Solar cells and photovoltaic modules

Abstract

Embodiments of the present invention provide a solar cell and a photovoltaic module. The solar cell includes a first region and a second region, and includes: a substrate and a tunneling layer, the substrate having a first surface and a second surface, the tunneling layer covering the second surface; a first emitter, the first emitter being located on the tunneling layer in the first region; a second emitter, the second emitter being located on the tunneling layer in the second region and on the first emitter, the second emitter having a different conductivity type from the first emitter; a first electrode, located in the first region, extending through the second emitter and electrically connected to the first emitter; and a second electrode, located in the second region and electrically connected to the second emitter. Embodiments of the present invention are beneficial for improving the electrical performance of the solar cell and reducing the manufacturing cost of the solar cell.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of photovoltaics, and in particular to solar cells and photovoltaic modules. Background Art

[0002] Solar cells are well-known devices for converting solar radiation into electrical energy. A solar cell has a light-receiving surface that faces the sun during normal operation to collect solar radiation, and a back surface opposite the light-receiving surface. In a full back-contact solar cell, all electrodes and the corresponding emitter electrodes are formed on the back surface of the solar cell. An external circuit (such as a load) can be connected to the electrodes of the solar cell to provide power.

[0003] In order to enhance the commercial value of solar cells, it is necessary to improve the electrical performance of solar cells and reduce the preparation cost of solar cells. Summary of the Invention

[0004] The embodiments of the present invention provide a solar cell and a photovoltaic module, which are beneficial to improving the electrical performance of the solar cell and reducing the preparation cost of the solar cell.

[0005] To solve the above problems, an embodiment of the present invention provides a solar cell, comprising a first region and a second region, and comprising: a substrate and a tunneling layer, the substrate having a first surface and a second surface, the tunneling layer covering the second surface; a first emitter, the first emitter being located on the tunneling layer in the first region; a second emitter, the second emitter being located on the tunneling layer in the second region and on the first emitter, the conductivity type of the second emitter being different from the conductivity type of the first emitter; a first electrode, being located in the first region, penetrating the second emitter and being electrically connected to the first emitter; and a second electrode, being located in the second region and being electrically connected to the second emitter.

[0006] In addition, a side wall surface of the first emitter is in contact with a side wall surface of the second emitter.

[0007] In addition, in a direction perpendicular to the second surface, the thickness of the second emitter is 30 nm to 200 nm.

[0008] In addition, the base of the second region is raised relative to the base of the first region, the first emitter has a third surface facing away from the tunneling layer, the second emitter has a fourth surface in contact with the tunneling layer, and the third surface is flush with or lower than the fourth surface.

[0009] In addition, the tunneling layer includes a first dielectric layer and a second dielectric layer, the first dielectric layer is located between the first emitter and the substrate, the second dielectric layer covers the substrate surface of the second region and covers the third surface and sidewall of the first emitter, the third surface is the surface of the first emitter facing away from the first dielectric layer, the second emitter is located on the second dielectric layer, and the first electrode also passes through the second dielectric layer.

[0010] In addition, the material of the second dielectric layer is different from that of the first dielectric layer.

[0011] In addition, the material of the first dielectric layer includes at least one of oxysilicide, nitride siliconide or carbon siliconide.

[0012] In addition, the second emitter includes a first doping portion and a second doping portion, at least a portion of the second doping portion is located between the first doping portion and the first electrode, the doping concentration of the first doping portion is greater than or equal to the doping concentration of the second doping portion, and in the direction from the first doping portion toward the first electrode, the doping concentration of different regions of the second doping portion decreases.

[0013] In addition, the concentration gradient of the second doping part is 5E16cm -3 / cm~2E22cm -3 / cm.

[0014] In addition, in a direction from the first doping portion toward the first electrode, the width of the second doping portion is greater than 20 μm.

[0015] In addition, the conductivity type of the first emitter is P type, and the conductivity type of the second emitter is N type.

[0016] Accordingly, an embodiment of the present invention further provides a photovoltaic assembly, comprising: a cell string formed by connecting any of the above-mentioned solar cells; a packaging film for covering the surface of the cell string; and a cover plate for covering the surface of the packaging film facing away from the cell string.

