Solar cell, stacked cell, and photovoltaic module

Abstract

The application relates to the technical field of solar cells, in particular to a solar cell, a laminated cell and a photovoltaic module. A groove structure is located in a second area, the groove bottom surface has a first pyramid, the groove sidewall is divided into a first sidewall and a second sidewall with different inclination angles, the second sidewall has a second pyramid, the incident light is reflected on the groove bottom surface and the groove sidewall multiple times, the optical path of the light in the cell is greatly lengthened, the probability of light absorption is increased, the absorption of long-wavelength red light and near-infrared light can be improved, the angle between the perpendicular line of the first pyramid and the perpendicular line of the second pyramid is less than 90 DEG, the second pyramid on the second sidewall can capture low-angle incident light, and high optical efficiency can be maintained under different incident angles; the groove sidewall is divided into the first sidewall and the second sidewall with different inclination angles, which is beneficial to reducing the transmission distance of carriers on the groove sidewall.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell, a tandem cell, and a photovoltaic module. Background Technology

[0002] With the accelerated transition from traditional fossil fuels and the increasing demand for sustainable development, solar cells, as a clean and renewable energy technology, are increasingly becoming an important component of the energy system. A solar cell is essentially a semiconductor device that directly converts solar energy into electrical energy. Its working principle is based on the photovoltaic effect: when sunlight shines on the cell, photon energy excites electron-hole pairs (i.e., charge carriers) to be generated inside the semiconductor. These charge carriers then separate under the influence of a built-in electric field, forming a potential difference. By effectively extracting these charge carriers through the metal electrodes on the front and back of the cell, direct current can be generated for use in external circuits, thus achieving the efficient conversion and utilization of solar energy into electrical energy.

[0003] In related technologies, in order to improve the electrical performance of solar cells, the regions of solar cells connected to the electrodes and those not connected to the electrodes are designed differently. However, the problem of high recombination rate still exists, which is not conducive to improving conversion efficiency. Summary of the Invention

[0004] In view of the above problems, this application provides a solar cell, a tandem cell, and a photovoltaic module to solve the aforementioned technical problems that are not conducive to improving conversion efficiency.

[0005] In a first aspect, embodiments of this application provide a solar cell, comprising: A substrate having a first surface and a second surface disposed opposite to each other along a thickness direction, the first surface having a first region and a second region alternately disposed along a first direction; The groove structure located in the second region includes a groove bottom surface formed by the base of the second region being recessed along the thickness direction, and a groove sidewall connecting the first region and the groove bottom surface. The groove sidewall includes a first sidewall connected to the first region and a second sidewall connected to the first sidewall and the groove bottom surface respectively. The second sidewall is inclined toward the first region, and the angle between the first sidewall and the groove bottom surface is smaller than the angle between the second sidewall and the groove bottom surface. The doping concentration at the bottom of the groove is less than that in the first region. The bottom of the groove has a first pyramid, and the second sidewall has a second pyramid. The angle between the perpendicular line of the first pyramid and the perpendicular line of the second pyramid is less than 90°.

[0006] Optionally, the height of the second pyramid is 0.1 μm to 5 μm.

[0007] Optionally, the density of the second pyramid is 1,000 to 1,000,000. .

[0008] Optionally, the second sidewall includes a first inclined region near the first sidewall and a second inclined region near the bottom of the groove, the second pyramid is located in the first inclined region, and the roughness of the second inclined region is less than that of the first inclined region.

[0009] Optionally, the first sidewall is perpendicular to the bottom surface of the groove.

[0010] Optionally, the first sidewall has a non-pyramid texture structure, and the roughness of the first sidewall is less than that of the second sidewall.

[0011] Optionally, the first sidewall is a smooth sidewall.

[0012] Optionally, the substrate is doped with a first conductivity type, and the bottom surface of the trench is not doped with a second conductivity type, or the doping concentration of the second conductivity type element at the bottom surface of the trench is less than or equal to 5E17. The first conductivity type and the second conductivity type are opposite.

[0013] Optionally, along the first direction, the ratio of the length of the first region to the length of the second region is 0.3 to 3.

[0014] Secondly, embodiments of this application provide a stacked battery, comprising: Top cell, which can be a perovskite cell, cadmium telluride solar cell, copper indium gallium selenide solar cell, or gallium arsenide solar cell; Intermediate connecting layer; and The bottom battery is the aforementioned solar cell; The top battery, the intermediate connecting layer, and the bottom battery are stacked and connected.

[0015] Thirdly, embodiments of this application provide a photovoltaic module, including the aforementioned solar cell or the aforementioned tandem cell.

