A topcon solar cell, manufacturing method, cell module, and photovoltaic system

Abstract

The application relates to the technical field of solar cells and discloses a TOPCon solar cell, a manufacturing method, a cell module and a photovoltaic system. The TOPCon solar cell comprises a silicon base body, the silicon base body has a front surface and a back surface, the back surface comprises a back surface first area and a back surface second area, the back surface second area is provided with a doped layer doped with a second doping element, the back surface first area is provided with a doped polysilicon layer doped with a first doping element, the doped layer and the doped polysilicon layer have a composite contact structure at a side surface junction, and the composite contact structure connects the doped layer and the doped polysilicon layer. The TOPCon solar cell can realize local composite leakage, effectively reduces the reverse breakdown voltage of the cell piece and reduces the hot spot risk of the module.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a TOPCon solar cell, its manufacturing method, cell module, and photovoltaic system. Background Technology

[0002] TOPCon (Tunnel Oxide Passivating Contact) solar cells are tunnel oxide passivating contact solar cells with a silicon substrate. TOPCon cells utilize tunnel oxide, which has excellent charge transport characteristics, as the charge transport layer on the back of the cell. A thin layer of doped polycrystalline silicon is then deposited to form the back passivating contact structure, effectively reducing surface recombination and metal-to-metal recombination, improving turn-on voltage, and increasing energy conversion efficiency. However, existing TOPCon solar cells pose a significant risk of hot spots and fire hazards when shaded.

[0003] Therefore, there is an urgent need to provide a TOPCon solar cell, manufacturing method, battery module, and photovoltaic system to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a TOPCon solar cell, a manufacturing method, a cell module, and a photovoltaic system that can achieve localized compound leakage current, effectively reduce the reverse breakdown voltage of the cell, and reduce the risk of hot spots in the module.

[0005] This invention is achieved through the following technical solution:

[0006] A TOPCon solar cell includes a silicon substrate having a front side and a back side disposed opposite to each other. The back side includes a first back side region and a second back side region located on one side of the first back side region. The second back side region has a doped layer doped with a second doping element, and the first back side region has a doped polycrystalline silicon layer doped with a first doping element. A composite contact structure is formed at the side boundary between the doped layer and the doped polycrystalline silicon layer, and the composite contact structure connects the doped layer and the doped polycrystalline silicon layer.

[0007] As an alternative, at the side interface between the doped layer and the doped polysilicon layer, the second dopant element diffuses along the side direction into the silicon substrate and the doped polysilicon layer to form the composite contact structure.

[0008] As an alternative, the diffusion depth of the second dopant element into the doped polycrystalline silicon layer along the lateral direction is 50 nm to 200 nm.

[0009] As an alternative, the front and the second region of the back are both textured surfaces, the first region of the back is a smooth surface, the textured surface is provided with the doped layer, the smooth surface is provided with a tunneling oxide layer and the doped polycrystalline silicon layer covering the surface of the tunneling oxide layer.

[0010] As an optional option, the tunneling oxide layer is a SiOx tunneling oxide layer.

[0011] As an alternative, a first passivation layer is disposed on the outer side of the doped layer, a second passivation layer is disposed on the outer side of the doped polysilicon layer, a front metal electrode is disposed on the front side, a back metal electrode is disposed in the first region of the back side, the front metal electrode passes through the first passivation layer and contacts the doped layer, and the back metal electrode passes through the second passivation layer and contacts the doped polysilicon layer.

[0012] As an alternative, the first doping element includes boron, and the second doping element includes phosphorus;

[0013] Alternatively, the first doping element may include phosphorus, and the second doping element may include boron.

[0014] A method for manufacturing a TOPCon solar cell, comprising the following steps:

[0015] S10. Polish the silicon substrate on both sides;

[0016] S20. A tunneling oxide layer and a silicon material layer are sequentially prepared from the inside to the outside on the back or both sides of the silicon substrate.

[0017] S30. Diffusion of the first doping element is performed on the back or both sides of the silicon substrate to transform the silicon material layer into a doped polycrystalline silicon layer doped with the first doping element, and a first silicon glass layer doped with the first doping element is formed on the outside of the doped polycrystalline silicon layer.

[0018] S40. Remove the first silicon glass layer located in the second region on the back side by laser;

[0019] S50. Texturing is performed on the front side and the second region of the back side of the silicon substrate to form a textured surface;

[0020] S60. Diffusion of the second doping element is performed to form a doped layer doped with the second doping element on the textured surface, and a second silicon glass layer doped with the second doping element is formed on the outside of the doped layer.

[0021] S70: Remove the first silicon glass layer located in the first region of the back side and the second silicon glass layer located in the second region of the back side.

[0022] As an optional solution, in S20, the silicon material layer includes one or a combination of two or more of intrinsic amorphous silicon, intrinsic polycrystalline silicon, intrinsic microcrystalline silicon, intrinsic nanocrystalline silicon, and doped silicon.

[0023] As an optional solution, in S60, during the diffusion of the second dopant element, at the side interface between the doped layer and the doped polysilicon layer, the second dopant element can diffuse along the side direction into the silicon substrate and the doped polysilicon layer to form a composite contact structure.