[0017] Compared with the prior art, the technical solution provided by the embodiment of the present invention has the following advantages:

[0018] In the above technical solution, the second emitter is arranged based on the first emitter. In the process of forming the first emitter and the second emitter, only one patterning process is required to form the first emitter, and the second emitter does not need to be patterned etched to adjust the position accuracy after the maskless deposition process. In this way, it is only necessary to control the position accuracy of the first emitter, which is beneficial to reducing the alignment accuracy requirements in the preparation process of solar cells. At the same time, only one mask and one dry etching process are required, which is beneficial to reducing the preparation cost of solar cells.

[0019] In addition, providing the first dielectric layer and the second dielectric layer is beneficial for isolating the first emitter and the second emitter without adding a patterned etching process, suppressing the short circuit problem and the mutual penetration of doped ions that may occur when the first emitter and the second emitter contact, and ensuring that the solar cell has a high photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0021] Figure 1 and Figure 2 A schematic structural diagram of a solar cell provided by an embodiment of the present invention;

[0022] Figure 3 A schematic structural diagram of another solar cell provided by an embodiment of the present invention;

[0023] Figure 4 A schematic structural diagram of another solar cell provided by an embodiment of the present invention;

[0024] Figure 5 A schematic structural diagram of another solar cell provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the embodiments of the present invention to help readers better understand the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0026] refer to Figure 1 and Figure 2 , Figure 2 for Figure 1The three-dimensional schematic diagram of the structure shown is that the solar cell includes a first region 101 and a second region 102, and includes: a substrate 10 and a tunneling layer 11, the substrate 10 has a first surface 10a and a second surface 10b, and the tunneling layer 11 covers the second surface 10b; a first emitter 12, the first emitter 12 is located on the tunneling layer 11 in the first region 101; a second emitter 13, the second emitter 13 is located on the tunneling layer 11 in the second region 102 and on the first emitter 12, and the conductivity type of the second emitter 13 is different from the conductivity type of the first emitter 12; a first electrode 15, located in the first region 101, penetrating the second emitter 13 and electrically connected to the first emitter 12; a second electrode 16, located in the second region 102 and electrically connected to the second emitter 13.

[0027] In some embodiments, the substrate 10 is a silicon substrate material, such as one or more of single crystal silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon; in other embodiments, the substrate material can also be a carbon element, an organic material or a multi-component compound, and the multi-component compound can include but is not limited to perovskite, gallium arsenide, cadmium telluride, copper indium selenide and other materials.

[0028] In some embodiments, the first surface 10a is a light receiving surface, and the second surface 10b is a back surface opposite to the light receiving surface. The first surface 10a can be set to a pyramid velvet surface to reduce the reflection of light by the first surface 10a, increase the absorption and utilization rate of light, and improve the conversion efficiency of the solar cell; the solar cell can also include a first passivation layer 14, the first passivation layer 14 covers the surface of the first emitter 12 and the second emitter 13 away from the substrate 10, and the material of the first passivation layer 14 includes one or more materials such as silicon nitride, silicon oxynitride, carbon nitride silicon oxynitride, titanium oxide, hafnium oxide, aluminum oxide, etc.; accordingly, the solar cell can also include a second passivation layer 17, the second passivation layer 17 covers the second surface 10b, and the material of the second passivation layer 17 includes silicon nitride or silicon oxide, etc.

[0029] In some embodiments, the substrate 10 includes an N-type dopant element (such as phosphorus, arsenic, etc.), the first emitter 12 includes a P-type dopant element, the second emitter 13 includes an N-type dopant element, the first emitter 12 forms a PN junction with the substrate 10, the first electrode 15 connected to the first emitter 12 serves as the positive electrode of the solar cell, and the second electrode 16 connected to the second emitter 13 serves as the negative electrode of the solar cell; in other embodiments, the first emitter 12 includes an N-type dopant element, the second emitter 13 includes a P-type dopant element, and the second emitter 13 forms a PN junction with the substrate 10.

