Topcon solar cell, photovoltaic module and photovoltaic system

Abstract

The embodiment of the utility model provides a Topcon solar cell, a photovoltaic module and a photovoltaic system. The Topcon solar cell comprises a substrate layer; the first tunneling layer, the first buffer composite layer, the second tunneling layer, the second buffer composite layer and the polycrystalline silicon layer are sequentially stacked on the lower surface of the substrate layer. According to the embodiment of the invention, the first buffer composite layer, the second buffer composite layer and the heavily-doped polycrystalline silicon layer jointly form a three-layer in-situ phosphorus-doped film layer structure, so that the diffusion depth of doped phosphorus atoms in crystalline silicon can be remarkably increased, and the adjustment of phosphorus doping distribution in the polycrystalline silicon film is realized; therefore, the sufficient field passivation effect is ensured, and the recombination loss caused by phosphorus diffusion to the substrate is reduced at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a Topcon solar cell, a photovoltaic module, and a photovoltaic system. Background Art

[0002] Solar cells have become the mainstream manufacturing method for solar cells due to their passivated contact structure, which effectively reduces carrier recombination losses at the metal contacts on the back of the cell. Due to cost and performance considerations, the main methods for preparing polysilicon thin films in the TopCon process are plasma-enhanced chemical vapor deposition (PECVD) and low-pressure chemical vapor deposition (LPCVD). Compared with LPCVD, PECVD offers higher film deposition rates, minimal wraparound, and other desirable qualities. Therefore, tubular PECVD technology, capable of preparing tunnel oxide layers and in-situ doping of polysilicon, holds great potential for industrial mass production of TopCon solar cells.

[0003] At present, the amorphous silicon film deposited after the PE Poly process is mainly amorphous silicon heavily doped with phosphorus (P). After subsequent annealing, it crystallizes and becomes a heavily doped polysilicon layer. In-situ doping with phosphorus (P) can effectively inhibit the release level of hydrogen and reduce the residual stress during the annealing process. At the same time, it ensures the crystallization rate of polysilicon and the conductivity of the polysilicon film, avoiding the loss of cell efficiency.

[0004] However, during the annealing process, phosphorus (P) within the heavily doped polysilicon film diffuses into the crystalline silicon substrate, forming an internal doping region near the interface. This phosphorus penetration can severely affect the passivation quality of the tunneling layer, causing recombination losses and severely impacting the photovoltaic conversion efficiency of the cell.

[0005] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the Invention

[0006] The embodiments of the present application provide a Topcon solar cell, photovoltaic module and photovoltaic system, which aim to solve the problem that phosphorus penetration during annealing will seriously affect the passivation quality of the tunneling layer, cause recombination loss, and seriously affect the photoelectric conversion efficiency of the cell.

[0007] In a first aspect, an embodiment of the present application provides a Topcon solar cell, comprising:

[0008] substrate layer;

[0009] A first tunneling layer, a first buffer composite layer, a second tunneling layer, a second buffer composite layer, and a polysilicon layer are sequentially stacked on the lower surface of the substrate layer.

[0010] In summary, according to the above-mentioned Topcon solar cell, by setting a first buffer composite layer and a second buffer composite layer to form a three-layer in-situ phosphorus-doped film structure together with the heavily doped polysilicon layer, the diffusion depth of the doped phosphorus atoms in the crystalline silicon can be significantly increased, thereby achieving the adjustment of the phosphorus doping distribution in the polysilicon film. Specifically, the phosphorus in the heavily doped phosphorus polysilicon layer needs to be buffered by the second buffer composite layer and then diffused to the second tunneling layer, which can not only ensure the contact performance between the polysilicon layer and the second tunneling layer, but also preliminarily reduce the phosphorus diffusion of the polysilicon layer. By setting the first buffer composite layer, the diffusion of phosphorus to the silicon substrate can be further blocked. In addition, by setting the first tunneling layer to form a passivation structure with the second tunneling layer, the passivation effect of the Topcon solar cell can be improved. In addition, by setting the first buffer composite layer and the second buffer composite layer, the degree of diffusion of phosphorus atoms to the tunneling layer is alleviated, the carrier Auger recombination velocity is reduced, and it is beneficial to improve the conversion efficiency of the solar cell.

