Back contact solar cells and photovoltaic modules

Abstract

The application provides a back contact solar cell and a photovoltaic module, and relates to the technical field of photovoltaics. The back contact solar cell comprises a substrate, an N-type doped layer and a P-type doped layer which are arranged at a first surface of the substrate, a first edge isolation region between the N-type doped layer and a side wall, and a second edge isolation region between the P-type doped layer and the side wall. The first edge isolation region comprises a first segment which is adjacent to the side wall and comprises a first textured structure, and a second segment. The second edge isolation region comprises a third segment which is adjacent to the side wall, and a fourth segment which is adjacent to the third segment and continuous with the third segment. The third segment is inclined relative to the fourth segment, and the third segment and the fourth segment both comprise a second textured structure. The application improves the isolation effect of the edge and reduces the entry of water vapor.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a back-contact solar cell and a photovoltaic module. Background Technology

[0002] Back-contact solar cells, due to their grid-free structure on the light-facing side, can make full use of sunlight, resulting in higher efficiency. Furthermore, the grid-free structure on the light-facing side makes the module appearance more aesthetically pleasing, thus offering broad application prospects.

[0003] In back-contact solar cells, two doped layers with opposite doping types are both placed on the back side of the substrate. Therefore, the back side of the back-contact cell has a more complex structure and suffers from insufficient edge isolation. Summary of the Invention

[0004] This invention provides a back-contact solar cell and a photovoltaic module, which aims to solve the problem of insufficient edge isolation in existing back-contact solar cells.

[0005] A first aspect of the present invention provides a back-contact solar cell, comprising:

[0006] A substrate, along its thickness direction, having opposing first surfaces, second surfaces, and sidewalls connecting the first and second surfaces;

[0007] An N-type doped layer and a P-type doped layer are disposed at intervals on the first surface;

[0008] A first edge isolation region is provided between the N-type doped layer and the sidewall;

[0009] A second edge isolation region is provided between the P-type doped layer and the sidewall;

[0010] The first edge isolation region includes: a first segment adjacent to the sidewall, the surface of the first segment having an inclined surface relative to the substrate surface where the N-type doped layer is located, and including a first textured structure; and a second segment further away from the sidewall than the first segment, the surface of the second segment being approximately parallel to the substrate surface where the N-type doped layer is located.

[0011] The second edge isolation region includes: a third segment adjacent to the sidewall, the surface of the third segment having an inclined surface relative to the substrate surface where the P-type doped layer is located; and a fourth segment adjacent to and continuous with the third segment; the third segment being inclined relative to the fourth segment, and both the third and fourth segments including a second textured structure.

[0012] In this application, by setting a first edge isolation region between the N-type doped layer and the sidewall, and a second edge isolation region between the P-type doped layer and the sidewall, the isolation effect can be strengthened. The aforementioned second textured structure on the first surface has a longer interface distance from the sidewall to the P-type doped layer, which can increase the interface path length for water vapor or other undesirable elements to enter the back contact solar cell, thereby reducing the entry of water vapor or other undesirable elements and preventing water vapor or other undesirable elements from affecting the passivation contact performance. At the same time, the film quality of the passivation antireflection layer in the N region is improved, especially since the surface of the N-type doped layer and the surface of the substrate have a certain height difference, which further strengthens the edge isolation effect.

[0013] Optionally, the surface of the second segment is a generally planar polished structure.

[0014] Optionally, the back-contact solar cell further includes a passivation antireflection layer, which covers the P-type doped layer, the N-type doped layer, the first surface of the substrate, the second surface of the substrate, and the sidewall.

[0015] Optionally, an interface passivation layer may be included between the N-type doped layer and the substrate, and between the P-type doped layer and the substrate.

[0016] Optionally, the first edge isolation zone further includes a fifth segment located between the first segment and the second segment, the fifth segment having sidewalls inclined relative to the surfaces of the second segment and the first segment.

[0017] Optionally, the lateral width of the first segment is 1 micrometer to 45 micrometers, the lateral width of the second segment is 0.2 micrometers to 8 micrometers, and the lateral width of the fifth segment is 0.5 micrometers to 10 micrometers.

[0018] Optionally, the second edge isolation region further includes a sixth segment, which is located between the fourth segment and the P-type doped layer.

[0019] Optionally, the lateral width of the third segment is 5 micrometers to 50 micrometers, the lateral width of the fourth segment is 5 micrometers to 250 micrometers, and the lateral width of the sixth segment is 0.5 micrometers to 10 micrometers.

[0020] Optionally, the lateral width of the first edge isolation region is 2 micrometers to 50 micrometers, and the lateral width of the second edge isolation is 20 micrometers to 300 micrometers; or,

[0021] The lateral width of the second edge isolation zone is greater than the width of the first edge isolation zone.

[0022] Optionally, the morphology of the first velvet structure is different from that of the second velvet structure on the third segment.

[0023] Optionally, the first velvet structure includes: a plurality of first-type pyramid structures; the second velvet structure on the third segment includes: a plurality of second-type pyramid structures;

[0024] The distribution density of the first type of pyramid structure is less than the distribution density of the second type of pyramid structure;

[0025] or,

[0026] The average interval between adjacent first-type pyramid structures is greater than the average interval between adjacent second-type pyramid structures.

[0027] or,

[0028] The apex angle of the first type of pyramid structure is greater than the apex angle of the second type of pyramid structure; or,

[0029] The aspect ratio of the first type of pyramid structure is smaller than that of the second type of pyramid structure.

[0030] Optionally, the second surface has a third velvet structure; the third velvet structure includes: a plurality of third-type pyramid structures;

[0031] The apex angle of the second type of pyramid structure is larger than the apex angle of the third type of pyramid structure.

