Poly nitrogen doping method and TOPCon battery

Abstract

The invention discloses a Poly nitrogen doping method and a TOPCon battery, the TOPCon battery comprises a back Poly structure, the method comprises the following steps: S1, inserting a battery piece into a graphite boat, feeding the graphite boat into a PECVD furnace tube, and carrying out reaction preparation; s2, nitrous oxide is introduced into the furnace tube, and oxidation is carried out on the back surface of the battery piece to form a first tunneling oxide layer; s3, silane, ammonia gas, hydrogen and phosphine are introduced into the furnace tube for deposition, and a first amorphous silicon layer is formed on the first tunneling oxide layer; s4, nitrous oxide is introduced into the furnace tube for oxidation, and a second tunneling oxide layer is formed on the first amorphous silicon layer; s5, silane, hydrogen and phosphorane are introduced into the furnace tube for deposition, and a second amorphous silicon layer is formed on the second tunneling oxide layer; and S6, high-temperature annealing and vacuum breaking treatment are carried out, and preparation of the back Poly structure is completed. According to the invention, by optimizing Poly nitrogen doping process parameters and combining a Poly double tunneling process, ammonia gas is introduced into the furnace tube, and the back Poly structure is prepared, so that the conversion efficiency of the TOPCon cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly relates to a Poly nitrogen doping method and a TOPCon cell. Background Art

[0002] Under the background of the accelerating transformation of the global energy structure, the photovoltaic industry is an important part of the clean energy field; among them, as the core component of the photovoltaic power generation system, the improvement of the photoelectric conversion efficiency of the battery chip is closely related to the market competitiveness and power generation cost of photovoltaic products. Therefore, the technology for improving the efficiency of the battery chip has become the focus of attention in the photovoltaic research and industrial circles. With the development of N-type battery technology, especially technologies such as PERT, TOPCon, and HJT, the technology for improving the efficiency of the battery chip is particularly important; N-type batteries have characteristics such as weak light response, low temperature coefficient, and low attenuation rate, but the passivation effect of the traditional polysilicon layer of the battery is poor, resulting in low interface quality and carrier transport efficiency of the battery chip, thus leading to low conversion efficiency of the battery. Summary of the Invention

[0003] The main object of the present invention is to provide a Poly nitrogen doping method, aiming to solve the problem that the passivation effect of the traditional polysilicon layer of the battery is poor, resulting in low interface quality and carrier transport efficiency of the battery chip, and thus low conversion efficiency of the battery.

[0004] To achieve the above object, the present invention proposes a Poly nitrogen doping method, which includes: S1. Insert the battery chip into a graphite boat and then send it into a PECVD furnace tube for reaction preparation; S2. Introduce nitrous oxide into the furnace tube to form a first tunneling oxide layer on the back of the battery chip by oxidation; S3. Introduce silane, ammonia, hydrogen, and phosphine into the furnace tube for deposition to form a first amorphous silicon layer on the first tunneling oxide layer; S4. Introduce nitrous oxide into the furnace tube for oxidation to form a second tunneling oxide layer on the first amorphous silicon layer; S5. Introduce silane, hydrogen, and phosphine into the furnace tube for deposition to form a second amorphous silicon layer on the second tunneling oxide layer; S6. Perform high-temperature annealing and vacuum breaking treatment to complete the preparation of the back Poly structure.

[0005] In one embodiment, the volume flow rate of silane in step S3 is 3260 sccm, the volume flow rate of ammonia is 90 sccm, the volume flow rate of hydrogen is 8136 sccm, and the volume flow rate of phosphine is 650 sccm.

[0006] In one embodiment, the volume flow rate of nitrous oxide in steps S2 and S4 is 11076 sccm, and the set power range is 13000 - 13500 W.

[0007] In one embodiment, the volume flow rate of silane in step S5 is 3260 sccm, the volume flow rate of hydrogen is 8136 sccm, and the volume flow rate of phosphine is 850 sccm.

