Solar cell and photovoltaic module

Abstract

Embodiments of the present disclosure relate to a solar cell and a photovoltaic module.SOLUTION: A solar cell, comprising a substrate having a front surface and a back surface opposite to each other, a tunneling layer located on the back surface of the substrate, and a doped conductive layer located on a surface of the tunneling layer away from the substrate, wherein the tunneling layer comprises a first region and a second region alternately arranged along a first direction; The first region includes a first dopant atom, the doped conductive layer includes a first doped region facing the first region and a second doped region facing the second region, the first doped region and the second doped region have different doping types, the first doped region includes the first dopant atom, and an atomic percentage of the first dopant atom in the first doped region is less than an atomic percentage of the first dopant atom in the first region. It is at least beneficial to improve the open-circuit voltage and the photoelectric conversion efficiency of the solar cell.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to the field of solar cells, and more particularly to solar cells and photovoltaic modules. [Background technology]

[0002] While fossil energy pollutes the atmosphere and has limited reserves, solar energy has the advantages of being clean, pollution-free, and abundant, making it an increasingly important clean energy source. Solar cells, with their excellent photoelectric conversion efficiency, are at the center of clean energy applications.

[0003] To maximize the efficiency of solar cells and their utilization of incident light, tunnel oxide passivated contact (TOPCon) cells and interdigitated back contact (IBC) crystalline silicon solar cells have emerged. The tunnel oxide layer and doped conductive layer on the back surface of TOPCon cells form a passivation contact structure, significantly improving the passivation effect and open circuit voltage of the solar cell and increasing the solar cell's photoelectric conversion efficiency. In IBC cells, both electrodes are located on the back surface of the cell, avoiding light blocking by electrodes on the front surface of the cell and significantly improving the solar cell's light absorption and photoelectric conversion efficiency. Summary of the Invention [Problem to be solved by the invention]

[0004] The present embodiments provide solar cells and photovoltaic modules that are advantageous in reducing carrier recombination losses in at least solar cells. [Means for solving the problem]

[0005] In an embodiment of the present application, a solar cell is provided, the solar cell including: a substrate having opposing front and back surfaces; a tunnel layer located on the back surface of the substrate; and a doped conductive layer located on the surface of the tunnel layer away from the substrate, the tunnel layer including first and second regions alternately arranged along a first direction, the first region including first dopant atoms, the doped conductive layer including a first doped region facing the first region and a second doped region facing the second region, the first doped region and the second doped region having different doping types, the first doped region including the first dopant atoms, and the atomic percentage of the first dopant atoms in the first doped region being smaller than the atomic percentage of the first dopant atoms in the first region.

[0006] In some embodiments, the ratio of the atomic percentage of the first dopant atoms in the first region to the atomic percentage of the first dopant atoms in the first doped region is 1-5.

[0007] In some embodiments, the atomic percentage of the first dopant atoms in the first region is between 1% and 10%.

[0008] In some embodiments, the atomic percentage of the first dopant atoms in the first doped region is between 0.2% and 5%.

[0009] In some embodiments, the first dopant atoms are N-type atoms.

[0010] In some embodiments, the atomic percentage of the first dopant atoms in the first doped region decreases in a gradient perpendicular to the back surface of the substrate and in a direction away from the substrate.

[0011] In some embodiments, the first region includes a first portion, the first portion contacting the substrate, and an atomic percentage of the first dopant atoms in the first portion is greater than an atomic percentage of the first dopant atoms in the first region.

[0012] In some embodiments, the atomic percentage of the first dopant atoms in the first portion is between 2% and 20%.

[0013] In some embodiments, the ratio of the thickness of the first portion to the thickness of the first region in a direction perpendicular to the rear surface of the substrate is 0.25 to 0.5.

[0014] In some embodiments, the first portion has a thickness of 0.25 nm to 1 nm in a direction perpendicular to the rear surface of the substrate.

[0015] In some embodiments, the first region includes a second portion, the second portion contacting the first doped region, and the atomic percentage of the first dopant atoms in the second portion is greater than the atomic percentage of the first dopant atoms in the first region.

[0016] In some embodiments, the atomic percentage of the first dopant atoms in the second portion is between 2% and 20%.

[0017] In some embodiments, the ratio of the thickness of the second portion to the thickness of the first region in a direction perpendicular to the rear surface of the substrate is 0.25 to 0.5.

[0018] In some embodiments, the second portion has a thickness of 0.25 nm to 1 nm in a direction perpendicular to the rear surface of the substrate.

[0019] Accordingly, the present embodiment further provides a photovoltaic module, which includes a cell string formed by connecting a plurality of the solar cells, an encapsulation layer for covering a surface of the cell string, and a cover plate for covering a surface of the encapsulation layer away from the cell string. [Effects of the Invention]

[0020] The technical solutions provided in the embodiments of the present application have at least the following advantages:

[0021] In the solar cell provided in one embodiment of the present application, the rear surface of the substrate has a passivation contact structure consisting of a tunnel layer and a doped conductive layer, which significantly reduces carrier recombination on the rear surface of the substrate, thereby reducing the recombination current on the rear surface of the substrate and lowering the carrier recombination loss of the solar cell. [Brief explanation of the drawings]

[0022] One or more embodiments are illustratively illustrated in the accompanying drawing figures, but these illustrative illustrations are not intended to be limiting of the embodiments, and unless otherwise specified, the accompanying drawing figures are not drawn to scale. [Figure 1] FIG. 1 is a diagram showing the overall structure of a solar cell provided in one embodiment of the present application. [Figure 2] FIG. 2 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 3] FIG. 3 is a top view of a tunneling layer provided in one embodiment of the present application. [Figure 4] FIG. 4 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 5] FIG. 5 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 6] FIG. 6 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 7] FIG. 7 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 8] FIG. 8 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 9]FIG. 9 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 10] FIG. 10 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 11] FIG. 11 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 12] FIG. 12 is a diagram showing the overall structure of another solar cell provided in one embodiment of the present application. [Figure 13] FIG. 13 is a diagram showing the structure of a photovoltaic module provided in another embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0023] 1 , an IBC cell generally includes a substrate 10, a tunnel dielectric layer 20, a doped conductive layer 30, and a plurality of electrodes 40. Here, the substrate 10 has opposing front and back surfaces, the tunnel dielectric layer 20 is located on the back surface of the substrate 10, the doped conductive layer 30 is located on the surface of the tunnel dielectric layer 20 away from the substrate 10, and the doped conductive layer 30 includes a first doping region 31 and a second doping region 32, where the first doping region 31 and the second doping region 32 have different doping types. Some of the electrodes 40 are in electrical contact with the first doping region 31, and the remaining electrodes 40 are in electrical contact with the second doping region 32, and the electrodes electrically contacting different doping regions are insulated from each other.

