Back contact solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to a back contact solar cell and a preparation method thereof, 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, tunneling layers are arranged between the P-type doped layers and the substrate, and tunneling layers are arranged between the N-type doped layers and the substrate. The first fine grid is arranged on the N-type doped layer, and the second fine grid is arranged on the P-type doped layer. A first barrier layer is arranged in the N-type doping layer, the area of the first barrier layer is smaller than that of the N-type doping layer, the projection of the first fine grid falls into the projection of the first barrier layer in the thickness direction of the substrate, and the first barrier layer is used for preventing doping elements in the N-type doping layer and metal crystal grains in the first fine grid from diffusing towards the substrate. And the possibility that the tunneling layer and the substrate are damaged by doping elements and metal crystal grains is reduced. The first barrier layer and the tunneling layer can simultaneously realize selective transportation of carriers, and the efficiency of the back contact solar cell is improved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a back-contact solar cell and a preparation method thereof and a photovoltaic module. Background Art

[0002] Back contact solar cells can convert sunlight into electrical energy. The back side of the back contact cell uses phosphorus-doped polysilicon, boron-doped polysilicon and a tunneling layer to form a tunneling passivation contact structure. However, the boron element, phosphorus element and metal grains in the metal electrode will damage the tunneling layer and the substrate, and affect the passivation performance of the tunneling layer, phosphorus-doped polysilicon and boron-doped polysilicon, thereby affecting the performance of the back contact solar cell. Summary of the invention

[0003] In view of this, the present application provides a back-contact solar cell and a preparation method thereof and a photovoltaic module, so as to solve the above-mentioned problems in the prior art and improve the performance of the back-contact solar cell.

[0004] In a first aspect, an embodiment of the present application provides a back-contact solar cell, comprising a substrate, a first fine grid and a second fine grid, wherein the substrate comprises a first surface and a second surface arranged opposite to each other along its own thickness direction, a P-type doping layer and an N-type doping layer arranged alternately along a first direction are arranged on the first surface, a tunneling layer is arranged between the P-type doping layer and the substrate and between the N-type doping layer and the substrate along the thickness direction of the substrate, a first passivation layer is arranged on the side of the P-type doping layer and the N-type doping layer away from the substrate, a second passivation layer is arranged on the second surface, and the first fine grid is arranged on the N On the N-type doped layer, at least a portion of the structure of the first fine gate penetrates the first passivation layer, and the second fine gate is arranged on the P-type doped layer, and at least a portion of the structure of the second fine gate penetrates the first passivation layer, wherein a first barrier layer is arranged in the N-type doped layer, and the area of ​​the first barrier layer is smaller than the area of ​​the N-type doped layer, and along the thickness direction of the substrate, the projection of the first fine gate falls within the projection of the first barrier layer, and the first barrier layer is used to prevent the doping elements in the N-type doped layer and the metal grains in the first fine gate from diffusing into the substrate, and the first direction is orthogonal to the thickness direction of the substrate.

[0005] In a possible implementation, along the first direction, the width of the first barrier layer is greater than the width of the first fine gate, wherein the width W1 of the first barrier layer satisfies: 30 um≤W1≤80 um.

[0006] In a possible implementation, along the thickness direction of the substrate, the thickness D1 of the first barrier layer satisfies: 0.5 nm≤D1≤1.5 nm.

[0007] In a possible implementation, along the thickness direction of the substrate, the distance from the first barrier layer to the tunneling layer is L1, the thickness of the N-type doping layer is D2, and the ratio of L1 to D2 satisfies: 0.5≤L1 / D2≤0.8.

[0008] In a possible embodiment, a second barrier layer is provided in the P-type doped layer, and the second barrier layer is used to prevent the doping elements in the P-type doped layer and the metal grains in the second fine gate from diffusing into the substrate. Along the thickness direction of the substrate, the projection of the second barrier layer coincides with the projection of the P-type doped layer, and the thickness D3 of the second barrier layer satisfies: 0.5nm≤D3≤1.5nm.

[0009] In a possible implementation, along the thickness direction of the substrate, the distance from the second barrier layer to the tunneling layer is L2, the thickness of the P-type doped layer is D4, and the ratio of L2 to D4 satisfies: 0.2≤L2 / D4≤0.5.

[0010] In a possible implementation, the thickness D2 of the N-type doped layer satisfies: 100nm≤D2≤250nm, the thickness D5 of the tunneling layer between the substrate and the N-type doped layer satisfies: 1nm≤D5≤2nm, and / or the thickness D4 of the P-type doped layer satisfies: 150nm≤D4≤300nm, and the thickness D6 of the tunneling layer between the substrate and the P-type doped layer satisfies: 1.5nm≤D6≤2.5nm.

[0011] In a possible implementation, the first barrier layer includes at least one of silicon oxide, silicon nitride and silicon carbide, and / or the second barrier layer includes at least one of silicon oxide, silicon nitride and silicon carbide.

[0012] In a second aspect, an embodiment of the present application provides a photovoltaic module, comprising a cover plate, a packaging layer and at least one battery string, wherein the packaging layer is located between the cover plate and the battery string, the cover plate is connected to the battery string through the packaging layer, and the battery string comprises a plurality of back-contact solar cells as described in any one of the above items.

[0013] In a third aspect, an embodiment of the present application provides a method for preparing a back-contact solar cell, wherein the back-contact solar cell includes a substrate, and the method for preparing the back-contact solar cell includes: depositing a tunneling layer on a first surface of the substrate, depositing a first doping layer on a side of the tunneling layer away from the substrate, performing laser processing on a local area of ​​the first doping layer to form a first barrier layer including silicon oxide in the local area, and depositing a second doping layer on a side of the first doping layer away from the substrate.

