Topcon photovoltaic cell based on p-type silicon substrate and preparation method thereof

Abstract

The application discloses a TOPCon photovoltaic cell based on a p-type silicon substrate, which comprises a p-type silicon wafer, wherein the back surface of the p-type silicon wafer is sequentially provided with a tunneling layer, a p-type CuAlO2 layer and a back electrode from near to far; and the front surface of the p-type silicon wafer is sequentially provided with an n-type beta-Ga2O3 layer, a passivation layer and an anti-reflection layer from near to far; a pair of top electrodes are arranged on the n-type beta-Ga2O3 layer, and the two top electrodes sequentially penetrate through the passivation layer and the anti-reflection layer and extend out of the anti-reflection layer. The application solves the problem of low photoelectric conversion efficiency of the cell caused by poor passivation quality and poor light trapping capacity of the p-TOPCon due to the complex defects caused by B-O in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic cells, and in particular relates to a TOPCon photovoltaic cell based on a p-type silicon substrate. The present invention also relates to a preparation method of the TOPCon photovoltaic cell based on a p-type silicon substrate. Background Art

[0002] Tunneling oxide passivation contact (TOPCon) of silicon-based solar cells has attracted widespread attention in recent years due to its simple ohmic contact structure, high photoelectric conversion efficiency, and ease of industrialization. Existing TOPCon technology is mostly applied to the back surface of the cell. It consists of an extremely thin oxide layer and a thin layer of polysilicon. It has a good passivation effect on minority carriers and excellent conductivity for majority carriers. The front side uses doped polysilicon as the emitter, Al2O3 thin film and SiN x The films are used as passivation layer and anti-reflection layer respectively. + -poly-Si / SiO x The n-TOPCon structure is widely used because of its excellent passivation quality and high photoelectric conversion efficiency. However, the p-TOPCon made on the p-type c-Si wafer can be directly used in the PERC cell production line, using the same front emitter in the production process, with only limited modifications to the production process on the back of the cell. In addition, p-TOPCon can be applied to double-sided TOPCon photovoltaic cells, high-efficiency perovskite / c-Si double-junction solar cells, or used as a selective emitter under the front metal contact of traditional n-TOPCon photovoltaic cells. Therefore, improving the efficiency of p-TOPCon is of great significance to the solar photovoltaic industry. At present, the conversion efficiency of p-TOPCon is mainly limited by poor passivation quality and weak light capture ability. Among them, the poor passivation quality is generally believed to be caused by the composite defects brought about by the boron-oxygen bond (BO), and the weak light capture ability is generally believed to be caused by the absorption of visible light by the polysilicon layer on the front.

[0003] CuAlO2 thin film is an intrinsic p-type semiconductor material with excellent photoelectric properties. + Compared with polysilicon, gallium oxide (β-Ga2O3) has a larger band gap width and higher hole concentration. As a new type of direct band gap wide band gap semiconductor material, it has a larger band gap width and higher hole concentration than polysilicon. + Compared with polycrystalline silicon, it has a larger band gap. The TOPCon photovoltaic cell based on CuAlO2 / SiO2 designed in the present invention can significantly improve the conversion efficiency of p-TOPCon cells and has great application prospects. Summary of the Invention

[0004] The purpose of the present invention is to provide a TOPCon photovoltaic cell based on a p-type silicon substrate, which solves the problem of low cell photoelectric conversion efficiency caused by poor p-TOPCon passivation quality and poor light capture ability due to composite defects brought by BO in the prior art.

[0005] The first technical solution adopted by the present invention is a TOPCon photovoltaic cell based on a p-type silicon substrate, including a p-type silicon wafer, on the back of which a tunneling layer, a p-type CuAlO2 layer, and a back electrode are sequentially arranged from near to far; on the front of the p-type silicon wafer, an n-type β-Ga2O3 layer, a passivation layer, and an anti-reflection layer are sequentially arranged from near to far; a pair of top electrodes are arranged on the n-type β-Ga2O3 layer, and the two top electrodes pass through the passivation layer and the anti-reflection layer in sequence and extend out of the anti-reflection layer.

