Back contact solar cell and preparation method thereof and photovoltaic module

Abstract

The application 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 P-type doped layer and an N-type doped layer are arranged on a first surface of the substrate in an alternating mode 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, a first fine grid is arranged on the N-type doped layer, and a second fine grid is arranged on the P-type doped layer. A first barrier layer is arranged in the N-type doped layer, the area of the first barrier layer is smaller than that of the N-type doped layer, the projection of the first fine grid falls into the projection of the first barrier layer along the thickness direction of the substrate, the first barrier layer is used for hindering the diffusion of a doped element in the N-type doped layer and a metal grain in the first fine grid to the substrate, and the possibility of damage caused by the doped element and the metal grain to the tunneling layer and the substrate is reduced. The first barrier layer and the tunneling layer can simultaneously realize the 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, in particular to a back contact solar cell, a preparation method thereof and a photovoltaic module. BACKGROUND

[0002] The back contact solar cell can convert sunlight into electric energy. A 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 metal grains in the metal electrode can cause damage to 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. SUMMARY

[0003] Therefore, the present application provides a back contact solar cell, a preparation method thereof and a 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, an embodiment of the present application provides a back contact solar cell, including a substrate, a first fine grid and a second fine grid. The substrate includes 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, a tunneling layer is arranged 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 a side away from the substrate. The second surface is provided with a second passivation layer. The first fine grid is arranged on the N-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 P-type doped layer, and at least part of the structure of the second fine grid penetrates the first passivation layer. The N-type doped layer is provided with a first barrier layer. The area of the first barrier layer is smaller than the area of the N-type doped 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 hinder the diffusion of doped elements in the N-type doped layer and metal grains in the first fine grid to the substrate. 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 grid. The width W1 of the first barrier layer satisfies: 30um≤W1≤80um.

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

[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, and the thickness of the N-type doped layer is D2, and the ratio of L1 to D2 satisfies: 0.5≤L1 / D2≤0.8.

[0008] In a possible implementation, the P-type doped layer is provided with a second barrier layer, the second barrier layer is configured to impede diffusion of a doped element in the P-type doped layer and a metal grain in the second fine grid to 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, and 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, including a cover plate, an encapsulation layer, and at least one cell string, the encapsulation layer is located between the cover plate and the cell string, the cover plate is connected with the cell string through the encapsulation layer, and the cell string includes a plurality of back contact solar cells according to any one of the above embodiments.

[0013] In a third aspect, an embodiment of the present application provides a preparation method of a back contact solar cell, the back contact solar cell includes a substrate, and the preparation method includes: depositing a tunneling layer on a first surface of the substrate, depositing a first doped 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, and depositing a second doped layer on a side of the first doped layer away from the substrate.

[0014] The embodiment of the present application provides a back contact solar cell, a preparation method thereof and a photovoltaic module. The back contact solar cell comprises a substrate, the substrate comprises a first surface and a second surface which are oppositely arranged along the 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 the side of the P-type doped layer and the N-type doped 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 doped layer, at least part of the structure of the first fine grid penetrates the first passivation layer, a second fine grid is arranged on the P-type doped layer, at least part of the structure of the second fine grid penetrates the first passivation layer, a first barrier layer is arranged in the N-type doped layer, the area of the first barrier layer is smaller than the area of the N-type doped layer, the projection of the first fine grid falls into the projection of the first barrier layer along the thickness direction of the substrate, the first barrier layer is used for hindering the diffusion of the doped elements in the N-type doped layer and the metal grains in the first fine grid to the substrate, and the first direction is orthogonal to the thickness direction of the substrate. By arranging the first barrier layer in the N-type doped layer, the possibility that the phosphorus elements and the metal grains diffuse to the substrate and cause damage to the tunneling layer and the substrate can be reduced, and the passivation performance of the tunneling layer and the N-type doped layer is improved. Meanwhile, the first barrier layer and the tunneling layer can simultaneously realize the selective transportation of the carriers, the passivation effect on the substrate is enhanced, and the efficiency of the back contact solar cell is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] 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 as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 A partial schematic view of a back contact solar cell provided by an embodiment of the present application is shown in the figure.

[0017] Figure 2 A partial schematic view of a back contact solar cell provided by another embodiment of the present application is shown in the figure.

[0018] Figure 3 A partial schematic view of a back contact solar cell provided by another embodiment of the present application is shown in the figure.

[0019] Figure 4 A schematic view of a photovoltaic module provided by an embodiment of the present application is shown in the figure.

[0020] Figure 5a A schematic view of depositing a tunneling layer on a substrate in an embodiment of the present application is shown in the figure.

