Solar cell, method of manufacturing the same, and cell assembly

Abstract

The embodiment of the present application relates to the field of photovoltaics, and provides a solar cell, a preparation method thereof and a battery assembly. The solar cell comprises a substrate, the substrate comprising a first region and a second region; a first passivation layer is located on a side of a first doped region away from the substrate, and a second passivation layer is located on a side of the substrate away from the first doped region; a third passivation layer is located on a side of a second doped region away from the substrate, a first electrode is located on a side of the third passivation layer away from the second doped region, a tunneling layer is located on a side of the substrate away from the second doped region, a doped conductive layer is located on a side of the tunneling layer away from the substrate, a fourth passivation layer is located on a side of the doped conductive layer away from the tunneling layer, and a second electrode is located on a side of the fourth passivation layer away from the doped conductive layer; and the minimum distance between the first doped region and the second passivation layer is less than the minimum distance between the second doped region and the tunneling layer. The solar cell provided by the embodiment of the present application can at least improve the performance of the solar cell.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and in particular to a solar cell, a method for preparing a solar cell, and a cell module. Background Technology

[0002] Solar cells, also known as photovoltaic cells, are devices that directly convert sunlight into electrical energy. Their working principle is based on the photovoltaic effect in semiconductor physics. When sunlight shines on a semiconductor material, photon energy is absorbed and excites electrons to jump to the conduction band, thus generating free electron-hole pairs. These charge carriers move under the influence of an electric field inside the semiconductor, forming an electric current, and thus generating electrical energy.

[0003] Currently, the main solar cell technologies on the market include IBC cells, TOPCon cells, PERC cells, and heterojunction cells (HJT). These cells, through carefully designed multilayer film structures and material properties, aim to minimize optical losses during the light-to-electricity conversion process, while effectively reducing carrier recombination on the silicon substrate surface and within the substrate, thereby improving the photoelectric conversion efficiency of the cells.

[0004] However, the performance of solar cells in existing technologies is still not ideal. Summary of the Invention

[0005] This application provides a solar cell, a method for preparing a solar cell, and a battery module, which at least helps to improve the performance of the solar cell.

[0006] According to some embodiments of this application, one aspect of this application provides a solar cell, including a substrate, wherein the substrate includes a first region and a second region; a first doped region, a first passivation layer, and a second passivation layer located in the first region, the first passivation layer being located on the side of the first doped region away from the substrate, and the second passivation layer being located on the side of the substrate away from the first doped region; a second doped region, a third passivation layer, a first electrode, a tunneling layer, a doped conductive layer, a fourth passivation layer, and a second electrode located in the second region, wherein the third passivation layer is located on the side of the second doped region away from the substrate, the first electrode is located on the side of the third passivation layer away from the second doped region, the tunneling layer is located on the side of the substrate away from the second doped region, the doped conductive layer is located on the side of the tunneling layer away from the substrate, the fourth passivation layer is located on the side of the doped conductive layer away from the tunneling layer, and the second electrode is located on the side of the fourth passivation layer away from the doped conductive layer, the minimum distance between the first doped region and the second passivation layer is a first distance, the minimum distance between the second doped region and the tunneling layer is a second distance, and the first distance is less than the second distance.

[0007] In some embodiments, an absolute value of a difference between the first distance and the second distance is 2-15 μm.

[0008] In some other embodiments, a junction depth of the first doped region is greater than a junction depth of the second doped region.

[0009] In some other embodiments, a junction depth of the first doped region is 0.5-5 μm, and a junction depth of the second doped region is 0.1-2 μm.

[0010] In some other embodiments, a sheet resistance of the first doped region is greater than a sheet resistance of the second doped region.

[0011] In some other embodiments, a sheet resistance of the first doped region is 100-500 Ω / square, and a sheet resistance of the second doped region is 500-1000 Ω / square.

[0012] In some other embodiments, a doping concentration of the first doped region is less than a doping concentration of the second doped region.

[0013] In some other embodiments, a doping concentration of the first doped region is 1x10 15 -1x10 19 at / cm 3 , and a doping concentration of the second doped region is 1x10 18 -1x10 23 at / cm 3 .

[0014] In some other embodiments, the solar cell further comprises: a first anti-reflective layer located on a side of the first passivation layer away from the first doped region; a second anti-reflective layer located on a side of the second passivation layer away from the substrate; a third anti-reflective layer located between the third passivation layer and the first electrode; and a fourth anti-reflective layer located between the fourth passivation layer and the second electrode.

[0015] In some other embodiments, a thickness of the doped conductive layer is 20-400 nm.

[0016] In some other embodiments, a thickness of the tunneling layer is 0.5-2 nm.

[0017] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a preparation method of a solar cell, a substrate is provided, wherein the substrate has opposite first and second surfaces, and the substrate comprises a first region and a second region; a diffusion layer and a BSG layer are sequentially formed on the first surface; the BSG layer and part of the diffusion layer in the first region are removed by processing the BSG layer and the diffusion layer in the first region, so as to obtain a first doped region and a second doped region, wherein the remaining diffusion layer in the first region forms the first doped region, and the remaining diffusion layer in the second region forms the second doped region; a tunneling layer and a doped conductive layer are sequentially formed on the second region of the second surface; a first passivation layer, a second passivation layer, a third passivation layer and a fourth passivation layer are respectively formed on the first region of the first surface, the first region of the second surface, the second region of the first surface and the second region of the second surface; a first electrode is formed on a side of the third passivation layer away from the second doped region; and a second electrode is formed on a side of the fourth passivation layer away from the doped conductive layer.

