Preparation method and application of back doping layer of single crystal battery

Abstract

The invention provides a preparation method and application of a back doping layer of a single crystal battery. The preparation method comprises the steps that pre-ventilation, preparation of a first deposition layer, preparation of a second deposition layer, preparation of a third deposition layer and preparation of a fourth deposition layer are sequentially carried out on the back face of a single-crystal-layer cell, preparation of the doped layer on the back face of the single-crystal-layer cell is completed, and the concentration of SiH4 in the first deposition layer is gt; the concentration of SiH4 in the second deposition layer is gt, and the concentration of SiH4 in the fourth deposition layer is gt; and the concentration of SiH4 in the third deposition layer. According to the method, the deposition of the original production line is divided into four steps, namely, the deposition temperature is divided into four steps, the doping layer can be deposited more uniformly, the passivation efficiency is higher, and the open voltage of the battery piece is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of solar single crystal cell preparation, and in particular relates to a preparation method and application of a back doping layer of a single crystal cell. Background Art

[0002] In the field of solar single crystal cell preparation technology, since the metal electrode of the PERC cell is still in direct contact with the silicon substrate, the contact interface between the metal and the semiconductor will produce band bending due to work function mismatch, and produce a large number of minority carrier recombination centers, which will have a negative impact on the efficiency of the solar cell. Therefore, some scholars have proposed a solution to isolate the metal from the silicon substrate with a thin film in the battery design to reduce minority carrier recombination, prepare an ultra-thin silicon oxide layer on the back of the battery, and then deposit a thin layer of doped silicon, and the two together form a passivation contact structure. A method for passivating the P-type doping layer of an N-type silicon solar cell and a battery structure. The emitter of the non-metallic contact area of ​​the P-type emitter junction on the back of the N-type CZ monocrystalline silicon substrate forms a floating junction through a phosphorus diffusion layer, and the floating junction is isolated from the metal grid line on the back by a dielectric film, and a passivation film is made on the surface of the floating junction. This process can effectively increase the Uoc of polycrystalline cells by up to 10mV. However, the thickness of the passivation film has a great influence on the current. For every 10nm increase in the doping layer on the back, the short-circuit loss is about 0.05mA / cm 2 Therefore, thin and high-concentration doping layers of different heights are the best means to improve efficiency. In the doping process, the best Uoc improvement effect can be achieved by optimizing the deposition time and controlling the SiH4 flow and temperature before and after the deposition process.

[0003] CN115148857A discloses a method for preparing a solar cell and a solar cell process, in which two doping layers are deposited on the back to passivate the back, and the thickness of the first doping layer is not thin enough, which affects the long-wave response, and the doping concentration is also low, which affects the passivation. CN206864484U discloses a passivation contact solar cell process, which improves the passivation effect by making the thickness of the doping layer greater than 100nm. WO2021098018A1 discloses a photovoltaic cell local tunneling layer passivation contact structure and photovoltaic module process. This patent also only deposits two doping layers on the back to passivate the back. WO2023273313A1 discloses a solar cell and its manufacturing method, the structure is a doping layer for passivation. None of the above doping processes specifically mention how to form the doping layer, and the influence of process temperature and SiH4 gas flow on passivation. Therefore, no inspiration can be given on how to further improve the passivation effect.

[0004] How to prepare a doping method with high passivation effect to improve the opening voltage performance of battery cells is an important research direction in this field. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing a back doping layer of a single crystal cell and its application.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] One of the purposes of the present invention is to provide a method for preparing a back doping layer of a single crystal cell, the preparation method comprising:

[0008] Pre-ventilation, preparation of the first deposition layer, preparation of the second deposition layer, preparation of the third deposition layer and preparation of the fourth deposition layer are carried out in sequence on the back side of the single crystal layer battery to complete the preparation of the doping layer on the back side of the single crystal battery, wherein the concentration of SiH4 in the first deposition layer is greater than the concentration of SiH4 in the second deposition layer, and the concentration of SiH4 in the fourth deposition layer is greater than the concentration of SiH4 in the third deposition layer.

