Annealing method of passive film, solar cell and preparation method thereof, and photovoltaic module

Abstract

The embodiment of the invention provides an annealing method of a passive film, a solar cell, a preparation method of the solar cell and a photovoltaic module. The annealing method of the passive film comprises the following steps: providing a substrate, wherein the passive film is arranged on the surface of at least one side of the substrate; the passive film is sequentially subjected to first-stage plasma annealing and second-stage annealing, the first-stage plasma annealing treatment takes a mixed gas source of laughing gas and argon as process gas, and the first-stage plasma annealing treatment has a first temperature T1 and a first pressure P1; the second temperature T2 and the second pressure P2 of the second-stage annealing treatment meet the condition of T1 < lt >; p1 and P2 meet the condition of P1lt; p2. According to the method provided by the embodiment of the invention, the ionized process gas is introduced under the low-pressure and low-temperature conditions to form the plasma for annealing, and then the second-stage annealing is performed under the high-temperature and high-pressure conditions, so that the passivation performance of the passivation film can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and particularly to an annealing method for a passivation film, a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] A crystalline silicon solar cell is a device that converts light energy into electrical energy by using the photovoltaic effect of a PN junction. Different from conventional solar cells, it adopts the technologies of dielectric film passivation and local metal contact on the back surface of the cell, which significantly reduces the back surface recombination rate and increases the back reflection of the cell, thereby greatly enhancing the long-wave effect of the cell.

[0003] Currently, in existing cell structures, a structure combining a passivation layer (AlO x ) and an antireflection layer (SiN b ) is usually used to provide hydrogen for polysilicon contacts. In existing processes, plate-type and tube-type atomic layer deposition (ALD) are usually used to prepare AlO x , and SiN b antireflection layer is prepared by PECVD after annealing. The AlO x film prepared in this way still has room for improvement in terms of the passivation effect of surface chemical passivation and field passivation; and there is plasma bombardment damage to the silicon wafer substrate, which further destroys the chemical passivation effect of the silicon wafer surface. Therefore, how to improve the passivation effect of the passivation film is particularly important.

[0004] It should be noted that the above content is not necessarily prior art and is not used to limit the patent protection scope of the present application. Summary of the Invention

[0005] Embodiments of the present application provide an annealing method for a passivation film, a solar cell and a preparation method thereof, and a photovoltaic module to solve or alleviate one or more of the above technical problems.

[0006] In a first aspect of embodiments of the present application, an annealing method for a passivation film is provided, including: providing a substrate, and a passivation film is disposed on at least one surface of the substrate; sequentially performing a first-stage plasma annealing and a second-stage annealing on the passivation film, wherein the first-stage plasma annealing treatment uses a mixed gas source of nitrous oxide and argon as a process gas, and a first temperature T1 and a first pressure P1 of the first-stage plasma annealing treatment, a second temperature T2 and a second pressure P2 of the second-stage annealing treatment, T1 and T2 satisfy T1 < T2, and P1 and P2 satisfy P1 < P2.

[0007] The method of the embodiments of the present application first uses low-pressure and low-temperature ventilation to ionize plasma for annealing, and then performs high-temperature and high-pressure oxidation annealing, which can improve the passivation performance of the passivation film.

[0008] Specifically, the plasma mixed gas is controlled to bombard the passivation film under low-pressure and low-temperature conditions, which can reduce the plasma-induced degradation effect caused by the high energy of vacuum ultraviolet photons, and thus improve the passivation quality of the passivation film surface. In addition, argon can promote the decomposition of nitrous oxide and release oxygen atoms, increasing the oxygen atom concentration. The increased oxygen atoms are beneficial to repairing the oxygen defects in the passivation film (such as the alumina passivation film). In addition, the bombardment of the nitrous oxide and argon plasma mixture can break the O-H bonds in the passivation film, and the released hydrogen penetrates into the passivation film and the interface between the passivation film and the substrate. Argon can effectively inhibit the generation of particles at the passivation film interface at lower pressures and lower temperatures, further improving the passivation performance of the passivation film.

[0009] In addition, the first-stage plasma annealing treatment is carried out under low pressure and low temperature (T1 < T2 between T1 and T2, P1 < P2 between P1 and P2). In this way, under the bombardment of argon ions, the atomic bond angles in the passivation film (such as the Al-O-Al bond angle in the alumina passivation film) will be relaxed, thus improving the quality of the passivation film; in the second-stage annealing, at higher annealing temperatures and pressures, oxygen atoms can obtain sufficient energy to repair the oxygen defects in the passivation film.

