Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention belongs to the field of solar cells. The invention provides a solar cell, a preparation method thereof and a photovoltaic module. The method comprises the following steps that a substrate is provided, the substrate comprises a first surface, a second surface and a plurality of end faces, the first surface and the second surface are oppositely arranged, the end faces surround the first surface and the second surface, and the first surface and the second surface are suede surfaces respectively and independently; depositing boron-doped amorphous silicon on the first surface by adopting a plasma enhanced chemical deposition mode to obtain a boron-doped amorphous silicon layer; performing crystallization treatment on the boron-doped amorphous silicon layer so as to convert amorphous silicon in the boron-doped amorphous silicon layer into polycrystalline silicon and obtain a boron-doped layer; performing removal treatment on the substrate with the boron-doped layer to remove the silicon oxide layers on the end face and the second surface; and growing a tunneling oxide layer on the second surface of the removed object. The solar cell prepared by the method has a relatively good double-sided rate.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] At present, TOPCon (tunneling oxide passivation contact) solar cells and modules are widely welcomed by the market, and with the improvement of TOPCon cell efficiency and the reduction of amorphous silicon cost, the product advantages of TOPCon cells are becoming more and more obvious. However, the profit of PERC (emitter and rear passivation) cells is decreasing, so the market direction of upgrading PERC cell workshops to TOPCon is gradually becoming clear.

[0003] At present, there are two main routes for TOPCon cells in the market. The first one is texturing, front side doping, back side wrap-around etching, back side in-situ doping, back side crystallization annealing, front side wrap-around etching, front side aluminum oxide passivation, front side anti-reflection film deposition, back side anti-reflection film deposition, front and back side screen printing and sintering, and light injection; the second one is texturing, front side doping, back side wrap-around etching, back side polysilicon deposition, back side phosphorus diffusion, front side wrap-around etching, front side aluminum oxide passivation, front side anti-reflection film deposition, back side anti-reflection film deposition, front and back side screen printing and sintering, and light injection.

[0004] However, the bifaciality of TOPCon cells prepared by these methods is at a low level. Therefore, it is urgent to propose a method to improve the bifaciality of cells.

[0005] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0006] The embodiments of the present application provide a solar cell and a method for preparing the same, and a photovoltaic module to solve or alleviate one or more of the technical problems mentioned above.

[0007] According to a first aspect of an embodiment of the present application, a method for preparing a solar cell is proposed, comprising the following steps: providing a substrate, the substrate comprising a first surface and a second surface arranged opposite to each other and a plurality of end faces surrounding the first surface and the second surface, the first surface and the second surface being independently velvet surfaces; depositing boron-doped amorphous silicon on the first surface by plasma enhanced chemical deposition to obtain a boron-doped amorphous silicon layer; crystallizing the boron-doped amorphous silicon layer to convert the amorphous silicon in the boron-doped amorphous silicon layer into polycrystalline silicon and obtain a boron-doped layer; performing a removal treatment on the substrate having the boron-doped layer to remove the silicon oxide layer on the end faces and the second surface; and growing a tunneling oxide layer on the second surface of the product obtained by the removal treatment.

[0008] The method of the embodiment of the present application can obtain a solar cell with a high bifaciality. This is because the substrate is textured on both sides (the first surface and the second surface are arranged oppositely), and the first surface of the substrate is precisely deposited by plasma enhanced chemical deposition, that is, boron-doped amorphous silicon is deposited almost only on the first surface of the substrate, and there is almost no boron-doped amorphous silicon on the second surface and the end surface of the substrate; the amorphous silicon is converted into polycrystalline silicon during the crystallization process to obtain a boron-doped layer; and then the substrate with the boron-doped layer is removed to remove the silicon oxide layer on the end surface and the second surface of the substrate, and a tunneling oxide layer is formed on the second surface after the removal process. In this process, the second surface is treated to remove the silicon oxide layer, which almost does not damage the velvet surface of the second surface, that is, the velvet layer of the second surface is retained. In this way, the solar cell obtained after the tunneling oxide layer is formed on the second surface can reflect and refract the incident light multiple times on its back side (second surface), so as to improve the photoelectric conversion efficiency of the back side of the battery, thereby improving the bifaciality of the solar cell. In addition, the method of the present application does not require etching and polishing. On the one hand, it can save the cost of chemical solutions and reduce the process of preparing solar cells, thereby reducing the process time; on the other hand, the absence of etching and polishing steps can also greatly reduce the risk of battery leakage.