[0021] Figure 5b A schematic diagram of depositing a first doped layer on the tunneling layer in an embodiment of the present application;

[0022] Figure 5c A schematic diagram of forming a first barrier layer in the first doped layer in an embodiment of the present application;

[0023] Figure 5d A schematic diagram of depositing a second doped layer on the first doped layer in an embodiment of the present application;

[0024] Figure 6a A schematic diagram of depositing a silicon nitride layer and an intrinsic amorphous silicon layer on the first doped layer in an embodiment of the present application;

[0025] Figure 6b A schematic diagram of a substrate after laser treatment in yet another embodiment of the present application;

[0026] Figure 6c A schematic diagram of a substrate after etching treatment in yet another embodiment of the present application.

[0027] Reference signs:

[0028] 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 grid; 18 - second fine grid; 191 - first barrier layer; 192 - second barrier layer; 193 - silicon nitride layer; 194 - intrinsic amorphous silicon layer;

[0029] 100 - photovoltaic module; 10 - cell string; 20 - first cover plate; 30 - first encapsulation layer; 40 - second encapsulation layer; 50 - second cover plate. DETAILED DESCRIPTION

[0030] In order to better understand the technical solutions of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0031] 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 a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0032] The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in the description of the embodiments of the present application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0033] It should be understood that the term "and / or" used herein only means an association relationship of the associated objects, and 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 in an "or" relationship.

[0034] As shown in Figure 1 The embodiments of the present application provide a back contact solar cell 1, which includes a substrate 11, which 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, which can be one or a combination of a phosphorus element, an arsenic element, or an antimony element, etc. The P-type substrate 11 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 will be described below taking the N-type substrate as an example.

[0035] The substrate 11 includes a first surface 111 and a second surface 112 oppositely arranged along its own thickness direction Z. The first surface 111 can be the back surface of the substrate 11, i.e., the surface not directly illuminated by sunlight. The second surface 112 can be the front surface of the substrate 11, i.e., the 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.

[0036] The first surface 111 is provided with P-type doped layers 13 and N-type doped layers 12 alternately arranged along a first direction X, which is orthogonal to the thickness direction Z of the substrate 11. The P-type doped layers 13 are doped with the above-mentioned P-type element (e.g., boron element), and the P-type doped layers 13 and the substrate 11 (i.e., the N-type substrate 11) form a PN junction. The N-type doped layers 12 are doped with the above-mentioned N-type element (e.g., phosphorus or antimony element), and the concentration of the N-type element doped in the N-type doped layers 12 can be greater than the concentration of the N-type element doped in the substrate 11 (i.e., the N-type substrate).

[0037] The tunneling layer 14 can 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 can be well matched with the lattice of the substrate 11, i.e., the tunneling layer 14 can well passivate the first surface 111 of the substrate 11 to reduce the rate of recombination of photo-generated electrons and photo-generated holes at the first surface 111 of the substrate 11. The tunneling layer 14 and the P-type doped layer 13 can form a tunneling passivation contact structure, which can improve the efficiency of the P-type doped layer 13 in collecting holes. The tunneling layer 14 and the N-type doped layer 12 can form a tunneling passivation contact structure, which can improve the efficiency of the N-type doped layer 12 in collecting electrons.

[0038] In some embodiments, the tunneling layer 14 can include a P-type tunneling layer (i.e., the tunneling layer contains P-type doped elements) corresponding to the P-type doped layer 13, and an N-type tunneling layer (i.e., the tunneling layer contains N-type doped elements) corresponding to the N-type doped layer 12, i.e., the tunneling layer 14 between the P-type doped layer 13 and the substrate 11 can be a P-type tunneling layer, and the tunneling layer 14 between the N-type doped layer 12 and the substrate 11 can be an N-type tunneling layer.

[0039] The N-type doped layer 12 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.

[0040] The P-type doped layer 13 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.

[0041] The first surface 111 includes first regions 111a and second regions 111b arranged alternately along the first direction X, the P-type doped layer 13 is disposed on the first regions 111a, and the N-type doped layer 12 is disposed on the second regions 111b. An isolation groove 111c recessed from the first surface 111 to the second surface 112 is disposed between adjacent first regions 111a and second regions 111b. The isolation groove 111c separates the P-type doped layer 13 and the N-type doped layer 12, reduces 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.

[0042] 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 along the thickness direction Z of the substrate 11. That is, the N-type doped layer 12 can be closer to the second surface 112 than the P-type doped layer 13, so that the N-type doped layer 12 and the P-type doped layer 13 are arranged staggered in the thickness direction Z of the substrate 11, 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.

[0043] 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. Among them, the size of the P-type doped layer 13 is greater than the size of the N-type doped layer 12, which ensures that the back contact solar cell 1 has good collection effect for both holes and electrons, thereby improving the performance and efficiency of the back contact solar cell 1.

[0044] The first surface 111 can be provided with a first passivation layer 15, and the first passivation layer 15 can 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 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, and the first passivation layer 15 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 thereby improve the cell efficiency.

[0045] The back contact solar cell 1 sets all the grid lines (i.e. metal electrodes) on the back surface of the substrate 11 (i.e. the first surface 111 described above), and the front surface of the substrate 11 (i.e. the second surface 112 described above) is not blocked by grid lines, reducing the light-shielding area of the front surface of the substrate 11, eliminating the light-shielding current loss of the grid lines, and maximizing the utilization of incident photons, thereby improving the photoelectric conversion efficiency of the back contact solar cell 1.

