Back contact cell, preparation method thereof and photovoltaic module

Abstract

The application relates to the technical field of photovoltaic modules, and particularly relates to a back contact cell, a preparation method thereof and a photovoltaic module. The back contact cell comprises a silicon substrate, the back surface of the silicon substrate comprises a first region, a second region and an overlapping region between the first region and the second region. The first region comprises a first subregion and a second subregion. The first subregion is provided with a first doped layer, the second subregion and the overlapping region are provided with a second doped layer, the thickness of the first doped layer is greater than the thickness of the second doped layer along the thickness direction of the back contact cell. The doping concentration of the first doped layer is greater than the doping concentration of the second doped layer. By arranging the second doped layer with a relatively thin thickness and a relatively low doping concentration in the overlapping region, the lateral diffusion range in the second doped layer can be controlled, and the second doped layer is prevented from extending to excessive contact with other structure layers, so that the risk of electric leakage of the back contact cell is effectively reduced, and the use safety of the back contact cell is improved.

Description

TECHNICAL FIELD

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

[0002] Photovoltaic modules can convert solar energy into electrical energy, have the advantages of no pollution, no geographical restrictions, inexhaustible, etc., and are the main direction of developing new energy. Photovoltaic modules are mainly composed of photovoltaic cells, photovoltaic glass, adhesive film, back plate and frame. As one of the photovoltaic cells, the back contact cell can reduce the shading of the grid lines to the light, increase the light receiving area and improve the use performance by setting the positive and negative electrodes on the back surface of the cell. However, the back contact cell has a risk of electric leakage during use, which affects the use safety of the back contact cell. SUMMARY

[0003] Therefore, the present application provides a back contact cell, a preparation method thereof and a photovoltaic module to solve the technical problem of high risk of electric leakage of the back contact cell in the prior art.

[0004] In a first aspect, the embodiments of the present application provide a back contact cell, which comprises a silicon substrate, the back surface of the silicon substrate comprises a first region and a second region, and an overlapping region between the first region and the second region; the first region comprises a first sub-region and a second sub-region; wherein the first sub-region is provided with a first doped layer, and the second sub-region and the overlapping region are provided with a second doped layer; along the thickness direction of the back contact cell, the thickness of the first doped layer is greater than the thickness of the second doped layer; the doping concentration of the first doped layer is greater than the doping concentration of the second doped layer.

[0005] In the embodiment, the first sub-region is a region in contact with the metal electrode, and the area of the first sub-region can be greater than or equal to the area of the metal electrode, the second sub-region is a region in the first region except the first sub-region, and the overlapping region is an overlapping region of the first region and the second region of different polarities. The embodiment has the beneficial effects that: by arranging the first doped stack with a larger thickness and a higher doping concentration in the first sub-region, the field passivation effect can be strengthened, the carrier separation and collection can be accelerated, and the surface recombination loss can be reduced, so as to improve the open-circuit voltage and the fill factor of the back contact cell, optimize the series resistance, and thus improve the working performance of the back contact cell. Moreover, by arranging the second doped stack with a thinner thickness and a lower doping concentration in the second sub-region, the parasitic absorption of the second sub-region can be reduced, the double-side rate of the back contact cell can be improved, and thus the power generation of the whole back contact cell is improved, so as to improve the use efficiency. Meanwhile, by arranging the second doped stack with a thinner thickness and a lower doping concentration in the overlapping region, the lateral diffusion range in the second doped stack can be controlled, and the second doped stack is prevented from extending to excessive contact with other structure layers, so as to effectively reduce the risk of electric leakage of the back contact cell and improve the use safety of the back contact cell.

[0006] In a specific embodiment, along the thickness direction of the back contact cell, the first doped stack comprises a first oxide layer, a first doped layer, a second oxide layer and a second doped layer arranged in sequence; and the second doped stack comprises a first oxide layer and a first doped layer arranged in sequence.

[0007] In a specific embodiment, the thickness D1 of the first doped stack satisfies 50nm < D1 ≤ 250nm, and / or the thickness D2 of the second doped stack satisfies D2 ≤ 50nm.

[0008] In a specific embodiment, the doping concentration W1 of the first doped layer satisfies 1E19 cm -3 ≤ W1 ≤ 1E20 cm -3 , and / or the doping concentration W2 of the second doped layer satisfies 1E20 cm -3 ≤ W2 ≤ 5E20 cm -3 .

[0009] In a specific embodiment, along the thickness direction of the back contact cell, the first doped stack comprises a silicon substrate doped layer, a first oxide layer, a first doped layer, a second oxide layer and a second doped layer arranged in sequence; and the second doped stack comprises a silicon substrate doped layer.

