TOPCon solar cell and preparation method thereof, photovoltaic module

Abstract

The present application belongs to the field of solar cell technology and mainly provides a TOPCon solar cell and its preparation method, as well as a photovoltaic module. The preparation method of the TOPCon solar cell includes: providing a silicon substrate, 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 the first surface of the silicon substrate; after annealing, 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 size of the first P-type doped layer, the second P-type doped layer, and the third P-type doped layer increases layer by layer. The preparation method of the TOPCon solar cell of the technical solution of the present application can improve the passivation performance and electrical performance of the TOPCon solar cell.

Description

Technical Field

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

[0002] TOPCon cells mainly grow a tunneling oxide layer on the back surface of the silicon wafer, and then deposit a thin layer of amorphous silicon or polycrystalline silicon doped with phosphorus or boron. After annealing, the two together form a passivation contact structure, which reduces the recombination of carriers in the metal contact area on the back of the cell, provides good interface passivation for the back of the silicon wafer, and thus improves the performance of the cell.

[0003] In existing TOPCon cell technology, amorphous boron-doped poly-Si layers are primarily prepared using a gas mixture of silane, hydrogen, and trimethylboron. Because the amorphous poly-Si layer has a large optical band gap, low-energy photons are unable to excite electrons at the top of the valence band to the conduction band. Consequently, more photons are less likely to be absorbed by electrons in the valence band, reducing its photoelectric conversion efficiency. Furthermore, the structural disorder of the amorphous poly-Si layer causes changes in the bond lengths and angles of some Si-Si bonds within it, placing the Si-Si bonds in a strained state. These highly strained Si-Si bonds break under prolonged exposure to strong light or current, forming Si-H bonds with internal H atoms or recombining to form Si-Si bonds with higher bond energy. If these broken Si-Si bonds do not recombine, they form new dangling bond defects, which degrade the film's performance and ultimately lead to severe efficiency degradation (photoinduced degradation) in the resulting cell.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the Invention

[0005] The present invention provides a TOPCon solar cell and a method for manufacturing the same, as well as a photovoltaic module, to solve or alleviate the above-mentioned technical problems. The method for manufacturing the TOPCon solar cell according to the present invention can improve the passivation performance and electrical performance of the TOPCon solar cell.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a TOPCon solar cell, comprising:

[0007] Providing a silicon substrate, wherein the silicon substrate comprises a first surface and a second surface disposed opposite to each other;

[0008] forming a tunneling oxide layer on the first surface of the silicon substrate;

[0009] forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer in sequence on the tunneling oxide layer;

[0010] After annealing, 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;

[0011] The grain sizes of the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer increase layer by layer.

[0012] 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 in sequence on the tunnel oxide layer includes:

[0013] 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 tunnel oxide layer;

[0014] 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;

[0015] 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.

[0016] Optionally, the first gas flow ratio is 0.4-0.5, the second gas flow ratio is 0.3-0.42, and the third gas flow ratio is 0.2-0.33.

[0017] 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

[0018] 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

[0019] 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.

[0020] 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 flow rate of trimethyl boron gas is increased layer by layer.

[0021] Optionally, when forming the P-type doped amorphous silicon layer, the flow rate of trimethylboron gas is 10 sccm-120 sccm; and / or

[0022] When forming the P-type doped amorphous / microcrystalline silicon layer, the flow rate of trimethylboron gas is 130 sccm-500 sccm; and / or

[0023] When forming the P-type doped microcrystalline silicon layer, the flow rate of trimethylboron gas is 510 sccm-1000 sccm.

[0024] Optionally, the step of forming the P-type doped amorphous / microcrystalline silicon layer includes:

[0025] forming a first sub-P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer;

[0026] forming a second sub-P-type doped amorphous / microcrystalline silicon layer on the first sub-P-type doped amorphous / microcrystalline silicon layer, wherein 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;

[0027] The step of forming the second P-type doped layer includes:

[0028] After annealing treatment, the first sub-P-type doped amorphous / microcrystalline silicon layer is converted into a first sub-P-type doped layer, and the second sub-P-type doped amorphous / microcrystalline silicon layer is converted into a second sub-P-type doped layer. The first sub-P-type doped layer and the second sub-P-type doped layer together constitute the second P-type doped layer.

