TOPCon solar cell

Abstract

The embodiment of the utility model provides a TOPCon solar cell. The TOPCon solar cell comprises a silicon substrate, a first composite layer, a back tunneling layer, a second composite layer, a first doped polycrystalline silicon layer, a first antireflection layer and a first electrode, wherein the first composite layer, the back tunneling layer, the second composite layer, the first doped polycrystalline silicon layer, the first antireflection layer and the first electrode are sequentially stacked on the back of the silicon substrate; the first electrode penetrates through the first antireflection layer and is in contact with the first doped polycrystalline silicon layer; the first composite layer and the second composite layer are used for preventing doping elements from diffusing towards the back tunneling layer. According to the technical scheme of the embodiment of the invention, the first composite layer and the second composite layer are arranged on the two sides of the back tunneling layer, so that the trend of diffusion of doping elements in the silicon substrate and the first doped polycrystalline silicon layer to the back tunneling layer is slowed down, and the damage of the doping elements to the back tunneling layer is reduced; due to the protection of the second composite layer, the concentration of doped elements in the first doped polycrystalline silicon layer is improved, and the concentration of carriers is improved, so that the efficiency and the yield of the battery are improved.

Description

Technical Field

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

[0002] Solar cells are the core part of solar power generation. As a new type of solar cell, how to improve the photoelectric conversion efficiency of TOPCon solar cells is the current key research direction.

[0003] TOPCon cells include N-type TOPCon cells and P-type TOPCon cells. N-type TOPCon cells have significant potential for efficiency improvement, and the efficiency and yield of N-type TOPCon cells can be significantly improved through polysilicon optimization. However, during the mass production or efficiency improvement process of the back-side polysilicon of N-type TOPCon cells, the tunneling layer is very easily damaged by P (phosphorus) atoms in the silicon substrate. It is also damaged by P (phosphorus) atoms pushed downward during the P doping process, causing damage to the tunneling layer or even pushing through the tunneling layer. This allows holes to pass through the tunneling layer, destroying the selective tunneling effect of the tunneling layer and significantly affecting the efficiency and yield of the cell.

[0004] 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. Utility Model Content

[0005] The embodiments of the present application provide a TOPCon solar cell to solve or alleviate one or more of the technical problems mentioned above.

[0006] The present invention provides a TOPCon solar cell, comprising a silicon substrate, a first composite layer, a back tunneling layer, a second composite layer, a first doped polysilicon layer, a first anti-reflection layer, and a first electrode stacked in sequence on the back side of the silicon substrate; the first electrode penetrates the first anti-reflection layer and contacts the first doped polysilicon layer;

[0007] The first composite layer is used to block the doping elements in the silicon substrate from diffusing into the back tunneling layer, and the second composite layer is used to block the doping elements in the first doped polysilicon layer from diffusing into the back tunneling layer.

[0008] Optionally, the first composite layer includes a first tunneling layer and a first transmission layer stacked together, the first tunneling layer is connected to the silicon substrate, and the first transmission layer is connected to the back tunneling layer;

[0009] The second composite layer includes a second tunneling layer and a second transmission layer stacked together, the second tunneling layer is connected to the first doped polysilicon layer, and the second transmission layer is connected to the back tunneling layer;

[0010] The first transport layer and the second transport layer are both used for transport of electrons and holes, and the thicknesses of the first tunneling layer and the second tunneling layer are both less than the thickness of the back tunneling layer.

[0011] Optionally, the first transport layer is a first intrinsic silicon layer, and the second transport layer is a second intrinsic silicon layer.

[0012] Optionally, the first transport layer is a first doped layer, and the doping concentration of the first doped layer is lower than the doping concentration of the silicon substrate.

[0013] The second transport layer is a second doped layer, and the doping concentration of the second doped layer is lower than the doping concentration of the first doped polysilicon layer.

[0014] The doping concentration of the first doped layer is lower than the doping concentration of the second doped layer.

[0015] Optionally, the thickness of the first tunneling layer is 0.3-0.5 nm, and the thickness of the first transport layer is 5-10 nm.

[0016] The thickness of the second tunneling layer is 0.3-0.5 nm, and the thickness of the second transport layer is 5-10 nm.

