TOPCon solar cell, preparation method thereof and photovoltaic system

Abstract

The invention relates to the technical field of solar cells, and particularly provides a TOPCon solar cell, a preparation method thereof and a photovoltaic system. The method comprises the following steps: texturing a silicon substrate; the textured surface appearance of texturing comprises an inverted pyramid shape; preparing a boron diffusion layer and a passivation layer on the first surface of the textured silicon substrate; preparing a tunneling oxide layer and a crystalline silicon layer on the second surface of the textured silicon substrate; preparing a metal grid line on the surface of the passivation layer; carrying out laser sintering on the metal grid lines; the laser sintering comprises the following steps of: irradiating the metal grid line by adopting laser; the scanning path of the laser is that periodic up-and-down reciprocating scanning is carried out in the axial direction of the metal grid line. By setting the textured morphology of the inverted pyramid structure, the refractive index of the cell is increased, meanwhile, the scanning route of laser is regulated and controlled, an effective electron transmission path is established, the contact resistance is reduced, and the electrical performance of the cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly relates to a TOPCon solar cell, a preparation method thereof, and a photovoltaic system. Background Art

[0002] In recent years, the integrated development of various photovoltaic technologies has continuously improved the efficiency of industrial solar cells. The Tunnel Oxide Passivated Contact (TOPCon) solar cell has become the technology with the largest production capacity ratio at present due to its comprehensive advantages in cost and efficiency. The core processes include silicon wafer texturing and Laser-Enhanced Contact Optimization (LECO) technology. As a highly promising texturing process, the inverted pyramid texture structure can not only produce a uniform pyramid texture on the cell, but also can experience three times of antireflection incident light, which is extremely important for the upper limit of the subsequent solar cell efficiency. Laser-Enhanced Contact Optimization (LECO) is used as a post-firing treatment method to reduce the contact firing temperature, which can make the open-circuit voltage of TOPCon solar cells in industrial production higher, and at the same time, the fill factor value is also higher. At present, the application of LECO technology in TOPCon cell production lines has brought a battery efficiency gain of more than 0.2 percentage points, and theoretically, the efficiency improvement space can be increased by more than 0.5% at most. Therefore, it is particularly important to further optimize the LECO process and improve the matching TOPCon solar cells subsequently.

[0003] For TOPCon solar cells, the conventional inverted pyramid structure is easily affected by insufficient alkali solution reaction, and certain damage will occur at the upper edge part of the structure, thereby reducing the reflectivity of the cell. Laser-Enhanced Contact Optimization, as an alternative to the traditional sintering process, theoretically has great potential to effectively reduce the contact sintering temperature and improve the open-circuit voltage and higher fill factor of the cell. However, in the actual application of LECO, the best effect has not been achieved, and there are few studies on the optimization of the LECO laser scanning pattern. Therefore, there is an urgent need to develop an efficient crystalline silicon solar cell that can improve the comprehensive electrochemical performance of TOPCon solar cells. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the present invention is to provide a TOPCon solar cell, a preparation method thereof, and a photovoltaic system, by matching the inverted pyramid structure texturing process, regulating the laser scanning route, reducing the contact resistance, and improving the electrical performance of the TOPCon solar cell.

[0005] The first aspect of the present invention provides a method for preparing a TOPCon solar cell, comprising the following steps:

[0006] Texturize the silicon substrate; the surface texture of the texturization includes an inverted pyramid shape;

[0007] Prepare a boron diffusion layer and a passivation layer on the first surface of the texturized silicon substrate;

[0008] Prepare a tunneling oxide layer and a crystalline silicon layer on the second surface of the texturized silicon substrate;

[0009] Prepare metal grid lines on the surface of the passivation layer; perform laser sintering on the metal grid lines;

[0010] The laser sintering includes: irradiating the metal grid lines with a laser;

[0011] The scanning path of the laser is: performing periodic reciprocating scanning up and down along the axial direction of the metal grid line.

