Preparation method of solar cell and solar cell

Abstract

The invention relates to the technical field of solar cells, and provides a preparation method of a solar cell piece and the solar cell piece, the solar cell piece is formed by cutting the whole cell piece, the solar cell piece is provided with a cutting surface formed by cutting, and the method comprises the following steps: providing a substrate; coating a substrate with the passivation slurry to form a passivation film with a nanoscale thickness on the substrate; and transferring the passivation film on the substrate to the cutting surface of the solar cell by using a transfer printing process so as to form a passivation layer on the cutting surface. The problem that in an existing half-wafer passivation process, passivation slurry is prone to being diffused to a non-target area, and therefore the performance of a battery piece is affected is solved.

Description

Technical Field

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

[0002] Currently, in the half-cell passivation process, during the deposition of the passivation layer, the passivation paste easily diffuses into non-target areas, affecting the performance of the solar cell wafer. Summary of the Invention

[0003] The main object of the present application is to provide a method for preparing a solar cell wafer and a solar cell wafer, so as to solve the problem that in the existing half-cell passivation process, the passivation paste easily diffuses into non-target areas, thereby affecting the performance of the solar cell wafer.

[0004] To achieve the above object, according to one aspect of the present application, there is provided a method for preparing a solar cell wafer, the solar cell wafer being formed by cutting a whole solar cell wafer, the solar cell wafer having a cut surface formed by cutting, the method comprising: providing a substrate; coating a passivation paste on the substrate to form a passivation film with a nanoscale thickness on the substrate; using a transfer process to transfer the passivation film on the substrate to the cut surface of the solar cell wafer to form a passivation layer on the cut surface.

[0005] Optionally, the thickness of the passivation film is 5 nm to 20 nm, and the transfer process includes hot embossing transfer.

[0006] Optionally, the passivation paste includes a passivating agent and a solvent. After transferring the passivation film on the substrate to the cut surface of the solar cell wafer to form a passivation layer, the method further comprises: pre-drying the solar cell wafer having the passivation layer at a temperature of 100 °C to 150 °C to remove the solvent.

[0007] Optionally, after pre-drying the solar cell wafer having the passivation layer at a temperature of 100 °C to 150 °C, the method further comprises: annealing the pre-dried solar cell wafer at 400 °C to 800 °C.

[0008] Optionally, the passivating agent includes alumina, the pre-drying duration is 1 minute to 2 minutes, and the annealing duration is 5 minutes to 20 minutes.

[0009] Optionally, the flower basket has a plurality of independent flower basket structures, and each of the flower basket structures is used to load the solar cell wafers one by one. Before coating the passivation paste on the substrate, the method further includes: loading the plurality of solar cell wafers into the flower basket structures one by one, and exposing the cutting surfaces of the solar cell wafers.

[0010] Optionally, the temperature of the hot embossing transfer is 100°C to 150°C.

[0011] Optionally, before transferring the passivation film on the substrate to the cutting surface of the solar cell wafer, the method further includes: providing a substrate having opposite first and second surfaces; forming a first doped layer, a first passivation film, and a first antireflection film stacked in sequence on the first surface; forming a second doped layer, a second passivation film, and a second antireflection film stacked in sequence on the second surface, wherein the doping type of the second doped layer is different from that of the first doped layer; forming a first electrode on the surface of the first antireflection film away from the substrate; forming a second electrode on the surface of the second antireflection film away from the substrate to obtain the whole wafer; cutting the whole wafer to obtain the solar cell wafer.

[0012] Optionally, the material of the substrate includes at least one of the following: polyethylene terephthalate and polytetrafluoroethylene.

[0013] According to another aspect of the present application, there is provided a solar cell wafer, which is prepared by using any one of the preparation methods of the solar cell wafers. The solar cell wafer includes: a solar cell wafer formed by cutting a whole wafer, and the solar cell wafer has a cutting surface formed by cutting; a passivation layer located on the cutting surface.

