A solar cell and photovoltaic module

Abstract

The application relates to the photovoltaic technical field, in particular to a solar cell and a photovoltaic module, the solar cell comprising a substrate, an emitter and a passivation contact structure, the substrate having a first side and a second side opposite to the first side, the first side being divided into a first region and a second region arranged at intervals, and the second side being divided into a third region and a fourth region arranged at intervals; the emitter is arranged in the first region; the passivation contact structure is arranged in the third region; wherein the first surface of the substrate in the first region has a hill-shaped texture structure, the second surface in the second region has a first tower-shaped texture structure, the third surface in the third region has a first groove-shaped texture structure, and the fourth surface in the fourth region has a second tower-shaped texture structure or a second groove-shaped texture structure. In the application, different texture structures are arranged on the first surface, the second surface, the third surface and the fourth surface, so that the photoelectric conversion efficiency of the solar cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic technology, and in particular to a solar cell and a photovoltaic module. BACKGROUND

[0002] The photovoltaic module can directly convert solar radiation energy into electrical energy, mainly based on the photovoltaic effect of crystalline silicon, that is, when the light quantum of sunlight is absorbed by the semiconductor crystalline silicon, an electron-hole pair is generated, and when the electron-hole pair reaches the p-n junction composed of p-type crystalline silicon and n-type crystalline silicon, it is separated by the junction electric field to the two sides of the p-n junction, and when it is externally connected to a load, a photoelectric current is formed, and electrical energy is output.

[0003] The existing photovoltaic module has low photoelectric conversion efficiency, and how to improve the photoelectric conversion efficiency of the photovoltaic module is a problem that needs to be solved urgently. SUMMARY

[0004] The present application provides a solar cell and a photovoltaic module to solve the problem of low photoelectric conversion efficiency of the photovoltaic module.

[0005] The solar cell provided by the present application comprises:

[0006] A substrate having a first side and a second side opposite to the first side, the first side being divided into a first region and a second region arranged at intervals, and the second side being divided into a third region and a fourth region arranged at intervals;

[0007] An emitter arranged in the first region;

[0008] A passivation contact structure arranged in the third region;

[0009] The first surface of the substrate in the first region has a hill-shaped texture structure, the second surface in the second region has a first tower-shaped texture structure, the third surface in the third region has a first groove-shaped texture structure, and the fourth surface in the fourth region has a second tower-shaped texture structure or a second groove-shaped texture structure.

[0010] In a possible implementation, the hill-shaped texture structure has a hill part, and the first tower-shaped texture structure has a first tower part, and the curvature radius of the top end of the hill part is greater than the curvature radius of the top end of the first tower part.

[0011] In a possible implementation, the curvature radius of the top end of the hill part satisfies 500nm-1000nm; and / or, the curvature radius of the top end of the first tower part satisfies 5nm-200nm.

[0012] In a possible implementation, the hill-shaped texture structure has a hill portion, the first tower-shaped texture structure has a first tower portion, and an angle of inclination between the hill portion and a horizontal direction is smaller than an angle of inclination between the first tower portion and the horizontal direction.

[0013] In a possible implementation, the angle of inclination between the hill portion and the horizontal direction is smaller than 25°; and / or, the angle of inclination between the first tower portion and the horizontal direction satisfies 45°-52°.

[0014] In a possible implementation, along a thickness direction of the solar cell, the first surface is higher than the second surface.

[0015] In a possible implementation, along the thickness direction of the solar cell, a height difference between the first surface and the second surface satisfies 2.1 μm-2.7 μm.

[0016] In a possible implementation, a ratio of an area of the first region to a sum of areas of the first region and the second region satisfies 5%-50%.

[0017] In a possible implementation, along the thickness direction of the solar cell, a projection of the first region and a projection of the third region at least partially coincide, and / or, a projection of the second region and a projection of the fourth region at least partially coincide.

[0018] In a possible implementation, the solar cell further includes a first passivation layer, a portion of the first passivation layer is arranged on a side of the emitter away from the substrate, and another portion of the first passivation layer is arranged on the second surface.

[0019] In a possible implementation, the solar cell further includes a second passivation layer, a portion of the second passivation layer is arranged on a side of the passivation contact structure away from the substrate, and another portion of the second passivation layer is arranged on the fourth surface.

[0020] The photovoltaic module provided by the embodiments of the present application includes a cover plate, at least one cell string, and an encapsulation layer, the cell string includes a plurality of solar cells described above, the encapsulation layer is located between the cover plate and the cell string, and the cover plate is connected with the cell string through the encapsulation layer.

[0021] In the present application, the first surface has a hill-shaped texture structure, which makes the contact area of the first electrode with the emitter larger and the contact resistance smaller, and is beneficial to reduce the loss of carriers in the transmission process; the first tower-shaped texture structure of the second surface can reduce the reflection of sunlight on the second surface and increase the light absorption rate of the substrate; the first groove texture structure of the third surface makes the contact area of the second electrode with the passivation contact structure larger and the contact resistance smaller, which is beneficial to reduce the loss of carriers in the transmission process; when the fourth surface is a second tower-shaped texture structure, it can reduce the refraction of sunlight on the fourth surface and increase the light absorption rate of the substrate; when the fourth surface is a second groove texture structure, it can make the contact area of the fourth surface with the second passivation layer larger, so that the passivation effect of the second passivation layer on the substrate in contact with it is better.

