Back contact solar cell and photovoltaic module

Abstract

The utility model relates to a back contact solar cell and a photovoltaic module, the back contact solar cell comprises a substrate, a first surface of the substrate is provided with P-type doped layers and N-type doped layers which are alternately arranged along a first direction, and tunneling layers are arranged between the P-type doped layers and the substrate and between the N-type doped layers and the substrate. A first passivation layer is arranged on the side, away from the substrate, of the P-type doping layer and the side, away from the substrate, of the N-type doping layer, the first fine grid is arranged on the P-type doping layer, the second fine grid is arranged on the N-type doping layer, a first dielectric layer is arranged in the P-type doping layer, and the first dielectric layer is used for preventing doping elements in the P-type doping layer and metal crystal grains in the first fine grid from diffusing towards the substrate. A second dielectric layer is arranged in the N-type doping layer, and the second dielectric layer is used for preventing doping elements in the N-type doping layer and metal crystal grains in the second fine grid from diffusing to the substrate. According to the design, the possibility that doped elements and metal crystal grains damage the tunneling layer and the substrate is reduced, and the performance of the back contact solar cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a back contact solar cell and photovoltaic module. BACKGROUND

[0002] The back contact solar cell can convert sunlight into electricity. The back surface of the back contact solar cell is provided with a tunneling passivation contact structure formed by phosphorus-doped polysilicon, boron-doped polysilicon and a tunneling layer. However, the boron element, the phosphorus element and the metal grains in the metal electrode can damage the tunneling layer and the substrate, and affect the passivation performance of the tunneling layer, the phosphorus-doped polysilicon and the boron-doped polysilicon, thereby affecting the performance of the back contact solar cell. CONTENT

[0003] Therefore, the present application provides a back contact solar cell and photovoltaic module to solve the above problems in the prior art and improve the performance of the back contact solar cell.

[0004] In a first aspect, the embodiments of the present application provide a back contact solar cell, comprising: a substrate, a first fine grid and a second fine grid, the substrate comprises a first surface and a second surface oppositely arranged along its own thickness direction, the first surface is provided with P-type doped layers and N-type doped layers alternately arranged along a first direction, along the thickness direction of the substrate, the P-type doped layers and the substrate and the N-type doped layers and the substrate are both provided with a tunneling layer, the side of the P-type doped layers and the N-type doped layers away from the substrate is provided with a first passivation layer, the second surface is provided with a second passivation layer, the first fine grid is arranged on the P-type doped layer, at least part of the structure of the first fine grid penetrates the first passivation layer, the second fine grid is arranged on the N-type doped layer, at least part of the structure of the second fine grid penetrates the first passivation layer, wherein the P-type doped layer is provided with a first dielectric layer, the first dielectric layer is used to hinder the diffusion of the doped elements in the P-type doped layer and the metal grains in the first fine grid to the substrate; the N-type doped layer is provided with a second dielectric layer, the second dielectric layer is used to hinder the diffusion of the doped elements in the N-type doped layer and the metal grains in the second fine grid to the substrate, and the first direction is orthogonal to the thickness direction of the substrate.

[0005] In a possible implementation, along the thickness direction of the substrate, the projection of the first dielectric layer coincides with the projection of the P-type doped layer, the thickness D1 of the first dielectric layer satisfies: 0.5nm≤D1≤1.5nm, and / or, along the thickness direction of the substrate, the projection of the second dielectric layer coincides with the projection of the N-type doped layer, the thickness D2 of the second dielectric layer satisfies: 0.5nm≤D2≤1.5nm.

[0006] In a possible implementation, along the thickness direction of the substrate, the distance from the first dielectric layer to the tunnel layer is L1, and the thickness of the P-type doped layer is D3, and the ratio of L1 to D3 satisfies: 0.25≤L1 / D3≤0.5.

[0007] In a possible implementation, the thickness D3 of the P-type doped layer satisfies: 150nm≤D3≤300nm.

[0008] In a possible implementation, along the thickness direction of the substrate, the distance from the second dielectric layer to the tunnel layer is L2, and the thickness of the N-type doped layer is D4, and the ratio of L2 to D4 satisfies: 0.5≤L2 / D4≤0.75.

[0009] In a possible implementation, the thickness D4 of the N-type doped layer satisfies: 100nm≤D4≤250nm.

[0010] In a possible implementation, the first dielectric layer includes at least one of silicon oxide, silicon nitride, and silicon carbide, and / or the second dielectric layer includes at least one of silicon oxide, silicon nitride, and silicon carbide.

[0011] In a possible implementation, the thickness D5 of the tunnel layer between the substrate and the P-type doped layer satisfies: 1.5nm≤D5≤2.5nm, and / or the thickness D6 of the tunnel layer between the substrate and the N-type doped layer satisfies: 1nm≤D6≤2nm.

