TOPCon solar cell manufacturing method and TOPCon solar cell

Abstract

The embodiment of the present application provides a TOPCon solar cell and a method for preparing the same. A method for preparing a TOPCon solar cell includes: sequentially forming a tunneling oxide layer, an initial first N-type polysilicon layer, and an initial second N-type polysilicon layer on the back of a silicon substrate; using a first non-ionic bombardment oxidation method to anneal and crystallize the initial first N-type polysilicon layer and the initial second N-type polysilicon layer to form a first N-type polysilicon layer and a second N-type polysilicon layer; at the same time, generating a first silicon oxide layer on the second N-type polysilicon layer. The technical solution of the present application uses a first non-ionic bombardment oxidation method for a one-time high-temperature annealing, crystallization, and oxidation treatment, so that the first N-type polysilicon layer and the second N-type polysilicon layer are crystallized and formed, and at the same time, a first silicon oxide layer is generated on the second N-type polysilicon layer, thereby reducing the damage to the interface production line of the second N-type polysilicon layer, thereby effectively improving the problem of battery efficiency attenuation.

Description

Technical Field

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

[0002] With the improvement of my country's energy structure, more and more new energy sources have replaced traditional thermal power generation. Among them, solar energy is a renewable new energy source. The installation form of solar power generation is simple, the site requirements are small, and it is suitable for use in various occasions. Therefore, it is widely used in various fields.

[0003] TOPCon technology has become one of the most promising new high-efficiency battery technologies due to its process route's high compatibility with traditional battery production lines and its significant efficiency gain, and its related research is increasing day by day. With the development of technology, the reliability of TOPCon batteries has also attracted more and more attention. In the process of preparing the front and back films of TOPCon batteries, there is ion bombardment on the surface, which causes damage to the surface and also leads to the problem of TOPCon battery efficiency attenuation.

[0004] 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

[0005] The embodiments of the present application provide a method for preparing a TOPCon solar cell and a TOPCon solar cell to solve or alleviate one or more of the technical problems mentioned above.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a TOPCon solar cell, comprising the following steps: forming a tunneling oxide layer, an initial first N-type polysilicon layer and an initial second N-type polysilicon layer in sequence on the back side of the silicon substrate; Adopting a first non-ion bombardment oxidation method to anneal and crystallize the initial first N-type polysilicon layer and the initial second N-type polysilicon layer to form a first N-type polysilicon layer and a second N-type polysilicon layer respectively; and at the same time, adopting the first non-ion bombardment oxidation method to generate a first silicon oxide layer on the second N-type polysilicon layer; The doping concentration of the first N-type polysilicon layer is lower than the doping concentration of the second N-type polysilicon layer.

[0007] Optionally, the first non-ionic bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the first non-ionic bombardment oxidation method is thermal oxidation, the temperature is 750-950°C.

[0008] Optionally, the first non-ionic bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the first non-ionic bombardment oxidation method is thermal oxidation, the special gas flow rate of oxygen is 5000-10000sccm.

[0009] Optionally, the first non-ionic bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the first non-ionic bombardment oxidation method is thermal oxidation, the special gas flow rate of nitrogen is 1-3slm.

[0010] Optionally, the first silicon oxide layer has a thickness of 5-10 nm.

[0011] Optionally, the forming of the initial first doped polysilicon layer comprises: using PECVD, under the conditions of silane SiH4 gas flow rate of 2000-4000sccm, phosphine PH3 gas flow rate of 150-450sccm, hydrogen H2 gas flow rate of 5000-10000sccm, duty cycle of 50:500-50:800, pulse power of 12000-18000W, time of 80-200s, forming the initial first doped polysilicon layer on the tunneling oxide layer; and / or The forming of the initial second doped polysilicon layer includes: using PECVD, under the conditions of silane SiH4 special gas flow rate of 2000-4000sccm, phosphine PH3 special gas flow rate of 500-1000sccm, hydrogen H2 special gas flow rate of 5000-10000sccm, duty cycle of 50:500-50:800, pulse power of 12000-18000W, and time of 450-800s, forming an initial second doped polysilicon layer on the initial first doped polysilicon layer.

[0012] Optionally, the method further includes: performing a boron diffusion process on the front side of the silicon substrate to form a P+ emitter layer; A second non-ion bombardment oxidation method is adopted to form a second silicon oxide layer on the P+ emitter layer.

[0013] Optionally, it also includes: forming an aluminum oxide passivation layer, a first silicon nitride anti-reflection layer and a third silicon oxide layer in sequence on the second silicon oxide layer, and forming a second silicon nitride anti-reflection layer on the first silicon oxide layer; A front metal electrode is prepared on the third silicon oxide layer, and a back metal electrode is prepared on the second silicon nitride anti-reflection layer.

[0014] Optionally, the second non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; When the second non-ion bombardment oxidation method is a thermal oxidation method, the temperature is 750-950° C., the special gas flow rate of oxygen is 5000-10000 sccm, and the special gas flow rate of nitrogen is 1-3 slm.

