Back-contact cell and system

Abstract

The present disclosure is applicable to the technical field of solar cells. Provided are a back-contact cell and a system. The back-contact cell comprises: a silicon wafer comprising a first doped region on the back surface thereof, wherein a textured surface of the first doped region comprises a plurality of pyramid-like structures, and recesses are formed at the junctions between adjacent pyramid-like structures; and the thickness of a first doped layer located at the recesses in the first doped region is greater than the thickness of the first doped layer located at pyramid apexes.

Description

Back contact battery and system

[0001] Cross-references

[0002] This disclosure incorporates, in its entirety, Chinese Patent Publication No. 202520289066.0, filed on February 21, 2025, entitled “A Back Contact Solar Cell, Battery Module and Photovoltaic System”. Technical Field

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

[0004] A solar cell is a semiconductor device that converts solar energy into electrical energy. Under sunlight, a photocurrent is generated inside the solar cell, which outputs electrical energy through electrodes. In recent years, solar cell manufacturing technology has continuously advanced, production costs have decreased, and conversion efficiency has continuously improved. Solar cell power generation has become increasingly widespread and is an important energy source for electricity supply. Among them, the interdigitated back contact (IBC) solar cell, also known as a cross-linked back contact solar cell, has both its positive and negative electrode grids designed on the back of the cell. This completely avoids the shading of the metal grids on the front surface, eliminating optical losses caused by grid shading. At the same time, the electrode grids can be designed to be wider than existing ones, reducing series resistance losses and thus significantly improving cell conversion efficiency.

[0005] In existing technologies, to reduce the reflectivity of incident light on the back side of a back-contact solar cell, a cone-shaped textured surface is fabricated in the doped region on the back side of the cell. This doped region is either P-type or N-type doped, thereby improving the bifaciality of the cell and increasing the power generation of the module. However, the thickness relationship of the doped layer in different regions of the textured surface is usually not controlled, and the doped layer thickness distribution on the textured surface is not conducive to improving cell efficiency, resulting in a persistent problem of suboptimal cell efficiency.

[0006] Public content

[0007] This disclosure provides a back-contact solar cell, which aims to solve the problem that the thickness distribution of the doped layer on the textured surface of the doped region in the prior art back-contact solar cell is not conducive to improving the cell efficiency, resulting in poor cell efficiency.

[0008] This disclosure is implemented by providing a back-contact solar cell, comprising:

[0009] A silicon wafer having a front side and a back side disposed opposite to each other, the back side including a first doped region, the first doped region being a P-type doped region or an N-type doped region, the first doped region being provided with a textured surface, the textured surface including a plurality of cone-like structures, each cone-like structure having a cone surface and a cone apex, and a recess being formed at the junction of adjacent cone-like structures;

[0010] A first doped layer is disposed in the first doped region, wherein the thickness of the first doped layer at the recess is greater than the thickness of the first doped layer at the cone apex.

[0011] In some embodiments, the thickness of the first doped layer at the apex of the cone is greater than the thickness of the first doped layer at the surface of the cone.

[0012] In some embodiments, the back side includes a second doped region having the textured surface; the back contact solar cell further includes:

[0013] A second doped layer is provided in the second doped region, the doping type of the second doped layer is opposite to that of the first doped layer, and the thickness of the second doped layer in the recess is greater than the thickness of the second doped layer in the cone.

[0014] In some embodiments, the thickness of the second doped layer at the apex of the cone is greater than the thickness of the second doped layer at the surface of the cone.

[0015] In some embodiments, the first doped layer is a stack of one or more of the following: a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

[0016] In some embodiments, the second doped layer is a stack of one or more of the following: a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

[0017] In some embodiments, the first doped region has at least two stacked first doped layers, wherein the thickness of each first doped layer in the recess is greater than the thickness of each first doped layer in the cone apex.

[0018] In some embodiments, the thickness of each first doped layer at the apex of the cone is greater than the thickness of each first doped layer at the surface of the cone.

[0019] In some embodiments, the thickness of the first doped layer farther from the silicon wafer is greater than the thickness of the first doped layer closer to the silicon wafer.

[0020] In some implementations, it also includes:

[0021] A first passivation layer is located on the side of the first doped layer opposite to the silicon wafer. The thickness of the first passivation layer at the recess is greater than the thickness of the first passivation layer at the cone apex, and the thickness of the first passivation layer at the cone apex is greater than the thickness of the first passivation layer at the cone surface.

[0022] In some implementations, it also includes:

[0023] A second passivation layer is located on the side of the second doped layer opposite to the silicon wafer. The thickness of the second passivation layer in the recess is greater than the thickness of the second passivation layer at the cone apex, and the thickness of the second passivation layer at the cone apex is greater than the thickness of the second passivation layer at the cone surface.

[0024] In some implementations, it also includes:

[0025] A first tunneling layer is located between the first doped layer and the back surface. The thickness of the first tunneling layer at the recess is greater than the thickness of the first tunneling layer at the cone apex, and the thickness of the first tunneling layer at the cone apex is greater than the thickness of the first tunneling layer at the cone surface.

[0026] In some implementations, it also includes:

[0027] A second tunneling layer is located between the second doped layer and the back surface. The thickness of the second tunneling layer at the recess is greater than the thickness of the second tunneling layer at the cone apex, and the thickness of the second tunneling layer at the cone apex is greater than the thickness of the second tunneling layer at the cone surface.