[0032] Optionally, the apex angle of the first type of pyramid structure is 70° to 100°, the apex angle of the second type of pyramid structure is 65° to 95°, and the apex angle of the third type of pyramid structure is 60° to 90°.

[0033] Optionally, in the orthographic projection of the substrate, the projected area of ​​the first velvet structure is smaller than the projected area of ​​the second velvet structure.

[0034] Optionally, the outline of the first edge isolation zone on the sidewall includes wavy segments.

[0035] Optionally, the first surface includes a third isolation region located between adjacent N-type doped layers and P-type doped layers; the third isolation region has a fourth textured structure, the fourth textured structure including a plurality of fourth-type pyramid structures; the size of the fourth-type pyramid structure is larger than the size of the second-type pyramid structure. Optionally, the surface of the first segment and the surface of the second segment have a first included angle, and the sidewall of the fifth segment and the surface of the second segment have a second included angle, the first included angle being larger than the second included angle.

[0036] A second aspect of the present invention provides a method for fabricating a back-contact solar cell, comprising:

[0037] A substrate is provided, having opposing first and second surfaces along the thickness direction of the substrate, and a sidewall connecting the first and second surfaces;

[0038] A P-type doped layer is formed and patterned on the first surface of the substrate;

[0039] An N-type doped layer is formed and patterned on the first surface of the substrate;

[0040] When the N-type doped layer and / or the P-type doped layer are patterned, a first edge isolation region is formed between the N-type doped layer and the sidewall, and a second edge isolation region is formed between the P-type doped layer and the sidewall. The first edge isolation region includes: a first segment adjacent to the sidewall, the surface of the first segment having an inclined surface relative to the substrate surface where the N-type doped layer is located, and including a first textured structure; and a second segment further away from the sidewall than the first segment, the surface of the second segment being approximately parallel to the substrate surface where the N-type doped layer is located. The second edge isolation region includes: a third segment adjacent to the sidewall, the surface of the third segment having an inclined surface relative to the substrate surface where the P-type doped layer is located; and a fourth segment adjacent to and continuous with the third segment; the third segment being inclined relative to the fourth segment, and both the third and fourth segments including a second textured structure.

[0041] A third aspect of the present invention provides a photovoltaic module comprising: a plurality of any of the aforementioned back-contact solar cells.

[0042] The aforementioned back-contact solar cells and photovoltaic modules have the same or similar beneficial effects, and will not be repeated here to avoid repetition. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 and Figure 2 A partial structural schematic diagram of two back-contact solar cells in an embodiment of the present invention is shown;

[0045] Figures 3 to 9Partial SEM images of several back-contact solar cells in embodiments of the present invention are shown.

[0046] Explanation of the attached drawing numbers:

[0047] 1-Substrate, 11-First surface, 12-Second surface, 13-Sidewall, 2-N-type doped layer, 3-P-type doped layer, 4-First edge isolation region, 41-First segment, 42-Second segment, 43-Fifth segment, 5-Second edge isolation region, 51-Third segment, 52-Fourth segment, 53-Sixth segment, 6-Third isolation region, 7-Interface passivation layer. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] This invention provides a back-contact solar cell. Figure 1 and Figure 2 This section primarily illustrates the main structure of the back-contact solar cell, including the first and second edge isolation regions; other details are omitted. Figure 1 and Figure 2 The wavy line in the text indicates omission. (See reference...) Figure 1 and Figure 2 The back-contact solar cell includes a substrate 1, an N-type doped layer 2, and a P-type doped layer 3. An interface passivation layer 7, such as a tunneling oxide layer, is also included between the N-type doped layer 2 and the substrate 1, and between the P-type doped layer 3 and the substrate 1. The SEM image is a scanning electron microscope image. The material of the substrate 1 can be silicon (Si), germanium (Ge), or gallium arsenide (GaAs). Regarding conductivity type, the substrate 1 can be an intrinsically conductive substrate, an N-type conductive substrate, or a P-type conductive substrate. For example, if the substrate 1 is an N-type conductive substrate, N-type silicon substrates have advantages such as high minority carrier lifetime, no light decay, and good performance in low-light conditions.

[0050] Along the thickness direction Q of the substrate 1, the substrate 1 has a first surface 11, a second surface 12, and a sidewall 13 connecting the first surface 11 and the second surface 12. During normal operation of the back-contact solar cell, the surface of the substrate 1 that mainly absorbs light is the second surface 12, which is the light-facing surface of the substrate 1. The first surface 11 is the back-facing surface of the substrate 1, and the sidewall 13 connects the first surface 11 and the second surface 12. Here, the sidewall 13 refers to all or most of the sidewalls connecting the first surface 11 and the second surface 12.

[0051] The N-type doped layer 2 and the P-type doped layer 3 are spaced apart on the first surface 11, and the spacing here is used to avoid short circuits.

[0052] Reference Figure 1 and Figure 2 Between the N-type doped layer 2 and the sidewall 13, there is a first edge isolation region 4, which refers to the first edge isolation region 4 between the N-type doped layer 2 and the sidewall immediately adjacent to the sidewall 13. Between the P-type doped layer 3 and the sidewall 13, there is a second edge isolation region 5, which refers to the second edge isolation region 5 between the P-type doped layer 3 and the sidewall 13 immediately adjacent to the sidewall 13. This edge isolation region separates the boundaries of the doped layers (N-type doped layer 2 and P-type doped layer 3) from the sidewall of the substrate 1.