[0009] In the present invention, the deposition of the original production line is divided into four steps, that is, the deposition temperature is four steps, so that the doping layer can be deposited more evenly and the passivation efficiency is higher, which is used to increase the opening voltage of the battery cell.

[0010] In the present invention, the deposition of the original production line is divided into four steps, so that the doping layer is deposited more evenly and the passivation efficiency is higher, thereby improving the opening voltage of the battery cell.

[0011] In the present invention, one-step deposition is designed as four-step deposition, the concentration of the first layer is greater than that of the second layer, the concentration of the fourth layer is greater than that of the third layer, and the concentration difference of each deposition step forms a high-low junction structure, that is, the deposition layer is divided into structures with different doping concentrations. The high-low junction structure is passivated by back-side doping, which solves the incompatibility problem between the overall passivation of the passivation contact structure and light absorption and metal electrode penetration loss.

[0012] As a preferred technical solution of the present invention, the material of the single crystal layer battery includes silicon wafer.

[0013] Preferably, the thickness of the first deposition layer is 5 to 20 nm, wherein the thickness may be 5 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] In the present invention, the first deposition layer has the thinnest thickness, which can increase the response to long waves while ensuring a good passivation effect.

[0015] Preferably, the thickness of the second deposition layer is 30 to 40 nm, wherein the thickness may be 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 38 nm, 39 nm or 40 nm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the thickness of the third deposition layer is 50 to 60 nm, wherein the thickness may be 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm or 60 nm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the thickness of the fourth deposition layer is 15 to 30 nm, wherein the thickness may be 15 nm, 17 nm, 19 nm, 21 nm, 23 nm, 24 nm, 26 nm, 28 nm or 30 nm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] The present invention designs a first deposition layer with a relatively thin thickness. In order to avoid the tunnel oxide layer being burned through by the slurry and causing a sharp increase in the recombination, four deposition layers with different thicknesses and concentrations are designed, so that both a relatively thin doping layer and high-concentration doping layers of different heights can be obtained.

[0019] As a preferred technical solution of the present invention, the pre-ventilation includes: alkaline polishing the back of the single crystal battery and then placing it in a doping furnace for pre-ventilation.

[0020] Preferably, the pre-ventilation pressure is 150-250 mbar, wherein the pressure may be 150 mbar, 160 mbar, 170 mbar, 180 mbar, 190 mbar, 200 mbar, 210 mbar, 220 mbar, 230 mbar, 240 mbar or 250 mbar, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the pre-ventilation temperature is 500-580°C, wherein the temperature may be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C or 580°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the pre-ventilation is conducted into SIH4.

[0023] Preferably, the pre-ventilation includes ventilation at both ends of the doping furnace, the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end.

[0024] Preferably, the flow rate of SiH4 at the front end of the doping furnace is 300-800sccm, where the flow rate can be 300sccm, 400sccm, 500sccm, 600sccm, 700sccm or 800sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the flow rate of SiH4 in the rear end ventilation of the doping furnace is 700-980sccm, wherein the flow rate can be 700sccm, 720sccm, 740sccm, 760sccm, 780sccm, 800sccm, 820sccm, 840sccm, 860sccm, 880sccm, 900sccm, 920sccm, 940sccm, 960sccm or 980sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] As a preferred technical solution of the present invention, the pre-ventilation time is 40 to 60 seconds, wherein the time can be 40s, 42s, 44s, 46s, 48s, 50s, 52s, 54s, 56s, 58s or 60s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] As a preferred technical solution of the present invention, the pressure for preparing the first deposition layer is 150-250 mbar, wherein the pressure can be 150 mbar, 160 mbar, 170 mbar, 180 mbar, 190 mbar, 200 mbar, 210 mbar, 220 mbar, 230 mbar, 240 mbar or 250 mbar, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the temperature for preparing the first deposition layer is 500-580°C, wherein the temperature may be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C or 580°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, SiH4 is introduced during the preparation of the first deposition layer.

