A back contact solar cell and a solar cell module

Abstract

The application provides a back contact solar cell and a solar cell module. The back contact solar cell comprises a silicon substrate, the silicon substrate comprises a light-receiving surface and a back surface opposite to the light-receiving surface, and the back surface has a first region, a leakage recombination region and a second region arranged alternately in sequence along a direction perpendicular to the thickness of the silicon substrate; the first region and the second region have opposite doping polarities; along a direction away from the thickness of the silicon substrate, the leakage recombination region is sequentially provided with a tunneling medium layer, a first doped layer and a second doped layer in a stacked mode, the second doped layer protrudes from one side of the first region and has a brim structure; at least part of the brim structure contains a third doped layer, the third doped layer has a spacing with the first doped layer in a first direction, and the first direction is a direction in which the brim structure horizontally faces the first region. The application changes the transmission path of carriers, reduces the scattering and recombination probability of carriers in the transmission process, and improves the photocurrent of the cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a back-contact solar cell and a solar cell module. Background Technology

[0002] Back-contact solar cells (IBC cells) integrate both the emitter and base contact electrodes on the back surface (non-light-receiving surface) of the cell. Since there are no metal electrodes blocking the light-receiving surface, they can receive incident light to the maximum extent, effectively increasing the short-circuit current. At the same time, the optimized back electrode design can reduce the series resistance, making it one of the important directions of photovoltaic technology research.

[0003] In the fabrication of IBC cells, to achieve precise isolation between the emitter and base, suppress leakage current, and optimize carrier collection, a "brim" structure (i.e., a structure in which the doped layer protrudes into the first region) is typically constructed in the second region (the region outside the electrode contact area) of the backlight surface of the silicon substrate. In existing technologies, the doped layers (mostly polycrystalline silicon doped layers, or poly layers for short) in these brim structures are distributed in a continuous state.

[0004] However, this continuous brim structure has certain drawbacks: the doped layer under the brim structure has difficulty absorbing back-reflected light, reducing the absorption of photocurrent and lowering the efficiency of the solar cell.

[0005] Therefore, how to overcome the limitations of existing continuous-state doped layers, reduce carrier recombination, improve the carrier collection efficiency of the battery, and thus increase the photocurrent of the battery is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a back-contact solar cell and a solar cell module. By incorporating a third doped layer into the cap structure of the back-contact solar cell, the present invention successfully overcomes the limitations of existing continuous-state doped layers, altering the carrier transport path and reducing the scattering and recombination probabilities of carriers during transport. Furthermore, the third doped layer reduces the probability of carrier trapping, optimizes the carrier collection area, and enables more carriers to be effectively collected. Simultaneously, this unique cap structure allows for timely and efficient collection of more carriers, significantly improving the carrier collection efficiency of the cell and ultimately increasing the photocurrent, laying the foundation for improving the cell's conversion efficiency.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a back-contact solar cell, the back-contact solar cell comprising a silicon substrate, the silicon substrate comprising a light-receiving surface and a back-lighting surface facing away from each other, the back-lighting surface having a first region, a leakage recombination region and a second region arranged alternately in a direction perpendicular to the thickness of the silicon substrate; the doping polarities of the first region and the second region are opposite.

[0009] Along the thickness direction away from the silicon substrate, a tunneling dielectric layer, a first doped layer, and a second doped layer are sequentially stacked on the leakage recombination region, and the second doped layer protrudes to one side of the first region and has a brim structure.

[0010] At least a portion of the brim structure contains a third doped layer, the third doped layer having a gap with the first doped layer in a first direction, the first direction being the direction in which the brim structure is horizontally oriented toward the first region.

[0011] This invention successfully breaks through the limitations of existing continuous-state doped layers by setting an isolated third doped layer in the cap structure of the back-contact solar cell. This alters the carrier transport path and reduces the probability of carrier scattering and recombination during transport. Furthermore, the third doped layer reduces the probability of carrier capture, absorbs light reflected from the back, and optimizes the carrier collection area, enabling more carriers to be effectively collected. This significantly improves the carrier collection efficiency of the cell, ultimately increasing the photocurrent and laying the foundation for improving the cell's conversion efficiency.

[0012] In this application, the silicon substrate can be a P-type silicon wafer or an N-type silicon wafer, preferably an N-type silicon wafer, but no specific limitation is made here.

