Passivation contact structure and preparation method and application thereof

Abstract

The invention relates to a passivation contact structure and a preparation method and application thereof. The preparation method of the passivation contact structure comprises the following steps: preparing a tunneling oxide layer on any surface of a silicon wafer; hydrogen, phosphorane, silane and ammonia gas are introduced, and primary deposition is carried out on the surface of the tunneling oxide layer; after the primary deposition is finished, hydrogen, phosphorane, silane and ammonia gas are continuously introduced for secondary deposition, so that a doped polycrystalline silicon nitride layer is formed on the surface of the tunneling oxide layer; a passivation contact structure is formed on the surface of the silicon wafer through annealing treatment; the flow ratio of hydrogen to phosphine in the primary deposition is greater than that of hydrogen to phosphine in the secondary deposition, and the difference value is 1.4-3.1; the temperature of the primary deposition is greater than or equal to the temperature of the secondary deposition, and the difference value is less than 10 DEG C. The passivation contact structure prepared by the preparation method is beneficial to reducing optical parasitic absorption loss and improving the photoelectric conversion efficiency of a photovoltaic cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a passivated contact structure, a preparation method thereof, and an application thereof. Background Art

[0002] Photovoltaic is a renewable energy source that is a key research focus globally. With the continuous development of photovoltaic cell technology, industry researchers have been pursuing higher photoelectric conversion efficiencies. TOPCon solar cells are a type of tunnel oxide passivated contact solar cell based on the principle of selective carrier transport. Its cell structure is an N-type silicon substrate cell. An ultrathin tunneling layer is prepared on the back surface of the cell, and then a doped thin layer is deposited. The two together form a passivated contact structure, effectively reducing surface recombination and metal contact recombination, providing more room for further improvement of the cell conversion efficiency.

[0003] In the prior art, TOPCon cells usually adopt a passivated contact structure formed by combining a tunneling oxide layer and a doped polysilicon layer. However, when the doped polysilicon layer prepared by traditional processes is applied to solar cell devices, current loss will occur due to its large optical parasitic absorption, and the optimal photoelectric conversion efficiency cannot be achieved. Summary of the Invention

[0004] Based on this, it is necessary to provide a passivated contact structure, a preparation method thereof, and an application thereof for the above problems. In the passivated contact structure prepared by the preparation method, the doped polycrystalline silicon nitride layer not only has high light transmittance, but also can provide excellent transport and passivation capabilities for charge carriers, which is beneficial to reducing optical parasitic absorption losses, thereby improving the photoelectric conversion efficiency of photovoltaic cells.

[0005] A preparation method of a passivated contact structure in a solar cell includes the following steps:

[0006] Prepare a tunneling oxide layer on any surface of a silicon wafer;

[0007] Introduce hydrogen, phosphine, silane, and ammonia gas, and perform a first deposition on the surface of the tunneling oxide layer;

[0008] After the first deposition is completed, continue to introduce hydrogen, phosphine, silane, and ammonia gas for a second deposition to form a doped polycrystalline silicon nitride layer on the surface of the tunneling oxide layer;

[0009] Form a passivated contact structure on the surface of the silicon wafer through annealing treatment;

[0010] Among them, the flow rate ratio of hydrogen to phosphine in the first deposition is greater than that in the second deposition, and the difference is 1.4 - 3.1; the temperature of the first deposition is greater than or equal to the temperature of the second deposition, and the difference is less than 10°C.

[0011] In one embodiment, the flow rate of hydrogen in the first deposition is greater than the flow rate of hydrogen in the second deposition;

[0012] and / or, the flow rate of phosphine in the first deposition is less than the flow rate of phosphine in the second deposition;

[0013] and / or, the flow rate of silane in the first deposition is equal to the flow rate of silane in the second deposition;

[0014] and / or, the flow rate of ammonia in the first deposition is equal to the flow rate of ammonia in the second deposition.

[0015] In one embodiment, in the first deposition, the flow rate ratio of hydrogen, phosphine, silane, and ammonia is (19 - 25):(4 - 5):(5 - 7):(14 - 18).

