A solar cell with a doped polysilicon layer structure and its preparation process

Abstract

The present invention relates to the technical field of solar cells, and in particular to a solar cell with a doped polysilicon layer structure and a preparation process thereof. The process comprises the following steps: surface texturing of a silicon wafer; passivation of the texturized silicon wafer and preparation of an insulating dielectric film layer; preparation of a bottom cell and composite of stacked cells. The present invention prepares a layer of precursor fiber membrane on the back of a pre-passivated silicon wafer, and then performs secondary temperature sintering, thereby simultaneously achieving the purpose of crystallizing the phosphorus-doped amorphous silicon layer, advancing phosphorus, and generating a porous SiO2 nanofiber membrane. The preparation efficiency is high, and the obtained porous SiO2 nanofiber membrane is evenly arranged, has a stable pore structure, and has good mechanical properties. The perovskite top cell can only be in partial contact with the bottom cell, thereby further reducing the ineffective recombination of carriers in the middle layer of the stacked cell, and can better transmit carriers. In addition, the preparation process of the porous SiO2 nanofiber membrane is simple and will not damage the bottom cell, thereby improving the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell with a doped polysilicon layer structure and a preparation process thereof. Background Art

[0002] With the continuous growth of global energy demand and the increasing emphasis on renewable energy, solar power generation devices, as representatives of clean and renewable energy, have become a hot spot for research and development. Solar power generation devices, also known as photovoltaic cells or solar cells, are based on the photovoltaic effect of semiconductor PN junctions and can directly convert solar energy into batteries.

[0003] Due to the limited conversion efficiency of traditional crystalline silicon solar cells, stacked solar cells have gradually become one of the research directions of high-efficiency solar cells in recent years. By stacking a top cell on a crystalline silicon cell, stacked solar cells can break through the efficiency limit of a single cell and obtain higher photoelectric conversion efficiency. However, in stacked solar cells, carrier recombination is prone to occur in the middle layer between the top cell and the silicon bottom cell, resulting in a decrease in the open circuit voltage and short circuit current of the cell, thereby affecting the photoelectric conversion efficiency of the entire cell. In addition, during the high-temperature treatment of the stacked cell, the middle layer is prone to unsaturated bonds due to the breaking of hydrogen bonds, thereby increasing the recombination with carriers and reducing the photoelectric conversion efficiency of the cell. Summary of the Invention

[0004] In order to solve the above technical defects, the present invention has developed a solar cell with a doped polysilicon layer structure and a preparation process thereof, which has good texturing effect, can effectively reduce ineffective recombination of carriers, and has high photoelectric conversion efficiency.

[0005] A process for preparing a solar cell having a doped polysilicon layer structure comprises the following steps:

[0006] S1: Surface texturing of silicon wafers

[0007] Sodium citrate and polyvinyl alcohol ether are added to a potassium hydroxide solution and stirred evenly to obtain a texturing alkali solution. An N-type single crystal silicon wafer is first cleaned with an HF solution, and then acid-washed, alkaline-washed, and rinsed with deionized water to obtain a pre-cleaned silicon wafer. The texturing alkali solution is placed in a container equipped with an ultrasonic vibrating rod. After heating, the pre-cleaned silicon wafer is immersed in the texturing alkali solution for etching. The pre-cleaned silicon wafer is periodically vibrated by the ultrasonic vibrating rod. Mannitol is then added and stirred evenly. Etching is continued while maintaining the on frequency of the ultrasonic vibrating rod. After cleaning and drying, the texturing silicon wafer is obtained.

[0008] S2: Passivation of textured silicon wafers and preparation of insulating dielectric films

[0009] Methyl orthosilicate, triethylhexyl phosphoric acid and an aqueous solution are mixed and stirred, and then polystyrene is added and stirred continuously to obtain a SiO2 insulating medium spinning solution. Boron is diffused into a texturing silicon wafer, and the BSG layer on the back is removed. Alkali washing and polishing are then performed to obtain an alkali-polished silicon wafer. A tunneling oxide layer and a phosphorus-doped amorphous silicon layer are sequentially deposited on the back of the alkali-polished silicon wafer. The phosphorus-doped amorphous silicon on the front is removed by alkali washing and then plated to obtain a pre-passivated silicon wafer. The SiO2 insulating medium spinning solution is used to perform electrostatic spinning on the back of the pre-passivated silicon wafer, and then sintering is performed to obtain a film-coated passivated silicon wafer.

[0010] S3: Preparation of bottom battery and laminated battery composite

[0011] The film-coated passivated silicon wafer was immersed in toluene for ultrasonic cleaning, and then the front side of the film-coated passivated silicon wafer was pickled with HF solution. After being rinsed with deionized water, it was blown dry with nitrogen. Aluminum oxide was first deposited on the front side by ALD, and then a SiN layer was deposited on the front side by PECVD to obtain a bottom cell. A perovskite top cell was prepared on the back side of the bottom cell to obtain a stacked cell. Silver paste electrodes were printed on the front and back sides of the stacked cell by screen printing. After sintering, a solar cell with a doped polycrystalline silicon layer structure was obtained.

[0012] Furthermore, step S1 of texturing the surface of the silicon wafer comprises the following steps:

[0013] S1.1: Place a 30-35 g / L potassium hydroxide solution in a container, add sodium citrate and polyvinyl alcohol ether C-201, and stir evenly. Control the concentration of sodium citrate to 2-3 g / L and the concentration of polyvinyl alcohol ether C-201 to 1-2 mL / L to obtain a texturing alkali solution.

[0014] S1.2: Soak the N-type monocrystalline silicon wafer in a 5-6% HF solution for 1.5-2 minutes, then soak it in an alkaline cleaning solution at 65-70°C for 10-15 minutes, and then soak it in an acidic cleaning solution at 65-70°C for 10-15 minutes. After cleaning with the alkaline cleaning solution and the acidic cleaning solution, the N-type monocrystalline silicon wafer needs to be soaked in a 5-6% HF solution for 1.5-2 minutes, and then rinsed with deionized water for 6-8 minutes to obtain a pre-cleaned silicon wafer.