[0015] Optionally, forming a P+ emitter layer includes: Under the condition of temperature of 600-960° C., liquid source boron trichloride and oxygen are used to form a borosilicate glass layer on the front side of the silicon substrate; wherein the special gas flow rate of the liquid source boron trichloride is 150-250 sccm, the special gas flow rate of the oxygen is 500-1000 sccm, and the sheet resistance of the borosilicate glass layer is 120-200 Ω / sq; The borosilicate glass layer is diffused at a temperature of 850-1050° C. and a special oxygen gas flow rate of 10-20 slm to form the P+ emitter layer; wherein the sheet resistance of the P+ emitter layer is 250-350Ω / sq.

[0016] Optionally, the second silicon oxide layer has a thickness of 5-10 nm.

[0017] In a second aspect, an embodiment of the present application provides a TOPCon solar cell, wherein the TOPCon solar cell is manufactured by the above-mentioned method for manufacturing a TOPCon solar cell.

[0018] The above technical solution adopted in the embodiment of the present application may have the following advantages: By adopting the first non-ion bombardment oxidation method, a one-time high-temperature annealing crystallization oxidation treatment is performed to respectively crystallize the first N-type polysilicon layer and the second N-type polysilicon layer while generating a first silicon oxide layer on the second N-type polysilicon layer, thereby reducing the interface production line damage to the second N-type polysilicon layer, thereby making the battery have better UV resistance, and thus effectively improving the problem of battery efficiency attenuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 1 It is a schematic diagram of the structure of the TOPCon solar cell provided in the embodiment of the present application.

[0021] Description of reference numerals: 1. Silicon substrate; 2. P+ emitter layer; 3. First silicon oxide layer; 4. Tunneling oxide layer; 5. First N-type polysilicon layer; 6. Second N-type polysilicon layer; 7. Second silicon oxide layer; 8. Aluminum oxide passivation layer; 9. First silicon nitride anti-reflection layer; 10. Third silicon oxide layer; 11. Second silicon nitride anti-reflection layer; 12. Front metal electrode; 13. Back metal electrode. DETAILED DESCRIPTION

[0022] 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.

[0023] 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 disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present application discloses the existence of the first element, component, region, layer or part.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The following provides an explanation of the terms used in this application.

[0028] The first non-ionic bombardment oxidation method and the second non-ionic bombardment oxidation method are both non-ionic bombardment oxidation methods, that is, no ion bombardment method is used to crystallize or prepare the silicon oxide layer (the first silicon oxide layer and / or the second silicon oxide layer).

[0029] 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.

[0030] forming a tunneling oxide layer, an initial first N-type polysilicon layer and an initial second N-type polysilicon layer in sequence on the back side of the silicon substrate; The first non-ion bombardment oxidation method is used to anneal and crystallize the initial first N-type polysilicon layer and the initial second N-type polysilicon layer to form a first N-type polysilicon layer and a second N-type polysilicon layer respectively; at the same time, a first silicon oxide layer is generated on the second N-type polysilicon layer; The doping concentration of the first N-type polysilicon layer is lower than the doping concentration of the second N-type polysilicon layer.

[0031] In this embodiment, a first non-ion bombardment oxidation method is adopted, and after a one-time high-temperature annealing crystallization oxidation treatment, the first N-type polysilicon layer and the second N-type polysilicon layer are crystallized and formed respectively, and at the same time, a first silicon oxide layer is generated on the second N-type polysilicon layer. In the process of generating the first silicon oxide layer, the interface production line damage to the second N-type polysilicon layer is reduced, thereby effectively improving the problem of battery efficiency attenuation.

[0032] It should be noted that in the conventional technology, after the first N-type polysilicon layer and the second N-type polysilicon layer are crystallized by the first high-temperature annealing by PECVD, the second N-type polysilicon layer is crystallized by the second high-temperature annealing by PECVD to form the first silicon oxide layer. The conventional preparation method requires multiple annealing crystallization treatments, and when the first silicon oxide layer is deposited by PECVD, the surface of the second N-type polysilicon layer is damaged by PECVD, which will cause the surface state density of the second N-type polysilicon layer to increase. The preparation method of the embodiment of the present application only needs to be processed by a one-time high-temperature annealing crystallization oxidation treatment, and the preparation method is simpler, saving process steps and production costs, and also reducing the damage to the interface of the second N-type polysilicon layer, so that the battery has better UV resistance.

[0033] In addition, the first silicon oxide layer used in the present application can act as a buffer layer, eliminating the problem of increased surface state density of the second N-type polysilicon layer caused by the PECVD method used in traditional technology, thereby effectively improving the UV resistance of the battery and reducing the problem of battery efficiency attenuation.

[0034] In an optional embodiment, it also includes: Boron diffusion treatment is performed on the front side of the silicon substrate to form a P+ emitter layer; A second non-ion bombardment oxidation method is adopted to form a second silicon oxide layer on the P+ emitter layer.

[0035] In this embodiment, a second non-ion bombardment oxidation method is used to generate a second silicon oxide layer on the P+ emitter layer, thereby reducing the damage to the interface production line of the P+ emitter layer. By reducing the surface defects of the P+ emitter layer, the long-term performance stability of the battery is effectively improved and its service life is extended.