[0028] In some embodiments, the ratio of the thickness of the first doped layer at the recess to the thickness of the first doped layer at the apex of the cone is 1.2 to 1.8.

[0029] In some embodiments, the ratio of the thickness of the first doped layer at the apex of the cone to the thickness of the first doped layer at the surface of the cone is 1.1 to 1.5.

[0030] In some embodiments, the cone apex is formed by an arc surface, and the first doped layer at the cone apex is also formed by an arc surface, wherein the curvature of the first doped layer at the cone apex is less than the curvature of the cone apex.

[0031] This disclosure also provides a battery assembly including the solar cell described above.

[0032] This disclosure also provides a photovoltaic system including the aforementioned battery module.

[0033] This disclosure provides a back-contact solar cell that utilizes a textured surface composed of several cone-like structures in the first doped region. This textured surface reduces the reflectivity of the first doped region to incident light from the back of the cell, increasing the bifaciality of the back-contact solar cell and thus improving the power output of the solar module. Because the defect density at the apex of the cone-like structure is higher than the defect density at the concave portion of the cone-like structure, the thickness of the first doped layer in the concave portion is controlled to be greater than the thickness at the apex of the cone; that is, the thickness of the first doped layer at the apex of the cone is thinner than the thickness in the concave portion. A thinner first doped layer at the apex of a cone-shaped structure generates a stronger field effect, which helps reduce recombination losses at the apex. The thickness relationship between the apex and recess of the first doped layer on the textured surface can well adapt to the uneven defect density distribution of the cone-like structure, thereby effectively improving battery efficiency. Moreover, since light undergoes more reflections at the apex than in the recess, controlling the thickness of the first doped layer in the recess to be greater than that at the apex helps reduce parasitic absorption side effects of the first doped layer, improves light utilization, and enhances battery efficiency, resulting in better battery performance. Attached Figure Description

[0034] Figure 1 is a schematic diagram of a back-contact solar cell provided in an embodiment of this disclosure;

[0035] Figure 2 is a schematic diagram of the structure of a silicon wafer for a back-contact solar cell provided in an embodiment of this disclosure;

[0036] Figure 3 is a SEM image of the first doped layer and the first passivation layer of a back contact solar cell provided in an embodiment of the present disclosure on the textured surface of the first doped region;

[0037] Figure 4 is a SEM image of the second doped layer and the second passivation layer of a back contact solar cell provided in an embodiment of this disclosure on the textured surface of the second doped region.

[0038] Explanation of reference numerals in the attached figures: 1. Silicon wafer; 2. Front side; 3. Back side; 4. First doped layer; 5. Second doped layer; 6. First passivation layer; 7. Second passivation layer; 8. First tunneling layer; 9. Second tunneling layer; 10. First electrode; 11. Second electrode; 30. Conical structure; 31. First doped region; 32. Second doped region; 33. Isolation region; 301. Conical surface; 302. Conical apex; 303. Recess. Detailed Implementation

[0039] 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.

[0040] In the description of this disclosure, it should be understood that the terms "upper", "lower", "back", "front", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0041] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0042] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0043] Please refer to Figures 1-3. This disclosure provides a back-contact solar cell, comprising:

[0044] Silicon wafer 1 has a front side 2 and a back side 3 disposed opposite to each other. The back side 3 includes a first doped region 31, which is a P-type doped region or an N-type doped region. The first doped region 31 is provided with a textured surface, which includes a plurality of cone-shaped structures 30. Each cone-shaped structure 30 has a cone surface 301 and a cone apex 302. A recess 303 is formed at the junction of adjacent cone-shaped structures.

[0045] The first doped layer 4 is located in the first doped region 31, and the thickness of the first doped layer 4 in the recess 303 is greater than the thickness of the first doped layer 4 in the cone apex 302.

[0046] In this embodiment of the present disclosure, the silicon wafer 1 includes a front side 2 and a back side 3 disposed opposite to each other. The front side 2 of the silicon wafer 1 is the side facing the sunlight when the back-contact solar cell is working, and the back side 3 of the silicon wafer 1 is the side facing away from the sunlight when the back-contact solar cell is working.

[0047] In this embodiment of the present disclosure, the first doped region 31 can be either a P-type doped region or an N-type doped region. When the first doped region 31 can be a P-type doped region, the first doped layer 4 is a P-type doped layer, which is doped with P-type elements; when the first doped region 31 can be an N-type doped region, the first doped layer 4 is an N-type doped layer, which is doped with N-type elements.

[0048] In this embodiment, the first doped region 31 is provided with a textured surface, which includes a plurality of cone-like structures 30, which can be pyramidal or conical structures. The plurality of cone-like structures 30 are arranged in an array, with adjacent cone-like structures 30 spaced apart or partially overlapping. When adjacent cone-like structures 30 overlap, a V-shaped or U-shaped recess 303 is formed at the junction of the adjacent cone-like structures 30. Each cone-like structure 30 includes a cone surface 301 and a cone apex 302, where the cone apex 302 is the highest point of the cone-like structure 30. The cone surface 301 of the cone-like structure 30 is the collection of all the side surfaces of the cone-like structure 30, that is, all surfaces of the cone-like structure 30 except for the bottom surface and the cone apex 302. The pyramidal structure 30 can be a pyramidal structure with three sides and one base; or, it can be a pyramidal structure with four sides and one base; or, it can be a pyramidal structure with five sides and one base; or, it can be a pyramidal structure with six sides and one base; of course, the pyramidal structure 30 can also be a pyramidal structure with a greater number of sides and one base. The top of the pyramidal structure 30 can be pointed or rounded.

