TOPCon solar cell, preparation method thereof and photovoltaic module

Abstract

The invention belongs to the technical field of solar cells, and mainly provides a TOPCon solar cell, a preparation method thereof and a photovoltaic module. The preparation method of the TOPCon solar cell comprises the following steps: providing a silicon substrate, and sequentially forming a tunneling oxide layer, a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer and a P-type doped microcrystalline silicon layer on a first surface of the silicon substrate; through annealing treatment, the P-type doped amorphous silicon layer is converted into a first P-type doped layer, the P-type doped amorphous / microcrystalline silicon layer is converted into a second P-type doped layer, and the P-type doped microcrystalline silicon layer is converted into a third P-type doped layer; wherein the grain sizes of the first P-type doped layer, the second P-type doped layer and the third P-type doped layer are increased layer by layer. According to the preparation method of the TOPCon solar cell in the technical scheme, the passivation performance and the electrical performance of the TOPCon solar cell can be improved.

Description

Technical Field

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

[0002] The TOPCon cell mainly grows a tunneling oxide layer on the back surface of the silicon wafer, and then deposits a thin layer of amorphous silicon or polycrystalline silicon doped with phosphorus or boron. After annealing, the two together form a passivation contact structure, reducing the recombination of carriers in the metal contact area on the back of the cell, providing good interface passivation for the back of the silicon wafer, and thus improving the performance of the cell.

[0003] In the existing TOPCon cell technology, a gas mixture of silane, hydrogen, and trimethylboron is mainly used to prepare the amorphous boron-doped poly Si layer. Due to the too large optical band gap of the poly Si layer with amorphous structure, low-energy photons cannot excite the electrons at the valence band top to the conduction band, and more photons will be difficult to be absorbed by the electrons in the valence band, thus reducing its photoelectric conversion efficiency. In addition, due to the disorder in the structure of the amorphous poly Si layer, the bond lengths and bond angles of some Si-Si bonds inside it change, causing the Si-Si bonds to be in a strained state. The highly strained Si-Si will break after long-term strong light irradiation or current passing, forming Si-H bonds with the internal H or recombining to form Si-Si bonds with greater bond energy. If the broken Si-Si bonds do not recombine, new dangling bond defect states will be formed, resulting in a decline in the use performance of the thin film, and ultimately leading to a serious efficiency degradation phenomenon (light-induced degradation effect) in the prepared cell.

[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] The embodiments of the present application provide a TOPCon solar cell, a preparation method thereof, and a photovoltaic module to solve or alleviate the above-mentioned technical problems. The preparation method of the TOPCon solar cell in the embodiments of the present application can improve the passivation performance and electrical performance of the TOPCon solar cell.

[0006] In a first aspect, the embodiments of the present application provide a preparation method of a TOPCon solar cell, including: Providing a silicon substrate, the silicon substrate including a first surface and a second surface disposed opposite to each other; Forming a tunneling oxide layer on the first surface of the silicon substrate; Sequentially forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer; After annealing treatment, the P-type doped amorphous silicon layer is transformed into a first P-type doped layer, the P-type doped amorphous / microcrystalline silicon layer is transformed into a second P-type doped layer, and the P-type doped microcrystalline silicon layer is transformed into a third P-type doped layer; Among them, the grain sizes of the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer increase layer by layer.

[0007] Optionally, forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer in sequence includes: Using PECVD, introducing silane gas, trimethylboron gas, and hydrogen gas, and forming the P-type doped amorphous silicon layer, the P-type doped amorphous / microcrystalline silicon layer, and the P-type doped microcrystalline silicon layer on the tunneling oxide layer in sequence; Among them, when forming the P-type doped amorphous silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a first gas flow rate ratio; when forming the P-type doped amorphous / microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a second gas flow rate ratio; when forming the P-type doped microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a third gas flow rate ratio; The first gas flow rate ratio is greater than the second gas flow rate ratio, and the second gas flow rate ratio is greater than the third gas flow rate ratio.

[0008] Optionally, the first gas flow rate ratio is 0.4 - 0.5, the second gas flow rate ratio is 0.3 - 0.42, and the third gas flow rate ratio is 0.2 - 0.33.

[0009] Optionally, when forming the P-type doped amorphous silicon layer, the silane gas flow rate is 2700 sccm - 2800 sccm, and the hydrogen gas flow rate is 4000 sccm - 8000 sccm; and / or When forming the P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate is 2550 sccm - 2690 sccm, and the hydrogen gas flow rate is 6000 sccm - 11000 sccm; and / or When forming the P-type doped microcrystalline silicon layer, the silane gas flow rate is 2300 sccm - 2540 sccm, and the hydrogen gas flow rate is 8000 sccm - 14000 sccm.

[0010] Optionally, when forming the P-type doped amorphous silicon layer, the P-type doped amorphous / microcrystalline silicon layer, and the P-type doped microcrystalline silicon layer, the trimethylboron gas flow rate increases layer by layer.

[0011] Optionally, when forming the P-type doped amorphous silicon layer, the trimethylboron gas flow rate is 10 sccm - 120 sccm; and / or When forming the P-type doped amorphous / microcrystalline silicon layer, the flow rate of trimethylboron gas is 130 sccm - 500 sccm; and / or When forming the P-type doped microcrystalline silicon layer, the flow rate of trimethylboron gas is 510 sccm - 1000 sccm.