[0014] The beneficial effects of the present application are as follows: First, a substrate is provided, and then a passivation paste is coated on the substrate to form a passivation film with a nanoscale thickness on the substrate. Finally, using a transfer process, the passivation film on the substrate is transferred to the cut surface of the solar cell to form a passivation layer on the cut surface. Compared with the problem in the existing half-cell passivation process that the passivation paste easily diffuses into non-target areas, thereby affecting the performance of the cell, in the present application, the passivation paste is first coated on the substrate to form a passivation film, and then the passivation film on the substrate is transferred to the cut surface of the solar cell. The present application uses the substrate as an intermediate, and the thickness of the passivation film coated on the substrate is set to a nanoscale thickness (i.e., the passivation film is very thin), avoiding the problem that when the passivation paste is directly coated or sprayed on the cut surface, the paste flows to the non-cut surface of the cell due to the large fluidity of the paste and the relatively thick paste being difficult to control. At the same time, the process duration is short, ensuring that there is less diffusion of the passivation paste to the non-cut surface during the passivation process, and ensuring better performance of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings forming a part of this application are used to provide a further understanding of the application. The schematic embodiments and descriptions thereof of the application are used to explain the application and do not constitute an improper limitation of the application. In the drawings:

[0016] Figure 1 shows a schematic flow chart of a method for preparing a solar cell according to an embodiment of the present application;

[0017] Figure 2 shows a schematic structural diagram of forming a passivation film on a substrate according to an embodiment of the present application;

[0018] Figure 3 shows a schematic structural diagram of transferring a passivation film on a substrate to the cut surface of a solar cell according to an embodiment of the present application;

[0019] Figure 4 shows a schematic structural diagram of forming a passivation layer on the cut surface of a solar cell according to an embodiment of the present application.

[0020] Among them, the above-mentioned drawings include the following reference numerals:

[0021] 10. Substrate; 11. Passivation film; 12. Solar cell; 121. Cut surface; 13. Passivation layer; 14. Basket. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element can be directly on the other element, or there can also be an intermediate element. Moreover, in the specification and claims, when an element is described as "connected" to another element, the element can be "directly connected" to the other element, or "connected" to the other element through a third element.

[0025] Most of the existing passivation processes use Atomic Layer Deposition (ALD) technology to deposit a passivation layer such as aluminum oxide on the cut surface of a half-cell wafer. When the ALD technology is used to process a half-cell wafer, the process time is long. During the deposition process of the passivation layer, the passivation slurry is prone to spread to non-target areas due to the long process time, which affects the performance of the wafer. Currently, it takes 3 - 4 hours to deposit an aluminum oxide film layer using ALD.

[0026] As introduced in the background art, in the existing half-cell passivation process, the passivation slurry is prone to spread to non-target areas, thereby affecting the performance of the wafer. To solve the above problems, embodiments of the present application provide a method for preparing a solar cell wafer and a wafer.

[0027] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0028] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0029] Figure 1 is a flowchart of a method for cutting a wafer according to an embodiment of the present application. The above-mentioned solar cell wafer is formed by cutting a whole wafer, and the above-mentioned solar cell wafer has a cut surface formed by cutting. As Figure 1 shown, the method includes the following steps:

[0030] Step S101, as Figure 2 shown, provide a substrate 10;

[0031] Specifically, the material of the substrate can be selected from organic materials such as polyimide or polytetrafluoroethylene. In the actual application process, those skilled in the art can flexibly select the appropriate material of the substrate according to actual needs, and this application does not make specific limitations thereon.

[0032] Specifically, the thickness of the substrate for transfer is generally between 25 microns and 200 microns. For polyimide materials, the thickness is generally between 25 microns and 50 microns to ensure the flexibility and strength of the substrate. Those skilled in the art can set the thickness of the substrate according to empirical values or obtain it through multiple experiments, and this application does not make specific limitations thereon.

[0033] Specifically, before coating, the surface of the substrate can be specially treated, such as cleaning, applying a primer or surface modification, to improve the adhesion of the subsequent passivation paste thereto; before coating, a thermal release coating can also be added to the surface of the substrate to easily peel off the passivation film during transfer. The thermal release coating should have good temperature sensitivity, chemical stability, thermal stability, and appropriate peeling performance. The material of the thermal release coating can be selected from silicone resin, fluoride coating, etc.

[0034] Step S102, as Figure 2 shown, coat a passivation paste (not shown) on the above-mentioned substrate 10 to form a passivation film 11 with a nanoscale thickness on the above-mentioned substrate 10;

[0035] Specifically, a coating device (the coating method can be slot coating, doctor blade coating or inkjet coating) can be used to uniformly coat the passivation paste on the substrate. During the coating process, the thickness and uniformity of the passivation paste need to be controlled to ensure the formation of a passivation film with a nanoscale thickness.

