Solar cell, manufacturing method thereof, cell module and photovoltaic system

Abstract

The invention provides a solar cell and a manufacturing method thereof, a cell module and a photovoltaic system, a first doping structure of the solar cell comprises a first doping layer, a second doping layer and a third doping layer which are sequentially stacked from a substrate, the doping concentration of a first doping element in the second doping layer is the highest, and the doping concentration of a second doping element in the third doping layer is the same as the doping concentration of a second doping element in the third doping layer. The thickness of the first doped layer is larger than or equal to 5 nm, the thickness of the second doped layer is larger than or equal to 0.5 nm, and the thickness of the second doped layer accounts for 1%-10% of the total thickness of the first doped layer. Thus, the doping concentrations of the first doping layer, the second doping layer and the third doping layer are specifically designed, the concentration of a first doping element in the first doping layer is set to be low, and the thickness of the first doping element is set to be larger than or equal to 5 nm; the passivation performance deterioration caused by the fact that the peak concentration of the first doping element in the first doping structure is too close to the substrate can be effectively avoided, so that the field passivation effect of the region corresponding to the first doping structure is improved, and interface recombination of carriers is reduced.

Description

Technical Field

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

[0002] Currently, the doping structure in solar cells is a key component for achieving selective carrier transport and surface passivation. For example, Topcon cells have doped layers on both the front and back sides to form a tunneling oxide passivation contact structure. Back-contact cells use alternating regions of two different doping types on the back side to achieve electrode separation and carrier collection. The field passivation performance of these doped structures directly affects the cell's electrical performance and overall conversion efficiency. Therefore, improving the field passivation effect of the doped structure in solar cells has become a key technical challenge for researchers. Summary of the Invention

[0003] This application provides a solar cell, a method for manufacturing the same, a battery module, and a photovoltaic system.

[0004] This application is implemented as follows: the solar cell in the embodiments of this application includes: substrate; and A first doped structure is stacked on the substrate. The first doped structure is doped with a first doping element. The first doped structure includes a first doped layer, a second doped layer and a third doped layer stacked on the substrate in sequence. The doping concentration of the first doping element in the first doped layer is less than the doping concentration of the first doping element in the second doped layer. The doping concentration of the first doping element in the third doped layer is also less than the doping concentration of the first doping element in the second doped layer. The thickness of the first doped layer is greater than or equal to 5 nm, the thickness of the second doped layer is greater than or equal to 0.5 nm, and the thickness of the second doped layer accounts for 1%-10% of the total thickness of the first doped structure.

[0005] In some embodiments, the thickness of the first doped layer is greater than 10 nm, and the thickness of the second doped layer is 0.5 nm to 30 nm.

[0006] In some embodiments, the thickness of the first doped layer is 10nm-350nm, and the thickness of the second doped layer is 5nm-30nm.

[0007] In some embodiments, the thickness of the third doped layer is less than or equal to the thickness of the first doped layer.

[0008] In some embodiments, the peak concentration of the first dopant element in the second doped layer is greater than or equal to 10. 20atom / cm 3 .

[0009] In some embodiments, the first doped structure further includes a plurality of fourth doped layers and a plurality of fifth doped layers alternately stacked on the third doped layer; Among the plurality of fourth doped layers and the plurality of fifth doped layers, the doped layer closest to the third doped layer is the fourth doped layer, and the doped layer located on the outermost layer of the substrate is either the fourth or the fifth doped layer. The doping concentration of the first doping element in the fourth doped layer is greater than that of the first doping element in the third and fifth doped layers.

[0010] In some embodiments, the thickness of the fourth doped layer is less than or equal to the thickness of the second doped layer, and the thickness of the fifth doped layer is less than or equal to the thickness of the first doped layer.

[0011] In some embodiments, the thickness of the fourth doped layer accounts for 1%-10% of the total thickness of the first doped structure.

[0012] In some embodiments, in the first doped structure, the number of the fourth doped layer is 1-13 layers.

[0013] In some embodiments, the overall thickness of the first doped structure is 50 nm to 400 nm.

[0014] In some embodiments, the first dopant element is boron.

[0015] In some embodiments, the substrate includes a silicon substrate and a dielectric layer stacked on the silicon substrate, wherein the first doped structure is stacked on the dielectric layer.

[0016] This application also provides a method for preparing a solar cell, the method comprising: Provide a substrate; A first doped structure doped with boron is prepared on the substrate; The first doped structure includes a first doped layer, a second doped layer, and a third doped layer stacked sequentially from the substrate. The boron doping concentration in the first doped layer is less than that in the second doped layer, and the boron doping concentration in the third doped layer is also less than that in the second doped layer. The thickness of the first doped layer is greater than or equal to 5 nm, the thickness of the second doped layer is greater than or equal to 0.5 nm, and the thickness of the second doped layer accounts for 1%-10% of the total thickness of the first doped structure.

[0017] In some embodiments, the first doped structure doped with boron element deposited on the substrate includes: A first intrinsic amorphous silicon layer, a first in-situ boron-doped amorphous silicon layer, and a second intrinsic amorphous silicon layer are sequentially deposited on the substrate; wherein, the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are deposited using an LPCVD deposition process without introducing a boron source, and the first in-situ boron-doped amorphous silicon layer is formed using an LPCVD in-situ doping process with a boron source introduced. The substrate is heat-treated to transform the first intrinsic amorphous silicon layer into a first doped layer, the first in-situ boron-doped amorphous silicon layer into a second doped layer, and the second intrinsic amorphous silicon layer into a third doped layer.

