has the same conductivity type as the first doped layer; The second doped region further includes a second inner extension layer located between the substrate layer and the second tunneling oxide layer, the second inner extension layer having the same conductivity type as the second doped layer.

8. The back-contact solar cell according to claim 7, characterized in that, The second cross-section is formed within the first inner expansion layer or the second inner expansion layer; the first cross-section extends from the surface of the first doped layer or the second doped layer to the interior of the first inner expansion layer or the second inner expansion layer.

9. The back-contact solar cell according to claim 1, characterized in that, The angle between the first cross-section and the second cross-section is 30~90°; The width of the second cross-section is 0.5~10 μm; the distance between the second cross-section and the backlight surface is 0.1~2.0 μm; The first cross-section is a plane or a curved surface; the second cross-section is a plane or a curved surface.

10. The back-contact solar cell according to claim 1, characterized in that, The length of the velvety slope region accounts for 1 / 5 to 4 / 5 of the length of the third cross section.

11. A method for fabricating a back-contact solar cell, used to fabricate the back-contact solar cell as described in any one of claims 1 to 10, characterized in that, include: A substrate layer is provided, comprising a light-receiving surface and a backlighting surface disposed opposite to each other; A first doped region and a second doped region are formed on the back surface side of the substrate layer, and the first doped region and the second doped region are alternately arranged. An isolation groove is formed between adjacent first and second doped regions, the isolation groove extending into the substrate layer; at least one sidewall of the isolation groove includes a first cross-section, a second cross-section, and a third cross-section, the first cross-section and the second cross-section being formed within the first or second doped region, the first cross-section extending from the surface of the first or second doped region to the interior of the first or second doped region, the second cross-section connecting the first cross-section and the third cross-section, the third cross-section being formed at least within the substrate layer and connected to the bottom of the isolation groove; The third cross-section is inclined relative to the backlight surface; the third cross-section includes a velvety slope area and a smooth slope area; the velvety slope area is relatively close to the bottom of the isolation groove and is connected to the bottom of the isolation groove; the smooth slope area is connected to the second cross-section.

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