Back contact photovoltaic cell with high concentration co-doped regions and method of manufacture and use

Abstract

The application belongs to the technical field of back contact photovoltaic cells, and particularly relates to a back contact photovoltaic cell with a high-concentration co-doped region, a preparation method and application, which comprises setting N-type doped regions and P-type doped regions which are alternately distributed on the back light surface of an intrinsic amorphous silicon layer, and setting a high-concentration co-doped region between the N-type doped regions and the P-type doped regions, wherein the doping source of the co-doped region comprises a doping source phosphorus of the N-type doped region and a doping source boron of the P-type doped region, the co-doped region and the doping sources of the N-type doped regions and the P-type doped regions form a specific concentration gradient structure, and the specific concentration gradient structure satisfies that the doping concentration of phosphorus contained in the co-doped region is greater than the phosphorus doping concentration in the N-type doped region, and the doping concentration of boron contained in the co-doped region is greater than the boron doping concentration in the P-type doped region. The application optimizes the carrier transport and collection efficiency, improves the fill factor and open-circuit voltage, improves the cell conversion efficiency and stability, and the preparation process is simple and does not need multiple etching openings.

Description

Technical Field

[0001] This invention belongs to the field of back-contact photovoltaic cell technology, specifically relating to a back-contact photovoltaic cell with a high concentration of co-doped regions, its manufacturing method, and its application. Background Technology

[0002] In traditional photovoltaic cell structures, carrier recombination within the cell is an unavoidable phenomenon, severely impacting conversion efficiency. To reduce carrier recombination, researchers have explored various methods, including optimizing cell structure, improving material properties, and employing novel cell technologies. For example, introducing passivation layers can reduce surface recombination, or heterojunction structures can improve carrier separation efficiency. However, these methods have limitations in practical applications, such as high cost, complex processes, and limited effectiveness.

[0003] Despite progress in reducing carrier recombination, existing technologies still present several challenges and limitations: First, traditional passivation layer materials and structural designs struggle to effectively suppress carrier recombination, resulting in limited improvements in open-circuit voltage and fill factor. Second, while heterojunction structures can enhance carrier separation efficiency, their fabrication processes are complex (requiring multiple etching processes for openings) and costly, hindering large-scale application. Furthermore, while existing technologies improve battery conversion efficiency, they often come at the cost of unstable battery performance and shortened battery life.

[0004] It should be noted that this part of the present invention only provides background technology related to the present invention, and does not necessarily constitute prior art or known technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing back-contact photovoltaic cells, such as limited improvement in open-circuit voltage and fill factor, limited improvement in cell conversion efficiency, and inability to simultaneously address the complex fabrication process. This invention provides a back-contact photovoltaic cell with a high concentration of co-doped regions, its fabrication method, and its application. This invention optimizes carrier transport and collection efficiency, improves fill factor and open-circuit voltage, enhances cell conversion efficiency and stability, and simplifies the fabrication process, eliminating the need for multiple etching of openings.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a back-contact photovoltaic cell with a high-concentration co-doped region. The back-contact photovoltaic cell includes a silicon substrate, an intrinsic amorphous silicon layer disposed on the back surface of the silicon substrate, and alternating N-type doped regions and P-type doped regions disposed on the back surface of the intrinsic amorphous silicon layer. A high-concentration co-doped region is disposed between the N-type doped regions and the P-type doped regions. The doping source of the co-doped region includes phosphorus doping source of the N-type doped region and boron doping source of the P-type doped region. The co-doped region and the doping sources of the N-type and P-type doped regions form a specific concentration gradient structure, and the specific concentration gradient structure satisfies that: the phosphorus doping concentration in the co-doped region is greater than the phosphorus doping concentration in the N-type doped region, and the boron doping concentration in the co-doped region is greater than the boron doping concentration in the P-type doped region.

[0007] In some preferred embodiments of the present invention, the ratio of the highest phosphorus doping concentration in the co-doped region to the highest phosphorus doping concentration in the N-type doped region is (1.1-10):1, and / or the ratio of the highest boron doping concentration in the co-doped region to the highest boron doping concentration in the P-type doped region is (1.05-8):1.

[0008] In some preferred embodiments of the present invention, the ratio of the highest phosphorus doping concentration in the co-doped region to the highest phosphorus doping concentration in the N-type doped region is (1.3-5):1, and / or the ratio of the highest boron doping concentration in the co-doped region to the highest boron doping concentration in the P-type doped region is (1.2-3.5):1.