[0012] By optimizing the scanning path of the laser in the laser sintering, the present invention establishes an effective electron transport path, forms contact sites with uniform and moderate sizes, and has a small impact on the PN junction. Through the laser sintering treatment of the present application, the open-circuit voltage and energy conversion efficiency of the solar cell can be significantly improved, but there will be a loss of short-circuit current. To solve the problem of current loss, the inventor designs a surface texture with an inverted pyramid structure in the solar cell. The surface texture with an inverted pyramid structure can increase the refractive index of the cell. By coordinating the inverted pyramid surface texture and the new laser scanning path, the present invention can reduce the contact resistance while reducing the current loss, comprehensively improving the electrochemical performance of the TOPCon solar cell.

[0013] In some embodiments of the present invention, the bottom side length of the inverted pyramid is 100 - 300 nm, and the height of the tower is 120 - 180 nm. Thus, the light absorption efficiency of the inverted pyramid surface texture can be further improved, the generation of photo-generated carriers can be increased, and thus the short-circuit current of the cell can be improved.

[0014] In some embodiments of the present invention, the texturization includes: successively performing metal-assisted catalytic etching and alkaline etching on the silicon substrate to obtain a surface texture with an inverted pyramid shape.

[0015] In some embodiments of the present invention, the metal-assisted catalytic etching includes: depositing metal nanoparticles on the surface of the silicon substrate.

[0016] In some embodiments of the present invention, the raw materials for the alkaline etching include an alkaline substance and H2O2. The inverted pyramid surface texture prepared by the alkaline substance and H2O2 has a more uniform size distribution and can significantly reduce the reflectivity of the silicon wafer surface.

[0017] In some embodiments of the present invention, the cross-section of each scanning period is an isosceles trapezoid, with the upper base of the isosceles trapezoid being 20 - 400 μm in length, the lower base being 40 - 800 μm in length, and the height being 200 - 400 μm. The height of the isosceles trapezoid is perpendicular to the metal grid line, and the distance from the upper base of the isosceles trapezoid to the metal grid line is equal to the distance from the lower base to the metal grid line. Controlling the scanning period as an isosceles trapezoid can regulate the contact site size within a reasonable range while having a relatively small impact on the PN junction.

[0018] In some embodiments of the present invention, the laser power is 18 - 30 W. Optimizing the transmission speed facilitates precise control of the energy input in the sintering area, ensuring uniform fusion between the metal grid line and the silicon wafer, forming stable contact points, and further improving the photoelectric conversion efficiency of the solar cell.

[0019] In some embodiments of the present invention, the laser scanning speed is 1.5*10 4 -2*10 5 mm / s. Optimizing the transmission speed can ensure that the shape and depth of each contact point are consistent, improve the uniformity and yield of the cell, and can also control the sintering time to improve efficiency.

[0020] In some embodiments of the present invention, the temperature of the laser sintering is 850 - 900 °C. The temperature of 850 - 900 °C can effectively reduce the organic solvents and other additives in the metal grid line. At the same time, the high temperature can promote the alloying between the particles and the silicon wafer surface, form good ohmic contact, and reduce the contact resistance between the electrode and the silicon wafer.

[0021] In some embodiments of the present invention, the metal grid line includes fine grids and main grids; the laser sintering is performed on the fine grids. Laser sintering the fine grids can optimize the contact performance between the fine grids and the silicon wafer, thereby improving the photoelectric conversion efficiency of the cell.

[0022] In some embodiments of the present invention, the spacing of the fine grids is 400 - 1000 μm. By optimizing the spacing of the fine grid lines, the resistance loss during the lateral current transmission can be significantly reduced, the carrier collection efficiency can be improved, and the light absorption can be optimized.

[0023] In some embodiments of the present invention, the width of the fine grids is 2 - 20 μm, and the height is 2 - 10 μm. Optimizing the width of the fine grids can reduce the light shielding effect on the incident light, improving the light absorption efficiency of the cell. Controlling the height of the fine grids can improve the mechanical strength of the electrode and reduce the risk of fracture in subsequent processes (such as lamination and encapsulation).