[0036] It should be noted that when TOPCon cells are used in areas with strong ultraviolet rays in the northwest and high altitudes, the ultraviolet attenuation of TOPCon cells is particularly serious. The ultraviolet attenuation of TOPCon cells is mainly due to the characteristics of short wavelength and high energy of ultraviolet light. Long-term exposure to places with strong ultraviolet light can easily lead to an increase in the surface state density and surface fixed charge of the cell, weakening the passivation performance, and causing the cell efficiency to decay. TOPCon cells generally have a hydrogen-containing silicon nitride layer as a passivation layer, but the higher energy of ultraviolet light can completely break the Si-H bond, greatly weakening the passivation of the passivation layer. The second silicon oxide layer has strong stability. The second silicon oxide layer complements the passivation performance lost by the first silicon nitride anti-reflection layer, and cooperates with the first silicon nitride anti-reflection layer to enhance the passivation performance of the cell, so as to improve the cell's anti-ultraviolet performance; the second silicon oxide layer can also partially absorb and block the incident ultraviolet rays, reduce the direct exposure of ultraviolet rays to the P+ emitter layer, thereby reducing the problem of increased surface state density of the P+ emitter layer, and effectively improving the problem of cell efficiency decay.

[0037] The second silicon oxide layer has high chemical stability and heat resistance, which prevents oxidation, hydrolysis and other chemical reactions, thereby protecting the P+ emitter layer from damage by environmental factors, preventing it from being directly damaged by ultraviolet radiation and increasing the surface state density, thereby effectively enhancing the battery's anti-ultraviolet performance and improving the battery's weather resistance.

[0038] In an optional embodiment, it also includes: forming an aluminum oxide passivation layer, a first silicon nitride anti-reflection layer and a third silicon oxide layer in sequence on the second silicon oxide layer; forming a second silicon nitride anti-reflection layer on the first silicon oxide layer; preparing a front metal electrode on the third silicon oxide layer; A back metal electrode is prepared on the second silicon nitride anti-reflection layer.

[0039] In this embodiment, the third silicon oxide layer covers the first silicon nitride anti-reflection layer, which can adjust the incident angle and refractive index of light, so that the battery can maximize the absorption of light and reduce reflection loss, thereby improving the photoelectric conversion efficiency. At the same time, it can further enhance the overall stability and weather resistance of the battery and extend the service life of the battery. In addition, the third silicon oxide layer has good optical transmittance and absorption characteristics, and can partially absorb and reflect ultraviolet rays, reducing the energy of ultraviolet rays directly irradiating the first silicon nitride anti-reflection layer, thereby reducing the possibility of Si-H bond breakage, thereby improving the problem of battery efficiency attenuation.

[0040] In an optional embodiment, the first non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the first non-ion bombardment oxidation method is thermal oxidation, the temperature is 750-950°C, for example 750°C, 800°C, 950°C.

[0041] In an optional embodiment, the first non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the first non-ion bombardment oxidation method is thermal oxidation, the oxygen gas flow rate is 5000-10000 sccm, for example 5000 sccm, 8000 sccm, 10000 sccm.

[0042] In an optional embodiment, the first non-ionic bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the first non-ionic bombardment oxidation method is thermal oxidation, the nitrogen gas flow rate is 1-3slm, for example 1slm, 2slm, 3slm.

[0043] In an optional embodiment, the preparation method of the initial first doped polysilicon layer includes: using PECVD, the silane SiH4 special gas flow rate is 2000-4000sccm, such as 2000sccm, 3000sccm, 4000sccm; the phosphine PH3 special gas flow rate is 150-450sccm, such as 150sccm, 200sccm, 450sccm; the hydrogen H2 special gas flow rate is 5000-10000sccm m, for example, 5000sccm, 8000sccm, 10000sccm; duty ratio is 50:500-50:800, for example, 50:500, 50:600, 50:800; pulse power is 12000-18000W, for example, 12000W, 16000W, 18000W; the initial first N-type polysilicon layer is formed under the condition of time of 80-200s, for example, time of 80s, 150s, 200s; The preparation method of the initial second doped polysilicon layer includes: using PECVD, the silane SiH4 special gas flow rate is 2000-4000sccm, for example, 2000sccm, 3000sccm, 4000sccm; the phosphine PH3 special gas flow rate is 500-1000sccm, for example, 500sccm, 800sccm, 1000sccm; the hydrogen H2 special gas flow rate is 5000-10000sccm, for example The initial second N-type polysilicon layer is formed under the conditions of 5000sccm, 8000sccm, 10000sccm; the duty cycle is 50:500-50:800, for example, 50:500, 50:600, 50:800; the pulse power is 12000-18000W, for example, 12000W, 16000W, 18000W; and the time is 450s, 600s, 800s.

[0044] In this embodiment, the first N-type polysilicon layer is a lightly doped layer with a lower doping concentration; while the second N-type polysilicon layer is a heavily doped layer with a higher doping concentration. The doping concentration gradient design of the first N-type polysilicon layer and the second N-type polysilicon layer can effectively improve the collection efficiency of electrons; the doping concentration of the first N-type polysilicon layer is low, which helps to reduce the surface recombination rate; while the doping concentration of the second N-type polysilicon layer is high, which can improve the conductivity and collection efficiency of electrons and ensure that more electrons are effectively transported to the back electrode of the battery; the doping concentration of the first N-type polysilicon layer and the second N-type polysilicon layer between the tunneling oxide layer and the first silicon oxide layer is from low to high, which can effectively reduce the reflectivity of the back of the battery, so that more light can be absorbed and converted into electrical energy, thereby improving the photoelectric conversion efficiency of the battery. In addition, the doping concentration of the first N-type polysilicon layer and the second N-type polysilicon layer is from low to high, which helps to reduce the defect density of the surface and interface, reduce the charge recombination rate, thereby extending the service life of the battery and improving its stability.