[0016] The solar cells, tandem cells, and photovoltaic modules provided in this application embodiment feature a groove structure in the second region. The bottom surface of the groove has a first pyramid, and the groove sidewalls are divided into first and second sidewalls with different inclination angles. The second sidewall has a second pyramid. Incident light undergoes multiple reflections on the bottom surface and sidewalls of the groove, significantly extending the optical path within the cell and increasing the probability of light absorption. This enhances the absorption of long-wavelength red and near-infrared light. The angle between the perpendiculars of the first and second pyramids is less than 90°, allowing the second pyramid on the second sidewall to capture low-angle incident light, maintaining high optical efficiency at different incident angles. The division of the groove sidewalls into first and second sidewalls with different inclination angles helps reduce the transport distance of charge carriers on the groove sidewalls, thereby reducing the recombination probability of charge carriers and improving the photoelectric conversion efficiency of the photovoltaic cell. The bottom surface of the groove has a relatively lower doping concentration, which helps reduce defects on the bottom surface of the groove, further reducing the recombination probability of charge carriers and improving the photoelectric conversion efficiency of the photovoltaic cell.

[0017] These or other aspects of this application will become more apparent in the following description of the embodiments. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of a solar cell provided in an embodiment of this application is shown.

[0019] Figure 2 A schematic diagram of the structure of the second pyramid in the solar cell provided in this application embodiment is shown.

[0020] Figure 3 This paper presents another schematic diagram of the second pyramid structure in a solar cell provided in an embodiment of this application.

[0021] Figure 4 Another structural schematic diagram of the solar cell provided in an embodiment of this application is shown.

[0022] Figure 5 A schematic diagram of the structure of the battery string in the photovoltaic module provided in this application embodiment is shown.

[0023] Figure 6 A schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application is shown.

[0024] Figure 7 Schematic diagrams of the solar cells in Comparative Example 1 and Comparative Example 2 are shown.

[0025] Figure 8 This is a scanning electron microscope image of a solar cell according to an embodiment of this application. Detailed Implementation

[0026] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0027] To enable those skilled in the art to better understand the solutions of this application, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] In the embodiments of this application, it should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0029] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0030] In the description of the embodiments of this application, the words "example" or "for example" are used to indicate exemplification, illustration, or description. Any embodiment or design described as "example" or "for example" in the embodiments of this application is not to be construed as being more preferred or having more advantages than another embodiment or design. The use of the words "example" or "for example" is intended to present relative concepts in a clear manner.

[0031] Furthermore, in the embodiments of this application, "multiple" refers to two or more. Therefore, in the embodiments of this application, "multiple" can also be understood as "at least two". "At least one" can be understood as one or more, such as one, two, or more. For example, including at least one means including one, two, or more, and is not limited to which ones are included. For example, including at least one of A, B, and C, then it could include A, B, C, A and B, A and C, B and C, or A and B and C.

[0032] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.

[0033] One embodiment of this application provides a solar cell 100; please refer to [link / reference]. Figure 1 and Figure 2 As shown, the solar cell 100 includes a substrate 11 and a groove structure 12 disposed on the substrate. The substrate 11 has a first surface 11a and a second surface 11b disposed opposite to each other along its thickness direction. The first surface 11a has a first region 13 and a second region 14 disposed alternately along a first direction.

[0034] The groove structure 12 is provided in the second region 14. The groove structure 12 includes a groove bottom surface 121 and a groove sidewall 122. The groove bottom surface 121 is formed by the base 11 of the second region 14 being recessed along the thickness direction. The groove sidewall 122 connects the first region 13 and the groove bottom surface 121.

[0035] The groove sidewall 122 includes a first sidewall 122a and a second sidewall 122b. The first sidewall 122a is connected to the first region 13, and the second sidewall 122b is connected to both the first sidewall 122a and the groove bottom surface 121. The second sidewall 122b is inclined toward the first region 13. The angle α1 between the first sidewall 122a and the groove bottom surface 121 is smaller than the angle α2 between the second sidewall 122b and the groove bottom surface 121, meaning that the first sidewall 122a is steeper than the second sidewall 122b.

[0036] The doping concentration of the bottom surface 121 of the groove is less than that of the first region 13. The bottom surface 121 of the groove has a first pyramid, and the second sidewall 122b has a second pyramid. The angle α3 between the perpendicular line of the first pyramid and the perpendicular line of the second pyramid is less than 90°.

[0037] For example, please refer to Figure 2 As shown, the first pyramid can be an upright pyramid, and the perpendicular line L1 of the first pyramid is a straight line passing through its apex and perpendicular to the bottom surface 121 of the groove; the second pyramid can be an upright pyramid, and the perpendicular line L2 of the second pyramid is a straight line passing through its apex and perpendicular to the second side wall 122b.

[0038] For example, please refer to Figure 3As shown, the first pyramid can be a regular pyramid, and the perpendicular line L1 of the first pyramid is a straight line passing through its vertex and perpendicular to the bottom surface 121 of the groove; the second pyramid can be an inclined pyramid, and the second pyramid can be regarded as a regular pyramid 1221 spliced ​​with a wedge-shaped structure 1222. The perpendicular line L2 of the second pyramid is not perpendicular to the second side wall 122b. The vertex of the second pyramid is the vertex of the regular pyramid 1221, and the perpendicular line L2 of the second pyramid is the perpendicular line of the regular pyramid 1221, that is, a straight line passing through its vertex and perpendicular to the bottom surface of the regular pyramid 1221.

