Back contact battery piece, preparation method thereof and photovoltaic module
By setting doped layers with different thicknesses and doping concentrations in different areas of the back contact cell, the leakage risk of the back contact cell is solved, and its performance and safety are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JINKO SOLAR (HAINING) CO LTS
- Filing Date
- 2025-09-03
- Publication Date
- 2026-04-21
AI Technical Summary
Back-contact battery cells pose a risk of leakage during use, affecting their safety.
A first doped stack with a relatively large thickness and high doping concentration is set in the first sub-region of the back contact cell, and a second doped stack with a relatively thin thickness and low doping concentration is set in the second sub-region and the overlapping region. This structural design enhances the field passivation effect, reduces surface recombination loss, improves open circuit voltage and fill factor, and reduces leakage risk.
It improves the working performance and power generation of the back contact cells, while significantly reducing the risk of leakage and improving safety.
Smart Images
Figure CN121908696A_ABST
Abstract
Description
[0001] This application is a divisional application of the patent application filed on September 3, 2025, with application number 2025112545549 and invention title "A back contact solar cell and its preparation method, a back contact tandem solar cell and a photovoltaic module". Technical Field
[0002] This application relates to the field of photovoltaic module technology, specifically to a back contact solar cell, its preparation method, and a photovoltaic module. Background Technology
[0003] Photovoltaic modules convert solar energy into electrical energy, offering advantages such as being pollution-free, not geographically limited, and inexhaustible, making them a major direction for developing new energy sources. Photovoltaic modules mainly consist of photovoltaic cells, photovoltaic glass, encapsulating film, backsheet, and frame. Back-contact cells, a type of photovoltaic cell, place both the positive and negative electrodes on the back side of the cell, reducing light obstruction by the grid lines, increasing the light-receiving area, and improving performance. However, back-contact cells pose a risk of leakage during use, affecting their safety. Summary of the Invention
[0004] In view of this, this application provides a back-contact solar cell, its preparation method, and a photovoltaic module, in order to solve the technical problem of high leakage risk in the prior art.
[0005] In a first aspect, embodiments of this application provide a back contact solar cell, the back contact solar cell comprising a silicon substrate, the back side of the silicon substrate comprising a first region, a second region, and an overlapping region located between the first region and the second region; the first region comprising a first sub-region and a second sub-region; wherein, the first sub-region is provided with a first doped stack along the thickness direction of the back contact solar cell, the first doped stack comprising a first oxide layer and a first doped layer stacked sequentially; the second sub-region is provided with a conductive thin film.
[0006] In this embodiment, by providing a first oxide layer, a first doped layer, and a second oxide layer in the first sub-region, the field passivation effect can be enhanced, carrier separation and collection can be accelerated, and surface recombination losses can be reduced, thereby improving the open-circuit voltage and fill factor of the back contact cell, optimizing the series resistance, and thus improving the working performance of the back contact cell. Furthermore, by not providing doped layers in the second sub-region and the overlapping region, the parasitic absorption in the second sub-region can be further reduced, effectively improving the bifaciality of the back contact cell, while also significantly reducing the leakage risk in the overlapping region.
[0007] In one specific embodiment, the second sub-region and the overlapping region are provided with a second doped stack; the second doped stack includes a silicon substrate doped layer.
[0008] In one specific embodiment, along the thickness direction of the back contact cell, the first doped stack includes a silicon substrate doped layer, a first oxide layer, a first doped layer, a second oxide layer, and a second doped layer stacked sequentially.
[0009] In one specific embodiment, the doping concentration W2 of the second doped layer satisfies 1E20 cm⁻¹. -3 <W2≤5E20cm -3 .
[0010] In one specific embodiment, the doping concentration W3 of the silicon substrate doped layer satisfies 1E17cm. -3 <W3≤1E19cm -3 .
[0011] Secondly, embodiments of this application provide a back contact solar cell, the back contact solar cell comprising a silicon substrate, the back side of the silicon substrate comprising a first region and a second region, and an overlapping region located between the first region and the second region; the first region comprising a first sub-region and a second sub-region; wherein, the first sub-region is provided with a first doped stack, and the second sub-region and the overlapping region are provided with a second doped stack; along the thickness direction of the back contact solar cell, the thickness of the first doped stack is greater than the thickness of the second doped stack; the doping concentration of the first doped stack is greater than the doping concentration of the second doped stack.
