Back contact solar cell and preparation method thereof, photovoltaic module

Abstract

A back-contact solar cell and its preparation method, and a photovoltaic module, belonging to the technical field of solar cells. The back-contact solar cell comprises: a silicon substrate; a first region on a first surface of the silicon substrate comprises a first doped polysilicon layer; a second region on the first surface of the silicon substrate comprises a second doped polysilicon layer; a passivation anti-reflection layer is provided on the second surface; the first doped polysilicon layer comprises a first doping element, the second doped polysilicon layer comprises a second doping element, the first doped polysilicon layer is a P-type doped polysilicon layer, the second doped polysilicon layer is an N-type doped polysilicon layer, and the concentration of impurities in the first region of the silicon substrate corresponding to N is N. 110 , the concentration of impurities in the isolation region of the silicon substrate N 130 , the concentration N of impurities in the second region of the silicon substrate 120 Satisfied: N 130 ≤N 120 <N 110 , which can reduce the recombination of carriers in the isolation region, thereby improving the efficiency of back-contact solar cells.

Description

Technical Field

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

[0002] Back-contact solar (BC) cells are solar cells with no electrodes on the light-facing side of the cell. Both the positive and negative electrodes are located on the backside of the cell. This reduces shading of the cell by the electrodes, increases the cell's short-circuit current, and improves the cell's energy conversion efficiency. TBC cells, on the other hand, use a Topcon structure for both polarities on the backside of the cell. They offer high open-circuit voltage and fill factor, as well as high current, resulting in higher cell efficiency.

[0003] The concentration of impurities in the silicon substrate of TBC cells is crucial to the efficiency of TBC cells. Therefore, how to control the concentration of impurities to further improve the efficiency of TBC cells is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The purpose of the present application is to provide a back-contact solar cell to reduce the concentration of impurities in a silicon substrate and improve the efficiency of the back-contact solar cell.

[0005] In order to achieve the above objectives, the present application provides a back-contact solar cell and a preparation method thereof, and a photovoltaic module.

[0006] In a first aspect, a back-contact solar cell is provided, comprising: a silicon substrate, the silicon substrate having a first surface and a second surface opposite to each other, the first surface being provided with a first region, a second region, and an isolation region located between the first region and the second region; the first region comprising a first tunneling oxide layer, a first doped polycrystalline silicon layer, a first passivation layer, and a first electrode arranged in sequence along the thickness direction of the silicon substrate; the second region comprising a second tunneling oxide layer, a second doped polycrystalline silicon layer, a second passivation layer, and a second electrode arranged in sequence along the thickness direction of the silicon substrate; a passivation anti-reflection layer being provided on the second surface; the first doped polycrystalline silicon layer comprising a first doping element, the second doped polycrystalline silicon layer comprising a second doping element, the first doped polycrystalline silicon layer being a P-type doped polycrystalline silicon layer, and the second doped polycrystalline silicon layer being an N-type doped polycrystalline silicon layer; wherein a surface of the isolation region adjacent to the second region comprises the second doping element, and the sum of the concentrations of the first doping element and the second doping element on a surface of the silicon substrate adjacent to the passivation anti-reflection layer is less than 1×10 16 atom / cm 3The silicon substrate includes impurities, the impurities include at least one of iron, nickel, and chromium, and the concentration of the impurities in the silicon substrate corresponding to the first region N 110 , the concentration N of impurities in the silicon substrate corresponding to the isolation region 130 , the concentration N of impurities in the second region of the silicon substrate corresponding to 120 Satisfied: N 130 ≤N 120 <N 110 .

[0007] In the embodiment of the present application, the first doped polysilicon layer is a P-type doped polysilicon layer, the second doped polysilicon layer is an N-type doped polysilicon layer, the surface of the isolation region adjacent to the second region includes a second doping element, and the sum of the concentrations of the first doping element and the second doping element in the passivation anti-reflection layer is less than 1×10 16 atom / cm 3 , and the impurity concentrations in each region of the silicon substrate satisfy the above range, which is beneficial to reducing the recombination of carriers in the isolation region, thereby improving the efficiency of the back-contact solar cell.

[0008] In some embodiments, the diffusion depth of the second doping element in the silicon substrate is less than the diffusion depth of the first doping element in the silicon substrate, where the diffusion depth of the first doping element in the silicon substrate is 0.05 μm to 0.6 μm, and the diffusion depth of the second doping element in the silicon substrate is 0.03 μm to 0.3 μm. This helps reduce the concentration of impurities in the silicon substrate, reduces the recombination of minority carriers, and increases the lifetime of minority carriers. At the same time, it can avoid or reduce damage to the first tunneling oxide layer and the second tunneling oxide layer, thereby improving the efficiency of the back-contact solar cell.

[0009] In some embodiments, a diffusion depth of the first doping element in the silicon substrate is 0.1 μm to 0.2 μm, and a diffusion depth of the second doping element in the silicon substrate is 0.03 μm to 0.08 μm.

[0010] By controlling the diffusion depth of the first doping element in the silicon substrate and the diffusion depth of the second doping element in the silicon substrate to meet the above range, the concentration of impurities in the silicon substrate can be reduced, and damage to the first tunneling oxide layer and the second tunneling oxide layer can be avoided or reduced, which is beneficial to improving the efficiency of the back-contact solar cell.

[0011] In some embodiments, the diffusion depth of the second doping element in the silicon substrate is 0.03 μm to 0.05 μm. This can reduce the concentration of impurities in the silicon substrate while further reducing damage to the second tunneling oxide layer, thereby improving the efficiency of the back-contact solar cell.

[0012] In some embodiments, the concentration N of impurities in the silicon substrate corresponding to the first region is 110 , the concentration N of impurities in the silicon substrate corresponding to the isolation region 130 , the concentration N of impurities in the second region of the silicon substrate corresponding to 120 Meet at least one of the following conditions:

[0013] 1×10 10 atom / cm 3 ≤N 110 ≤1×10 16 atom / cm 3 ;

[0014] 1×10 8 atom / cm 3 ≤N 120 ≤1×10 16 atom / cm 3 ;

[0015] 1×10 8 atom / cm 3 ≤N 130 ≤1×10 16 atom / cm 3 .

