Method for preparing passivation layer on back surface of TOPCon battery
By adopting a variable temperature deposition process during the preparation of the passivation layer on the back of the TOPCon battery, the temperature and gas flow rate are optimized, and the problems of long process time, low production capacity and high cost in the existing technology are solved, and the performance of the battery is significantly improved.
Patent Information
- Application Number
- CN202510866591.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-07-25
AI Technical Summary
The existing TOPCon battery back passivation layer preparation method has problems such as long process time, low production capacity, high cost and need to be improved.
The temperature variable deposition process is adopted, by setting different reaction temperatures at different process stages, the nucleation and growth rates of grains are controlled, and the material performance is optimized, including deposition of tunneled oxide layer, first Poly-Si layer, molecular sieve layer and MASK layer, the temperature and gas flow are gradually adjusted, and the doping concentration and thickness of the poly silicon layer are optimized.
It significantly improves the photoelectric conversion efficiency of the battery cell, shortens the process time of the back passivation layer, reduces the preparation cost, and improves the passivation effect, reduces the surface composite and metal contact composite, and increases the open circuit voltage and short circuit current.
Smart Images
Figure CN120379386A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of solar cells, and particularly to a method for preparing a back passivation layer of a TOPCon cell. Background Art
[0002] TOPCon (Tunnel Oxide Passivated Contact) cells, also known as Tunnel Oxide Passivated Contact cells, have attracted much attention in the field of solar cells due to their high photoelectric conversion efficiency. The core of TOPCon cells lies in the back passivation contact technology. By preparing an ultrathin tunneling silicon oxide (about 1.2 - 2.5 nm) on the back of the cell and depositing a doped poly-silicon layer, a passivation contact structure is formed. This structure provides good surface passivation for the back of the silicon wafer. The ultrathin oxide layer allows majority electrons to tunnel into the poly-silicon layer while blocking the recombination of minority holes. Then, the electrons are laterally transported in the poly-silicon layer and collected by the metal, thus greatly reducing the metal contact recombination current and improving the open-circuit voltage and short-circuit current of the cell.
[0003] However, there are some deficiencies in the existing methods for preparing the back passivation layer of TOPCon cells, such as long process time, low production capacity, high cost, and the need for further improvement in passivation effect, etc. Summary of the Invention
[0004] (I) Technical Problems to be Solved In view of the deficiencies of the prior art, the present invention provides a method for preparing a back passivation layer of a TOPCon cell, which solves at least one of the technical problems proposed in the background art.
[0005] (II) Technical Solutions The technical solution adopted by the present invention is: a method for preparing a back passivation layer of a TOPCon cell, the preparation method comprising: Step S1: Depositing a tunneling oxide layer at a temperature of T1, introducing nitrous oxide and controlling the pressure in the furnace. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the tunneling oxide layer; Step S2: Depositing a first Poly-Si layer at a temperature of T2, introducing silane, hydrogen, and phosphine, and controlling the pressure in the furnace. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is H2 seconds; Step S3: Depositing a molecular sieve layer at a temperature of T3, introducing nitrous oxide and controlling the pressure in the furnace. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the molecular sieve layer; Step S4; Predeposit the second Poly-Si layer at a temperature of T4, introduce silane, hydrogen, and phosphine, and control the pressure inside the furnace. After predeposition, perform glow discharge through a radio frequency power supply to deposit the first Poly-Si layer for H4 seconds; Step S5; Deposit the MASK layer at a temperature of T5, introduce silane, hydrogen, and phosphine, and control the pressure inside the furnace. After predeposition, perform glow discharge through a radio frequency power supply to deposit the MASK layer; Wherein the temperatures T1, T2, T3, T4, and T5 increase gradually in sequence.
[0006] Preferably, the temperatures T1, T2, T3, T4, and T5 increase by 5°C in sequence.
[0007] Preferably, after glow discharge is completed in each of steps S1, S2, S3, S4, and S5, evacuate the furnace tube.
[0008] Preferably, before step S1, it is necessary to preheat the furnace tube and evacuate the furnace tube at the same time.
[0009] Preferably, the value of H2 / (H2 + H4) is 0.24 to 0.27.
[0010] Preferably, the predeposition time in both step S2 and step S4 is 10 seconds.
[0011] Preferably, the predeposition time in step S1 is 30 seconds; the deposition time H1 is 90 seconds.
[0012] Preferably, the predeposition time in step S3 is 10 seconds, and the deposition time H3 is 35 seconds.