[0010] According to an embodiment of the present application, the first temperature T1 of the first-stage plasma annealing treatment is 430-480 °C. Thereby, the passivation performance of the passivation film is further improved.

[0011] According to an embodiment of the present application, the first pressure P1 of the first-stage plasma annealing treatment is 1500-1600 mbar.

[0012] According to an embodiment of the present application, the volume ratio of the process gases nitrous oxide and argon in the first-stage plasma annealing treatment is 6:(1-3); According to an embodiment of the present application, the time of the first-stage plasma annealing treatment is 40-80 s.

[0013] According to an embodiment of the present application, the second pressure P2 of the second-stage annealing treatment is 1600-1700 mbar.

[0014] According to an embodiment of the present application, the second temperature T2 of the second-stage annealing treatment is 500-550 °C; According to an embodiment of the present application, the time of the second-stage annealing treatment is 3-5 min.

[0015] In a second aspect of the embodiments of the present application, a method for manufacturing a solar cell is provided, including the following steps: providing a substrate; forming a passivation film on at least one surface of the substrate, and annealing the passivation film by using the method described in the first aspect.

[0016] The preparation method of the solar cell of the embodiment of the present application uses laughing gas and argon as process gases, and performs a two-step passivation process on the passivation film by first-stage plasma annealing and second-stage annealing, so as to obtain a solar cell with good photoelectric performance. Specifically, low-pressure and low-temperature ventilation ionization plasma is first used, and then high-temperature and high-pressure oxidation annealing is performed, which almost avoids the reduction of surface passivation quality caused by high energy; then, the oxygen element released by laughing gas is used to repair the oxygen vacancy defects in the passivation film (such as aluminum oxide passivation film), thereby improving the quality of the passivation film; secondly, the destruction of the O-H bond in the passivation film (such as aluminum oxide passivation film) will also occur during the two-stage process, and additional H will be released, which will help improve the passivation quality and thus improve the photoelectric conversion efficiency of the solar cell.

[0017] According to an embodiment of the present application, the substrate preparation method includes: providing a silicon wafer, the back side of the silicon wafer having a first region, a second region and an insulating region, the first region and the second region are distributed in a finger shape, and the insulating region is between the first region and the second region; forming a first tunneling oxide layer and a boron-doped layer in the first region of the silicon wafer in sequence, and forming a second tunneling oxide layer and a phosphorus-doped layer in the second region of the silicon wafer in sequence.

[0018] According to an embodiment of the present application, the first anti-reflection film and the second anti-reflection film are sequentially deposited on the front side of the silicon wafer, wherein the first anti-reflection film comprises SiN with a refractive index of 2.1 to 2.3. b The second anti-reflection film includes SiN with a refractive index of 1.5 to 1.7. m O n This further improves the photoelectric performance of the battery. This helps more light to be captured and transmitted to the silicon wafer, thereby improving the photoelectric conversion efficiency of the battery.

[0019] According to an embodiment of the present application, a third anti-reflection film is deposited on a side of the passivation film away from the silicon wafer, wherein the third anti-reflection film comprises SiN with a refractive index of 1.9 to 2.2. b .

[0020] According to an embodiment of the present application, the method further includes baking the cell on which the third anti-reflection film has been deposited, and the baking temperature is 810-900°C.

[0021] According to a third aspect of the embodiment of the present application, a solar cell is provided, which is prepared by the method of the second aspect. The solar cell has a good passivation effect and a high photoelectric conversion efficiency.

[0022] According to a fourth aspect of the embodiments of the present application, a photovoltaic module is provided, wherein the photovoltaic module comprises the solar cell according to the third aspect.

[0023] In a fifth aspect of the embodiments of the present application, a photovoltaic system is provided, comprising the photovoltaic module in any of the above embodiments. The photovoltaic system also has the advantages of the above photovoltaic modules, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 is a schematic structural diagram of a substrate in some embodiments; Figure 2 is a schematic structural diagram of a back-contact solar cell according to some embodiments.