[0016] In the above technical solution, the first region, the second region, and the isolation region of the silicon substrate have relatively low impurity concentrations, which is beneficial to improving the efficiency of the back-contact solar cell.

[0017] In some embodiments, the concentration of impurities N on the surface of the silicon substrate near the passivation anti-reflection layer is 101 Satisfied: N 101 ≤N 120 <N 110 In this way, the surface of the silicon substrate close to the passivation anti-reflection layer has a lower impurity concentration, which is beneficial to improving the efficiency of the back-contact solar cell.

[0018] In some embodiments, the concentration of impurities N on the surface of the silicon substrate near the passivation anti-reflection layer is 101 Satisfy 1×10 10 atom / cm 3 ≤N 101 ≤1×10 15 atom / cm 3 In this way, the surface of the silicon substrate close to the passivation anti-reflection layer has a lower impurity concentration, which is beneficial to improving the efficiency of the back-contact solar cell.

[0019] In some embodiments, the concentration of impurities N on the surface of the silicon substrate near the passivation anti-reflection layer is 101 The concentration N of the impurities in the isolation region corresponding to the silicon substrate 130 In this way, the surface of the silicon substrate close to the passivation anti-reflection layer has a lower impurity concentration, which is beneficial to improving the efficiency of the back contact solar cell.

[0020] In some embodiments, the concentration of impurities in the silicon substrate gradually increases along the thickness of the silicon substrate, from the center of the silicon substrate toward the first surface or the second surface. Thus, the center of the silicon substrate has a lower impurity concentration, which is beneficial for improving the efficiency of the back-contact solar cell.

[0021] In some embodiments, the first doping element includes element B, and the second doping element includes element P. Elements B and P are beneficial for absorbing impurities in the silicon substrate, thereby reducing the concentration of impurities in the silicon substrate, thereby achieving higher efficiency of the back-contact solar cell.

[0022] In a second aspect, a method for preparing a back-contact solar cell is provided, comprising: preparing a first tunneling oxide layer and a first polysilicon layer on a first surface of a silicon substrate; doping a first doping source into the silicon substrate provided with the first polysilicon layer by thermal diffusion to obtain the first doped polysilicon layer, wherein the thermal diffusion temperature of the first doping source is 910°C to 1000°C, and the thermal diffusion time of the first doping source is 10 min to 60 min; etching a second region of the silicon substrate provided with the first doped polysilicon layer and the first tunneling oxide layer to expose the second region of the silicon substrate; and performing a first etching process on the second region of the silicon substrate. A second tunneling oxide layer and a second polysilicon layer are prepared on a surface; a second doping source is doped into a silicon substrate provided with the second polysilicon layer by thermal diffusion to obtain the second doped polysilicon layer, wherein the thermal diffusion temperature of the second doping source is 850° C. to 920° C. and the thermal diffusion time of the second doping source is 3 min to 60 min; an isolation region is provided between the first doped polysilicon layer and the second doped polysilicon layer; a first passivation layer and a second passivation layer are provided on the surfaces of the first doped polysilicon layer and the second doped polysilicon layer, respectively; and a first electrode and a second electrode are provided on the surfaces of the first passivation layer and the second passivation layer, respectively.

[0023] In the above embodiment, controlling the thermal diffusion time and temperature of the first and second doping sources facilitates the diffusion of the doping elements to the corresponding locations on the silicon substrate, thereby effectively absorbing impurities from the silicon substrate, reducing the amount of impurities in the silicon substrate and improving the efficiency of the back-contact solar cell. Furthermore, this preparation method does not require additional steps to process the back-contact solar cell, simplifying the preparation process for the back-contact solar cell.

[0024] In some embodiments, the thermal diffusion temperature of the first dopant source is 960°C to 980°C, and the thermal diffusion time of the first dopant source is 20 minutes to 40 minutes; the thermal diffusion temperature of the second dopant source is 890°C to 910°C, and the thermal diffusion time of the second dopant source is 5 minutes to 30 minutes. This helps further reduce the concentration of impurities in the silicon substrate while avoiding or reducing damage to the first tunneling oxide layer and the second tunneling oxide layer, thereby achieving higher efficiency of the back-contact solar cell.

[0025] In some embodiments, the first doping source includes BCl 3 and the second doping source includes POCl 3. The B element and the P element are beneficial for absorbing impurities in the silicon substrate and reducing the concentration of impurities in the silicon substrate, thereby achieving higher efficiency of the back-contact solar cell.

[0026] In a third aspect, a photovoltaic module is provided, comprising the back-contact solar cell according to the first aspect and any embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0028] Figure 1 This is a schematic structural diagram of a back-contact solar cell according to an embodiment of the present application;

[0029] Figure 2 Schematic diagram of a method for preparing a back-contact solar cell according to an embodiment of the present application.

[0030] Figure numerals: 100: back contact solar cell; 1: silicon substrate; 110: first region; 120: second region; 130: isolation region; 2: first tunneling oxide layer; 3: first doped polysilicon layer; 71: first passivation layer; 8: first electrode; 4: second tunneling oxide layer; 5: second doped polysilicon layer; 72: second passivation layer; 9: second electrode; 6: passivation anti-reflection layer. DETAILED DESCRIPTION

[0031] The back-contact solar cell and its preparation method, as well as the embodiment of the photovoltaic module of the present application are described in detail with appropriate reference to the drawings, but there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0032] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0034] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0036] Back-contact solar (BC) cells are solar cells with no electrodes on the light-facing side of the cell. Both the positive and negative electrodes are located on the backside of the cell. This reduces shading of the cell by the electrodes, increases the cell's short-circuit current, and improves the cell's energy conversion efficiency. TBC cells, on the other hand, use a Topcon structure for both polarities on the backside of the cell. They offer high open-circuit voltage and fill factor, as well as high current, resulting in higher cell efficiency.

