Back contact solar cell and method of manufacturing the same, cell string, cell module, and photovoltaic system

Abstract

This invention discloses a back-contact solar cell, its fabrication method, a cell string, a cell module, and a photovoltaic system. The back-contact solar cell includes: a silicon substrate configured with a first conductivity type, comprising a first surface and a second surface; a first doped layer configured with the first conductivity type and located on the first surface; a second doped layer configured with the second conductivity type and located on the first surface; the first and second doped layers are alternately arranged along a first direction; a first electrode layer; a second electrode layer; the first doped layer in contact with the first electrode layer along the first direction is arc-shaped; and / or, the second doped layer in contact with the second electrode layer along the first direction is arc-shaped. The technical solution of this invention can increase the contact area between the electrode layer and the doped layer, thereby reducing contact resistance and improving photoelectric conversion efficiency.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a back-contact solar cell, its fabrication method, cell string, cell module, and photovoltaic system. Background Technology

[0002] Solar cells are used to directly convert sunlight into electrical energy. With the continuous development of photovoltaic technology, solar cell products, as semiconductor devices that convert solar energy into electrical energy, have been rapidly developed, with the development direction being low cost and high efficiency.

[0003] In existing solar cells, the morphology of the doped layer beneath the metal grid line affects the ohmic contact between the metal grid line and the doped layer. A larger surface area is more conducive to reducing contact resistivity, thereby reducing series resistance and contributing to improved cell conversion efficiency. However, a larger surface area of ​​the doped layer also means increased roughness, which is detrimental to surface passivation and affects the cell's open-circuit voltage. Therefore, how to balance contact resistance and open-circuit voltage to achieve the goal of improving conversion efficiency has become an urgent problem to be solved. Summary of the Invention

[0004] This invention provides a back-contact solar cell and its fabrication method, a cell string, a cell module, and a photovoltaic system, which increases the contact area between the electrode layer and the doped layer, thereby reducing the contact resistance between the electrode layer and the doped layer and improving the photoelectric conversion efficiency of the back-contact solar cell.

[0005] According to one aspect of the present invention, a back-contact solar cell is provided, the back-contact solar cell comprising: A silicon substrate, configured with a first conductivity type; the silicon substrate includes a first surface and a second surface disposed opposite to each other; The first doped layer is configured with a first conductivity type and is located on the first surface; The second doped layer is configured with a second conductivity type and is located on the first surface; the first doped layer and the second doped layer are arranged alternately along the first direction; The first electrode layer is located on the side of the first doped layer away from the first surface; The second electrode layer is located on the side of the second doped layer away from the first surface; Along the first direction, the first doped layer in contact with the first electrode layer is arc-shaped; And / or, along the first direction, the second doped layer in contact with the second electrode layer is arc-shaped.

[0006] Optionally, the radius of curvature of the arc-shaped first doped layer is greater than or equal to 0.2 micrometers and less than or equal to 300 micrometers; And / or, the radius of curvature of the arc-shaped second doped layer is greater than or equal to 0.5 micrometers and less than or equal to 300 micrometers.

[0007] Optionally, along the first direction, the first surface of the silicon substrate is planar; Along the second direction, the distance between the arc-shaped first doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 400 nm; And / or, along the second direction, the distance between the arc-shaped second doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 400 nm; the first direction is perpendicular to the second direction, and the second direction is the thickness direction of the back-contact solar cell.

[0008] Optionally, along the first direction, the first surface of the silicon substrate is wavy; Along the second direction, the arc-shaped first doped layer is parallel to the first surface, and the distance between the arc-shaped first doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 180 nm. And / or, along the second direction, the arc-shaped second doped layer is parallel to the first surface, and the distance between the arc-shaped second doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 180 nm.

[0009] Optionally, along the first direction, the first doped layer includes a first region and a second region; wherein, the first doped layer in contact with the first electrode layer is the first region; and the first doped layer not in contact with the first electrode layer is the second region. Along the first direction, the second doped layer includes a third region and a fourth region; wherein, the second doped layer in contact with the second electrode layer is the third region; and the second doped layer not in contact with the second electrode layer is the fourth region. The ratio of the radius of curvature of the first region to the radius of curvature of the second region is greater than or equal to 1.2 and less than or equal to 3; And / or, the ratio of the radius of curvature of the third region to the radius of curvature of the fourth region is greater than or equal to 1.5 and less than or equal to 2.8.

[0010] Optionally, the back-contact solar cell also includes a polyhedral structure; The vertical projected area of ​​the polyhedral structure corresponding to the first region on the silicon substrate is smaller than the vertical projected area of ​​the polyhedral structure corresponding to the second region on the silicon substrate. And / or, the vertical projected area of ​​the polyhedral structure corresponding to the third region on the silicon substrate is smaller than the vertical projected area of ​​the polyhedral structure corresponding to the fourth region on the silicon substrate.

[0011] Optionally, along the second direction, the height difference between the highest point of the first region and the lowest point of the second region is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers; And / or, along the second direction, the height difference between the highest point of the third region and the lowest point of the fourth region is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers.