[0012] Optionally, the step of forming the P-type doped amorphous / microcrystalline silicon layer includes: Forming a first sub P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer; Forming a second sub P-type doped amorphous / microcrystalline silicon layer on the first sub P-type doped amorphous / microcrystalline silicon layer, and the first sub P-type doped amorphous / microcrystalline silicon layer and the second sub P-type doped amorphous / microcrystalline silicon layer together constitute the P-type doped amorphous / microcrystalline silicon layer; The step of forming the second P-type doped layer includes: Through annealing treatment, converting the first sub P-type doped amorphous / microcrystalline silicon layer into a first sub P-type doped layer, and converting the second sub P-type doped amorphous / microcrystalline silicon layer into a second sub P-type doped layer, and the first sub P-type doped layer and the second sub P-type doped layer together constitute the second P-type doped layer.

[0013] Optionally, when forming the first sub P-type doped amorphous silicon layer, the ratio of the flow rate of silane gas to the flow rate of hydrogen gas is a fourth gas flow rate ratio; when forming the second sub P-type doped amorphous / microcrystalline silicon layer, the ratio of the flow rate of silane gas to the flow rate of hydrogen gas is a fifth gas flow rate ratio; wherein, the fourth gas flow rate ratio is greater than the fifth gas flow rate ratio.

[0014] Optionally, the fourth gas flow rate ratio is 0.36 - 0.42, and the fifth gas flow rate ratio is 0.3 - 0.35.

[0015] In a second aspect, an embodiment of the present application provides a TOPCon solar cell, including: A silicon substrate, the silicon substrate includes a first surface and a second surface arranged oppositely; A tunneling oxide layer formed on the first surface of the silicon substrate; A first P-type doped layer, a second P-type doped layer, and a third P-type doped layer stacked in sequence along a first direction on the tunneling oxide layer; wherein, the grain sizes of the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer increase layer by layer.

[0016] Optionally, the grains of the first P-type doped layer are 0 - 4 nm, the grains of the second P-type doped layer are 5 nm - 20 nm, and the grains of the third P-type doped layer are 30 nm - 50 nm.

[0017] Optionally, the crystallization rate of the first P-type doped layer is 0-5%, the crystallization rate of the second P-type doped layer is 10%-30%, and the crystallization rate of the third P-type doped layer is 40%-70%.

[0018] In a third aspect, embodiments of the present application provide a photovoltaic module, including: a TOPCon solar cell prepared by the method for preparing a TOPCon solar cell provided in any one of the above embodiments, or a TOPCon solar cell provided in any one of the above embodiments.

[0019] The embodiments of the present application adopting the above technical solutions may include the following advantages: In the method for preparing a TOPCon solar cell according to an embodiment of the present application, a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer are sequentially formed on the tunneling oxide layer. In the subsequent annealing process, the amorphous-structured P-type doped amorphous silicon layer is transformed into a small-crystal first P-type doped layer, which can reduce the accumulation of dopant impurities (e.g., boron impurities) at the tunneling oxide layer, thereby reducing the damage of the dopant to the tunneling oxide layer and ensuring the integrity and chemical passivation of the tunneling oxide layer; the microcrystalline structure of the P-type doped microcrystalline silicon layer has orderliness, and can form a third P-type doped layer of large crystals with a vertical orientation, having a relatively high carrier mobility and dopant concentration, which is beneficial to the inward diffusion of dopants (e.g., boron element), and there is no light-induced degradation effect, further providing passivation performance; the P-type doped amorphous / microcrystalline silicon layer is transformed into a second P-type doped layer with a medium crystal size as a transition layer. The embodiments of the present application form a first P-type doped layer, the second P-type doped layer, and the third P-type doped layer with a gradient grain size, which can improve the passivation performance and electrical performance of the TOPCon solar cell. Description of the Drawings

[0020] In the drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed according to the present application and should not be regarded as limiting the scope of the present application.

[0021] Figure 1 is a schematic structural diagram of a TOPCon solar cell provided in Embodiment 1 of the present application; Figure 2 is a schematic structural diagram of a TOPCon solar cell provided in Embodiment 4 of the present application.

[0022] Description of the Reference Numerals: 100, silicon substrate; 200, tunneling oxide layer; 310, first P-type doped layer; 320, second P-type doped layer; 330, third P-type doped layer; 321, first sub-P-type doped layer, 322, second sub-P-type doped layer. Detailed implementation manners

[0023] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. Among them, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0024] As Figures 1 to 2 shown, the embodiment of the present application provides a TOPCon solar cell, including: Providing a silicon substrate 100, the silicon substrate 100 includes a first surface and a second surface arranged oppositely; Forming a tunneling oxide layer 200 on the first surface of the silicon substrate 100; Sequentially forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer 200; After annealing treatment, the P-type doped amorphous silicon layer is transformed into the first P-type doped layer 310, the P-type doped amorphous / microcrystalline silicon layer is transformed into the second P-type doped layer 320, and the P-type doped microcrystalline silicon layer is transformed into the third P-type doped layer 330; Among them, the grain sizes of the first P-type doped layer 310, the second P-type doped layer 320, and the third P-type doped layer 330 increase layer by layer.