[0018] In some embodiments, sequentially fabricating a first intrinsic amorphous silicon layer, a first in-situ boron-doped amorphous silicon layer, and a second intrinsic amorphous silicon layer on the substrate includes: The LPCVD deposition process is used to deposit a first intrinsic amorphous silicon layer on the substrate by introducing silane into the deposition chamber. The silicon source gas flow rate is 1000 sccm-3000 sccm, the deposition temperature is 450℃-650℃, the pressure is 300 mTorr-800 mTorr, and the deposition time is 200 s-5000 s. The LPCVD deposition process is used to simultaneously introduce silicon source gas and boron source gas into the deposition chamber to deposit a first in-situ boron-doped amorphous silicon layer on the first intrinsic amorphous silicon layer. The flow rate of the boron source gas is 10 sccm-60 sccm, the flow rate of the silicon source gas is 100 sccm-500 sccm, the deposition temperature is 450℃-650℃, the pressure is 50 mTorr-500 mTorr, and the deposition time is 10 s-1000 s. The LPCVD deposition process is used to introduce silicon source gas into the deposition chamber to form a second intrinsic amorphous silicon layer on the first in-situ boron-doped amorphous silicon layer. The silicon source gas flow rate is 1000 sccm-3000 sccm, the deposition temperature is 450℃-650℃, the pressure is 300 mTorr-800 mTorr, and the deposition time is 200 s-5000 s.

[0019] In some embodiments, the first doped structure further includes a plurality of fourth doped layers and a plurality of fifth doped layers alternately stacked on the third doped layer, wherein the fabrication method further includes, before heat treatment of the substrate: A plurality of second in-situ boron-doped amorphous silicon layers and a plurality of third intrinsic amorphous silicon layers are alternately prepared on the second intrinsic amorphous silicon layer; among the plurality of second in-situ boron-doped amorphous silicon layers and the plurality of third intrinsic amorphous silicon layers, the layer closest to the second intrinsic amorphous silicon layer is the second in-situ boron-doped amorphous silicon layer, and the layer located on the outermost layer of the substrate is either the second in-situ boron-doped amorphous silicon layer or the third intrinsic amorphous silicon layer. During the heat treatment of the substrate, the second in-situ boron-doped amorphous silicon layer is transformed into a fourth doped layer, and the third intrinsic amorphous silicon layer is transformed into a fifth doped layer; the boron doping concentration in the fourth doped layer is greater than that in the third and fifth doped layers.

[0020] This application also provides a solar cell, which is made by the method for preparing a solar cell described in any of the above claims.

[0021] This application also provides a battery assembly comprising a plurality of solar cells as described in any of the preceding claims.

[0022] This application also provides a photovoltaic system, which includes the aforementioned battery components.

[0023] In the solar cells, fabrication methods, battery modules, and photovoltaic systems of this application embodiment, the first doped structure of the solar cell consists of a first doped layer, a second doped layer, and a third doped layer stacked sequentially from the substrate. The second doped layer has the highest doping concentration of the first doping element. The thickness of the first doped layer is greater than or equal to 5 nm, the thickness of the second doped layer is greater than or equal to 0.5 nm, and the thickness of the second doped layer accounts for 1%-10% of the total thickness of the first doped structure. Thus, by specifically designing the relationship between the doping concentrations of the first, second, and third doped layers, and by setting the concentration of the first doping element in the first doped layer to be relatively low and its thickness to be greater than or equal to 5 nm, it is possible to effectively avoid the peak concentration of the first doping element in the first doped structure being too close to the substrate, which would lead to deterioration of passivation performance. This improves the field passivation effect in the region corresponding to the first doped structure and reduces interfacial recombination of charge carriers. On the other hand, through careful research and demonstration by the inventors of this application, by setting the thickness of the second doped layer 22 to be greater than or equal to 0.5 nm and optimizing the thickness ratio of the second doped layer 22 within a specific range of 1%-10%, the defects caused by impurities in the second doped layer 22 can be controlled at a low level. Simultaneously, the first doped structure 20 can also exhibit a stronger field passivation effect, thereby providing better passivation and improving battery efficiency. Furthermore, by controlling the thickness ratio of the second doped layer 22, which has the highest doping concentration, the average doping concentration in the first doped structure 20 can be controlled, thereby adjusting the uniformity of the in-plane sheet resistance of the solar cell 100.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a photovoltaic system module provided in an embodiment of this application; Figure 2 This is a schematic diagram of a battery assembly provided in an embodiment of this application; Figure 3 This is a cross-sectional schematic diagram of the solar cell provided in an embodiment of this application; Figure 4 This is another cross-sectional schematic diagram of the solar cell provided in the embodiments of this application; Figure 5 This is a schematic diagram of the doping concentration distribution of the first doped element in the solar cell provided in this application embodiment; Figure 6 This is another cross-sectional schematic diagram of the solar cell provided in the embodiments of this application; Figure 7 This is another cross-sectional schematic diagram of the solar cell provided in the embodiments of this application; Figure 8 A schematic flowchart illustrating a method for fabricating a solar cell is provided for the purposes of this application. Figure 9 Another schematic flowchart of a method for fabricating a solar cell is provided for the purposes of this application. Figure 10 This provides another schematic flowchart of a method for fabricating a solar cell, which is an embodiment of this application. Figure 11 This provides another schematic flowchart of a method for fabricating a solar cell, which is an embodiment of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0027] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "top", "bottom", "lateral", "longitudinal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "several," "multiple," and "more than" mean two (roots) or more, unless otherwise explicitly specified.

[0029] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being 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 being 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.

[0031] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0032] Please see Figures 1-2 The photovoltaic system 10001000 in this application embodiment may include the battery module 200 in this application embodiment. The battery module 200 in this application embodiment may include a plurality of battery strings, and the battery strings may include a plurality of solar cells 100 in this application embodiment.

[0033] In this application, the individual battery strings in the battery assembly 200 can be connected in series, in parallel, or in a series-parallel combination to achieve current collection and output. For example, the connection between the individual battery strings can be achieved through busbars. Each battery string may include several solar cells 100 and several solder strips. The solar cells 100 can be arranged along a predetermined direction, and the solder strips connect the solar cells 100 in the battery string sequentially.

[0034] Specifically, in the embodiments of this application, the photovoltaic system 1000 can be applied in photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants. It can also be applied to equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system 1000 are not limited to these; that is, the photovoltaic system 1000 can be applied in all fields that require solar energy for power generation. Taking a photovoltaic power generation system network as an example, the photovoltaic system 1000 may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple battery modules 200. For example, multiple battery modules 200 can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, which can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into AC power required by the mains power grid before being connected to the mains power grid to achieve solar power supply.