[0013] Preferably, the predeposition time in step S5 is 10 seconds, and the deposition time H5 is 60 seconds.
[0014] Preferably, the deposition time H2 in step S2 is 140 seconds, and the deposition time H4 in step S4 is 390 seconds.
[0015] (III) Beneficial effects The present invention provides a method for preparing a back surface passivation layer of a TOPCon battery, which has the following beneficial effects compared with the prior art: 1. By setting different reaction temperatures at different process stages, the present invention changes the constant-temperature deposition to variable-temperature deposition, precisely regulates the temperature parameters of different process steps, thereby controlling the nucleation and growth rates of grains, achieving the optimization of material properties, and improving the conversion efficiency of solar cells. In the process step of the ultra-thin tunneling layer, by promoting uniform nucleation at the low-temperature stage and accelerating longitudinal growth at the high-temperature stage, the denseness of the tunneling layer is ensured, and an ultra-thin tunneling layer with a thickness of about 1.2 - 2.5 nm is formed; in the process step of the poly-silicon layer, by regulating the thermal decomposition rate of silane (SiH4) with variable temperature, precise control of the thickness, grain size, and doping concentration of the poly-silicon layer is achieved, significantly improving the cell performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The present invention will be further described below in conjunction with the drawings and embodiments: Figure 1 is a schematic diagram of the film layer structure of a TOPCon solar cell; Figure 2 is a schematic diagram of the Poly structure of a TOPCon solar cell. SPECIFIC IMPLEMENTATION METHODS 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 are clearly and completely described. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Such as Figure 1 And and Figure 2The N-type TOPCon cell shown is a tunneling oxide passivated contact (Tunnel-Oxide-Passivated-Contact) solar cell technology based on the principle of selective carriers. The main characteristics of its cell structure lie in the N-type silicon wafer substrate and the passivated contact structure formed by the ultra-thin silicon oxide and doped poly-silicon film on the back. Specifically, the structure of the N-type TOPCon cell from the front to the back of the cell is as follows: Passivation / anti-reflection film (SiNx film): about 75 nm thick, rich in hydrogen atoms, which can chemically passivate the defects on the surface and in the body during the heat treatment process, thereby reducing the recombination of surface electrons. Al2O3 film: This layer is newly added to the TOPCon cell compared with other types of cells (such as PERC cells) to further passivate the surface and improve the cell performance. P-type emitter (p+): Different from the N-type emitter of the PERC cell, the TOPCon cell uses a P-type emitter. N-type silicon wafer substrate: This is the core part of the TOPCon cell, using an N-type silicon wafer as the substrate. Ultra-thin tunneling layer (ultra-thin silicon oxide layer): about 1 - 2 nm thick, which is one of the key parts of the TOPCon cell technology and is used to form the passivated contact structure. N-type poly-silicon film: about 100 nm thick, used on the outside to increase the built-in electric field, promote carrier separation, and improve the conversion efficiency. Anti-reflection film: Located on the back of the cell to reduce light reflection and improve light absorption rate.
[0018] The embodiment of this application is to form the ultra-thin tunneling layer (ultra-thin silicon oxide layer) and poly-silicon layer of the TOPCon cell. To better understand the above technical solution, the above technical solution will be described in detail below in combination with the specification drawings and specific implementation manners: Provide a preparation method for the back passivation layer of a TOPCon cell, the preparation method comprising: Step S1; Deposit a tunneling oxide layer at a temperature of T1, introduce nitrous oxide and control the furnace pressure. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the tunneling oxide layer, and the deposition time is H1 seconds; Step S2; Deposit the first Poly-Si layer at a temperature of T2, introduce silane, hydrogen, and phosphine, and control the furnace pressure. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is H2 seconds; Step S3; Deposit a molecular sieve layer at a temperature of T3, introduce nitrous oxide and control the furnace pressure. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the molecular sieve layer, and the deposition time is H3 seconds; Step S4; Pre-deposit the second Poly-Si layer at a temperature of T4, introduce silane, hydrogen, and phosphine, and control the furnace pressure. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is H4 seconds; Step S5: Deposit the MASK layer at a temperature of T5. Introduce silane, hydrogen, and phosphine, and control the pressure in the furnace. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the MASK layer, and the deposition time is H5 seconds. Among them, the temperatures T1, T2, T3, T4, and T5 increase gradually in sequence.