[0009] In some preferred embodiments of the present invention, the phosphorus doping concentration and boron doping concentration in the co-doped region are each independently at 2e19cm. -3 -5e23cm -3 ; and / or,

[0010] The phosphorus doping concentration in the N-type doped region is 2e18cm⁻¹ -3 -8e22cm -3 The boron doping concentration in the P-type doped region is 2e18cm. -3 -8e22cm -3 .

[0011] In some preferred embodiments of the present invention, the co-doped region has hydrogen doping, and the hydrogen doping concentration in the co-doped region is higher than that in the N-type doped region and / or the P-type doped region.

[0012] In some preferred embodiments of the present invention, the ratio of hydrogen doping concentration in the co-doped region to that in the N-type or P-type doped region is (0.5-3):1, and / or the hydrogen doping concentration in the co-doped region is 1e19cm. -3 -5e22cm -3 .

[0013] In some preferred embodiments of the present invention, the back-contact photovoltaic cell also has at least one of the following structures:

[0014] Structure 1: The width ratio of the co-doped region to the N-type doped region or P-type doped region is (0.01-0.4):1, and / or the thickness ratio of the co-doped region to the N-type doped region or P-type doped region is (0.5-1.4):1;

[0015] Structure 2: The width of the co-doped region is 5-130 μm, and / or the thickness of the co-doped region is 5-30 nm;

[0016] Structure 3: The widths of the N-type doped region and the P-type doped region are each independently between 200-1000 μm, and / or the thicknesses of the N-type doped region and the P-type doped region are each independently between 5-20 nm;

[0017] Structure 4: The thickness of the intrinsic amorphous silicon layer is 5-15 nm, and / or the ratio of the thickness of the intrinsic amorphous silicon layer to the thickness of the N-type doped region or the P-type doped region is (0.3-2):1;

[0018] Structure 5: In the width direction, the N-type doped region and the co-doped region, as well as the co-doped region and the P-type doped region, are in contact with each other and are distributed continuously as a whole;

[0019] Structure 6: The N-type doped region and the P-type doped region are doped regions formed after doping a portion of the intrinsic amorphous silicon layer, or they are additional doped film layers deposited on the back surface of the intrinsic amorphous silicon layer.

[0020] Structure 7: The back contact photovoltaic cell also includes a light-receiving surface passivation and anti-reflection layer disposed on the light-receiving surface of the silicon substrate;

[0021] Structure 8, the back contact photovoltaic cell also includes: a conductive film layer disposed on the outer surface of the N-type doped region and the P-type doped region, and a metal electrode disposed outside the conductive film layer, wherein an isolation trench is disposed between the conductive film layer disposed on the outer surface of the N-type doped region and the conductive film layer disposed on the outer surface of the P-type doped region, and at least a portion of the isolation trench is located on the outer surface of the co-doped region.

[0022] Structure 9: The light-receiving surface of the silicon substrate is a textured surface, and the back-lighting surface is a polished surface.

[0023] Secondly, the present invention provides a method for preparing a back-contact photovoltaic cell, which is used to prepare the back-contact photovoltaic cell with a high concentration of co-doped region as described in the first aspect. The preparation method includes the following steps:

[0024] S1, Provides a silicon substrate;

[0025] S2. Deposit an intrinsic amorphous silicon layer on the back surface of a silicon substrate;

[0026] S3. Alternating N-type doped regions, P-type doped regions, and co-doped regions between the N-type doped regions and P-type doped regions are pre-distributed on the outer surface of the intrinsic amorphous silicon layer.

[0027] An N-type doped region, a P-type doped region, and a co-doped region are formed in each preset region using a template method. The phosphorus doping concentration in the co-doped region is controlled to be greater than that in the N-type doped region, and the boron doping concentration in the co-doped region is greater than that in the P-type doped region, thus forming a specific concentration gradient structure.

[0028] In some preferred embodiments of the present invention, the preparation method further includes at least one of the following processes:

[0029] Process 1: The template method is used to form N-type doped regions, P-type doped regions, and co-doped regions in each preset region, respectively. The process includes: using the template method to dope each preset region with target dopant ions, thereby forming N-type doped regions, P-type doped regions, and co-doped regions respectively.

[0030] Process 2, the preparation method also includes:

[0031] S4. A conductive film is deposited on the outer surface of the intrinsic amorphous layer after S3 doping, and an isolation trench is formed by opening in at least a portion of the conductive film located on the outer surface of the co-doped region.

[0032] S5. Metal electrodes are formed on the outer surface of the conductive film in the corresponding regions of the N-type doped region and the P-type doped region, respectively.