[0035] In some embodiments, the battery assembly 200 may further include a metal frame, a backsheet, photovoltaic glass, and an encapsulating film. The encapsulating film may be filled between the front and back of the solar cells 100, the photovoltaic glass, adjacent solar cells 100, etc. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the encapsulating film may be an EVA film or a POE film, and the specific choice can be made according to the actual situation, without limitation.

[0036] Photovoltaic glass can be applied to the encapsulating film on the front side of the solar cell 100. This photovoltaic glass can be ultra-clear glass, possessing high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance of over 93%, protecting the solar cell 100 while minimizing impact on its efficiency. Simultaneously, the encapsulating film bonds the photovoltaic glass and the solar cell 100 together, providing sealing, insulation, and waterproofing / moisture protection for the solar cell 100.

[0037] The backsheet can be attached to the encapsulant film on the back of the solar cell 100. The backsheet provides protection and support for the solar cell 100, and possesses reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, acrylic glass, and aluminum alloy TPT composite encapsulant film, etc. The specific choice depends on the specific circumstances and is not limited here. The backsheet, solar cell 100, encapsulant film, and photovoltaic glass can be housed within a metal frame. The metal frame serves as the main external support structure for the entire battery module 200, providing stable support and installation for the battery module 200. For example, the battery module 200 can be installed at the desired location using the metal frame.

[0038] Please see Figure 3 The solar cell 100 in this embodiment may include a substrate 10 and a first doped structure 20 stacked on the substrate 10, wherein the first doped structure 20 is doped with a first doping element.

[0039] The first doped structure 20 may include a first doped layer 21, a second doped layer 22 and a third doped layer 23 sequentially stacked on the substrate 10. The doping concentration of the first doped element in the first doped layer 21 is less than the doping concentration of the first doped element in the second doped layer 22, and the doping concentration of the first doped element in the third doped layer 23 is also less than the doping concentration of the first doped element in the second doped layer 22.

[0040] The thickness of the first doped layer 21 is greater than or equal to 5 nm, the thickness of the second doped layer 22 is greater than or equal to 0.5 nm, and the thickness of the second doped layer 22 accounts for 1%-10% of the total thickness of the first doped structure 20.

[0041] In the solar cell 100, cell module 200, and photovoltaic system 1000 of this application embodiment, the first doped structure 20 of the solar cell 100 consists of a first doped layer 21, a second doped layer 22, and a third doped layer 23 sequentially stacked from the substrate 10. The first doped element in the second doped layer 22 has the highest doping concentration. The thickness of the first doped layer 21 is greater than or equal to 5 nm, and the thickness of the second doped layer 22 is greater than or equal to 0.5 nm. The thickness of the second doped layer 22 accounts for 1%-10% of the total thickness of the first doped structure 20. Thus, by specifically designing the doping concentration relationship of the first doped layer 21, the second doped layer 22, and the third doped layer 23, and setting the concentration of the first doped element in the first doped layer 21 to be relatively low and its thickness to be greater than or equal to 5 nm, it is possible to effectively avoid the peak concentration of the first doped element in the first doped structure 20 being too close to the substrate 10, which would lead to a deterioration in passivation performance. This improves the field passivation effect in the region corresponding to the first doped structure 20 and reduces interfacial recombination of charge carriers. On the other hand, through careful research and demonstration by the inventors of this application, by setting the thickness of the second doped layer 22 to be greater than or equal to 0.5 nm and optimizing the thickness ratio of the second doped layer 22 within a specific range of 1%-10%, the defects caused by impurities in the second doped layer 22 can be controlled at a low level. Simultaneously, the first doped structure 20 can also exhibit a stronger field passivation effect, thereby providing better passivation and improving battery efficiency. Furthermore, by controlling the thickness ratio of the second doped layer 22, which has the highest doping concentration, the average doping concentration in the first doped structure 20 can be controlled, thereby adjusting the uniformity of the in-plane sheet resistance of the solar cell 100.

[0042] Specifically, in the embodiments of this application, the thickness of the first doped layer 21 may be, for example, 5nm, 10nm, 15nm, 20nm, 25nm, etc., and the thickness of the second doped layer 22 may be 0.5nm, 1nm, 2nm, 3nm, 4nm, 5nm, 10nm, 15nm, etc.

[0043] The thickness of the second doped layer 22 can account for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or 1%-10% of the total thickness of the first doped structure 20.

[0044] Through research and demonstration by the inventors of this application, it has been found that in some embodiments, the thickness percentage of the second doped layer 22 is preferably 4%-6%, for example, 4%, 4.5%, 5%, 5.5%, or 6%. Thus, when the thickness percentage of the second doped layer 22 is in the range of 4%-6%, the passivation effect of the region corresponding to the first doped structure 20 is optimal.

[0045] In some embodiments, the thickness of the first doped layer 21 is preferably greater than 10 nm, and the thickness of the second doped layer 22 is 0.5 nm to 30 nm.

[0046] In this way, the first doped layer 21 can have a sufficiently large thickness to prevent the peak doping concentration in the first doped structure 20 from being too close to the substrate 10, thereby effectively suppressing interface recombination. Simultaneously, it ensures that the layer has sufficient physical thickness to adequately passivate surface defects and reduce carrier recombination losses. Furthermore, controlling the thickness of the second doped layer 22 within the range of 0.5 nm to 30 nm ensures efficient carrier transport. That is to say, through this synergistic control mechanism of thickness parameters, the first doped structure 20 can improve field passivation performance while effectively avoiding performance degradation caused by inappropriate layer thickness.

[0047] Furthermore, in some embodiments, the thickness of the first doped layer 21 is preferably 10nm-350nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, or other values ​​between 10nm and 350nm, without specific limitations. The thickness of the second doped layer 22 is preferably 0.5nm-30nm, and most preferably 5nm-30nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, or other values ​​between 5nm and 30nm.

