Back contact battery piece, preparation method thereof and photovoltaic module

Abstract

The invention relates to the technical field of photovoltaic modules, in particular to a back contact battery piece, a preparation method thereof and a photovoltaic module. The back contact battery piece comprises a silicon substrate, and the back face of the silicon substrate comprises a first area, a second area and an overlapping area located between the first area and the second area. The first region includes a first sub-region and a second sub-region. Wherein the first sub-region is provided with a first doped laminated layer, the second sub-region and the overlapping region are provided with a second doped laminated layer, and the thickness of the first doped laminated layer is greater than that of the second doped laminated layer along the thickness direction of the back contact cell. The doping concentration of the first doping lamination layer is greater than the doping concentration of the second doping lamination layer. According to the back contact battery piece, by arranging the second doping lamination layer which is relatively thin in thickness and relatively low in doping concentration in the overlapping region, the transverse diffusion range in the second doping lamination layer can be controlled, the second doping lamination layer is prevented from extending to generate excessive contact with other structural layers, so that the electric leakage risk of the back contact battery piece is effectively reduced, and the use safety of the back contact battery piece is improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic modules, and in particular to a back-contact cell, a preparation method thereof, and a photovoltaic module. Background Art

[0002] Photovoltaic modules convert solar energy into electricity, offering advantages such as being pollution-free, geographically unrestricted, and inexhaustible, making them a key focus for developing new energy sources. PV modules primarily consist of photovoltaic cells, photovoltaic glass, film, backsheet, and frame. Back-contact cells, a type of photovoltaic cell, reduce grid lines blocking light by placing both the positive and negative electrodes on the backlight side of the cell, increasing the light-receiving area and improving performance. However, back-contact cells carry the risk of electrical leakage during use, impacting their safety. Summary of the Invention

[0003] In view of this, the present application provides a back-contact cell, a preparation method thereof, and a photovoltaic module, so as to solve the technical problem of high leakage risk of back-contact cells in the prior art.

[0004] In a first aspect, an embodiment of the present application provides a back-contact cell, comprising a silicon substrate, the back side of the silicon substrate comprising a first region, a second region, and an overlapping region 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 cell, 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.

[0005] In this embodiment, the first sub-region is the area 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 area within the first region excluding the first sub-region, and the overlapping region is the overlapping region of the first and second regions of different polarities. This embodiment has the following beneficial effects: by providing a thicker and more highly doped first doped layer in the first sub-region, field passivation 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 enhancing the operating performance of the back-contact cell. Furthermore, by providing a thinner and less highly doped 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 efficiency. Furthermore, by providing a thinner and less highly doped second doped layer in the overlapping region, the lateral diffusion range of the second doped layer can be controlled, preventing it from extending into excessive contact with other structural layers, thereby effectively reducing the risk of leakage in the back-contact cell and improving the safety of the back-contact cell.

[0006] In a 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 in sequence; the second doped stack includes a first oxide layer and a first doped layer stacked.

[0007] In a specific embodiment, the thickness D1 of the first doped stack satisfies 50 nm<D1≤250 nm, and / or the thickness D2 of the second doped stack satisfies D2≤50 nm.

[0008] In a specific embodiment, the doping concentration W1 of the first doping layer satisfies 1E19 cm -3 ≤W1≤1E20cm -3 , and / or, the doping concentration W2 of the second doping layer satisfies 1E20cm -3 <W2≤5E20cm -3 .

[0009] In a specific embodiment, along the thickness direction of the back contact cell, the first doped stack includes a silicon base doped layer, a first oxide layer, a first doped layer, a second oxide layer and a second doped layer stacked in sequence; the second doped stack includes a silicon base doped layer.

[0010] In a specific embodiment, the doping concentration W2 of the second doping layer satisfies 1E20 cm -3 <W2≤5E20cm -3 , and / or, the doping concentration W3 of the silicon substrate doping layer satisfies 1E17cm-3 <W3≤1E19cm -3 .