[0037] The concentration of impurities in the silicon substrate of TBC cells is crucial to the efficiency of TBC cells. Therefore, how to control the concentration of impurities to further improve the efficiency of TBC cells is a technical problem that needs to be solved urgently.

[0038] In view of this, an embodiment of the present application provides a back-contact solar cell, comprising: a silicon substrate, the silicon substrate having a first surface and a second surface opposite to each other; the first surface being provided with a first region, a second region, and an isolation region located between the first region and the second region; the first region comprising a first tunneling oxide layer, a first doped polycrystalline silicon layer, a first passivation layer, and a first electrode arranged in sequence along the thickness direction of the silicon substrate; the second region comprising a second tunneling oxide layer, a second doped polycrystalline silicon layer, a second passivation layer, and a second electrode arranged in sequence along the thickness direction of the silicon substrate; a passivation anti-reflection layer being provided on the second surface; the first doped polycrystalline silicon layer comprising a first doping element, the second doped polycrystalline silicon layer comprising a second doping element, the first doped polycrystalline silicon layer being a P-type doped polycrystalline silicon layer, and the second doped polycrystalline silicon layer being an N-type doped polycrystalline silicon layer; wherein a surface of the isolation region near the second region comprises the second doping element, and the sum of the concentrations of the first doping element and the second doping element on the surface of the silicon substrate near the passivation anti-reflection layer is less than 1×10 16 atom / cm 3 The silicon substrate includes impurities, the impurities include at least one of iron, nickel, and chromium, and the concentration of the impurities in the first region of the silicon substrate corresponds to N 110 , the concentration of impurities in the isolation region of the silicon substrate N 130 , the concentration N of impurities in the second region of the silicon substrate 120Satisfied: N 130 ≤N 120 <N 110 This helps reduce the recombination of carriers in the isolation region, thereby improving the efficiency of the back-contact solar cell.

[0039] Figure 1 FIG. 1 is a schematic diagram of the structure of a back-contact solar cell according to an embodiment of the present application. Figure 1 As shown, the back-contact solar cell 100 includes a silicon substrate 1 having a first surface and a second surface opposite to each other.

[0040] The first surface is provided with a first region 110 , a second region 120 , and an isolation region 130 located between the first region 110 and the second region 120 .

[0041] Along the first direction, the isolation region 130 is located between the first region 110 and the second region 120 to insulate and isolate the first region 110 from the second region 120. For example, the first direction is Figure 1 The x direction in .

[0042] The isolation region 130 may be a groove recessed from the first surface toward the second surface. As an example, the groove has a depth of 1 μm to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value within the above range.

[0043] The first region 110 includes a first tunneling oxide layer 2 , a first doped polysilicon layer 3 , a first passivation layer 71 and a first electrode 8 , which are sequentially arranged along the thickness direction of the silicon substrate 1 .

[0044] The material of the first tunnel oxide layer 2 may include SiO2, the material of the first doped polysilicon layer 3 may be polysilicon with doping elements, and the material of the first passivation layer 71 may include aluminum oxide (Al2O3), silicon nitride (SiN x ), silicon oxynitride (SiON) or silicon oxide (SiO y ), the material of the first electrode 8 may include metal, such as silver.

[0045] The second region 120 includes a second tunneling oxide layer 4 , a second doped polysilicon layer 5 , a second passivation layer 72 and a second electrode 9 which are sequentially arranged along the thickness direction of the silicon substrate 1 .

[0046] The second doped polysilicon layer 5 and the first doped polysilicon layer 3 have opposite polarities, and the first electrode 8 and the second electrode 9 can be used to collect majority carriers and minority carriers, respectively.

[0047] The material of the second tunnel oxide layer 4 may include SiO2, the material of the second doped polysilicon layer 5 may be polysilicon with doping elements, and the material of the second passivation layer 72 may include aluminum oxide (Al2O3), silicon nitride (SiN x ), silicon oxynitride (SiON) or silicon oxide (SiO y ), the material of the second electrode 9 may include metal, such as silver.

[0048] The second surface of the silicon substrate is provided with a passivation anti-reflection layer 6. Providing the passivation anti-reflection layer 6 on the second surface is beneficial to reducing the reflection of sunlight on the second surface, making it easier for the back contact solar cell to absorb more sunlight and improve efficiency.

[0049] The first doped polysilicon layer 3 includes a first doping element, the second doped polysilicon layer 5 includes a second doping element, the first doped polysilicon layer 3 is a P-type doped polysilicon layer, and the second doped polysilicon layer 5 is an N-type doped polysilicon layer.

[0050] By setting the first doping element, the first doped polysilicon layer 3 is a P-type doped polysilicon layer, and by setting the second doping element, the second doped polysilicon layer 5 is an N-type doped polysilicon layer. For example, the first doping element includes B element, and the second doping element includes P element.

[0051] In the process of preparing the first doped polysilicon layer 3 using the first doping element and preparing the second doped polysilicon layer 5 using the second doping element, the first doping element and the second doping element will diffuse into the silicon substrate. The doping elements have a certain ability to absorb impurities and can reduce the concentration of impurities in the silicon substrate.

[0052] A surface of the isolation region 130 adjacent to the second region 120 includes a second doping element.

[0053] As an example, after the first and second polysilicon layers are doped with the first and second doping elements, the surface of the isolation region 130 adjacent to the second region 120 includes the second doping element. For example, if the isolation region 130 is a recess, the sidewall of the recess adjacent to the second region 120 includes the second doping element.

[0054] The sum of the concentrations of the first doping element and the second doping element on the surface of the silicon substrate 1 close to the passivation anti-reflection layer 6 is less than 1×10 16 atom / cm 3 For example, the concentration of the first doping element and the second doping element on the surface of the silicon substrate 1 near the passivation anti-reflection layer 6 is 0 or close to 0, that is, the surface of the silicon substrate 1 near the passivation anti-reflection layer 6 almost does not include the first doping element and the second doping element.

