Interdigitated-back-contact photovoltaic cell, and system

Abstract

Disclosed in the present disclosure is an interdigitated-back-contact photovoltaic cell, comprising: a silicon substrate, wherein the back surface of the silicon substrate comprises a P-type doped region and an N-type doped region, at least one of which is provided with a non-polished surface, the non-polished surface including at least one of conical structure, pyramidal structure, inverted conical structure, inverted pyramidal structure, truncated conical structure, truncated pyramidal structure, wormhole structure, polygonal pit structure, and vertical pore structure.

Description

Back contact photovoltaic cells and systems

[0001] Cross-reference to related applications

[0002] This disclosure takes priority from the patent application filed on February 10, 2025, with application number 2025202101301 and entitled "A Back Contact Solar Cell, Photovoltaic Module and Photovoltaic System", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of solar cell technology, and in particular to a back-contact solar cell, photovoltaic module, and photovoltaic system. Background Technology

[0004] Interdigitated back contact (IBC) solar cells, also known as interdigitated back contact solar cells, have both positive and negative electrode grids located on the back of the cell. This completely eliminates the shading caused by the metal grids on the front surface, preventing optical losses. Furthermore, the electrode grids can be designed to be wider than existing types, reducing series resistance losses and significantly improving cell conversion efficiency. In addition, the absence of electrode grids on the front results in a more aesthetically pleasing product, making it suitable for various applications.

[0005] In existing technologies, back-contact solar cells typically only have a textured surface prepared on the front side of the silicon substrate, while the P-type and N-type doped regions on the back side of the silicon substrate are usually prepared into polished surfaces using alkaline polishing or acid polishing. This results in a low bifaciality of the cells, affecting the power output of photovoltaic modules composed of back-contact solar cells, and thus impacting power generation.

[0006] Application content

[0007] This disclosure provides a back-contact solar cell, which aims to solve the problem of low bifaciality of existing back-contact solar cells, thus affecting power generation.

[0008] This disclosure is implemented by providing a back-contact solar cell, including a silicon substrate having a front side and a back side disposed opposite to each other, the back side including a P-type doped region and an N-type doped region, at least one of the P-type doped region and the N-type doped region being provided with a non-polished surface;

[0009] The microstructure of the unpolished surface includes one of the following: a conical structure, a pyramidal structure, an inverted conical structure, an inverted pyramidal structure, a truncated conical structure, a truncated pyramidal structure, a wormhole structure, a polygonal pit structure, and a vertical hole structure; the side surfaces of the conical structure, the pyramidal structure, the truncated conical structure, and the truncated pyramidal structure, as well as the inner surfaces of the inverted conical structure and the inverted pyramidal structure, are provided with a plurality of anti-reflection structures; or,

[0010] The microstructure of the unpolished surface includes at least two of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, the pyramidal structure with its apex removed, the wormhole structure, the polygonal pit structure, and the vertical hole structure, either superimposed or combined.

[0011] In some embodiments, the antireflective structure is a pit structure, wherein the average maximum size of the opening of all the pits per unit area is less than 300 nanometers.

[0012] In some embodiments, the antireflective structure is a raised structure, and the average value of the maximum bottom surface size of all the raised structures per unit area is less than 300 nanometers.

[0013] In some embodiments, the microstructure of the unpolished surface satisfies at least one of the following: the cone angle of the conical structure is 15 to 45 degrees; the cone angle of the cone structure with the tip removed is 15 to 45 degrees.

[0014] In some embodiments, the microstructure of the unpolished surface includes a plurality of first pyramidal structures and a plurality of second pyramidal structures, wherein the base area of ​​the first pyramidal structure is larger than the base area of ​​the second pyramidal structure, and at least a portion of the first pyramidal structures are stacked on the surface away from the front face with the second pyramidal structure.

[0015] In some embodiments, the side surfaces of the conical structure, the pyramidal structure, the cone structure with its apex removed, or the pyramidal structure with its apex removed are provided with a textured surface.

[0016] In some embodiments, the textured structure is a ring or spiral shape surrounding the side surface.

[0017] In some embodiments, the top of the conical structure, the pyramidal structure, the cone structure with its apex removed, or the pyramidal structure with its apex removed has a concave-convex structure.

[0018] In some embodiments, the microstructure of the unpolished surface satisfies at least one of the following: the top surface area of ​​the cone structure with the apex removed is greater than 10 square nanometers; the top surface area of ​​the pyramid structure with the apex removed is greater than 10 square nanometers.

[0019] In some embodiments, the inner wall of the wormhole structure is provided with at least one of the pyramidal structure and the conical structure.

[0020] In some embodiments, the inner wall surface of the wormhole structure is provided with a plurality of the anti-reflection structures.

[0021] In some embodiments, the ratio of the depth of the wormhole structure to the maximum size of the opening of the wormhole structure is less than 0.5.

[0022] In some embodiments, the average maximum size of the openings of all the polygonal pit structures per unit area is 100 nanometers to 10 micrometers.

[0023] In some embodiments, the inner wall of the polygonal pit structure is provided with a plurality of the anti-reflection structures.

[0024] In some embodiments, the cross-section of the vertical hole structure is a circular hole or an elliptical hole.

[0025] In some embodiments, the aperture of the vertical hole structure decreases sequentially from the back side to the front side.

[0026] In some embodiments, the aperture of the vertical hole structure increases sequentially from the back side to the front side.

[0027] In some embodiments, the average pore size of all the vertical pore structures per unit area is 10 nanometers to 10 micrometers.

[0028] In some embodiments, the microstructure of the unpolished surface of the P-type doped region is one of the wormhole structure, the polygonal pit structure, and the vertical hole structure.

[0029] In some embodiments, the microstructure of the unpolished surface of the N-type doped region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with the apex removed, and the pyramidal structure with the apex removed.

[0030] In some embodiments, the microstructure of the unpolished surface of the P-type doped region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with the apex removed, and the pyramidal structure with the apex removed.

[0031] The microstructure of the unpolished surface of the N-type doped region is a superposition of at least two of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the truncated conical structure, and the truncated pyramidal structure.

[0032] In some embodiments, the microstructure of the unpolished surface of the P-type doped region is one of the wormhole structure, the polygonal pit structure, and the vertical hole structure;

[0033] The microstructure of the unpolished surface of the N-type doped region is one of the following: a wormhole structure superimposed with at least one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the truncated conical structure, and the truncated pyramidal structure; the polygonal pit structure; the vertical hole structure.

[0034] In some embodiments, the back surface further includes an isolation region located between the P-type doped region and the N-type doped region, wherein the surface microstructure of the isolation region is one of the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the truncated conical structure, and the truncated pyramidal structure.

[0035] In some embodiments, the back surface further includes an isolation region located between the P-type doped region and the N-type doped region, the surface of which is a polished surface.

[0036] In some embodiments, the back-contact solar cell further includes an electrode disposed on the back side, and the unpolished surface includes an electrode region corresponding to the position of the electrode and a non-electrode region not corresponding to the position of the electrode;

[0037] The microstructure of the unpolished surface of the electrode region is a superposition of at least two of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, and the pyramidal structure with its apex removed; the microstructure of the unpolished surface of the non-electrode region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, and the pyramidal structure with its apex removed.