[0045] In an optional embodiment, the second non-ionic bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; when the second non-ionic bombardment oxidation method is thermal oxidation, the temperature is 750-950°C (for example, 750°C, 800°C, 950°C), the special gas flow rate of oxygen is 5000-10000sccm (for example, 5000sccm, 8000sccm, 10000sccm), and the special gas flow rate of nitrogen is 1-3slm (for example, 1slm, 2slm, 3slm).

[0046] In the present embodiment, when the second silicon oxide layer is generated on the P+ emitter layer and the first silicon oxide layer is generated on the second N-type polysilicon layer by using thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation, the surfaces of the P+ emitter layer and the second N-type polysilicon layer will not be damaged by the production line, so the problem of increased surface state density will not be caused, thereby reducing the attenuation of battery efficiency.

[0047] In an optional embodiment, the thickness of the first silicon oxide layer is 5-10 nm; the thickness of the second silicon oxide layer is 5-10 nm. For example, the thickness of the first silicon oxide layer can be 5 nm, 6 nm, 7.5 nm, 9 nm and 10 nm; the thickness of the second silicon oxide layer can be 5 nm, 6 nm, 7.5 nm, 9 nm and 10 nm.

[0048] In this embodiment, when the thickness of the first silicon oxide layer is less than 5nm, it cannot provide sufficient stability. Long-term exposure to ultraviolet radiation will still cause the P+ emitter layer to have an increased surface state density and weakened passivation performance, and poor anti-ultraviolet ability; when the thickness of the first silicon oxide layer and the second silicon oxide layer is higher than 10nm, the thickness is too thick to reduce the transmittance of light, reduce the energy of light entering the battery, thereby reducing the photoelectric conversion efficiency, and hinder the effective transmission of electrons and holes, affecting the collection and transfer efficiency of the internal charge of the battery, thereby reducing the performance of the battery. In addition, the production cost and production difficulty are also increased. Therefore, the thickness of the first silicon oxide layer and the second silicon oxide layer set in this application is between 5-10nm, which can improve the anti-ultraviolet radiation ability of the battery, and at the same time, it can not affect the photoelectric conversion efficiency of the battery.

[0049] In an optional embodiment, during the process of forming the P+ emitter layer, liquid source boron trichloride and oxygen are reacted at a temperature of 600-960°C, for example, 600°C, 700°C, 800°C, 960°C, to form a borosilicate glass layer (BSG) on the front side of the silicon substrate, wherein the special gas flow rate of the liquid source boron trichloride is 150-250sccm, for example, 150sccm, 200sccm, 250sccm. The special gas flow rate of oxygen is 500-1000sccm, for example, 500sccm, 600sccm, 700sccm, 800sccm, 1000sccm; the boron diffusion square resistance of the borosilicate glass layer is 120-200Ω / sq, for example, 120Ω / sq, 150Ω / sq, 200Ω / sq; then the borosilicate glass layer (BSG) is diffused at a temperature of 850-1050°C (for example, 850°C, 900°C, 1050°C) and the special gas flow rate of oxygen is 10-20slm (for example, 10slm, 15slm, 20slm) to form a P+ emitter layer, and the square resistance of the P+ emitter layer is controlled at 250-350Ω / sq, for example, 250Ω / sq, 300Ω / sq, 350Ω / sq. The use of a mixed gas of liquid source boron trichloride and oxygen to form the P+ emitter layer has significant advantages in terms of doping depth, uniformity, square resistance control and process controllability.

[0050] In an optional embodiment, during the alkali texturing treatment of the silicon substrate, the silicon substrate uses an N-type single crystal silicon wafer, and the alkali texturing treatment uses one or more of KOH and NaOH for texturing, and the texturing pyramid size is 8-15μm. For example, the texturing pyramid size is 8μm, 10μm, and 15μm. The alkali texturing treatment can accurately control the texture and morphology of the silicon wafer surface, forming a uniform and controllable pyramid structure, effectively enhancing the light absorption capacity of the silicon wafer surface, improving the photoelectric conversion efficiency, and the pyramid shape can reduce light reflection and improve light utilization.

[0051] In an optional embodiment, in the process of preparing the tunneling oxide layer, the preparation method of the tunneling oxide layer adopts PECVD, and the tunneling oxide layer is formed under the conditions of N2O flow rate of 10-15slm, for example, 10slm, 12slm, 51slm; duty cycle of 20:600-20:3000, for example, 20:600, 20:1500, 20:3000; pulse power of 12000-18000W, for example, 12000W, 16000W, 18000W; time of 80-110s, for example, time of 80s, 100s, 110s; the thickness of the tunneling oxide layer is 1.5-2.0nm, for example, 1.5nm, 1.8nm, 2.0nm.

