Back contact battery piece, photovoltaic module and preparation method of back contact battery piece

Abstract

The invention discloses a back contact battery piece, a photovoltaic module and a preparation method of the back contact battery piece, and belongs to the technical field of photovoltaics. The back contact battery piece comprises a silicon wafer, a first doping layer and a second doping layer, the first doping layer and the second doping layer are arranged on the backlight face of the silicon wafer and are opposite in doping type, the first doping layer is located in a first doping area, the second doping layer is located in a second doping area, and the first doping area and the second doping area are arranged in a staggered mode in the direction parallel to the plane where the silicon wafer is located without intervals. Wherein the first doping layer is a first diffusion structure formed by diffusion of a doping source on the shady face of the silicon wafer, the distance between the face, close to the silicon wafer, of the first diffusion structure and the face, away from the silicon wafer, of the second doping layer is a preset distance, and the thickness of the silicon wafer located in the first doping area is larger than that of the silicon wafer located in the second doping area. According to the cell, effective isolation between the two doping layers with opposite doping types is realized through the silicon wafer with enough thickness, and laser etching of an isolation region is not needed.

Description

Technical Field

[0001] This application belongs to the field of photovoltaic technology, and particularly relates to a back-contact cell, a photovoltaic module, and a preparation method of the back-contact cell. Background Art

[0002] In a back-contact (BC) cell, both the PN junction and the metal contact of the cell are designed on the back side of the cell. Different from traditional crystalline silicon cells, there are no grid lines blocking on the front side of the BC cell, which can maximize the utilization of incident light, reduce optical losses, and thus improve the conversion efficiency of the cell.

[0003] In the BC cell, isolation regions are usually provided in the P-type conductive region and the N-type conductive region to prevent the direct contact of the PN junction, which may cause the short-circuit failure of the cell. The isolation regions are mainly prepared by a high-precision laser patterning process, and the laser etching accuracy directly affects the alignment of the subsequent metallization process. Even a very small deviation is likely to cause the attenuation of the cell performance. If there are connected defects in the isolation regions, it will cause a short circuit and lead to the failure of the cell.

[0004] Existing BC cells have defects such as a narrow process window, large fluctuations in process yield, and limited photoelectric conversion efficiency. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems existing in the prior art. For this purpose, this application provides a back-contact cell, a photovoltaic module, and a preparation method of the back-contact cell, which can achieve effective isolation between different doping regions without laser etching the isolation regions, significantly broaden the process compatibility window, and effectively improve production stability and cell efficiency.

[0006] In a first aspect, this application provides a back-contact cell, including: a silicon wafer, and a first doping layer and a second doping layer with opposite doping types provided on the backlight surface of the silicon wafer, the first doping layer is located in a first doping region, the second doping layer is located in a second doping region, and the first doping region and the second doping region are arranged alternately and without a gap along a direction parallel to the plane where the silicon wafer is located; wherein, the first doping layer is a first diffusion structure formed by diffusing a doping source on the backlight surface of the silicon wafer, the distance between the side of the first diffusion structure close to the silicon wafer and the side of the second doping layer far from the silicon wafer is a preset distance, and the thickness of the silicon wafer in the first doping region is greater than the thickness of the silicon wafer in the second doping region.

[0007] For the back-contact cell of the present application, a first doped layer is prepared by diffusing a doping source in a first doping region, a second doped layer is provided in a second doping region, there is no gap between adjacent first doping regions and second doping regions, the thickness of the silicon wafer in the first doping region is greater than the thickness of the silicon wafer in the second doping region, the distance between one side of the first diffusion structure close to the silicon wafer and one side of the second doped layer far from the silicon wafer is set as a preset distance, a silicon wafer with sufficient thickness is used to achieve effective isolation between two doped layers with opposite doping types, without laser etching the isolation region, significantly broadening the process compatibility window, and effectively improving production stability and cell efficiency.

[0008] For the back-contact cell of the present application, the second doped layer includes a second tunneling layer and a second doped crystalline silicon layer stacked in sequence along the direction away from the silicon wafer; The distance between one side of the first diffusion structure close to the silicon wafer and one side of the second doped crystalline silicon layer far from the silicon wafer is the preset distance.

[0009] According to an embodiment of the present application, the second doped layer is a second diffusion structure formed by diffusing a doping source on the backlight side of the silicon wafer, and the distance between one side of the first diffusion structure close to the silicon wafer and one side of the second diffusion structure far from the silicon wafer is the preset distance.

