Preparation method of solar cell and solar cell

Abstract

The invention relates to the technical field of photovoltaic cells, in particular to a preparation method of a solar cell and the solar cell. The preparation method of the solar cell comprises the following steps: preparing a silicon substrate; depositing a tunneling oxide layer on the silicon substrate; a doped polycrystalline silicon layer is generated on the tunneling oxide layer, and the doping concentration of the doped polycrystalline silicon layer is gradually reduced in the direction away from the tunneling oxide layer. In the preparation method of the solar cell, the doping concentration of the generated doped polycrystalline silicon layer is gradually reduced along the direction far away from the tunneling oxide layer, and even if the doping concentration value at the contact interface of the doped polycrystalline silicon layer and the tunneling oxide layer is relatively high, the doping concentration value of the doped polycrystalline silicon layer and the tunneling oxide layer is relatively high; therefore, the defect density at the contact interface of the doped polycrystalline silicon layer and the tunneling oxide layer can be reduced, carrier recombination caused by abrupt change of an energy band at the interface is avoided, recombination loss is reduced, the open-circuit voltage and the fill factor of the solar cell are further improved, and the working efficiency of the solar cell is further improved.

Description

Technical Field

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

[0002] Photovoltaic cells can convert solar energy into electrical energy, and have the advantages of being pollution-free, having no geographical restrictions, and being inexhaustible, etc., and are the main direction for developing new energy. The Topcon cell is a type of photovoltaic cell. The back surface of the Topcon cell includes a tunneling oxide layer and a doped polysilicon layer, and the two together form a passivation contact structure, which provides good interface passivation for the back surface of the silicon wafer. However, in the existing preparation process, the doping concentration at the contact interface between the doped polysilicon layer and the tunneling oxide layer is relatively low, resulting in an easy mutation of the energy band at the contact interface between the doped polysilicon layer and the tunneling oxide layer, triggering carrier recombination and affecting the photoelectric conversion efficiency of the Topcon cell. Summary of the Invention

[0003] To solve the above technical problems, the present application provides a preparation method of a solar cell and a solar cell, so as to facilitate solving the technical problem of relatively low photoelectric conversion efficiency of the solar cell prepared in the prior art.

[0004] In a first aspect, the present application provides a preparation method of a solar cell, and the preparation method of the solar cell includes: Preparing a silicon substrate; Depositing a tunneling oxide layer on the silicon substrate; Generating a doped polysilicon layer on the tunneling oxide layer, and along the direction away from the tunneling oxide layer, gradually reducing the doping concentration of the doped polysilicon layer.

[0005] In this embodiment, the beneficial effects of adopting the above preparation method of the solar cell are as follows: when generating the doped polysilicon layer on the tunneling oxide layer, gradually reducing the doping concentration of the doped polysilicon layer, so that the generated doped polysilicon layer has the characteristic of gradient change of doping concentration, which can improve the conductivity of carriers in the doped polysilicon layer, reduce the series resistance of the solar cell, improve the fill factor and open circuit voltage of the solar cell, and further improve the working efficiency of the solar cell. At the same time, in the above preparation method of the solar cell, along the direction away from the tunneling oxide layer, the doping concentration of the generated doped polysilicon layer gradually decreases, that is, the doping concentration value at the contact interface between the doped polysilicon layer and the tunneling oxide layer is relatively high, so that the defect density at the contact interface between the doped polysilicon layer and the tunneling oxide layer can be reduced, the energy band mutation at the interface can be avoided from causing carrier recombination, the recombination loss can be reduced, and the open circuit voltage and fill factor of the solar cell can be further improved, thereby further improving the working efficiency of the solar cell.

[0006] In a specific embodiment, in the step of forming a doped polysilicon layer on the tunneling oxide layer and gradually decreasing the doping concentration of the doped polysilicon layer in a direction away from the tunneling oxide layer, the method for manufacturing the solar cell specifically includes: Deposit an intrinsic polysilicon layer on the tunneling oxide layer, while introducing a doping reaction gas and gradually decreasing the flow rate of the doping reaction gas.

[0007] In a specific embodiment, the doped polysilicon layer has a first end and a second end, the first end faces the tunneling oxide layer, and the second end is away from the tunneling oxide layer. The step of forming a doped polysilicon layer on the tunneling oxide layer specifically includes: When depositing the first end, the flow rate of the doping reaction gas is 18 sccm - 22 sccm; When depositing the second end, the flow rate of the doping reaction gas is gradually decreased to 4 sccm - 6 sccm.