[0046] 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 arranged on the N-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 negative electrode of the back contact solar cell 1. The second fine grid 18 is arranged on the P-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 positive electrode of the back contact solar cell 1.

[0047] As mentioned above, the P-type doped layer 13 and the N-type doped layer 12 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.

[0048] Continue as Figure 1 As shown, a first barrier layer 191 is disposed in the N-type doped layer 12, which can be understood as the first barrier layer 191 being formed inside the N-type doped layer 12. The first barrier layer 191 is used to prevent the diffusion of dopants in the N-type doped layer 12 and metal grains in the first fine gate 17 to the substrate 11. The area of ​​the first barrier layer 191 is smaller than the area of ​​the N-type doped layer 12; that is, the first barrier layer 191 is only disposed in a local region of the N-type doped 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, meaning the position of the first barrier layer 191 corresponds to the position of the first fine gate 17.

[0049] Specifically, phosphorus can be doped into the N-type doped layer 12. Phosphorus tends to accumulate at the interface between the tunneling layer 14 and the substrate 11, damaging both layers and affecting the passivation effect of the tunneling layer 14, thus impacting the efficiency of the back contact solar cell 1. The first barrier layer 191 can prevent phosphorus from diffusing from the N-type doped layer 12 into the substrate 11, thereby reducing the possibility of phosphorus damaging the tunneling layer 14 and the substrate 11, ensuring the passivation effect of the tunneling layer 14, and improving the performance and efficiency of the back contact solar cell 1.

[0050] The first fine grid 17 on the N-type doped layer 12 can be made of metal paste. During sintering, it will also induce a wedge effect, that is, metal grains will form a wedge-shaped 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, thereby preventing the metal grains in the first fine grid 17 from diffusing into the substrate 11 and causing damage to 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. Meanwhile, by setting the first barrier layer 191, it is no longer necessary to increase the thickness of the N-type doped layer 12 to hinder the diffusion of the metal grains of the first fine grid 17, thereby realizing the thinning design of the N-type doped layer 12, which in turn reduces the optical parasitic absorption of the N-type doped layer 12 and improves the short-circuit current of the back contact solar cell 1.

[0051] The diffusion of phosphorus in the N-type doped layer 12 and the diffusion of metal grains of the first fine grid 17 to the substrate 11 mentioned above also affect the passivation performance of the N-type doped layer 12. Therefore, by arranging the first barrier layer 191, the passivation performance of the N-type doped layer 12 can be improved, so as to improve the efficiency of the back contact solar cell 1.

[0052] The N-type doped layer 12 can allow a large number of carriers (i.e. electrons) to be effectively transmitted to the first fine grid 17 and reduce the recombination of minority carriers (i.e. holes). The first barrier layer 191 in the N-type doped layer 12 also hinders the transmission of carriers to a certain extent. Therefore, the area of the first barrier layer 191 is designed to be smaller than the area of the N-type doped layer 12, so as to reduce the blocking area of the first barrier layer 191 to the carriers, so as to ensure the effective transmission of the carriers, thereby improving the efficiency of the back contact solar cell 1.

[0053] In some embodiments, the tunneling layer 14 and the first barrier layer 191 can both be silicon oxide layers. The tunneling layer 14 and the first barrier layer 191 can both achieve 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 the carriers can be effectively improved, so that the majority electrons can tunnel into the N-type doped layer 12 while the minority holes are blocked from recombining, so as to improve the efficiency of the back contact solar cell 1.

[0054] In summary, the first barrier layer 191 in the N-type doped layer 12 in the embodiments of the present application can reduce the possibility of damage to the tunneling layer 14 and the substrate 11 caused by the diffusion of phosphorus and metal grains to the substrate 11, and improve the passivation performance of the tunneling layer 14 and the N-type doped layer 12. At the same time, the first barrier layer 191 and the tunneling layer 14 can both achieve selective transport of carriers, and the passivation effect on the substrate 11 is enhanced, thereby further improving the efficiency of the back contact solar cell 1.

[0055] As Figure 2As shown, in one possible implementation, along the first direction X, the width of the first barrier layer 191 is greater than the width of the first fine gate 17. The width W1 of the first barrier layer 191 satisfies: 30µm ≤ W1 ≤ 80µm. For example, W1 can be 30µm, 35µm, 40µm, 45µm, 50µm, 55µm, 60µm, 65µm, 70µm, 75µm, or 80µm, or other values ​​within the aforementioned range. If the size of W1 is small and smaller than the width of the first fine gate 17, the blocking effect of the first barrier layer 191 on the metal grains of the first fine gate 17 is weakened, thereby increasing the risk of damage to the tunneling layer 14 and the silicon substrate 11. If the size of W2 is too large, the risk of the first barrier layer 191 hindering the transport of charge carriers increases, which can easily affect the efficiency of the back contact solar cell 1. By ensuring that the width W1 of the first barrier layer 191 meets the above-mentioned range, it is possible to guarantee the blocking effect of the first barrier layer 191 on the metal grains while ensuring the effective transport of charge carriers, thereby improving the efficiency of the back contact solar cell 1.