[0010] According to an embodiment of the present application, the preset distance is 10 μm - 15 μm.

[0011] According to an embodiment of the present application, the area of the first doping region is greater than or equal to the area of the second doping region.

[0012] According to an embodiment of the present application, the silicon wafer is an N-type silicon wafer or a P-type silicon wafer.

[0013] In a second aspect, the present application provides a photovoltaic module, which includes: The back-contact cell as described in the first aspect above.

[0014] In a third aspect, the present application provides a method for manufacturing a back-contact cell, which includes: Performing surface treatment on the silicon wafer; Preparing a first doped layer on the backlight side of the silicon wafer; Removing the first doped layer and part of the silicon wafer in the second doping region, so that the thickness of the silicon wafer in the first doping region is greater than the thickness of the silicon wafer in the second doping region, and the first doping region and the second doping region are arranged in a staggered manner and without a gap along the direction parallel to the plane where the silicon wafer is located; A second doped layer is prepared in the second doped region, the doping types of the first doped layer and the second doped layer are opposite, the first doped layer is a first diffusion structure formed by diffusing a doping source on the backlight side of the silicon wafer, and the distance between the side of the first diffusion structure close to the silicon wafer and the side of the second doped layer far from the silicon wafer is a preset distance.

[0015] According to the method for manufacturing a back-contact solar cell of the present application, a first doped layer is prepared by diffusing a doping source. After removing the first doped layer in the second doped region and part of the silicon wafer, a second doped layer is provided in the second doped region. There is no gap between adjacent first doped regions and second doped regions. The thickness of the silicon wafer in the first doped region is greater than the thickness of the silicon wafer in the second doped region. The distance between the side of the first diffusion structure close to the silicon wafer and the side of the second doped layer far from the silicon wafer is set as a preset distance. A silicon wafer with sufficient thickness is used to effectively isolate two doped layers with opposite doping types, eliminating the need for laser etching of isolation regions, significantly broadening the process compatibility window, and effectively improving production stability and cell efficiency.

[0016] According to an embodiment of the present application, the preset distance is 10 μm - 15 μm.

[0017] According to an embodiment of the present application, preparing the first doped layer on the backlight side of the silicon wafer includes: Diffusing on the backlight side of the silicon wafer to form a first diffusion structure, and forming a first protective film layer on the side of the first diffusion structure facing away from the silicon wafer; Removing the first doped layer in the second doped region and part of the silicon wafer includes: Laser-removing the first protective film layer in the second doped region; Wet-etching the first doped layer in the second doped region and part of the silicon wafer.

[0018] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Description of the Drawings

[0019] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 is one of the schematic structural diagrams of the back-contact solar cell provided by the embodiment of the present application; Figure 2 is another schematic structural diagram of the back-contact solar cell provided by the embodiment of the present application; Figure 3 is yet another schematic structural diagram of the back-contact solar cell provided by the embodiment of the present application; Figure 4 is a schematic flow chart of a method for manufacturing a back-contact solar cell provided by an embodiment of the present application; Figure 5 is one of the schematic diagrams of the intermediate structure of the back-contact solar cell provided by an embodiment of the present application; Figure 6 is another schematic diagram of the intermediate structure of the back-contact solar cell provided by an embodiment of the present application; Figure 7 is the third schematic diagram of the intermediate structure of the back-contact solar cell provided by an embodiment of the present application.

[0020] Reference numerals: silicon wafer 100, first doping region 110, second doping region 120, first doping layer 210, first protective film layer 211, second doping layer 220, second tunneling layer 221, second doped crystalline silicon layer 222, second diffusion structure 223, passivation layer 230, antireflection layer 240, first electrode 310, second electrode 320. Detailed Description of the Embodiment

[0021] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where 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 only for explaining the present application and should not be construed as limiting the present application.

[0022] The back-contact solar cell, photovoltaic module, and method for manufacturing the back-contact solar cell provided by the embodiments of the present application will be described in detail below with reference to the accompanying drawings through specific embodiments and their application scenarios.

[0023] As Figure 1 shown, the back-contact solar cell of the embodiment of the present application includes a silicon wafer 100 and a first doping layer 210 and a second doping layer 220 with opposite doping types provided on the backlight side of the silicon wafer 100.

[0024] Among them, the silicon wafer 100 has two opposite sides, a light-facing side facing the light source and a backlight side facing away from the light source.