[0013] Preferably, the first region is an N-type doped region, and the second region is a P-type doped region. For example, the P-type doped region includes a first tunneling dielectric layer and a first doped layer; the N-type doped region includes an N-type doped layer.

[0014] Preferably, the transition between the leakage current composite area and the first area is a ramp transition.

[0015] Preferably, a first dielectric layer is stacked between the first doped layer and the second doped layer along the thickness direction away from the silicon substrate, and the material of the first dielectric layer includes doped silicon dioxide; wherein the doping polarities of the first doped layer and the second doped layer are opposite. For example, the first doped layer is an n-type doped polysilicon layer or a p-type doped polysilicon layer, and the second doped layer is a p-type doped polysilicon layer or an n-type doped polysilicon layer.

[0016] Preferably, the first dielectric layer protrudes to the side facing the first region and extends into the brim structure.

[0017] Preferably, the back contact solar cell further includes a tunneling oxide layer, which covers the silicon substrate, the tunneling dielectric layer and the side of the first doped layer near the first region in the thickness direction of the silicon substrate.

[0018] Preferably, the second doped layer continuously covers the first dielectric layer and the tunneling oxide layer.

[0019] Preferably, the region where the spacing is located also contains the second doped layer.

[0020] Preferably, the doping polarity of the third doped layer is the same as that of the first doped layer.

[0021] In this invention, the doping polarity of the third doped layer is the same as that of the first doped layer, and the cross-section of the third doped layer along the paper can be connected to the first doped layer, thereby achieving the effect of carrier separation through the built-in electric field.

[0022] Preferably, the length of the third doped layer in the first direction is 0.05μm-5μm, for example, it can be 0.05μm, 0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm, etc.

[0023] Preferably, the length of the third doped layer in the second direction is 0.05μm-10μm, for example, it can be 0.05μm, 0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm, etc.; the first direction and the second direction intersect each other on the same horizontal plane.

[0024] Preferably, the doping elements in the third doped layer include those in the first doped layer, and the doping concentration is 1×10⁻⁶. 19 cm -3 -20×10 19 cm -3 For example, it could be 1×10 19 cm -3 5×10 19 cm -3 10×10 19 cm -3 15×10 19 cm -3 Or 20×10 19 cm -3 wait.

[0025] Preferably, the doping elements of the third doped layer include the doping elements of the first doped layer and the doping elements of the second doped layer, which are respectively referred to as the first element and the second element.

[0026] Preferably, the doping concentration of the second element is 1-50% of the concentration of the doped element in the second doped layer, for example, it can be 1%, 5%, 10%, 20%, 30%, 40% or 50%.

[0027] Preferably, the doping concentration of the first element is 1×10⁻⁶. 19 cm -3 -20×10 19 cm -3 For example, it could be 1×10 19 cm -3 5×10 19 cm -3 10×10 19 cm -3 15×10 19 cm -3 Or 20×10 19 cm -3 wait.

[0028] Preferably, the doping concentration of the second element is 0.5 × 10⁻⁶. 20 cm -3 -4×10 20 cm -3 For example, it could be 0.5 × 10 20 cm -3 1×10 20 cm -3 2×10 20 cm -3 3×10 20 cm -3 Or 4×10 20 cm -3 wait.

[0029] Preferably, in the third doped layer, the concentration of the first element is greater than the concentration of the second element.

[0030] Preferably, along the thickness direction of the silicon substrate, the projected area of ​​the third doped layer on the silicon substrate accounts for 0.01%-10% of the total projected area of ​​the silicon substrate, for example, it can be 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0031] Preferably, the projected area of ​​a single third doped layer on the silicon substrate accounts for 0.001%-5% of the total projected area of ​​the silicon substrate, for example, it can be 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4% or 5%, etc.

[0032] Preferably, the brim structure includes a second dielectric layer.

[0033] Preferably, the surface of the third doped layer is at least partially phase-separated from the second doped layer by a second dielectric layer.

[0034] In this invention, the purpose of separating the surface of the third doped layer from the second doped layer by at least a partial phase through the second dielectric layer is to reduce local recombination losses caused by direct contact between the two.

[0035] Preferably, the material of the second dielectric layer includes any one or a combination of at least two of amorphous silicon, doped silicon oxide, silicon dioxide, aluminum oxide, or silicon oxynitride.