[0018] In some other embodiments, the processing of the BSG layer and the diffusion layer in the first region to remove the BSG layer and part of the diffusion layer to obtain the first doped region and the second doped region comprises: performing first laser processing on the first region to diffuse ions in the diffusion layer to the substrate, wherein the first laser processing is red laser processing, the power of the first laser processing is 5w-100w, and the scanning speed of the first laser processing is 5000-40000mm / s; and performing etching processing on the first region by using an alkali solution to remove the BSG layer and part of the diffusion layer, wherein the temperature of the etching processing is 50-90℃, the time of the etching processing is 10-400s, the volume of the alkali solution is 1-30L, and the depth of the etching processing is 0.5-5μm.

[0019] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a photovoltaic module, which comprises a cell string connected by any one of the solar cells, an encapsulation layer for covering the surface of the cell string, and a cover plate for covering the surface of the side of the encapsulation layer away from the cell string.

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

[0021] On the one hand, by differentiating the first region and the second region of the solar cell, i.e., by reserving part of the first doped region in the first region, the carrier recombination caused by doping B, P, Ga and other heterogeneous elements in the first region can be eliminated, the open circuit voltage can be improved, and thus the performance of the solar cell can be improved.

[0022] On the other hand, the minimum distance between the first doped region and the second passivation layer is less than the minimum distance between the second doped region and the tunneling layer, which can realize the localized design for the first region, weaken the parasitic absorption effect of the polysilicon, improve the short-circuit current, and thus improve the performance of the solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0023] One or more embodiments are illustrated by way of example in the figures that form a part of this disclosure and which demonstrate aspects of the application. Such illustrations are not limiting of the embodiments, unless otherwise specified, and do not provide an exhaustive list of possibilities. For clarity, the description herein refers to terms such as "one embodiment," "another embodiment," "an embodiment," "some embodiments," etc. that typically refer to one or more implementations of the subject matter. Thus, these terms, when used, are not necessarily referring to the same embodiment. Furthermore, the terms "embodiment" and "exemplary embodiment" do not require that all embodiments include the discussed feature, advantage or object. Thus, processes or signals implicated in one embodiment can or can not be present in another embodiment. The skilled artisan will understand that terms such as "front," "back," "up," "down," "right," "left," "upright," "horizontal," "vertical," and the like are used herein for convenience and are not intended to be limiting, unless otherwise indicated, to the particular orientation or manner of use.

[0024] Figure 1 A structural schematic diagram of a solar cell according to an embodiment of the present application;

[0025] Figure 2 A structural schematic diagram of a solar cell according to another embodiment of the present application;

[0026] Figure 3 A flowchart of a preparation method of a solar cell according to another embodiment of the present application;

[0027] Figure 4 A structural schematic diagram corresponding to a flowchart of a preparation method of a solar cell according to an embodiment of the present application;

[0028] Figure 5 A structural schematic diagram of a photovoltaic module according to another embodiment of the present application.

[0029] In the above drawings, the following reference signs are used:

[0030] 10, substrate; 101, first region; 102, second region; 11, first doped region; 12, first passivation layer; 13, second passivation layer; 14, second doped region; 15, third passivation layer; 16, first electrode; 17, tunneling layer; 18, doped conductive layer; 19, fourth passivation layer; 20, second electrode; 21, first anti-reflection layer; 22, second anti-reflection layer; 23, third anti-reflection layer; 24, fourth anti-reflection layer; 25, diffusion layer; 26, BSG layer; 40, solar cell; 402, conductive band; 41, encapsulation layer; 42, cover plate. DETAILED DESCRIPTION

[0031] As known from the background art, by introducing specific impurity elements into semiconductor materials to construct PN junction, the commonly used dopants include boron (B), phosphorus (P) and gallium (Ga) and the like, which can change the conductivity of the semiconductor to form P-type (with holes as the main carrier) and N-type (with electrons as the main carrier) regions. However, although increasing the doping concentration can enhance the electric field intensity of the PN junction, which is beneficial to the separation and collection of carriers, too high doping concentration will increase the defect density in the material, causing the Auger recombination process, in which the carriers interact with the impurity atoms, release energy, and cause the significant shortening of the carrier lifetime, thereby reducing the open-circuit voltage and overall conversion efficiency of the battery.

[0032] To solve the above problems, the embodiments of the present application provide a solar cell, as shown in Figure 1 and Figure 2 comprising:

[0033] a substrate 10, wherein the substrate 10 comprises a first region 101 and a second region 102;

[0034] Specifically, the substrate is responsible for absorbing sunlight and exciting to generate electron-hole pairs, i.e. photo-generated carriers, in the process. The substrate can be doped with elements such as phosphorus (P), bismuth (Bi), antimony (Sb) or arsenic (As) to optimize its conductivity. The first region and the second region are arranged along a first direction, wherein the first direction is perpendicular to the thickness direction of the substrate. It is worth noting that the subsequent manufacturing process will form an electrode on at least one side of the substrate, which coincides with the projection of the second region on the substrate. In the first direction, the width of the second region can be designed to exceed the width of the first electrode or the second electrode to ensure sufficient contact area and current conduction efficiency. The first region is located outside the projection range of the electrode on the substrate, and can also be defined as the remaining part outside the second region. Although the first region does not directly participate in current conduction, it can provide passivation effect, reduce parasitic absorption and control the recombination process of carriers, thereby improving the photoelectric conversion efficiency and stability of the battery. In some embodiments, the opposite surfaces of the first region can be textured, which can improve the double-sided rate of the battery while improving the open-circuit voltage and short-circuit current.