[0033] Thirdly, the present invention provides a photovoltaic module, including a back-contact photovoltaic cell with a high concentration of co-doped region as described in the first aspect, or a back-contact photovoltaic cell prepared by the method described in the second aspect.

[0034] Beneficial effects:

[0035] This invention, through the aforementioned technical solution, particularly by setting a high-concentration co-doped region between the N-type and P-type doped regions, and by forming a specific concentration gradient structure between this co-doped region and the doping sources of the N-type and P-type doped regions, optimizes carrier transport and collection efficiency, effectively reduces carrier recombination, improves the fill factor and open-circuit voltage, and enhances battery conversion efficiency and stability. One possible explanation for this specific concentration gradient structure's ability to improve battery conversion efficiency is that the strong built-in electric field formed within the high-concentration co-doped region forces electrons and holes away from each other, reducing their chances of meeting and recombination at interface defects, thus creating efficient "field-effect passivation." This prevents carrier diffusion to the interface, fundamentally reducing the interface recombination rate and allowing more carriers to be effectively collected by the electrodes; significantly increasing the open-circuit voltage, thereby significantly improving battery conversion efficiency; and by coordinating the doping concentration of the co-doped region with the doping concentrations of the N-type and P-type doped regions to obtain a specific concentration gradient structure, optimizing carrier transport and collection efficiency, improving the fill factor, further enhancing battery conversion efficiency, and simultaneously improving battery stability.

[0036] Compared with the complex preparation process of existing heterojunction structures, the preparation method of this invention simplifies the preparation process, reduces production costs, and is conducive to large-scale application; at the same time, it also improves battery conversion efficiency.

[0037] In a preferred embodiment of the present invention, the co-doped region adopts a moderately higher H doping concentration compared to the N-type doped region and the P-type doped region, which can further reduce recombination, optimize transport, and avoid causing battery performance degradation. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a specific embodiment of the back-contact photovoltaic cell of the present invention.

[0040] Explanation of reference numerals in the attached figures

[0041] 1. Silicon substrate; 2. Intrinsic amorphous silicon layer; 3. N-type doped region; 4. P-type doped region; 5. Co-doped region; 6. Conductive film layer; 7. Isolation trench; 8. Metal electrode. Detailed Implementation

[0042] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoint values ​​of the ranges, the endpoint values ​​of the ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "optional" mean that they may or may not be included (or may or may not be present).

[0045] In this invention, the area closer to the silicon substrate is considered the inside, and the area farther from the silicon substrate is considered the outside.

[0046] In a first aspect, the present invention provides a back-contact photovoltaic cell with a high-concentration co-doped region. The back-contact photovoltaic cell includes a silicon substrate, an intrinsic amorphous silicon layer disposed on the back surface of the silicon substrate, and alternating N-type and P-type doped regions disposed on the back surface of the intrinsic amorphous silicon layer. A high-concentration co-doped region is disposed between the N-type and P-type doped regions. The doping source of the co-doped region includes phosphorus from the N-type doped region and boron from the P-type doped region. The co-doped region and the doping sources of the N-type and P-type doped regions form a specific concentration gradient structure, which satisfies the following conditions: the phosphorus doping concentration in the co-doped region is greater than the phosphorus doping concentration in the N-type doped region, and the boron doping concentration in the co-doped region is greater than the boron doping concentration in the P-type doped region. The back-contact photovoltaic cell of the present invention has a specific concentration gradient structure including a high-concentration co-doped region, which optimizes carrier transport and collection efficiency, effectively reduces carrier recombination, improves the fill factor and open-circuit voltage, and improves cell conversion efficiency and stability.

[0047] In some preferred embodiments of the present invention, the ratio of the highest phosphorus doping concentration in the co-doped region to the highest phosphorus doping concentration in the N-type doped region is (1.1-10):1, specifically, it can be 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 2.9:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, or any range between any two points.

[0048] In some preferred embodiments of the present invention, the ratio of the highest phosphorus doping concentration in the co-doped region to the highest phosphorus doping concentration in the N-type doped region is (1.3-5):1. This preferred embodiment further improves electron collection efficiency.

[0049] In some preferred embodiments of the present invention, the ratio of the highest boron doping concentration in the co-doped region to the highest boron doping concentration in the P-type doped region is (1.05-8):1, specifically, it can be 1.05:1, 1.08:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.75:1, 1.8:1, 1.83:1, 1.84:1, 1.85:1, 1.87:1, 1.9:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 2.9:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, or 8:1, as well as any range between two points.