[0038] This disclosure also provides a photovoltaic module, including the aforementioned back-contact solar cell.

[0039] This disclosure also provides a photovoltaic system including the photovoltaic module described above.

[0040] This disclosure provides a back-contact solar cell by providing an unpolished surface in at least one of the P-type doped region and the N-type doped region. The microstructure of the unpolished surface includes one or more of the following: a conical structure, a pyramidal structure, an inverted conical structure, an inverted pyramidal structure, a truncated conical structure, a truncated pyramidal structure, a wormhole structure, a polygonal pit structure, and a vertical hole structure, or a combination of two of these structures. The unpolished surface structure reduces the reflectivity of incident light from the back of the silicon substrate, increases the bifaciality of the back-contact solar cell, thereby increasing the power of the photovoltaic module composed of the back-contact solar cell and increasing the power generation of the photovoltaic module. At the same time, by providing an unpolished surface in at least one of the P-type doped region and the N-type doped region, the surface roughness of the P-type doped region and / or the surface roughness of the N-type doped layer can be increased, which can increase the bonding pull between the electrodes of the P-type doped region and / or the electrodes of the N-type doped region, thereby improving the structural stability of the back-contact solar cell. Attached Figure Description

[0041] Figure 1 is a schematic diagram of the structure of a back-contact solar cell provided in an embodiment of this disclosure;

[0042] Figure 2 is a schematic diagram of the silicon substrate structure of the back-contact solar cell provided in an embodiment of this disclosure;

[0043] Figure 3 is a schematic diagram of the first type of microstructure of the unpolished surface of the back contact solar cell provided in an embodiment of this disclosure;

[0044] Figure 4 is a schematic diagram of the second microstructure of the unpolished surface of the back-contact solar cell provided in an embodiment of this disclosure;

[0045] Figure 5 is a schematic diagram of the third microstructure of the unpolished surface of the back-contact solar cell provided in an embodiment of this disclosure;

[0046] Figure 6 is a schematic diagram of the fourth microstructure of the unpolished surface of the back-contact solar cell provided in an embodiment of this disclosure;

[0047] Figure 7 is a schematic diagram of the fifth microstructure of the unpolished surface of the back-contact solar cell provided in the embodiments of this disclosure;

[0048] Figure 8 is a schematic diagram of the sixth microstructure of the unpolished surface of the back-contact solar cell provided in the embodiments of this disclosure;

[0049] Figure 9 is a schematic diagram of the seventh microstructure of the unpolished surface of the back-contact solar cell provided in the embodiments of this disclosure;

[0050] Figure 10 is a schematic diagram of the eighth microstructure of the unpolished surface of the back-contact solar cell provided in the embodiments of this disclosure;

[0051] Figure 11 is a schematic diagram of the ninth microstructure of the unpolished surface of the back-contact solar cell provided in the embodiments of this disclosure. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this disclosure and are not intended to limit this disclosure.

[0053] This disclosure provides a back-contact solar cell by providing an unpolished surface in at least one of the P-type doped region and the N-type doped region. The microstructure of the unpolished surface includes one or more of the following: a conical structure, a pyramidal structure, an inverted conical structure, an inverted pyramidal structure, a truncated conical structure, a truncated pyramidal structure, a wormhole structure, a polygonal pit structure, and a vertical hole structure, or a combination of two of these. The unpolished surface structure reduces the reflectivity of the back side of the silicon substrate to back-incident light, increasing the bifaciality of the back-contact solar cell, thereby increasing the power output of the photovoltaic module composed of the back-contact solar cell and increasing the power generation of the photovoltaic module. Simultaneously, by providing an unpolished surface in at least one of the P-type doped region and the N-type doped region, the surface roughness of the P-type doped layer in the P-type doped region and / or the surface roughness of the N-type doped layer in the N-type doped region can be increased, thereby increasing the bonding pull of the electrodes in the P-type doped region and / or the bonding pull of the electrodes in the N-type doped region, thus improving the structural stability of the back-contact solar cell.

[0054] Please refer to Figures 1-2. The present disclosure provides a back-contact solar cell, which includes a silicon substrate 1. The silicon substrate 1 has a front side 2 and a back side 3 disposed opposite to each other. The back side 3 includes a P-type doped region 31 and an N-type doped region 32. At least one of the P-type doped region 31 and the N-type doped region 32 is provided with a non-polished surface.

[0055] Please refer to Figures 3-11. The microstructure of the unpolished surface includes one of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure (not shown), an inverted pyramidal structure 54, a conical structure with its apex removed (not shown), a pyramidal structure with its apex removed (not shown), a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57. The side surfaces of the conical structure 51, pyramidal structure 52, the conical structure with its apex removed, and the pyramidal structure with its apex removed are provided with several anti-reflection structures. The inner surfaces of the inverted conical structure and the inverted pyramidal structure 54 are provided with several anti-reflection structures.

[0056] The microstructure of the unpolished surface includes at least two of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, truncated conical structure, truncated pyramidal structure, wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57, in combination or in combination.

[0057] In this embodiment, the front side 2 of the silicon substrate 1 is the side facing sunlight when the back-contact solar cell is operating, and the back side 3 of the silicon substrate 1 is the side facing away from sunlight when the back-contact solar cell is operating. An isolation region 33 is provided between the P-type doped region 31 and the N-type doped region 32 to physically isolate them. The specific number of P-type doped regions 31 and N-type doped regions 32 is not limited. Optionally, there are multiple P-type doped regions 31 and N-type doped regions 32, which are arranged alternately and at intervals.

[0058] In this embodiment, the front side of the silicon substrate 1 is textured to reduce the front light reflectivity. The P-type doped region 31 is the region where the P-type doped layer 6 is disposed, and the N-type doped region 32 is the region where the N-type doped layer 7 is disposed. The P-type doped layer 6 can be one or a combination of P-type polycrystalline silicon, P-type microcrystalline silicon, P-type nanocrystalline silicon, and P-type amorphous silicon, and the N-type doped layer 7 can be one or a combination of N-type polycrystalline silicon, N-type microcrystalline silicon, N-type nanocrystalline silicon, and N-type amorphous silicon.

[0059] In this embodiment of the present disclosure, at least one of the P-type doped region 31 and the N-type doped region 32 is provided with a non-polished surface. This can be understood as the P-type doped region 31 and the N-type doped region 32 being provided with non-polished surfaces simultaneously, or the P-type doped region 31 or the N-type doped region 32 being provided with a non-polished surface.