[0015] S1.3: Place the texturing alkali solution in a container equipped with an ultrasonic vibrator, heat it in a water bath to 80-85℃ and maintain the temperature, then immerse the pre-cleaned silicon wafer in the texturing alkali solution for etching. The pre-cleaned silicon wafer is in contact with the ultrasonic vibrator, which is turned on every 1-2 minutes and vibrates at a frequency of 1-2Hz for 2-3 seconds each time. After etching for 8-10 minutes, add mannitol to make the mannitol concentration 10-12g / L, stir evenly and continue etching for 10-12 minutes while maintaining the on frequency of the ultrasonic vibrator. Then take it out and place it in an ultrasonic cleaning machine and use deionized water for ultrasonic cleaning for 10-15 minutes, then blow it dry with nitrogen to obtain the texturing silicon wafer.

[0016] Furthermore, step S2 of texturing the passivation of the silicon wafer and preparing the insulating dielectric film layer includes the following steps:

[0017] S2.1: Methyl orthosilicate, triethylhexyl phosphoric acid, and an aqueous solution are mixed in a mass ratio of 1:(0.08-0.1):(10-12) in a container and magnetically stirred at a rotation speed of 120-150 rpm for 15-20 minutes. Polystyrene accounting for 20-30% by mass of methyl orthosilicate is then added, and magnetic stirring is continued at a rotation speed of 150-200 rpm for 20-25 minutes to obtain a SiO2 insulating medium spinning solution;

[0018] S2.2: Place the textured silicon wafer in a tubular diffusion furnace, introduce BBr3 gas at a flow rate of 100-120 mL / min, and perform boron diffusion at 800-850°C for 15-20 minutes to obtain a boron-diffused silicon wafer. Then, use a 1-2% HF solution to wet-etch the BSG layer on the back of the boron-diffused silicon wafer, and then polish it by alkali washing to obtain an alkali-polished silicon wafer.

[0019] S2.3: Place the alkali-polished silicon wafer in the deposition chamber of the PECVD system, first introduce N2O gas at a flow rate of 30-35 mL / min, adjust the gas pressure to 0.5-0.6 Torr, and deposit a 1-2 nm thick tunneling oxide layer on the back side at a power of 4-6 W. Then, introduce amorphous silicon deposition gas at a flow rate of 40-45 mL / min, adjust the gas pressure to 0.6-0.8 Torr, and deposit a 120-150 nm thick phosphorus-doped amorphous silicon layer on the back side at a power of 6-8 W. Remove the phosphorus-doped amorphous silicon plating on the front side by alkali washing to obtain a pre-passivated silicon wafer;

[0020] S2.4: Place the pre-passivated silicon wafer under the electrospinning machine with the back side facing up and 15-20 cm away from the spinneret. At 10-30°C, set the voltage to 15-25 kV and the infusion rate of the SiO2 insulating medium spinning solution to 0.1-0.5 mL / h. Perform electrospinning by controlling the speed and moving direction of the spinneret to uniformly adhere a layer of precursor fiber membrane with a thickness of 100-120 nm on the phosphorus-doped amorphous silicon layer on the back of the pre-passivated silicon wafer. Then place it in a tubular furnace and heat it to 250-300°C at a heating rate of 5-10°C / min in a high-purity nitrogen atmosphere, then heat it to 700-800°C and keep it warm for 20-25 minutes to crystallize the phosphorus-doped amorphous silicon layer, advance phosphorus and sinter the precursor fiber membrane. Then cool it to room temperature with the furnace to obtain a coated passivated silicon wafer.

[0021] Furthermore, step S3 of preparing the bottom cell and compounding the laminated cell comprises the following steps:

[0022] S3.1: Immerse the film-coated passivated silicon wafer in toluene and ultrasonically clean it for 5-10 minutes. Then, pickle the front surface of the film-coated passivated silicon wafer with a 1-2% HF solution for 1-2 minutes. Rinse it with deionized water 3-4 times and blow dry it with nitrogen. Then, use ALD to deposit 8-10nm thick aluminum oxide on the front surface. Then, place it in a PECVD system and pass NH3 and SiH4 to deposit a 75-80nm thick SiN layer on the front surface to obtain a bottom cell.

[0023] S3.2: Place the bottom cell in a nitrogen glove box with a water and oxygen content of less than 1 ppm, with the back side facing up, and evenly spin-coat a 1-2 mg / mL MeO-2PACz solution on the back of the bottom cell. Then, heat the sample on a hot plate at 100-120°C for 10-15 minutes. Then, use a one-step extraction spin-coating method to prepare a CsFAMA perovskite layer. Then, continue to heat on the hot plate for 15-20 minutes, and then deposit 20-25 nm of C by thermal evaporation. 60 , 10-12nm BCP and 1-2nm Ag, and then sputter 100-120nm IZO top electrode on the Ag layer through PVD under the condition of RF power of 80-85W to obtain a stacked battery, and print silver paste electrodes on the front and back of the stacked battery by screen printing. After sintering, a solar cell with a doped polysilicon layer structure is obtained.

[0024] Furthermore, the N-type single crystal silicon wafer in step S1.2 has a thickness of 160 μm, a resistivity of 0.8 Ω·cm, and a size of 4×4 cm 2 .

[0025] Furthermore, the alkaline cleaning solution in step S1.2 is prepared from NH4OH:H2O2:H2O in a mass ratio of 1:1:5, and the acidic cleaning solution is prepared from HCl:H2O2:H2O in a mass ratio of 1:1:5.

[0026] Furthermore, the polishing thickness in step S2.2 is 3-5 μm.