[0009] According to an embodiment of the present application, the method also includes: forming a phosphorus-doped layer on a side of the tunneling oxide layer away from the substrate; performing wrap-around etching on the product obtained by forming the phosphorus-doped layer to remove the phosphosilicate glass layer; forming a passivation layer on a side of the boron-doped layer of the product obtained by wrap-around etching away from the substrate; and independently forming an anti-reflection layer on a side of the passivation layer away from the boron-doped layer and on a side of the phosphorus-doped layer away from the tunneling oxide layer to obtain a solar cell.

[0010] According to an embodiment of the present application, the temperature of the plasma enhanced chemical deposition is 100-300°C.

[0011] According to an embodiment of the present application, the process gas of the plasma enhanced chemical deposition includes a first gas and a second gas, the first gas includes silane, and the second gas includes borane and / or diborane.

[0012] According to an embodiment of the present application, the crystallization treatment method includes annealing oxidation, laser induced annealing or laser induced oxidation.

[0013] According to an embodiment of the present application, the annealing oxidation includes an oxidation stage and a crystallization stage, the temperature of the crystallization stage is 700-1000°C, and the temperature of the oxidation stage is 900-1200°C.

[0014] According to an embodiment of the present application, the removal treatment is chain pickling using HF solution.

[0015] According to an embodiment of the present application, the concentration of HF is 10-30wt%.

[0016] According to an embodiment of the present application, the thickness of the boron doped layer is 30-200 nm.

[0017] According to an embodiment of the present application, the thickness of the passivation layer is 3-10 nm.

[0018] According to an embodiment of the present application, the thickness of the phosphorus-doped layer is 50-300 nm.

[0019] According to an embodiment of the present application, the thickness of the tunnel oxide layer is 1-2 nm.

[0020] According to an embodiment of the present application, the thickness of the anti-reflection layer is 25-40 nm.

[0021] The second aspect of the embodiment of the present application provides a solar cell. The solar cell includes a substrate, the substrate includes a first surface and a second surface arranged opposite to each other and a plurality of end faces surrounding the first surface and the second surface, the first surface and the second surface are respectively and independently velvet; a boron-doped layer, the boron-doped layer is located on the first surface of the substrate, and a tunneling oxide layer, the tunneling oxide layer is located on the second surface of the substrate. The cell has a good bifaciality. This is because the substrate of the cell is a double velvet substrate, which effectively reduces the local leakage of the cell itself and also improves the passivation effect of the cell, thereby improving the photoelectric performance of the cell, and thus making the solar cell show a better bifaciality.

[0022] According to an embodiment of the present application, the solar cell further includes: a passivation layer, the passivation layer is located on a side of the boron-doped layer away from the substrate; a phosphorus-doped layer, the phosphorus-doped layer is located on a side of the tunneling oxide layer away from the substrate; an anti-reflection layer, an anti-reflection layer is provided on a side of the phosphorus-doped layer away from the tunneling oxide layer and a side of the passivation layer away from the boron-doped layer.

[0023] According to an embodiment of the present application, the bifaciality of the solar cell is 90%-96%.

[0024] In a third aspect of the embodiments of the present application, a photovoltaic component is provided, wherein the photovoltaic component includes the solar cell according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0026] Figure 1 is a schematic diagram of a process for preparing a solar cell in some embodiments; Figure 2 Schematic diagram of the structure of solar cells in some embodiments.