[0014] The embodiment of the present application provides a back-contact solar cell and a preparation method thereof and a photovoltaic module. The back-contact solar cell includes a substrate, the substrate includes a first surface and a second surface arranged opposite to each other along the thickness direction of the substrate, a P-type doping layer and an N-type doping layer arranged alternately along a first direction are arranged on the first surface, a tunneling layer is arranged between the P-type doping layer and the substrate and between the N-type doping layer and the substrate along the thickness direction of the substrate, a first passivation layer is arranged on the side of the P-type doping layer and the N-type doping layer away from the substrate, a second passivation layer is arranged on the second surface, a first fine grid is arranged on the N-type doping layer, and at least a part of the structure of the first fine grid penetrates the first passivation layer, a second fine grid is arranged on the P-type doping layer, and at least a part of the structure of the second fine grid penetrates the first passivation layer, wherein a first barrier layer is arranged in the N-type doping layer, the area of ​​the first barrier layer is smaller than the area of ​​the N-type doping layer, along the thickness direction of the substrate, the projection of the first fine grid falls within the projection of the first barrier layer, the first barrier layer is used to prevent the doping elements in the N-type doping layer and the metal grains in the first fine grid from diffusing to the substrate, and the first direction is orthogonal to the thickness direction of the substrate. By providing the first barrier layer in the N-type doped layer, the possibility of phosphorus elements and metal grains diffusing to the substrate and causing damage to the tunneling layer and the substrate can be reduced, thereby improving the passivation performance of the tunneling layer and the N-type doped layer. At the same time, the first barrier layer can achieve selective carrier transport with the tunneling layer, and enhance the passivation effect on the substrate, further improving the efficiency of the back contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 A partial schematic diagram of a back-contact solar cell provided in one embodiment of the present application; Figure 2 A partial schematic diagram of a back-contact solar cell provided by another embodiment of the present application; Figure 3 A partial schematic diagram of a back-contact solar cell provided in yet another embodiment of the present application; Figure 4 A schematic diagram of a photovoltaic module provided by an embodiment of the present application; Figure 5a It is a schematic diagram of depositing a tunneling layer on a substrate in one embodiment of the present application; Figure 5b It is a schematic diagram of depositing a first doping layer on a tunneling layer in one embodiment of the present application; Figure 5c It is a schematic diagram of forming a first barrier layer in a first doping layer in one embodiment of the present application; Figure 5d It is a schematic diagram of depositing a second doping layer on the first doping layer in one embodiment of the present application; Figure 6a It is a schematic diagram of depositing a silicon nitride layer and an intrinsic amorphous silicon layer on the first doped layer in one embodiment of the present application; Figure 6b This is a schematic diagram of a substrate after laser processing in another embodiment of the present application; Figure 6c This is a schematic diagram of a substrate after etching in another embodiment of the present application.

[0017] Reference numerals: 1-back contact solar cell; 11-substrate; 111-first surface; 111a-first region; 111b-second region; 111c-isolation groove; 111d-target region; 111e-non-target region; 112-second surface; 12-N-type doped layer; 121-first doped layer; 122-second doped layer; 13-P-type doped layer; 14-tunneling layer; 15-first passivation layer; 16-second passivation layer; 17-first fine gate; 18-second fine gate; 191-first barrier layer; 192-second barrier layer; 193-silicon nitride layer; 194-intrinsic amorphous silicon layer; 100 - photovoltaic module; 10 - battery string; 20 - first cover plate; 30 - first packaging layer; 40 - second packaging layer; 50 - second cover plate. DETAILED DESCRIPTION

[0018] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0019] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0020] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0021] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0022] like Figure 1 As shown, an embodiment of the present application provides a back-contact solar cell 1, including a substrate 11, and the substrate 11 can be an N-type substrate or a P-type substrate. The N-type substrate 11 can be a silicon substrate doped with an N-type element, and the N-type element can specifically be one or a combination of pentavalent elements such as phosphorus, arsenic, or antimony. The P-type substrate 11 can be a silicon substrate doped with a P-type element, and the P-type element can specifically be one or a combination of trivalent elements such as boron, indium, or gallium. The structure of the back-contact solar cell 1 is described below using an N-type substrate as an example.

[0023] The substrate 11 includes a first surface 111 and a second surface 112 that are arranged opposite to each other along its thickness direction Z. The first surface 111 may be the back surface of the substrate 11, that is, the surface that is not directly irradiated by sunlight. The second surface 112 may be the front surface of the substrate 11, that is, the surface that can be directly irradiated by sunlight. Both the first surface 111 and the second surface 112 can receive sunlight and convert light energy into electrical energy.

[0024] The first surface 111 is provided with a P-type doping layer 13 and an N-type doping layer 12 alternately arranged along a first direction X, and the first direction X is orthogonal to the thickness direction Z of the substrate 11. The P-type doping layer 13 is doped with the above-mentioned P-type element (for example, boron), and the P-type doping layer 13 and the substrate 11 (that is, the N-type substrate 11) form a PN junction. The N-type doping layer 12 is doped with the above-mentioned N-type element (for example, phosphorus or antimony), and the concentration of the N-type element doped in the N-type doping layer 12 can be greater than the concentration of the N-type element doped in the substrate 11 (that is, the N-type substrate).

[0025] Along the thickness direction Z of the substrate 11, a tunneling layer 14 is provided between the P-type doping layer 13 and the substrate 11 and between the N-type doping layer 12 and the substrate 11. The tunneling layer 14 may include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon and polycrystalline silicon. The lattice of the tunneling layer 14 may be well matched with the lattice of the substrate 11, that is, the tunneling layer 14 may well passivate the first surface 111 of the substrate 11 to reduce the rate of recombination of photogenerated electrons and photogenerated holes in the substrate 11 at the first surface 111 of the substrate 11. The tunneling layer 14 and the P-type doping layer 13 may form a tunneling passivation contact structure, which may improve the efficiency of the P-type doping layer 13 in collecting holes. The tunneling layer 14 and the N-type doping layer 12 may form a tunneling passivation contact structure, which may improve the efficiency of the N-type doping layer 12 in collecting electrons.

[0026] In some implementations, the tunneling layer 14 may include a P-type tunneling layer corresponding to the P-type doping layer 13 (i.e., the tunneling layer contains a P-type doping element), and an N-type tunneling layer corresponding to the N-type doping layer 12 (i.e., the tunneling layer contains an N-type doping element). In other words, the tunneling layer 14 between the P-type doping layer 13 and the substrate 11 may be a P-type tunneling layer, and the tunneling layer 14 between the N-type doping layer 12 and the substrate 11 may be an N-type tunneling layer.

[0027] The N-type doping layer 12 may 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.

[0028] The P-type doping layer 13 may 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.

[0029] The first surface 111 includes a first region 111a and a second region 111b alternately arranged along a first direction X, a P-type doped layer 13 is disposed on the first region 111a, an N-type doped layer 12 is disposed on the second region 111b, and an isolation groove 111c is disposed between the adjacent first region 111a and the second region 111b, which is recessed from the first surface 111 to the second surface 112. The isolation groove 111c is disposed to separate the P-type doped layer 13 from the N-type doped layer 12, thereby reducing the possibility of leakage current between the N-type doped layer 12 and the P-type doped layer 13, 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.