[0027] Furthermore, the amorphous silicon deposition gas in step S2.3 is made by mixing SiH4:H2:PH3:CH4 in a volume ratio of 1:(2-2.5):(0.6-0.8):(0.5-0.6).

[0028] Furthermore, the ion composition of the perovskite layer in step S3.2 is (CsFAMA)Pb(BrI)3.

[0029] A solar cell with a doped polysilicon layer structure is prepared by the above-mentioned preparation process for a solar cell with a doped polysilicon layer structure.

[0030] The beneficial effects are as follows: 1. The present invention prepares SiO2 insulating medium spinning solution by using methyl orthosilicate, triethylhexyl phosphoric acid, polystyrene and solution, and then spins it on the back of a pre-passivated silicon wafer deposited with a tunneling oxide layer and a phosphorus-doped amorphous silicon layer by electrospinning technology to form a precursor fiber membrane with a thickness of 100-120nm, which is then placed in a tubular furnace for secondary temperature sintering, thereby achieving the purpose of crystallization of the phosphorus-doped amorphous silicon layer, phosphorus advancement and generation of a porous SiO2 nanofiber membrane. The preparation efficiency is high, and the precursor fiber membrane releases gas at a uniform rate during the heating process and discharges it to the outside of the fiber to form a porous structure, which is then heated. Continue calcining at high temperature to oxidize and crack the unhydrolyzed organic groups on the chain molecular chain, and finally obtain a porous SiO2 nanofiber membrane. The obtained porous SiO2 nanofiber membrane has uniform pore arrangement, stable pore structure and good mechanical properties. When preparing perovskite top cells, the porous SiO2 nanofiber membrane can make the top cell only partially contact with the bottom cell, thereby further reducing the ineffective recombination of carriers in the middle layer of the stacked cell, and can better transmit carriers. In addition, the preparation process of the porous SiO2 nanofiber membrane is simple and will not damage the bottom cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0031] 2. The present invention generates a porous SiO2 nanofiber membrane by subjecting the precursor fiber membrane to secondary sintering at a high temperature. During this process, the precursor fiber membrane also generates water, which evaporates at high temperature. When the temperature is cooled to the hydrogen bond breaking temperature with the furnace, the water vapor can form hydrogen chemical bonds with the unpaired electron dangling bonds of the outermost layer of the doped polysilicon layer atoms during the formation of the doped polysilicon layer, reducing the recombination of unsaturated bonds and carriers, improving the passivation level, and further improving the photoelectric conversion efficiency of the obtained solar cell.

[0032] 3. The present invention prepares a texturing alkali solution by mixing potassium hydroxide, sodium citrate and polyvinyl alcohol ether C-201, and then immerses the N-type single crystal silicon wafer in the texturing alkali solution for texturing, wherein the polyvinyl alcohol ether C-201 can accelerate the texturing rate, and the sodium citrate can maintain the stability of the alkali solution to prevent the occurrence of local uneven texturing rate. During the texturing process, an ultrasonic vibration rod is set to contact the N-type single crystal silicon wafer and periodically vibrate the N-type single crystal silicon wafer. The vibration effectively removes the hydrogen attached to the surface of the N-type single crystal silicon wafer generated during the texturing process, thereby avoiding The influence of hydrogen bubbles on texturing makes a more uniform pyramid light-trapping structure formed inside the velvet microstructure. When the texturing process is halfway through, mannitol is added and stirred evenly to reduce the texturing rate. When the pyramid structures appear in different sizes due to different etching rates, the large pyramid structure has a large contact area with mannitol, and the texturing rate is reduced more, while the small pyramid structure has a small contact area with mannitol, and the texturing rate is reduced less, further ensuring the uniformity of the pyramid structure, thereby effectively reducing the unevenness of the battery's light absorption and improving the battery's photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of a process for preparing a solar cell with a doped polysilicon layer structure used in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1: A solar cell with a doped polysilicon layer structure and its preparation process, such as Figure 1 As shown, the following steps are included:

[0036] S1: Surface texturing of silicon wafers

[0037] S1.1: Place a 30g / L potassium hydroxide solution in a container, add sodium citrate and polyvinyl alcohol ether C-201, and stir until uniform. Control the concentration of sodium citrate to 2g / L and the concentration of polyvinyl alcohol ether C-201 to 1mL / L to obtain a texturing alkali solution.

[0038] S1.2: Soak an N-type single crystal silicon wafer in a 5% HF solution for 2 minutes. The N-type single crystal silicon wafer has a thickness of 160 μm, a resistivity of 0.8 Ω·cm, and a size of 4×4 cm. 2 , then immersed in an alkaline cleaning solution prepared by NH4OH:H2O2:H2O at a mass ratio of 1:1:5 at 65°C for 10 minutes, and then immersed in an acidic cleaning solution prepared by HCl:H2O2:H2O at a mass ratio of 1:1:5 at 65°C for 10 minutes. After cleaning with the alkaline cleaning solution and the acidic cleaning solution, the N-type single crystal silicon wafer needs to be immersed in a 5% HF solution for 2 minutes, and then rinsed with deionized water for 6 minutes to obtain a pre-cleaned silicon wafer;

[0039] S1.3: Place the texturing alkali solution in a container equipped with an ultrasonic vibrator, heat it to 80°C in a water bath and maintain the temperature, then immerse the pre-cleaned silicon wafer in the texturing alkali solution for etching. The pre-cleaned silicon wafer is in contact with the ultrasonic vibrator, which is turned on once every 1 minute and vibrates at a frequency of 1 Hz for 3 seconds each time. After etching for 8 minutes, add mannitol to make the mannitol concentration 10 g / L, stir evenly and continue etching for 10 minutes while maintaining the on frequency of the ultrasonic vibrator. Then take it out and place it in an ultrasonic cleaning machine for ultrasonic cleaning with deionized water for 10 minutes, then blow it dry with nitrogen to obtain the texturing silicon wafer.