[0006] The first technical solution of the present invention is also characterized in that:

[0007] The thickness of the p-type silicon wafer is 100 μm to 200 μm, and the resistivity is 0.1 Ω·cm to 5 Ω·cm. The material of the tunneling layer is one of SiO2, Al2O3 or SiC, and the thickness is 1 nm to 3 nm. The thickness of the p-type CuAlO2 layer is 100 nm to 200 nm. The n-type β-Ga2O3 layer is a β-Ga2O3 (-201) crystal plane, β-Ga2O3 (001) crystal plane or β-Ga2O3 (010) crystal plane material doped with one of Sn, Si and Al, and the doping concentration is 10 18 ~10 20 cm ～3 , with a thickness of 50nm to 200nm; the material of the passivation layer is Al2O3, with a thickness of 5nm to 20nm, and the material of the anti-reflection layer is one of Si3N4 or Si2N2O, with a thickness of 60nm to 150nm.

[0008] The second technical solution adopted by the present invention is a method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate, which is specifically implemented according to the following steps:

[0009] Step 1: alkaline polishing of the p-type silicon wafer;

[0010] Step 2: Texturing the front surface of the P-type silicon wafer polished in step 1 to form a surface pyramid structure;

[0011] Step 3: Cleaning the p-type silicon wafer obtained in step 2 and briefly immersing it in hydrofluoric acid (HF);

[0012] Step 4: growing an oxide layer on the back of the p-type silicon wafer cleaned in step 3;

[0013] Step 5: growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4;

[0014] Step 6: growing an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer;

[0015] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6. x film;

[0016] Step 8: AlO obtained in step 7 x SiN film deposition x film;

[0017] Step 9: fabricating a back electrode on the p-type CuAlO2 layer obtained in step 5;

[0018] Step 10: SiN obtained in step 8 x A top electrode is prepared on the film, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0019] The second technical solution of the present invention is also characterized in that:

[0020] In step 1, a KOH solution with a concentration of 3% to 5% is used to perform alkaline polishing on the p-type silicon wafer to remove surface damage. In step 2, a NaOH solution with a concentration of 3% to 5% is used to uniformly corrode the surface of the p-type silicon wafer during texturing.

[0021] The specific cleaning process in step 3 is as follows: the p-type silicon wafer is cleaned step by step using cleaning solution 1, cleaning solution 2, hydrofluoric acid, alcohol, and deionized water in sequence, wherein cleaning solution 1 is composed of NH3H2O:H2O2:deionized water in a ratio of 1:1:5; cleaning solution 2 is composed of HCl:H2O2:deionized water in a ratio of 1:1:5; the concentration of hydrofluoric acid is 3% to 6%; and the concentration of alcohol is 99.9%.

[0022] In step 4, the oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, the oxide layer plated on the front side is removed using an HF / HNO3 solution. The details are as follows:

[0023] Step 4.1, place the p-type silicon wafer in a 65% to 70% HNO3 solution for 3 to 5 minutes at a temperature of 90°C to 110°C;

[0024] Step 4.2: Plasma-enhanced chemical vapor deposition oxidation is performed on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the RF power to 5W-20W, and the duration to 250s-300s;

[0025] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:1.5 to 335:2.5 to clean the front and edge of the p-type silicon wafer for 160s to 220s.

[0026] Step 5: Using Cu(NO3)2·5H2O as the Cu source, Al(NO3)3·9H2O as the Al source, and polyvinyl alcohol (PVA) as the stabilizer, a sol-gel method is used to grow a P-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0027] Step 5.1. Prepare sol: Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a molar ratio of 1:1, then add polyvinyl alcohol (PVA) and deionized water to the mixed solution of Cu(NO3)2·5H2O and Al(NO3)3·9H2O to adjust the concentration of PVA in the solution to 0.05 mol / L to 0.15 mol / L.

[0028] Step 5.2: Stir the solution obtained in step 5.1 at 80°C to 90°C for 3 to 5 hours, and then cool to room temperature;

[0029] Step 5.3: Spin-coat the solution prepared in step 5.2 on the oxide layer at a spin-coating speed of 2500-3000 rpm for 30-45 seconds. Heat-treat the sample obtained in an air environment for 5-10 minutes at a heat treatment temperature of 300°C-400°C.