[0016] In one embodiment, in the first deposition, the flow rate of hydrogen is 9500 sccm - 10500 sccm, the flow rate of phosphine is 1800 sccm - 2500 sccm, the flow rate of silane is 2500 sccm - 3500 sccm, and the flow rate of ammonia is 7000 sccm - 9000 sccm.

[0017] In one embodiment, in the second deposition, the flow rate ratio of hydrogen, phosphine, silane, and ammonia is (15 - 17):(7 - 9):(5 - 7):(14 - 18).

[0018] In one embodiment, in the second deposition, the flow rate of hydrogen is 7500 sccm - 8500 sccm, the flow rate of phosphine is 3500 sccm - 4500 sccm, the flow rate of silane is 2500 sccm - 3500 sccm, and the flow rate of ammonia is 7000 sccm - 9000 sccm.

[0019] In one embodiment, the temperature of the first deposition is 440°C - 450°C, and the time is 440 s - 450 s;

[0020] and / or, the temperature of the second deposition is 450°C - 460°C, and the time is 600 s - 680 s;

[0021] and / or, the pressure of the first deposition is equal to the pressure of the second deposition;

[0022] And / or, the temperature of the annealing treatment is 800°C - 1000°C.

[0023] A passivation contact structure prepared by the method for preparing a passivation contact structure as described above, in the doped polycrystalline silicon nitride layer of the passivation contact structure, the doping concentration of phosphorus ions near the surface of the tunneling oxide layer is less than the doping concentration of phosphorus ions far from the surface of the tunneling oxide layer.

[0024] A method for preparing a TOPCon solar cell, including the method for preparing a passivation contact structure as described above.

[0025] A TOPCon solar cell prepared by the method for preparing a TOPCon solar cell as described above.

[0026] In the method for preparing a passivation contact structure according to the present invention, through the synergistic effect of two-step deposition with a specific temperature and a specific hydrogen-to-phosphine flow ratio, on the one hand, the doping amount of phosphorus ions in the two-step deposition is precisely controlled, so that the doping concentration of phosphorus ions in the doped polycrystalline silicon nitride layer formed by the first deposition is less, which is beneficial to reducing the loss of optical parasitic absorption. At the same time, the doping concentration of phosphorus ions in the doped polycrystalline silicon nitride layer formed by the second deposition is more, which is beneficial to forming a better ohmic contact and can provide excellent transport and passivation capabilities for charge carriers, thereby improving the photoelectric conversion efficiency of the photovoltaic cell; on the other hand, when the doped polycrystalline silicon nitride layer reaches a certain deposition thickness, it not only has high light transmittance, which is beneficial to further reducing the loss of optical parasitic absorption, but also can ensure that the tunneling oxide layer is not easily electrically broken down, making the passivation contact structure have high quality and high performance.

[0027] Therefore, in the passivation contact structure prepared by the preparation method of the present invention, the doped polycrystalline silicon nitride layer not only has high light transmittance, but also can provide excellent transport and passivation capabilities for charge carriers, can minimize the loss of optical parasitic absorption, and thus improve the photoelectric conversion efficiency of the photovoltaic cell. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a quantum efficiency curve graph of TOPCon solar cells prepared from Example 1 and a blank sample. Among them, A is the quantum efficiency curve of the TOPCon solar cell prepared from Example 1, and B is the quantum efficiency curve of the TOPCon solar cell prepared from the blank sample. Detailed implementation mode

[0030] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, these embodiments or examples are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items.

[0032] The present invention provides a method for preparing a passivation contact structure in a solar cell, comprising the following steps:

[0033] S1, preparing a tunneling oxide layer on any surface of the silicon wafer;

[0034] S2, introducing hydrogen, phosphine, silane and ammonia, and performing a first deposition on the surface of the tunneling oxide layer;

[0035] S3, after the first deposition is completed, continue to introduce hydrogen, phosphine, silane and ammonia for a second deposition to form a doped polycrystalline silicon nitride layer on the surface of the tunneling oxide layer;

[0036] S4, through annealing treatment, forming a passivation contact structure on the surface of the silicon wafer.