[0048] Thus, by setting the thickness of the first doped layer 21 to be less than or equal to 350 nm, the increased carrier transport resistance and optical loss caused by an excessively thick first doped layer 21 can be avoided. Simultaneously, it ensures that the layer can form a sufficiently thick transition region, allowing the peak concentration in the first doped structure 20 to maintain a sufficient distance from the substrate 10 interface to prevent poor passivation. Meanwhile, limiting the thickness of the second doped layer 22 to the range of 5 nm to 30 nm effectively prevents the second doped layer 22 from being too thin, which would lead to discontinuous doping regions and unstable concentration distribution.

[0049] In the embodiments of this application, the solar cell 100 may be a Topcon solar cell 100 or a back-contact solar cell 100, and there is no specific limitation here.

[0050] In some embodiments, the substrate 10 may include a silicon substrate 11 and a dielectric layer 12 stacked on the silicon substrate 11, and a first doped structure 20 is stacked on the dielectric layer 12. The dielectric layer 12 may be, for example, a tunneling silicon oxide layer. Of course, in some embodiments, the dielectric layer 12 may also be one or a combination of silicon oxide layer, silicon nitride layer, silicon oxynitride layer, etc., and no specific limitation is made here.

[0051] For example, please see Figure 3 In some embodiments, the solar cell 100 may be a Topcon solar cell 100. In such cases, the first doped structure 20 may be located on one surface of the substrate 10, while a second doped structure 30 with a doping conductivity type opposite to that of the first doped structure 20 is provided on the other surface. The second doped structure 30 is doped with a second doping element. In some possible embodiments, a dielectric layer 12 may also be provided on the surface corresponding to the second doped structure 30.

[0052] For example, please refer to Figure 4 In some embodiments, the solar cell 100 may be a back-contact cell. In this case, the silicon substrate 11 has a first polar region and a second polar region, and a dielectric layer 12 is provided on both the first and second polar regions. The specific material of the dielectric layer 12 may be as described above. A first doped structure 20 is located on the first polar region, and a second doped structure 30 may be provided on the second polar region. The second doped structure 30 is doped with a second doping element, and the doping conductivity type of the second doped structure 30 is opposite to that of the first doped structure 20. In some embodiments, the first doping element may be a Group 3 element, and the second doping element may be a Group 5 element.

[0053] In some embodiments, the first dopant element may be boron, and the second dopant element may be phosphorus. Specifically, the doped layer with boron as the dopant element is a p-type doped layer. The passivation effect of the p-type doped layer is inherently poor. Based on this, by specifically optimizing the doping concentration of the first doped layer 21, the second doped layer 22, and the third doped layer 23 in the first doped structure 20, as well as the thickness of the first doped layer 21 and the second doped layer 22, the problem of poor passivation effect of the p-type doped layer can be effectively compensated. This reduces interfacial recombination in the p-type region and improves the field passivation effect in the p-type region.

[0054] In some embodiments, the thickness of the third doped layer 23 is less than or equal to the thickness of the first doped layer 21.

[0055] In this way, the excessive thickness of the third doped layer 23 can be effectively avoided, which would lead to excessively high manufacturing costs.

[0056] Please see Figure 5In some embodiments, the peak concentration of the first dopant element in the second doped layer 22 is greater than or equal to 10. 20 atom / cm 3 .

[0057] Thus, by setting the peak doping concentration of the second doped layer 22 to be greater than or equal to 10... 20 atom / cm 3 This can improve the field passivation effect and increase the photoelectric conversion efficiency of the photovoltaic cell 10.

[0058] Furthermore, in some embodiments, the peak concentration of the first dopant element in the second doped layer 22 is less than 10. 21 atom / cm 3 .

[0059] In this way, the peak concentration in the second doped layer 22 can be avoided to reduce parasitic absorption and recombination loss.

[0060] Specifically, such as Figure 5 As shown, Figure 5 This is a schematic diagram of the doping concentration distribution of the first doped element in solar cell 100, obtained using the ECV test method. The curve is an ECV curve, with the horizontal axis representing depth (µm) and the vertical axis representing the concentration of the first doped element. Figure 5 The structure of the first doped structure 20 of the solar cell 100 is as follows: Figure 3 and Figure 4 As shown, the first doped structure 20 includes only a first doped layer 21, a second doped layer 22, and a third doped layer 23. Figure 5 In the curves shown, region A represents the distribution concentration of the first dopant element in the first doped layer 21, and region B represents the distribution concentration of the first dopant element in the second doped layer 22. The peak concentration in the second doped layer 22 is greater than 10. 21 atom / cm 3 Region C represents the distribution concentration of the first dopant element in the third doped layer 23.

[0061] Depend on Figure 5 It can be seen that, in this embodiment, the peak concentration of the second doped layer 22 is located at 10. 20 atom / cm 3 -10 21 atom / cm 3 between.

[0062] Please see Figure 6 and Figure 7 In some embodiments, the first doped structure 20 may further include a plurality of fourth doped layers 24 and a plurality of fifth doped layers 25 alternately stacked on the third doped layer 23; Among the several fourth doped layers 24 and several fifth doped layers 25, the doped layer closest to the third doped layer 23 is the fourth doped layer 24, and the doped layer located on the outermost layer of the substrate 10 is either the fourth doped layer 24 or the fifth doped layer 25. The doping concentration of the first doped element in the fourth doped layer 24 is greater than that of the first doped element in the third doped layer 23 and the fifth doped layer 25.

[0063] Thus, by setting several fourth doped layers 24 and several fifth doped layers 25, several doped layer stacking cycles with the first doped layers 21 to the third doped layers 23 can be formed on the substrate 10 in a "low-high-low" doping concentration arrangement, thereby further improving the field passivation effect of the region corresponding to the first doped structure 20.

[0064] Furthermore, in such embodiments, the number of fourth doped layers 24 can be 1-13 layers, and the number of fifth doped layers 25 can also be 1-13 layers. Preferably, the number of fourth doped layers 24 can be 3-7 layers, and the number of fifth doped layers 25 can also be 3-7 layers.