[0019] Specifically, the temperatures T1, T2, T3, T4, and T5 increase by 5°C in sequence.
[0020] By adopting the above process scheme to prepare the back passivation layer, the process time of the back passivation layer can be greatly shortened, the production capacity of the battery chip can be improved, and the preparation cost of the back passivation layer of the TOPCon battery can be significantly reduced. At the same time, the back passivation layer prepared by this scheme has a good passivation effect, can effectively reduce the surface recombination and metal contact recombination, improve the open circuit voltage and short circuit current of the battery, and thus improve the photoelectric conversion efficiency of the TOPCon battery. By setting different reaction temperatures at different process stages, changing the constant temperature deposition to variable temperature deposition, and precisely regulating the temperature parameters of different process steps, the nucleation and growth rate of grains are controlled, the optimization of material properties is realized, and the conversion efficiency of the battery chip is improved. In the ultra-thin tunneling layer process step, by promoting uniform nucleation at the low temperature stage and accelerating longitudinal growth at the high temperature stage, the denseness of the tunneling layer is ensured, and an ultra-thin tunneling layer with a thickness of about 1.2 - 2.5 nm is formed; in the poly-silicon layer process step, by regulating the thermal decomposition rate of silane (SiH4) with variable temperature, precise control of the thickness, grain size, and doping concentration of the poly-silicon layer is achieved, and the battery performance is significantly improved.
[0021] In some embodiments, after the glow discharge of each of the steps S1, S2, S3, S4, and S5 is completed, the furnace tube is evacuated.
[0022] In some embodiments, before step S1, the furnace tube needs to be preheated and the furnace tube is evacuated at the same time.
[0023] In some embodiments, H2 / (H2 + H4) is 0.24 - 0.27. Through the hierarchical design optimization of shallow doping and heavy doping of the Poly layer, that is, optimizing the ratio of step S2 and step S4, where step S2 is shallow doping and step S4 is heavy doping. Shallow doping can reduce the density of defect states in the poly-silicon layer, reduce carrier recombination, and thus improve the passivation effect and open circuit voltage; heavy doping significantly reduces the contact resistance between the poly-silicon layer and the metal electrode, improves the fill factor (FF), and at the same time, heavy doping can improve the conductivity of the poly-silicon layer, reduce the risk of potential induced degradation, and improve the battery reliability.
[0024] In some embodiments, the pre-deposition time of both step S2 and step S4 is 10 seconds.
[0025] In some embodiments, the pre - deposition in step S1 is for 30 seconds, and the deposition time H1 is 90 seconds.
[0026] In some embodiments, the pre - deposition time of step S3 is 10 seconds, and the deposition time H3 is 35 seconds.
[0027] In some embodiments, the pre - deposition time of step S5 is 10 seconds, and the deposition time H5 is 60 seconds.
[0028] In some embodiments, the deposition time H2 of step S2 is 140 seconds, and the deposition time H4 of step S4 is 390 seconds.
[0029] Through the variable - temperature deposition process above, the initial reaction temperature is reduced, the pre - heating and temperature - rising time is shortened, and the production capacity is greatly improved: when the total production capacity of the whole workshop remains unchanged, after the process time of the back - side passivation layer is shortened, the number of machines required for the back - passivation process can be reduced, and the production cost can be lowered.
[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention is further described in detail.