[0052] In an optional embodiment, in the process of forming the aluminum oxide passivation layer, the aluminum oxide passivation layer is deposited by ALD; wherein the thickness of the aluminum oxide passivation layer is 5-15nm, for example, 5nm, 10nm, 15nm. When the thickness of the aluminum oxide passivation layer is greater than 15nm, the possibility of electron tunneling in the layer will increase, resulting in increased current leakage, thereby affecting the reverse characteristics and stability of the battery. When the thickness of the aluminum oxide passivation layer is less than 5nm, the reflectivity cannot be effectively reduced, affecting the light absorption rate and photoelectric conversion efficiency of the battery.

[0053] In an optional embodiment, the first silicon nitride anti-reflection layer and the second silicon nitride anti-reflection layer are both formed by PECVD; wherein the thickness of the first silicon nitride anti-reflection layer is 70-90nm, for example, 70nm, 80nm, 90nm; the thickness of the second silicon nitride anti-reflection layer is 80-100nm, for example, 80nm, 90nm, 100nm. The thickness range of the first silicon nitride anti-reflection layer set in the present application is to improve the optical effect, reduce the reflectivity, and increase the current; and the thickness range of the second silicon nitride anti-reflection layer is set to prioritize the passivation performance to improve Voc, and then reduce the reflectivity on this basis.

[0054] In an optional embodiment, in the process of using laser to perform laser thinning on the front and back side secondary grid lines, the laser spot size is 70-100um, for example 70um, 85um, 100um; the laser target speed is 20000-50000mm / s, for example 20000mm / s, 30000mm / s, 50000mm / s.

[0055] like Figure 1 As shown, an embodiment of the present application provides a TOPCon solar cell. The TOPCon solar cell is formed by the preparation method of any of the above embodiments, including a silicon substrate 1, the front side of the silicon substrate 1 is sequentially stacked with a P+ emitter layer 2, a second silicon oxide layer 3, an aluminum oxide passivation layer 8, a first silicon nitride anti-reflection layer 9 and a third silicon oxide layer 10 from the inside to the outside; the back side of the silicon substrate 1 is sequentially stacked with a tunneling oxide layer 4, a first N-type polysilicon layer 5, a second N-type polysilicon layer 6, a first silicon oxide layer 7 and a second silicon nitride anti-reflection layer 11 from the inside to the outside; and also includes a front metal electrode 12 arranged on the front side of the silicon substrate 1 and a back metal electrode 13 arranged on the back side of the silicon substrate 1.

[0056] In this embodiment, when the TOPCon solar cell is used in areas with strong ultraviolet rays in the northwest and high altitudes, long-term exposure to strong ultraviolet light can easily lead to an increase in the surface state density of its P+ emitter layer. By setting a more stable second silicon oxide layer, the passivation performance of the battery can be enhanced, and the P+ emitter layer can be protected from direct damage by ultraviolet radiation and an increase in surface state density, thereby effectively enhancing the anti-ultraviolet performance of the battery and improving the weather resistance of the battery. The second silicon oxide layer and the first silicon oxide layer have good weather resistance and chemical stability, and can protect the battery surface from pollutants and ultraviolet radiation in the environment for a long time.

[0057] In addition, the second silicon oxide layer, the aluminum oxide passivation layer, the first silicon nitride anti-reflection layer and the third silicon oxide layer form a composite passivation layer, which can not only effectively protect the P+ emitter layer, the first N-type polysilicon layer and the second N-type polysilicon layer of the battery, and extend the service life of the battery, but also improve the stability and performance of the battery in a strong ultraviolet environment, and effectively improve the problem of battery performance attenuation caused by strong ultraviolet radiation, thereby improving the long-term reliability and efficiency of solar cells. It should be noted that the first silicon nitride anti-reflection layer contains hydrogen elements, and the higher energy of ultraviolet light can also break the Si-H bond and reduce the passivation performance of the first silicon nitride anti-reflection layer. The setting of the second silicon oxide layer can cooperate with the first silicon nitride anti-reflection layer to jointly achieve the passivation effect, reduce the thickness of the first silicon nitride anti-reflection layer, and enable the second silicon oxide layer to compensate for the passivation performance of the first silicon nitride anti-reflection layer that is reduced due to the breakage of the Si-H bond caused by ultraviolet light. At the same time, the third silicon oxide layer has good optical transmittance and absorption properties, and can partially absorb and reflect ultraviolet rays, reducing the energy of ultraviolet rays directly irradiating the first silicon nitride anti-reflection layer, thereby reducing the possibility of Si-H bond breakage, and further improving the problem of battery efficiency attenuation.

[0058] The following will conduct performance tests on the structure or manufacturing method of the TOPCon solar cell provided in the embodiments of the present application and related comparative examples.

[0059] [Example 1] like Figure 1As shown, an embodiment of the present application provides a TOPCon solar cell, which may include: a silicon substrate 1, wherein a P+ emitter layer 2, a second silicon oxide layer 3, an aluminum oxide passivation layer 8, a first silicon nitride anti-reflection layer 9 and a third silicon oxide layer 10 are stacked in sequence from the inside to the outside on the front side of the silicon substrate 1; a tunneling oxide layer 4, a first N-type polysilicon layer 5, a second N-type polysilicon layer 6, a first silicon oxide layer 7 and a second silicon nitride anti-reflection layer 11 are stacked in sequence from the inside to the outside on the back side of the silicon substrate 1; and a front metal electrode 12 is arranged on the front side of the silicon substrate 1 and a back metal electrode 13 is arranged on the back side of the silicon substrate 1.