[0024] As an optional approach, S41 is further included between S40 and S50: front etching to remove the first silicon glass layer and the first dopant element located on the front side, as well as the first silicon glass layer located at the edge.

[0025] As an optional solution, S80 and S90 are further included after S70, wherein S80: a first passivation layer is formed on the outside of the doped layer, and a second passivation layer is formed on the outside of the doped polysilicon layer;

[0026] S90: Prepare a front metal electrode and a back metal electrode, so that the front metal electrode is electrically connected to the doped layer and the back metal electrode is electrically connected to the doped polycrystalline silicon layer.

[0027] As an optional approach, in S60, the diffusion sheet resistance of the second doped element is greater than 100 Ω / sq.

[0028] A battery assembly comprising the TOPCon solar cell described above or the TOPCon solar cell manufactured by the method described above.

[0029] A photovoltaic system comprising the aforementioned battery module.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention provides a TOPCon solar cell with a composite contact structure at the side interface between the doped layer with a second doping element and the doped polycrystalline silicon layer with a first doping element. The composite contact structure enables local composite leakage, improving the leakage capability of the solar cell and giving the composite leakage region high reverse leakage characteristics. Thus, with the improvement of leakage capability, at the module end, when the solar cell is shaded, when the leakage current of the solar cell reaches the maximum power point current (Impp), the composite contact structure can effectively reduce the reverse breakdown voltage at both ends of the shaded cell, thereby reducing the heat generation power of the solar cell and reducing the risk of hot spots in the module.

[0032] The present invention also provides a method for manufacturing a TOPCon solar cell, which is used to prepare the above-mentioned TOPCon solar cell. The composite contact structure can realize local composite leakage, effectively reduce the reverse breakdown voltage of the cell, and reduce the risk of hot spots in the module.

[0033] The present invention also provides a battery module. By using the TOPCon solar cell described above or the TOPCon solar cell manufacturing method described above, the composite contact structure can realize local composite leakage, effectively reduce the reverse breakdown voltage of the cell, and reduce the risk of hot spots in the module.

[0034] The present invention also provides a photovoltaic system in which the composite contact structure can achieve local composite leakage by adopting the above-mentioned battery module, effectively reducing the reverse breakdown voltage of the battery cell and reducing the risk of hot spots in the module. Attached Figure Description

[0035] To more clearly and understandably illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a cross-sectional view of the TOPCon solar cell provided in Embodiment 1 of the present invention;

[0037] Figure 2 This is a partial schematic diagram of the TOPCon solar cell provided in Embodiment 1 of the present invention;

[0038] Figure 3 This is a cross-sectional view of the structure obtained after step S30 in Embodiment 1 of the present invention;

[0039] Figure 4 This is a cross-sectional view of the structure obtained after step S40 in Embodiment 1 of the present invention;

[0040] Figure 5 This is a cross-sectional view of the structure obtained after step S60 in Embodiment 1 of the present invention;

[0041] Figure 6 This is a cross-sectional view of the structure obtained after step S70 in Embodiment 1 of the present invention;

[0042] Figure 7 This is a flowchart of the method for manufacturing a TOPCon solar cell provided in Embodiment 1 of the present invention;

[0043] Figure 8 This is a cross-sectional view of the structure obtained after step S30 in Embodiment 2 of the present invention;

[0044] Figure 9 This is a cross-sectional view of the structure obtained after step S40 in Embodiment 2 of the present invention;

[0045] Figure 10 This is a cross-sectional view of the structure obtained after step S60 in Embodiment 2 of the present invention;

[0046] Figure 11 This is a cross-sectional view of the structure obtained after step S70 in Embodiment 2 of the present invention;

[0047] Figure 12 This is a cross-sectional view of the TOPCon solar cell obtained after step S90 in Embodiment 2 of the present invention;

[0048] Figure 13 This is a flowchart of the manufacturing method of the TOPCon solar cell provided in Embodiment 2 of the present invention.

[0049] In the picture:

[0050] 1. Silicon substrate; 11. Front side; 12. Back side; 121. First region on the back side; 122. Second region on the back side; 2. Tunneling oxide layer; 3. Doped polycrystalline silicon layer; 4. First silicon glass layer; 5. Doped layer; 6. Second silicon glass layer; 71. First passivation layer; 72. Second passivation layer; 8. Front metal electrode; 9. Back metal electrode; 10. Composite contact structure. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0052] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0053] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0054] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0055] TOPCon (Tunnel Oxide Passivating Contact) solar cells are tunnel oxide passivating contact solar cells with silicon substrate as the substrate. TOPCon cells use tunnel oxide, which has excellent charge transport characteristics, as the charge transport layer on the back of the cell. A thin layer of doped polycrystalline silicon is then deposited to form a back tunnel passivation structure, which can effectively reduce surface recombination and metal contact recombination, improve turn-on voltage, and improve energy conversion efficiency.

[0056] In existing TOPCon solar cells, the front metal electrode and the back metal electrode are located on the front and back of the solar cell, respectively. The doped layer and the doped polycrystalline silicon layer are also located on the front and back of the silicon substrate, respectively. Furthermore, the doped layer and the doped polycrystalline silicon layer are insulated from each other, which fails to achieve the shading resistance characteristics of the solar cell. When the cell is shaded, there is a significant risk of hot spots and fire hazards.