[0011] In a second aspect, an embodiment of the present application provides a method for preparing a back-contact cell, the method comprising: Prepare a silicon substrate, wherein the back side of the silicon substrate has a first region, a second region, and an overlapping region between the first region and the second region, and the first region has a first sub-region and a second sub-region; 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 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.

[0012] In this embodiment, by providing a first doped stack in the first sub-region, the open-circuit voltage and fill factor of the back-contact cell can be increased, the series resistance can be optimized, and the operating performance of the back-contact cell can be improved. Simultaneously, providing a second doped stack in the second sub-region and the overlap region can reduce parasitic absorption in the second sub-region, increase the bifaciality of the back-contact cell, and reduce the risk of leakage in the overlap region, thereby improving the safety of the back-contact cell.

[0013] In a specific embodiment, in the step 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 cell specifically includes: sequentially forming a first oxide layer, a first doping layer, a second oxide layer, and a second doping layer on the back side of the silicon substrate; The second doping layer and the second oxide layer in the overlapping region and the second sub-region are removed, and the first oxide layer, the first doping layer, the second oxide layer and the second doping layer in the first sub-region are retained.

[0014] In a specific embodiment, in the step 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 cell specifically includes: sequentially forming a first oxide layer, a first doping layer, a second oxide layer, and a second doping layer on the back side of the silicon substrate; The first oxide layer, the first doping layer, the second oxide layer and the second doping layer in the overlapping area and the second sub-area are removed, and the first oxide layer, the first doping layer, the second oxide layer and the second doping layer in the first sub-area are retained.

[0015] In a specific embodiment, the method for preparing the back contact cell specifically includes: depositing a mask layer on the back side of the second doped layer; removing the mask layer in the second region, the overlapping region, and the second sub-region; removing the first oxide layer, the first doping layer, the second oxide layer and the second doping layer in the second region, and removing the second doping layer and the second oxide layer in the second sub-region and the overlapping region by wet chemical cleaning; The wet chemical cleaning time T1 satisfies 60s≤T1≤300s.

[0016] In a specific embodiment, the method for preparing the back contact cell specifically includes: depositing a mask layer on the back side of the second doped layer; removing the mask layer in the second region, the overlapping region, and the second sub-region; removing the first oxide layer, the first doped layer, the second oxide layer and the second doped layer in the second region, and removing 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 by wet chemical cleaning; The wet chemical cleaning time T2 satisfies 100s≤T2≤500s.

[0017] In a specific embodiment, after 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 cell further includes: Depositing a first passivation layer and an anti-reflection layer on the front surface of the silicon substrate; depositing a second passivation layer and a third doping layer on the back side of the silicon substrate at low temperature; removing the second passivation layer and the third doping layer in the second sub-region; depositing a conductive film on the back side of the silicon substrate; removing a portion of the conductive film in the overlapping area to form an isolation area; A metal electrode is prepared on the back side of the silicon substrate.

[0018] In a third aspect, an embodiment of the present application further provides a photovoltaic module, which includes a back-contact cell.

[0019] In this embodiment, the photovoltaic module can be composed of the back-contact cell, photovoltaic glass, adhesive film, backsheet, and frame described in the above embodiments. The back-contact cell produced using the back-contact cell preparation method described in the above embodiments can improve the operating performance of the back-contact cell and reduce the risk of leakage, thereby ensuring the overall operating efficiency and safety of the photovoltaic module. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 This is a schematic structural diagram of a back-contact cell provided in this application in a specific embodiment; Figure 2 This is a schematic structural diagram of step S11 in the method for preparing a back-contact solar cell provided in this application; Figure 3 This is a schematic structural diagram of step S12 in the method for preparing a back-contact solar cell provided in this application; Figure 4 This is a schematic structural diagram of step S12 in the method for preparing a back-contact solar cell provided in this application; Figure 5 for Figure 4 This is a schematic structural diagram of step S12 in the method for preparing a back-contact solar cell provided in this application; Figure 6a for Figure 1 A schematic structural diagram of the back contact cell in step S12 provided in ; Figure 6b for Figure 7 A schematic structural diagram of the back contact cell in step S12 provided in ; Figure 7 This is a schematic structural diagram of another specific embodiment of the back contact cell provided in this application; Figure 8a for Figure 1 Schematic diagram of the structure of the back contact cell in step S13; Figure 8b for Figure 7 Schematic diagram of the structure of the back contact cell in step S13; Figure 9a for Figure 1 Schematic diagram of the structure of the back contact cell in step S14; Figure 9b for Figure 7 Schematic diagram of the structure of the back contact cell in step S14; Figure 10a for Figure 1 A schematic structural diagram of the back contact cell in step S15; Figure 10b for Figure 7A schematic structural diagram of the back contact cell in step S15; Figure 11a for Figure 1 A schematic structural diagram of the back contact cell in step S16; Figure 11b for Figure 7 Schematic diagram of the structure of the back contact cell in step S16.