[0010] In a specific embodiment, the doping concentration W2 of the second doped layer satisfies 1E20 cm -3 ≤ W2 ≤ 5E20 cm -3 , and / or the doping concentration W3 of the silicon substrate doped layer satisfies 1E17 cm-3 ≤ 1E19 cm -3 .

[0011] In a second aspect, the embodiments of the present application provide a preparation method of a back contact cell, the preparation method of the back contact cell comprising:

[0012] preparing a silicon substrate, wherein a back surface of the silicon substrate has a first region, a second region, and an overlap region between the first region and the second region, the first region having a first sub-region and a second sub-region;

[0013] generating a first doped layer in the first sub-region and a second doped layer in the second sub-region and the overlap region;

[0014] wherein a thickness of the first doped layer is greater than a thickness of the second doped layer, and a doping concentration of the first doped layer is greater than a doping concentration of the second doped layer.

[0015] In the embodiments, by setting the first doped layer in the first sub-region, the open-circuit voltage and the fill factor of the back contact cell can be improved, and the series resistance can be optimized to improve the working performance of the back contact cell. Meanwhile, by setting the second doped layer in the second sub-region and the overlap region, the parasitic absorption of the second sub-region can be reduced, the bifaciality of the back contact cell can be improved, and the risk of electric leakage of the overlap region can be reduced, thereby improving the use safety of the back contact cell.

[0016] In a specific embodiment, in the step of generating the first doped layer in the first sub-region and the second doped layer in the second sub-region and the overlap region, the preparation method of the back contact cell specifically comprises:

[0017] generating a first oxide layer, a first doped layer, a second oxide layer, and a second doped layer on the back surface of the silicon substrate in sequence;

[0018] removing the second doped layer and the second oxide layer of the overlap region and the second sub-region, and retaining the first oxide layer, the first doped layer, the second oxide layer, and the second doped layer of the first sub-region.

[0019] In a specific embodiment, in the step of generating the first doped layer in the first sub-region and the second doped layer in the second sub-region and the overlap region, the preparation method of the back contact cell specifically comprises:

[0020] generating a first oxide layer, a first doped layer, a second oxide layer, and a second doped layer on the back surface of the silicon substrate in sequence;

[0021] removing the first oxide layer, the first doped layer, the second oxide layer and the second doped layer of the second region, the overlap region and the second sub-region, and retaining the first oxide layer, the first doped layer, the second oxide layer and the second doped layer of the first sub-region.

[0022] In a specific embodiment, the method for preparing the back contact cell specifically comprises:

[0023] depositing a mask layer on the back surface of the second doped layer;

[0024] removing the mask layer of the second region, the overlap region and the second sub-region;

[0025] wet chemical cleaning to remove the first oxide layer, the first doped layer, the second oxide layer and the second doped layer of the second region, and to remove the second doped layer and the second oxide layer of the second sub-region and the overlap region;

[0026] wherein the wet chemical cleaning time T1 satisfies 60s≤T1≤300s.

[0027] In a specific embodiment, the method for preparing the back contact cell specifically comprises:

[0028] depositing a mask layer on the back surface of the second doped layer;

[0029] removing the mask layer of the second region, the overlap region and the second sub-region;

[0030] wet chemical cleaning to remove the first oxide layer, the first doped layer, the second oxide layer and the second doped layer of the second region, and to remove the second doped layer, the second oxide layer, the first doped layer and the first oxide layer of the second sub-region and the overlap region;

[0031] wherein the wet chemical cleaning time T2 satisfies 100s≤T2≤500s.

[0032] In a specific embodiment, after generating the first doped stack in the first sub-region and generating the second doped stack in the second sub-region and the overlap region, the method for preparing the back contact cell further comprises:

[0033] depositing a first passivation layer and an anti-reflective layer on the front surface of the silicon substrate;

[0034] depositing a second passivation layer and a third doped layer at low temperature on the back surface of the silicon substrate;

[0035] removing the second passivation layer and the third doped layer of the second sub-region;

[0036] depositing a conductive thin film on the back surface of the silicon substrate;

[0037] removing part of the conductive thin film in the overlapping area to form an isolation area;

[0038] preparing a metal electrode on the back surface of the silicon substrate.

[0039] In a third aspect, the embodiment of the present application further provides a photovoltaic module, which comprises a back contact cell.

[0040] In the embodiment, the photovoltaic module can be composed of the back contact cell, the photovoltaic glass, the adhesive film, the back plate and the frame as described in the above embodiment. The back contact cell prepared by using the preparation method of the back contact cell in the above embodiment can improve the working performance of the back contact cell and reduce the risk of electric leakage, so as to guarantee the working efficiency and safety of the photovoltaic module as a whole. BRIEF DESCRIPTION OF DRAWINGS

[0041] 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.