[0012] In a possible implementation, the first surface includes first regions and second regions arranged alternately along the first direction, and a separation groove recessed from the first surface to the second surface is arranged between adjacent first regions and second regions, along the thickness direction of the substrate, the distance from the first regions to the second surface is greater than the distance from the second regions to the second surface, the P-type doped layer is arranged on the first regions, the N-type doped layer is arranged on the second regions, and along the first direction, the size of the P-type doped layer is greater than the size of the N-type doped layer.

[0013] In a second aspect, an embodiment of the present application provides a photovoltaic module, including: a cover plate, an encapsulation layer, and at least one cell string, the cell string including a plurality of back contact solar cells according to any one of the above embodiments, the encapsulation layer being located between the cover plate and the cell string, and the cover plate being connected with the cell string through the encapsulation layer.

[0014] The embodiment of the present application provides a back contact solar cell and a photovoltaic module, which comprises a substrate, a first fine grid and a second fine grid, the substrate comprises a first surface and a second surface which are oppositely arranged along the thickness direction of the substrate, the first surface is provided with P-type doped layers and N-type doped layers which are alternately arranged along a first direction, along the thickness direction of the substrate, the P-type doped layers and the N-type doped layers are both provided with tunneling layers between the P-type doped layers and the substrate and between the N-type doped layers and the substrate, the P-type doped layers and the N-type doped layers are provided with a first passivation layer on the side away from the substrate, the second surface is provided with a second passivation layer, the first fine grid is arranged on the P-type doped layer, at least part of the structure of the first fine grid penetrates the first passivation layer, the second fine grid is arranged on the N-type doped layer, at least part of the structure of the second fine grid penetrates the first passivation layer, wherein the P-type doped layer is provided with a first dielectric layer, the first dielectric layer is used for hindering the diffusion of doped elements in the P-type doped layer and metal grains in the first fine grid to the substrate, the N-type doped layer is provided with a second dielectric layer, the second dielectric layer is used for hindering the diffusion of doped elements in the N-type doped layer and metal grains in the second fine grid to the substrate, and the first direction is orthogonal to the thickness direction of the substrate. The first dielectric layer and the second dielectric layer can hinder the doped elements and the metal grains, reduce the possibility of causing damage to the tunneling layer and the substrate due to the diffusion of the doped elements and the metal grains to the substrate, ensure the passivation effect of the tunneling layer, the P-type doped layer and the N-type doped layer, and thus improve the performance of the back contact solar cell.

[0015] It should be understood that the above general description and the following detailed description are only exemplary and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0017] Figure 1 It is a partial schematic view of a back contact solar cell in an embodiment of the present application.

[0018] Figure 2 It is a partial schematic view of a back contact solar cell in another embodiment of the present application.

[0019] Figure 3 It is a partial schematic view of a back contact solar cell in another embodiment of the present application.

[0020] Figure 4 It is a schematic view of a photovoltaic module in an embodiment of the present application.

[0021] REFERENCE SIGNS:

[0022] 1 - back contact solar cell; 11 - substrate; 111 - first surface; 111a - first region; 111b - second region; 111c - isolation groove; 112 - second surface; 12 - P-type doped layer; 13 - N-type doped layer; 14 - tunneling layer; 15 - first passivation layer; 16 - second passivation layer; 17 - first fine grid; 18 - second fine grid; 191 - first dielectric layer; 192 - second dielectric layer;

[0023] 100 - photovoltaic module; 10 - cell string; 20 - first cover plate; 30 - first encapsulation layer; 40 - second encapsulation layer; 50 - second cover plate. DETAILED DESCRIPTION

[0024] For better understanding of the technical solutions of the present application, the embodiments of the present application are described in detail below with reference to the drawings.

[0025] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0026] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0027] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0028] As Figure 1 shown, the back contact solar cell 1 provided by the embodiments of the present application includes a substrate 11, which can be an N-type substrate or a P-type substrate. The N-type substrate can be a silicon substrate doped with an N-type element, which can be one or a combination of a phosphorus element, an arsenic element or an antimony element, etc. The P-type substrate can be a silicon substrate doped with a P-type element, which can be one or a combination of a boron element, an indium element or a gallium element, etc. The structure of the back contact solar cell 1 is described below taking the N-type substrate as an example.

[0029] The substrate 11 includes a first surface 111 and a second surface 112 oppositely arranged along a thickness direction Z thereof. The first surface 111 can be a back surface of the substrate 11, i.e., a surface not directly illuminated by sunlight. The second surface 112 can be a front surface of the substrate 11, i.e., a surface that can be directly illuminated by sunlight. Both the first surface 111 and the second surface 112 can receive sunlight and convert light energy into electrical energy.