[0022] Reference numerals: 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 doping layer; 16- second oxide layer; 17- second doping layer; 18- first passivation layer; 19-antireflection layer; 20- second passivation layer; 21- third doping layer; 22-conductive film; 23-Isolated area; 24-metal electrode; 25-Mask layer. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0026] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. Furthermore, the character " / " in this document generally indicates an "or" relationship between the associated objects.

[0027] Photovoltaic modules convert solar energy into electricity, offering advantages such as being pollution-free, geographically unrestricted, and inexhaustible, making them a key focus for renewable energy development. PV modules primarily consist of photovoltaic cells, photovoltaic glass, film, backsheet, and frame. Back-contact cells, a type of photovoltaic cell, reduce grid lines blocking light by placing both the positive and negative electrodes on the backlight side of the cell, increasing the light-receiving area and improving performance. However, the co-location of the positive and negative electrodes can lead to leakage issues in back-contact cells, compromising their safety.

[0028] In order to solve the above technical problems, Figure 1 As shown, an embodiment of the present application provides a back-contact cell 1, comprising a silicon substrate 11. The back side of the silicon substrate 11 includes a first region 111, a second region 112, and an overlapping region 113 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 layer 12, and the second sub-region 111b and the overlapping region 113 may be provided with a second doped layer 13. Along the thickness direction of the back-contact cell 1, the thickness of the first doped layer 12 may be greater than the thickness of the second doped layer 13, and the doping concentration of the first doped layer 12 may be greater than the doping concentration of the second doped layer 13.

[0029] 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 between the first region 111 and the second region 112 of different polarities. Providing a thicker and more highly doped first doped layer 12 in the first sub-region 111a enhances field passivation, accelerates carrier separation and collection, and reduces surface recombination losses, thereby increasing the open-circuit voltage and fill factor of the back-contact cell 1, optimizing the series resistance, and thus improving the operating performance of the back-contact cell 1. Furthermore, providing a thinner and less highly doped second doped layer 13 in the second sub-region 111b reduces parasitic absorption in the second sub-region 111b, improving the bifaciality of the back-contact cell 1, and thereby increasing the overall power generation of the back-contact cell 1 and its efficiency. At the same time, by setting a second doping stack 13 with a thinner thickness and lower doping concentration in the overlapping area 113, the lateral diffusion range in the second doping stack 13 can be controlled to prevent it from extending to excessive contact with other structural layers, thereby effectively reducing the leakage risk of the back contact battery cell 1 and improving the safety of the back contact battery cell 1.

[0030] In the embodiment of the present application, the first region 111 may be an N-type doped region, and the second region 112 may be a P-type doped region.

[0031] The present application also provides a method for preparing a back contact cell 1. Figures 1 to 5 and Figure 6a As shown, the preparation method includes but is not limited to the following steps: S11: preparing 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 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: forming a first doped stack 12 in the first sub-region 111 a, and forming a second doped stack 13 in the second sub-region 111 b and the overlapping region 113; The thickness of the first doped layer 12 is greater than that of the second doped layer 13 , and the doping concentration of the first doped layer 12 is greater than that of the second doped layer 13 .

