A chain type pretreatment and efficiency improving device for raw silicon wafer of TOPCon cell

Abstract

The application discloses a chain type pretreatment and efficiency improving equipment for TOPCon cell raw material silicon wafers. The equipment has a heating cavity with a silicon wafer conveying roller, and a temperature sensor and gas inlet and outlet pipelines are arranged in the heating cavity; heating, gas circulation and alarm functions of a central computer control device are provided. The core of the equipment is that the high temperature set in the furnace cavity can be reached, and the stability and uniformity of the temperature in the cavity are ensured; through the high temperature above 1100 DEG C and the oxygen atmosphere, the oxygen precipitation and vacancy defects in the photovoltaic N-type silicon are ablated and repaired, the recombination center in the material body is reduced, the bulk lifetime of the silicon is increased, and thus the cell efficiency is improved; the time required for pretreatment is greatly shortened, and the equipment is favorable for large-scale industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of TOPCon cell preparation, in particular to a chain type pretreatment and efficiency improvement equipment for TOPCon cell raw material silicon wafer. BACKGROUND

[0002] With the deepening of industrialization process, human society has entered a period of rapid development in the past two centuries, but various emerging scientific and technological have brought convenience and efficiency to human life, while also constantly encroaching on the ecological environment of the earth. The large-scale use of vehicles such as cars and ships relying on internal combustion engines and the emission of various industrial waste gases have caused air quality to decline year by year. In order to improve environmental quality, more and more power technologies have begun to transform to electric power driving, and automobile enterprises using lithium batteries, sodium batteries and other power sources have surpassed traditional oil cars. But at present, the source of electricity is mainly generated by thermal power, which itself will cause serious damage to the environment, so the development and layout of clean energy has become an urgent task. As a stable and versatile clean energy, photovoltaic has attracted much attention. In recent years, the photovoltaic industry in China has achieved rapid growth, and the key links in the industry chain have maintained strong development momentum. In the first half of 2022, the production of polysilicon, silicon wafer, battery and module increased by more than 45%. Among them, the polysilicon production was about 36.5x104t, an increase of 53.4%; the silicon wafer production was about 152.8GW, an increase of 45.5%; the battery wafer production was about 135.5GW, an increase of 46.6%; and the module production was about 123.6GW, an increase of 54.1%. At present, China's photovoltaic module production accounts for more than three-quarters of the global market, and the cumulative installed capacity ranks first in the world.

[0003] TOPCon cell is one of the main forces of current photovoltaic cells, which has significantly higher efficiency than PERC cell and relatively low production line transformation cost. More and more photovoltaic enterprises begin to layout TOPCon cell, and the highest efficiency of mass production can reach 24.8%. In addition to optimizing the diffusion parameters, passivation effect and sintering process of TOPCon cell, the silicon wafer as the substrate material of TOPCon cell is also an important gain point. The N-type monocrystalline silicon grown by the Czochralski method is generally used as the substrate material of TOPCon cell, and a faster pulling speed is generally used to balance the production capacity and crystal quality. The crystal pulled in this way usually contains a higher concentration of oxygen (generally 10 17 ~10 18The single crystal silicon grown by the Czochralski method inevitably introduces a large amount of oxygen elements during the crystal pulling process due to the contact between the melt and the crucible wall. These oxygen elements form precipitation cores during the cooling process and gradually grow during the high-temperature process of the TOPCon, and vacancies also form agglomerates. These high-density and large-size oxygen precipitation cores will recombine the carriers in the battery body, and the oxygen precipitation and vacancy agglomerates are deep recombination centers, which will cause significant attenuation of the minority carrier lifetime and obvious deterioration of the open-circuit voltage of the material, thereby affecting the conversion efficiency of the battery. Oxygen precipitation can be ablated by high temperature above 1100 DEG C. If most of the oxygen precipitation in the body is ablated by heat treatment, the performance of the substrate material can be significantly improved, and the conversion efficiency of the battery can be optimized. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a chain pretreatment equipment for TOPCon battery raw material silicon wafer. The equipment can improve the performance of the raw material silicon wafer of the photovoltaic TOPCon battery, reduce the recombination center in the material body, and improve the conversion efficiency of the battery.