[0008] In one embodiment, the reaction preparation in step S1 is as follows: Vacuum pumping: Nitrogen is introduced into the furnace tube for purging to remove the air in the furnace tube and reach a low-pressure state. Temperature raising treatment: The temperature in the furnace tube is heated to the deposition required temperature range of 400 - 450 °C, and kept at a constant temperature while continuing to reduce the pressure. Leak detection: Detection of the vacuum state is carried out under a low-pressure state.

[0009] In one embodiment, the vacuum-breaking treatment in step S6 is: Nitrogen is introduced into the furnace tube to restore the normal pressure state.

[0010] The present invention also provides a TOPCon cell, which includes a back Poly structure obtained by the above Poly nitrogen doping method.

[0011] The technical solution of the present invention optimizes the Poly nitrogen doping process parameters and combines the Poly double tunneling process, introduces ammonia into the furnace tube to prepare the back Poly structure, so as to improve the conversion efficiency of the TOPCon cell, enhance the stability, and improve the optical properties. Description of the Drawings

[0012] Figure 1 It is a flow chart of the Poly nitrogen doping method of the present invention; Figure 2 It is a structural diagram of the back Poly structure of the TOPCon cell of the present invention. Detailed Embodiments

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown here can be arranged and designed in various different configurations.

[0014] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0016] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0017] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0018] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] As the core component of photovoltaic power generation system, the improvement of photoelectric conversion efficiency of solar cells is closely related to the market competitiveness and power generation cost of photovoltaic products. Therefore, the technology of improving the efficiency of solar cells has become the focus of attention of photovoltaic scientific research and industry. With the development of N-type battery technology, especially PERT, TOPCon and HJT technologies, the technology of improving the efficiency of solar cells is particularly important; N-type batteries have the characteristics of weak light response, low temperature coefficient and low attenuation rate, but the traditional battery polysilicon layer has poor passivation effect, which makes the interface quality and carrier transmission efficiency of the solar cell low, thus resulting in low conversion efficiency of the battery.

[0020] In order to solve the above problems, the present invention proposes a Poly nitrogen doping method. The specific implementation of the present invention is described in detail below with reference to the accompanying drawings.

[0021] As Figure 1-2 shown, the Poly nitrogen doping method includes the following steps: S1. Insert the cell into the graphite boat and then send it into the PECVD furnace tube for reaction preparation; S2. Introduce nitrous oxide into the furnace tube to form a first tunneling oxide layer on the back of the cell by oxidation; S3. Introduce silane, ammonia, hydrogen and phosphine into the furnace tube for deposition to form a first amorphous silicon layer on the first tunneling oxide layer; S4. Introduce nitrous oxide into the furnace tube for oxidation to form a second tunneling oxide layer on the first amorphous silicon layer; S5. Introduce silane, hydrogen and phosphine into the furnace tube for deposition to form a second amorphous silicon layer on the second tunneling oxide layer; S6. Perform high-temperature annealing and vacuum breaking treatment to complete the preparation of the back Poly structure.

[0022] In one embodiment, the volume flow rate of silane in step S3 is 3260 sccm, the volume flow rate of ammonia is 90 sccm, the volume flow rate of hydrogen is 8136 sccm, and the volume flow rate of phosphine is 650 sccm.

[0023] In one embodiment, the vacuum breaking treatment in step S6 is: introducing nitrogen into the furnace tube to restore the normal pressure state.

[0024] In the existing cell manufacturing process, Poly nitrogen doping is a key step, that is, introducing nitrogen atoms into the polysilicon layer to change the electrical and optical properties of the material, which can significantly affect the performance of the cell; Table 1 is the table of existing Poly nitrogen doping process parameters:

[0025] Based on the existing Poly nitrogen doping process, 90 sccm of ammonia is added in steps 11 and 12 and 350 sccm of phosphine is increased at the same time in this embodiment, that is, the volume flow rate of ammonia in this embodiment is 90 sccm and the volume flow rate of phosphine is 650 sccm. Finally, N-poly-si with a thickness range of 20 - 40 nm is deposited and formed. The table of Poly nitrogen doping process parameters of the present invention is shown in Table 2:

[0026] In order to verify that the TOPCon cell composed of the back Poly structure obtained by the Poly nitrogen doping method of the present invention has better performance, an experimental group and a reference group are provided to test the TOPCon cell composed of the back Poly structure obtained by this method. The detailed electrical parameters are shown in Table 3:

[0027] From the data in Table 3, it can be seen that the experimental result efficiency in this embodiment has been significantly improved. The conversion efficiency of the TOPCon cell has increased by 0.028%, mainly manifested as the advantage of open-circuit voltage filling.