[0012] In this embodiment, the first sub-region is the region in contact with the metal electrode, and the area of the first sub-region can be greater than or equal to the area of the metal electrode. The second sub-region is the region within the first region excluding the first sub-region. The overlapping region is the overlapping area of the first and second regions with different polarities. The beneficial effects of this embodiment are as follows: By setting a thicker and more concentrated first doped layer in the first sub-region, the field passivation effect can be enhanced, carrier separation and collection can be accelerated, and surface recombination losses can be reduced, thereby improving the open-circuit voltage and fill factor of the back contact cell, optimizing the series resistance, and thus improving the working performance of the back contact cell. Furthermore, by setting a thinner and less concentrated second doped layer in the second sub-region, parasitic absorption in the second sub-region can be reduced, increasing the bifaciality of the back contact cell, thereby increasing the overall power generation of the back contact cell and improving its utilization efficiency. Simultaneously, by setting a thinner and less concentrated second doped layer in the overlapping region, the lateral diffusion range in the second doped layer can be controlled, preventing it from extending to other structural layers and causing excessive contact, thereby effectively reducing the leakage risk of the back contact cell and improving the safety of its use.
[0013] In one specific embodiment, along the thickness direction of the back contact cell, the first doped stack includes a first oxide layer, a first doped layer, a second oxide layer, and a second doped layer stacked sequentially; the second doped stack includes a first oxide layer and a first doped layer stacked sequentially.
[0014] In one specific embodiment, the thickness D1 of the first doped stack satisfies 50nm < D1 ≤ 250nm, and / or the thickness D2 of the second doped stack satisfies D2 ≤ 50nm.
[0015] In one specific embodiment, the doping concentration W1 of the first doped layer satisfies 1E19 cm⁻¹. -3 ≤W1≤1E20cm -3 And / or, the doping concentration W2 of the second doped layer satisfies 1E20cm -3 <W2≤5E20cm -3 .
[0016] In one specific embodiment, along the thickness direction of the back contact cell, the first doped stack includes a silicon substrate doped layer, a first oxide layer, a first doped layer, a second oxide layer, and a second doped layer stacked sequentially; the second doped stack includes a silicon substrate doped layer.
[0017] Thirdly, embodiments of this application provide a method for preparing a back contact battery cell, the method comprising: A silicon substrate is prepared, wherein the back side of the silicon substrate has a first region, a second region, and an overlapping region located between the first region and the second region, and the first region has a first sub-region and a second sub-region; A first doped stack is generated in the first sub-region, and a second doped stack is generated in the second sub-region and the overlapping region; Wherein, the thickness of the first doped stack is greater than the thickness of the second doped stack; and the doping concentration of the first doped stack is greater than the doping concentration of the second doped stack.
[0018] In this embodiment, by setting a first doped layer in the first sub-region, the open-circuit voltage and fill factor of the back contact cell can be improved, and the series resistance can be optimized to enhance the working performance of the back contact cell. Simultaneously, by setting a second doped layer in the second sub-region and the overlapping region, parasitic absorption in the second sub-region can be reduced, the bifaciality of the back contact cell can be increased, and the leakage risk in the overlapping region can be reduced, thus improving the safety of the back contact cell in use.
[0019] In one specific embodiment, the method for fabricating the back contact solar cell, in the steps of generating a first doped stack in the first sub-region and generating a second doped stack in the second sub-region and the overlapping region, specifically includes: A first oxide layer, a first doped layer, a second oxide layer, and a second doped layer are sequentially formed on the back side of the silicon substrate; Remove the second doped layer and the second oxide layer from the overlapping region and the second sub-region, and retain the first oxide layer, the first doped layer, the second oxide layer and the second doped layer of the first sub-region.
[0020] In one specific embodiment, the method for fabricating the back contact solar cell, in the steps of generating a first doped stack in the first sub-region and generating a second doped stack in the second sub-region and the overlapping region, specifically includes: A first oxide layer, a first doped layer, a second oxide layer, and a second doped layer are sequentially formed on the back side of the silicon substrate; Remove the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer from the overlapping region and the second sub-region, and retain the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer from the first sub-region.
