Preparation method of solar cell and solar cell

Abstract

The invention provides a preparation method of a solar cell and the solar cell, and the method comprises the steps: carrying out the cutting treatment of a whole cell, obtaining a pretreatment cell with a first cutting surface, and enabling the depth of the cutting treatment to be smaller than the thickness of the whole cell; carrying out heat treatment on the pretreated battery along the first cutting surface to obtain a plurality of slice batteries with second cutting surfaces, and the second cutting surfaces comprise the first cutting surface; performing laser treatment on at least part of the surface of each second cutting surface; forming a protective layer on each second cutting surface, wherein the protective layer is made of a silicon-rich material; and forming a passivation layer on the side, away from the second cutting surface, of the protection layer. The method solves the problem that in the prior art, the cell efficiency is affected by edge damage of the sliced solar cell after cutting.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and more particularly, to a method for manufacturing a solar cell and a solar cell. Background Art

[0002] The half-cell cutting technology of solar cell wafers can improve the efficiency of solar cells and the power of photovoltaic modules. In the traditional cutting process, high-energy lasers are used to cut the cell wafers to form a half-cell or multi-cell structure. Although this process can effectively divide the cell wafers, the laser cutting and subsequent thermal cracking processes often cause damage to the new edges.

[0003] Therefore, there is an urgent need for a method to solve the problem that the edge damage of sliced solar cells after cutting affects the cell efficiency. Summary of the Invention

[0004] The main object of the present invention is to provide a method for manufacturing a solar cell and a solar cell, so as to solve the problem in the prior art that the edge damage of sliced solar cells after cutting affects the cell efficiency.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a method for manufacturing a solar cell, including: performing a cutting process on a whole cell to obtain a pre-treated cell having a first cutting surface, wherein the depth of the cutting process is less than the thickness of the whole cell; performing a heat treatment along the first cutting surface to obtain a plurality of sliced cells having a second cutting surface, the second cutting surface including the first cutting surface; performing a laser treatment on at least a part of each second cutting surface; forming a protective layer on each second cutting surface, the material of the protective layer being a silicon-rich material; and forming a passivation layer on a side of the protective layer away from the second cutting surface.

[0006] Further, performing a laser treatment on at least a part of each second cutting surface includes: performing a moving irradiation treatment on at least a part of each second cutting surface with a femtosecond laser, the wavelength of the femtosecond laser being 515 - 1030 nm, the pulse width of the femtosecond laser being 100 - 1000 fs, the repetition frequency of the femtosecond laser being 100 - 1000 kHz, the pulse energy of the femtosecond laser being 5 - 40 μJ, and the scanning speed of the femtosecond laser being 100 - 500 mm / s; and performing an inert gas purging treatment on each second cutting surface to reduce the temperature of the second cutting surface.

[0007] Further, the minimum distance between the focus of the femtosecond laser and the second cutting surface is 50 - 100 μm.

[0008] Further, a femtosecond laser is used to perform a moving irradiation treatment on at least a part of the second cutting surface, including: during each moving irradiation treatment, a plurality of light spots are formed on the second cutting surface, two adjacent light spots overlap, and the ratio of the area of the overlapping part of two adjacent light spots to the average area of the light spots is 20-50%.

[0009] Further, the ratio of the depth of the cutting treatment to the thickness of the whole battery is 2-40%, and the temperature of the heat treatment is 80-300 °C.

[0010] Further, a protective layer is formed on each second cutting surface, including: introducing silane into the chamber where the sliced battery is located, and performing a thermal ionization treatment on the silane to obtain the protective layer.

[0011] Further, the temperature of the thermal ionization treatment is 150-800 °C, the power of the thermal ionization treatment is 1000-9000 W, the pressure of the chamber is 10-200 mpa, the flow rate of the silane is 10-1000 sccm, and the thickness of the protective layer is 2-12 nm.

[0012] Further, a passivation layer is formed on the side of the protective layer away from the second cutting surface, including: forming a plurality of sub-passivation layers on the side of the protective layer away from the second cutting surface, and the plurality of sub-passivation layers form the passivation layer, wherein, in the first direction, the thickness of the sub-passivation layer increases in turn, and the first direction is the direction from the side close to the protective layer to the side away from the protective layer.

[0013] Further, forming a plurality of sub-passivation layers on the side of the protective layer away from the second cutting surface to obtain the passivation layer, including: a feeding step, introducing an inert gas carrying a nitrogen source and a water source into the chamber where the sliced battery is located, and performing a heating treatment on the sliced battery to obtain the sub-passivation layer, wherein the temperature of the heating treatment is 80-250 °C; a repeating step, repeating the feeding step multiple times, and during the repeating process, the temperature of the heating treatment is higher than that in the previous repeating process until a plurality of sub-passivation layers are formed.

[0014] To achieve the above object, according to another aspect of the present invention, a solar cell is provided, and the solar cell is prepared by using the above preparation method.