[0050] In some preferred embodiments of the present invention, the ratio of the highest boron doping concentration in the co-doped region to the highest boron doping concentration in the P-type doped region is (1.2-3.5):1, which is more conducive to improving the hole collection efficiency.

[0051] In some preferred embodiments of the present invention, the phosphorus doping concentration and boron doping concentration in the co-doped region are each independently at 2e19cm. -3 -5e23cm -3 The phosphorus dopant and boron dopant contained in the co-doped region of the present invention can each be uniformly doped or non-uniformly doped. Non-uniform doping, such as gradient doping, is acceptable as long as it satisfies the specific concentration gradient structure of the present application that includes a high-concentration co-doped region.

[0052] In some preferred embodiments of the present invention, the phosphorus doping concentration in the N-type doped region is 2e18cm⁻¹. -3 -8e22cm-3 The boron doping concentration in the P-type doped region is 2e18cm. -3 -8e22cm -3 .

[0053] In some preferred embodiments of the invention, the co-doped region is hydrogen-doped.

[0054] Preferably, the hydrogen doping concentration in the co-doped region is higher than that in the N-type doped region and / or P-type doped region. The co-doped region of this invention employs a moderately higher H doping concentration compared to the N-type and P-type doped regions, which can further reduce recombination, optimize transport, and avoid causing battery performance degradation.

[0055] In some preferred embodiments of the present invention, the ratio of hydrogen doping concentration in the co-doped region to hydrogen doping concentration in the N-type doped region or P-type doped region is (0.5-3):1, specifically 0.5:1, 0.6:1, 0.7:1, 0.8:1, 1:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.4:1, 1.45:1, 1.5:1, 1.55:1, 1.6:1, 1.7:1, 1.75:1, 1.8:1, 1.83:1, 1.84:1, 1.85:1, 1.87:1, 1.9:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 2.9:1, or 3:1, as well as any range between two points. This preferred approach is more conducive to reducing bulk and interface defects in the co-doped region, thereby further effectively reducing carrier recombination, improving the fill factor and open-circuit voltage, and enhancing battery conversion efficiency and stability.

[0056] In some preferred embodiments of the present invention, the hydrogen doping concentration of the co-doped region is 1e19cm⁻¹. -3 -5e22cm -3 .

[0057] In some preferred embodiments of the present invention, the width ratio of the co-doped region to the N-type doped region or P-type doped region is (0.01-0.4):1, specifically, it can be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.1:1, 0.12:1, 0.15:1, 0.17:1, 0.2:1, 0.22:1, 0.25:1, 0.27:1, 0.3:1, 0.32:1, 0.35:1, 0.37:1, 0.39:1, or 0.4:1, or any range between any two values. The present invention employs a suitable width ratio for the co-doped region and the N-type doped region or P-type doped region, which is more conducive to suppressing interface recombination and reducing the risk of short circuits.

[0058] In some preferred embodiments of the present invention, the thickness ratio of the co-doped region to the N-type doped region or P-type doped region is (0.5-1.4):1, specifically, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.3:1, 1.35:1, or 1.4:1, or any range between any two values. The present invention employs a suitable thickness ratio for the co-doped region and the N-type or P-type doped region, which is more conducive to forming effective field passivation and preventing leakage current.

[0059] In some preferred embodiments of the present invention, the width of the co-doped region is 5-130 μm.

[0060] In some preferred embodiments of the present invention, the thickness of the co-doped region is 5-30 nm.

[0061] In some preferred embodiments of the present invention, the widths of the N-type doped region and the P-type doped region are each independently between 200-1000 μm. The widths of the N-type doped region and the P-type doped region may be the same or different.

[0062] In some preferred embodiments of the present invention, the thicknesses of the N-type doped region and the P-type doped region are each independently between 5-20 nm. The thicknesses of the N-type doped region and the P-type doped region may be the same or different.

[0063] In some preferred embodiments of the present invention, the thickness of the intrinsic amorphous silicon layer is 5-15 nm.

[0064] In some preferred embodiments of the present invention, the ratio of the thickness of the intrinsic amorphous silicon layer to the thickness of the N-type doped region or P-type doped region is (0.3-2):1, specifically, it can be 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.3:1, 1.35:1, 1.4:1, 1.5:1, 1.7:1, 1.8:1, 1.9:1, or 2:1, or any range between any two values. The present invention employs an intrinsic amorphous silicon layer with an appropriate thickness ratio to the N-type doped region or P-type doped region, which is more conducive to achieving good passivation and selective contact of charge carriers, thereby improving the conversion efficiency of the battery.