[0056] like Figure 2 As shown, in one possible implementation, along the thickness direction Z of the substrate 11, the thickness D1 of the first barrier layer 191 satisfies: 0.5nm ≤ D1 ≤ 1.5nm. The thickness D1 of the first barrier layer 191 satisfies: 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 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 and metal grains will be 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 will severely hinder the transport of charge carriers, making it impossible to guarantee that charge carriers can be transported effectively, thereby affecting the efficiency of the back contact solar cell 1. Therefore, by limiting the range of values ​​for D1, the barrier effect of the first barrier layer 191 can be guaranteed while ensuring that charge carriers can be transported effectively.

[0057] like Figure 2As shown, in one 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, and the thickness of the N-type doped layer 12 is D2. The ratio of L1 to D2 satisfies: 0.5 ≤ L1 / D2 ≤ 0.8. 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, or other values ​​within the above range. When L1 / D2 equals 0.5, the first barrier layer 191 is located in the middle of the N-type doped layer 12. Understandably, the larger the value of L1 / D2, the farther the first barrier layer 191 is from the tunneling layer 14.

[0058] The doping concentration of the N-type doped 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 of the N-type doped layer 12 or at the end of the N-type doped 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 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 12 can be improved.

[0059] like Figure 1 As shown, in one possible implementation, a second barrier layer 192 is provided in the P-type doped layer 13, which can be understood as the second barrier layer 192 being formed inside the P-type doped layer 13. The second barrier layer 192 is used to prevent the diffusion of dopants in the P-type doped layer 13 and metal grains in the second fine gate 18 to the substrate 11.

[0060] Specifically, boron can be doped into the P-type doped layer 13. Boron tends to accumulate at the interface between the tunneling layer 14 and the substrate 11, damaging both layers and affecting the passivation effect of the tunneling layer 14, thus impacting the efficiency of the back contact solar cell 1. The second barrier layer 192 prevents the diffusion of boron from the P-type doped layer 13 into the substrate 11, thereby reducing the possibility of damage to the tunneling layer 14 and the substrate 11 and ensuring the passivation effect of the tunneling layer 14. This is beneficial for improving the performance and efficiency of the back contact solar cell 1.

[0061] The second fine grid 18 on the P-type doped layer 13 can be fabricated from metal paste. During the sintering process of the metal paste, metal grains in the paste diffuse into the substrate 11, thereby triggering a wedge effect, which 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, preventing them from diffusing into the substrate 11 and causing damage to 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 setting the second barrier layer 192, it is no longer necessary to increase the thickness of the P-type doped layer 13 to hinder the diffusion of metal grains in the second fine grid 18, thereby achieving a thinner design of the P-type doped layer 13, which in turn reduces the optical parasitic absorption of the P-type doped layer 13 and improves the short-circuit current of the back contact solar cell 1.

[0062] The diffusion of boron from the P-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 P-type doped layer 13. Therefore, by setting the second barrier layer 192, the passivation performance of the P-type doped layer 13 can be improved, thereby improving the efficiency of the back contact solar cell 1.

[0063] 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, meaning 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, or 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 boron and metal grains becomes worse, 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 greater than 1.5 nm, then the second barrier layer 192 will severely hinder 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 11. Therefore, by limiting the range of values ​​for D3, the effective transport of charge carriers can be guaranteed while ensuring the blocking effect of the second barrier layer 192.

[0064] The thickness of the first barrier layer 191 and the thickness of the second barrier layer 192 may be the same or different.

[0065] like Figure 3In one possible implementation, as shown, the distance between the second barrier layer 192 and the tunneling layer 14 along the thickness direction Z of the substrate 11 is L2, and the thickness of the P-type doped layer 13 is D4. 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. Of course, L2 and D4 can also be other values within the above range. When L2 / D4 is equal to 0.5, the second barrier layer 192 is located at the middle position of the P-type doped layer 13. It can be understood that the smaller the value of L2 / D4, the closer the second barrier layer 192 is to the tunneling layer 14.