[0030] Step 5.4: After the sample obtained in step 5.3 is cooled to room temperature in air, repeat step 5.3 to control the thickness of the CuAlO2 heteroepitaxial layer;

[0031] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample obtained in step 5.4 is placed in an Ar gas environment for annealing at a temperature of 900°C to 1100°C for 4 to 6 hours.

[0032] In step 6, metallic gallium with a purity of 99.99999% is used as the gallium source, inert gas is used as the carrier gas, O2 is used as the growth source gas, and SiH4 is used as the doping source gas, as follows:

[0033] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0034] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0035] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0036] Step 6.4: Simultaneously heating the quartz boat containing the metal gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures in temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the metal gallium source in temperature zone 1 is 550° C. to 650° C.; and the operating temperature of the substrate in temperature zone 2 is 700° C. to 1050° C.;

[0037] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 in the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas to carry O2 and SiH4 into the quartz reaction tube; set the growth time to 1 to 3 hours to deposit an n-type β-Ga2O3 thin film on the substrate; Step 6.6: After the growth of the n-type β-Ga2O3 thin film is completed, close the O2 gas line and the SiH4 gas line and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0038] Step 7 uses atomic layer deposition technology ALD, with Al(CH3)3 and H2O as precursors, and the deposition temperature is 100℃~350℃; Step 8 uses plasma enhanced chemical vapor deposition technology PECVD, with SiH4 and NH3 as gas sources, the p-type silicon wafer temperature is 200℃~500℃, and the RF power is 3W~5W; Step 9 uses thermal evaporation to evaporate the Ag back electrode.

[0039] In step 10, the AlO at the top electrode position is removed by photolithography. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0040] The beneficial effect of the present invention is that the TOPCon photovoltaic cell based on the p-type silicon substrate adopts the CuAlO2 / SiO2 structure to replace the existing p-type silicon substrate. + -poly-Si / SiO x The structure utilizes the intrinsic p-type characteristics of CuAlO2 material to avoid the compound defects caused by BO, improves the passivation quality of p-TOPCon, and thus improves the cell efficiency; at the same time, the n-type β-Ga2O3 layer is used to replace the traditional n-type polysilicon layer. Its large bandgap width also makes the photovoltaic cell have a higher transmittance in the visible light range, improves the light capture ability, and thus effectively improves the conversion efficiency of the photovoltaic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1This is a schematic structural diagram of a TOPCon photovoltaic cell based on a p-type silicon substrate according to the present invention;

[0042] Figure 2 This is a flow chart of a method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate according to the present invention.

[0043] In the figure, 1. Tunneling layer, 2. p-type CuAlO2 layer, 3. Back electrode, 4. n-type β-Ga2O3 layer, 5. Passivation layer, 6. Anti-reflection layer, 7. Top electrode, 8. p-type silicon wafer. DETAILED DESCRIPTION

[0044] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] The TOPCon photovoltaic cell based on the p-type silicon substrate of the present invention has a structure as follows Figure 1 As shown, it includes a p-type silicon wafer 8, and the back side of the p-type silicon wafer 8 is provided with a tunneling layer 1, a p-type CuAlO2 layer 2, and a back electrode 3 in sequence from near to far; the front side of the p-type silicon wafer is provided with an n-type β-Ga2O3 layer 4, a passivation layer 5, and an anti-reflection layer 6 in sequence from near to far; a pair of top electrodes 7 are provided on the n-type β-Ga2O3 layer 4, and the two top electrodes 7 pass through the passivation layer 5 and the anti-reflection layer 6 in sequence and extend out of the anti-reflection layer 6.

[0046] The thickness of the p-type silicon wafer 8 is 100 μm to 200 μm, and the resistivity is 0.1 Ω·cm to 5 Ω·cm. The material of the tunneling layer 1 is one of SiO2, Al2O3 or SiC, and the thickness is 1 nm to 3 nm. The thickness of the p-type CuAlO2 layer 2 is 100 nm to 200 nm. The n-type β-Ga2O3 layer 4 is a β-Ga2O3 (-201) crystal plane, β-Ga2O3 (001) crystal plane or β-Ga2O3 (010) crystal plane material doped with one of Sn, Si and Al, and the doping concentration is 10 18 ~10 20 cm ～3 the material of the passivation layer 5 is Al2O3, with a thickness of 5nm to 20nm, and the material of the anti-reflection layer 6 is one of Si3N4 or Si2N2O, with a thickness of 60nm to 150nm.