[0024] During the process of forming the IBC cell, all electrodes 40 are disposed on the backside of the substrate 10, so the front side of the resulting IBC cell does not have an electrode 40. This avoids light blocking by the electrode 40 disposed on the front side of the IBC cell, significantly increasing the actual light-receiving area of ​​the front side of the IBC cell. The back side of the substrate 10 has a passivation contact structure consisting of the tunnel dielectric layer 20 and the doped conductive layer 30, significantly reducing carrier recombination loss on the back side of the substrate 10. In addition, the IBC cell has a higher light utilization rate than conventional IBC cells, significantly improving photoelectric conversion efficiency.

[0025] The IBC cell may also include an isolation layer 50 extending through the thickness of the doped conductive layer 30. The isolation layer 50 is located between the first doping region 31 and the second doping region 32 and serves to isolate the first doping region 31 and the second doping region 32, which have different doping types. The isolation layer 50 may be a deposited insulating dielectric layer or a groove formed by patterned etching. While FIG. 1 illustrates an example in which the isolation layer 50 extends through only the doped conductive layer 30, in specific applications, the isolation layer 50 may extend into the tunnel dielectric layer 20 and further through the tunnel dielectric layer 20. This is not a limitation of the embodiments of the present application.

[0026] Note that some drawings in the examples of the present application only show a portion of the structure of the IBC cell, and the IBC cell may include other film layers, such as a passivation anti-reflective layer located on the surface of the doped conductive layer away from the substrate and / or a passivation anti-reflective layer located on the front surface of the substrate, but these will not be described here.

[0027] One embodiment of the present application provides a solar cell, in which the back surface of the substrate has a passivation contact structure consisting of a tunnel layer and a doped conductive layer, which significantly reduces carrier recombination on the back surface of the substrate, thereby reducing the recombination current on the back surface of the substrate and lowering the carrier recombination loss of the solar cell. Because the doped conductive layer is composed of a first doped region and a second doped region with different doping types, both electrodes of the solar cell can be provided on the back surface of the solar cell, which significantly reduces the influence of electrodes provided on the front surface of the solar cell on the light absorption of the solar cell and improves the light absorption of the solar cell. The tunnel layer is composed of first and second regions alternately arranged along a first direction, the first region facing the first doping region, the first region and the first doping region both containing first dopant atoms, and the atomic percentage of the first dopant atoms in the first region is lower than the atomic percentage of the first dopant atoms in the first doping region, so that the first dopant atoms are concentrated in the tunnel layer, thereby increasing the open circuit voltage of the solar cell; and further, doping the tunnel layer with the first dopant atoms improves the tunneling ability of carriers in the tunnel layer, thereby significantly increasing the photoelectric conversion efficiency of the solar cell.

[0028] Hereinafter, each embodiment of the present application will be described in detail with reference to the accompanying drawings. However, as will be understood by those skilled in the art, although many technical details are proposed in the embodiments of the present application to help readers better understand the present application, the technical solution claimed for protection by the present application can be realized without these technical details and various changes and modifications based on the following embodiments.

[0029] One embodiment of the present application provides a solar cell, as shown in FIGS. 2 and 3, where FIG. 2 is a diagram showing the overall structure of the solar cell and FIG. 3 is a top view of a tunnel layer, where the X direction is a first direction.

[0030] The solar cell includes a substrate 101 having opposing front and back surfaces, a tunnel layer 102 located on the back surface of the substrate 101, and a doped conductive layer 103 located on the surface of the tunnel layer 102 away from the substrate 101, wherein the tunnel layer 102 includes first regions 121 and second regions 122 alternately arranged along a first direction, the first region 121 including first dopant atoms, the doped conductive layer 103 including a first doping region 131 facing the first region 121 and a second doping region 132 facing the second region 122, the first doping region 131 and the second doping region 132 having different doping types, the first doping region 131 including the first dopant atoms, and the atomic percentage of the first dopant atoms in the first doping region 131 being smaller than the atomic percentage of the first dopant atoms in the first region 121.

[0031] In the solar cell, the back surface of the substrate 101 has a passivation contact structure consisting of a tunnel layer 102 and a doped conductive layer 103. The tunnel layer 102 passivates defects on the surface of the substrate 101 through bonding, and the doped conductive layer 103 applies field passivation to the substrate 101 through the electric field formed therein, significantly reducing carrier recombination on the back surface of the substrate 101 and lowering carrier recombination loss in the solar cell. The doped conductive layer 103 is composed of a first doped region 131 and a second doped region 132 with different doping types. This allows both electrodes of the solar cell to be provided on the back surface, thereby avoiding the light-blocking effect of electrodes provided on the front surface of the solar cell and enhancing light absorption in the solar cell. Here, the front surface of the solar cell refers to the surface on the side where the incident light received by the solar cell is stronger, and the back surface of the solar cell refers to the surface on the side where the incident light received by the solar cell is weaker.

[0032] The tunnel layer 102 is composed of a first region 121 and a second region 122 alternately arranged along a first direction, the first region 121 facing the first doping region 131, the doping type of the first region 121 and the first doping region 131 being the same, and the atomic percentage of the first dopant atoms in the first region 121 being greater than the atomic percentage of the first dopant atoms in the first doping region 131, and the first dopant atoms being concentrated in the first region 121 of the tunnel layer 102, so that the passivation contact structure can achieve a better passivation effect on the substrate 101 and increase the open circuit voltage of the solar cell. Furthermore, since the first region 121 is doped with the first dopant atoms, the tunneling ability of carriers in the first region 121 is improved, which significantly reduces the carrier collection loss of the solar cell and improves the photoelectric conversion efficiency of the solar cell.

[0033] 2 illustrates an example in which the first doping region 131 and the second doping region 132 are adjacent to each other, but as shown in FIGS. 2 and 4, FIG. 4 illustrates the overall structure of a solar cell, where the X direction is the first direction. The solar cell may include a plurality of isolation layers 50 penetrating the thickness of the stacked structure consisting of the tunnel layer 102 and the doped conductive layer 103. The isolation layers 50 are used to separate the first region 121 and the second region 122 and the first doping region 131 and the second doping region 132. The isolation layers 50 may be grooves directly penetrating the thickness of the stacked structure, or may be dielectric layers made of a non-conductive insulating dielectric material. In FIG. 4, an example is described in which the isolation layer 50 directly penetrates the tunnel layer 102 and the doped conductive layer 103. However, the isolation layer 50 may penetrate only the thickness of the doped conductive layer 103, or may penetrate only the thickness of the doped conductive layer 103 and further extend a certain distance into the tunnel layer 102; however, the embodiments of the present application are not limited to this.