[0024] The second aspect of the present invention provides a TOPCon solar cell prepared by the preparation method of the above TOPCon solar cell.

[0025] In a third aspect of the present invention, a photovoltaic system includes the TOPCon solar cell described above, and / or a TOPCon solar cell prepared by the method for preparing the above TOPCon solar cell.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0028] Figure 1 A schematic diagram of an inverted pyramid structure according to an embodiment of the present invention is shown;

[0029] Figure 2 A laser scanning route diagram according to an embodiment of the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. Wherever the same or similar reference numerals are used throughout, they denote the same or similar elements or elements having the same or similar functions. The embodiments described below by reference to the accompanying drawings are exemplary only for explaining the present application and should not be construed as limiting the present application. It should be noted that, without conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0031] It should be understood that when an element or layer is referred to as being "on...", "adjacent to...", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on...", "directly adjacent to...", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not imply that the present disclosure necessarily has a first element, component, region, layer, or part.

[0032] In this application, unless otherwise clearly specified or limited, terms such as "install", "connect", "link", "fix", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily 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 processes, methods, products, or devices.

[0034] The existing Laser-enhanced Contact Optimization (LECO) is to irradiate the laser parallelly but not in contact with the fine grid. Under the action of the bias voltage, the local laser beam generates local current, which causes rapid diffusion between silver and silicon in a short time to form silver-silicon alloy, reducing the contact resistance and increasing the fill factor and open-circuit voltage. However, the hot spots caused by laser heating usually damage the passivation layers including silicon nitride, alumina, etc. on the local silicon wafer. Therefore, the present invention optimizes the scanning path of the laser in laser sintering, establishes an effective electron transport path, forms contact sites with uniform and appropriate sizes, and has little influence on the PN junction. Through the laser sintering treatment of this application, the open-circuit voltage and energy conversion efficiency of the solar cell can be significantly improved, but it will cause a loss of short-circuit current. To solve the problem of current loss, the inventor designs a textured surface morphology with an inverted pyramid structure in the solar cell. The textured surface morphology with an inverted pyramid structure can increase the refractive index of the cell. The present invention can reduce the contact resistance while reducing the current loss by coordinating the inverted pyramid textured surface morphology and the new laser scanning path, comprehensively improving the electrochemical performance of the TOPCon solar cell.

[0035] The first aspect of the present invention provides a method for preparing a TOPCon solar cell, including the following steps:

[0036] S1. Texture the silicon substrate; the textured surface morphology includes an inverted pyramid shape. The inverted pyramid textured structure can increase the light absorption efficiency and improve the short - circuit current of the battery.

[0037] The inverted pyramid textured structure of the present invention enables the incident light to experience three reflections on the surface. Compared with the traditional forward pyramid structure (two reflections), it significantly reduces the light reflectivity, thereby improving the light absorption efficiency. In addition, the inverted pyramid textured structure has a stronger ability to absorb weak light: under scattered light or non - direct light conditions, the inverted pyramid texture shows better light trapping ability and is suitable for various lighting environments.

[0038] In some embodiments of the present invention, the silicon substrate can be textured on one side or both sides.

[0039] In some embodiments of the present invention, the bottom side length of the pyramid is 100 - 300 nm, and the height of the pyramid is 120 - 180 nm. As an example, the bottom side length can be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300 nm, and the height can be 120, 120, 130, 140, 150, 160, 170, 180 nm. Thereby, the light absorption efficiency of the inverted pyramid texture can be further improved, the generation of photo - carriers can be increased, and the short - circuit current of the battery can be improved.

[0040] In some embodiments of the present invention, the texturing includes: successively performing metal - assisted catalytic etching and alkaline etching on the silicon substrate to obtain an inverted pyramid - shaped textured surface morphology. Metal - assisted catalytic etching can achieve precise control of the textured surface morphology.