[0057] To solve the above problems, such as Figure 1As shown, this embodiment provides a TOPCon solar cell, including a silicon substrate 1. The silicon substrate 1 has a front side 11 and a back side 12 disposed opposite to each other. The back side 12 includes a first back side region 121 and a second back side region 122 located on one side of the first back side region 121. The second back side region 122 has a doped layer 5 doped with a second doping element. The first back side region 121 has a tunneling oxide layer 2 and a doped polycrystalline silicon layer 3 doped with a first doping element, arranged sequentially from the inside to the outside. The tunneling oxide layer 2 and the doped polycrystalline silicon layer 2 of the back side 12 protrude from the doped layer 5. It should be noted that the front side 11 of the silicon substrate 1 corresponds to the light-receiving surface of the solar cell, and the back side 12 of the silicon substrate 1 corresponds to the back light-receiving surface of the solar cell. The first back side region 121 is the region corresponding to the doped polycrystalline silicon layer 3 doped with the first doping element on the back side 12, and the second back side region 122 is the region corresponding to the doped layer 5 doped with the second doping element on the back side 12.

[0058] In this embodiment, the tunneling oxide layer 2 can be a SiOx tunneling oxide layer, and the thickness of the tunneling oxide layer 2 is 1nm to 2nm.

[0059] It is worth noting that on the back side 12 of the silicon substrate 1, there is a junction between the first back side region 121 and the second back side region 122. This junction is the side junction between the doped layer 5 and the doped polycrystalline silicon layer 3 on the back side 12. Specifically, as shown... Figure 2 As shown, a composite contact structure 10 is present at the side interface between the doped layer 5 and the doped polysilicon layer 3. The composite contact structure 10 is used to connect the doped multilayer 5 and the doped polysilicon layer 3. Specifically, on the back side 12 of the silicon substrate 1, there are four interfaces between the first back side region 121 and the second back side region 122, that is, there are four side interface interfaces between the doped layer 5 and the doped polysilicon layer 3, and each side interface has a composite contact structure 10. Therefore, there is no insulation between the doped layer 5 and the doped polysilicon layer 3, and they form a composite contact at the side interface.

[0060] Thus, the composite contact structure 10 can achieve local composite leakage, improve the leakage capability of the solar cell, and make the composite leakage area have high reverse leakage characteristics. In this way, with the improvement of leakage capability, at the module end, when the solar cell is shaded, when the leakage current of the solar cell reaches the maximum power point current (Impp), the composite contact structure 10 can effectively reduce the reverse breakdown voltage at both ends of the shaded cell, and the heat generation power of the solar cell will be reduced, thereby reducing the risk of hot spots in the module.

[0061] Specifically, in the fabrication of TOPCon solar cells, one step involves diffusing a second dopant element into the front side 11 and the second back side region 122 of the silicon substrate 1, thereby forming a doped layer 5 with the second dopant element on the front side 11 and the second back side region 122. Simultaneously with the diffusion of the second dopant element into the silicon substrate 1, a reference... Figure 3 At the junction of the doped layer 5 and the doped polysilicon layer 3, the second dopant element diffuses along the side direction into the silicon substrate 1 and the doped polysilicon layer 3, thereby forming the aforementioned composite contact structure 10. In other words, the doped polysilicon layer 3 originally contains the first dopant element, and a portion of this layer is doped with the second dopant element, thus forming a composite doped region, i.e., the composite contact structure 10, which is doped with both the first and second dopant elements.

[0062] Optionally, the diffusion depth H of the second dopant element within the doped polysilicon layer 3 is 50 nm to 200 nm. Typically, this diffusion depth H is around 200 nm. It should be noted that because the tunneling oxide layer 2 is a SiOx tunneling oxide layer, which is relatively dense, the second dopant element has difficulty diffusing. Therefore, the diffusion depth of the second dopant element within the tunneling oxide layer 2 does not reach 200 nm. However, the thickness of the tunneling oxide layer 2 is only about 2 nm. Figure 3 In the vertical direction, the diffusion depth of the second dopant element in the tunneling oxide layer 2 does not affect the continuity of the composite contact structure 10 between the doped layer 5 and the doped polysilicon layer 3.

[0063] In existing TOPCon solar cell structures, the back side often uses a full-surface tunneling oxide + doped polycrystalline silicon structure. For the tunneling passivation structure, if it is textured, the surface irregularity is high, resulting in poor uniformity of tunneling oxide layer growth. This leads to poor passivation performance of the tunneling passivation structure on the textured surface. Therefore, due to the special characteristics of the tunneling passivation structure, the back side is usually polished in the existing technology. As a result, it is difficult to further improve the bifacial power generation of the cell. At the same time, the heavy doping of the entire back side results in a high recombination rate and high recombination loss on the back side of the cell, making it difficult to further improve the cell efficiency.