[0036] Specifically, high-purity passivation paste can be prepared in advance to ensure that its particle size is uniform and its dispersibility is good. The passivation paste includes a passivating agent, a solvent, and an adhesive. When preparing, an appropriate amount of solvent and adhesive can be added to the passivating agent to improve the coating performance and adhesion of the passivation paste. High purity means that the mass ratio of the passivating agent in the passivation paste is 80%-90%. The solvent is used to dilute the passivating agent so that it can be evenly distributed during the coating process. Commonly used solvents include alcohols (such as ethanol, isopropanol), organic acids (such as acetic acid), water, or mixed solvents; ethanol is a commonly used solvent because it has good volatility, is easy to dry, and can dissolve a variety of passivating agents. Its use helps to control the viscosity and fluidity of the passivation paste, thus achieving a uniform coating. Commonly used adhesives include polyvinyl butyral (PVB), polytetrafluoroethylene (PTFE), or organic adhesives designed specifically for high-temperature applications; PVB is a high-temperature resistant adhesive that can effectively connect the passivating agent particles to the silicon surface and maintain good stability even during high-temperature annealing. The addition of PVB improves the adhesion and durability of the passivation layer and reduces the risk of interlayer peeling. The solvent usually accounts for about 10% of the total mass of the passivation paste to ensure the fluidity and coating performance of the solution, and the adhesive usually accounts for 1% to 5% of the total mass of the passivation paste to provide sufficient adhesion without affecting the quality of the passivation layer.

[0037] Step S103, as Figure 3 and Figure 4 shown, using a transfer process, transfer the above-mentioned passivation film 11 on the above-mentioned substrate 10 to the above-mentioned cut surface 121 of the above-mentioned solar cell 12 to form a passivation layer 13 on the above-mentioned cut surface 121.

[0038] Specifically, the thickness of the passivation layer is also on the nanometer scale.

[0039] Specifically, the cut surface of the solar cell needs to be cleaned and pretreated before transfer to remove impurities and improve the adhesion effect of the passivation layer.

[0040] Specifically, the transfer process can be selected from laser transfer, hot press transfer, chemical-assisted transfer, etc. Those skilled in the art can flexibly select a suitable transfer process according to actual needs, and this application does not make specific limitations on this.

[0041] In this embodiment, a substrate is first provided, and then a passivation paste is coated on the substrate to form a passivation film with a nanoscale thickness on the substrate. Finally, using a transfer process, the passivation film on the substrate is transferred to the cut surface of the solar cell to form a passivation layer on the cut surface. Compared with the problem in the existing half-cell passivation process that the passivation paste easily diffuses into non-target areas, thereby affecting the performance of the cell, in this application, the passivation paste is first coated on the substrate to form a passivation film, and then the passivation film on the substrate is transferred to the cut surface of the solar cell. This application uses the substrate as an intermediate, and the thickness of the passivation film coated on the substrate is set to a nanoscale thickness (i.e., the passivation film is very thin), avoiding the problem that when the passivation paste is directly coated or sprayed on the cut surface, the paste flows to the non-cut surface of the cell due to the large fluidity and thick thickness of the paste, which is not easy to control. At the same time, the process duration is short, ensuring that there is less diffusion of the passivation paste to the non-cut surface during the passivation process, and ensuring better performance of the solar cell.

[0042] Specifically, the diffusion of the passivation paste into non-target areas refers to the diffusion of the passivation paste onto the non-cut surface.

[0043] In an alternative solution, the thickness of the above-mentioned passivation film is 5 nm to 20 nm, and the above-mentioned transfer process includes hot embossing transfer. In this embodiment, the thickness of the passivation film is set to 5 nm to 20 nm. If the thickness is too thin, the passivation layer transferred to the cut surface will also be too thin to effectively passivate the cut surface defects. If the thickness is too thick, it will affect the control of the passivation paste in the transfer process. In addition, at a thickness of 5 nm to 20 nm, the adhesion of the passivation film to the substrate is moderate, which is easy to form a stable layer on the substrate and is also convenient to be accurately transferred to the cut surface of the cell by hot embossing transfer technology; by using hot embossing transfer, high temperature helps to improve the chemical reaction activity between the passivation paste and the cut surface of the solar cell, thereby enhancing the adhesion of the passivation layer. In addition, compared with cold transfer, hot embossing transfer can usually be completed in a shorter time, which is beneficial to improving production efficiency and can further reduce the problem of the passivation paste diffusing to the non-cut surface.