[0029] Optionally, when forming the first sub-P-type doped amorphous silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a fourth gas flow rate ratio; when forming the second sub-P-type doped amorphous / microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is a fifth gas flow rate ratio;

[0030] Wherein, the fourth gas flow ratio is greater than the fifth gas flow ratio.

[0031] Optionally, the fourth gas flow ratio is 0.36-0.42, and the fifth gas flow ratio is 0.3-0.35.

[0032] In a second aspect, an embodiment of the present application provides a TOPCon solar cell, comprising:

[0033] A silicon substrate, the silicon substrate comprising a first surface and a second surface disposed opposite to each other;

[0034] forming a tunneling oxide layer on the first surface of the silicon substrate;

[0035] A first P-type doping layer, a second P-type doping layer, and a third P-type doping layer are located on the tunnel oxide layer and are stacked in sequence along a first direction;

[0036] The grain sizes of the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer increase layer by layer.

[0037] Optionally, the grain size of the first P-type doping layer is 0-4 nm, the grain size of the second P-type doping layer is 5 nm-20 nm, and the grain size of the third P-type doping layer is 30 nm-50 nm.

[0038] Optionally, the crystallization rate of the first P-type doping layer is 0-5%, the crystallization rate of the second P-type doping layer is 10%-30%, and the crystallization rate of the third P-type doping layer is 40%-70%.

[0039] In a third aspect, an embodiment of the present application provides a photovoltaic module, comprising: a TOPCon solar cell prepared by the method for preparing a TOPCon solar cell provided by any of the above embodiments, or a TOPCon solar cell provided by any of the above embodiments.

[0040] The above technical solution adopted in the embodiments of the present application may have the following advantages:

[0041] In the preparation method of the TOPCon solar cell of the 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 P-type doped amorphous silicon layer with an amorphous structure is converted into a first P-type doped layer with small crystals, which can reduce the accumulation of dopant impurities (e.g., boron impurities) in 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 is orderly and can form a third P-type doped layer with large vertical crystals, which has a relatively high carrier mobility and dopant concentration, is conducive to the internal diffusion of dopants (e.g., boron elements), and does not suffer from the photodegradation effect, further improving the passivation performance; the P-type doped amorphous / microcrystalline silicon layer is converted into a second P-type doped layer with a medium crystal size, which serves as a transition layer. The embodiment of the present application forms the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer with gradient grain sizes, which can improve the passivation performance and electrical performance of the TOPCon solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent 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 in this application and should not be construed as limiting the scope of this application.

[0043] Figure 1 Schematic diagram of the structure of the TOPCon solar cell provided in Example 1 of the present application;

[0044] Figure 2 This is a schematic structural diagram of the TOPCon solar cell provided in Example 4 of the present application.

[0045] Description of reference numerals:

[0046] 100 , silicon substrate; 200 , tunneling oxide layer; 310 , first P-type doping layer; 320 , second P-type doping layer; 330 , third P-type doping layer; 321 , first sub-P-type doping layer; 322 , second sub-P-type doping layer. DETAILED DESCRIPTION

[0047] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, the sizes of layers, regions, and elements and their relative sizes may be exaggerated for clarity. The same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other unless there is a conflict.

[0048] like Figures 1 to 2 As shown, the embodiment of the present application provides a TOPCon solar cell, comprising:

[0049] Providing a silicon substrate 100, the silicon substrate 100 comprising a first surface and a second surface opposite to each other;

[0050] forming a tunnel oxide layer 200 on the first surface of the silicon substrate 100;

[0051] forming a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer in sequence on the tunnel oxide layer 200;

[0052] After annealing, the P-type doped amorphous silicon layer is transformed into a first P-type doped layer 310 , the P-type doped amorphous / microcrystalline silicon layer is transformed into a second P-type doped layer 320 , and the P-type doped microcrystalline silicon layer is transformed into a third P-type doped layer 330 ;

[0053] The grain sizes of the first P-type doping layer 310 , the second P-type doping layer 320 , and the third P-type doping layer 330 increase layer by layer.