[0025] In actual implementation, the silicon wafer 100 can be an N-type silicon wafer or a P-type silicon wafer.

[0026] It can be understood that the N-type silicon wafer and the P-type silicon wafer have opposite doping types. At the same time, the silicon wafers 100 of the two doping types have differences in aspects such as light-induced attenuation characteristics, electrical properties, efficiency, and cost. The N-type silicon wafer or the P-type silicon wafer can be selected as the silicon substrate of the back-contact solar cell according to specific requirements.

[0027] The doping types of the first doping layer 210 and the second doping layer 220 are opposite. When the first doping layer 210 corresponds to the P region for hole transport, the second doping layer 220 corresponds to the N region for electron transport; when the first doping layer 210 corresponds to the N region for electron transport, the second doping layer 220 corresponds to the P region for hole transport.

[0028] In this embodiment, the first doping layer 210 is located in the first doping region 110, and the second doping layer 220 is located in the second doping region 120. The first doping region 110 and the second doping region 120 are arranged in an interleaved manner in a direction parallel to the plane where the silicon wafer 100 is located and there is no gap.

[0029] In actual implementation, one of the first doping layer 210 and the second doping layer 220 is used to collect holes and transport them to the corresponding electrode, and the other is used to collect electrons and transport them to the corresponding electrode, realizing the separation and collection of photo-generated carriers.

[0030] It can be understood that the photo-generated current formed by the first doping layer 210 and the second doping layer 220 is collected by the metal electrodes. The first electrode 310 is in contact with the first doping layer 210, and the second electrode 320 is in contact with the second doping layer 220, realizing the selective separation of electrons and holes and leading out the photo-generated current.

[0031] Among them, the first electrode 310 and the second electrode 320 can be grid line structures such as fine grids and main grids.

[0032] In actual implementation, the back contact cell can also be provided with structures such as a passivation layer 230 and an antireflection layer 240 to reduce carrier recombination and increase light absorption. On the backlight side, the first electrode 310 passes through the passivation layer 230 and the antireflection layer 240 and is in contact with the first doping layer 210, and the second electrode 320 passes through the passivation layer 230 and the antireflection layer 240 and is in contact with the second doping layer 220.

[0033] Among them, the passivation layer 230 can be prepared with aluminum oxide (Al2O3), the thickness of the passivation layer 230 can be 2nm - 10nm, the antireflection layer 240 can be a single-layer structure or a multi-layer structure of a silicon nitride (SiNx) layer, a silicon oxide (SiOx) layer, and a silicon oxynitride (SiOxNy) layer, and the thickness of the antireflection layer 240 can be 10nm - 100nm.

[0034] It should be noted that the first doping region 110 and the second doping region 120 are arranged in an interleaved manner in a direction parallel to the plane where the silicon wafer 100 is located and there is no gap. There is no gap between adjacent first doping regions 110 and second doping regions 120. When preparing the back contact cell, there is no need to laser etch an isolation area between the first doping region 110 and the second doping region 120.

[0035] For example, as Figure 1As shown, the first doped region 110 and the second doped region 120 are arranged in an interleaved manner in the direction from right to left parallel to the plane of the silicon wafer 100, and there is no gap between the first doped region 110 and the second doped region 120.

[0036] It should be noted that the thickness of the silicon wafer 100 in the first doped region 110 is greater than the thickness of the silicon wafer 100 in the second doped region 120. The first doped layer 210 in the first doped region 110 and the second doped layer 220 in the second doped region 120 form a height difference in the direction perpendicular to the plane of the silicon wafer 100 (i.e., the thickness direction of the silicon wafer 100), so that the first doped layer 210 and the second doped layer 220 can be spaced apart in the thickness direction.

[0037] In this embodiment, the first doped layer 210 is a first diffusion structure formed by diffusing a doping source on the backlight surface of the silicon wafer 100.

[0038] In actual implementation, a doping source can be used to diffuse on the backlight surface of the silicon wafer 100, and a first diffusion structure is formed by diffusing in the thickness direction from the backlight surface to the light surface. The preparation equipment is simple and the process is mature. During the preparation process, parameters such as diffusion time, temperature, and gas flow can be controlled to control the doping depth and concentration distribution of the first diffusion structure.

[0039] Wherein, the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doped layer 220 far from the silicon wafer 100 is a preset distance.