[0049] In this embodiment, a textured surface composed of several cone-shaped structures 30 is prepared in the first doped region 31 on the back side 3 of the back-contact solar cell. The textured surface in the first doped region 31 reduces the reflectivity of incident light on the back side 3 of the cell, improves 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. Moreover, since the defect density at the cone apex 302 of the cone-shaped structure 30 is higher than the defect density at the concave portion 303 at the junction of the cone-shaped structure 30, the first doped layer 4 is controlled to be located in the concave portion 3. The thickness of the first doped layer 4 at the cone apex 302 is greater than the thickness of the first doped layer 4 at the concave portion 303. This thinner thickness at the cone apex 302 of the cone-like structure 30 allows for a stronger field effect, reducing recombination losses at the cone apex 302. This allows the thickness relationship between the cone apex 302 and the concave portion 303 of the textured surface to effectively address the uneven defect density distribution of the cone-like structure 30, thereby improving battery efficiency. Furthermore, since light undergoes more reflections at the cone apex 302 than at the concave portion 303, controlling the thickness of the first doped layer 4 at the concave portion 303 to be greater than that at the cone apex 302 helps reduce parasitic absorption side effects of the first doped layer 4, improving light utilization and thus enhancing battery efficiency. The doping concentration of the first doped layer 4 at the cone apex 302 is greater than that at the concave portion 303, which further facilitates the generation of a stronger field effect by the first doped layer 4 at the cone apex 302 of the cone-like structure 30.

[0050] In this embodiment, the first doped layer 4 is one or a combination of a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer. In some embodiments, the first doped layer 4 is a doped polycrystalline silicon layer.

[0051] In this embodiment, the first doped layer 4 can be a single-layer structure or a stacked structure with two, three, or more layers. When the first doped layer 4 is a stacked structure with at least two layers, a barrier layer 40 is provided between adjacent first doped layers 4 to prevent electrode paste from being ablated and entering the silicon wafer 1. The barrier layer 40 can be one or a combination of silicon oxide, silicon nitride, and silicon oxynitride. In Figure 1, the first doped layer 4 is shown as two layers, with the barrier layer 40 provided between the two first doped layers 4.

[0052] As some embodiments of this disclosure, the first doped region 31 is provided with at least two stacked first doped layers 4, and the thickness of each first doped layer 4 in the recess 303 is greater than its thickness in the cone apex 302.

[0053] In this embodiment, the first doped region 31 has at least two stacked first doped layers 4. Compared with a single-layer first doped layer 4, this is beneficial for improving the passivation effect of the first doped region 31 and can also improve the barrier capability of the film structure of the first doped region 31 against electrode paste ablation, preventing the electrode paste from burning through the film and entering the silicon wafer 1. In this embodiment, the first doped region 31 is preferably a P-type doped region, and the first doped layer 4 is a P-type doped layer. This can greatly improve the passivation effect of the P-type doped region and enhance the barrier capability of the first doped layer 4 of the P-type doped region against electrode paste.

[0054] As some embodiments of this disclosure, the thickness of each first doped layer 4 at the cone apex 302 is greater than its thickness at the cone surface 301.

[0055] In this embodiment, the thickness of each first doped layer 4 at the cone apex 302 is greater than its thickness at the cone surface 301. This is beneficial for each first doped layer 4 to adapt to the problem of uneven defect density distribution in the cone-like structure 30, thereby effectively improving battery efficiency. Moreover, it is beneficial to reduce the parasitic absorption side effects of each first doped layer 4, improve light utilization, and enhance battery efficiency.

[0056] As some embodiments of this disclosure, the thickness of the first doped layer 4 away from the silicon wafer 1 is greater than the thickness of the first doped layer 4 close to the silicon wafer 1.

[0057] In this embodiment, it can be understood that the thickness of the outer first doped layer 4 is greater than the thickness of the inner first doped layer 4, so that the outer first doped layer 4 has a better ability to block the electrode paste ablation and improves the ability of the first doped layer 4 to block the metallization paste from burning through.

[0058] As some embodiments of this disclosure, the thickness of each first doped layer 4 at the cone apex 302 is greater than its thickness at the cone surface 301.

[0059] In this embodiment, the thickness of each first doped polysilicon layer located in the recess 303 is controlled to be greater than the thickness of each first doped layer 4 located at the cone apex 302. At the same time, the thickness of each first doped polysilicon layer located at the cone apex 302 is controlled to be greater than the thickness of each first doped layer 4 located at the cone surface 301. This makes the thickness of each first doped layer 4 located at the cone surface 301 thinner than the thickness of each first doped layer 4 located at the cone apex 302. This can reduce the parasitic absorption side effects of each first doped layer 4 located on the cone surface 301, further improve light utilization, and thus improve battery efficiency.