[0011] Optionally, the first buffer composite layer includes a first buffer sub-layer, a second buffer sub-layer and a third buffer sub-layer alternately stacked in a first preset period;

[0012] The sublayer of the first buffer composite layer close to the second tunneling layer is the third buffer sublayer;

[0013] The thickness of the third buffer sublayer is greater than that of the second buffer sublayer, and the thickness of the second buffer sublayer is greater than that of the first buffer sublayer.

[0014] Optionally, the first preset period is 1-7, and the thickness of the first buffer composite layer is 20-30 nm.

[0015] Optionally, the second buffer composite layer includes a fourth buffer sublayer, a fifth buffer sublayer and a sixth buffer sublayer alternately stacked in a second preset period;

[0016] The sublayer of the second buffer composite layer close to the polysilicon is the sixth buffer sublayer;

[0017] The thickness of the sixth buffer sublayer is greater than that of the fifth buffer sublayer, and the thickness of the fifth buffer sublayer is greater than that of the fourth buffer sublayer.

[0018] Optionally, the second preset period is 3-11, and the thickness of the second buffer composite layer is 25-40 nm.

[0019] Optionally, the thickness of the second buffer composite layer is greater than the thickness of the first buffer composite layer.

[0020] Optionally, the thickness of the first buffer sublayer, the second buffer sublayer, the third buffer sublayer, the fourth buffer sublayer, the fifth buffer sublayer, and the sixth barrier are all 0.5-3 nm.

[0021] Optionally, the first buffer sublayer is an n-poly-si layer, and the second buffer sublayer, the third buffer sublayer, the fourth buffer sublayer, the fifth buffer sublayer, and the sixth buffer sublayer are all n-poly-si layers. + -poly-si layer, the polysilicon layer is n ++ -poly-si layer.

[0022] In a second aspect, an embodiment of the present application provides a photovoltaic module including the above-mentioned Topcon solar cell.

[0023] In a third aspect, an embodiment of the present application provides a photovoltaic system comprising the above-mentioned photovoltaic assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0025] Figure 1 This is a schematic structural diagram of a Topcon solar cell provided in one embodiment of the present application;

[0026] Figure 2 1 is a schematic structural diagram of a first tunneling layer, a first buffer composite layer, and a second tunneling layer provided in one embodiment of the present application;

[0027] Figure 3 1 is a schematic structural diagram of a second tunneling layer, a second buffer composite layer, and a polysilicon layer provided in one embodiment of the present application;

[0028] Figure 4 This is a flow chart of a method for preparing a Topcon solar cell provided in one embodiment of the present application.

[0029] Description of reference numerals:

[0030] 10-substrate layer; 20-first tunneling layer; 30-first buffer composite layer; 40-second tunneling layer; 50-second buffer composite layer; 60-polysilicon layer; 70-silicon oxide layer; 80-electrode; 301-first buffer sublayer; 302-second buffer sublayer; 303-third buffer sublayer; 501-fourth buffer sublayer; 502-fifth buffer sublayer; 503-sixth buffer sublayer. DETAILED DESCRIPTION

[0031] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, the sizes of layers, regions, and elements and their relative sizes may be exaggerated for clarity. The same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other unless there is a conflict.

[0032] It should be understood that when an element or layer is referred to as being "on," "below," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "below," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Thus, a first element, component, region, layer, or portion discussed below may be represented as a second element, component, region, layer, or portion without departing from the teachings of the present disclosure. When a second element, component, region, layer or section is discussed, it does not necessarily mean that the first element, component, region, layer or section must be present in the present disclosure.