[0030] It should be noted that although Figure 1In the structure shown, the first emitter 12 and the second emitter 13 are in direct contact, but this does not mean that the positive and negative poles of the solar cell are short-circuited. This is because the first emitter 12 and the second emitter 13 contain different types of doping ions, and the transmission efficiency of the same carrier in the first emitter 12 and the second emitter 13 is very different. That is, when the transmission path length is the same, the transmission path resistance of the same carrier in different emitters is very different, which makes the carriers in the first emitter 12 always tend to flow out through the first electrode 15; at the same time, because the thickness of the second emitter 13 is generally thin and the cross-sectional area is small in the direction perpendicular to the second surface 10b, the resistance that the carriers in the second emitter 13 need to resist for lateral transmission is much greater than the resistance that they need to resist when directly converging in the second electrode 16. Therefore, the carriers that pass through the tunneling layer 11 and flow to the second emitter 13 always tend to converge toward the second electrode 16. That is to say, even if the first emitter 12 and the second emitter 13 with different conductivity types are in contact with each other, due to the limitation of the transmission path resistance, the solar cell has clearly separate positive and negative poles, and the solar cell will not have an obvious positive and negative pole short circuit problem. This structure overcomes the prejudice of the existing technology.

[0031] In some embodiments, the sidewall surface of the first emitter 12 contacts the sidewall surface of the second emitter 13. Furthermore, in a direction perpendicular to the second surface 10b, the thickness of the second emitter 13 is 30 nm to 200 nm, such as 40 nm, 70 nm, 90 nm, 120 nm, 150 nm, or 160 nm. If the thickness of the second emitter 13 is less than the aforementioned threshold, the field passivation effect of the second emitter 13 in the second region 102 is weak, and carrier recombination in the second region 102 is more serious. If the thickness of the second emitter 13 is greater than the aforementioned threshold, the resistance to lateral transport of carriers in the second emitter 13 is low, making it easier for carriers in the second emitter 13 in the second region 102 to transport laterally and move to the first electrode 15, which is not conducive to preventing the short circuit between the first emitter 12 and the second emitter 13.

[0032] Furthermore, by setting the first electrode 15 away from the second region 102, the path resistance of the carriers transmitted from the second emitter 13 of the second region 102 to the first electrode 15 can be increased, thereby suppressing the short-circuit current between the first electrode 15 and the second electrode 16; similarly, by setting the second electrode 16 to extend into the second emitter 13, the path resistance of the carriers transmitted from the second region 102 to the second electrode 16 can be reduced, thereby promoting the carriers to converge on the second electrode 16.

[0033] In some embodiments, the substrate 10 has a flat second surface 10b, the surface of the first emitter 12 facing the substrate 10 is flush with the surface of the second emitter 13 of the second region 102 facing the substrate 10, and the second emitter 13 covers the sidewall surface of the first emitter 12. The specific process for forming the above structure includes: providing a substrate 10 having a flat second surface 10b and a tunneling layer 11 having a uniform film thickness; sequentially performing a maskless deposition process and a patterned etching process to form a patterned first emitter 12; and performing a second maskless deposition process to form the second emitter 13. In other words, the formation process of the above structure only requires a single patterned etching process. Compared to the traditional method of using two patterned etching processes to define the positions of the first emitter 12 and the second emitter 13 respectively, this helps reduce the precision alignment requirements and the number of masks required, thereby improving the electrical performance of the solar cell and reducing the production cost of the solar cell.

[0034] In addition, compared with the textured surface, providing a flat second surface 10b is also beneficial to preventing sunlight incident from the first surface 10a from being transmitted through the second surface 10b, thereby reducing light transmission loss of the solar cell and improving the light absorption efficiency of the solar cell.