[0025] In the preparation method of the TOPCon solar cell according to the application embodiment, a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer are sequentially formed on the tunneling oxide layer. In the subsequent annealing process, the amorphous P-type doped amorphous silicon layer is transformed into a small-crystal first P-type doped layer, which can reduce the accumulation of dopant impurities (such as boron impurities) at the tunneling oxide layer, thereby reducing the damage of the dopant to the tunneling oxide layer and ensuring the integrity and chemical passivation of the tunneling oxide layer; the microcrystalline structure of the P-type doped microcrystalline silicon layer has orderliness, and can form a third P-type doped layer of large crystals with vertical orientation, having relatively high carrier mobility and dopant concentration, which is beneficial to the inward diffusion of dopants (such as boron element), and there is no light-induced degradation effect, further providing passivation performance; the P-type doped amorphous / microcrystalline silicon layer is transformed into a second P-type doped layer with a medium crystal size as a transition layer. The application embodiment forms a first P-type doped layer, a second P-type doped layer, and a third P-type doped layer with gradient grain sizes, which can improve the passivation performance and electrical performance of the TOPCon solar cell.

[0026] In the present application, the silicon substrate can be an N-type silicon substrate or a P-type silicon substrate. Among them, the N-type silicon substrate is an N-type monocrystalline silicon substrate (for example, the crystal phase is <100> or <111>), and the P-type silicon substrate is a P-type monocrystalline silicon substrate (for example, the crystal phase is <100> or <111>).

[0027] The doping element of the P-type doped layer is a P-type semiconductor material, and the P-type semiconductor material includes boron element and can also include other elements, such as gallium element.

[0028] In some embodiments, forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer in sequence includes: Using PECVD, introducing silane gas, trimethylboron gas, and hydrogen gas, and sequentially forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer; Among them, when forming the P-type doped amorphous silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is the first gas flow ratio; when forming the P-type doped amorphous / microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is the second gas flow ratio; when forming the P-type doped microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is the third gas flow ratio; The first gas flow ratio is greater than the second gas flow ratio, and the second gas flow ratio is greater than the third gas flow ratio.

[0029] By adjusting the flow rates of silane gas, hydrogen gas, and trimethylboron gas, especially by gradually decreasing the ratio of the silane gas flow rate to the hydrogen gas flow rate layer by layer, a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer with gradually increasing grain sizes are formed; then, combined with an annealing process, the finally formed P-type doped layer includes a first P-type doped layer, a second P-type doped layer, and a third P-type doped layer with gradually increasing grain sizes, which can more precisely control the structures and properties of each layer and ensure that the finally formed P-type doped layer has an ideal grain size gradient distribution.

[0030] In some embodiments, the first gas flow ratio is 0.4 - 0.5 (for example, 0.40, 0.41, 0.42, 0.44, 0.45, 0.46, 0.48, 0.49, 0.50), the second gas flow ratio is 0.3 - 0.42 (for example, 0.30, 0.32, 0.33, 0.34, 0.36, 0.38, 0.40, 0.42), and the third gas flow ratio is 0.2 - 0.33 (for example, 0.20, 0.22, 0.23, 0.24, 0.25, 0.27, 0.28, 0.30, 0.31, 0.32, 0.33).

[0031] In the embodiments of the present application, reasonably controlling the ratio of the silane gas flow rate to the hydrogen gas flow rate can ensure that the grain sizes and properties of each layer reach the best balance, further improving the passivation effect and electrical properties of the battery.

[0032] In some embodiments, when forming the P-type doped amorphous silicon layer, the silane gas flow rate is 2700 sccm - 2800 sccm (for example, 2700 sccm, 2720 sccm, 2740 sccm, 2750 sccm, 2760 sccm, 2780 sccm, 2800 sccm), and the hydrogen gas flow rate is 4000 sccm - 8000 sccm (for example, 4000 sccm, 4500 sccm, 5000 sccm, 5500 sccm, 6000 sccm, 6500 sccm, 7000 sccm, 7500 sccm, 8000 sccm).

[0033] In some embodiments, when forming the P-type doped amorphous / microcrystalline silicon layer, the flow rate of silane gas is 2550 sccm - 2690 sccm (for example, 2560 sccm, 2580 sccm, 2600 sccm, 2620 sccm, 2650 sccm, 2660 sccm, 2680 sccm, 2690 sccm), and the flow rate of hydrogen gas is 6000 sccm - 11000 sccm (for example, 6000 sccm, 6500 sccm, 7000 sccm, 7500 sccm, 8000 sccm, 8500 sccm, 9000 sccm, 9500 sccm, 10000 sccm, 10500 sccm, 11000 sccm).

[0034] In some embodiments, when forming the P-type doped microcrystalline silicon layer, the flow rate of silane gas is 2300 sccm - 2540 sccm (for example, 2300 sccm, 2350 sccm, 2400 sccm, 2420 sccm, 2450 sccm, 2460 sccm, 2480 sccm, 2500 sccm, 2520 sccm, 2540 sccm), and the flow rate of hydrogen gas is 8000 sccm - 14000 sccm (for example, 8000 sccm, 9000 sccm, 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm, 14000 sccm).