[0040] S2: Passivation of textured silicon wafers and preparation of insulating dielectric films

[0041] S2.1: Methyl orthosilicate, triethylhexyl phosphoric acid, and an aqueous solution were mixed in a mass ratio of 1:0.08:10 in a container and magnetically stirred at 120 rpm for 15 minutes. Polystyrene (20% by mass of methyl orthosilicate) was then added and magnetically stirred at 150 rpm for 20 minutes to obtain a SiO2 insulating medium spinning solution.

[0042] S2.2: Place the textured silicon wafer in a tubular diffusion furnace, introduce BBr3 gas at a flow rate of 100 mL / min, and perform boron diffusion at 800°C for 15 minutes to obtain a boron-diffused silicon wafer. Then, use a 1% HF solution to wet-etch the BSG layer on the back of the boron-diffused silicon wafer. Then, polish the wafer to a thickness of 3 μm using alkaline washing to obtain an alkaline-polished silicon wafer.

[0043] S2.3: Place the alkali-polished silicon wafer in the deposition chamber of the PECVD system, first introduce N2O gas at a flow rate of 30 mL / min, adjust the gas pressure to 0.5 Torr, and deposit a 1 nm thick tunnel oxide layer on the back side at a power of 4 W. Then, introduce amorphous silicon deposition gas at a flow rate of 40 mL / min. The amorphous silicon deposition gas is made of a mixture of SiH4:H2:PH3:CH4 in a volume ratio of 1:2:0.6:0.5. Adjust the gas pressure to 0.6 Torr, and deposit a 120 nm thick phosphorus-doped amorphous silicon layer on the back side at a power of 6 W. Remove the phosphorus-doped amorphous silicon coating on the front side by alkali washing to obtain a pre-passivated silicon wafer;

[0044] S2.4: Place the pre-passivated silicon wafer under the electrospinning machine with the back side facing up and 15 cm away from the spinneret. At 10°C, set the voltage to 15 kV and the infusion rate of the SiO2 insulating medium spinning solution to 0.1 mL / h. Perform electrospinning by controlling the speed and moving direction of the spinneret to evenly adhere a layer of 100 nm thick precursor fiber membrane to the phosphorus-doped amorphous silicon layer on the back of the pre-passivated silicon wafer. Then place it in a tubular furnace and heat it to 250°C at a heating rate of 5°C / min in a high-purity nitrogen atmosphere, then heat it to 700°C and keep it warm for 20 minutes to crystallize the phosphorus-doped amorphous silicon layer, advance phosphorus and sinter the precursor fiber membrane. Then cool it to room temperature with the furnace to obtain a coated passivated silicon wafer.

[0045] S3: Preparation of bottom battery and laminated battery composite

[0046] S3.1: Immerse the film-coated passivated silicon wafer in toluene and ultrasonically clean it for 5 minutes. Then, pickle the front surface of the film-coated passivated silicon wafer with a 1% HF solution for 1 minute, rinse it with deionized water three times, and blow dry it with nitrogen. Then, use ALD to deposit 8nm thick aluminum oxide on the front surface. Then, place it in a PECVD system and pass NH3 and SiH4 to deposit a 75nm thick SiN layer on the front surface to obtain a bottom cell.

[0047] S3.2: The bottom cell was placed in a nitrogen glove box with a water and oxygen content of less than 1 ppm, with the back side facing up. A 1 mg / mL MeO-2PACz solution was evenly spin-coated on the back side of the bottom cell. The sample was then placed on a hot plate at 100°C and heated for 10 minutes. The perovskite layer of CsFAMA was prepared by a one-step extraction spin coating method. The ion composition of the perovskite layer was (CsFAMA)Pb(BrI)3. The sample was then placed on a hot plate and heated for 15 minutes. 20 nm of C was then deposited in sequence by thermal evaporation. 60, 10nm BCP and 1nm Ag, and then sputter a 100nm IZO top electrode on the Ag layer through PVD at an RF power of 80W to obtain a stacked battery. Silver paste electrodes are printed on the front and back of the stacked battery by screen printing, and after sintering, a solar cell with a doped polysilicon layer structure is obtained.

[0048] Example 2: A solar cell with a doped polysilicon layer structure and its preparation process, such as Figure 1 As shown, the following steps are included:

[0049] S1: Surface texturing of silicon wafers

[0050] S1.1: Place a 30g / L potassium hydroxide solution in a container, add sodium citrate and polyvinyl alcohol ether C-201, and stir until uniform. Control the concentration of sodium citrate to 3g / L and the concentration of polyvinyl alcohol ether C-201 to 2mL / L to obtain a texturing alkali solution.

[0051] S1.2: Soak an N-type single crystal silicon wafer in a 5% HF solution for 2 minutes. The N-type single crystal silicon wafer has a thickness of 160 μm, a resistivity of 0.8 Ω.cm, and a size of 4 × 4 cm. 2 , then immersed in an alkaline cleaning solution prepared by NH4OH:H2O2:H2O at a mass ratio of 1:1:5 at 65°C for 10 minutes, and then immersed in an acidic cleaning solution prepared by HCl:H2O2:H2O at a mass ratio of 1:1:5 at 65°C for 10 minutes. After cleaning with the alkaline cleaning solution and the acidic cleaning solution, the N-type single crystal silicon wafer needs to be immersed in a 5% HF solution for 2 minutes, and then rinsed with deionized water for 6 minutes to obtain a pre-cleaned silicon wafer;

[0052] S1.3: Place the texturing alkali solution in a container equipped with an ultrasonic vibrator, heat it to 80°C in a water bath and maintain the temperature, then immerse the pre-cleaned silicon wafer in the texturing alkali solution for etching. The pre-cleaned silicon wafer is in contact with the ultrasonic vibrator, which is turned on once every 1 minute and vibrates at a frequency of 1Hz for 3 seconds each time. After etching for 8 minutes, add mannitol to make the mannitol concentration 12g / L, stir evenly and continue etching for 10 minutes while maintaining the on frequency of the ultrasonic vibrator. Then take it out and place it in an ultrasonic cleaning machine for ultrasonic cleaning with deionized water for 10 minutes, then blow it dry with nitrogen to obtain the texturing silicon wafer.