[0033] In this application, unless otherwise specified or limited, the terms "disposed," "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] To facilitate those skilled in the art to understand the technical solutions provided in the embodiments of the present application, the following describes the relevant technologies:

[0036] The applicant discovered that during the annealing process, phosphorus (P) within the heavily doped polysilicon film diffuses into the crystalline silicon substrate, forming an internal doping region near the interface. This phosphorus penetration can severely affect the passivation quality of the tunneling layer, causing recombination losses and severely impacting the photovoltaic efficiency of the cell.

[0037] In view of the above problems, a Topcon solar cell proposed in an embodiment of the present application optimizes the film structure of the polysilicon layer and adjusts the doping distribution within the polysilicon film. While ensuring sufficient doping concentration to ensure contact performance, it controls the phosphorus doping amount, blocks the diffusion of phosphorus into the silicon substrate, and increases the passivation effect to obtain an increase in the opening voltage and achieve higher cell efficiency.

[0038] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0039] Example 1

[0040] like Figure 1 As shown, the embodiment of the present application provides a Topcon solar cell, which includes:

[0041] The substrate layer 10 and the first tunneling layer 20 , the first buffer composite layer 30 , the second tunneling layer 40 , the second buffer composite layer 50 , the polysilicon layer 60 , the silicon oxide layer 70 and the electrode 80 are sequentially stacked on the lower surface of the substrate layer 10 .

[0042] In some embodiments, in order to further improve the effect of the first buffer composite layer 30 in blocking phosphorus diffusion, as shown in FIG. Figure 2As shown, the first buffer composite layer 30 includes a first buffer sublayer 301, a second buffer sublayer 302 and a third buffer sublayer 303 alternately stacked in a first preset period, and the sublayer in the first buffer composite layer 30 close to the second tunneling layer 40 is the third buffer sublayer 303, that is, the first buffer sublayer 301 is stacked on the lower surface of the first tunneling layer 20, and the third buffer sublayer 303 is stacked on the upper surface of the second tunneling layer 40, and the thickness of the third buffer sublayer 303 is greater than the thickness of the second buffer sublayer 302, and the thickness of the second buffer sublayer 302 is greater than the thickness of the first buffer sublayer 301, so as to provide a step-by-step buffer for the phosphorus diffused from the polysilicon layer 60 containing heavily doped phosphorus.

[0043] In some embodiments, the phosphorus content of the first buffer sublayer 301 is less than that of the second buffer sublayer 302 , and the phosphorus content of the second buffer sublayer 302 is less than that of the third buffer layer, so as to ensure the contact performance of each layer while buffering or even blocking the diffusion of phosphorus into the substrate layer 10 .

[0044] In some embodiments, the first preset period is 1-7, and the thickness of the first buffer composite layer 30 is 20-30 nm. If the thickness of the first buffer composite layer 30 is too thick, parasitic absorption will be high. If the thickness is too thin, the effect of buffering phosphorus diffusion will be affected. For example, the first preset period can be 1, 3, 5, 7, etc., and the total thickness of the first buffer composite layer 30 can be 20 nm, 25 nm, 30 nm, etc.

[0045] It should be noted that, since phosphorus diffusion will occur in the heavily phosphorus-doped polysilicon layer 60 during actual use, the purpose of providing the first buffer composite layer 30 and the second buffer composite layer 50 is to hinder this phenomenon and reduce the degree of phosphorus diffusion. Based on this, during actual use, the first buffer composite layer 30 and the second buffer composite layer 50 will both be doped with phosphorus themselves due to phosphorus diffusion, thereby ensuring the contact performance of each layer. Therefore, in some embodiments, the phosphorus content of the first buffer sublayer 301 in the present application can be set to zero or non-zero.