[0030] Along 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. That is, the N-type doping layer 12 can be closer to the second surface 112 than the P-type doping layer 13, so that the N-type doping layer 12 and the P-type doping layer 13 are staggered in the thickness direction Z of the substrate 11, reducing the possibility of leakage current between the N-type doping layer 12 and the P-type doping layer 13, 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.

[0031] In the first direction X, the size of the P-type doped layer 13 is the same as the size of the first region 111a, and the size of the N-type doped layer 12 is the same as the size of the second region 111b. The size of the P-type doped layer 13 is larger than the size of the N-type doped layer 12. This design ensures that the back-contact solar cell 1 has a good collection effect on both holes and electrons, so as to improve the performance and efficiency of the back-contact solar cell 1.

[0032] A first passivation layer 15 may be provided on the first surface 111, and the first passivation layer 15 may be located on the side of the P-type doped layer 13 and the N-type doped layer 12 away from the substrate 11. The first passivation layer 15 may include at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, and aluminum oxide. A second passivation layer 16 may be provided on the second surface 112, and the first passivation layer 15 may include at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, and aluminum oxide. Providing the first passivation layer 15 and the second passivation layer 16 can enhance the surface carrier concentration of the back contact solar cell 1, increase the short-circuit current and open-circuit voltage of the back contact solar cell 1, and thus improve the battery efficiency.

[0033] The back-contact solar cell 1 has all the grid lines (i.e., metal electrodes) arranged on the back side of the substrate 11 (i.e., the first surface 111 mentioned above), and the front side of the substrate 11 (i.e., the second surface 112 mentioned above) is not blocked by the grid lines, thereby reducing the shading area of ​​the front side of the substrate 11 to eliminate the shading current loss of the grid lines, realize the maximum utilization of the incident photons, and thus improve the photoelectric conversion efficiency of the back-contact solar cell 1.

[0034] Specifically, a first fine grid 17 and a second fine grid 18 are provided on the back contact solar cell 1. The first fine grid 17 is provided on the N-type doped layer 12, and at least a portion of the structure of the first fine grid 17 penetrates the first passivation layer 15. The first fine grid 17 can be regarded as the negative electrode of the back contact solar cell 1. The second fine grid 18 is provided on the P-type doped layer 13, and at least a portion of the structure of the second fine grid 18 penetrates the first passivation layer 15. The second fine grid 18 can be regarded as the positive electrode of the back contact solar cell 1.

[0035] As mentioned above, the P-type doped layers 13 and the N-type doped layers 12 are alternately arranged along the first direction X, that is, the first fine grids 17 and the second fine grids 18 are alternately arranged on the first surface 111 of the back-contact solar cell 1 .

[0036] Continue as Figure 1 As shown, a first barrier layer 191 is provided in the N-type doping layer 12, that is, it can be understood that the first barrier layer 191 is formed inside the N-type doping layer 12. The first barrier layer 191 is used to prevent the doping elements in the N-type doping layer 12 and the metal grains in the first fine gate 17 from diffusing to the substrate 11. Among them, the area of ​​the first barrier layer 191 is smaller than the area of ​​the N-type doping layer 12, that is, the first barrier layer 191 is only provided in a local area of ​​the N-type doping layer 12. Along the thickness direction Z of the substrate 11, the projection of the first fine gate 17 falls within the projection of the first barrier layer 191, that is, the position of the first barrier layer 191 corresponds to the position of the first fine gate 17.

[0037] Specifically, phosphorus may be doped in the N-type doped layer 12. Phosphorus is likely to aggregate 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, thereby affecting the efficiency of the back-contact solar cell 1. The first barrier layer 191 can prevent the phosphorus in the N-type doped layer 12 from diffusing to the substrate 11, that is, it can block the phosphorus, thereby reducing the possibility of phosphorus damaging the tunneling layer 14 and the substrate 11, so as to ensure the passivation effect of the tunneling layer 14, which is beneficial to improving the performance and efficiency of the back-contact solar cell 1.

[0038] The first fine grid 17 on the N-type doped layer 12 can be prepared from a metal paste, which will also induce a sharp wedge effect during the sintering process, that is, the metal grains will form a wedge-like structure and penetrate into the tunneling layer 14 and the substrate 11, thereby damaging the tunneling layer 14 and the substrate 11 and affecting the passivation effect of the tunneling layer 14. The projection of the first fine grid 17 falls within the projection range of the first barrier layer 191, so that the first barrier layer 191 can block the metal grains in the first fine grid 17 to prevent the metal grains in the first fine grid 17 from diffusing to 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 first blocking layer 191, there is no need to increase the thickness of the N-type doping layer 12 to hinder the diffusion of the metal grains of the first fine gate 17, thereby realizing a thinning design of the N-type doping layer 12, thereby reducing the optical parasitic absorption of the N-type doping layer 12 and improving the short-circuit current of the back-contact solar cell 1.

[0039] The diffusion of the phosphorus element in the N-type doped layer 12 into the substrate 11 and the diffusion of the metal grains of the first fine gate 17 into the substrate 11 mentioned above will also affect the passivation performance of the N-type doped layer 12. Therefore, by setting the first barrier layer 191, the passivation performance of the N-type doped layer 12 can also be improved to improve the efficiency of the back-contact solar cell 1.

[0040] The N-type doped layer 12 can allow the majority carriers (i.e., electrons) to be effectively transferred to the first fine grid 17 and reduce the recombination of the minority carriers (i.e., holes). The first blocking layer 191 in the N-type doped layer 12 also has a certain hindering effect on the transfer of carriers. Therefore, the area of ​​the first blocking layer 191 is designed to be smaller than the area of ​​the N-type doped layer 12, thereby reducing the blocking area of ​​the first blocking layer 191 for carriers, so as to ensure the effective transfer of carriers, thereby facilitating the improvement of the efficiency of the back contact solar cell 1.

[0041] In some embodiments, the tunneling layer 14 and the first barrier layer 191 may both be silicon oxide layers. Both the tunneling layer 14 and the first barrier layer 191 can realize the selective transport of carriers. Under the joint action of the tunneling layer 14 and the first barrier layer 191, the passivation effect on the substrate 11 can be improved, and the selectivity of carriers can be effectively improved, so that the majority electrons tunnel into the N-type doped layer 12 while blocking the recombination of minority holes, so as to improve the efficiency of the back contact solar cell 1.