[0015] The method for preparing a solar cell provided by this application is as follows. First, the entire cell is cut to obtain a pre-treated cell with a first cut surface, and the depth of the cutting process is less than the thickness of the entire cell. Then, the pre-treated cell is heat-treated along the first cut surface to obtain multiple sliced cells with a second cut surface, and the second cut surface includes the first cut surface. At least part of each second cut surface is laser-treated. Then, a protective layer made of a silicon-rich material is formed on each second cut surface. Finally, a passivation layer is formed on the side of the protective layer away from the second cut surface. In this method, by cutting and heat-treating the entire cell successively, sliced cells with a second cut surface are obtained. Then, the second cut surface is laser-treated to remove the oxide layer generated during the cutting process and reduce the burrs that appear during the cutting process. Further, by forming a silicon-rich protective layer on the cut surface, the surface dangling bonds of the cut surface can be saturated, the carrier recombination on the cut surface can be reduced, the minority carrier lifetime can be increased, the recombination current can be reduced, and thus the efficiency of the solar cell can be improved, solving the problem in the prior art that the edge damage of sliced solar cells after cutting affects the cell efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. In the drawings:

[0017] Figure 1 FIG. shows a schematic flow chart of a method for preparing a solar cell according to an embodiment of this application;

[0018] Figure 2 FIG. shows a schematic diagram of the second cut surface of a sliced cell according to an embodiment of this application;

[0019] Figure 3 FIG. shows a schematic structural diagram of forming a protective layer on each second cut surface;

[0020] Figure 4 FIG. shows on the basis of Figure 3 a schematic structural diagram of forming a passivation layer;

[0021] Figure 5 FIG. shows a schematic structural diagram of a solar cell prepared by the method for preparing a solar cell according to an embodiment of this application.

[0022] Among them, the above-mentioned drawings include the following reference numerals:

[0023] 100, sliced battery; 101, first cutting surface; 102, second cutting surface; 103, heat treatment surface; 104, protective layer; 105, passivation layer; 106, emitter; 107, front passivation layer; 108, antireflection layer; 109, tunneling dielectric layer; 110, doped conductive layer; 111, back passivation layer; 112, first electrode; 113, second electrode. Detailed implementation manners

[0024] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0025] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to describe the embodiments of the present invention here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these process, method, product or device.

[0027] As introduced in the background art, the edge damage of the sliced solar cell in the prior art affects the battery efficiency. To solve the above technical problems, the present application proposes a preparation method of a solar cell and a solar cell.

[0028] Figure 1 is a schematic flow chart of a method for manufacturing a solar cell according to an embodiment of the present application. As Figure 1 shown, it includes:

[0029] Step S201, performing a cutting process on the whole battery to obtain a preprocessed battery with a first cutting surface, wherein the depth of the above cutting process is less than the thickness of the above whole battery;

[0030] In practical applications, the above-mentioned whole cell can be any one of a passivated emitter and rear cell (PERC cell for short), a passivated emitter and rear totally diffused cell (PERT cell for short), a tunnel oxide passivated contact cell (TOPCon cell for short), and a heterojunction cell (HIT or HJT cell for short). In some other embodiments, the above-mentioned whole cell can also be any one of a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, and a multi-component compound solar cell. For example, the multi-component compound solar cell can specifically be a cadmium sulfide solar cell, a gallium arsenide solar cell, a copper indium selenide solar cell, or a perovskite solar cell.

[0031] In practical applications, the above-mentioned cutting process can adopt a contact cutting or non-contact cutting process. Among them, the contact cutting process includes, for example, a mechanical cutting process, and the non-contact cutting process includes, for example, a laser cutting process. The mechanical cutting process includes wire saw cutting and blade cutting. In wire saw cutting, ultra-fine and high-strength cutting wires are used. Up to 1000 cutting wires are wound around the guide wheels parallel to each other to form a horizontal cutting wire mesh. The guide wheels are driven to move the cutting wires at a speed of 5 to 25 meters per second. At the same time, a nozzle sprays a grinding slurry containing suspended silicon carbide particles onto the cutting wires. The battery wafer is fixed on the cutting table, and the cutting table cuts the silicon block into silicon wafers through the moving cutting wire mesh. Since the battery wafer is a brittle material, blade cutting easily causes cracks at the edges. The laser cutting process uses a 1064 nm fiber pulsed laser with an average power of more than ten watts to hundreds of watts for cutting. First, the battery wafer is scanned and cut according to the pre-defined dividing line, and the cutting depth is 40%-60% of the thickness of the battery wafer. The principle is to use the laser to process a cutting channel that penetrates the surface on the back of the battery, and then the battery wafer is broken along the cutting channel by a mechanical method. During the process of cutting the whole cell, if the whole cell is directly cut to the bottom to obtain a sliced cell, it may cause mechanical stress at the edges of the battery wafer, resulting in cracks or surface damage, affecting the mechanical strength or performance of the sliced cell. Therefore, in the thickness direction of the whole cell, a relatively shallow depth is first cut to obtain a pre-treated cell, and then it is divided to obtain a sliced cell. In a specific embodiment, the depth of the above-mentioned cutting process is less than half of the thickness of the whole cell.