[0028] After this embodiment completes step S5, within the same temperature and power range, silane with a volume flow rate range of 1000 - 2000 sccm and dinitrogen monoxide with a volume flow rate range of 7000 - 9000 sccm are introduced into the furnace tube, and the reaction time range is 30 - 70 S. Finally, a Mask protective layer with a thickness range of 10 - 70 nm is formed on the second amorphous silicon layer.

[0029] In step S6 of this embodiment, high-temperature annealing is performed at a temperature of 880 - 920 degrees for an annealing time of 25 - 35 min, and the temperature is reduced to a temperature at which the furnace tube can be opened to prevent equipment damage.

[0030] This embodiment optimizes the Poly nitrogen doping process parameters and adopts the Poly double tunneling process. Ammonia gas is introduced into the PECVD furnace tube as a precursor to introduce N atoms into the polysilicon thin film. The greater the volume flow rate of NH3, the more N atoms in the polysilicon. N atoms diffuse into silicon during high-temperature annealing and accumulate at the SiOx interface. Thanks to the excellent H-trapping ability of N atoms, the H content in the thin film is also effectively increased. Especially at the SiOx interface, a high concentration of H atoms is conducive to the improvement of passivation. The presence of N atoms inhibits the activation and diffusion of P atoms, making the P inward diffusion situation significantly improved. The incorporation of N atoms effectively increases the optical band gap of the thin film. In the full spectrum range, the light absorption decreases and the transmittance increases. It can be understood that the Poly nitrogen doping method of the present invention improves the interface quality and carrier transport efficiency of the cell by optimizing the Poly nitrogen doping process parameters and combining the Poly double tunneling process to improve the conversion efficiency of the TOPCon cell.

[0031] In one embodiment, the volume flow rate of dinitrogen monoxide in steps S2 and S4 is 11076 sccm, and the power range is set to 13000 - 13500 W.

[0032] In this embodiment, in step S2, at a temperature of 400 - 450 °C, 11076 sccm of nitrous oxide is introduced into the furnace tube, the power range is set to 13000 - 13500 W, and oxidation of the tunneling oxide layer is carried out at a certain ratio. The oxidation time is 80 - 120 S, and finally a first tunneling oxide layer with a thickness of 1 - 2 nm is formed; in step S4, at the same temperature and power range, 200 - 400 sccm of silane is introduced into the furnace tube, deposited for 20 - 50 S, an appropriate amount of hydrogen can be added according to the actual situation, and then 11076 sccm of nitrous oxide is introduced and oxidized for 20 - 40 S, finally forming a second tunneling oxide layer with a thickness of 0.5 - 1 nm.

[0033] In one embodiment, the volume flow rate of silane in step S5 is 3260 sccm, the volume flow rate of hydrogen is 8136 sccm, and the volume flow rate of phosphine is 850 sccm.

[0034] In this embodiment, in step S5, at the same temperature and power range, 2000 - 5000 sccm of silane, 600 - 800 sccm of phosphine, and 8000 - 12000 sccm of hydrogen are introduced into the furnace tube, and the reaction time is 100 - 300 S, finally forming a second amorphous silicon layer with a thickness of 20 - 40 nm; among them, the volume flow rate of silane can preferably be 3260 sccm, the volume flow rate of hydrogen can preferably be 8136 sccm, and the volume flow rate of phosphine can preferably be 850 sccm.