[0042] In summary, the embodiment of the present application provides the first barrier layer 191 in the N-type doped layer 12 to reduce the possibility of phosphorus elements and metal grains diffusing into the substrate 11 and damaging the tunneling layer 14 and the substrate 11, thereby improving the passivation performance of the tunneling layer 14 and the N-type doped layer 12. At the same time, the first barrier layer 191 can achieve selective carrier transport with the tunneling layer 14, and enhance the passivation effect on the substrate 11, further improving the efficiency of the back contact solar cell 1.

[0043] like Figure 2As shown, in a possible implementation manner, along the first direction X, the width of the first barrier layer 191 is greater than the width of the first fine grid 17, wherein the width W1 of the first barrier layer 191 satisfies: 30um≤W1≤80um, for example, W1 may be 30um, 35um, 40um, 45um, 50um, 55um, 60um, 65um, 70um, 75um or 80um, and of course may be other values ​​within the above range. If the size of W1 is small and smaller than the width of the first fine grid 17, the blocking effect of the first barrier layer 191 on the metal grains of the first fine grid 17 is weakened, thereby increasing the risk of damage to the tunneling layer 14 and the silicon substrate 11, and if the size of W2 is too large, the risk of the first barrier layer 191 hindering the transport of carriers is increased, thereby easily affecting the efficiency of the back contact solar cell 1. By making the width W1 of the first barrier layer 191 meet the above range, effective carrier transmission can be ensured while ensuring the barrier effect of the first barrier layer 191 on metal grains, so as to improve the efficiency of the back contact solar cell 1.

[0044] like Figure 2 As shown, in a possible implementation manner, along the thickness direction Z of the substrate 11, the thickness D1 of the first barrier layer 191 satisfies: 0.5 nm ≤ D1 ≤ 1.5 nm. The thickness D1 of the first barrier layer 191 satisfies: 0.5 nm ≤ D1 ≤ 1.5 nm, for example, D1 may be 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm or 1.5 nm, and may of course be other values ​​within the above range. If the thickness D1 of the first barrier layer 191 is too small, for example, D1 is less than 0.5 nm, then the barrier effect of the first barrier layer 191 on phosphorus elements and metal grains becomes poor, increasing the risk of damage to the tunneling layer 14 and the substrate 11. If the thickness D1 of the first barrier layer 191 is too large, for example, D1 is greater than 1.5 nm, then the first barrier layer 191 forms a serious obstacle to the transmission of carriers, and it is impossible to ensure that the carriers can be effectively transmitted, thereby affecting the efficiency of the back contact solar cell 1. Therefore, by limiting the value range of D1, the barrier effect of the first barrier layer 191 is ensured while ensuring that the carriers can be effectively transmitted.

[0045] like Figure 2As shown, in a possible implementation, along the thickness direction Z of the substrate 11, the distance from the first barrier layer 191 to the tunneling layer 14 is L1, the thickness of the N-type doping layer 12 is D2, and the ratio of L1 to D2 satisfies: 0.5≤L1 / D2≤0.8, and the ratio of L1 to D2 can be 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78 or 0.8, and of course, it can also be other values ​​within the above range. When L1 / D2 is equal to 0.5, the first barrier layer 191 is located in the middle of the N-type doping layer 12. It can be understood that the larger the value of L1 / D2, the farther the first barrier layer 191 is from the tunneling layer 14.

[0046] The doping concentration of the N-type doping layer 12 is usually high, and the burn-through performance of the metal paste used to prepare the first fine gate 17 is relatively weak. Therefore, by setting the first barrier layer 191 in the middle position of the N-type doping layer 12 or at one end of the N-type doping layer 12 away from the tunneling layer 14, the blocking effect of the first barrier layer 191 on the metal grains of the first fine gate 17 can be improved, the possibility of the metal grains causing damage to the tunneling layer 14 and the substrate 11 can be reduced, and the passivation performance of the tunneling layer 14 and the N-type doping layer 12 can be improved.

[0047] like Figure 1 As shown, in a possible implementation, a second barrier layer 192 is provided in the P-type doping layer 13, that is, it can be understood that the second barrier layer 192 is formed inside the P-type doping layer 13. The second barrier layer 192 is used to prevent the doping elements in the P-type doping layer 13 and the metal grains in the second fine gate 18 from diffusing into the substrate 11.

[0048] Specifically, the P-type doped layer 13 may be doped with boron. Boron tends to gather 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, thereby affecting the efficiency of the back-contact solar cell 1. The second barrier layer 192 can prevent the boron element in the P-type doped layer 13 from diffusing toward the substrate 11, that is, it has a blocking effect on the boron element, thereby reducing the possibility of boron element damaging the tunneling layer 14 and the substrate 11, so as to ensure the passivation effect of the tunneling layer 14, which is beneficial to improving the performance and efficiency of the back-contact solar cell 1.

[0049] The second fine grid 18 on the P-type doped layer 13 can be prepared by metal paste. During the sintering process of the metal paste, the metal grains in the metal paste will diffuse into the substrate 11, thereby causing the wedge effect. The wedge effect has been explained in detail above and will not be repeated here. The second barrier layer 192 can block the metal grains in the second fine grid 18 to prevent 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 barrier layer 192, there is no need to increase the thickness of the P-type doped layer 13 to hinder the diffusion of the metal grains in the second fine grid 18, thereby realizing the thinning design of the P-type doped layer 13, thereby reducing the optical parasitic absorption of the P-type doped layer 13 and improving the short-circuit current of the back contact solar cell 1.

[0050] The diffusion of the boron element in the P-type doped layer 13 mentioned above into the substrate 11 and the diffusion of the metal grains of the second fine gate 18 into the substrate 11 will also affect the passivation performance of the P-type doped layer 13. Therefore, by setting the second barrier layer 192, the passivation performance of the P-type doped layer 13 can also be improved to improve the efficiency of the back-contact solar cell 1.

[0051] like Figure 3 As shown, along the thickness direction Z of the substrate 11, the projection of the second barrier layer 192 coincides with the projection of the P-type doped layer 13, that is, the area of ​​the second barrier layer 192 is the same as the area of ​​the P-type doped layer 13. The thickness D3 of the second barrier layer 192 satisfies: 0.5nm≤D3≤1.5nm, for example, D3 can be 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm or 1.5nm, and of course, it can also be other values ​​within the above range. If the thickness D3 of the second barrier layer 192 is too small, for example, D3 is less than 0.5nm, then the barrier effect of the second barrier layer 192 on the boron element and the metal grains becomes poor, increasing the risk of damage to the tunneling layer 14 and the substrate 11. If the thickness D3 of the second barrier layer 192 is too large, for example, D3 is greater than 1.5 nm, the second barrier layer 192 will seriously hinder the transmission of carriers, and it is impossible to ensure that the carriers can be effectively transmitted, thereby affecting the performance of the back contact solar cell 11. Therefore, by limiting the value range of D3, the effective transmission of carriers can be ensured while ensuring the blocking effect of the second barrier layer 192.