[0021] In one specific embodiment, the method for preparing the back contact battery cell specifically includes: A mask layer is deposited on the back side of the second doped layer; Remove the mask layer from the second region, the overlapping region, and the second sub-region; Wet chemical cleaning removes the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer in the second region, and removes the second doped layer and the second oxide layer in the second sub-region and the overlapping region; The wet chemical cleaning time T1 satisfies 60s≤T1≤300s.
[0022] In one specific embodiment, the method for preparing the back contact battery cell specifically includes: A mask layer is deposited on the back side of the second doped layer; Remove the mask layer from the second region, the overlapping region, and the second sub-region; Wet chemical cleaning removes the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer in the second region; it also removes the second doped layer, the second oxide layer, the first doped layer, and the first oxide layer in the second sub-region and the overlapping region. Among them, the wet chemical cleaning time T2 satisfies 100s≤T2≤500s.
[0023] In one specific embodiment, after generating a first doped stack in the first sub-region and a second doped stack in the second sub-region and the overlapping region, the method for fabricating the back contact solar cell further includes: A first passivation layer and an antireflection layer are deposited on the front side of the silicon substrate; A second passivation layer and a third doped layer are deposited at low temperature on the back side of the silicon substrate; Remove the second passivation layer and the third doped layer from the second sub-region; A conductive thin film is deposited on the back side of the silicon substrate; A portion of the conductive film in the overlapping area is removed to form an isolation region; A metal electrode is fabricated on the back side of the silicon substrate.
[0024] Thirdly, embodiments of this application also provide a photovoltaic module, the photovoltaic module including back contact cells.
[0025] In this embodiment, the photovoltaic module can be composed of the back contact solar cell, photovoltaic glass, encapsulant film, backsheet, and frame described in the above embodiments. By using the back contact solar cell fabrication method described in the above embodiments, the overall efficiency and safety of the photovoltaic module can be guaranteed by improving the performance of the back contact solar cell and reducing the risk of leakage. Attached Figure Description
[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0027] Figure 1 This is a schematic diagram of the structure of the back contact battery cell provided in this application in a specific embodiment; Figure 2 This is a schematic diagram of step S11 in the method for preparing the back contact battery cell provided in this application; Figure 3 This is a schematic diagram of step S12 in the method for preparing the back contact battery cell provided in this application; Figure 4 This is a schematic diagram of step S12 in the method for preparing the back contact battery cell provided in this application; Figure 5 for Figure 4 This is a schematic diagram of step S12 in the method for preparing the back contact battery cell provided in this application; Figure 6a for Figure 1 The schematic diagram of the back contact cell in step S12 provided in the figure; Figure 6b for Figure 7The schematic diagram of the back contact cell in step S12 provided in the figure; Figure 7 This is a schematic diagram of the structure of the back contact battery cell provided in this application in another specific embodiment; Figure 8a for Figure 1 A schematic diagram of the back contact cell in step S13; Figure 8b for Figure 7 A schematic diagram of the back contact cell in step S13; Figure 9a for Figure 1 A schematic diagram of the back contact cell in step S14; Figure 9b for Figure 7 A schematic diagram of the back contact cell in step S14; Figure 10a for Figure 1 A schematic diagram of the back contact cell in step S15; Figure 10b for Figure 7 A schematic diagram of the back contact cell in step S15; Figure 11a for Figure 1 A schematic diagram of the back contact cell in step S16; Figure 11b for Figure 7 A schematic diagram of the back contact cell in step S16.
[0028] Figure label: 1- Back contact cell; 11-Silicon substrate; 111-First region; 111a-First sub-region; 111b-Second sub-region; 112-Second region; 113-Overlapping region; 12 - First doped stack; 13-Second doped stack; 14 - First oxide layer; 15 - First doped layer; 16 - Second oxide layer; 17 - Second doped layer; 18 - First passivation layer; 19-Antireflective layer; 20 - Second passivation layer; 21-Third doped layer; 22-Conductive thin film; 23 - Isolation Zone; 24-Metal electrode; 25 - Mask layer. Detailed Implementation
[0029] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.
[0030] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.
[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.