[0032] Step S202: Heat-treat the pre-treated battery along the above-mentioned first cutting surface to obtain a plurality of sliced batteries having a second cutting surface, where the second cutting surface includes the first cutting surface;

[0033] Heat-treating the pre-treated battery can achieve a more controllable crack trajectory and avoid problems such as uneven cracks or deviation from the predetermined path that may occur in the traditional full-cutting method. Figure 2 It is a schematic diagram of the second cutting surface of the sliced battery according to an embodiment of the present application. As Figure 2 shown, as Figure 2 shown, the whole battery is cut to obtain a pre-treated battery having a first cutting surface 101, where the first cutting surface 101 corresponds to the cutting area obtained by the cutting process. Then, the pre-treated battery is heat-treated along the first cutting surface 101 to form a heat-treated surface 103, where the heat-treated surface 103 corresponds to the heat-cracked area obtained by the heat treatment, and the first cutting surface 101 and the heat-treated surface 103 together form the second cutting surface 102. In practical applications, after the cutting process, the residual particles after the cutting process recrystallize and are partially oxidized during the temperature drop, generating silicon slag and silicon oxide that adhere to the surface of the second cutting surface 102, causing unevenness. And due to different treatment methods, the roughness of the first cutting surface 101 and the heat-treated surface 103 is not the same. In practical applications, the temperature control range of the above heat treatment can be 800 - 250 °C, and then the solar cell is cooled. And the accuracy of the above heat treatment can reach ±0.05 mm. The present application does not limit the quantity and shape of the above sliced batteries, and those skilled in the art can select according to the actual situation. In addition, the above sliced battery can be a single-sided battery, that is, one surface of the sliced battery serves as the light-receiving surface for receiving incident light, and the other surface serves as the backlight surface. The above sliced battery can also be a double-sided battery, that is, both opposite surfaces of the sliced battery serve as light-receiving surfaces and are both used to receive incident light.

[0034] Step S203: Perform laser treatment on at least part of the surfaces of each of the above second cutting surfaces;

[0035] During the process of performing laser treatment on multiple second cutting surfaces, the second cutting surfaces of different sliced batteries can be sequentially subjected to laser treatment; or multiple sliced batteries can be stacked and directly subjected to laser treatment on the stacked sliced batteries. The above laser treatment can remove the naturally formed uneven oxide layer generated during the previous cutting process, and at the same time remove the silicon slag attached to the cutting surface, reducing the burrs that may appear during the cutting process, thereby forming a flat cutting surface.

[0036] Step S204, form a protective layer 104 on each of the above-mentioned second cutting surfaces 102 of the sliced battery 100. The material of the protective layer 104 is a silicon-rich material, obtaining the structure as shown in Figure 3 the figure;

[0037] In practical applications, techniques such as Plasma-Enhanced Atomic Layer Deposition (PE-ALD), Plasma-Enhanced Chemical Vapor Deposition (PECVD), Low Pressure Chemical Vapor Deposition (LPCVD), and magnetron sputtering can be used to form the above-mentioned protective layer. Since the material of the protective layer is a silicon-rich material, a large amount of silicon can saturate the surface dangling bonds on the second cutting surface, and can further effectively reduce the carrier recombination at the battery edge.

[0038] Step S205, form a passivation layer 105 on the side of the protective layer 104 away from the second cutting surface 102 of the sliced battery 100, obtaining the structure as shown in Figure 4 the figure.

[0039] The material of the passivation layer can be at least one of silicon oxide, aluminum oxide, silicon nitride, silicon carbide, silicon oxynitride, and carbon oxynitride, and the passivation layer can be a single-layer structure or a multi-layer structure. Those skilled in the art can select the material of the passivation layer and the number of film layers of the passivation layer according to actual needs. In practical applications, the above-mentioned passivation layer can be formed by physical vapor deposition process or chemical vapor deposition process.

[0040] The preparation method of the solar cell provided by this application is as follows. First, the whole cell is cut to obtain a pre-treated cell with a first cut surface, and the depth of the cutting process is less than the thickness of the whole cell. Then, the pre-treated cell is heat-treated along the first cut surface to obtain multiple sliced cells with a second cut surface, and the second cut surface includes the first cut surface. At least part of the surface of each second cut surface is subjected to laser treatment. Then, a protective layer made of silicon-rich material is formed on each second cut surface. Finally, a passivation layer is formed on the side of the protective layer away from the second cut surface. In this method, by cutting and heat-treating the whole cell successively, sliced cells with a second cut surface are obtained. Then, the second cut surface is subjected to laser treatment to remove the oxide layer generated during the cutting process and reduce the burrs that appear during the cutting process. Further, by forming a silicon-rich protective layer on the cut surface, the surface dangling bonds of the cut surface can be saturated, the carrier recombination of the cut surface can be reduced, the minority carrier lifetime can be increased, the recombination current can be reduced, and thus the efficiency of the solar cell can be improved, solving the problem that the edge damage of the sliced solar cell affects the cell efficiency in the prior art.