[0065] In some preferred embodiments of the present invention, the N-type doped region and the co-doped region, and the co-doped region and the P-type doped region are in contact with each other and are distributed continuously in the width direction.

[0066] In some preferred embodiments of the present invention, the N-type doped region and the P-type doped region are respectively doped regions formed after doping a portion of the intrinsic amorphous silicon layer, or respectively doped film layers additionally deposited on the back surface of the intrinsic amorphous silicon layer.

[0067] In some preferred embodiments of the present invention, the back-contact photovoltaic cell further includes a light-receiving surface passivation and anti-reflection layer disposed on the light-receiving surface of the silicon substrate. The light-receiving surface passivation and anti-reflection layer includes a passivation layer and / or an anti-reflection layer, and specific details can be found in the prior art, both of which can be used in the present invention.

[0068] In some preferred embodiments of the present invention, the back-contact photovoltaic cell further includes: a conductive film layer disposed on the outer surfaces of the N-type doped region and the P-type doped region, and a metal electrode disposed outside the conductive film layer, wherein an isolation groove is disposed between the conductive film layer disposed on the outer surface of the N-type doped region and the conductive film layer disposed on the outer surface of the P-type doped region, and at least a portion of the isolation groove is located on the outer surface of the co-doped region.

[0069] The light-receiving surface and the back-lighting surface of the silicon substrate of the present invention can each be a textured surface or a polished surface. In some preferred embodiments of the present invention, the light-receiving surface of the silicon substrate is a textured surface and the back-lighting surface is a polished surface.

[0070] Secondly, the present invention provides a method for preparing a back-contact photovoltaic cell, which is used to prepare the back-contact photovoltaic cell with a high concentration of co-doped region as described in the first aspect. The preparation method includes the following steps:

[0071] S1, Provides a silicon substrate;

[0072] S2. Deposit an intrinsic amorphous silicon layer on the back surface of a silicon substrate;

[0073] S3. Alternating N-type doped regions, P-type doped regions, and co-doped regions between the N-type doped regions and P-type doped regions are pre-distributed on the outer surface of the intrinsic amorphous silicon layer.

[0074] An N-type doped region, a P-type doped region, and a co-doped region are formed in each preset region using a template method. The phosphorus doping concentration in the co-doped region is controlled to be greater than that in the N-type doped region, and the boron doping concentration in the co-doped region is greater than that in the P-type doped region, thus forming a specific concentration gradient structure.

[0075] The pre-defined alternating distribution of N-type doped regions, P-type doped regions, and co-doped regions between the N-type and P-type doped regions on the outer surface of the intrinsic amorphous silicon layer refers to dividing the area into three regions at the locations where the N-type doped regions, P-type doped regions, and co-doped regions need to be set, to facilitate subsequent steps.

[0076] The formation of N-type doped regions, P-type doped regions, and co-doped regions can be achieved by doping a portion of the intrinsic amorphous silicon layer or by depositing a new film layer on the outer surface of the intrinsic amorphous silicon layer.

[0077] In some preferred embodiments of the present invention, the process of forming N-type doped regions, P-type doped regions, and co-doped regions in each preset region using a template method includes: doping each preset region with target dopant ions using a template method, thereby forming N-type doped regions, P-type doped regions, and co-doped regions respectively. Specifically, an intrinsic amorphous silicon layer can be formed first, followed by regional ion doping in the areas not covered by the template; alternatively, a template can be directly used to mask non-target doped regions to form N-type doped regions, P-type doped regions, and co-doped regions respectively. Specific doping methods can refer to existing technologies, as long as the target structure film layer of the present invention is obtained through doping, and will not be elaborated further here.

[0078] In some preferred embodiments of the present invention, the process of forming N-type doped regions, P-type doped regions, and co-doped regions in each preset area using the template method includes: firstly, using a first hard mask to block the preset P-type doped region and the preset co-doped region on the backlight surface, and growing N-type doped silicon of the target thickness on the backlight surface to form an N-type doped region; then, using a second hard mask to block the preset N-type doped region and the preset co-doped region on the backlight surface, and growing P-type doped silicon of the target thickness to form a P-type doped region; finally, using a third hard mask to block the N-type doped region and the P-type doped region, and growing a co-doped region of the target thickness.

[0079] In some preferred embodiments of the present invention, the preparation method further includes: S4, depositing a conductive film layer on the outer surface of the intrinsic amorphous layer after S3 doping, and forming an isolation trench by opening an opening in at least a portion of the conductive film layer located on the outer surface of the co-doped region.