[0060] When the P-type doped region 31 has a non-polished surface, only a portion of the P-type doped region 31 can be non-polished, or the entire P-type doped region 31 can be non-polished. When only a portion of the P-type doped region 31 is non-polished, each P-type doped region 31 can have a non-polished surface, but at least one P-type doped region 31 can have a portion of a polished surface; or, only a portion of the P-type doped regions 31 can have a non-polished surface, while the other portion can have a polished surface. In this way, the P-type doped region 31 utilizes a combination of non-polished and polished surfaces. The non-polished surface improves the utilization rate of sunlight by the P-type doped region 31 on the back side, increasing the bifaciality of the battery. Simultaneously, the polished surface reduces surface recombination losses of the P-type doped region 31 and improves the passivation performance of the back film layer of the P-type doped region 31, thus improving battery efficiency.

[0061] Similarly, when the N-type doped region 32 has a non-polished surface, only a portion of the N-type doped region 32 can be non-polished, or the entire N-type doped region 32 can be non-polished. When only a portion of the N-type doped region 32 is non-polished, each N-type doped region 32 can have a non-polished surface, but at least one N-type doped region 32 can have a portion of a polished surface; or, only a portion of the N-type doped regions 32 can have a non-polished surface, while the other portion can have a polished surface. In this way, the N-type doped region 32 utilizes a combination of non-polished and polished surfaces. The non-polished surface improves the utilization rate of sunlight by the N-type doped region 32 on the back side, increasing the bifaciality of the battery. Simultaneously, the polished surface reduces surface recombination losses of the N-type doped region 32 and improves the passivation performance of the back film layer of the N-type doped region 32, thus improving battery efficiency.

[0062] In this embodiment, the isolation region 33 can be textured to further reduce the reflectivity of the back side of the silicon substrate 1 to back-incident sunlight, thereby improving the bifaciality of the cell. The microstructure of the textured surface of the isolation region 33 can be the same as or different from the microstructure of the unpolished surface of the P-type doped region 31 or the N-type doped region 32. Of course, in some other embodiments, the isolation region 33 can also be polished.

[0063] As an embodiment of this disclosure, both the P-type doped region 31 and the N-type doped region 32 are provided with unpolished surfaces. The fact that both the P-type doped region 31 and the N-type doped region 32 are provided with unpolished surfaces can simultaneously improve the utilization rate of sunlight by the P-type doped region 31 and the N-type doped region 32 on the back side, further improving the bifaciality of the cell. Moreover, it is beneficial to increase the bonding pull of the electrode of the P-type doped region 31 and the electrode of the N-type doped region 32, and at the same time, it can increase the bonding force of the back film layer, thereby further improving the structural stability of the back contact solar cell.

[0064] As an embodiment of this disclosure, the microstructure of the unpolished surface includes one of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, a pyramidal structure with its apex removed, a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57; the side surfaces of the conical structure 51, the pyramidal structure 52, the conical structure with its apex removed, and the pyramidal structure with its apex removed, as well as the inner surfaces of the inverted conical structure and the inverted pyramidal structure 54, are provided with a plurality of anti-reflection structures.

[0065] In this embodiment, the microstructure of the unpolished surface is one of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, conical structure with truncated apex, pyramidal structure with truncated apex, wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57. Setting the microstructure of the unpolished surface to one of the above-mentioned types can reduce the light reflectivity of the back side of the silicon substrate 1 and improve the bifaciality of the back contact solar cell compared to the polished surface. Moreover, the microstructure of the unpolished surface is of a single type, which facilitates the processing and fabrication of the unpolished surface.

[0066] In this embodiment of the disclosure, the anti-reflection structure can be a pit or a protrusion. By setting a number of anti-reflection structures on the side surface of the conical structure, pyramidal structure, conical structure with the tip removed, pyramidal structure with the tip removed, and the inner surface of the inverted conical structure and inverted pyramidal structure, the anti-reflection structure is used to further reduce the light reflectivity of the non-polished surface when sunlight shines on the back side, thereby further improving the utilization rate of sunlight on the back side of the battery.

[0067] As one embodiment of this disclosure, the anti-reflection structure is a pit, and the average maximum opening size of all pits within a unit area is less than 300 nanometers. The unit area can be a portion of the unpolished surface or the entire unpolished surface. The maximum opening size of the pit is the maximum distance between two points on the edge of the pit's opening. The pit can be a polygonal pit or an irregularly shaped pit. By controlling the average maximum opening size of all pits within a unit area to be less than 300 nanometers, the light reflectivity of the unpolished surface can be further reduced, improving the bifaciality of the battery. Further, in some embodiments, the anti-reflection structure is a pit, and the average maximum opening size of all pits within a unit area is less than 100 nanometers, which can further reduce the light reflectivity of the unpolished surface.

[0068] As another embodiment of this disclosure, the antireflective structure is a protrusion, and the average value of the maximum bottom surface size of all protrusions per unit area is less than 300 nanometers.

[0069] The unit area can be a portion or the entire area of ​​the unpolished surface. The maximum dimension of the bottom surface of the protrusion is the maximum distance between two points on the bottom surface of the protrusion. The protrusion can be a regular pyramidal protrusion, an irregular pyramidal protrusion, or a protrusion of other shapes. By controlling the average maximum dimension of the bottom surface of all protrusions within a unit area to be less than 300 nanometers, the light reflectivity of the unpolished surface can be further reduced, and the bifaciality of the battery can be improved.

[0070] Furthermore, in some embodiments, the antireflection structure is a protrusion, and the average value of the maximum bottom surface size of all protrusions per unit area is less than 100 nanometers, which can further reduce the light reflectivity of the unpolished surface.

[0071] Referring to Figure 3, as an embodiment of this disclosure, the microstructure of the unpolished surface is a conical structure 51. Using the conical structure 51 as the microstructure of the unpolished surface can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. The unpolished surface is composed of several conical structures 51; these conical structures 51 can be spaced apart from each other, and adjacent conical structures 51 can be stacked on top of each other. The dimensions of different conical structures 51 can be the same or different.

[0072] In some embodiments, the cone angle of the conical structure 51 is 15 to 45 degrees. For example, the cone angle of the conical structure 51 can be any value among 15, 20, 22, 28, 30, 35, 40, and 45 degrees. The cone angle of the conical structure 51 is the angle between the two generatrices of the axial section of the cone (the section passing through the axis of the cone). By setting the cone angle of the conical structure 51 to 15 to 45 degrees, a lower light reflectivity on the unpolished surface can be achieved, increasing the utilization rate of sunlight on the back of the battery.

[0073] As an embodiment of this disclosure, the side surface of the conical structure 51 is provided with a plurality of the aforementioned anti-reflection structures. Among them, the anti-reflection structure on the side surface of the conical structure 51 shown in FIG3 is a pit 511.

[0074] When the microstructure of the non-polished surface is a conical structure 51, the conical structure 51 can be prepared by reactive ion etching or wet black silicon technology.