[0052] The thickness of the first barrier layer 191 and the thickness of the second barrier layer 192 may be the same or different.

[0053] like Figure 3As shown, in a possible implementation manner, along the thickness direction Z of the substrate 11, the distance from the second barrier layer 192 to the tunneling layer 14 is L2, the thickness of the P-type doped layer 13 is D4, and the ratio of L2 to D4 satisfies: 0.2≤L2 / D4≤0.5, L2 and D4 can be 0.2, 0.22, 0.24, 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, and of course can be other values ​​within the above range. When L2 / D4 is equal to 0.5, the second barrier layer 192 is located in the middle of the P-type doped layer 13. It can be understood that the smaller the value of L2 / D4, the closer the position of the second barrier layer 192 is to the tunneling layer 14.

[0054] Combination Figure 1 As shown, the doping concentration of the P-type doping layer 13 is usually low, and the metal paste used to prepare the second fine grid 18 has a strong burn-through performance. If the second barrier layer 192 is arranged at the end of the P-type doping layer 13 away from the tunneling layer 14, that is, the distance between the second barrier layer 192 and the tunneling layer 14 in the thickness direction Z of the substrate 11 is increased, so that the second barrier layer 192 is closer to the outer layer of the P-type doping layer 13, resulting in a smaller distance between the second barrier layer 192 and the second fine grid 18 in the thickness direction Z of the substrate 11. Since the second barrier layer 192 has a blocking effect on the metal grains of the second fine grid 18, the contact area (that is, ohmic contact) between the second fine grid 18 and the P-type doping layer 13 is reduced, and the contact resistivity of the second fine grid 18 is increased, thereby affecting the efficiency of the back contact solar cell 1. At the same time, the small distance between the second barrier layer 192 and the second fine grid 18 in the thickness direction Z of the substrate 11 will reduce the blocking effect of the second barrier layer 192 on the metal grains of the second fine grid 18, and increase the risk of the metal grains diffusing to the tunneling layer 14 and the substrate 11 and causing the wedge effect. Therefore, by arranging the second barrier layer 192 in the middle of the P-type doping layer 13 or at one end of the P-type doping layer 13 close to the tunneling layer 14, the blocking effect of the second barrier layer 192 on the metal grains of the second fine grid 18 can be improved, and at the same time, the contact area between the second fine grid 18 and the P-type doping layer 13 can be increased, the contact resistivity of the second fine grid 18 can be reduced, and the efficiency of the back contact solar cell 1 can be improved.

[0055] like Figure 2As shown, in a possible implementation, the thickness D2 of the N-type doping layer 12 satisfies: 100nm≤D2≤250nm, for example, D2 can be 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm or 250nm, and of course, it can also be other values ​​within the above range. If the thickness D2 of the N-type doping layer 12 is too small, for example, D2 is less than 100nm, then it is easy to increase the contact resistivity of the first fine grid 17, and at the same time affect the passivation performance of the N-type doping layer 12. If the thickness D2 of the N-type doping layer 12 is too large, for example, D2 is greater than 250nm, then the optical parasitic absorption of the N-type doping layer 12 will increase, affecting the performance of the back contact solar cell 1. Therefore, by making the thickness D2 of the N-type doped layer 12 satisfy: 100nm≤D2≤250nm, it is beneficial to reduce the contact resistivity of the first fine gate 17, ensure the passivation performance of the N-type doped layer 12, and reduce the optical parasitic absorption of the N-type doped layer 12, so as to achieve the best performance of the back-contact solar cell 1.

[0056] like Figure 3 As shown, the thickness D4 of the P-type doping layer 13 satisfies: 150nm≤D4≤300nm, for example, D4 ​​can be 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm or 300nm, and of course it can also be other values ​​within the above range. If the thickness D4 of the P-type doping layer 13 is too small, for example, D4 ​​is less than 150nm, then it is easy to increase the contact resistivity of the second fine grid 18, and at the same time affect the passivation performance of the P-type doping layer 13. If the thickness D4 of the P-type doping layer 13 is too large, for example, D4 ​​is greater than 300nm, then it is easy to increase the optical parasitic absorption of the P-type doping layer 13, affecting the performance of the back contact solar cell 1. Therefore, by making the thickness D4 of the P-type doping layer 13 satisfy: 150nm≤D4≤300nm, it is beneficial to reduce the contact resistivity of the second fine gate 18, ensure the passivation performance of the P-type doping layer 13, and at the same time reduce the optical parasitic absorption of the P-type doping layer 13, so as to achieve the best performance of the back-contact solar cell 1.

[0057] like Figure 2 As shown, the thickness D5 of the tunneling layer 14 between the substrate 11 and the N-type doped layer 12 satisfies: 1nm≤D5≤2nm, for example, D5 can be 1nm, 1.2nm, 1.4nm, 1.6nm, 1.8nm, 1.9nm or 2nm, and of course can be other values ​​within the above range. The tunneling layer 14 can be the N-type tunneling layer mentioned above.

[0058] like Figure 3As shown, the thickness D6 of the tunneling layer 14 between the substrate 11 and the P-type doped layer 13 satisfies: 1.5nm≤D6≤2.5nm. For example, D6 may be 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, 2nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm or 2.5nm, and may be other values ​​within the above range. The tunneling layer 14 may be the P-type tunneling layer mentioned above. 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 transmission of carriers. Therefore, limiting the thickness of the tunneling layer 14 can ensure the passivation effect of the tunneling layer 14 and ensure the transmission efficiency of carriers.

[0059] In some embodiments, the thickness D6 of the tunneling layer 14 between the substrate 11 and the P-type doped layer 13 is greater than the thickness D5 of the tunneling layer 14 between the substrate 11 and the N-type doped layer 12. The tunneling layer 14 itself has a weak barrier performance against the boron element. By appropriately increasing the thickness of the tunneling layer 14 between the substrate 11 and the P-type doped layer 13, the barrier effect of the tunneling layer 14 against the boron element can be increased, and the possibility of the boron element diffusing into the substrate 11 can be reduced.