[0032] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0033] Photovoltaic modules convert solar energy into electrical energy, offering advantages such as being pollution-free, not geographically limited, and inexhaustible, making them a major direction for developing new energy sources. Photovoltaic modules mainly consist of photovoltaic cells, photovoltaic glass, encapsulating film, backsheet, and frame. Back-contact cells, a type of photovoltaic cell, place both the positive and negative electrodes on the back side of the cell, reducing light shading by the grid lines, increasing the light-receiving area, and improving performance. However, because the positive and negative electrodes are on the same side, back-contact cells are prone to leakage, affecting their safety.
[0034] To solve the above technical problems, such as Figure 1 As shown, this application embodiment provides a back contact solar cell 1, including a silicon substrate 11. The back side of the silicon substrate 11 includes a first region 111 and a second region 112, and an overlapping region 113 located between the first region 111 and the second region 112. The first region 111 includes a first sub-region 111a and a second sub-region 111b. The first sub-region 111a may be provided with a first doped stack 12, and the second sub-region 111b and the overlapping region 113 may be provided with a second doped stack 13. Along the thickness direction of the back contact solar cell 1, the thickness of the first doped stack 12 may be greater than the thickness of the second doped stack 13, and the doping concentration of the first doped stack 12 may be greater than the doping concentration of the second doped stack 13.
[0035] In this embodiment, the first sub-region 111a is the region in contact with the metal electrode 24, and the area of the first sub-region 111a can be greater than or equal to the area of the metal electrode 24. The second sub-region 111b is the region within the first region 111 excluding the first sub-region 111a. The overlapping region 113 is the overlapping region of the first region 111 and the second region 112 of different polarities. By providing a first doped stack 12 with a relatively large thickness and high doping concentration in the first sub-region 111a, the field passivation effect can be enhanced, the carrier separation and collection can be accelerated, and the surface recombination loss can be reduced, thereby improving the open-circuit voltage and fill factor of the back contact cell 1, optimizing the series resistance, and thus improving the working performance of the back contact cell 1. Furthermore, by providing a second doped stack 13 with a relatively thin thickness and low doping concentration in the second sub-region 111b, the parasitic absorption of the second sub-region 111b can be reduced, the bifaciality of the back contact cell 1 can be increased, thereby increasing the overall power generation of the back contact cell 1 and improving its utilization efficiency. Meanwhile, by setting a thinner second doped stack 13 with a lower doping concentration in the overlapping region 113, the lateral diffusion range in the second doped stack 13 can be controlled, preventing it from extending to other structural layers and causing excessive contact, thereby effectively reducing the leakage risk of the back contact cell 1 and improving the safety of the back contact cell 1.
[0036] In this embodiment, the first region 111 can be an N-type doped region, and the second region 112 can be a P-type doped region.
[0037] This application also provides a method for preparing a back contact battery cell 1, such as... Figures 1 to 5 and Figure 6a As shown, the preparation method includes, but is not limited to, the following steps: S11: Prepare a silicon substrate 11, wherein the back side of the silicon substrate 11 has a first region 111, a second region 112, and an overlapping region 113 located between the first region 111 and the second region 112, and the first region 111 has a first sub-region 111a and a second sub-region 111b. S12: A first doped stack 12 is generated in the first sub-region 111a, and a second doped stack 13 is generated in the second sub-region 111b and the overlapping region 113. The thickness of the first doped stack 12 is greater than the thickness of the second doped stack 13, and the doping concentration of the first doped stack 12 is greater than the doping concentration of the second doped stack 13.
[0038] In this embodiment, by providing a first doped stack 12 in the first sub-region 111a, the open-circuit voltage and fill factor of the back contact cell 1 can be improved, and the series resistance can be optimized to enhance the operating performance of the back contact cell 1. Simultaneously, by providing a second doped stack 13 in the second sub-region 111b and the overlapping region 113, the parasitic absorption in the second sub-region 111b can be reduced, the bifaciality of the back contact cell 1 can be improved, and the leakage risk in the overlapping region 113 can be reduced, thus enhancing the safety of the back contact cell 1 in use.
[0039] In one specific embodiment, such as Figure 1 As shown, along the thickness direction of the back contact cell 1, the first doped stack 12 may include a first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 stacked sequentially. The second doped stack 13 may include the first oxide layer 14 and the first doped layer 15 stacked together.