[0035] In one embodiment, the reaction preparation in step S1 is as follows: Vacuum pumping: Nitrogen is introduced into the furnace tube for purging to remove the air in the furnace tube and reach a low - pressure state. Heating treatment: The temperature in the furnace tube is heated to the deposition - required temperature range of 400 - 450 °C, kept at a constant temperature, and the pressure is further reduced. Leak detection: Detection of the vacuum state is carried out under a low - pressure state.

[0036] In this embodiment, at a temperature of 400 - 450 °C, 5000 - 50000 sccm of nitrogen is introduced into the furnace tube for purging to fully remove the air in the furnace tube until a low - pressure state is reached.

[0037] The present invention also proposes a TOPCon cell, which includes a back - side Poly structure, and the back - side Poly structure is obtained by the above - mentioned Poly nitrogen - doping method; the specific steps of the Poly nitrogen - doping method refer to the above - mentioned embodiments. Since this TOPCon cell adopts all the technical solutions of the above - mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above - mentioned embodiments, which will not be elaborated here one by one.

[0038] In summary, the Poly nitrogen doping method of the present invention optimizes the process parameters of Poly nitrogen doping. Combining with the Poly double tunneling process, ammonia gas is introduced into the furnace tube to prepare the back Poly structure, so as to improve the conversion efficiency of TOPCon cells, enhance stability and improve optical properties. Specifically, nitrogen doping can improve the passivation effect of the polysilicon layer, reduce surface recombination, thereby increasing the open circuit voltage and fill factor of the cell, and further improving the conversion efficiency of the cell. Nitrogen doping can improve the thermal stability and chemical stability of the polysilicon layer, reduce the performance degradation under high temperature and harsh environments, and extend the service life of the cell. Nitrogen doping can also change the refractive index and absorption coefficient of the polysilicon layer, thereby increasing the absorption efficiency of the cell for sunlight and reducing reflection losses.

[0039] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A Poly nitrogen doping method, characterized in that: The Poly nitrogen doping method comprises the following steps: S1, insert the battery cell into the graphite boat and send it into the PECVD furnace tube, and prepare for the reaction; S2, introducing nitrous oxide into the furnace tube to oxidize the back side of the cell to form a first tunneling oxide layer; S3, introducing silane, ammonia, hydrogen and phosphine into the furnace tube for deposition to form a first amorphous silicon layer on the first tunneling oxide layer; S4, introducing nitrous oxide into the furnace tube for oxidation to form a second tunneling oxide layer on the first amorphous silicon layer; S5, introducing silane, hydrogen and phosphine into the furnace tube for deposition to form a second amorphous silicon layer on the second tunneling oxide layer; S6, performing high temperature annealing and vacuum breaking treatment to complete the preparation of the back side Poly structure.

2. The poly nitrogen doping method according to claim 1, characterized in that: In step S3, the volume flow rate of silane is 3260 sccm, the volume flow rate of ammonia is 90 sccm, the volume flow rate of hydrogen is 8136 sccm, and the volume flow rate of phosphine is 650 sccm.

3. The poly nitrogen doping method according to claim 1, characterized in that: The volume flow rate of nitrous oxide in step S2 and step S4 is 11076 sccm, and the power range is set to 13000-13500W.

4. The poly nitrogen doping method according to claim 1, characterized in that: In step S5, the volume flow rate of silane is 3260 sccm, the volume flow rate of hydrogen is 8136 sccm, and the volume flow rate of phosphine is 850 sccm.

5. The poly nitrogen doping method according to claim 1, characterized in that: The reaction preparation in step S1 is as follows: Vacuuming: Introduce nitrogen into the furnace tube for purging to remove the air in the furnace tube and achieve a low pressure state; Heating treatment: Heat the temperature in the furnace tube to the required temperature range of 400-450°C for deposition, maintain constant temperature, and continue to reduce pressure; Leak detection: vacuum detection under low pressure.

6. The poly nitrogen doping method according to claim 1, characterized in that: The vacuum breaking process in step S6 is as follows: nitrogen is introduced into the furnace tube to restore the normal pressure state.

7. A TOPCon battery, characterized in that: The TOPCon battery comprises a back Poly structure, and the back Poly structure is obtained by the Poly nitrogen doping method according to any one of claims 1 to 6.

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