[0054] In the preparation method of the TOPCon solar cell of 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 converted into a first P-type doped layer with small crystals, which can reduce the accumulation of dopant impurities (e.g., boron impurities) in 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 P-type doped microcrystalline silicon layer has an ordered microcrystalline structure and can form a third P-type doped layer with large vertical crystals. It has a relatively high carrier mobility and dopant concentration, which is conducive to the internal diffusion of dopants (e.g., boron elements) and does not suffer from the photodegradation effect, further improving the passivation performance. The P-type doped amorphous / microcrystalline silicon layer is converted into a second P-type doped layer with intermediate crystal size, which serves as a transition layer. The embodiments of the present application form a first P-type doping layer, a second P-type doping layer, and a third P-type doping layer with gradient grain sizes, which can improve the passivation performance and electrical performance of the TOPCon solar cell.

[0055] In the present application, the silicon substrate may be an N-type silicon substrate or a P-type silicon substrate. The N-type silicon substrate is an N-type single crystal silicon substrate (for example, the crystal phase is <100> or <111> ), the P-type silicon substrate is a P-type single crystal silicon substrate (for example, the crystal phase is <100> or <111> ).

[0056] The doping element of the P-type doping layer is a P-type semiconductor material. The P-type semiconductor material includes boron and may also include other elements, such as gallium.

[0057] 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 in sequence on the tunnel oxide layer includes:

[0058] Using PECVD, silane gas, trimethylboron gas and hydrogen are introduced to sequentially form 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 tunnel oxide layer;

[0059] When forming a 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 a 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 a 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;

[0060] 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.

[0061] By adjusting the flow rates of silane gas, hydrogen gas, and trimethylboron gas, and in particular, by gradually reducing the ratio of the silane gas flow rate to the hydrogen flow rate, a P-type doped amorphous silicon layer, a P-type doped amorphous / microcrystalline silicon layer, and a P-type doped microcrystalline silicon layer are formed, each with a gradually increasing grain size. This is then combined with an annealing process so that the resulting P-type doped layer includes a first P-type doped layer, a second P-type doped layer, and a third P-type doped layer, each with a gradually increasing grain size. This allows for more precise control of the structure and performance of each layer, ensuring that the resulting P-type doped layer has an ideal grain size gradient distribution.

[0062] In some embodiments, the first gas flow ratio is 0.4-0.5 (e.g., 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 (e.g., 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 (e.g., 0.20, 0.22, 0.23, 0.24, 0.25, 0.27, 0.28, 0.30, 0.31, 0.32, 0.33).

[0063] In the embodiments of the present application, reasonable control of the ratio of the silane gas flow rate to the hydrogen gas flow rate can ensure that the grain size and performance of each layer are optimally balanced, further improving the passivation effect and electrical performance of the battery.

[0064] In some embodiments, when forming a 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).

[0065] In some embodiments, when forming a P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate is 2550sccm-2690sccm (for example, 2560sccm, 2580sccm, 2600sccm, 2620sccm, 2650sccm, 2660sccm, 2680sccm, 2690sccm), and the hydrogen gas flow rate is 6000sccm-11000sccm (for example, 6000sccm, 6500sccm, 7000sccm, 7500sccm, 8000sccm, 8500sccm, 9000sccm, 9500sccm, 10000sccm, 10500sccm, 11000sccm).

[0066] In some embodiments, when forming a P-type doped microcrystalline silicon layer, the silane gas flow rate 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 hydrogen gas flow rate is 8000 sccm-14000 sccm (for example, 8000 sccm, 9000 sccm, 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm, 14000 sccm).