[0053] S2: Passivation of textured silicon wafers and preparation of insulating dielectric films

[0054] S2.1: Methyl orthosilicate, triethylhexyl phosphoric acid, and an aqueous solution were mixed in a mass ratio of 1:0.1:12 in a container and magnetically stirred at 120 rpm for 15 minutes. Polystyrene containing 30% by mass of methyl orthosilicate was then added and magnetically stirred at 150 rpm for 20 minutes to obtain a SiO2 insulating medium spinning solution.

[0055] S2.2: Place the textured silicon wafer in a tubular diffusion furnace, introduce BBr3 gas at a flow rate of 100 mL / min, and perform boron diffusion at 800°C for 15 minutes to obtain a boron-diffused silicon wafer. Then, use a 1% HF solution to wet-etch the BSG layer on the back of the boron-diffused silicon wafer. Then, polish the wafer to a thickness of 3 μm using alkaline washing to obtain an alkaline-polished silicon wafer.

[0056] S2.3: Place the alkali-polished silicon wafer in the deposition chamber of the PECVD system, first introduce N2O gas at a flow rate of 30 mL / min, adjust the gas pressure to 0.5 Torr, and deposit a 1 nm thick tunnel oxide layer on the back side at a power of 4 W. Then, introduce amorphous silicon deposition gas at a flow rate of 40 mL / min. The amorphous silicon deposition gas is made of a mixture of SiH4:H2:PH3:CH4 in a volume ratio of 1:2.5:0.8:0.6. Adjust the gas pressure to 0.6 Torr, and deposit a 120 nm thick phosphorus-doped amorphous silicon layer on the back side at a power of 6 W. Remove the phosphorus-doped amorphous silicon coating on the front side by alkali washing to obtain a pre-passivated silicon wafer;

[0057] S2.4: Place the pre-passivated silicon wafer under the electrospinning machine with the back side facing up and 15 cm away from the spinneret. At 10°C, set the voltage to 15 kV and the infusion rate of the SiO2 insulating medium spinning solution to 0.1 mL / h. Perform electrospinning by controlling the speed and moving direction of the spinneret to evenly adhere a layer of 100 nm thick precursor fiber membrane to the phosphorus-doped amorphous silicon layer on the back of the pre-passivated silicon wafer. Then place it in a tubular furnace and heat it to 250°C at a heating rate of 5°C / min in a high-purity nitrogen atmosphere, then heat it to 700°C and keep it warm for 20 minutes to crystallize the phosphorus-doped amorphous silicon layer, advance phosphorus and sinter the precursor fiber membrane. Then cool it to room temperature with the furnace to obtain a coated passivated silicon wafer.

[0058] S3: Preparation of bottom battery and laminated battery composite

[0059] S3.1: Immerse the film-coated passivated silicon wafer in toluene and ultrasonically clean it for 5 minutes. Then, pickle the front surface of the film-coated passivated silicon wafer with a 1% HF solution for 1 minute, rinse it with deionized water three times, and blow dry it with nitrogen. Then, use ALD to deposit 8nm thick aluminum oxide on the front surface. Then, place it in a PECVD system and pass NH3 and SiH4 to deposit a 75nm thick SiN layer on the front surface to obtain a bottom cell.

[0060] S3.2: The bottom cell was placed in a nitrogen glove box with a water and oxygen content of less than 1 ppm, with the back side facing up. A 1 mg / mL MeO-2PACz solution was evenly spin-coated on the back side of the bottom cell. The sample was then placed on a hot plate at 100°C and heated for 10 minutes. The perovskite layer of CsFAMA was prepared by a one-step extraction spin coating method. The ion composition of the perovskite layer was (CsFAMA)Pb(BrI)3. The sample was then placed on a hot plate and heated for 15 minutes. 20 nm of C was then deposited in sequence by thermal evaporation. 60 , 10nm BCP and 1nm Ag, and then sputter a 100nm IZO top electrode on the Ag layer through PVD at an RF power of 80W to obtain a stacked battery. Silver paste electrodes are printed on the front and back of the stacked battery by screen printing, and after sintering, a solar cell with a doped polysilicon layer structure is obtained.

[0061] Example 3: A solar cell with a doped polysilicon layer structure and its preparation process, such as Figure 1 As shown, the following steps are included:

[0062] S1: Surface texturing of silicon wafers

[0063] S1.1: Place a 30g / L potassium hydroxide solution in a container, add sodium citrate and polyvinyl alcohol ether C-201, and stir until uniform. Control the concentration of sodium citrate to 2g / L and the concentration of polyvinyl alcohol ether C-201 to 1mL / L to obtain a texturing alkali solution.