[0040] It should be noted that the side of the first diffusion structure close to the silicon wafer 100 is related to the doping depth of the first diffusion structure. By adjusting process parameters such as diffusion temperature, time, and impurity source concentration, the depth of impurity diffusion can be controlled, that is, the doping depth is controllable. The impurity boundary of the first diffusion structure close to the silicon wafer 100 can be approximated as a plane, that is, the side of the first diffusion structure close to the silicon wafer 100. By setting the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doped layer 220 far from the silicon wafer 100 as a preset distance, in the thickness direction (such as Figure 1 the direction from top to bottom in the figure), enough thickness of the silicon wafer 100 is reserved for the first doped layer 210 and the second doped layer 220. While achieving effective electrical isolation, the process precision requirements for diffusion temperature, time, impurity source concentration, etc. can be reduced.

[0041] In the embodiment of the present application, the thickness of the silicon wafer 100 in the first doping region 110 is greater than the thickness of the silicon wafer 100 in the second doping region 120. The first doping layer 210 in the first doping region 110 and the second doping layer 220 in the second doping region 120 form a height difference in the thickness direction of the silicon wafer 100. For the first diffusion structure formed by the diffusion doping source of the first doping layer 210, the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doping layer 220 far from the silicon wafer 100 is set as a preset distance. The effective isolation between two doping layers with opposite doping types is achieved through the silicon wafer 100 with sufficient thickness (i.e., the preset distance), which can prevent short circuits caused by the contact of doping layers with different doping types.

[0042] Meanwhile, the first doping layer 210 and the second doping layer 220 are isolated by the silicon wafer 100 with sufficient thickness, and there is no gap between the adjacent first doping region 110 and the second doping region 120. When fabricating the back contact cell, there is no need to laser etch the isolation region between the first doping region 110 and the second doping region 120, which can reduce the requirements for laser etching accuracy during the fabrication process, significantly broaden the process compatibility window, and effectively improve the production stability and cell efficiency.

[0043] According to the back contact cell provided by the embodiment of the present application, the first doping layer 210 is prepared by diffusing a doping source in the first doping region 110, the second doping layer 220 is arranged in the second doping region 120, there is no gap between the adjacent first doping region 110 and the second doping region 120, the thickness of the silicon wafer 100 in the first doping region 110 is greater than the thickness of the silicon wafer 100 in the second doping region 120, the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doping layer 220 far from the silicon wafer 100 is set as a preset distance, the effective isolation between two doping layers with opposite doping types is achieved by using the silicon wafer 100 with sufficient thickness, there is no need to laser etch the isolation region, significantly broaden the process compatibility window, and effectively improve the production stability and cell efficiency.

[0044] In the embodiment of the present application, the first doping layer 210 is the first diffusion structure formed by diffusing the doping source on the backlight side of the silicon wafer 100, the second doping layer 220 can be the second diffusion structure 223 formed by diffusing the doping source on the backlight side of the silicon wafer 100, and the second doping layer 220 can also be a stacked layer structure.

[0045] I. The second doping layer 220 is a stacked layer structure.

[0046] In some embodiments, the second doping layer 220 includes a second tunneling layer 221 and a second doped crystalline silicon layer 222 stacked in sequence in the direction away from the silicon wafer 100; the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doped crystalline silicon layer 222 far from the silicon wafer 100 is the preset distance.

[0047] Among them, the second tunneling layer 221 can be prepared using silicon dioxide (SiO2). The second tunneling layer 221 is in contact with the silicon wafer 100. The second tunneling layer 221 and the second doped crystalline silicon layer 222 can form a passivation contact structure, which helps to reduce the recombination of carriers and reduce the contact recombination loss.

[0048] As Figure 2 shown, the first doped layer 210 is the first diffusion structure formed by diffusing the doping source on the backlight side of the silicon wafer 100. The second doped layer 220 includes a second tunneling layer 221 and a second doped crystalline silicon layer 222 stacked in sequence in the direction away from the silicon wafer 100. The distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doped crystalline silicon layer 222 away from the silicon wafer 100 is a preset distance h.

[0049] In this embodiment, the first doped layer 210 located in the first doped region 110 and the second doped layer 220 located in the second doped region 120 form a height difference in the thickness direction of the silicon wafer 100. The distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doped crystalline silicon layer 222 away from the silicon wafer 100 is set to the preset distance h. The isolation between the first diffusion structure and the second doped crystalline silicon layer 222 is achieved through a silicon wafer 100 with sufficient thickness to prevent short - circuit caused by the contact between the P - region and the N - region.