[0075] Referring to Figures 4 and 5, in one embodiment of this disclosure, the microstructure of the unpolished surface is a pyramidal structure 52. Using the pyramidal structure 52 as a textured surface reduces the light reflectivity of the unpolished surface and improves the utilization rate of sunlight on the back of the battery. The unpolished surface is composed of several pyramidal structures 52; these pyramidal structures 52 can be spaced apart from each other, and adjacent pyramidal structures 52 can be stacked to form a composite pyramidal structure 52 (as shown in Figure 4). The pyramidal structure 52 of the unpolished surface can be a standard pyramidal structure (as shown in Figure 4) or an irregularly shaped pyramidal structure (as shown in Figure 5). The pyramidal structure 52 can have three sides and one base, i.e., a pyramidal structure; or, the pyramidal structure 52 can have four sides and one base; or, the pyramidal structure 52 can have five sides and one base; or, the pyramidal structure 52 can have six sides and one base; of course, the pyramidal structure 52 can also have an even greater number of sides and one base.

[0076] As an embodiment of this disclosure, the side surface of the pyramidal structure 52 is provided with a plurality of the aforementioned anti-reflection structures. By providing a plurality of anti-reflection structures on the side surface of the pyramidal structure 52, the reflection of sunlight by the side surface of the cone structure 51 is further reduced by the pyramidal structure 52, thereby further reducing the light reflectivity of the unpolished surface and further improving the utilization rate of sunlight on the back of the battery.

[0077] When the microstructure of the non-polished surface is a pyramidal structure 52, the pyramidal structure 52 can be prepared by reactive ion etching.

[0078] As one embodiment of this disclosure, the microstructure of the unpolished surface is an inverted cone structure (not shown). Using an inverted cone structure as a textured surface can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. The unpolished surface is composed of several inverted cone structures; these inverted cone structures can be spaced apart from each other, and adjacent inverted cone structures can be stacked to form a composite inverted cone structure.

[0079] As one embodiment of this disclosure, a plurality of the aforementioned anti-reflection structures are provided on the side surface of the inverted conical structure. By providing a plurality of anti-reflection structures on the side surface of the inverted conical structure, the reflection of sunlight by the side surface of the inverted conical structure is further reduced, thereby further reducing the light reflectivity of the unpolished surface and further improving the utilization rate of sunlight on the back of the battery.

[0080] Referring to Figure 7, as an embodiment of this disclosure, the microstructure of the unpolished surface is an inverted pyramidal structure 54. Using the inverted pyramidal structure 54 as a textured surface can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. The unpolished surface is composed of an array of several inverted pyramidal structures 54; the several inverted pyramidal structures 54 can be spaced apart from each other, and adjacent inverted pyramidal structures 54 can also be stacked. Specifically, the inverted pyramidal structure 54 can be formed using wet black silicon technology or copper ion-assisted acid etching.

[0081] As one embodiment of this disclosure, the inner surface of the inverted pyramid structure 54 is provided with a plurality of the aforementioned anti-reflection structures. By providing a plurality of anti-reflection structures on the inner surface of the inverted pyramid structure 54, the reflection of sunlight by the inner surface of the inverted pyramid structure is further reduced by utilizing the inverted cone structure, thereby further reducing the light reflectivity of the unpolished surface and further improving the utilization rate of sunlight on the back of the battery.

[0082] As one embodiment of this disclosure, the microstructure of the unpolished surface is a cone structure with its tip truncated (not shown). Using a cone structure with its tip truncated as a textured surface can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. Simultaneously, since the top of the truncated cone structure is relatively flat, surface recombination losses on the unpolished surface can be reduced, thereby improving the passivation performance of the back film layer on the unpolished surface.

[0083] The unpolished surface consists of several conical structures with their tips removed; these conical structures can be spaced apart from each other, and adjacent conical structures with their tips removed can also be stacked on top of each other.

[0084] In some embodiments, the cone angle of the truncated cone structure is between 15 and 45 degrees. For example, the cone angle of the truncated cone structure can be any value among 15, 20, 22, 28, 30, 35, 40, and 45 degrees. The cone angle of the truncated cone structure is the angle between the two generatrices of the axial section of the cone (the section passing through the axis of the cone). By setting the cone angle of the truncated cone structure to 15–30 degrees, a lower light reflectivity on the unpolished surface can be achieved, increasing the utilization rate of sunlight on the back of the battery.

[0085] As one embodiment of this disclosure, the top surface area of ​​the cone structure with the tip removed is greater than 10 square nanometers, making the top of the cone structure with the tip removed flatter, which can give the unpolished surface a better passivation effect.

[0086] As one embodiment of this disclosure, a plurality of the aforementioned anti-reflection structures are provided on the side surface of the cone structure with its tip removed. By providing a plurality of anti-reflection structures on the side surface of the cone structure with its tip removed, the reflection of sunlight by the side surface of the cone structure with its tip removed is further reduced, thereby further reducing the light reflectivity of the unpolished surface and further improving the utilization rate of sunlight on the back of the battery.

[0087] As one embodiment of this disclosure, the microstructure of the unpolished surface is a pyramidal structure with its apex truncated (not shown). Using this truncated pyramidal structure as a textured surface reduces the light reflectivity of the unpolished surface, improving the utilization rate of sunlight on the back of the battery. Simultaneously, because the top of the truncated pyramidal structure is relatively flat, surface recombination losses on the unpolished surface can be reduced, thus improving the passivation performance of the back film layer on the unpolished surface.

[0088] The unpolished surface is composed of an array of several pyramidal structures with their apexes removed; these pyramidal structures can be spaced apart from each other, and adjacent pyramidal structures with their apexes removed can also be stacked on top of each other.

[0089] As one embodiment of this disclosure, a plurality of anti-reflection structures are provided on the side surface of the truncated pyramidal structure. By providing a plurality of anti-reflection structures on the side surface of the truncated pyramidal structure, the reflection of sunlight by the side surface of the truncated pyramidal structure is further reduced, thereby further reducing the light reflectivity of the unpolished surface and further improving the utilization rate of sunlight on the back of the battery.

[0090] As one embodiment of this disclosure, the top surface area of ​​the truncated pyramidal structure is greater than 10 square nanometers, which can give the unpolished surface a better passivation effect.

[0091] Referring to Figures 8 and 9, as an embodiment of this disclosure, the microstructure of the unpolished surface is a wormhole structure 55. The wormhole structure 55 is a wormhole-shaped structure with an opening at the top. The length or width of the opening of the wormhole structure 55 may be equal or unequal. The unpolished surface is composed of an array of several wormhole structures 55; the several wormhole structures 55 may be spaced apart from each other, and adjacent wormhole structures 55 may overlap. The depths of different wormhole structures 55 may be the same or different; the opening areas of different wormhole structures 55 may be the same or different; and the shapes and sizes of different wormhole structures 55 may be the same or different.

[0092] In this embodiment, the wormhole structure 55 is used as a textured surface structure, which can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. Since the wormhole structure 55 is flatter than the conical structure 51 or the pyramidal structure 52, it is also conducive to reflecting sunlight from the front, thus taking into account both back and front light reflection; at the same time, it can reduce the surface recombination loss of the unpolished surface and improve the passivation performance of the back film layer of the unpolished surface.

[0093] In this embodiment, when the microstructure of the non-polished surface is a wormhole structure 55, it can be prepared by acid etching, alkaline etching, metal ion-assisted etching, or reactive ion etching. Specifically, the microstructure of the non-polished surface shown in Figure 8 is prepared by acid etching; the microstructure of the non-polished surface shown in Figure 9 is prepared by alkaline etching, metal ion-assisted etching, or reactive ion etching.