[0012] Optionally, along the second direction, with the lowest point of the arc-shaped first doped layer as the vertex, the angle formed between the outline tangent of the first doped layer and the first direction is greater than or equal to 1° and less than or equal to 35°. And / or, along the second direction, with the lowest point of the arc-shaped second doped layer as the vertex, the angle formed between the outline tangent of the second doped layer and the first direction is greater than or equal to 1° and less than or equal to 35°.

[0013] Optionally, the back-contact solar cell further includes: a first tunneling layer and a second tunneling layer; The first tunneling layer is located between the first surface and the first doped layer; the thickness of the first tunneling layer is greater than or equal to 0.2 nm and less than or equal to 3 nm; The second tunneling layer is located between the first surface and the second doped layer; the thickness of the second tunneling layer is greater than or equal to 0.2 nm and less than or equal to 3 nm.

[0014] Optionally, the back-contact solar cell may also include: an anti-reflection layer; The antireflection layer is located on the side of the first doped layer and the second doped layer away from the first surface.

[0015] According to another aspect of the present invention, a method for fabricating a back-contact solar cell is provided, the method comprising: A silicon substrate is provided; the silicon substrate is configured with a first conductivity type; the silicon substrate includes a first surface and a second surface disposed opposite to each other; A first doped layer is formed on the first surface; the first doped layer is configured with a first conductivity type. A second doped layer is formed on the first surface; the second doped layer is configured with a second conductivity type; the first doped layer and the second doped layer are arranged alternately along the first direction; A first electrode layer is formed on the side of the first doped layer away from the first surface; A second electrode layer is formed on the side of the second doped layer away from the first surface; wherein, along the first direction, the first doped layer in contact with the first electrode layer is arc-shaped; and / or, along the first direction, the second doped layer in contact with the second electrode layer is arc-shaped.

[0016] According to another aspect of the present invention, a battery string is provided, including a back-contact solar cell according to any embodiment of the present invention.

[0017] According to another aspect of the present invention, a battery assembly is provided, including a back-contact solar cell or a battery string according to any embodiment of the present invention.

[0018] According to another aspect of the present invention, a photovoltaic system is provided, including a battery module according to any embodiment of the present invention.

[0019] The technical solution of this invention involves an arc-shaped first doped layer in contact with the first electrode layer along a first direction; and / or an arc-shaped second doped layer in contact with the second electrode layer along the first direction. This arrangement allows for a larger specific surface area and rougher surface in the areas covered by the first and / or second electrode layers, while a smaller specific surface area and flatter surface in the areas not covered by the first electrode layer. This reduces contact resistivity while avoiding interference with surface passivation and minimizing open-circuit voltage. Furthermore, the arc-shaped first doped layer in contact with the first electrode layer increases the contact area between the first electrode layer and the first doped layer, thereby reducing the contact resistance between them. Similarly, the arc-shaped second doped layer in contact with the second electrode layer increases the contact area between the second electrode layer and the second doped layer, further reducing their contact resistance and improving the conversion efficiency of the back-contact solar cell.

[0020] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a top view schematic diagram of a back-contact solar cell according to an embodiment of the present invention; Figure 2 This is a top view microstructure diagram of a back-contact solar cell according to an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of a back-contact solar cell according to an embodiment of the present invention. Figure 4 This is a schematic cross-sectional view of another back-contact solar cell provided according to an embodiment of the present invention; Figure 5 It is provided according to the embodiments of the present invention. Figure 1 A schematic diagram of the cross-sectional profile structure along the A1-A2 direction; Figure 6 It is provided according to the embodiments of the present invention. Figure 1 A schematic diagram of the cross-sectional profile along the A3-A4 direction; Figure 7 It is provided according to the embodiments of the present invention. Figure 1 A top view of the structure along the A1-A2 direction; Figure 8 This is a flowchart of a method for fabricating a back-contact solar cell according to an embodiment of the present invention. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] Figure 1 This is a top view schematic diagram of a back-contact solar cell according to an embodiment of the present invention. Figure 2 This is a top view microstructure diagram of a back-contact solar cell provided according to an embodiment of the present invention. Figure 3 This is a schematic cross-sectional view of a back-contact solar cell according to an embodiment of the present invention. Figure 1 , Figure 2 and Figure 3As shown, the back-contact solar cell includes: a silicon substrate 10 configured with a first conductivity type; the silicon substrate 10 includes a first surface 101 and a second surface 102 disposed opposite to each other; a first doped layer 20 configured with the first conductivity type and located on the first surface 101; a second doped layer 30 configured with the second conductivity type and located on the first surface 101; the first doped layer 20 and the second doped layer 30 are alternately arranged along a first direction X; a first electrode layer 40 is located on the side of the first doped layer 20 away from the first surface 101; a second electrode layer 50 is located on the side of the second doped layer 30 away from the first surface 101; the first doped layer 20 in contact with the first electrode layer 40 along the first direction X is arc-shaped; and / or, the second doped layer 30 in contact with the second electrode layer 50 along the first direction X is arc-shaped.