[0041] In some embodiments of the present invention, the metal - assisted catalytic etching includes: depositing metal nanoparticles on the surface of the silicon substrate.

[0042] In some embodiments of the present invention, the metal nanoparticles include one or more of gold nanoparticles, silver nanoparticles, and copper nanoparticles.

[0043] The present invention has no special requirements for the method of depositing metal nanoparticles. In some embodiments of the present invention, the metal nanoparticles can be deposited on the surface of the silicon substrate by sputtering, evaporation, or electroless plating.

[0044] In some embodiments of the present invention, the raw materials for the alkaline etching include an alkaline substance and H2O2. The inverted pyramid texture prepared by the alkaline substance and H2O2 has a more uniform size distribution and can significantly reduce the reflectivity of the silicon wafer surface.

[0045] In some embodiments of the present invention, the alkaline substance includes one or more of sodium hydroxide and potassium hydroxide.

[0046] In some embodiments of the present invention, the concentration of the alkaline substance is 1-5 wt%. As an example, when the alkaline substance is a potassium hydroxide solution, the concentration of sodium hydroxide in the potassium hydroxide solution can be 1, 2, 3, 4, or 5 wt%.

[0047] In some embodiments of the present invention, H2O2 is preferably used in the form of a solution, and the content of H2O2 in the H2O2 solution is 0.1-0.8 wt%. As an example, the content of H2O2 in the H2O2 solution can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8 wt%.

[0048] In some embodiments of the present invention, before texturing the silicon substrate, the silicon substrate is pre-cleaned. Pre-cleaning can effectively remove impurities and particles on the surface of the silicon wafer, improve the surface cleaning quality, thereby improving the uniformity of the inverted pyramid structure textured surface morphology, and further improving the overall electrochemical performance of the battery.

[0049] In some embodiments of the present invention, one or more of water, acetone, and ethanol can be selected for pre-cleaning.

[0050] S2. Prepare a boron diffusion layer and a passivation layer on the first surface of the textured silicon substrate.

[0051] In some embodiments of the present invention, at 800-1100 °C, a boron source is used to perform boron diffusion on the front side of the textured silicon wafer to form a PN junction and obtain a boron diffusion layer.

[0052] In some embodiments of the present invention, after forming the boron diffusion layer, the silicon substrate is sequentially oxidized and de-borosilicate glass treated.

[0053] In some embodiments of the present invention, the oxidation is carried out at 800-1000 °C. High-temperature oxidation can promote the PN junction to reduce the surface concentration.

[0054] In some embodiments of the present invention, HF is used to remove borosilicate glass.

[0055] In some embodiments of the present invention, the passivation layer includes an alumina layer. The alumina layer can be prepared by atomic layer deposition, plasma-enhanced chemical vapor deposition, or low-pressure chemical vapor deposition.

[0056] In some embodiments of the present invention, the passivation layer further includes a silicon nitride layer; the silicon nitride layer is provided on the side of the alumina layer away from the boron diffusion layer.

[0057] S3. Prepare a tunneling oxide layer and a crystalline silicon layer on the second surface of the textured silicon substrate.

[0058] In some embodiments of the present invention, the tunneling oxide layer and the crystalline silicon layer can be formed by any one of atmospheric pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, and physical vapor deposition.

[0059] In some embodiments of the present invention, S3 further includes: performing phosphorus diffusion and annealing treatment on the surface of the crystalline silicon layer. Phosphorus diffusion forms an N+ layer (N-type semiconductor layer) on the back surface of the silicon wafer having the crystalline silicon layer, and phosphorus doping is performed to form a passivated contact structure.

[0060] In some embodiments of the present invention, POCl3 can be used as the phosphorus source for phosphorus diffusion.

[0061] In some embodiments of the present invention, the annealing temperature is 900 - 1000 °C, and the annealing time is 1 - 5 min.