[0030] The first surface 111 is provided with P-type doped layers 12 and N-type doped layers 13 alternately arranged along a first direction X orthogonal to the thickness direction Z of the substrate 11. The P-type doped layers 12 are doped with P-type elements (e.g., boron elements) as described above, and the P-type doped layers 12 and the substrate 11 (i.e., the N-type substrate 11) form PN junctions. The N-type doped layers 13 are doped with N-type elements (e.g., phosphorus or antimony elements) as described above, and the N-type doped layers 13 can have a higher concentration of N-type elements than the substrate 11 (i.e., the N-type substrate).

[0031] Along the thickness direction Z of the substrate 11, the P-type doped layers 12 and the substrate 11, and the N-type doped layers 13 and the substrate 11 are both provided with tunneling layers 14, which can include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon, and polycrystalline silicon. The lattice of the tunneling layers 14 can be well matched with the lattice of the substrate 11, i.e., the tunneling layers 14 can well passivate the first surface 111 of the substrate 11 to reduce the recombination rate of photo-generated electrons and photo-generated holes at the first surface 111 of the substrate 11. The tunneling layers 14 and the P-type doped layers 12 can form a tunneling passivation contact structure, which can improve the efficiency of the P-type doped layers 12 in collecting holes. The tunneling layers 14 and the N-type doped layers 13 can form a tunneling passivation contact structure, which can improve the efficiency of the N-type doped layers 13 in collecting electrons.

[0032] In some embodiments, the tunneling layers 14 can include P-type tunneling layers (i.e., the tunneling layers contain P-type doped elements) corresponding to the P-type doped layers 12, and N-type tunneling layers (i.e., the tunneling layers contain N-type doped elements) corresponding to the N-type doped layers 13, i.e., the tunneling layers 14 between the P-type doped layers 12 and the substrate 11 can be P-type tunneling layers, and the tunneling layers 14 between the N-type doped layers 13 and the substrate 11 can be N-type tunneling layers.

[0033] The P-type doped layers 12 can include at least one of P-type doped amorphous silicon, P-type doped polycrystalline silicon, P-type doped microcrystalline silicon, and P-type doped silicon carbide.

[0034] The N-type doped layers 13 can include at least one of N-type doped amorphous silicon, N-type doped polycrystalline silicon, N-type doped microcrystalline silicon, and N-type doped silicon carbide.

[0035] The first surface 111 can be provided with a first passivation layer 15, which can be located on the side of the P-type doped layer 12 and the N-type doped layer 13 away from the substrate 11. The first passivation layer 15 can include at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, and aluminum oxide. The second surface 112 can be provided with a second passivation layer 16, which can include at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, and aluminum oxide. The provision of the first passivation layer 15 and the second passivation layer 16 can enhance the surface carrier concentration of the back contact solar cell 1, improve the short-circuit current and open-circuit voltage of the back contact solar cell 1, and thus improve the cell efficiency.

[0036] The back contact solar cell 1 provides all the grid lines (i.e., metal electrodes) on the back surface (i.e., the first surface 111) of the substrate 11, and the front surface (i.e., the second surface 112) of the substrate 11 is not blocked by the grid lines, thereby reducing the light-blocking area of the front surface of the substrate 11, eliminating the light-blocking current loss of the grid lines, achieving maximum utilization of incident photons, and thus improving the photoelectric conversion efficiency of the back contact solar cell 1.

[0037] Specifically, the back contact solar cell 1 is provided with a first fine grid 17 and a second fine grid 18. The first fine grid 17 is provided on the P-type doped layer 12, and at least part of the structure of the first fine grid 17 penetrates the first passivation layer 15. The first fine grid 17 can be regarded as a positive electrode of the back contact solar cell 1. The second fine grid 18 is provided on the N-type doped layer 13, and at least part of the structure of the second fine grid 18 penetrates the first passivation layer 15. The second fine grid 18 can be regarded as a negative electrode of the back contact solar cell 1.

[0038] As mentioned above, the P-type doped layer 12 and the N-type doped layer 13 are arranged alternately along the first direction X, that is, the first fine grid 17 and the second fine grid 18 are arranged alternately on the first surface 111 of the back contact solar cell 1.

[0039] The P-type doped layer 12 is provided with a first dielectric layer 191, that is, the first dielectric layer 191 is formed in the P-type doped layer 12. The P-type doped layer 12 can be doped with boron elements. The boron elements tend to accumulate at the interface between the tunneling layer 14 and the substrate 11, causing damage to the tunneling layer 14 and the substrate 11, affecting the passivation effect of the tunneling layer 14, and thus affecting the efficiency of the back contact solar cell 1. The first dielectric layer 191 can hinder the spread of boron elements in the P-type doped layer 12 to the substrate 11, that is, the first dielectric layer 191 can block the boron elements, thereby reducing the possibility of damage to the tunneling layer 14 and the substrate 11 caused by the boron elements, ensuring the passivation effect of the tunneling layer 14, and being conducive to improving the performance and efficiency of the back contact solar cell 1.