[0026] In this embodiment of the invention, the silicon substrate 10 includes a first surface 101 and a second surface 102. For example, the first surface 101 can be a non-light-receiving surface (backlight surface), and the second surface 102 can be a light-receiving surface. The light-receiving surface is the side that receives illumination from a light source, while the backlight surface is located on the side opposite to the light-receiving surface. The first doped layer 20 has the same conductivity type as the silicon substrate 10, and the second doped layer 30 has the opposite conductivity type to the silicon substrate 10. The first conductivity type can be N-type or P-type. Furthermore, the first conductivity type is opposite to the second conductivity type; when the first conductivity type is N-type, the second conductivity type is P-type; when the first conductivity type is P-type, the second conductivity type is N-type. For example, the silicon substrate 10 can be an N-type silicon substrate, the first doped layer 20 can be an N-type doped layer, and the second doped layer 30 can be a P-type doped layer. Alternatively, the silicon substrate 10 can be a P-type silicon substrate, the first doped layer 20 can be a P-type doped layer, and the second doped layer 30 can be an N-type doped layer. The P-type dopant can be at least one of boron (B), aluminum (Al), or gallium (Ga), and this embodiment of the invention does not specifically limit it. The N-type dopant can be at least one of phosphorus (P), arsenic (As), or antimony (Sb), and this embodiment of the invention does not specifically limit it.

[0027] This embodiment of the invention uses an N-type silicon substrate 10 as an example. The first doped layer 20 can be an N-type polycrystalline silicon doped layer, and the second doped layer 30 can be a P-type polycrystalline silicon doped layer. The first doped layer 20 is used to collect electrons, and the second doped layer 30 is used to collect holes. The collected carriers are then transferred to the first electrode layer 40 and the second electrode layer 50, respectively, forming a pathway with the external load. Therefore, the first doped layer 20 and the second doped layer 30 cannot be in direct contact; otherwise, the carriers cannot be effectively collected.

[0028] The first surface 101 includes a plurality of first carrier collection regions 11 and a plurality of second carrier collection regions 12 alternately distributed along a first direction X; an isolation region 13 is disposed between adjacent first carrier collection regions 11 and second carrier collection regions 12; the first carrier collection region 11 can be an electron collection region, and the second carrier collection region 12 can be a hole collection region. The isolation region 13 between adjacent first carrier collection regions 11 and second carrier collection regions 12 can be an insulating isolation structure, such as an isolation trench. The first electrode layer 40 and the second electrode layer 50 can be formed on the side of the first doped layer 20 and the second doped layer 30 away from the first surface 101 by screen printing or electroplating, respectively.

[0029] On the side of the second surface 102 away from the first surface 101, an aluminum oxide layer 103, a silicon nitride layer 104, and a silicon oxide layer 105 may be sequentially disposed to protect the silicon substrate 10, optimize the optical performance of the back-contact solar cell, and improve the stability of the back-contact solar cell. The aluminum oxide layer 103 is used for passivation protection, reducing surface defects and charge recombination of the silicon substrate 10, while also blocking the intrusion of external contaminants such as moisture or impurities. The silicon nitride layer 104 is used for anti-reflection and passivation, reducing the reflection loss of incident light, allowing more light to enter the light-receiving surface, and further improving the passivation effect. The silicon oxide layer 105 is used for insulation and protection, improving the insulation performance of the back-contact solar cell surface and blocking mechanical wear and chemical corrosion.

[0030] In the technical solution of this invention, the first doped layer 20, which contacts the first electrode layer 40, is arc-shaped along the first direction X; and / or, the second doped layer 30, which contacts the second electrode layer 50, is arc-shaped along the first direction X. This arrangement allows the area covered by the first electrode layer 40 and / or the second electrode layer 50 to have a large specific surface area and a rough surface, while the area not covered by the first electrode layer 40 and / or the second electrode layer 50 has a small specific surface area and a flat surface. This reduces contact resistivity while avoiding interference with surface passivation and reducing open-circuit voltage. Furthermore, the arc-shaped first doped layer 20 in contact with the first electrode layer 40 increases the contact area between the first electrode layer 40 and the first doped layer 20, thereby reducing the contact resistance between the first electrode layer 40 and the first doped layer 20. Similarly, the arc-shaped second doped layer 30 in contact with the second electrode layer 50 increases the contact area between the second electrode layer 50 and the second doped layer 30, thereby reducing the contact resistance between the second electrode layer 50 and the second doped layer 30, thus improving the conversion efficiency of the back-contact solar cell.

[0031] In an optional embodiment of the present invention, reference is made to... Figure 3The first doped layer 20, which is arc-shaped, has a radius of curvature greater than or equal to 0.2 micrometers and less than or equal to 300 micrometers; and / or, the second doped layer 30, which is arc-shaped, has a radius of curvature greater than or equal to 0.5 micrometers and less than or equal to 300 micrometers.

[0032] In this embodiment of the invention, the smaller the radius of curvature, the sharper the arc-shaped bend; the larger the radius of curvature, the smoother the bend. When the radius of curvature is too small, lattice defects are prone to occur at the bend, and local electric field concentration is prone to occur at the tip. In this embodiment of the invention, the radius of curvature of the arc-shaped first doped layer 20 is set to be greater than or equal to 0.2 micrometers, which can avoid lattice damage and process edge defects, and can also smooth the electric field distribution and suppress local leakage. Setting the radius of curvature of the first doped layer 20 to be less than or equal to 300 micrometers can ensure that the electrical gain of the arc-shaped structure does not fail. In this embodiment of the invention, the radius of curvature of the second doped layer 30 is set to be greater than or equal to 0.5 micrometers and less than or equal to 300 micrometers, which can suppress the lateral diffusion of high-concentration doping and optimize electrode contact and ohmic conduction.