[0062] S4. Prepare metal gate lines on the surface of the passivation layer; perform laser sintering on the metal gate lines;

[0063] The laser sintering includes: irradiating the metal gate lines with a laser;

[0064] The scanning path of the laser is: performing periodic up and down reciprocating scanning along the axial direction of the metal gate lines.

[0065] In some embodiments of the present invention, the cross-section of each scanning period is an isosceles trapezoid. The upper base length of the isosceles trapezoid is 20 - 400 μm, the lower base length is 40 - 800 μm, the height is 200 - 400 μm. The height of the isosceles trapezoid is perpendicular to the metal gate lines, and the distance from the upper base to the metal gate lines is equal to the distance from the lower base to the metal gate lines. Controlling the scanning period as an isosceles trapezoid can adjust the contact site size within a reasonable range and have a relatively small impact on the PN junction.

[0066] In some embodiments of the present invention, by way of example, the upper base length of the isosceles trapezoid can be 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400 μm, the lower base length can be 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800 μm, and the height can be 200, 250, 300, 350, 400 μm.

[0067] In some preferred embodiments of the present invention, the upper base length of the isosceles trapezoid is 200 - 400 μm, the lower base length is 400 - 800 μm, and the height is 200 - 300 μm.

[0068] In some embodiments of the present invention, the metal grid line includes a fine grid and a main grid; the fine grid is subjected to the laser sintering.

[0069] In some embodiments of the present invention, the method for preparing the metal grid line can be selected from one or more of screen printing, laser transfer printing, and steel plate printing. The paste used for preparing the metal grid line is a silver paste. It is possible to select to prepare the metal grid line on the front or back of the TOPCon solar cell, or it is also possible to select to prepare the metal grid line on both the front and back of the TOPCon solar cell simultaneously. Prepare the metal grid line as needed, and then send it to the sintering process.

[0070] In some embodiments of the present invention, the laser power is 18 - 30 W. As an example, the power of the laser can be 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 W. Optimizing the transmission speed facilitates precise control of the energy input in the sintering area, ensures uniform fusion between the metal grid line and the silicon wafer, forms stable contact points, and further improves the photoelectric conversion efficiency of the solar cell.

[0071] In some embodiments of the present invention, the laser scanning speed is 1.5×10 4 -2×10 5 mm / s. As an example, the laser scanning speed can be 1.5×10 4 、2×10 4 、2.5×10 4 、3×10 4 、3.5×10 4 、4×10 4 、4.5×10 4 、5×10 4 、5.5×10 4 、6×10 4 、6.5×10 4 、7×10 4 、7.5×10 4 、8×10 4 、8.5×10 4 、9×10 4 、1×10 5 、1.5×10 5 、2×10 5 mm / s. Optimizing the transmission speed can ensure that the shape and depth of each contact point are consistent, improve the uniformity and yield of the cell, and can also control the sintering time and improve the efficiency.

[0072] In some embodiments of the present invention, the depth of the laser etching is 1-5 μm. As an example, the depth of the laser etching can be 1, 2, 3, 4, 5 μm. An appropriate sintering depth can ensure a good ohmic contact between the metal grid lines (such as silver paste) and the silicon wafer, reduce the contact resistance, and thus improve the photoelectric conversion efficiency of the solar cell.

[0073] In some embodiments of the present invention, the number of laser processing times is 1-5 times, and the scanning texture ratio is 30%-60%. As the number of laser processing times increases, the scanning texture ratio gradually increases. As an example, the number of laser processing times can be 1, 2, 3, 4, 5 times; the scanning texture ratio can be 30%, 35%, 40%, 45%, 50%, 55%, 60%.

[0074] In some embodiments of the present invention, the temperature of the laser sintering is 850-900 °C. As an example, the temperature of the laser sintering can be 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C. The temperature of 850-900 °C can effectively reduce the organic solvents and other additives in the metal grid lines. At the same time, the high temperature can promote the alloying of the particles and the surface of the silicon wafer, form a good ohmic contact, and reduce the contact resistance between the electrode and the silicon wafer.