[0031] Example 1: It includes the following steps: Send the graphite boat loaded with silicon wafers into the furnace tube through a silicon carbide slurry rod. After the rod withdraws, the furnace door is closed, and the furnace tube is pre - heated while starting to pump vacuum to a low pressure; specifically: a tube - type plasma poly - silicon deposition furnace. After the pre - heating is completed, start leak detection to check whether the leak rate of the furnace tube meets the process requirements. After the leak detection meets the process requirements, evacuate the residual gas in the furnace tube. Pre - deposit a tunneling oxide layer at a temperature of 445 °C, with a nitrous oxide flow rate of 11076 sccm / min, and control the pressure in the furnace at 2000 mTorr. The pre - deposition time is 30 seconds. Perform glow discharge on the silicon wafer through a radio - frequency power supply to deposit a tunneling oxide layer, and the deposition time is 93 seconds. After the glow discharge is completed, evacuate the furnace tube. Pre - deposit the first Poly - Si layer at a temperature of 450 °C, with a silane flow rate of 3260 sccm / min, a hydrogen flow rate of 8136 sccm / min, and a phosphine flow rate of 300 sccm / min, and control the pressure in the furnace at 2950 mTorr. The pre - deposition time is 10 seconds. Perform glow discharge on the silicon wafer through a radio - frequency power supply to deposit the first Poly - Si layer, and the deposition time is 105 seconds. After the glow discharge is completed, evacuate the furnace tube. Pre-deposit a molecular sieve layer at a temperature of 455 °C, with a nitrous oxide flow rate of 11076 sccm / min, control the furnace pressure at 2000 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit a molecular sieve layer, and the deposition time is 35 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the second Poly-Si layer at a temperature of 460 °C, with a silane flow rate of 3260 sccm / min, a hydrogen flow rate of 8136 sccm / min, and a phosphine flow rate of 850 sccm / min, control the furnace pressure at 3000 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the second Poly-Si layer, and the deposition time is 415 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the MASK layer at a temperature of 465 °C, with a silane flow rate of 2000 sccm / min and a nitrous oxide flow rate of 9800 sccm / min, control the furnace pressure at 1700 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the MASK layer, and the deposition time is 60 seconds; After the glow discharge is completed, evacuate the furnace tube; Purge the furnace tube with nitrogen. After purging, restore the pressure in the furnace tube to normal atmospheric pressure; Open the furnace door, extend the silicon carbide paddle rod to take out the graphite boat from the furnace tube.
[0032] Example 2: Send the graphite boat loaded with silicon wafers into the furnace tube of the tubular plasma poly-silicon deposition furnace through the silicon carbide paddle rod. After the paddle rod withdraws, close the furnace door. The furnace tube is preheated and at the same time, evacuation starts until the low pressure is reached; After the preheating is completed, start leak detection to check whether the leak rate of the furnace tube meets the process requirements; After the leak detection meets the process requirements, evacuate the residual gas in the furnace tube; Pre-deposit a tunneling oxide layer at a temperature of (435 ± 15) °C, with a nitrous oxide flow rate of 11076 sccm / min, control the furnace pressure at 2000 mTorr, and the pre-deposition time is 30 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit a tunneling oxide layer, and the deposition time is 93 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the first Poly-Si layer at a temperature of (435±15) °C, with a silane flow rate of 3260 sccm / min, a hydrogen flow rate of 8136 sccm / min, a phosphine flow rate of 300 sccm / min, control the furnace pressure at 2950 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is 140 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the molecular sieve layer at a temperature of (435±15) °C, with a nitrous oxide flow rate of 11076 sccm / min, control the furnace pressure at 2000 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the molecular sieve layer, and the deposition time is 45 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the second Poly-Si layer at a temperature of (435±15) °C, with a silane flow rate of 3260 sccm / min, a hydrogen flow rate of 8136 sccm / min, a phosphine flow rate of 850 sccm / min, control the furnace pressure at 3000 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the second Poly-Si layer, and the deposition time is 390 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the MASK layer at a temperature of (435±15) °C, with a silane flow rate of 2000 sccm / min, a nitrous oxide flow rate of 9800 sccm / min, control the furnace pressure at 1700 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the MASK layer, and the deposition time is 60 seconds; After the glow discharge is completed, evacuate the furnace tube; Use nitrogen to purge the furnace tube, and after the purging is completed, restore the pressure inside the furnace tube to normal atmospheric pressure; Open the furnace door, and extend the silicon carbide paddle rod to take out the graphite boat from the furnace tube.
[0033] Example 3: It includes the following steps: Send the graphite boat loaded with silicon wafers into the furnace tube through the silicon carbide paddle rod. After the paddle rod withdraws, close the furnace door, and preheat the furnace tube while starting to evacuate to low pressure; specifically: a tube-type plasma poly-silicon deposition furnace; After the preheating is completed, leak detection is started to check whether the leak rate of the furnace tube meets the process requirements; After the leak detection meets the process requirements, evacuate the residual gas in the furnace tube; Pre-deposit a tunneling oxide layer at a temperature of 445 °C, with a nitrous oxide flow rate of 11076 sccm / min, control the furnace pressure at 2000 mTorr, and the pre-deposition time is 30 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit a tunneling oxide layer, and the deposition time is 93 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the first Poly-Si layer at a temperature of 450 °C, with a silane flow rate of 3260 sccm / min, a hydrogen flow rate of 8136 sccm / min, and a phosphine flow rate of 300 sccm / min, control the furnace pressure at 2950 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is 140 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit a molecular sieve layer at a temperature of 455 °C, with a nitrous oxide flow rate of 11076 sccm / min, control the furnace pressure at 2000 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit a molecular sieve layer, and the deposition time is 35 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the second Poly-Si layer at a temperature of 460 °C, with a silane flow rate of 3260 sccm / min, a hydrogen flow rate of 8136 sccm / min, and a phosphine flow rate of 850 sccm / min, control the furnace pressure at 3000 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the second Poly-Si layer, and the deposition time is 390 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit a MASK layer at a temperature of 465 °C, with a silane flow rate of 2000 sccm / min and a nitrous oxide flow rate of 9800 sccm / min, control the furnace pressure at 1700 mTorr, and the pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit a MASK layer, and the deposition time is 60 seconds; After the glow discharge is completed, evacuate the furnace tube; Purge the furnace tube with nitrogen. After purging is completed, restore the pressure inside the furnace tube to normal atmospheric pressure; Open the furnace door, extend the silicon carbide paddle rod to take out the graphite boat from the furnace tube.