[0040] In this embodiment, the first doped stack 12 includes two oxide layers and two doped layers. Compared with the second doped stack 13 which only has one oxide layer and one doped layer, the first doped stack 12 can have a thicker thickness and a higher doping concentration to improve the working performance of the back contact cell 1. At the same time, the second doped stack 13 has a smaller thickness and doping concentration to reduce the risk of parasitic absorption and leakage of the back contact cell 1.
[0041] In the above embodiments, such as Figure 6a As shown, the thickness D1 of the first doped stack 12 can satisfy 50nm < D1 ≤ 250nm, and the thickness D2 of the second doped stack 13 can satisfy D2 ≤ 50nm.
[0042] In this embodiment, the thickness D1 of the first doped stack 12 can be 60nm, 100nm, 150nm, 200nm, 250nm, etc., to reduce the series resistance of the first doped stack 12, improve the photoelectric conversion efficiency of the back contact cell, and avoid increased carrier transport loss due to excessive thickness of the first doped stack 12. Meanwhile, the thickness D2 of the second doped stack 13 can be 5nm, 20nm, 30nm, 40nm, 50nm, etc., to reduce parasitic absorption of the second doped stack 13, improve the bifaciality of the back contact cell, and avoid excessively low carrier collection efficiency due to excessively thin thickness of the second doped stack 13.
[0043] In other embodiments, the thickness D1 of the first doped stack 12 and the thickness D2 of the second doped stack 13 can also be other values. In this embodiment, the specific values of the thickness of the first doped stack 12 and the thickness of the second doped stack 13 are not limited, and can be adjusted adaptively according to the actual situation.
[0044] In the above embodiments, such as Figure 6a As shown, the doping concentration W1 of the first doped layer 15 can satisfy 1E19 cm⁻¹. -3 ≤W1≤1E20 cm -3 And / or, the doping concentration W2 of the second doped layer 17 can satisfy 1E20cm -3 <W2≤5E20cm -3 .
[0045] In this embodiment, the doping concentration of the first doped layer 15 can be 1E19 cm⁻¹. -3 3E19 cm -3 5E19 cm -3 7E19 cm -3 1E20 cm -3 The doping concentration of the second doped layer 17 can be 2E20 cm⁻¹. -3 3E20 cm -3 4E20 cm -3 5E20 cm -3 The first doped stack 12 includes a first doped layer 15 and a second doped layer 17, and the second doped stack 13 includes only the first doped layer 15, so that the doping concentration of the second doped layer 17 is greater than the doping concentration of the first doped layer 15, thereby making the overall doping concentration of the first doped stack 12 greater than the overall doping concentration of the second doped stack 13. This improves the fill factor and open-circuit voltage of the first sub-region 111a, and reduces the parasitic absorption and leakage risk of the overlapping region of the second sub-region 111b, significantly improving the working performance of the back contact cell.
[0046] In other embodiments, the doping concentration W1 of the first doped layer 15 and the doping concentration W2 of the second doped layer 17 can also be other values. In this application embodiment, the doping concentration of the first doped layer 15 and the second doped layer 17 is not specifically limited, and can be adaptively adjusted according to the actual situation.
[0047] In the above embodiments, the doping concentration of the first doped stack 12 can be the average doping concentration within the overall thickness range of the second doped layer 17, and the doping concentration of the second doped stack 13 can be the average doping concentration within the overall thickness range of the first doped layer 15.
[0048] In another specific embodiment, the doping concentration of the first doped stack 12 can also be the average doping concentration within the overall thickness range of the first oxide layer 14, the first doped layer 15, the second oxide layer 16, and the second doped layer 17, and the doping concentration of the second doped stack 13 can also be the average doping concentration within the overall thickness range of the first oxide layer 14 and the first doped layer 15.
[0049] In the two embodiments described above, electrochemical capacitance-voltage profiling (ECV) can be used to measure the average doping concentration of different structural layers.
[0050] like Figures 1 to 5 , Figure 6a As shown, step S12 above may include, but is not limited to, the following specific steps: S121: A first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 are sequentially formed on the back side of the silicon substrate 11. S122a: Remove the second doped layer 17 and the second oxide layer 16 of the overlapping region 113 and the second sub-region 111b, and retain the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the first sub-region 111a.