[0060] The specific preparation process of a TOPCon solar cell is as follows: Step S1: performing alkaline texturing treatment on the silicon substrate using KOH, and removing mechanical damage and contaminants on the front side of the silicon substrate; Step S2: forming a borosilicate glass layer (BSG) on the front side of the silicon substrate under the conditions of a temperature of 800°C and a sheet resistance of a boron diffusion layer of 150Ω / sq by using liquid source boron trichloride and oxygen, wherein the special gas flow rate of the liquid source boron trichloride is 200sccm and the special gas flow rate of oxygen is 800sccm; performing high temperature diffusion of the borosilicate glass layer (BSG) under the conditions of a temperature of 900°C and a special gas flow rate of oxygen of 15slm to form a P+ emitter layer, and the sheet resistance of the P+ emitter layer is controlled to be 300Ω / sq; Step S3: using a wet HF acid solution to remove the BSG layer on the back and edge of the silicon substrate, retaining the BSG on the front, and then using a KOH alkaline solution to form a 10 um tower base morphology on the back; Step S4-1: The tunnel oxide layer is prepared by PECVD under the conditions of N2O flow rate of 12 slm, duty cycle of 20:2000, pulse power of 16000 W, and time of 100 s to form a tunnel oxide layer; wherein the thickness of the tunnel oxide layer is 1.8 nm; Step S4-2: In the process of preparing the initial first N-type polysilicon layer, the preparation method of the initial first N-type polysilicon layer adopts PECVD, under the conditions of silane (SiH4) special gas flow rate of 3000sccm, phosphine (PH3) special gas flow rate of 300sccm, hydrogen (H2) special gas flow rate of 8000sccm, duty cycle of 50:600, pulse power of 16000W, time of 150s, to form the initial first N-type polysilicon layer; Step S4-3: In the process of preparing the initial second N-type polysilicon layer, the preparation method of the initial second N-type polysilicon layer adopts PECVD, under the conditions of silane (SiH4) special gas flow rate of 3000sccm, phosphine (PH3) special gas flow rate of 800sccm, hydrogen (H2) special gas flow rate of 8000sccm, duty cycle of 50:600, pulse power of 16000W, time of 600s, to form the initial second N-type polysilicon layer; Step S5: removing the PSG layer on the front side of the silicon substrate by a wet chain HF acid solution, then removing the initial first N-type polysilicon layer and the initial second N-type polysilicon layer on the front side of the silicon substrate by a KOH alkaline solution, and finally completely removing the BSG on the front side of the silicon substrate by a wet bath HF acid solution; Step S6: Under the conditions of a temperature of 850° C., a special gas flow rate of oxygen of 8000 sccm, and a special gas flow rate of nitrogen of 2 slm, the initial first N-type polysilicon layer and the initial second N-type polysilicon layer are subjected to high-temperature annealing, crystallization, and oxidation treatment to form a first N-type polysilicon layer and a second N-type polysilicon layer, respectively, and at the same time, a first silicon oxide layer is generated on the second N-type polysilicon layer, and a second silicon oxide layer is generated on the P+ emitter layer; wherein the thickness of the first N-type polysilicon layer is 30 nm, the thickness of the second N-type polysilicon layer is 85 nm, the thickness of the first silicon oxide layer is 7.5 nm, and the thickness of the second silicon oxide layer is 7.5 nm; wherein the doping concentration of the first N-type polysilicon layer is lower than the doping concentration of the second N-type polysilicon layer; Step S7: using nitrogen gas carrying trimethylaluminum (the special gas flow rate is 2000 sccm) and nitrogen gas carrying water at 2000 sccm as precursor gases, and growing an aluminum oxide passivation layer with a thickness of 10 nm on the front side of the silicon substrate by plate-type ALD; Step S8: forming a first silicon nitride anti-reflection layer with a thickness of 80 nm on the front side of the silicon substrate by PECVD, forming a third silicon oxide layer with a thickness of 8 nm on the upper surface of the first silicon nitride anti-reflection layer, and forming a second silicon nitride anti-reflection layer with a thickness of 90 nm on the back side of the silicon substrate; forming the first silicon nitride anti-reflection layer under the conditions of a silane special gas flow rate of 2000 sccm, a ammonia special gas flow rate of 15000 sccm, a duty ratio of 50:650, a pulse power of 16000 W, and a time of 700 s; forming the second silicon nitride anti-reflection layer under the conditions of a silane special gas flow rate of 2000 sccm, a ammonia special gas flow rate of 15000 sccm, a duty ratio of 50:650, a pulse power of 16000 W, and a time of 700 s; Under the conditions of silane gas flow rate of 2000sccm, nitrous oxide gas flow rate of 15000sccm, duty ratio of 40:600, pulse power of 16000W, and time of 150s, a third silicon oxide layer was formed; Step S9: Use laser to perform laser thinning on the front and back secondary grid lines, select a laser spot size of 85um, and a target speed of 30,000 mm / s. After the thinning process is completed, prepare the front metal electrode and the back metal electrode respectively, and then complete the sintering in a chain sintering furnace at a temperature of 750°C to form a TOPCon solar cell.