[0055] The silicon substrate 1 includes impurities, which include at least one of iron, nickel, and chromium. The concentration N of the impurities in the first region 110 of the silicon substrate 1 is 110 , the concentration N of impurities in the silicon substrate 1 corresponding to the isolation region 130 130 , the impurity concentration N of the silicon substrate 1 corresponding to the second region 120 120 Satisfied: N 130 ≤N 120 <N 110 .

[0056] Impurities in the silicon substrate are elements other than silicon and doping elements, such as iron, nickel, and chromium.

[0057] The silicon substrate may have different impurity concentrations at different locations. For example, the impurity concentration in the first region 110 of the silicon substrate is greater than the impurity concentration in the second region 120 of the silicon substrate.

[0058] In the embodiment of the present application, the first doped polysilicon layer is a P-type doped polysilicon layer, the second doped polysilicon layer is an N-type doped polysilicon layer, the surface of the isolation region adjacent to the second region includes a second doping element, and the sum of the concentrations of the first doping element and the second doping element in the passivation anti-reflection layer is less than 1×10 16 atom / cm 3 , and the impurity concentrations in each region of the silicon substrate satisfy the above range, which is beneficial to reducing the recombination of carriers in the isolation region, thereby improving the efficiency of the back-contact solar cell.

[0059] In some embodiments, the diffusion depth of the second doping element in the silicon substrate 1 is less than the diffusion depth of the first doping element in the silicon substrate 1, the diffusion depth of the first doping element in the silicon substrate 1 is 0.05 μm to 0.6 μm, and the diffusion depth of the second doping element in the silicon substrate 1 is 0.03 μm to 0.3 μm.

[0060] The diffusion depth of the first doping element in the silicon substrate 1 can be 0.05μm, 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm or any value within the above range, and the diffusion depth of the second doping element in the silicon substrate 1 can be 0.03μm, 0.04μm, 0.06μm, 0.08μm, 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm or any value within the above range.

[0061] The diffusion depth of the first doping element in the silicon substrate can be the distance between the side surface of the first tunneling oxide layer 2 away from the silicon substrate and the position of the silicon substrate having the first doping element; the diffusion depth of the second doping element in the silicon substrate can be the distance between the side surface of the second tunneling oxide layer 4 away from the silicon substrate and the position of the silicon substrate having the second doping element.

[0062] When the diffusion depth of the first doping element in the silicon substrate is greater than or equal to 0.05μm, it has a better effect of absorbing impurities in the silicon substrate, which is beneficial to improving the efficiency of the back-contact solar cell; when the diffusion depth of the first doping element in the silicon substrate is less than or equal to 0.6μm, it has a better effect of absorbing impurities while also reducing damage to the first tunneling oxide layer 2, which is beneficial to improving the efficiency of the back-contact solar cell.

[0063] When the diffusion depth of the second doping element in the silicon substrate is greater than or equal to 0.03μm, it has a better effect of absorbing impurities in the silicon substrate, which is beneficial to improving the efficiency of the back-contact solar cell; when the diffusion depth of the second doping element in the silicon substrate is less than or equal to 0.3μm, it has a better effect of absorbing impurities while also reducing damage to the second tunneling oxide layer 4, which is beneficial to improving the efficiency of the back-contact solar cell.

[0064] In some embodiments, the diffusion depth of the first doping element in the silicon substrate 1 is 0.1 μm to 0.2 μm, and the diffusion depth of the second doping element in the silicon substrate 1 is 0.03 μm to 0.8 μm.

[0065] In the above embodiment, by controlling the diffusion depth of the first doping element in the silicon substrate 1 and the diffusion depth of the second doping element in the silicon substrate 1 to meet the above range, the concentration of impurities in the silicon substrate 1 can be reduced, and the damage to the first tunneling oxide layer 2 and the second tunneling oxide layer 4 can be avoided or reduced, which is beneficial to improving the efficiency of the back-contact solar cell.

[0066] In some embodiments, the diffusion depth of the second doping element in the silicon substrate 1 is 0.03 μm to 0.05 μm. This can reduce the concentration of impurities in the silicon substrate while further reducing damage to the second tunneling oxide layer, thereby improving the efficiency of the back-contact solar cell.

[0067] In some embodiments, the concentration N of impurities in the first region 110 of the silicon substrate 1 is 110 , the concentration N of impurities in the silicon substrate 1 corresponding to the isolation region 130 130 , the impurity concentration N of the silicon substrate 1 corresponding to the second region 120 120 Meet at least one of the following conditions:

[0068] 1×10 10 atom / cm 3 ≤N 110 ≤1×10 16 atom / cm 3 ;

[0069] 1×10 8 atom / cm 3 ≤N 120 ≤1×10 16 atom / cm 3 ;

[0070] 1×10 8 atom / cm 3 ≤N 130 ≤1×10 16 atom / cm 3 .

[0071] The concentration N of impurities in the first region 110 of the silicon substrate 1 is 110 It can be 1×10 10 atom / cm 3 , 1×10 11 atom / cm 3 , 1×10 12 atom / cm 3 , 1×10 13 atom / cm 3 , 1×10 14 atom / cm 3 , 1×10 15 atom / cm 3 , 1×10 16 atom / cm 3 Or any value within the above range, the concentration N of impurities in the second region 120 of the silicon substrate 1 is 120 It can be 1×10 8 atom / cm 3 , 1×10 9 atom / cm 3 , 1×10 10 atom / cm 3 , 1×10 11 atom / cm 3 , 1×10 12 atom / cm 3 , 1×10 13 atom / cm 3 , 1×10 14 atom / cm 3 , 1×10 15 atom / cm3 , 1×10 16 atom / cm 3 Or any value within the above range, the concentration N of impurities in the silicon substrate 1 corresponding to the isolation region 130 is 130 It can be 1×10 8 atom / cm 3 , 1×10 9 atom / cm 3 , 1×10 10 atom / cm 3 , 1×10 11 atom / cm 3 , 1×10 12 atom / cm 3 , 1×10 13 atom / cm 3 , 1×10 14 atom / cm 3 , 1×10 15 atom / cm 3 , 1×10 16 atom / cm 3 Or any value within the above range.