[0036] Preferably, the thickness of the second dielectric layer is 0.5nm-50nm, for example, it can be 0.5nm, 1nm, 3nm, 5nm, 10nm, 25nm or 50nm.

[0037] Preferably, the materials of the tunneling dielectric layer and the tunneling oxide layer each independently include any one or a combination of at least two of silicon dioxide, aluminum oxide, or silicon oxynitride.

[0038] Preferably, the thickness of the tunneling dielectric layer and the tunneling oxide layer are each independently 0.5nm-3nm, for example, 0.5nm, 0.8nm, 1.2nm, 1.6nm, 2nm, 2.5nm or 3nm, etc.

[0039] Preferably, the thickness of the second dielectric layer is 1nm-25nm.

[0040] Preferably, the first dielectric layer comprises a doped silicon dioxide layer. For example, it may be a phosphorus-doped SiO2 layer or a boron-doped SiO2 layer.

[0041] Preferably, the thickness of the first dielectric layer is 1nm-50nm, for example, it can be 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, etc.

[0042] Preferably, the material of the third doped layer is n-type doped polycrystalline silicon or p-type doped polycrystalline silicon.

[0043] Preferably, the thickness of the third doped layer along the thickness direction of the silicon substrate is 20nm-400nm, for example, it can be 20nm, 50nm, 100nm, 150nm, 180nm or 200nm, etc.

[0044] In this invention, a third doped layer of suitable thickness is beneficial to simplifying the preparation process, and can be formed simultaneously when preparing the first doped layer and the second doped layer.

[0045] Preferably, the thickness of the third doped layer along the thickness direction of the silicon substrate is 20nm-400nm, for example, it can be 20nm, 50nm, 100nm, 200nm, 300nm or 400nm.

[0046] In this invention, a third doped layer of suitable thickness is beneficial for enhancing local reflection in the brim area, increasing the reabsorption of photogenerated current, and improving the photoelectric conversion efficiency of the solar cell.

[0047] Preferably, the thickness of the first doped layer is 20nm-400nm, for example, it can be 20nm, 50nm, 80nm, 100nm, 150nm, 180nm, 200nm, 300nm or 400nm, etc.

[0048] Preferably, the thickness of the second doped layer is 30nm-200nm, for example, it can be 30nm, 50nm, 80nm, 100nm, 150nm, 180nm or 200nm, etc.

[0049] Preferably, the thickness ratio of the first doped layer to the second doped layer is 1:(0.3-3), for example, it can be 1:0.3, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0050] In a second aspect, the present invention provides a solar cell module, the solar cell module comprising a back-contact solar cell as described in the first aspect.

[0051] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] This invention successfully overcomes the limitations of existing continuous-state doped layers by incorporating a third doped layer in the cap structure of a back-contact solar cell. This alters the carrier transport path, reducing the scattering and recombination probabilities of carriers during transport. Furthermore, the third doped layer reduces the probability of carrier trapping, optimizes the carrier collection area, and allows for the effective collection of more carriers. Simultaneously, this unique cap structure increases the effective contact area between the third and second doped layers through the second dielectric layer. This increased contact area enables more carriers to be collected promptly and efficiently, significantly improving the cell's carrier collection efficiency and ultimately enhancing the photocurrent, thus laying the foundation for improving the cell's conversion efficiency. Attached Figure Description

[0054] Figure 1 This is a schematic cross-sectional view of a portion of the back structure of a solar cell provided in Embodiment 1 of the present invention.

[0055] Figure 2 This is a three-dimensional cross-sectional view of a portion of the back structure of the solar cell provided in Embodiment 1 of the present invention.

[0056] Figure 3 This is a cross-sectional SEM image of a portion of the back structure of the solar cell provided in Embodiment 1 of the invention.

[0057] Figure 4 This is a schematic cross-sectional view of a portion of the back structure of a solar cell provided in Embodiment 5 of the present invention.

[0058] Figure 5 This is a schematic cross-sectional view of a portion of the back structure of the solar cell provided in Comparative Example 1 of this invention.