[0034] In some embodiments, the substrate 101 may be a P-type semiconductor substrate or an N-type semiconductor substrate, where the doping type of one of the first doping region 131 and the second doping region 132 is P-type and the doping type of the other is N-type, and the doping concentration of the doping region of the doped conductive layer 103 that has the same doping type as that of the substrate 101 is greater than that of the substrate 101. Here, the doping concentration may be expressed as the atomic percentage of the doping element in the film layer.

[0035] The N-type semiconductor substrate is doped with an N-type doping element, which may be any one of Group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type doping element, which may be any one of Group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). Similarly, the P-type doping element in the doped conductive layer 103 may be any one of the above Group III elements, and the N-type doping element may be any one of the above Group V elements.

[0036] In some embodiments, the material of the substrate 101 may be an elemental semiconductor material, which may be composed of a single element, such as silicon or germanium, where the elemental semiconductor material may be in a monocrystalline state, a polycrystalline state, an amorphous state, or a microcrystalline state (a state having both monocrystalline and amorphous states is called a microcrystalline state), for example, silicon may be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0037] In some embodiments, the material of the substrate 101 may be a compound semiconductor material. Common compound semiconductor materials include, but are not limited to, silicon germanium, silicon carbide, gallium arsenide, indium gallide, perovskites, cadmium telluride, copper indium selenide, etc. The substrate 101 may be a sapphire substrate, a silicon-on-insulator substrate, or a germanium-on-insulator substrate.

[0038] In some embodiments, the material of the tunnel layer 102 may be at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or magnesium fluoride.

[0039] In some embodiments, the material of the doped conductive layer 103 may be at least one of the following materials: nanocrystalline silicon, polycrystalline silicon, microcrystalline silicon, amorphous silicon, silicon carbide, or titanium nitride.

[0040] In some embodiments, the ratio of the atomic percentage of the first dopant atoms in the first region 121 to the atomic percentage of the first dopant atoms in the first doped region 131 is between 1-5.

[0041] For ease of understanding, take as an example that the substrate 101 is an N-type substrate, the doping type of the first region 121 and the first doped region 131 is N-type, and the dopant is phosphorus. The main functions of the tunnel layer 102 and the doped conductive layer 103 are to provide excellent passivation for the substrate 101, reduce carrier recombination on the back surface of the substrate 101, and improve the open circuit voltage and photoelectric conversion efficiency of the solar cell.

[0042] When the atomic percentage of phosphorus in the first region 121 is significantly greater than the atomic percentage of phosphorus in the first doping region 131, the phosphorus is concentrated in the first region 121 of the tunnel layer 102, and the passivation contact structure on the back surface of the substrate 101 provides a better passivation effect for the substrate 101, which can further increase the open circuit voltage of the solar cell and reduce the carrier recombination on the back surface of the substrate 101.

[0043] Another function of the tunnel layer 102 is to realize selective carrier transport. When the doped conductive layer 103 is composed of a first doping region 131 and a second doping region 132 with different doping types, the portions of the tunnel layer 102 directly facing the first doping region 131 and the second doping region 132 must realize selective transport of holes and electrons, respectively. The dopant in both the first region 121 and the first doping region 131 is phosphorus, and the first region 121 must selectively transport holes to the first doping region 131. The large amount of phosphorus concentrated in the first region 121 improves the tunneling ability of holes in the first region 121, and electrons that overflow from the first region 121 also recombine with holes. Furthermore, the higher the phosphorus doping concentration in the first region 121, the greater the recombination of electrons and holes.

[0044] Therefore, in the process of forming the tunnel layer 102 and the doped conductive layer 103, the ratio of the atomic percentage of the first dopant atoms in the first region 121 to the atomic percentage of the first dopant atoms in the first doped region 131 can be set to 1 to 5, for example, 1.1, 1.2, 1.35, 1.5, 1.75, 2, 2.4, 2.8, 3.25, 3.75, 4.5, or 4.85. By setting the ratio of the doping concentration of the first region 121 to the doping concentration of the first doping region 131 within an appropriate range, the open circuit voltage of the solar cell is effectively improved, the carrier collection loss on the back surface of the substrate 101 is reduced, and the recombination effect of holes and electrons in the first region 121 is controlled within a small range, so that the impact of the improved solar cell passivation effect and carrier tunneling ability on the solar energy photoelectric conversion efficiency is greater than the impact of the carrier recombination in the first region 121 on the solar cell photoelectric conversion efficiency, thereby effectively improving the photoelectric conversion efficiency of the solar cell.

[0045] In some embodiments, the atomic percentage of the first dopant atoms in the first doped region 131 is between 0.2% and 5%.

[0046] As can be seen from the above analysis and description of the doped conductive layer 103 and the tunnel layer 102, the first doped region 131, together with the first region 121, applies passivation to the substrate 101, while the first doped region 131 also serves to provide a basis for lateral transport of carriers, so that carriers in the first doped region 131 are concentrated in the electrode that is in electrical contact with the first doped region 131.

[0047] If the atomic percentage of the first dopant atoms in the first doping region 131 is too small, i.e., if the doping concentration of the first doping region 131 is too low, the number of mobile carriers in the first doping region 131 is too small, and the carriers transported to the first doping region 131 cannot be effectively concentrated at the electrode in electrical contact with the first doping region 131, resulting in too much carrier collection loss in the solar cell. If the atomic percentage of the first dopant atoms in the first doping region 131 is too high, i.e., if the doping concentration of the first doping region 131 is too high, the atomic percentage of the first dopant atoms in the first region 121 becomes too high, and the carrier recombination loss due to the electron-hole recombination effect in the first region 121 increases significantly. As a result, the impact of the increased carrier recombination loss in the first region 121 exceeds the impact of the reduced carrier recombination loss on the back surface of the substrate 101.