[0041] In some embodiments, the above step S203 can be implemented through the following steps: Step S2031, the at least part of the above second cut surface is irradiated by moving a femtosecond laser, wherein the wavelength of the femtosecond laser is 515 - 1030 nm, the pulse width of the femtosecond laser is 100 - 1000 fs, the repetition frequency of the femtosecond laser is 100 - 1000 kHz, the pulse energy of the femtosecond laser is 5 - 40 μJ, and the scanning speed of the femtosecond laser is 100 - 500 mm / s; Step S2032, an inert gas purging treatment is performed on each of the above second cut surfaces to reduce the temperature of the above second cut surface. The wavelength, pulse width, repetition frequency, pulse energy, and scanning speed of the femtosecond laser within an appropriate range can further improve the quality, efficiency, and accuracy of the above laser treatment, and the temperature of the second surface can be cooled in a timely manner by using an inert gas for the second cut surface, further preventing the influence of too high temperature on the quality of the second cut surface.

[0042] In practical applications, the wavelength of the above-mentioned femtosecond laser is 515 - 1030 nm. For example, it can be 515 - 600 nm, 600 - 770 nm, 770 - 880 nm, or 880 - 1030 nm. The solar cell has good light absorption in this wavelength range and can further effectively transfer energy to the material surface without causing deep heating. The pulse width of the above-mentioned femtosecond laser is 100 - 1000 fs. For example, it can be 100 fs, 200 fs, 300 fs, 400 fs, 500 fs, 600 fs, 700 fs, 800 fs, 900 fs, or 1000 fs. Among them, the above pulse width can have a higher peak power and a shorter action time, which can reduce heat diffusion and thus reduce the heat affected zone. The repetition frequency of the above-mentioned femtosecond laser is 100 - 1000 kHz. For example, it can be 100 kHz, 200 kHz, 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz, 900 kHz, or 1000 kHz. A lower repetition frequency has concentrated energy, which is beneficial for repairing surfaces with low roughness. A higher repetition frequency can provide continuous energy input, which is beneficial for repairing surfaces with high roughness. The pulse energy of the above-mentioned femtosecond laser is 5 - 40 μJ. For example, it can be 5 μJ, 10 μJ, 15 μJ, 20 μJ, 25 μJ, 30 μJ, 35 μJ, or 40 μJ. A femtosecond laser with a lower pulse energy has less thermal influence and is suitable for repairing surfaces with low roughness. A higher pulse energy can quickly remove surface materials and improve the repair efficiency. The scanning speed of the above-mentioned femtosecond laser is 100 - 500 mm / s. For example, it can be 100 mm / s, 200 mm / s, 300 mm / s, 400 mm / s, or 500 mm / s. A lower scanning speed can increase energy input, and a higher scanning speed can reduce heat accumulation. The above inert gas can be at least one of nitrogen, argon, helium, and neon.

[0043] In some other embodiments, the minimum distance between the focus of the above-mentioned femtosecond laser and the above second cutting surface is 50 - 100 μm. An appropriate focus position can make the energy of the laser treatment more concentrated, thereby further improving the repair efficiency of the laser treatment for surface damage.

[0044] The minimum distance between the focus of the above-mentioned femtosecond laser and the above second cutting surface is 50 - 100 μm. For example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm.

[0045] In order to further improve the repair efficiency of laser treatment, in some embodiments, step S2031 can be implemented through the following steps. For example: step S20311, during each of the above-mentioned moving irradiation processes, a plurality of light spots are formed on the second cutting surface, and two adjacent light spots overlap. The ratio of the area of the overlapping part of two adjacent light spots to the average area of the light spots is 20-50%. The setting of the above overlapping rate can ensure that the laser energy is evenly distributed in the repair area, thereby further reducing the situation of too high or too low local energy, and further improving the repair efficiency of laser treatment for surface damage.

[0046] The ratio of the area of the overlapping part of two adjacent light spots to the average area of the light spots is 20-50%, and can be, for example, 20%, 30%, 40% or 50%. In practical applications, those skilled in the art can select an appropriate laser overlap rate according to the material properties of the second cutting surface, repair requirements, laser scanning speed and power.