[0050] II. The second doped layer 220 is a diffusion structure.

[0051] In some embodiments, the second doped layer 220 is a second diffusion structure 223 formed by diffusing the doping source on the backlight side of the silicon wafer 100. The distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second diffusion structure 223 away from the silicon wafer 100 is a preset distance.

[0052] In this embodiment, the doping source can be used to diffuse on the backlight side of the silicon wafer 100, and the second diffusion structure 223 is formed by diffusion in the thickness direction from the backlight side towards the light side.

[0053] It can be understood that both the first doped layer 210 and the second doped layer 220 are diffusion structures formed by diffusing the diffusion source on the backlight side of the silicon wafer 100. The same preparation process can be selected during preparation to reduce the production complexity and production cost.

[0054] In actual implementation, the doping depth and concentration distribution of the first diffusion structure and the second diffusion structure 223 can be controlled by controlling parameters such as diffusion time, temperature, and gas flow rate.

[0055] As Figure 3As shown, the first diffusion structure is located in the first doping region 110, and the second diffusion structure 223 is located in the second doping region 120. The distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second diffusion structure 223 far from the silicon wafer 100 is a preset distance h.

[0056] In this embodiment, the first doping layer 210 located in the first doping region 110 and the second doping layer 220 located in the second doping region 120 form a height difference in the thickness direction of the silicon wafer 100. The distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second diffusion structure 223 far from the silicon wafer 100 is a preset distance h. The isolation between the first diffusion structure and the second diffusion structure 223 is achieved through a silicon wafer 100 with sufficient thickness to prevent short - circuit caused by the contact between the P region and the N region.

[0057] For example, the first doping layer 210 is the first diffusion structure diffused with boron as the doping source, that is, the P region, and the second doping layer 220 is the second diffusion structure 223 diffused with phosphorus as the doping source, that is, the N region. The distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second diffusion structure 223 far from the silicon wafer 100 is a preset distance h. The P region and the N region are isolated by a silicon wafer 100 with sufficient thickness, effectively preventing short - circuit.

[0058] In some embodiments, the preset distance is 10μm - 15μm.

[0059] In this embodiment, for the first doping region 110 and the second doping region 120 without a lateral spacer region, a silicon wafer 100 with a thickness of 10μm - 15μm is reserved in the longitudinal direction (i.e., the thickness direction of the silicon wafer 100) to isolate the first doping layer 210 and the second doping layer 220. The silicon wafer 100 with sufficient thickness prevents short - circuit caused by the contact between the P region and the N region. Without setting a lateral spacer region, the area ratio of the effective photoelectric conversion regions (the first doping region 110 and the second doping region 120) on the silicon wafer 100 can be increased. At the same time, the thickness difference of 10μm - 15μm will not have a great impact on subsequent processes such as electrode printing and solder ribbon welding.

[0060] In some embodiments, the area of the first doping region 110 is greater than or equal to the area of the second doping region 120.

[0061] In this embodiment, it can be that the total area of the first doping regions 110 on the silicon wafer 100 is greater than or equal to the total area of the second doping regions 120, or it can be that the area of a single first doping region 110 in the silicon wafer 100 is greater than or equal to the area of a single second doping region 120.

[0062] In actual implementation, the area ratios of the first doping region 110 and the second doping region 120 can be designed by comprehensively considering electrical properties, optical losses, process feasibility, etc. Among them, the area of the first doping region 110 can be set according to the number of carriers collected by the first doping layer 210, and the area of the second doping region 120 can be set according to the number of carriers collected by the second doping layer 220.

[0063] For example, the first doping layer 210 is the first diffusion structure obtained by diffusing a boron doping source, that is, the P region, and the first doping layer 210 is the second diffusion structure 223 obtained by diffusing a phosphorus doping source, that is, the N region. The total area of the first doping region 110 on the silicon wafer 100 is larger than the total area of the second doping region 120, and a slightly larger P region area is used to balance the hole collection efficiency.

[0064] The embodiment of the present application also provides a photovoltaic module.

[0065] The photovoltaic module includes the back contact cell as described above.

[0066] In actual implementation, multiple back contact cells can be interconnected by welding tapes to form a battery string, and after a series of encapsulation processes, a photovoltaic module is obtained.