[0008] In a specific embodiment, in the step of introducing a doping reaction gas and gradually decreasing the flow rate of the doping reaction gas, the decreasing rate of the flow rate of the doping reaction gas is 0.5 sccm / min - 1 sccm / min.

[0009] In a specific embodiment, in the step of forming a doped polysilicon layer on the tunneling oxide layer, the deposition rate of the doped polysilicon layer is 2 nm / min - 5 nm / min.

[0010] In a specific embodiment, in the step of introducing a doping reaction gas, the method for manufacturing the solar cell specifically includes: Use a closed-loop gas flow control system to control the flow rate of the doping reaction gas, and combine real-time mass spectrometry to detect the flow rate of the doping reaction gas.

[0011] In a specific embodiment, after the step of forming a doped polysilicon layer on the tunneling oxide layer and gradually decreasing the doping concentration of the doped polysilicon layer in a direction away from the tunneling oxide layer, the method for manufacturing the solar cell further includes: Perform an annealing treatment on the silicon substrate at a temperature of 650 °C - 750 °C for a time of 30 min - 60 min.

[0012] In a second aspect, an embodiment of the present application provides a solar cell, which is manufactured by the method for manufacturing the solar cell described above.

[0013] In this embodiment, for the solar cell prepared by the above-mentioned method for preparing a solar cell, along the direction from the first end to the second end, the doping concentration of the doped polysilicon layer gradually decreases, that is, the doping concentration value at the first end of the doped polysilicon layer is relatively high, reducing the defect density at the contact interface between the doped polysilicon layer and the tunneling oxide layer, thereby optimizing the selective transport path of carriers, ensuring the carrier transport effect, reducing the recombination loss caused by carrier recombination, and thus improving the photoelectric conversion efficiency of the solar cell. At the same time, since the doping concentration in the doped polysilicon layer gradually changes along the thickness direction of the solar cell, the doped polysilicon layer also has the characteristic of a gradient change in doping concentration, which can further improve the conductivity of carriers, reduce the series resistance of the solar cell, increase the fill factor and open-circuit voltage of the solar cell, and thus can further improve the working efficiency of the solar cell.

[0014] In a specific embodiment, the solar cell includes a silicon substrate, a tunneling oxide layer, and a doped polysilicon layer stacked; along the thickness direction of the solar cell, the doped polysilicon layer has a first end and a second end disposed opposite to each other, the first end is in contact with the tunneling oxide layer, and the second end is away from the tunneling oxide layer; along the direction from the first end to the second end, the doping concentration in the doped polysilicon layer gradually decreases.

[0015] In a specific embodiment, the thickness of the doped polysilicon layer is 50 nm - 100 nm; the doping concentration at the first end is 0.8×10 20 cm -3 -1.2×10 20 cm -3 , and the doping concentration at the second end is reduced to 4×10 19 cm -3 -6×10 19 cm -3 . Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic structural diagram of the solar cell provided by the present application in a specific embodiment; Figure 2 is Figure 1 a schematic structural diagram of the silicon substrate, the tunneling oxide layer, and the doped polysilicon layer in

[0018] Reference Signs: 1 - Solar cell; 11 - Silicon substrate; 12 - Tunneling oxide layer; 13 - Doped polysilicon layer; 131 - First end; 132 - Second end; 14 - First metal electrode; 15 - First passivation layer; 16 - Emitter; 17 - Second metal electrode; 18 - Second passivation layer. Detailed implementation manners

[0019] For a better understanding of the technical solutions of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0020] It should be clear that the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0021] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms of "a", "the" and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0022] It should be understood that the term " / and" used herein is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0023] Photovoltaic cells can convert solar energy into electrical energy, and have the advantages of being pollution-free, having no geographical restrictions, and being inexhaustible. They are the main direction for developing new energy in the future. The Topcon cell is a new type of passivated contact cell, and a tunneling oxide layer and a doped polysilicon layer are provided on its back. The two together form a passivated contact structure, providing good interface passivation for the back of the silicon wafer. However, in the existing preparation process, the doping concentration at the contact interface between the doped polysilicon layer and the tunneling oxide layer of the Topcon cell is relatively low, resulting in an easy mutation of the energy band at the contact interface between the doped polysilicon layer and the tunneling oxide layer, triggering carrier recombination, increasing the recombination loss, and affecting the photoelectric conversion efficiency of the Topcon cell.