[0059] Wherein, 1-silicon substrate; 2-third doped layer; 3-tunneling dielectric layer; 4-first doped layer; 5-first dielectric layer; 6-second doped layer; 7-tunneling oxide layer; 8-second dielectric layer. Detailed Implementation

[0060] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., 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 with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0061] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0063] Example 1

[0064] Please see Figure 1 and Figure 2 This embodiment provides a back-contact solar cell, which includes:

[0065] A silicon substrate 1, which is an n-type silicon wafer, includes a light-receiving surface and a backlight surface facing away from each other. The backlight surface has a first region, a leakage recombination region, and a second region alternately arranged in a direction perpendicular to the thickness of the silicon substrate. The first region and the second region have opposite doping polarities. The first region is an N-type doped region, and the second region is a P-type doped region. The leakage recombination region is farther away from the silicon substrate 1 than the first region. The leakage recombination region and the first region are connected by a slope transition.

[0066] Along the thickness direction of the silicon substrate 1, a tunneling dielectric layer 3, a first doped layer 4, a first dielectric layer 5, and a second doped layer 6 are sequentially stacked on the leakage recombination region; the thickness of the tunneling dielectric layer 3 is 1.8 nm, and the material is silicon dioxide; along the thickness direction away from the silicon substrate 1, the first dielectric layer 5 and the second doped layer 6 protrude towards the first region and form a brim structure; at least part of the brim structure contains a third doped layer 2, and the third doped layer 2 has a gap between it and the first doped layer 4 in a first direction, the first direction being the direction in which the brim structure is horizontally oriented towards the first region.

[0067] Along the thickness direction away from the silicon substrate 1, the N-type doped region includes an n-type doped polysilicon layer, and the P-type doped region includes a stacked silicon dioxide layer and a p-type doped polysilicon layer; the first doped layer 4 is a p-type doped polysilicon layer with a thickness of 150 nm and a doping concentration of 7 × 10⁻⁶. 19 cm -3The first dielectric layer 5 is a boron-doped SiO2 layer with a thickness of 25 nm; the second doped layer 6 is an n-type doped polysilicon layer with a thickness of 150 nm. The thickness ratio of the first doped layer 4 to the second doped layer 6 is 1:1, and the doping concentration is 1.25 × 10⁻⁶. 20 cm -3 The back-contact solar cell further includes a tunneling oxide layer 7, which continuously covers the silicon substrate 1, the tunneling dielectric layer 3, and the side of the first doped layer 4 near the first region in the thickness direction of the silicon substrate; the second doped layer 6 continuously covers the first dielectric layer 5 and the tunneling oxide layer 7; the second doped layer 6 is also distributed in the region where the spacing is located; the tunneling oxide layer 7 is made of silicon dioxide and has a thickness of 1.8 nm.

[0068] The third doped layer 2 contains boron and phosphorus as dopants, denoted as the first element and the second element, respectively. The doping concentration of the second element is 40% of the doping concentration in the second doped layer, and the doping concentration of the first element is the same as that in the first doped layer 4. The third doped layer 2 has a length of 1 μm in a first direction, which is the direction in which the first doped layer 4 protrudes towards the first region. The third doped layer 2 has a length of 5 μm in a second direction. The first and second directions are perpendicular to each other on the same horizontal plane. The thickness of the third doped layer 2 is 150 nm along the thickness direction of the silicon substrate 1. The projected area of ​​the third doped layer 2 on the silicon substrate 1 along the thickness direction of the silicon substrate 1 accounts for 1% of the total projected area of ​​the silicon substrate 1.

[0069] The third doped layer 2 is in contact with the bottom surface of the first dielectric layer 5 in the brim structure; the surface of the third doped layer 2 and the second doped layer 6 are completely separated by the second dielectric layer 8; the material of the second dielectric layer 8 includes silicon dioxide and the thickness is 1.8 nm.

[0070] Furthermore, a first electrode and a second electrode are also disposed on the backlight surface of the silicon substrate 1. Both the first electrode and the second electrode are silver electrodes. The first electrode is electrically connected to the first doped layer 4, and the second electrode is electrically connected to the second doped layer 6.

[0071] Furthermore, the light-receiving surface of the silicon substrate 1 includes a front passivation layer and a front antireflection layer sequentially stacked along a direction away from the silicon substrate 1. The front passivation layer is a silicon oxide layer, and the front antireflection layer is a silicon nitride layer.