[0047] In some other embodiments, the ratio of the depth of the above cutting process to the thickness of the whole battery is 2-40%, and the temperature of the above heat treatment is 80-300 °C. The above settings of the cutting depth and the heat treatment temperature can reduce cracks or surface damage caused by excessive mechanical stress, and further improve the mechanical strength and performance of the sliced battery.

[0048] The ratio of the depth of the above cutting process to the thickness of the whole battery is 2-40%, and can be, for example, 2%, 12%, 22%, 32% or 40%. The temperature of the above heat treatment is 80-300 °C, and can be, for example, 80 °C, 120 °C, 160 °C, 200 °C, 240 °C, 280 °C or 300 °C.

[0049] In some other embodiments, the above step S204 can be implemented through the following steps: step S2041, introducing silane into the chamber where the sliced battery is located, and performing thermal ionization treatment on the silane to obtain the above protective layer. By thermally ionizing silane, other impurities can be effectively removed, and a protective layer with a higher silicon purity can be further decomposed and generated.

[0050] In practical applications, the above silane can be directly obtained, or can be generated by reacting magnesium silicide and ammonium chloride in a liquid ammonia medium. During the process of thermally ionizing silane, at high temperature, silane decomposes, and free silicon atoms are deposited on the second cutting surface to obtain the above protective layer. Further, the deposition rate and uniformity of the protective layer can be adjusted by controlling the temperature, pressure and gas flow rate in the chamber, and the thickness and purity of the protective layer can be optimized by adjusting the reaction time, temperature and silane concentration. Finally, by annealing the deposited protective layer, its crystallinity and electrical properties can be further improved.

[0051] In some embodiments, the temperature of the above-mentioned thermal ionization treatment is 150-800 °C, the power of the above-mentioned thermal ionization treatment is 1000-9000 W, the pressure of the above-mentioned chamber is 10-200 mpa, the flow rate of the above-mentioned silane is 10-1000 sccm, and the thickness of the above-mentioned protective layer is 2-12 nm. Appropriate thermal ionization treatment temperature, power and silane flow rate can promote the thermal decomposition of silane, thereby further improving the deposition rate and crystallization quality of the protective layer. The above-mentioned chamber pressure setting can help the uniform distribution of silane, thereby further reducing the impurity content. The above-mentioned protective layer thickness setting can further improve the interface quality between the internal layers of the sliced battery, reduce interface defects, and have good passivation performance; moreover, solar cells containing a silicon-rich protective layer perform better than many other types of solar cells under low-light conditions, and can effectively absorb light and generate electricity even in insufficient light conditions, which can further improve the efficiency of solar cells.

[0052] The temperature of the above-mentioned thermal ionization treatment is 150-800 °C, for example, it can be 150 °C, 300 °C, 450 °C, 600 °C or 800 °C. The power of the above-mentioned thermal ionization treatment is 1000-9000 W, for example, it can be 1000 W, 2000 W, 3000 W, 4000 W, 5000 W, 6000 W, 7000 W, 8000 W or 9000 W. The pressure of the above-mentioned chamber is 10-200 mpa, for example, it can be 10 mpa, 40 mpa, 70 mpa, 100 mpa, 130 mpa, 160 mpa, 190 mpa or 200 mpa. The flow rate of the above-mentioned silane is 10-1000 sccm, for example, it can be 10 sccm, 200 sccm, 400 sccm, 600 sccm, 800 sccm or 1000 sccm. The thickness of the above-mentioned protective layer is 2-12 nm, for example, it can be 2 nm, 4 nm, 6 nm, 8 nm, 10 nm or 12 nm.

[0053] The above-mentioned step S205 can be implemented through the following steps. For example: Step S2051, form a plurality of sub-passivation layers on the side of the above-mentioned protective layer away from the above-mentioned second cutting surface, and the above-mentioned plurality of sub-passivation layers form the above-mentioned passivation layer. Among them, in the first direction, the thickness of the above-mentioned sub-passivation layers increases in sequence, and the first direction is the direction from the side close to the above-mentioned protective layer to the side far from the above-mentioned protective layer. For the thickness setting of each sub-passivation layer in the above-mentioned passivation layer, the thinner sub-passivation layer closer to the protective layer can further reduce surface defect states and surface recombination, and the thicker sub-passivation layer farther from the protective layer can further provide additional mechanical protection and chemical stability.

[0054] The material of the above-mentioned sub-passivation layer can be at least one of silicon oxide, aluminum oxide, silicon nitride, silicon carbide, silicon oxynitride, and carbon oxynitride.

[0055] The above-mentioned step S2051 can be realized through the following steps. For example: step S20511, a feeding step, introducing an inert gas carrying a nitrogen source and a water source into the chamber where the above-mentioned sliced cell is located, and performing a heating treatment on the above-mentioned sliced cell to obtain the above-mentioned sub-passivation layer, wherein the temperature of the above-mentioned heating treatment is 80-250 °C; step S20512, a repeating step, repeating the above-mentioned feeding step multiple times, and during the repeating process, the temperature of the above-mentioned heating treatment is higher than that in the previous repeating process until the above-mentioned multiple sub-passivation layers are formed. By performing a heating treatment on the sliced cell, it can ensure that the reactants at the furnace mouth and the furnace tail in the equipment for preparing the passivation layer have the same heat, thereby making the reaction of the reactants more sufficient and further improving the uniformity of the sub-passivation layer.