[0022] By distinguishingly setting different texture structures on the first surface, the second surface, the third surface and the fourth surface, the open circuit voltage and the fill factor of the solar cell are improved, so as to improve the photoelectric conversion efficiency of the solar cell.

[0023] It should be understood that the above general description and the following detailed description are only exemplary and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Structure schematic diagram of the photovoltaic module provided in the present application in a specific embodiment;

[0025] Figure 2 Structure schematic diagram of the solar cell provided in the present application in a specific embodiment;

[0026] Figure 3 Structure schematic diagram of the substrate, the emitter and the passivation contact structure in Figure 1

[0027] Structure schematic diagram of the first surface in Figure 4 Figure 3 Structure schematic diagram of the second surface in

[0028] Figure 5 Structure schematic diagram of the third surface in Figure 3

[0029] Structure schematic diagram of the fourth surface in Figure 6 Figure 3 Structure schematic diagram of the silicon wafer obtained after the step of performing the first texturing on the silicon wafer;

[0030] Figure 7 Structure schematic diagram of the silicon wafer obtained after the step of performing the first doping treatment on the silicon wafer;

[0031] Figure 8 Structure schematic diagram of the silicon wafer obtained after the step of performing the first doping treatment on the silicon wafer;​​

[0032] Figure 9 Structure of the silicon wafer after the first laser treatment of the second region;

[0033] Figure 10 Structure of the silicon wafer after the first etching treatment of the silicon wafer;

[0034] Figure 11 Structure of the silicon wafer after the oxidation treatment of the silicon wafer;

[0035] Figure 12 Structure of the silicon wafer after the second etching treatment of the second side of the silicon wafer;

[0036] Figure 13 Structure of the silicon wafer after the formation of the passivation contact structure on the second side of the silicon wafer;

[0037] Figure 14 Structure of the silicon wafer after the second laser treatment of the fourth region;

[0038] Figure 15 Structure of the silicon wafer during the third etching treatment of the silicon wafer;

[0039] Figure 16 Structure of the silicon wafer after the third etching treatment of the silicon wafer;

[0040] Figure 17 Structure of the silicon wafer after the fourth etching treatment of the silicon wafer;

[0041] Figure 18 Structure of the silicon wafer after the passivation of the silicon wafer.

[0042] Reference signs:

[0043] a - first region; b - second region; c - third region; d - fourth region;

[0044] 1 - substrate; 11 - first surface; 11a - hill; 12 - second surface; 12a - first tower; 13 - third surface; 13a - groove; 14 - fourth surface; 2 - emitter; 21 - first doped portion; 22 - activated portion; 23 - silicon oxide; 24 - borosilicate glass; 3 - passivation contact structure; 31 - phosphosilicate glass; 32 - loose portion; 4 - first passivation layer; 5 - second passivation layer; 6 - first electrode; 7 - second electrode;

[0045] 10 - first cover plate; 20 - first encapsulation layer; 30 - cell string; 40 - second encapsulation layer; 50 - second cover plate.

[0046] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate embodiments consistent with the application and serve to explain the principles of the application. DETAILED DESCRIPTION

[0047] For a better understanding of the technical solutions of the present application, the embodiments of the present application are described in detail below with reference to the drawings.

[0048] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0049] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0050] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are in an "or" relationship.

[0051] It should be noted that the "up", "down", "left", "right" and other directional words described in the embodiments of the present application are described from the angle shown in the drawings, and should not be understood as a limitation on the embodiments of the present application. In addition, in the context, it should also be understood that when referring to an element connected to another element "on" or "under", it can not only be directly connected to another element "on" or "under", but also indirectly connected to another element "on" or "under" through an intermediate element.

[0052] The embodiments of the present application provide a photovoltaic module, as shown in Figure 1 As shown, the photovoltaic module comprises a cover plate, at least one cell string 30 and an encapsulation layer, the cell string 30 comprises a plurality of solar cells, the encapsulation layer is located between the cover plate and the cell string 30, and the cover plate is connected with the cell string 30 through the encapsulation layer.

[0053] Specifically, the solar cells are electrically connected in a whole piece or multiple pieces to form a cell string 30. The encapsulation layer includes a first encapsulation layer 20 and a second encapsulation layer 40 respectively located on two sides of the cell string 30, and the first encapsulation layer 20 and the second encapsulation layer 40 can be one of Ethylene-Vinyl Acetate Copolymer (EVA), Polyolefin Elastomer (POE), Polyvinyl Butyral (PVB), EVA-POE-EVA co-extrusion adhesive film (EPE), EVA-POE co-extrusion adhesive film (EP) and the like. The encapsulation layer can prevent external water vapor, dust and the like from contacting the solar cells, thereby protecting the solar cells and slowing down the aging of the solar cells.

[0054] The cover plate includes a first cover plate 10 and a second cover plate 50 respectively located on two sides of the cell string 30, and the first cover plate 10 and the second cover plate 50 can be one of tempered glass, Polyethylene Terephthalate (PET), Polycarbonate (PC) and the like rigid materials, or one of Polyvinyl Fluoride (PVF), Ethylene-Tetra-Fluoro-Ethylene (ETFE), Polyvinylidene Fluoride (PVDF) and the like flexible materials. The above materials have high light transmittance, which can improve the photoelectric conversion efficiency of the photovoltaic module and ensure the power of the photovoltaic module. The cover plate can resist external impact to a certain extent, reduce the probability of damage to the photovoltaic module, and prolong the service life of the photovoltaic module.