[0067] In the embodiment of the present application, on the basis of controlling the first gas flow ratio to be greater than the second gas flow ratio, and the second gas flow ratio to be greater than the third gas flow ratio, the specific silane gas flow rate and hydrogen flow rate for forming the P-type doping layer are limited, which can reduce the product performance differences caused by fluctuations in process parameters, more accurately control the grain size of each layer, and ensure that the produced TOPCon solar cells have stable high quality and high performance.

[0068] In some embodiments, 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 flow rate of the trimethylboron gas is increased layer by layer.

[0069] During the formation of 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 is increased layer by layer, resulting in a gradient doping concentration in the resulting P-type doped layers (first, second, and third P-type doped layers). In the first P-type doped layer, close to the tunnel oxide layer, the lower doping concentration reduces boron impurity accumulation in the tunnel oxide layer, preventing damage and maintaining good chemical passivation. In the third P-type doped layer, further away from the tunnel oxide layer, the higher doping concentration provides a higher carrier concentration, enhancing the electric field and thus improving carrier mobility and collection efficiency. The second P-type doped layer, with an intermediate doping concentration, serves as a transition layer, exhibiting moderate chemical passivation and carrier mobility.

[0070] In some embodiments, when forming the P-type doped amorphous silicon layer, the flow rate of the trimethylboron gas is 10 sccm-120 sccm (eg, 10 sccm, 30 sccm, 50 sccm, 70 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm).

[0071] In some embodiments, when forming the P-type doped amorphous / microcrystalline silicon layer, the flow rate of the trimethylboron gas is 130 sccm-500 sccm (eg, 130 sccm, 150 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm).

[0072] In some embodiments, when forming the P-type doped microcrystalline silicon layer, the flow rate of the trimethylboron gas is 510 sccm-1000 sccm (eg, 510 sccm, 600 sccm, 700 sccm, 800 sccm, 840 sccm, 900 sccm, 1000 sccm).

[0073] like Figure 2 As shown, in some embodiments, the step of forming a P-type doped amorphous / microcrystalline silicon layer includes:

[0074] forming a first sub-P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer;

[0075] forming a second sub-P-type doped amorphous / microcrystalline silicon layer on the first sub-P-type doped amorphous / microcrystalline silicon layer, wherein the first sub-P-type doped amorphous / microcrystalline silicon layer and the second sub-P-type doped amorphous / microcrystalline silicon layer together constitute a P-type doped amorphous / microcrystalline silicon layer;

[0076] The step of forming the second P-type doped layer 320 includes:

[0077] After annealing treatment, the first sub-P-type doped amorphous / microcrystalline silicon layer is converted into a first sub-P-type doped layer 321, and the second sub-P-type doped amorphous / microcrystalline silicon layer is converted into a 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.

[0078] In the embodiment of the present application, by step-by-step forming of the first sub-P-type doped amorphous / microcrystalline silicon layer and the second sub-P-type doped amorphous / microcrystalline silicon layer, which together constitute the P-type doped amorphous / microcrystalline silicon layer, the structure and performance of the P-type doped amorphous / microcrystalline silicon layer can be more accurately controlled. By separately regulating the characteristics of the first sub-layer and the second sub-layer, the performance of the final second P-type doped layer can be optimized, thereby improving its matching with the upper and lower layers and the electrical performance of the overall battery.

[0079] In some embodiments, when forming the first sub-P-type doped amorphous silicon layer, the ratio of the silane gas flow rate to the hydrogen flow rate is a fourth gas flow ratio; when forming the second sub-P-type doped amorphous / microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen flow rate is a fifth gas flow ratio; wherein the fourth gas flow ratio is greater than the fifth gas flow ratio.

[0080] In some embodiments, the fourth gas flow ratio is 0.36-0.42 (eg, 0.36, 0.38, 0.40, 0.42) and the fifth gas flow ratio is 0.3-0.35 (eg, 0.30, 0.32, 0.34, 0.35).