[0027] Reference numerals: 1: substrate; 2: boron-doped amorphous silicon layer; 3: silicon oxide layer; 4: boron-doped layer; 5: passivation layer; 6: anti-reflection layer; 7: tunneling oxide layer; 8: phosphorus-doped layer; 9: metal electrode. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers, regions, elements and their relative sizes may be exaggerated. Wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0029] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can 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. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. When the second element, component, region, layer or part is discussed, it does not indicate that the present application necessarily has the first element, component, region, layer or part.

[0030] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0033] According to a first aspect of an embodiment of the present application, there is provided a method for preparing a solar cell, comprising the following steps: (1) providing a substrate, the substrate comprising a first surface and a second surface arranged opposite to each other and a plurality of end surfaces surrounding the first surface and the second surface, the first surface and the second surface being independently velvet surfaces; (2) depositing boron-doped amorphous silicon on the first surface by plasma enhanced chemical deposition to obtain a boron-doped amorphous silicon layer; (3) performing a crystallization treatment on the boron-doped amorphous silicon layer to convert the amorphous silicon in the boron-doped amorphous silicon layer into polycrystalline silicon and obtain a boron-doped layer; (4) performing a removal treatment on the substrate having the boron-doped layer to remove the silicon oxide layer on the end surface and the second surface of the substrate; and (5) growing a tunneling oxide layer on the second surface of the product obtained by the removal treatment.

[0034] The method of the embodiment of the present application can obtain a solar cell with a high bifaciality. This is because the substrate is textured on both sides (the first surface and the second surface are arranged oppositely), and the first surface of the substrate is precisely deposited by plasma enhanced chemical deposition, and boron-doped amorphous silicon is deposited almost only on the first surface of the substrate, and there is almost no boron-doped amorphous silicon on the second surface and the end surface of the substrate; the amorphous silicon is converted into polycrystalline silicon during the crystallization process to obtain a boron-doped layer; and then the substrate with the boron-doped layer is removed to remove the silicon oxide layer on the end surface and the second surface of the substrate, and a tunneling oxide layer is formed on the second surface after the removal process. In this process, the second surface is treated to remove the silicon oxide layer, which will hardly damage the velvet surface of the second surface, that is, the velvet layer of the second surface is retained. In this way, the solar cell obtained after the tunneling oxide layer is formed on the second surface can reflect and refract the incident light multiple times on its back side (second surface), so as to improve the photoelectric conversion efficiency of the back side of the battery, thereby improving the bifaciality of the solar cell. In addition, the method of the present application does not require etching and polishing. On the one hand, it can save the cost of chemical solutions and reduce the process of preparing solar cells, thereby reducing the process time; on the other hand, the absence of etching and polishing steps can also greatly reduce the risk of battery leakage.

[0035] In some embodiments, the solar cell comprises a TOPCon cell.

[0036] According to the embodiments of the present application, reference Figure 1 In step (1), a substrate 1 is provided. The substrate includes a first surface and a second surface arranged opposite to each other and a plurality of end surfaces surrounding the first surface and the second surface, and the first surface and the second surface are independently velvet. In some embodiments, the substrate 1 includes an N-type silicon wafer.

[0037] In some embodiments, the first surface and the second surface of the substrate are made into a velvet surface by a velvet cleaning method. The velvet cleaning method can also remove dirt and metal impurities on the surface of the substrate, remove the mechanical damage layer of the substrate generated during the cutting process, reduce the recombination center, and then form an undulating velvet surface to increase the absorption rate of photons.

[0038] Optionally, the pile height is 0.5 μm-3 μm.

[0039] According to the embodiments of the present application, reference Figure 1 In step (2), a boron-doped amorphous silicon layer 2 is prepared. In this step, boron-doped amorphous silicon is deposited on the first surface by plasma enhanced chemical deposition to obtain a boron-doped amorphous silicon layer. The first surface of the substrate is precisely deposited by plasma enhanced chemical deposition, that is, the boron-doped amorphous silicon is deposited almost only on the first surface of the substrate, and the second surface and end surface of the substrate are almost free of boron-doped amorphous silicon.