[0055] The application also provides a solar cell, as shown in the accompanying drawings. Figure 2 As shown in the accompanying drawings, the solar cell includes a substrate 1, an emitter 2 and a passivation contact structure 3, the substrate 1 is of a first conductive type, the emitter 2 is of a second conductive type, the first conductive type and the second conductive type are opposite, and the emitter 2 and the substrate 1 form a PN junction.

[0056] Exemplarily, the first conductive type is N type, the substrate 1 has N type doping elements, and the N type doping elements can be V group elements such as phosphorus (P), arsenic (As), bismuth (Bi) and antimony (Sb); the second conductive type is P type, the emitter 2 has P type doping elements, and the P type doping elements can be III group elements such as boron (B), aluminum (Al), gallium (Ga) and indium (In). It can be understood that in other embodiments, the first conductive type can also be P type and the second conductive type can also be N type.

[0057] For example, the emitter 2 can be part of the substrate 1. A dopant of a second conductivity type is doped on one side of the substrate 1 to form the emitter 2. At this time, the emitter 2 contains a dopant of a first conductivity type, and the concentration of the dopant of the second conductivity type is greater than the concentration of the dopant of the first conductivity type, so that the emitter 2 is of the second conductivity type.

[0058] The substrate 1 has a first side and a second side opposite to each other along its thickness direction. The first side can be the front side of the substrate 1, that is, the side directly exposed to sunlight, and the second side can be the back side of the substrate 1, that is, the side not directly exposed to sunlight. Both the first side and the second side can receive sunlight and convert light energy into electrical energy.

[0059] The first side is divided into a first zone a and a second zone b, which are spaced apart. The second side is divided into a third zone c and a fourth zone d, which are spaced apart. The first zone a and the second zone b are arranged alternately, and the third zone c and the fourth zone d are arranged alternately.

[0060] Emitter 2 is only located in the first region a, and there is no emitter 2 in the second region b. By setting a localized emitter 2, the area covered by emitter 2 on the first side is reduced, thereby reducing the parasitic absorption of light by emitter 2, allowing more light to enter the substrate 1, improving the utilization rate of light by the solar cell, and thus improving the photoelectric conversion efficiency of the solar cell.

[0061] The passivation contact structure 3 is only set in the third region c, and there is no passivation contact structure 3 in the fourth region d. By setting the localized passivation contact structure 3, the area covered by the passivation contact structure 3 on the second side is reduced, thereby reducing the parasitic absorption of light by the passivation contact structure 3, allowing more light to be absorbed by the substrate 1, improving the utilization rate of light by the solar cell, and thus improving the photoelectric conversion efficiency of the solar cell.

[0062] Specifically, the passivated contact structure 3 may include a tunneling layer and a doped conductive layer. The tunneling layer is directly disposed on the substrate 1, and the doped conductive layer is disposed on the side of the tunneling layer away from the substrate 1. The tunneling layer can serve as a tunneling layer for majority carriers, while simultaneously chemically passivating the substrate 1 and reducing interface states. The doped conductive layer can form band bends, enabling selective carrier transport, reducing recombination losses, and ensuring carrier transport efficiency.

[0063] The tunneling layer can be made of one or more of amorphous silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. The doped conductive layer has a first conductivity type, meaning its conductivity type is the same as that of the substrate 1. For example, when the substrate 1 contains N-type dopant, the material of the doped conductive layer can be amorphous silicon, microcrystalline silicon, polycrystalline silicon, etc., with N-type dopant; when the substrate 1 contains P-type dopant, the material of the doped conductive layer can be amorphous silicon, microcrystalline silicon, polycrystalline silicon, etc., with P-type dopant.

[0064] The solar cell also includes a first electrode 6 and a second electrode 7. The first electrode 6 is disposed on a first side for electrical connection with the emitter 2, and the second electrode 7 is disposed on a second side for electrical connection with the doped conductive layer of the passivation contact structure 3. The first electrode 6 can be a first grid line formed on the first side, with multiple first grid lines spaced apart on the first side. The second electrode 7 can be a second grid line formed on the second side, with multiple second grid lines spaced apart on the second side, to collect the generated charge carriers.

[0065] like Figure 3 As shown, the substrate 1 has a first surface 11 located in a first region a, a second surface 12 located in a second region b, a third surface 13 located in a third region c, and a fourth surface 14 located in a fourth region d. The first surface 11 and the second surface 12 are arranged alternately, and the third surface 13 and the fourth surface 14 are arranged alternately.

[0066] The solar cell also includes a first passivation layer 4 and a second passivation layer 5. A portion of the first passivation layer 4 is disposed on the side of the emitter 2 away from the substrate 1, and another portion of the first passivation layer 4 is disposed on the second surface 12. A portion of the second passivation layer 5 is disposed on the side of the passivation contact structure 3 away from the substrate 1, and another portion of the second passivation layer 5 is disposed on the fourth surface 14.

[0067] The first passivation layer 4 passivates the surface of the emitter 2 away from the substrate 1 and the second surface 12, thereby reducing carrier recombination at the interface. The second passivation layer 5 passivates the surface of the doped conductive layer away from the substrate 1 and the fourth surface 14, thereby reducing carrier recombination at the interface and improving the photoelectric conversion efficiency of the solar cell. The first passivation layer 4 and the second passivation layer 5 can be made of one or more of metal oxides, non-metal nitrides, or non-metal oxide nitrides. The material of the first passivation layer 4 can be the same as or different from the material of the second passivation layer 5.