[0072] In the above technical solution, the first region 110 , the second region 120 , and the isolation region 130 of the silicon substrate 1 have relatively low impurity concentrations, which is beneficial to improving the efficiency of the back-contact solar cell.

[0073] In some embodiments, the concentration N of impurities on the surface of the silicon substrate 1 near the passivation anti-reflection layer 6 is 101 Satisfied: N 101 ≤N 120 <N 110 In this way, the surface of the silicon substrate 1 close to the passivation anti-reflection layer 6 has a lower impurity concentration, which is beneficial to improving the efficiency of the back-contact solar cell.

[0074] In some embodiments, the concentration N of impurities on the surface of the silicon substrate 1 near the passivation anti-reflection layer 6 is 101 Satisfy 1×10 10 atom / cm 3 ≤N 101 ≤1×10 15 atom / cm 3 .

[0075] N 101 It can be 1×10 10 atom / cm 3 , 1×10 11 atom / cm 3 , 1×10 12atom / cm 3 , 1×10 13 atom / cm 3 , 1×10 14 atom / cm 3 , 1×10 15 atom / cm 3 Or any value within the above range.

[0076] In this embodiment, the surface of the silicon substrate close to the passivation anti-reflection layer has a lower impurity concentration, which is beneficial to improving the efficiency of the back-contact solar cell.

[0077] In some embodiments, the concentration N of impurities on the surface of the silicon substrate 1 near the passivation anti-reflection layer 6 is 101 The concentration of impurities in the isolation region corresponding to the silicon substrate is N 130 In this way, the surface of the silicon substrate close to the passivation anti-reflection layer has a lower impurity concentration, which is beneficial to improving the efficiency of the back contact solar cell.

[0078] In some embodiments, the concentration N of impurities on the surface of the silicon substrate 1 near the passivation anti-reflection layer 6 is 101 The concentration of impurities in the isolation region corresponding to the silicon substrate is N 130 near.

[0079] In some embodiments, the concentration of impurities in the silicon substrate 1 gradually increases along the thickness direction of the silicon substrate 1, from the center of the silicon substrate 1 toward the first surface or the second surface. Thus, the center of the silicon substrate 1 has a lower impurity concentration, which is beneficial for improving the efficiency of the back-contact solar cell.

[0080] In some embodiments, the first doping element includes element B, and the second doping element includes element P. Elements B and P are beneficial for absorbing impurities in the silicon substrate 1 and reducing the concentration of impurities in the silicon substrate 1 , thereby achieving higher efficiency of the back-contact solar cell.

[0081] In some embodiments, there is a height difference between the first tunnel oxide layer 2 and the second tunnel oxide layer 4 , and the height difference is 0.05 μm to 3 μm, which facilitates the preparation of back-contact solar cells.

[0082] The height difference between the first tunnel oxide layer 2 and the second tunnel oxide layer 4 can be 0.05μm, 0.08μm, 0.1μm, 0.12μm, 0.15μm, 0.18μm, 0.2μm, 0.22μm, 0.25μm, 0.28μm, 0.3μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm or any value within the above range.

[0083] Figure 2 Schematic diagram of a method for preparing a back-contact solar cell according to an embodiment of the present application. The present application provides a method for preparing a back-contact solar cell, for example, Figure 2 As shown, the method 200 for preparing a back-contact solar cell includes the following steps.

[0084] Step 210 : forming a first tunneling oxide layer 2 and a first polysilicon layer on a first surface of a silicon substrate 1 .

[0085] As an example, before step 210, the silicon wafer is polished with alkaline solution to remove the damaged layer and form a flat planar structure, so as to obtain the silicon substrate 1 and prepare the first tunneling oxide layer 2 and the first polysilicon layer on the first surface of the silicon substrate 1.

[0086] As an example, in step 210, a first tunneling oxide layer 2 is first formed on the first surface of the silicon substrate 1, and then a first polysilicon layer is formed. Specifically, an LPCVD device is used to deposit the first tunneling oxide layer 2 and the first polysilicon layer on the first surface of the silicon substrate 1, wherein the material of the first tunneling oxide layer 2 includes SiO2, the deposition temperature of the first tunneling oxide layer 2 can be 550°C to 650°C, the thickness of the first tunneling oxide layer 2 can be 0.5nm to 2.5nm, and the deposition temperature of the first polysilicon layer can be 550°C to 650°C, and the thickness of the first polysilicon layer can be 100nm to 400nm.

[0087] In step 220 , a first doping source is doped into the silicon substrate 1 provided with the first polysilicon layer by thermal diffusion to obtain a first doped polysilicon layer 3 . The thermal diffusion temperature of the first doping source is 910° C. to 1000° C., and the thermal diffusion time of the first doping source is 10 min to 60 min.

[0088] As an example, during the preparation of the first doped polysilicon layer 3 , the addition of the first doping source will form a B-containing film (also referred to as BSG) with a certain thickness, which can then be removed by laser or etching slurry.

[0089] Step 230 , etching the second region 120 of the silicon substrate 1 provided with the first doped polysilicon layer 3 and the first tunnel oxide layer 2 to expose the second region 120 of the silicon substrate 1 .

[0090] As an example, in step 230 , in addition to exposing the second region 120 of the silicon substrate 1 , the isolation region 130 may also be exposed.

[0091] As an example, at least a portion of the BSG is removed according to a specific pattern to expose the first doped polysilicon layer 3 corresponding to the second region 120 .

[0092] Step 240 : forming a second tunneling oxide layer 4 and a second polysilicon layer on the first surface of the second region 120 of the silicon substrate 1 .