[0005] The first aspect of the present application provides a chain pretreatment efficiency improvement equipment for TOPCon battery raw material silicon wafer; mainly for photovoltaic TOPCon battery substrate material. The equipment mainly consists of a heating system and a mechanical and electrical system, wherein:

[0006] The heating system comprises a heating cavity, an electric heater for providing a heat source for the cavity, and a furnace door provided at the end of the heating cavity, and the outer layer of the heating cavity is provided with heat insulation filler;

[0007] The mechanical and electrical system comprises a silicon wafer conveying roller, a motor for providing power for the rotation of the silicon wafer conveying roller, a temperature sensor for directly measuring the temperature inside the heating cavity, an air inlet / outlet pipeline, an air flow valve for controlling the gas flow in the air inlet / outlet pipeline, an alarm device and a central computer; the alarm device alarms the equipment abnormity;

[0008] For the technical solution described above, further, the inner wall of the heating cavity is made of high-temperature resistant ceramic material; the silicon wafer conveying roller is arranged in the cavity space of the heating cavity, the electric heater and the temperature sensors are embedded on the inner wall of the heating cavity, and the electric heater is separated from the silicon wafer conveying roller by a certain distance;

[0009] For the technical solution described above, further, the air inlet / outlet pipeline is used to provide a circulating flow of gas in the heating cavity;

[0010] Furthermore, the central computer is used to control the motor, temperature sensor, airflow valve, and alarm device, thereby controlling and recording the equipment's program and parameters, and automatically stopping the machine based on early warnings.

[0011] Furthermore, in the technical solution described above, the temperature sensor is installed inside the heating chamber and is equipped with a thermocouple to monitor the accuracy and uniformity of the internal temperature of the heating chamber. The temperature sensor can directly measure the ambient temperature inside the chamber. Numerous studies have shown that oxygen precipitates generally require temperatures above 1100℃ to obtain sufficient dissociation activation energy for dissolution. If the temperature does not reach this baseline, the nucleation and growth of oxygen precipitates will become dominant, leading to a significant decrease in silicon wafer performance. Therefore, during operation, the internal temperature of the heating chamber should be maintained between 1100℃ and 1250℃ throughout the process, while ensuring minimal temperature fluctuations to prevent the emergence of new vacancy defects or other lattice defects that could affect material properties.

[0012] Furthermore, in the above-described technical solution, the heating cavity is wrapped with heat-insulating filler; the heat-insulating filler is used to isolate the temperature inside the heating cavity from external heat transfer, thereby providing heat preservation.

[0013] Furthermore, the silicon wafer conveying rollers described above are long cylindrical structures arranged side by side. The conveying width formed by the arranged silicon wafer conveying rollers can accommodate the transmission of multiple silicon wafers at the same time. The spacing between each adjacent silicon wafer conveying roller is small, ensuring that no silicon wafers are missed during the conveying process and ensuring that the movement of the silicon wafers is stable.

[0014] Furthermore, in the above-described technical solution, the motor provides power for the rotation of the silicon wafer conveying rollers and controls the rotation speed of the silicon wafer conveying rollers.

[0015] Furthermore, in the technical solution described above, the air inlet / outlet pipe provides a channel for the gas circulation flow within the heating chamber.

[0016] Furthermore, regarding the technical solution described above, the airflow valve can be controlled by a central computer, which can realize the opening and closing of the airflow valve, the gas flow rate, and the pressure.

[0017] Furthermore, in the above-described technical solution, the air inlet / outlet pipes are respectively placed at both ends of the cavity, with the pipe openings directly exposed to the internal space of the cavity, which allows the gas to be evenly distributed inside the heating cavity; the airflow valve is placed on the air inlet / outlet pipes.