[0026] Description of reference numerals: 1: silicon wafer; 2: first tunneling oxide layer; 3: boron-doped layer; 4: second tunneling oxide layer; 5: phosphorus-doped layer; 6: passivation film; 7: first anti-reflection film; 8: second anti-reflection film; 9: third anti-reflection film. DETAILED DESCRIPTION

[0027] 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 and regions and their relative sizes may be exaggerated. 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 the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0028] It should be understood that when a layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another layer, it may be directly on, adjacent to, connected to, or coupled to the other layer, or there may be intervening layers. It should be understood that although the terms first, second, third, etc. may be used to describe various regions, layers, and / or portions, these regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one region, layer, or portion from another region, layer, or portion. Therefore, without departing from the teachings of the present application, the first region, layer, or portion discussed below may be represented as the second region, layer, or portion. When the second region, layer, or portion is discussed, it does not mean that the first region, layer, or portion necessarily exists in the present application.

[0029] It should be noted that in the description and claims of this application and the above-mentioned drawings, the terms "first", "second", etc. are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of this application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] In this application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as 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 combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of quantitative intervals such as percentage intervals, ratio intervals, and ratio value intervals.

[0031] In a first aspect of the embodiments of this application, a method for annealing a passivation film is provided, which includes providing a substrate, and a passivation film is disposed on at least one surface of the substrate; sequentially performing a first-stage plasma annealing and a second-stage annealing on the passivation film, wherein the first-stage plasma annealing process uses a mixed gas source of nitrous oxide and argon as the process gas, and the first temperature T1 and the first pressure P1 of the first-stage plasma annealing process, the second temperature T2 and the second pressure P2 of the second-stage annealing process, and T1 < T2 is satisfied between T1 and T2, and P1 < P2 is satisfied between P1 and P2.

[0032] The method of the embodiments of this application first uses low-pressure and low-temperature venting and ionization plasma for annealing, and then high-temperature and high-pressure oxidation annealing, which can improve the passivation performance of the passivation film.

[0033] Specifically, the plasma mixed gas is controlled to bombard the passivation film under low pressure and low temperature conditions, which can reduce the plasma-induced degradation effect caused by the high energy of vacuum ultraviolet photons, and thus improve the passivation quality of the passivation film surface. In addition, argon can promote the decomposition of nitrous oxide and release oxygen atoms, increasing the oxygen atom concentration. The increased oxygen atoms are beneficial to repairing oxygen defects in the passivation film (such as alumina passivation film). In addition, the bombardment of the nitrous oxide and argon plasma mixture can break the O-H bonds in the passivation film, and the released hydrogen penetrates into the passivation film and the interface between the passivation film and the substrate. Argon can effectively inhibit the generation of particles at the passivation film interface at lower pressures and lower temperatures, further improving the passivation performance of the passivation film.

[0034] In addition, the first-stage plasma annealing treatment is carried out at a relatively low pressure and low temperature (T1 < T2 between T1 and T2, P1 < P2 between P1 and P2). In this way, under the bombardment of argon ions, the atomic bond angles in the passivation film (such as the Al-O-Al bond angle in the alumina passivation film) will be relaxed, thereby improving the quality of the passivation film; in the second-stage annealing, at a higher annealing temperature and pressure, oxygen atoms can obtain sufficient energy to repair oxygen defects in the passivation film.

[0035] In some embodiments, the temperature T1 of the first-stage plasma annealing treatment is 430 - 480 °C, such as 430 °C, 450 °C, 480 °C, etc. Thus, the lower temperature is beneficial to the bombardment of the passivation film by argon particles, relaxing the atomic bond angles in the passivation film, and further improving the quality of the passivation film.

[0036] In some embodiments, the pressure P1 of the first-stage plasma annealing is 1500 - 1600 mbar, such as 1500 mbar, 1550 mbar, 1600 mbar, etc. Thus, the lower pressure is beneficial to the bombardment of the passivation film by argon particles, relaxing the atomic bond angles in the passivation film, and further improving the quality of the passivation film.

[0037] In some embodiments, the volume ratio of nitrous oxide to argon is 6∶(1 - 3), such as 6∶1, 6∶2, 6∶3, etc. Thus, the passivation quality of the passivation film surface is further improved.