[0046] In some embodiments, in order to further improve the effect of the second buffer composite layer 50 in blocking phosphorus diffusion, as shown in FIG. Figure 3As shown, the second buffer composite layer 50 includes a fourth buffer sublayer 501, a fifth buffer sublayer 502, and a sixth buffer sublayer 503 alternately stacked in a second predetermined period. The sublayer of the second buffer composite layer 50 close to the polysilicon is the sixth buffer sublayer 503; that is, the sixth buffer sublayer 503 is stacked on the upper surface of the polysilicon layer 60, and the fourth buffer sublayer 501 is stacked on the lower surface of the second tunneling layer 40. The thickness of the sixth buffer sublayer 503 is greater than that of the fifth buffer sublayer 502, and the thickness of the fifth buffer sublayer 502 is greater than that of the fourth buffer sublayer 501, thereby initially achieving a barrier effect on phosphorus diffusion from the polysilicon layer 60. The purpose of setting a gradient thickness is to improve the barrier effect. In some embodiments, the phosphorus content of the fourth buffer sublayer 501 is lower than that of the fifth buffer sublayer 502, and the phosphorus content of the fifth buffer sublayer 502 is lower than that of the sixth buffer sublayer 503, so as to ensure the contact performance of each layer while buffering the diffusion of phosphorus into the substrate layer 10. In addition, in order to make the phosphorus distribution from the polysilicon layer 60 to the substrate layer 10 present a step-down trend, the phosphorus content of the fourth buffer sublayer 501 can be selected to be greater than or equal to the phosphorus content of the third buffer sublayer 303 .

[0047] By way of example but not limitation, the phosphorus content (number of phosphorus atoms per cubic centimeter) of the first buffer sublayer 301, the second buffer sublayer 302 and the third buffer sublayer 303 are all in the range of 1E20 to 2E20, the phosphorus content of the fourth buffer sublayer 501, the fifth buffer sublayer 502 and the sixth buffer sublayer 503 are all in the range of 2E20 to 3E20, and the phosphorus content of the polysilicon layer 60 is 4-5E20.

[0048] In some embodiments, the second preset period is 3-11, and the thickness of the second buffer composite layer 50 is 25-40 nm. If the thickness of the second buffer composite layer 50 is too thick, parasitic absorption will be high. If the thickness of the second buffer composite layer 50 is too thin, the effect of buffering phosphorus diffusion will also be affected. For example, the second preset period can be 3, 5, 7, 9, 11, etc., and the thickness of the second buffer composite layer 50 can be 25 nm, 30 nm, 35 nm, 40 nm, etc.

[0049] Specifically, the total thickness of the second buffer composite layer 50 is greater than the total thickness of the first buffer composite layer 30. In addition, the thickness range of the first buffer sublayer 301, the second buffer sublayer 302 and the third buffer sublayer 303 are all within 1 to 10 nm, and the thickness range of the fourth buffer sublayer 501, the fifth buffer sublayer 502 and the sixth buffer sublayer 503 are all within 1 to 15 nm.

[0050] In some embodiments, the first buffer sublayer 301 is an n-poly-si layer, the second buffer sublayer 302, the third buffer sublayer 303, the fourth buffer sublayer 501, the fifth buffer sublayer 502, and the sixth buffer sublayer 503 are all n-poly-si layers.+ -poly-si layer, the polysilicon layer 60 is n ++ -poly-si layer, that is, the first buffer sublayer 301 is a poly-si layer not doped with phosphorus, and the second buffer sublayer 302, the third buffer sublayer 303, the fourth buffer sublayer 501, the fifth buffer sublayer 502, and the sixth buffer sublayer 503 are all doped with phosphorus. The purpose is to make the phosphorus distribution tend to decrease from the polysilicon to the substrate layer 10, while ensuring the contact between the layers.