[0037] The present invention does not limit the specific preparation methods and conditions for step S1, and existing preparation methods and conditions can be adopted, for example:

[0038] (1) Loading the boat: placing the silicon wafer in the deposition device, introducing nitrogen with a flow rate of 2000 sccm - 3000 sccm, setting the time to 500 s - 600 s, setting the temperature to 400 °C - 420 °C, and setting the pressure to be close to atmospheric pressure;

[0039] (2) Vacuum stabilization: waiting for the deposition device to be pumped to the set vacuum pressure, setting the time to 60 s - 100 s, setting the temperature at 400 °C - 420 °C, and closing all gas inlets;

[0040] (3) Heating: Wait until the temperature inside the deposition device rises to the set temperature of 400°C - 420°C, set the nitrogen flow rate to be introduced as 3000 sccm - 4000 sccm, and set the time to 300 s - 350 s;

[0041] (4) Constant temperature: Wait until the temperature inside the deposition device stabilizes within the range of the set temperature ±5°C;

[0042] (5) Constant pressure: Keep the constant temperature, pump the inside of the deposition device to the set vacuum pressure, set the time to 60 s - 80 s, close all gas inlets, and set the pressure inside the deposition device to 800 mtorr - 1000 mtorr;

[0043] (6) Depositing the tunneling oxide layer: Set the time to 115 s - 150 s, set the temperature at 400°C - 420°C, and set the NO 2 flow rate to 3000 sccm - 3200 sccm, and set the pressure to 11000 mtorr - 12000 mtorr.

[0044] In step S2 and step S3, by setting two-step deposition, control the flow rate ratio of hydrogen to phosphine in the first deposition to be greater than that in the second deposition, and the difference is 1.4 - 3.1; the temperature of the first deposition is greater than or equal to the temperature of the second deposition, and the difference is less than 10°C. Then, under the synergistic effect of a specific temperature and a specific hydrogen-to-phosphine flow rate ratio, on the one hand, precisely regulate the doping amount of phosphorus ions in the two-step deposition, so that the phosphorus ion doping concentration in the doped polycrystalline silicon nitride layer formed by the first deposition is less, which is beneficial to reducing the optical parasitic absorption loss. At the same time, the phosphorus ion doping concentration in the doped polycrystalline silicon nitride layer formed by the second deposition is more, which is beneficial to forming a better ohmic contact and can provide excellent transport and passivation capabilities for charge carriers, thereby improving the photoelectric conversion efficiency of the photovoltaic cell.

[0045] On the other hand, when the doped polycrystalline silicon nitride layer reaches a certain deposition thickness, it not only has high light transmittance, which is beneficial to further reducing the optical parasitic absorption loss, but also can ensure that the tunneling oxide layer is not easily electrically broken down, making the passivation contact structure have high quality and high performance.

[0046] In one embodiment, the flow rate of hydrogen in the first deposition is greater than the flow rate of hydrogen in the second deposition;

[0047] and / or, the flow rate of phosphine in the first deposition is less than the flow rate of phosphine in the second deposition;

[0048] and / or, the flow rate of silane in the first deposition is equal to the flow rate of silane in the second deposition;

[0049] and / or, the flow rate of ammonia in the first deposition is equal to the flow rate of ammonia in the second deposition.

[0050] By coordinately regulating the flow rates of hydrogen, phosphine, silane, and ammonia in the first deposition and the second deposition, it is beneficial to further adjust the doping concentration difference of phosphorus ions in the doped polycrystalline silicon nitride layer, achieving minimizing the optical parasitic absorption loss to the greatest extent and improving the photoelectric conversion efficiency of the photovoltaic cell.

[0051] In one embodiment, in the first deposition, the flow rate ratio of hydrogen, phosphine, silane, and ammonia is (19 - 25):(4 - 5):(5 - 7):(14 - 18).

[0052] Preferably, in the first deposition, the flow rate of hydrogen is 9500 sccm - 10500 sccm, the flow rate of phosphine is 1800 sccm - 2500 sccm, the flow rate of silane is 2500 sccm - 3500 sccm, and the flow rate of ammonia is 7000 sccm - 9000 sccm.