[0068] More specifically, such as Figure 3 and Figure 4As shown in FIG. 1, the first surface 11 has a mounded shape texture formed by a large number of mound portions 11a, which are shaped like hills, i.e. the mounded shape texture is shaped like a continuous hill.

[0069] In the first aspect, the mounded shape texture of the first surface 11 makes the contact area between the first electrode 6 and the emitter 2 larger and the contact resistance smaller, which is conducive to reducing the loss of carriers in the transmission process.

[0070] In the second aspect, the top end of the mound portion 11a is relatively rounded, which provides a relatively gentle transmission path for the carriers, so that the carriers can be more evenly dispersed into the first electrode 6, and the carriers are not easy to excessively gather at the top end of the mound portion 11a, thereby avoiding the phenomenon that the local current density is too high to increase the carrier recombination and the interface between the first electrode 6 and the emitter 2 is damaged by Joule heat.

[0071] In the third aspect, the mound portion 11a can make the light inside the cell reflect uniformly and reduce local strong reflection, thereby improving the light absorption effect of the substrate 1.

[0072] In the fourth aspect, the top end of the mound portion 11a is relatively rounded, and the stress distribution at the first surface 11 is relatively uniform, which is not easy to cause stress concentration, and is conducive to improving the mechanical stability and reliability of the solar cell.

[0073] In the fifth aspect, the top end of the mound portion 11a is relatively rounded, and the contact area between the emitter 2 and the first passivation layer 4 is larger, so that the passivation effect of the first passivation layer 4 on the emitter 2 is better.

[0074] As shown in FIG. 1, Figure 3 and Figure 5 the second surface 12 has a first tower shape texture formed by a large number of first tower portions 12a, which are shaped like pyramids.

[0075] The second surface 12 has a first tower shape texture, so that the first passivation layer 4 formed thereon also has a first tower shape texture. The first tower shape texture can reduce the reflection of the second surface 12 to sunlight, increase the light absorption rate of the substrate 1, and improve the photoelectric conversion efficiency of the solar cell.

[0076] Specifically, the curvature radius of the top end of the mound portion 11a is greater than the curvature radius of the top end of the first tower portion 12a. According to the profile of the mound portion 11a and the first tower portion 12a in the photographed electron microscope image, a curvature circle is drawn, and the radius of the curvature circle is the curvature radius. Figure 4 One of the curvature circles and the curvature radius is shown in FIG. 1.

[0077] The curvature radius is the inverse of the curvature, and the greater the value of the curvature indicates the greater the degree of bending of the curve, and the greater the value of the curvature radius indicates the smaller the degree of bending of the curve. That is, the degree of bending of the top end of the mound 11a is smaller than that of the top end of the first tower 12a, and the top end of the mound 11a is rounder than the top end of the first tower 12a.

[0078] More specifically, the curvature radius of the top end of the mound 11a satisfies: 500nm~1000nm. For example, the curvature radius of the top end of the mound 11a can be specifically: 500nm, 510nm, 520nm, 550nm, 580nm, 600nm, 620nm, 650nm, 680nm, 700nm, 720nm, 750nm, 780nm, 800nm, 820nm, 850nm, 880nm, 900nm, 920nm, 950nm, 960nm, 980nm, 990nm, 1000nm, etc., and of course the curvature radius of the top end of the mound 11a can also be other values within the above range.

[0079] The curvature radius of the top end of the mound 11a should not be too large or too small. If the curvature radius is too large (for example, greater than 1000nm), the top end of the mound 11a is too flat, which is not conducive to increasing the contact area of the first electrode 6 and the emitter 2, and cannot effectively reduce the loss of carriers in the transmission process. If the curvature radius is too small (for example, less than 500nm), the top end of the mound 11a is not round enough, and the carriers are prone to excessive aggregation at the top end of the mound 11a, resulting in an excessively high local current density and an increase in carrier recombination. Therefore, the curvature radius of the top end of the mound 11a should be set within a suitable range.

[0080] Preferably, the size of the top end of the mound 11a satisfies: 1μm~1.3μm, and can be specifically: 1μm, 1.05μm, 1.1μm, 1.15μm, 1.2μm, 1.25μm, 1.3μm, etc.

[0081] The curvature radius of the top end of the first tower 12a satisfies: 5nm~200nm. For example, the curvature radius of the top end of the first tower 12a can be specifically: 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 50nm, 60nm, 80nm, 100nm, 120nm, 150nm, 160nm, 180nm, 185nm, 190nm, 195nm, 200nm, etc., and of course the curvature radius of the top end of the first tower 12a can also be other values within the above range.

[0082] The curvature radius of the top end of the first tower portion 12a should not be too large or too small. If the curvature radius is too large (for example, greater than 200 nm), the top end of the first tower portion 12a is too flat, which is not conducive to reducing the reflection of the second surface 12 to sunlight. If the curvature radius is too small (for example, less than 5 nm), the top end of the first tower portion 12a is too sharp, which is not conducive to the formation of the first passivation layer 4 thereon. Therefore, the curvature radius of the top end of the first tower portion 12a should be set within a suitable range.