[0030] Preferably, the preparation of the first deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end.

[0031] Preferably, the flow rate of SiH4 at the front end of the doping furnace is 300-800sccm, where the flow rate can be 300sccm, 400sccm, 500sccm, 600sccm, 700sccm or 800sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the flow rate of SiH4 in the rear end ventilation of the doping furnace is 700-980sccm, wherein the flow rate can be 700sccm, 720sccm, 740sccm, 760sccm, 780sccm, 800sccm, 820sccm, 840sccm, 860sccm, 880sccm, 900sccm, 920sccm, 940sccm, 960sccm or 980sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] As a preferred technical solution of the present invention, the time for preparing the first deposition layer is 150 to 300 s, wherein the time may be 150 s, 160 s, 170 s, 180 s, 190 s, 200 s, 210 s, 220 s, 230 s, 240 s, 250 s, 260 s, 270 s, 280 s, 290 s or 300 s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] As a preferred technical solution of the present invention, the pressure for preparing the second deposition layer is 150-250 mbar, wherein the pressure can be 150 mbar, 160 mbar, 170 mbar, 180 mbar, 190 mbar, 200 mbar, 210 mbar, 220 mbar, 230 mbar, 240 mbar or 250 mbar, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the temperature for preparing the second deposition layer is 550-650°C, wherein the temperature may be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C or 650°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, SiH4 is introduced during the preparation of the second deposition layer.

[0037] Preferably, the preparation of the second deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end.

[0038] Preferably, the flow rate of SiH4 at the front end of the doping furnace is 200-500sccm, where the flow rate can be 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm or 500sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the flow rate of SiH4 in the rear end ventilation of the doping furnace is 400-700sccm, wherein the flow rate may be 400sccm, 450sccm, 500sccm, 550sccm, 600sccm, 650sccm or 700sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the time for preparing the second deposition layer is 200 to 500 s, wherein the time may be 200 s, 250 s, 300 s, 350 s, 400 s, 450 s or 500 s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, the pressure for preparing the third deposition layer is 150-250 mbar, wherein the pressure can be 150 mbar, 160 mbar, 170 mbar, 180 mbar, 190 mbar, 200 mbar, 210 mbar, 220 mbar, 230 mbar, 240 mbar or 250 mbar, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the temperature for preparing the third deposition layer is 550-650°C, wherein the temperature may be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C or 650°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, SiH4 is introduced during the preparation of the third deposition layer.

[0044] Preferably, the preparation of the third deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end.

[0045] Preferably, the flow rate of SiH4 at the front end of the doping furnace is 200-500sccm, where the flow rate can be 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm or 500sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the flow rate of the SiH4 ventilation at the rear end of the doping furnace is 600-900sccm, where the flow rate can be 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, 850sccm or 900sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] Preferably, the time for preparing the third deposition layer is 500 to 700 s, wherein the time may be 500 s, 550 s, 600 s, 650 s or 700 s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] As a preferred technical solution of the present invention, the pressure for preparing the fourth deposition layer is 150-250 mbar, wherein the pressure can be 150 mbar, 160 mbar, 170 mbar, 180 mbar, 190 mbar, 200 mbar, 210 mbar, 220 mbar, 230 mbar, 240 mbar or 250 mbar, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the temperature for preparing the fourth deposition layer is 550-680°C, wherein the temperature may be 550°C, 580°C, 600°C, 620°C, 640°C, 660°C or 680°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, SiH4 is introduced during the preparation of the fourth deposition layer.

[0051] Preferably, the preparation of the fourth deposition layer includes ventilation at both ends of the doping furnace, the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end.