[0064] To solve the above problems, such as Figure 1 As shown, in this embodiment, the front side 11 and the second back side region 122 are both textured surfaces, and the first back side region 121 is a smooth surface. The textured surface is provided with the aforementioned doped layer 5, and the smooth surface is provided with the aforementioned tunneling oxide layer 2 and a doped polycrystalline silicon layer 3 covering the surface of the tunneling oxide layer 2.

[0065] The TOPCon solar cell provided in this embodiment has a textured surface on the entire front side 11 of the silicon substrate 1 and a textured surface on a portion of the back side 12. This achieves that the textured area of ​​the back side 12, namely the second back side region 122, is a region without the tunneling oxide layer 2 and the doped polycrystalline silicon layer 3, while the area of ​​the back side 12 with the tunneling oxide layer 2 and the doped polycrystalline silicon layer 3, namely the first back side region 121, remains a polished surface. Compared with the polished surface of the entire back side 12 in the prior art, the bifacial power generation of the cell can be increased without significantly increasing the process flow, reducing the efficiency loss caused by high recombination in the heavily doped region of the back side 12, and improving the photoelectric conversion efficiency of the cell.

[0066] The doped layer 5 can be a polycrystalline silicon layer formed by first depositing a layer of polycrystalline silicon on the textured surface of the silicon substrate 1 and then doping the polycrystalline silicon with a second doping element, or the doped layer 5 can be a doped layer formed by directly doping the second doping element on the silicon substrate 1.

[0067] In one optional embodiment, the first dopant element is boron and the second dopant element is phosphorus. In this case, the doped polysilicon layer 3 doped with the first dopant element is a boron-doped polysilicon layer (P-Poly), and the doped layer 5 doped with the second dopant element is a phosphorus-doped polysilicon layer. In another optional embodiment, the first dopant element is phosphorus and the second dopant element is boron. In this case, the doped polysilicon layer 3 doped with the first dopant element is a phosphorus-doped polysilicon layer (N-Poly), and the doped layer 5 doped with the second dopant element is a boron-doped polysilicon layer. Of course, in other optional embodiments, the first dopant element may also be gallium, and the second dopant element may also be arsenic, or vice versa; no specific limitation is made here.

[0068] Optionally, such as Figure 1 As shown, a first passivation layer 71 is disposed on the outer side of the doped layer 5, and a second passivation layer 72 is disposed on the outer side of the doped polycrystalline silicon layer 3. A front metal electrode 8 is disposed on the front side 11, and a back metal electrode 9 is disposed on the first region 121 of the back side. The front metal electrode 8 passes through the first passivation layer 71 and contacts the doped layer 5, while the back metal electrode 9 passes through the second passivation layer 72 and contacts the doped polycrystalline silicon layer 3. Both the first passivation layer 71 and the second passivation layer 72 are passivation films used to improve the photoelectric conversion efficiency and stability of the solar cell, reduce surface damage and oxidation reactions of the solar cell, and extend the service life of the solar cell.

[0069] This embodiment also provides a method for manufacturing a TOPCon solar cell, used to prepare the aforementioned TOPCon solar cell.

[0070] Specifically, such as Figure 7 As shown, the fabrication method of the TOPCon solar cell provided in this embodiment includes the following specific steps:

[0071] S10: Polish the silicon substrate 1 on both sides.

[0072] S20: As Figure 3 As shown, a tunneling oxide layer 2 and a silicon material layer are sequentially fabricated from the inside out on the back side 12 of the silicon substrate 1. "From the inside out" refers to the direction away from the silicon substrate 1. The tunneling oxide layer 2 covers the back side 12 of the silicon substrate 1, and the silicon material layer covers the tunneling oxide layer 2. The silicon material layer includes one or a combination of two or more of intrinsic amorphous silicon, intrinsic polycrystalline silicon, intrinsic microcrystalline silicon, intrinsic nanocrystalline silicon, and doped silicon.

[0073] S30: As Figure 3 As shown, a first dopant element is diffused onto the back side 12 of the silicon substrate 1, transforming the silicon material layer into a doped polycrystalline silicon layer 3 doped with the first dopant element. Simultaneously, a first silicon glass layer 4 doped with the first dopant element is formed on the outer side of the doped polycrystalline silicon layer 3. The tunneling passivation structure of the TOPCon solar cell can be realized on the back side 12 of the silicon substrate 1 through the tunneling oxide layer 2 and the doped polycrystalline silicon layer 3, thereby improving the passivation effect of the cell.

[0074] S40: As Figure 4 As shown, the first silicon glass layer 4 located in the second region 122 on the back side is removed by laser.

[0075] S50: such as Figure 5 As shown, the front side 11 and the second back side region 122 of the silicon substrate 1 are texturized to form a textured surface. This step forms an uneven pyramid structure on the front side 11 and the second back side region 122 of the silicon substrate 1. The light-trapping effect of the uneven textured surface increases the absorption of sunlight, reduces reflectivity, increases short-circuit current, and improves the photoelectric conversion efficiency of the solar cell.

[0076] S60: As Figure 5 As shown, the diffusion of a second doping element is performed to form a doped layer 5 doped with the second doping element on the textured surface, while a second silicon glass layer 6 doped with the second doping element is formed on the outside of the doped layer 5.