[0094] As one embodiment of this disclosure, the ratio of the depth of the wormhole structure 55 to the maximum size of the opening of the wormhole structure 55 is less than 0.5.

[0095] In this embodiment, the maximum size of the opening of the wormhole structure 55 is the maximum distance between two points on the edge of the opening of the wormhole structure 55. The ratio of the depth of the wormhole structure 55 to the length of the longest diagonal of its opening is controlled to be less than 0.5. At this ratio, the wormhole structure 55 has a low light reflectivity, improving the utilization rate of sunlight on the back of the battery. Simultaneously, the shallow depth of the wormhole structure 55 allows for good passivation performance of the non-polished back film layer, enabling the battery to have good photoelectric conversion efficiency.

[0096] As one embodiment of this disclosure, the inner wall surface of the wormhole structure 55 is provided with a plurality of the aforementioned anti-reflection structures. By providing a plurality of anti-reflection structures on the inner wall surface of the wormhole structure 55, the reflection of sunlight by the inner wall surface of the wormhole structure 55 is further reduced by the anti-reflection structures, thereby further reducing the reflectivity of sunlight on the back side of the non-polished surface and further improving the utilization rate of sunlight on the back side of the battery.

[0097] Referring to Figure 9, the inner wall surface of the wormhole structure 55 is provided with several pyramidal structures 52 to form a composite velvety structure of the wormhole structure 55 and the pyramidal structure 52, which can further reduce the light reflectivity of the non-polished surface.

[0098] Please refer to Figure 10. As an embodiment of this disclosure, the microstructure of the non-polished surface is a polygonal pit structure 56.

[0099] The polygonal pit structure 56 is a pit-shaped structure with polygonal openings. The length or width of the openings in the wormhole structure 55 can be equal or unequal. The unpolished surface is composed of an array of polygonal pit structures 56; these polygonal pit structures 56 can be spaced apart from each other, and adjacent polygonal pit structures 56 can overlap. The depths of different polygonal pit structures 56 can be the same or different; the opening sizes of different polygonal pit structures 56 can be the same or different. The openings of the polygonal pit structures 56 can be quadrilateral, pentagonal, hexagonal, octagonal, or other shapes.

[0100] In this embodiment, the polygonal pit structure 56 is used as a textured surface structure, which can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. Moreover, since the opening of the polygonal pit structure 56 has sharp edges and is flatter than the pyramid structure, it can take into account the light reflection effect of the back and the light reflection effect of the front, thereby achieving a balance between the light reflection effect of the back and the light reflection effect of the front, and also helps to maintain a good passivation effect on the back.

[0101] In this embodiment, when the microstructure of the non-polished surface is a polygonal pit structure 56, it can be prepared using wet black silicon technology or alkaline etching.

[0102] As one embodiment of this disclosure, the inner wall of the polygonal pit structure 56 is provided with a plurality of anti-reflection structures.

[0103] In this embodiment, by setting a plurality of anti-reflection structures on the inner wall surface of the polygonal pit structure 56, the reflection of sunlight on the inner wall surface of the polygonal pit structure 56 is further reduced by the anti-reflection structures, thereby further reducing the reflectivity of sunlight on the back side of the non-polished surface and further improving the utilization rate of sunlight on the back side of the battery.

[0104] As one embodiment of this disclosure, the average maximum size of the openings of all polygonal pit structures 56 per unit area is 100 nanometers to 10 micrometers.

[0105] The unit area can be a portion or the entire area of ​​the unpolished surface. The maximum size of the opening of the polygonal pit structure 56 is the maximum distance between two points on the edge of the opening of the polygonal pit structure 56. By controlling the average maximum size of the openings of all polygonal pit structures 56 within a unit area to be between 100 nanometers and 10 micrometers, the light reflectivity of the unpolished surface can be further reduced, and the bifaciality of the battery can be improved.

[0106] Referring to Figure 11, as an embodiment of this disclosure, the microstructure of the non-polished surface is a vertical hole structure 57. The central axis of the vertical hole structure 57 is perpendicular to the back surface of the silicon substrate 1, that is, the central axis of the vertical hole structure 57 is along the thickness direction of the silicon substrate 1. The depth of the vertical hole structure 57 is greater than the maximum size of its opening. The aperture of the vertical hole structure 57 can be uniformly or non-uniformly distributed.

[0107] In this embodiment, the unpolished surface includes a plurality of vertical hole structures 57. Utilizing the vertical hole structures 57 as a textured surface can reduce the light reflectivity of the unpolished surface and improve the utilization rate of sunlight on the back of the battery. The unpolished surface is composed of an array of a plurality of vertical hole structures 57; the plurality of vertical hole structures 57 can be arranged at intervals between each other, and adjacent vertical hole structures 57 can also partially overlap each other.

[0108] As one embodiment of this disclosure, the cross-section of the vertical hole structure 57 is a circular hole or an elliptical hole.

[0109] In this embodiment, the cross-section of the vertical hole structure 57 is perpendicular to the thickness direction of the silicon substrate 1. The cross-section of the vertical hole structure 57 is a circular hole or an elliptical hole. Of course, the cross-section of the vertical hole structure 57 can also be other irregular shapes.

[0110] As one embodiment of this disclosure, the aperture of the vertical hole structure 57 is 10 nanometers to 10 micrometers, which can further reduce back light reflection.

[0111] As one embodiment of this disclosure, the aperture of the vertical hole structure 57 decreases sequentially from the back side 3 to the front side 2.

[0112] In this embodiment, the aperture of the vertical aperture structure 57 gradually decreases from the back side 3 to the front side 2, making the outer aperture of the vertical aperture structure 57 larger. This allows the light receiving area of ​​the vertical aperture structure 57 to be larger, thereby improving the light conversion efficiency.

[0113] In another embodiment of this disclosure, the aperture of the vertical hole structure 57 increases sequentially from the back side 3 to the front side 2.

[0114] In this embodiment, the aperture of the vertical hole structure 57 gradually increases from the back side 3 to the front side 2, making the outer aperture of the vertical hole structure 57 smaller, which is beneficial to improving the light trapping effect. Sunlight entering the vertical hole structure 57 is not easily reflected out, which is beneficial to further reduce back light reflection.

[0115] As an embodiment of this disclosure, the inner surface of the vertical aperture structure 57 is provided with a plurality of the above-mentioned anti-reflection structures to further reduce the light reflectivity of the vertical aperture structure 57.

[0116] As another embodiment of this disclosure, the microstructure of the unpolished surface includes a superposition of at least two of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, a pyramidal structure with its apex removed, a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57.

[0117] In this embodiment, the microstructure of the non-polished surface is a superposition of at least two of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, conical structure with the tip removed, pyramidal structure with the tip removed, wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57, with the two different microstructures being at least partially superimposed.