[0083] Further, the slope angle a between the hill portion 11a and the horizontal direction is less than the slope angle b between the first tower portion 12a and the horizontal direction, so that the first surface 11 is flatter than the second surface 12, the leveling of the slurry for forming the first electrode 6 on the first surface 11 is better, the distribution of the slurry on the first surface 11 is more uniform, and the burrs of the formed first electrode 6 are less, which is conducive to improving the contact effect of the first electrode 6 and the emitter 2 and is not prone to local poor contact or local grid breakage.

[0084] According to the photographed electron microscope image, a horizontal line is drawn, and the included angle between the profile of the hill portion 11a and the horizontal line is the slope angle a, and the included angle between the profile of the first tower portion 12a and the horizontal line is the slope angle b. Figure 3 The slope angle a of one of the hill portions 11a is illustrated in FIG. Figure 4 The slope angle b of one of the first tower portions 12a is illustrated in FIG. It can be understood that the slope angles a of different hill portions 11a can not be exactly the same, and the slope angles b of different first tower portions 12a can not be exactly the same.

[0085] Further, the slope angle a between the hill portion 11a and the horizontal direction is less than 25°. For example, the slope angle a can be 25°, 24°, 23°, 22°, 21°, 20°, 19°, 18°, 17°, 16°, 15°, etc.

[0086] The slope angle a between the hill portion 11a and the horizontal direction should not be too large. If the slope angle a is too large (for example, greater than 25°), it will affect the flatness of the first surface 11 and the leveling of the slurry for forming the first electrode 6 on the first surface 11.

[0087] The slope angle b between the first tower portion 12a and the horizontal direction satisfies 45°~52°. For example, the slope angle b can be 45°, 45°30', 46°, 47°, 48°, 49°, 50°, 51°, 51°30', 52°, etc.

[0088] The slope angle β between the first tower portion 12a and the horizontal direction should not be too large or too small. If the slope angle β is too large (for example, greater than 52°), the sidewall of the first tower portion 12a is relatively steep, the light entering the base 1 through the first tower portion 12a is relatively concentrated, and the light absorption effect of the base 1 is affected. If the slope angle β is too small (for example, less than 45°), the sidewall of the first tower portion 12a is relatively flat, and the reflection of the second surface 12 to the sunlight cannot be effectively reduced, which is not conducive to improving the photoelectric conversion efficiency of the solar cell. Therefore, the slope angle β between the first tower portion 12a and the horizontal direction should be set within a suitable range.

[0089] At the same time, the slope angle β between the first tower portion 12a and the horizontal direction satisfies: 45°~52°, which can also make the density of the hanging bonds on the second surface 12 smaller, reduce the carrier recombination, and further improve the photoelectric conversion efficiency of the solar cell.

[0090] As shown in Figure 3 and Figure 6 , the third surface 13 has a first groove texture structure, and the first groove texture structure is formed by a large number of grooves 13a.

[0091] The first groove texture structure of the third surface 13 makes the contact area between the second electrode 7 and the passivation contact structure 3 larger and the contact resistance smaller, which is conducive to reducing the loss of carriers in the transmission process.

[0092] The fourth surface 14 has a second tower texture structure or a second groove texture structure.

[0093] When the fourth surface 14 is a second tower texture structure, the refraction of the fourth surface 14 to the sunlight can be reduced, and the light absorption rate of the base 1 can be increased. The second tower structure can be the same as the first tower structure, or can be slightly different in size.

[0094] When the fourth surface 14 is a second groove texture structure, the contact area between the fourth surface 14 and the second passivation layer 5 can be larger, and the passivation effect of the second passivation layer 5 on the base 1 in contact with it can be better. The second groove texture structure can be the same as the first groove texture structure, or can be slightly different in size.

[0095] In the present application, by distinguishing and setting different texture structures on the first surface 11, the second surface 12, the third surface 13 and the fourth surface 14, the open-circuit voltage and the fill factor of the solar cell are improved, and the photoelectric conversion efficiency of the solar cell is improved.

[0096] In the above embodiments, the ratio K1 of the area of the first region a to the sum of the areas of the first region a and the second region b satisfies: 5%~50%. For example, the ratio K1 can be specifically 5%, 6%, 7%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 46%, 48%, 49%, 50%, etc., and of course the ratio K1 can also be other values within the above range.

[0097] The ratio K1 of the area of the first region a to the sum of the areas of the first region a and the second region b should not be too large or too small. If the ratio K1 is too large (for example, greater than 50%), the coverage of the emitter 2 on the first side of the substrate 1 is too high, the emitter 2 has more parasitic absorption of light, relatively less light enters the substrate 1, and the photoelectric conversion efficiency of the solar cell is lower. If the ratio K1 is too small (for example, less than 5%), the coverage of the emitter 2 on the first side of the substrate 1 is too low, the efficiency of the carrier flowing to the first electrode 6 through the emitter 2 is low, the carrier recombination increases, and the photoelectric conversion efficiency of the solar cell is lower. Therefore, the ratio K1 of the area of the first region a to the sum of the areas of the first region a and the second region b should be set within an appropriate range to make the photoelectric conversion efficiency of the solar cell higher.

[0098] Similarly, the ratio K2 of the area of the third region c to the sum of the areas of the third region c and the fourth region d satisfies: 5%~50%. For example, the ratio K2 can be specifically 5%, 6%, 7%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 46%, 48%, 49%, 50%, etc., and of course the ratio K2 can also be other values within the above range.