[0024] To solve the above technical problems, asFigure 1 and Figure 2 As shown in Figure 2 , an embodiment of the present application provides a method for manufacturing a solar cell 1. The method for manufacturing the solar cell 1 includes, but is not limited to, the following steps: S11: Prepare a silicon substrate 11; S12: Deposit a tunneling oxide layer 12 on the silicon substrate 11; S13: Generate a doped polysilicon layer 13 on the tunneling oxide layer 12, and along the direction away from the tunneling oxide layer 12, gradually reduce the doping concentration of the doped polysilicon layer 13.

[0025] In this embodiment, when generating the doped polysilicon layer 13 on the tunneling oxide layer 12, the doping concentration of the doped polysilicon layer 13 is gradually reduced, so that the generated doped polysilicon layer 13 has the characteristic of a gradient change in doping concentration, which can improve the conductivity of carriers in the doped polysilicon layer 13, reduce the series resistance of the solar cell 1, improve the fill factor and open-circuit voltage of the solar cell 1, and further improve the working efficiency of the solar cell 1. At the same time, in the above method for manufacturing the solar cell 1, along the direction away from the tunneling oxide layer 12, the doping concentration of the generated doped polysilicon layer 13 gradually decreases, that is, the doping concentration value at the contact interface between the doped polysilicon layer 13 and the tunneling oxide layer 12 is relatively high, so that the defect density at the contact interface between the doped polysilicon layer 13 and the tunneling oxide layer 12 can be reduced, the band abrupt change at the interface can be avoided from causing carrier recombination, the recombination loss can be reduced, and the open-circuit voltage and fill factor of the solar cell 1 can be further improved, thereby further improving the working efficiency of the solar cell 1.

[0026] As Figure 1 and Figure 2 shown, an embodiment of the present application further provides a solar cell 1. The solar cell 1 is manufactured by the above method for manufacturing the solar cell 1. The solar cell 1 may include a silicon substrate 11, a tunneling oxide layer 12, and a doped polysilicon layer 13 that are stacked. Along the thickness direction of the solar cell 1, the doped polysilicon layer 13 has a first end 131 and a second end 132 that are oppositely arranged. The first end 131 is in contact with the tunneling oxide layer 12, and the second end 132 is away from the tunneling oxide layer 12. Along the direction from the first end 131 to the second end 132, the doping concentration in the doped polysilicon layer 13 gradually decreases.

[0027] In this embodiment, for the solar cell 1 prepared by the above method for preparing a solar cell 1, along the direction from the first end 131 to the second end 132, the doping concentration of the doped polysilicon layer 13 gradually decreases, that is, the doping concentration value at the first end 131 of the doped polysilicon layer 13 is relatively high, reducing the defect density at the contact interface between the doped polysilicon layer 13 and the tunneling oxide layer 12, thereby optimizing the selective transport path of carriers, ensuring the carrier transport effect, reducing the recombination loss caused by carrier recombination, and thus improving the photoelectric conversion efficiency of the solar cell 1. At the same time, since the doping concentration in the doped polysilicon layer 13 gradually changes along the thickness direction of the solar cell 1, the doped polysilicon layer 13 also has the characteristic of a gradient change in doping concentration, which can further improve the conductivity of carriers, reduce the series resistance of the solar cell 1, increase the fill factor and open-circuit voltage of the solar cell 1, and thus can further improve the working efficiency of the solar cell 1.

[0028] The solar cell 1 in the above embodiment can be a Topcon cell, such as Figure 1 As shown, the Topcon cell may further include structures such as a metal electrode, a passivation layer, and an emitter. Along its thickness direction, the Topcon cell may sequentially include a first metal electrode 14, a first passivation layer 15, an emitter 16, a silicon substrate 11, a tunneling oxide layer 12, a doped polysilicon layer 13, a second passivation layer 18, and a second metal electrode 17. Among them, the tunneling oxide layer 12 and the doped polysilicon layer 13 can jointly form a passivated contact structure, which can block the recombination of minority carrier holes and increase the open-circuit voltage of the solar cell 1. Specifically, the tunneling oxide layer 12 can allow majority carrier electrons to tunnel into the doped polysilicon layer 13 while blocking the recombination of minority carrier holes, having a good passivation effect. The doped polysilicon layer 13 can induce band bending, thereby forming a field passivation effect. The probability of electron tunneling increases significantly, the contact resistance decreases, the open-circuit voltage of the solar cell 1 is increased, and thus the photoelectric conversion efficiency of the solar cell 1 is improved.