[0081] In an optional embodiment, in 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).

[0082] In an optional embodiment, the method for preparing a TOPCon solar cell further includes: sequentially forming a passivation layer and an electrode on the third P-type doped layer. The material of the passivation layer includes, but is not limited to, one or both of aluminum oxide 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. The electrode can be prepared by thermal evaporation, vacuum evaporation, sputtering, atomic layer deposition, 3D printing, screen printing, inkjet printing, and the like. The thickness of the electrode can be 40-300 nm.

[0083] In an optional embodiment, the method for preparing a TOPCon solar cell further includes: forming a passivation layer on the second surface of the silicon substrate, wherein the material of the passivation layer includes but is not limited to one or both of aluminum oxide and silicon nitride.

[0084] The present application provides a TOPCon solar cell, comprising:

[0085] A silicon substrate, the silicon substrate comprising a first surface and a second surface arranged opposite to each other;

[0086] forming a tunneling oxide layer on the first surface of the silicon substrate;

[0087] A first P-type doping layer, a second P-type doping layer, and a third P-type doping layer are located on the tunneling oxide layer and are sequentially stacked along a first direction;

[0088] The grain sizes of the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer increase layer by layer.

[0089] In some embodiments, the grain size of the first P-type doping layer is 0-4nm (for example, 0-3nm, 1nm-4nm, 1nm-3nm), the grain size of the second P-type doping layer is 5nm-20nm (for example, 8nm-18nm, 10nm-18nm, 8nm-15nm), and the grain size of the third P-type doping layer is 30nm-50nm (for example, 35nm-45nm, 35nm-40nm, 40nm-45nm).

[0090] In some embodiments, the crystallization rate of the first P-type doping layer is 0-5% (for example, 0%, 1%, 2%, 3%, 4%, 5%), the crystallization rate of the second P-type doping layer is 10%-30% (for example, 10%, 15%, 20%, 25%, 30%), and the crystallization rate of the third P-type doping layer is 40%-70% (for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%).

[0091] If the crystallinity of the P-type doped layer is too high, the degree of recombination between electrons and holes in the valence band will be high, resulting in additional fill factor loss. If the crystallinity of the P-type doped layer is too low, it may be detrimental to carrier transport. In the embodiment of the present application, the crystallinity is controlled by providing multiple sublayers. The first P-type doped layer near the tunnel oxide layer has a lower crystallinity, reducing recombination losses, while the first P-type doped layer near the tunnel oxide layer has a higher crystallinity, which can have a higher carrier concentration and improve electrical performance.

[0092] In some embodiments, the thickness of the first P-type doping layer is 30 nm-40 nm, the thickness of the second P-type doping layer is 60 nm-70 nm, and the thickness of the third P-type doping layer is 60 nm-70 nm.

[0093] An embodiment of the present application provides a photovoltaic module, comprising: a TOPCon solar cell prepared by the method for preparing a TOPCon solar cell provided by any of the above embodiments, or a TOPCon solar cell provided by any of the above embodiments.

[0094] The following specific examples further illustrate the present invention, but should not be construed as limiting the present invention. Modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and substance of the present invention are within the scope of the present invention.

[0095] Example 1

[0096] like Figure 1 As shown, the structure of the TOPCon solar cell of Example 1 includes:

[0097] A silicon substrate 100, comprising a first surface and a second surface opposite to each other;

[0098] A tunneling oxide layer 200 is formed on the first surface of the silicon substrate 100;

[0099] A first P-type doping layer 310 , a second P-type doping layer 320 , and a third P-type doping layer 330 are located on the tunneling oxide layer 200 and are sequentially stacked along a first direction;

[0100] The grain sizes of the first P-type doping layer 310 , the second P-type doping layer 320 , and the third P-type doping layer 330 increase layer by layer.