[0039] In this embodiment, the groove structure located in the second region has a first pyramid on its bottom surface and its sidewalls divided into first and second sidewalls with different inclination angles. The second sidewall has a second pyramid. Incident light undergoes multiple reflections on the bottom surface and sidewalls of the groove, significantly extending the optical path within the cell and increasing the probability of light absorption. This enhances the absorption of long-wavelength red and near-infrared light. The angle between the perpendiculars of the first and second pyramids is less than 90°, allowing the second pyramid on the second sidewall to capture low-angle incident light and maintain high optical efficiency at different incident angles. Dividing the sidewalls into first and second sidewalls with different inclination angles helps reduce the transport distance of charge carriers on the sidewalls, thereby reducing the recombination probability and improving the photoelectric conversion efficiency of the photovoltaic cell. The bottom surface of the groove has a relatively lower doping concentration, which helps reduce defects on the bottom surface and further reduces the recombination probability, thus improving the photoelectric conversion efficiency of the photovoltaic cell.

[0040] In one implementation, the height of the second pyramid is 0.1 μm to 5 μm, and further, the height of the first pyramid is 0.5 μm to 10 μm.

[0041] In this embodiment, the height of the second pyramid can be less than that of the first pyramid. The relatively flat structure helps to reduce the transmission distance of charge carriers on the sidewall 122 of the groove, thereby reducing the recombination probability of charge carriers and improving the photoelectric conversion efficiency of the photovoltaic cell.

[0042] In one implementation, the density of the second pyramid is 1,000 to 1,000,000. Furthermore, the density of the first pyramid is 300,000 to 360,000. For example, the density of the second pyramid is 1000. 5000 10000 50000 100000 500,000 or 1,000,000 .

[0043] In this embodiment, by adjusting the density of the second pyramid, the specific surface area of ​​the second sidewall 122b can be adjusted to balance the light trapping function and reduce the carrier recombination function.

[0044] As one implementation method, please refer to Figure 2 As shown, the second sidewall 122b includes a first inclined surface region 122c near the first sidewall 122a and a second inclined surface region 122d near the bottom surface 121 of the groove. The second pyramid is located in the first inclined surface region 122c. The second inclined surface region 122d can be a smooth inclined surface or have a non-pyramid texture structure. The roughness of the second inclined surface region 122d is less than the roughness of the first inclined surface region 122c.

[0045] In this embodiment, the second inclined region 122d has a smaller surface area and a smoother interface, which is beneficial to reducing the surface recombination rate of charge carriers during transport in this region. Furthermore, the smoother surface of the second inclined region 122d is beneficial to improving reflectivity, which will reflect light that does not match the angle of the bottom surface 121 of the groove back to the bottom surface of the groove or the sidewall of the groove, thereby improving light absorption.

[0046] As one implementation method, please refer to Figure 2 As shown, the first sidewall 122a is perpendicular to the bottom surface 121 of the groove.

[0047] In this embodiment, the vertical first sidewall 122a reduces the additional lateral diffusion rate that may be caused by the inclined sidewall, greatly shortens the residence time and path length of photogenerated carriers in the surface recombination risk zone, and enables photogenerated carriers formed on the bottom surface 121 of the groove to reach the first region 13 with a shorter transmission distance, thereby helping to reduce the recombination probability of carriers and improve the photoelectric conversion efficiency of photovoltaic cells.

[0048] For example, the first sidewall 122a has a non-pyramid texture structure, and the roughness of the first sidewall 122a is less than the roughness of the second sidewall 122b.

[0049] For example, the first sidewall 122b is a smooth sidewall.

[0050] In one implementation, the substrate 11 is doped with a first conductivity type, while the bottom surface 121 of the groove is not doped with a second conductivity type. Specifically, the first pyramid of the bottom surface 121 and the area below it are not doped with a second conductivity type, and the first and second conductivity types are opposite. For example, the first conductivity type is N-type and the second conductivity type is P-type, or vice versa. In this case, the bottom surface 121 has no emitter, and the area below the bottom surface 121 has no emitter. A PN junction electric field cannot be formed on the bottom surface 121 and the area below it, which increases the passivation effect of the bottom surface 121 and reduces the recombination probability of charge carriers on and below the bottom surface 121, thus improving photoelectric conversion efficiency.

[0051] In one embodiment, the substrate 11 is doped with a first conductivity type, and the doping concentration of the second conductivity type element on the bottom surface 121 of the trench is less than or equal to 5E17. That is, the bottom surface 121 of the groove can have very shallow doping of the second conductivity type. At this time, the bottom surface 121 of the groove cannot form a strong PN junction electric field, but it can effectively form field-effect passivation and suppress Auger recombination. Specifically, there are many defects in the first region 13 and the bottom surface 121 of the groove, which are prone to recombination. The main purpose of doping the bottom surface 121 of the groove here is not to form a PN junction, but to form a fixed charge layer on the surface of the bottom surface 121 of the groove, and to form an electric field on the first surface of the substrate 11 to prevent photogenerated carriers (e.g., minority carriers) from reaching the surface of the substrate 11 and reduce the recombination probability.