[0093] As an example, when the first doped polysilicon layer of the exposed second area 120 is removed by using alkaline solution and additives to form a polished morphology, a height difference is formed between the part where the BSG area is not removed and the part where the BSG area is removed. The height difference can range from 0.05μm to 0.3μm, and the thickness of the BSG area where the BSG is not removed is about 10nm to 30nm.

[0094] As an example, after forming the height difference, an LPCVD device is used to deposit a second tunnel oxide layer 4 and a second polysilicon layer, wherein the material of the second tunnel oxide layer 4 includes SiO2, the deposition temperature of the second tunnel oxide layer 4 can be 550°C~650°C, the thickness of the second tunnel oxide layer 4 is 0.5nm~2.5nm, the deposition temperature of the second polysilicon layer can be 550°C~650°C, and the thickness of the second polysilicon layer is 100nm~300nm.

[0095] In step 250 , a second doping source is doped into the silicon substrate 1 provided with a second polysilicon layer by thermal diffusion to obtain a second doped polysilicon layer 5 . The thermal diffusion temperature of the second doping source is 850° C. to 920° C., and the thermal diffusion time of the second doping source is 3 min to 60 min.

[0096] During the preparation of the second doped polysilicon layer 5, a thin film comprising P (also referred to as PSG) is formed. The thickness of the PSG region is 40 nm to 60 nm. Subsequently, the PSG region (e.g., the PSG region corresponding to the first region and at least a portion of the PSG region corresponding to the second region) can be removed using a laser. During the preparation of the second doped polysilicon layer 5, a second doped polysilicon layer is also formed in the portion of the silicon substrate corresponding to the first region. To facilitate the production of the back-contact solar cell of the present application, the second doped polysilicon layer formed in the first region can be removed using a laser or etching method.

[0097] In step 260 , an isolation region 130 is provided between the first doped polysilicon layer 3 and the second doped polysilicon layer 5 .

[0098] The isolation region 130 can be a groove extending along the thickness direction of the silicon substrate, with a depth of 1 μm to 3 μm. Accordingly, a chain machine is used to remove the plating from the second surface of the silicon substrate, and then the substrate is placed in a slotted texturing tank for texturing, forming a pyramid-shaped textured surface on the front surface to obtain the passivation anti-reflection layer 6.

[0099] In step 270 , a first passivation layer 71 and a second passivation layer 72 are respectively provided on the surfaces of the first doped polysilicon layer 3 and the second doped polysilicon layer 5 .

[0100] The materials of the first passivation layer 71 and the second passivation layer 72 may include aluminum oxide (Al2O3), silicon nitride (SiN x ), silicon oxynitride (SiON) or silicon oxide (SiO x ) two or more of them.

[0101] In step 280 , a first electrode 8 and a second electrode 9 are formed on the surfaces of the first passivation layer 71 and the second passivation layer 72 , respectively.

[0102] As an example, silver paste is printed on the surfaces of the first passivation layer 71 and the second passivation layer 72 , and after sintering, the first electrode 8 and the second electrode 9 are obtained.

[0103] In the above embodiment, controlling the thermal diffusion time and temperature of the first and second doping sources facilitates the diffusion of the doping elements to the corresponding locations on the silicon substrate 1, thereby effectively absorbing impurities from the silicon substrate 1, reducing the amount of impurities in the silicon substrate 1, and improving the efficiency of the back-contact solar cell. Furthermore, this preparation method does not require additional steps to process the back-contact solar cell (e.g., pre-treatment of the silicon substrate to remove impurities before forming the first tunneling oxide layer), thereby simplifying the preparation process for the back-contact solar cell.

[0104] In some embodiments, the thermal diffusion temperature of the first doping source is 960°C to 980°C, and the thermal diffusion time of the first doping source is 20 minutes to 40 minutes; the thermal diffusion temperature of the second doping source is 890°C to 910°C, and the thermal diffusion time of the second doping source is 5 minutes to 30 minutes. This helps further reduce the concentration of impurities in the silicon substrate 1 while avoiding or reducing damage to the first tunneling oxide layer 2 and the second tunneling oxide layer 4, thereby achieving higher efficiency of the back-contact solar cell.

[0105] In some embodiments, the first doping source includes BCl 3 and the second doping source includes POCl 3. The B element and the P element are beneficial for absorbing impurities in the silicon substrate 1 and reducing the concentration of impurities in the silicon substrate 1, thereby achieving higher efficiency of the back-contact solar cell.

[0106] The present application provides a photovoltaic module including the back-contact solar cell in any embodiment.

[0107] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0108] In Example 1, the back contact cell was prepared as follows.

[0109] (1) Polishing: Use alkaline solution to polish the silicon wafer to remove the damaged layer and form a flat plane structure to obtain a silicon substrate;

[0110] (2) Deposition: Depositing a first tunnel oxide layer (SiO2) and a first polysilicon layer on the first surface of the silicon substrate using an LPCVD device, wherein the thickness of the first tunnel oxide layer is 1.5 nm and the deposition temperature is 615°C, and the thickness of the first polysilicon layer is 300 nm and the deposition temperature is 570°C;

[0111] (3) Boron diffusion: The silicon substrate on which the first polysilicon layer has been deposited is doped by thermal diffusion to form a P-type doped region with a certain amount of borosilicate glass film (also known as BSG). The diffusion source is BCl3, the diffusion temperature is 970°C, and the diffusion time is 25 minutes.

[0112] (4) Patterning 1: Using laser or etching slurry to remove the BSG formed in step 3 according to a specific pattern, exposing the P-type doped region (the first doped polysilicon layer);

[0113] (5) Alkali polishing: The P-type doped area exposed in step 4 is removed to form a polished topography, while the area where BSG is not removed is retained, thereby forming a height difference (GAP). The GAP range is 1 μm, and the remaining thickness of BSG in the unremoved area is 25 nm.