[0044] Specifically, the thickness of the above-mentioned passivation film can be set to 5 nm, or 8 nm, or 15 nm or 20 nm, etc., as long as it is within the range of 5 nm to 20 nm. This application does not make specific restrictions on this.

[0045] Specifically, the transfer process can also use pressure transfer, that is, by applying physical pressure, the passivation paste is transferred from the substrate to the cut surface of the solar cell.

[0046] Specifically, hot press transfer printing refers to applying pressure under heating conditions, and softening and transferring the passivation film by the dual action of temperature and pressure. This transfer printing method is particularly suitable for coating materials whose viscosity increases at higher temperatures.

[0047] Specifically, after coating is completed, the passivation film is transferred to the cut surface by pressure transfer printing or hot press transfer printing. During the transfer process, it is necessary to ensure that the passivation layer is in close contact with the cut surface to avoid bubbles or defects.

[0048] In the actual application process, those skilled in the art can set the pressure value applied in the above pressure transfer printing or the above hot press transfer printing according to empirical values, or obtain it through multiple experiments. This application does not make specific restrictions on this.

[0049] Specifically, the pressure range applied in pressure transfer printing is usually between 0.1 MPa and 5 MPa, and more commonly in the range of 1 MPa to 2 MPa. This pressure level is sufficient to ensure good contact between the passivation layer and the silicon surface, while avoiding physical damage to the fragile solar cell wafers. The pressure range of hot press transfer printing is generally between 0.01 and 1 MPa. Considering the role of temperature in the hot press process, a relatively low pressure is generally used to prevent excessive pressure at high temperatures from causing material deformation or damage to the cell wafers. For most hot press transfer printing applications, a pressure range of 0.01 to 0.5 MPa is more common. However, in some cases, in order to ensure the integrity of the coating and better bonding between the coating and the cut surface, it may be necessary to increase it to 0.5 to 1 MPa.

[0050] According to some exemplary embodiments of the present application, the above passivation paste includes a passivating agent and a solvent. After transferring the above passivation film on the above substrate to the above cut surface of the above solar cell wafer to form a passivation layer on the above cut surface, the method further includes: pre-drying the above solar cell wafer with the formed passivation layer at a temperature of 100°C to 150°C to remove the above solvent. In this embodiment, the solvent mainly plays a role of dispersing and carrying the passivating agent in the passivation paste. However, after coating and transfer printing are completed, the presence of the solvent will reduce the stability and adhesion of the film layer. The evaporation of the solvent can promote the recombination of molecules inside the film layer to form a denser structure, thereby enhancing the bonding force between the passivation layer and the cut surface. After pre-drying, the passivation layer adheres more firmly to the cut surface, reducing the risk of film layer peeling off during subsequent high-temperature treatment or use; the remaining solvent may form micropores or defects in the film layer, and these defects can become centers of carrier recombination, increasing the recombination loss of the battery and reducing the open-circuit voltage. By removing the solvent, these potential recombination centers can be eliminated, improving the electrical performance of the battery.

[0051] Specifically, the temperature of pre-drying can be 100°C, 120°C, 140°C, 150°C, etc., and the present application does not make specific restrictions on this.

[0052] Specifically, the selection of the pre-drying temperature is based on the heat resistance of the passivating agent and the volatility of the solvent, ensuring the formation quality of the passivation layer. This method is not limited to using thermal drying, including but not limited to other methods that can effectively remove the solvent, such as vacuum drying, infrared drying, etc., and the present application does not make specific restrictions on this.