[0066] In combination Figure 1 As shown, the doping concentration of the P-type doped layer 13 is generally low, and the metal paste used to prepare the second fine grid 18 has strong burn-through performance. If the second barrier layer 192 is arranged at the end of the P-type doped layer 13 away from the tunneling layer 14, that is, the distance between the second barrier layer 192 and the tunneling layer 14 along the thickness direction Z of the substrate 11 is increased, the second barrier layer 192 is closer to the outer layer of the P-type doped layer 13, which results in a smaller distance between the second barrier layer 192 and the second fine grid 18 along the thickness direction Z of the substrate 11. Since the second barrier layer 192 can block the metal grains of the second fine grid 18, the contact area (i.e., ohmic contact) between the second fine grid 18 and the P-type doped layer 13 is reduced, the contact resistivity of the second fine grid 18 is increased, and the efficiency of the back contact solar cell 1 is affected. At the same time, the smaller distance between the second barrier layer 192 and the second fine grid 18 along the thickness direction Z of the substrate 11 reduces the blocking effect of the second barrier layer 192 on the metal grains of the second fine grid 18, and increases the risk of diffusion of the metal grains to the tunneling layer 14 and the substrate 11 and the occurrence of the sharp wedge effect. Therefore, by arranging the second barrier layer 192 at the middle position of the P-type doped layer 13 or at the end of the P-type doped 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 the contact area between the second fine grid 18 and the P-type doped 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.

[0067] As Figure 2As shown, in a possible implementation, the thickness D2 of the N-type doped layer 12 satisfies: 100 nm≤D2≤250 nm, for example, D2 can be 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm or 250 nm, and of course can also be other values within the above range. If the thickness D2 of the N-type doped layer 12 is too small, for example, D2 is less than 100 nm, then the contact resistivity of the first fine grid 17 is easily increased, and the passivation performance of the N-type doped layer 12 is also affected. If the thickness D2 of the N-type doped layer 12 is too large, for example, D2 is greater than 250 nm, then the optical parasitic absorption of the N-type doped layer 12 is increased, and the performance of the back contact solar cell 1 is affected. Therefore, by making the thickness D2 of the N-type doped layer 12 satisfy: 100 nm≤D2≤250 nm, it is beneficial to reduce the optical parasitic absorption of the N-type doped layer 12 while reducing the contact resistivity of the first fine grid 17 and ensuring the passivation performance of the N-type doped layer 12, so as to achieve the best performance of the back contact solar cell 1.

[0068] As shown, Figure 3 As shown, the thickness D4 of the P-type doped layer 13 satisfies: 150 nm≤D4≤300 nm, for example, D4 can be 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm or 300 nm, and of course can also be other values within the above range. If the thickness D4 of the P-type doped layer 13 is too small, for example, D4 is less than 150 nm, then the contact resistivity of the second fine grid 18 is easily increased, and the passivation performance of the P-type doped layer 13 is also affected. If the thickness D4 of the P-type doped layer 13 is too large, for example, D4 is greater than 300 nm, then the optical parasitic absorption of the P-type doped layer 13 is increased, and the performance of the back contact solar cell 1 is affected. Therefore, by making the thickness D4 of the P-type doped layer 13 satisfy: 150 nm≤D4≤300 nm, it is beneficial to reduce the optical parasitic absorption of the P-type doped layer 13 while reducing the contact resistivity of the second fine grid 18 and ensuring the passivation performance of the P-type doped layer 13, so as to achieve the best performance of the back contact solar cell 1.

[0069] As shown, Figure 2 As shown, the thickness D5 of the tunneling layer 14 between the substrate 11 and the N-type doped layer 12 satisfies: 1 nm≤D5≤2 nm, for example, D5 can be 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 1.9 nm or 2 nm, and of course can also be other values within the above range. The tunneling layer 14 can be the N-type tunneling layer mentioned above.

[0070] As shown, 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 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 14 can be the P-type tunneling layer mentioned above.

[0071] 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.

[0072] 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 relatively weak barrier effect against boron. 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 boron can be increased, reducing the possibility of boron diffusion into the substrate 11.

[0073] In one 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 composed of two or three of silicon oxide, silicon nitride, and silicon carbide.

[0074] The second barrier layer 192 includes at least one of silicon oxide, silicon nitride, and silicon carbide. For example, the second barrier layer 192 may be a silicon oxide layer, a silicon nitride layer, or a silicon carbide layer, or the second barrier layer 192 may be a film layer composed of two or three of silicon oxide, silicon nitride, and silicon carbide.

[0075] 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. By using the above-mentioned material, it is beneficial to improve the blocking effect of the first barrier layer 191 and the second barrier layer 192.

[0076] like Figure 4 As shown in the figure, a photovoltaic module 100 according to an embodiment of this application includes a cover plate, an encapsulation layer, and at least one cell string 10. The encapsulation layer is located between the cover plate and the cell string 10, and the cover plate is connected to the cell string 10 through the encapsulation layer. The cell string 10 includes a plurality of back-contact solar cells 1 as described above.

[0077] 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.

[0078] 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 the 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, which also protects the cell string 10, and 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.

[0079] Since the back contact solar cell 1 has the above technical effects, the photovoltaic module 100 with the back contact solar cell 1 also has the above technical effects, which will not be described here.

[0080] The embodiment of the present application provides a preparation method of a back contact solar cell. Hereinafter, the preparation method of the back contact solar cell is described by taking an example of an N-type doped layer being a phosphorus-doped polysilicon layer (i.e., N-type doped polysilicon) and a P-type doped layer being a boron-doped polysilicon layer (i.e., P-type doped polysilicon).