[0032] In this embodiment, by providing the 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 increased, the series resistance can be optimized, and the operating performance of the back-contact cell 1 can be improved. Simultaneously, by providing the second doped stack 13 in the second sub-region 111b and the overlapping region 113, parasitic absorption in the second sub-region 111b can be reduced, thereby increasing the bifaciality of the back-contact cell 1 and reducing the risk of leakage in the overlapping region 113, thereby improving the safety of the back-contact cell 1.

[0033] In a specific embodiment, Figure 1 As shown, along the thickness direction of the back contact cell 1, the first doped layer 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 in sequence. The second doped layer stack 13 may include a first oxide layer 14 and a first doped layer 15 stacked in sequence.

[0034] In this embodiment, the first doped stack 12 includes two oxide layers and two doped layers. Compared with the second doped stack 13 having only 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 battery cell 1. At the same time, the thickness and doping concentration of the second doped stack 13 are smaller to reduce the parasitic absorption and leakage risks of the back contact battery cell 1.

[0035] In the above embodiment, if Figure 6a As shown, the thickness D1 of the first doped stack 12 may satisfy 50 nm < D1 ≤ 250 nm, and the thickness D2 of the second doped stack 13 may satisfy D2 ≤ 50 nm.

[0036] In this embodiment, the thickness D1 of the first doped layer 12 can be 60 nm, 100 nm, 150 nm, 200 nm, 250 nm, etc., to reduce the series resistance of the first doped layer 12, improve the photoelectric conversion efficiency of the back-contact cell, and avoid increased carrier transmission losses due to an excessive thickness of the first doped layer 12. Meanwhile, the thickness D2 of the second doped layer 13 can be 5 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc., to reduce parasitic absorption of the second doped layer 13, improve the bifaciality of the back-contact cell, and avoid low carrier collection efficiency due to an excessively thin second doped layer 13.

[0037] In other embodiments, the thickness D1 of the first doped stack 12 and the thickness D2 of the second doped stack 13 may also be other values. In the embodiment of the present application, 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 adaptively adjusted according to actual conditions.

[0038] In the above embodiment, if Figure 6a As shown, the doping concentration W1 of the first doping layer 15 can meet 1E19 cm -3 ≤W1≤1E20 cm -3 , and / or, the doping concentration W2 of the second doping layer 17 may satisfy 1E20cm -3 <W2≤5E20cm -3 .

[0039] In this embodiment, the doping concentration of the first doping layer 15 can be 1E19 cm -3 、3E19 cm -3 、5E19 cm -3 、7E19 cm -3 、1E20 cm -3 The doping concentration of the second doping layer 17 can be 2E20 cm -3 、3E20 cm -3 、4E20 cm -3 、5E20 cm -3 The first doping stack 12 includes a first doping layer 15 and a second doping layer 17, and the second doping stack 13 only includes the first doping layer 15, so that the doping concentration of the second doping layer 17 is greater than the doping concentration of the first doping layer 15, so that the doping concentration of the first doping stack 12 as a whole is greater than the doping concentration of the second doping stack 13 as a whole, so as to improve the fill factor and open-circuit voltage of the first sub-region 111a, and reduce the parasitic absorption of the second sub-region 111b and the leakage risk of the overlapping area, thereby significantly improving the working performance of the back contact battery cell.

[0040] In other embodiments, the doping concentration W1 of the first doping layer 15 and the doping concentration W2 of the second doping layer 17 may also be other values. The embodiment of the present application does not specifically limit the doping concentrations of the first doping layer 15 and the second doping layer 17, and can be adaptively adjusted according to actual conditions.

[0041] In the above embodiment, the doping concentration of the first doping stack 12 may be the average doping concentration within the entire thickness of the second doping layer 17 , and the doping concentration of the second doping stack 13 may be the average doping concentration within the entire thickness of the first doping layer 15 .

[0042] In another specific embodiment, the doping concentration of the first doped stack 12 can also be the average doping concentration within the entire thickness range of the first oxide layer 14, the first doping layer 15, the second oxide layer 16 and the second doping layer 17, and the doping concentration of the second doped stack 13 can also be the average doping concentration within the entire thickness range of the first oxide layer 14 and the first doping layer 15.