[0052] Preferably, the flow rate of SiH4 at the front end of the doping furnace is 400-900sccm, wherein the flow rate may be 400sccm, 450sccm, 500sccm, 550sccm, 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, 850sccm or 900sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, the flow rate of SiH4 in the rear end ventilation of the doping furnace is 800-1100sccm, wherein the flow rate may be 800sccm, 850sccm, 900sccm, 950sccm, 1000sccm, 1050sccm or 1100sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] As a preferred technical solution of the present invention, the time for doping the fourth deposition layer is 50 to 300 s, wherein the time may be 50 s, 100 s, 150 s, 200 s, 250 s or 300 s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] The second object of the present invention is to provide a solar single crystal cell, wherein the solar cell comprises a single crystal cell back doping layer prepared by the preparation method as described in the first object.

[0056] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The method for preparing the back doping layer of a single crystal cell provided by the present invention can shorten the time of the original production line from 2200s to 1400s. The prepared back doping layer of the single crystal cell can increase the absorption of long waves and increase the short-circuit current by 0.25mA / cm 2 above;

[0059] (2) The present invention changes the original one-step doping into a four-step doping, where the concentration of the first layer is greater than that of the second layer, and the concentration of the fourth layer is greater than that of the third layer, forming a high-low junction structure. By using the passivated high-low junction structure, the incompatibility problem between the full passivation of the passivated contact structure and light absorption and metal electrode penetration loss is solved. Compared with the original process, the SiH4 doping concentration is 1×10 21 ~2×10 21 / cm 3 Increased to 5×10 21 ~9×10 21 / cm 3 , greatly improving the passivation effect;

[0060] (3) As a combination of thin doping layer thickness and high concentration, the present invention achieves maximum current turn-on voltage, and the current turn-on voltage reaches more than 718mv. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0062] Example 1

[0063] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0064] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace is 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace is 300 sccm, which lasts for 50 seconds.

[0065] (2) Preparation of the first deposition layer: The pressure was pumped to 200 mbar and the temperature was controlled at 580°C. The preparation of the first deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 700 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 300 sccm, which lasted for 250 s.

[0066] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 400 s.

[0067] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0068] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 950 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 150 s.

[0069] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0070] Example 2

[0071] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0072] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0073] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0074] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 400 s.

[0075] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0076] (5) Preparation of the fourth deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 950 sccm and the flow rate of the front SiH4 was 500 sccm, which lasted for 150 s.

[0077] The thickness of the first deposition layer is 5 nm, the thickness of the second deposition layer is 30 nm, the thickness of the third deposition layer is 50 nm, and the thickness of the fourth deposition layer is 15 nm.

[0078] Example 3

[0079] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0080] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace is 800 sccm, which lasts for 50 seconds.

[0081] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 800 sccm, which lasted for 250 s.

[0082] (3) Preparation of the second deposition layer: pump the pressure to 200 mbar and control the temperature at 600. The preparation of the second deposition layer includes ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace is 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace is 260 sccm, which lasts for 400 s.

[0083] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0084] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 950 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 150 s.

[0085] The thickness of the first deposition layer is 20 nm, the thickness of the second deposition layer is 40 nm, the thickness of the third deposition layer is 60 nm, and the thickness of the fourth deposition layer is 30 nm.

[0086] Example 4

[0087] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0088] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0089] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0090] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 400 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 200 sccm, which lasted for 400 s.

[0091] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0092] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 950 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 150 s.

[0093] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0094] Example 5

[0095] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0096] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0097] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0098] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 400 s.

[0099] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0100] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 950 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 150 s.

[0101] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0102] Example 6

[0103] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0104] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0105] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0106] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 400 s.

[0107] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 200 sccm, which lasted for 600 s.

[0108] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 950 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 150 s.

[0109] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0110] Example 7

[0111] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0112] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0113] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0114] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 400 s.

[0115] (4) Preparation of the third deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 900 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 600 s.

[0116] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 950 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 500 sccm, which lasted for 150 s.

[0117] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0118] Example 8

[0119] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0120] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0121] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0122] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 400 s.

[0123] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0124] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 800 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 400 sccm, which lasted for 150 s.