[0118] For example, a cone structure 51 may be stacked with one, two, or more of the following: a pyramidal structure 52, an inverted cone structure, an inverted pyramidal structure 54, a cone structure with its apex removed, or a pyramidal structure with its apex removed. Similarly, a pyramidal structure 52 may be stacked with one, two, or more of the following: a cone structure 51, an inverted cone structure, an inverted pyramidal structure 54, a cone structure with its apex removed, or a pyramidal structure with its apex removed. Likewise, an inverted cone structure may be stacked with one, two, or more of the following: a cone structure 51, a pyramidal structure 52, an inverted pyramidal structure 54, a cone structure with its apex removed, or a pyramidal structure with its apex removed. Furthermore, the inner wall surface of a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57 may be provided with a cone structure 51, a pyramidal structure 52, an inverted cone structure, an inverted pyramidal structure 54, a cone structure with its apex removed, or a pyramidal structure with its apex removed. As shown in Figure 9, the inner wall surface of the wormhole structure 55 is provided with a pyramidal structure 52, forming a composite velvety structure composed of the wormhole structure 55 and the pyramidal structure 52. Alternatively, at least one of the following can be provided on the surface of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, or a pyramidal structure with its apex removed: wormhole structure 55, polygonal pit structure 56, or vertical hole structure 57.

[0119] In this embodiment, the microstructure of the unpolished surface includes at least two of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, a pyramidal structure with its apex removed, a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57. This allows the microstructure of the unpolished surface to have two different morphological structures superimposed, which can increase the specific surface area of ​​the unpolished surface and further increase its roughness, resulting in better light trapping effect, further reducing the light reflectivity of the unpolished surface, and improving the adhesion between the electrodes and the film layer of the back contact solar cell, thereby enhancing the stability of the battery structure.

[0120] Please refer to Figure 4 again. As an embodiment of this disclosure, when the microstructure of the non-polished surface includes a pyramidal structure 52, the microstructure of the non-polished surface includes a plurality of first pyramidal structures 521 and a plurality of second pyramidal structures 522. The base area of ​​the first pyramidal structure 521 is larger than the base area of ​​the second pyramidal structure 522, and at least a portion of the first pyramidal structures 521 are stacked with second pyramidal structures 522.

[0121] In this embodiment, the microstructure of the unpolished surface is formed by superimposing two pyramidal structures 52 of different sizes to create a composite pyramidal structure 52 as a textured surface. The unpolished surface may have only a portion of the first pyramidal structures 52 superimposed with the second pyramidal structure 52, or all of the first pyramidal structures 52 on the unpolished surface may be superimposed with the second pyramidal structure 52. By superimposing pyramidal structures 52 of different sizes, the light reflectivity of the unpolished surface can be further reduced, thus reducing the reflectivity of the battery's back surface.

[0122] Please refer to Figure 5 again. As an embodiment of this disclosure, the side surfaces of the conical structure 51, the pyramidal structure 52, the truncated conical structure, or the truncated pyramidal structure are provided with a textured surface 520, which can further reduce the light reflectivity of the side surfaces of the conical structure 51, the pyramidal structure 52, the truncated conical structure, or the truncated pyramidal structure. Figure 5 only illustrates the textured surface 520 on the side surface of the pyramidal structure 52.

[0123] In this embodiment, the raised texture structure 520 is a ring or spiral shape surrounding the side surface. The raised texture structure 520 is an uneven structure, which can be a multi-turn ring or spiral texture; of course, the raised texture structure 520 can also be a dendritic texture. Using the raised texture structure 520 can further reduce back-side light reflection and improve the double-sided ratio. Specifically, the raised texture structure 520 can be formed by reactive ion etching.

[0124] Referring to Figure 6, as another embodiment of this disclosure, the top of the conical structure 51, the pyramidal structure 52, the conical structure with its apex removed, or the pyramidal structure with its apex removed is provided with a concave-convex structure 523.

[0125] In this embodiment, the top of the conical structure 51, the pyramidal structure 52, or the truncated conical or pyramidal structure is provided with a concave-convex structure 523. The concave-convex structure 523 reduces light reflection at the top of the conical structure 51, the pyramidal structure 52, or the truncated conical or pyramidal structure, improving the bifaciality and further enhancing the battery's bifaciality. The specific shape of the concave-convex structure 523 is not limited; it can be a regular or irregular uneven structure. Figure 6 only illustrates that the top of the irregular pyramidal structure 52 has a concave-convex structure 523, which can be formed by two alkaline etching processes.

[0126] As another embodiment of this disclosure, the microstructure of the unpolished surface includes at least two of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, a pyramidal structure with its apex removed, a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57.

[0127] In this embodiment, the non-polished surface region is at least one of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, truncated conical structure, truncated pyramidal structure, wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57. Furthermore, the non-polished surface region is at least another of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, truncated conical structure, truncated pyramidal structure, wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57. That is, the non-polished surface has at least two regions with different microstructures. The non-polished surface utilizes at least two different microstructure combinations, increasing the variety of microstructures and further reducing the light reflectivity of the non-polished surface. Moreover, it can simultaneously improve the surface structure stability of the non-polished surface, thus enhancing the stability of the battery structure.

[0128] In this embodiment, a portion of the P-type doped region 31 may be at least one of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a truncated conical structure, a truncated pyramidal structure, a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57. Furthermore, a portion of the P-type doped region 31 may be at least another of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a truncated conical structure, a truncated pyramidal structure, a wormhole structure 55, a polygonal pit structure 56, and a vertical hole structure 57. For example, a portion of the N-type doped region 32 may be a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a truncated conical structure, or a truncated pyramidal structure, and a portion of the N-type doped region 32 may be a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57. For example, a portion of the P-type doped region 31 may be a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, or a pyramidal structure with its apex removed. Another portion of the P-type doped region 31 may be a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57. This is beneficial for improving the passivation performance of the P-type doped region 31.

[0129] As an embodiment of this disclosure, the microstructure of the unpolished surface of the P-type doped region is one of the following: wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57.

[0130] In this embodiment, since the wormhole structure 55, polygonal pit structure 56, and vertical hole structure 57 are flatter than the cone structure 51, pyramid structure 52, inverted cone structure, inverted pyramid structure 54, cone structure with truncated tip, and pyramid structure with truncated tip, the passivation performance of the P-type doped region 31 can be improved.

[0131] As an embodiment of this disclosure, the microstructure of the unpolished surface of the N-type doped region 32 is one of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with the tip removed, or a pyramidal structure with the tip removed.

[0132] In this embodiment, since the conical structure 51, the pyramidal structure 52, the inverted conical structure, the inverted pyramidal structure 54, the conical structure with the tip removed, and the pyramidal structure with the tip removed have low light reflectivity, the N-type doped region 32 can maintain a low light reflectivity, thereby improving the light utilization rate of the N-type doped region 32.

[0133] As an embodiment of this disclosure, the microstructure of the unpolished surface of the P-type doped region 31 is one of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its tip removed, and a pyramidal structure with its tip removed; the microstructure of the unpolished surface of the N-type doped region 32 is a superposition of at least two of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its tip removed, and a pyramidal structure with its tip removed.