[0048] Therefore, the atomic percentage of the first dopant atoms in the first doping region 131 can be set to 0.2% to 5%, for example, 0.25%, 0.5%, 0.8%, 1.2%, 1.5%, 1.8%, 2.25%, 2.75%, 3.5%, or 4.5%, etc. This ensures good lateral transport ability of carriers in the first doping region 131 and reduces carrier collection loss of the solar cell, while effectively controlling the carrier recombination effect in the first region 121 and ensuring a reduction in carrier recombination loss of the entire solar cell, thereby effectively improving the photoelectric conversion efficiency of the solar cell.

[0049] In some embodiments, the atomic percentage of the first dopant atoms in the first doped region 131 decreases in a gradient perpendicular to the back surface of the substrate 101 and in a direction away from the substrate 101 .

[0050] During the process of forming the doped conductive layer 103, the first doped region 131 of the doped conductive layer 103 can be doped with first dopant atoms by at least one of multiple doping processes, such as ion implantation or in-situ doping, and the distribution order of the first dopant atoms in the first doped region 131 can be adjusted by adjusting the deposition process of the doped conductive layer 103 and / or the doping process of the first doped region 131.

[0051] As can be seen from the above analysis of the first doping region 131, the atomic percentage of the first dopant atoms in the first doping region 131 mainly affects the passivation effect of the passivation contact structure on the substrate 101 and the collection loss of carriers collected to the electrode via the first doping region 131. In the process of carriers being collected to the electrode in the first doping region 131, the lateral movement distance of the carriers in the first doping region 131 decreases as the distance between the carriers and the electrode decreases.

[0052] Therefore, the atomic percentage of the first dopant atoms in the first doping region 131 can be set to decrease in a gradient in a direction perpendicular to the back surface of the substrate 101 and away from the substrate 101. When the atomic percentage of the first dopant atoms in the first doping region 131 is constant, the gradient decrease in atomic percentage can ensure the carrier collection efficiency in the first doping region 131 and can provide stronger field passivation for the substrate 101, further reducing carrier recombination on the back surface of the substrate 101.

[0053] In addition, the atomic percentage of the first dopant atoms in the first doping region 131 can be set to change in a gradient manner, and the atomic percentage of the first dopant atoms in the first region 121 can be set to decrease in a gradient manner in a direction perpendicular to the back surface of the substrate 101 and away from the substrate 101, thereby reducing electron-hole recombination in the first region 121.

[0054] In some embodiments, the atomic percentage of the first dopant atoms in the first region 121 is between 1% and 10%.

[0055] As can be seen from the above analysis and explanation of the atomic percentage of the first dopant atoms in the first region 121, if the atomic percentage of the first dopant atoms in the first region 121 is too small, the passivation contact structure on the back surface of the substrate 101 will have a limited effect on improving the passivation effect on the back surface of the substrate 101, resulting in a small reduction in carrier recombination loss on the back surface of the substrate 101. If the atomic percentage of the first dopant atoms in the first region 121 is too large, the recombination effect of holes and electrons in the first region 121 will be too large in the process of transporting carriers to the first doped region 131, resulting in a significant increase in carrier recombination loss in the first region 121, which is likely to result in an adverse increase in carrier recombination loss of the entire solar cell.

[0056] Therefore, in the process of forming the tunnel layer 102, the atomic percentage of the first dopant atoms in the first region 121 can be set to 1% to 10%, such as 1.25%, 1.5%, 2%, 2.5%, 3.5%, 5%, 6.5%, 8%, or 9.5%. Setting the atomic percentage of the first dopant atoms in the first region 121 within an appropriate range improves the tunneling ability of carriers in the first region 121, reduces carrier recombination loss on the back surface of the substrate 101, and prevents excessive carrier recombination loss in the first region 121. This reduces the carrier recombination loss of the entire solar cell, thereby improving the open circuit voltage and photoelectric conversion efficiency of the solar cell.

[0057] 2 and 5, FIG. 5 illustrates the overall structure of another solar cell, where the X direction is a first direction and the Y direction is a direction perpendicular to the back surface of the substrate 201. In some embodiments, the first region 221 includes a first portion 223, the first portion 223 contacts the substrate 201, and the atomic percentage of the first dopant atoms in the first portion 223 is greater than the atomic percentage of the first dopant atoms in the first region 221.

[0058] In the solar cell shown in FIG. 5, the substrate 201, the doped conductive layer 203, the first doped region 231, the second doped region 232 and the second region 222 of the tunnel layer 202 are similar to the above-mentioned substrate 101, the doped conductive layer 103, the first doped region 131, the second doped region 132 and the second region 122 of the tunnel layer 102, respectively, and therefore will not be described here.

[0059] As can be seen from the analysis and explanation of the first region 121 above, one function of the first region 221 is to provide a passivation effect to the substrate 201, and another function is to selectively transport specific carriers to the first doping region 231 directly opposite the first region 221.

[0060] Therefore, in the process of forming the first region 221, the first region 221 can be formed in a film layer having a heavily doped portion, and the heavily doped portion faces the substrate 201, i.e., the first region 221 has a first portion 223, the first portion 223 contacts the back surface of the substrate 201, and the atomic percentage of the first dopant atoms in the first portion 223 is greater than the atomic percentage of the first dopant atoms in the first region 221. Here, the atomic percentage of the first dopant atoms in the first region 221 refers to the average atomic percentage of the first dopant atoms in the first region 221 including the first portion 223. That is, the first region 221 can be considered to be composed of two portions, i.e., the first portion 223 and a portion other than the first portion 223, and the doping concentration of the dopant in the first portion 223 is higher than the doping concentration of the dopant in the portion of the first region 221 excluding the first portion 223.

[0061] One of the main ways in which first region 221 provides a passivation effect to substrate 201 is by forming an electric field between it and substrate 201 through a film layer with a doping concentration higher than that of substrate 201, which adjusts the mobility tendencies of carriers of different polarities so that the number of carriers of one polarity on the back surface of substrate 201 opposite first region 221 is much greater than the number of carriers of the other polarity. As a result, after first portion 223 is formed, the electric field for adjusting the mobility tendencies of carriers of different polarities is stronger, which further improves the passivation effect of first region 221 and first doped region 231 on substrate 101, reduces carrier loss on the back surface of substrate 201, and increases the open-circuit voltage of the solar cell.

[0062] 5 and 6, FIG. 6 is a diagram showing the overall structure of a solar cell, and the solar cell may further include a plurality of isolation layers 50. Here, the structure of the isolation layer 50 in FIG. 6 is similar to the structure of the isolation layer 50 described above, so the specific materials and specification parameters will not be described here. The isolation layer 50 can prevent recombination of holes and electrons between the first doping region 231 and the second doping region 232, and improve the carrier lifetime.