[0040] The first fine grid 17 on the P-type doped layer 12 can be prepared by a metal paste. During sintering of the metal paste, metal grains in the metal paste can diffuse to the substrate 11, causing a wedge effect, i.e. the metal grains form a wedge-like structure penetrating into the tunneling layer 14 and the substrate 11, thus damaging the tunneling layer 14 and the substrate 11 and affecting the passivation effect of the tunneling layer 14. The first dielectric layer 191 can block the metal grains in the first fine grid 17, preventing the metal grains in the first fine grid 17 from diffusing to the substrate 11 and damaging the tunneling layer 14 and the substrate 11, thus ensuring the passivation effect of the tunneling layer 14 and improving the performance and efficiency of the back contact solar cell 1. At the same time, by providing the first dielectric layer 191, there is no need to thicken the P-type doped layer 12 to prevent the diffusion of the metal grains in the first fine grid 17, thus realizing the thinning design of the P-type doped layer 12, which can reduce the optical parasitic absorption of the P-type doped layer 12 and improve the short-circuit current of the back contact solar cell 1.

[0041] The diffusion of boron in the P-type doped layer 12 and the diffusion of the metal grains in the first fine grid 17 to the substrate 11 mentioned above can also affect the passivation performance of the P-type doped layer 12. Therefore, by providing the first dielectric layer 191, the passivation performance of the P-type doped layer 12 can also be improved to improve the efficiency of the back contact solar cell 1.

[0042] The second dielectric layer 192 is provided in the N-type doped layer 13, i.e. the second dielectric layer 192 is formed inside the N-type doped layer 13. The N-type doped layer 13 can be doped with phosphorus. Phosphorus is prone to accumulate at the interface between the tunneling layer 14 and the substrate 11 and damage the tunneling layer 14 and the substrate 11, affecting the passivation effect of the tunneling layer 14 and thus the efficiency of the back contact solar cell 1. The second dielectric layer 192 can block the diffusion of phosphorus in the N-type doped layer 13 to the substrate 11, i.e. block the phosphorus, thus reducing the possibility of damage to the tunneling layer 14 and the substrate 11 by phosphorus, ensuring the passivation effect of the tunneling layer 14 and being conducive to improving the performance and efficiency of the back contact solar cell 1.

[0043] The second fine grid 18 on the N-type doped layer 13 can be prepared from metal paste, which will also induce a wedge effect during sintering. The wedge effect has been explained in detail above and will not be repeated here. The second dielectric layer 192 can block the metal grains in the second fine grid 18, preventing the metal grains in the second fine grid 18 from diffusing into the substrate 11 and causing damage to the tunneling layer 14 and the substrate 11, thereby ensuring the passivation effect of the tunneling layer 14 and improving the performance and efficiency of the back contact solar cell 1. At the same time, by setting the second dielectric layer 192, it is no longer necessary to thicken the N-type doped layer 13 to hinder the diffusion of metal grains in the second fine grid 18, thereby realizing the thinning design of the N-type doped layer 13, which can reduce the optical parasitic absorption of the N-type doped layer 13 and improve the short-circuit current of the back contact solar cell 1.

[0044] The diffusion of phosphorus from the N-type doped layer 13 to the substrate 11 and the diffusion of metal grains from the second fine grid 18 to the substrate 11 mentioned above also affect the passivation performance of the N-type doped layer 13. Therefore, by setting the second dielectric layer 192, the passivation performance of the N-type doped layer 13 can also be improved, thereby improving the efficiency of the back contact solar cell 1.

[0045] like Figure 2 As shown, in one possible implementation, along the thickness direction Z of the substrate 11, the projection of the first dielectric layer 191 coincides with the projection of the P-type doped layer 12, that is, the area of ​​the first dielectric layer 191 is the same as the area of ​​the P-type doped layer 12, which helps to increase the blocking area of ​​the first dielectric layer 191 against boron and metal grains, thereby improving the blocking effect of the first dielectric layer 191.