[0035] In the embodiments of the present application, on the basis of controlling that the first gas flow rate ratio is greater than the second gas flow rate ratio and the second gas flow rate ratio is greater than the third gas flow rate ratio, the specific flow rates of silane gas and hydrogen gas for forming the P-type doped layer are limited, which can reduce the product performance differences caused by process parameter fluctuations, more accurately regulate the grain sizes of each layer, and ensure that the produced TOPCon solar cells have stable high quality and high performance.

[0036] In some embodiments, when forming the P-type doped amorphous silicon layer, P-type doped amorphous / microcrystalline silicon layer, and P-type doped microcrystalline silicon layer, the flow rate of trimethylboron gas increases layer by layer.

[0037] During the formation of the P-type doped amorphous silicon layer, P-type doped amorphous / microcrystalline silicon layer, and P-type doped microcrystalline silicon layer, the flow rate of trimethylboron gas increases layer by layer, causing the doping concentration of the finally formed P-type doped layer (the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer) to increase layer by layer, with the doping concentration showing a gradient distribution. In the first P-type doped layer close to the tunneling oxide layer, the lower doping concentration can reduce the accumulation of boron impurities at the tunneling oxide layer, avoid damaging the tunneling oxide layer, and maintain its good chemical passivation. In the third P-type doped layer far from the tunneling oxide layer, the higher doping concentration can provide a higher carrier concentration, enhance the formation of the electric field, and thus improve the carrier mobility and collection efficiency. The second P-type doped layer with a medium doping concentration belongs to the transition layer and has moderate chemical passivation and carrier mobility.

[0038] In some embodiments, when forming the P-type doped amorphous silicon layer, the flow rate of trimethylboron gas is 10 sccm - 120 sccm (for example, 10 sccm, 30 sccm, 50 sccm, 70 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm).

[0039] In some embodiments, when forming the P-type doped amorphous / microcrystalline silicon layer, the flow rate of trimethylboron gas is 130 sccm - 500 sccm (for example, 130 sccm, 150 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm).

[0040] In some embodiments, when forming the P-type doped microcrystalline silicon layer, the flow rate of trimethylboron gas is 510 sccm - 1000 sccm (for example, 510 sccm, 600 sccm, 700 sccm, 800 sccm, 840 sccm, 900 sccm, 1000 sccm).

[0041] As Figure 2 shown, in some embodiments, the steps of forming the P-type doped amorphous / microcrystalline silicon layer include: Forming a first sub-P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer; Forming a second sub-P-type doped amorphous / microcrystalline silicon layer on the first sub-P-type doped amorphous / microcrystalline silicon layer, where the first sub-P-type doped amorphous / microcrystalline silicon layer and the second sub-P-type doped amorphous / microcrystalline silicon layer together constitute the P-type doped amorphous / microcrystalline silicon layer; The steps of forming the second P-type doped layer 320 include: After annealing treatment, the first sub P-type doped amorphous / microcrystalline silicon layer is transformed into the first sub P-type doped layer 321, and the second sub P-type doped amorphous / microcrystalline silicon layer is transformed into the second sub P-type doped layer 322. The first sub P-type doped layer 321 and the second sub P-type doped layer 322 together constitute the second P-type doped layer 320.

[0042] In the embodiments of the present application, by forming two layers of the first sub P-type doped amorphous / microcrystalline silicon layer and the second sub P-type doped amorphous / microcrystalline silicon layer step by step to jointly form the P-type doped amorphous / microcrystalline silicon layer, the structure and performance of the P-type doped amorphous / microcrystalline silicon layer can be controlled more precisely. By respectively regulating the characteristics of the first sub-layer and the second sub-layer, the performance of the final second P-type doped layer is optimized, and its matching with the upper and lower layers and the electrical performance of the overall battery are improved.

[0043] In some embodiments, when forming the first sub P-type doped amorphous silicon layer, the ratio of the flow rate of silane gas to the flow rate of hydrogen gas is the fourth gas flow ratio; when forming the second sub P-type doped amorphous / microcrystalline silicon layer, the ratio of the flow rate of silane gas to the flow rate of hydrogen gas is the fifth gas flow ratio; wherein, the fourth gas flow ratio is greater than the fifth gas flow ratio.

[0044] In some embodiments, the fourth gas flow ratio is 0.36 - 0.42 (for example, 0.36, 0.38, 0.40, 0.42), and the fifth gas flow ratio is 0.3 - 0.35 (for example, 0.30, 0.32, 0.34, 0.35).

[0045] In an alternative embodiment, during the process of forming the P-type doped amorphous silicon layer, the P-type doped amorphous / microcrystalline silicon layer, and the P-type doped microcrystalline silicon layer, the time for forming each layer is 100s - 300s (for example, 100s, 150s, 172s, 200s, 272s, 300s), the pressure is 2000mtorr - 3000mtorr (for example, 2000mtorr, 2200mtorr, 2400mtorr, 2600mtorr, 2800mtorr, 3000mtorr), and the power is 7000W - 9000W (for example, 7000W, 7500W, 8000W, 8500W, 9000W).