[0063] In some embodiments, the atomic percentage of the first dopant atoms in first portion 223 is between 2% and 20%.

[0064] When the first region 221 is provided in a structure including the first portion 223, the atomic percentage of the first dopant atoms in the first portion 223 affects the electric field strength. If the atomic percentage of the first dopant atoms in the first portion 223 is low, the field passivation effect of the first portion 223 is not significantly improved, and the carrier recombination on the back surface of the substrate 201 cannot be effectively reduced. If the atomic percentage of the first dopant atoms in the first portion 223 is too high, the recombination of electrons and holes in the first portion 223 is too strong during the process of transporting carriers to the first doped region 231, which can significantly increase the overall carrier recombination loss in the first region 221 and ultimately the overall carrier recombination loss of the solar cell.

[0065] Therefore, in the process of forming the tunnel layer 202, the atomic percentage of the first dopant atoms in the first portion 223 can be set to 2% to 20%, such as 2.5%, 3%, 4%, 5%, 7.5%, 10%, 13%, 16%, or 19%. Setting the doping concentration of the dopant in the first portion 223 within an appropriate range significantly enhances the passivation effect of the passivation contact structure on the substrate 201 and the tunneling ability of carriers in the first region 221, effectively suppresses the overall carrier recombination loss in the first region 221, significantly reduces the carrier recombination loss of the solar cell, and improves the photoelectric conversion efficiency of the solar cell.

[0066] The tunnel layer 202 includes a plurality of first regions 221, and the atomic percentage of the first dopant atoms in the first portions 223 of each first region 221 may be the same or different, although this is not limited in the embodiments of the present application.

[0067] In some embodiments, the ratio of the thickness of the first portion 223 to the thickness of the first region 221 in a direction perpendicular to the rear surface of the substrate 201 is 0.25 to 0.5.

[0068] In a direction perpendicular to the back surface of the substrate 201, the thickness of the first portion 223 refers to the average distance h1 between the two opposing surfaces of the first portion 223 in the direction perpendicular to the back surface of the substrate 201, and the thickness of the first region 221 refers to the average distance h2 between the two opposing surfaces of the first region 221 in the direction perpendicular to the back surface of the substrate 201.

[0069] As can be seen from the above description and analysis of the first portion 223, while the first portion 223 contributes to strengthening the passivation effect of the passivation contact structure on the substrate 201, it also significantly strengthens the electron-hole recombination effect in the first portion 223, which is likely to affect the carrier recombination loss in the first region 221 and the entire solar cell.

[0070] Factors that affect the magnitude of carrier recombination loss in the first portion 223 include the atomic percentage of the first dopant atoms in the first portion 223 and the distance traveled by carriers while passing through the first portion 223. When the atomic percentage of the first dopant atoms is constant, the thicker the first portion 223, the greater the carrier recombination loss in the first portion 223. Furthermore, when the atomic percentage of the first dopant atoms in the first region 221 is constant, the thicker the first portion 223, the lower the atomic percentage of the first dopant atoms per unit thickness in the first portion 223, which is likely to result in a smaller improvement in the passivation effect of the passivation contact structure on the substrate 201.

[0071] Therefore, in the process of providing the tunnel layer 202, the ratio of the thickness of the first portion 223 to the thickness of the first region 221 in the direction perpendicular to the rear surface of the substrate 201 can be set to 0.25 to 0.5, and may be, for example, 0.275, 0.3, 0.325, 0.375, 0.425, or 0.45. The first portion 223 can significantly enhance the passivation effect of the passivation contact structure on the substrate 201, and can also suppress the carrier recombination loss in the first region 221 to a small range, thereby significantly reducing the carrier recombination loss of the entire solar cell.

[0072] In some embodiments, the thickness of first portion 223 is 0.25 nm to 1 nm in a direction perpendicular to the rear surface of substrate 201. As can be seen from the above description and analysis of the thickness of first portion 223, the thickness of tunnel layer 202 itself, which is a tunnel oxide layer in the passivation contact structure, is typically 1 nm to 2 nm. Therefore, in the process of providing tunnel layer 202, the thickness of first portion 223 in a direction perpendicular to the rear surface of substrate 201 can be set to 0.25 nm to 1 nm, and may be, for example, 0.3 nm, 0.35 nm, 0.5 nm, 0.7 nm, or 0.9 nm.

[0073] 2 and 7, FIG. 7 illustrates the overall structure of another solar cell, where the X direction is the first direction and the Y direction is the direction perpendicular to the back surface of the substrate 301. In some embodiments, the first region 321 includes a second portion 324, the second portion 324 contacts the first doped region 331, and the atomic percentage of the first dopant atoms in the second portion 324 is greater than the atomic percentage of the first dopant atoms in the first region 321.

[0074] In the solar cell shown in FIG. 7, the substrate 301, the doped conductive layer 303, the first doped region 331, the second doped region 332 and the second region 322 of the tunnel layer 302 are similar to the substrate 101, the doped conductive layer 103, the first doped region 131, the second doped region 132 and the second region 122 of the tunnel layer 102 described above, respectively, and therefore will not be described here.

[0075] As can be seen from the above description and analysis of the first region 121, one function of the first region 321 is to provide a passivation effect for the substrate 301, and the other function is to selectively transport specific carriers to the first doping region 331 opposite the first region 321. The passivation effect of the first region 321 on the substrate 301 mainly includes two aspects: first, hydrogen overflowing from the first region 321 bonds with the rear surface of the substrate 301 to passivate defects on the rear surface of the substrate 301; and second, due to the difference in doping concentration and / or doping type between the first region 321 and the substrate 301, an electric field is formed on the rear surface of the substrate 301, and the electric field is used to adjust the mobility tendencies of carriers of different polarities, so that the number of carriers of one polarity on the rear surface of the substrate 301 opposite the first region 321 is much greater than the number of carriers of the other polarity.

[0076] Therefore, in the process of forming the first region 321, the first region 321 can be set to a film layer having a heavily doped portion, and the heavily doped portion is away from the substrate 301. That is, the first region 321 has a second portion 324, which is located on a side of the first region 321 away from the back surface of the substrate 301, and the atomic percentage of the first dopant atoms in the second portion 324 is greater than the atomic percentage of the first dopant atoms in the first region 321. Here, the atomic percentage of the first dopant atoms in the first region 321 is the average atomic percentage of the first dopant atoms in the first region 321 including the second portion 324. That is, the first region 321 can be considered to be composed of two parts: the second part 324 and the part other than the second part 324, and the doping concentration of the dopant in the second part 324 is higher than the doping concentration of the dopant in the part of the first region 321 other than the second part 324.