[0065] like Figure 6 and Figure 7 As shown, in some embodiments, the outermost doped layer of the substrate 10 can be a fifth doped layer 25, that is, the outermost doped layer of the substrate 10 is a fifth doped layer 25 with a lower doping concentration. In this way, the surface doping concentration of the first doped structure 20 can be avoided from being too high, which would cause an increase in surface recombination.

[0066] In some embodiments, the thickness of the fourth doped layer 24 is less than or equal to the thickness of the second doped layer 22, and the thickness of the fifth doped layer 25 is less than or equal to the thickness of the first doped layer 21.

[0067] Thus, by rationally optimizing and controlling the thickness of the fourth doped layer 24 and the fifth doped layer 25, the passivation effect can be guaranteed while controlling manufacturing costs.

[0068] Specifically, in some embodiments, the thickness of the fourth doped layer 24 may be the same as the thickness of the second doped layer 22, and the thickness of the fifth doped layer 25 may be the same as the thickness of the first doped layer 21. For example, in some embodiments, the thickness of the fourth doped layer 24 is preferably 0.5nm-30nm, most preferably 5nm-30nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, or other values ​​between 5nm and 30nm. The thickness of the fifth doped layer 25 may be 10nm-350nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, or other values ​​between 10nm and 350nm, and is not specifically limited here.

[0069] In some embodiments, the thickness of the fourth doped layer 24 may account for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or 1%-10% of the total thickness of the first doped structure 20. Through research and demonstration by the inventors of this application, it has been found that in some embodiments, the thickness percentage of the fourth doped layer 24 is preferably 4%-6%, for example, 4%, 4.5%, 5%, 5.5%, or 6%. Thus, when the thickness percentage of the fourth doped layer 24 is within the range of 4%-6%, the passivation effect of the region corresponding to the first doped structure 20 is optimal.

[0070] In some embodiments, the overall thickness of the first doped structure 20 may be 50nm-400nm, such as 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm or other values ​​between 50nm and 400nm, and no specific limitation is made here.

[0071] Thus, by setting the lower limit of the thickness of the first doped structure 20 to 50 nm, it is ensured that the first doped structure 20 can fully passivate the defect states on the surface of the substrate 10, thereby effectively suppressing carrier recombination. Setting the upper limit of the thickness to 400 nm avoids the loss of incident light absorption and the decrease in manufacturing process stability caused by the increase in thickness. The precise control of this thickness range, combined with the design of the concentration gradient of each layer in the first doped structure 20, optimizes the electric field distribution, while taking into account both optical performance and process feasibility, forming a complete field passivation performance regulation mechanism.

[0072] In the embodiments of this application, the first doping element is preferably boron, and the first doping layer 21, the second doping layer 22, the third doping layer 23, the fourth doping layer 24 and the fifth doping layer 25 are all boron doping layers.

[0073] Based on this, please refer to Figure 8 This application also provides a method for preparing a solar cell 100, the method comprising the following steps: S10: Provides a substrate 10; S20: A first doped structure 20 doped with boron is prepared on substrate 10; The first doped structure 20 includes a first doped layer 21, a second doped layer 22, and a third doped layer 23 sequentially stacked from the substrate 10. The boron doping concentration in the first doped layer 21 is less than that in the second doped layer 22, and the boron doping concentration in the third doped layer 23 is also less than that in the second doped layer 22. The thickness of the first doped layer 21 is greater than or equal to 5 nm, the thickness of the second doped layer 22 is greater than or equal to 0.5 nm, and the thickness of the second doped layer 22 accounts for 1%-10% of the total thickness of the first doped structure 20.

[0074] In this way, the field passivation effect of the region corresponding to the first doped structure 20 can be improved, and the interfacial recombination of charge carriers can be reduced.

[0075] Please see Figure 9 In some embodiments, step S20 may include the following steps: S21: A first intrinsic amorphous silicon layer, a first in-situ boron-doped amorphous silicon layer, and a second intrinsic amorphous silicon layer are sequentially deposited on substrate 10; wherein, the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are deposited using LPCVD deposition process without introducing a boron source, and the first in-situ boron-doped amorphous silicon layer is formed using LPCVD in-situ doping process with the introduction of a boron source. S22: Heat treatment is performed on the substrate 10 to transform the first intrinsic amorphous silicon layer into the first doped layer 21, the first in-situ boron-doped amorphous silicon layer into the second doped layer 22, and the second intrinsic amorphous silicon layer into the third doped layer 23.

[0076] Thus, the second doped layer 22 can be obtained by first forming a boron-doped amorphous silicon layer using LPCVD in-situ doping and then annealing it, which can improve the utilization rate of the boron source. At the same time, this stacking method can also ensure the field passivation performance of the first doped layer 21 structure.

[0077] It is easy to understand that in related technologies, in the LPCVD fabrication route, the growth of boron-doped polycrystalline silicon typically involves first depositing an amorphous silicon layer on the surface of a substrate 10. Then, the substrate 10 is fed into a diffusion furnace, where boron source gas and oxygen are introduced to dope boron into the amorphous silicon layer, simultaneously transforming it into a polycrystalline silicon layer, thus forming a boron-doped polycrystalline silicon layer. However, due to the different solubilities of boron in silicon dioxide and silicon, boron tends to accumulate more in silicon dioxide. In the diffusion furnace, a borosilicate glass layer enriched with boron is formed on the surface of the substrate 10. Since this borosilicate glass layer subsequently affects the fabrication of other films on the substrate 10, it is removed. This means that most of the boron is enriched in the borosilicate glass, and its subsequent absorption is removed. Consequently, most of the boron source does not participate in the growth and diffusion of the boron-doped polycrystalline silicon, resulting in low utilization of the boron source.

[0078] However, in the preparation method of this embodiment, a new process technology is used: during the preparation of the amorphous silicon layer using the LPCVD method, a boron source is simultaneously introduced to complete the boron doping. Then, by performing heat treatment on the substrate 10 at the back end, the in-situ boron-doped amorphous silicon layer can be transformed into a boron-doped polycrystalline silicon layer, thereby effectively improving the utilization rate of the boron source and reducing manufacturing costs.