[0051] Example 2

[0052] like Figure 4 As shown, the embodiment of the present application provides a method for preparing a Topcon solar cell, which is used to prepare the above-mentioned Topcon solar cell, and the steps are as follows:

[0053] Step S101: preparing a first tunneling layer by passing N2O;

[0054] Step S101: preparing a first buffer sublayer by passing SiH4 and H2, and preparing a second buffer sublayer and a third buffer sublayer by passing SiH4, H2 and low-flow PH3 respectively;

[0055] Step S103: Prepare a second tunneling layer by passing N2O.

[0056] Step S104: preparing a fourth buffer sublayer, a fifth buffer sublayer, and a sixth buffer sublayer respectively by passing SiH4, H2, and low-flow PH3;

[0057] Step S105: preparing a heavily phosphorus-doped polysilicon layer by passing SiH4, H2, and high-flow PH3;

[0058] Step S106: high temperature annealing to crystallize the amorphous silicon layer;

[0059] Step S107: preparing a silicon oxide layer and electrodes.

[0060] As an example of this embodiment, the preparation method of the Topcon solar cell is as follows:

[0061] 1. Set the N2O flow rate to 11800 sccm and the deposition time to 95 s to obtain the first tunneling layer;

[0062] 2. Set the flow rates of SiH4 and H2 to 2950 sccm and 9800 sccm respectively, and the deposition time to 50 s to obtain the first buffer sublayer;

[0063] 3. Set the flow rates of SiH4, H2, and PH3 to 2950 sccm, 9800 sccm, and 100 sccm, respectively, and the deposition time to 70 s to obtain the second buffer sublayer;

[0064] 4. Set the flow rates of SiH4, H2, and PH3 to 2950 sccm, 9800 sccm, and 200 sccm, respectively, and the deposition time to 90 s to obtain the third buffer sublayer;

[0065] 5. Set the N2O flow rate to 11800 sccm and the deposition time to 95 s to obtain the second tunneling layer;

[0066] 6. Set the flow rates of SiH4, H2, and PH3 to 2950 sccm, 9800 sccm, and 300 sccm, respectively, and the deposition time to 60 s to obtain the fourth buffer sublayer;

[0067] 7. Set the flow rates of SiH4, H2, and PH3 to 2950 sccm, 9800 sccm, and 400 sccm, respectively, and deposit for 80 seconds to obtain the fifth buffer sublayer;

[0068] 8. Set the flow rates of SiH4, H2, and PH3 to 2950 sccm, 9800 sccm, and 500 sccm, respectively, and deposit for 100 s to obtain the sixth buffer sublayer;

[0069] 9. Set the flow rates of SiH4, H2, and PH3 to 2950 sccm, 9800 sccm, and 850 sccm, respectively, and the deposition time to 310 s to deposit a heavily phosphorus-doped polysilicon layer;

[0070] 10. Set the flow rates of SiH4 and N2O2 to 2000 sccm and 9800 sccm respectively, and the deposition time to 70 s to deposit a silicon oxide layer.

[0071] According to the above-mentioned Topcon solar cell, by setting a first buffer composite layer and a second buffer composite layer to form a three-layer in-situ phosphorus-doped film structure together with the heavily doped polysilicon layer, the diffusion depth of the doped phosphorus atoms in the crystalline silicon can be significantly increased, thereby achieving the adjustment of the phosphorus doping distribution in the polysilicon film. Specifically, the phosphorus in the heavily doped phosphorus polysilicon layer needs to be buffered by the second buffer composite layer and then diffused to the second tunneling layer, which can not only ensure the contact performance between the polysilicon layer and the second tunneling layer, but also preliminarily reduce the phosphorus diffusion of the polysilicon layer. By setting the first buffer composite layer, the diffusion of phosphorus to the silicon substrate can be further blocked. In addition, by setting the first tunneling layer to form a passivation structure with the second tunneling layer, the passivation effect of the Topcon solar cell can be improved. In addition, by setting the first buffer composite layer and the second buffer composite layer, the degree of diffusion of phosphorus atoms to the tunneling layer is alleviated, the carrier Auger recombination velocity is reduced, and it is beneficial to improve the conversion efficiency of the solar cell.