[0053] Reference Figure 1 The first edge isolation region 4 includes a first segment 41 and a second segment 42. The first segment 41 is adjacent to the sidewall 13. The surface of the first segment 41 is inclined relative to the substrate surface where the N-type doped layer 2 is located. That is, the surface of the first segment 41 is inclined relative to the area of ​​the first surface corresponding to the N-type doped layer 2. The surface of the first segment 41 has a first textured structure. The surface of the second segment 42 is approximately parallel to the substrate surface where the N-type doped layer is located. That is, the surface of the second segment 42 is approximately parallel to the area of ​​the first surface corresponding to the N-type doped layer 2.

[0054] Reference Figure 1 and Figure 2 The second edge isolation region 5 includes a third segment 51 and a fourth segment 52. The third segment 51 is adjacent to the sidewall 13. The surface of the third segment 51 is inclined relative to the substrate surface where the P-type doped layer 3 is located, that is, the surface of the third segment 51 is inclined relative to the region in the first surface corresponding to the P-type doped layer 3. The third segment 51 is inclined relative to the fourth segment 52, and the fourth segment 52 is adjacent to and continuous with the third segment 51. (Refer to...) Figure 3 Both the third segment 51 and the fourth segment 52 include a second velvet structure.

[0055] In the above structure, when using an N-type substrate, the region where the P-type doped layer 3 is located is the junction region of the cell, which is opposite to the conductivity type of the substrate. Furthermore, after the cell is fabricated into a module, the front and back sides of the back-contact solar cell are protected by a multi-layered structure. Moisture or other unwanted elements in the environment can more easily penetrate from the sidewalls of the back-contact solar cell. The passivation layer at the interface between the doped layer and the substrate 1 also tends to absorb moisture, thus affecting the passivation layer and disrupting the passivation contact function between the doped layer and the substrate 1. Since the P-type doped layer 3 is the junction region, it significantly impacts the cell efficiency. In this application, both the third segment 51 and the fourth segment 52 have a second textured structure. Because the substrate near the P-type doped layer 3 is textured, when moisture or other unwanted elements penetrate into the back-contact solar cell from the sidewalls, the moisture tends to penetrate at the interfaces of each layer. Therefore, the textured structure increases the interface creepage distance and also increases insulation, thereby better preventing the erosion of moisture or other elements. Furthermore, since the N-type doped layer 2 has the same conductivity type as the substrate 1, forming a field region, the tolerance for damage to the passivation layer at the interface between the N-type doped layer 2 and the substrate 1 is higher than that of the P-region. Based on this, in order to improve the film quality of the passivation antireflection layer, especially since the surface of the N-type doped layer 2 and the surface of the substrate have a certain height difference, which affects the deposition quality of the passivation antireflection layer, the second segment 42 adjacent to the N-type doped layer 2 is set to be approximately a polished structure, or the surface roughness of the second segment 42 is less than that of the first textured structure of the first segment 41, which can improve the overall film quality of the passivation antireflection layer and improve the passivation antireflection effect.

[0056] In some embodiments, the surface of the first segment 41 is inclined relative to the substrate surface where the N-type doped layer is located. Compared to a flat surface, the inclined surface makes the distance between the side of the first segment 41 away from the sidewall 13 and the sidewall 13 greater, enhancing the surface creep distance and increasing the interface distance for moisture entry. It should be noted that the inclined surface of the first segment 41 relative to the substrate surface where the N-type doped layer is located mainly means that the surface of the first segment 41 has a certain angle relative to the substrate surface where the N-type doped layer is located. The surface of the first segment 41 may include a flat or curved surface, that is, the surface of the first segment 41 and the substrate surface where the N-type doped layer is located are not parallel. The inclination trend of the first segment 41 is roughly as follows: along the thickness direction Q of the substrate 1, the end of the surface of the first segment 41 closer to the sidewall 13 is farther away from the substrate surface where the N-type doped layer is located than other positions on the surface of the first segment 41.

[0057] Reference Figure 1 and Figure 2Compared to the first segment 41, the second segment 42 is further away from the sidewall 13. The second segment 42 is adjacent to the N-type doped layer 2, and its surface is roughly parallel to the substrate surface where the N-type doped layer is located. This is beneficial for obtaining a high-quality N-type doped layer 2 and the passivation anti-reflection film on it, thereby improving the passivation anti-reflection quality and effect.

[0058] In some embodiments, the tilted surface of the third segment 51 relative to the substrate surface containing the P-type doped layer mainly means that the surface of the third segment 51 has a certain angle relative to the substrate surface containing the P-type doped layer. The surface of the third segment 51 may include a planar or curved surface, that is, the surface of the third segment 51 and the substrate surface containing the P-type doped layer are not parallel. The tilting trend of the third segment 51 is roughly as follows: along the thickness direction Q of the substrate 1, the end of the surface of the third segment 51 near the sidewall 13 may be farther away from the substrate surface containing the P-type doped layer than other positions on the surface of the third segment 51. Here, the tilt of the third segment 51 relative to the fourth segment 52 means that the third segment 51 and the fourth segment 52 are not parallel. Whether the fourth segment 52 and the substrate surface containing the P-type doped layer are parallel is not limited; for example, they may be parallel or not parallel.

[0059] Optional, refer to Figure 1 and Figure 2 The surface of the second segment 42 is a roughly planar polished structure. The surface of the second segment 42 is flatter, which is conducive to obtaining a high-quality N-type doped layer 2 and its passivation and anti-reflection layer. It can also ensure the passivation and anti-reflection quality and effect of the area adjacent to the N-type doped layer 2 in the first surface 11.