[0053] By controlling the flow rate ratio of hydrogen, phosphine, silane, and ammonia in the first deposition, the optimal doping concentration of phosphorus ions is achieved in the formed first part of the doped polycrystalline silicon nitride layer, which is beneficial to achieving less parasitic absorption loss.

[0054] In one embodiment, in the second deposition, the flow rate ratio of hydrogen, phosphine, silane, and ammonia is (15 - 17):(7 - 9):(5 - 7):(14 - 18).

[0055] Preferably, in the second deposition, the flow rate of hydrogen is 7500 sccm - 8500 sccm, the flow rate of phosphine is 3500 sccm - 4500 sccm, the flow rate of silane is 2500 sccm - 3500 sccm, and the flow rate of ammonia is 7000 sccm - 9000 sccm.

[0056] By controlling the flow rate ratio of hydrogen, phosphine, silane, and ammonia in the second deposition, the doping concentration of phosphorus ions in the formed second part of the doped polycrystalline silicon nitride layer is higher than that in the first part of the doped polycrystalline silicon nitride layer formed by the first deposition, which is beneficial to providing excellent transport and passivation capabilities for charge carriers while achieving minimizing the optical parasitic absorption loss to the greatest extent.

[0057] In one embodiment, the temperature of the first deposition is 440°C - 450°C, and the time is 440 s - 450 s;

[0058] And / or, the temperature of the second deposition is 450°C - 460°C, and the time is 600 s - 680 s;

[0059] And / or, the pressure of the first deposition is equal to the pressure of the second deposition.

[0060] In one embodiment, after the secondary deposition is completed, vacuum pumping is first performed to extract the remaining gas in the deposition apparatus, and then a large amount of nitrogen gas is introduced into the deposition apparatus to restore the deposition apparatus to atmospheric pressure, so as to prepare for opening the deposition apparatus to take out the silicon wafer subsequently.

[0061] In step S4, annealing is preferably carried out at a temperature of 800 °C - 1000 °C, which can effectively activate the phosphorus doping in the doped polycrystalline silicon nitride layer.

[0062] The present invention provides a passivation contact structure prepared by the preparation method of the passivation contact structure as described above. In the doped polycrystalline silicon nitride layer of the passivation contact structure, the phosphorus ion doping concentration near the surface of the tunneling oxide layer is less than the phosphorus ion doping concentration far from the surface of the tunneling oxide layer. Preferably, the difference in phosphorus ion doping concentration is 1.5E 20 -2.5E 20 .

[0063] The passivation contact structure prepared by the preparation method of the present invention can minimize the optical parasitic absorption loss and improve the photoelectric conversion efficiency of the photovoltaic cell.

[0064] In one embodiment, the thickness of the doped polycrystalline silicon nitride layer is 65 nm - 95 nm.

[0065] The present invention provides a preparation method of a TOPCon solar cell, including the preparation method of the passivation contact structure as described above.

[0066] The present invention does not limit the specific preparation methods and conditions for TOPCon solar cells, and existing preparation methods and conditions can be adopted, for example:

[0067] (1) Wet chemical texturing is performed on the silicon wafer to form a textured surface on the silicon wafer surface;

[0068] (2) High-temperature boron diffusion is performed on any surface of the texturized silicon wafer to form a PN junction as the front side;

[0069] (3) Etching is performed on the opposite surface of the silicon wafer after boron diffusion to remove the borosilicate glass layer (BSG) and the diffusion bypass, as the back side;

[0070] (4) A tunneling oxide layer (SiO x ) is prepared on the back surface of the silicon wafer. Preferably, the thickness of the tunneling oxide layer is 1 nm - 3 nm;

[0071] (5) A doped polycrystalline silicon nitride layer is prepared on the surface of the tunneling oxide layer. Preferably, the thickness of the doped polycrystalline silicon nitride layer is 65 nm - 95 nm;

[0072] (6) Anneal at a temperature of 800 °C - 1000 °C to activate the phosphorus doping in the doped polycrystalline silicon nitride layer;

[0073] (7) Use a wet process to remove the front and edge phosphosilicate glass layers (PSG);