[0038] In some embodiments, the time of the first-stage plasma annealing treatment is 40 - 80 s, such as 40 s, 50 s, 60 s, 80 s, etc. This can provide sufficient treatment of the process gas, enabling the process gas to be ionized and bombard the passivation film, thereby improving the surface passivation quality of the passivation film.

[0039] In some embodiments, the frequency of the plasma power supply is 30-40 kHz, the power is 1500-2500 W, and the radio frequency on-off ratio is 1:(25-35). This is beneficial for the ionization of the process gas to bombard the passivation film, thereby improving the surface passivation quality of the passivation film.

[0040] In some embodiments, the pressure P2 of the second stage annealing treatment is 1600-1700 mbar, such as 1600 mbar, 1650 mbar, 1700 mbar, etc. The second stage annealing treatment is performed at a higher pressure, which can increase the concentration of oxygen atoms decomposed by N2O, and the increased oxygen atoms are beneficial to repairing oxygen defects in the passivation film (such as aluminum oxide passivation film).

[0041] In some embodiments, the temperature T2 of the second stage annealing treatment is 500-550°C, such as 500°C, 530°C, 550°C, etc. The second stage annealing treatment is performed at a higher temperature, which can increase the concentration of oxygen atoms decomposed by N2O, and the increased oxygen atoms are beneficial to repairing oxygen defects in the passivation film (such as aluminum oxide passivation film).

[0042] In some embodiments, the second annealing treatment lasts for 3 to 5 minutes, such as 3 minutes, 4 minutes, 5 minutes, etc. In this way, the passivation film can be subjected to a relatively sufficient passivation treatment (second stage annealing).

[0043] In some embodiments, the passivation film includes AlO x , TiO2, SiO2, and ZnO.

[0044] In some embodiments, reference Figure 1 The substrate comprises a silicon wafer 1, a first tunneling oxide layer 2, a boron-doped layer 3, a second tunneling oxide layer 4, a phosphorus-doped layer 5, and a passivation film 6. The first tunneling oxide layer and the second tunneling oxide layer are interdigitated and located on the back of the silicon wafer, the boron-doped layer is located on a side of the first tunneling oxide layer away from the silicon wafer, the phosphorus-doped layer is located on a side of the second tunneling oxide layer away from the silicon wafer, the passivation film is located on a side of the boron-doped layer and the phosphorus-doped layer away from the silicon wafer, and is located in an insulating region between the first tunneling oxide layer and the second tunneling oxide layer.

[0045] In a second aspect of an embodiment of the present application, a method for preparing a solar cell is provided, comprising the following steps: providing a substrate, forming a passivation film on at least one surface of the substrate, and annealing the passivation film using the method of the first aspect.

[0046] The preparation method of the solar cell of the embodiment of the present application uses laughing gas and argon as process gases, and performs a two-step passivation process on the passivation film by first-stage plasma annealing and second-stage annealing, so as to obtain a solar cell with good photoelectric performance. Specifically, low-pressure and low-temperature ventilation ionization plasma is first used, and then high-temperature and high-pressure oxidation annealing is performed, which almost avoids the reduction of surface passivation quality caused by high energy; then, the oxygen element released by laughing gas is used to repair the oxygen vacancy defects in the passivation film (such as aluminum oxide passivation film), thereby improving the quality of the passivation film; secondly, the destruction of the O-H bond in the passivation film (such as aluminum oxide passivation film) will also occur during the two-stage process, and additional H will be released, which will help improve the passivation quality and thus improve the photoelectric conversion efficiency of the solar cell.

[0047] According to an embodiment of the present application, in step (1), a substrate is provided.

[0048] In some embodiments, in step (1), the preparation method of the substrate includes: providing a silicon wafer, the back side of the silicon wafer having a first region, a second region and an insulating region, the first region and the second region are distributed in a finger shape, and the insulating region is between the first region and the second region; forming a first tunneling oxide layer and a boron-doped layer in the first region in sequence, and forming a second tunneling oxide layer and a phosphorus-doped layer in the second region in sequence.

[0049] In some embodiments, in step (1), a first tunneling oxide layer and an intrinsic microcrystalline amorphous mixed layer are sequentially deposited on the back side of a silicon wafer using an LPCVD device, boron is diffused on the surface of the intrinsic microcrystalline amorphous mixed layer, and the intrinsic microcrystalline amorphous mixed layer is crystallized into a polycrystalline silicon layer, so as to form a boron-doped layer and a borosilicate glass layer on a side of the first tunneling oxide layer away from the silicon wafer, and a borosilicate glass layer with a thickness of 200 to 400 μm is formed on the front and side surfaces of the silicon wafer.