[0064] S1.2: Soak an N-type single crystal silicon wafer in a 6% HF solution for 1.5 minutes. The N-type single crystal silicon wafer has a thickness of 160 μm, a resistivity of 0.8 Ω·cm, and a size of 4×4 cm. 2 , then immersed in an alkaline cleaning solution prepared by NH4OH:H2O2:H2O at a mass ratio of 1:1:5 at 70°C for 15 minutes, and then immersed in an acidic cleaning solution prepared by HCl:H2O2:H2O at a mass ratio of 1:1:5 at 70°C for 15 minutes. After cleaning with the alkaline cleaning solution and the acidic cleaning solution, the N-type single crystal silicon wafer needs to be immersed in a 6% HF solution for 1.5 minutes, and then rinsed with deionized water for 8 minutes to obtain a pre-cleaned silicon wafer;

[0065] S1.3: Place the texturing alkali solution in a container equipped with an ultrasonic vibrator, heat it to 85°C in a water bath and maintain the temperature, then immerse the pre-cleaned silicon wafer in the texturing alkali solution for etching. The pre-cleaned silicon wafer is in contact with the ultrasonic vibrator, which is turned on every 2 minutes and vibrates at a frequency of 2Hz for 2 seconds each time. After etching for 10 minutes, add mannitol to make the mannitol concentration 10g / L, stir evenly and continue etching for 12 minutes while maintaining the on frequency of the ultrasonic vibrator. Then take it out and place it in an ultrasonic cleaning machine for ultrasonic cleaning with deionized water for 15 minutes, and then blow it dry with nitrogen to obtain the texturing silicon wafer.

[0066] S2: Passivation of textured silicon wafers and preparation of insulating dielectric films

[0067] S2.1: Methyl orthosilicate, triethylhexyl phosphoric acid, and an aqueous solution were mixed in a mass ratio of 1:0.08:10 in a container and magnetically stirred at 150 rpm for 20 minutes. Polystyrene (20% by mass of methyl orthosilicate) was then added and magnetically stirred at 200 rpm for another 25 minutes to obtain a SiO2 insulating medium spinning solution.

[0068] S2.2: Place the textured silicon wafer in a tubular diffusion furnace, introduce BBr3 gas at a flow rate of 120 mL / min, and perform boron diffusion at 850°C for 20 minutes to obtain a boron-diffused silicon wafer. Then, remove the BSG layer on the back of the boron-diffused silicon wafer by wet etching using a 2% HF solution. Then, polish the wafer by alkaline washing to a polishing thickness of 5 μm to obtain an alkaline-polished silicon wafer.

[0069] S2.3: Place the alkali-polished silicon wafer in the deposition chamber of the PECVD system, first introduce N2O gas at a flow rate of 35 mL / min, adjust the gas pressure to 0.6 Torr, and deposit a 2 nm thick tunnel oxide layer on the back side at a power of 6 W. Then, introduce amorphous silicon deposition gas at a flow rate of 45 mL / min. The amorphous silicon deposition gas is made of a mixture of SiH4:H2:PH3:CH4 in a volume ratio of 1:2:0.6:0.5. Adjust the gas pressure to 0.8 Torr, and deposit a 150 nm thick phosphorus-doped amorphous silicon layer on the back side at a power of 8 W. Remove the phosphorus-doped amorphous silicon plating on the front side by alkali washing to obtain a pre-passivated silicon wafer;

[0070] S2.4: Place the pre-passivated silicon wafer under the electrospinning machine with the back side facing up and 20 cm away from the spinneret. At 30°C, set the voltage to 25 kV and the infusion rate of the SiO2 insulating medium spinning solution to 0.5 mL / h. Perform electrospinning by controlling the speed and moving direction of the spinneret to evenly adhere a layer of 120 nm thick precursor fiber membrane to the phosphorus-doped amorphous silicon layer on the back of the pre-passivated silicon wafer. Then place it in a tubular furnace and heat it to 300°C at a heating rate of 10°C / min in a high-purity nitrogen atmosphere, then heat it to 800°C and keep it warm for 25 minutes to crystallize the phosphorus-doped amorphous silicon layer, advance phosphorus and sinter the precursor fiber membrane. Then cool it to room temperature with the furnace to obtain a coated passivated silicon wafer.

[0071] S3: Preparation of bottom battery and laminated battery composite

[0072] S3.1: Immerse the film-coated passivated silicon wafer in toluene and ultrasonically clean it for 10 minutes. Then, pickle the front surface of the film-coated passivated silicon wafer with a 2% HF solution for 2 minutes, rinse it with deionized water four times, and blow dry it with nitrogen. Then, use ALD to deposit a 10nm thick aluminum oxide layer on the front surface. Then, place it in a PECVD system and pass NH3 and SiH4 to deposit an 80nm thick SiN layer on the front surface to obtain a bottom cell.

[0073] S3.2: The bottom cell was placed in a nitrogen glove box with a water and oxygen content of less than 1 ppm, with the back side facing up. A 2 mg / mL MeO-2PACz solution was evenly spin-coated on the back side of the bottom cell. The sample was then placed on a hot plate at 120°C and heated for 15 minutes. The perovskite layer of CsFAMA was prepared by a one-step extraction spin coating method. The ion composition of the perovskite layer was (CsFAMA)Pb(BrI)3. The sample was then placed on a hot plate and heated for 20 minutes. 25 nm of C was then deposited in sequence by thermal evaporation. 60 , 12nm BCP and 2nm Ag, and then sputter a 120nm IZO top electrode on the Ag layer through PVD at an RF power of 85W to obtain a stacked battery, and print silver paste electrodes on the front and back of the stacked battery by screen printing. After sintering, a solar cell with a doped polysilicon layer structure is obtained.

[0074] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step S2.1 is removed in Comparative Example 1, and electrospinning is not performed on the back of the pre-passivated silicon wafer in step S2.4. The remaining steps are the same as in Example 1, and a solar cell is prepared, which is recorded as Comparative Example 1.

[0075] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 removes step S1.1 and replaces the subsequent texturing alkali solution with a potassium hydroxide solution with a concentration of 30 g / L. The remaining steps are the same as Example 1 to produce a solar cell, which is recorded as Comparative Example 2.

[0076] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 removes the ultrasonic vibration rod in step S1.3 and does not perform periodic ultrasonic vibration. The remaining steps are the same as Example 1. A solar cell is produced, which is recorded as Comparative Example 3.

[0077] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that mannitol is not added in step S1.3 of Comparative Example 4, and the remaining steps are the same as those of Example 1 to prepare a solar cell, which is recorded as Comparative Example 4.