[0018] Further, in the process of device operation, O2 is introduced through the gas inlet pipe, and the remaining oxygen after reaction is transported through the gas outlet pipe; further, the gas flow rate is controlled by the gas flow valve to be 10000-20000sccm, and the pressure is 800-1500mBar.

[0019] Further, the furnace door is closed when the device is on standby or heating, so as to prevent heat loss inside the heating cavity.

[0020] Further, the alarm device is connected with the central computer and is arranged outside the heat insulation filler.

[0021] Another aspect of the present application discloses a method for using the device described above, which comprises the following operation steps:

[0022] In the process of high-temperature pretreatment, O2 is introduced through the gas inlet pipe, and the remaining oxygen after reaction is transported through the gas outlet pipe; the oxygen gas flow rate is 10000-20000sccm, and the pressure is 800-1500mBar; the surface of the silicon wafer will undergo rapid self-heating oxidation to generate a layer of SiO2; due to the continuous oxidation process, the volume of the SiO2 layer expands, and gap silicon atoms are injected into the silicon wafer body, which will fill the vacancies in the silicon wafer. The repair of the vacancies not only eliminates the recombination center, but also squeezes the space required for the growth of oxygen precipitates to release stress, so as to inhibit the nucleation and growth of oxygen precipitates. Through the above means, the device can effectively improve the quality of the silicon wafer.

[0023] Before formal operation, the device is first preheated, the temperature in the cavity is heated to the required temperature through the heating system, oxygen is circulated in the cavity through the gas inlet / outlet pipe, and the gas flow rate is controlled by the gas flow valve to reach the set value; after a period of time, the feeding is started; during operation, the silicon wafer is first horizontally conveyed to the upper side of the silicon wafer conveying roller through the automatic feeding device (the feeding and discharging system is a common technical knowledge in the field, so the feeding and discharging system is not included in the figure), and the silicon wafer is laid on the silicon wafer conveying roller; after a row of silicon wafers is laid, the silicon wafer conveying roller is driven to rotate, and the silicon wafer moves forward horizontally with the silicon wafer conveying roller; the silicon wafer moves in units of rows, and there is a certain distance between the middle of every two rows and different silicon wafers in the same row. The silicon wafer reaches the cavity through the furnace door, and then passes through the entire heating cavity at a set speed. Subsequently, the silicon wafer is conveyed to the downstream process through the automatic discharging device, and the rapid heat treatment process is completed.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The core of the device is that the high temperature required by the furnace cavity can be reached, and the stability and uniformity of the temperature in the cavity can be ensured.

[0026] 2. The pre-treatment device melts and repairs oxygen precipitation and vacancy defects in photovoltaic N-type silicon by high temperature above 1100℃ and oxygen atmosphere, reduces the recombination center in the material body, thereby increasing the bulk lifetime of silicon, and thus improving the cell efficiency.

[0027] 3. The device adopts a chain rapid thermal treatment method, greatly shortens the time required for pre-treatment, and has less impact on production capacity. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 . Structure diagram of TOPCon chain pre-treatment device;

[0029] In the figure: 1. Silicon wafer conveying roller; 2. Alarm device; 3. Furnace door; 4. Motor; 5. Electric heater; 6. Heating cavity; 7. Temperature sensor; 8. Inlet and outlet pipeline; 9. Air flow valve; 10. Heat insulation filler; 11. Central computer. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments.

[0031] In this document, spatial relative terms, such as "below", "beneath", "lower", "above", "upper", and the like, can be used to describe the relationship between one element or feature to another element or feature as shown in the drawings. It will be understood that the spatial relative terms are intended to encompass different orientations of the object in use or operation, in addition to the orientations depicted in the figures. For example, if an object is turned over, then the element which is described as being "below" or "beneath" the other element or feature would be oriented "above" the other element or feature. Thus, the exemplary term "below" can encompass both the positions above and below. The object can also have other orientations (rotated 90 degrees or at other orientations) and the spatial relative terms used herein should be interpreted accordingly.