[0079] Specifically, it should be noted that in such an embodiment, the first intrinsic amorphous silicon layer, the first in-situ boron-doped amorphous silicon layer, and the second intrinsic amorphous silicon layer in step S21 can be deposited and formed in the same device, as follows: In the initial stage, LPCVD deposition is used, with only silicon source gases such as silane introduced to deposit a first intrinsic amorphous silicon layer without boron doping on substrate 10 to complete the first deposition cycle. In the next deposition cycle, LPCVD in-situ boron doping deposition is used, with both silicon source gases such as silane and boron source gases introduced simultaneously, to deposit a boron-doped amorphous silicon layer on the first intrinsic amorphous layer to complete the second deposition structure. Then, in the next deposition cycle, LPCVD deposition is used, with only silicon source gases such as silane introduced to deposit a second intrinsic amorphous silicon layer without boron doping on the first in-situ boron-doped amorphous silicon layer. Thus, in this process, a stacked structure of "intrinsic amorphous silicon layer - boron-doped amorphous silicon layer - intrinsic amorphous silicon layer" is formed on the silicon substrate. Subsequently, the substrate 10 is subjected to heat treatment, such as annealing activation treatment. During the heat treatment, the intrinsic amorphous silicon layer is transformed into a polycrystalline silicon layer, that is, both the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are transformed into intrinsic polycrystalline silicon layers, and the first in-situ boron-doped amorphous silicon layer is transformed into a first boron-doped polycrystalline silicon layer (i.e., the second doped layer 22). During the heat treatment, the boron element in the first boron-doped polycrystalline silicon layer is at least partially activated, and the boron element diffuses to the intrinsic polycrystalline silicon layers on both sides, thereby making the first intrinsic amorphous silicon layer into a first doped layer 21 containing boron element, and making the second intrinsic amorphous silicon layer into a second doped layer 22 containing boron element. The doping concentration of boron element in the first doped layer 21 and the third doped layer 23 is less than the doping concentration of boron element in the second doped layer 22.

[0080] In this embodiment, on the one hand, by employing LPCVD in-situ boron doping technology to prepare the boron-doped polycrystalline silicon layer, the utilization rate of the boron source can be improved. On the other hand, by setting the first doped structure 20 as a stacked structure including at least a first doped layer 21, a second doped layer 22, and a third doped layer 23, and by specifically designing the doping concentration and thickness of the first doped layer 21 and the second doped layer 22, the field passivation effect of the first doped structure 20 can be effectively improved, overcoming the deficiency of insufficient passivation caused by the LPCVD in-situ doping process in traditional technologies. That is to say, by employing LPCVD in-situ boron doping technology and specifically designing the film structure thickness and concentration of the first doped structure 20, the field passivation effect of the first doped structure 20 can be guaranteed while improving the utilization of the boron source, thereby improving the efficiency of the solar cell 100.

[0081] In the preparation method of this application, the silicon source gas can be a gas such as silane, and the boron source can be a boron source gas such as boron chloride; there are no specific limitations here.

[0082] Please see Figure 10 Furthermore, in some embodiments, step S21 may include the following steps: S211: The LPCVD deposition process is adopted. A silicon source gas is introduced into the deposition chamber to deposit the first intrinsic amorphous silicon layer on the substrate 10. The silicon source gas flow rate is 1000 sccm-3000 sccm, the deposition temperature is 450℃-650℃, the pressure is 300 mTorr-800 mTorr, and the deposition time is 200S-5000S. S212: The LPCVD deposition process is adopted, and silicon source gas and boron source gas are simultaneously introduced into the deposition chamber to deposit a first in-situ boron-doped amorphous silicon layer on the first intrinsic amorphous silicon layer. The flow rate of boron source gas is 10 sccm-60 sccm, the flow rate of silicon source gas is 100 sccm-500 sccm, the deposition temperature is 450℃-650℃, the pressure is 50 mTorr-500 mTorr, and the deposition time is 10S-1000S. S213: The LPCVD deposition process is adopted. A silicon source gas is introduced into the deposition chamber to form a second intrinsic amorphous silicon layer on the first in-situ boron-doped amorphous silicon layer. The silicon source gas flow rate is 1000 sccm-3000 sccm, the deposition temperature is 450℃-650℃, the pressure is 300 mTorr-800 mTorr, and the deposition time is 200S-5000S.

[0083] Thus, by employing the LPCVD deposition process and specifically optimizing and matching the process parameters such as silicon source gas flow rate, boron source gas flow rate, deposition temperature, deposition pressure, and deposition time at each deposition stage, the concentration optimization design of the first doped layer 21, the second doped layer 22, and the third doped layer 23 can be achieved. At the same time, the thickness matching design of the first doped layer 21 and the second doped layer 22 can be achieved, thereby improving the field passivation effect of the first doped structure 20 while improving the utilization rate of the boron source, and ultimately achieving the goal of improving the efficiency of the solar cell 100.

[0084] Specifically, the thicknesses of the first doped layer 21, the second doped layer 22, and the third doped layer 23 are as described above and will not be repeated here. The specific thicknesses of the three can be controlled by controlling the flow rate of the introduced gas, the deposition temperature, and the deposition time. Through the optimized matching design of the three, the thicknesses of the first doped layer 21, the second doped layer 22, and the third doped layer 23 can reach the range described above, thereby ensuring the field passivation effect of the first doped structure 20.

[0085] In the embodiments of this application, the annealing activation temperature of the substrate 10 during the annealing activation heat treatment can be 700℃-1000℃.