[0101] The preparation method of the TOPCon solar cell of Example 1 is as follows:

[0102] S100a: Providing a silicon substrate (N-type silicon substrate), the silicon substrate including a first surface and a second surface opposite to each other;

[0103] S200a: forming a tunneling oxide layer on the first surface of the silicon substrate;

[0104] S310a: Using PECVD, silane gas, trimethylboron gas and hydrogen are introduced to form a P-type doped amorphous silicon layer on the tunnel oxide layer; wherein the silane gas flow rate F1 Si 2750sccm, hydrogen flow rate F1 H2 The trimethylborane gas flow rate is 6000sccm, 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 0.46;

[0105] S320a: forming a P-type doped amorphous / microcrystalline silicon layer on the P-type doped amorphous silicon layer; wherein the silane gas flow rate F2 Si 2650sccm, hydrogen flow rate F2 H2 The trimethylborane gas flow rate F2 is 8000sccm 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 0.33;

[0106] S330a: forming a P-type doped microcrystalline silicon layer on the P-type doped amorphous / microcrystalline silicon layer; wherein the silane gas flow rate F3 Si 2450sccm, hydrogen flow rate F3 H2 The trimethylborane gas flow rate F3 is 10000sccm 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 0.245;

[0107] S400a: After 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, in the first P-type doped layer, the grain G1 is 0-4nm, the crystallization rate C1 is 0-5%, and the thickness is 35nm; in the second P-type doped layer, the grain G2 is 5nm-20nm, the crystallization rate C2 is 10%-30%, and the thickness is 65nm; in the third P-type doped layer, the grain G3 is 30nm-50nm, the crystallization rate C3 is 40%-70%, and the thickness is 65nm.

[0108] Example 2

[0109] The TOPCon solar cell of Example 2 was prepared by referring to the preparation method of Example 1, except that, in Example 2,

[0110] When forming a P-type doped amorphous silicon layer, the silane gas flow rate F1 Si 2700sccm, hydrogen flow rate F1 H2The trimethylborane gas flow rate is 5500sccm, 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 0.49;

[0111] When forming a P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate F2 Si 2600sccm, hydrogen flow rate F2 H2 The trimethylborane gas flow rate F2 is 7000sccm 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 0.37;

[0112] When forming a P-type doped microcrystalline silicon layer, the silane gas flow rate F3 Si 2500sccm, hydrogen flow rate F3 H2 9000sccm, trimethylborane gas flow rate F3 B The flow rate of the silane gas 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.

[0113] Example 3

[0114] The TOPCon solar cell of Example 3 was prepared by referring to the preparation method of Example 1, except that, in Example 3,

[0115] When forming a P-type doped amorphous silicon layer, the silane gas flow rate F1 Si 2800sccm, hydrogen flow rate F1 H2 The trimethylborane gas flow rate is 7000sccm, 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;

[0116] When forming a P-type doped amorphous / microcrystalline silicon layer, the silane gas flow rate F2 Si 2690sccm, hydrogen flow rate F2 H2 The trimethylborane gas flow rate F2 is 8700sccm 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;

[0117] When forming a P-type doped microcrystalline silicon layer, the silane gas flow rate F3 Si 2400sccm, hydrogen flow rate F3 H2 The trimethylborane gas flow rate F3 is 11000sccm B The flow rate of the silane gas 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.

[0118] Example 4

[0119] like Figure 2 As shown, the structure of the TOPCon solar cell of Example 4 is basically the same as the structure of the TOPCon solar cell of Example 1, and the only difference is that, in Example 4, the second P-type doping layer 320 includes a first sub-P-type doping layer 321 and a second sub-P-type doping layer 322 stacked in sequence.