[0134] In this embodiment, the microstructure of the unpolished surface of the P-type doped region 31 has a larger specific surface area and a rougher surface than that of the unpolished surface of the N-type doped region 32. This can further reduce the back light reflection effect of the N-type doped region 32 and improve the passivation performance of the P-type doped region 31. This achieves a match between the good back light reflection performance of the N-type doped region 32 and the good passivation performance of the P-type doped region 31, which is beneficial to further improve battery efficiency.

[0135] For example, the microstructure of the unpolished surface of the P-type doped region 31 is a number of pyramidal structures 52; the microstructure of the unpolished surface of the N-type doped region 32 is a number of pyramidal structures 52 on which conical structures 51, pyramidal structures 52, inverted conical structures, or inverted pyramidal structures 54 are superimposed.

[0136] As an embodiment of this disclosure, the microstructure of the unpolished surface of the P-type doped region 31 is one of a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57; the microstructure of the unpolished surface of the N-type doped region 32 is a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57 superimposed with at least one of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its tip removed, or a pyramidal structure with its tip removed.

[0137] In this embodiment, when the microstructure of the unpolished surface of the P-type doped region 31 is a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57, the microstructure of the unpolished surface of the N-type doped region 32 is also a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57. Simultaneously, the wormhole structure 55, polygonal pit structure 56, or vertical hole structure 57 of the N-type doped region 32 is superimposed with at least one of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a truncated conical structure, or a truncated pyramidal structure. This makes the microstructure of the unpolished surface of the N-type doped region 32 a composite textured surface structure. This allows the P-type doped region 31 to have better passivation performance than the N-type doped region 32, and the N-type doped region 32 to have lower light reflectivity than the P-type doped region 31. This facilitates a balance between the good passivation performance of the P-type doped region 31 and the good optical performance of the N-type doped region 32, further improving battery efficiency.

[0138] As an embodiment of this disclosure, the back surface 3 also includes an isolation region 33 located between the P-type doped region 31 and the N-type doped region 32. The surface microstructure of the isolation region 33 is one of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with the tip removed, or a pyramidal structure with the tip removed.

[0139] In this embodiment, one of the following structures is provided in the isolation region 33: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its apex removed, or a pyramidal structure with its apex removed, as the surface microstructure of the isolation region 33. This can reduce the light reflectivity of the isolation region 33 and further improve battery efficiency.

[0140] As another embodiment of this disclosure, the back surface 3 also includes an isolation region 33 located between the P-type doped region 31 and the N-type doped region 32, and the surface of the isolation region 33 is a polished surface.

[0141] In this embodiment, since at least one of the P-type doped region 31 and the N-type doped region 32 is provided with a non-polished surface, while the surface of the isolation region 33 is a polished surface, the passivation performance of the isolation region 33 can be improved. This can take into account both the optical performance and passivation performance of the back of the battery. By balancing the optical performance and passivation performance of the back of the battery, good battery conversion efficiency can be achieved.

[0142] Please refer to Figure 1 again. As an embodiment of this disclosure, the back-contact solar cell further includes:

[0143] A P-type doped layer 6 is provided in the P-type doped region 31;

[0144] An N-type doped layer 7 is provided in the N-type doped region 32.

[0145] In this embodiment, the P-type doped layer 6 is one or a combination of P-type polycrystalline silicon, P-type microcrystalline silicon, P-type nanocrystalline silicon, and P-type amorphous silicon, and the N-type doped layer 7 is one or a combination of N-type polycrystalline silicon, N-type microcrystalline silicon, N-type nanocrystalline silicon, and N-type amorphous silicon.

[0146] As one embodiment of this disclosure, the back-contact solar cell further includes:

[0147] The first passivation layer 8 is disposed between the P-type doped layer 6 and the back side of the silicon substrate 1, and between the N-type doped layer 7 and the back side of the silicon substrate 1.

[0148] Specifically, the first passivation layer 8 can be a silicon oxide layer. The first passivation layer 8 passesivates the back side of the silicon substrate 1, further enhancing the passivation effect of the P-type doped region 31 and the N-type doped region 32. The first passivation layer 8 can be silicon oxide, silicon nitride, or silicon oxynitride.

[0149] As an embodiment of this disclosure, it also includes an electrode 9 disposed on the back surface 3. The non-polished surface includes an electrode region corresponding to the position of the electrode 9 and a non-electrode region not corresponding to the position of the electrode 9. The microstructure of the electrode region is a superposition of at least two of the following: a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its tip removed, and a pyramidal structure with its tip removed.

[0150] The microstructure of the non-electrode region is one of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, conical structure with the apex removed, and pyramidal structure with the apex removed.

[0151] In this embodiment, electrode 9 can be the main grid electrode or the sub-grid electrode of the back-contact solar cell. By setting the microstructure of the electrode region as a superposition of at least two of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, conical structure with truncated tips, and pyramidal structure with truncated tips, the roughness of the corresponding electrode region on the non-polished surface can be increased, the welding pull of the electrode can be improved, and the stability of the battery structure can be enhanced.

[0152] In this embodiment, electrode 9 is disposed on the side of P-type doped layer 6 away from silicon substrate 1 and on the side of N-type doped layer 7 away from silicon substrate 1. Electrode 9 of P-type doped region 31 is in contact with P-type doped layer 6, and electrode 9 of N-type doped region 32 is in contact with N-type doped layer 7.

[0153] As an embodiment of this disclosure, the area of ​​the solder joint on the main gate electrode corresponding to the non-polished surface is a superposition of at least two of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, conical structure with the tip removed, and pyramidal structure with the tip removed.

[0154] In this embodiment, when the electrode is the main grid electrode, the area of ​​the solder joint on the non-polished surface corresponding to the main grid electrode is a superposition of at least two of the following: conical structure 51, pyramidal structure 52, inverted conical structure, inverted pyramidal structure 54, conical structure with the tip removed, and pyramidal structure with the tip removed. This increases the variety of microstructures in the solder joint area and increases the roughness of the corresponding solder joint area on the back of the silicon wafer. This can increase the welding pull force at the main grid solder joint position, further improve the welding pull force of the solder joint, and enhance the stability of the battery structure.

[0155] As another embodiment of this disclosure, it also includes an electrode 9 disposed on the back surface 3. The non-polished surface includes an electrode region corresponding to the position of the electrode 9 and a non-electrode region not corresponding to the position of the electrode 9. The microstructure of the non-electrode region is one of a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57. The microstructure of the non-polished surface of the electrode region is a wormhole structure 55, a polygonal pit structure 56, or a vertical hole structure 57 superimposed with at least one of a conical structure 51, a pyramidal structure 52, an inverted conical structure, an inverted pyramidal structure 54, a conical structure with its tip removed, or a pyramidal structure with its tip removed. This can also increase the roughness of the electrode region, improve the welding pull of the electrode, thereby improving the stability of the battery structure and maintaining good passivation performance of the non-electrode region.

[0156] As one embodiment of this disclosure, it also includes:

[0157] The second passivation layer 10 covers both the P-type doped layer 6 and the N-type doped layer 7.