[0099] The ratio K2 of the area of the third region c to the sum of the areas of the third region c and the fourth region d should not be too large or too small. If the ratio K2 is too large (for example, greater than 50%), the coverage of the passivation contact structure 3 on the second side of the substrate 1 is too high, the passivation contact structure 3 has more parasitic absorption of light, relatively less light enters the substrate 1, and the photoelectric conversion efficiency of the solar cell is lower. If the ratio K2 is too small (for example, less than 5%), the coverage of the passivation contact structure 3 on the second side of the substrate 1 is too low, the efficiency of the carrier flowing to the second electrode 7 through the passivation contact structure 3 is low, the carrier recombination increases, and the photoelectric conversion efficiency of the solar cell is lower. Therefore, the ratio K2 of the area of the third region c to the sum of the areas of the third region c and the fourth region d should be set within an appropriate range to make the photoelectric conversion efficiency of the solar cell higher.

[0100] Optionally, the ratio K1 is equal to the ratio K2, the ratio K1 is greater than the ratio K2, or the ratio K1 is less than the ratio K2.

[0101] Furthermore, along the thickness direction of the solar cell, the projection of the first region a and the projection of the third region c at least partially coincide, that is, the projection of the emitter 2 and the projection of the passivation contact structure 3 at least partially coincide. This ensures that the carrier transport path jointly constructed by the substrate 1, the emitter 2, and the passivation contact structure 3 is basically aligned with or has a small angle with the thickness direction of the solar cell, resulting in a shorter carrier transport path. This helps reduce energy loss during carrier transport, leading to higher photoelectric conversion efficiency of the solar cell. Correspondingly, the projection of the second region b and the projection of the fourth region d at least partially coincide.

[0102] Preferably, the ratio K1 is equal to the ratio K2, the projection of the first region a completely coincides with the projection of the third region c, and the projection of the second region b completely coincides with the projection of the fourth region d.

[0103] This application also provides a method for manufacturing a solar cell, comprising:

[0104] S1: The silicon wafer is texturized for the first time.

[0105] In this step, such as Figure 7 As shown, the first and second sides of the silicon wafer form an undulating, uneven textured surface.

[0106] S2: Perform the first doping treatment on the silicon wafer.

[0107] In this step, such as Figure 8 As shown, a first doped portion 21 containing boron is formed on the first side of the silicon wafer to form a PN junction within the silicon wafer.

[0108] Specifically, boron sources are deposited via ion implantation, spin coating, low-pressure chemical vapor deposition (LPCVD), or plasma-enhanced chemical vapor deposition (PECVD). Boron precursors include, but are not limited to, boron chloride (BCl3), boron bromide (BBr3), trimethylboron (C3H9B), and boron-containing slurries.

[0109] S3: Perform the first laser treatment on the second region b.

[0110] In this step, such as Figure 9 As shown, the first doped portion 21 located in the second region b is transformed into an activated portion 22 under the action of laser.

[0111] Specifically, the first laser treatment can use red nanosecond laser, green nanosecond laser or violet nanosecond laser to irradiate the second region b, so as to reduce the doping concentration of boron elements in the first doped part 21 located in the second region b, and thus convert the first doped part 21 located in the second region b into an activated part 22. The order of the lattice in the activated part 22 is higher, and the activated part 22 is more easily etched.

[0112] S4: performing a first etching treatment on the silicon wafer.

[0113] In this step, as shown in FIG. 4, the activated part 22 located in the second region b is etched and removed, and a rough and uneven textured structure is formed on the surface of the silicon wafer in the second region b. Figure 10

[0114] Specifically, the first etching treatment includes two etching processes in sequence, that is, a chain hydrofluoric acid process is first performed for etching, and then a second texturing is performed for etching, so as to remove the activated part 22 and form a textured structure in the second region b.

[0115] S5: performing an oxidation treatment on the silicon wafer.

[0116] In this step, as shown in FIG. 5, the boron elements in the first doped part 21 further diffuse into the substrate 1, so as to deepen the junction depth of the first doped part 21 and convert the first doped part 21 into an emitter 2. At the same time, the second region b, the third region c and the fourth region d form a silicon oxide 23, and the first region a forms a borosilicate glass 24. Figure 11 Specifically, the doping concentration of the boron elements in the emitter 2 satisfies: 4x10 18 atom / cm 3 ~7x10 18 atom / cm 3 .

[0117] S6: performing a second etching treatment on the second side of the silicon wafer.

[0118] In this step, as shown in FIG. 6, the silicon oxide 23 located on the second side is etched and removed, and a relatively flat surface is formed on the second side of the silicon wafer.

[0119] Figure 12 Specifically, the second etching treatment includes two etching processes in sequence, that is, a chain hydrofluoric acid process is first performed for etching, and then an alkaline polishing is performed for etching, so as to remove the silicon oxide 23 located on the second side.

[0120] Preferably, the surface formed on the second side of the silicon wafer can have a third groove texture structure, so that the passivation contact structure 3 formed in the subsequent step has a larger contact area with the substrate 1 and has a better passivation effect on the substrate 1. The third groove texture structure can be the same as the first groove texture structure, or can be slightly different in size.

[0121] Preferably, the surface formed on the second side of the silicon wafer can have a third groove texture structure, so that the passivation contact structure 3 formed in the subsequent step has a larger contact area with the substrate 1 and has a better passivation effect on the substrate 1. The third groove texture structure can be the same as the first groove texture structure, or can be slightly different in size. ​​

[0122] S7: A passivated contact structure 3 is formed on the second side of the silicon wafer.