[0053] In other embodiments, after pre-drying the above-mentioned solar cell wafers on which the above-mentioned passivation layer is formed at a temperature of 100°C to 150°C, the above method further includes: annealing the pre-dried above-mentioned solar cell wafers at 400°C to 800°C. In this embodiment, the high-temperature annealing treatment can promote the chemical reaction between the passivation layer and the silicon surface (i.e., the cut surface), making the passivation layer more dense and uniform, forming a high-quality passivation interface, and this process can also eliminate possible micro-defects remaining in the pre-drying stage, such as micropores or cracks, further improving the integrity and stability of the passivation layer. Therefore, through high-temperature annealing, the quality of the passivation layer is significantly improved, the surface recombination is reduced, the open-circuit voltage of the solar cell wafer is further increased, and it helps to further improve the conversion efficiency.

[0054] Specifically, the annealing temperature can be 400°C, 600°C, 650°C, 800°C, etc., and the present application does not make specific restrictions on this.

[0055] Specifically, the selection of the annealing temperature is based on the reaction activity of the passivating agent and the thermal stability of the solar cell wafer material, ensuring the optimization of the passivation layer performance. The annealing treatment is not limited to using heat treatment, including but not limited to other methods that can optimize the passivation layer performance, such as photothermal annealing, plasma annealing, etc., and the present application does not make specific restrictions on this.

[0056] According to some other exemplary embodiments of the present application, the above-mentioned passivating agent includes alumina, the pre-drying duration is 1 minute to 2 minutes, and the annealing duration is 5 minutes to 20 minutes. In this embodiment, the pre-drying duration is controlled within 1 minute to 2 minutes, aiming to quickly remove the solvent used in the coating and transfer processes. This short-time pre-drying can not only meet the requirements of solvent evaporation but also minimize the residence time of the cell wafer in the pre-drying stage, thus not significantly increasing the cycle of the entire manufacturing process and further maintaining a high production efficiency; the annealing duration is set to 5 minutes to 20 minutes, and this range aims to promote a deeper chemical reaction between alumina and the silicon surface through high temperature to further form a high-quality passivation interface. At the same time, controlling the annealing time within a reasonable range can avoid material decomposition or cell wafer damage caused by over-annealing and maintain the integrity of the cell wafer; the selection of alumina as the passivating agent is based on its excellent chemical stability and passivation effect.

[0057] Specifically, the annealing duration can be 5 minutes, 7 minutes, 12 minutes, 15 minutes, 20 minutes, etc., and the present application does not make specific limitations thereto. The annealing duration can be set corresponding to the annealing temperature.

[0058] Specifically, it is not limited to using alumina as the passivation agent, including but not limited to using other materials with excellent passivation effects, such as silicon dioxide, silicon nitride, etc., and the present application does not make specific limitations thereto. The alumina passivation layer significantly reduces the recombination rate of the cut surface, improves the open-circuit voltage and conversion efficiency of the solar cell; the alumina layer protects the cut surface and reduces the influence of environmental factors on the performance of the solar cell; the cut surface covered with the passivation layer can reduce the resistance loss and hot spot risk of the solar cell.

[0059] Specifically, pre-drying: The solar cells forming the passivation layer are pre-dried at a low temperature (such as 100°C to 150°C) to remove the solvent in the passivation paste.

[0060] In some alternative embodiments of the present application, such as Figure 3 and Figure 4 shown, the carrier 14 has a plurality of independent carrier structures (not labeled), and each of the above carrier structures is used to load the above solar cells 12 in a one-to-one correspondence. Before coating the passivation paste (not shown) on the substrate 10, the above method further includes: loading the plurality of above solar cells 12 into the above carrier structures in a one-to-one correspondence, and exposing the cut surface 121 of the above solar cells 12. In this embodiment, by loading the solar cells into the independent carrier structures in a one-to-one correspondence and ensuring that the cut surface is completely exposed, the coating uniformity of the passivation paste on the cells can be greatly improved. This loading method reduces the mutual interference between adjacent cells and further avoids the accumulation of the passivation paste between the cells.

[0061] Specifically, use a high-temperature resistant metal carrier (such as stainless steel or special alloy) to ensure that it can withstand subsequent high-temperature processes. The carrier design needs to ensure that the solar cells are firmly fixed and at the same time facilitate the coating and transfer operations. Load the plurality of solar cells neatly into the carrier, ensuring that the cut surface faces upward and is exposed.