[0072] The embodiment of the present application further provides a photovoltaic module (not shown), including the above-mentioned Topcon solar cell.

[0073] The embodiments of the present application also provide a photovoltaic system, including the photovoltaic components in any of the above embodiments. The advantages of the above photovoltaic components are also possessed by the photovoltaic system, which will not be repeated here. The application field of the above photovoltaic system is wide, not only limited to photovoltaic power stations, such as ground power stations, rooftop power stations and water surface power stations, but also includes various equipment and devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars and solar buildings. Of course, it is understandable that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be used in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array can be an array combination of multiple photovoltaic components. For example, multiple photovoltaic components can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can merge the current generated by the photovoltaic array. The merged current flows through the inverter to convert it into the alternating current required by the mains power grid and then connects to the mains power network to achieve solar power supply.

[0074] It should be noted that the terms "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting this application. The directional words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0075] It should also be noted that references to "one embodiment," "another embodiment," "an embodiment," and the like in this application refer to specific features, structures, or characteristics described in conjunction with that embodiment as included in at least one embodiment generally described in this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in conjunction with any embodiment, it is intended that such feature, structure, or characteristic, when implemented in conjunction with other embodiments, also fall within the scope of this application.

[0076] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0077] It should also be noted that the above are only preferred embodiments of the present application and do not limit the scope of patent protection of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present application.

Claims

1. A Topcon solar cell, characterized in that: include: substrate layer; A first tunneling layer, a first buffer composite layer, a second tunneling layer, a second buffer composite layer, and a polysilicon layer are sequentially stacked on the lower surface of the substrate layer.

2. The Topcon solar cell according to claim 1, characterized in that The first buffer composite layer includes a first buffer sublayer, a second buffer sublayer and a third buffer sublayer alternately stacked in a first preset period; The sublayer of the first buffer composite layer close to the second tunneling layer is the third buffer sublayer; The thickness of the third buffer sublayer is greater than that of the second buffer sublayer, and the thickness of the second buffer sublayer is greater than that of the first buffer sublayer.

3. The Topcon solar cell according to claim 2, characterized in that The first preset period is 1-7, and the thickness of the first buffer composite layer is 20-30 nm.

4. The Topcon solar cell according to claim 2, characterized in that The second buffer composite layer includes a fourth buffer sublayer, a fifth buffer sublayer, and a sixth buffer sublayer alternately stacked in a second preset period; The sublayer of the second buffer composite layer close to the polysilicon is the sixth buffer sublayer; The thickness of the sixth buffer sublayer is greater than that of the fifth buffer sublayer, and the thickness of the fifth buffer sublayer is greater than that of the fourth buffer sublayer.

5. The Topcon solar cell according to claim 4, characterized in that The second preset period is 3-11, and the thickness of the second buffer composite layer is 25-40 nm.

6. The Topcon solar cell according to claim 4, characterized in that The thickness of the second buffer composite layer is greater than that of the first buffer composite layer.

7. The Topcon solar cell according to claim 4, characterized in that The thickness of the first buffer sublayer, the second buffer sublayer, the third buffer sublayer, the fourth buffer sublayer, the fifth buffer sublayer, and the sixth buffer sublayer are all 0.5-3 nm.

8. The Topcon solar cell according to claim 4, characterized in that The first buffer sublayer is an n-poly-si layer, and the second buffer sublayer, the third buffer sublayer, the fourth buffer sublayer, the fifth buffer sublayer, and the sixth buffer sublayer are all n-poly-si layers. + -poly-si layer, the polysilicon layer is n ++ -poly-si layer.

9. A photovoltaic module, characterized in that: The method comprises the Topcon solar cell according to any one of claims 1 to 8.

10. A photovoltaic system, characterized in that: Comprising the photovoltaic module according to claim 9.

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