[0077] S70: As Figure 6 As shown, the first silicon glass layer 4 located in the first region 121 on the back side and the second silicon glass layer 6 located in the second region 122 on the back side are removed.

[0078] Through the above steps S40 and S50, texturing of the entire front side 11 of the silicon substrate 1 and texturing of a portion of the back side 12 can be achieved. The texturing area of ​​the back side 12, namely the second back side region 122, is the area without the tunneling oxide layer 2 and the doped polycrystalline silicon layer 3. The area of ​​the back side 12 with the tunneling oxide layer 2 and the doped polycrystalline silicon layer 3, namely the first back side region 121, remains a polished surface. Compared with the full-surface polishing of the back side 12 in the prior art, the bifacial power generation efficiency of the solar cell can be increased without significantly increasing the process flow, reducing the efficiency loss caused by high recombination in the heavily doped area of ​​the back side 12, and improving the photoelectric conversion efficiency of the solar cell.

[0079] In step S30, the diffusion process inevitably forms a first silicon glass layer 4 and a first dopant element on the front side 11 of the silicon substrate 1, and also forms a first silicon glass layer 4 at the edge of the silicon substrate 1. Edge diffusion can easily cause short circuits, and front diffusion can easily affect subsequent passivation, so they need to be removed. Therefore, in this embodiment, S41 is also included between S40 and S50: front etching, which removes the first silicon glass layer 4 and the first dopant element located on the front side 11 of the silicon substrate 1, as well as the first silicon glass layer 4 located at the edge, by etching.

[0080] Furthermore, following the S70 is the S80: such as Figure 1 As shown, a first passivation layer 71 is formed on the outer side of the doped layer 5, and a second passivation layer 72 is formed on the outer side of the doped polycrystalline silicon layer 3. Both the first passivation layer 71 and the second passivation layer 72 are passivation films used to improve the photoelectric conversion efficiency and stability of the solar cell, reduce surface damage and oxidation reactions, and extend the lifespan of the solar cell. Optionally, the first passivation layer 71 and the second passivation layer 72 may include any one or more of the following: silicon nitride layer, silicon oxynitride layer, silicon oxide layer, aluminum oxide layer, aluminum nitride layer, aluminum oxynitride layer, and magnesium fluoride layer.

[0081] Furthermore, following the S80 is the S90: such as Figure 1 As shown, a front metal electrode 8 and a back metal electrode 9 are fabricated, with the front metal electrode 8 electrically connected to the doped layer 5 and the back metal electrode 9 electrically connected to the doped polycrystalline silicon layer 3, ultimately forming a structure as shown. Figure 1 The overall structure of the TOPCon solar cell shown is such that the front metal electrode 8 and the back metal electrode 9 have opposite polarities.

[0082] In step S10, the silicon substrate 1 can be an N-type silicon substrate, with a thickness of 160-170 μm and a resistivity range of 3-5 ohm·cm. The polishing of the silicon substrate 1 can be performed using mechanical polishing, chemical mechanical polishing, electrochemical polishing, or photocatalytic-assisted chemical mechanical polishing, etc., without specific limitations. The purpose is to enhance the polishing effect, improve the surface roughness of the silicon substrate 1, and increase the material removal rate.

[0083] In step S20, an ultrathin tunneling oxide layer 2 and a silicon material layer can be prepared by low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD). In this embodiment, the tunneling oxide layer 2 can be a SiOx tunneling oxide layer, with a thickness of 1 nm to 2 nm, and the silicon material layer has a thickness of 60 nm to 100 nm. The specific preparation process is existing technology and will not be described in detail here.

[0084] Furthermore, such as Figure 3 As shown, in step S30, the first doping element is diffused into the silicon material layer on the back side 12 of the silicon substrate 1. The silicon material layer then crystallizes and transforms into a doped polycrystalline silicon layer 3 doped with the first doping element. At the same time as the doped polycrystalline silicon layer 3 is generated, a first silicon glass layer 4 doped with the first doping element is also formed on the outside of the doped polycrystalline silicon layer 3.

[0085] Furthermore, such as Figure 4 As shown, in step S40, the first silicon glass layer 4 on the back side 12 is patterned by laser, and the first silicon glass layer 4 located in the second region 122 on the back side is removed to facilitate the subsequent texturing of the second region 122 on the back side. The first silicon glass layer 4 located in the first region 121 on the back side is retained to protect the doped polycrystalline silicon layer 3 in the first region 121 on the back side. The patterned first silicon glass layer 4 covers the doped polycrystalline silicon layer 3 located in the first region 121 on the back side and exposes the doped polycrystalline silicon layer 3 located in the second region 122 on the back side.