[0060] In a possible implementation, the first barrier layer 191 includes at least one of silicon oxide, silicon nitride and silicon carbide. For example, the first barrier layer 191 may be a silicon oxide layer, a silicon nitride layer or a silicon carbide layer, or the first barrier layer 191 may be a film layer formed by mixing two or three of silicon oxide, silicon nitride and silicon carbide.

[0061] The second barrier layer 192 includes at least one of silicon oxide, silicon nitride and silicon carbide. For example, the second barrier layer 192 can be a silicon oxide layer, a silicon nitride layer or a silicon carbide layer, or the second barrier layer 192 can be a film layer formed by mixing two or three of silicon oxide, silicon nitride and silicon carbide.

[0062] Taking silicon oxide as an example, silicon oxide can slow down the diffusion rate of doping elements (i.e., the above-mentioned boron element or phosphorus element) and metal grains in its interior due to its own lattice characteristics, thereby preventing the diffusion of doping elements and metal grains to the substrate. By using the above-mentioned materials, it is beneficial to improve the barrier effect of the first barrier layer 191 and the second barrier layer 192.

[0063] like Figure 4 As shown, a photovoltaic module 100 according to an embodiment of the present application includes a cover plate, an encapsulation layer and at least one battery string 10, wherein the encapsulation layer is located between the cover plate and the battery string 10, and the cover plate is connected to the battery string 10 through the encapsulation layer. The battery string 10 includes a plurality of the above-mentioned back-contact solar cells 1.

[0064] The cover plate may include a first cover plate 20 and a second cover plate 50, the first cover plate 20 may be located on the upper layer of the photovoltaic module 100, and the second cover plate 50 may be located on the 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 may be located between the first cover plate 20 and the battery string 10, and the second encapsulation layer 40 may be located between the second cover plate 50 and the battery string 10.

[0065] The first cover plate 20, the first encapsulation layer 30, the battery string 10, the second encapsulation layer 40 and the second cover plate 50 can be arranged along the thickness direction Z of the photovoltaic module 100 and laminated together. Among them, 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 battery string 10 together to play a role in encapsulation and protection of the battery string 10. 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 battery layer and the second cover plate 50 together, which also plays a role in encapsulation and protection of the battery 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.

[0066] Since the back-contact solar cell 1 has the above-mentioned technical effects, the photovoltaic module 100 having the back-contact solar cell 1 also has the above-mentioned technical effects, which will not be described in detail here.

[0067] An embodiment of the present application provides a method for preparing a back-contact solar cell. The preparation method of the back-contact cell is described below by taking the N-type doped layer being a phosphorus-doped polysilicon layer (i.e., N-type doped polysilicon) and the P-type doped layer being a boron-doped polysilicon layer (i.e., P-type doped polysilicon) as an example.

[0068] The method for preparing a back contact solar cell comprises: like Figure 5a As shown, step S201: depositing a tunneling layer 14 on the first surface 111 of the substrate 11. For example, the tunneling layer 14 can be formed on the first surface 111 of the substrate 11 using PECVD (plasma enhanced chemical vapor deposition) technology. Specifically, the tunneling layer 14 can include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon and polycrystalline silicon. It should be noted that the above-mentioned tunneling layer is a tunneling layer arranged between the substrate and the N-type doped layer, that is, the tunneling layer can be an N-type tunneling layer.

[0069] like Figure 5bAs shown, after step S201 , the process proceeds to step S202 : depositing a first doping layer 121 on a side of the tunneling layer 14 away from the substrate 11 .

[0070] In step S202, a polysilicon layer can be first deposited on the side of the tunneling layer 14 away from the substrate 11 using PECVD technology. The polysilicon layer is an intrinsic polysilicon layer, that is, an undoped polysilicon layer. Then, phosphorus is diffused on the substrate 11 to introduce phosphorus into the intrinsic polysilicon layer, thereby forming a first doped layer 121. In other words, the first doped layer 121 is a phosphorus-doped polysilicon layer.

[0071] like Figure 5c As shown, after step S202 , step S203 is entered: laser processing is performed on a local area of ​​the first doping layer 121 to form a first barrier layer 191 including silicon oxide in the local area.

[0072] After laser processing, a silicon oxide layer may be formed in a local area of ​​the first doping layer 121, and the silicon oxide layer is the first barrier layer 191. The effect of the first barrier layer 191 has been described in detail above and will not be repeated here.

[0073] like Figure 5d As shown, after step S203 , the process proceeds to step S204 : depositing a second doping layer 122 on a side of the first doping layer 121 away from the substrate 11 .

[0074] Step S204 is similar to step S202. PECVD technology can be used to first deposit a polysilicon layer on the side of the first doping layer 121 away from the substrate 11. The polysilicon layer is an intrinsic polysilicon layer. Then, phosphorus diffusion treatment is performed on the substrate 11 to introduce phosphorus elements into the intrinsic polysilicon layer to form a second doping layer 122. That is, the second doping layer 122 is a phosphorus-doped polysilicon layer.

[0075] The doping concentrations of the first doping layer 121 and the second doping layer 122 may be the same, and the first doping layer 121 and the second doping layer 122 may together constitute a complete N-type doping layer 12 (eg, Figure 1 As shown in FIG. 1 , the first doping layer 121 and the second doping layer 122 can both be regarded as part of the film structure of the N-type doping layer 12. The area of ​​the first doping layer 121 is the same as that of the second doping layer 122, the area of ​​the first barrier layer 191 is smaller than that of the first doping layer 121, and the area of ​​the second doping layer 122 is smaller than that of the first doping layer 121.

[0076] It can be seen from the above that the N-type doped layer 12 of the back-contact solar cell 1 in the embodiment of the present application can be formed by two deposition steps and a phosphorus diffusion step in succession, so that the first barrier layer 191 can be formed in the N-type doped layer 12 .

[0077] In the embodiment of the present application, a second barrier layer including silicon oxide may be formed in the P-type doped layer by laser processing the P-type doped layer. The process flow for preparing the second barrier layer is similar to the process flow for preparing the first barrier layer. Specifically, the method for preparing a back contact solar cell may include: Step S301: Depositing a tunneling layer on the first surface of the substrate. The tunneling layer may be formed on the first surface of the substrate using PECVD (plasma enhanced chemical vapor deposition) technology. Specifically, the tunneling layer may include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon and polycrystalline silicon. It should be noted that the above-mentioned tunneling layer is a tunneling layer disposed between the substrate and the P-type doped layer, that is, the tunneling layer may be a P-type tunneling layer.