[0042] Figure 1 Structure schematic diagram of the back contact cell provided by the present application in a specific embodiment;

[0043] Figure 2 Structure schematic diagram of step S11 in the preparation method of the back contact cell provided by the present application;

[0044] Figure 3 Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application;

[0045] Figure 4 Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application;

[0046] Figure 5 Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application; Figure 4 Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application;

[0047] Figure 6a Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application; Figure 1 Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application;

[0048] Figure 6b Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application; Figure 7 Structure schematic diagram of step S12 in the preparation method of the back contact cell provided by the present application;

[0049] Figure 7 Structure of the back contact cell in another embodiment of the application;

[0050] Figure 8a Structure of the back contact cell in another embodiment of the application; Figure 1 Structure of the back contact cell in another embodiment of the application;

[0051] Figure 8b Structure of the back contact cell in another embodiment of the application; Figure 7 Structure of the back contact cell in another embodiment of the application;

[0052] Figure 9a Structure of the back contact cell in another embodiment of the application; Figure 1 Structure of the back contact cell in another embodiment of the application;

[0053] Figure 9b Structure of the back contact cell in another embodiment of the application; Figure 7 Structure of the back contact cell in another embodiment of the application;

[0054] Figure 10a Structure of the back contact cell in another embodiment of the application; Figure 1 Structure of the back contact cell in another embodiment of the application;

[0055] Figure 10b Structure of the back contact cell in another embodiment of the application; Figure 7 Structure of the back contact cell in another embodiment of the application;

[0056] Figure 11a Structure of the back contact cell in another embodiment of the application; Figure 1 Structure of the back contact cell in another embodiment of the application;

[0057] Figure 11b Structure of the back contact cell in another embodiment of the application. Figure 7 Structure of the back contact cell in another embodiment of the application.

[0058] Reference signs:

[0059] 1 - back contact cell

[0060] 11 - silicon substrate; 111 - first region; 111a - first sub-region; 111b - second sub-region; 112 - second region; 113 - overlap region

[0061] 12 - first doped stack

[0062] 13 - second doped stack

[0063] 14 - first oxide layer

[0064] 15 - first doped layer

[0065] 16 - second oxide layer

[0066] 17 - second doped layer;

[0067] 18 - first passivation layer;

[0068] 19 - anti-reflective layer;

[0069] 20 - second passivation layer;

[0070] 21 - third doped layer;

[0071] 22 - conductive thin film;

[0072] 23 - isolation region;

[0073] 24 - metal electrode;

[0074] 25 - mask layer. DETAILED DESCRIPTION

[0075] For better understanding of the technical solutions of the present application, the embodiments of the present application are described in detail below in combination with the drawings.

[0076] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor, fall within the scope of protection of the present application.

[0077] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0078] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0079] The photovoltaic module can convert solar energy into electrical energy, has the advantages of no pollution, no regional restriction, inexhaustible, etc., and is the main direction of developing new energy. The photovoltaic module is mainly composed of photovoltaic cells, photovoltaic glass, adhesive film, back plate and frame. As one of the photovoltaic cells, the back contact cell can reduce the shading of the grid lines to the light, increase the light receiving area and improve the use performance by setting the positive and negative electrodes on the back light surface of the cell. However, since the positive and negative electrodes are located on the same surface, the back contact cell also has the problem of electric leakage, which affects the use safety of the back contact cell.

[0080] To solve the above technical problems, as shown inFigure 1 As shown in FIG. 1, the embodiment of the present application provides a back contact cell 1, which comprises a silicon substrate 11, and the back surface of the silicon substrate 11 comprises a first region 111 and a second region 112, and an overlapping region 113 between the first region 111 and the second region 112. The first region 111 comprises a first sub-region 111a and a second sub-region 111b. The first sub-region 111a can be provided with a first doped layer 12, and the second sub-region 111b and the overlapping region 113 can be provided with a second doped layer 13. In the thickness direction of the back contact cell 1, the thickness of the first doped layer 12 can be greater than the thickness of the second doped layer 13, and the doping concentration of the first doped layer 12 can be greater than the doping concentration of the second doped layer 13.

[0081] In the embodiment, the first sub-region 111a is the region in contact with the metal electrode 24, and the area of the first sub-region 111a can be greater than or equal to the area of the metal electrode 24. The second sub-region 111b is the region in the first region 111 except the first sub-region 111a. The overlapping region 113 is the overlapping region of the first region 111 and the second region 112 with different polarities. By providing the first doped layer 12 with a greater thickness and a higher doping concentration in the first sub-region 111a, the field passivation effect can be strengthened, the carrier separation and collection can be accelerated, and the surface recombination loss can be reduced, so as to improve the open-circuit voltage and the fill factor of the back contact cell 1, optimize the series resistance, and thus improve the working performance of the back contact cell 1. Moreover, by providing the second doped layer 13 with a thinner thickness and a lower doping concentration in the second sub-region 111b, the parasitic absorption of the second sub-region 111b can be reduced, the bifaciality of the back contact cell 1 can be improved, and thus the power generation of the whole back contact cell 1 can be improved, so as to improve the use efficiency. Meanwhile, by providing the second doped layer 13 with a thinner thickness and a lower doping concentration in the overlapping region 113, the lateral diffusion range in the second doped layer 13 can be controlled, and the second doped layer 13 can be prevented from extending to excessive contact with other structure layers, so as to effectively reduce the risk of electric leakage of the back contact cell 1 and improve the use safety of the back contact cell 1.