[0074] (8) Prepare an alumina passivation layer on the front and back of the silicon wafer by atomic layer deposition (ALD) or plasma enhanced chemical vapor deposition (PECVD). The thicknesses of the front alumina passivation layer and the back alumina passivation layer are independently selected from 2 nm - 8 nm;

[0075] (9) Prepare a silicon nitride, silicon oxynitride, silicon oxide stack antireflection film layer on the front and back of the silicon wafer by plasma enhanced chemical vapor deposition (PECVD). Preferably, the thickness of the front antireflection film layer is 70 nm - 100 nm, and preferably the thickness of the back antireflection film is 80 nm - 120 nm;

[0076] (11) Screen print and sinter the silicon wafer to form electrodes.

[0077] The present invention also provides a TOPCon solar cell prepared by the preparation method of the TOPCon solar cell as described above.

[0078] In one embodiment, in the TOPCon solar cell, the back structure includes a tunneling oxide layer, a doped polycrystalline silicon nitride layer, a passivation antireflection layer, and a back metal electrode sequentially stacked on a silicon substrate. Among them, the back metal electrode penetrates the passivation layer to form an ohmic contact with the doped polycrystalline silicon nitride layer; the front structure includes a PN junction, a passivation antireflection layer, and a front metal electrode sequentially stacked on the silicon substrate. Among them, the front metal electrode penetrates the passivation layer to form an ohmic contact with the PN junction. Preferably, the passivation antireflection layer is selected from a stacked structure of alumina and silicon nitride, silicon oxynitride, or silicon oxide.

[0079] Hereinafter, the passivation contact structure, its preparation method, and application will be further described through the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0080] Blank sample

[0081] Prepare a TOPCon solar cell according to the traditional passivation contact structure process as a blank sample. Among them, the specific process steps are as follows:

[0082] (1) Loading the wafer: Feed the silicon wafer into the high-temperature adaptation furnace tube. Set the time to 600 s, the temperature to 400 °C, the nitrogen flow rate to 2000 sccm, and the pressure to 760000 mtorr;

[0083] (2) Vacuum stabilization: Wait until the set vacuum pressure is reached inside the furnace tube. Set the time to 60 s, the temperature to 350 °C, turn off all gas inlets, and set the furnace tube pressure to 0 mbar;

[0084] (3) Heating up: Wait until the furnace tube heats up to the set temperature. Set the time to 300 s, the temperature to 400 °C, and the nitrogen flow rate to 3000 mtorr;

[0085] (4) Constant temperature: Wait until the furnace tube stabilizes within the set temperature range of 400 °C ± 5 °C;

[0086] (5) Constant pressure: Wait until the set vacuum pressure is reached inside the furnace tube. Set the time to 60 s, the temperature to 400 °C, turn off all gas inlets, and set the furnace tube pressure to 1000 mtorr;

[0087] (6) Depositing the tunneling oxide layer: Set the time to 115 s, the temperature to 400 °C, and the NO 2 flow rate to 11000 sccm, and the furnace tube pressure to 1000 mtorr;

[0088] (7) Depositing the doped polysilicon layer: Set the time to 1150 s, the temperature to 450 °C, and simultaneously introduce silane with a flow rate of 3000 sccm, hydrogen with a flow rate of 8000 sccm, and phosphine with a flow rate of 3300 sccm, and set the furnace tube pressure to 3000 mtorr;

[0089] (9) Evacuating the vacuum: Extract the remaining gas inside the downcomer;

[0090] (10) Filling with nitrogen: Introduce a large amount of nitrogen into the furnace tube to restore the normal pressure state of the furnace tube. Set the time to 240 s, the temperature to 300 °C, the large nitrogen flow rate to 3000 sccm, and the furnace tube pressure to 760000 mtorr;

[0091] (11) Unloading the wafer: Open the furnace door and take out the quartz boat. Set the time to 600 s, the temperature to 300 °C, the large nitrogen flow rate to 2000 sccm, and the furnace tube pressure to 760000 mtorr.

[0092] The thickness of the doped polysilicon layer is measured to be 100 nm, and the transmittance is 60%. The doping concentration of phosphorus ions in the phosphorus-doped polysilicon layer is measured by electrochemical capacitance-voltage method (ECV). The doping concentration of phosphorus ions in the phosphorus-doped polysilicon layer is measured to be 3E 20 .