[0060] In this embodiment, the thickness of a portion of the first doped layer 4 can be measured using instruments such as a transmission electron microscope. The thickness of this portion can be the directly measured average thickness of that portion, or it can be the average thickness obtained by measuring multiple points within that portion. The selection is based on the measurability of the actual measurement target and is not specifically limited. The direction of this thickness is perpendicular to the tangent at the corresponding position on the outer surface of the first doped layer 4.

[0061] This can be understood as follows: the thickness of the first doped layer 4 in the recess 303 can be the average thickness of the first doped layer 4 in the recess 303, and the thickness of the first doped layer 4 in the cone apex 302 can be the average thickness of the first doped layer 4 in the cone apex 302. The average thickness of the first doped layer 4 in the recess 303 is greater than the average thickness of the first doped layer 4 in the cone apex 302. Alternatively, the thickness of the first doped layer 4 in the recess 303 can be the thickness of the first doped layer 4 at any position in the recess 303, and the thickness of the first doped layer 4 in the cone apex 302 can be the thickness of the first doped layer 4 at any position in the cone apex 302. The thickness of the first doped layer 4 at any position in the recess 303 is greater than the thickness of the first doped layer 4 at any position in the cone apex 302.

[0062] As some embodiments of this disclosure, the thickness of the first doped layer 4 at the cone apex 302 is greater than the thickness of the first doped layer 4 at the cone surface 301.

[0063] In this embodiment, it can be understood that the thickness of the first doped layer 4 on the conical surface 301 is the average thickness of the first doped layer 4 on the conical surface 301, and the average thickness of the first doped layer 4 on the cone apex 302 is greater than the average thickness of the first doped layer 4 on the conical surface 301; or, the thickness of the first doped layer 4 on the conical surface 301 is the thickness of the first doped layer 4 at any position on the conical surface 301, and the thickness of the first doped layer 4 at any position on the cone apex 302 is greater than the thickness of the first doped layer 4 at any position on the conical surface 301.

[0064] In this embodiment, the thickness of the first doped layer 4 at the recess 303 is controlled to be greater than the thickness of the first doped layer 4 at the cone apex 302, and the thickness of the first doped layer 4 at the cone apex 302 is controlled to be greater than the thickness of the first doped layer 4 at the cone surface 301. This makes the thickness of the first doped layer 4 at the cone surface 301 thinner than the thickness of the first doped layer 4 at the cone apex 302, which can reduce the parasitic absorption side effects of the first doped layer 4 at the cone surface 301, further improve the light utilization rate, and thus improve the battery efficiency.

[0065] As some embodiments of this disclosure, the thickness of the first doped layer 4 on the conical surface 301 gradually decreases from the concave portion 303 to the apex 302.

[0066] In this embodiment, since the defect density is higher closer to the cone apex 302 than the cone surface 301, the thickness of the first doped layer 4 on the cone surface 301 is controlled to gradually decrease from the concave portion 303 to the cone apex 302. That is, the thickness of the first doped layer 4 on the cone surface 301 is thinner closer to the cone apex 302. The doping concentration of the first doped layer 4 on the cone surface 301 gradually increases from the concave portion 303 to the cone apex 302. The field effect of the first doped layer 4 on the cone surface 301 increases sequentially from the concave portion 303 to the cone apex 302. The thickness of the first doped layer 4 on the cone surface 301 is beneficial to adapting to the defect density distribution of the cone surface 301, thereby effectively improving the battery efficiency. Moreover, it is beneficial to reduce the parasitic absorption side effects of the first doped layer 4 on the cone surface 301 and improve the light utilization rate, thus also improving the battery efficiency.

[0067] Please refer to Figures 1 and 4. As some embodiments of this disclosure, the back surface 3 includes a second doped region 32, which also has the aforementioned textured surface; the back contact solar cell further includes:

[0068] The second doped layer 5 is provided in the second doped region 32. The doping type of the second doped layer 5 is opposite to that of the first doped layer. The thickness of the second doped layer 5 in the recess 303 is greater than the thickness of the second doped layer 5 in the cone apex 302.

[0069] In this embodiment, the first doped region 31 and the second doped region 32 are respectively a P-type doped region and an N-type doped region. When the first doped region 31 is a P-type doped region, the second doped region 32 is an N-type doped region; when the first doped region 31 is an N-type doped region, the second doped region 32 is a P-type doped region.

[0070] As shown in Figure 4, the textured surface of both the second doped region 32 and the first doped region 31 includes several cone-like structures 30. Each cone-like structure 30 has a cone surface 301 and a cone apex 302, and a recess 303 is formed at the junction of adjacent cone-like structures 30. The cone-like structures 30 of the textured surface of the second doped region 32 and the textured surface of the first doped region 31 can be identical or different. When there is a difference between the cone-like structures 30 of the textured surface of the second doped region 32 and the textured surface of the first doped region 31, it could be due to a difference in the apex angle of the cone-like structures 30. For example, the first doped region 31 is a P-type doped region and the second doped region 32 is an N-type doped region. The apex angle of the cone-like structure 30 on the textured surface of the first doped region 31 is larger than the apex angle of the cone-like structure 30 on the textured surface of the second doped region 32, making the textured surface of the first doped region 31 flatter than that of the second doped region 32. This is beneficial to improving the passivation effect of the P-type doped region and improving the battery efficiency.