[0078] After step S301, step S302 is entered: a third doped layer is deposited on the side of the tunneling layer away from the substrate. In step S302, a polysilicon layer may be first deposited on the side of the tunneling layer away from the substrate using PECVD technology, the polysilicon layer being an intrinsic polysilicon layer, and then boron diffusion is performed on the substrate to dope boron into the intrinsic polysilicon layer, thereby forming a third doped layer, that is, the third doped layer is a boron-doped polysilicon layer.

[0079] After step S302, step S303 is performed: laser processing is performed on the third doped layer to form a second barrier layer including silicon oxide in the third doped layer, wherein the area of ​​the second barrier layer is the same as the area of ​​the third doped layer. After laser treatment, a silicon oxide layer can be formed in the third doped layer, and the silicon oxide layer is the second barrier layer mentioned above. The effect of the second barrier layer has been described above and will not be repeated here.

[0080] After step S303, the process proceeds to step S304: depositing a fourth doped layer on the side of the third doped layer away from the substrate. Step S304 is similar to step S302, and a polysilicon layer may be first deposited on the side of the third doped layer away from the substrate 11 using PECVD technology, the polysilicon layer being an intrinsic polysilicon layer, and then the substrate is subjected to boron diffusion treatment to dope boron into the intrinsic polysilicon layer, thereby forming a fourth doped layer, that is, the fourth doped layer is a boron-doped polysilicon layer.

[0081] The doping concentration of the third doping layer and the fourth doping layer can be the same, and the third doping layer and the fourth doping layer can together constitute a complete P-type doping layer on the back contact solar cell, that is, the third doping layer and the fourth doping layer can both be regarded as part of the P-type doping layer film structure. The third doping layer, the fourth doping layer and the second barrier layer have the same area.

[0082] It can be seen from the above that the P-type doped layer of the back-contact solar cell in the embodiment of the present application can also be formed by two deposition steps and a phosphorus diffusion step in succession, thereby forming a second barrier layer in the P-type doped layer.

[0083] In the above-mentioned method for preparing a back-contact solar cell, the first surface and the second surface of the substrate may be polished to remove mechanical damage on the surface of the substrate, and then a tunneling layer (i.e., a P-type tunneling layer) and a P-type doping layer may be formed on the first surface of the substrate using the method provided in the above-mentioned steps S301 to S304, wherein the P-type doping layer has a second barrier layer. As mentioned above, the first surface of the substrate has a first region and a second region, the P-type doping layer is disposed on the first region, and the N-type doping layer is disposed on the second region, so after the P-type doping layer is formed, the second region needs to be laser opened and wet etched to remove the P-type doping layer and the tunneling layer (i.e., the P-type tunneling layer) on the second region.

[0084] When removing the P-type doped layer and the tunneling layer (i.e., the P-type tunneling layer) on the second region, since a second barrier layer is provided in the P-type doped layer, the second barrier layer has high corrosion resistance, thereby being able to improve the process window of wet etching, that is, reducing the limit on the concentration of the chemical solution used for wet etching. At the same time, providing the second barrier layer can also improve the process window of laser film opening, that is, reducing the limit on laser power, so as to ensure the stability and reliability of the preparation process of the back-contact solar cell.

[0085] After removing the P-type doping layer and the tunneling layer (i.e., the P-type tunneling layer) on the second region, a tunneling layer (i.e., the N-type tunneling layer) and an N-type doping layer can be formed on the first surface of the substrate using the method provided in the above steps S201 to S204, so that the second region has a tunneling layer (i.e., the N-type tunneling layer) and an N-type doping layer, and the N-type doping layer has a first barrier layer. Since the N-type doping layer and the tunneling layer (i.e., the N-type tunneling layer) in steps S201 to S204 are deposited on the entire surface of the first surface of the substrate, after forming the N-type doping layer, it is necessary to perform laser film opening and wet etching on the first region to remove the tunneling layer (i.e., the N-type tunneling layer) and the N-type doping layer formed on the P-type doping layer, so that the first region has a tunneling layer (i.e., the P-type tunneling layer) and a P-type doping layer, and the second region has a tunneling layer (i.e., the N-type tunneling layer) and an N-type doping layer.

[0086] After removing the tunneling layer (i.e., N-type tunneling layer) formed on the P-type doped layer and the N-type doped layer, an isolation groove may be opened between the first region and the second region to isolate the first region from the second region. Thereafter, the second surface of the substrate may be textured, and then a passivation film may be plated and a metal paste may be screen printed.

[0087] The method for preparing a back-contact solar cell described above can be applicable to the case where the first barrier layer and the second barrier layer are silicon oxide layers. In the embodiment of the present application, the first barrier layer and the second barrier layer can also be silicon nitride layers or silicon carbide layers. The method for preparing a back-contact solar cell in an embodiment of the present application is described below by taking the case where both the first barrier layer and the second barrier layer are silicon nitride layers as an example.

[0088] The method for preparing a back contact solar cell comprises: Step S401: depositing a tunneling layer on the first surface of the substrate. Step S401 is the same as the above-mentioned step 201 and will not be described again here.

[0089] After step S401, the process proceeds to step S402: depositing a first doping layer on the side of the tunneling layer away from the substrate. Step S401 is the same as the above-mentioned step S202, and will not be described again.

[0090] like Figure 6a As shown, after step S402 , step S403 is entered: a silicon nitride layer 193 and an intrinsic amorphous silicon layer 194 are deposited on a side of the first doped layer 121 away from the substrate 11 , and the intrinsic amorphous silicon layer 194 is located on a side of the silicon nitride layer 193 away from the substrate 11 .

[0091] like Figure 6b As shown, after step S403, step S404 is entered: laser treatment is performed on the intrinsic amorphous silicon layer 194 in the non-target area 111e. The first surface of the substrate 11 may include a target area 111d and a non-target area 111e. In step S404, the intrinsic amorphous silicon layer 194 in the non-target area 111e is removed by laser, while the intrinsic amorphous silicon layer 194 in the target area 111d is retained. In other words, step S404 is to remove part of the intrinsic amorphous silicon layer 194 by laser treatment.

[0092] Combination Figure 6b and Figure 6c As shown, after step S404, step S405 is entered: the first surface of the substrate 11 is etched to remove the silicon nitride layer 193 in the non-target area 111e, and to remove the intrinsic amorphous silicon layer 194 in the target area 111d. Specifically, the silicon nitride layer 193 in the non-target area 111e can be removed by an acid solution, and the intrinsic amorphous silicon layer 194 in the target area 111d can be removed by an alkaline solution.