[0043] In the above two embodiments, electrochemical capacitance-voltage profiling (ECV) can be used to measure the average doping concentration of different structural layers.

[0044] like Figures 1 to 5 、 Figure 6a As shown, the above step S12 may include but is not limited to the following specific steps: S121: forming a first oxide layer 14, a first doping layer 15, a second oxide layer 16 and a second doping layer 17 in sequence on the back side of the silicon substrate 11; S122a: removing the second doping layer 17 and the second oxide layer 16 in the overlapping region 113 and the second sub-region 111b, and retaining the first oxide layer 14, the first doping layer 15, the second oxide layer 16 and the second doping layer 17 in the first sub-region 111a.

[0045] In this embodiment, along the direction away from the silicon substrate 11, the back side of the back contact cell 1 is stacked with a first oxide layer 14, a first doping layer 15, a second oxide layer 16 and a second doping layer 17 in sequence. The doping concentration of the second doping layer 17 is greater than the doping concentration of the first doping layer 15. Therefore, when the second doping layer 17 and the second oxide layer 16 are removed, the second doping stack 13 formed only includes the first doping layer 15 and the first oxide layer 14 with lower doping concentrations, so that the doping concentration of the first doping stack 12 can be greater than the doping concentration of the second doping stack 13, so that the overlapping area 113 and the second sub-area 111b generate a thinner second doping stack 13 with a lower doping concentration, and the first sub-area 111a generates a thicker first doping stack 12 with a higher doping concentration.

[0046] In the above embodiment, if Figure 4 、 Figure 5 and Figure 6a As shown, step S122a may further specifically include but not be limited to the following steps: S122a1: depositing a mask layer 25 on the back side of the second doped layer 17; S122a2: removing the mask layer 25 from the second region 112, the overlapping region 113 and the second sub-region 111b; S122a3: removing the first oxide layer 14, the first doping layer 15, the second oxide layer 16 and the second doping layer 17 of the second region 112 by wet chemical cleaning, and removing the second doping layer 17 and the second oxide layer 16 of the second sub-region 111b and the overlapping region 113; The wet chemical cleaning time T1 may satisfy 60s≤T1≤300s.

[0047] In this embodiment, a mask layer 25 is deposited on the back side of the second doping layer 17, and the mask layer 25 of the second region 112, the overlapping region 113 and the second sub-region 111b is removed, thereby retaining the mask layer 25 of the first sub-region 111a. During the subsequent wet chemical cleaning process, the first doping stack 12 of the first sub-region 111a is not affected by the cleaning. At the same time, by controlling the time of the wet chemical cleaning, the second doping 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.

[0048] Among them, 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 embodiment of the present application does not limit the specific value of the wet chemical cleaning time T1, and can be adaptively adjusted according to actual conditions.

[0049] The present application also provides another embodiment, such as Figure 7 As shown, along the thickness direction of the back contact cell 1, the first doped layer stack 12 may include a silicon base doped layer, a first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 stacked in sequence. The second doped layer stack may include a silicon base doped layer (not shown in the figure).

[0050] In this embodiment, during the process of forming 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, thereby forming a silicon substrate doped layer on a portion of the structure of the silicon substrate 11. In this embodiment, the second doped layer stack comprises only the silicon substrate doped layer, which further reduces the parasitic absorption of the second sub-region 111b, effectively improving the bifaciality of the back-contact solar cell 1, and significantly reducing the risk of leakage in the overlap region 113.

[0051] In the above embodiment, if Figure 7 As shown, the doping concentration W2 of the second doping layer 17 can meet 1E20 cm -3 <W2≤5E20 cm -3 The doping concentration W3 of the silicon substrate doping layer can meet 1E17cm -3 <W3≤1E19cm -3 .