[0125] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0126] Example 9

[0127] This embodiment provides a method for preparing a back doping layer of a single crystal cell, the method comprising:

[0128] (1) Pre-ventilation: Place the alkali-polished silicon wafer into a quartz boat and push it into the furnace tube of the doping furnace. Pump the pressure to 200 mbar and control the temperature at 580°C. The pre-ventilation includes ventilation at both ends of the doping furnace. The front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end of the doping furnace is 980 sccm, and the flow rate of the SiH4 ventilation at the front end of the doping furnace is 500 sccm, which lasts for 50 seconds.

[0129] (2) Preparation of the first deposition layer: The pressure was pumped down to 200 mbar and the temperature was controlled at 580°C. Preparation of the first deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 at the rear end ventilation in the doping furnace was 980 sccm, and the flow rate of the SiH4 at the front end ventilation in the doping furnace was 500 sccm, which lasted for 250 s.

[0130] (3) Preparation of the second deposition layer: the pressure was pumped down to 200 mbar and the temperature was controlled at 600°C. The preparation of the second deposition layer included ventilation at both ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 600 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 400 s.

[0131] (4) Preparation of the third deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 610°C. The preparation of the third deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 700 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 260 sccm, which lasted for 600 s.

[0132] (5) Preparation of the fourth deposition layer: the pressure was pumped to 200 mbar and the temperature was controlled at 650°C. The preparation of the fourth deposition layer included ventilation at the front and rear ends of the doping furnace. The front ventilation airflow flowed from the front end to the rear end, and the rear ventilation airflow flowed from the rear end to the front end. The flow rate of the SiH4 ventilation at the rear end in the doping furnace was 1100 sccm, and the flow rate of the SiH4 ventilation at the front end in the doping furnace was 900 sccm, which lasted for 150 s.

[0133] The thickness of the first deposition layer is 10 nm, the thickness of the second deposition layer is 35 nm, the thickness of the third deposition layer is 55 nm, and the thickness of the fourth deposition layer is 20 nm.

[0134] Comparative Example 1

[0135] This comparative example is the original production line Baseline doping process, which adopts a one-step doping process.

[0136] The cells after the back doping layer of the single crystal cells in Examples 1-9 and Comparative Example 1 was completed were subjected to an open voltage test, and the test results are shown in Table 1.

[0137] Among them, the concentration test instrument is ECV, and the open voltage test method is IV electrical performance test.

[0138] Table 1

[0139] concentration UOC Example 1 <![CDATA[5.5×1021 / cm 3 ]]> 718mv Example 2 <![CDATA[5.0×1021 / cm 3 ]]> 723mv Example 3 <![CDATA[9.0×1021 / cm 3 ]]> 719mv Example 4 <![CDATA[5.9×1021 / cm 3 ]]> 718mv Example 5 <![CDATA[7.4×1021 / cm 3 ]]> 720mv Example 6 <![CDATA[6.5×1021 / cm 3 ]]> 719mv Example 7 <![CDATA[8.8×1021 / cm 3 ]]> 720mv Example 8 <![CDATA[6.7×1021 / cm 3 ]]> 721mv Example 9 <![CDATA[6×1021 / cm 3 ]]> 718mv Comparative Example 1 <![CDATA[1.2×1021 / cm 3 ]]> 715mv

[0140] From the above table, it can be seen from the comparison between Examples 1-9 and Comparative Example 1 that the SiH4 doping concentration is 1×10 21 ~2×10 21 / cm 3 Increased to 5×10 21 ~9×10 21 / cm 3 , greatly improving the passivation effect. As a combination of thin doping layer thickness and high concentration, Example 1-9 achieves maximum current opening voltage, and the current opening voltage reaches more than 718mv.