[0052] In some embodiments, the doping concentration of the second conductivity type element in the first region 13 can be 5E17. ~1E21 .

[0053] In this embodiment, the doping concentration of the second conductivity type element in the first region 13 is controlled within the above range, which can reduce the contact resistance and improve the fill factor.

[0054] In some embodiments, along the first direction, the ratio of the length of the first region 13 to the length of the second region 14 is 0.3 to 3.

[0055] In this embodiment, by controlling the length ratio of the first region 13 and the second region 14 along the first direction within the above-mentioned range, the area of ​​the first region 13 and the second region 14 can be precisely controlled, which is beneficial to balancing the area ratio of different functional regions on the surface of the solar cell, so as to balance the light trapping function and the carrier generation function.

[0056] In some implementations, the first region 13 is a metallized region and the second region 14 is a non-metallized region.

[0057] In this embodiment, the first region 13 is a metallized region and can be connected to an electrode. At the same time, the first region 13 has an emitter below it, and the generated photogenerated carriers can be directly transported to the collection region corresponding to the electrode position, which greatly reduces the lateral transmission distance and thus greatly reduces the recombination rate. The second region 14 is a non-metallized region and has no emitter below it or has very shallow doping, which reduces the recombination rate of the second region 14.

[0058] For example, during the fabrication of the solar cell 100, the first surface 11a of the substrate 11 can be texturized to form a third pyramid on the first surface 11a of the substrate 11; the first surface 11a of the substrate 11 can be doped to form an initial emitter layer, and the positions of each second region 14 on the first surface 11a of the substrate 11 are the initial second regions; each initial second region on the first surface 11a of the substrate 11 is then irradiated with a laser, and each initial second region after laser irradiation is then subjected to alkaline etching, which destroys the initial emitter layer on the initial second region. An initial groove structure is formed in the initial second region through laser irradiation and alkaline etching, and at least a portion of the initial emitter layer thickness of the initial second region is removed; subsequently, the bottom surface of the initial groove structure is texturized to form a first pyramid on the bottom surface of the initial groove; subsequently, the second sidewall 122b of the initial groove structure is texturized to form a second pyramid on the second sidewall 122b, resulting in the groove structure 12. The different thicknesses of the initial emitter layer in the initial second region damaged by laser irradiation will result in different doping concentrations of the second conductivity type element in the second region (bottom surface 121 of the groove). The greater the thickness of the initial emitter layer damaged in the initial second region, the lower the doping concentration of the second conductivity type element in the second region (bottom surface 121 of the groove). If the initial emitter layer in the initial second region is completely damaged, then there is no emitter in the second region (bottom surface 121 of the groove).

[0059] For example, when the initial second region on the first surface 11a of the substrate 11 is irradiated with a laser, and the energy of the laser spot is relatively uniform, a shape will be formed as shown in the figure. Figure 1 The groove structure 12 shown has a first energy at the center of the laser spot and a second energy at the edge of the laser spot. The ratio of the first energy to the second energy is greater than 0.8 and less than 1.2. For example, the ratio of the first energy to the second energy can be 0.85, 0.9, 0.95, 1.0, 1.05, 1.10, 1.15 or 1.2.

[0060] In some embodiments, the solar cell 100 may be a PERC cell (Passivated Emitter RearCell), an IBC cell (Interdigitated Back Contact), a TOPCon cell (Tunnel Oxide Passivated Contact), or a HIT / HJT cell (Heterojunction Technology).

[0061] For example, taking a TOPCon cell as an example, the structure of the solar cell 100 will be described in detail. Please refer to [link to relevant documentation]. Figure 4 As shown, the direction from the first surface 11a to the second surface 11b is defined as the third direction. The solar cell 100 includes a substrate 11, a passivation layer 120 and a first antireflection layer 17 sequentially stacked on the first surface 11a, and a first electrode 181. The first electrode 181 is correspondingly disposed in the first region 13. The solar cell 100 also includes a tunneling oxide layer 191, a doped polycrystalline silicon layer 192, a back passivation layer 193, a second antireflection layer 194, and a second electrode 182 sequentially stacked on the second surface 11b. The second electrode 182 is disposed in the thickness direction of the substrate 11 corresponding to the first region 13.

[0062] The first surface 11a of the substrate 11 is a positive surface. The first surface 11a of the substrate 11 includes a first region 13 and a second region 14. The emitter 131 is located below the first region 13, and there may be no emitter below the second region 14. A passivation layer 120 covers the first region 13 and the second region 14 (the bottom surface 121 of the groove and the side wall 122 of the groove). A first antireflection layer 17 covers the passivation layer 120. A first electrode 181 is disposed in the region where the first region 13 is located. The first electrode 181 extends through the first antireflection layer 17 and the passivation layer 120 in the thickness direction of the substrate 11 to the emitter 131 below the first region 13. The first electrode 181 is connected to the emitter 131.