[0029] In a specific embodiment, such as Figure 1 and Figure 2 As shown, when the doped polysilicon layer 13 is formed on the tunneling oxide layer 12 and the doping concentration of the doped polysilicon layer 13 gradually decreases along the direction away from the tunneling oxide layer 12, the above step S13 may specifically include but is not limited to: S131: Deposit an intrinsic polysilicon layer on the tunneling oxide layer 12 while introducing a doping reaction gas and gradually reducing the flow rate of the doping reaction gas.

[0030] In this embodiment, low-pressure chemical vapor deposition (LPCVD) can be used to deposit the intrinsic polysilicon layer. At the same time, doping reaction gas is introduced during the doping process, so that the intrinsic polysilicon layer can be doped while being deposited, converting the deposited intrinsic polysilicon layer into the doped polysilicon layer 13. As the reaction proceeds, the flow rate of the introduced doping reaction gas gradually decreases, so that the doping concentration of the subsequently formed doped polysilicon layer 13 also decreases as the flow rate of the introduced doping reaction gas gradually decreases, so that the doping concentration of the formed doped polysilicon layer 13 gradually decreases in the direction away from the tunneling oxide layer 12.

[0031] Among them, the flow rate of the introduced doping reaction gas can show a linear decreasing trend. In other embodiments, the flow rate of the introduced doping reaction gas can also show a decreasing trend of slow first and then fast, or a decreasing trend of fast first and then slow, or a spiral decreasing trend, etc. Therefore, in the embodiments of the present application, the decreasing trend of the flow rate of the introduced doping reaction gas is not specifically limited, and can be adaptively adjusted according to the actual preparation situation so that it meets the requirement that the doping concentration of the doped polysilicon layer in the prepared solar cell decreases in the direction away from the tunneling oxide layer.

[0032] Compared with the preparation method of the solar cell in the related art, for example: to increase the doping concentration at the contact interface between the doped polysilicon layer and the tunneling oxide layer, simply increasing the total flow rate of the doping reaction gas can, to a certain extent, increase the overall doping concentration in the doped polysilicon layer, but this solar cell preparation method will increase the production cost and is likely to cause damage to the tunneling oxide layer. However, in the preparation method of the solar cell 1 provided in the embodiments of the present application, by introducing a doping reaction gas with a gradually decreasing flow rate for doping while depositing the intrinsic polysilicon layer, it is possible to make the doping concentration value at the first end 131 of the contact interface between the generated doped polysilicon layer 13 and the tunneling oxide layer 12 relatively high, and at the same time, it can ensure that the overall flow rate of the doping reaction gas remains unchanged, avoiding cost increase, and can also avoid damage to the tunneling oxide layer 12 caused by too large a flow rate of the doping reaction gas during the doping process of the intrinsic polysilicon layer, thereby causing a decrease in the efficiency of the solar cell 1.

[0033] In a specific embodiment, as Figure 1 and Figure 2 shown, the above step S131 may specifically include but is not limited to: S1311: When depositing the first end 131, the flow rate of the doping reaction gas can be 18 sccm - 22 sccm; S1312: When depositing the second end 132, the flow rate of the doping reaction gas can gradually decrease to 4 sccm - 6 sccm.

[0034] In this embodiment, when starting to prepare the doped polysilicon layer 13, the flow rate of the doped reaction gas introduced can be 18 sccm - 22 sccm. For example, the flow rate of the doped reaction gas can be 18 sccm, 20 sccm, 22 sccm, etc., so that the doping concentration at the first end 131 of the generated doped polysilicon layer 13 is relatively high, thereby being able to reduce the defect density at the contact interface between the doped polysilicon layer 13 and the tunneling oxide layer 12, optimize the carrier selective transmission path, avoid the carrier transmission being blocked at the interface and causing carrier recombination and resulting in recombination loss, and further achieve the effect of improving the open circuit voltage and fill factor and enhancing the working efficiency of the solar cell 1.

[0035] At the same time, as the reaction time gradually increases, the flow rate of the doped reaction gas introduced also gradually decreases. When the preparation process is about to end, the flow rate of the doped reaction gas introduced can be 4 sccm - 6 sccm. For example, the flow rate of the doped reaction gas can be 4 sccm, 5 sccm, 6 sccm, etc., so that the doping concentration at the second end 132 of the generated doped polysilicon layer 13 is relatively low, thereby being able to ensure that during the process of preparing the doped polysilicon layer 13, the total flow rate of the doped reaction gas introduced remains unchanged, avoid increasing costs, and avoid the doping concentration at the second end 132 being too low and affecting the conductivity of carriers in this region. At the same time, it can also make the doped polysilicon layer 13 form a characteristic of gradient change in doping concentration inside, further enhance the carrier conductivity in the doped polysilicon layer 13, and thus enhance the photoelectric conversion efficiency of the solar cell 1.