[0060] Optional, refer to Figure 2 The first edge isolation region 4 further includes a fifth segment 43 located between the first segment 41 and the second segment 42. This fifth segment 43 has sidewalls that are inclined relative to the surfaces of the second segment 42 and the first segment 41. The structure of the first edge isolation region 4 is more complex, increasing the creepage distance between the N-type doped layer 2 and the sidewall 13. The longer distance from the sidewall to the surface of the N-type doped layer increases the path length for water vapor entry, reducing water vapor ingress and thus preventing water vapor interference. It also improves the light-trapping effect. The fifth segment 43 having sidewalls inclined relative to the surfaces of the second segment 42 and the first segment 41 means that the sidewalls of the fifth segment 43 are not parallel to either the second segment 42 or the first segment 41. Optionally, refer to... Figure 2The surface of the first segment 41 and the surface of the second segment 42 have a first included angle α, and the sidewall of the fifth segment 43 and the surface of the second segment 42 have a second included angle β. The first included angle α is greater than the second included angle β. In this application, α > β, which is relative to β > α. Therefore, the first segment 41, the fifth segment 43 and the second segment 42 are not arranged in a gradually flat manner, but have large protrusions at the second segment 42 and the fifth segment 43, which makes the structure of the first edge isolation region 4 more complex, increases the isolation effect between the N-type doped layer 2 and the sidewall 13, and the water vapor isolation effect.

[0061] Optionally, the first included angle a here is 95° to 170°; the second included angle b here is 90° to 150°; the above angle range is easy to achieve in processing, and the protrusion is not too abrupt, avoiding hidden cracks, etc.

[0062] For example, the first included angle 'a' here can be 95°, 100°, 105°, 110°, 120°, 125°, 130°, 140°, 145°, 150°, 160°, or 170°. As another example, the second included angle 'b' here can be 90°, 100°, 105°, 110°, 115°, 120°, 125°, 130°, 140°, 145°, or 150°.

[0063] Optionally, the second edge isolation region 5 further includes a sixth segment 53, located between the fourth segment 52 and the P-type doped layer 3. The sixth segment 53 includes sidewalls that are inclined relative to the surfaces of the fourth segment 42 and the substrate 1 containing the P-type doped layer 3. This increases the creepage distance between the P-type doped layer 3 and the sidewall 13. The longer distance from the sidewall to the surface of the P-type doped layer 3 increases the path length for water vapor entry, reduces water vapor entry, and thus prevents water vapor interference. It also improves the light trapping effect. The fact that the sixth segment 53 has sidewalls inclined relative to the surfaces of the fourth segment 42 and the substrate 1 containing the P-type doped layer 3 means that the sidewalls of the sixth segment 53 are not parallel to the surfaces of the fourth segment 42 and the substrate 1 containing the P-type doped layer 3.

[0064] Optionally, the sixth segment 53 has a dimension of 2 micrometers to 9 micrometers in the thickness direction Q; the angle between the sixth segment 53 and the fourth segment 52 is smaller than the angle between the third segment 51 and the fourth segment 52. The above settings can increase or decrease the overall height difference of the second edge isolation zone 5, increase the climbing distance and the isolation effect.

[0065] Optionally, the morphology of the first velvet structure on the first edge isolation region 4 is different from that of the second velvet structure on the third segment of the second edge isolation region. The difference in morphology here may refer to the fact that the degree of protrusion, degree of depression, number of protrusions, number of depressions, distribution density of protrusions, and distribution density of depression of the first velvet structure are different from those of the second velvet structure on the third segment of the second edge isolation region.

[0066] Optionally, the first velvet structure includes: several first-type pyramid structures, the number of first-type pyramid structures in the first velvet structure is not specifically limited; the second velvet structure on the third segment includes: several second-type pyramid structures, the number of second-type pyramid structures in the second velvet structure on the third segment is not specifically limited; the distribution density of the first-type pyramid structures in the first velvet structure is less than the distribution density of the second-type pyramid structures in the second velvet structure on the third segment, that is, within the same area or unit area, the number of first-type pyramid structures in the first velvet structure is less than the number of second-type pyramid structures in the second velvet structure on the third segment, where the size of the same dimension or unit size is not limited; it can be that the number of first-type pyramid structures within one or more areas of the same area or unit area of ​​the first velvet structure is less than the number of second-type pyramid structures within one or more areas of the same area or unit area of ​​the second velvet structure on the third segment. In the above scheme, the edge of the P-type doped layer 3 is more focused on effectively blocking the influence of water vapor or other undesirable elements, while the edge of the N-type doped layer 2 is more focused on the quality of the passivation and antireflection layer, thereby comprehensively improving the stability and efficiency of the solar cell.

[0067] For example, refer to Figure 3 , Figure 3 The area outlined by the dashed line represents the second velvet structure on the third segment 51, where the second type of pyramidal structure is densely and continuously distributed. For example... Figure 4 This is a partial SEM image of the second velvet structure on the third segment 51. Figure 5 This is a partial SEM image of the first velvet structure. Figure 4 and Figure 5 These are SEM images within the same area. In the third segment 51, the distribution density of the second type of pyramid structure in the second velvet structure is greater than the distribution density of the first type of pyramid structure in the first velvet structure.

[0068] Optional, refer to Figure 4 and Figure 5The undulation of the first velvet structure is greater than that of the second velvet structure on the third segment 51. In one case, the degree of protrusion and / or depression of the first velvet structure may be greater than that of the second velvet structure on the third segment 51. In another case, the arrangement of protrusions and / or depressions of the first velvet structure may be more disordered than that of the second velvet structure on the third segment 51. In yet another case, the height of the protrusions and / or the depth of the depressions of the first velvet structure may be greater than the height of the protrusions and / or the depth of the depressions of the second velvet structure on the third segment 51.