[0120] The TOPCon solar cell of Example 4 was prepared by referring to the preparation method of Example 1, except that, in Example 4,

[0121] 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 2700sccm, hydrogen flow rate F4 H2 7000sccm, trimethylborane 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 rate ratio R4) is 0.385;

[0122] A second P-type doped amorphous / microcrystalline silicon layer is formed on the first P-type doped amorphous / microcrystalline silicon layer; wherein the silane gas flow rate F5 Si 2650sccm, hydrogen flow rate F5 H2 8000sccm, trimethylborane 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 rate ratio R5) is 0.33;

[0123] The first sub-P-type doped amorphous / microcrystalline silicon layer and the second sub-P-type doped amorphous / microcrystalline silicon layer together constitute a P-type doped amorphous / microcrystalline silicon layer;

[0124] S400a is: after annealing, the P-type doped amorphous silicon layer is converted into a first P-type doped layer, the first sub-P-type doped amorphous / microcrystalline silicon layer is converted into a first sub-P-type doped layer, the second sub-P-type doped amorphous / microcrystalline silicon layer is converted into a second sub-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. The first sub-P-type doped layer and the second sub-P-type doped layer together constitute a second P-type doped layer.

[0125] Among them, in the first P-type doped layer, the grain G1 is 0-4nm, the crystallization rate C1 is 0-5%, and the thickness is 35nm; in the first sub-P-type doped layer, the grain G2 is 5nm-10nm, the crystallization rate C2 is 10%-20%, and the thickness is 30nm; in the second sub-P-type doped layer, the grain G2 is 11nm-20nm, the crystallization rate C2 is 21%-30%, and the thickness is 35nm; in the third P-type doped layer, the grain G3 is 30nm-50nm, the crystallization rate C3 is 40%-70%, and the thickness is 65nm.

[0126] In order 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.

[0127] Comparative Example 1

[0128] The structure of the TOPCon solar cell of Comparative Example 1 comprises:

[0129] A silicon substrate, the silicon substrate comprising a first surface and a second surface arranged opposite to each other;

[0130] forming a tunneling oxide layer on the first surface of the silicon substrate;

[0131] A P-type doped layer is located on the tunneling oxide layer.

[0132] The preparation method of the TOPCon solar cell of Comparative Example 1 is:

[0133] S100b: Providing a silicon substrate (N-type silicon substrate), the silicon substrate including a first surface and a second surface opposite to each other;

[0134] S200b: forming a tunneling oxide layer on the first surface of the silicon substrate;

[0135] S300b: PECVD is performed by introducing silane gas, trimethyl boron gas, and hydrogen gas to form a P-type doped microcrystalline silicon layer on the tunnel oxide layer. The silane gas flow rate is 2450 sccm, the hydrogen gas flow rate is 10000 sccm, the trimethyl boron gas flow rate is 840 sccm, and the ratio of the silane gas flow rate to the hydrogen gas flow rate is 0.245.

[0136] S400b: After annealing, the P-type doped microcrystalline silicon layer is converted into a P-type doped layer; wherein, in the third P-type doped layer, the grain size is 30nm-50nm, the crystallization rate is 40%-70%, and the thickness is 65nm.

[0137] For stability testing, the TOPCon solar cells were all packaged. The device performance of the TOPCon solar cells of Examples 1-4 and Comparative Example 1 was tested to obtain the saturated dark current density J0, open-circuit voltage iVoc, fill factor iFF, and carrier lifetime of the corresponding cell devices. The test results are shown in Table 1.

[0138] Table 1

[0139]

[0140] It can be seen from the data in Table 1 that, compared with Comparative Example 1, the saturated dark current density of the corresponding cell devices of the TOPCon solar cells of Examples 1-4 of the present application is slightly decreased, the open circuit voltage and fill factor are slightly improved, and the carrier lifetime is significantly improved.

[0141] In summary, in the preparation method of the TOPCon solar cell of the embodiment of the 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 P-type doped amorphous silicon layer is converted into a first P-type doped layer with small crystals, which can reduce the accumulation of dopant impurities (e.g., boron impurities) in 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 is orderly, and can form a third P-type doped layer with large vertical crystals, which has a relatively high carrier mobility and dopant concentration, is conducive to the internal diffusion of dopants (e.g., boron elements), and does not suffer from the photodegradation effect, further improving the passivation performance; the P-type doped amorphous / microcrystalline silicon layer is converted into a second P-type doped layer with intermediate crystal size, which serves as a transition layer. The embodiment of the present application forms the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer with gradient grain sizes, which can improve the passivation performance and electrical performance of the TOPCon solar cell.