[0062] Specifically, during the high-temperature treatment process, such as annealing or sintering, if multiple solar cells are directly stacked and in contact with each other, especially when the passivation layer or paste is not fully dried, adhesion is likely to occur. The independent carrier structure ensures that each solar cell has sufficient space during the treatment process, avoiding direct contact, thereby reducing the risk of adhesion and reducing the phenomenon of grid line shedding.

[0063] Specifically, such as Figure 2As shown, when passivating multiple solar cells (not shown), during the coating process, it is necessary to coat a passivation paste at the corresponding positions of the substrate 10 and each solar cell to form multiple passivation films 11 with a nanoscale thickness on the substrate 10.

[0064] In some other alternative embodiments of the present application, the temperature of the above hot embossing transfer is 100°C to 150°C. In this embodiment, the precise control of the hot embossing transfer temperature between 100°C and 150°C is based on the thermal stability of the passivating agent and the thermal sensitivity of the solar cell material. This temperature range can ensure a good physical and chemical bond between the paste and the cut surface of the solar cell, while reducing the potential damage of high temperature to the performance of the solar cell.

[0065] Specifically, high-temperature annealing: Place the carrier holding multiple solar cells into a high-temperature furnace and perform annealing treatment at 400°C - 800°C. At high temperature, alumina reacts with the silicon surface (i.e., the cut surface) to form a dense nanoscale passivation layer. The annealing time needs to be precisely controlled according to the process requirements (usually 5 - 20 minutes).

[0066] In other embodiments, before transferring the above passivation film on the above substrate to the above cut surface of the above solar cell, the above method further includes: providing a substrate having opposite first and second surfaces; forming a first doped layer, a first passivation film, and a first antireflection film stacked in sequence on the first surface; forming a second doped layer, a second passivation film, and a second antireflection film stacked in sequence on the second surface, where the doping type of the second doped layer is different from that of the first doped layer; forming a first electrode on the surface of the first antireflection film away from the substrate; forming a second electrode on the surface of the second antireflection film away from the substrate to obtain the above whole solar cell; cutting the above whole solar cell to obtain the above solar cell. In this embodiment, the manufacturing process of the whole solar cell includes the formation of multiple functional layers, which is to construct a complete battery structure and ensure the photoelectric conversion efficiency and stability of the solar cell.

[0067] Specifically, the first electrode is electrically connected to the first doped layer, and the second electrode is electrically connected to the second doped layer.

[0068] Specifically, the whole solar cell can be cut into half cells using laser cutting or mechanical cutting to obtain multiple solar cells. After cutting, the cut surface needs to be cleaned to remove residual debris and contaminants.

[0069] Specifically, the material of the substrate can be at least one of single-crystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon; the material of the passivation film (i.e., the first passivation film and the second passivation film) can include one or more of materials such as silicon oxide, silicon nitride, silicon oxynitride, carbon oxynitride, titanium oxide, hafnium oxide, or aluminum oxide. The passivation film can be a single-layer structure or a stacked structure. For example, the single-layer structure can be a single-layer aluminum oxide film layer, a single-layer silicon oxide film layer, a single-layer silicon nitride film layer, or a single-layer silicon oxynitride film layer, and the stacked structure can be composed of at least two film layers of aluminum oxide film layer, silicon oxide film layer, silicon nitride film layer, or silicon oxynitride film layer stacked. The substrate can be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type doping element, and the N-type doping element can be at least one of group V elements such as phosphorus (P) element, bismuth (Bi) element, antimony (Sb) element, or arsenic (As) element. The P-type semiconductor substrate is doped with a P-type element, and the P-type doping element can be at least one of group III elements such as boron (B) element, aluminum (Al) element, gallium (Ga) element, or indium (In) element; the materials of the antireflection films (i.e., the first antireflection film and the second antireflection film) both include at least one of silicon oxide, silicon nitride, or silicon oxynitride. The antireflection film can be a single-layer structure or a multi-layer structure. For the multi-layer structure, the materials of different layers can be different from each other, or the materials of some number of layers can be the same and different from the materials of other layers.

[0070] Specifically, the solar cell can be any one of a PERC cell (Passivated Emitter and Rear Cell), a PERT cell (Passivated Emitter and Rear Totally diffused cell), a TOPCon cell (Tunnel Oxide Passivated Contact), a HIT / HJT cell (Heterojunction Technology), or a BC cell (Back Contact). This application does not make specific limitations thereto.