[0093] Example 1

[0094] The difference between Example 1 and the blank sample is that the preparation method of the passivation contact structure provided by the present invention is used instead of the traditional process. The specific steps are as follows:

[0095] (1) Loading the boat: Feed the silicon wafer into the high-temperature compatible furnace tube. Set the time to 600 s, the temperature to 400 °C, the nitrogen flow rate to 2000 sccm, and the pressure to 760000 mtorr;

[0096] (2) Vacuum stabilization: Wait until the set vacuum pressure is reached inside the furnace tube. Set the time to 60 s, the temperature to 350 °C, close all gas inlets, and set the furnace tube pressure to 0 mbar;

[0097] (3) Heating up: Wait until the furnace tube heats up to the set temperature. Set the time to 300 s, the temperature to 400 °C, and the nitrogen flow rate to 3000 mtorr;

[0098] (4) Constant temperature: Wait until the furnace tube stabilizes within the range of the set temperature of 400 °C ± 5 °C;

[0099] (5) Constant pressure: Wait until the set vacuum pressure is reached inside the furnace tube. Set the time to 60 s, the temperature to 400 °C, close all gas inlets, and set the furnace tube pressure to 1000 mtorr;

[0100] (6) Depositing the tunneling oxide layer: Set the time to 115 s, the temperature to 400 °C, NO 2 flow rate to 11000 sccm, and the furnace tube pressure to 1000 mtorr;

[0101] (7) First deposition of the doped polycrystalline silicon nitride layer: Set the time to 540 s, the temperature to 450 °C, and simultaneously introduce silane with a flow rate of 3000 sccm, hydrogen with a flow rate of 9900 sccm, ammonia with a flow rate of 8000 sccm, and phosphine with a flow rate of 2000 sccm. Set the furnace tube pressure to 3100 mtorr;

[0102] (8) Second deposition of the doped polycrystalline silicon nitride layer: Set the time to 600 s, the temperature to 460 °C, and simultaneously introduce silane with a flow rate of 3000 sccm, hydrogen with a flow rate of 7700 sccm, ammonia with a flow rate of 8000 sccm, and phosphine with a flow rate of 3800 sccm. Set the furnace tube pressure to 3100 mtorr;

[0103] (9) Vacuum pumping: Pump out the remaining gas inside the downcomer;

[0104] (10) Filling with nitrogen: Introduce a large amount of nitrogen into the furnace tube to restore the normal pressure state of the furnace tube. Set the time to 240 s, the temperature to 300 °C, the large nitrogen flow rate to 3000 sccm, and the furnace tube pressure to 760000 mtorr;

[0105] (11) Removing the boat: Open the furnace door and take out the quartz boat. Set the time to 600 s, the temperature to 300 °C, the large nitrogen flow rate to 2000 sccm, and the furnace tube pressure to 760000 mtorr.

[0106] The thickness of the doped polycrystalline silicon nitride layer is measured to be 80 nm, and the light transmittance is 85%. The doping concentration of phosphorus ions in the doped polycrystalline silicon nitride layer is tested by the electrochemical capacitance-voltage method (ECV). In the doped polycrystalline silicon nitride layer, the doping concentration of phosphorus ions on the surface of the doped polycrystalline silicon nitride layer close to the tunneling oxide layer is 2.5E 20 , while the doping concentration of phosphorus ions on the surface of the doped polycrystalline silicon nitride layer farthest from the tunneling oxide layer is 4E 20 , and the difference in the doping concentration of phosphorus ions is 1.5E 20 .

[0107] Example 2

[0108] The difference between Example 2 and Example 1 is that the time for the first deposition is set to 540 s, the temperature is set to 450 °C, and at the same time, silane with a flow rate of 2500 sccm, hydrogen with a flow rate of 10000 sccm, ammonia with a flow rate of 9000 sccm, and phosphine with a flow rate of 2500 sccm are introduced, and the furnace tube pressure is set to 3100 mtorr; the time for the second deposition is set to 600 s, the temperature is set to 460 °C, and at the same time, silane with a flow rate of 2500 sccm, hydrogen with a flow rate of 7500 sccm, ammonia with a flow rate of 9000 sccm, and phosphine with a flow rate of 4500 sccm are introduced, and the furnace tube pressure is set to 3100 mtorr.