[0051] In this embodiment, along the direction away from the silicon substrate 11, a first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 are sequentially stacked on the back side of the back contact cell 1. The doping concentration of the second doped layer 17 is greater than that of the first doped layer 15. Therefore, when the second doped layer 17 and the second oxide layer 16 are removed, the second doped stack 13 formed only includes the first doped layer 15 and the first oxide layer 14 with lower doping concentrations. This allows the doping concentration of the first doped stack 12 to be greater than that of the second doped stack 13, so that the overlapping region 113 and the second sub-region 111b form a thinner second doped stack 13 with a lower doping concentration, and the first sub-region 111a forms a thicker first doped stack 12 with a higher doping concentration.
[0052] In the above embodiments, such as Figure 4 , Figure 5 and Figure 6a As shown, step S122a may also include, but is not limited to, the following steps: S122a1: Deposit mask layer 25 on the back side of the second doped layer 17; S122a2: Remove the mask layer 25 from the second region 112, the overlapping region 113, and the second sub-region 111b; S122a3: Wet chemical cleaning removes the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the second region 112, and removes the second doped layer 17 and the second oxide layer 16 of the second sub-region 111b and the overlapping region 113. Among them, the wet chemical cleaning time T1 can meet the requirement of 60s≤T1≤300s.
[0053] In this embodiment, by depositing a mask layer 25 on the back side of the second doped layer 17 and removing the mask layer 25 of the second region 112, the overlapping region 113, and the second sub-region 111b, the mask layer 25 of the first sub-region 111a is retained. During the subsequent wet chemical cleaning process, the first doped stack 12 of the first sub-region 111a is not affected by the cleaning. At the same time, by controlling the wet chemical cleaning time, the second doped layer 17 and the second oxide layer 16 of the second sub-region 111b and the overlapping region 113 are removed, thereby achieving the effect of removing part of the structural layer.
[0054] The wet chemical cleaning time T1 can be 60s, 100s, 200s, 250s, 300s, etc. In other embodiments, the wet chemical cleaning time T1 can also be other specific values. The specific value of the wet chemical cleaning time T1 is not limited in the embodiments of this application, and can be adjusted adaptively according to the actual situation.
[0055] This application also provides another embodiment, such as... Figure 7 As shown, along the thickness direction of the back contact cell 1, the first doped stack 12 may include a silicon substrate doped layer, a first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 stacked sequentially. The second doped stack may include a silicon substrate doped layer (not shown in the figure).
[0056] In this embodiment, during the formation of the first doped layer 15 and the second doped layer 17 on the back side of the silicon substrate 11, some doping elements enter the interior of the silicon substrate 11, causing a portion of the structure of the silicon substrate 11 to form a silicon substrate doped layer. In this embodiment, the second doped stack consists only of the silicon substrate doped layer, which can further reduce the parasitic absorption of the second sub-region 111b, effectively improve the bifaciality of the back contact cell 1, and significantly reduce the leakage risk of the overlapping region 113.
[0057] In the above embodiments, such as Figure 7 As shown, the doping concentration W2 of the second doped layer 17 can satisfy 1E20 cm⁻¹. -3 <W2≤5E20 cm -3 The doping concentration W3 of the silicon substrate doped layer can meet the 1E17cm standard. -3 <W3≤1E19cm -3 .
[0058] In this embodiment, the doping concentration of the second doped layer 17 can be 2E20 cm⁻¹. -3 3E20 cm -3 4E20 cm -3 5E20 cm -3 The doping concentration of the silicon substrate doped layer can be 1E17 cm⁻¹. -35E17 cm -3 1E18 cm -3 5E18 cm -3 1E19 cm -3 The first doped stack 12 includes a first doped layer 15 and a second doped layer 17, while the second doped stack only includes a silicon substrate doped layer. The doping concentrations of the first doped layer 15 and the second doped layer 17 are both greater than those of the silicon substrate doped layer. This results in the overall doping concentration of the first doped stack 12 being significantly greater than that of the second doped stack. This improves the fill factor and open-circuit voltage of the first sub-region 111a, reduces the parasitic absorption of the second sub-region 111b and the leakage risk of the overlapping region 113, and significantly improves the working performance of the back contact cell 1.