[0017] Optionally, the solar cell further comprises a second doped polysilicon layer, a passivation layer, a second anti-reflection layer and a second electrode which are sequentially stacked on the front side of the silicon substrate, wherein the second electrode penetrates through the back anti-reflection layer and the passivation layer and contacts the second doped polysilicon layer.

[0018] Optionally, the preparation materials of the first anti-reflection layer and the second anti-reflection layer are one of silicon nitride and silicon oxynitride, respectively and independently.

[0019] Optionally, the preparation material of the passivation layer is one of aluminum oxide, silicon oxide, silicon nitride, aluminum nitride, zinc oxide and silicon oxynitride.

[0020] Optionally, the thickness of the back tunneling layer is 1.5-2 nm.

[0021] Optionally, the doping concentration of the first doped polysilicon layer is higher than the doping concentration of the silicon substrate.

[0022] The technical solution of the embodiment of the present application can include the following advantages:

[0023] By arranging the first composite layer and the second composite layer on both sides of the back tunneling layer, the tendency of the silicon substrate and the doping elements in the first doped polysilicon layer to diffuse to the back tunneling layer can be slowed down, the damage of the doping elements to the back tunneling layer is reduced, and the back tunneling layer is protected. At the same time, due to the protection of the second composite layer, the concentration and temperature of the doping elements in the first doped polysilicon layer can be greatly improved, the concentration of the carriers is increased, the series resistance Rs is reduced, and the fill factor FF is improved, so as to improve the efficiency and yield of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0024] In the drawings, like reference numerals refer to like elements throughout the various drawings. The drawings are not necessarily to scale, the emphasis instead being placed upon illustrating the principles of the application. It should be understood that the drawings are merely depictions of some embodiments of the application and should not be interpreted in a limiting sense.

[0025] Figure 1 FIG. 1 is a structural schematic diagram of a TOPCon solar cell provided by an embodiment of the application.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] 1, silicon substrate; 11, first tunneling layer; 12, first transport layer; 13, second tunneling layer; 14, second transport layer; 2, back tunneling layer; 3, first doped polysilicon layer; 4, first anti-reflection layer; 5, first electrode; 6, second doped polysilicon layer; 7, passivation layer; 8, second anti-reflection layer; 9, second electrode. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and embodiments. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict. The application will be described in detail below with reference to the drawings and embodiments.

[0029] It should be noted that the terms "first", "second", and the like in the specification and claims of the application and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] 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.

[0031] like Figure 1 As shown, the TOPCon solar cell may include a silicon substrate 1. The silicon substrate 1 used in the embodiment of the present application may be an N-type silicon substrate 1. A first composite layer, a back tunneling layer 2, a second composite layer, a first doped polysilicon layer 3, a first anti-reflection layer 4, and a first electrode 5 are sequentially stacked on the back side of the silicon substrate 1. The first electrode 5 penetrates the first anti-reflection layer 4 and contacts the first doped polysilicon layer 3. The first composite layer is used to block the diffusion of dopant elements in the silicon substrate 1 into the back tunneling layer 2, and the second composite layer is used to block the diffusion of dopant elements in the first doped polysilicon layer 3 into the back tunneling layer 2. It should be noted that since the silicon substrate 1 is an N-type silicon substrate 1, the dopant element in the first doped polysilicon layer 3 is P (phosphorus).

[0032] In this embodiment, by providing a first composite layer and a second composite layer on both sides of the back tunneling layer 2, the diffusion tendency of the dopant elements in the silicon substrate 1 and the first doped polysilicon layer 3 into the back tunneling layer 2 can be slowed down, reducing damage to the back tunneling layer 2 caused by the dopant elements, thereby protecting the back tunneling layer 2. At the same time, due to the protection of the second composite layer, the concentration and temperature of the dopant elements in the first doped polysilicon layer 3 can be significantly increased, thereby increasing the carrier concentration, thereby reducing the series resistance Rs and increasing the fill factor FF, thereby improving the efficiency and yield of the cell. It should be noted that in N-type TOPCon solar cells, the tunneling layer is often very susceptible to damage by P atoms in the N-type silicon wafer during the mass production or efficiency improvement of the back polysilicon. While simply increasing the thickness of the tunneling layer can reduce the damage caused by P atoms, an excessively thick tunneling layer will increase the transmission path of electrons and holes in the tunneling layer, thereby increasing the resistance loss of electrons and holes. This, in turn, affects the effective collection and transfer efficiency of carriers and reduces the photoelectric conversion efficiency of the cell. Furthermore, the tunneling layer requires more materials and a complex manufacturing process, which increases costs and complicates the manufacturing process. Therefore, the structural design of the present application not only improves the problem of tunneling layer damage, but also enhances the passivation effect. On this basis, it can also increase the concentration of the P element in the first doped polysilicon layer 3, thereby improving the efficiency and yield of the cell.