[0033] In an optional embodiment of the present invention, reference is made to... Figure 3 Along the first direction X, the first surface 101 of the silicon substrate 10 is planar; along the second direction Z, the distance between the arc-shaped first doped layer 20 and the first surface 101 is greater than or equal to 20 nm and less than or equal to 400 nm; and / or, along the second direction Z, the distance between the arc-shaped second doped layer 30 and the first surface 101 is greater than or equal to 20 nm and less than or equal to 400 nm; the first direction X is perpendicular to the second direction Z, and the second direction Z is the thickness direction of the back-contact solar cell.

[0034] In this embodiment of the invention, when the first surface 101 of the silicon substrate 10 is planar, the distance between the arc-shaped first doped layer 20 and the first surface 101 is greater than or equal to 20 nm, and / or the distance between the arc-shaped second doped layer 30 and the first surface 101 is greater than or equal to 20 nm. This ensures that the arc-shaped morphology is effectively formed and can be distinguished during photolithography / etching processes. At the same time, the distance between the arc-shaped first doped layer 20 and the first surface 101 is less than or equal to 400 nm, and / or the distance between the arc-shaped second doped layer 30 and the first surface 101 is less than or equal to 400 nm. This avoids excessive fluctuations that could cause lattice damage, reduces the difficulty of subsequent metal electrode coverage, decreases series resistance, and improves the reliability of the back contact solar cell.

[0035] It should be noted that the distance between the arc-shaped first doped layer 20 and the first surface 101, or the distance between the arc-shaped second doped layer 30 and the first surface 101, is the distance between the highest point along the second direction Z and the first surface 101 of the silicon substrate 10. Furthermore, Figure 3Only the arc-shaped structure of the first doped layer 20 is shown. The arc-shaped structure of the second doped layer 30 and the structure in which both the first doped layer 20 and the second doped layer 30 are arc-shaped can be shown according to... Figure 3 Therefore, the embodiments of the present invention are not specifically limited herein.

[0036] Figure 4 This is a schematic cross-sectional view of another back-contact solar cell provided according to an embodiment of the present invention. In an optional embodiment of the present invention, refer to... Figure 4 Along the first direction X, the first surface 101 of the silicon substrate 10 is wavy; along the second direction Z, the arc-shaped first doped layer 20 is parallel to the first surface 101, and the distance between the arc-shaped first doped layer 20 and the first surface 101 is greater than or equal to 20 nm and less than or equal to 180 nm; and / or, along the second direction Z, the arc-shaped second doped layer 30 is parallel to the first surface 101, and the distance between the arc-shaped second doped layer 30 and the first surface 101 is greater than or equal to 20 nm and less than or equal to 180 nm.

[0037] In this embodiment of the invention, the doped layer is parallel to the wave pattern of the silicon substrate 10, and the interlayer spacing is consistent throughout, avoiding local variations in distance, resulting in a more uniform electric field distribution and better stress matching. This reduces the deformation and defects of the silicon substrate 10. Along the second direction Z, the distance between the arc-shaped first doped layer 20 and the first surface 101 is greater than or equal to 20 nm and less than or equal to 180 nm, and / or the distance between the arc-shaped second doped layer 30 and the first surface 101 is greater than or equal to 20 nm and less than or equal to 180 nm. This effectively suppresses interfacial tunneling recombination and process defects, controls interlayer resistance and film internal stress, prevents film cracking and peeling, and improves the performance of the back contact solar cell.

[0038] Figure 5 It is provided according to the embodiments of the present invention. Figure 1 A schematic diagram of the cross-sectional profile structure along the A1-A2 direction. Figure 6 It is provided according to the embodiments of the present invention. Figure 1 A schematic diagram of the cross-sectional profile along the A3-A4 direction. In an optional embodiment of the invention, refer to... Figure 5 and Figure 6Along the first direction X, the first doped layer includes a first region 21 and a second region 22; wherein the first doped layer in contact with the first electrode layer is the first region 21; the first doped layer not in contact with the first electrode layer is the second region 22; along the first direction X, the second doped layer includes a third region 31 and a fourth region 32; wherein the second doped layer in contact with the second electrode layer is the third region 31; the second doped layer not in contact with the second electrode layer is the fourth region 32; the ratio of the radius of curvature of the first region 21 to the radius of curvature of the second region 22 is greater than or equal to 1.2 and less than or equal to 3; and / or, the ratio of the radius of curvature of the third region 31 to the radius of curvature of the fourth region 32 is greater than or equal to 1.5 and less than or equal to 2.8.