[0081] The preparation method of the back contact solar cell includes the following steps.

[0082] As shown in FIG. 1, the preparation method of the back contact solar cell includes the following steps. Figure 5a As shown in FIG. 1, the preparation method of the back contact solar cell includes the following steps.

[0083] As shown in FIG. 1, the preparation method of the back contact solar cell includes the following steps.Figure 5b As shown, after step S201, step S202 is performed: a first doped layer 121 is deposited on the side of the tunneling layer 14 away from the substrate 11.

[0084] In step S202, a polysilicon layer can be deposited on the side of the tunneling layer 14 away from the substrate 11 using PECVD technology. This polysilicon layer is an intrinsic polysilicon layer, that is, an undoped polysilicon layer. Then, phosphorus diffusion is performed on the substrate 11 to incorporate 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.

[0085] like Figure 5c As shown, after step S202, step S203 is performed: a local area of ​​the first doped layer 121 is laser-processed to form a first barrier layer 191 including silicon oxide in the local area.

[0086] Laser processing can form a silicon oxide layer in a localized area of ​​the first doped layer 121, which is the first barrier layer 191. The effect of the first barrier layer 191 has been explained in detail above and will not be repeated here.

[0087] like Figure 5d As shown, after step S203, step S204 is performed: a second doped layer 122 is deposited on the side of the first doped layer 121 away from the substrate 11.

[0088] Step S204 is similar to step S202. First, a polysilicon layer can be deposited on the side of the first doped layer 121 away from the substrate 11 using PECVD technology. This polysilicon layer is an intrinsic polysilicon layer. Then, the substrate 11 is subjected to phosphorus diffusion treatment to incorporate phosphorus into the aforementioned intrinsic polysilicon layer, thereby forming a second doped layer 122, i.e., the second doped layer 122 is a phosphorus-doped polysilicon layer.

[0089] The doping concentrations of the first doped layer 121 and the second doped layer 122 can be the same, and the first doped layer 121 and the second doped layer 122 can together form a complete N-type doped layer 12 on the back contact solar cell 1 (e.g., Figure 1 As shown in the figure, both the first doped layer 121 and the second doped layer 122 can be considered as part of the N-type doped layer 12 film structure. The area of ​​the first doped layer 121 is the same as the area of ​​the second doped layer 122, the area of ​​the first barrier layer 191 is smaller than the area of ​​the first doped layer 121, and the area of ​​the second doped layer 122 is smaller.

[0090] As can be seen from the above, in the embodiments of this application, the N-type doped layer 12 of the back contact solar cell 1 can be formed by two deposition steps and a phosphorus diffusion step, thereby enabling the formation of a first barrier layer 191 in the N-type doped layer 12.

[0091] In the embodiments of the present application, the second barrier layer including silicon oxide can be formed in the P-type doped layer by laser processing. The process of preparing the second barrier layer is similar to the process of preparing the first barrier layer. Specifically, the method for preparing the back contact solar cell can include:

[0092] In step S301, a tunneling layer is deposited on the first surface of the substrate. The tunneling layer can be formed on the first surface of the substrate by using a PECVD (Plasma Enhanced Chemical Vapor Deposition) technique. Specifically, the tunneling layer 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 tunneling layer described above is a tunneling layer arranged between the substrate and the P-type doped layer, i.e., the tunneling layer can be a P-type tunneling layer.

[0093] After step S301, step S302 is entered, in which a third doped layer is deposited on the side of the tunneling layer away from the substrate. In step S302, a polycrystalline silicon layer, which is an intrinsic polycrystalline silicon layer, can be first deposited on the side of the tunneling layer away from the substrate by using a PECVD technique, and then boron diffusion is performed on the substrate to dope boron elements into the intrinsic polycrystalline silicon layer, thereby forming the third doped layer, i.e., the third doped layer is a boron-doped polycrystalline silicon layer.

[0094] After step S302, step S303 is entered, in which the third doped layer is processed by laser 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,

[0095] After laser processing, a silicon oxide layer can be formed in the third doped layer, which is the second barrier layer described above. The effect of the second barrier layer has been described above and will not be repeated here.

[0096] After step S303, step S304 is entered, in which a fourth doped layer is deposited on the side of the third doped layer away from the substrate. Step S304 is similar to step S302, in which a polycrystalline silicon layer, which is an intrinsic polycrystalline silicon layer, can be first deposited on the side of the third doped layer away from the substrate 11 by using a PECVD technique, and then boron diffusion is performed on the substrate to dope boron elements into the intrinsic polycrystalline silicon layer, thereby forming the fourth doped layer, i.e., the fourth doped layer is a boron-doped polycrystalline silicon layer.

[0097] The doping concentrations of the third doped layer and the fourth doped layer can be the same, and the third doped layer and the fourth doped layer can jointly constitute a complete P-type doped layer on the back contact solar cell, i.e., the third doped layer and the fourth doped layer can be regarded as part of the P-type doped layer film layer structure. The areas of the third doped layer, the fourth doped layer, and the second barrier layer are the same.