[0071] In a specific embodiment, the solar cell is a TOPCon cell, and the solar cell further includes a tunneling oxide layer. The tunneling oxide layer can be located between the substrate and the first doping layer, or between the substrate and the second doping layer, or between the substrate and the first doping layer and between the substrate and the second doping layer. This application does not make specific limitations thereto. The material of the tunneling oxide layer can include at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or magnesium fluoride.

[0072] Specifically, taking TOPCON cells as an example, the preparation method of solar cell wafers specifically includes the following steps:

[0073] Step 1: Provide an n-type silicon wafer (i.e., provide a substrate), and perform double-sided texturing on the n-type silicon wafer;

[0074] Step 2: Perform boron diffusion on the textured silicon wafer (i.e., form a first doped layer) to form a PN junction;

[0075] Step 3: Chain to remove BSG, remove the BSG on the back of the cell, then perform alkali polishing to polish the back of the cell, and then chain to remove BSG to remove the BSG on the front of the cell;

[0076] Step 4: Deposit the tunneling oxide layer (i.e., form the tunneling oxide layer) and the intrinsic amorphous silicon layer on the back of the cell by means of double insertion using LPCVD (Low Pressure Chemical Vapor Deposition), and crystallize the intrinsic amorphous silicon layer to obtain an intrinsic polycrystalline silicon layer;

[0077] Step 5: Perform phosphorus doping annealing on the back of the cell by means of double insertion (i.e., form a second doped layer);

[0078] Step 6: Chain to remove PSG, remove the PSG on the back of the cell and the overplating on the front;

[0079] Step 7: Use ALD to deposit aluminum oxide passivation films on the front and back of the cell (i.e., form a first passivation film and a second passivation film);

[0080] Step 8: Use PECVD (Plasma Enhanced Chemical Vapor Deposition) to coat films on the front and back of the cell (i.e., form a first antireflection film and a second antireflection film);

[0081] Step 9: Screen printing, print the pastes on the front and back of the cell, sinter and laser-assisted sinter (i.e., form a first electrode and a second electrode) to obtain a whole cell wafer;

[0082] Step 10: Cut the whole cell wafer to obtain multiple solar cell wafers;

[0083] Step 11: Passivate the solar cell wafers: Provide a substrate; coat the passivation paste on the substrate to form a passivation film with a nanoscale thickness on the substrate; use a transfer process to transfer the passivation film on the substrate to the cut surface of the solar cell wafer to form a passivation layer on the cut surface;

[0084] Step 12: Perform efficiency testing on the passivated solar cell wafers.

[0085] According to some other exemplary embodiments of the present application, the material of the above substrate includes at least one of the following: polyethylene terephthalate and polytetrafluoroethylene. The PET film (i.e., polyethylene terephthalate) can resist the chemical components in the passivation paste and maintain the integrity and stability of the substrate; the Teflon coating (i.e., polytetrafluoroethylene) ensures that the passivation paste is easy to coat on the coating and can be easily detached after transfer, reducing the amount of material remaining on the substrate.

[0086] In the actual application process, those skilled in the art can flexibly select the material of the substrate according to actual needs, and the present application does not make specific restrictions on this.

[0087] The embodiment of the present application also provides a solar cell. The above battery is prepared by using any one of the above preparation methods of the solar cell, such as Figure 4 As shown, the above battery includes: a solar cell 12, the above solar cell 12 is formed by cutting a whole battery cell (not shown), and the above solar cell 12 has a cut surface 121 formed by cutting; a passivation layer 13, located on the above cut surface 121.

[0088] Specifically, in the prior art, the atomic layer deposition (ALD) technology is used to deposit a passivation layer on the cut surface of the solar cell. The passivation methods of the present application and the prior art are respectively used to passivate 1000 solar cells of the same size. The passivation duration, the diffusion rate of the passivation paste (as long as the diffusion area of the passivation paste on the non-cut surface exceeds the diffusion limit, it is regarded as diffusion), the short-circuit current (Isc), the fill factor (FF), the open-circuit voltage (Voc) of the battery cell, and the thickness of the passivation layer are respectively counted. The results are shown in Table 1.