[0080] The preparation method of the present invention may also include the preparation of other conventional films. In some preferred embodiments of the present invention, S5, metal electrodes are formed on the outer surface of the conductive film in the corresponding regions of the N-type doped region and the P-type doped region, respectively.

[0081] Compared with the complex preparation process of existing heterojunction structures, the preparation method of this invention simplifies the preparation process, reduces production costs, and is conducive to large-scale application; at the same time, it also improves battery conversion efficiency.

[0082] Thirdly, the present invention provides a photovoltaic module, including a back-contact photovoltaic cell with a high concentration of co-doped region as described in the first aspect, or a back-contact photovoltaic cell prepared by the method described in the second aspect.

[0083] The embodiments of the present invention described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0084] Example 1

[0085] A back-contact photovoltaic cell, the structure of which is as follows: Figure 1 As shown, the specific steps include the following:

[0086] S1, Provide silicon substrate 1;

[0087] S2. An intrinsic amorphous silicon layer 2 with a thickness of 13 nm is deposited on the back surface of the silicon substrate 1.

[0088] S3. An alternating N-type doped region 3, a P-type doped region 4, and a co-doped region 5 between the N-type doped region 3 and the P-type doped region 4 are pre-distributed on the outer surface of the intrinsic amorphous silicon layer 2.

[0089] A template method is used to dope each preset region with target dopant ions, forming an N-type doped region 3, a P-type doped region 4, and a co-doped region 5. During the formation of the target doped region, other non-target doped regions are first masked before doping, thus forming the N-type doped region 3, P-type doped region 4, and co-doped region 5 sequentially. The phosphorus doping concentration in the co-doped region 5 is controlled to be higher than that in the N-type doped region 3, and the boron doping concentration in the co-doped region 5 is controlled to be higher than that in the P-type doped region 4, forming a specific concentration gradient structure. The phosphorus and boron doping concentrations in the co-doped region 5 are controlled to be 1e22cm⁻¹. -3 9.2e21cm -3 The hydrogen doping concentration is 5e21cm. -3 The co-doped region 5 has a width of 20 μm and a thickness of 6 nm. The phosphorus doping concentration in the N-type doped region 3 is 7e21cm³. -3 The hydrogen doping concentration is 4e21cm. -3 The width is 300 μm and the thickness is 7 nm. The boron doping concentration in P-type doped region 4 is 5e21 cm⁻¹. -3 The hydrogen doping concentration is 5e21cm. -3 The width is 500 μm and the thickness is 10 nm. Calculations show that the phosphorus doping concentration ratio in co-doped region 5 to that in N-type doped region 3 is 1.4:1; the boron doping concentration ratio in co-doped region 5 to that in P-type doped region 4 is 1.8:1; the hydrogen doping concentration ratio in co-doped region 5 to that in N-type doped region 3 is 1.25:1; and the hydrogen doping concentration ratio in co-doped region 5 to that in P-type doped region 4 is 1:1.

[0090] S4. A mask is applied to the outer surface of the co-doped region 5 using a template method. Then, a transparent conductive film layer 6 (i.e., ITO) with a thickness of 60 nm is deposited on the outer surface of the intrinsic amorphous layer after S3 doping. An isolation trench 7 is formed in the masked area.

[0091] S5. Metal electrodes 8 are formed on the outer surfaces of the conductive film layers 6 in the corresponding regions of N-type doped region 3 and P-type doped region 4, respectively.

[0092] Example 2

[0093] The procedure was carried out in accordance with Example 1, except that the phosphorus doping concentration in the co-doped region 5 was adjusted to 2e22cm. -3 This results in a phosphorus doping concentration ratio of 2.8:1 between the phosphorus doping concentration in the co-doped region 5 and the phosphorus doping concentration in the N-type doped region 3.

[0094] Example 3

[0095] The procedure was carried out in accordance with Example 1, except that the boron doping concentration in the co-doped region 5 was adjusted to 1.5e22cm. -3 This results in a boron doping concentration ratio of 3:1 between the boron doping concentration in the co-doped region 5 and the boron doping concentration in the P-type doped region 4.

[0096] Example 4

[0097] The procedure was carried out in accordance with Example 1, except that the H doping concentration in the co-doped region 5 was adjusted to 4e21cm. -3 This results in the ratios of hydrogen doping concentration in co-doped region 5 to hydrogen doping concentration in N-type doped region 3 and P-type doped region 4 being 1:1 and 0.8:1, respectively.