[0040] In some embodiments, in step (2), the temperature of plasma enhanced chemical deposition is 100-300° C., such as 100° C., 200° C., 300° C., etc. In this way, the growth rate of the obtained boron-doped amorphous silicon layer is uniform during the film formation process, and the obtained boron-doped amorphous silicon layer has good uniformity and stability.

[0041] In some embodiments, in step (2), the process gas for boron-doped amorphous silicon includes a first gas and a second gas, wherein the first gas includes silane, and the second gas includes borane and / or diborane.

[0042] In some embodiments, in step (2), the plasma enhanced chemical deposition device is a plate-type PEVCD. The plate-type PEVCD device has less wrap-around plating on the second surface.

[0043] According to the embodiments of the present application, reference Figure 1 In step (3), crystallization treatment is performed. In this step, the boron-doped amorphous silicon layer is crystallized to convert the amorphous silicon in the boron-doped amorphous silicon layer into polycrystalline silicon, and a boron-doped layer is obtained.

[0044] In some embodiments, reference Figure 1 During the crystallization process, a silicon oxide layer 3 is also formed on the surface of the boron-doped layer and the end face and second surface of the substrate.

[0045] In some embodiments, in step (3), the crystallization treatment includes annealing oxidation, laser induced annealing or laser induced oxidation.

[0046] In some embodiments, in step (3), the annealing oxidation includes a crystallization stage and an oxidation stage. The annealing oxidation is performed in a tube furnace, and the crystallization stage and the oxidation stage can be completed in the same equipment, and the conditions are easy to control.

[0047] Optionally, the temperature of the crystallization stage is 700-1000° C., such as 700° C., 800° C., 900° C., 1000° C., etc. In this way, in the process of converting amorphous silicon to polycrystalline silicon, internal defects of the crystal can be reduced and the crystallization effect can be improved.

[0048] Optionally, the temperature of the oxidation stage is 900-1200° C., such as 900° C., 1000° C., 1100° C., 1200° C., etc. In this way, defects inside the boron-doped layer are reduced while forming a boron-doped layer of moderate thickness.

[0049] In some embodiments, in step (3), the thickness of the boron-doped layer is 70-200 nm, for example, 70 nm, 100 nm, 130 nm, 160 nm, 200 nm, etc.

[0050] According to the embodiments of the present application, reference Figure 1 In step (4), the silicon oxide layer 3 on the end face and the second surface of the substrate is removed. In this step, the second surface does not need to be polished, that is, the suede layer on the second surface is retained, which can increase the absorption of incident light by the back side (second surface), thereby improving the bifaciality of the solar cell.

[0051] In some embodiments, the removal process is chain pickling with HF solution, so that only the silicon oxide layer on the end face and the second surface of the substrate is removed, and the suede layer on the second surface is retained, so as to enhance the absorption of photons by the substrate and reduce the probability of recombination of surface dangling bonds on the second surface of the substrate.

[0052] Optionally, the concentration of HF is 10-30wt%, for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, etc.

[0053] According to an embodiment of the present application, in step (5), a tunneling oxide layer is prepared. In this step, a tunneling oxide layer is grown on the second surface of the product obtained after the removal treatment. The tunneling oxide layer can provide a tunneling channel, selectively pass electrons, and form an interface chemical passivation to prevent excessive phosphorus in the N-type doped layer (phosphorus doped layer) from entering the silicon wafer.

[0054] In some embodiments, the method further includes: in step (6), forming an N-type doped layer (phosphorus doped layer).

[0055] In some embodiments, the tunneling oxide layer and the phosphorus-doped layer are formed by in-situ doping followed by recrystallization annealing, or by amorphous silicon deposition followed by phosphorus diffusion.

[0056] Optionally, the conditions for forming a tunneling oxide layer and an N-type doped layer (phosphorus-doped layer) by first depositing amorphous silicon and then diffusing phosphorus include: using LPCVD equipment to grow a tunneling oxide layer and an intrinsic amorphous silicon layer (a-Si) on the second surface of the substrate at a temperature of 400-650°C, wherein the thickness of the tunneling oxide layer is 1-2nm, and the thickness of the phosphorus-doped layer is 50-300nm.