[0072] Figure 3 A cross-sectional SEM image of a portion of the back structure of the solar cell provided in this embodiment is shown, where the red box represents the third doped layer 2 in the brim structure.

[0073] Example 2

[0074] This embodiment provides a back-contact solar cell, the back-contact solar cell comprising:

[0075] The silicon substrate, which is an n-type silicon wafer, includes a light-receiving surface and a backlighting surface facing away from each other. The backlighting surface has a first region, a leakage recombination region, and a second region alternately arranged in a direction perpendicular to the thickness of the silicon substrate. The first region and the second region have opposite doping polarities. The first region is an N-type doped region, and the second region is a P-type doped region. The leakage recombination region is farther away from the silicon substrate than the first region. The leakage recombination region and the first region are connected by a slope transition.

[0076] Along the thickness direction of the silicon substrate, a tunneling dielectric layer, a first doped layer, a first dielectric layer, and a second doped layer are sequentially stacked on the leakage recombination region; the thickness of the tunneling dielectric layer is 1.8 nm, and the material is silicon dioxide; the first dielectric layer and the second doped layer protrude towards one side of the first region and form a brim structure; at least part of the brim structure contains a third doped layer, and the third doped layer has a gap with the first doped layer in a first direction, the first direction being the direction in which the brim structure is horizontally oriented towards the first region.

[0077] Along the thickness direction away from the silicon substrate, the N-type doped region includes an n-type doped polysilicon layer, and the P-type doped region includes a stacked silicon dioxide layer and a p-type doped polysilicon layer; the first doped layer is a p-type doped polysilicon layer with a thickness of 120 nm and a doping concentration of 7 × 10⁻⁶. 19 cm -3 The first dielectric layer is a boron-doped SiO2 layer with a thickness of 18 nm; the second doped layer is an n-type doped polysilicon layer with a thickness of 120 nm. The thickness ratio of the first doped layer to the second doped layer is 1:1, and the doping concentration is 1.25 × 10⁻⁶. 20 cm -3 The back-contact solar cell further includes a tunneling oxide layer, which continuously covers the silicon substrate, the tunneling dielectric layer, and the side of the first doped layer near the first region in the thickness direction of the silicon substrate; the second doped layer continuously covers the first dielectric layer and the tunneling oxide layer; the region where the spacing is located is also distributed with the second doped layer; the tunneling oxide layer is made of silicon dioxide and has a thickness of 1.8 nm.

[0078] The third doped layer comprises boron and phosphorus, denoted as the first element and the second element, respectively. The doping concentration of the second element is 40% of the doping concentration of the second doped layer, and the doping concentration of the first element is the same as that of the first doped layer. The third doped layer has a length of 1 μm in a first direction, which is the direction in which the first doped layer protrudes towards the first region. The third doped layer has a length of 5 μm in a second direction. The first and second directions are perpendicular to each other on the same horizontal plane. The thickness of the third doped layer is 120 nm along the thickness direction of the silicon substrate. The projected area of ​​the third doped layer on the silicon substrate accounts for 1% of the total projected area of ​​the silicon substrate.

[0079] The third doped layer is in contact with the bottom surface of the first dielectric layer in the brim structure; the surface of the third doped layer and the second doped layer are completely separated by the second dielectric layer; the material of the second dielectric layer includes silicon dioxide and doped silicon oxide, and the total thickness is 5nm.

[0080] Furthermore, a first electrode and a second electrode are disposed on the backlight surface of the silicon substrate. Both the first electrode and the second electrode are silver electrodes. The first electrode is electrically connected to the first doped layer, and the second electrode is electrically connected to the second doped layer.

[0081] Furthermore, the light-receiving surface of the silicon substrate includes a front passivation layer and a front antireflection layer sequentially stacked along a direction away from the silicon substrate. The front passivation layer is a silicon oxide layer, and the front antireflection layer is a silicon nitride layer.

[0082] Example 3

[0083] This embodiment provides a back-contact solar cell, the back-contact solar cell comprising:

[0084] The silicon substrate, which is an n-type silicon wafer, includes a light-receiving surface and a backlighting surface facing away from each other. The backlighting surface has a first region, a leakage recombination region, and a second region alternately arranged in a direction perpendicular to the thickness of the silicon substrate. The first region and the second region have opposite doping polarities. The first region is an N-type doped region, and the second region is a P-type doped region. The leakage recombination region is farther away from the silicon substrate than the first region. The leakage recombination region and the first region are connected by a slope transition.