[0082] In the embodiment of the present application, the first region 111 can be an N-type doped region, and the second region 112 can be a P-type doped region.

[0083] The embodiment of the present application further provides a preparation method of the back contact cell 1, as shown in FIG. 2 and FIG. 3, which comprises the following steps but is not limited to the following steps: Figures 1 to 5 Figure 6a As shown in FIG. 2 and FIG. 3, the preparation method of the back contact cell 1 comprises the following steps but is not limited to the following steps:

[0084] ​S11: preparing a silicon substrate 11, wherein the back surface of the silicon substrate 11 has a first region 111, a second region 112, and an overlapping region 113 between the first region 111 and the second region 112, the first region 111 has a first sub-region 111a and a second sub-region 111b;

[0085] S12: generating a first doped layer 12 in the first sub-region 111a, and generating a second doped layer 13 in the second sub-region 111b and the overlapping region 113;

[0086] wherein the thickness of the first doped layer 12 is greater than the thickness of the second doped layer 13, and the doping concentration of the first doped layer 12 is greater than the doping concentration of the second doped layer 13.

[0087] In the embodiment, by setting the first doped layer 12 in the first sub-region 111a, the open-circuit voltage and the fill factor of the back contact battery piece 1 can be improved, and the series resistance can be optimized to improve the working performance of the back contact battery piece 1. At the same time, by setting the second doped layer 13 in the second sub-region 111b and the overlapping region 113, the parasitic absorption of the second sub-region 111b can be reduced, the double-side rate of the back contact battery piece 1 can be improved, and the risk of electric leakage of the overlapping region 113 can be reduced, and the use safety of the back contact battery piece 1 can be improved.

[0088] In a specific embodiment, as shown in FIG. 1, Figure 1 along the thickness direction of the back contact battery piece 1, the first doped layer 12 can include a first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 which are sequentially stacked. The second doped layer 13 can include a first oxide layer 14 and a first doped layer 15 which are stacked.

[0089] In the embodiment, the first doped layer 12 includes two oxide layers and two doped layers. Compared with the second doped layer 13 which only includes one oxide layer and one doped layer, the first doped layer 12 can have a greater thickness and a higher doping concentration to improve the working performance of the back contact battery piece 1, and at the same time, the thickness and the doping concentration of the second doped layer 13 are relatively small to reduce the parasitic absorption and the risk of electric leakage of the back contact battery piece 1.

[0090] In the above embodiment, as shown in FIG. 1, Figure 6a the thickness D1 of the first doped layer 12 can satisfy 50nm < D1 ≤ 250nm, and the thickness D2 of the second doped layer 13 can satisfy D2 ≤ 50nm.

[0091] In the embodiment, the thickness D1 of the first doped layer 12 can be 60 nm, 100 nm, 150 nm, 200 nm, 250 nm, etc., so as to reduce the series resistance of the first doped layer 12, improve the photoelectric conversion efficiency of the back contact cell, and avoid the increase of carrier transmission loss caused by the too thick thickness of the first doped layer 12. At the same time, the thickness D2 of the second doped layer 13 can be 5 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc., so as to reduce the parasitic absorption of the second doped layer 13, improve the bifaciality of the back contact cell, and avoid the too low carrier collection efficiency caused by the too thin thickness of the second doped layer 13.

[0092] In other embodiments, the thickness D1 of the first doped layer 12 and the thickness D2 of the second doped layer 13 can also be other values, and the specific values of the thickness of the first doped layer 12 and the thickness of the second doped layer 13 in the embodiment of the present application are not limited, and can be adaptively adjusted according to actual conditions.

[0093] In the above embodiments, as shown in FIG. 1, Figure 6a the doping concentration W1 of the first doped layer 15 can satisfy 1E19 cm -3 ≤ W1 ≤ 1E20 cm -3 , and / or the doping concentration W2 of the second doped layer 17 can satisfy 1E20 cm -3 ≤ W2 ≤ 5E20 cm -3 .