[0098] As can be seen from the above, the P-type doped layer of the back contact solar cell in the embodiment of the present application can also be formed through two deposition steps and a phosphorus diffusion step in sequence, so that the second barrier layer can be formed in the P-type doped layer.

[0099] In the preparation method of the back contact solar cell described above, the first surface and the second surface of the substrate can be polished first to remove mechanical damage on the surfaces of the substrate, and then the method provided in steps S301-S304 described above can be used to form the tunneling layer (i.e., the P-type tunneling layer) and the P-type doped layer with the second barrier layer in the P-type doped layer on the first surface of the substrate. As described above, the first surface of the substrate has a first region and a second region, the P-type doped layer is arranged on the first region, and the N-type doped layer is arranged on the second region. Therefore, after the P-type doped layer is formed, the second region needs to be subjected to laser film opening processing and wet etching processing to remove the P-type doped layer and the tunneling layer (i.e., the P-type tunneling layer) on the second region.

[0100] When the P-type doped layer and the tunneling layer (i.e., the P-type tunneling layer) on the second region are removed, since the second barrier layer is arranged in the P-type doped layer, the second barrier layer has high corrosion resistance, so that the process window of the wet etching is improved, i.e., the limitation of the concentration of the chemical solution used in the wet etching is reduced, and at the same time, the second barrier layer can also improve the process window of the laser film opening, i.e., the limitation of the laser power is reduced, so as to ensure the stability and reliability of the preparation process flow of the back contact solar cell.

[0101] After the P-type doped layer and the tunneling layer (i.e., the P-type tunneling layer) on the second region are removed, the method provided in steps S201-S204 described above can be used to form the tunneling layer (i.e., the N-type tunneling layer) and the N-type doped layer with the first barrier layer in the N-type doped layer on the first surface of the substrate, so that the second region has the tunneling layer (i.e., the N-type tunneling layer) and the N-type doped layer with the first barrier layer in the N-type doped layer. Since the N-type doped layer and the tunneling layer (i.e., the N-type tunneling layer) in steps S201-S204 are deposited on the entire first surface of the substrate, after the N-type doped layer is formed, the first region also needs to be subjected to laser film opening processing and wet etching processing to remove the tunneling layer (i.e., the N-type tunneling layer) and the N-type doped layer formed on the P-type doped layer, so that the first region has the tunneling layer (i.e., the P-type tunneling layer) and the P-type doped layer, and the second region has the tunneling layer (i.e., the N-type tunneling layer) and the N-type doped layer.

[0102] After removing the tunneling layer (i.e., the N-type tunneling layer) and the N-type doped layer formed on the P-type doped layer, an isolation trench can be formed between the first region and the second region to isolate them. Subsequently, the second surface of the substrate can be texturized, followed by processes such as depositing a passivation film and screen printing metal paste.

[0103] The fabrication method for a back-contact solar cell described above is applicable to situations where the first and second barrier layers are silicon oxide layers. In the embodiments of this application, the first and second barrier layers can also be silicon nitride layers or silicon carbide layers. The fabrication method of a back-contact solar cell in one embodiment of this application will be described below using an example where both the first and second barrier layers are silicon nitride layers.

[0104] Methods for fabricating back-contact solar cells include:

[0105] Step S401: Deposit a tunneling layer on the first surface of the substrate. Step S401 is the same as step 201 above, and will not be repeated here.

[0106] After step S401, proceed to step S402: deposit a first doped layer on the side of the tunneling layer away from the substrate. Step S401 is the same as step S202 described above, and will not be repeated here.

[0107] like Figure 6a As shown, after step S402, step S403 is performed: a silicon nitride layer 193 and an intrinsic amorphous silicon layer 194 are deposited on the side of the first doped layer 121 away from the substrate 11. The intrinsic amorphous silicon layer 194 is located on the side of the silicon nitride layer 193 away from the substrate 11.

[0108] like Figure 6b As shown, after step S403, the process proceeds to step S404: laser processing is performed on the intrinsic amorphous silicon layer 194 within the non-target region 111e. The first surface of the substrate 11 may include the target region 111d and the non-target region 111e. In step S404, the intrinsic amorphous silicon layer 194 within the non-target region 111e is removed using a laser, while the intrinsic amorphous silicon layer 194 within the target region 111d is retained. In other words, step S404 involves removing a portion of the intrinsic amorphous silicon layer 194 using laser processing.

[0109] Combination Figure 6b and Figure 6cAs shown, after step S404, step S405 is entered: etching treatment is performed on the first surface of the substrate 11 to remove the silicon nitride layer 193 within the non-target region 111e and to remove the intrinsic amorphous silicon layer 194 within the target region 111d. Specifically, the silicon nitride layer 193 within the non-target region 111e can be removed by using an acid solution, and the intrinsic amorphous silicon layer 194 within the target region 111d can be removed by using an alkali solution.