[0034] Comparative example: Send the graphite boat containing silicon wafers into the furnace tube of the tubular plasma poly-silicon deposition furnace through the silicon carbide slurry rod. After the paddle rod withdraws, close the furnace door. The furnace tube is preheated and vacuum pumping starts until the low pressure is reached; After preheating is completed, start leak detection to check whether the leak rate of the furnace tube meets the process requirements; After the leak detection meets the process requirements, evacuate the residual gas inside the furnace tube; Pre-deposit the tunneling oxide layer at a temperature of (435 ± 15) °C, with the nitrous oxide flow rate of 11076 sccm / min, and control the furnace pressure at 2000 mTorr. The pre-deposition time is 30 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the tunneling oxide layer. The deposition time is 93 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the first Poly-Si layer at a temperature of (435 ± 15) °C, with the silane flow rate of 3260 sccm / min, hydrogen flow rate of 8136 sccm / min, phosphine flow rate of 300 sccm / min, and control the furnace pressure at 2950 mTorr. The pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the first Poly-Si layer. The deposition time is 105 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the molecular sieve layer at a temperature of (435 ± 15) °C, with the nitrous oxide flow rate of 11076 sccm / min, and control the furnace pressure at 2000 mTorr. The pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the molecular sieve layer. The deposition time is 45 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre-deposit the second Poly-Si layer at a temperature of (435 ± 15) °C, with the silane flow rate of 3260 sccm / min, hydrogen flow rate of 8136 sccm / min, phosphine flow rate of 850 sccm / min, and control the furnace pressure at 3000 mTorr. The pre-deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio frequency power supply to deposit the second Poly-Si layer. The deposition time is 415 seconds; After the glow discharge is completed, evacuate the furnace tube; Pre - deposit the MASK layer at a temperature of (435 ± 15) °C. The flow rate of silane is 2000 sccm / min and the flow rate of nitrous oxide is 9800 sccm / min. Control the pressure in the furnace at 1700 mTorr, and the pre - deposition time is 10 seconds; Perform glow discharge on the silicon wafer through a radio - frequency power supply to deposit the MASK layer, and the deposition time is 60 seconds; After the glow discharge is completed, evacuate the furnace tube; Purge the furnace tube with nitrogen. After purging, restore the pressure in the furnace tube to normal atmospheric pressure; Open the furnace door, extend the silicon carbide paddle rod to take out the graphite boat from the furnace tube.
[0035] In Example 3, compared with the comparative example, the process temperature is changed from constant temperature to variable temperature. The process constant temperature of the comparative example means that the temperature of all deposition steps is relative. And the distribution ratio of shallow doping and heavy doping of the poly - silicon layer is optimized. Specifically, H2 / (H2 + H4) in Example 3 is 26%, while that in the comparative example is 20%. Through the above two process designs, the passivation effect on the back of the cell can be significantly improved, and the cell performance can be enhanced. At the same time, variable - temperature deposition + ratio optimization can greatly shorten the process time of the back passivation layer, improve the production capacity of the cell, and can significantly reduce the preparation cost of the back passivation layer of the TOPCon cell.