[0063] Wherein, the second surface 11b of the substrate 11 is the back surface. In the thickness direction of the substrate 11, along the direction from the first surface 11a to the second surface 11b, a tunneling oxide layer 191, a doped polysilicon layer 192, a back passivation layer 193 and a second antireflection layer 194 are sequentially deposited on the second surface 11b. The second electrode 182 is disposed in the region corresponding to the first region 13. In the thickness direction of the substrate 11, the second electrode 182 extends through the second antireflection layer 194 and the back passivation layer 193 to the doped polysilicon layer 192 along the direction from the second surface 11b to the first surface 11a. The second electrode 182 is connected to the doped polysilicon layer 192.

[0064] In some embodiments, the substrate 11 can be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant element, which can 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 dopant element, which can be any one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0065] In some embodiments, the solar cell can be a single-sided cell, with the front surface (first surface 11a) serving as the light-receiving surface for receiving incident light and the back surface (second surface 11b) serving as the back-lighting surface.

[0066] In some embodiments, the solar cell can be a bifacial cell, meaning that both the first surface 11a and the second surface 11b of the substrate 11 can serve as light-receiving surfaces and can be used to receive incident light. The back surface (second surface 11b) can also receive incident light, but its efficiency in receiving incident light is somewhat lower than that of the light-receiving surface (first surface 11a).

[0067] In some embodiments, the emitter 131 may be formed by doping the original substrate 11. The emitter 131 and the substrate 11 are made of the same base material. Specifically, a portion of the original substrate corresponding to the first region 13 may be doped. The doped original substrate serves as the emitter 131, and the undoped original substrate serves as the substrate 11. Furthermore, the doping element type in the emitter 131 is different from the doping element type in the substrate 11. For example, if the substrate 11 is an N-type silicon substrate, the emitter 131 is formed by P-type doping of a portion of the N-type silicon substrate.

[0068] In some embodiments, the passivation layer 120 can be a single-layer structure or a stacked structure, and the material used to prepare the passivation layer 120 can be one or more of the following materials: silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, titanium oxide, hafnium oxide, or aluminum oxide.

[0069] In some embodiments, the material used to prepare the first antireflection layer 17 may be one or more of silicon nitride or silicon oxynitride.

[0070] In some embodiments, the tunneling oxide layer 191 may be a silicon dioxide layer.

[0071] In some embodiments, the doping type of the doped polysilicon layer 192 is the same as the doping type of the substrate 11. For example, if the substrate 11 is doped with an N-type dopant, then the doped polysilicon layer 192 is doped with an N-type dopant. The tunneling oxide layer 191 and the doped polysilicon layer 192 together form a passivation contact structure.

[0072] In some embodiments, the back passivation layer 193 can be a single-layer structure or a stacked structure, and the material used to prepare the back passivation layer 193 can be one or more of the following materials: silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, titanium oxide, hafnium oxide, or aluminum oxide.

[0073] In some embodiments, the material used to prepare the second antireflection layer 194 can be one or more of silicon nitride or silicon oxynitride.

[0074] In some embodiments, the first electrode 181 and the second electrode 182 have opposite polarities.

[0075] One embodiment of this application provides a stacked battery, which includes a top battery, an intermediate connecting layer and a bottom battery, wherein the intermediate connecting layer is connected between the top battery and the bottom battery.

[0076] The top cell is one of a perovskite cell, a cadmium telluride solar cell, a copper indium gallium selenide solar cell, or a gallium arsenide solar cell, and the bottom cell is the aforementioned solar cell 100.

[0077] In some implementations, the interlayer can be a transparent material with a high refractive index. To reduce light reflection and absorption at the interlayer interface and achieve good conductivity to minimize the impact of series resistance on device performance, the interlayer typically needs to have high light transmittance. For example, the interlayer can be a transparent conductive metal oxide thin film (ITO).

[0078] One embodiment of this application provides a photovoltaic module 200. Please refer to [link / reference]. Figure 5 and Figure 6 As shown, it includes a battery string 201, an encapsulating film 202, and a cover plate 203. Please refer to [the provided text]. Figure 5 As shown, the battery string 201 is formed by connecting multiple solar cells 100 as described above; the encapsulating film 202 is used to cover the surface of the battery string 201; the cover plate 203 is used to cover the surface of the encapsulating film 202 facing away from the surface of the battery string 201.

[0079] In some embodiments, the battery string 201 may also be formed by connecting multiple stacked batteries as described above.

[0080] In some embodiments, multiple solar cells 100 can be electrically connected to each other by solder ribbon 20, which is connected to each pair of adjacent solar cells 100. The solder ribbon 20 is connected to the front surface of the first solar cell 100 and the back surface of the second solar cell 100, respectively.

[0081] In some embodiments, the solar cells 100 may be spaced apart, and during string bonding, the solder strip 20 extends from the front surface of the first solar cell 100 to the gap, passes through the gap, and extends to the back surface of the second solar cell 100.

[0082] In some embodiments, no gap is provided between the solar cells 100, that is, two adjacent solar cells 100 overlap each other.

[0083] In some embodiments, the encapsulating film 202 includes a first encapsulating film and a second encapsulating film. The first encapsulating film covers one of the front or back sides of the solar cell 100, and the second encapsulating film covers the other of the front or back sides of the solar cell 100. Specifically, at least one of the first or second encapsulating film can be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene coelastomer (POE) film, or polyethylene terephthalate (PET) film.