[0069] Optionally, in the first velvet structure, there is a gap between adjacent first-type pyramid structures, or adjacent first-type pyramid structures are continuously distributed. In the case of continuous distribution of adjacent first-type pyramid structures, the gap between adjacent first-type pyramid structures is 0. Optionally, in the second velvet structure on the third segment 51, there is a gap between adjacent second-type pyramid structures, or adjacent second-type pyramid structures are continuously distributed. In the case of continuous distribution of adjacent second-type pyramid structures, the gap between adjacent second-type pyramid structures is 0.

[0070] Optional, refer to Figure 4 and Figure 5 The average spacing between adjacent first-type pyramidal structures in the first textured structure is greater than the average spacing between adjacent second-type pyramidal structures in the second textured structure on the third segment 51. A larger average spacing between adjacent first-type pyramidal structures in the first textured structure is beneficial to the film quality of the passivation antireflective layer. The average spacing between pyramidal structures refers to the average spacing between different types of pyramids within a unit area or a specified area.

[0071] Optionally, the apex angle of the first type of pyramid structure is greater than the apex angle of the second type of pyramid structure. For a given first type of pyramid structure, the apex angle is the included angle between two opposite side edges passing through the apex of the pyramid structure. The apex of the pyramid structure is the highest point in the pyramid structure. When the highest part of the pyramid structure is a plane formed by multiple points of equal height, the pyramid can be the geometric center of that plane. "The apex angle of the first type of pyramid structure is greater than the apex angle of the second type of pyramid structure" means that: in the first textured structure, at least one apex angle of the first type of pyramid structure is greater than at least one apex angle of the second type of pyramid structure; or, in the first textured structure, the average of the apex angles of multiple first type of pyramid structures is greater than the average of the apex angles of multiple second type of pyramid structures. A larger apex angle of the first type of pyramid structure is beneficial to the film quality of the passivation antireflection coating.

[0072] Optionally, the aspect ratio of the first type of pyramid structure is smaller than that of the second type of pyramid structure. The pyramid-like structure includes a bottom outline opposite the apex, which is the outline closest to the base of the pyramid-like structure. The height of the pyramid-like structure refers to the distance from the apex to the bottom outline in a plane perpendicular to the bottom outline. The width of the pyramid-like structure refers to the maximum dimension of its bottom outline. The aspect ratio of the first type of pyramid structure is the ratio of the height of any first type of pyramid structure to its width in the first textured surface structure, or the average height of multiple first type of pyramid structures in the first textured surface structure divided by the average width of those multiple first type of pyramid structures. The aspect ratio of the second type of pyramid structure is determined in the same way as that of the first type of pyramid structure, and will not be repeated here to avoid repetition. The second type of pyramid is taller and narrower, which is more conducive to increasing surface creep distance.

[0073] Figure 6 Here is a partial SEM image of the second surface of substrate 1. Optional, refer to... Figure 6 The second surface of substrate 1, i.e., the light-facing surface of substrate 1, has a third textured structure. This third textured structure includes several third-type pyramid structures, the number of which is not specifically limited. The method for determining the apex angle of the third-type pyramid structure is the same as that for determining the apex angle of the first-type pyramid structure. The apex angle of the second-type pyramid structure is larger than that of the third-type pyramid structure. Since the apex angle of the first-type pyramid structure is larger than that of the second-type pyramid structure, both the apex angles of the first and second-type pyramid structures are larger than the apex angle of the third-type pyramid structure. The apexes of the first and second-type pyramid structures on the backlight surface are relatively smooth, facilitating the obtaining of a film layer with better backlight quality and improving passivation effects. Furthermore, the light-facing surface of the solar cell is more conducive to suppressing light reflection.

[0074] Optionally, the apex angle of the first type of pyramid structure is 70° to 100°, the apex angle of the second type of pyramid structure is 65° to 95°, and the apex angle of the third type of pyramid structure is 60° to 90°.

[0075] For example, the apex angle of the third type of pyramid structure can be 60°, 90°, 62°, 65°, 68°, 75°, 70°, 71°, 80°, 85°, 84°, 88°, or 90°; as another example, the apex angle of the first type of pyramid structure can be 70°, 75°, 80°, 85°, 84°, 90°, 95°, 76.7°, 83.9°, 98.7°, or 100°; as yet another example, the apex angle of the second type of pyramid structure can be 65°, 70°, 75°, 80°, 85°, 90°, 88°, 95°, 77.8°, 86.3°, 91.7°, or 82.3°.

[0076] The orthographic projection of the textured structure onto the first surface 11 refers to the projection of the textured structure onto the first surface 11 when illuminated by light perpendicular to the first surface 11. Optionally, in the orthographic projection onto the substrate, the projected area of ​​the first textured structure is smaller than the projected area of ​​the second textured structure. The projected area of ​​the textured structure in the orthographic projection onto the first surface can be the area of ​​the textured structure projected onto the first surface, or the area of ​​the textured structure projected onto the second surface. That is, the distribution range of the first textured structure is narrower than that of the second textured structure. The doping type of the substrate 1 is the same as the doping type of the N-type doped layer structure and opposite to the doping type of the P-type doped layer structure. Therefore, there is a short-circuit risk between the P-type doped layer and the substrate. The wider distribution range of the second textured structure further reduces the short-circuit risk.

[0077] Figure 7 This is a view of the sidewall taken along a direction perpendicular to the thickness direction Q of the substrate. Optionally, the outline of the first edge isolation zone on the sidewall 13 includes wavy segments. The wavy segments of the first edge isolation zone on the sidewall 13 have a large degree of undulation, which can increase the surface area and the light-absorbing area, thus improving efficiency.