[0046] In an alternative embodiment, the method for manufacturing a TOPCon solar cell further includes: forming a passivation layer and an electrode on the third P-type doped layer in sequence. The material of the passivation layer includes, but is not limited to, one or both of alumina and silicon nitride. The electrode includes a metal electrode or a transparent conductive electrode; the material of the metal electrode includes, but is not limited to, one or more of Au, Ag, Al, and Cu, and the transparent conductive electrode includes one or more of indium tin oxide, indium zinc oxide, tungsten-doped indium oxide, and aluminum-doped zinc oxide. Methods such as thermal evaporation, vacuum evaporation, sputtering, atomic layer deposition, 3D printing, screen printing, and inkjet printing can be used to manufacture the electrode. The thickness of the electrode can be 40 - 300 nm.

[0047] In an alternative embodiment, the method for manufacturing a TOPCon solar cell further includes: forming a passivation layer on the second surface of the silicon substrate. The material of the passivation layer includes, but is not limited to, one or both of alumina and silicon nitride.

[0048] An embodiment of the present application provides a TOPCon solar cell, including: A silicon substrate, the silicon substrate includes a first surface and a second surface that are oppositely arranged; A tunneling oxide layer formed on the first surface of the silicon substrate; A first P-type doped layer, a second P-type doped layer, and a third P-type doped layer that are stacked in sequence along the first direction on the tunneling oxide layer; Among them, the grain sizes of the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer increase layer by layer.

[0049] In some embodiments, the grains of the first P-type doped layer are 0 - 4 nm (for example, 0 - 3 nm, 1 nm - 4 nm, 1 nm - 3 nm), the grains of the second P-type doped layer are 5 nm - 20 nm (for example, 8 nm - 18 nm, 10 nm - 18 nm, 8 nm - 15 nm), and the grains of the third P-type doped layer are 30 nm - 50 nm (for example, 35 nm - 45 nm, 35 nm - 40 nm, 40 nm - 45 nm).

[0050] In some embodiments, the crystallization rate of the first P-type doped layer is 0 - 5% (for example, 0%, 1%, 2%, 3%, 4%, 5%), the crystallization rate of the second P-type doped layer is 10% - 30% (for example, 10%, 15%, 20%, 25%, 30%), and the crystallization rate of the third P-type doped layer is 40% - 70% (for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%).

[0051] If the crystallization rate of the P-type doped layer is too high, the recombination degree of electrons and holes in the valence band is relatively high, which will bring an additional loss of fill factor; if the crystallization rate of the P-type doped layer is too low, it may be unfavorable for carrier transport. In the embodiments of the present application, the crystallization rate is controlled by setting multiple sub-layers. The first P-type doped layer close to the tunneling oxide layer has a lower crystallization rate to reduce recombination loss, and the first P-type doped layer close to the tunneling oxide layer has a higher crystallization rate, which can have a higher carrier concentration and improve electrical properties.

[0052] In some embodiments, the thickness of the first P-type doped layer is 30 nm - 40 nm, the thickness of the second P-type doped layer is 60 nm - 70 nm, and the thickness of the third P-type doped layer is 60 nm - 70 nm.

[0053] The embodiments of the present application provide a photovoltaic module, including: a TOPCon solar cell prepared by the preparation method of the TOPCon solar cell provided in any one of the above embodiments, or a TOPCon solar cell provided in any one of the above embodiments.

[0054] The following specific embodiments further illustrate the present application in detail, but should not be construed as a limitation to the present application. Without departing from the spirit and essence of the present application, any modification or replacement made to the methods, steps or conditions of the present application belongs to the scope of the present application.

[0055] Embodiment 1 As Figure 1 shown, the structure of the TOPCon solar cell of Embodiment 1 includes: A silicon substrate 100, the silicon substrate 100 includes a first surface and a second surface arranged oppositely; A tunneling oxide layer 200 is formed on the first surface of the silicon substrate 100; A first P-type doped layer 310, a second P-type doped layer 320, and a third P-type doped layer 330 which are sequentially stacked along a first direction on the tunneling oxide layer 200; Among them, the grain sizes of the first P-type doped layer 310, the second P-type doped layer 320, and the third P-type doped layer 330 increase layer by layer.

[0056] The preparation method of the TOPCon solar cell of Embodiment 1 is: S100a: Provide a silicon substrate (N-type silicon substrate), the silicon substrate includes a first surface and a second surface arranged oppositely; S200a: Form a tunneling oxide layer on the first surface of the silicon substrate; S310a: Use PECVD to introduce silane gas, trimethylboron gas and hydrogen to form a P-type doped amorphous silicon layer on the tunneling oxide layer; wherein, the flow rate F1 of the silane gas Siis 2750 sccm, the hydrogen gas flow rate F1 H2 is 6000 sccm, the trimethylboron gas flow rate F1 B is 100 sccm, the ratio of the silane gas flow rate to the hydrogen gas flow rate (the first gas flow ratio R1) is 0.46; S320a: Form a P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer; wherein, the silane gas flow rate F2 Si is 2650 sccm, the hydrogen gas flow rate F2 H2 is 8000 sccm, the trimethylboron gas flow rate F2 B is 150 sccm, the ratio of the silane gas flow rate to the hydrogen gas flow rate (the second gas flow ratio R2) is 0.33; S330a: Form a P-type doped microcrystalline silicon layer on the P-type doped amorphous / microcrystalline silicon layer; wherein, the silane gas flow rate F3 Si is 2450 sccm, the hydrogen gas flow rate F3 H2 is 10000 sccm, the trimethylboron gas flow rate F3 B is 840 sccm, the ratio of the silane gas flow rate to the hydrogen gas flow rate (the third gas flow ratio R3) is 0.245; S400a: Through annealing treatment, convert the P-type doped amorphous silicon layer into the first P-type doped layer, convert the P-type doped amorphous / microcrystalline silicon layer into the second P-type doped layer, and convert the P-type doped microcrystalline silicon layer into the third P-type doped layer; wherein, in the first P-type doped layer, the grain size G1 is 0 - 4 nm, the crystallization rate C1 is 0 - 5%, and the thickness is 35 nm; in the second P-type doped layer, the grain size G2 is 5 nm - 20 nm, the crystallization rate C2 is 10% - 30%, and the thickness is 65 nm; in the third P-type doped layer, the grain size G3 is 30 nm - 50 nm, the crystallization rate C3 is 40% - 70%, and the thickness is 65 nm.