[0032] The present application provides a device for improving the performance of TOPCon cell substrate material, mainly for photovoltaic TOPCon cell substrate material. The device mainly consists of a heating system and a mechanical and electrical system, and the device structure diagram and component description are shown in Figure 1 As shown.

[0033] The heating system mainly includes: electric heater 5: cavity heating source; heating cavity 6: the inner wall of the cavity is made of high-temperature resistant ceramic material; heat insulation filler 10: used to isolate the cavity from the outside heat conduction, and plays a heat preservation role.

[0034] The connecting relationship of each component is that the silicon wafer conveying roller 1 is arranged in the inner space of the heating cavity 6, the electric heating body 5 and the plurality of temperature sensors 7 are inlaid on the inner wall of the heating cavity 6, and the electric heating body 5 is separated from the silicon wafer conveying roller 1 by a certain distance; the temperature sensor 7 can directly measure the environmental temperature in the cavity; a large number of documents show that high temperature above 1100 DEG C can effectively ablate oxygen precipitates or significantly reduce the size thereof, and reduce the capture cross-sectional area thereof for carriers; therefore, in the application, the temperature of the heating cavity 6 in the pretreatment equipment can be heated to 1100 DEG C to 1250 DEG C.

[0035] The silicon wafer conveying roller 1 is driven by the motor 4, and a small interval is kept between each silicon wafer conveying roller; the furnace door 3 is located at the head and tail of the heating cavity, and is arranged to prevent heat loss when standby or heating; the heating cavity 6 is wrapped by the heat insulation filler 10; the gas inlet / outlet pipeline 8 is arranged at the two end portions of the cavity 6, and the pipe opening is directly exposed to the inner space of the cavity, so that the gas can be uniformly distributed in the heating cavity 6; the airflow valve 9 is arranged on the gas inlet / outlet pipeline 8; the alarm device 2 is connected with the central computer 11 and is arranged outside the heat insulation filler 10, and the alarm device 2 is connected with the temperature sensor 7, the airflow valve 9 and the central computer 11.

[0036] In the process of high-temperature pretreatment, O2 is introduced through the gas inlet pipeline 8, and the remaining oxygen gas is transported through the gas outlet pipeline; the oxygen gas flow rate is 10000-20000 sccm, and the pressure is 800-1500 mBar; the surface of the silicon wafer will be rapidly self-heated and oxidized to generate a layer of SiO2; due to the continuous oxidation process, the volume of the SiO2 layer expands, and interstitial silicon atoms are injected into the silicon wafer body, which will fill the original vacancies in the silicon or the vacancies generated in the rapid heat treatment process. In addition to eliminating the recombination center, the repair of the vacancies also squeezes the space required for the growth of oxygen precipitates to release stress, so as to inhibit the nucleation and growth of the oxygen precipitates. Through the above methods, the device can effectively improve the quality of the silicon wafer.

[0037] The mechanical and electrical system mainly comprises: a silicon wafer conveying roller 1, the silicon wafer conveying roller 1 is a long cylindrical structure arranged side by side, the conveying width formed by the silicon wafer conveying roller 1 arranged in parallel can simultaneously accommodate the transmission of multiple silicon wafers, the spacing between each adjacent silicon wafer conveying roller is small, so that the silicon wafers are not missed during the conveying process, and the movement of the silicon wafers is stable; a furnace door 3, which is closed when the equipment is on standby or heating to prevent heat loss; a motor 4, which provides power for the rotation of the silicon wafer conveying roller 1 and controls the rotation speed of the silicon wafer conveying roller 1; an air inlet / outlet pipeline 8, which is a gas circulation flow channel; an air flow valve 9, which can be controlled by a central computer 11 to open and close the valve, the gas flow rate and the pressure; the temperature sensor 7, which is equipped with a thermocouple to monitor the accuracy and uniformity of the internal temperature of the furnace cavity; an alarm device 2, which is connected to the temperature sensor 7, the air flow valve 9 and the central computer 11, and performs operations such as alarming, recording and automatic shutdown on equipment abnormalities; and the central computer 11, which is used to control the programs and parameters of the equipment.