[0067] According to the photovoltaic module provided by the embodiment of the present application, in the back contact cell of the photovoltaic module, the first doping layer 210 is prepared by diffusing a doping source in the first doping region 110, the second doping layer 220 is provided in the second doping region 120, there is no gap between the adjacent first doping region 110 and the second doping region 120, the thickness of the silicon wafer 100 in the first doping region 110 is greater than the thickness of the silicon wafer 100 in the second doping region 120, the distance between one side of the first diffusion structure close to the silicon wafer 100 and one side of the second doping layer 220 far from the silicon wafer 100 is set as a preset distance, and a silicon wafer 100 with sufficient thickness is used to achieve effective isolation between two doping layers with opposite doping types, without laser etching the isolation region, significantly broadening the process compatibility window, and effectively improving production stability and cell efficiency.

[0068] The embodiment of the present application also provides a preparation method of a back contact cell, and this preparation method can be used to prepare the back contact cell as described above.

[0069] As Figure 4 shown, the preparation method of the back contact cell includes: step 410, step 420, step 430 and step 440.

[0070] Step 410: Perform surface treatment on the silicon wafer 100.

[0071] In actual implementation, the silicon wafer 100 can be an N-type silicon wafer or a P-type silicon wafer.

[0072] In this step, surface treatment processes such as cleaning and texturing of the silicon wafer 100 can be carried out to facilitate subsequent preparation of structures such as the first doped layer 210.

[0073] For example, the silicon wafer 100 is selected as an N-type silicon wafer with a resistivity of 0.3 Ω·cm - 7 Ω·cm. The N-type silicon wafer is placed in an alkaline polishing trough machine, and the original silicon wafer 100 is polished on both sides using alkaline etching to form a tower base.

[0074] Among them, the size of the tower base can be 10 μm - 20 μm, the treatment time in the alkaline tank can be set to 50 s - 500 s, the treatment temperature can be set to 50 °C - 90 °C, the alkaline concentration is set to 0.5% - 2%, and the additive concentration is set to 0.5% - 1%.

[0075] It should be noted that along the direction parallel to the plane where the silicon wafer 100 is located, the first doped region 110 and the second doped region 120 that are alternately arranged and have no gap can be pre-divided. The first doped region 110 is used to form the first doped layer 210, and the second doped region 120 is used to form the second doped layer 220.

[0076] Step 420: Prepare the first doped layer 210 on the backlight side of the silicon wafer 100.

[0077] Among them, the first doped layer 210 is the first diffusion structure formed by the diffusion of the doping source on the backlight side of the silicon wafer 100.

[0078] In this step, within the entire range of the backlight side of the silicon wafer 100 (including the first doped region 110 and the second doped region 120), the doping source is used for diffusion to form the first diffusion structure. At this time, the first diffusion structure is distributed in the first doped region 110 and the second doped region 120.

[0079] It can be understood that during the battery preparation process, the first doped layer 210 can be distributed in the first doped region 110 and the second doped region 120, and only the first doped layer 210 in the first doped region 110 is retained in the obtained back-contact battery chip.

[0080] Step 430: Remove the first doped layer 210 in the second doped region 120 and part of the silicon wafer 100.

[0081] In this step, the first doped layer 210 in the second doped region 120 is removed, and then part of the silicon wafer 100 in the second doped region 120 is removed, so that the thickness of the silicon wafer 100 in the first doped region 110 is greater than the thickness of the silicon wafer 100 in the second doped region 120.

[0082] Step 440: Prepare the second doped layer 220 in the second doped region 120.

[0083] The doping types of the first doping layer 210 and the second doping layer 220 are opposite, and the distance between a side of the first diffusion structure close to the silicon wafer 100 and a side of the second doping layer 220 away from the silicon wafer 100 is a preset distance.

[0084] In this step, the thickness of the silicon wafer 100 located in the first doping region 110 is greater than the thickness of the silicon wafer 100 located in the second doping region 120, and a second doping layer 220 is prepared in the second doping region 120. The first doping layer 210 located in the first doping region 110 and the second doping layer 220 located in the second doping region 120 form a height difference in a direction perpendicular to the plane of the silicon wafer 100 (i.e., the thickness direction of the silicon wafer 100), so that the first doping layer 210 and the second doping layer 220 can be spaced apart in the thickness direction.

[0085] The first doping layer 210 and the second doping layer 220 are isolated by a silicon wafer 100 of sufficient thickness (i.e., a preset distance), so that doping layers of different doping types can be prevented from contacting each other and causing a short circuit. There is no gap between adjacent first doping regions 110 and second doping regions 120. When preparing a back-contact cell, there is no need to laser-etch an isolation region between the first doping region 110 and the second doping region 120, which can reduce the laser etching accuracy requirements during the preparation process, significantly broaden the process compatibility window, and effectively improve production stability and battery efficiency.