[0052] In this embodiment, the doping concentration of the second doping layer 17 can be 2E20 cm -3 、3E20 cm -3 、4E20 cm -3 、5E20 cm -3 The doping concentration of the silicon substrate doping layer can be 1E17 cm -3、5E17 cm -3 、1E18 cm -3 、5E18 cm -3 、1E19 cm -3 The first doping stack 12 includes a first doping layer 15 and a second doping layer 17, and the second doping stack only includes a silicon substrate doping layer, and the doping concentrations of the first doping layer 15 and the second doping layer 17 are both greater than those of the silicon substrate doping layer, so that the overall doping concentration of the first doping stack 12 is significantly greater than the overall doping concentration of the second doping stack, so as to improve the fill factor and open-circuit voltage of the first sub-region 111a, and reduce the parasitic absorption of the second sub-region 111b and the leakage risk of the overlapping region 113, thereby significantly improving the working performance of the back contact battery cell 1.

[0053] In other embodiments, the doping concentration W2 of the second doping layer 17 and the doping concentration W3 of the silicon substrate doping layer may also be other values. In the embodiment of the present application, the specific values ​​of the doping concentrations of the second doping layer 17 and the silicon substrate doping layer are not limited and can be adaptively adjusted according to actual conditions.

[0054] In the above embodiment, the doping concentration of the first doping stack 12 can be the average doping concentration within the entire thickness range of the second doping layer 17, and the doping concentration of the second doping stack 13 can be the average doping concentration of the silicon substrate doping layer, wherein the average doping concentration of the silicon substrate doping 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.

[0055] In the above embodiment, electrochemical capacitance-voltage profiling (ECV) can be used to measure the average doping concentration of different structural layers.

[0056] In the above embodiment, if Figures 3 to 5 、 Figure 6b As shown, step S12 may also include but is not limited to the following steps: S121: forming a first oxide layer 14, a first doping layer 15, a second oxide layer 16 and a second doping layer 17 in sequence on the back side of the silicon substrate 11; S122b: Remove the first oxide layer 14, the first doping layer 15, the second oxide layer 16, and the second doping layer 17 in the overlapping region 113 and the second sub-region 111b, and retain the first oxide layer 14, the first doping layer 15, the second oxide layer 16, and the second doping layer 17 in the first sub-region 111a.

[0057] In this embodiment, the first oxide layer 14, the first doping layer 15, the second oxide layer 16 and the second doping layer 17 of the first sub-region 111a are retained to form a first doping stack 12 with a relatively thick thickness and a relatively high doping concentration. At the same time, the first oxide layer 14, the first doping layer 15, the second oxide layer 16 and the second doping layer 17 of the overlapping region 113 and the second sub-region 111b are removed so that the second doping stack only includes the silicon base doping layer with a relatively low doping concentration.

[0058] In the above embodiment, if Figure 4 、 Figure 5 and Figure 6b As shown, step S122b may also include but is not limited to the following steps: S122b1: depositing a mask layer 25 on the back side of the second doped layer 17; S122b2: removing the mask layer 25 from the second region 112, the overlapping region 113 and the second sub-region 111b; S122b3: wet chemical cleaning to remove the first oxide layer 14, the first doping layer 15, the second oxide layer 16, and the second doping layer 17 of the second region 112, and the second doping layer 17, the second oxide layer 16, the first doping layer 15, and the first oxide layer 14 of the second sub-region 111b and the overlapping region 113; The wet chemical cleaning time T2 satisfies 300s<T2≤500s.

[0059] In this embodiment, a mask layer 25 is deposited on the back side of the second doping layer 17, and the mask layer 25 of the second region 112, the overlapping region 113, and the second sub-region 111b is removed, thereby retaining the mask layer 25 of the first sub-region 111a. During the subsequent wet chemical cleaning process, the first doping stack 12 of the first sub-region 111a is not affected by the cleaning. At the same time, by controlling the time of the wet chemical cleaning, the first oxide layer 14, the first doping layer 15, the second oxide layer 16, and the second doping layer 17 of the second sub-region 111b and the overlapping region 113 are removed.

[0060] Among them, 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 embodiment of the present application does not limit the specific value of the wet chemical cleaning time T2, and can be adaptively adjusted according to actual conditions.