[0038] Before formal operation, the equipment is first preheated, the temperature in the cavity is heated to the required temperature by the heating system, at the same time, oxygen is circulated in the cavity 6 through the air inlet / outlet pipeline 8, and the gas flow rate is controlled by the air flow valve 9 to reach the set value, after a period of time, the feeding is started; during operation, the silicon wafer is first conveyed horizontally to the upper side of the silicon wafer conveying roller 1 by the automatic feeding device (the feeding and discharging system is a common technical knowledge in the art, therefore, the feeding and discharging system is not included in the figure), the silicon wafer is laid flat on the silicon wafer conveying roller, after a row is filled, the motor 4 drives the silicon wafer conveying roller 1 to rotate, the silicon wafer moves horizontally forward with the silicon wafer conveying roller, the silicon wafer moves in rows, and there is a certain distance between the middle of every two rows and different silicon wafers in the same row. The silicon wafer reaches the inside of the cavity 6 through the furnace door 3, and then passes through the entire heating cavity 6 at a set speed. Subsequently, the silicon wafer is conveyed to the downstream process by the automatic discharging device, and the rapid heat treatment process is completed.

[0039] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A chain type pretreatment and efficiency improvement equipment for TOPCon cell raw material silicon wafer, characterized in that, The device mainly consists of a heating system and a mechanical and electrical system, wherein: The heating system comprises a heating cavity (6), an electric heater (5) providing a heat source for the cavity, and a furnace door (3) arranged at the end of the heating cavity (6), and the outer layer of the heating cavity (6) is provided with heat insulation filler (10); The mechanical and electrical system comprises a silicon wafer conveying roller (1), a motor (4) providing power for the rotation of the silicon wafer conveying roller (1), a temperature sensor (7) measuring the temperature inside the heating cavity (6), an air inlet / outlet pipeline (8), an alarm device (2), and a central computer (11); The silicon wafer conveying roller (1) is arranged in the cavity space of the heating cavity (6), and the electric heater (5) and the temperature sensor (7) are embedded in the inner wall of the heating cavity (6); The silicon wafer conveying roller (1) is arranged in the cavity space of the heating cavity (6), and the electric heater (5) and the temperature sensor (7) are embedded in the inner wall of the heating cavity (6); The silicon wafer conveying roller (1) is arranged in the cavity space of the heating cavity (6), and the electric heater (5) and the temperature sensor (7) are embedded in the inner wall of the heating cavity (6); The air inlet / outlet pipeline (8) is arranged at the two ends of the heating cavity (6), and the pipe opening of the air inlet / outlet pipeline (8) is directly exposed to the internal space of the heating cavity (6); 2. The chain type pretreatment and efficiency improvement equipment for TOPCon cell raw material silicon wafer according to claim 1, characterized in that, The air flow valve (9) is arranged on the air inlet / outlet pipeline (8); the air flow valve (9) is used for controlling the gas flow in the heating cavity (6).

3. The chain type pretreatment and efficiency improvement equipment for TOPCon cell raw material silicon wafer according to claim 1, characterized in that, The internal temperature of the heating cavity (6) is kept at 1100℃-1250℃ during the operation of the device.

4. The chain type pretreatment and efficiency improvement equipment for TOPCon cell raw material silicon wafer according to claim 1, characterized in that, During the operation of the device, O2 is introduced into the internal space of the heating cavity (6) through the air inlet pipeline in the air inlet / outlet pipeline (8), and the remaining oxygen after the reaction is transported through the air outlet pipeline in the air inlet / outlet pipeline (8).

5. The chain type pretreatment and efficiency improvement equipment for TOPCon cell raw material silicon wafer according to claim 1, characterized in that, During the operation of the device, the gas flow rate in the heating cavity (6) is controlled by the air flow valve (9) to be 10000-20000 sccm, and the pressure is 800-1500 mBar. The central computer (11) is used for controlling the motor (4), the temperature sensor (7), the air flow valve (9), and the alarm device (2).

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