[0035] In some embodiments, reference Figure 3 , the substrate 20 of the second region 202 is raised relative to the substrate 20 of the first region 201, the first emitter 22 has a third surface (not marked) away from the tunneling layer 21, the second emitter 23 has a fourth surface (not marked) in contact with the tunneling layer 21, and the third surface is flush with or lower than the fourth surface. The specific process for forming the above structure includes: patterning the substrate 20 to form a relatively concave and convex second surface 20b; covering the second surface 20b with a tunneling layer 21 having a uniform film thickness; sequentially performing a deposition process and a flattening process to form a first emitter 22 located in the first region 201, the third surface of the first emitter 22 is lower than or flush with the fourth surface of the tunneling layer 21; performing a maskless deposition process to form the second emitter 23. In other words, the above structure also only requires one patterning etching process to be formed, and the second emitter 23 in the structure has a flat surface away from the substrate 20, which is beneficial to reduce the complexity of subsequent coating of the conductive paste and ensure the first electrode 15 (reference Figure 2 ) and the second electrode 16 (reference Figure 2 ) has good alignment accuracy.

[0036] When the third surface is lower than the fourth surface, in a direction perpendicular to the second surface 20 b , a vertical distance between the third surface and the fourth surface can be set to 0.1 μm to 5 μm, such as 1 μm, 2 μm or 3 μm.

[0037] In some embodiments, reference Figure 4 The tunneling layer 31 includes a first dielectric layer 311 and a second dielectric layer 312. The first dielectric layer 311 is located between the first emitter 32 and the substrate 30, that is, the first dielectric layer 311 is only in the first region 301. The second dielectric layer 312 covers the second surface 30b of the second region 302 and covers the third surface and sidewall of the first emitter 32. The third surface is the surface of the first emitter 32 facing away from the first dielectric layer 311. The second emitter 33 is located on the second dielectric layer 312. The first electrode 35 sequentially penetrates the first passivation layer 34, the second emitter 33 and the second dielectric layer 312 and is in electrical contact with the first emitter 32.

[0038] Similarly, the above structure can be formed using only a single patterned etching process, which sequentially etches the stacked first emitter film and first dielectric film to form the first emitter 32 and first dielectric layer 311. Furthermore, the second dielectric layer 312 and second emitter 33 can both be formed using a maskless deposition process. This design allows for the separation of the first and second emitters 32, 33 by the second dielectric layer 312 without requiring additional patterned etching processes. This prevents carrier recombination and dopant ion interpenetration between the first and second emitters 32, 33, ensuring high photoelectric conversion efficiency for the solar cell.

[0039] In some embodiments, the material of the second dielectric layer 312 is different from the material of the first dielectric layer 311. For example, the dielectric constant of the material of the second dielectric layer 312 is smaller than the dielectric constant of the material of the first dielectric layer 311, so that the first dielectric layer 311 has a better tunneling effect and the second dielectric layer 312 has a better isolation effect. In other embodiments, the film thicknesses of the first dielectric layer 311 and the second dielectric layer 312 are different. For example, when the dielectric constant of the material of the second dielectric layer 312 is smaller than the dielectric constant of the material of the first dielectric layer 311 and the tunneling effect of the material of the second dielectric layer 312 is weaker than the tunneling effect of the material of the first dielectric layer 311, the film thickness of the second dielectric layer 312 can be set to be smaller than the film thickness of the first dielectric layer 311, so that the second dielectric layer 312 has a good tunneling effect while meeting the isolation requirements.

[0040] The material of the second dielectric layer 312 is different from the material of the first dielectric layer 311, including at least two situations: first, the first dielectric layer 311 and the second dielectric layer 312 are each composed of a different single material; second, the first dielectric layer 311 is composed of a single material, and the second dielectric layer 312 includes multiple sub-layers, each of which is made of a different material. For example, the second dielectric layer 312 includes a first sub-layer (not shown) and a second sub-layer (not shown), wherein the first sub-layer covers the second surface 30b and the surface of the first emitter 32, and the second sub-layer covers the surface of the first sub-layer. In this way, by adjusting the material of the first sub-layer, the first sub-layer can have a good passivation effect, reducing surface defects and carrier recombination on the second surface 30b of the substrate 30, and by adjusting the material of the second sub-layer, good electrical isolation can be achieved between the first emitter 32 and the second emitter 33.

[0041] The material of the first dielectric layer 311 includes at least one of oxysilicide, nitride siliconide or carbon siliconide.