[0094] In the embodiment, the doping concentration of the first doped layer 15 can be 1E19 cm -3 , 3E19 cm -3 , 5E19 cm -3 , 7E19 cm -3 , 1E20 cm -3 , etc., and the doping concentration of the second doped layer 17 can be 2E20 cm -3 , 3E20 cm -3 , 4E20 cm -3 , 5E20 cm -3 , etc., the first doped layer 15 and the second doped layer 17 are included in the first doped layer 12, and only the first doped layer 15 is included in the second doped layer 13, so that the doping concentration of the second doped layer 17 is greater than the doping concentration of the first doped layer 15, so that the overall doping concentration of the first doped layer 12 is greater than the overall doping concentration of the second doped layer 13, so as to improve the fill factor and open circuit voltage of the first sub-area 111a, and reduce the parasitic absorption of the second sub-area 111b and the risk of leakage of the overlapping area, and significantly improve the working performance of the back contact cell.

[0095] In other embodiments, the doping concentration W1 of the first doped layer 15 and the doping concentration W2 of the second doped layer 17 can also be other values. In this application embodiment, the doping concentration of the first doped layer 15 and the second doped layer 17 is not specifically limited, and can be adaptively adjusted according to the actual situation.

[0096] In the above embodiments, the doping concentration of the first doped stack 12 can be the average doping concentration within the overall thickness range of the second doped layer 17, and the doping concentration of the second doped stack 13 can be the average doping concentration within the overall thickness range of the first doped layer 15.

[0097] In another specific embodiment, the doping concentration of the first doped stack 12 can also be the average doping concentration within the overall thickness range of the first oxide layer 14, the first doped layer 15, the second oxide layer 16, and the second doped layer 17, and the doping concentration of the second doped stack 13 can also be the average doping concentration within the overall thickness range of the first oxide layer 14 and the first doped layer 15.

[0098] In the two embodiments described above, electrochemical capacitance-voltage profiling (ECV) can be used to measure the average doping concentration of different structural layers.

[0099] like Figures 1 to 5 , Figure 6a As shown, step S12 above may include, but is not limited to, the following specific steps:

[0100] S121: A first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 are sequentially formed on the back side of the silicon substrate 11.

[0101] S122a: Remove the second doped layer 17 and the second oxide layer 16 of the overlapping region 113 and the second sub-region 111b, and retain the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the first sub-region 111a.

[0102] In the embodiment, the back surface of the back contact cell 1 is sequentially stacked with the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 in the direction away from the silicon substrate 11. The doping concentration of the second doped layer 17 is greater than the doping concentration of the first doped layer 15. Therefore, after the second doped layer 17 and the second oxide layer 16 are removed, only the first doped layer 15 with a lower doping concentration and the first oxide layer 14 are included in the second doped stack 13 formed, so that the doping concentration of the first doped stack 12 is greater than the doping concentration of the second doped stack 13, so as to make the overlapping area 113 and the second sub-area 111b generate the second doped stack 13 with a thinner thickness and a lower doping concentration, and make the first sub-area 111a generate the first doped stack 12 with a thicker thickness and a higher doping concentration.

[0103] In the above embodiment, as shown in Figure 4 、 Figure 5 and Figure 6a , the step S122a can further specifically include but is not limited to the following steps:

[0104] S122a1: depositing a mask layer 25 on the back surface of the second doped layer 17;

[0105] S122a2: removing the mask layer 25 of the second region 112, the overlapping area 113 and the second sub-area 111b;

[0106] S122a3: removing the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the second region 112 by wet chemical cleaning, and removing the second doped layer 17 and the second oxide layer 16 of the second sub-area 111b and the overlapping area 113;

[0107] wherein the wet chemical cleaning time T1 can satisfy 60s≤T1≤300s.

[0108] In the embodiment, by depositing the mask layer 25 on the back surface of the second doped layer 17 and removing the mask layer 25 of the second region 112, the overlapping area 113 and the second sub-area 111b, the mask layer 25 of the first sub-area 111a is retained. In the subsequent process of wet chemical cleaning, the first doped stack 12 of the first sub-area 111a is not affected by cleaning. At the same time, by controlling the time of wet chemical cleaning, the second doped layer 17 and the second oxide layer 16 of the second sub-area 111b and the overlapping area 113 are removed, so as to achieve the effect of removing part of the structure layer.

[0109] wherein the wet chemical cleaning time T1 can be 60s, 100s, 200s, 250s, 300s, etc. In other embodiments, the wet chemical cleaning time T1 can also be other specific values, and the specific value of the wet chemical cleaning time T1 is not limited in the embodiment of the application, and can be adjusted adaptively according to the actual situation.

[0110] Another embodiment is provided by the embodiments of the present application, as shown in Figure 7 The first doped stack 12 can include, in sequence from bottom to top, a silicon substrate doped layer, a first oxide layer 14, a first doped layer 15, a second oxide layer 16, and a second doped layer 17 along the thickness direction of the back contact cell 1. The second doped stack can include a silicon substrate doped layer (not shown in the figure).