[0089] Table 1

[0090]

[0091] It can be seen from Table 1 that compared with the prior passivation method, when the passivation method of the present application is used to passivate the solar cell, the passivation duration is shorter, the diffusion rate of the passivation paste is less, the performance of the passivated battery cell is better, and the thickness of the passivation layer is smaller, and there is also an advantage in consumption cost.

[0092] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0093] The preparation method of the solar cell of the present application first provides a substrate, then coats a passivation paste on the substrate to form a passivation film with a nanoscale thickness on the substrate, and finally uses a transfer process to transfer the passivation film on the substrate to the cut surface of the solar cell to form a passivation layer on the cut surface. Compared with the problem in the existing half-cell passivation process that the passivation paste easily diffuses into non-target areas, thus affecting the performance of the cell, in the present application, the passivation paste is first coated on the substrate to form a passivation film, and then the passivation film on the substrate is transferred to the cut surface of the solar cell. The present application uses the substrate as an intermediate, and the thickness of the passivation film coated on the substrate is set to a nanoscale thickness (that is, the passivation film is very thin), avoiding the problem that when directly coating or spraying the passivation paste on the cut surface, the paste flows to the non-cut surface of the cell due to the large fluidity of the paste and the difficulty in controlling the relatively thick paste. At the same time, the process duration is short, ensuring that there is less diffusion of the passivation paste to the non-cut surface during the passivation process, and ensuring better performance of the solar cell.

[0094] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: The solar cell is formed by cutting a whole cell, and the solar cell has a cutting surface formed by cutting. The method comprises: providing a substrate; Applying a passivation slurry on the substrate to form a passivation film with a nanometer-scale thickness on the substrate; The passivation film on the substrate is transferred to the cut surface of the solar cell by a transfer process to form a passivation layer on the cut surface.

2. The method for preparing a solar cell according to claim 1, characterized in that: The thickness of the passivation film is 5nm-20nm, and the transfer process includes hot pressing transfer.

3. The method for preparing a solar cell according to claim 1, characterized in that: The passivation slurry includes a passivator and a solvent. After the passivation film on the substrate is transferred to the cut surface of the solar cell to form a passivation layer on the cut surface, the method further includes: The solar cell sheet having the passivation layer formed thereon is pre-dried at a temperature of 100° C. to 150° C. to remove the solvent.

4. The method for preparing a solar cell according to claim 3, characterized in that: After pre-drying the solar cell sheet having the passivation layer formed thereon at a temperature of 100° C. to 150° C., the method further comprises: The pre-dried solar cell is annealed at 400°C to 800°C.

5. The method for preparing a solar cell according to claim 4, characterized in that: The passivating agent includes aluminum oxide, the pre-drying time is 1 minute to 2 minutes, and the annealing time is 5 minutes to 20 minutes.

6. The method for preparing a solar cell according to claim 1, characterized in that: The flower basket has a plurality of independent flower basket structures, each of which is used to load the solar cell sheets in a one-to-one correspondence. Before the passivation slurry is coated on the substrate, the method further includes: A plurality of the solar cells are loaded one by one in the basket structure, and the cut surfaces of the solar cells are exposed.

7. The method for preparing a solar cell according to claim 2, characterized in that: The temperature of the hot pressing transfer is 100°C to 150°C.

8. The method for preparing a solar cell according to claim 1, characterized in that: Before transferring the passivation film on the substrate to the cut surface of the solar cell, the method further includes: providing a substrate having opposing first and second surfaces; forming a first doping layer, a first passivation film and a first anti-reflection film stacked in sequence on the first surface; forming a second doping layer, a second passivation film and a second anti-reflection film stacked in sequence on the second surface, wherein the doping type of the second doping layer is different from the doping type of the first doping layer; forming a first electrode on a surface of the first anti-reflection film away from the substrate; forming a second electrode on a surface of the second anti-reflection film away from the substrate to obtain the whole cell; The whole solar cell is cut to obtain the solar cell.

9. The method for preparing a solar cell according to claim 1, characterized in that: The material of the substrate includes at least one of the following: polyethylene terephthalate and polytetrafluoroethylene.

10. A battery cell, characterized in that: The cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 9, and the cell comprises: A solar cell sheet, wherein the solar cell sheet is formed by cutting a whole cell sheet, and the solar cell sheet has a cutting surface formed by cutting; A passivation layer is located on the cutting surface.

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