[0057] Example 2 Refer to the preparation method of Example 1 to prepare the TOPCon solar cell of Example 2, the difference is only that in Example 2, When forming the P-type doped amorphous silicon layer, the silane gas flow rate F1 Si is 2700 sccm, the hydrogen gas flow rate F1 H2 is 5500 sccm, the trimethylboron gas flow rate F1 B is 100 sccm, the ratio of the silane gas flow rate to the hydrogen gas flow rate (the first gas flow ratio R1) is 0.49; When forming the P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate F2 Si is 2600 sccm, the hydrogen gas flow rate F2 H2 is 7000 sccm, the trimethylboron gas flow rate F2B is 150 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the second gas flow rate ratio R2) is 0.37; When forming the P-type doped microcrystalline silicon layer, the silane gas flow rate F3 Si is 2500 sccm, and the hydrogen gas flow rate F3 H2 is 9000 sccm, and the trimethylboron gas flow rate F3 B is 840 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the third gas flow rate ratio R3) is 0.28.

[0058] Example 3 The TOPCon solar cell of Example 3 was prepared with reference to the preparation method of Example 1, except that in Example 3, When forming the P-type doped amorphous silicon layer, the silane gas flow rate F1 Si is 2800 sccm, and the hydrogen gas flow rate F1 H2 is 7000 sccm, and the trimethylboron gas flow rate F1 B is 100 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the first gas flow rate ratio R1) is 0.4; When forming the P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate F2 Si is 2690 sccm, and the hydrogen gas flow rate F2 H2 is 8700 sccm, and the trimethylboron gas flow rate F2 B is 150 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the second gas flow rate ratio R2) is 0.31; When forming the P-type doped microcrystalline silicon layer, the silane gas flow rate F3 Si is 2400 sccm, and the hydrogen gas flow rate F3 H2 is 11000 sccm, and the trimethylboron gas flow rate F3 B is 840 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the third gas flow rate ratio R3) is 0.22.

[0059] Example 4 As Figure 2 shown, the structure of the TOPCon solar cell of Example 4 is basically the same as that of the TOPCon solar cell of Example 1, except that in Example 4, the second P-type doped layer 320 includes a first sub-P-type doped layer 321 and a second sub-P-type doped layer 322 stacked in sequence.

[0060] The TOPCon solar cell of Example 4 was prepared with reference to the preparation method of Example 1, except that in Example 4, S320a is: forming a first sub-P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer; wherein, the silane gas flow rate F4 Si is 2700 sccm, the hydrogen gas flow rate F4 H2 is 7000 sccm, the trimethylboron gas flow rate F4 B is 150 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the fourth gas flow ratio R4) is 0.385; forming a second sub-P-type doped amorphous / microcrystalline silicon layer on the first sub-P-type doped amorphous / microcrystalline silicon layer; wherein, the silane gas flow rate F5 Si is 2650 sccm, the hydrogen gas flow rate F5 H2 is 8000 sccm, the trimethylboron gas flow rate F5 B is 300 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate (the fifth gas flow ratio R5) is 0.33; The first sub-P-type doped amorphous / microcrystalline silicon layer and the second sub-P-type doped amorphous / microcrystalline silicon layer together constitute the P-type doped amorphous / microcrystalline silicon layer; S400a is: through annealing treatment, converting the P-type doped amorphous silicon layer into a first P-type doped layer, converting the first sub-P-type doped amorphous / microcrystalline silicon layer into a first sub-P-type doped layer, converting the second sub-P-type doped amorphous / microcrystalline silicon layer into a second sub-P-type doped layer, converting the P-type doped amorphous / microcrystalline silicon layer into a second P-type doped layer, converting the P-type doped microcrystalline silicon layer into a third P-type doped layer, and the first sub-P-type doped layer and the second sub-P-type doped layer together constitute the second P-type doped layer; Among them, in the first P-type doped layer, the grain size G1 is 0 - 4 nm, the crystallization rate C1 is 0 - 5%, and the thickness is 35 nm; in the first sub-P-type doped layer, the grain size G2 is 5 nm - 10 nm, the crystallization rate C2 is 10% - 20%, and the thickness is 30 nm; in the second sub-P-type doped layer, the grain size G2 is 11 nm - 20 nm, the crystallization rate C2 is 21% - 30%, and the thickness is 35 nm; in the third P-type doped layer, the grain size G3 is 30 nm - 50 nm, the crystallization rate C3 is 40% - 70%, and the thickness is 65 nm.