[0123] In this step, such as Figure 13 As shown, a passivation contact structure 3 is also formed on the first side of the silicon wafer, and a phosphosilicate glass 31 is formed on the side of the passivation contact structure 3 away from the substrate 1.

[0124] Specifically, the passivated contact structure 3 can be prepared by low-pressure chemical vapor deposition or plasma-enhanced chemical vapor deposition. The phosphorus doping concentration in the doped conductive layer of the passivated contact structure 3 satisfies: 1 × 10⁻⁶. 18 atom / cm 3 ~1×10 21 atom / cm 3 .

[0125] S8: Perform a second laser treatment on the fourth region d.

[0126] In this step, such as Figure 14 As shown, the phosphorosilicate glass 31 located in the fourth region d is transformed into a porous part 32 under the action of laser.

[0127] Specifically, the second laser treatment can use a purple laser, a green laser, a green-flying laser, or a purple-flying laser to irradiate the fourth region d, so that the phosphorus silicate glass 31 becomes loose and porous, making it easier to be etched.

[0128] It is worth noting that red, green, and violet nano lasers are all nanosecond lasers, meaning the laser used in the first laser processing can be a short-pulse laser. Violet and green nano lasers are picosecond lasers, while green and violet femtosecond lasers are femtosecond lasers. Both picosecond and femtosecond lasers are ultrashort-pulse lasers, meaning the laser used in the second laser processing can be an ultrashort-pulse laser. In other words, the pulse width of the laser used in the first laser processing is greater than the pulse width of the laser used in the second laser processing.

[0129] S9: Perform the third etching process on the silicon wafer.

[0130] In this step, such as Figure 15 As shown, the phosphorus-silicon glass 31 located on the first side is first etched using a chain-type hydrofluoric acid process, as follows: Figure 16 As shown, the passivation contact structure 3 on the first side, the borosilicate glass 24 in the first region a, and the silicon oxide 23 in the second region b are then etched through a third texturing process. Since the borosilicate glass 24 is more difficult to etch than the silicon oxide 23, the first region a forms a more rounded mound-like texture structure, and the second region b forms a partially rounded first tower-like texture structure.

[0131] In the process, the loose part 32 and the passivation contact structure 3 located in the fourth area d are also etched, and the second tower-shaped texture structure is etched on the fourth surface 14.

[0132] Specifically, as shown in Figure 2 and Figure 16 , along the thickness direction of the solar cell, the first surface 11 is higher than the second surface 12, so that the etching degree of the first surface 11 is greater than that of the second surface 12, and further, the texture structure of the first surface 11 and the texture structure of the second surface 12 are different.

[0133] Specifically, along the thickness direction of the solar cell, the height difference between the first surface 11 and the second surface 12 satisfies: 2.1 μm~2.7 μm. For example, the height difference between the first surface 11 and the second surface 12 can be specifically: 2.1 μm, 2.12 μm, 2.15 μm, 2.18 μm, 2.2 μm, 2.25 μm, 2.3 μm, 2.35 μm, 2.4 μm, 2.45 μm, 2.5 μm, 2.55 μm, 2.6 μm, 2.65 μm, 2.68 μm, 2.7 μm, etc., and of course the height difference between the first surface 11 and the second surface 12 can also be other values within the above range.

[0134] The height difference between the first surface 11 and the second surface 12 should not be too large or too small. If the height difference is too large (for example, greater than 2.7 μm), the thinnest part of the solar cell wafer will be too thin, and the strength of the solar cell will be low, and it will be easy to break. If the height difference is too small (for example, less than 2.1 μm), the etching difficulty of the solar cell will be greater, and the texture structure of the first surface 11 and the texture structure of the second surface 12 will be close. Therefore, the height difference between the first surface 11 and the second surface 12 should be set within a suitable range.

[0135] S10: performing fourth etching treatment on the silicon wafer.

[0136] In this step, as shown in Figure 17 , first, the phosphosilicate glass 31 located in the fourth area d is etched by a chain hydrofluoric acid process, and then a first groove texture structure is etched on the third surface 13 by a groove etching process, and a second groove texture structure is etched on the fourth surface 14 or the fourth surface 14 is not etched. It should be noted that Figure 4 , Figure 5 and Figure 6 The electron micrograph in the Figure 17 state is taken.

[0137] The groove etching process includes a first groove etching process and a second groove etching process. The first etching process etches an initial groove on the third surface 13, and the second groove etching process increases the size of the initial groove, thereby forming the groove 13a.

[0138] The first etching process uses a first etching solution, and the second etching process uses a second etching solution. Both the first etching solution and the second etching solution contain sodium hydroxide, and the mass fraction of sodium hydroxide in the first etching solution is less than or equal to the mass fraction of sodium hydroxide in the second etching solution, that is, the alkalinity of the first etching solution is lower than that of the second etching solution, thereby facilitating the etching rate of the first etching process on the third surface 13 to be less than the etching rate of the second etching process on the third surface 13. Optionally, the mass fraction of sodium hydroxide in the first etching solution is 0.5% to 2%, and the mass fraction of sodium hydroxide in the second etching solution can be 2% to 4%.