[0059] In other embodiments, the doping concentration W2 of the second doped layer 17 and the doping concentration W3 of the silicon substrate doped layer can also be other values. In this embodiment, the specific values of the doping concentrations of the second doped layer 17 and the silicon substrate doped layer are not limited, and can be adjusted adaptively according to the actual situation.
[0060] In the above embodiments, the doping concentration of the first doped stack 12 can be the average doping concentration within the overall thickness range of the second doped layer 17, and the doping concentration of the second doped stack 13 can be the average doping concentration of the silicon substrate doped layer. The average doping concentration of the silicon substrate doped layer can be obtained by measuring the average doping concentration within the thickness range of 0.1μm-0.25μm on the back side of the silicon substrate.
[0061] In the above embodiments, electrochemical capacitance-voltage profiling (ECV) can be used to measure the average doping concentration of different structural layers.
[0062] In the above embodiments, such as Figures 3 to 5 , Figure 6b As shown, step S12 may also include, but is not limited to, the following steps: S121: A first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 are sequentially formed on the back side of the silicon substrate 11. S122b: Remove the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 from the overlapping region 113 and the second sub-region 111b, and retain the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 from the first sub-region 111a.
[0063] In this embodiment, the first oxide layer 14, the first doped layer 15, the second oxide layer 16, and the second doped layer 17 of the first sub-region 111a are retained to form a first doped stack 12 with a thicker thickness and a higher doping concentration. At the same time, the first oxide layer 14, the first doped layer 15, the second oxide layer 16, and the second doped layer 17 of the overlapping region 113 and the second sub-region 111b are removed so that the second doped stack only includes a silicon substrate doped layer with a lower doping concentration.
[0064] In the above embodiments, such as Figure 4 , Figure 5 and Figure 6b As shown, step S122b may also include, but is not limited to, the following steps: S122b1: A mask layer 25 is deposited on the back side of the second doped layer 17; S122b2: Remove the mask layer 25 from the second region 112, the overlapping region 113, and the second sub-region 111b; S122b3: Wet chemical cleaning removes the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the second region 112, and removes the second doped layer 17, the second oxide layer 16, the first doped layer 15 and the first oxide layer 14 of the second sub-region 111b and the overlapping region 113. Among them, the wet chemical cleaning time T2 satisfies 300s<T2≤500s.
[0065] In this embodiment, by depositing a mask layer 25 on the back side of the second doped layer 17 and removing the mask layer 25 of the second region 112, the overlapping region 113, and the second sub-region 111b, the mask layer 25 of the first sub-region 111a is retained. During the subsequent wet chemical cleaning process, the first doped stack 12 of the first sub-region 111a is not affected by the cleaning. At the same time, by controlling the wet chemical cleaning time, the first oxide layer 14, the first doped layer 15, the second oxide layer 16, and the second doped layer 17 of the second sub-region 111b and the overlapping region 113 are removed.
[0066] The wet chemical cleaning time T2 can be 350s, 400s, 450s, 500s, etc. In other embodiments, the wet chemical cleaning time T2 can also be other specific values. The embodiments of this application do not limit the specific value of the wet chemical cleaning time T2, and can be adjusted adaptively according to the actual situation.
[0067] In the two embodiments described above, such as Figure 1 and Figure 7As shown, by setting two oxide layers and two doped layers in the first doped stack 12, and making the doping concentrations of the first doped layer 15 and the second doped layer 17 different, the first doped stack 12 also has a doping concentration gradient, which can further increase the conductivity of charge carriers in the first doped stack 12, reduce the series resistance, and thus further improve the working performance of the back contact cell.
[0068] In one specific embodiment, such as Figure 1 , Figures 7 to 1 1 (i.e., including) Figure 8a , Figure 8b , Figure 9a , Figure 9b , Figure 10a , Figure 10b , Figure 11a and Figure 11b As shown in the figure, after step S12, the method for preparing the back contact cell may also include, but is not limited to, the following steps: S13: Deposit a first passivation layer 18 and an anti-reflection layer 19 on the front side of the silicon substrate 11; S14: Deposit a second passivation layer 20 and a third doped layer 21 at low temperature on the back side of the silicon substrate; S15: Remove the second passivation layer 20 and the third doped layer 21 from the second sub-region 111b; S16: Deposit a conductive thin film 22 on the back side of the silicon substrate 11; S17: Remove part of the conductive film 22 in the overlapping region 113 to form the isolation region 23; S18: Fabricate a metal electrode 24 on the back side of the silicon substrate 11.