[0098] Example 5

[0099] The procedure was carried out in accordance with Example 1, except that the H doping concentration in the co-doped region 5 was adjusted to 6e21cm. -3 This results in the ratios of hydrogen doping concentration in co-doped region 5 to hydrogen doping concentration in N-type doped region 3 and P-type doped region 4 being 1.5:1 and 1.2:1, respectively.

[0100] Example 6

[0101] The same procedure was followed as in Example 1, except that the width of the co-doped region 5 was adjusted to 30 μm, so that the width ratio of the co-doped region 5 to the width of the N-type doped region 3 and the P-type doped region 4 was 0.1:1 and 0.06:1, respectively.

[0102] Comparative Example 1

[0103] The procedure was carried out in accordance with Example 1, except that the phosphorus doping concentration in the co-doped region 5 was adjusted to 6e21cm. -3 This results in a phosphorus doping concentration ratio of 0.86:1 between the phosphorus doping concentration in the co-doped region 5 and the phosphorus doping concentration in the N-type doped region 3.

[0104] Comparative Example 2

[0105] The procedure was carried out in accordance with Example 1, except that the boron doping concentration in the co-doped region 5 was adjusted to 5e21cm. -3This results in a boron doping concentration ratio of 1:1 between the boron doping concentration in the co-doped region 5 and the boron doping concentration in the P-type doped region 4.

[0106] Test case

[0107] The back-contact photovoltaic cells obtained in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0108] Table 1

[0109] Performance indicators Open circuit voltage (V) Fill factor (%) Battery conversion efficiency (%) Reverse leakage current (A) Example 1 0.7483 85.6 27.16 0.08 Example 2 0.7477 85.3 27.08 0.10 Example 3 0.7472 85.3 27.02 0.13 Example 4 0.7465 85.4 27.05 0.11 Example 5 0.7474 85.2 27.00 0.09 Example 6 0.7479 85.3 27.05 0.10 Comparative Example 1 0.7462 85.1 26.90 0.15 Comparative Example 2 0.7460 84.9 26.85 0.16

[0110] The results above show that, compared with the comparative example, the embodiment of the present invention is beneficial to improving the fill factor and open-circuit voltage, and thus improving the battery conversion efficiency and stability.

[0111] Furthermore, as can be seen from Examples 1 and 2-6, the preferred scheme of the present invention is more conducive to improving the fill factor and open circuit voltage, and improving the battery conversion efficiency and stability.

[0112] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A back-contact photovoltaic cell with a high concentration of co-doped regions, characterized in that, This back-contact photovoltaic cell includes a silicon substrate, an intrinsic amorphous silicon layer disposed on the back surface of the silicon substrate, and alternating N-type and P-type doped regions disposed on the back surface of the intrinsic amorphous silicon layer. A high-concentration co-doped region is disposed between the N-type and P-type doped regions. The doping source of the co-doped region includes phosphorus from the N-type doped region and boron from the P-type doped region. The co-doped region, together with the doping sources of the N-type and P-type doped regions, forms a specific concentration gradient structure. This specific concentration gradient structure satisfies the following conditions: the phosphorus doping concentration in the co-doped region is greater than the phosphorus doping concentration in the N-type doped region, and the boron doping concentration in the co-doped region is greater than the boron doping concentration in the P-type doped region. The phosphorus and boron doping concentrations in the co-doped region are each independently within a 2e19 cm⁻¹. -3 -5e23cm -3 The phosphorus doping concentration in the N-type doped region is 2e18cm. -3 -8e22cm -3 The boron doping concentration in the P-type doped region is 2e18cm. -3 -8e22cm -3 .

2. The back contact photovoltaic cell with a high concentration of co-doped region according to claim 1, characterized in that, The ratio of the highest phosphorus doping concentration in the co-doped region to the highest phosphorus doping concentration in the N-type doped region is (1.1-10):1, and / or the ratio of the highest boron doping concentration in the co-doped region to the highest boron doping concentration in the P-type doped region is (1.05-8):

1.

3. The back contact photovoltaic cell with a high concentration of co-doped region according to claim 2, characterized in that, The ratio of the highest phosphorus doping concentration in the co-doped region to the highest phosphorus doping concentration in the N-type doped region is (1.3-5):

1.

4. The back contact photovoltaic cell with a high concentration of co-doped region according to claim 2, characterized in that, The ratio of the highest boron doping concentration in the co-doped region to the highest boron doping concentration in the P-type doped region is (1.2-3.5):

1.