[0042] In some embodiments, reference Figure 5 The second emitter 43 includes a first doped portion 431 and a second doped portion 432. At least a portion of the second doped portion 432 is located between the first doped portion 431 and the first electrode 45. The doping concentration of the first doped portion 431 is greater than or equal to the doping concentration of the second doped portion 432. The doping concentration of different regions of the second doped portion 432 decreases as the first doped portion 431 approaches the first electrode 45. Compared to providing intrinsic polysilicon for isolation between the second emitter 43 and the first electrode 45, providing the second doped portion 432 with a concentration gradient helps reduce concentration differences between different interfaces, weakens the diffusion force of dopant ions in the second emitter 43, prevents uniform doping of the intrinsic polysilicon due to strong diffusion force, ensures a high contact resistance at the interface between the first electrode 45 and the second doped portion 432, and thus suppresses short-circuit current between the first electrode 45 and the second emitter 43.

[0043] If the doping concentration of the surface layer of the second doping portion 432 facing the first doping portion 431 can be considered equal to the doping concentration of the first doping portion 431, it can be understood that the smaller the concentration gradient of the second doping portion 432, the smaller the diffusion force of the dopant ions in the first doping portion 431 due to the concentration difference, and the better the barrier effect of the second doping portion 432. If the extreme difference in doping concentration between different regions of the second doping portion 432 remains unchanged, the smaller the concentration gradient of the second doping portion 432, the wider the width of the second doping portion 432 in the direction from the first doping portion 431 toward the first electrode 45; in other words, if the width of the second doping portion 432 remains unchanged and the minimum doping concentration of the second doping portion 432 remains unchanged, the smaller the concentration gradient of the second doping portion 432, the lower the doping concentration of the first doping portion 431, and the weaker the conductivity of the first doping portion 431.

[0044] In some embodiments, the concentration gradient of the second doping portion 432 is 5E16 cm -3 / cm~2E22cm -3 / cm, for example 1E21cm -3 / cm、1E20cm -3 / cm、1E19cm -3 / cm、1E18cm -3 / cm or 1E17cm -3 If the concentration gradient is less than the threshold, the width of the second doped portion 432 may be too wide to cover the second surface of the second region, or the doping concentration of the first doped portion 431 may be too low, which is not conducive to the carriers in the substrate being concentrated in the second electrode 46 through the second emitter 43. If the concentration gradient is greater than the threshold, it is not conducive to blocking the doping ions in the first doped portion 431 from diffusing to the first electrode 45.

[0045] In some embodiments, the width of the second doped portion 432 is greater than 20 μm in the direction from the first doped portion 431 toward the first electrode 45. If the width is less than this value, while the concentration gradient of the second doped portion 432 and the doping concentration of the first doped portion 431 remain unchanged, the doping concentration at the interface between the second doped portion 432 and the first electrode 45 may be higher, resulting in weaker electrical isolation of the second doped portion 432. If the width is less than this value, while the concentration gradient and minimum doping concentration of the second doped portion 432 remain unchanged, the doping concentration of the first doped portion 431 may be lower, resulting in weaker carrier transport capability of the second emitter 43.

[0046] It should be noted that, in some embodiments, the second emitter 43 in contact with the tunneling layer 41 is located only on the opposite side of the first emitter 42, that is, the second region 402 is located only on the opposite side of the first region 401. In this case, the second doped portion 432 is only arranged on the opposite side of the first electrode 45 to block the carriers that pass through the tunneling layer 41 and enter the second emitter 43; in other embodiments, the second region 402 and the first region 401 are arranged crosswise, the second region 402 is located on the opposite sides of part of the first region 401, and the second emitter 43 in contact with the tunneling layer 41 is located on the opposite sides of the first emitter 42. In this case, the second doped portion 432 is arranged on the opposite sides of the first electrode 45.

[0047] In this embodiment, the second emitter is arranged based on the first emitter. In the process of forming the first emitter and the second emitter, only one patterning process is required to form the first emitter, and the second emitter does not need to be patterned etched to adjust the position accuracy after the maskless deposition process. In this way, it is only necessary to control the position accuracy of the first emitter, which is beneficial to reducing the alignment accuracy requirements in the process of preparing solar cells; at the same time, only one mask and one dry etching process are required, which is beneficial to reducing the preparation cost of solar cells.