[0114] (6) Deposition: The silicon substrate after step 5 is deposited with a second tunneling oxide layer (SiO2) and a second polysilicon layer using an LPCVD device, wherein the thickness of the second tunneling oxide layer is 1.5 nm and the deposition temperature is 600°C, and the thickness of the second polysilicon layer is 200 nm and the deposition temperature is 605°C;

[0115] (7) Phosphorus diffusion: The silicon substrate from step 6 is placed in a diffusion furnace. The diffusion source is POCl3. After diffusion, an N-type doped region (second doped polysilicon layer) with a certain thickness of phosphorus silicon glass film (also called PSG) is formed. The diffusion temperature is 900°C and the diffusion time is 10 min.

[0116] (8) Patterning 2: Use laser to remove PSG on the P-type doped area and part of the N-type doped area;

[0117] (9) Chain stripping and post-texturing: Use a chain machine to remove the wrap-around plating on the second surface of the silicon substrate, and then place it in a slot-type texturing tank to complete the texturing, so that a pyramid-shaped velvet surface is formed on the front side. In addition, the N-type doped layer on the P-type doped area on the second surface of the silicon substrate is also removed synchronously, and a groove (isolation area) is formed between the P-type doped area and the N-type doped area;

[0118] (10) Passivation: Depositing a passivation film on the second surface to prepare a surface passivation layer, wherein the material of the surface passivation layer is a laminated passivation film of aluminum oxide and silicon nitride;

[0119] (11) Preparing electrodes: printing electrode paste on the surface of the surface passivation layer at positions corresponding to the P-type doping region and the N-type doping region, and sintering them to obtain a first electrode and a second electrode, wherein the electrode paste includes silver.

[0120] The difference between Example 2-3 and Example 1 is that the diffusion temperature and time of boron diffusion and phosphorus diffusion are different.

[0121] In Example 2, the diffusion temperature of boron diffusion is 960° C., and the diffusion time is 30 minutes; the diffusion temperature of phosphorus diffusion is 890° C., and the diffusion time is 10 minutes.

[0122] In Example 3, the diffusion temperature of boron diffusion is 980° C., and the diffusion time is 20 minutes; the diffusion temperature of phosphorus diffusion is 910° C., and the diffusion time is 10 minutes.

[0123] The difference between Example 4-5 and Example 1 is that the diffusion temperature and time of boron diffusion and phosphorus diffusion are different, and the diffusion depths of the first doping source and the second doping source are different.

[0124] In Example 4, the diffusion temperature of boron diffusion is 900° C., and the diffusion time is 30 minutes; the diffusion temperature of phosphorus diffusion is 840° C., and the diffusion time is 20 minutes.

[0125] In Example 5, the diffusion temperature of boron diffusion is 1020° C., and the diffusion time is 20 minutes; the diffusion temperature of phosphorus diffusion is 930° C., and the diffusion time is 10 minutes.

[0126] The performance test of the back-contact solar cell was carried out, and the test conditions and results are as follows.

[0127] Specifically, at 25°C, under standard simulated sunlight (AM1.5G, 1000W / m 2 ) irradiation, back-contact solar cells were tested for performance and IV curves were obtained. Based on the IV curves and data from the test equipment, the short-circuit current Jsc, open-circuit voltage Voc, maximum light output voltage Vmpp, and maximum power point current Impp were determined. The fill factor (FF) of the back-contact solar cell was calculated using the formula FF = (Jmpp × Vmpp) / (Jsc × Voc). The conversion efficiency (Eff) of the back-contact solar cell was calculated using the formula Eff = Jsc × Voc × FF / Pin, where Pin is the input power.

[0128] In Table 1, D1 is the diffusion depth of the first doping element B in the silicon substrate, D2 is the diffusion depth of the second doping element P in the silicon substrate, N 110 is the concentration of impurities in the silicon substrate of the first region, N 120 is the concentration of impurities in the silicon substrate of the second region, N 130 is the concentration of impurities in the silicon substrate in the isolation region, and E is the efficiency of the back contact solar cell.

[0129] Table 1 Test results of the embodiment

[0130]

[0131] Combined with the examples 1-5, set N 130 ≤N 120 <N 110 , back-contact solar cells have higher efficiency.

[0132] In combination with Examples 1-3 and Example 4, by setting the diffusion depth of the first doping element in the silicon substrate to be greater than or equal to 0.05 μm, the diffusion depth of the second doping element in the silicon substrate to be greater than or equal to 0.03 μm, and the diffusion depth of the first doping element in the silicon substrate to be greater than the diffusion depth of the second doping element in the silicon substrate, it is beneficial to reduce the concentration of impurities in the silicon substrate and improve the efficiency of the back-contact solar cell; in combination with Examples 1-3 and Example 5, by setting the diffusion depth of the first doping element in the silicon substrate to be less than or equal to 0.6 μm, the diffusion depth of the second doping element in the silicon substrate to be less than or equal to 0.3 μm, and the diffusion depth of the first doping element in the silicon substrate to be greater than the diffusion depth of the second doping element in the silicon substrate, it is beneficial to reduce the impurities in the silicon substrate while reducing the damage to the first tunneling oxide layer and the second tunneling oxide layer, thereby improving the efficiency of the back-contact solar cell.

[0133] (1) Diffusion depth test method

[0134] The electrochemical capacitance-voltage (ECV) method is used to test the diffusion depths of the first and second doping elements. As an example, a back-contact solar cell is tested. The location in the first region where a characteristic element of the first doping element (e.g., B) is not detected is recorded, along with the distance between that location and the first tunneling oxide layer. This serves as the diffusion depth of the first doping element. The location in the second region where a characteristic element of the second doping element (e.g., P) is not detected is recorded, along with the distance between that location and the second tunneling oxide layer. This serves as the diffusion depth of the second doping element.

[0135] (2) Test method for impurity concentration

[0136] Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the concentration of impurities at different locations on the silicon substrate.