[0036] Based on the above data, it can be known that Count is the total number of experiments, that is, the total number of cells in this group; the difference 1 shown in the table is the data result difference between Example 1 and the comparative example, the difference 2 is the data result difference between Example 2 and the comparative example, and the difference 3 is the data result difference between Example 3 and the comparative example; Among them, the conversion efficiency of Example 1 (variable - temperature deposition) is 0.037% higher than that of the comparative example, mainly manifested as a short - circuit current 14 mA higher and FF 0.02 higher; the conversion efficiency of Example 2 (ratio optimization) is 0.032% higher than that of the comparative example, mainly manifested as a short - circuit current 20 mA higher and FF 0.14 higher; the conversion efficiency of Example 3 (deposition + ratio optimization) is 0.100% higher than that of the comparative example, mainly manifested as a short - circuit current 40 mA higher and FF 0.21 higher.
[0037] Process time: The above - mentioned process time (s / tube) indicates the total process duration per tube. In the embodiment of the present invention, a tube - type plasma deposition furnace has 6 tubes.
[0038] Production capacity improvement: Machine savings: The TOPCon cell prepared in Example 3 (temperature-variable deposition + proportional distribution) of the present invention is compared with the comparative example (constant-temperature deposition), which can greatly shorten the process time of the back passivation layer, improve the production capacity of the cell wafers, and can significantly reduce the preparation cost of the back passivation layer of the TOPCon cell. At the same time, the back passivation layer prepared by this solution has a good passivation effect, can effectively reduce the surface recombination and metal contact recombination, improve the open-circuit voltage and short-circuit current of the cell, and thus improve the photoelectric conversion efficiency of the TOPCon cell.
[0039] It should be noted that in this text, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.
[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.
Claims
1. A method for preparing a back passivation layer of a TOPCon cell, characterized in that, The preparation method includes: Step S1: Deposit a tunneling oxide layer at a temperature of T1. Nitrous oxide is introduced and the pressure in the furnace is controlled. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the tunneling oxide layer; Step S2: Deposit a first Poly-Si layer at a temperature of T2. Silane, hydrogen, and phosphine are introduced and the pressure in the furnace is controlled. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is H2 seconds; Step S3: Deposit a molecular sieve layer at a temperature of T3. Nitrous oxide is introduced and the pressure in the furnace is controlled. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the molecular sieve layer; Step S4: Pre-deposit a second Poly-Si layer at a temperature of T4. Silane, hydrogen, and phosphine are introduced and the pressure in the furnace is controlled. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the first Poly-Si layer, and the deposition time is H4 seconds; Step S5: Deposit a MASK layer at a temperature of T5. Silane, hydrogen, and phosphine are introduced and the pressure in the furnace is controlled. After pre-deposition, glow discharge is carried out through a radio frequency power supply to deposit the MASK layer; Wherein the temperatures T1, T2, T3, T4, and T5 increase gradually in sequence.
2. The preparation method of the back passivation layer of the TOPCon battery according to claim 1, wherein, The temperatures T1, T2, T3, T4, and T5 increase by 5°C in sequence.
3. The preparation method of the back passivation layer of the TOPCon battery according to claim 1, wherein After glow discharge is completed in each of Step S1, Step S2, Step S3, Step S4, and Step S5, the furnace tube is evacuated.
4. The preparation method of the back passivation layer of the TOPCon battery according to claim 1, characterized in that, Before Step S1, the furnace tube needs to be preheated and the furnace tube is evacuated at the same time.
5. The preparation method of the back passivation layer of the TOPCon battery according to any one of claims 1-4, characterized in that, The value of H2 / (H2 + H4) is 0.24 to 0.
27.
6. The preparation method of the back passivation layer of the TOPCon battery according to any one of claims 1-4, characterized in that, The pre-deposition time in both Step S2 and Step S4 is 10 seconds.
7. The preparation method of the back passivation layer of the TOPCon battery according to any one of claims 1-4, characterized in that, The pre-deposition time in Step S1 is 30 seconds; the deposition time H1 for depositing the tunneling oxide layer is 90 seconds.
8. The preparation method of the back passivation layer of the TOPCon battery according to any one of claims 1-4, characterized in that, The pre-deposition time in Step S3 is 10 seconds, and the deposition time H3 for depositing the molecular sieve layer is 35 seconds.
9. The preparation method of the back passivation layer of the TOPCon battery according to any one of claims 1-4, characterized in that, The pre-deposition time in Step S5 is 10 seconds, and the deposition time H5 for depositing the MASK layer is 60 seconds.
10. The preparation method of the back passivation layer of the TOPCon battery according to any one of claims 1-4, characterized in that, The deposition time H2 in Step S2 is 140 seconds, and the deposition time H4 in Step S4 is 390 seconds.