[0046] The thickness D1 of the first dielectric layer 191 satisfies the condition: 0.5nm ≤ D1 ≤ 1.5nm. For example, D1 can be 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, or 1.5nm, or other values ​​within the above range. If the thickness D1 of the first dielectric layer 191 is too small, for example, D1 is less than 0.5nm, then the blocking effect of the first dielectric layer 191 on boron and metal grains becomes worse, increasing the risk of damage to the tunneling layer 14 and the substrate 11. If the thickness D1 of the first dielectric layer 191 is too large, for example, D1 is greater than 1.5nm, then the first dielectric layer 191 severely hinders the transport of charge carriers, making it impossible to guarantee the effective transport of charge carriers, thereby affecting the performance of the back contact solar cell 1. Therefore, by limiting the range of values ​​for D1, the blocking effect of the first dielectric layer 191 can be guaranteed while ensuring the effective transport of charge carriers.

[0047] like Figure 3As shown, along the thickness direction Z of the substrate 11, the projection of the second dielectric layer 192 coincides with the projection of the N-type doped layer 13, that is, the area of ​​the second dielectric layer 192 is the same as the area of ​​the N-type doped layer 13, which helps to increase the blocking area of ​​the second dielectric layer 192 against phosphorus and metal grains, thereby improving the blocking effect of the second dielectric layer 192.

[0048] The thickness D2 of the second dielectric layer 192 satisfies the condition: 0.5nm ≤ D2 ≤ 1.5nm. For example, D1 can be 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, or 1.5nm, or other values ​​within the above range. If the thickness D2 of the second dielectric layer 192 is too small, for example, less than 0.5nm, the blocking effect of the second dielectric layer 192 on phosphorus and metal grains will be poor, increasing the risk of damage to the tunneling layer 14 and the substrate 11. If the thickness D2 of the second dielectric layer 192 is too large, for example, greater than 1.5nm, the second dielectric layer 192 will severely hinder the transport of charge carriers, making it impossible to guarantee the effective transport of charge carriers, thus affecting the performance of the back contact solar cell 1. Therefore, by limiting the range of values ​​for D2, the blocking effect of the second dielectric layer 192 can be guaranteed while ensuring the effective transport of charge carriers.

[0049] The thickness D1 of the first dielectric layer 191 and the thickness D2 of the second dielectric layer 192 may be the same or different.

[0050] like Figure 2 As shown, in one possible implementation, along the thickness direction Z of the substrate 11, the distance from the first dielectric layer 191 to the tunneling layer 14 is L1, and the thickness of the p-type doped layer 12 is D3. The ratio of L1 to D3 satisfies: 0.25 ≤ L1 / D3 ≤ 0.5. For example, the value of L1 / D3 can be 0.25, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, or 0.5, or other values ​​within the above range. When L1 / D3 equals 0.5, the first dielectric layer 191 is located in the middle of the p-type doped layer 12. It can be understood that the smaller the value of L1 / D3, the closer the first dielectric layer 191 is to the tunneling layer 14.

[0051] The doping concentration of the P-type doped layer 12 is usually low, resulting in strong burn-through performance of the metal paste used to fabricate the first fine grid 17. If the first dielectric layer 191 is disposed at the end of the P-type doped layer 12 away from the tunneling layer 14, that is, the distance between the first dielectric layer 191 and the tunneling layer 14 in the thickness direction Z of the substrate 11 is increased, the first dielectric layer 191 is brought closer to the outer surface layer of the P-type doped layer 12, resulting in a smaller distance between the first dielectric layer 191 and the first fine grid 17 in the thickness direction Z of the substrate 11. Since the first dielectric layer 191 will act as a barrier to the metal grains of the first fine grid 17, the contact area (i.e., ohmic contact) between the first fine grid 17 and the P-type doped layer 12 is reduced, the contact resistivity of the first fine grid 17 is increased, and thus the efficiency of the back contact solar cell 1 is affected. Meanwhile, a smaller distance between the first dielectric layer 191 and the first fine gate 17 in the thickness direction Z of the substrate 11 reduces the blocking effect of the first dielectric layer 191 on the metal grains of the first fine gate 17, increasing the risk of metal grains diffusing into the tunneling layer 14 and the substrate 11 and causing a wedge effect. Therefore, by placing the first dielectric layer 191 in the middle of the P-type doped layer 12 or at one end of the P-type doped layer 12 near the tunneling layer 14, the blocking effect of the first dielectric layer 191 on the metal grains of the first fine gate 17 can be improved. At the same time, the contact area between the first fine gate 17 and the P-type doped layer 12 can be increased, the contact resistivity of the first fine gate 17 can be reduced, and the efficiency of the back contact solar cell 1 can be improved.