[0056] The above-mentioned inert gas can be at least one of nitrogen, argon, helium, and neon. In a specific embodiment, the above-mentioned nitrogen source can be TMA, and the above-mentioned water source can be water or ozone. In practical applications, the temperature of the heating treatment can be controlled according to the different thicknesses of each layer of the deposited sub-passivation layer. For example, when depositing five layers of sub-passivation layers, the thickness gradually increases from the inside to the outside in the first direction, and the temperature gradually increases. In addition, those skilled in the art can also control and adjust according to the on-site process conditions. In the feeding step, introducing an inert gas carrying a nitrogen source and a water source into the chamber where the above-mentioned sliced cell is located and performing a heating treatment on the above-mentioned sliced cell can ensure that the nitrogen source and the water source are fully vaporized, avoid condensation, and thus stabilize the precursor concentration. This helps to improve the uniform distribution in the reaction chamber and reduce the local concentration difference. In addition, if the carrier gas heating and the reaction chamber temperature control cooperate, the uniformity of the substrate surface temperature can be maintained, avoiding the difference in reaction rate caused by the thermal gradient, and further improving the film uniformity.

[0057] Next, the method for preparing a solar cell of the present application will be specifically described in combination with specific examples and comparative examples.

[0058] Example 1

[0059] In this example, a method for preparing a solar cell is provided. The solar cell is a TOPCon cell, and the method includes the following steps:

[0060] Step S31: Provide a whole piece of battery. The whole piece of battery includes a substrate which has two opposite surfaces. An emitter 106, a front passivation layer 107, an antireflection layer 108 and a first electrode 112 are sequentially arranged on one surface. Among them, the material of the substrate is an N-type silicon wafer, the emitter 106 is a boron-diffused emitter, the material of the front passivation layer 107 is alumina, and the material of the antireflection layer 108 is silicon nitride. On the other surface, a tunneling dielectric layer 109, a doped conductive layer 110, a back passivation layer 111 and a second electrode 113 are sequentially arranged. Among them, the material of the tunneling dielectric layer 109 is silicon dioxide, the material of the doped conductive layer 110 is heavily doped polysilicon, and the material of the back passivation layer 111 is silicon nitride;

[0061] Step S32: Perform laser cutting on the whole piece of battery with a cutting depth of 40% of the whole piece of battery to obtain a pre-treated battery with a first cutting surface;

[0062] Step S33: Heat-treat the pre-treated battery along the first cutting surface to obtain a plurality of sliced batteries with a second cutting surface 102. The second cutting surface includes the first cutting surface. Among them, the temperature of the heat treatment is 250 °C;

[0063] Step S34: Perform laser treatment on at least part of the surface of each second cutting surface 102;

[0064] Step S35: Form a protective layer 104 on each second cutting surface 102. Among them, the material of the protective layer 104 is a silicon-rich material;

[0065] Step S36: Introduce an inert gas carrying a nitrogen source and a water source into the chamber where the sliced batteries are located, and form a passivation layer 105 on the side of the protective layer 104 away from the second cutting surface to obtain the structure as Figure 5 shown.

[0066] Embodiment 2

[0067] In this embodiment, a preparation method of a solar cell is provided. The solar cell is a TOPCon cell. The only difference between this method and Embodiment 1 is that Step S36 is realized through the following steps:

[0068] Step S361: The introduction step. Introduce an inert gas carrying a nitrogen source and a water source into the chamber where the sliced batteries are located, and perform a heating treatment on the sliced batteries to obtain the sub-passivation layer. Among them, the temperature of the heating treatment is 80 - 250 °C;

[0069] Step S362: Repeat the steps. Repeat the above feeding steps multiple times, and during the repetition process, the temperature of the above heat treatment is higher than that in the previous repetition process until the above multiple sub-passivation layers are formed.

[0070] Comparative example

[0071] In this embodiment, a method for preparing a solar cell is provided. The solar cell is a TOPCon cell, and the method includes the following steps:

[0072] Step S41: Provide a whole piece of cell. The whole piece of cell includes a substrate, which has two opposite surfaces. An emitter, a front passivation layer, an antireflection layer, and a first electrode are sequentially arranged on one surface. Among them, the material of the substrate is an N-type silicon wafer, the emitter is a boron-diffused emitter, the material of the antireflection layer is silicon nitride, and the material of the front passivation layer is aluminum oxide. A tunneling dielectric layer, a doped conductive layer, a back passivation layer, and a second electrode are sequentially arranged on the other surface. Among them, the material of the tunneling dielectric layer is silicon dioxide, the material of the doped conductive layer is heavily doped polysilicon, and the material of the back passivation layer is silicon nitride;

[0073] Step S42: Perform a laser cutting process on the whole piece of cell. The cutting depth is 60% of the thickness of the whole piece of cell, and mechanical breaking is used to obtain a plurality of sliced cells with a second cutting surface;

[0074] Step S43: Form a passivation layer on the above second cutting surface.