[0078] The first surface 11 includes a third isolation region 6 located between adjacent N-type doped layers 2 and P-type doped layers 3, the third isolation region being used to prevent short circuits between adjacent N-type doped layers 2 and P-type doped layers 3.

[0079] Optionally, the third isolation zone 6 has a fourth velvet structure, which includes several fourth-type pyramid structures. The size of the fourth-type pyramid structure is larger than that of the second-type pyramid structure, and the fourth-type pyramid structure has a larger specific surface area, resulting in a more significant isolation effect and a lower short-circuit risk.

[0080] Figure 8 SEM image of the fourth type of pyramid structure in the third isolation region 6, near the N-type doped layer 2; Figure 9This is a SEM image of the fourth type of pyramid structure located near the P-type doped layer 3 in the third isolation region 6. The distribution density of the fourth type of pyramid structure near the N-type doped layer 2 in the third isolation region 6 is less than or equal to the distribution density near the P-type doped layer in the third isolation region. In other words, within the same area or unit area, the number of fourth type pyramid structures near the N-type doped layer 2 in the third isolation region 6 is less than or equal to the number of fourth type pyramid structures near the P-type doped layer 3 in the same area or unit area. Therefore, the fourth type of pyramid structure is sparser near the N-type doped layer 2 and denser near the P-type doped layer 3 in the same area or unit area. The doping type of substrate 1 is the same as that of the N-type doped layer structure and opposite to that of the P-type doped layer structure. Therefore, there is a short-circuit risk between the P-type doped layer and the substrate. The higher distribution density of the fourth type of pyramid structure near the P-type doped layer in the third isolation region further reduces this short-circuit risk.

[0081] Optional, refer to Figure 8 and Figure 9 In the third isolation region 6, near the N-type doped layer 2, the apex of the fourth type pyramid structure is the first apex; near the P-type doped layer 3, the apex of the fourth type pyramid structure is the second apex. The difference between the first and second apex is less than or equal to 5% of the ratio of the first or second apex, meaning that the first and second apex are approximately equal and the difference is small. This allows for compatibility in the processes used to form the first and second apex, simplifying the process. For example, both the first and second apex angles can be between 70° and 80°.

[0082] Optionally, the second type of pyramid structure of the second velvet structure on the fourth segment 52 is substantially the same as the fourth type of pyramid structure.

[0083] Optional, refer to Figure 2The lateral width d1 of the first edge isolation region 4 is between 2 micrometers and 50 micrometers (μm). A width exceeding 50 micrometers will significantly reduce the collection efficiency of photogenerated carriers generated at the edge, while a width less than 2 micrometers will result in insufficient edge isolation distance in the N-region, leading to inadequate protection of the N-type doped layer and the interface passivation layer. Therefore, setting the lateral width of the first edge isolation region 4 within the aforementioned range can improve the collection efficiency of photogenerated carriers and provide sufficient protection for the N-type doped layer and the interface passivation layer. It should be noted that all lateral widths mentioned in this application are perpendicular to the direction of the thickness Q of the substrate 1 and parallel to the direction in which the N-type and P-type doped layers are alternately arranged. Alternatively, all lateral widths mentioned in this application refer to the vertical distance along the sidewall of the solar cell into the interior of the cell in a top-down vertical projection from the back of the solar cell.

[0084] For example, d1 can be 2μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm.

[0085] Optionally, the lateral width d2 of the second edge isolation region 5 is 20 micrometers to 300 micrometers. Since the second edge isolation region 5 is adjacent to the P-type doped layer and serves as an isolation for the junction region, a second edge isolation region smaller than 20 micrometers is insufficient for isolating the P-region structure and providing inadequate protection; while a width greater than 300 micrometers will affect the junction area and thus the battery efficiency.

[0086] For example, d2 can be 20μm, 50μm, 100μm, 125μm, 150μm, 175μm, 200μm, 225μm, 250μm, 275μm, or 300μm.

[0087] Optionally, the lateral width d2 of the second edge isolation region 5 is greater than the width d1 of the first edge isolation region 4. Further, the ratio of the lateral width of the second edge isolation region 5 to the lateral width of the first edge isolation region 4 is between 3 and 50. This satisfies the different edge isolation requirements of the P-region and the N-region, comprehensively ensuring both battery efficiency and module stability. For example, the ratio of the lateral width of the second edge isolation region 5 to the lateral width of the first edge isolation region 4 can be 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50.

[0088] Optionally, the lateral width d3 of the third isolation region 6 is 25-200 micrometers. Within this range, effective isolation between the P-region and the N-region can be achieved while ensuring an effective junction area, which is beneficial for the low probability of solar cells. For example, d3 can be 20μm, 50μm, 100μm, 125μm, 150μm, 175μm, or 200μm.

[0089] Optionally, the lateral width of the first segment 41 is 1-45 micrometers, the lateral width of the second segment 42 is 0.2-8 micrometers, and the lateral width of the fifth segment 43 is 0.5-10 micrometers. Within the above ranges, the edge isolation and passivation anti-reflection effects of the N-region are comprehensively considered. For example, the lateral width of the first segment 41 can be 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, or 40μm; the lateral width of the second segment 42 can be 0.2μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, or 8μm; and the lateral width of the fifth segment 43 can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 8.5μm, 9μm, or 10μm.

[0090] Optionally, the lateral width d4 of the third segment 51 is 5-50 micrometers, the lateral width d5 ​​of the fourth segment 52 is 5-250 micrometers, and the lateral width d6 of the sixth segment 53 is 0.5-10 micrometers. Within the above range, the edge isolation and passivation anti-reflection effect of the P area are taken into account. For example, the lateral width d4 of the third segment 51 can be 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm; the lateral width d5 ​​of the fourth segment 52 can be 5μm, 10μm, 50μm, 100μm, 150μm, 200μm, or 250μm; and the lateral width d6 of the sixth segment 53 can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 8.5μm, 9μm, or 10μm.