[0111] In the embodiment, in the process of generating the first doped layer 15 and the second doped layer 17 on the back of the silicon substrate 11, part of the doped elements will enter the inside of the silicon substrate 11, so that part of the structure of the silicon substrate 11 forms a silicon substrate doped layer. In the embodiment, the second doped stack only includes the silicon substrate doped layer, which can further reduce the parasitic absorption of the second sub-area 111b, effectively improve the bifaciality of the back contact cell 1, and significantly reduce the risk of electric leakage of the overlapping area 113.

[0112] In the above embodiment, as shown in Figure 7 The doping concentration W2 of the second doped layer 17 can satisfy 1E20 cm -3 ≤ W2 ≤ 5E20 cm -3 , and the doping concentration W3 of the silicon substrate doped layer can satisfy 1E17 cm -3 ≤ W3 ≤ 1E19 cm -3 .

[0113] In the embodiment, the doping concentration of the second doped layer 17 can be 2E20 cm -3 , 3E20 cm -3 , 4E20 cm -3 , 5E20 cm -3 , etc., the doping concentration of the silicon substrate doped layer can be 1E17 cm -3 , 5E17 cm -3 , 1E18 cm -3 , 5E18 cm -3 , 1E19 cm -3 , etc., the first doped stack 12 includes the first doped layer 15 and the second doped layer 17, the second doped stack only includes the silicon substrate doped layer, and the doping concentrations of the first doped layer 15 and the second doped layer 17 are both greater than that of the silicon substrate doped layer, so that the overall doping concentration of the first doped stack 12 is significantly greater than that of the second doped stack, to improve the fill factor and open-circuit voltage of the first sub-area 111a, reduce the parasitic absorption of the second sub-area 111b and the risk of electric leakage of the overlapping area 113, and significantly improve the working performance of the back contact cell 1.

[0114] In other embodiments, the doping concentration W2 of the second doped layer 17 and the doping concentration W3 of the silicon substrate doped layer can also be other values. In the embodiments of the present application, the specific values of the doping concentrations of the second doped layer 17 and the silicon substrate doped layer are not limited, and can be adaptively adjusted according to actual conditions.

[0115] In the above embodiments, the doping concentration of the first doped layer 12 can be an average doping concentration in the overall thickness range of the second doped layer 17, and the doping concentration of the second doped layer 13 can be an average doping concentration of the silicon substrate doped layer, wherein the average doping concentration of the silicon substrate doped layer can be obtained by measuring the average doping concentration in the thickness range of 0.1-0.25 μm on the back surface of the silicon substrate.

[0116] In the above embodiments, the average doping concentration of different structure layers can be measured by electrochemical capacitance-voltage profiling (ECV).

[0117] In the above embodiments, as shown in Figures 3 to 5 , Figure 6b , the step S12 can further include but is not limited to the following steps:

[0118] S121: generating the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 on the back surface of the silicon substrate 11 in sequence;

[0119] S122b: removing the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the overlapping region 113 and the second sub-region 111b, and retaining the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the first sub-region 111a.

[0120] In the embodiments, the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the first sub-region 111a are retained to form the first doped layer 12 with a relatively thick thickness and a relatively high doping concentration, and the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the overlapping region 113 and the second sub-region 111b are removed so that the second doped layer only includes the silicon substrate doped layer with a relatively low doping concentration.

[0121] In the above embodiments, as shown in Figure 4 , Figure 5 and Figure 6b , the step S122b can further include but is not limited to the following steps:

[0122] S122b1: depositing a mask layer 25 on the back surface of the second doped layer 17;

[0123] S122b2: removing the mask layer 25 of the second region 112, the overlap region 113 and the second sub-region 111b;

[0124] S122b3: removing the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the second region 112 by wet chemical cleaning, removing the second doped layer 17, the second oxide layer 16, the first doped layer 15 and the first oxide layer 14 of the second sub-region 111b and the overlap region 113;

[0125] The wet chemical cleaning time T2 satisfies 300s < T2≤ 500s.

[0126] In the embodiment, the mask layer 25 is deposited on the back surface of the second doped layer 17, and the mask layer 25 of the second region 112, the overlap region 113 and the second sub-region 111b is removed, so as to retain the mask layer 25 of the first sub-region 111a. In the subsequent wet chemical cleaning process, the first doped layer 12 of the first sub-region 111a is not affected by the cleaning, and at the same time, by controlling the time of the wet chemical cleaning, the first oxide layer 14, the first doped layer 15, the second oxide layer 16 and the second doped layer 17 of the second sub-region 111b and the overlap region 113 are removed.