[0033] In an optional embodiment, the first composite layer comprises a first tunneling layer 11 and a first transport layer 12 arranged in a stack, the first tunneling layer 11 is connected to the silicon substrate 1 in a stack, and the first transport layer 12 is connected to the back tunneling layer 2 in a stack. The second composite layer comprises a second tunneling layer 13 and a second transport layer 14 arranged in a stack, the second tunneling layer 13 is connected to the first doped polysilicon layer 3 in a stack, and the second transport layer 14 is connected to the back tunneling layer 2 in a stack. The first transport layer 12 and the second transport layer 14 are both used for the transmission of electrons and holes, and the thicknesses of the first tunneling layer 11 and the second tunneling layer 13 are both less than the thickness of the back tunneling layer 2. In the embodiment of the present application, the first tunneling layer 11, the second tunneling layer 13, and the back tunneling layer 2 are all made of silicon oxide.

[0034] In the embodiment, the first tunneling layer 11 can reduce the tendency of the doped P element in the silicon substrate 1 to diffuse into the back tunneling layer 2, and the second tunneling layer 13 can reduce the tendency of the doped P element in the first doped polysilicon layer 3 to diffuse into the back tunneling layer 2, thereby reducing the damage of the doped element to the back tunneling layer 2. The thicknesses of the first tunneling layer 11 and the second tunneling layer 13 are both less than the thickness of the back tunneling layer 2, the thinness of the first tunneling layer 11 and the second tunneling layer 13 is conducive to the transmission of electrons, and the first transport layer 12 and the second transport layer 14 are both used for the transmission of electrons and holes. Therefore, the first composite layer and the second composite layer not only protect the back tunneling layer 2 from being damaged by the doped element, but also greatly reduce the resistance to electron transmission, without reducing the tunneling effect, and improve the passivation effect, thereby improving Voc, and further improving the conversion efficiency of the battery.

[0035] In an optional embodiment, the first transport layer 12 is a first intrinsic silicon layer, and the second transport layer 14 is a second intrinsic silicon layer, i.e., the first transport layer 12 and the second transport layer 14 are both not doped with elements.

[0036] In the embodiment, the first intrinsic silicon layer and the second intrinsic silicon layer have high electron and hole mobility, which is conducive to the effective transmission and concentration of charges, thereby improving the performance and efficiency of the battery. The first intrinsic silicon layer and the first tunneling layer 11 are arranged in a stack to form the first composite layer, and the second intrinsic silicon layer and the second tunneling layer 13 are arranged in a stack to form the second composite layer. The stack of the tunneling layer and the intrinsic silicon layer is conducive to optimizing the tunneling effect, blocking the reverse flow of charges through the quantum tunneling effect, and the intrinsic silicon layer provides good electron and hole transport performance, ensuring the efficient flow of charges inside the device.

[0037] In an optional embodiment, the first transport layer 12 is a first doped layer, and the doping concentration of the first doped layer is lower than the doping concentration of the silicon substrate 1. The second transport layer 14 is a second doped layer, and the doping concentration of the second doped layer is lower than the doping concentration of the first doped polysilicon layer 3. In this embodiment, the doping concentration of the first doped layer is lower than the doping concentration of the second doped layer, and the doping concentration of the first doped polysilicon layer 3 is higher than the doping concentration of the silicon substrate 1.

[0038] In this embodiment, the first doped layer and the second doped layer are both P-element doped polysilicon layers. The first doped layer and the second doped layer are located on both sides of the back tunneling layer 2, and both of them are low-concentration P-element doped layers, which can be used as buffer layers to protect the back tunneling layer 2 and reduce the damage of the doping elements in the first doped polysilicon layer 3 and the N-type silicon substrate 1 to the back tunneling layer 2.