[0110] As shown, after step S405, the silicon nitride layer 193 within the target region 111d is not etched and is reserved, at this time, the first doped layer 121 only has the reserved silicon nitride layer 193, and the silicon nitride layer 193 is the first barrier layer described above, and the area of the silicon nitride layer 193 is smaller than the area of the first doped layer 121. Figure 6c

[0111] After step S405, step S406 is entered: a second doped layer is deposited on the side of the first doped layer away from the substrate. Step S406 is the same as step S204 described above, and will not be described here.

[0112] The doping concentrations of the first doped layer and the second doped layer can be the same, and the first doped layer and the second doped layer can jointly constitute a complete N-type doped layer on the back contact solar cell.

[0113] The method of forming a silicon nitride layer in a P-type doped layer is similar in principle to the method of forming a silicon nitride layer in an N-type doped layer described above. Specifically, the method of manufacturing the back contact solar cell 1 can further include:

[0114] Step S501: depositing a tunneling layer on the first surface of the substrate. Step S501 is the same as step S301 described above, and will not be described here.

[0115] After step S501, step S502 is entered: depositing a third doped layer on the side of the tunneling layer away from the substrate. Step S502 is the same as step S302 described above, and will not be described here.

[0116] After step S502, step S503 is entered: depositing 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 by using PECVD technology. The silicon nitride layer is the second barrier layer described above, and the area of the silicon nitride layer is the same as the area of the third doped layer.

[0117] After step S503, step S504 is entered: depositing a fourth doped layer on the side of the third doped layer away from the substrate. Step S504 is the same as step S304 described above, and will not be described here.

[0118] ​The doping concentration of the third doped layer and the fourth doped layer can be the same, and the third doped layer and the fourth doped layer can jointly constitute a complete P-type doped layer on the back contact solar cell.

[0119] To sum up, the preparation method of the back contact solar cell provided by the embodiments of the present application can form the first barrier layer in the N-type doped layer and the second barrier layer in the P-type doped layer, and the preparation of the first barrier layer and the second barrier layer does not need additional equipment, thereby simplifying the production process of the back contact solar cell. 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.

[0120] The above only is the preferred embodiment of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various changes and changes. 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: The substrate includes a first surface and a second surface disposed opposite to each other along its own thickness direction. The first surface is provided with P-type doped layers and N-type doped layers arranged alternately along a first direction. Along the thickness direction of the substrate, tunneling layers are provided between the P-type doped layer and the substrate, and between the N-type doped layer and the substrate. A first passivation layer is provided on the side of the P-type doped layer and the N-type doped layer away from the substrate. A second passivation layer is provided on the second surface. A first fine gate is disposed on the N-type doped layer, and at least a portion of the structure of the first fine gate penetrates the first passivation layer; A second fine gate is disposed on the P-type doped layer, and at least a portion of the structure of the second fine gate penetrates the first passivation layer; The N-type doped layer is provided with a first barrier layer. The area of ​​the first barrier layer is smaller than the area of ​​the N-type doped layer. Along the thickness direction of the substrate, the projection of the first fine gate falls into the projection of the first barrier layer. 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 width of the N-type doped layer along the first direction is smaller than the width of the P-type doped layer along the first direction. The width of the first barrier layer along the first direction is smaller than the width of the N-type doped layer along the first direction, but larger than the width of the first fine gate along the first direction. The width W1 of the first barrier layer satisfies: 30um≤W1≤80um. 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 thickness direction of the substrate, the thickness D1 of the first barrier layer satisfies: 0.5nm ≤ D1 ≤ 1.5nm.

3. 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 doped layer is D2; The ratio of L1 to D2 satisfies: 0.5≤L1 / D2≤0.

8.

4. The back-contact solar cell according to any one of claims 1 to 3, characterized in that, The P-type doped layer is provided with a second barrier layer, which is used to prevent the doping elements in the P-type doped layer and the metal grains in the second fine gate from diffusing to 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.

5. The back-contact solar cell according to claim 4, 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.

6. The back-contact solar cell according to any one of claims 1 to 3, characterized in that, The thickness D2 of the N-type doped layer satisfies: 100nm≤D2≤250nm, and 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.

7. The back-contact solar cell according to claim 4, 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.

8. A photovoltaic module, characterized in that, include: Cover plate; At least one battery string, the battery string comprising a plurality of back-contact solar cells as described in any one of claims 1 to 7; An 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.

9. A method for fabricating a back-contact solar cell, characterized in that, The method for preparing the back-contact solar cell is used to prepare the back-contact solar cell according to any one of claims 1 to 7; The back-contact solar cell includes a substrate, and the method for fabricating the back-contact solar cell includes: A tunneling layer is deposited on the first surface of the substrate; A first doped layer is deposited on the side of the tunneling layer away from the substrate; A localized region of the first doped layer is laser-processed to form a first barrier layer comprising silicon oxide in the localized region; A second doped layer is deposited on the side of the first doped layer away from the substrate.

Images