[0084] Example 1 The structure of the solar cell in this embodiment 1 is as follows: Figure 1 and Figure 4 As shown, the method for fabricating the solar cell in Example 1 includes the following steps: Step 1-1: Provide a texturized N-type silicon wafer. The front surface of the N-type silicon wafer has a third pyramid with an average size of 2μm to 4μm, an average height of 1.2μm, and a density of 300,000 pyramids / mm². 2 .

[0085] Steps 1-2 involve boron diffusion doping of the N-type silicon wafer to form an initial doped layer on the positive surface. The sheet resistance of the positive surface after boron diffusion doping is... .

[0086] Steps 1-3 employ an ultraviolet picosecond laser with a wavelength of 266nm to 355nm, setting the repetition rate to 500kHz to 1MHz, and setting the laser energy density to 0.5 to 1 J / L for the metallized region. The metallized region is surface activated; a laser is used to perform laser film-opening treatment on the non-metallized region on the positive surface of the boron-diffused N-type silicon wafer to initially remove at least a portion of the initial doped layer of the non-metallized region, obtaining the first intermediate cell. The laser provided is an ultraviolet picosecond laser (wavelength 266nm to 355nm, spot diameter 200μm to 300μm, frequency 600kHz, scanning speed 50m / s to 60m / s, pulse width 6ps to 15ps, energy density 0.1–3 J / L). By adjusting the energy focusing of the light spot through a diffractive optical element (DOE), the direction and distribution of light are changed, thereby controlling the ratio of energy at the center of the light spot to energy at the edge of the light spot, so that the energy ratio between the center and the edge of the light spot is greater than 0.8 and less than 1.2. Laser preprocessing is performed on the transition region adjacent to the metallized region and the groove structure by laser scanning with staggered splicing and blurred edges. The offset of the center of adjacent light spots is 70% to 90% of the diameter of the light spot. By adjusting the Q switch or acousto-optic modulator or the energy focusing of the light spot, the energy at the edge of the light spot is reduced by 20% to 40% relative to the center (i.e., edge blurring).

[0087] Steps 1-4 involve using an alkaline etching solution to perform alkaline etching on the intermediate body of the first solar cell to remove at least a portion of the initial doped layer thickness in the non-metallized region, thereby forming a groove structure 12. The groove sidewalls 122 of the groove structure 12 have the following morphology: Figure 1 As shown, the depth of the groove structure after alkaline etching (the height difference between the laser-etched area and the non-laser-etched area) is 0.3 μm to 18 μm. During the alkaline etching process, secondary texturing is performed on the bottom surface 121 of the groove to form a second textured surface in the laser-etched area, and secondary texturing is performed on the second sidewall 122b to form a second pyramid, resulting in a second intermediate battery cell. The alkaline etching solution is prepared by mixing water, alkaline solution, and an alkaline etching additive. The alkaline solution is a 49% NaOH solution, and the volume ratio of the alkaline solution to the total volume of the alkaline etching solution is 5% to 10%. The alkaline etching additive is liquid, and the volume ratio of the alkaline etching additive to the total volume of the alkaline etching solution is 0.5% to 1%. The alkaline etching additive is a product of Shaoxing Topband New Energy Co., Ltd., model TB22BV03. The second textured surface includes a first pyramid, with an average size of 2 μm to 4 μm, an average height of 1 μm, and a density of 360,000 pyramids / mm². 2 The second pyramid has a height of 1 μm and a density of 360,000 particles / mm². 2Subsequently, the second battery cell intermediate was placed in a mixed acid solution of HF and HNO3 with a mass concentration of 2% to 5% (volume ratio of 1:3 to 1:5) for 30 to 60 seconds. Due to the more severe lattice damage and higher chemical activity in the laser pretreatment region (transition region), isotropic accelerated corrosion occurred in this region in the mixed acid solution, resulting in corrosion pits that extend from the apex regions into the interior of the pyramids in at least a portion of the apex regions of the first pyramid and at least a portion of the apex regions of the second pyramid.

[0088] Steps 1-5 involve oxidizing the second solar cell intermediate to oxidize the initial doped layer of at least a partial thickness in the metallized region of the front surface to form a first oxide layer, and to form a second oxide layer of at least a partial thickness on the bottom surface and sidewalls of the groove in the non-metallized region. The oxidation conditions are as follows: oxygen is introduced at a flow rate of 20,000-80,000 sccm at 800-1050°C for 1-4 hours to oxidize the second solar cell intermediate; the first oxide layer is borosilicate glass with a thickness of 80 nm to 120 nm, and the second oxide layer is also borosilicate glass with a thickness of 80 nm to 120 nm; simultaneously, a third oxide layer is formed on the back surface, also made of borosilicate glass with a thickness of 80 nm to 120 nm. During the oxidation process, the PN junction in the metallized region is advanced. After oxidation, the depth of the PN junction in the metallized region is 2.0 μm to 2.5 μm, and the surface concentration of boron in the metallized region is 5E17. ~1E21 .