[0036] In this embodiment, by restricting the flow rate of the doped reaction gas introduced at the beginning and end of the preparation process, it is possible to achieve the effect that the doping concentration of the generated doped polysilicon layer 13 gradually decreases along the direction away from the tunneling oxide layer 12.

[0037] Among them, in the embodiment of the present application when generating the doped polysilicon layer 13, it is necessary to use silane as the precursor and phosphine as the doped reaction gas in a vacuum reaction chamber (pressure 10 Pa - 100 Pa) and perform deposition and doping in an environment with a temperature of 550 °C - 650 °C.

[0038] In other embodiments, during the preparation process of the solar cell 1, the flow rates of the doped reaction gas introduced at the first end 131 and the second end 132 can also be other values. Therefore, the specific values are not limited in the embodiment of the present application and can be adjusted according to the actual situation.

[0039] In a specific embodiment, as Figure 1 and Figure 2 shown, the doping concentration of the first end 131 in the doped polysilicon layer 13 of the solar cell 1 prepared through the above step S131 can be 0.8×1020 cm -3 -1.2×10 20 cm -3 , the doping concentration of the second end 132 can be reduced to 4×10 19 cm -3 -6×10 19 cm -3 .

[0040] In this embodiment, the doping concentration of the first end 131 of the doped polysilicon layer 13 is 0.8×10 20 cm -3 -1.2×10 20 cm -3 , for example, the doping concentration of the first end 131 can be 0.8×10 20 cm -3 、0.8×10 20 cm -3 、1.2×10 20 cm -3 etc. Even if the doping concentration of the first end 131 is relatively high, it can reduce the defect density at the contact interface between the doped polysilicon layer 13 and the tunneling oxide layer 12, optimize the carrier selective transmission path, avoid the carrier transmission being blocked at the interface and causing carrier recombination and composite loss, and thus achieve the effect of improving the open-circuit voltage and fill factor and enhancing the working efficiency of the solar cell 1.

[0041] At the same time, since the doping concentration in the doped polysilicon layer 13 gradually decreases along the direction from the first end 131 to the second end 132, therefore, the doping concentration of the second end 132 of the doped polysilicon layer 13 is 4×10 19 cm -3 -6×10 19 cm -3 . For example, the doping concentration of the second end 132 can be 4×10 19 cm -3 、5×10 19 cm -3 、6×10 19 cm -3 etc. Even if the doping concentration of the second end 132 is relatively low, it can ensure that the total flow rate of the doping reaction gas introduced remains unchanged during the preparation of the doped polysilicon layer 13, avoid increasing costs, and avoid the doping concentration at the second end 132 being too low and affecting the conductivity of carriers in this region. At the same time, it can also form a characteristic of gradient change in doping concentration inside the doped polysilicon layer 13, further enhance the carrier conductivity in the doped polysilicon layer 13, and thus improve the photoelectric conversion efficiency of the solar cell 1.

[0042] In other embodiments, during the preparation of the solar cell 1, the doping concentrations at the first end 131 and the second end 132 may also be other values, that is, the trend of the decreasing doping concentration in the doped polysilicon layer 13 may be gentler or more intense. The embodiments of the present application do not limit the specific situation thereof, and can be adaptively adjusted according to the actual situation.

[0043] In a specific embodiment, as Figure 1 and Figure 2 shown, the thickness of the doped polysilicon layer 13 may be 50 nm - 100 nm. And when preparing the doped polysilicon layer 13 of the solar cell 1 through the above step S131, the deposition rate of the intrinsic polysilicon layer may be 2 nm / min - 5 nm / min, and the decreasing rate of the flow rate of the doping reaction gas may be 0.5 sccm / min - 1 sccm / min.

[0044] In this embodiment, the thickness of the doped polysilicon layer 13 may be 50 nm - 100 nm. For example, the thickness of the doped polysilicon layer 13 may be 50 nm, 70 nm, 100 nm, etc. During the deposition of the intrinsic polysilicon layer, the deposition rate of the intrinsic polysilicon layer may be 2 nm / min - 5 nm / min. For example, the deposition rate of the intrinsic polysilicon layer may be 2 nm / min, 3 nm / min, 5 nm / min, etc. By limiting the deposition rate, the uniformity during the deposition process can be ensured. At the same time, by limiting the thickness and deposition rate of the doped polysilicon layer 13, the deposition time can be limited accordingly.