[0052] like Figure 2 As shown, in one possible implementation, the thickness D3 of the P-type doped layer 12 satisfies: 150nm ≤ D3 ≤ 300nm; for example, D3 can be 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, or 300nm, or other values ​​within the above range. If the thickness D3 of the P-type doped layer 12 is too small, for example, D3 is less than 150nm, then the contact resistivity of the first fine gate 17 is easily increased, and the passivation performance of the P-type doped layer 12 will also be affected. If the thickness D3 of the P-type doped layer 12 is too large, for example, D3 is greater than 300nm, then the optical parasitic absorption of the P-type doped layer 12 is easily increased, affecting the performance of the back contact solar cell 1. Therefore, by ensuring that the thickness D3 of the P-type doped layer 12 satisfies 150nm≤D3≤300nm, it is beneficial to reduce the contact resistivity of the first fine grid 17, ensure the passivation performance of the P-type doped layer 12, and reduce the optical parasitic absorption of the P-type doped layer 12, so as to achieve the best performance of the back contact solar cell 1.

[0053] like Figure 3As shown, in one possible implementation, along the thickness direction Z of the substrate 11, the distance from the second dielectric layer 192 to the tunneling layer 14 is L2, and the thickness of the N-type doped layer 13 is D4. The ratio of L2 to D4 satisfies: 0.5 ≤ L2 / D4 ≤ 0.75. For example, the value of L2 / D4 can be 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.74, or 0.75, or other values ​​within the above range. When L2 / D4 equals 0.5, the second dielectric layer 192 is located in the middle of the N-type doped layer 13. Understandably, the larger the value of L2 / D4, the farther the second dielectric layer 192 is from the tunneling layer 14.

[0054] The doping concentration of the N-type doped layer 13 is usually high, so the burn-through performance of the metal paste used to prepare the second fine gate 18 can be relatively weak. Therefore, by setting the second dielectric layer 192 in the middle of the N-type doped layer 13 or at the end of the N-type doped layer 13 away from the tunneling layer 14, the blocking effect of the second dielectric layer 192 on the metal grains of the second fine gate 18 can be improved, the possibility of metal grains damaging the tunneling layer 14 and the substrate 11 can be reduced, and the passivation performance of the tunneling layer 14 and the N-type doped layer 13 can be improved.

[0055] like Figure 3 As shown, in one possible implementation, the thickness D4 of the N-type doped layer 13 satisfies: 100nm ≤ D4 ≤ 250nm. For example, D4 ​​can be 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, or 250nm, or other values ​​within the above range. If the thickness D4 of the N-type doped layer 13 is too small, for example, D4 ​​is less than 100nm, the contact resistivity of the second fine gate 18 will easily increase, and the passivation performance of the N-type doped layer 13 will also be affected. If the thickness D4 of the N-type doped layer 13 is too large, for example, D4 ​​is greater than 250nm, the optical parasitic absorption of the N-type doped layer 13 will increase, affecting the performance of the back contact solar cell 1. Therefore, by ensuring that the thickness D4 of the N-type doped layer 13 satisfies 100nm≤D3≤250nm, it is beneficial to reduce the contact resistivity of the second fine grid 18, ensure the passivation performance of the N-type doped layer 13, and reduce the optical parasitic absorption of the N-type doped layer 13, so as to achieve the best performance of the back contact solar cell 1.

[0056] The thickness D3 of the P-type doped layer 12 can be greater than the thickness D4 of the N-type doped layer 13, or the thickness D3 of the P-type doped layer 12 can be equal to the thickness D4 of the N-type doped layer 13.

[0057] like Figure 1As shown, in one possible implementation, the first dielectric layer 191 includes at least one of silicon oxide, silicon nitride, and silicon carbide. For example, the first dielectric layer 191 may be a silicon oxide layer, a silicon nitride layer, or a silicon carbide layer, or the first dielectric layer 191 may be a film layer composed of two or three of silicon oxide, silicon nitride, and silicon carbide.

[0058] The second dielectric layer 192 includes at least one of silicon oxide, silicon nitride, and silicon carbide. For example, the second dielectric layer 192 may be a silicon oxide layer, a silicon nitride layer, or a silicon carbide layer, or the second dielectric layer 192 may be a film layer composed of two or three of silicon oxide, silicon nitride, and silicon carbide.

[0059] Taking silicon oxide as an example, due to its lattice characteristics, silicon oxide can slow down the diffusion rate of dopant elements (i.e., the aforementioned boron or phosphorus elements) and metal grains within it, thereby hindering the diffusion of dopant elements and metal grains into the substrate 11. By using the above-mentioned material, it is beneficial to improve the blocking effect of the first dielectric layer 191 and the second dielectric layer 192.

[0060] like Figure 2 As shown, in one possible implementation, the thickness D5 of the tunneling layer 14 between the substrate 11 and the P-type doped layer 12 satisfies: 1.5nm ≤ D5 ≤ 2.5nm. For example, D5 can be 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, 2nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm, or 2.5nm, or other values ​​within the above range. This tunneling layer can be the P-type tunneling layer mentioned above.