[0077] After the first region 321 is installed in the structure with the second portion 324, the atomic percentage of the first dopant atoms in the second portion 324 is higher than the average atomic percentage of the first dopant atoms in the first region 324, which can form a stronger electric field between the second portion 324 and the substrate 301 and thereby improve the field passivation effect of the passivation contact structure on the back surface of the substrate 301. At the same time, because the percentage of the first dopant atoms in the second portion 324 is higher, when the average percentage of the first dopant atoms in the first region 321 is constant, the first region 321 has a lower first dopant atom concentration in the portion adjacent to the back surface of the substrate 301. This allows the first region 321 to better overflow hydrogen and passivate defects on the back surface of the substrate 301, further reducing carrier recombination on the back surface of the substrate 301 and thereby reducing carrier recombination loss in the solar cell.

[0078] 7 and 8, FIG. 8 is a diagram showing the overall structure of a solar cell, and the solar cell may further include a plurality of isolation layers 50. Here, the structure of the isolation layer 50 in FIG. 8 is similar to the structure of the isolation layer 50 described above, so the specific materials and specification parameters will not be described here. The isolation layer 50 can prevent recombination of holes and electrons between the first doping region 331 and the second doping region 332 and improve carrier lifetime.

[0079] In some embodiments, the atomic percentage of the first dopant atoms in second portion 324 is between 2% and 20%.

[0080] When the first region 321 is provided in a structure including the second portion 324, the atomic percentage of the first dopant atoms in the second portion 324 affects the electric field strength. If the atomic percentage of the first dopant atoms in the second portion 324 is low, the passivation effect of the second portion 324 is not significantly improved, and the carrier recombination on the back surface of the substrate 301 cannot be effectively reduced. If the atomic percentage of the first dopant atoms in the second portion 324 is too high, the recombination of electrons and holes in the second portion 324 is too strong during the process of transporting carriers to the first doped region 331, which can significantly increase the overall carrier recombination loss in the first region 321 and, ultimately, the carrier recombination loss of the entire solar cell.

[0081] Therefore, during the process of forming the tunnel layer 302, the atomic percentage of the first dopant atoms in the second portion 324 can be set to 2% to 20%, such as 2.5%, 3%, 4%, 5%, 7.5%, 10%, 13%, 16%, or 19%. Setting the doping concentration of the dopant in the second portion 324 within an appropriate range can significantly enhance the passivation effect of the passivation contact structure on the substrate 301, effectively suppress the overall carrier recombination loss in the first region 321, significantly reduce the carrier recombination loss of the solar cell, and improve the photoelectric conversion efficiency of the solar cell.

[0082] The tunnel layer 302 includes a plurality of first regions 321, and the atomic percentage of the first dopant atoms in the second portions 324 of the first regions 321 may be the same or different, although this is not limited in the embodiments of the present application.

[0083] In some embodiments, the ratio of the thickness of the second portion 324 to the thickness of the first region 221 in the direction perpendicular to the rear surface of the substrate 201 is 0.25 to 0.5.

[0084] In a direction perpendicular to the rear surface of the substrate 301, the thickness of the second portion 324 refers to the average distance h3 between the two opposing surfaces of the second portion 324 in a direction perpendicular to the rear surface of the substrate 301, and the thickness of the first region 321 refers to the average distance h2 between the two opposing surfaces of the first region 321 in a direction perpendicular to the rear surface of the substrate 301.

[0085] As can be seen from the above description and analysis of the second portion 324, while the second portion 324 contributes to strengthening the passivation effect of the passivation contact structure on the substrate 301, the electron-hole recombination effect in the second portion 324 is also significantly strengthened, which is likely to affect the carrier recombination loss in the first region 321 and the entire solar cell.

[0086] Factors that affect the magnitude of carrier recombination loss in second portion 324 include the atomic percentage of the first dopant atoms in second portion 324 and the distance traveled by carriers while passing through second portion 324. When the atomic percentage of the first dopant atoms is constant, the thicker second portion 324 is, the greater the carrier recombination loss in second portion 324. Furthermore, when the atomic percentage of the first dopant atoms in first region 321 is constant, the thicker second portion 324 is, the lower the atomic percentage of the first dopant atoms per unit thickness in second portion 324 is, which is likely to result in a smaller improvement in the passivation effect of the passivation contact structure on substrate 301.

[0087] Therefore, in the process of providing the tunnel layer 302, the ratio of the thickness of the second portion 324 to the thickness of the first region 321 in the direction perpendicular to the rear surface of the substrate 301 can be set to 0.25 to 0.5, such as 0.275, 0.3, 0.325, 0.375, 0.425, or 0.45. The second portion 324 significantly enhances the passivation effect of the passivation contact structure on the substrate 301, and also minimizes the carrier recombination loss in the first region 321, thereby significantly reducing the carrier recombination loss of the entire solar cell.

[0088] In some embodiments, the thickness of second portion 324 is 0.25 nm to 1 nm in a direction perpendicular to the back surface of substrate 301. As can be seen from the above description and analysis of the thickness of second portion 324, in the passivation contact structure, the thickness of tunnel layer 302 itself, which is a tunnel oxide layer, is typically 1 nm to 2 nm. Therefore, in the process of disposing tunnel layer 302, the thickness of second portion 324 in a direction perpendicular to the back surface of substrate 301 can be set to 0.25 nm to 1 nm, and may be, for example, 0.3 nm, 0.35 nm, 0.5 nm, 0.7 nm, or 0.9 nm.

[0089] In some embodiments, the solar cell may further include a first passivation layer and a plurality of electrodes located on the surface of the doped conductive layer 303 away from the substrate 301, the electrodes electrically contacting the doped conductive layer 303 through the first passivation layer. The material of the first passivation layer may include at least one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride. The first passivation layer may have a single-layer structure or a stacked structure. In the case of a stacked structure, the layers are stacked sequentially along a first direction, and the materials of the different layers may be different from each other, or some layers may be the same and different from the materials of the other layers. For example, the stacked structure may be a two-layer structure consisting of a silicon nitride layer and an aluminum oxide layer stacked one on top of the other.

[0090] In some embodiments, the solar cell may further include a second passivation layer located on the front surface of the substrate 301, and the material of the second passivation layer may include at least one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride. Similarly, the second passivation layer may have a single-layer structure or a multilayer structure. The embodiments of the present application are not limited thereto.