[0086] Furthermore, such as Figure 5As shown, in step S50, based on the patterned silicon substrate 1 after step S40, the front side 11 and the second back side region 122 of the silicon substrate 1 are texturized to form a textured surface. Texturing refers to processing the front side 11 and the second back side region 122 of the silicon substrate 1 using a specific process to form a pyramid-shaped textured surface on the front side 11 and the second back side region 122. This utilizes the light-trapping principle of the textured surface to increase absorption, reduce light reflectivity, and increase short-circuit current, thereby improving photoelectric conversion efficiency. Optionally, the texturing process includes, but is not limited to, acid texturing, alkaline texturing, mechanical texturing, electrochemical texturing, reactive ion etching texturing, laser texturing, and mask texturing, etc., which will not be elaborated here. It should be noted that the thickness of the textured surface is much greater than the sum of the thicknesses of the tunneling oxide layer 2 and the doped polysilicon layer 3. Therefore, during texturing, the tunneling oxide layer 2 and the doped polysilicon layer 3 of the second back side region 122 are simultaneously removed, leaving only the silicon substrate 1 and forming the textured surface.

[0087] After that, as Figure 5 As shown, in step S60, a second dopant element is diffused into the textured silicon substrate 1 on both sides, thereby forming a doped layer 5 doped with the second dopant element on the front side 11 and the second region 122 on the back side of the silicon substrate 1, i.e., the textured surface. Simultaneously with the formation of the doped layer 5, a second silicon glass layer 6 doped with the second dopant element is formed on the outer side of the doped layer 5. At this time, the second region 122 on the back side and the front side 11 of the silicon substrate 1 form a passivation contact structure through the doped layer 5, improving the overall passivation effect of the battery.

[0088] After that, as Figure 5 and Figure 6 As shown, in step S70, the first silicon glass layer 4 located in the first region 121 on the back side and the second silicon glass layer 6 located in the second region 122 on the back side can be removed by etching. For example, the structure obtained after step S60 can be placed in an etching solution to remove the first silicon glass layer 4 and the second silicon glass layer 6. The etching solution can be an aqueous solution of H2SO4 (sulfuric acid) and HF (hydrofluoric acid) or a solution that can etch the first silicon glass layer 4 and the second silicon glass layer 6, and is not limited here. It should be noted that when the second dopant element is diffused on both sides in step S60, while the doped layer 5 is formed on the textured surface, the second silicon glass layer 6 is mainly formed on the outside of the doped layer 5 in the second region 122 on the back side, while only a portion of the front side 11 has the edge-expanded second silicon glass layer 6. Therefore, the main purpose of step S70 is to completely remove the second silicon glass layer 6 in the second region 122 on the back side.

[0089] In step S80, the appropriate preparation method can be selected according to the specific types of the first passivation layer 71 and the second passivation layer 72. For example, the corresponding passivation layer can be prepared using PECVD equipment or ALD (Atomic Layer Deposition). The specific process is existing technology and will not be described in detail here.

[0090] In step S90, a front metal electrode 8 can be fabricated on the front side 11 and a back metal electrode 9 can be fabricated in the first region 121 on the back side using screen printing or electroplating. Taking screen printing as an example, a metal conductive paste is used. After the front metal electrode 8 and the back metal electrode 9 are formed by screen printing, a high-temperature sintering process is performed to evaporate the organic solvent in the metal paste, burn through the first passivation layer 71 of the front side 11 and the second passivation layer 72 of the first region 121 on the back side, and form metal-semiconductor contacts between the metal particles and the doped polycrystalline silicon layer 3, and between the metal particles and the doped layer 5, thereby achieving good electrical connection.

[0091] In an optional embodiment, the first dopant element is boron, and the second dopant element is phosphorus. That is, step S30 is a back-side boron expansion operation, and step S60 is a double-sided phosphorus expansion operation. The doped polycrystalline silicon layer 3, doped with the first dopant element, is a boron-doped polycrystalline silicon layer (P-Poly), the first silicon glass layer 4 is a borosilicate glass layer (BSG), the doped layer 5, doped with the second dopant element, is a phosphorus-doped polycrystalline silicon layer, and the second silicon glass layer 6 is a phosphosilicate glass layer (PSG). The boron source used in step S30 can be BBr3 or BCl3, and the phosphorus source used in step S60 can be POCl3. The processes for boron expansion and phosphorus expansion are similar and are both existing technologies, and will not be described in detail here.

[0092] In another optional embodiment, the boron-doping and phosphorus-doping steps can be interchanged, while the remaining steps are the same, i.e., the first doping element is phosphorus and the second doping element is boron. That is, step S30 is a back-side phosphorus-doping operation, and step S60 is a double-sided boron-doping operation. The doped polysilicon layer 3 with the first doping element is a phosphorus-doped polysilicon layer (N-Poly), the first silicon glass layer 4 is a phosphorus-silicon glass layer (PSG), the doped layer 5 with the second doping element is a boron-doped polysilicon layer, and the second silicon glass layer 6 is a borosilicate glass layer (BSG).

[0093] Of course, in other alternative embodiments, the first doping element may also be gallium, and the second doping element may also be arsenic, or the first doping element may also be arsenic and the second doping element may also be gallium, without specific limitations.

[0094] In an optional embodiment, in step S60, the diffusion sheet resistance of the second dopant element is greater than 100 Ω / sq. Taking phosphorus as an example, the phosphorus diffusion in step S60 is a high sheet resistance phosphorus diffusion, with a diffusion sheet resistance greater than 100 Ω / sq, which can greatly reduce the high recombination loss caused by heavy doping.