[0050] In some embodiments, in step (1), after the borosilicate glass layer in the non-first region of the silicon wafer is removed by a laser etching process, an alkaline solution (such as an aqueous potassium hydroxide solution) is used to etch the boron-doped layer in the non-first region on the back side of the silicon wafer and on the front side.

[0051] In some embodiments, in step (1), after cleaning the product obtained by alkaline solution polishing, a second tunneling oxide layer and an intrinsic microcrystalline amorphous mixed layer are prepared on the surface of the silicon wafer using LPCVD equipment, and phosphorus diffusion and conversion of amorphous silicon to polycrystalline silicon are performed on the intrinsic microcrystalline amorphous mixed layer to form a phosphorus-doped layer and a phosphosilicate glass layer with a thickness of 200 to 300 μm.

[0052] In some embodiments, in step (1), a second laser is used to open the phosphosilicate glass layer on the back side so that the phosphorus-doped layer and the boron-doped layer are insulated. Then, the surface phosphosilicate glass layer is etched, and a single-sided chain hydrofluoric acid cleaning machine is used to remove the phosphosilicate glass layer coated on the front and side of the silicon wafer. Subsequently, an alkaline solution is used to remove the phosphorus-doped layer on the non-second area and the front of the silicon wafer. Finally, an alkaline solution is used to texturize the front side so that the front side of the silicon wafer has a pyramid morphology, and the texturized product is subjected to HF until the back side is completely hydrophobic.

[0053] According to an embodiment of the present application, in step (2), a passivation film is formed on at least one surface of the substrate, and the passivation film is annealed using the method described in the first aspect.

[0054] In some embodiments, in step (2), a 5-10 nm passivation film is deposited on the front side of the substrate using atomic layer deposition (ALD).

[0055] Furthermore, the passivation film comprises AlO x , TiO2, SiO2, and ZnO.

[0056] In some embodiments, step (2) further includes sequentially depositing a first anti-reflection film and a second anti-reflection film on a side of the passivation film away from the front surface of the silicon wafer, wherein the first anti-reflection film comprises SiN with a refractive index of 2.1 to 2.3. b The second anti-reflection film includes SiN with a refractive index of 1.5 to 1.7. m O n The refractive index of light increases from air (n=1) to silicon (n=3.88). The anti-reflection films (first anti-reflection film and second anti-reflection film) designed in this way are conducive to capturing more light and transmitting it to the silicon wafer, thereby improving the photoelectric conversion efficiency of the battery.

[0057] Optionally, the number of deposited layers of the first anti-reflection film is 2-6 layers, for example, 2, 3, 4, 5, 6, etc.

[0058] Optionally, the number of deposited layers of the second anti-reflection film is 1-4 layers, for example, 1, 2, 3, 4, etc.

[0059] Optionally, the thickness of the first anti-reflection film and the second anti-reflection film are independently 1-5 μm.

[0060] In some embodiments, step (2) further includes depositing a third anti-reflection film on the back side of the silicon wafer, wherein the third anti-reflection film includes SiN with a refractive index of 1.9 to 2.2. bThe refractive index of light increases from air (n=1) to silicon (n=3.88). The anti-reflection film (third anti-reflection film) designed in this way is conducive to capturing more light and transmitting it to the silicon wafer, thereby improving the photoelectric conversion efficiency of the battery.

[0061] Furthermore, the number of deposited layers of the third anti-reflection film is 2 to 6 layers, for example, 2, 3, 4, 5, 6, etc.

[0062] Optionally, the thickness of the third anti-reflection films is independently 1-5 μm.

[0063] In some embodiments, the process further includes baking the cell on which the third anti-reflection film has been deposited, and the baking temperature is 810-900°C, such as 810°C, 830°C, 850°C, 900°C, etc. Baking is beneficial for the screen printing paste to burn through the anti-reflection film (the first anti-reflection film and the second anti-reflection film) and the passivation film to form an ohmic contact with the emitter. During baking, if the temperature is too high, the paste will burn through the silicon substrate, causing a short circuit in the cell, and will reduce the cell life and affect the cell performance; if the temperature is too low, the paste will not be able to penetrate the anti-reflection film and the passivation film to form contact with the emitter, resulting in poor cell contact.