5. The back-contact photovoltaic cell with a high concentration of co-doped region according to any one of claims 1-4, characterized in that, The co-doped region is hydrogen-doped, and the hydrogen doping concentration in the co-doped region is higher than that in the N-type doped region and / or P-type doped region.

6. The back-contact photovoltaic cell with a high concentration of co-doped regions according to claim 5, characterized in that, The ratio of hydrogen doping concentration in the co-doped region to that in the N-type or P-type doped region is (0.5-3):1, and / or the hydrogen doping concentration in the co-doped region is 1e19cm. -3 -5e22cm -3 .

7. The back-contact photovoltaic cell with a high concentration of co-doped region according to any one of claims 1-4, characterized in that, Back-contact photovoltaic cells also have at least one of the following structures: Structure 1: The width ratio of the co-doped region to the N-type doped region or P-type doped region is (0.01-0.4):1, and / or the thickness ratio of the co-doped region to the N-type doped region or P-type doped region is (0.5-1.4):1; Structure 2: The width of the co-doped region is 5-130 μm, and / or the thickness of the co-doped region is 5-30 nm; Structure 3: The widths of the N-type doped region and the P-type doped region are each independently between 200-1000 μm, and / or the thicknesses of the N-type doped region and the P-type doped region are each independently between 5-20 nm; Structure 4: The thickness of the intrinsic amorphous silicon layer is 5-15 nm, and / or the ratio of the thickness of the intrinsic amorphous silicon layer to the thickness of the N-type doped region or the P-type doped region is (0.3-2):1; Structure 5: In the width direction, the N-type doped region and the co-doped region, as well as the co-doped region and the P-type doped region, are in contact with each other and are distributed continuously as a whole; Structure 6: The N-type doped region and the P-type doped region are doped regions formed after doping a portion of the intrinsic amorphous silicon layer, or they are additional doped film layers deposited on the back surface of the intrinsic amorphous silicon layer. Structure 7: The back contact photovoltaic cell also includes a light-receiving surface passivation and anti-reflection layer disposed on the light-receiving surface of the silicon substrate; Structure 8, the back contact photovoltaic cell also includes: a conductive film layer disposed on the outer surface of the N-type doped region and the P-type doped region, and a metal electrode disposed outside the conductive film layer, wherein an isolation trench is disposed between the conductive film layer disposed on the outer surface of the N-type doped region and the conductive film layer disposed on the outer surface of the P-type doped region, and at least a portion of the isolation trench is located on the outer surface of the co-doped region. Structure 9: The light-receiving surface of the silicon substrate is a textured surface, and the backlighting surface is a polished surface.

8. A method for preparing a back-contact photovoltaic cell, characterized in that, It is used to prepare a back-contact photovoltaic cell with a high concentration of co-doped region as described in any one of claims 1-7, and its preparation method includes the following steps: S1, Provides a silicon substrate; S2. Deposit an intrinsic amorphous silicon layer on the back surface of a silicon substrate; S3. Alternating N-type doped regions, P-type doped regions, and co-doped regions between the N-type doped regions and P-type doped regions are pre-distributed on the outer surface of the intrinsic amorphous silicon layer. The template method is used to form N-type doped regions, P-type doped regions, and co-doped regions in the above-mentioned preset regions, respectively; wherein, the phosphorus doping concentration in the co-doped region is controlled to be greater than the phosphorus doping concentration in the N-type doped region, and the boron doping concentration in the co-doped region is greater than the boron doping concentration in the P-type doped region, thus forming a specific concentration gradient structure.

9. The method for preparing a back-contact photovoltaic cell according to claim 8, characterized in that, The preparation method also includes at least one of the following processes: Process 1: The above-mentioned preset regions are formed into N-type doped regions, P-type doped regions, and co-doped regions using the template method. The process includes: doping the above-mentioned preset regions with target dopant ions using the template method, thereby forming N-type doped regions, P-type doped regions, and co-doped regions respectively. Process 2, the preparation method also includes: S4. A conductive film is deposited on the outer surface of the intrinsic amorphous layer after S3 doping, and an isolation trench is formed by opening in at least a portion of the conductive film located on the outer surface of the co-doped region. S5. Metal electrodes are formed on the outer surface of the conductive film in the corresponding regions of the N-type doped region and the P-type doped region, respectively.

10. A photovoltaic module, characterized in that, Includes a back-contact photovoltaic cell with a high concentration of co-doped regions as described in any one of claims 1-7, or a back-contact photovoltaic cell prepared by the method described in claim 8 or 9.

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