[0039] In an optional embodiment, the thickness of the first tunneling layer 11 is 0.3-0.5 nm (e.g., 0.3 nm, 0.4 nm, 0.5 nm), the thickness of the first transport layer 12 is 5-10 nm (e.g., 5 nm, 8 nm, 10 nm), the thickness of the second tunneling layer 13 is 0.3-0.5 nm (e.g., 0.3 nm, 0.4 nm, 0.5 nm), the thickness of the second transport layer 14 is 5-10 nm (e.g., 5 nm, 8 nm, 10 nm), and the thickness of the back tunneling layer 2 is 1.5-2 nm (e.g., 1.5 nm, 1.8 nm, 2 nm). In this embodiment, the thickness of the first tunneling layer 11 and the second tunneling layer 13 is 0.3 nm, the thickness of the first transport layer 12 and the second transport layer 14 is 10 nm, and the thickness of the back tunneling layer 2 is 2 nm.

[0040] In this embodiment, the thin first tunneling layer 11 and the second tunneling layer 13 can reduce the damage to the transport of electrons and holes. The thickness of the first transport layer 12 and the second transport layer 14 should not exceed 10 nm, and the thickness of the two layers is too thick, which will reduce the efficiency of light absorption. In addition, when the thickness of the back tunneling layer 2 is less than 1.5 nm, it will cause the decrease of light absorption and transmission and the increase of electron transport path, thereby reducing the photoelectric conversion efficiency of the battery. When the thickness of the back tunneling layer 2 is greater than 2 nm, it will not effectively block the reverse flow, which will reduce the performance of the battery, and due to the inability to provide sufficient shielding and protection function, it will also cause the stability and reliability problems of the device.

[0041] In an optional embodiment, the solar cell further comprises a second doped polysilicon layer 6, a passivation layer 7, a second anti-reflection layer 8, and a second electrode 9 which are sequentially stacked on the front side of the silicon substrate 1, and the second electrode 9 penetrates through the back anti-reflection layer and the passivation layer 7 and contacts the second doped polysilicon layer 6. In this embodiment, the second doped polysilicon layer 6 is a B-element doped polysilicon layer.

[0042] In an optional embodiment, the material of the first anti-reflective layer 4 and the second anti-reflective layer 8 is one of silicon nitride and silicon oxynitride, respectively and independently. In the embodiment of the present application, the material of the first anti-reflective layer 4 and the second anti-reflective layer 8 can be silicon nitride.

[0043] In the embodiment of the present application, silicon nitride has good optical performance and chemical stability, can effectively reduce the reflection of light, improve the transmittance of light on the surface, and thus enhance the photoelectric conversion efficiency of the optoelectronic device. Silicon oxynitride can adjust optical properties such as refractive index and transmittance, and thus optimize the application effect in the optoelectronic device.

[0044] In an optional embodiment, the material of the passivation layer 7 is one of aluminum oxide, silicon oxide, silicon nitride, aluminum nitride, zinc oxide and silicon oxynitride. In the embodiment of the present application, the material of the passivation layer 7 can be aluminum oxide (Al2O3). The passivation layer 7 can reduce the loss of surface charge carriers and the surface recombination rate, improve the open-circuit voltage of the cell, and help to reduce the reverse recombination of electrons and holes inside the device, thus improving the effective collection rate of photo-generated carriers. At the same time, the aluminum oxide passivation layer 7 has high transparency and transmittance, which can optimize the transmission and reflection characteristics of light, and thus enhance the photoelectric conversion efficiency of the solar cell.

[0045] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that, when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations, devices, components and / or combinations thereof.

[0046] For the convenience of description, the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal", and "top, bottom" and the like indicated orientation or position relationship are usually based on the orientation or position relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, without making the opposite statement, these orientation words do not indicate and imply that the indicated device or element must have a specific orientation or be constructed and operated in a specific orientation, therefore, it cannot be understood as a limitation on the scope of protection of the present application; the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself. For example, if the device in the drawing is inverted, the device described as "above" or "on" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, 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 herein are interpreted accordingly.