[0075] The thickness and uniformity of the passivation layer of the solar cell prepared by using the method of the above comparative example are shown in Table 1:

[0076] Table 1

[0077]

[0078] The thickness and uniformity of the passivation layer of the solar cell prepared by using the method of the above Embodiment 1 are shown in Table 2:

[0079] Table 2

[0080]

[0081]

[0082] The thickness and uniformity of the passivation layer of the solar cell prepared by using the method in the above Embodiment 2 are shown in Table 3:

[0083] Table 3

[0084]

[0085] It can be seen from the above experimental data that the uniformity of the passivation layer of the solar cells in Example 1 and Example 2 is better, and the uniformity of the passivation layer of the solar cell in Example 2 is better than that in Example 1. Therefore, it can be shown that the preparation method of the above solar cell of the present application can improve the uniformity of the passivation layer. It should be noted that the central thickness in Tables 1 to 3 above is the thickness at the geometric center of the passivation layer, the thickness of corner 1 is the thickness at the upper left corner of the passivation layer, the thickness of corner 2 is the thickness at the upper right corner of the passivation layer, the thickness of corner 3 is the thickness at the lower left corner of the passivation layer, and the thickness of corner 4 is the thickness at the lower right corner of the passivation layer.

[0086] The performance of the solar cells prepared by using the above comparative examples, Example 1 and Example 2 was tested, and the test results are shown in Table 4:

[0087] Table 4

[0088] Solar cell number Eta (%) Uoc (V) Isc (A) FF (%) Positive inspection winding plating (%) Back inspection winding plating (%) Comparative example 26.573 0.7329 7.920 87.04 0.12 0.11 Example 1 26.823 0.7403 7.945 87.20 0.08 0.06 Example 2 26.903 0.7421 7.933 87.39 0.06 0.04

[0089] It can be seen from the above experimental data that the photoelectric conversion efficiency (Eta) in Example 1 and Example 2 is higher than that in the comparative example, and the fill factor (FF) in Example 1 and Example 2 is higher than that in the comparative example, indicating that the solar cell of the present application can reduce the carrier recombination loss and improve the photoelectric conversion efficiency. It can also be seen from the above experimental data that the open circuit voltage (Uoc) and short circuit current (Isc) in Example 1 and Example 2 are higher than those in the comparative example, indicating that the solar cell of the present application can increase the open circuit voltage and short circuit current of the solar cell. Moreover, the photoelectric conversion efficiency, fill factor, open circuit voltage, short circuit current and fill factor in Example 2 are all greater than those in Example 1, indicating that introducing an inert gas carrying a nitrogen source and a water source into the chamber where the above sliced cells are located and heating the above sliced cells can further improve the efficiency of the solar cell.

[0090] The embodiments of the present application also provide a solar cell as described above, and the solar cell is made by using any one of the above preparation methods of the solar cell.

[0091] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0092] 1. Preparation method of the solar cell of the present application. First, the whole cell is subjected to a cutting process to obtain a pre-treated cell with a first cutting surface, and the depth of the cutting process is less than the thickness of the whole cell; then, the pre-treated cell is heat-treated along the first cutting surface to obtain a plurality of sliced cells with a second cutting surface, and the second cutting surface includes the first cutting surface; at least part of the surface of each second cutting surface is subjected to a laser treatment; then, a protective layer is formed on each second cutting surface, and the material of the protective layer is a silicon-rich material; finally, a passivation layer is formed on the side of the protective layer away from the second cutting surface. In this method, by successively performing a cutting process and a heat treatment on the whole cell, sliced cells with a second cutting surface are obtained; then, the second cutting surface is subjected to a laser treatment to remove the oxide layer generated during the cutting process and reduce the burrs that appear during the cutting process; further, by forming a silicon-rich protective layer on the cutting surface, the surface dangling bonds of the cutting surface can be saturated, the carrier recombination on the cutting surface can be reduced, the minority carrier lifetime can be improved, the recombination current can be reduced, and thus the efficiency of the solar cell can be enhanced, solving the problem in the prior art that the edge damage of sliced solar cells after cutting affects the cell efficiency.