[0078] Experiment 1: The photoelectric conversion efficiency of the solar cells with doped polycrystalline silicon layer structures prepared in Examples 1-3 and Comparative Examples 1-4 was measured. The measurement method was based on the national standard GB / T34160-2017 "Test Method for Photoelectric Conversion Efficiency of Terrestrial Photovoltaic Modules". The test was performed three times and the data were recorded and tabulated as shown in Table 1.

[0079] It can be seen that the photoelectric conversion efficiency of the solar cells with doped polycrystalline silicon layer structures prepared in Examples 1-3 is greater than that of Comparative Examples 1-4, which proves that preparing a layer of porous SiO2 nanofiber membrane between the perovskite top cell and the bottom cell can reduce the ineffective recombination of carriers in the middle layer of the stacked cell, thereby improving the photoelectric conversion efficiency of the solar cell; it can also be proved that the texturing of N-type single crystal silicon wafers by using a texturing alkali solution prepared by mixing potassium hydroxide, sodium citrate and polyvinyl alcohol ether C-201 can improve the photoelectric conversion efficiency of the solar cell; and it is proved that introducing an ultrasonic vibrator to periodically vibrate the N-type single crystal silicon wafers during the texturing process can avoid the influence of hydrogen bubbles on texturing, thereby improving the photoelectric conversion efficiency of the solar cell; it can also be proved that adding mannitol to continue texturing when the texturing process is halfway through can ensure the uniformity of the pyramid structure and improve the photoelectric conversion efficiency of the solar cell.

[0080] Table 1: Photovoltaic conversion efficiency of solar cells

[0081] Photoelectric conversion efficiency / % first Second time The third time Example 1 26.81 26.83 27.84 Example 2 26.89 26.92 26.91 Example 3 27.02 27.05 27.04 Comparative Example 1 24.81 24.85 24.82 Comparative Example 2 26.31 26.28 26.33 Comparative Example 3 26.13 26.15 26.12 Comparative Example 4 26.23 26.25 26.26

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A process for preparing a solar cell having a doped polysilicon layer structure, characterized in that: The following steps are involved: S1: Surface texturing of silicon wafers Sodium citrate and polyvinyl alcohol ether are added to a potassium hydroxide solution and stirred evenly to obtain a texturing alkali solution. An N-type single crystal silicon wafer is first cleaned with an HF solution, and then acid-washed, alkaline-washed, and rinsed with deionized water to obtain a pre-cleaned silicon wafer. The texturing alkali solution is placed in a container equipped with an ultrasonic vibrating rod. After heating, the pre-cleaned silicon wafer is immersed in the texturing alkali solution for etching. The pre-cleaned silicon wafer is periodically vibrated by the ultrasonic vibrating rod. Mannitol is then added and stirred evenly. Etching is continued while maintaining the on frequency of the ultrasonic vibrating rod. After cleaning and drying, the texturing silicon wafer is obtained. S2: Passivation of texturing silicon wafers and preparation of insulating dielectric films Methyl orthosilicate, triethylhexyl phosphoric acid and an aqueous solution are mixed and stirred, and then polystyrene is added and stirred continuously to obtain a SiO2 insulating medium spinning solution. Boron is diffused into a texturing silicon wafer, and the BSG layer on the back is removed. Alkali washing and polishing are then performed to obtain an alkali-polished silicon wafer. A tunneling oxide layer and a phosphorus-doped amorphous silicon layer are sequentially deposited on the back of the alkali-polished silicon wafer. The phosphorus-doped amorphous silicon on the front is removed by alkali washing and then plated to obtain a pre-passivated silicon wafer. The SiO2 insulating medium spinning solution is used to perform electrostatic spinning on the back of the pre-passivated silicon wafer, and then sintering is performed to obtain a film-coated passivated silicon wafer. S3: Preparation of bottom battery and laminated battery composite The film-coated passivated silicon wafer was immersed in toluene for ultrasonic cleaning, and then the front side of the film-coated passivated silicon wafer was pickled with HF solution. After being rinsed with deionized water, it was blown dry with nitrogen. Aluminum oxide was first deposited on the front side by ALD, and then a SiN layer was deposited on the front side by PECVD to obtain a bottom cell. A perovskite top cell was prepared on the back side of the bottom cell to obtain a stacked cell. Silver paste electrodes were printed on the front and back sides of the stacked cell by screen printing. After sintering, a solar cell with a doped polycrystalline silicon layer structure was obtained.

2. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 1, characterized in that: Step S1: Texturing the surface of the silicon wafer, including the following steps: S1.1: Place a 30-35 g / L potassium hydroxide solution in a container, add sodium citrate and polyvinyl alcohol ether C-201, and stir evenly. Control the concentration of sodium citrate to 2-3 g / L and the concentration of polyvinyl alcohol ether C-201 to 1-2 mL / L to obtain a texturing alkali solution. S1.2: Soak the N-type monocrystalline silicon wafer in a 5-6% HF solution for 1.5-2 minutes, then soak it in an alkaline cleaning solution at 65-70°C for 10-15 minutes, and then soak it in an acidic cleaning solution at 65-70°C for 10-15 minutes. After cleaning with the alkaline cleaning solution and the acidic cleaning solution, the N-type monocrystalline silicon wafer needs to be soaked in a 5-6% HF solution for 1.5-2 minutes, and then rinsed with deionized water for 6-8 minutes to obtain a pre-cleaned silicon wafer. S1.3: Place the texturing alkali solution in a container equipped with an ultrasonic vibrator, heat it in a water bath to 80-85℃ and maintain the temperature, then immerse the pre-cleaned silicon wafer in the texturing alkali solution for etching. The pre-cleaned silicon wafer is in contact with the ultrasonic vibrator, which is turned on every 1-2 minutes and vibrates at a frequency of 1-2Hz for 2-3 seconds each time. After etching for 8-10 minutes, add mannitol to make the mannitol concentration 10-12g / L, stir evenly and continue etching for 10-12 minutes while maintaining the on frequency of the ultrasonic vibrator. Then take it out and place it in an ultrasonic cleaning machine and use deionized water for ultrasonic cleaning for 10-15 minutes, then blow it dry with nitrogen to obtain the texturing silicon wafer.

3. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 2, characterized in that: Step S2 is to prepare the passivation of the silicon wafer and the insulating dielectric film layer, including the following steps: S2.1: Methyl orthosilicate, triethylhexyl phosphoric acid, and an aqueous solution are mixed in a mass ratio of 1:(0.08-0.1):(10-12) in a container and magnetically stirred at a rotation speed of 120-150 rpm for 15-20 minutes. Polystyrene accounting for 20-30% by mass of methyl orthosilicate is then added, and magnetic stirring is continued at a rotation speed of 150-200 rpm for 20-25 minutes to obtain a SiO2 insulating medium spinning solution; S2.2: Place the textured silicon wafer in a tubular diffusion furnace, introduce BBr3 gas at a flow rate of 100-120 mL / min, and perform boron diffusion at 800-850°C for 15-20 minutes to obtain a boron-diffused silicon wafer. Then, use a 1-2% HF solution to wet-etch the BSG layer on the back of the boron-diffused silicon wafer, and then polish it by alkali washing to obtain an alkali-polished silicon wafer. S2.3: Place the alkali-polished silicon wafer in the deposition chamber of the PECVD system, first introduce N2O gas at a flow rate of 30-35 mL / min, adjust the gas pressure to 0.5-0.6 Torr, and deposit a 1-2 nm thick tunneling oxide layer on the back side at a power of 4-6 W. Then, introduce amorphous silicon deposition gas at a flow rate of 40-45 mL / min, adjust the gas pressure to 0.6-0.8 Torr, and deposit a 120-150 nm thick phosphorus-doped amorphous silicon layer on the back side at a power of 6-8 W. Remove the phosphorus-doped amorphous silicon plating on the front side by alkali washing to obtain a pre-passivated silicon wafer; S2.4: Place the pre-passivated silicon wafer under the electrospinning machine with the back side facing up and 15-20 cm away from the spinneret. At 10-30°C, set the voltage to 15-25 kV and the infusion rate of the SiO2 insulating medium spinning solution to 0.1-0.5 mL / h. Perform electrospinning by controlling the speed and moving direction of the spinneret to uniformly adhere a layer of precursor fiber membrane with a thickness of 100-120 nm on the phosphorus-doped amorphous silicon layer on the back of the pre-passivated silicon wafer. Then place it in a tubular furnace and heat it to 250-300°C at a heating rate of 5-10°C / min in a high-purity nitrogen atmosphere, then heat it to 700-800°C and keep it warm for 20-25 minutes to crystallize the phosphorus-doped amorphous silicon layer, advance phosphorus and sinter the precursor fiber membrane. Then cool it to room temperature with the furnace to obtain a coated passivated silicon wafer.

4. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 3, characterized in that: Step S3: preparation of the bottom cell and composite of the stacked cells, including the following steps: S3.1: Immerse the film-coated passivated silicon wafer in toluene and ultrasonically clean it for 5-10 minutes. After removing it, immerse it in toluene and ultrasonically clean it again. Then, pickle the front side of the film-coated passivated silicon wafer with a 1-2% HF solution for 1-2 minutes. Rinse it with deionized water 3-4 times and blow dry it with nitrogen. Then, use ALD to deposit 8-10nm thick aluminum oxide on the front side. Then, place it in a PECVD system and pass NH3 and SiH4 to deposit a 75-80nm thick SiN layer on the front side to obtain a bottom cell. S3.2: Place the bottom cell in a nitrogen glove box with a water and oxygen content of less than 1 ppm, with the back side facing up, and evenly spin-coat a 1-2 mg / mL MeO-2PACz solution on the back of the bottom cell. Then, heat the sample on a hot plate at 100-120°C for 10-15 minutes. Then, use a one-step extraction spin-coating method to prepare a CsFAMA perovskite layer. Then, continue to heat on the hot plate for 15-20 minutes, and then deposit 20-25 nm of C by thermal evaporation. 60 , 10-12nm BCP and 1-2nm Ag, and then sputter 100-120nm IZO top electrode on the Ag layer through PVD under the condition of RF power of 80-85W to obtain a stacked battery, and print silver paste electrodes on the front and back of the stacked battery by screen printing. After sintering, a solar cell with a doped polysilicon layer structure is obtained.

5. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 2, wherein: The N-type single crystal silicon wafer in step S1.2 has a thickness of 160 μm, a resistivity of 0.8 Ω·cm, and a size of 4×4 cm. 2 .

6. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 2, characterized in that: The alkaline cleaning solution in step S1.2 is prepared from NH4OH:H2O2:H2O in a mass ratio of 1:1:5, and the acidic cleaning solution is prepared from HCl:H2O2:H2O in a mass ratio of 1:1:

5.

7. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 2, wherein: The polishing thickness in step S2.2 is 3-5 μm.

8. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 3, characterized in that: The amorphous silicon deposition gas in step S2.3 is composed of SiH4:H2:PH3:CH4 in a ratio of 1: The volume ratio of (2-2.5): (0.6-0.8): (0.5-0.6) is mixed.

9. The process for preparing a solar cell having a doped polysilicon layer structure according to claim 4, characterized in that: The ionic composition of the perovskite layer in step S3.2 is (CsFAMA)Pb(BrI)3.

10. A solar cell having a doped polysilicon layer structure, characterized in that: The solar cell is prepared by the preparation process of a solar cell having a doped polycrystalline silicon layer structure according to any one of claims 1 to 9.

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