[0061] [Example 2] The TOPCon solar cell of Example 2 is prepared by referring to the preparation method of Example 1, except that, in step S6: at a temperature of 750°C, a special gas flow rate of oxygen of 5000sccm, and a special gas flow rate of nitrogen of 1slm, the initial first N-type polycrystalline silicon layer and the initial second N-type polycrystalline silicon layer are subjected to a high-temperature annealing, crystallization, and oxidation treatment to form a first N-type polycrystalline silicon layer and a second N-type polycrystalline silicon layer, and at the same time, a first silicon oxide layer is generated on the second N-type polycrystalline silicon layer, and a second silicon oxide layer is generated on the P+ emitter layer; wherein, the thickness of the first N-type polycrystalline silicon layer is 30nm, the thickness of the second N-type polycrystalline silicon layer is 85nm, the thickness of the first silicon oxide layer is 5nm, and the thickness of the second silicon oxide layer is 5nm.

[0062] [Example 3] The TOPCon solar cell of Example 3 is prepared by referring to the preparation method of Example 1, except that, step S6: under the conditions of a temperature of 950°C, a special gas flow rate of oxygen of 10000 sccm, and a special gas flow rate of nitrogen of 3 slm, the initial first N-type polycrystalline silicon layer and the initial second N-type polycrystalline silicon layer are subjected to a high-temperature annealing, crystallization, and oxidation treatment to form a first N-type polycrystalline silicon layer and a second N-type polycrystalline silicon layer, and at the same time, a first silicon oxide layer is generated on the second N-type polycrystalline silicon layer, and a second silicon oxide layer is generated on the P+ emitter layer; wherein, the thickness of the first N-type polycrystalline silicon layer is 30 nm, the thickness of the second N-type polycrystalline silicon layer is 85 nm, the thickness of the first silicon oxide layer is 10 nm, and the thickness of the second silicon oxide layer is 10 nm.

[0063] [Comparative Example 1] A TOPCon solar cell of Comparative Example 1 was prepared by referring to the preparation method of Example 1, except that, in step S6, the initial first N-type polycrystalline silicon layer and the initial second N-type polycrystalline silicon layer were treated at a temperature of 850° C. and a nitrogen special gas flow rate of 1 slm, and then high-temperature annealing and crystallization were completed to form a first N-type polycrystalline silicon layer and a second N-type polycrystalline silicon layer; wherein the thickness of the first N-type polycrystalline silicon layer was 30 nm, and the thickness of the second N-type polycrystalline silicon layer was 85 nm (without an oxide layer).

[0064] [Comparative Example 2] The TOPCon solar cell of Comparative Example 2 was prepared by referring to the preparation method of Example 1, except that, in step S6: The initial first N-type polysilicon layer and the initial second N-type polysilicon layer are treated at a temperature of 850° C. and a nitrogen gas flow rate of 1 slm, and then high-temperature annealing and crystallization are completed to form a first N-type polysilicon layer and a second N-type polysilicon layer; Then, a PECVD method is used to form a first silicon oxide layer on the second N-type polysilicon layer, and a second silicon oxide layer on the P+ emitter layer under the conditions of a silane gas flow rate of 2000 sccm, a nitrous oxide N2O gas flow rate of 15000 sccm, a duty cycle of 40:600, a pulse power of 16000 W, and a time of 200 s. The thickness of the first N-type polysilicon layer is 30 nm, the thickness of the second N-type polysilicon layer is 85 nm, the thickness of the first silicon oxide layer is 7.5 nm, and the thickness of the second silicon oxide layer is 7.5 nm.

[0065] The TOPCon solar cell modules provided in Examples 1-3 and Comparative Examples 1-2 of the present application are subjected to performance tests in accordance with IEC61215-2:2016 to obtain the short-circuit current density Jsc, open-circuit voltage Voc, fill factor Fill Factor, and maximum module power of the corresponding battery devices. The test results are shown in Table 1.

[0066] Table 1 Performance test results of TOPCON solar cells of Examples 1-3 and Comparative Examples 1-2

[0067] It can be seen from Table 1 and Examples 1-3 and Comparative Examples 1-2 that when the TOPCon solar cell is used in an area with strong ultraviolet rays and high temperatures, the solar cell prepared in Examples 1-3 can still maintain a relatively high maximum output power, indicating that the arrangement of the first silicon oxide layer and the second silicon oxide layer can protect the P+ emitter layer, the first N-type polysilicon layer and the second N-type polysilicon layer, and prevent them from being directly damaged by ultraviolet radiation and the increase of the surface state density; at the same time, the third silicon oxide layer can also protect the first silicon nitride anti-reflection layer, thereby effectively enhancing the anti-ultraviolet performance of the battery and improving the weather resistance of the battery. And the attenuation rate of the battery prepared in Examples 1-3 is significantly lower than the attenuation rate of the battery in Comparative Examples 1-2, and has a relatively high anti-ultraviolet performance. In combination with Example 1 and Comparative Example 1, it can be seen that in Comparative Example 1, there is no first silicon oxide layer and second silicon oxide layer, the anti-ultraviolet performance is poor, and the battery efficiency attenuation is more serious.