[0035] a first doped region 11, a first passivation layer 12 and a second passivation layer 13 located in the first region 101 of the substrate 10, the first passivation layer 12 is located on the side of the first doped region 11 away from the substrate 10, and the second passivation layer 13 is located on the side of the substrate 10 away from the first doped region 11;

[0036] In practical applications, the first doped region and the first passivation layer are sequentially arranged in the first region of the first surface, and the second passivation layer is arranged in the first region of the second surface. The first doped region can be obtained by ion diffusion doping of the surface layer of the substrate, and the doped part of the substrate is converted into the first doped region. The first passivation layer and the second passivation layer can be a single-layer structure or a stacked structure, and the materials of the first passivation layer and the second passivation layer can be one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride, titanium oxide, hafnium oxide, or aluminum oxide.

[0037] The second doped region 14, the third passivation layer 15, the first electrode 16, the tunneling layer 17, the doped conductive layer 18, the fourth passivation layer 19, and the second electrode 20 are located in the second region 102. The third passivation layer 15 is located on the side of the second doped region 14 away from the substrate 10, the first electrode 16 is located on the side of the third passivation layer 15 away from the second doped region 14, the tunneling layer 17 is located on the side of the substrate 10 away from the second doped region 14, the doped conductive layer 18 is located on the side of the tunneling layer 17 away from the substrate 10, the fourth passivation layer 19 is located on the side of the doped conductive layer 18 away from the tunneling layer 17, and the second electrode 20 is located on the side of the fourth passivation layer 19 away from the doped conductive layer 18. The minimum distance between the first doped region 11 and the second passivation layer 13 is a first distance L1, the minimum distance between the second doped region 14 and the tunneling layer 17 is a second distance L2, and the first distance L1 is less than the second distance L2.

[0038] Specifically, the second doped region, the third passivation layer, and the first electrode are sequentially arranged in the second region of the first surface, and the tunneling layer, the doped conductive layer, and the fourth passivation layer are sequentially arranged in the second region of the second surface. The second doped region can be obtained by ion diffusion doping of the surface layer of the substrate, and the doped part of the substrate is converted into the second doped region. The materials of the first electrode and the second electrode can include one or more of aluminum, silver, gold, nickel, molybdenum, or copper. The tunneling layer is located between the substrate and the doped conductive layer, and is used to achieve interface passivation of the surface of the substrate, has a chemical passivation effect, reduces interface states, and can form a passivation contact layer together with the doped conductive layer. The material of the tunneling layer can be a dielectric material, such as any one of silicon oxide, magnesium fluoride, silicon oxide, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, and titanium oxide. The doped conductive layer can be a single-layer structure or a multi-layer structure. The third passivation layer and the fourth passivation layer can be a single-layer structure or a stacked structure, and the materials of the third passivation layer and the fourth passivation layer can be one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride, titanium oxide, hafnium oxide, or aluminum oxide.

[0039] In the solar cell of the present application, on the one hand, by differentiating the design of the first region and the second region of the solar cell, i.e. reserving part of the first doped region in the first region, the carrier recombination caused by doping B, P, Ga and other heterogeneous elements in the first region can be eliminated, the open circuit voltage can be improved, and thus the performance of the solar cell can be improved; on the other hand, the minimum distance between the first doped region and the second passivation layer is less than the minimum distance between the second doped region and the tunneling layer, which can realize the localized design of the first region, weaken the parasitic absorption effect of the polysilicon, improve the short circuit current, and thus improve the performance of the solar cell.

[0040] In some other embodiments, the absolute value of the difference between the first distance and the second distance is 2-15 μm. The difference between the first distance and the second distance is set in a suitable range, which can take into account the quality of the substrate, while further improving the performance of the solar cell.

[0041] In practical applications, the first distance is the minimum distance between the first doped region and the second passivation layer, i.e. the thickness of the substrate of the first region, the second distance is the minimum distance between the second doped region and the tunneling layer, i.e. the thickness of the substrate of the second region, and the first distance is less than the second distance, i.e. the thickness of the substrate of the first region is less than the thickness of the substrate of the second region.

[0042] In some other embodiments, the junction depth of the first doped region is greater than the junction depth of the second doped region. The first doped region has a larger junction depth, which can strengthen the built-in electric field, help to separate electrons and holes faster and move them to the electrode, reduce the carrier recombination in the first region, and further improve the open circuit voltage and the short circuit current. The second doped region has a smaller junction depth, which can reduce the absorption of incident light by the second region, especially in the short wavelength spectral range, which means that more photons can directly reach the active region of the cell, rather than being absorbed in the near-surface region, thereby further improving the light utilization and the short circuit current of the cell.

[0043] In practical applications, those skilled in the art can set the junction depths of the first doped region and the second doped region according to actual conditions, as long as the junction depth of the first doped region is greater than the junction depth of the second doped region.