[0086] According to the method for preparing a back-contact cell provided in an embodiment of the present application, a first doping layer 210 is prepared by diffusion of a doping source, and after removing the first doping layer 210 and a portion of the silicon wafer 100 in the second doping region 120, a second doping layer 220 is arranged in the second doping region 120, and there is no gap between adjacent first doping regions 110 and second doping regions 120. The thickness of the silicon wafer 100 located in the first doping region 110 is greater than the thickness of the silicon wafer 100 located in the second doping region 120. The distance between a side of the first diffusion structure close to the silicon wafer 100 and a side of the second doping layer 220 away from the silicon wafer 100 is set to a preset distance, and a silicon wafer 100 of sufficient thickness is used to achieve effective isolation between two doping layers of opposite doping types, without the need for laser etching of the isolation region, thereby significantly broadening the process compatibility window and effectively improving production stability and cell efficiency.

[0087] In some embodiments, the predetermined distance is 10 μm-15 μm.

[0088] In some embodiments, the first doping layer 210 is formed on the backlight surface of the silicon wafer 100, including: Diffusion is performed on the backlight surface of the silicon wafer 100 to form a first diffusion structure, and a first protective film layer 211 is formed on a side of the first diffusion structure away from the silicon wafer 100; Removing the first doping layer 210 of the second doping region 120 and a part of the silicon wafer 100 includes: Removing the first protective film layer 211 of the second doping region 120 by laser; Wet-etching the first doping layer 210 of the second doping region 120 and a part of the silicon wafer 100.

[0089] As Figure 5 shown, the first doping layer 210 is prepared over the entire range of the backlight surface of the silicon wafer 100. First, a first diffusion structure is formed, and then a first protective film layer 211 is formed on the side of the first diffusion structure facing away from the silicon wafer 100.

[0090] It can be understood that the first protective film layer 211 can protect the first diffusion structure. During the process of preparing the first doping layer 210, after the first diffusion structure is formed, the first protective film layer 211 can be formed on the side of the first diffusion structure facing away from the silicon wafer 100.

[0091] For example, boron trichloride (BCl3) or boron tribromide (BBr3) is used as the boron doping source to perform diffusion on the backlight surface of the silicon wafer 100 to form a first diffusion structure. After the diffusion is completed, the process parameters are adjusted, and a first protective film layer 211 is formed on the side of the first diffusion structure facing away from the silicon wafer 100. The first protective film layer 211 is borosilicate glass (BSG).

[0092] For another example, a phosphorus doping source is used to perform diffusion on the backlight surface of the silicon wafer 100 to form a first diffusion structure. After the diffusion is completed, the process parameters are adjusted, and a first protective film layer 211 is formed on the side of the first diffusion structure facing away from the silicon wafer 100. The first protective film layer 211 is phosphosilicate glass (PSG).

[0093] As Figure 6 shown, the first protective film layer 211 of the second doping region 120 can be removed by laser, exposing the first doping layer 210 of the second doping region 120. As Figure 7 shown, the first doping layer 210 of the second doping region 120 and a part of the silicon wafer 100 are then wet-etched to facilitate the subsequent preparation of the second doping layer 220.

[0094] It can be understood that wet etching refers to selectively removing a part of the silicon wafer 100 through a chemical reaction with the material surface in an acid solution (such as hydrofluoric acid) or an alkaline solution to form the required electrical structure.

[0095] In this embodiment, after the first protective film layer 211 of the second doping region 120 is removed by laser, the first doping layer 210 of the second doping region 120 is exposed. The first doping layer 210 of the second doping region 120 is removed by an acid solution or an alkaline solution. At this time, the first doping layer 210 of the first doping region 110 is protected by the first protective film layer 211 and will not be etched.

[0096] In actual implementation, after removing the first doping layer 210 of the second doping region 120, the silicon wafer 100 of the second doping region 120 is continuously removed, wherein the etching depth h of the silicon wafer 100 is 10 μm - 15 μm, so that the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doping layer 220 far from the silicon wafer 100 is a preset distance h = 10 μm - 15 μm, and effective isolation between two doping layers with opposite doping types is achieved through the silicon wafer 100 with sufficient thickness.