[0085] Along the thickness direction of the silicon substrate, a tunneling dielectric layer, a first doped layer, a first dielectric layer, and a second doped layer are sequentially stacked on the leakage recombination region; the thickness of the tunneling dielectric layer is 1.8 nm, and the material is silicon dioxide; the first dielectric layer and the second doped layer protrude towards one side of the first region and form a brim structure; at least part of the brim structure contains a third doped layer, and the third doped layer has a gap with the first doped layer in a first direction, the first direction being the direction in which the brim structure is horizontally oriented towards the first region.

[0086] Along the thickness direction away from the silicon substrate, the N-type doped region includes an n-type doped polysilicon layer, and the P-type doped region includes a stacked silicon dioxide layer and a p-type doped polysilicon layer; the first doped layer is a p-type doped polysilicon layer with a thickness of 100 nm and a doping concentration of 7 × 10⁻⁶. 19 cm -3 The first dielectric layer is a boron-doped SiO2 layer with a thickness of 20 nm; the second doped layer is an n-type doped polysilicon layer with a thickness of 100 nm. The thickness ratio of the first doped layer to the second doped layer is 1:1, and the doping concentration is 1.25 × 10⁻⁶. 20 cm -3 The back-contact solar cell further includes a tunneling oxide layer, which continuously covers the silicon substrate, the tunneling dielectric layer, and the side of the first doped layer near the first region in the thickness direction of the silicon substrate; the second doped layer continuously covers the first dielectric layer and the tunneling oxide layer; the region where the spacing is located is also distributed with the second doped layer; the tunneling oxide layer is made of silicon dioxide and has a thickness of 1.8 nm.

[0087] The third doped layer comprises boron and phosphorus, denoted as the first element and the second element, respectively. The doping concentration of the second element is 40% of the doping concentration of the second doped layer, and the doping concentration of the first element is the same as that of the first doped layer. The third doped layer has a length of 1 μm in a first direction, which is the direction in which the first doped layer protrudes towards the first region. The third doped layer has a length of 5 μm in a second direction. The first and second directions are perpendicular to each other on the same horizontal plane. The thickness of the third doped layer is 100 nm along the thickness direction of the silicon substrate. The projected area of ​​the third doped layer on the silicon substrate accounts for 1% of the total projected area of ​​the silicon substrate.

[0088] The third doped layer is in contact with the bottom surface of the first dielectric layer in the brim structure; the surface of the third doped layer and the second doped layer are completely separated by the second dielectric layer; the material of the second dielectric layer includes silicon dioxide and doped silicon oxide, and the total thickness is 10 nm.

[0089] Furthermore, a first electrode and a second electrode are disposed on the backlight surface of the silicon substrate. Both the first electrode and the second electrode are silver electrodes. The first electrode is electrically connected to the first doped layer, and the second electrode is electrically connected to the second doped layer.

[0090] Furthermore, the light-receiving surface of the silicon substrate includes a front passivation layer and a front antireflection layer sequentially stacked along a direction away from the silicon substrate. The front passivation layer is a silicon oxide layer, and the front antireflection layer is a silicon nitride layer.

[0091] Example 4

[0092] The difference between this embodiment and Embodiment 1 is that the doping element of the third doped layer is only boron, and the doping concentration is equal to that of the first doped layer.

[0093] The remaining structure and parameters are consistent with those of Example 1.

[0094] Example 5

[0095] The difference between this embodiment and Embodiment 1 is that the surface of the third doped layer and the second doped layer are partially separated by a second dielectric layer, such as... Figure 4 As shown.

[0096] The remaining structure and parameters are consistent with those of Example 1.

[0097] Example 6

[0098] The difference between this embodiment and Embodiment 1 is that the doping element of the third doped layer is only boron, and its doping concentration is less than that of the first doped layer. That is, the boron doping concentration of the isolated third doped layer is 6 × 10⁻⁶. 19 cm -3 .

[0099] The remaining structure and parameters are consistent with those of Example 1.

[0100] Example 7

[0101] The difference between this embodiment and Embodiment 1 is that the surface of the third doped layer is in direct contact with the second doped layer without any gap.