[0044] In some embodiments, the junction depth of the first doped region is 0.5~5 μm, and the junction depth of the second doped region is 0.1~2 μm. The junction depth of the first doped region being in the range of 0.5~5 μm ensures a relatively large junction depth, reducing carrier recombination in the first region, while also preventing excessively large junction depths, thus further avoiding increased optical losses due to excessive junction depth. The junction depth of the second doped region being in the range of 0.1~2 μm ensures a relatively small junction depth, while also preventing problems such as low charge separation efficiency and insufficient built-in electric field strength caused by excessively small junction depths.

[0045] Specifically, the junction depth of the first doped region can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm. The junction depth of the second doped region can be 0.1 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.9 μm, and 2 μm.

[0046] In some embodiments, the sheet resistance of the first doped region is greater than that of the second doped region. A higher sheet resistance in the first doped region allows for a reduction in its doping concentration, thereby providing better surface passivation, reducing surface recombination, and increasing carrier lifetime. A lower sheet resistance in the second doped region indicates good conductivity, which reduces the series resistance within the battery and thus improves the overall battery efficiency.

[0047] In other embodiments, the sheet resistance of the first doped region is 100~500Ω / square, and the sheet resistance of the second doped region is 500~1000Ω / square.

[0048] The sheet resistance of the first doped region can be 100 Ω / square, 200 Ω / square, 300 Ω / square, 400 Ω / square, and 500 Ω / square. The sheet resistance of the second doped region can be 500 Ω / square, 600 Ω / square, 700 Ω / square, 800 Ω / square, 900 Ω / square, and 1000 Ω / square.

[0049] In some embodiments, the first doped region has a doping concentration less than the doping concentration of the second doped region. The first doped region has a smaller doping concentration, which can maintain a better passivation effect and further improve the open circuit voltage and short circuit current of the solar cell. The second doped region has a larger doping concentration, which can make the second doped region have a smaller sheet resistance and increase the transport efficiency of the carriers in the second region.

[0050] In some embodiments, the first doped region has a doping concentration of 1×10 15 at / cm 19 at / cm 3 The second doped region has a doping concentration of 1×10 18 at / cm 23 at / cm 3 The first doped region has a doping concentration in a range of 1×10 15 at / cm 19 at / cm 3 This range of the doping concentration of the first doped region can make the first doped region have a smaller amount of doped elements, which can maintain a better passivation effect and further improve the open circuit voltage and short circuit current of the solar cell. The second doped region has a doping concentration in a range of 1×10 18 at / cm 23 at / cm 3 This range of the doping concentration of the second doped region can ensure a high doping concentration of the second doped region, which can make the second doped region have a smaller sheet resistance and increase the transport efficiency of the carriers. In addition, the top surface of the second doped region does not have a too large doping concentration, which can avoid a problem that a large amount of doped elements in the second doped region become strong recombination centers and cause the second doped region to have a poor passivation effect.

[0051] For example, the first doped region has a doping concentration of 1×10 15 at / cm 3 , 1×10 16 at / cm 3 , 1×10 17 at / cm 3 , 1×10 18 at / cm 3 , and 1×10 19 at / cm 3 The second doped region has a doping concentration of 1×10 18 at / cm 3 , 1×10 19 at / cm 3 , 1×10 20 at / cm 3 , 1×1021 at / cm 3 1×10 22 at / cm 3 and 1×10 23 at / cm 3 .

[0052] In some other embodiments, such as Figure 2 As shown, the solar cell further includes: a first antireflection layer 21 located on the side of the first passivation layer 12 away from the first doped region 11; a second antireflection layer 22 located on the side of the second passivation layer 13 away from the substrate 10; a third antireflection layer 23 located between the third passivation layer 15 and the first electrode 16; and a fourth antireflection layer 24 located between the fourth passivation layer 19 and the second electrode 20. The arrangement of the first antireflection layer 21, the second antireflection layer 22, the third antireflection layer 23, and the fourth antireflection layer 24 can effectively reduce the reflectivity of the cell surface, thereby increasing the light transmittance and enhancing the light absorption rate of the cell.

[0053] Specifically, the materials of the first antireflection layer, the second antireflection layer, the third emission layer, and the fourth antireflection layer can be at least one of alumina, silicon nitride, and silicon oxynitride.

[0054] In some embodiments, the thickness of the doped conductive layer is 20-400 nm. The thickness of the doped conductive layer should not be too thick, as this may affect the overall thickness of the solar cell, hindering its miniaturization and thinning. Conversely, the thickness should not be too thin, as this may affect its conductivity. This optimal thickness setting of the doped conductive layer further ensures both the conductivity of the doped conductive layer and the requirement for a thinner solar cell.

[0055] For example, the thickness of the doped conductive layer can be 20nm, 60nm, 100nm, 140nm, 180nm, 220nm, 260nm, 300nm, 320nm, 360nm, and 400nm.

[0056] In other embodiments, the thickness of the tunneling layer is 0.5~2 nm. The thickness of the tunneling layer should not be too thick, as this may affect quantum tunneling of majority carriers in the tunneling dielectric layer, thus affecting the selective transport of charge carriers. Conversely, the thickness of the tunneling layer should not be too thin, as this may negatively impact the performance. The specific thickness settings of the first doped conductive layer and the tunneling layer can further ensure both the isolation effect of the isolation structure and the requirement for a thinner solar cell.