[0091] Optionally, this application also includes a passivation antireflection layer, which covers the P-type doped layer 3, the N-type doped layer 2, and the first surface 11, the second surface 12, and the sidewall 13 of the substrate; optionally, the material of the passivation antireflection layer can be one or more layers of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, or amorphous silicon to provide a good passivation and antireflection effect.

[0092] Optionally, this application also includes electrodes, including a first electrode in contact with the N-type doped layer 2 and a second electrode in contact with the P-type doped layer 3, to conduct current.

[0093] This application also provides a method for fabricating a back-contact solar cell, comprising the following steps.

[0094] Step 101: Provide a substrate, which has opposing first and second surfaces along its thickness direction, and a sidewall connecting the first and second surfaces.

[0095] Referring to the aforementioned relevant records, and to avoid repetition, further details will not be repeated here.

[0096] Step 102: Forming and patterning a P-type doped layer on the first surface of the substrate; forming and patterning an N-type doped layer on the first surface of the substrate; when patterning the N-type doped layer and / or the P-type doped layer, forming a first edge isolation region between the N-type doped layer and the sidewall, and a second edge isolation region between the P-type doped layer and the sidewall, wherein the first edge isolation region includes: a first segment, the first segment being adjacent to the sidewall, and the surface of the first segment having an inclined surface relative to the substrate surface where the N-type doped layer is located. It includes a first textured structure; and a second segment further away from the sidewall than the first segment, the surface of the second segment being approximately parallel to the substrate surface where the N-type doped layer is located; the second edge isolation region includes: a third segment adjacent to the sidewall, the surface of the third segment having an inclined surface relative to the substrate surface where the P-type doped layer is located; and a fourth segment adjacent to and continuous with the third segment; the third segment being inclined relative to the fourth segment, both the third and fourth segments including the second textured structure.

[0097] The method for fabricating the back-contact solar cell may further include: forming a passivation and antireflection layer covering an N-type doped layer 2, a P-type doped layer 3, a first edge isolation region 4, and a second edge isolation region 5; forming a first electrode connected to the N-type doped layer 2; and forming a second electrode connected to the P-type doped layer 3.

[0098] Typically, substrate 1 can be inserted into a basket. Substrate 1 requires polishing and cleaning to remove damage. The processes for forming the N-type doped layer 2 and P-type doped layer 3 on substrate 1 can include plasma chemical vapor deposition (PECVD), hot-filament chemical vapor deposition, physical vapor deposition (PVD), low-pressure chemical vapor deposition (LPCVD), or catalytic chemical vapor deposition. Patterning processes for the P-type and N-type doped layers 2 can include laser etching, ion milling, plasma etching, reactive ion etching, alkaline etching, and acid etching.

[0099] In some embodiments, the N-type doped layer 2 and the P-type doped layer 3 are formed by in-situ doping or non-in-situ doping. That is, the N-type doped layer 2 and the P-type doped layer 3 can be formed directly, or the intrinsic semiconductor layer can be formed first, and then doped to form the N-type doped layer 2 and the P-type doped layer 3 respectively.

[0100] In some embodiments, the formation of the first edge isolation region 4 and the second edge isolation region can be achieved by combining etching solution and laser processes. For example, to achieve a relatively uniform textured surface structure in the formation of the second edge isolation region 5, laser irradiation followed by etching solution cleaning can be used, and the laser energy, spot size, and etching rate of the etching solution can be adjusted. When forming the first edge isolation region, local mask protection and chain-process control of the etching solution can be used, which provides a relatively flexible implementation.

[0101] It should be noted that, in the case where the etching solution or polishing cleaning solution in this application is an alkaline solution, one possible formulation of the alkaline solution is: 0.2%-10% NaOH (sodium hydroxide) and 0.2%-10% additives by volume, with the remainder of the alkaline solution mainly being pure water.

[0102] In some embodiments, the widths of the first and second electrodes range from 5 μm to 100 μm. The processes for forming the first and second electrodes can include electroplating, transfer printing (e.g., laser transfer printing, thermal transfer printing), screen printing, physical vapor deposition of metal or metal oxide electrodes, etc. Obviously, various processes can also be used in combination; for example, a seed layer can be printed first, and then electroplating can be used on the seed layer to form the final first and second electrodes; or a metal oxide vapor deposition process can be used, for example, transparent conductive oxide (TCO) can be used, and then the first and second electrodes can be formed by screen printing or transfer printing, etc.

[0103] In some embodiments, the process for forming the passivation antireflection layer can be plasma chemical vapor deposition (PECVD), hot filament chemical vapor deposition, physical vapor deposition (PVD), low pressure chemical vapor deposition (LPCVD), or catalysis, etc.

[0104] In some embodiments, the method for forming the first and second electrodes can also involve coating an electrode paste onto a passivation layer, followed by sintering, so that the electrode paste penetrates the passivation layer and forms electrical contacts with the N-type doped layer 2 and the P-type doped layer 3, respectively. When the back-contact solar cell has a passivation layer and the first and second electrodes are partial contact electrodes, the method for forming the first and second electrodes can also involve first creating a first opening and a second opening in the passivation layer, and then using methods such as printing paste, laser transfer, electroplating, chemical plating, photo-induced electroplating, or physical vapor deposition such as vacuum evaporation or magnetron sputtering to form the partial contact first and second electrodes. The opening method can include laser film opening or using an etching paste that can react with the passivation layer. Electrical contact through openings allows the back-contact solar cell to achieve lower metal recombination, ensuring high conversion efficiency. Obviously, one or more of the above methods can also be combined to form the first and second electrodes. For example, methods using physical vapor deposition (PVD) seed layers in conjunction with printed electrodes, or screen-printed electrode paste in conjunction with electroplating, or a combination of laser transfer and screen printing sintering methods, etc.