[0057] Optionally, phosphorus diffusion is to load the silicon wafer after amorphous silicon deposition into a tubular phosphorus diffusion furnace tube, using POCl 3 Phosphorus is diffused and annealed on the back of the battery by diffusion, and a phosphorus-doped polysilicon layer and a phosphorus-silicon glass layer are formed on the back.

[0058] Optionally, the conditions for forming a tunneling oxide layer and a phosphorus-doped layer by first performing in-situ doping and then performing crystallization annealing include: using an electric field to ionize nitrous oxide to form a plasma gas, which then reacts with silicon to form a tunneling oxide layer, and then using PEVCD (enhanced plasma deposition) to introduce silane and phosphine to react, and in-situ doping to form a phosphorus-doped layer, wherein the thickness of the tunneling oxide layer is 1-2nm, and the thickness of the phosphorus-doped layer is 50-300nm.

[0059] In some embodiments, the method further comprises: step (7): wrap-around etching. In this step, wrap-around etching is performed on the product obtained by forming the phosphorus-doped layer to remove the phosphorus-silicate glass layer.

[0060] Optionally, the wrap-around etching includes sequentially performing the steps of pickling, washing, pre-dehydration and drying, wherein the pickling is performed with hydrofluoric acid for 200-300 seconds; the washing is performed with deionized water for 100-200 seconds; the pre-dehydration is performed for 5-20 seconds, and the pickling, washing and pre-dehydration can be performed at room temperature (20-30° C.). The drying is performed with hot air for 400-700 seconds at a temperature of 80-100° C.

[0061] In some embodiments, the method further comprises step (8): forming a passivation layer. In this step, a passivation layer is formed on a side of the boron-doped layer of the product obtained by the wrap-around etching away from the substrate.

[0062] In some embodiments, in step (8), the passivation layer comprises aluminum oxide.

[0063] In some embodiments, in step (8), the thickness of the passivation layer is 3-10 nm, for example, 3 nm, 7 nm, 9 nm, 10 nm, etc.

[0064] In some embodiments, the method further comprises step (9): forming an anti-reflection layer. In this step, the anti-reflection layer is independently formed on a side of the passivation layer away from the boron-doped layer and on a side of the phosphorus-doped layer away from the tunnel oxide layer.

[0065] In some embodiments, in step (9), the anti-reflection layer comprises AlO x Layer, SiN a Layer, SiO b N c Layer, SiO d One or more layers.

[0066] In this application, the chemical formula containing x, a, b, c, d (AlOx, SiNa, SiO b N c 、SiO d ) in which the values ​​of x, a, b, c, and d may be integers or non-integers. Since a chemical formula represents a relative atomic ratio rather than a strict chemical structure, the chemical formula may include one or more stoichiometric compounds and / or one or more non-stoichiometric compounds. As used in this application, the term "non-stoichiometric compound" means and includes a compound having a certain element composition that cannot be represented by a ratio of well-defined natural numbers and violates the law of definite proportions.

[0067] In some embodiments, in step (9), the thickness of the anti-reflection layer is 25-40 nm, for example, 25 nm, 30 nm, 35 nm, 40 nm, etc.

[0068] In some embodiments, the method further comprises step (10): preparing a metal electrode and metallizing the substrate on which the passivation anti-reflection layer is deposited.

[0069] Optionally, the metallization method is to print silver paste electrodes on the anti-reflection layer in sequence by screen printing, and then sinter them to obtain a solar cell.

[0070] In a second aspect of the embodiments of the present application, a solar cell is provided. The solar cell comprises a substrate, wherein the substrate comprises two opposite side surfaces, namely a first surface and a second surface, and a plurality of end surfaces surrounding the first surface and the second surface, wherein the first surface and the second surface are independently velvet surfaces; a boron-doped layer, wherein the boron-doped layer is located on the first surface of the substrate, and a tunneling oxide layer, wherein the tunneling oxide layer is located on the second surface of the substrate.