[0057] For example, the thickness of the tunneling layer can be 0.5 nm, 1 nm, 1.5 nm, and 2 nm.

[0058] Embodiments of the present application also provide a method for manufacturing the above-mentioned solar cell, Figure 3 is a flow chart of a method for manufacturing the solar cell according to embodiments of the present application. As shown in Figure 3 , the method comprises the following steps:

[0059] In step S301, a substrate 10 is provided, wherein the substrate 10 has opposite first and second surfaces, and the substrate 10 comprises a first region 101 and a second region 102, obtaining a structure as shown in Figure 4 (a);

[0060] Specifically, the substrate is responsible for absorbing sunlight and exciting electron-hole pairs, i.e. photo-generated carriers, in the process. The substrate can be doped with elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As) to optimize its electrical conductivity. The first and second regions are arranged along a first direction, wherein the first direction is perpendicular to the thickness direction of the substrate. It is worth noting that the subsequent manufacturing process will form an electrode on at least one side of the substrate, which coincides with the projection of the second region on the substrate. In the first direction, the width of the second region can be designed to exceed the width of the first or second electrode to ensure sufficient contact area and current conduction efficiency. The first region is located outside the projection range of the electrode on the substrate, and can also be defined as the remaining part outside the second region. Although the first region does not directly participate in current conduction, it can provide passivation, reduce parasitic absorption, and control the recombination process of carriers, thereby improving the photoelectric conversion efficiency and stability of the cell. In some embodiments, the opposite two surfaces of the first region can be textured, which can improve the open-circuit voltage and short-circuit current while improving the bifacial rate of the cell.

[0061] In step S302, a diffusion layer 25 and a BSG layer 26 are formed in sequence on the first surface, obtaining a structure as shown in Figure 4 (b);

[0062] Specifically, the thickness of the BSG layer can be 20-200 nm.

[0063] In step S303, the BSG layer 26 and the diffusion layer 25 of the first region 101 are processed to remove the BSG layer 26 and part of the diffusion layer 25, obtaining a first doped region 11 and a second doped region 14, wherein the remaining diffusion layer 25 of the first region 101 forms the first doped region 11, and the remaining diffusion layer 25 of the second region 102 forms the second doped region 14, obtaining a structure as shown in Figure 4 (c);

[0064] Specifically, the BSG layer and the diffusion layer can be removed by laser etching.

[0065] Step S304, a tunneling layer 17 and a doped conductive layer 18 are sequentially formed on the second region 102 of the second surface, to obtain a structure as shown in FIG. 2D. Figure 4

[0066] Specifically, the tunneling layer is located between the substrate and the doped conductive layer, and is used to realize interface passivation of the surface of the substrate, to have a chemical passivation effect and reduce interface states. The tunneling layer can be made of a dielectric material, such as any one of silicon oxide, magnesium fluoride, silicon oxide, amorphous silicon, polysilicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, and titanium oxide. The doped conductive layer can be a single-layer structure or a multi-layer structure.

[0067] Step S305, a first passivation layer 12, a second passivation layer 13, a third passivation layer 15, and a fourth passivation layer 19 are respectively formed on the first region 101 of the first surface, the first region 101 of the second surface, the second region 102 of the first surface, and the second region 102 of the second surface, to obtain a structure as shown in FIG. 2E. Figure 4

[0068] Specifically, the first passivation layer, the second passivation layer, the third passivation layer, and the fourth passivation layer can be a single-layer structure or a stacked structure, and the material of the first passivation layer, the second passivation layer, the third passivation layer, and the fourth passivation layer can be one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbon oxynitride, titanium oxide, hafnium oxide, or aluminum oxide.

[0069] Step S306, a first electrode 16 is formed on the side of the third passivation layer 15 away from the second doped region 14, to obtain a structure as shown in FIG. 2F. Figure 4

[0070] Specifically, the material of the first electrode can include one or more of aluminum, silver, gold, nickel, molybdenum, or copper. In actual applications, the first electrode can be prepared by slurry coating, vapor deposition, electroplating, or the like.

[0071] Step S307, a second electrode 20 is formed on the side of the fourth passivation layer 19 away from the doped conductive layer 18, to obtain a structure as shown in FIG. 2G. Figure 1

[0072] Specifically, the material of the second electrode can include one or more of aluminum, silver, gold, nickel, molybdenum, or copper. In actual applications, the second electrode can be prepared by slurry coating, vapor deposition, electroplating, or the like.​​​​

[0073] Through the above embodiment, on the one hand, by differentiating the design of the first region and the second region of the solar cell, that is, reserving part of the first doped region in the first region, the carrier recombination caused by doping B, P, Ga and other heterogeneous elements in the first region can be eliminated, the open circuit voltage is improved, and thus the performance of the solar cell is improved; on the other hand, the minimum distance between the first doped region and the second passivation layer is less than the minimum distance between the second doped region and the tunneling layer, which can realize the localized design of the first region, weaken the parasitic absorption effect of the polysilicon, and improve the short-circuit current, thereby improving the performance of the solar cell.