[0105] This application may also provide a photovoltaic module, which may include any of the aforementioned back-contact solar cells. The photovoltaic module may also include encapsulating films located on the light-facing side and the back-light-reflecting side of the back-contact solar cells. The specific structure of the photovoltaic module is not limited.

[0106] The photovoltaic module may also include electrical connectors, which serve as conductive interconnects. For example, the electrical connector may be a solder strip or a conductive backsheet; no specific limitation is made regarding the electrical connector. The electrical connector is electrically connected to the electrodes of at least two of the aforementioned solar cells. This connection can be direct or indirect; no limitation is made in either direction. The electrical connector can also electrically connect the first electrode of one of two adjacent solar cells to the second electrode of the other solar cell, achieving conductive interconnection.

[0107] It should be noted that the photovoltaic module, any of the aforementioned back-contact solar cells, and the aforementioned preparation methods of back-contact solar cells are related and can be referred to each other, and have the same or similar beneficial effects. To avoid repetition, they will not be described again here.

[0108] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0109] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized by, The semiconductor device comprises: a substrate having opposite first and second surfaces and a sidewall connecting the first and second surfaces along a thickness direction of the substrate; an N-type doped layer and a P-type doped layer disposed at the first surface; a first edge isolation region between the N-type doped layer and the sidewall; a second edge isolation region between the P-type doped layer and the sidewall; the first edge isolation region comprises: a first segment adjacent to the sidewall, a surface of the first segment has an inclined surface relative to a surface of the substrate where the N-type doped layer is located, and comprises a first textured structure; and a second segment further away from the sidewall than the first segment, a surface of the second segment is substantially parallel to the surface of the substrate where the N-type doped layer is located; the second edge isolation region comprises: a third segment adjacent to the sidewall, a surface of the third segment has an inclined surface relative to a surface of the substrate where the P-type doped layer is located; and a fourth segment adjacent to and continuous with the third segment; the third segment is inclined relative to the fourth segment, and the third and fourth segments each comprise a second textured structure.

2. The back contact solar cell of claim 1, wherein, the surface of the second segment is a substantially planar polished structure.

3. The back contact solar cell of claim 1, wherein, a passivation anti-reflection layer covering the P-type doped layer, the N-type doped layer, the first surface, the second surface and the sidewall of the substrate.

4. The back contact solar cell of claim 1, wherein, an interface passivation layer between the N-type doped layer and the substrate, and between the P-type doped layer and the substrate.

5. The back contact solar cell of claim 1, wherein, the first edge isolation region further comprises: a fifth segment between the first segment and the second segment, the fifth segment has a sidewall inclined relative to surfaces of the second segment and the first segment.

6. The back contact solar cell of claim 5, wherein, a lateral width of the first segment is 1-45 microns, a lateral width of the second segment is 0.2-8 microns, and a lateral width of the fifth segment is 0.5-10 microns.

7. The back contact solar cell of claim 1 wherein, the second edge isolation region further comprises: a sixth segment between the fourth segment and the P-type doped layer.

8. The back contact solar cell of claim 7, wherein, a lateral width of the third segment is 5-50 microns, a lateral width of the fourth segment is 5-250 microns, and a lateral width of the sixth segment is 0.5-10 microns.

9. The back contact solar cell of claim 1 wherein, a lateral width of the first edge isolation region is 2-50 microns, and a lateral width of the second edge isolation region is 20-300 microns; or, the lateral width of the second edge isolation region is greater than the width of the first edge isolation region.

10. The back contact solar cell of claim 1 wherein, the first textured structure and the second textured structure on the third segment have different topographies.

11. The back contact solar cell of any of claims 1 to 10, wherein, the first textured structure comprises a plurality of first pyramidal structures, and the second textured structure on the third segment comprises a plurality of second pyramidal structures; a distribution density of the first pyramidal structures is less than a distribution density of the second pyramidal structures; or, an average spacing between adjacent first pyramidal structures is greater than an average spacing between adjacent second pyramidal structures; or, ​ The first type of pyramid structure has a larger top angle than the second type of pyramid structure; or The first type of pyramid structure has a smaller aspect ratio than the second type of pyramid structure.

12. The back contact solar cell of claim 11, wherein, The second surface has a third textured structure; the third textured structure includes a plurality of third type of pyramid structures. The second type of pyramid structure has a larger top angle than the third type of pyramid structure.

13. The back contact solar cell of any one of claims 1-10, wherein In the orthographic projection of the substrate, the first textured structure has a smaller projected area than the second textured structure.

14. The back contact solar cell of any one of claims 1-10, wherein The profile line of the first edge isolation region on the sidewall includes a wavy segment.

15. The back contact solar cell of claim 11, wherein, The first surface includes a third isolation region between the adjacent N-type doped layer and P-type doped layer; the third isolation region has a fourth textured structure thereon, the fourth textured structure includes a plurality of fourth type of pyramid structures; the fourth type of pyramid structure has a larger size than the second type of pyramid structure.

16. The back contact solar cell of claim 5, wherein, The surface of the first segment has a first included angle with the surface of the second segment, and the sidewall of the fifth segment has a second included angle with the surface of the second segment, the first included angle being larger than the second included angle.

17. A photovoltaic module, characterized by The back contact solar cell of any one of claims 1-16. The back contact solar cell of any one of claims 1-16.

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