[0086] Please see Figure 11In some embodiments, the first doped structure 20 further includes a plurality of fourth doped layers 24 and a plurality of fifth doped layers 25 alternately stacked on the third doped layer 23, wherein, before heat treatment of the substrate 10, i.e., before step S22, the fabrication method may further include: S23: Several second in-situ boron-doped amorphous silicon layers and several third intrinsic amorphous silicon layers are alternately prepared on the second intrinsic amorphous silicon layer; among the several second in-situ boron-doped amorphous silicon layers and several third intrinsic amorphous silicon layers, the one closest to the second intrinsic amorphous silicon layer is the second in-situ boron-doped amorphous silicon layer, and the one located on the outermost layer of the substrate 10 is either the second in-situ boron-doped amorphous silicon layer or the third intrinsic amorphous silicon layer. During the heat treatment of the substrate 10, that is, in step S22, the second in-situ boron-doped amorphous silicon layer is transformed into the fourth doped layer 24, and the third intrinsic amorphous silicon layer is transformed into the fifth doped layer 25; the boron doping concentration in the fourth doped layer 24 is greater than the boron doping concentration in the third doped layer 23 and the fifth doped layer 25.

[0087] Thus, by alternately preparing the fourth doped layer 24 and the fifth doped layer 25 in the third doped layer 23, the field passivation effect of the first doped structure 20 can be further guaranteed.

[0088] Specifically, in such an embodiment, after depositing the second intrinsic amorphous silicon layer, a cyclic structure of "second in-situ boron-doped amorphous silicon layer - third intrinsic amorphous silicon layer" can be prepared on the second intrinsic amorphous silicon layer. That is, multiple deposition cycles of the second in-situ boron-doped layer and the third intrinsic amorphous silicon layer can be performed. In this case, the final deposition step can be either the deposition of the third intrinsic amorphous silicon layer or the deposition of the second in-situ boron-doped amorphous silicon layer. It is easy to understand that in such an embodiment, through multiple deposition cycles, multiple alternating "intrinsic amorphous layer - boron-doped amorphous silicon layer" cycles will be formed on the substrate 10.

[0089] Subsequently, the substrate 10 undergoes heat treatment. During this process, the intrinsic amorphous silicon layer transforms into an intrinsic polycrystalline silicon layer, and the boron-doped polycrystalline silicon transforms into a boron-doped polycrystalline silicon layer. The boron element in the boron-doped polycrystalline silicon layer is at least partially activated and diffuses to the intrinsic polycrystalline silicon layers on both sides to transform them into boron-doped polycrystalline silicon layers with a lower boron doping concentration. That is, after the heat treatment, a first doped layer 21, a second doped layer 22, and a third doped layer 23 are formed sequentially on the substrate 10, and an alternating cyclic structure of a fourth doped layer 24 and a fifth doped layer 25 is also formed on the third doped layer 23.

[0090] In some possible embodiments, after the second intrinsic amorphous silicon layer is deposited, 1-13 cycles of “second in-situ boron-doped amorphous silicon layer - third intrinsic amorphous silicon layer” can be performed.

[0091] As described above, in such a preparation method, in some embodiments, the thickness of the fourth doped layer 24 is less than or equal to the thickness of the second doped layer 22, and the thickness of the fifth doped layer 25 is less than or equal to the thickness of the first doped layer 21.

[0092] In some embodiments, the thickness of the fourth doped layer 24 may account for 1%-10% of the total thickness of the first doped structure 20.

[0093] In the preparation method of this application, regardless of whether the fourth doped layer 24 and the fifth doped layer 25 are present, the overall thickness of the first doped structure 20 is controlled within the range of 50nm-400nm.

[0094] In some embodiments, the second in-situ boron-doped layer can also be formed using an LPCVD deposition process, where silicon source gas and boron source gas are simultaneously introduced into the deposition chamber for deposition. The flow rate of the boron source gas can be 10 sccm-60 sccm, the flow rate of the silicon source gas can be 100 sccm-500 sccm, the deposition temperature can be 450℃-650℃, the pressure can be 50 mTorr-500 mTorr, and the deposition time can be 10 s-1000 s. The third intrinsic amorphous silicon layer can also be formed using an LPCVD deposition process, where silicon source gas is introduced into the deposition chamber for deposition. The flow rate of the silicon source gas can be 1000 sccm-3000 sccm, the deposition temperature can be 450℃-650℃, the pressure can be 300 mTorr-800 mTorr, and the deposition time can be 200 s-5000 s.

[0095] The specific thicknesses of the two layers can be controlled by adjusting the flow rate of the introduced gas, the deposition temperature, and the deposition time. Through the optimized matching design of the three, the thicknesses of the fourth doped layer 24 and the fifth doped layer 25 can reach the range described above, thereby further ensuring the field passivation effect of the first doped structure 20.

[0096] Please refer to Table 1 below. The comparative examples in Table 1 are the electrical performance parameters of the region where the first doped structure 21 is provided in the back contact battery prepared by the preparation method in the embodiments of this application and the first doped layer 21 structure only includes the first doped layer 21, the second doped layer 22 and the third doped layer 23, and the electrical performance parameters of the corresponding region in the conventional back contact battery prepared by the conventional diffusion process in the prior art. Table 1 Examples 1-5 are five samples prepared using the in-situ boron doping method of this application. Figure 4The back-contact battery shown has electrical performance parameters at the P-type region corresponding to the first doped structure 21. Comparative Examples 1-2 show the electrical performance parameters of the corresponding P-type region of the back-contact battery prepared by diffusion process in conventional technology. Table 1 shows that the sheet resistance of the experimental group (in-situ doped samples) is around 140 ohms, while the sheet resistance of the comparative examples is around 150 ohms. Regarding passivation, Examples 1-5 have lower recombination current J0 and better passivation effect, which is beneficial for improving battery efficiency.

[0097] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0098] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A solar cell, characterized in that, include: substrate; and A first doped structure is stacked on the substrate. The first doped structure is doped with a first doping element. The first doped structure includes a first doped layer, a second doped layer and a third doped layer stacked on the substrate in sequence. The doping concentration of the first doping element in the first doped layer is less than the doping concentration of the first doping element in the second doped layer. The doping concentration of the first doping element in the third doped layer is also less than the doping concentration of the first doping element in the second doped layer. The thickness of the first doped layer is greater than or equal to 5 nm, the thickness of the second doped layer is greater than or equal to 0.5 nm, and the thickness of the second doped layer accounts for 1%-10% of the total thickness of the first doped structure.