[0091] The surface of the first passivation layer away from the substrate 301 may be smooth or uneven, i.e., the side of the first passivation layer away from the substrate 301 has an uneven shape, which can extend the optical path length of incident light in the solar cell. The surface of the second passivation layer away from the substrate 301 may also be smooth or uneven, and when the side of the second passivation layer away from the substrate 301 has an uneven shape, the second passivation layer significantly reduces the light reflection of the incident light in the solar cell, which in turn improves the light absorption amount of the solar cell and increases the photoelectric conversion efficiency of the solar cell.

[0092] 2 and 9, Fig. 9 is a diagram showing the overall structure of a solar cell, and the cell structures shown in the above-described embodiments of the present application are described using the example of an IBC cell as the solar cell. In some embodiments, the solar cell may be a TOPCon cell. When the solar cell is a TOPCon cell, the back surface of the substrate 401 has a tunnel layer 402 and a doped conductive layer 403 located on the surface of the tunnel layer 402 away from the substrate 401. The front surface of the substrate 401 has an emitter 404, and the doping conductive layer 403 has the same doping type as the substrate 401, but the emitter 404 and the substrate 401 have different doping types. That is, the substrate 401 and the doping conductive layer 403 both contain first dopant atoms, and the emitter 404 contains second dopant atoms. The atomic percentage of the first dopant atoms in the doped conductive layer 403 is higher than the atomic percentage of the first dopant atoms in the substrate 401 and lower than the atomic percentage of the first dopant atoms in the tunnel layer 402. That is, the first dopant atoms can be concentrated in the tunnel layer 402 on the back side of the TOPCon cell, which can improve the passivation effect and open circuit voltage of the TOPCon cell.

[0093] In some embodiments, the ratio of the atomic percentage of the first dopant atoms in the tunnel layer 402 to the atomic percentage of the first dopant atoms in the doped conductive layer 403 may be between 1 and 5, such as 1.1, 1.2, 1.35, 1.5, 1.75, 2, 2.4, 2.8, 3.25, 3.75, 4.5, or 4.85.

[0094] In some embodiments, the atomic percentage of the first dopant atoms in the doped conductive layer 403 may be between 0.2% and 5%, such as 0.25%, 0.5%, 0.8%, 1.2%, 1.5%, 1.8%, 2.25%, 2.75%, 3.5%, or 4.5%.

[0095] In some embodiments, the atomic percentage of the first dopant atoms in the doped conductive layer 403 decreases in a gradient along a direction perpendicular to the back surface of the substrate 401 and away from the substrate 401 .

[0096] In some embodiments, the atomic percentage of the first dopant atoms in the tunnel layer 402 may be between 1% and 10%, such as 1.25%, 1.5%, 2%, 2.5%, 3.5%, 5%, 6.5%, 8%, or 9.5%.

[0097] The substrate 410 in the TOPCon cell is similar to the substrate 101 in the IBC cell, and therefore will not be described here. The doped conductive layer 403 in the TOPCon cell can be analogized to the first doped region 131 in the IBC cell, the tunnel layer 402 in the TOPCon cell can be analogized to the first region 121 in the IBC cell, and the emitter 404 in the TOPCon cell can be analogized to the second doped region 132 in the IBC cell.

[0098] Furthermore, the material of the doped conductive layer 403 is similar to that of the first doping region 131, and the material of the tunnel layer 402 is similar to that of the first region 121, so a description thereof will be omitted here. The material of the emitter 404 may be similar to that of the substrate 401 and may include at least one of aluminum oxide, silicon oxide, and silicon nitride.

[0099] 9 and 10, FIG. 10 illustrates the overall structure of another solar cell, where the Y direction is perpendicular to the rear surface of the substrate 401. In some embodiments, the tunnel layer 402 includes a first portion 421, which is in contact with the substrate 401. The atomic percentage of the first dopant atoms in the first portion 421 is greater than the atomic percentage of the first dopant atoms in the tunnel layer 402. Here, the atomic percentage of the first dopant atoms in the tunnel layer 402 refers to the average atomic percentage of the first dopant atoms in the tunnel layer 402, including the first portion 421. That is, the tunnel layer 402 can be considered to be composed of two portions, the first portion 421 and a portion other than the first portion 421, and the doping concentration of the dopant in the first portion 421 is higher than the doping concentration of the dopant in the portion of the tunnel layer 402 excluding the first portion 421.

[0100] In some embodiments, the ratio of the thickness of the first portion 421 to the thickness of the tunnel layer 402 in a direction perpendicular to the rear surface of the substrate 401 is 0.25 to 0.5, and may be, for example, 0.275, 0.3, 0.325, 0.375, 0.425, or 0.45. The thickness of the first portion 421 in a direction perpendicular to the rear surface of the substrate 401 is 0.25 nm to 1 nm, and may be, for example, 0.3 nm, 0.35 nm, 0.5 nm, 0.7 nm, or 0.9 nm.

[0101] 9 and 11, FIG. 11 illustrates the overall structure of another solar cell, where the Y direction is perpendicular to the rear surface of the substrate 401. In some embodiments, the tunnel layer 402 includes a second portion 422, which is in contact with the doped conductive layer 403, and the atomic percentage of the first dopant atoms in the second portion 422 is greater than the atomic percentage of the first dopant atoms in the tunnel layer 402. Here, the atomic percentage of the first dopant atoms in the tunnel layer 402 refers to the average atomic percentage of the first dopant atoms in the tunnel layer 402, including the second portion 422. That is, the tunnel layer 402 can be considered to be composed of two portions, the second portion 422 and a portion other than the second portion 422, and the doping concentration of the dopant in the second portion 422 is higher than the doping concentration of the dopant in the portion of the tunnel layer 402 excluding the second portion 422.

[0102] In some embodiments, the ratio of the thickness of second portion 422 to the thickness of tunnel layer 402 in a direction perpendicular to the rear surface of substrate 401 is 0.25 to 0.5, and may be, for example, 0.275, 0.3, 0.325, 0.375, 0.425, or 0.45. The thickness of second portion 422 in a direction perpendicular to the rear surface of substrate 401 is 0.25 nm to 1 nm, and may be, for example, 0.3 nm, 0.35 nm, 0.5 nm, 0.7 nm, or 0.9 nm.