[0061] In the above two embodiments, Figure 1 and Figure 7As shown, by providing two oxide layers and two doping layers in the first doping stack 12, and making the doping concentrations of the first doping layer 15 and the second doping layer 17 different, so that the first doping stack 12 also has a doping concentration gradient change, the conductivity of the carriers in the first doping stack 12 can be further increased, the series resistance can be reduced, and the working performance of the back contact cell can be further improved.

[0062] In a specific embodiment, Figure 1 、 Figure 7 to Figure 1 1 (including Figure 8a 、 Figure 8b 、 Figure 9a 、 Figure 9b 、 Figure 10a 、 Figure 10b 、 Figure 11a and Figure 11b ), after step S12, the method for preparing the back contact cell may further include but is not limited to the following steps: S13: depositing a first passivation layer 18 and an anti-reflection layer 19 on the front surface of the silicon substrate 11; S14: depositing a second passivation layer 20 and a third doping layer 21 on the back side of the silicon substrate at low temperature; S15: removing the second passivation layer 20 and the third doping layer 21 of the second sub-region 111 b; S16: depositing a conductive film 22 on the back side of the silicon substrate 11; S17: removing part of the conductive film 22 in the overlapping region 113 to form an isolation region 23; S18 : preparing a metal electrode 24 on the back side of the silicon substrate 11 .

[0063] In this embodiment, a complete back contact cell 1 is prepared through the above steps.

[0064] The present application also provides a photovoltaic module (not shown) that can be composed of the back-contact cell, photovoltaic glass, adhesive film, backsheet, and frame described in the above embodiments. The back-contact cell produced using the back-contact cell preparation method described in the above embodiments can improve the operating performance of the back-contact cell and reduce the risk of leakage, thereby ensuring the overall operating efficiency and safety of the photovoltaic module.

[0065] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A back contact solar cell, characterized in that: The back contact cell (1) comprises a silicon substrate (11), the back side of the silicon substrate (11) comprising a first region (111), a second region (112), and an overlapping region (113) located between the first region (111) and the second region (112); the first region (111) comprises a first sub-region (111a) and a second sub-region (111b); The first sub-region (111a) is provided with a first doped stack (12), and the second sub-region (111b) and the overlapping region (113) are provided with a second doped stack (13); along the thickness direction of the back contact cell (1), 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).

2. The back contact cell according to claim 1, characterized in that: Along the thickness direction of the back contact cell (1), the first doped layer stack (12) comprises a first oxide layer (14), a first doped layer (15), a second oxide layer (16), and a second doped layer (17) stacked in sequence; The second doped stack (13) comprises a first oxide layer (14) and a first doped layer (15) which are stacked.

3. The back contact cell according to claim 2, characterized in that: The thickness D1 of the first doped stack (12) satisfies 50 nm < D1 ≤ 250 nm, and / or the thickness D2 of the second doped stack (13) satisfies D2 ≤ 50 nm.

4. The back contact cell according to claim 3, characterized in that: The doping concentration W1 of the first doping layer (15) satisfies 1E19 cm -3 ≤W1≤1E20 cm -3 , and / or, the doping concentration W2 of the second doping layer (17) satisfies 1E20cm -3 <W2≤5E20cm -3 .

5. The back contact cell according to claim 1, characterized in that: Along the thickness direction of the back contact cell (1), the first doped layer stack (12) comprises a silicon base doped layer, a first oxide layer (14), a first doped layer (15), a second oxide layer (16), and a second doped layer (17) stacked in sequence; The second doped layer stack (13) includes the silicon substrate doped layer.

6. The back contact cell according to claim 5, characterized in that: The doping concentration W2 of the second doping layer (17) satisfies 1E20 cm -3 <W2≤5E20 cm -3 , and / or, the doping concentration W3 of the silicon substrate doping layer satisfies 1E17cm -3 <W3≤1E19cm -3 .

7. A method for preparing a back contact solar cell, characterized in that: The method for preparing the back contact cell (1) comprises: A silicon substrate (11) is prepared, 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); Generating a first doped stack (12) in the first sub-region (111a), and generating a second doped stack (13) 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).