[0048] The embodiment of the present invention further provides a solar cell, Figure 1 The difference of the solar structure shown is that the second emitter located in the second area is electrically isolated from the second emitter located in the first area, a gap is provided between the first emitter and the second emitter located in the second area, and the second emitters in the first area and the second area can be formed using the same process steps.

[0049] The embodiment of the present invention further provides a photovoltaic module, which is used to convert received light energy into electrical energy. The photovoltaic module includes a battery string, a packaging film and a cover plate; the battery string is formed by connecting multiple solar cells, and the solar cells can be any of the aforementioned solar cells (including but not limited to Figure 1-Figure 5 The solar cell is provided as described above; the encapsulating film may be an organic encapsulating film such as EVA or POE, covering the surface of the cell string to seal it; the cover plate may be a glass cover plate or a plastic cover plate, covering the surface of the encapsulating film facing away from the cell string. In some embodiments, the cover plate is provided with a light-trapping structure to increase the utilization of incident light. The photovoltaic module has a high current collection capacity and a low carrier recombination rate, thereby achieving a high photoelectric conversion efficiency.

[0050] Those skilled in the art will appreciate that the above-described embodiments are specific examples of the present invention, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present invention. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A solar cell comprising a first region and a second region, characterized in that: include: A substrate and a tunneling layer, wherein the substrate has a first surface and a second surface, and the tunneling layer covers the second surface; a first emitter, the first emitter being located on the tunneling layer in the first region; a second emitter, the second emitter being located on the tunneling layer in the second region and on the first emitter, and the conductivity type of the second emitter being different from the conductivity type of the first emitter; a first electrode, located in the first region, penetrating the second emitter and electrically connected to the first emitter; a second electrode located in the second region and electrically connected to the second emitter; The base of the second region is raised relative to the base of the first region, the first emitter has a third surface facing away from the tunneling layer, the second emitter has a fourth surface in contact with the tunneling layer, and the third surface is flush with or lower than the fourth surface; The second emitter includes a first doping portion and a second doping portion, at least a portion of the second doping portion is located between the first doping portion and the first electrode, the doping concentration of the first doping portion is greater than or equal to the doping concentration of the second doping portion, and in the direction from the first doping portion toward the first electrode, the doping concentration of different regions of the second doping portion decreases.

2. The solar cell according to claim 1, wherein A side wall surface of the first emitter contacts a side wall surface of the second emitter.

3. The solar cell according to claim 2, wherein In a direction perpendicular to the second surface, the thickness of the second emitter is 30 nm to 200 nm.

4. The solar cell according to claim 1, wherein The tunneling layer includes a first dielectric layer and a second dielectric layer, the first dielectric layer is located between the first emitter and the substrate, the second dielectric layer covers the substrate surface of the second region and covers the third surface and sidewall of the first emitter, the third surface is the surface of the first emitter facing away from the first dielectric layer, the second emitter is located on the second dielectric layer, and the first electrode also penetrates the second dielectric layer.

5. The solar cell according to claim 4, wherein The material of the second dielectric layer is different from that of the first dielectric layer.

6. The solar cell according to claim 4, characterized in that The material of the first dielectric layer includes at least one of oxysilicide, nitride siliconide or carbon siliconide.

7. The solar cell according to claim 1, wherein The concentration gradient of the second doping part is 5E16cm -3 / cm~2E22cm -3 / cm.

8. The solar cell according to claim 1, wherein In a direction from the first doping portion toward the first electrode, the width of the second doping portion is greater than 20 μm.

9. The solar cell according to claim 1, wherein The conductivity type of the first emitter is P type, and the conductivity type of the second emitter is N type.

10. A photovoltaic module, characterized in that: include: A battery string formed by connecting a plurality of solar cells according to any one of claims 1 to 9; A packaging film, used to cover the surface of the battery string; A cover plate is used to cover the surface of the packaging film facing away from the battery string.

Images