[0064] In some embodiments, the method further includes preparing an emitter, wherein the emitter comprises silver.

[0065] According to a third aspect of the embodiment of the present application, a solar cell is provided, which is prepared by the method of the second aspect. The solar cell has a good passivation effect and a high photoelectric conversion efficiency.

[0066] In some embodiments, the iVoc of the solar cell increases by at least 2 mV. This is because the passivation film is annealed using the method of the first aspect, which improves the passivation performance of the passivation film, thereby increasing the iVoc of the solar cell by at least 2 mV.

[0067] In some embodiments, the solar cell includes a passivated tunneling solar cell and a back contact solar cell.

[0068] In some embodiments, reference Figure 2The back contact solar cell comprises a silicon wafer 1, a first tunneling oxide layer 2, a boron doped layer 3, a second tunneling oxide layer 4, a phosphorus doped layer 5, a passivation film 6, a first anti-reflection film 7, a second anti-reflection film 8 and a third anti-reflection film 9. The first tunneling oxide layer and the second tunneling oxide layer are arranged on the back of the silicon wafer in a forked shape, the boron doped layer is arranged on a side of the first tunneling oxide layer away from the silicon wafer, the phosphorus doped layer is arranged on a side of the second tunneling oxide layer away from the silicon wafer, the passivation film is arranged on a side of the boron doped layer and the phosphorus doped layer away from the silicon wafer, and an insulating region is arranged between the first tunneling oxide layer and the second tunneling oxide layer, three layers of the first anti-reflection film 7 and two layers of the second anti-reflection film 8 are arranged on the front of the silicon wafer in sequence, and two layers of the third anti-reflection film 9 are arranged on a side of the passivation film away from the substrate.

[0069] According to a fourth aspect of the embodiments of the present application, a photovoltaic module is provided, wherein the photovoltaic module comprises the solar cell according to the third aspect.

[0070] 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 the solar cell described above. A plurality of solar cells in series form a cell string, and adjacent solar cells can be connected together by string welding.

[0071] In a fifth aspect of the embodiments of the present application, a photovoltaic system is provided, comprising the photovoltaic module in any of the above embodiments. The photovoltaic system also has the advantages of the above photovoltaic modules, which will not be described in detail here.

[0072] 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 is understandable that the application scenarios of photovoltaic systems are not limited to this, that is to say, photovoltaic systems can be used in all fields that require solar energy to generate electricity. 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 can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. 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.

[0073] 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.

[0074] Example 1 S1: Deposit a tunnel oxide layer and an intrinsic microcrystalline amorphous mixed layer on the back of the silicon wafer using LPCVD, perform boron diffusion on the surface of the intrinsic microcrystalline amorphous mixed layer, and crystallize the intrinsic microcrystalline amorphous mixed layer into a polycrystalline layer to form a 320μm boron doped layer and a 65μm borosilicate glass layer. S2: After the borosilicate glass layer on the non-first area on the back side of the silicon wafer and the front side of the silicon wafer is removed by laser etching, an alkaline solution (50wt% KOH) is used to remove the boron-doped layer on the non-first area on the back side of the silicon wafer and the front side of the silicon wafer.

[0075] S3: After the product obtained in step S2 is cleaned by RCA and HF, a second tunneling oxide layer and an intrinsic microcrystalline amorphous mixed layer are prepared on the surface by LPCVD method, and phosphorus diffusion and amorphous silicon to polycrystalline silicon are converted on the intrinsic microcrystalline amorphous mixed layer to form a 250μm phosphorus-doped layer and a 45μm phosphosilicate glass layer.

[0076] S4: At 50W power, the second laser is used to open the phosphosilicate glass layer on the back and etch the surface phosphosilicate glass layer. Then a single-sided chain hydrofluoric acid cleaning machine is used to remove the phosphosilicate glass layer on the silicon wafer.

[0077] S5: Use alkaline solution (50wt% KOH) to polish and remove the phosphorus-doped layer on the back side and the non-second area on the front side. Use alkaline solution (50wt% KOH) to make a texture, and the front side has a pyramid morphology. The textured product is passed through HF until the back side is completely hydrophobic.