[0069] In this embodiment, the complete back contact battery cell 1 is prepared through the above steps.
[0070] This application also provides a photovoltaic module (not shown in the figure), which can be composed of the back contact solar cell, photovoltaic glass, encapsulant film, backsheet, and frame described in the above embodiments. By using the back contact solar cell fabrication method described in the above embodiments, the overall efficiency and safety of the photovoltaic module can be guaranteed by improving the working performance of the back contact solar cell and reducing the risk of leakage.
[0071] The above description is merely an optional embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A back contact battery cell, characterized in that, The back contact cell includes a silicon substrate, and the back side of the silicon substrate includes a first region, a second region, and an overlapping region located between the first region and the second region; the first region includes a first sub-region and a second sub-region; The first sub-region is provided with a first doped stack, which includes a first oxide layer and a first doped layer stacked sequentially along the thickness direction of the back contact cell; the second sub-region is provided with a conductive thin film.
2. The back contact battery cell according to claim 1, characterized in that, The second sub-region and the overlapping region are provided with a second doped stack; the second doped stack includes a silicon substrate doped layer.
3. The back contact battery cell according to claim 1, characterized in that, Along the thickness direction of the back contact cell, the first doped stack includes a silicon substrate doped layer, a first oxide layer, a first doped layer, a second oxide layer, and a second doped layer stacked sequentially.
4. The back contact battery cell according to claim 3, characterized in that, The doping concentration W2 of the second doped layer satisfies 1E20 cm⁻¹ -3 <W2≤5E20 cm -3 .
5. The back contact battery cell according to claim 2, characterized in that, The doping concentration W3 of the silicon substrate doped layer satisfies 1E17cm. -3 <W3≤1E19cm -3 .
6. A method for preparing a back contact solar cell, used to prepare the back contact solar cell according to any one of claims 1-5, characterized in that, The method for preparing the back contact battery cell includes: A silicon substrate is prepared, wherein the back side of the silicon substrate has a first region, a second region, and an overlapping region located between the first region and the second region, and the first region has a first sub-region and a second sub-region; A first doped stack is generated in the first sub-region, and a second doped stack is generated in the second sub-region and the overlapping region; Wherein, the thickness of the first doped stack is greater than the thickness of the second doped stack; and the doping concentration of the first doped stack is greater than the doping concentration of the second doped stack.
7. The method for preparing a back contact battery cell according to claim 6, characterized in that, In the steps of generating a first doped stack in the first sub-region and generating a second doped stack in the second sub-region and the overlapping region, the method for preparing the back contact solar cell specifically includes: A first oxide layer, a first doped layer, a second oxide layer, and a second doped layer are sequentially formed on the back side of the silicon substrate; Remove the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer from the overlapping region and the second sub-region, and retain the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer from the first sub-region.
8. The method for preparing a back contact battery cell according to claim 7, characterized in that, In the step of removing the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer from the overlapping region and the second sub-region, the method for preparing the back contact solar cell specifically includes: A mask layer is deposited on the back side of the second doped layer; Remove the mask layer from the second region, the overlapping region, and the second sub-region; Wet chemical cleaning removes the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer in the second region; it also removes the second doped layer, the second oxide layer, the first doped layer, and the first oxide layer in the second sub-region and the overlapping region. Among them, the wet chemical cleaning time T2 satisfies 100s≤T2≤500s.
9. The method for preparing a back contact battery cell according to claim 6, characterized in that, After generating a first doped stack in the first sub-region and a second doped stack in the second sub-region and the overlapping region, the method for fabricating the back contact solar cell further includes: A first passivation layer and an antireflection layer are deposited on the front side of the silicon substrate; A second passivation layer and a third doped layer are deposited at low temperature on the back side of the silicon substrate; Remove the second passivation layer and the third doped layer from the second sub-region; A conductive thin film is deposited on the back side of the silicon substrate; A portion of the conductive film in the overlapping area is removed to form an isolation region; A metal electrode is fabricated on the back side of the silicon substrate.
10. A photovoltaic module, characterized in that, The photovoltaic module includes the back-contact solar cell as described in any one of claims 1-5.