[0109] The thickness of the doped polycrystalline silicon nitride layer is measured to be 80 nm, and the light transmittance is 85%. The doping concentration of phosphorus ions in the doped polycrystalline silicon nitride layer is tested by the electrochemical capacitance-voltage method (ECV). In the doped polycrystalline silicon nitride layer, the doping concentration of phosphorus ions on the surface of the doped polycrystalline silicon nitride layer close to the tunneling oxide layer is 2.3E 20 , while the doping concentration of phosphorus ions on the surface of the doped polycrystalline silicon nitride layer farthest from the tunneling oxide layer is 4.2E 20 , and the difference in the doping concentration of phosphorus ions is 1.9E 20 .

[0110] Example 3

[0111] Example 3 is different from Example 1 in that the time for primary deposition is set to 540 s, the temperature is set at 440 °C, and silane with a flow rate of 3500 sccm, hydrogen with a flow rate of 9500 sccm, ammonia with a flow rate of 7000 sccm, and phosphine with a flow rate of 2200 sccm are introduced simultaneously, and the furnace tube pressure is set to 3100 mtorr; the time for secondary deposition is set to 600 s, the temperature is set at 450 °C, and silane with a flow rate of 3500 sccm, hydrogen with a flow rate of 8000 sccm, ammonia with a flow rate of 7000 sccm, and phosphine with a flow rate of 3600 sccm are introduced simultaneously, and the furnace tube pressure is set to 3100 mtorr.

[0112] The thickness of the doped polycrystalline silicon nitride layer is measured to be 80 nm, and the light transmittance is 85%. The doping concentration of phosphorus ions in the doped polycrystalline silicon nitride layer is tested by electrochemical capacitance-voltage method (ECV). In the doped polycrystalline silicon nitride layer, the doping concentration of phosphorus ions on the surface of the doped polycrystalline silicon nitride layer close to the tunneling oxide layer is 2E 20 , while the doping concentration of phosphorus ions on the surface of the doped polycrystalline silicon nitride layer farthest from the tunneling oxide layer is 4.5E 20 , and the difference in the doping concentration of phosphorus ions is 2.5E 20 .

[0113] Comparative Example 1

[0114] Comparative Example 1 is different from Example 1 in that a one-step deposition of the doped polycrystalline silicon nitride layer is adopted: the time is set to 1200 s, the temperature is set at 450 °C, and silane with a flow rate of 3000 sccm, hydrogen with a flow rate of 10000 sccm, ammonia with a flow rate of 8000 sccm, and phosphine with a flow rate of 3000 sccm are introduced simultaneously.

[0115] Comparative Example 2

[0116] Comparative Example 2 is different from Example 1 in that the temperature for secondary deposition is 440 °C.

[0117] Comparative Example 3

[0118] Comparative Example 3 is different from Example 1 in that the temperature for secondary deposition is 475 °C.

[0119] Comparative Example 4

[0120] Comparative Example 4 is different from Example 1 in that in the secondary deposition, the flow rate of hydrogen is 11000 sccm and the flow rate of phosphine is 1800 sccm.

[0121] Comparative Example 5

[0122] The difference between Comparative Example 5 and Example 1 is that in the secondary deposition, the flow rate of hydrogen is 8800 sccm and the flow rate of phosphine is 2200 sccm.

[0123] Comparative Example 6

[0124] The difference between Comparative Example 6 and Example 1 is that in the secondary deposition, the flow rate of hydrogen is 7300 sccm and the flow rate of phosphine is 4600 sccm.