[0142] It should be noted that the terms "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting this application. The directional words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0143] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0144] It should also be noted that references to "one embodiment," "another embodiment," "an embodiment," etc., in this application refer to specific features, structures, or characteristics described in conjunction with that embodiment as included in at least one embodiment generally described in this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in conjunction with any embodiment, it is intended that such feature, structure, or characteristic, when implemented in conjunction with other embodiments, also fall within the scope of this application.

[0145] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0146] It should also be noted that the above are only preferred embodiments of the present application and do not limit the scope of patent protection of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present application.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that: include: Providing a silicon substrate, wherein the silicon substrate comprises 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; Using PECVD, silane gas, trimethylboron gas and hydrogen are introduced to sequentially form 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 tunnel oxide layer; 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 ratio is greater than the second gas flow ratio, and the second gas flow ratio is greater than the third gas flow ratio; After annealing, 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; The grain sizes of the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer increase layer by layer.

2. The method for preparing a TOPCon solar cell according to claim 1, wherein: The first gas flow ratio is 0.4-0.5, the second gas flow ratio is 0.3-0.42, and the third gas flow ratio is 0.2-0.

33.

3. The method for preparing a TOPCon solar cell according to claim 1, wherein: 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.

4. The method for preparing a TOPCon solar cell according to claim 1, wherein: 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 flow rate of trimethylboron gas is increased layer by layer.

5. The method for preparing a TOPCon solar cell according to claim 1, wherein: When forming the P-type doped amorphous silicon layer, the flow rate of trimethylboron gas 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.

6. The method for preparing a TOPCon solar cell according to any one of claims 1 to 5, characterized in that: The step of forming the P-type doped amorphous / microcrystalline silicon layer comprises: 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, wherein 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: After annealing treatment, the first sub-P-type doped amorphous / microcrystalline silicon layer is converted into a first sub-P-type doped layer, and the second sub-P-type doped amorphous / microcrystalline silicon layer is converted into a second sub-P-type doped layer. The first sub-P-type doped layer and the second sub-P-type doped layer together constitute the second P-type doped layer.

7. The method for preparing a TOPCon solar cell according to claim 6, characterized in that: When forming the first sub-P-type doped amorphous silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is the fourth gas flow rate ratio; when forming the second sub-P-type doped amorphous / microcrystalline silicon layer, the ratio of the silane gas flow rate to the hydrogen gas flow rate is the fifth gas flow rate ratio; Wherein, the fourth gas flow ratio is greater than the fifth gas flow ratio.

8. The method for preparing a TOPCon solar cell according to claim 7, wherein: The fourth gas flow ratio is 0.36-0.42, and the fifth gas flow ratio is 0.3-0.

35.

9. A TOPCon solar cell, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8, comprising: A silicon substrate, the silicon substrate comprising 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; A first P-type doping layer, a second P-type doping layer, and a third P-type doping layer are located on the tunnel oxide layer and are stacked in sequence along a first direction; The grain sizes of the first P-type doping layer, the second P-type doping layer, and the third P-type doping layer increase layer by layer.

10. The TOPCon solar cell according to claim 9, characterized in that: The grain size of the first P-type doping layer is 0-4 nm, the grain size of the second P-type doping layer is 5 nm-20 nm, and the grain size of the third P-type doping layer is 30 nm-50 nm.

11. The TOPCon solar cell according to claim 9, characterized in that The crystallization rate of the first P-type doping layer is 0-5%, the crystallization rate of the second P-type doping layer is 10%-30%, and the crystallization rate of the third P-type doping layer is 40%-70%.

12. A photovoltaic module, characterized in that: include: A TOPCon solar cell prepared by the method for preparing a TOPCon solar cell according to any one of claims 1 to 8, or a TOPCon solar cell according to any one of claims 9 to 11.

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