[0071] The solar cell of the embodiment of the present application has a good bifaciality. This is because the substrate of the cell is a double-suede substrate, which effectively reduces the local leakage of the cell itself and improves the passivation effect of the cell, thereby improving the photoelectric performance of the cell, and thus making the solar cell show a better bifaciality.

[0072] In some embodiments, reference Figure 2 The solar cell comprises a substrate 1, a boron-doped layer 4, a passivation layer 5, an anti-reflection layer 6, a tunneling oxide layer 7, a phosphorus-doped layer 8 and a metal electrode 9. The boron-doped layer is located on the first surface of the substrate, the passivation layer is located on a side of the boron-doped layer away from the substrate; the tunneling oxide layer is located on the second surface of the substrate, the phosphorus-doped layer is located on a side of the tunneling oxide layer away from the substrate, the side of the phosphorus-doped layer away from the tunneling oxide layer and the side of the passivation layer away from the boron-doped layer are both provided with an anti-reflection layer, and the metal electrode is in contact with the phosphorus-doped layer or the boron-doped layer.

[0073] In some embodiments, the solar cell has a velvet surface on both the first surface and the second surface opposite to the substrate, and the velvet structure is beneficial for improving the absorption rate of photons, thereby making the solar cell exhibit a higher double-sided process.

[0074] Optionally, the bifaciality of the solar cell is 90%-96%.

[0075] In some embodiments, the velvet height of the first and second surfaces of the solar cell substrate is 0.5 μm-3 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm, etc. The width of the base of the pyramid is 1 μm-3 μm, such as 1 μm, 2 μm, 3 μm, etc. Such a velvet surface can effectively increase the short-circuit current of the solar cell; the high specific surface area can increase the light expansion block resistance, reduce the silicon wafer surface recombination, increase the short-circuit current, and thus improve the photoelectric conversion efficiency of the monocrystalline silicon solar cell.

[0076] In a third aspect of the embodiments of the present application, a photovoltaic component is provided, wherein the photovoltaic component includes the solar cell according to the second aspect.

[0077] In some embodiments, the photovoltaic module includes a plurality of solar cells connected in series and / or in parallel; wherein at least one solar cell is a solar cell of the second aspect of the present application. A plurality of solar cells in series form a cell string, and adjacent heterojunction solar cells can be connected together by string welding.

[0078] In the fourth aspect of the embodiment of the present application, a photovoltaic system is provided, including the photovoltaic assembly of the third aspect of the present application. The advantages possessed by the above-mentioned photovoltaic assembly are also possessed by the photovoltaic system, which will not be repeated here. The above-mentioned photovoltaic system has a wide range of applications, not only limited to photovoltaic power stations, such as ground power stations, rooftop power stations and water power stations, but also includes various equipment and devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars and solar buildings. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be used in all fields where solar energy is required for power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple photovoltaic components. For example, multiple photovoltaic components may form multiple photovoltaic arrays. The photovoltaic array is connected to a junction box, and the junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid, and then connected to the mains network to realize solar power supply.

[0079] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments described herein.

[0080] Example 1 S1: Texturing and cleaning The N-type silicon wafer with a thickness of 120 μm was textured and cleaned to form a uniform "positive pyramid" texture surface on the two opposite surfaces of the silicon wafer, and the texture surface height was 3 μm.

[0081] S2: Preparation of boron-doped amorphous silicon layer Boron-doped amorphous silicon is deposited on the first surface of an N-type silicon wafer by plasma enhanced chemical deposition, wherein the temperature of the plasma enhanced chemical deposition is 200° C., and the equipment for the plasma enhanced chemical deposition is a plate-type PEVCD.

[0082] S3: Crystallization The amorphous silicon is crystallized into polycrystalline silicon by annealing and oxidation, and a boron-doped layer with a thickness of 150 nm is obtained. The temperature of the crystallization stage during the annealing and oxidation process is 900° C., and the temperature of the oxidation stage is 1000° C.