[0074] In the specific implementation process, the above step S303 can be implemented by the following steps: step S3031, performing first laser processing on the above first region to diffuse ions in the above diffusion layer to the above substrate, wherein the above first laser processing is red laser, the power of the above first laser processing is 5w~100w, and the scanning speed of the above first laser processing is 5000~40000mm / s; step S3032, etching processing is performed on the above first region by using alkali solution to remove the above BSG layer and part of the above diffusion layer, wherein the temperature of the above etching processing is 50~90℃, the time of the above etching processing is 10~400s, the volume of the above alkali solution is 1~30L, and the depth of the above etching processing is 0.5~5μm. The parameter settings of the above laser processing and the parameter settings of the etching processing can further improve the accuracy of forming the above first doped region and the second doped region.

[0075] Specifically, the power of the above first laser processing can be 5w, 25w, 50w, 75w and 100w, and the scanning speed of the above first laser processing can be 5000mm / s, 10000mm / s, 15000mm / s, 20000mm / s, 25000mm / s, 30000mm / s, 35000mm / s and 40000mm / s. The temperature of the above etching processing can be 50℃, 60℃, 70℃, 80℃ and 90℃, the time of the above etching processing can be 10s, 100s, 200s, 300s and 400s, the volume of the above alkali solution can be 1L, 10L, 20L and 30L, and the depth of the above etching processing can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm and 5μm.

[0076] As shown in FIG. 1, Figure 5 The embodiment of the present application also provides a photovoltaic module, which comprises:

[0077] A cell string is connected by a plurality of the above solar cells 40 in any one of the above embodiments.

[0078] Specifically, two adjacent battery strings can be electrically connected by the conductive strips 402. In some embodiments, the electrodes of the same polarity of the solar cells 40 are oriented in the same direction, and the conductive strips 402 connect the electrodes of different polarities of two adjacent solar cells 40, respectively. In other embodiments, the solar cells 40 can also be arranged according to the electrodes of different polarities, i.e., the electrodes of adjacent solar cells are sequentially arranged in the order of the first polarity, the second polarity, and the first polarity, and the conductive strips 402 connect two adjacent solar cells on the same side. In some embodiments, there is no gap between the solar cells, i.e., the solar cells overlap each other.

[0079] The encapsulation layer 41 is used to cover the surface of the above-mentioned battery string;

[0080] Specifically, the encapsulation layer 41 includes a first encapsulation layer and a second encapsulation layer, the first encapsulation layer covers one of the front surface or the back surface of the solar cell string, and the second encapsulation layer covers the other of the front surface or the back surface of the solar cell string. Specifically, the material of the encapsulation layer 41 can be at least one of polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene copolymer (POE) film, or polyethylene terephthalate (PET) film, etc. In actual application, there is a gap between the first encapsulation layer and the second encapsulation layer during lamination, but the first encapsulation layer and the second encapsulation layer jointly form the above-mentioned encapsulation layer 41 after lamination.

[0081] The cover plate 42 is used to cover the surface of the above-mentioned encapsulation layer 41 away from the above-mentioned battery string.

[0082] Specifically, the material of the cover plate 42 can include glass or plastic, etc. having light transmission function. In addition, the surface of the cover plate 42 facing the encapsulation layer 41 can be a concave-convex surface, thereby increasing the utilization rate of incident light. The cover plate 42 includes a first cover plate and a second cover plate, the first cover plate is arranged opposite to the first encapsulation layer, and the second cover plate is arranged opposite to the second encapsulation layer.

[0083] The above-mentioned solar cell of the present application will be specifically described below in combination with specific embodiments and comparative examples.

[0084] Embodiment 1

[0085] The present embodiment provides a solar cell, comprising:

[0086] The substrate, wherein the substrate includes a first region and a second region;

[0087] The first doped region, the first passivation layer and the second passivation layer are located in the first region, the first passivation layer is located on the side of the first doped region away from the substrate, the second passivation layer is located on the side of the substrate away from the first doped region, the junction depth of the first doped region is 2.5 μm, the sheet resistance of the first doped region is 300 Ω / square, and the doping concentration of the first doped region is 1×10 17 at / cm 3 ;

[0088] The second doped region, the third passivation layer, the first electrode, the tunneling layer, the doped conductive layer, the fourth passivation layer and the second electrode are located in the second region, the third passivation layer is located on the side of the second doped region away from the substrate, the first electrode is located on the side of the third passivation layer away from the second doped region, the tunneling layer is located on the side of the substrate away from the second doped region, the doped conductive layer is located on the side of the tunneling layer away from the substrate, the fourth passivation layer is located on the side of the doped conductive layer away from the tunneling layer, the second electrode is located on the side of the fourth passivation layer away from the doped conductive layer, the minimum distance between the first doped region and the second passivation layer is a first distance, the minimum distance between the second doped region and the tunneling layer is a second distance, the absolute value of the difference between the first distance and the second distance is 8 μm, the junction depth of the second doped region is 1 μm, the sheet resistance of the second doped region is 750 Ω / square, and the doping concentration of the second doped region is 1×10 20 at / cm 3 .

[0089] Embodiment 2

[0090] The solar cell provided in the present application is only different from the solar cell of embodiment 1 in that the absolute value of the difference between the first distance and the second distance is 15 μm.

[0091] Embodiment 3

[0092] The solar cell provided in the present application is only different from the solar cell of embodiment 1 in that the absolute value of the difference between the first distance and the second distance is 2 μm.

[0093] Embodiment 4

[0094] The solar cell provided in the present application is only different from the solar cell of embodiment 1 in that the junction depth of the first doped region is 5 μm and the junction depth of the second doped region is 2 μm.