[0089] Steps 1-6 involve removing the borosilicate glass from the back surface of the second solar cell intermediate using hydrofluoric acid (HF), followed by alkaline polishing and etching of the back surface of the intermediate with an alkaline polishing solution to expose a clean, flat, and parasitic-doped N-type monocrystalline silicon surface. The etched base size is 3μm to 30μm. The alkaline polishing solution is prepared by mixing water, an alkaline solution, and an alkaline polishing additive. The alkaline solution is a 49% (w / w) NaOH solution, and the volume ratio of the alkaline solution to the total volume of the alkaline polishing solution is 5% to 10%. The alkaline polishing additive is liquid, and the volume ratio of the alkaline polishing additive to the total volume of the alkaline polishing solution is 0.5% to 3%. The alkaline polishing additive is a product manufactured by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd., model AT37-2. Please refer to [link / reference]. Figure 8 As shown, the tower base is a structure formed after the back surface of the velvet surface is polished. The tower base is a tower-shaped structure that is recessed into the interior of the base 11. Along the thickness direction of the base 11, the tower base structure has a certain recess depth H4. The tower base size can be the average value of the side length of the tower base.

[0090] Steps 1-7: A tunneling oxide layer and a polycrystalline silicon layer are sequentially formed on the back surface of the second solar cell intermediate. The polycrystalline silicon layer is then phosphorus-doped to obtain a phosphorus-doped polycrystalline silicon layer (Poly). The thickness of the tunneling oxide layer is 0.6 nm to 3 nm, the thickness of the phosphorus-doped polycrystalline silicon layer (Poly) is 40 nm to 220 nm, and the phosphorus doping surface concentration is 1E18. up to 8E21 During this process, a portion of the phosphorus-doped polycrystalline silicon layer forms a fourth oxide layer, which is a phosphorus-silicon glass with a thickness of 20 nm to 50 nm.

[0091] Steps 1-8 involve removing the first and second oxide layers on the front surface using an acid solution. The acid solution is an HF solution with a volume concentration of 5-20%, and the acid treatment time is 20-80 seconds. Then, an alkaline etching solution is used to remove the polycrystalline silicon layer coated on the front surface. The alkaline solution is prepared by mixing water, NaOH solution, and a decoupling additive. The NaOH solution has a NaOH mass concentration of 49%, and the volume ratio of the NaOH solution to the total volume of the alkaline solution is 2-8%. The decoupling additive is in liquid form, and the volume ratio of the decoupling additive to the total volume of the alkaline solution is 1%. The decoupling additive is a commercial product, model PR21V03, manufactured by Shaoxing Topband New Energy Co., Ltd. The alkaline solution temperature is 60-75℃, and the alkaline treatment time is 220-480 seconds. Finally, an acid solution is used to remove the fourth oxide layer on the back surface and the remaining oxide layer on the front surface. The acid solution is an HF solution with a volume concentration of 5-20%, and the acid treatment time is 20-80 seconds.

[0092] Steps 1-9 involve passivating the second battery cell intermediate to form passivation layers on the front and back surfaces, and then forming an anti-reflection layer covering the passivation layers to obtain the battery cell. The passivation layer can be aluminum oxide with a thickness of 1 nm to 18 nm, and the anti-reflection layer can be silicon nitride with a thickness of 50 nm to 150 nm.

[0093] Steps 1-10: Print and sinter the first electrode on the front surface of the solar cell to form a first electrode, and print and sinter the second electrode on the back surface of the solar cell to form a second electrode, thus obtaining a solar cell.

[0094] The solar cell prepared in Example 1 has a boron doping concentration (surface) of 4.75E17 at the bottom of the groove. .

[0095] Example 2 The structure of the solar cell in Example 2 is basically the same as that in Example 1, except that there is no emitter on the bottom surface of the groove in the solar cell of Example 2, that is, the boron doping concentration on the bottom surface of the groove is below the detection limit.

[0096] Accordingly, in steps 1-5 of Example 2, the second battery cell intermediate is oxidized to form a first oxide layer by oxidizing the initial doped layer of at least a portion of the thickness of the metallized region on the front surface, and a second oxide layer is formed on the bottom surface and sidewalls of the groove in the non-metallized region with at least a portion of the thickness. The first oxide layer is borosilicate glass with a thickness of 80 nm to 120 nm. The second oxide layer on the bottom surface of the groove is a silicon oxide layer, and the second oxide layer on the first sidewall is borosilicate glass. On the second sidewall, the second oxide layer near the first region is borosilicate glass, and the second oxide layer near the bottom surface of the groove is either a silicon oxide layer or borosilicate glass. The thickness of the second oxide layer is 80 nm to 120 nm. Simultaneously, a third oxide layer is formed on the back surface. The third oxide layer is borosilicate glass with a thickness of 80 nm to 120 nm. During the oxidation process of the second battery cell intermediate, the PN junction of the metallized region is advanced. After the oxidation process, the depth of the PN junction in the metallized region is 2.0 μm to 2.5 μm, and the surface concentration of boron in the metallized region is 5E17. ~1E21 .