[0047] Unless specifically stated and limited otherwise, the terms "mount", "connect", "connection", "fixed", and the like, should be broadly interpreted, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection, or communication; it can be direct connection, or indirect connection through intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0048] Unless specifically stated and limited otherwise, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is higher than the second feature in horizontal height. The first feature "under", "below" and "under" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is lower than the second feature in horizontal height.

[0049] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0050] It should also be noted that references to "one embodiment," "another embodiment," "an embodiment," and the like throughout this specification refer to specific features, structures, or characteristics described in conjunction with that embodiment as included in at least one embodiment generally described herein. The appearance of the same expression in multiple places in this 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.

[0051] 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.

[0052] 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, The solar cell comprises a silicon substrate (1), a first composite layer, a back tunneling layer (2), a second composite layer, a first doped polysilicon layer (3), a first anti-reflection layer (4) and a first electrode (5) which are sequentially stacked on the back of the silicon substrate (1); the first electrode (5) is in contact with the first doped polysilicon layer (3) through the first anti-reflection layer (4). The first composite layer is used to block the diffusion of the doped elements in the silicon substrate (1) to the back tunneling layer (2), and the second composite layer is used to block the diffusion of the doped elements in the first doped polysilicon layer (3) to the back tunneling layer (2). The first composite layer comprises a first tunneling layer (11) and a first transmission layer (12) which are sequentially stacked, the first tunneling layer (11) is connected with the silicon substrate (1), and the first transmission layer (12) is connected with the back tunneling layer (2).

2. The TOPCon solar cell according to claim 1, characterized in that The second composite layer comprises a second tunneling layer (13) and a second transmission layer (14) which are sequentially stacked, the second tunneling layer (13) is connected with the first doped polysilicon layer (3), and the second transmission layer (14) is connected with the back tunneling layer (2). The first transmission layer (12) and the second transmission layer (14) are both used for the transmission of electrons and holes, and the thicknesses of the first tunneling layer (11) and the second tunneling layer (13) are both less than the thickness of the back tunneling layer (2). The first transmission layer (12) is a first intrinsic silicon layer, and the second transmission layer (14) is a second intrinsic silicon layer.

3. The TOPCon solar cell according to claim 2, characterized in that The first transmission layer (12) is a first doped layer, and the doping concentration of the first doped layer is lower than the doping concentration of the silicon substrate (1).

4. The TOPCon solar cell according to claim 2, characterized in that The second transmission layer (14) is a second doped layer, and the doping concentration of the second doped layer is lower than the doping concentration of the first doped polysilicon layer (3). The doping concentration of the first doped layer is lower than the doping concentration of the second doped layer. The thickness of the first tunneling layer (11) is 0.3-0.5 nm, and the thickness of the first transmission layer (12) is 5-10 nm.

5. The TOPCon solar cell according to claim 2, characterized in that The thickness of the second tunneling layer (13) is 0.3-0.5 nm, and the thickness of the second transmission layer (14) is 5-10 nm. The solar cell further comprises a second doped polysilicon layer (6), a passivation layer (7), a second anti-reflection layer (8) and a second electrode (9) which are sequentially stacked on the front of the silicon substrate (1), wherein the second electrode (9) is in contact with the second doped polysilicon layer (6) through the second anti-reflection layer and the passivation layer (7).

6. The TOPCon solar cell according to any one of claims 1 to 5, characterized in that The preparation materials of the first anti-reflection layer (4) and the second anti-reflection layer (8) are one of silicon nitride and silicon oxynitride, respectively and independently.

7. The TOPCon solar cell according to claim 6, characterized in that The preparation material of the passivation layer (7) is one of aluminum oxide, silicon oxide, silicon nitride, aluminum nitride, zinc oxide and silicon oxynitride.

8. The TOPCon solar cell according to claim 6, characterized in that The thickness of the back tunneling layer (2) is 1.5-2 nm.

9. The TOPCon solar cell according to any one of claims 1 to 5, characterized in that The doping concentration of the first doped polysilicon layer (3) is higher than the doping concentration of the silicon substrate (1).

10. The TOPCon solar cell according to any one of claims 1 to 5, characterized in that ​

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