[0078] S6: Using atomic layer deposition (ALD), 8 nm of AlO is deposited on both the front and back sides of the product obtained in step S5. x film.

[0079] S7: Plasma enhanced vapor deposition (PECVD) on AlO x Anti-reflection layer is deposited on the film to further improve the AlO x To improve the film quality, N2O / Ar plasma treatment and high-temperature oxidation were performed before the anti-reflection layer was deposited. The first stage plasma treatment conditions were: N2O / Ar volume ratio of 6:2, pressure P1 of 1600mbar, temperature T1 of 450℃, time of 60s, plasma power frequency of 40kHz, power of 2500W, and RF on-off ratio of 1:25. The second stage annealing conditions were: pressure P2 of 1700mbar, temperature T2 of 500℃, and time of 4min.

[0080] S8: Three layers of SiN are deposited on the AlOx passivation film on the front side of the silicon wafer using PECVD. b The first anti-reflection film (thickness 0.5μm), two layers of SiN mO n The second anti-reflection film (thickness 0.2μm), SiN b The refractive index of SiN is 2.2. m O n The refractive index is 1.6. Three layers of SiN are deposited on the back of the silicon wafer. b The third anti-reflection film (thickness 0.3μm) has a refractive index of 2.1.

[0081] S9: Sinter the product obtained in step S8 at 850° C. for 10 seconds.

[0082] S10: Making electrodes and injecting light to obtain a solar cell.

[0083] Example 2-3 The solar cell was prepared in the manner of Example 1, except that the first temperature T1 of the first stage plasma annealing treatment was 430° C. and 480° C. respectively.

[0084] Example 4 A solar cell was prepared in the manner of Example 1, except that the first pressure P1 of the first stage plasma annealing treatment was 1500 mbar.

[0085] Embodiment 5-6 A solar cell was prepared in the manner of Example 1, except that the volume ratios of laughing gas and argon gas in the first stage plasma annealing were 6:1 and 6:3, respectively.

[0086] Embodiment 7-8 The solar cell was prepared in the manner of Example 1, except that the duration of the first stage plasma annealing treatment was 40 s and 80 s respectively.

[0087] Example 9 A solar cell was prepared in the same manner as in Example 1, except that the second temperature T2 of the second stage annealing treatment was 550°C.

[0088] Example 10 A solar cell was prepared in the manner of Example 1, except that the second pressure P2 of the second stage annealing treatment was 1610 mbar.

[0089] Examples 11-12 The solar cell was prepared in the same manner as in Example 1, except that the time of the second stage annealing treatment was 3 minutes and 5 minutes respectively.

[0090] Comparative Example 1 A solar cell was prepared in the manner of Example 1, except that the first temperature T1 of the first stage plasma annealing treatment was 450° C. and the first pressure was 1600 mbar, and the second temperature T2 of the second stage annealing treatment was 400° C. and the second pressure P2 was 1700 mbar.

[0091] Comparative Example 2 A solar cell was prepared in the manner of Example 1, except that the first temperature T1 of the first stage plasma annealing treatment was 450° C. and the first pressure was 1600 mbar, and the second temperature T2 of the second stage annealing treatment was 500° C. and the second pressure P2 was 1500 mbar.

[0092] Comparative Example 3 A solar cell was prepared in the manner of Example 1, except that the first temperature T1 of the first stage plasma annealing treatment was 450° C. and the first pressure was 1600 mbar, and the second temperature T2 of the second stage annealing treatment was 400° C. and the second pressure P2 was 1500 mbar.

[0093] Comparative Example 4 A solar cell was prepared in the same manner as in Example 1, except that the process gas was hydrogen.

[0094] Test Case The solar cells of the above-mentioned embodiments and comparative examples were subjected to the following performance tests, and the results are shown in Table 1: Open circuit voltage test: The specific test method is to place the battery under a light source of 100 mW / cm 2 The results are obtained by connecting a source meter using the four-wire method under AM 1.5G simulated sunlight at 25°C.

[0095] Detection of impurities and defect distribution of battery cells (PL test): Detection of impurities and defect distribution of batteries at 1Sun and 0.2v.