[0097] Example 3 The structure of the solar cell in Example 3 is basically the same as that in Example 1, except that the boron doping concentration (surface) of the bottom surface of the groove in the solar cell of Example 3 is 3E17. .

[0098] Comparative Example 1 The structure of the solar cell in Comparative Example 1 is basically the same as that in Example 1, except that the groove structure of Comparative Example 1 is as follows: Figure 7 As shown, in the groove structure of Comparative Example 1, the groove sidewalls are sloped and have a pyramid texture.

[0099] The difference between Comparative Example 1 and Example 1 is that: in steps 1-3, when laser-opening the non-metallized region, the energy ratio between the center and edge of the laser spot is less than 0.8 or greater than 1.2. When the energy of the laser spot is not uniform, it will form as shown in the figure. Figure 7 The groove structure shown.

[0100] The difference between Comparative Example 1 and Example 1 is that there is no subsequent treatment with mixed acid solution in steps 1-4.

[0101] Comparative Example 2 The structure of the solar cell in Comparative Example 2 is basically the same as that in Example 2, except that the groove structure of Comparative Example 2 is as follows: Figure 7 As shown, in the groove structure of Comparative Example 2, the groove sidewalls are sloped and have a pyramid texture.

[0102] Steps 1-3 and 1-4 of Comparative Example 2 are the same as those of Comparative Example 1.

[0103] Comparative Example 3 The structure of the solar cell in Comparative Example 3 is basically the same as that in Example 1, except that the groove structure of Comparative Example 3 is as follows: Figure 7 As shown, in the groove structure of Comparative Example 3, the groove sidewalls are sloped and have a pyramid texture.

[0104] The difference between Comparative Example 3 and Example 1 lies in the following: During laser film opening of the non-metallized region in steps 1-3, the energy ratio between the center and edge of the laser spot is less than 0.8 or greater than 1.2. When the energy of the laser spot is uneven, it will form... Figure 7 The groove structure shown.

[0105] The solar cells of Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to performance comparison tests. The test conditions were as follows: using a pulsed solar simulator, under an ambient temperature of 25°C, AM1.5 atmospheric mass, and a solar irradiance of 1000 W / m², the electrical performance parameters of the cells, including photoelectric conversion efficiency (Eta), fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Isc), were measured. The results are shown in Table 1. Table 1. Performance Test Comparison Table of Examples and Comparative Examples The above description is merely an embodiment of this application. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of this application, but these improvements all fall within the protection scope of this application.

Claims

1. A solar cell, characterized in that, include: A substrate having a first surface and a second surface disposed opposite to each other along a thickness direction, the first surface having a first region and a second region alternately disposed along a first direction; The groove structure located in the second region includes a groove bottom surface formed by the base of the second region being recessed along the thickness direction, and a groove sidewall connecting the first region and the groove bottom surface. The groove sidewall includes a first sidewall connected to the first region and a second sidewall connected to the first sidewall and the groove bottom surface respectively. The second sidewall is inclined toward the first region, and the angle between the first sidewall and the groove bottom surface is smaller than the angle between the second sidewall and the groove bottom surface. The doping concentration at the bottom of the groove is less than that in the first region. The bottom of the groove has a first pyramid, and the second sidewall has a second pyramid. The angle between the perpendicular line of the first pyramid and the perpendicular line of the second pyramid is less than 90°.

2. The solar cell according to claim 1, characterized in that, The height of the second pyramid is 0.1μm to 5μm.

3. The solar cell according to claim 1, characterized in that, The density of the second pyramid is 1,000 to 1,000,000. .

4. The solar cell according to any one of claims 1 to 3, characterized in that, The second sidewall includes a first inclined area near the first sidewall and a second inclined area near the bottom of the groove. The second pyramid is located in the first inclined area, and the roughness of the second inclined area is less than that of the first inclined area.

5. The solar cell according to claim 1, characterized in that, The first sidewall is perpendicular to the bottom surface of the groove.

6. The solar cell according to claim 1, characterized in that, The first sidewall has a non-pyramidal texture structure, and the roughness of the first sidewall is less than that of the second sidewall.

7. The solar cell according to claim 1, characterized in that, The first sidewall is a smooth sidewall.

8. The solar cell according to claim 1, characterized in that, The substrate is doped with a first conductivity type, and the bottom surface of the trench does not have a second conductivity type doping, or the doping concentration of the second conductivity type element on the bottom surface of the trench is less than or equal to 5E17. The first conductivity type and the second conductivity type are opposite.

9. The solar cell according to claim 1, characterized in that, Along the first direction, the ratio of the length of the first region to the length of the second region is 0.3 to 3.

10. A stacked battery, characterized in that, include: Top cell, which can be a perovskite cell, cadmium telluride solar cell, copper indium gallium selenide solar cell, or gallium arsenide solar cell; Intermediate connection layer; and The base cell is the solar cell according to any one of claims 1-9; The top battery, the intermediate connecting layer, and the bottom battery are stacked and connected.

11. A photovoltaic module, characterized in that, Includes the solar cell according to any one of claims 1-9, or the tandem cell according to claim 10.

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