[0102] The remaining structure and parameters are consistent with those of Example 1.

[0103] Example 8

[0104] The difference between this embodiment and Embodiment 1 is that the thickness of the third doped layer is 500 nm.

[0105] The remaining structure and parameters are consistent with those of Example 1.

[0106] Example 9

[0107] The difference between this embodiment and Embodiment 1 is that the length of the third doped layer in the first direction is 6 μm.

[0108] The remaining structure and parameters are consistent with those of Example 1.

[0109] Comparative Example 1

[0110] Please see Figure 5 The difference between this comparative example and Example 1 is that the brim structure does not contain a third doped layer.

[0111] The remaining structure and parameters are consistent with those of Example 1.

[0112] Performance testing

[0113] The photoelectric performance of the back-contact solar cells provided in the above embodiments and comparative examples was tested. The test method was as follows: a standard solar simulator was used, and a dedicated photovoltaic IV tester was used to apply a continuously adjustable bias voltage to the BC solar cell, and the corresponding current value was collected simultaneously to generate a current-voltage (IV) curve. The open-circuit voltage, short-circuit current density, fill factor and photoelectric conversion efficiency were extracted from the curve.

[0114] The conditions for photoelectric performance testing were: AM1.5G, 1000±50W / m², 25℃, and one standard atmosphere.

[0115] The test results are shown in Table 1.

[0116] Table 1

[0117]

[0118] analyze:

[0119] As shown in Table 1, this invention successfully overcomes the limitations of existing continuous-state doped layers by setting a third doped layer in the cap structure of the back-contact solar cell. This alters the carrier transport path and reduces the scattering and recombination probabilities of carriers during transport. Furthermore, the third doped layer reduces the probability of carrier capture, optimizes the carrier collection area, and allows more carriers to be effectively collected. Simultaneously, this unique cap structure increases the effective contact area between the third and second doped layers through the second dielectric layer. This increased contact area enables more carriers to be collected promptly and efficiently, significantly improving the carrier collection efficiency of the cell and ultimately increasing the photocurrent, laying the foundation for improving the cell's conversion efficiency.

[0120] A comparison between Example 1 and Example 6 shows that if the doping element of the third doped layer is only boron and its doping concentration is less than that of the first doped layer, it is not conducive to the field passivation effect of the cap structure region, increases the surface recombination rate, reduces the open circuit voltage, and further reduces the photoelectric conversion efficiency of the solar cell.

[0121] As can be seen from the comparison between Example 1 and Example 7, if the surface of the third doped layer is in direct contact with the second doped layer without any gap, the probability of contact recombination between the third doped region and the second doped layer will increase, the open circuit voltage will decrease, and the photoelectric conversion efficiency will be further reduced.

[0122] As can be seen from the comparison between Example 1 and Examples 8-9, if the thickness of the third doped layer is too large, the local parasitic absorption will be too high, and the bulk recombination of the doped layer will increase, thereby reducing the open-circuit voltage and short-circuit current density and reducing the photoelectric conversion efficiency. If the length of the third doped layer is too long, it will increase the resistance of the carriers at the third doped layer to be collected by the first electrode, while increasing the carrier transport path, increasing the recombination probability, reducing the open-circuit voltage, and ultimately reducing the photoelectric conversion efficiency of the solar cell.

[0123] As can be seen from the comparison between Example 1 and Comparative Example 1, if the cap structure does not contain a third doped layer, the back light gain is low, the back reflected light gain at the cap is small, the short-circuit current density is low, the photogenerated carriers have no field passivation effect at the cap structure, the surface recombination rate is high, and the photoelectric conversion efficiency of the solar cell is low.

[0124] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A back-contact solar cell, characterized in that, The back-contact solar cell includes a silicon substrate, which includes a light-receiving surface and a back-lighting surface facing away from each other. The back-lighting surface has a first region, a leakage recombination region, and a second region arranged alternately in a direction perpendicular to the thickness of the silicon substrate. The first region and the second region have opposite doping polarities. Along the thickness direction away from the silicon substrate, a tunneling dielectric layer, a first doped layer, and a second doped layer are sequentially stacked on the leakage recombination region, and the second doped layer protrudes to one side facing the first region and has a brim structure. At least a portion of the brim structure contains a third doped layer, the third doped layer having a gap with the first doped layer in a first direction, the first direction being the direction in which the brim structure is horizontally oriented toward the first region.