[0096] Table 1

[0097] As can be seen from the above table, by comparing Examples 1-12 with Comparative Examples 1-4, it can be seen that the photoelectric performance of the battery of Examples 1-12 is better than that of Comparative Examples 1-4. This is because the passivation performance of the passivation film is improved by first using low-pressure and low-temperature ventilated ionized plasma for annealing and then high-temperature and high-pressure oxidation annealing.

[0098] Comparing Example 1 with Comparative Examples 1-3, it can be seen that the photoelectric performance of the battery of Example 1 is better than that of Comparative Examples 1-3. This is because Example 1 first uses low-pressure and low-temperature ventilated ionized plasma for annealing, and then high-temperature and high-pressure oxidation annealing, which can improve the passivation performance of the passivation film. In the comparative examples, high temperature first, high pressure first, or high temperature and high pressure first will all lead to degradation of the passivation film.

[0099] By comparing Example 1 with Comparative Example 4, it can be seen that the photoelectric performance of the battery of Example 1 is better than that of Comparative Example 4. This is because the mixed gas of nitrous oxide and argon is used as the process gas. Argon can promote the decomposition of nitrous oxide and release oxygen atoms, so that the concentration of oxygen atoms increases. The increased oxygen atoms are conducive to repairing oxygen defects in the passivation film (such as aluminum oxide passivation film). In addition, the bombardment of the mixture of nitrous oxide and argon plasma can break the OH bond in the passivation film, and the released hydrogen penetrates into the passivation film and the interface between the passivation film and the substrate. Argon can effectively inhibit the generation of particles at the interface of the passivation film at a lower pressure and a lower temperature, and further improve the passivation performance of the passivation film; while when hydrogen is used as the process gas, the aforementioned effects of hydrogen are minimal.

[0100] 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.

[0101] 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.

[0102] 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 annealing a passivation film, characterized in that: Including: Providing a substrate, on at least one side surface of which a passivation film is provided; Successively performing a first-stage plasma annealing and a second-stage annealing on the passivation film, wherein, in the first-stage plasma annealing treatment, a mixed gas source of nitrous oxide and argon is used as the process gas, and a first temperature T1 and a first pressure P1 in the first-stage plasma annealing treatment, a second temperature T2 and a second pressure P2 in the second-stage annealing treatment, and T1 < T2 is satisfied between T1 and T2, and P1 < P2 is satisfied between P1 and P2.

2. The annealing method according to claim 1, characterized in that: The first-stage plasma annealing treatment satisfies at least one of the following conditions: T1 is 430 - 480 °C; P1 is 1500 - 1600 mbar; The volume ratio of nitrous oxide to argon is 6∶(1 - 3); The time is 40 - 80 s.

3. The annealing method according to claim 1, characterized in that: The second-stage annealing treatment satisfies at least one of the following conditions: P2 is 1600 - 1700 mbar; T2 is 500 - 550 °C; The time is 3 - 5 min.

4. A method for preparing a solar cell, characterized in that: Including the following steps: Providing a substrate; Forming a passivation film on at least one side surface of the substrate, and annealing the passivation film by using the method according to any one of claims 1 - 3.

5. The method according to claim 4, characterized in that The substrate preparation method includes: Providing a silicon wafer, on the back surface of which there are a first region, a second region and an insulating region, the first region and the second region are finger-shapedly distributed, and the insulating region is between the first region and the second region; Successively forming a first tunneling oxide layer and a boron doping layer in the first region of the silicon wafer, and successively forming a second tunneling oxide layer and a phosphorus doping layer in the second region of the silicon wafer.

6. The method according to claim 5, characterized in that It further includes successively depositing a first antireflection film and a second antireflection film on the front surface of the silicon wafer, The first anti-reflection film includes SiN with a refractive index of 2.1 to 2.

3. b , The second anti-reflection film includes SiN with a refractive index of 1.5 to 1.7 m O n .

7. The method according to claim 6, characterized in that It further includes: A third anti-reflection film is deposited on a side of the passivation film away from the silicon wafer, wherein the third anti-reflection film comprises SiN with a refractive index of 1.9 to 2.

2. b .

8. The method according to claim 7, characterized in that It further includes baking the cell on which the third antireflection film is deposited, and the baking temperature is 810 - 900 °C.

9. A solar cell, characterized in that: Prepared by the method according to any one of claims 4 - 8.

10. A photovoltaic module, characterized in that: The photovoltaic module includes the solar cell according to claim 9.

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