[0071] In this embodiment, the thickness of a certain portion of the second doped layer 5 can be measured using instruments such as a transmission electron microscope. The thickness of this portion can be the directly measured average thickness of that portion, or it can be the average thickness obtained by measuring multiple points within that portion. The selection is based on the measurability of the actual measurement target and is not specifically limited. The direction of this thickness is perpendicular to the tangent at the corresponding position on the outer surface of the second doped layer 5.

[0072] In this embodiment, by preparing a textured second doped region 32 composed of several cone-shaped structures 30 in the second doped region 32, the textured surface reduces the reflectivity of incident light on the back side 3 of the battery, further improving 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; moreover, by controlling the thickness of the second doped layer 5 at the concave portion 303 to be greater than the thickness of the second doped layer 5 at the cone apex 302, that is, the thickness of the second doped layer 5 at the cone apex 302 is thinner than the thickness of the second doped layer 5 at the concave portion 303, the thinner polycrystalline silicon at the cone apex 302 position of the cone-shaped structure 30 can generate a stronger field effect, which is beneficial to reduce the recombination loss at the cone apex 302 position, so that the thickness relationship between the cone apex 302 position and the concave portion 303 position of the second doped layer 5 in the textured surface can be well adapted to the problem of uneven defect density distribution of the cone-shaped structure 30, thereby effectively improving the battery efficiency. Moreover, since light is reflected more times at the cone apex 302 position of the textured surface than at the recess 303 position, controlling the thickness of the second doped layer 5 at the recess 303 to be greater than the thickness of the second doped layer 5 at the cone apex 302 is beneficial to reduce the parasitic absorption side effects of the second doped layer 5 and improve light utilization, thus also improving battery efficiency.

[0073] As some embodiments of this disclosure, the thickness of the second doped layer 5 at the cone apex 302 is greater than the thickness of the second doped layer 5 at the cone surface 301.

[0074] In this embodiment, the thickness of the recess 303 of the textured surface of the second doped layer 5 in the second doped region 32 is controlled to be greater than the thickness of the cone apex 302 of the textured surface of the second doped layer 5 in the second doped region 32. At the same time, the thickness of the cone apex 302 of the textured surface of the second doped layer 5 in the second doped region 32 is controlled to be greater than the thickness of the cone surface 301 of the textured surface of the second doped layer 5 in the second doped region 32. This makes the thickness of the second doped layer 5 at the cone surface 301 thinner than the thickness of the second doped layer 5 at the cone apex 302, which can reduce the parasitic absorption side effects of the second doped layer 5 located on the cone surface 301, further improve the light utilization rate, and thus improve the battery efficiency.

[0075] As some embodiments of this disclosure, the thickness of the second doped layer 5 on the conical surface 301 gradually decreases from the concave portion 303 to the conical apex 302.

[0076] In this embodiment, the thickness of the cone surface 301 of the textured surface of the second doped layer 5 located in the second doped region 32 gradually decreases from the concave portion 303 to the cone apex 302. That is, the thickness of the second doped layer 5 on the cone surface 301 is thinner as it gets closer to the cone apex 302. This is beneficial for the thickness of the second doped layer 5 on the cone surface 301 to match the defect density distribution of the cone surface 301, thereby effectively improving the battery efficiency. Moreover, it is beneficial for reducing the parasitic absorption side effects of the second doped layer 5 on the cone surface 301 and improving the light utilization rate, thus also improving the battery efficiency.

[0077] As some embodiments of this disclosure, the back-contact solar cell further includes:

[0078] An isolation region 33 is provided between the first doped region 31 and the second doped region 32. The isolation region 33 is provided with a textured surface or is provided with a polished surface.

[0079] In this embodiment, the first doped region 31 and / or the second doped region 32 are textured, while the surface of the isolation region 33 is polished. This improves the passivation performance of the isolation region, thereby balancing the optical and passivation performance of the battery back side 3 and achieving good battery conversion efficiency. When the isolation region 33 is textured, the anti-reflection effect of incident light on the battery back side 3 can be further improved.

[0080] As some embodiments of this disclosure, the second doped layer 5 is one or a combination of a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer. In some embodiments, the second doped layer 5 is a doped polycrystalline silicon layer.

[0081] In this embodiment, the structure of the second doped layer 5 can be the same as that of the first doped layer 4, i.e., it can be a single-layer structure or a stacked structure with two, three, or more layers. Figure 1 illustrates the case where the first doped layer 4 is a stacked structure and the second doped layer 5 is a single-layer structure.

[0082] In this embodiment, the thicknesses of the first doped layer 4 in the recess 303, the cone apex 302, and the cone surface 301 can be flexibly set according to actual needs. For example, the thickness of the first doped layer 4 in the recess 303 can be 350–500 nm; the thickness of the first doped layer 4 in the cone apex 302 can be 300–460 nm; and the thickness of the first doped layer 4 in the cone surface 301 can be 200–400 nm. The thicknesses of the second doped layer 5 in the recess 303, the cone apex 302, and the cone surface 301 can also be flexibly set according to actual needs. For example, the thickness of the second doped layer 5 in the recess 303 can be 300–450 nm; the thickness of the second doped layer 5 in the cone apex 302 can be 250–350 nm; and the thickness of the second doped layer 5 in the cone surface 301 can be 180–230 nm.