[0095] Embodiment 5

[0096] This application provides a solar cell, the only difference from Example 1 being that the junction depth of the first doped region is 0.5 μm and the junction depth of the second doped region is 0.1 μm.

[0097] Example 6

[0098] This application provides a solar cell, the only difference from Embodiment 1 being that the sheet resistance of the first doped region is 500 Ω / square and the sheet resistance of the second doped region is 1000 Ω / square.

[0099] Example 7

[0100] This application provides a solar cell, the only difference from Embodiment 1 being that the sheet resistance of the first doped region is 100 Ω / square and the sheet resistance of the second doped region is 500 Ω / square.

[0101] Example 8

[0102] This application provides a solar cell, the only difference between this solar cell and Example 1 is that the doping concentration of the first doped region is 1×10⁻⁶. 19 at / cm 3 The doping concentration of the second doped region is 1×10⁻⁶. 23 at / cm 3 .

[0103] Example 9

[0104] This application provides a solar cell, the only difference between this solar cell and Example 1 is that the doping concentration of the first doped region is 1×10⁻⁶. 15 at / cm 3 The doping concentration of the second doped region is 1×10⁻⁶. 18 at / cm 3 .

[0105] Comparative Example 1

[0106] This application provides a solar cell, the only difference between this solar cell and Embodiment 1 is that the absolute value of the difference between the first distance and the second distance is 16 μm.

[0107] Comparative Example 2

[0108] This application provides a solar cell, the only difference between this solar cell and Embodiment 1 is that the absolute value of the difference between the first distance and the second distance is 1 μm.

[0109] Comparative Example 3

[0110] This application provides a solar cell, the only difference from Embodiment 1 being that the junction depth of the first doped region is 6 μm and the junction depth of the second doped region is 3 μm.

[0111] Comparative Example 4

[0112] This application provides a solar cell, the only difference from Embodiment 1 being that the junction depth of the first doped region is 0.1 μm and the junction depth of the second doped region is 0.05 μm.

[0113] Comparative Example 5

[0114] This application provides a solar cell, the only difference from Embodiment 1 being that the sheet resistance of the first doped region is 80 Ω / square and the sheet resistance of the second doped region is 400 Ω / square.

[0115] Comparative Example 6

[0116] This application provides a solar cell, the only difference from Embodiment 1 being that the sheet resistance of the first doped region is 700 Ω / square and the sheet resistance of the second doped region is 1200 Ω / square.

[0117] Comparative Example 7

[0118] This application provides a solar cell, the only difference between this solar cell and Example 1 is that the doping concentration of the first doped region is 1×10⁻⁶. 20 at / cm 3 The doping concentration of the second doped region is 1×10⁻⁶. 24 at / cm 3 .

[0119] Comparative Example 8

[0120] This application provides a solar cell, the only difference between this solar cell and Example 1 is that the doping concentration of the first doped region is 1×10⁻⁶. 14 at / cm 3 The doping concentration of the second doped region is 1×10⁻⁶. 17 at / cm 3 .

[0121] The performance of the solar cells using Examples 1-9 and Comparative Examples 1-8 was tested, and the test results are shown in Table 1:

[0122] Table 1

[0123]

[0124] From the above experimental data, it can be seen that the photoelectric conversion efficiency in examples 1 to 9 is higher than that in comparative examples 1 to 8, the fill factor in examples 1 to 9 is higher than that in comparative examples 1 to 8, indicating that the solar cell of the application can reduce the carrier recombination loss and improve the photoelectric conversion efficiency. From the above experimental data, it can also be seen that the open circuit voltage and short circuit current in examples 1 to 3 are higher than those in comparative examples 1 and 2, indicating that the solar cell of the application can improve the open circuit voltage and short circuit current of the solar cell.

[0125] From the above description, it can be seen that the above-mentioned embodiments of the application achieve the following technical effects:

[0126] The solar cell of the application, on the one hand, through the differential design of the first region and the second region of the solar cell, i.e. retaining part of the first doped region in the first region, can eliminate the carrier recombination caused by doping B, P, Ga and other heterogeneous elements in the first region, improve the open circuit voltage, and thus improve the performance of the solar cell; on the other hand, the minimum distance between the first doped region and the second passivation layer is less than the minimum distance between the second doped region and the tunneling layer, which can realize the localized design of the first region, weaken the parasitic absorption effect of the polysilicon, and improve the short circuit current, thereby improving the performance of the solar cell.

[0127] In the description of the embodiments of the application, the technical terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0128] In this document, referring to "embodiments" means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it independent or alternative to other embodiments. The skilled person in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0129] In the description of the embodiments of the application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can mean that A exists, A and B exist, and B exists. In addition, the character " / " in this document generally represents a "or" relationship between the front and rear associated objects.

[0130] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0131] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0132] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0133] In the corresponding drawings of the embodiments of the present application, the thickness and area of the layers are exaggerated for better understanding and ease of description. When describing that a component (such as a layer, a film, a region or a substrate) is on or on the surface of another component, the component can be "directly" on the surface of the other component, or there can be a third component between the two components. On the contrary, when describing that a component is on the surface of another component or that a component surface forms or is provided with another component, it means that there is no third component between the two components. In addition, when describing that a component is "formed substantially" on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a part of the edge of the entire surface.