[0039] In this embodiment of the invention, the radius of curvature of the first region 21 in the first doped layer that contacts the first electrode layer is greater than the radius of curvature of the second region 22 in the first doped layer that does not contact the first electrode layer. Furthermore, the ratio of the radius of curvature of the first region 21 to that of the second region 22 is set to be greater than or equal to 1.2 and less than or equal to 3. This results in a larger electrode contact area, reduced contact resistance, suppression of edge spike electric fields, and improved performance of the back-contact solar cell. Similarly, the radius of curvature of the third region 31 in the second doped layer that contacts the second electrode layer is greater than the radius of curvature of the fourth region 32 in the second doped layer that does not contact the second electrode layer. Furthermore, the ratio of the radius of curvature of the third region 31 to that of the fourth region 32 is set to be greater than or equal to 1.5 and less than or equal to 2.8. This also results in a larger electrode contact area, reduced contact resistance, suppression of edge spike electric fields, and improved performance of the back-contact solar cell.

[0040] Figure 7 It is provided according to the embodiments of the present invention. Figure 1 A top view of the structure along the A1-A2 direction. In an optional embodiment of the invention, refer to... Figures 5 to 7 The back-contact solar cell also includes a polyhedral structure 100; the vertical projection area of ​​the polyhedral structure 100 corresponding to the first region 21 on the silicon substrate 10 is smaller than the vertical projection area of ​​the polyhedral structure 100 corresponding to the second region 22 on the silicon substrate 10; and / or, the vertical projection area of ​​the polyhedral structure 100 corresponding to the third region 31 on the silicon substrate 10 is smaller than the vertical projection area of ​​the polyhedral structure 100 corresponding to the fourth region 32 on the silicon substrate 10.

[0041] In this embodiment of the invention, the polyhedral structure 100 is a tower-based structure. The polyhedral structures 100 corresponding to the first region 21 and the third region 31 have a small vertical projection area on the silicon substrate 10, so the number of polyhedral structures 100 per unit area is large, resulting in a significant increase in roughness, which improves diffuse reflection and thus increases light absorption, and also helps to reduce the contact resistance of the metal grid lines corresponding to the first region 21 and the third region 31. On the other hand, the polyhedral structures 100 corresponding to the second region 22 and the fourth region 32 have a large vertical projection area on the silicon substrate 10, which helps to passivate the surface, improve the open-circuit voltage, and ultimately improve the conversion efficiency of the back-contact solar cell.

[0042] In an optional embodiment of the present invention, reference is made to... Figure 5 and Figure 6 Along the second direction Z, the height difference H1 between the highest point of the first region 21 and the lowest point of the second region 22 is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers; and / or, along the second direction Z, the height difference H2 between the highest point of the third region 31 and the lowest point of the fourth region 32 is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers.

[0043] In this embodiment of the invention, setting the range of the height difference H1 between the highest point of the first region 21 and the lowest point of the second region 22, and / or setting the range of the height difference H2 between the highest point of the third region 31 and the lowest point of the fourth region 32, can ensure uniform and reliable electrode contact and reduce contact resistance. If the height difference is set too small, the light trapping effect of the first surface may be insignificant, and the effective contact area between the electrode layer and the doped layer may be limited. If the height difference is set too large, problems such as breakpoints or incomplete printing may occur during electrode printing or electroplating, reducing product yield.

[0044] For example, as shown in the table below: As shown in the table, Example 1 uses a height difference within the above range for testing, Example 2 uses a height difference greater than the above range for testing, and the comparative example uses a height difference of zero. Conversion efficiency, open-circuit voltage, short-circuit current, fill factor, and series resistance are measured respectively. From the data in the table, it can be concluded that although Example 2 shows improvement compared to the comparative example, the selected height difference is not within the optimal range, leading to problems such as a worsened passivation effect. Examples 1 and 2 show a significant improvement in fill factor and short-circuit current compared to the comparative example. This is due to the beneficial effect of reduced contact resistance, ultimately improving the conversion efficiency of the back-contact solar cell.

[0045] In optional embodiments of the present invention, reference continues to be made to... Figure 5 and Figure 6Along the second direction Z, with the lowest point of the arc-shaped first doped layer as the vertex, the angle α1 formed by the outline tangent of the first doped layer and the first direction X is greater than or equal to 1° and less than or equal to 35°; and / or, along the second direction Z, with the lowest point of the arc-shaped second doped layer as the vertex, the angle α2 formed by the outline tangent of the second doped layer and the first direction X is greater than or equal to 1° and less than or equal to 35°.

[0046] In this embodiment of the invention, setting the range of the angle α1 formed by the tangent of the first doped layer and the first direction X, and / or setting the range of the angle α2 formed by the tangent of the second doped layer and the first direction X, can ensure uniform and reliable electrode contact and reduce contact resistance. If the angle is set too small, the light trapping effect of the first surface may be insignificant and the effective contact area between the electrode layer and the doped layer may be limited; if the angle is set too large, it may cause problems such as breakpoints or incomplete printing during electrode printing or electroplating, reducing product yield.

[0047] In an optional embodiment of the present invention, reference is made to... Figure 3 or Figure 4 The back-contact solar cell further includes: a first tunneling layer 60 and a second tunneling layer 70; the first tunneling layer 60 is located between the first surface 101 and the first doped layer 20; the thickness of the first tunneling layer is greater than or equal to 0.2 nm and less than or equal to 3 nm; the second tunneling layer 70 is located between the first surface 101 and the second doped layer 30; the thickness of the second tunneling layer is greater than or equal to 0.2 nm and less than or equal to 3 nm.