[0103] 9 and 12, FIG. 12 illustrates the overall structure of another solar cell, where the Y direction is perpendicular to the rear surface of the substrate 401. In some embodiments, the solar cell may further include a passivation anti-reflection layer 405 and an electrode 406 located on the front and rear surfaces of the substrate 401, where the passivation anti-reflection layer 405 covers the semiconductor conductive layer located on the front and rear surfaces of the substrate 401, and the electrode 406 penetrates the passivation anti-reflection layer 405 to be in electrical contact with the semiconductor conductive layer, where the semiconductor conductive layer includes an emitter 404 and a doped conductive layer 403. The structure and material of the passivation anti-reflection layer 405 are similar to those of the first passivation layer described above, and therefore will not be described here.

[0104] The features of each of the above-described embodiments may not only be present independently in a solar cell, but may also be combined with each other without going beyond the inventive concept of the embodiments of the present application, provided that there are no technical discrepancies. Some of the embodiments of the present application are described using IBC cells as an example, and some of the embodiments are described using TOPCon cells as an example. As long as there are no technical discrepancies, features applied to one solar cell in each embodiment may be combined and applied to another solar cell. The description of the embodiments of the present application will be omitted here.

[0105] As described above, the present invention provides a solar cell having a passivation contact structure on the rear surface of the substrate, which is composed of a tunnel layer and a doped conductive layer, thereby significantly reducing carrier recombination on the rear surface of the substrate, thereby reducing the recombination current on the rear surface of the substrate and reducing carrier recombination loss in the solar cell. Because the doped conductive layer is composed of a first doped region and a second doped region with different doping types, both electrodes of the solar cell can be provided on the rear surface of the solar cell, which significantly reduces the effect of electrodes provided on the front surface of the solar cell on light absorption, thereby improving light absorption of the solar cell. The tunnel layer is composed of first regions and second regions alternately arranged along a first direction, the first regions facing the first doping region, both the first region and the first doping region containing first dopant atoms, the atomic percentage of the first dopant atoms in the first region being lower than the atomic percentage of the first dopant atoms in the first doping region, and the first dopant atoms being concentrated in the tunnel layer, thereby further improving the open circuit voltage of the solar cell, reducing carrier recombination loss, and increasing the photoelectric conversion efficiency of the solar cell.

[0106] 13, an embodiment of the present application provides a photovoltaic module including a cell string 1101 formed by connecting a plurality of the solar cells and / or cells formed by the manufacturing method, an encapsulation layer 1102 for covering the surface of the cell string 1101, and a cover plate 1103 for covering the surface of the encapsulation layer 1102 away from the cell string 1101. The solar cells are electrically connected as a whole or in a form of a plurality of divisions to form a plurality of cell strings 1101, and the plurality of cell strings 1101 are electrically connected in series and / or in parallel.

[0107] In some embodiments, the plurality of cell strings 1101 may be electrically connected by a conduction band 1104. The encapsulation layer 1102 covers the front and back surfaces of the solar cell. Specifically, the encapsulation layer 1102 may be an organic encapsulation adhesive film such as an ethylene vinyl acetate copolymer (EVA) adhesive film, a polyethylene-octene copolymer (POE) adhesive film, or a polyethylene terephthalate (PET) adhesive film. In some embodiments, the cover plate 1103 may be a light-transmitting cover plate 1103 such as a glass cover plate or a plastic cover plate. The surface of the cover plate 1103 facing the encapsulation layer 1102 may be an uneven surface, which can improve the utilization efficiency of incident light.

[0108] Although the present application has been disclosed as above in preferred embodiments, it does not limit the scope of the claims, and a person skilled in the art may make some possible variations and modifications without departing from the idea of ​​the present application, so the protection scope of the present application should be in accordance with the scope defined by the claims of the present application.

Claims

1. a substrate having opposing front and back surfaces; a tunnel layer located on the back surface of the substrate and in contact with the back surface of the substrate; a doped conductive layer located on a surface of the tunnel layer remote from the substrate; and a trench passing through a thickness of the doped conductive layer; the tunnel layer includes first and second regions alternately arranged along a first direction, the first regions include first dopant atoms; the doped conductive layer includes a first doping region opposite the first region and a second doping region opposite the second region, the first doping region and the second doping region having different doping types, the first doping region includes the first dopant atoms, and the atomic percentage of the first dopant atoms in the first doping region is smaller than the atomic percentage of the first dopant atoms in the first region; the trench is located between the first doped region and the second doped region; A solar cell characterized by:

2. the ratio of the atomic percentage of the first dopant atoms in the first region to the atomic percentage of the first dopant atoms in the first doped region is 1 to 5; The solar cell according to claim 1 .

3. the atomic percentage of the first dopant atoms in the first region is 1% to 10%; The solar cell according to claim 2 .

4. the atomic percentage of the first dopant atoms in the first doping region is 0.2% to 5%; The solar cell according to claim 2 .

5. the first dopant atoms are N-type atoms; The solar cell according to claim 1 .

6. the atomic percentage of the first dopant atoms in the first doped region decreases in a gradient in a direction perpendicular to the back surface of the substrate and away from the substrate; The solar cell according to claim 1 .

7. the first region includes a first portion, the first portion contacting the substrate, and an atomic percentage of the first dopant atoms in the first portion is greater than an atomic percentage of the first dopant atoms in the first region; The solar cell according to claim 1 .

8. the atomic percentage of the first dopant atoms in the first portion is between 2% and 20%; The solar cell according to claim 7 .

9. a ratio of a thickness of the first portion to a thickness of the first region in a direction perpendicular to a rear surface of the substrate is 0.25 to 0.5; The solar cell according to claim 7 .

10. The thickness of the first portion is 0.25 nm to 1 nm in a direction perpendicular to the rear surface of the substrate. The solar cell according to claim 9 .

11. the first region includes a second portion, the second portion contacting the first doped region, and the atomic percentage of the first dopant atoms in the second portion is greater than the atomic percentage of the first dopant atoms in the first region; The solar cell according to claim 1 .

12. the atomic percentage of the first dopant atoms in the second portion is between 2% and 20%; The solar cell according to claim 11 .

13. a ratio of a thickness of the second portion to a thickness of the first region in a direction perpendicular to a rear surface of the substrate is 0.25 to 0.5; The solar cell according to claim 11 .

14. The thickness of the second portion is 0.25 nm to 1 nm in a direction perpendicular to the rear surface of the substrate. The solar cell according to claim 13 .

15. a cell string formed by connecting a plurality of solar cells according to any one of claims 1 to 14; a sealing layer for covering a surface of the cell string; a cover plate for covering a surface of the sealing layer away from the cell string. A photovoltaic module characterized by:

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