[0127] The wet chemical cleaning time T2 can be 350s, 400s, 450s, 500s, etc. In other embodiments, the wet chemical cleaning time T2 can also be other specific values, and the specific value of the wet chemical cleaning time T2 is not limited in the embodiment of the application, and can be adjusted adaptively according to the actual situation.

[0128] In the above two embodiments, as shown in Figure 1 and Figure 7 , by setting two layers of oxide layers and two layers of doped layers in the first doped layer 12, and making the doping concentrations of the first doped layer 15 and the second doped layer 17 different, the first doped layer 12 also has a gradient change of the doping concentration, which can further increase the conductivity of the carriers in the first doped layer 12, reduce the series resistance, and further improve the working performance of the back contact cell piece.

[0129] In a specific embodiment, as shown in Figure 1 , Figures 7 to 1 1 (i.e. including Figure 8a , Figure 8b , Figure 9a , Figure 9b , Figure 10a , Figure 10b , Figure 11a and Figure 11b ), after the step S12, the preparation method of the back contact cell piece can further include but is not limited to the following steps:

[0130] S13: depositing a first passivation layer 18 and an anti-reflective layer 19 on the front surface of the silicon substrate 11;

[0131] S14: depositing a second passivation layer 20 and a third doped layer 21 on the back surface of the silicon substrate at low temperature;

[0132] S15: removing the second passivation layer 20 and the third doped layer 21 of the second sub-area 111b;

[0133] S16: depositing a conductive thin film 22 on the back surface of the silicon substrate 11;

[0134] S17: removing part of the conductive thin film 22 of the overlapping area 113 to form an isolation area 23;

[0135] S18: preparing a metal electrode 24 on the back surface of the silicon substrate 11.

[0136] In the embodiment, the complete back contact cell 1 is prepared through the above steps.

[0137] The embodiment of the present application also provides a photovoltaic module (not shown in the figure), which can be composed of the back contact cell, the photovoltaic glass, the adhesive film, the back plate and the frame as described in the above embodiment. The back contact cell prepared by using the preparation method of the back contact cell in the above embodiment can improve the working performance of the back contact cell and reduce the risk of electric leakage, so as to guarantee the working efficiency and safety of the photovoltaic module as a whole.

[0138] The above only describes optional embodiments 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 modifications 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 cell, characterized in that, The back contact cell piece (1) comprises a silicon substrate (11), the back surface of the silicon substrate (11) comprises a first region (111), a second region (112) and an overlapping region (113) between the first region (111) and the second region (112); the first region (111) comprises a first sub-region (111a) and a second sub-region (111b); Wherein, the first sub-region (111a) is provided with a first doped layer (12), the second sub-region (111b) and the overlapping region (113) are provided with a second doped layer (13); along the thickness direction of the back contact cell piece (1), the thickness of the first doped layer (12) is greater than the thickness of the second doped layer (13); the doping concentration of the first doped layer (12) is greater than the doping concentration of the second doped layer (13); Along the thickness direction of the back contact cell piece (1), the first doped layer (12) comprises a first oxide layer (14), a first doped layer (15), a second oxide layer (16) and a second doped layer (17) which are sequentially stacked; The second doped layer (13) comprises a first oxide layer (14) and a first doped layer (15) which are stacked.

2. The back contact cell of claim 1, wherein, The thickness D1 of the first doped layer (12) satisfies 50nm 3. The back contact cell of claim 2, wherein, The doping concentration W1 of the first doped layer (15) satisfies 1E19 cm -3 ≤ W1 ≤ 1E20 cm -3 , and / or the doping concentration W2 of the second doped layer (17) satisfies 1E20 cm -3 < W2 ≤ 5E20 cm -3 .

4. A back contact cell, characterized by The back contact cell piece (1) comprises a silicon substrate (11), the back surface of the silicon substrate (11) comprises a first region (111), a second region (112) and an overlapping region (113) between the first region (111) and the second region (112); the first region (111) comprises a first sub-region (111a) and a second sub-region (111b); Wherein, the first sub-region (111a) is provided with a first doped layer (12), the second sub-region (111b) and the overlapping region (113) are provided with a second doped layer (13); along the thickness direction of the back contact cell piece (1), the thickness of the first doped layer (12) is greater than the thickness of the second doped layer (13); the doping concentration of the first doped layer (12) is greater than the doping concentration of the second doped layer (13); Along the thickness direction of the back contact cell piece (1), the first doped layer (12) comprises a first oxide layer (14), a first doped layer (15), a second oxide layer (16) and a second doped layer (17) which are sequentially stacked; The second doped layer (13) comprises the silicon substrate doped layer.

5. The back contact cell of claim 4, wherein, The doping concentration W2 of the second doped layer (17) satisfies 1E20 cm -3 ≤ W2≤ 5E20 cm -3 , and / or the doping concentration W3 of the doped layer of the silicon substrate satisfies 1E17 cm -3 ≤ W3≤ 1E19 cm -3 .