[0125] A photovoltaic cell tester was used to test the performance of the blank sample and the TOPCon solar cells prepared in Examples 1-3 and Comparative Examples 1-6. The test results are as Figure 1 shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129] According to Table 1, compared with the blank sample and Comparative Examples 1-6, Examples 1-3 provided by the present invention have improved open-circuit voltage, short-circuit current, fill factor, and conversion efficiency. By testing the ratio of the average number of photoelectrons generated per unit time to the number of incident photons at different wavelengths, the quantum efficiency can be obtained. The quantum efficiency is an important parameter describing the optoelectronic conversion ability of optoelectronic devices. Combining Figure 1 as shown, it can be seen that in the long-wavelength spectral response of 800 nm - 1100 nm, the TOPCon solar cell prepared in Example 1 is significantly higher than the conventional TOPCon solar cell.

[0130] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0131] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A preparation method of a passivation contact structure in a solar cell, characterized in that, the preparation method comprises the following steps: Prepare a tunneling oxide layer on any surface of a silicon wafer; Introduce hydrogen, phosphine, silane and ammonia gas, and perform a first deposition on the surface of the tunneling oxide layer; After the first deposition is completed, continue to introduce hydrogen, phosphine, silane and ammonia gas for a second deposition to form a doped polycrystalline silicon nitride layer on the surface of the tunneling oxide layer; Through annealing treatment, a passivation contact structure is formed on the surface of the silicon wafer; Wherein, the flow rate ratio of hydrogen to phosphine in the first deposition is greater than the flow rate ratio of hydrogen to phosphine in the second deposition, and the difference is 1.4 - 3.1; the temperature of the first deposition is greater than or equal to the temperature of the second deposition, and the difference is less than 10 °C.

2. The preparation method of the passivation contact structure according to claim 1, characterized in that, the flow rate of hydrogen in the first deposition is greater than the flow rate of hydrogen in the second deposition; and / or, the flow rate of phosphine in the first deposition is less than the flow rate of phosphine in the second deposition; and / or, the flow rate of silane in the first deposition is equal to the flow rate of silane in the second deposition; and / or, the flow rate of ammonia gas in the first deposition is equal to the flow rate of ammonia gas in the second deposition.

3. The preparation method of the passivation contact structure according to claim 1, characterized in that, in the first deposition, the flow rate ratio of hydrogen, phosphine, silane and ammonia gas is (19 - 25):(4 - 5):(5 - 7):(14 - 18).

4. The preparation method of the passivation contact structure according to claim 3, characterized in that, in the first deposition, the flow rate of hydrogen is 9500 sccm - 10500 sccm, the flow rate of phosphine is 1800 sccm - 2500 sccm, the flow rate of silane is 2500 sccm - 3500 sccm, and the flow rate of ammonia gas is 7000 sccm - 9000 sccm.

5. The preparation method of the passivation contact structure according to claim 1, characterized in that, in the second deposition, the flow rate ratio of hydrogen, phosphine, silane and ammonia gas is (15 - 17):(7 - 9):(5 - 7):(14 - 18).

6. The preparation method of the passivation contact structure according to claim 5, characterized in that, in the second deposition, the flow rate of hydrogen is 7500 sccm - 8500 sccm, the flow rate of phosphine is 3500 sccm - 4500 sccm, the flow rate of silane is 2500 sccm - 3500 sccm, and the flow rate of ammonia gas is 7000 sccm - 9000 sccm.

7. The preparation method of the passivation contact structure according to claim 1, characterized in that, the temperature of the first deposition is 440 °C - 450 °C, and the time is 500 s - 600 s; and / or, the temperature of the second deposition is 450 °C - 460 °C, and the time is 600 s - 680 s; and / or, the pressure of the first deposition is equal to the pressure of the second deposition; and / or, the temperature of the annealing treatment is 800 °C - 1000 °C.

8. A passivated contact structure obtained by the preparation method of the passivated contact structure according to any one of claims 1-7, characterized in that, in the doped polycrystalline silicon nitride layer of the passivated contact structure, the doping concentration of phosphorus ions near the surface of the tunneling oxide layer is less than the doping concentration of phosphorus ions far from the surface of the tunneling oxide layer.

9. A preparation method of a TOPCon solar cell, characterized in that, it includes the preparation method of the passivated contact structure according to any one of claims 1-7.

10. A TOPCon solar cell obtained by the preparation method of the TOPCon solar cell according to claim 9.

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