[0061] To more clearly illustrate the technical effects of the embodiments of the present application, the present application also points out the structure and preparation method of the TOPCon solar cell of Comparative Example 1.

[0062] Comparative Example 1 The structure of the TOPCon solar cell of Comparative Example 1 includes: a silicon substrate, the silicon substrate includes a first surface and a second surface arranged opposite to each other; forming a tunneling oxide layer on the first surface of the silicon substrate; a P-type doped layer located on the tunneling oxide layer.

[0063] The preparation method of the TOPCon solar cell of Comparative Example 1 is as follows: S100b: Provide a silicon substrate (N-type silicon substrate), the silicon substrate includes a first surface and a second surface arranged opposite to each other; S200b: Form a tunneling oxide layer on the first surface of the silicon substrate; S300b: Use PECVD, introduce silane gas, trimethylboron gas and hydrogen, and form a P-type doped microcrystalline silicon layer on the tunneling oxide layer; wherein, the flow rate of silane gas is 2450 sccm, the flow rate of hydrogen is 10000 sccm, the flow rate of trimethylboron gas is 840 sccm, and the ratio of the flow rate of silane gas to the flow rate of hydrogen is 0.245; S400b: After annealing treatment, convert the P-type doped microcrystalline silicon layer into a P-type doped layer; wherein, in the third P-type doped layer, the grain size is 30 nm - 50 nm, the crystallization rate is 40% - 70%, and the thickness is 65 nm.

[0064] For stability testing, the above TOPCon solar cells were all encapsulated. The device performances of the TOPCon solar cells of Examples 1 - 4 and Comparative Example 1 of the present application were tested, so as to obtain the saturation dark current density J0, open circuit voltage iVoc, fill factor iFF, and carrier lifetime Lifetime of the corresponding battery devices, and the test results are shown in Table 1.

[0065] Table 1

[0066] It can be seen from the data in Table 1 that compared with Comparative Example 1, the saturation dark current density of the corresponding battery devices of the TOPCon solar cells of Examples 1 - 4 of the present application decreased slightly, the open circuit voltage and fill factor increased slightly, and the carrier lifetime increased significantly.

[0067] In summary, in the method for preparing a TOPCon solar cell according to the application embodiments, a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer are sequentially formed on the tunneling oxide layer. In the subsequent annealing process, the amorphous-structured P-type doped amorphous silicon layer is transformed into a first P-type doped layer of small crystals, which can reduce the accumulation of dopant impurities (e.g., boron impurities) at the tunneling oxide layer, thereby reducing the damage of the dopant to the tunneling oxide layer and ensuring the integrity and chemical passivation of the tunneling oxide layer; the microcrystalline structure of the P-type doped microcrystalline silicon layer has orderliness and can form a third P-type doped layer of large crystals with a vertical orientation, having a relatively high carrier mobility and dopant concentration, being conducive to the inward diffusion of the dopant (e.g., boron element), and having no light-induced degradation effect, further providing passivation performance; the P-type doped amorphous / microcrystalline silicon layer is transformed into a second P-type doped layer with a medium crystal size as a transition layer. The application embodiments form a first P-type doped layer, the second P-type doped layer, and the third P-type doped layer with a gradient grain size, which can improve the passivation performance and electrical performance of the TOPCon solar cell.

[0068] It should be noted that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present application. The orientation terms "inner" and "outer" refer to the inside and outside relative to the contour of each component itself. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "on top of other devices or structures" will be positioned "below other devices or structures" or "beneath other devices or structures" afterwards. Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the corresponding explanations for the relative spatial descriptions used here are made.

[0069] It should be noted that the terms "first", "second", etc. in the description, claims, and the above-mentioned drawings of the present application are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present 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 that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0070] It should also be noted that the "one embodiment", "another embodiment", "embodiment", etc. mentioned in the present application refer to the specific features, structures, or characteristics described in connection with that embodiment being included in at least one embodiment generally described in the present application. The same expression appearing in multiple places in the description does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure, or characteristic in connection with any embodiment, it is intended that implementing such feature, structure, or characteristic in connection with other embodiments also falls within the scope of the present application.

[0071] In the above embodiments, the descriptions of the respective embodiments have their own focuses. For parts not detailed 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 the preferred embodiments of the present application, and do not limit the patent protection scope of the present application. Any equivalent structural or equivalent process transformation made using the content of the description and drawings of the present application, or directly or indirectly applied in other related technical fields, is similarly included in the patent protection scope of the present application.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that, Comprising: Providing a silicon substrate, the silicon substrate including a first surface and a second surface disposed opposite to each other; Forming a tunneling oxide layer on the first surface of the silicon substrate; Sequentially forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer; Through annealing treatment, converting the P-type doped amorphous silicon layer into a first P-type doped layer, converting the P-type doped amorphous / microcrystalline silicon layer into a second P-type doped layer, and converting the P-type doped microcrystalline silicon layer into a third P-type doped layer; Wherein, the grain sizes of the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer increase layer by layer.