[0048] In this embodiment of the invention, both the first tunneling layer 60 and the second tunneling layer 70 are dielectric tunneling films, and the materials of the first tunneling layer 60 and the second tunneling layer 70 include, but are not limited to, silicon oxide, aluminum oxide, or silicon oxynitride. The provision of the first tunneling layer 60 and the second tunneling layer 70 can improve the interface passivation effect, increase the open-circuit voltage, and also enable selective tunneling transport, reducing contact resistance.

[0049] In optional embodiments of the present invention, reference continues to be made to... Figure 3 or Figure 4 The back-contact solar cell further includes an anti-reflection layer 80; the anti-reflection layer 80 is located on the side of the first doped layer 20 and the second doped layer 30 away from the first surface 101.

[0050] In this embodiment of the invention, the antireflection layer 80 may be one or more combinations of an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer. Providing the antireflection layer 80 can enhance the antireflection effect, increase light absorption and utilization, and thus improve the performance of the back-contact solar cell.

[0051] Figure 8This is a flowchart illustrating a method for fabricating a back-contact solar cell according to an embodiment of the present invention. This embodiment is applicable to the fabrication of back-contact solar cells, and the method for fabricating this back-contact solar cell can be performed by an apparatus for fabricating a back-contact solar cell. Figure 8 As shown, the fabrication method of this back-contact solar cell includes: S110, Provide a silicon substrate; The silicon substrate is configured with a first conductivity type; The silicon substrate includes a first surface and a second surface disposed opposite to each other.

[0052] For details, please refer to Figure 1 , Figure 2 and Figure 3 The silicon substrate 10 includes a first surface 101 and a second surface 102. Exemplarily, the first surface 101 can be a non-light-receiving surface (backlight surface), and the second surface 102 can be a light-receiving surface. The light-receiving surface is the side that receives illumination from a light source, while the backlight surface is located on the side opposite to the light-receiving surface. The first conductivity type can be N-type or P-type. Furthermore, the first conductivity type is opposite to the second conductivity type; when the first conductivity type is N-type, the second conductivity type is P-type; and when the first conductivity type is P-type, the second conductivity type is N-type. This embodiment of the invention uses an N-type silicon substrate as an example for illustration. The first surface 101 includes a plurality of first carrier collection regions 11 and a plurality of second carrier collection regions 12 alternately distributed along a first direction X; an isolation region 13 is provided between adjacent first carrier collection regions 11 and second carrier collection regions 12. The first carrier collection region 11 can be an electron collection region, and the second carrier collection region 12 can be a hole collection region. The isolation region 13 between adjacent first carrier collection region 11 and second carrier collection region 12 can be an insulating isolation structure, such as an isolation trench.

[0053] S120, A first doped layer is formed on the first surface; the first doped layer is configured as a first conductivity type.

[0054] For details, please refer to Figure 3 The first doped layer 20 has the same conductivity type as the silicon substrate 10. For example, the silicon substrate 10 can be an N-type silicon substrate, and the first doped layer 20 can be an N-type polycrystalline silicon doped layer. The N-type dopant element can be at least one of phosphorus (P), arsenic (As), or antimony (Sb), and this embodiment of the invention does not specifically limit the type of dopant.

[0055] S130, A second doped layer is formed on the first surface; the second doped layer is configured as a second conductivity type; the first doped layer and the second doped layer are arranged alternately along the first direction.

[0056] For details, please refer to Figure 3The second doped layer 30 has the opposite conductivity type to the silicon substrate 10. The second doped layer 30 can be a P-type polycrystalline silicon doped layer. The P-type dopant element can be at least one of boron (B), aluminum (Al), or gallium (Ga), and this embodiment of the invention is not specifically limited thereto. Alternatively, the silicon substrate 10 can be a P-type silicon substrate, the first doped layer 20 can be a P-type doped layer, and the second doped layer 30 can be an N-type doped layer.

[0057] S140, A first electrode layer is formed on the side of the first doped layer away from the first surface.

[0058] For details, please refer to Figure 3 The first electrode layer 40 can be formed by screen printing or electroplating on the side of the first doped layer 20 away from the first surface 101.

[0059] S150, a second electrode layer is formed on the side of the second doped layer away from the first surface; wherein, along the first direction, the first doped layer in contact with the first electrode layer is arc-shaped; and / or, along the first direction, the second doped layer in contact with the second electrode layer is arc-shaped.

[0060] For details, please refer to Figure 3 The second electrode layer 50 can be formed by screen printing or electroplating on the side of the second doped layer 30 away from the first surface 101.

[0061] In this embodiment of the invention, an arc-shaped morphology can be formed by adjusting the laser power or overlap rate of the mask removal process. Lower laser power results in less mask removal thickness, while higher laser power removes more mask thickness, or even complete removal. Similarly, a higher laser overlap rate means more laser scans of the same location, leading to greater mask removal thickness. Subsequent wet etching, due to the different etching rates of the mask and silicon substrate, takes longer to etch into the silicon substrate where there is more mask, while in areas with less or no mask, the silicon substrate can be etched directly. Therefore, locations with different mask thicknesses will form uneven morphologies. By controlling the laser process parameters and using different parameters at different locations, an arc-shaped first doped layer and / or second doped layer can be formed.