[0137] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate (1), the silicon substrate (1) having a first surface and a second surface opposite to each other, the first surface being provided with a first region (110), a second region (120), and an isolation region (130) located between the first region (110) and the second region (120); The first region (110) comprises a first tunneling oxide layer (2), a first doped polysilicon layer (3), a first passivation layer (71), and a first electrode (8) which are sequentially arranged along the thickness direction of the silicon substrate (1); The second region (120) comprises a second tunneling oxide layer (4), a second doped polysilicon layer (5), a second passivation layer (72), and a second electrode (9) sequentially arranged along the thickness direction of the silicon substrate (1); The second surface is provided with a passivation anti-reflection layer (6); The first doped polysilicon layer (3) includes a first doping element, the second doped polysilicon layer (5) includes a second doping element, the first doped polysilicon layer (3) is a P-type doped polysilicon layer, and the second doped polysilicon layer (5) is an N-type doped polysilicon layer; The isolation region (130) is a groove, the sidewall of the groove near the second region (120) includes the second doping element, and the sum of the concentrations of the first doping element and the second doping element near the surface of the passivation anti-reflection layer (6) of the silicon substrate is less than 1×10 16 atom / cm 3 ; The silicon substrate (1) includes impurities, the impurities including at least one of iron, nickel, and chromium, and the concentration N of the impurities in the silicon substrate (1) corresponding to the first region (110) is 110 , the concentration N of impurities in the silicon substrate (1) corresponding to the isolation region (130) 130 , the concentration N of impurities in the silicon substrate (1) corresponding to the second region (120) 120 Satisfied: N 130 ≤N 120 <N 110 , 1×10 8 atom / cm 3 ≤N 130 ≤1×10 16 atom / cm 3 .

2. The back contact solar cell according to claim 1, wherein: The diffusion depth of the second doping element in the silicon substrate (1) is less than the diffusion depth of the first doping element in the silicon substrate (1), the diffusion depth of the first doping element in the silicon substrate (1) is 0.05 μm to 0.6 μm, and the diffusion depth of the second doping element in the silicon substrate (1) is 0.03 μm to 0.3 μm.

3. The back contact solar cell according to claim 2, characterized in that The diffusion depth of the first doping element in the silicon substrate (1) is 0.1 μm to 0.2 μm, and the diffusion depth of the second doping element in the silicon substrate (1) is 0.03 μm to 0.08 μm.

4. The back contact solar cell according to claim 3, characterized in that The diffusion depth of the second doping element in the silicon substrate (1) is 0.03 μm to 0.05 μm.

5. The back contact solar cell according to claim 1, wherein: The concentration N of impurities in the silicon substrate (1) corresponding to the first region (110) 110 , the concentration N of impurities in the silicon substrate (1) corresponding to the second region (120) 120 Meet at least one of the following conditions: 1×10 10 atom / cm 3 ≤N 110 ≤1×10 16 atom / cm 3 , 1×10 8 atom / cm 3 ≤N 120 ≤1×10 16 atom / cm 3 , 6. The back contact solar cell according to claim 5, characterized in that The concentration N of impurities on the surface of the silicon substrate close to the passivation anti-reflection layer (6) 101 Satisfied: N 101 ≤N 120 <N 110 .

7. The back contact solar cell according to claim 1, wherein: The concentration N of impurities on the surface of the silicon substrate close to the passivation anti-reflection layer (6) 101 Satisfy 1×10 10 atom / cm 3 ≤N 101 ≤1×10 15 atom / cm 3 .

8. The back contact solar cell according to claim 1, wherein: The concentration N of impurities on the surface of the silicon substrate close to the passivation anti-reflection layer (6) 101 The concentration N of the impurities in the isolation region (130) corresponding to the silicon substrate (1) 130 same.

9. The back contact solar cell according to claim 1, wherein: Along the thickness direction of the silicon substrate (1), and in a direction from the center position of the silicon substrate (1) toward the first surface or the second surface, the concentration of impurities in the silicon substrate (1) gradually increases.

10. The back contact solar cell according to claim 1, wherein: The first doping element includes B element, and the second doping element includes P element.

11. A method for preparing a back-contact solar cell according to claim 1, characterized in that: include: Preparing a first tunneling oxide layer (2) and a first polysilicon layer on a first surface of a silicon substrate (1); A first doping source is doped into a silicon substrate (1) provided with the first polysilicon layer by thermal diffusion to obtain a first doped polysilicon layer (3), wherein the thermal diffusion temperature of the first doping source is 910° C. to 1000° C., and the thermal diffusion time of the first doping source is 10 min to 60 min; performing an etching process on the second region (120) of the silicon substrate (1) provided with the first doped polysilicon layer (3) and the first tunneling oxide layer (2) to expose the second region (120) of the silicon substrate (1); preparing a second tunneling oxide layer (4) and a second polysilicon layer on the first surface of the second region (120) of the silicon substrate (1); A second doping source is doped into a silicon substrate (1) provided with the second polysilicon layer by thermal diffusion to obtain a second doped polysilicon layer (5), wherein the thermal diffusion temperature of the second doping source is 850° C. to 920° C., and the thermal diffusion time of the second doping source is 3 min to 60 min; An isolation region (130) is provided between the first doped polysilicon layer (3) and the second doped polysilicon layer (5); Disposing a first passivation layer (71) and a second passivation layer (72) on the surfaces of the first doped polysilicon layer (3) and the second doped polysilicon layer (5), respectively; A first electrode (8) and a second electrode (9) are prepared on the surfaces of the first passivation layer (71) and the second passivation layer (72), respectively.

12. The method for preparing a back-contact solar cell according to claim 11, wherein: The thermal diffusion temperature of the first doping source is 960° C. to 980° C., and the thermal diffusion time of the first doping source is 20 min to 40 min; The thermal diffusion temperature of the second doping source is 890° C. to 910° C., and the thermal diffusion time of the second doping source is 5 min to 30 min.

13. The method for preparing a back contact solar cell according to claim 11, wherein: The first doping source includes BCl 3 , and the second doping source includes POCl 3 .

14. A photovoltaic module, characterized in that: Comprising a back-contact solar cell according to any one of claims 1-10.

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