[0075] In some embodiments of the present invention, the pitch of the fine grid is 400-1000 μm. As an example, the pitch of the fine grid can be 400, 500, 600, 700, 800, 900, 1000 μm. By optimizing the pitch of the fine grid lines, the resistance loss during the lateral current transmission can be significantly reduced, the carrier collection efficiency can be improved, and the light absorption can be optimized.

[0076] In some preferred embodiments of the present invention, the pitch of the fine grid is 600-1000 μm.

[0077] In some embodiments of the present invention, the width of the fine grid is 2-20 μm, and the height is 2-10 μm. As an example, the width of the fine grid can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 μm; the height of the fine grid can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 μm. Optimizing the width of the fine grid can reduce the light shielding of the incident light and improve the light absorption efficiency of the battery. Controlling the height of the fine grid can improve the mechanical strength of the electrode and reduce the risk of fracture in subsequent processes (such as lamination and encapsulation).

[0078] In some embodiments of the present invention, the laser sintering further includes: applying a deflection voltage to the metal grid line when irradiating the metal grid line with a laser.

[0079] In some embodiments of the present invention, the deflection voltage is 12 - 18V. As an example, the deflection voltage can be 12, 13, 14, 15, 16, 17, 18V. In the laser sintering process of TOPCon solar cells, irradiating the metal grid line with a laser and applying a deflection voltage of 12 - 18V to the metal grid line can, through the action of an electric field, accelerate the mutual diffusion of metal atoms and silicon atoms, reduce the contact resistance, and thus improve the conversion efficiency of the battery.

[0080] The second aspect of the present invention provides a TOPCon solar cell prepared by the preparation method of the above TOPCon solar cell.

[0081] The third aspect of the present invention is a photovoltaic system, including the above TOPCon solar cell, and / or a TOPCon solar cell prepared by the preparation method of the above TOPCon solar cell.

[0082] The solutions of the present disclosure will be explained below in conjunction with embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. For those without specific techniques or conditions noted in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0083] Example 1

[0084] The preparation method of the TOPcon solar cell in this example includes the following steps:

[0085] (1) Pre - cleaning: The silicon wafer with a thickness of 150μm is cleaned on both sides. It is cleaned with deionized water, acetone, deionized water, absolute ethanol, and deionized water for 10 minutes respectively to remove impurities on the surface of the silicon wafer.

[0086] (2) Texturing:

[0087] The pre - cleaned silicon wafer is placed in a texturing tank for metal - assisted catalytic etching (MACE) treatment of the silicon wafer: Using metal silver nanoparticles as a catalyst, silver nanoparticles are deposited on the surface of the silicon wafer by sputtering, and then the silicon wafer is treated with a mixed solution of 1wt% KOH and 0.2wt% H2O2 for 3 minutes, and local corrosion is carried out anisotropically to form an inverted pyramid texture structure. Then, a mixture of nitric acid and deionized water is used to clean for 20 minutes to remove residues on the surface of the silicon wafer. The inverted pyramid texture structure is as Figure 1As shown, the bottom side length of the inverted pyramid is 200 nm and the height of the pyramid is 160 nm.

[0088] (3) Boron diffusion: Using BCl3 as the boron source, the diffusion temperature is 1100 °C and the time is 20 minutes. Boron diffusion is carried out on the front side of the textured silicon wafer to form a PN junction, and the boron-diffused silicon wafer is obtained.

[0089] (4) Oxidation: The boron-diffused silicon wafer is oxidized. The oxidation temperature is set at 920 °C and the time is 2 h, and the oxidized silicon wafer is obtained.

[0090] (5) Removal of BSG: The boron-silicate glass (BSG) on the back and around the silicon wafer obtained in step (4) is removed by chain HF cleaning. The HF concentration by volume is 30%.

[0091] (6) Poly deposition: At 700 °C, a tunneling oxide layer and a polysilicon layer are deposited on the back of the silicon wafer obtained in step (5).