[0062] In optional embodiments of the present invention, the diffusion doping concentration can also be controlled to form an arc-shaped morphology. Specifically, the diffusion doping concentration also affects the corrosion resistance of the mask. The stronger the corrosion resistance, the stronger the mask's ability to resist corrosion, and the greater the difference in thickness between different mask areas. The doping concentration follows this rule: for boron doping, the higher the concentration, the stronger the corrosion resistance; for phosphorus doping, the higher the concentration, the weaker the corrosion resistance. The doping concentration can be adjusted according to different doping types of masks to improve the mask's corrosion resistance, thereby forming an arc-shaped first doped layer and / or a second doped layer.

[0063] The technical solution of this invention involves forming an arc-shaped first doped layer 20 in contact with the first electrode layer 40 along the first direction X; and / or forming an arc-shaped second doped layer 30 in contact with the second electrode layer 50 along the first direction X. This allows the area covered by the first electrode layer 40 and / or the second electrode layer 50 to have a large specific surface area and a rough surface, while the area not covered by the first electrode layer 40 and / or the second electrode layer 50 has a small specific surface area and a flat surface. This reduces contact resistivity while avoiding impact on surface passivation and reducing open-circuit voltage. Furthermore, the arc-shaped first doped layer 20 in contact with the first electrode layer 40 increases the contact area between the first electrode layer 40 and the first doped layer 20, thereby reducing the contact resistance between the first electrode layer 40 and the first doped layer 20. Similarly, the arc-shaped second doped layer 30 in contact with the second electrode layer 50 increases the contact area between the second electrode layer 50 and the second doped layer 30, thereby reducing the contact resistance between the second electrode layer 50 and the second doped layer 30, thus improving the conversion efficiency of the formed back-contact solar cell.

[0064] This invention provides a battery string, wherein the battery string includes any back-contact solar cell provided in any of the above embodiments of this invention, and possesses the beneficial effects of any back-contact solar cell provided in any of the above embodiments of this invention. The battery string can be formed by connecting multiple back-contact solar cells in series.

[0065] This invention provides a battery assembly, wherein the battery assembly includes any back-contact solar cell provided in any of the above embodiments of this invention, or the battery assembly includes a battery string provided in any of the above embodiments of this invention.

[0066] A battery module may include multiple back-contact solar cells, which can be connected in series to form a battery string. These battery strings can be connected in series, parallel, or a combination of series and parallel to achieve current output. For example, the connection between individual cells can be achieved by welding ribbons, or the connection between battery strings can be achieved by busbars. The battery module may also include a metal frame, a backsheet, photovoltaic glass, and an encapsulating film. The encapsulating film can be filled between the light-facing side of the back-contact solar cells and the photovoltaic glass, the back-facing side and the backsheet, and adjacent cells. As a filler, it can be a transparent colloid with good light transmittance and aging resistance; for example, the encapsulating film can be EVA film or POE film, and the specific choice can be made according to the actual situation, without limitation.

[0067] Photovoltaic glass can be applied to the encapsulating film on the light-facing side of the back-contact solar cell. This photovoltaic glass can be ultra-clear glass, possessing high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance of over 92%. It can protect the back-contact solar cell while minimizing impact on its efficiency. Simultaneously, the encapsulating film bonds the photovoltaic glass and the back-contact solar cell together, providing sealing, insulation, and waterproofing / moisture protection for the back-contact solar cell.

[0068] The backsheet can be attached to the adhesive film on the back side of the back-contact solar cell. The backsheet protects and supports the back-contact solar cell, providing reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, acrylic glass, and aluminum alloy TPT composite adhesive film, etc. The specific choice depends on the specific circumstances and is not limited here. The backsheet, back-contact solar cell, adhesive film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the main external support structure for the entire battery module, providing stable support and installation. For example, the battery module can be installed at the desired location using the metal frame.

[0069] The battery assembly provided in the embodiments of the present invention has the beneficial effects of any back-contact solar cell or battery string provided in any of the above embodiments of the present invention.

[0070] This invention provides a photovoltaic system, wherein the photovoltaic system includes the battery module provided in the above embodiments of this invention, and has the beneficial effects of the battery module provided in the above embodiments of this invention.

[0071] Photovoltaic systems can be applied in photovoltaic power plants, such as ground-mounted, rooftop, and floating power plants, as well as in equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it's understandable that the application scenarios of photovoltaic systems are not limited to these; that is, photovoltaic systems can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation network as an example, a photovoltaic system can include photovoltaic arrays, combiner boxes, and inverters. A photovoltaic array can be a combination of multiple battery modules; for example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic arrays are connected to combiner boxes, which collect the current generated by the photovoltaic arrays. The collected current flows through an inverter and is converted into AC power required by the mains grid before being connected to the mains grid to achieve solar power supply.

[0072] Since the battery module provided in the embodiments of the present invention has the beneficial effects of any back-contact solar cell or battery string provided in any of the above embodiments of the present invention, the photovoltaic system provided in the embodiments of the present invention has the beneficial effects of any back-contact solar cell or battery string provided in any of the above embodiments of the present invention.