[0141] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a back doping layer of a single crystal cell, characterized in that: The preparation method comprises: Pre-ventilation, preparation of the first deposition layer, preparation of the second deposition layer, preparation of the third deposition layer and preparation of the fourth deposition layer are sequentially performed on the back side of the single crystal layer battery to complete the preparation of the doping layer on the back side of the single crystal battery; Among them, the concentration of SiH4 in the first deposition layer is greater than the concentration of SiH4 in the second deposition layer, and the concentration of SiH4 in the fourth deposition layer is greater than the concentration of SiH4 in the third deposition layer.

2. The preparation method according to claim 1, characterized in that: The material of the single crystal layer cell includes silicon wafer; Preferably, the thickness of the first deposition layer is 5 to 20 nm; Preferably, the thickness of the second deposition layer is 30-40 nm; Preferably, the thickness of the third deposition layer is 50-60 nm; Preferably, the fourth deposition layer has a thickness of 15-30 nm.

3. The preparation method according to claim 1 or 2, characterized in that: The pre-ventilation comprises: alkaline polishing the back of the single crystal cell and then placing it in a doping furnace for pre-ventilation; Preferably, the pre-ventilation pressure is 150-250 mbar; Preferably, the pre-ventilation temperature is 500-580°C; Preferably, the pre-ventilation is conducted into SIH4; Preferably, the pre-ventilation includes ventilation at both ends of the doping furnace, the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end; Preferably, the flow rate of the SiH4 at the front end of the doping furnace is 300-800 sccm; Preferably, the flow rate of the SiH4 at the rear end of the doping furnace is 700-980 sccm; Preferably, the pre-ventilation time is 40 to 60 seconds.

4. The preparation method according to any one of claims 1 to 3, characterized in that The pressure for preparing the first deposition layer is 150-250 mbar; Preferably, the temperature for preparing the first deposition layer is 500-580°C; Preferably, SiH4 is introduced during the preparation of the first deposition layer; Preferably, the preparation of the first deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end; Preferably, the flow rate of the SiH4 at the front end of the doping furnace is 300-800 sccm; Preferably, the flow rate of the SiH4 at the rear end of the doping furnace is 700-980 sccm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The time for preparing the first deposition layer is 150 to 300 seconds.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The pressure for preparing the second deposition layer is 150-250 mbar; Preferably, the temperature for preparing the second deposition layer is 550-650°C; Preferably, SiH4 is introduced during the preparation of the second deposition layer; Preferably, the preparation of the second deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end; Preferably, the flow rate of the SiH4 at the front end of the doping furnace is 200-500 sccm; Preferably, the flow rate of the SiH4 at the rear end of the doping furnace is 400-700 sccm; Preferably, the time for preparing the second deposition layer is 200 to 500 seconds.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The pressure for preparing the third deposition layer is 150-250 mbar; Preferably, the temperature for preparing the third deposition layer is 550-650°C; Preferably, SiH4 is introduced during the preparation of the third deposition layer; Preferably, the preparation of the third deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end; Preferably, the flow rate of the SiH4 at the front end of the doping furnace is 200-500 sccm; Preferably, the flow rate of the SiH4 at the rear end of the doping furnace is 600-900 sccm; Preferably, the time for preparing the third deposition layer is 500-700 seconds.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The pressure for preparing the fourth deposition layer is 150-250 mbar; Preferably, the temperature for preparing the fourth deposition layer is 550-680° C.; Preferably, SiH4 is introduced during the preparation of the fourth deposition layer; Preferably, the preparation of the fourth deposition layer includes ventilation at both ends of the doping furnace, wherein the front ventilation airflow flows from the front end to the rear end, and the rear ventilation airflow flows from the rear end to the front end; Preferably, the flow rate of the SiH4 at the front end of the doping furnace is 400-900 sccm; Preferably, the flow rate of the SiH4 at the rear end of the doping furnace is 800-1100 sccm.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The time for preparing the fourth deposition layer is 50 to 300 seconds.

10. A solar single crystal cell, characterized in that: The solar cell comprises a single crystal cell back doping layer prepared by the preparation method according to any one of claims 1 to 9.