[0083] S4: Removal of the silicon oxide layer on the end surface and the second surface of the substrate The boron-doped substrate was chain pickled using a 23wt% HF solution.

[0084] S5: Tunneling oxide layer and phosphorus-doped layer Using LPCVD equipment, at a temperature of 650°C, a tunneling oxide layer and an intrinsic amorphous silicon layer (a-Si) are grown on the front and back sides of the silicon wafer, where the thickness of the tunneling oxide layer is 1.5nm and the thickness of the intrinsic amorphous silicon layer is 100nm.

[0085] Phosphorus diffusion is to load the silicon wafer after amorphous silicon deposition into a tubular phosphorus diffusion furnace tube, using POCl 3 Phosphorus is diffused and annealed on the back of the battery by diffusion, and a phosphorus-doped polysilicon layer and a phosphorus-silicon glass layer are formed on the back.

[0086] S6: Etching around the front side The product obtained in step S5 is subjected to acid washing, water washing, pre-dehydration and drying steps in sequence, wherein the acid washing adopts hydrofluoric acid for 300 seconds; the water washing adopts deionized water for 200 seconds; the pre-dehydration time is 20 seconds, and the acid washing, water washing and pre-dehydration can all be carried out at room temperature. The drying adopts hot air drying for 700 seconds at a temperature of 100°C.

[0087] S7: Deposition of passivation layer A 5 nm passivation layer was deposited on the front side of the product obtained after the front side wrap-around etching.

[0088] S8: Deposition of anti-reflection layer A 30 nm anti-reflection layer is independently formed on a side of the passivation layer away from the boron doping layer and on a side of the phosphorus doping layer away from the tunneling oxide layer.

[0089] S9: Forming metal electrodes Fabrication of metallic silver electrodes.

[0090] S10: Light injection The cell obtained in step S9 is subjected to light injection treatment to form a solar cell, wherein the light injection temperature is 220° C. and the time is 120 s, so as to obtain a solar cell.

[0091] Example 2-3 The solar cell was prepared in the manner of Example 1, except that in step S2, the temperatures of plasma enhanced chemical deposition were 100° C. and 300° C. respectively.

[0092] Embodiment 4-5 The solar cell was prepared in the manner of Example 1, except that in step S3, the temperatures in the crystallization stage were 700° C. and 1000° C. respectively.

[0093] Embodiment 6-7 A solar cell was prepared in the manner of Example 1, except that in step S3, HF solutions with concentrations of 10 wt % and 30 wt % were used to chain pickle the boron-doped substrate, respectively.

[0094] Comparative Example 1 The solar cell was prepared in the same manner as in Example 1, except that step S4 also included alkali polishing to polish the second surface. The alkali polishing conditions were KOH concentration of about 1.5% and temperature of 68°C.

[0095] Comparative Example 2 A solar cell is prepared in the manner of Example 1, except that in step S2, boron-doped amorphous silicon is deposited on the first surface of the N-type silicon wafer by using tubular PECVD.

[0096] Test Case The above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0097] Double-sidedness: Double-sidedness = (second surface photoelectric conversion efficiency × second surface light intensity) / (first surface photoelectric conversion efficiency × first surface light intensity). During the test, the light intensity is consistent.

[0098] Photovoltaic conversion efficiency: The battery is placed in a standard sunlight of AM1.5G (light intensity 100mW / cm 2 ) was used to scan the voltage-current curve using a Keithley 2400 source meter; the scanning range was -0.5-2 V, the scanning step was 20 mV, and the scanning time was 30 s.