6. A method for producing a back contact cell (1) according to any one of claims 1 or 4, characterized in that The preparation method of the back contact cell piece (1) comprises: Preparation of a silicon substrate (11), wherein the back surface of the silicon substrate (11) has a first region (111), a second region (112) and an overlapping region (113) between the first region (111) and the second region (112), and the first region (111) has a first sub-region (111a) and a second sub-region (111b); Preparation of a silicon substrate (11), wherein the back surface of the silicon substrate (11) has a first region (111), a second region (112) and an overlapping region (113) between the first region (111) and the second region (112), and the first region (111) has a first sub-region (111a) and a second sub-region (111b); A first doped layer (12) is formed in the first sub-region (111a), and a second doped layer (13) is formed in the second sub-region (111b) and the overlapping region (113); The thickness of the first doped layer (12) is greater than the thickness of the second doped layer (13); and the doping concentration of the first doped layer (12) is greater than the doping concentration of the second doped layer (13).

7. The method of claim 6, wherein the back contact cell is prepared by a method comprising: forming a back contact cell by forming a back contact on a front surface of a substrate, and forming a front contact on a back surface of the substrate. The preparation method of the back contact cell (1) specifically comprises the following steps: A first oxide layer (14), a first doped layer (15), a second oxide layer (16) and a second doped layer (17) are sequentially formed on the back surface of the silicon substrate (11); The second doped layer (17) and the second oxide layer (16) of the overlapping region (113) and the second sub-region (111b) are removed, and the first oxide layer (14), the first doped layer (15), the second oxide layer (16) and the second doped layer (17) of the first sub-region (111a) are retained.

8. The method of claim 6, wherein the back contact cell is prepared by a method comprising: The preparation method of the back contact cell (1) specifically comprises the following steps: ​ A first oxide layer (14), a first doped layer (15), a second oxide layer (16) and a second doped layer (17) are sequentially formed on the back surface of the silicon substrate (11); The first oxide layer (14), the first doped layer (15), the second oxide layer (16) and the second doped layer (17) of the overlapping region (113) and the second sub-region (111b) are removed, and the first oxide layer (14), the first doped layer (15), the second oxide layer (16) and the second doped layer (17) of the first sub-region (111a) are retained.

9. The method of claim 7, wherein the back contact cell is prepared by a method comprising: The preparation method of the back contact cell (1) specifically comprises the following steps: ​ A mask layer (25) is deposited on the back surface of the second doped layer (17); The mask layer (25) of the second region (112), the overlapping region (113) and the second sub-region (111b) is removed; The first oxide layer (14), the first doped layer (15), the second oxide layer (16) and the second doped layer (17) of the second region (112) are removed by wet chemical cleaning, and the second doped layer (17) and the second oxide layer (16) of the second sub-region (111b) and the overlapping region (113) are removed; The wet chemical cleaning time T1 satisfies 60s≤T1≤300s.

10. The method of claim 8, wherein the back contact cell is prepared by a method comprising: In the step of removing the first oxide layer (14), the first doped layer (15), the second oxide layer (16) and the second doped layer (17) of the second region (112), the overlapping region (113) and the second sub-region (111b), the preparation method of the back contact cell (1) specifically comprises: ​ depositing a mask layer (25) on the back of the second doped layer (17); removing the mask layer (25) of the second region (112), the overlapping region (113) and the second sub-region (111b); wet chemical cleaning to remove the first oxide layer (14), the first doped layer (15), the second oxide layer (16) and the second doped layer of the second region (112), and to remove the second doped layer (17), the second oxide layer (16), the first doped layer (15) and the first oxide layer (14) of the second sub-region (111b) and the overlapping region (113); wherein the wet chemical cleaning time T2 satisfies 100s≤T2≤500s.

11. The method of producing a back contact cell (1) according to claim 6, characterized in that, After the first doped layer (12) is generated in the first sub-region (111a) and the second doped layer (13) is generated in the second sub-region (111b) and the overlapping region (113), the preparation method of the back contact cell (1) further comprises: depositing a first passivation layer (18) and an anti-reflection layer (19) on the front of the silicon substrate (11); depositing a second passivation layer (20) and a third doped layer (21) at low temperature on the back of the silicon substrate (11); removing the second passivation layer (20) and the third doped layer (21) of the second sub-region (111b); depositing a conductive thin film (22) on the back of the silicon substrate (11); removing part of the conductive thin film (22) of the overlapping region (113) to form an isolation region (23); preparing a metal electrode (24) on the back of the silicon substrate (11).

12. A photovoltaic module, characterized by The photovoltaic module comprises the back contact cell (1) according to any one of the preceding claims 1-5. The photovoltaic module comprises the back contact cell (1) according to any one of the preceding claims 1-5.

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