[0045] Therefore, when generating the doped polysilicon layer 13, the decreasing rate of the flow rate of the doping reaction gas introduced is 0.5 sccm / min - 1 sccm / min. For example, the decreasing rate of the flow rate of the doping reaction gas introduced may be 0.5 sccm / min, 0.8 sccm / min, 1 sccm / min, etc., so as to ensure that within the limited deposition time, the decreasing rate of the flow rate of the doping reaction gas introduced can adapt to the deposition time required, so that the doping concentration of the formed doped polysilicon layer 13 meets the requirements in the above embodiments, and the quality of the generated doped polysilicon layer 13 is ensured, thereby being able to improve the working efficiency of the solar cell 1.

[0046] In other embodiments, the thickness, deposition rate, and decreasing rate of the doping reaction gas of the doped polysilicon layer 13 may also be other values. Therefore, in the embodiments of the present application, the specific values of the thickness, deposition rate, and decreasing rate of the doping reaction gas of the doped polysilicon layer 13 are not limited, and the specific values of the three can be adaptively adjusted according to the actual use situation.

[0047] In a specific embodiment, as shown in Table 1 below, solar cell A is the solar cell 1 prepared by the preparation method of the solar cell 1 provided in the embodiment of the present application. The doping concentration at the first end 131 of solar cell A is 0.8×10 20 cm -3 , and the doping concentration at the second end 132 is reduced to 4×10 19 cm -3 , and along the direction from the first end 131 to the second end 132, the doping concentration gradually decreases. Solar cell B is the solar cell prepared by the preparation method provided in the related art. The preparation method is: first deposit an intrinsic polysilicon layer, and then introduce a doping reaction gas with a constant flow rate to form a doped polysilicon layer. The doping concentration in solar cell B is approximately equal, and the average doping concentration is 6×10 19 cm -3 . Both solar cell A and solar cell B use N-type monocrystalline silicon wafers (thickness 180um, resistivity 1Ω·cm), and both use atomic layer deposition technology to prepare the tunneling oxide layer (thickness 1.2nm). At the same time, the total amount of doping reaction gas introduced during the preparation of solar cell A and solar cell B is the same, and the thickness of the formed doped polysilicon layer is 70nm for both.

[0048] Table 1

[0049] In this embodiment, the test results of solar cell A and solar cell B are as shown in Table 1 below. Compared with solar cell B, the open-circuit voltage of solar cell A is increased by 25mV, the carrier lifetime is increased by 2.2ms, the fill factor is increased by 3.0%, and the contact resistance is reduced by 3.2 mΩ·cm², thereby increasing the overall working efficiency of solar cell 1 by 1.6%. It can be seen that on the basis of maintaining the cost, compared with solar cell B prepared by the preparation method in the related art, solar cell A (i.e., solar cell 1) prepared by the preparation method provided in the embodiment of the present application has a higher working efficiency.

[0050] In a specific embodiment, as shown in Table 2 below, solar cell C is the solar cell 1 prepared by the preparation method of the solar cell 1 provided in the embodiment of the present application. The doping concentration at the first end 131 of solar cell C is 1.2×10 20 cm -3 , and the doping concentration at the second end 132 is reduced to 6×10 19 cm -3 , and along the direction from the first end 131 to the second end 132, the doping concentration gradually decreases. Solar cell D is the solar cell prepared by the above-mentioned preparation method provided in the related art. The doping concentration in solar cell D is approximately equal, and the average doping concentration is 9×1019 cm -3 Both solar cell C and solar cell D use N-type monocrystalline silicon wafers (with a thickness of 180 μm and a resistivity of 1 Ω·cm), and both use atomic layer deposition technology to prepare the tunneling oxide layer (with a thickness of 1.2 nm). At the same time, the total amount of doped reaction gas introduced during the preparation of solar cell C and solar cell D is the same, and the thickness of the doped polysilicon layer formed is 70 nm for both, and the total amount of doped reaction gas introduced is greater than the total amount of doped reaction gas when preparing solar cell A or solar cell B.