[0083] As some embodiments of this disclosure, the thickness ratio of the first doped layer 4 at the recess 303 to the thickness of the first doped layer 4 at the cone apex 302 is 1.2 to 1.8.

[0084] In this embodiment, the ratio of the thickness of the first doped layer 4 at the recess 303 to the thickness of the first doped layer 4 at the cone apex 302 is set to 1.2 to 1.8. Within this ratio range, the relationship between the thickness of the first doped layer 4 at the cone apex 302 and the thickness at the recess 303 can be well adapted to the problem of uneven defect density distribution in the cone-shaped structure 30. Moreover, the parasitic absorption side effects of the second doped layer 5 can be well reduced, and the light utilization rate can be improved.

[0085] For example, the ratio of the thickness of the first doped layer 4 in the recess 303 to the thickness of the first doped layer 4 in the cone 302 can be any value among 1.2, 1.25, 1.3, 1.5, 1.6, 1.7, 1.75, and 1.8.

[0086] As some embodiments of this disclosure, the thickness ratio of the first doped layer 4 at the cone apex 302 to the thickness of the first doped layer 4 at the cone surface 301 is 1.1 to 1.5.

[0087] In this embodiment, the ratio of the thickness of the first doped layer 4 at the cone apex 302 to the thickness of the first doped layer 4 at the cone surface 301 is set to 1.1 to 1.5. Within this ratio range, the parasitic absorption side effects of the first doped layer 4 can be effectively reduced, and the light utilization rate can be improved.

[0088] Similarly, the ratio of the thickness of the second doped layer 5 in the recess 303 to the thickness of the second doped layer 5 in the cone apex 302 can also be set to 1.2 to 1.8; the ratio of the thickness of the second doped layer 5 in the cone apex 302 to the thickness of the second doped layer 5 in the cone surface 301 can also be set to 1.1 to 1.5.

[0089] For example, as shown in Figure 3, the first doped layer 4 has a double-layer structure. The thicknesses of the two first doped layers 4 located in the recess 303 are 163nm and 268nm, respectively, that is, the thickness of the first doped layer 4 located in the recess 303 is 431nm; the thicknesses of the two first doped layers 4 located in the cone apex 302 are 149nm and 206nm, respectively, that is, the thickness of the first doped layer 4 located in the cone apex 302 is 355nm; and the thicknesses of the two first doped layers 4 located in the cone surface 301 are 86.5nm and 175nm, respectively, that is, the thickness of the first doped layer 4 located in the cone surface 301 is 261.5nm.

[0090] For example, as shown in Figure 4, the second doped layer 5 is a single-layer structure. The thickness of the second doped layer 5 in the recess 303 is 373 nm; the thickness of the second doped layer 5 in the cone apex 302 is 274 nm; and the thickness of the second doped layer 5 in the cone surface 301 is 218 nm.

[0091] As some embodiments of this disclosure, the cone apex 302 is provided with an arc surface, the first doped layer 4 is provided with an arc surface at the position of the cone apex 302, and the curvature of the first doped layer 4 at the position of the cone apex 302 is less than the curvature of the cone apex 302.

[0092] In this embodiment, the cone apex 302 is provided with an arc surface, which makes the position of the cone apex 302 smoother and is beneficial to improving the passivation performance of the cone apex 302 position of the first doped region 31. Moreover, the curvature of the first doped layer 4 at the cone apex 302 position is less than that at the cone apex 302 position, making the position of the first doped layer 4 at the cone apex 302 position flatter than the cone apex 302 position, which is beneficial to improving the passivation performance of the first doped layer 4 at the cone apex 302 position, and thus beneficial to improving battery efficiency.

[0093] Similarly, the second doped layer 5 is arranged in an arc shape at the cone apex 302 position, and the curvature of the second doped layer 5 at the cone apex 302 position is less than that of the second doped layer 5 at the cone apex 302 position. This is also beneficial to improving the passivation performance of the second doped layer 5 at the cone apex 302 position, thereby improving the battery efficiency.

[0094] As some embodiments of this disclosure, it also includes:

[0095] The first passivation layer 6 is located on the side of the first doped layer 4 facing away from the silicon wafer 1. The thickness of the first passivation layer 6 in the recess 303 is greater than the thickness of the first passivation layer 6 in the cone apex 302, and the thickness of the first passivation layer 6 in the cone apex 302 is greater than the thickness of the first passivation layer 6 in the cone surface 301.

[0096] In this embodiment, when the first doped layer 4 has two or more layers, the first passivation layer 6 is located on the outer surface of the first doped layer 4 furthest from the silicon wafer 1.

[0097] In this embodiment, the first passivation layer 6 can further improve the passivation effect of the battery and improve battery efficiency. Moreover, the thickness of the first passivation layer 6 at the recess 303 is greater than the thickness of the first passivation layer 6 at the cone apex 302, and the thickness of the first passivation layer 6 at the cone apex 302 is greater than the thickness of the first passivation layer 6 at the cone surface 301. Since the adjacent positions of the conical structures 30 are more complex, these recesses 303 require a thicker first passivation layer 6 to achieve a better passivation effect. Secondly, the cone apex 302 of the conical structure 30 is more complex than the cone surface 301. Therefore, the thickness of the first passivation layer 6 at the cone apex 302 is set to be thicker than the thickness of the first passivation layer 6 at the cone surface 301. This is beneficial to the good matching of the passivation effect of each region of the conical structure 30 in the first doped region 31, which is conducive to improving battery efficiency.