[0061] like Figure 3 As shown, the thickness D6 of the tunneling layer 14 between the substrate 11 and the N-type doped layer 13 satisfies: 1nm ≤ D6 ≤ 2nm. For example, D6 can be 1nm, 1.2nm, 1.4nm, 1.6nm, 1.8nm, 1.9nm, or 2nm, or other values ​​within the above range. This tunneling layer can be the N-type tunneling layer mentioned above.

[0062] If the thickness of the tunneling layer 14 is too small, it will easily affect the passivation effect of the tunneling layer 14. If the thickness of the tunneling layer 14 is too large, it will easily affect the transport of charge carriers. Therefore, limiting the thickness of the tunneling layer 14 can ensure the passivation effect of the tunneling layer 14 and ensure the transport efficiency of charge carriers.

[0063] In some embodiments, the thickness D5 of the tunneling layer 14 between the substrate 11 and the P-type doped layer 12 is greater than the thickness D6 of the tunneling layer 14 between the substrate 11 and the N-type doped layer 13. The tunneling layer 14 itself has weak blocking performance for boron elements. By appropriately increasing the thickness of the tunneling layer 14 between the substrate 11 and the P-type doped layer 12, the blocking effect of the tunneling layer 14 on boron elements can be increased, and the possibility of diffusion of boron elements to the substrate 11 can be reduced.

[0064] As shown in FIG. 1, in a possible implementation, the first surface 111 includes first regions 111a and second regions 111b arranged alternately along the first direction X, and a separation groove 111c recessed from the first surface 111 to the second surface 112 is arranged between adjacent first regions 111a and second regions 111b. The separation groove 111c separates the P-type doped layer 12 and the N-type doped layer 13, reduces the possibility of leakage current between the N-type doped layer 13 and the P-type doped layer 12, thereby improving the reliability of the back contact solar cell 1 and improving the efficiency and output power of the back contact solar cell 1. Figure 1 In the thickness direction Z of the substrate 11, the distance from the first region 111a to the second surface 112 is greater than the distance from the second region 111b to the second surface 112. The P-type doped layer 12 is arranged on the first region 111a, and the N-type doped layer 13 is arranged on the second region 111b, that is, the N-type doped layer 13 can be closer to the second surface 112 than the P-type doped layer 12, so that the N-type doped layer 13 and the P-type doped layer 12 are arranged in a staggered manner in the thickness direction Z of the substrate 11, thereby reducing the possibility of leakage current between the N-type doped layer 13 and the P-type doped layer 12, improving the reliability of the back contact solar cell 1, and improving the efficiency and output power of the back contact solar cell 1.

[0065] In the first direction X, the size of the P-type doped layer 12 is the same as the size of the first region 111a, and the size of the N-type doped layer 13 is the same as the size of the second region 111b. The size of the P-type doped layer 12 is greater than the size of the N-type doped layer 13, which ensures that the back contact solar cell has good collection effect for holes and electrons, thereby improving the performance and efficiency of the back contact solar cell 1.

[0066] As shown in FIG. 1, in a possible implementation, the first surface 111 includes first regions 111a and second regions 111b arranged alternately along the first direction X, and a separation groove 111c recessed from the first surface 111 to the second surface 112 is arranged between adjacent first regions 111a and second regions 111b. The separation groove 111c separates the P-type doped layer 12 and the N-type doped layer 13, reduces the possibility of leakage current between the N-type doped layer 13 and the P-type doped layer 12, thereby improving the reliability of the back contact solar cell 1 and improving the efficiency and output power of the back contact solar cell 1.

[0067] Figure 4 As shown in FIG. 1, in a possible implementation, the first surface 111 includes first regions 111a and second regions 111b arranged alternately along the first direction X, and a separation groove 111c recessed from the first surface 111 to the second surface 112 is arranged between adjacent first regions 111a and second regions 111b. The separation groove 111c separates the P-type doped layer 12 and the N-type doped layer 13, reduces the possibility of leakage current between the N-type doped layer 13 and the P-type doped layer 12, thereby improving the reliability of the back contact solar cell 1 and improving the efficiency and output power of the back contact solar cell 1.

[0068] ​The cover plate can include a first cover plate 20 and a second cover plate 50. The first cover plate 20 can be located at an upper layer of the photovoltaic module 100, and the second cover plate 50 can be located at a lower layer of the photovoltaic module 100. The encapsulation layer includes a first encapsulation layer 30 and a second encapsulation layer 40. The first encapsulation layer 30 can be located between the first cover plate 20 and the cell string 10, and the second encapsulation layer 40 can be located between the second cover plate 50 and the cell string 10.