[0134] In the description of the embodiments of the present application, when a certain component "includes" another component, unless otherwise specified, other components are not excluded from the encompassing component, and further components can be further included. Also, when a layer, a film, a region, a plate, or the like is referred to as "on" another component, it can be "directly on" the other component (i.e., positioned between the other component and another component without another component therebetween), or another component can be present therebetween. Also, when a layer, a film, a region, a plate, or the like is "directly on" another component, or when a layer, a film, a region, a plate, or the like is on a surface of another component, it means that no other component is positioned therebetween.

[0135] The terms used in the description of the various described embodiments herein are for the purpose of describing particular embodiments only and are not intended to be limiting. As used in the description of the various embodiments and the appended claims, the phrase "the part" is also intended to include plural forms, unless the context clearly indicates otherwise. Among them, the components include layers, films, regions, or plates.

[0136] The embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that in the embodiments of the present application, many technical details are presented in order to make the reader better understand the present application. However, the technical solutions claimed by the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0137] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present application, and in actual applications, various changes and modifications can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. A solar cell, characterized in that, include: A substrate, wherein the substrate includes a first region and a second region; The first doped region, the first passivation layer, and the second passivation layer are located in the first region, wherein the first passivation layer is located on the side of the first doped region away from the substrate, and the second passivation layer is located on the side of the substrate away from the first doped region. The second region comprises a second doped region, a third passivation layer, a first electrode, a tunneling layer, a doped conductive layer, a fourth passivation layer, and a second electrode. The third passivation layer is located on the side of the second doped region away from the substrate. The first electrode is located on the side of the third passivation layer away from the second doped region. The tunneling layer is located on the side of the substrate away from the second doped region. The doped conductive layer is located on the side of the tunneling layer away from the substrate. The fourth passivation layer is located on the side of the doped conductive layer away from the tunneling layer. The second electrode is located on the side of the fourth passivation layer away from the doped conductive layer. The minimum distance between the first doped region and the second passivation layer is a first distance, and the minimum distance between the second doped region and the tunneling layer is a second distance. The first distance is less than the second distance.

2. The solar cell according to claim 1, characterized in that, The absolute value of the difference between the first distance and the second distance is 2~15μm.

3. The solar cell according to claim 1, characterized in that, The junction depth of the first doped region is greater than that of the second doped region.

4. The solar cell according to claim 3, characterized in that, The junction depth of the first doped region is 0.5~5μm, and the junction depth of the second doped region is 0.1~2μm.

5. The solar cell according to claim 1, characterized in that, The sheet resistance of the first doped region is greater than that of the second doped region.

6. The solar cell according to claim 5, characterized in that, The sheet resistance of the first doped region is 100~500Ω / square, and the sheet resistance of the second doped region is 500~1000Ω / square.

7. The solar cell according to claim 1, characterized in that, The doping concentration of the first doped region is less than that of the second doped region.

8. The solar cell according to claim 7, characterized in that, The doping concentration of the first doped region is 1×10 15 ~1×10 19 at / cm 3 The doping concentration of the second doped region is 1×10⁻⁶. 18 ~1×10 23 at / cm 3 .

9. The solar cell according to claim 1, characterized in that, The solar cell also includes: The first antireflection layer is located on the side of the first passivation layer away from the first doped region; The second antireflection layer is located on the side of the second passivation layer away from the substrate; The third anti-reflection layer is located between the third passivation layer and the first electrode; The fourth antireflection layer is located between the fourth passivation layer and the second electrode.

10. The solar cell according to claim 1, characterized in that, The thickness of the doped conductive layer is 20~400nm.

11. The solar cell according to claim 1, characterized in that, The thickness of the tunneling layer is 0.5~2nm.

12. A method for preparing a solar cell, characterized in that, include: A substrate is provided, wherein the substrate has opposing first and second surfaces, and the substrate includes a first region and a second region; A diffusion layer and a BSG layer are sequentially formed on the first surface; The BSG layer and the diffusion layer in the first region are processed to remove the BSG layer and part of the diffusion layer to obtain a first doped region and a second doped region, wherein the remaining diffusion layer in the first region forms the first doped region and the remaining diffusion layer in the second region forms the second doped region. A tunneling layer and a doped conductive layer are sequentially formed in a second region of the second surface; A first passivation layer, a second passivation layer, a third passivation layer, and a fourth passivation layer are formed in a first region of the first surface, a first region of the second surface, a second region of the first surface, and a second region of the second surface, respectively. A first electrode is formed on the side of the third passivation layer away from the second doped region; A second electrode is formed on the side of the fourth passivation layer away from the doped conductive layer.

13. The method for preparing a solar cell according to claim 12, characterized in that, The BSG layer and the diffusion layer in the first region are processed to remove the BSG layer and part of the diffusion layer, resulting in a first doped region and a second doped region, including: The first region is subjected to a first laser treatment to diffuse ions in the diffusion layer toward the substrate. The first laser treatment is a red laser, the power of the first laser treatment is 5W to 100W, and the scanning speed of the first laser treatment is 5000 to 40000 mm / s. The first region is etched with an alkaline solution to remove the BSG layer and part of the diffusion layer. The etching temperature is 50-90°C, the etching time is 10-400s, the volume of the alkaline solution is 1-30L, and the etching depth is 0.5-5μm.

14. A battery assembly, characterized in that, include: A battery string, formed by connecting solar cells according to any one of claims 1 to 11; An encapsulation layer is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulation layer away from the battery string.

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