[0139] In addition, both the first etching solution and the second etching solution contain a protective agent to control the etched texture structure to be a groove texture structure, and the mass fraction of the protective agent in the first etching solution is less than the mass fraction in the second etching solution. Optionally, the mass fraction of the protective agent in the first etching solution is 0.5% to 0.8%, and the mass fraction of the protective agent in the second etching solution is 1% to 1.5%.

[0140] Specifically, as shown in Figure 2 and Figure 17 the third surface 13 is higher than the fourth surface 14 along the thickness direction of the solar cell.

[0141] More specifically, the height difference between the third surface 13 and the fourth surface 14 along the thickness direction of the solar cell satisfies: 2.1 μm to 2.7 μm. For example, the height difference between the third surface 13 and the fourth surface 14 can be specifically: 2.1 μm, 2.12 μm, 2.15 μm, 2.18 μm, 2.2 μm, 2.25 μm, 2.3 μm, 2.35 μm, 2.4 μm, 2.45 μm, 2.5 μm, 2.55 μm, 2.6 μm, 2.65 μm, 2.68 μm, 2.7 μm, etc. Of course, the height difference between the third surface 13 and the fourth surface 14 can also be other values within the above range.

[0142] The height difference between the third surface 13 and the fourth surface 14 should not be too large or too small. If the height difference is too large (for example, greater than 2.7 μm), the thinnest part of the solar cell wafer will be too thin, thereby making the solar cell have lower strength and be easy to break. If the height difference is too small (for example, less than 2.1 μm), the etching difficulty of the solar cell will be greater. Therefore, the height difference between the third surface 13 and the fourth surface 14 should be set within a suitable range.

[0143] S11: Passivating the silicon wafer.

[0144] In this step, as shown in Figure 18 the first side of the silicon wafer forms a first passivation layer 4, and the second side of the silicon wafer forms a second passivation layer 5.

[0145] S12: Forming an electrode on the silicon wafer.

[0146] In this step, as shown in Figure 2 the first region a forms a first electrode 6, and the first electrode 6 is electrically connected with the emitter 2 through the first passivation layer 4; the third region c forms a second electrode 7, and the second electrode 7 is electrically connected with the passivation contact structure 3 through the second passivation layer 5.

[0147] Specifically, the electrode is formed by screen printing or electroplating, and the material of the electrode can be one or a composite of silver, aluminum, nickel, and copper.

[0148] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A solar cell, characterized by, Comprising: a substrate (1) having a first side and a second side opposite to the first side, the first side being divided into a first region (a) and a second region (b) arranged in intervals, the second side being divided into a third region (c) and a fourth region (d) arranged in intervals; an emitter (2) arranged in the first region (a); a passivation contact structure (3) arranged in the third region (c); wherein the first surface (11) of the substrate (1) in the first region (a) has a hill-shaped texture structure, the second surface (12) in the second region (b) has a first tower-shaped texture structure, the third surface (13) in the third region (c) has a first groove-shaped texture structure, and the fourth surface (14) in the fourth region (d) has a second tower-shaped texture structure or a second groove-shaped texture structure; the hill-shaped texture structure has a hill part (11a), and the first tower-shaped texture structure has a first tower part (12a), and the slope angle between the hill part (11a) and the horizontal direction is smaller than the slope angle between the first tower part (12a) and the horizontal direction.

2. The solar cell according to claim 1, characterized in that, the hill-shaped texture structure has a hill part (11a), and the first tower-shaped texture structure has a first tower part (12a), and the curvature radius of the top end of the hill part (11a) is greater than the curvature radius of the top end of the first tower part (12a).

3. The solar cell according to claim 2, characterized in that, the curvature radius of the top end of the hill part (11a) satisfies: 500nm-1000nm; and / or, the curvature radius of the top end of the first tower part (12a) satisfies: 5nm-200nm.

4. The solar cell of claim 1, wherein the slope angle between the hill part (11a) and the horizontal direction is less than 25°; and / or, the slope angle between the first tower part (12a) and the horizontal direction satisfies: 45°-52°.

5. The solar cell of claim 1, wherein along the thickness direction of the solar cell, the first surface (11) is higher than the second surface (12).

6. The solar cell according to claim 5, characterized in that, along the thickness direction of the solar cell, the height difference between the first surface (11) and the second surface (12) satisfies: 2.1μm-2.7μm.

7. The solar cell of claim 1, wherein the ratio of the area of the first region (a) to the sum of the areas of the first region (a) and the second region (b) satisfies: 5%-50%.

8. The solar cell of claim 1, wherein, along the thickness direction of the solar cell, the projection of the first region (a) at least partially coincides with the projection of the third region (c), and / or the projection of the second region (b) at least partially coincides with the projection of the fourth region (d).

9. The solar cell of claim 1, wherein, The solar cell further comprises a first passivation layer (4), a part of the first passivation layer (4) is arranged on the side of the emitter (2) away from the substrate (1), and another part of the first passivation layer (4) is arranged on the second surface (12).

10. The solar cell of claim 1, wherein, The solar cell further comprises a second passivation layer (5), a part of the second passivation layer (5) is arranged on the side of the passivation contact structure (3) away from the substrate (1), and another part of the second passivation layer (5) is arranged on the fourth surface (14).

11. A photovoltaic module, characterized by Comprising: a cover plate; at least one cell string (30), the cell string (30) comprising a plurality of solar cells according to any one of claims 1-10; A packaging layer is located between the cover plate and the battery string (30), and the cover plate is connected with the battery string (30) through the packaging layer.

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