[0095] In an optional embodiment, during step S60, when the second dopant element diffuses into the textured surface, at the side interface between the doped layer 5 and the doped polysilicon layer 3, the second dopant element can also diffuse along the side direction into the silicon substrate 5 and the doped polysilicon layer 3 to form a composite contact structure 10. That is, a portion of the doped polysilicon layer 3 containing the first dopant element will be doped by the second dopant element, thereby forming a composite doped region, i.e., the composite contact structure 10.

[0096] Thus, the composite contact structure 10 can achieve local composite leakage, improve the leakage capability of the solar cell, and make the composite leakage area have high reverse leakage characteristics. In this way, with the improvement of leakage capability, at the module end, when the solar cell is shaded, when the leakage current of the solar cell reaches the maximum power point current (Impp), the composite contact structure 10 can effectively reduce the reverse breakdown voltage at both ends of the shaded cell, and the heat generation power of the solar cell will be reduced, thereby reducing the risk of hot spots in the module.

[0097] This embodiment also provides a battery module, including the TOPCon solar cell described above or the TOPCon solar cell manufactured by the above-described method. The battery module provided in this embodiment, using the TOPCon solar cell manufactured by the above-described method, has a composite contact structure 10 formed by a portion of the doped polycrystalline silicon layer 3, which is doped with a first doping element, being doped with a second doping element. This structure allows for localized recombination leakage, effectively reducing the reverse breakdown voltage of the cell and lowering the risk of hot spots. Furthermore, by texturing the entire front surface and only a portion of the back surface, the bifacial power generation efficiency of the cell can be increased without significantly increasing the process flow, reducing efficiency loss caused by high recombination in the heavily doped back surface region and improving the photoelectric conversion efficiency of the cell.

[0098] This embodiment also provides a photovoltaic system including the above-mentioned battery module. By using the above-mentioned battery module, a composite contact structure 10 is formed by a portion of the doped polycrystalline silicon layer 3 doped with a first doping element being doped with a second doping element. This structure can achieve local recombination leakage, which can effectively reduce the reverse breakdown voltage of the battery cell and reduce the risk of hot spots in the module. At the same time, by texturing the entire front side and partially texturing the back side, the bifacial power generation efficiency of the battery cell can be increased without significantly increasing the process flow, reducing the efficiency loss caused by high recombination in the heavily doped back side region, and improving the photoelectric conversion efficiency of the battery cell.

[0099] Example 2

[0100] The fabrication method of the TOPCon solar cell provided in this embodiment is basically the same as that of the TOPCon solar cell provided in Embodiment 1. The similarities will not be repeated here. The main difference lies in steps S20 and S30, as follows: Figures 8 to 13 As shown, the specific steps include:

[0101] S10: Polish the silicon substrate 1 on both sides.

[0102] S20: As Figure 8 As shown, a tunneling oxide layer 2 and a silicon material layer are sequentially prepared from the inside to the outside on both sides (front side 11 and back side 12) of the silicon substrate 1.

[0103] S30: As Figure 8 As shown, the first doping element is diffused on both sides (front side 11 and back side 12) of the silicon substrate 1 to transform the silicon material layer into a doped polycrystalline silicon layer 3 doped with the first doping element, and a first silicon glass layer 4 doped with the first doping element is formed on the outside of the doped polycrystalline silicon layer 3.

[0104] S40: As Figure 9 As shown, the first silicon glass layer 4 located in the second region 122 on the back side is removed by laser, while the first silicon glass layer 4 in the first region 121 on the back side is retained.

[0105] S41: As Figure 9 As shown, front etching removes the first silicon glass layer 4 and the first doped element located on the front side 11 of the silicon substrate 1, as well as the first silicon glass layer 4 located at the edge, by means of etching.

[0106] S50: such as Figure 10 As shown, the front side 11 and the second back side region 122 of the silicon substrate 1 are texturized to form a textured surface.

[0107] S60: As Figure 10As shown, the diffusion of a second doping element is performed to form a doped layer 5 doped with the second doping element on the textured surface, while a second silicon glass layer 6 doped with the second doping element is formed on the outside of the doped layer 5.

[0108] S70: As Figure 11 As shown, the first silicon glass layer 4 located in the first region 121 on the back side and the second silicon glass layer 6 located in the second region 122 on the back side are removed.

[0109] S80: such as Figure 12 As shown, a first passivation layer 71 is prepared on the outside of the doped layer 5, and a second passivation layer 72 is prepared on the outside of the doped polysilicon layer 3.

[0110] S90: such as Figure 12 As shown, a front metal electrode 8 and a back metal electrode 9 are prepared, such that the front metal electrode 8 is electrically connected to the doped layer 5 and the back metal electrode 9 is electrically connected to the doped polycrystalline silicon layer 3.

[0111] It should be noted that only steps S20 and S30 differ from those in Example 1; all other steps are the same, the beneficial effects are the same, and the structure of the final TOPCon solar cell is also the same. Therefore, they will not be described again here.