[0098] As some embodiments of this disclosure, it also includes:

[0099] The second passivation layer 7 is located on the side of the second doped layer 5 facing away from the silicon wafer 1. The thickness of the second passivation layer 7 in the recess 303 is greater than the thickness of the second passivation layer 7 in the cone apex 302, and the thickness of the second passivation layer 7 in the cone apex 302 is greater than the thickness of the second passivation layer 7 in the cone surface 301.

[0100] In this embodiment, the first passivation layer 6 can further improve the passivation effect of the battery and improve battery efficiency. Moreover, the thickness of the second passivation layer 7 at the recess 303 is greater than the thickness of the second passivation layer 7 at the cone apex 302, and the thickness of the second passivation layer 7 at the cone apex 302 is greater than the thickness of the second passivation layer 7 at the cone surface 301. Since the adjacent positions of the conical structures 30 are more complex, these recesses 303 require a thicker first passivation layer 6 to achieve a better passivation effect. Secondly, the cone apex 302 of the conical structure 30 is more complex than the cone surface 301. Therefore, the thickness of the second passivation layer 7 at the cone apex 302 is set to be thicker than the thickness of the second passivation layer 7 at the cone surface 301. This is beneficial to the good matching of the passivation effect of each region of the conical structure 30 in the second doped region 32, which is conducive to improving battery efficiency.

[0101] The first passivation layer 6 and the second passivation layer 7 are at least one or a combination of aluminum oxide film, silicon oxide film, silicon nitride film, silicon carbide film, and silicon oxynitride film, and there is no specific limitation here.

[0102] As some embodiments of this disclosure, it also includes:

[0103] The first tunneling layer 8 is located between the first doped layer 4 and the back surface 3 of the silicon wafer 1. The thickness of the first tunneling layer 8 in the recess 303 is greater than the thickness of the first tunneling layer 8 in the cone apex 302, and the thickness of the first tunneling layer 8 in the cone apex 302 is greater than the thickness of the first tunneling layer 8 in the cone surface 301.

[0104] In this embodiment, the first tunneling layer 8 can perform tunneling passivation, further improving the passivation effect of the battery and increasing battery efficiency. Since the surface conditions of the adjacent cone-shaped structures 30 in the first doped region 31 are relatively complex, and the cone apex 302 of the cone-shaped structure 30 is more complex than the cone surface 301, the thickness of the first tunneling layer 8 in the recess 303 is greater than the thickness of the first tunneling layer 8 in the cone apex 302. The thickness of the first tunneling layer 8 at the cone apex 302 is set to be thicker than that at the cone surface 301, which is beneficial for the first tunneling layer 8 in the first doped region 31 to achieve a better match with the tunneling passivation effect of each region of the cone-shaped structure 30, thus improving battery efficiency.

[0105] As some embodiments of this disclosure, it also includes:

[0106] The second tunneling layer 9 is located between the second doped layer 5 and the back surface 3 of the silicon wafer 1. The thickness of the second tunneling layer 9 in the recess 303 is greater than the thickness of the second tunneling layer 9 in the cone apex 302, and the thickness of the second tunneling layer 9 in the cone apex 302 is greater than the thickness of the second tunneling layer 9 in the cone surface 301.

[0107] In this embodiment, the second tunneling layer 9 can perform tunneling passivation, further improving the passivation effect and increasing battery efficiency. Since the surface conditions of the adjacent cone-shaped structures 30 in the second doped region 32 are relatively complex, and the cone apex 302 of the cone-shaped structure 30 is more complex than the cone surface 301, the thickness of the second tunneling layer 9 in the recess 303 is greater than that in the cone apex 302. The thickness of the second tunneling layer 9 at the cone apex 302 is set to be thicker than that at the cone surface 301, which facilitates a better match between the second tunneling layer 9 in the second doped region 32 and the tunneling passivation effect in each region of the cone-shaped structure 30, thus improving battery efficiency.

[0108] The first tunneling layer 8 and the second tunneling layer 9 are at least one or a combination of aluminum oxide film, silicon oxide film, and silicon oxynitride film, and there is no specific limitation here.

[0109] As some embodiments of this disclosure, it also includes:

[0110] The first electrode 10 passes through the first passivation layer 6 and contacts the first doped layer 4;

[0111] The second electrode 11 passes through the second passivation layer 7 and contacts the second doped layer 5.

[0112] In this embodiment, the first electrode 10 and the second electrode 11 have opposite polarities. For example, if the first doped layer 4 is P-type, then the first electrode 10 is the positive electrode; if the second doped layer 5 is N-type, then the second electrode 11 is the negative electrode.

[0113] This disclosure also provides a battery assembly including the back-contact solar cell described in the above embodiments. It should be noted that this battery assembly 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.

[0114] In this embodiment, multiple back-contact solar cells in the battery module can be connected in series to form a battery string, thereby achieving series current collection and output. For example, the battery cells can be connected in series by setting solder strips (busbars, interconnecting strips), conductive backplates, etc.