[0093] 2. Solar cell of the present application. The above-mentioned solar cell is manufactured by using any one of the above-mentioned preparation methods of the solar cell. First, the whole cell is subjected to a cutting process to obtain a pre-treated cell with a first cutting surface, and the depth of the cutting process is less than the thickness of the whole cell; then, the pre-treated cell is heat-treated along the first cutting surface to obtain a plurality of sliced cells with a second cutting surface, and the second cutting surface includes the first cutting surface; at least part of the surface of each second cutting surface is subjected to a laser treatment; then, a protective layer is formed on each second cutting surface, and the material of the protective layer is a silicon-rich material; finally, a passivation layer is formed on the side of the protective layer away from the second cutting surface. In this method, by successively performing a cutting process and a heat treatment on the whole cell, sliced cells with a second cutting surface are obtained; then, the second cutting surface is subjected to a laser treatment to remove the oxide layer generated during the cutting process and reduce the burrs that appear during the cutting process; further, by forming a silicon-rich protective layer on the cutting surface, the surface dangling bonds of the cutting surface can be saturated, the carrier recombination on the cutting surface can be reduced, the minority carrier lifetime can be improved, the recombination current can be reduced, and thus the efficiency of the solar cell can be enhanced, solving the problem in the prior art that the edge damage of sliced solar cells after cutting affects the cell efficiency.

Claims

1. A method for preparing a solar cell, characterized in that: include: Performing a cutting process on the whole battery to obtain a pre-processed battery having a first cutting surface, wherein the depth of the cutting process is less than the thickness of the whole battery; heat-treating the pre-treated battery along the first cutting surface to obtain a plurality of sliced ​​batteries having a second cutting surface, wherein the second cutting surface includes the first cutting surface; performing laser processing on at least a portion of each of the second cutting surfaces; forming a protective layer on each of the second cut surfaces, wherein the material of the protective layer is a silicon-rich material; A passivation layer is formed on a side of the protection layer away from the second cutting surface.

2. The method according to claim 1, characterized in that: Laser processing is performed on at least a portion of each of the second cutting surfaces, comprising: A femtosecond laser is used to perform mobile irradiation treatment on at least a portion of the second cutting surface, wherein the wavelength of the femtosecond laser is 515 to 1030 nm, the pulse width of the femtosecond laser is 100 to 1000 fs, the repetition frequency of the femtosecond laser is 100 to 1000 kHz, the pulse energy of the femtosecond laser is 5 to 40 μJ, and the scanning speed of the femtosecond laser is 100 to 500 mm / s; An inert gas purging process is performed on each of the second cutting surfaces to reduce the temperature of the second cutting surface.

3. The method according to claim 2, characterized in that The minimum distance between the focus of the femtosecond laser and the second cutting surface is 50-100 μm.

4. The method according to claim 2, characterized in that: Using a femtosecond laser to perform mobile irradiation treatment on at least a portion of the second cutting surface comprises: During each moving irradiation process, a plurality of light spots are formed on the second cutting surface, two adjacent light spots overlap, and the ratio of the area of ​​the overlapping portion of the two adjacent light spots to the average area of ​​the light spots is 20-50%.

5. The method according to claim 1, characterized in that The ratio of the depth of the cutting process to the thickness of the whole battery is 2-40%, and the temperature of the heat treatment is 80-300°C.

6. The method according to claim 1, characterized in that Forming a protective layer on each of the second cutting surfaces comprises: Silane is introduced into the chamber where the sliced ​​battery is located, and the silane is subjected to thermal ionization treatment to obtain the protective layer.

7. The method according to claim 6, characterized in that The temperature of the thermal ionization treatment is 150-800° C., the power of the thermal ionization treatment is 1000-9000 W, the pressure of the chamber is 10-200 MPa, the flow rate of the silane is 10-1000 sccm, and the thickness of the protective layer is 2-12 nm.

8. The method according to claim 1, characterized in that Forming a passivation layer on a side of the protection layer away from the second cutting surface, comprising: A plurality of sub-passivation layers are formed on a side of the protective layer away from the second cutting surface, and the plurality of sub-passivation layers form the passivation layer, wherein in a first direction, the thickness of the sub-passivation layers increases successively, and the first direction is a direction from a side close to the protective layer to a side away from the protective layer.

9. The method according to claim 8, characterized in that A plurality of sub-passivation layers are formed on a side of the protection layer away from the second cutting surface to obtain the passivation layer, comprising: A step of introducing an inert gas carrying a nitrogen source and a water source into a chamber where the sliced ​​battery is located, and heating the sliced ​​battery to obtain the sub-passivation layer, wherein the heating treatment temperature is 80 to 250° C.; The step of repeating is repeated for multiple times, and the temperature of the heating treatment during the repeated process is greater than the temperature of the heating treatment during the last repeated process, until the multiple sub-passivation layers are formed.

10. A solar cell, characterized in that: The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 9, and comprises a sliced ​​cell having a second cutting surface, a protective layer and a passivation layer, wherein the protective layer is located on one side of the second cutting surface, and the passivation layer is located on a side of the protective layer away from the second cutting surface.

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