2. The solar cell according to claim 1, characterized in that, The thickness of the first doped layer is greater than 10 nm, and the thickness of the second doped layer is 0.5 nm to 30 nm.

3. The solar cell according to claim 2, characterized in that, The thickness of the first doped layer is 10nm-350nm, and the thickness of the second doped layer is 5nm-30nm.

4. The solar cell according to claim 1, characterized in that, The thickness of the third doped layer is less than or equal to the thickness of the first doped layer.

5. The solar cell according to claim 1, characterized in that, The peak concentration of the first dopant element in the second doped layer is greater than or equal to 10. 20 atom / cm 3 .

6. The solar cell according to any one of claims 1-5, characterized in that, The first doped structure further includes a plurality of fourth doped layers and a plurality of fifth doped layers alternately stacked on the third doped layer; Among the plurality of fourth doped layers and the plurality of fifth doped layers, the doped layer closest to the third doped layer is the fourth doped layer, and the doped layer located on the outermost layer of the substrate is either the fourth or the fifth doped layer. The doping concentration of the first doping element in the fourth doped layer is greater than that of the first doping element in the third and fifth doped layers.

7. The solar cell according to claim 6, characterized in that, The thickness of the fourth doped layer is less than or equal to the thickness of the second doped layer, and the thickness of the fifth doped layer is less than or equal to the thickness of the first doped layer.

8. The solar cell according to claim 6, characterized in that, The thickness of the fourth doped layer accounts for 1%-10% of the total thickness of the first doped structure.

9. The solar cell according to claim 6, characterized in that, In the first doped structure, the number of the fourth doped layer is 1-13 layers.

10. The solar cell according to claim 1, characterized in that, The overall thickness of the first doped structure is 50nm-400nm.

11. The solar cell according to claim 1, characterized in that, The first doping element is boron.

12. The solar cell according to claim 1, characterized in that, The substrate includes a silicon substrate and a dielectric layer stacked on the silicon substrate, wherein the first doped structure is stacked on the dielectric layer.

13. A method for preparing a solar cell, characterized in that, The preparation method includes: Provide a substrate; A first doped structure doped with boron is prepared on the substrate; The first doped structure includes a first doped layer, a second doped layer, and a third doped layer stacked sequentially from the substrate. The boron doping concentration in the first doped layer is less than that in the second doped layer, and the boron doping concentration in the third doped layer is also less than that in the second doped layer. The thickness of the first doped layer is greater than or equal to 5 nm, the thickness of the second doped layer is greater than or equal to 0.5 nm, and the thickness of the second doped layer accounts for 1%-10% of the total thickness of the first doped structure.

14. The preparation method according to claim 13, characterized in that, The first doped structure deposited on the substrate, doped with boron, includes: A first intrinsic amorphous silicon layer, a first in-situ boron-doped amorphous silicon layer, and a second intrinsic amorphous silicon layer are sequentially deposited on the substrate; wherein, the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are deposited using an LPCVD deposition process without introducing a boron source, and the first in-situ boron-doped amorphous silicon layer is formed using an LPCVD in-situ doping process with a boron source introduced. The substrate is heat-treated to transform the first intrinsic amorphous silicon layer into a first doped layer, the first in-situ boron-doped amorphous silicon layer into a second doped layer, and the second intrinsic amorphous silicon layer into a third doped layer.

15. The preparation method according to claim 14, characterized in that, The sequential fabrication of a first intrinsic amorphous silicon layer, a first in-situ boron-doped amorphous silicon layer, and a second intrinsic amorphous silicon layer on the substrate includes: The LPCVD deposition process is used to deposit a first intrinsic amorphous silicon layer on the substrate by introducing silane into the deposition chamber. The silicon source gas flow rate is 1000 sccm-3000 sccm, the deposition temperature is 450℃-650℃, the pressure is 300 mTorr-800 mTorr, and the deposition time is 200 s-5000 s. The LPCVD deposition process is used to simultaneously introduce silicon source gas and boron source gas into the deposition chamber to deposit a first in-situ boron-doped amorphous silicon layer on the first intrinsic amorphous silicon layer. The flow rate of the boron source gas is 10 sccm-60 sccm, the flow rate of the silicon source gas is 100 sccm-500 sccm, the deposition temperature is 450℃-650℃, the pressure is 50 mTorr-500 mTorr, and the deposition time is 10 s-1000 s. The LPCVD deposition process is used to introduce silicon source gas into the deposition chamber to form a second intrinsic amorphous silicon layer on the first in-situ boron-doped amorphous silicon layer. The silicon source gas flow rate is 1000 sccm-3000 sccm, the deposition temperature is 450℃-650℃, the pressure is 300 mTorr-800 mTorr, and the deposition time is 200 s-5000 s.

16. The preparation method according to claim 14, characterized in that, The first doped structure further includes a plurality of fourth doped layers and a plurality of fifth doped layers alternately stacked on the third doped layer, wherein, before heat treatment of the substrate, the fabrication method further includes: A plurality of second in-situ boron-doped amorphous silicon layers and a plurality of third intrinsic amorphous silicon layers are alternately prepared on the second intrinsic amorphous silicon layer; among the plurality of second in-situ boron-doped amorphous silicon layers and the plurality of third intrinsic amorphous silicon layers, the layer closest to the second intrinsic amorphous silicon layer is the second in-situ boron-doped amorphous silicon layer, and the layer located on the outermost layer of the substrate is either the second in-situ boron-doped amorphous silicon layer or the third intrinsic amorphous silicon layer. During the heat treatment of the substrate, the second in-situ boron-doped amorphous silicon layer is transformed into a fourth doped layer, and the third intrinsic amorphous silicon layer is transformed into a fifth doped layer; the boron doping concentration in the fourth doped layer is greater than that in the third and fifth doped layers.

17. A solar cell, characterized in that, The solar cell is manufactured by the method for preparing a solar cell according to any one of claims 13-16.

18. A battery assembly, characterized in that, Includes the solar cells described in any one of claims 1-12.

19. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 18.

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