[0092] (7) Phosphorus diffusion and annealing: Using POCl3 as the phosphorus source, an N+ layer is formed on the back of the silicon wafer obtained in step (6) for phosphorus doping to form a passivated contact structure, and the passivated silicon wafer is obtained. Then, the passivated silicon wafer is annealed. The annealing temperature is 900 °C and the annealing time is 2 min.

[0093] (8) Post-cleaning: The silicon wafer obtained in step (7) is subjected to RCA (Radio Corporation of America Clean) cleaning to remove surface residues.

[0094] (9) Deposition of an alumina layer: Using trimethylaluminum and water as gas sources, an alumina layer with a thickness of 5 nm is deposited on the front of the silicon wafer obtained in step (8) by atomic layer deposition.

[0095] (10) Preparation of a silicon nitride layer: Deposition is carried out on the surface of the alumina layer using silane and ammonia as gas sources to form a silicon nitride layer.

[0096] (11) Screen printing: Print silver paste on the front side of the silicon wafer obtained in step (10) to form metal grid lines, dry at 80 °C, and cure the metal grid lines. The metal grid lines include fine grids and main grids; the spacing of the fine grids is 600 μm, the width is 2 μm, and the height is 2 μm. Use laser-assisted sintering for the fine grids, specifically including: irradiate the metal grid lines with a laser at 850 °C and apply a deflection voltage of 15 V to the metal grid lines to sinter the fine grids; the laser scanning speed is 15000 mm / s, the deflection voltage is 12 V, the laser power is 18 W, the number of laser processing times is 1 time, the scanning texture ratio is 30%, the depth of laser etching is 1 μm, and the laser scanning path is: perform periodic up-and-down reciprocating scanning along the axis of the fine grid. The cross-section of each scanning cycle is an isosceles trapezoid. As Figure 2 shown, the upper base length of the isosceles trapezoid is 100 μm, the lower base length is 200 μm, and the height is 300 μm. The height of the isosceles trapezoid is perpendicular to the fine grid, and the distance from the upper base of the isosceles trapezoid to the fine grid is equal to the distance from the lower base to the fine grid; after the laser-assisted sintering is completed, a TOPcon solar cell is obtained.

[0097] Comparative Example 1

[0098] The preparation method of the TOPcon solar cell in this comparative example is different from that of Example 1 in that: in the preparation process of this comparative example, the step of metal-assisted catalytic etching (MACE) treatment is omitted, and a silicon wafer is directly treated with a mixed solution of KOH with a concentration of 1 wt% and H2O2 with a concentration of 0.2 wt% to form a positive pyramid texture structure; the remaining steps are carried out according to the method in Example 1.

[0099] Comparative Example 2

[0100] The preparation method of the TOPcon solar cell in this comparative example is different from that of Example 1 in that: in this comparative example, the laser scanning path in step (11) is adjusted to a conventional parallel scan to the fine grid (the distance between the laser and the nearest fine grid is 5 μm), and the remaining steps are carried out according to the method in Example 1.

[0101] Comparative Example 3

[0102] The preparation method of the TOPcon solar cell in this comparative example is different from that of Example 1 in that: in the preparation process of this comparative example, the step of metal-assisted catalytic etching (MACE) treatment is omitted, and a silicon wafer is directly treated with a mixed solution of KOH with a concentration of 1 wt% and H2O2 with a concentration of 0.2 wt% to form a positive pyramid texture structure; the laser scanning path in step (11) is adjusted to a conventional parallel scan to the fine grid (the distance between the laser and the nearest fine grid is 5 μm), and the remaining steps are carried out according to the method in Example 1.

[0103] Example 2

[0104] The preparation method of the TOPcon solar cell in this embodiment is only different from that in Embodiment 1 in that: in this embodiment, the concentration of the H2O2 solution in step (2) is adjusted to 0.4 wt%, and the time is adjusted to 2 min. The remaining steps are carried out according to the method in Embodiment 1.