[0112] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A TOPCon solar cell, characterized in that, The device includes a silicon substrate (1) having a front side (11) and a back side (12) disposed opposite to each other. The back side (12) includes a first back side region (121) and a second back side region (122) located on one side of the first back side region (121). The second back side region (122) has a doped layer (5) doped with a second doping element. The first back side region (121) has a doped polysilicon layer (3) doped with a first doping element. The doped layer (5) and the doped polysilicon layer (3) have a composite contact structure (10) at the side junction of the doped layer (5) and the doped polysilicon layer (3). The composite contact structure (10) connects the doped layer (5) and the doped polysilicon layer (3). A first passivation layer (71) is provided on the outside of the doped layer (5), and a second passivation layer (72) is provided on the outside of the doped polysilicon layer (3). A front metal electrode (8) is provided on the front side (11), and a back metal electrode (9) is provided in the first region (121) on the back side. The front metal electrode (8) passes through the first passivation layer (71) and contacts the doped layer (5), and the back metal electrode (9) passes through the second passivation layer (72) and contacts the doped polysilicon layer (3).

2. The TOPCon solar cell according to claim 1, characterized in that At the junction of the doped layer (5) and the doped polysilicon layer (3) on the side, the second doping element diffuses along the side direction into the silicon substrate (1) and the doped polysilicon layer (3) to form the composite contact structure (10).

3. The TOPCon solar cell according to claim 2, characterized in that The diffusion depth of the second doping element into the doped polycrystalline silicon layer (3) along the side direction is 50 nm to 200 nm.

4. The TOPCon solar cell according to claim 1, characterized in that The front side (11) and the second area (122) on the back side are both textured surfaces, and the first area (121) on the back side is a smooth surface. The textured surface is provided with the doped layer (5), and the smooth surface is provided with a tunneling oxide layer (2) and a doped polycrystalline silicon layer (3) covering the surface of the tunneling oxide layer (2).

5. The TOPCon solar cell according to claim 4, characterized in that, The tunneling oxide layer (2) is a SiOx tunneling oxide layer.

6. The TOPCon solar cell according to claim 1, characterized in that The first doping element includes boron, and the second doping element includes phosphorus; Alternatively, the first doping element may include phosphorus, and the second doping element may include boron.

7. A manufacturing method of a TOPCon solar cell, for manufacturing the TOPCon solar cell according to any one of claims 1 to 6, characterized in that, The specific steps include: S10. Polish the silicon substrate (1) on both sides. S20. A tunneling oxide layer (2) and a silicon material layer are sequentially prepared from the inside out on the back side (12) or both sides of the silicon substrate (1); S30. Diffusion of the first doping element is performed on the back side (12) or both sides of the silicon substrate (1) to transform the silicon material layer into a doped polycrystalline silicon layer (3) doped with the first doping element, and at the same time, a first silicon glass layer (4) doped with the first doping element is formed on the outside of the doped polycrystalline silicon layer (3). S40. Remove the first silicon glass layer (4) located in the second region (122) on the back side by laser. S50. The front side (11) and the second region (122) of the back side of the silicon substrate (1) are texturized to form a textured surface; S60. Diffusion of the second doping element is performed to form a doped layer (5) doped with the second doping element on the textured surface, and a second silicon glass layer (6) doped with the second doping element is formed on the outside of the doped layer (5). S70: Remove the first silicon glass layer (4) located in the first region (121) on the back side and the second silicon glass layer (6) located in the second region (122) on the back side.

8. The method of manufacturing a TOPCon solar cell according to claim 7, wherein In S20, the silicon material layer includes one or a combination of two or more of intrinsic amorphous silicon, intrinsic polycrystalline silicon, intrinsic microcrystalline silicon, intrinsic nanocrystalline silicon, and doped silicon.

9. The method for manufacturing a TOPCon solar cell according to claim 7, characterized in that, In S60, during the diffusion of the second doping element, at the side junction of the doped layer (5) and the doped polysilicon layer (3), the second doping element can diffuse into the silicon substrate (1) and the doped polysilicon layer (3) along the side direction to form a composite contact structure (10).

10. The method of manufacturing a TOPCon solar cell according to claim 7, wherein Between S40 and S50, S41 is further included: front etching to remove the first silicon glass layer (4) and the first dopant element located on the front side (11) and the first silicon glass layer (4) located at the edge.

11. The method for manufacturing a TOPCon solar cell according to claim 7, characterized in that, S70 is followed by S80 and S90, wherein S80: a first passivation layer (71) is formed on the outside of the doped layer (5), and a second passivation layer (72) is formed on the outside of the doped polysilicon layer (3). S90: Prepare a front metal electrode (8) and a back metal electrode (9), so that the front metal electrode (8) is electrically connected to the doped layer (5) and the back metal electrode (9) is electrically connected to the doped polycrystalline silicon layer (3).

12. The method of manufacturing a TOPCon solar cell according to claim 7, wherein, In S60, the diffusion sheet resistance of the second doped element is greater than 100 Ω / sq.

13. A battery assembly characterized by, This includes the TOPCon solar cell as described in any one of claims 1 to 6 or the TOPCon solar cell manufactured by the method of manufacturing the TOPCon solar cell as described in any one of claims 7 to 12.

14. A photovoltaic system characterized by, Includes the battery assembly as described in claim 13.

Images