[0068] Combining Examples 1-3 with Comparative Example 2, it can be seen that in Comparative Example 2, PECVD is used to generate a first silicon oxide layer on the second N-type polysilicon layer, and a second silicon oxide layer is generated on the P+ emitter layer; the use of PECVD will lead to an increase in the interface state density of the second N-type polysilicon layer, thereby weakening the passivation performance of the battery and causing the battery efficiency to decay. However, Examples 1-3 of the present application use a one-time high-temperature annealing crystallization oxidation treatment, which can generate a first silicon oxide layer on the second N-type polysilicon layer while forming the first N-type polysilicon layer and the second N-type polysilicon layer, and generate a second silicon oxide layer on the P+ emitter layer. This eliminates the problem of interface production line damage to the second N-type polysilicon layer by using PECVD, greatly improving the problem of ultraviolet attenuation of the battery.

[0069] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. The orientation words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0070] It should also be noted that "one embodiment", "another embodiment", "embodiment", 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. Further, when describing a specific feature, structure or characteristic 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.

[0071] 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.

[0072] 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 TOPCon solar cell, characterized in that: The steps include: forming a tunneling oxide layer, an initial first N-type polysilicon layer and an initial second N-type polysilicon layer in sequence on the back side of the silicon substrate; Adopting a first non-ion bombardment oxidation method to anneal and crystallize the initial first N-type polysilicon layer and the initial second N-type polysilicon layer to form a first N-type polysilicon layer and a second N-type polysilicon layer respectively; and at the same time, adopting the first non-ion bombardment oxidation method to generate a first silicon oxide layer on the second N-type polysilicon layer; The doping concentration of the first N-type polysilicon layer is lower than the doping concentration of the second N-type polysilicon layer.

2. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The first non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; When the first non-ion bombardment oxidation method is a thermal oxidation method, the temperature is 750-950°C.

3. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The first non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; When the first non-ion bombardment oxidation method is a thermal oxidation method, the special gas flow rate of oxygen is 5000-10000 sccm.

4. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The first non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; When the first non-ionic bombardment oxidation method is a thermal oxidation method, the special gas flow rate of nitrogen is 1-3 slm.

5. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The thickness of the first silicon oxide layer is 5-10 nm.

6. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: The forming of the initial first doped polysilicon layer comprises: using PECVD, under the conditions of silane SiH4 gas flow rate of 2000-4000sccm, phosphine PH3 gas flow rate of 150-450sccm, hydrogen H2 gas flow rate of 5000-10000sccm, duty cycle of 50:500-50:800, pulse power of 12000-18000W, and time of 80-200s, to form the initial first doped polysilicon layer on the tunneling oxide layer; and / or The forming of the initial second doped polysilicon layer includes: using PECVD, under the conditions of silane SiH4 special gas flow rate of 2000-4000sccm, phosphine PH3 special gas flow rate of 500-1000sccm, hydrogen H2 special gas flow rate of 5000-10000sccm, duty cycle of 50:500-50:800, pulse power of 12000-18000W, and time of 450-800s, forming an initial second doped polysilicon layer on the initial first doped polysilicon layer.

7. The method for preparing a TOPCon solar cell according to any one of claims 1 to 6, characterized in that: Also includes: Boron diffusion treatment is performed on the front side of the silicon substrate to form a P+ emitter layer; A second non-ion bombardment oxidation method is adopted to form a second silicon oxide layer on the P+ emitter layer.

8. The method for preparing a TOPCon solar cell according to claim 7, characterized in that: Also includes: forming an aluminum oxide passivation layer, a first silicon nitride anti-reflection layer and a third silicon oxide layer in sequence on the second silicon oxide layer; forming a second silicon nitride anti-reflection layer on the first silicon oxide layer; Preparing a front metal electrode on the third silicon oxide layer; A back metal electrode is prepared on the second silicon nitride anti-reflection layer.

9. The method for preparing a TOPCon solar cell according to claim 7, characterized in that: The second non-ion bombardment oxidation method includes one of thermal oxidation, wet oxygen oxidation, dry oxygen oxidation and chemical oxidation; When the second non-ion bombardment oxidation method is a thermal oxidation method, the temperature is 750-950° C., the special gas flow rate of oxygen is 5000-10000 sccm, and the special gas flow rate of nitrogen is 1-3 slm.

10. The method for preparing a TOPCon solar cell according to claim 7, characterized in that: The forming of the P+ emitter layer comprises: Under the condition of temperature of 600-960° C., liquid source boron trichloride and oxygen are used to form a borosilicate glass layer on the front side of the silicon substrate; wherein the special gas flow rate of the liquid source boron trichloride is 150-250 sccm, the special gas flow rate of the oxygen is 500-1000 sccm, and the sheet resistance of the borosilicate glass layer is 120-200 Ω / sq; The borosilicate glass layer is diffused at a temperature of 850-1050° C. and a special oxygen gas flow rate of 10-20 slm to form the P+ emitter layer; wherein the sheet resistance of the P+ emitter layer is 250-350Ω / sq.

11. The method for preparing a TOPCon solar cell according to claim 7, characterized in that: The thickness of the second silicon oxide layer is 5-10 nm.

12. A TOPCon solar cell, characterized in that: The TOPCon solar cell is prepared by the preparation method of any one of claims 1 to 11.

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