[0093] like Figure 6cAs shown, after step S405, the silicon nitride layer 193 in the target area 111d is not etched but retained. At this time, the first doped layer 121 only has the retained silicon nitride layer 193, and the silicon nitride layer 193 is the first barrier layer mentioned above, and the area of ​​the silicon nitride layer 193 is smaller than the area of ​​the first doped layer 121.

[0094] After step S405, the process proceeds to step S406: depositing a second doping layer on a side of the first doping layer away from the substrate. Step S406 is the same as the above step S204 and will not be described again.

[0095] The doping concentrations of the first doping layer and the second doping layer may be the same, and the first doping layer and the second doping layer may together constitute a complete N-type doping layer on the back contact solar cell.

[0096] The method for forming a silicon nitride layer in a P-type doped layer is similar in principle to the method for forming a silicon nitride layer in an N-type doped layer. Specifically, the method for preparing the back contact solar cell 1 may further include: Step S501: depositing a tunneling layer on the first surface of the substrate. Step S501 is the same as the above-mentioned step S301 and will not be described in detail herein.

[0097] After step S501, the process proceeds to step S502: depositing a third doping layer on the side of the tunneling layer away from the substrate. Step S502 is the same as the above step S302 and will not be described again.

[0098] After step S502, proceed to step S503: deposit a silicon nitride layer on the side of the third doped layer away from the substrate. Specifically, the silicon nitride layer can be formed on the third doped layer using PECVD technology. The silicon nitride layer is the second barrier layer mentioned above, wherein the silicon nitride layer has the same area as the third doped layer.

[0099] After step S503, the process proceeds to step S504: depositing a fourth doping layer on the side of the third doping layer away from the substrate. Step S504 is the same as the above step S304 and will not be described again.

[0100] The doping concentrations of the third doping layer and the fourth doping layer may be the same, and the third doping layer and the fourth doping layer may together constitute a complete P-type doping layer on the back contact solar cell.

[0101] In summary, the method for preparing a back-contact solar cell provided in the embodiment of the present application can realize the formation of a first barrier layer in an N-type doped layer and a second barrier layer in a P-type doped layer, and the preparation of the first barrier layer and the second barrier layer does not require additional equipment, thereby simplifying the production process of the back-contact solar cell. Among them, the area of ​​the first barrier layer is smaller than the area of ​​the N-type doped layer, and the area of ​​the second barrier layer is equal to the area of ​​the P-type doped layer. The effects of the first barrier layer and the second barrier layer have been described in detail above and will not be repeated here.

[0102] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A back contact solar cell, characterized in that: include: A substrate, the substrate comprising a first surface and a second surface arranged opposite to each other along its own thickness direction, the first surface being provided with a P-type doping layer and an N-type doping layer arranged alternately along a first direction, a tunneling layer being provided between the P-type doping layer and the substrate and between the N-type doping layer and the substrate along the thickness direction of the substrate, a first passivation layer being provided on a side of the P-type doping layer and the N-type doping layer away from the substrate, and a second passivation layer being provided on the second surface; a first fine gate, the first fine gate being disposed on the N-type doping layer, and at least a portion of the structure of the first fine gate penetrating the first passivation layer; a second fine gate, the second fine gate being disposed on the P-type doped layer, and at least a portion of the structure of the second fine gate penetrating the first passivation layer; A first barrier layer is provided in the N-type doped layer, the area of ​​the first barrier layer is smaller than the area of ​​the N-type doped layer, and along the thickness direction of the substrate, the projection of the first fine gate falls within the projection of the first barrier layer, and the first barrier layer is used to prevent the doping elements in the N-type doped layer and the metal grains in the first fine gate from diffusing into the substrate; The first direction is orthogonal to the thickness direction of the substrate.

2. The back contact solar cell according to claim 1, characterized in that: Along the first direction, the width of the first barrier layer is greater than the width of the first fine gate; Wherein, the width W1 of the first barrier layer satisfies: 30um≤W1≤80um.

3. The back contact solar cell according to claim 2, characterized in that: Along the thickness direction of the substrate, the thickness D1 of the first barrier layer satisfies: 0.5 nm≤D1≤1.5 nm.

4. The back contact solar cell according to claim 1, characterized in that: Along the thickness direction of the substrate, the distance from the first barrier layer to the tunneling layer is L1, and the thickness of the N-type doping layer is D2; The ratio of L1 to D2 satisfies: 0.5≤L1 / D2≤0.

8.

5. The back-contact solar cell according to any one of claims 1 to 4, characterized in that: A second barrier layer is provided in the P-type doping layer, and the second barrier layer is used to prevent the doping elements in the P-type doping layer and the metal grains in the second fine gate from diffusing into the substrate; Along the thickness direction of the substrate, the projection of the second barrier layer coincides with the projection of the P-type doping layer, and the thickness D3 of the second barrier layer satisfies: 0.5 nm≤D3≤1.5 nm.

6. The back contact solar cell according to claim 5, characterized in that: Along the thickness direction of the substrate, the distance from the second barrier layer to the tunneling layer is L2, and the thickness of the P-type doped layer is D4; The ratio of L2 to D4 satisfies: 0.2≤L2 / D4≤0.

5.

7. The back-contact solar cell according to any one of claims 1 to 4, characterized in that: The thickness D2 of the N-type doped layer satisfies: 100 nm ≤ D2 ≤ 250 nm, the thickness D5 of the tunneling layer between the substrate and the N-type doped layer satisfies: 1 nm ≤ D5 ≤ 2 nm, and / or; The thickness D4 of the P-type doping layer satisfies: 150nm≤D4≤300nm, and the thickness D6 of the tunneling layer between the substrate and the P-type doping layer satisfies: 1.5nm≤D6≤2.5nm.

8. The back contact solar cell according to claim 5, characterized in that: The first barrier layer includes at least one of silicon oxide, silicon nitride and silicon carbide, and / or; The second barrier layer includes at least one of silicon oxide, silicon nitride and silicon carbide.

9. A photovoltaic module, characterized in that: include: Cover plate; At least one cell string, the cell string comprising a plurality of back-contact solar cells according to any one of claims 1 to 8; The encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

10. A method for preparing a back contact solar cell, characterized in that: The back-contact solar cell includes a substrate, and the method for preparing the back-contact solar cell includes: depositing a tunneling layer on the first surface of the substrate; Depositing a first doping layer on a side of the tunneling layer away from the substrate; performing laser processing on a local region of the first doped layer to form a first barrier layer including silicon oxide in the local region; A second doping layer is deposited on a side of the first doping layer away from the substrate.

Images