[0105] Embodiment 3

[0106] The preparation method of the TOPcon solar cell in this embodiment is only different from that in Embodiment 1 in that: in this embodiment, the concentration of the H2O2 solution in step (2) is adjusted to 0.6 wt%, and the time is adjusted to 2 min. The remaining steps are carried out according to the method in Embodiment 1.

[0107] Embodiment 4

[0108] The preparation method of the TOPcon solar cell in this embodiment is only different from that in Embodiment 1 in that: in this embodiment, the upper base length of the isosceles trapezoid is adjusted to 20 μm, the lower base length is adjusted to 40 μm, and the height is 200 μm. The remaining steps are carried out according to the method in Embodiment 1.

[0109] Test Example

[0110] IV tests were carried out on the TOPcon solar cells obtained in Embodiment 1 and Comparative Examples 1 and 2. The IV tests were carried out according to the standard of IEC.60904-9.2020, Third Edition. The test results are shown in Table 1. In Table 1, Eta refers to the photoelectric conversion efficiency of the cell, Voc refers to the open-circuit voltage of the solar cell, Isc refers to the short-circuit current, and FF refers to the fill factor.

[0111] Table 1

[0112] Eta(%) Voc(V) Isc(mA) FF(%) Example 1 26.87 0.73448 18.539 87.02 Comparative Example 1 26.80 0.73451 18.507 86.94 Comparative Example 2 26.77 0.73368 18.545 86.77 Comparative Example 3 26.73 0.73440 18.516 86.68

[0113] As can be seen from Table 1, the TOPcon solar cell obtained by using Embodiment 1 of the present invention has both a high photoelectric conversion efficiency and a fill factor.

[0114] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", "some implementation manners" or "some examples" means that the specific features, structures, materials or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0115] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that: The following steps are involved: The silicon substrate is textured; the textured surface morphology includes an inverted pyramid shape; Prepare a boron diffusion layer and a passivation layer on the first surface of the silicon substrate after texturing; Preparing a tunneling oxide layer and a crystalline silicon layer on the second surface of the textured silicon substrate; Preparing metal grid lines on the surface of the passivation layer; and performing laser sintering on the metal grid lines; The laser sintering comprises: irradiating the metal grid line with laser; The scanning path of the laser is: periodically scanning up and down along the axial direction of the metal grid line.

2. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The side length of the base of the inverted pyramid is 100-300 nm, and the height of the pyramid is 120-180 nm.

3. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The texturing comprises: performing metal-assisted catalytic etching and alkaline etching on the silicon substrate in sequence to obtain an inverted pyramid-shaped texturing surface morphology.

4. The method for preparing a TOPCon solar cell according to claim 3, characterized in that: The metal-assisted catalytic etching comprises: depositing metal nanoparticles on the surface of the silicon substrate.

5. The method for preparing a TOPCon solar cell according to claim 3, characterized in that: The raw materials for the alkaline etching include alkaline substances and H2O2.

6. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The cross section of each scanning cycle is an isosceles trapezoid, the upper base of the isosceles trapezoid is 20-400μm long, the lower base is 40-800μm long, and the height is 200-400μm. The height of the isosceles trapezoid is perpendicular to the metal grid line, and the distance from the upper base of the isosceles trapezoid to the metal grid line is equal to the distance from the lower base to the metal grid line.

7. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The laser power is 18-30W; And / or, the laser scanning speed is 1.5*10 4 -2*10 5 mm / s; And / or, the laser sintering temperature is 850-900°C.

8. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The metal grid line includes a fine grid and a main grid; the fine grid is subjected to laser sintering; Optionally, the spacing of the fine grid is 400-1000 μm; Optionally, the fine grid has a width of 2-20 μm and a height of 2-10 μm.

9. A TOPCon solar cell produced by the method for producing a TOPCon solar cell according to any one of claims 1 to 8.

10. A photovoltaic system, characterized in that: A TOPCon solar cell prepared by the method for preparing a TOPCon solar cell according to any one of claims 1 to 8, and / or a TOPCon solar cell according to claim 9.

Images