[0051] Table II

[0052] In this embodiment, the test results of solar cell C and solar cell D are shown in Table II below. Compared with solar cell D, the open-circuit voltage of solar cell C is increased by 26 mV, the carrier lifetime is increased by 2.3 ms, the fill factor is increased by 4.5%, and the contact resistance is reduced by 3.4 mΩ·cm², thereby increasing the overall working efficiency of solar cell 1 by 1.8%. It can be seen that on the basis of maintaining the cost, compared with solar cell D prepared by the preparation method in the related technology, solar cell C (i.e., solar cell 1) prepared by the preparation method provided in the embodiment of the present application has a higher working efficiency.

[0053] In addition, compared with solar cell B, the total amount of doped reaction gas introduced during the preparation of solar cell D is larger. Although it can increase the overall doping concentration of solar cell D to increase the doping concentration at the contact interface between the doped polysilicon layer and the tunneling oxide layer, monotonically increasing the overall doping concentration easily hinders the transport of carriers, resulting in a decrease in the fill factor and damage to the tunneling oxide layer.

[0054] In the above embodiments, the doping concentration of the first end 131 in solar cell A and solar cell C is obtained by respectively measuring the average doping concentration within 5 nm of the end of the doped polysilicon layer 13 in contact with the tunneling oxide layer 12. The doping concentration of the second end in solar cell A and solar cell C is obtained by respectively measuring the average doping concentration within 5 nm of the end of the doped polysilicon layer 13 far from the tunneling oxide layer 12.

[0055] The doping concentration of solar cell B and solar cell D is the average doping concentration of the entire thickness of their doped polysilicon layers.

[0056] In a specific embodiment, as Figure 1 and Figure 2 shown, when depositing an intrinsic polysilicon layer on the tunneling oxide layer 12 and introducing a doped reaction gas at the same time, the above step S131 may specifically include but is not limited to: S1313: Control the flow rate of the doping reaction gas using a closed-loop gas flow control system, and combine real-time mass spectrometry to detect the flow rate of the doping reaction gas.

[0057] In this embodiment, the closed-loop gas flow control system includes components such as a gas inlet, a gas outlet, a circulation mechanism, and a gas filtration mechanism to form a closed-loop gas circulation. While ensuring the purity of the doping reaction gas atmosphere, it can also improve the raw material utilization rate and reduce costs. Moreover, using the closed-loop gas flow control system can also enhance the gas mixing uniformity when introducing the deposition reaction gas and the doping reaction gas. At the same time, by combining real-time mass spectrometry to detect the flow rate of the doping reaction gas, the flow rate of the doping reaction gas introduced into the current preparation environment can be detected, and the flow rate of the introduced doping reaction gas can be adaptively adjusted according to the detection results, so as to control the preparation process and improve the quality of the prepared products.

[0058] In a specific embodiment, such as Figure 1 and Figure 2 shown, after the step of forming the doped polysilicon layer 13 on the tunneling oxide layer 12 and making the doping concentration of the doped polysilicon layer 13 gradually decrease along the direction away from the tunneling oxide layer 12, the preparation method of the solar cell 1 may further include but is not limited to: S14: Anneal the silicon substrate 11 at a temperature of 650°C - 750°C for a time of 30 min - 60 min.

[0059] In this embodiment, after forming the doped polysilicon layer 13 on the tunneling oxide layer 12, the silicon substrate 11 is annealed in a nitrogen atmosphere to activate the phosphorus dopant and repair the damage of the crystalline silicon. And the annealing temperature is 650°C - 750°C. For example, the annealing temperature can be 650°C, 700°C, 750°C, etc. Compared with the high-temperature annealing process in the related art, the low-temperature annealing process provided by this application embodiment can avoid the decrease of the minority carrier lifetime in the solar cell 1 and affect the working performance of the solar cell 1.

[0060] In other embodiments, the annealing temperature can also be other values. This application embodiment does not specifically limit the annealing temperature and can be adaptively adjusted according to the actual situation.

[0061] In a specific embodiment, such as Figure 1 and Figure 2 shown, in the step of preparing the silicon substrate 11, the preparation method of the solar cell 1 may further include but is not limited to: S111: Generate an emitter 16 on the front surface of the silicon substrate 11.

[0062] In this embodiment, by generating the emitter 16 on the front surface of the silicon substrate 11, the effects of reducing surface recombination, optimizing carrier collection, and enhancing compatibility can be achieved, thereby further improving the performance of the solar cell 1.