8. The method for preparing a back contact solar cell according to claim 7, characterized in that: In the steps of generating a first doped stack (12) in the first sub-region (111a) and generating a second doped stack (13) in the second sub-region (111b) and the overlapping region (113), the method for preparing the back contact cell (1) specifically comprises: sequentially generating a first oxide layer (14), a first doping layer (15), a second oxide layer (16), and a second doping layer (17) on the back side of the silicon substrate (11); The second doping layer (17) and the second oxide layer (16) of the overlapping region (113) and the second sub-region (111b) are removed, and the first oxide layer (14), the first doping layer (15), the second oxide layer (16) and the second doping layer (17) of the first sub-region (111a) are retained.

9. The method for preparing a back contact solar cell according to claim 7, characterized in that: In the steps of generating a first doped stack (12) in the first sub-region (111a) and generating a second doped stack (13) in the second sub-region (111b) and the overlapping region (113), the method for preparing the back contact cell (1) specifically comprises: sequentially generating a first oxide layer (14), a first doping layer (15), a second oxide layer (16), and a second doping layer (17) on the back side of the silicon substrate (11); The first oxide layer (14), the first doping layer (15), the second oxide layer (16), and the second doping layer (17) of the overlapping region (113) and the second sub-region (111b) are removed, and the first oxide layer (14), the first doping layer (15), the second oxide layer (16), and the second doping layer (17) of the first sub-region (111a) are retained.

10. The method for preparing a back contact solar cell according to claim 8, characterized in that: In the step of removing the second doping layer (17) and the second oxide layer (16) of the overlapping region (113) and the second sub-region (111b), the method for preparing the back contact cell (1) specifically comprises: depositing a mask layer (25) on the back side of the second doped layer (17); removing the mask layer (25) of the second region (112), the overlapping region (113), and the second sub-region (111b); Wet chemical cleaning removes the first oxide layer (14), the first doping layer (15), the second oxide layer (16), and the second doping layer (17) in the second region (112), and removes the second doping layer (17) and the second oxide layer (16) in the second sub-region (111b) and the overlapping region (113); The wet chemical cleaning time T1 satisfies 60s≤T1≤300s.

11. The method for preparing a back contact solar cell according to claim 9, characterized in that: In the step of removing the first oxide layer (14), the first doping layer (15), the second oxide layer (16), and the second doping layer (17) of the overlapping region (113) and the second sub-region (111b), the method for preparing the back contact cell (1) specifically comprises: depositing a mask layer (25) on the back side of the second doped layer (17); removing the mask layer (25) of the second region (112), the overlapping region (113), and the second sub-region (111b); Wet chemical cleaning removes the first oxide layer (14), the first doping layer (15), the second oxide layer (16), and the second doping layer in the second region (112), and removes the second doping layer (17), the second oxide layer (16), the first doping layer (15), and the first oxide layer (14) in the second sub-region (111b) and the overlapping region (113); The wet chemical cleaning time T2 satisfies 100s≤T2≤500s.

12. The method for preparing a back contact cell (1) according to claim 7, characterized in that: After generating a first doped stack (12) in the first sub-region (111a) and generating a second doped stack (13) in the second sub-region (111b) and the overlapping region (113), the method for preparing the back contact cell (1) further comprises: Depositing a first passivation layer (18) and an anti-reflection layer (19) on the front surface of the silicon substrate (11); Depositing a second passivation layer (20) and a third doping layer (21) on the back side of the silicon substrate (11) at low temperature; removing the second passivation layer (20) and the third doping layer (21) of the second sub-region (111b); Depositing a conductive film (22) on the back side of the silicon substrate (11); removing a portion of the conductive film (22) in the overlapping region (113) to form an isolation region (23); A metal electrode (24) is prepared on the back side of the silicon substrate (11).

13. A photovoltaic module, characterized in that: The photovoltaic module comprises the back contact cell (1) according to any one of claims 1 to 6.

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