[0158] In this embodiment, the electrode of the P-type doped region 31 passes through the second passivation layer 10 and contacts the P-type doped layer 6, while the electrode of the N-type doped region 32 passes through the second passivation layer 10 and contacts the N-type doped layer 7. The second passivation layer 10 can further improve the passivation effect of the battery and increase battery efficiency. The second passivation layer 10 is at least one or a combination of aluminum oxide film, silicon oxide film, silicon nitride film, silicon carbide film, and silicon oxynitride film. For example, in some embodiments, the second passivation layer 10 may include sequentially stacked aluminum oxide film and silicon nitride film; specific details are not limited here.

[0159] This disclosure also provides a photovoltaic module, which includes the back-contact solar cell described in the above embodiments. It should be noted that this photovoltaic module has the same or similar beneficial effects as the back-contact solar cell, and the related aspects between the two can be referred to each other; to avoid repetition, they will not be repeated here.

[0160] This disclosure also provides a photovoltaic system, which includes the photovoltaic modules described in the above embodiments. It should be noted that this photovoltaic system has the same or similar beneficial effects as the back-contact solar cell described above, and the related aspects between the two can be referred to each other; to avoid repetition, they will not be repeated here.

[0161] The above are merely preferred embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A back-contact solar cell, characterized in that, The invention includes a silicon substrate having a front side and a back side disposed opposite to each other, the back side including a P-type doped region and an N-type doped region, at least one of the P-type doped region and the N-type doped region being provided with a non-polished surface; The microstructure of the unpolished surface includes one of the following: a conical structure, a pyramidal structure, an inverted conical structure, an inverted pyramidal structure, a truncated conical structure, a truncated pyramidal structure, a wormhole structure, a polygonal pit structure, and a vertical hole structure; the side surfaces of the conical structure, the pyramidal structure, the truncated conical structure, and the truncated pyramidal structure, as well as the inner surfaces of the inverted conical structure and the inverted pyramidal structure, are provided with a plurality of anti-reflection structures; or, The microstructure of the unpolished surface includes at least two of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, the pyramidal structure with its apex removed, the wormhole structure, the polygonal pit structure, and the vertical hole structure, either superimposed or combined.

2. The back-contact solar cell according to claim 1, characterized in that, The antireflective structure is a pit structure, and the average maximum size of the opening of all the pits per unit area is less than 300 nanometers.

3. The back-contact solar cell according to claim 1, characterized in that, The antireflective structure is a raised structure, and the average value of the maximum bottom surface size of all the raised structures per unit area is less than 300 nanometers.

4. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface satisfies at least one of the following: The cone angle of the conical structure is 15 to 45 degrees; The cone angle of the truncated cone structure is 15 to 45 degrees.

5. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface includes a plurality of first pyramidal structures and a plurality of second pyramidal structures. The base area of ​​the first pyramidal structure is larger than the base area of ​​the second pyramidal structure. At least a portion of the first pyramidal structures are stacked on the surface away from the front face with the second pyramidal structure.

6. The back-contact solar cell according to claim 1, characterized in that, The side surfaces of the conical structure, the pyramidal structure, the conical structure with its apex removed, or the pyramidal structure with its apex removed are provided with a textured surface.

7. The back-contact solar cell according to claim 6, characterized in that, The textured structure is a ring or spiral shape arranged around the side surface.

8. The back-contact solar cell according to claim 7, characterized in that, The top of the conical structure, the pyramidal structure, the conical structure with its apex removed, or the pyramidal structure with its apex removed has a concave-convex structure.

9. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface satisfies at least one of the following: The top surface area of ​​the cone structure with its tip removed is greater than 10 square nanometers; The area of ​​the top surface of the truncated pyramidal structure is greater than 10 square nanometers.

10. The back-contact solar cell according to claim 1, characterized in that, The inner wall of the wormhole structure is provided with at least one of the pyramidal structure and the conical structure.

11. The back-contact solar cell according to claim 1, characterized in that, The inner wall of the wormhole structure is provided with a number of anti-reflection structures.

12. The back-contact solar cell according to claim 1, characterized in that, The ratio of the depth of the wormhole structure to the maximum size of the opening of the wormhole structure is less than 0.

5.

13. The back-contact solar cell according to claim 1, characterized in that, The average maximum size of the openings of all the polygonal pit structures per unit area is 100 nanometers to 10 micrometers.

14. The back-contact solar cell according to claim 1, characterized in that, The inner wall of the polygonal pit structure is provided with a number of anti-reflection structures.

15. The back-contact solar cell according to claim 1, characterized in that, The cross-section of the vertical hole structure is a circular hole or an elliptical hole.

16. The back-contact solar cell according to claim 1, characterized in that, The diameter of the vertical hole structure decreases sequentially from the back side to the front side.

17. The back-contact solar cell according to claim 1, characterized in that, The diameter of the vertical hole structure increases sequentially from the back side to the front side.

18. The back-contact solar cell according to claim 1, characterized in that, The average pore size of all the vertical pore structures per unit area is 10 nanometers to 10 micrometers.

19. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface of the P-type doped region is one of the following: the wormhole structure, the polygonal pit structure, and the vertical hole structure.

20. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface of the N-type doped region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with the apex removed, and the pyramidal structure with the apex removed.

21. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface of the P-type doped region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with the apex removed, and the pyramidal structure with the apex removed. The microstructure of the unpolished surface of the N-type doped region is a superposition of at least two of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the truncated conical structure, and the truncated pyramidal structure.

22. The back-contact solar cell according to claim 1, characterized in that, The microstructure of the unpolished surface of the P-type doped region is one of the following: the wormhole structure, the polygonal pit structure, and the vertical hole structure. The microstructure of the unpolished surface of the N-type doped region is one of the following: a wormhole structure superimposed with at least one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, and the pyramidal structure with its apex removed. The polygonal pit structure; the vertical hole structure.

23. The back-contact solar cell according to claim 1, characterized in that, The back surface also includes an isolation region located between the P-type doped region and the N-type doped region. The surface microstructure of the isolation region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the truncated conical structure, and the truncated pyramidal structure.

24. The back-contact solar cell according to claim 1, characterized in that, The back side also includes an isolation region located between the P-type doped region and the N-type doped region, and the surface of the isolation region is a polished surface.

25. The back-contact solar cell according to claim 1, characterized in that, The back-contact solar cell further includes an electrode disposed on the back side, and the unpolished surface includes an electrode area corresponding to the position of the electrode and a non-electrode area not corresponding to the position of the electrode; The microstructure of the unpolished surface of the electrode region is a superposition of at least two of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, and the pyramidal structure with its apex removed; the microstructure of the unpolished surface of the non-electrode region is one of the following: the conical structure, the pyramidal structure, the inverted conical structure, the inverted pyramidal structure, the conical structure with its apex removed, and the pyramidal structure with its apex removed.

26. A photovoltaic module, characterized in that, Including the back-contact solar cell as described in any one of claims 1 to 25.

27. A photovoltaic system, characterized in that, Including the photovoltaic module as described in claim 26.

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