[0069] The first cover plate 20, the first encapsulation layer 30, the cell string 10, the second encapsulation layer 40, and the second cover plate 50 can be arranged along a thickness direction Z of the photovoltaic module 100 and laminated together. The first cover plate 20 can be a glass cover plate, and the first cover plate 20 has a high light transmittance. The first encapsulation layer 30 bonds the first cover plate 20 and the cell string 10 together to protect the cell string 10, and the material of the first encapsulation layer 30 can be one or more of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), and polyvinyl butyral (PVB). The second encapsulation layer 40 connects the cell layer and the second cover plate 50 together, and also protects the cell string 10. The material of the second encapsulation layer 40 can be one or more of the above-mentioned EVA, POE, and PVB. The material of the second cover plate 50 can be glass, or the second cover plate 50 can also be composed of multiple polymer film layers.

[0070] The photovoltaic module 100 with the back contact solar cell 1 also has the above technical effects, and details are not repeated here.

[0071] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A back contact solar cell, characterized by, The application relates to a substrate, a first fine grid and a second fine grid. The substrate comprises a first surface and a second surface oppositely arranged along a thickness direction of the substrate, a P-type doped layer and an N-type doped layer are alternately arranged on the first surface along a first direction, a tunneling layer is arranged between the P-type doped layer and the substrate and between the N-type doped layer and the substrate along the thickness direction of the substrate, a first passivation layer is arranged on a side of the P-type doped layer and the N-type doped layer away from the substrate, and a second passivation layer is arranged on the second surface. The first fine grid is arranged on the P-type doped layer, and at least part of the structure of the first fine grid penetrates the first passivation layer. The second fine grid is arranged on the N-type doped layer, and at least part of the structure of the second fine grid penetrates the first passivation layer. The P-type doped layer is provided with a first dielectric layer for preventing diffusion of doped elements in the P-type doped layer and metal grains in the first fine grid to the substrate, and the N-type doped layer is provided with a second dielectric layer for preventing diffusion of doped elements in the N-type doped layer and metal grains in the second fine grid to the substrate. The first direction is orthogonal to the thickness direction of the substrate.

2. The back contact solar cell of claim 1, wherein, Along the thickness direction of the substrate, the projection of the first dielectric layer coincides with the projection of the P-type doped layer, the thickness D1 of the first dielectric layer satisfies 0.5nm<=D1<=1.5nm, and / or Along the thickness direction of the substrate, the projection of the second dielectric layer coincides with the projection of the N-type doped layer, the thickness D2 of the second dielectric layer satisfies 0.5nm<=D2<=1.5nm.

3. The back contact solar cell of claim 2, wherein, Along the thickness direction of the substrate, the distance between the first dielectric layer and the tunneling layer is L1, and the thickness of the P-type doped layer is D3. The ratio of L1 to D3 satisfies 0.25<=L1 / D3<=0.

5.

4. The back contact solar cell of claim 3, wherein, The thickness D3 of the P-type doped layer satisfies 150nm<=D3<=300nm.

5. The back contact solar cell of claim 2, wherein, Along the thickness direction of the substrate, the distance between the second dielectric layer and the tunneling layer is L2, and the thickness of the N-type doped layer is D4. The ratio of L2 to D4 satisfies 0.5<=L2 / D4<=0.

75.

6. The back contact solar cell of claim 5, wherein, The thickness D4 of the N-type doped layer satisfies 100nm<=D4<=250nm.

7. The back contact solar cell according to any one of claims 1 to 6, characterized in that, The first dielectric layer comprises at least one of silicon oxide, silicon nitride and silicon carbide, and / or The second dielectric layer comprises at least one of silicon oxide, silicon nitride and silicon carbide.

8. The back contact solar cell according to any one of claims 1 to 6, characterized in that, The thickness D5 of the tunneling layer between the substrate and the P-type doped layer satisfies 1.5nm<=D5<=2.5nm, and / or The thickness D6 of the tunneling layer between the substrate and the N-type doped layer satisfies 1nm<=D6<=2nm.

9. The back contact solar cell according to any one of claims 1 to 6, characterized in that, The first surface comprises a first region and a second region alternately arranged along the first direction. An isolation groove recessed from the first surface to the second surface is arranged between the first region and the second region adjacent to each other, and the distance from the first region to the second surface is greater than the distance from the second region to the second surface along the thickness direction of the substrate; The P-type doped layer is arranged on the first region, and the N-type doped layer is arranged on the second region, and the size of the P-type doped layer is greater than the size of the N-type doped layer along the first direction.

10. A photovoltaic module, characterized by, Comprise: A cover plate; At least one battery string comprising a plurality of back contact solar cells according to any one of claims 1 to 9; An encapsulation layer between the cover plate and the battery string, the cover plate being connected with the battery string through the encapsulation layer.

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