[0063] In a specific embodiment, as Figure 1 and Figure 2 shown, after the step of annealing the silicon substrate 11 at a temperature of 650 °C - 750 °C for a time of 30 min - 60 min, the method for manufacturing the solar cell 1 may further include, but is not limited to: S15: Depositing a first passivation layer 15 and a second passivation layer 18 on the front and back surfaces of the silicon substrate 11 respectively; S16: Screen-printing a first metal electrode 14 and a second metal electrode 17 on the front and back surfaces of the silicon substrate 11 respectively.

[0064] In this embodiment, after the doped polysilicon layer 13 is generated, depositing the first passivation layer 15 and the second passivation layer 18 on the front and back surfaces of the silicon substrate 11 respectively can further improve the passivation effect, and can also optimize light absorption and reduce light reflection. After depositing the passivation layer, screen-printing the first metal electrode 14 and the second metal electrode 17 on the front and back surfaces of the silicon substrate 11 respectively, thereby completing the manufacturing of the solar cell 1.

[0065] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: The method for preparing the solar cell (1) comprises: preparing a silicon substrate (11); Depositing a tunneling oxide layer (12) on the silicon substrate (11); A doped polysilicon layer (13) is generated on the tunneling oxide layer (12), and the doping concentration of the doped polysilicon layer (13) is gradually reduced in a direction away from the tunneling oxide layer (12).

2. The method for preparing a solar cell according to claim 1, characterized in that: In the step of generating a doped polysilicon layer (13) on the tunneling oxide layer (12), and gradually reducing the doping concentration of the doped polysilicon layer (13) in a direction away from the tunneling oxide layer (12), the method for preparing the solar cell (1) specifically comprises: An intrinsic polysilicon layer is deposited on the tunnel oxide layer (12), and a doping reaction gas is introduced at the same time, and the flow rate of the doping reaction gas is gradually reduced.

3. The method for preparing a solar cell according to claim 2, characterized in that: The doped polysilicon layer (13) has a first end (131) and a second end (132), the first end (131) faces the tunneling oxide layer (12), and the second end (132) is away from the tunneling oxide layer (12), and the step of generating the doped polysilicon layer (13) on the tunneling oxide layer (12) specifically comprises: When depositing the first end (131), the flow rate of the doping reaction gas is 18 sccm-22 sccm; When depositing the second end (132), the flow rate of the doping reaction gas is gradually reduced to 4 sccm-6 sccm.

4. The method for preparing a solar cell according to claim 3, characterized in that: In the step of introducing the doping reaction gas and gradually reducing the flow rate of the doping reaction gas, the flow rate reduction rate of the doping reaction gas is 0.5 sccm / min-1 sccm / min.

5. The method for preparing a solar cell according to claim 2, characterized in that: In the step of generating a doped polysilicon layer (13) on the tunnel oxide layer (12), the deposition rate of the doped polysilicon layer (13) is 2 nm / min-5 nm / min.

6. The method for preparing a solar cell according to claim 2, characterized in that: In the step of introducing the doping reaction gas, the method for preparing the solar cell (1) specifically comprises: A closed-loop gas flow control system is used to control the flow of the doping reaction gas, and the flow of the doping reaction gas is detected in combination with a real-time mass spectrometer.

7. The method for preparing a solar cell according to any one of claims 1 to 6, characterized in that: After the step of generating a doped polysilicon layer (13) on the tunneling oxide layer (12), and gradually reducing the doping concentration of the doped polysilicon layer (13) in a direction away from the tunneling oxide layer (12), the method for preparing the solar cell (1) further comprises: The silicon substrate (11) is subjected to an annealing treatment at a temperature of 650° C. to 750° C. and for a time of 30 min to 60 min.

8. A solar cell, characterized in that: The solar cell (1) comprises a stacked silicon substrate (11), a tunneling oxide layer (12) and a doped polysilicon layer (13); along the thickness direction of the solar cell (1), the doped polysilicon layer (13) has a first end (131) and a second end (132) which are arranged opposite to each other, the first end (131) being in contact with the tunneling oxide layer (12), and the second end (132) being away from the tunneling oxide layer (12); Along the direction from the first end (131) to the second end (132), the doping concentration in the doped polysilicon layer (13) gradually decreases.

9. The solar cell according to claim 8, characterized in that The thickness of the doped polysilicon layer (13) is 50nm-100nm.

10. The solar cell according to claim 9, characterized in that: The doping concentration of the first end (131) is 0.8×10 20 cm -3 -1.2×10 20 cm -3 , the doping concentration of the second end (132) is reduced to 4×10 19 cm -3 -6×10 19 cm -3 .

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