[0073] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0074] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A back-contact solar cell, characterized in that, include: A silicon substrate, configured with a first conductivity type; the silicon substrate includes a first surface and a second surface disposed opposite to each other; The first doped layer is configured with a first conductivity type and is located on the first surface; The second doped layer is configured with a second conductivity type and is located on the first surface; Along the first direction, the first doped layer and the second doped layer are arranged alternately; A first electrode layer is located on the side of the first doped layer away from the first surface; a second electrode layer is located on the side of the second doped layer away from the first surface. Along the first direction, the first doped layer in contact with the first electrode layer is arc-shaped; And / or, along the first direction, the second doped layer in contact with the second electrode layer is arc-shaped.

2. The back-contact solar cell according to claim 1, characterized in that, The radius of curvature of the arc-shaped first doped layer is greater than or equal to 0.2 micrometers and less than or equal to 300 micrometers; And / or, the radius of curvature of the arc-shaped second doped layer is greater than or equal to 0.5 micrometers and less than or equal to 300 micrometers.

3. The back-contact solar cell according to claim 2, characterized in that, Along the first direction, the first surface of the silicon substrate is planar; Along the second direction, the distance between the arc-shaped first doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 400 nm; And / or, along the second direction, the distance between the arc-shaped second doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 400 nm; the first direction is perpendicular to the second direction, and the second direction is the thickness direction of the back-contact solar cell.

4. The back-contact solar cell according to claim 2, characterized in that, Along the first direction, the first surface of the silicon substrate is wavy; Along the second direction, the arc-shaped first doped layer is parallel to the first surface, and the distance between the arc-shaped first doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 180 nm. And / or, along the second direction, the arc-shaped second doped layer is parallel to the first surface, and the distance between the arc-shaped second doped layer and the first surface is greater than or equal to 20 nm and less than or equal to 180 nm.

5. The back-contact solar cell according to claim 1, characterized in that, Along the first direction, the first doped layer includes a first region and a second region; wherein, the first doped layer in contact with the first electrode layer is the first region; and the first doped layer not in contact with the first electrode layer is the second region. Along the first direction, the second doped layer includes a third region and a fourth region; wherein, the second doped layer in contact with the second electrode layer is the third region; and the second doped layer not in contact with the second electrode layer is the fourth region. The ratio of the radius of curvature of the first region to the radius of curvature of the second region is greater than or equal to 1.2 and less than or equal to 3; And / or, the ratio of the radius of curvature of the third region to the radius of curvature of the fourth region is greater than or equal to 1.5 and less than or equal to 2.

8.

6. The back-contact solar cell according to claim 5, characterized in that, It also includes polyhedral structures; The vertical projected area of ​​the polyhedral structure corresponding to the first region on the silicon substrate is smaller than the vertical projected area of ​​the polyhedral structure corresponding to the second region on the silicon substrate. And / or, the vertical projected area of ​​the polyhedral structure corresponding to the third region on the silicon substrate is smaller than the vertical projected area of ​​the polyhedral structure corresponding to the fourth region on the silicon substrate.

7. The back-contact solar cell according to claim 5, characterized in that, Along the second direction, the height difference between the highest point of the first region and the lowest point of the second region is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers; And / or, along the second direction, the height difference between the highest point of the third region and the lowest point of the fourth region is greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers.

8. The back-contact solar cell according to claim 1, characterized in that, Along the second direction, with the lowest point of the arc-shaped first doped layer as the vertex, the angle formed between the outline tangent of the first doped layer and the first direction is greater than or equal to 1° and less than or equal to 35°. And / or, along the second direction, with the lowest point of the arc-shaped second doped layer as the vertex, the angle formed between the outline tangent of the second doped layer and the first direction is greater than or equal to 1° and less than or equal to 35°.

9. The back-contact solar cell according to claim 1, characterized in that, Also includes: First tunneling layer and second tunneling layer; The first tunneling layer is located between the first surface and the first doped layer; The thickness of the first tunneling layer is greater than or equal to 0.2 nm and less than or equal to 3 nm; The second tunneling layer is located between the first surface and the second doped layer; the thickness of the second tunneling layer is greater than or equal to 0.2 nm and less than or equal to 3 nm.

10. The back-contact solar cell according to claim 1, characterized in that, Also includes: Anti-reflective layer; The antireflection layer is located on the side of the first doped layer and the second doped layer away from the first surface.

11. A method for fabricating a back-contact solar cell, characterized in that, include: Provide silicon substrate; The silicon substrate is configured with a first conductivity type; the silicon substrate includes a first surface and a second surface disposed opposite to each other; A first doped layer is formed on the first surface; The first doped layer is configured with a first conductivity type; A second doped layer is formed on the first surface; The second doped layer is configured with a second conductivity type; Along the first direction, the first doped layer and the second doped layer are arranged alternately; A first electrode layer is formed on the side of the first doped layer away from the first surface; A second electrode layer is formed on the side of the second doped layer away from the first surface; wherein, along the first direction, the first doped layer in contact with the first electrode layer is arc-shaped; and / or, along the first direction, the second doped layer in contact with the second electrode layer is arc-shaped.

12. A battery string, characterized in that, Including the back-contact solar cell as described in any one of claims 1-10.

13. A battery assembly, characterized in that, This includes the back-contact solar cell as described in any one of claims 1-10 or the battery string as described in claim 12.

14. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 13.

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