[0097] It can be understood that by removing the first doping layer 210 and part of the silicon wafer 100 of the second doping region 120, the second doping layer 220 can be prepared in the second doping region 120.

[0098] In some embodiments, the second doping layer 220 includes a second tunneling layer 221 and a second doped polysilicon layer 222 stacked in sequence in a direction away from the silicon wafer 100; the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second doped polysilicon layer 222 far from the silicon wafer 100 is a preset distance.

[0099] In other embodiments, the second doping layer 220 is a second diffusion structure 223 formed by diffusing a doping source on the backlight side of the silicon wafer 100, and the distance between the side of the first diffusion structure close to the silicon wafer 100 and the side of the second diffusion structure 223 far from the silicon wafer 100 is a preset distance.

[0100] The terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of this application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are usually of the same type, and the number of objects is not limited. For example, the first object can be one or multiple. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / " generally represents an "or" relationship between the associated objects before and after.

[0101] In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "lateral", "thickness", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application.

[0102] In the description of the present application, the "first feature" and the "second feature" may include one or more of such features.

[0103] In the description of the present application, the meaning of "a plurality" is two or more.

[0104] In the description of the present application, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween.

[0105] In the description of the present application, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature.

[0106] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0107] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A back-contact solar cell, characterized in that, Comprising: A silicon wafer, a first doping layer and a second doping layer with opposite doping types provided on the backlight side of the silicon wafer, the first doping layer is located in a first doping region, the second doping layer is located in a second doping region, and the first doping region and the second doping region are arranged in a staggered manner along a direction parallel to the plane where the silicon wafer is located and there is no gap; Wherein, the first doping layer is a first diffusion structure formed by diffusing a doping source on the backlight side of the silicon wafer, the distance between the side of the first diffusion structure close to the silicon wafer and the side of the second doping layer far from the silicon wafer is a preset distance, and the thickness of the silicon wafer in the first doping region is greater than the thickness of the silicon wafer in the second doping region.

2. The back-contact solar cell according to claim 1, wherein The second doping layer includes a second tunneling layer and a second doped polysilicon layer stacked in sequence along the direction away from the silicon wafer; The distance between the side of the first diffusion structure close to the silicon wafer and the side of the second doped polysilicon layer far from the silicon wafer is the preset distance.

3. The back-contact cell according to claim 1, wherein, The second doping layer is a second diffusion structure formed by diffusing a doping source on the backlight side of the silicon wafer, and the distance between the side of the first diffusion structure close to the silicon wafer and the side of the second diffusion structure far from the silicon wafer is the preset distance.

4. The back-contact cell according to any one of claims 1-3, characterized in that, The preset distance is 10μm - 15μm.

5. The back-contact cell according to any one of claims 1-3, characterized in that, The area of the first doping region is greater than or equal to the area of the second doping region.

6. The back contact cell according to any one of claims 1-3, characterized in that, The silicon wafer is an N-type silicon wafer or a P-type silicon wafer.

7. A photovoltaic module, characterized in that, Comprising: The back contact cell according to any one of claims 1 - 6.

8. A preparation method of a back-contact battery cell, characterized in that, Comprising: Performing surface treatment on the silicon wafer; Preparing a first doping layer on the backlight side of the silicon wafer; Removing the first doping layer and part of the silicon wafer in the second doping region so that the thickness of the silicon wafer in the first doping region is greater than the thickness of the silicon wafer in the second doping region, and the first doping region and the second doping region are arranged in a staggered manner along a direction parallel to the plane where the silicon wafer is located and there is no gap; Preparing a second doping layer in the second doping region, the doping types of the first doping layer and the second doping layer are opposite, the first doping layer is a first diffusion structure formed by diffusing a doping source on the backlight side of the silicon wafer, and the distance between the side of the first diffusion structure close to the silicon wafer and the side of the second doping layer far from the silicon wafer is a preset distance.

9. The preparation method of the back-contact battery cell according to claim 8, wherein, The preset distance is 10μm - 15μm.

10. The method for manufacturing a back contact cell according to claim 8 or 9, characterized in that Preparing a first doping layer on the backlight side of the silicon wafer, comprising: Performing diffusion on the backlight side of the silicon wafer to form a first diffusion structure, and forming a first protective film layer on the side of the first diffusion structure away from the silicon wafer; Removing the first doping layer and part of the silicon wafer in the second doping region, comprising: Removing the first protective film layer in the second doping region by laser; Wet etching the first doping layer and part of the silicon wafer in the second doping region.

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