[0115] It is understood that in such embodiments, the battery assembly may also include a metal frame, a backsheet, photovoltaic glass, and an encapsulating film. The encapsulating film may be filled between the front and back of the back-contact solar cell, the photovoltaic glass, adjacent cells, etc. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the encapsulating film may be an EVA film or a POE film, and the specific choice can be made according to the actual situation, without limitation.

[0116] Photovoltaic glass can be applied to the encapsulating film on the front side of the back-contact solar cell. This photovoltaic glass can be ultra-clear glass, possessing high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance of over 92%. It can protect the back-contact solar cell while minimizing impact on its efficiency. Simultaneously, the encapsulating film bonds the photovoltaic glass and the back-contact solar cell together, providing sealing, insulation, and waterproofing / moisture protection for the back-contact solar cell.

[0117] The backsheet can be attached to the adhesive film on the back of the back-contact solar cell. The backsheet protects and supports the solar cell, providing reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, acrylic glass, and aluminum alloy TPT composite adhesive film, etc. The specific choice depends on the specific circumstances and is not limited here. The backsheet, back-contact solar cell, adhesive film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the main external support structure for the entire back-contact solar cell module, providing stable support and installation. For example, the back-contact solar cell module can be installed at the desired location using the metal frame.

[0118] This disclosure also provides a photovoltaic system including the battery module described above. 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.

[0119] In this embodiment, the photovoltaic system can be applied in photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants. It can also be applied to equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system are not limited to these; that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation system grid as an example, the photovoltaic system may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple back-contact solar cell modules. For example, multiple back-contact solar cell modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, which can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into AC power required by the mains power grid before being connected to the mains power grid to achieve solar power supply.

[0120] In the description of this specification, references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0121] 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, comprising: a silicon wafer having opposite front and back surfaces, the back surface comprising a first doped region, the first doped region being a P-type doped region or an N-type doped region, the first doped region being provided with a textured surface, the textured surface comprising a plurality of quasi-cone structures, each of the quasi-cone structures having a conical surface and a conical top, and a recess being formed at an intersection of adjacent ones of the quasi-cone structures; a first doped layer provided on the first doped region, the first doped layer having a thickness at the recess greater than a thickness at the conical top.

2. The back contact solar cell of claim 1, wherein, the first doped layer having a thickness at the conical top greater than a thickness at the conical surface.

3. The back contact solar cell of claim 1, wherein, the back surface comprising a second doped region, the second doped region being provided with the textured surface; the back contact solar cell further comprising: a second doped layer provided on the second doped region, the second doped layer having a doping type opposite to that of the first doped layer, the second doped layer having a thickness at the recess greater than a thickness at the conical top.

4. The back contact solar cell of claim 3, wherein, the second doped layer having a thickness at the conical top greater than a thickness at the conical surface.

5. The back contact solar cell of claim 1, wherein, the first doped layer being one or a stack of at least two of a doped polysilicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

6. The back contact solar cell of claim 3, wherein, the second doped layer being one or a stack of at least two of a doped polysilicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

7. The back contact solar cell of claim 1, wherein, the first doped region being provided with at least two layers of the first doped layer stacked one on another, each of the layers of the first doped layer having a thickness at the recess greater than a thickness at the conical top.

8. The back contact solar cell of claim 7, wherein, each of the layers of the first doped layer having a thickness at the conical top greater than a thickness at the conical surface.

9. The back contact solar cell of claim 7 or 8, wherein, a thickness of the first doped layer being greater away from the silicon wafer than close to the silicon wafer.

10. The back contact solar cell of claim 1, wherein, further comprising: a first passivation layer provided on a side of the first doped layer facing away from the silicon wafer, the first passivation layer having a thickness at the recess greater than a thickness at the conical top, and the first passivation layer having a thickness at the conical top greater than a thickness at the conical surface.

11. The back contact solar cell of claim 3, wherein, further comprising: a second passivation layer provided on a side of the second doped layer facing away from the silicon wafer, the second passivation layer having a thickness at the recess greater than a thickness at the conical top, the second passivation layer having a thickness at the conical top greater than a thickness at the conical surfaces.

12. The back contact solar cell of claim 1, wherein, further comprising: a first tunneling layer provided between the first doped layer and the back surface, the first tunneling layer having a thickness at the recess greater than a thickness at the conical top, and the second tunneling layer having a thickness at the conical top greater than a thickness at the conical surface.

13. The back contact solar cell of claim 3, wherein, Further comprising: a second tunneling layer provided between the second doped layer and the back surface, the second tunneling layer having a thickness at the recess greater than a thickness at the conical top, the second tunneling layer having a thickness at the conical top greater than a thickness at the second tunneling layer at the conical surface.

14. The back contact solar cell of claim 1, wherein, The ratio of the thickness of the first doped layer at the concave part to the thickness of the first doped layer at the tip is 1.2-1.

8.

15. The back contact solar cell of claim 1, wherein, The ratio of the thickness of the first doped layer at the tip to the thickness of the first doped layer at the conical surface is 1.1-1.

5.

16. The back contact solar cell of claim 1, wherein, The tip is provided in a circular arc surface, the first doped layer at the tip is provided in a circular arc surface, and the curvature of the first doped layer at the tip is smaller than the curvature of the tip.

17. A battery assembly comprising the solar cell according to any one of claims 1-16.

18. A photovoltaic system comprising the battery assembly according to claim 17.

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