2. The back-contact solar cell according to claim 1, characterized in that, Along the thickness direction away from the silicon substrate, a first dielectric layer is stacked between the first doped layer and the second doped layer, the material of the first dielectric layer including doped silicon dioxide; wherein the doping polarities of the first doped layer and the second doped layer are opposite.

3. The back-contact solar cell according to claim 2, characterized in that, The first dielectric layer protrudes from one side toward the first region and extends into the brim structure; The back-contact solar cell further includes a tunneling oxide layer, which covers the silicon substrate, the tunneling dielectric layer, and the side of the first doped layer near the first region in the thickness direction of the silicon substrate.

4. The back-contact solar cell according to claim 3, characterized in that, The second doped layer continuously covers the first dielectric layer and the tunneling oxide layer; The area where the spacing is located also contains the second doped layer.

5. The back-contact solar cell according to claim 1, characterized in that, The doping polarity of the third doped layer is the same as that of the first doped layer.

6. The back-contact solar cell according to claim 1, characterized in that, The length of the third doped layer in the first direction is 0.05 μm-5 μm.

7. The back-contact solar cell according to claim 6, characterized in that, The length of the third doped layer in the second direction is 0.05 μm-10 μm; the first direction and the second direction intersect each other on the same horizontal plane.

8. The back-contact solar cell according to claim 4, characterized in that, The doping elements in the third doped layer include those in the first doped layer, with a doping concentration of 1. 10 19 cm -3 -20 10 19 cm -3 .

9. The back-contact solar cell according to claim 1, characterized in that, The doping elements of the third doped layer include the doping elements of the first doped layer and the doping elements of the second doped layer, which are referred to as the first element and the second element, respectively.

10. The back-contact solar cell according to claim 9, characterized in that, The doping concentration of the second element is 1-50% of the concentration of the doping element in the second doped layer.

11. The back-contact solar cell according to claim 10, characterized in that, The doping concentration of the first element is 1. 10 19 cm -3 -20 10 19 cm -3 ; The doping concentration of the second element is 0.5%. 10 20 cm -3 -4 10 20 cm -3 .

12. The back-contact solar cell according to claim 9, characterized in that, In the third doped layer, the concentration of the first element is greater than the concentration of the second element.

13. The back-contact solar cell according to claim 1, characterized in that, Along the thickness direction of the silicon substrate, the projected area of ​​the third doped layer on the silicon substrate accounts for 0.01%-10% of the total projected area of ​​the silicon substrate.

14. The back-contact solar cell according to claim 1, characterized in that, The projected area of ​​a single third doped layer on the silicon substrate accounts for 0.001%-5% of the total projected area of ​​the silicon substrate.

15. The back-contact solar cell according to claim 3, characterized in that, The surface of the third doped layer is at least partially phase-separated from the second doped layer by a second dielectric layer; The material of the second dielectric layer includes any one or a combination of at least two of amorphous silicon, doped silicon oxide, silicon dioxide, aluminum oxide, or silicon oxynitride. The thickness of the second dielectric layer is 0.5nm-50nm.

16. The back-contact solar cell according to claim 15, characterized in that, The materials of the tunneling dielectric layer and the tunneling oxide layer each independently include any one or a combination of at least two of silicon dioxide, aluminum oxide, or silicon oxynitride. The thickness of the tunneling dielectric layer and the tunneling oxide layer are each independently 0.5 nm-3 nm; The thickness of the second dielectric layer is 1nm-25nm.

17. The back-contact solar cell according to claim 2, characterized in that, The first dielectric layer includes a doped silicon dioxide layer; The thickness of the doped silicon dioxide layer is 1nm-50nm.

18. The back-contact solar cell according to claim 1, characterized in that, Along the thickness direction of the silicon substrate, the thickness of the third doped layer is 20nm-400nm.

19. The back-contact solar cell according to claim 1, characterized in that, The thickness of the first doped layer is 20nm-400nm; The thickness of the second doped layer is 30nm-200nm; The thickness ratio of the first doped layer to the second doped layer is 1:(0.3-3).

20. A solar cell module, characterized in that, The solar cell module includes a back-contact solar cell as described in any one of claims 1-19.

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