[0099] Table 1

[0100] By comparing Examples 1-7 with Comparative Examples 1-2, it can be seen that the double-sidedness of the cells of Examples 1-7 is higher than that of Comparative Example 1. This is because, by using the method of the embodiments of the present application, both the first surface and the second surface of the substrate have a velvet surface, so that both the first surface and the second surface can absorb the incident light. The solar cell of Comparative Example 2 uses a tubular PEVCD device to prepare the boron-doped amorphous silicon layer, resulting in boron-doped amorphous silicon plating on the second surface, and the method of the embodiments of the present application does not perform a back etching process, which makes it difficult for the solar cell obtained in Comparative Example 2 to exert its photoelectric performance.

[0101] It should also be noted that the "some embodiments", "other embodiments", "embodiments", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure or characteristic is described in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0102] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0103] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: The following steps are involved: Providing a substrate, the substrate comprising a first surface and a second surface arranged opposite to each other and a plurality of end surfaces surrounding the first surface and the second surface, the first surface and the second surface being independently velvet surfaces; Depositing boron-doped amorphous silicon on the first surface by plasma enhanced chemical deposition to obtain a boron-doped amorphous silicon layer; Performing a crystallization process on the boron-doped amorphous silicon layer to convert amorphous silicon in the boron-doped amorphous silicon layer into polycrystalline silicon, and obtaining a boron-doped layer; Performing a removal process on the substrate having the boron-doped layer to remove the silicon oxide layer on the end face and the second surface; A tunnel oxide layer is grown on the second surface of the product obtained by the removal process.

2. The method according to claim 1, characterized in that Also includes: forming a phosphorus-doped layer on a side of the tunnel oxide layer away from the substrate; Performing wrap-around etching on the product obtained by forming the phosphorus-doped layer to remove the phosphorus-silicate glass layer; forming a passivation layer on a side of the boron-doped layer of the product obtained by the wrap-around etching away from the substrate; An anti-reflection layer is independently formed on a side of the passivation layer away from the boron doping layer and on a side of the phosphorus doping layer away from the tunneling oxide layer to obtain a solar cell.

3. The method according to claim 1 or 2, characterized in that: The plasma enhanced chemical deposition satisfies at least one of the following conditions: Temperature 100-300℃; The process gas includes a first gas and a second gas, wherein the first gas includes silane and the second gas includes borane and / or diborane.

4. The method according to claim 1 or 2, characterized in that: The crystallization treatment includes annealing oxidation, laser induced annealing or laser induced oxidation.

5. The method according to claim 4, characterized in that The annealing oxidation includes an oxidation stage and a crystallization stage. The temperature of the crystallization stage is 700-1000°C, and the temperature of the oxidation stage is 900-1200°C.

6. The method according to claim 1 or 2, characterized in that: The removal treatment is chain pickling using HF solution; And / or, the concentration of HF is 10-30wt%.

7. The method according to claim 2, characterized in that: The thickness of the boron doped layer is 30-200 nm; And / or, the thickness of the passivation layer is 3-10 nm; And / or, the thickness of the phosphorus-doped layer is 50-300 nm; And / or, the thickness of the tunnel oxide layer is 1-2 nm; And / or, the anti-reflection layer has a thickness of 25-40 nm.

8. A solar cell, characterized in that: include: A substrate, the substrate comprising a first surface and a second surface arranged opposite to each other and a plurality of end surfaces surrounding the first surface and the second surface, the first surface and the second surface being independently velvet surfaces; a boron-doped layer, wherein the boron-doped layer is located on the first surface of the substrate; A tunneling oxide layer is located on the second surface of the substrate.

9. The solar cell according to claim 8, characterized in that Also includes: a passivation layer, the passivation layer being located on a side of the boron-doped layer away from the substrate; a phosphorus-doped layer, wherein the phosphorus-doped layer is located on a side of the tunnel oxide layer away from the substrate; The anti-reflection layer, the side of the phosphorus-doped layer away from the tunnel oxide layer and the side of the passivation layer away from the boron-doped layer are both provided with an anti-reflection layer.

10. The solar cell according to claim 8 or 9, characterized in that: The bifaciality of the solar cell is 90%-96%.

11. A photovoltaic module, characterized in that: The photovoltaic module is a solar cell as described in any one of claims 8 to 10.

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