2. The preparation method of the TOPCon solar cell according to claim 1, wherein Sequentially forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer on the tunneling oxide layer, including: Using PECVD, introducing silane gas, trimethylboron gas, and hydrogen gas to sequentially form the P-type doped amorphous silicon layer, the P-type doped amorphous / microcrystalline silicon layer, and the P-type doped microcrystalline silicon layer on the tunneling oxide layer; Wherein, when forming the P-type doped amorphous silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a first gas flow rate ratio; when forming the P-type doped amorphous / microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a second gas flow rate ratio; when forming the P-type doped microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a third gas flow rate ratio; The first gas flow rate ratio is greater than the second gas flow rate ratio, and the second gas flow rate ratio is greater than the third gas flow rate ratio.

3. The preparation method of the TOPCon solar cell according to claim 2, wherein, The first gas flow rate ratio is 0.4 - 0.5, the second gas flow rate ratio is 0.3 - 0.42, and the third gas flow rate ratio is 0.2 - 0.

33.

4. The preparation method of the TOPCon solar cell according to claim 2, characterized in that When forming the P-type doped amorphous silicon layer, the silane gas flow rate is 2700 sccm - 2800 sccm, and the hydrogen gas flow rate is 4000 sccm - 8000 sccm; and / or When forming the P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate is 2550 sccm - 2690 sccm, and the hydrogen gas flow rate is 6000 sccm - 11000 sccm; and / or When forming the P-type doped microcrystalline silicon layer, the silane gas flow rate is 2300 sccm - 2540 sccm, and the hydrogen gas flow rate is 8000 sccm - 14000 sccm.

5. The manufacturing method of the TOPCon solar cell according to claim 2, characterized in that, When forming the P-type doped amorphous silicon layer, the P-type doped amorphous / microcrystalline silicon layer, and the P-type doped microcrystalline silicon layer, the trimethylboron gas flow rate increases layer by layer.

6. The preparation method of the TOPCon solar cell according to claim 2, characterized in that When forming the P-type doped amorphous silicon layer, the trimethylboron gas flow rate is 10 sccm - 120 sccm; and / or When forming the P-type doped amorphous / microcrystalline silicon layer, the trimethylboron gas flow rate is 130 sccm - 500 sccm; and / or When forming the P-type doped microcrystalline silicon layer, the trimethylboron gas flow rate is 510 sccm - 1000 sccm.

7. The method for preparing a TOPCon solar cell according to any one of claims 1 to 6, characterized in that the step of forming the P-type doped amorphous / microcrystalline silicon layer includes: forming a first sub-P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer; forming a second sub-P-type doped amorphous / microcrystalline silicon layer on the first sub-P-type doped amorphous / microcrystalline silicon layer, and the first sub-P-type doped amorphous / microcrystalline silicon layer and the second sub-P-type doped amorphous / microcrystalline silicon layer together constitute the P-type doped amorphous / microcrystalline silicon layer; the step of forming the second P-type doped layer includes: through annealing treatment, converting the first sub-P-type doped amorphous / microcrystalline silicon layer into a first sub-P-type doped layer, and converting the second sub-P-type doped amorphous / microcrystalline silicon layer into a second sub-P-type doped layer, and the first sub-P-type doped layer and the second sub-P-type doped layer together constitute the second P-type doped layer.

8. The preparation method of the TOPCon solar cell according to claim 7, wherein When forming the first sub-P-type doped amorphous silicon layer, the ratio of the flow rate of silane gas to the flow rate of hydrogen gas is the fourth gas flow rate ratio; when forming the second sub-P-type doped amorphous / microcrystalline silicon layer, the ratio of the flow rate of silane gas to the flow rate of hydrogen gas is the fifth gas flow rate ratio; wherein, the fourth gas flow rate ratio is greater than the fifth gas flow rate ratio.

9. The preparation method of the TOPCon solar cell according to claim 8, wherein, The fourth gas flow rate ratio is 0.36 - 0.42, and the fifth gas flow rate ratio is 0.3 - 0.

35.

10. A TOPCon solar cell, characterized in that, including: a silicon substrate, the silicon substrate includes a first surface and a second surface arranged oppositely; forming a tunneling oxide layer on the first surface of the silicon substrate; a first P-type doped layer, a second P-type doped layer, and a third P-type doped layer that are sequentially stacked along a first direction on the tunneling oxide layer; wherein, the grain sizes of the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer increase layer by layer.

11. The TOPCon solar cell according to claim 10, wherein The grains of the first P-type doped layer are 0 - 4 nm, the grains of the second P-type doped layer are 5 nm - 20 nm, and the grains of the third P-type doped layer are 30 nm - 50 nm.

12. The TOPCon solar cell according to claim 10, wherein, The crystallization rate of the first P-type doped layer is 0 - 5%, the crystallization rate of the second P-type doped layer is 10% - 30%, and the crystallization rate of the third P-type doped layer is 40% - 70%.

13. A photovoltaic module, characterized in that, including: a TOPCon solar cell prepared by the method for preparing a TOPCon solar cell according to any one of claims 1 to 9, or a TOPCon solar cell according to any one of claims 10 to 12.

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