[0047] The preparation method of TOPCon photovoltaic cells based on p-type silicon substrate is as follows: Figure 2 As shown, please follow the steps below:

[0048] Step 1: alkaline polishing of the p-type silicon wafer 8;

[0049] In step 1, a KOH solution with a concentration of 3% to 5% is used to perform alkaline polishing on the p-type silicon wafer to remove surface damage;

[0050] Step 2: Texturing the front surface of the p-type silicon wafer 8 polished in step 1 to form a surface pyramid structure;

[0051] During texturing in step 2, a NaOH solution with a concentration of 3% to 5% is used to uniformly etch the surface of the p-type silicon wafer.

[0052] Step 3: Cleaning the p-type silicon wafer obtained in step 2 and briefly immersing it in hydrofluoric acid (HF);

[0053] The specific cleaning process in step 3 is as follows: the p-type silicon wafer is cleaned step by step using cleaning solution 1, cleaning solution 2, hydrofluoric acid, alcohol, and deionized water in sequence, wherein cleaning solution 1 is composed of NH3H2O:H2O2:deionized water in a ratio of 1:1:5; cleaning solution 2 is composed of HCl:H2O2:deionized water in a ratio of 1:1:5; the concentration of hydrofluoric acid is 3% to 6%; and the concentration of alcohol is 99.9%.

[0054] Step 4: growing an oxide layer on the back side of the p-type silicon wafer 8 cleaned in step 3;

[0055] In step 4, the oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, the oxide layer plated on the front side is removed using an HF / HNO3 solution. The details are as follows:

[0056] Step 4.1, place the p-type silicon wafer in a 65% to 70% HNO3 solution for 3 to 5 minutes at a temperature of 90°C to 110°C;

[0057] Step 4.2: Use a radio frequency PECVD system to perform plasma enhanced chemical vapor deposition oxidation on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the radio frequency power to 5W to 20W, and the duration to 250s to 300s;

[0058] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:1.5 to 335:2.5 to clean the front and edge of the p-type silicon wafer for 160s to 220s.

[0059] Step 5: growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4;

[0060] Step 5: Using Cu(NO3)2·5H2O as the Cu source, Al(NO3)3·9H2O as the Al source, and polyvinyl alcohol (PVA) as the stabilizer, a sol-gel method is used to grow a P-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0061] Step 5.1. Prepare sol: Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a molar ratio of 1:1, then add polyvinyl alcohol (PVA) and deionized water to the mixed solution of Cu(NO3)2·5H2O and Al(NO3)3·9H2O to adjust the concentration of PVA in the solution to 0.05 mol / L to 0.15 mol / L.

[0062] Step 5.2: Stir the solution obtained in step 5.1 at 80°C to 90°C for 3 to 5 hours, and then cool to room temperature;

[0063] Step 5.3: Spin-coat the solution prepared in step 5.2 on the oxide layer at a spin-coating speed of 2500-3000 rpm for 30-45 seconds. Heat-treat the sample obtained in an air environment for 5-10 minutes at a heat treatment temperature of 300°C-400°C.

[0064] Step 5.4: After the sample obtained in step 5.3 is cooled to room temperature in air, repeat step 5.3 to control the thickness of the CuAlO2 heteroepitaxial layer;

[0065] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample obtained in step 5.4 is placed in an Ar gas environment for annealing at a temperature of 900°C to 1100°C for 4 to 6 hours.

[0066] Step 6: growing an n-type β-Ga2O3 heteroepitaxial layer on the front surface of the p-type silicon wafer 8;

[0067] In step 6, deposition is performed using chemical vapor deposition equipment, with metallic gallium with a purity of 99.99999% as the gallium source, an inert gas as the carrier gas, O2 as the growth source gas, and SiH4 as the doping source gas, as follows:

[0068] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0069] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0070] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0071] Step 6.4: Simultaneously heating the quartz boat containing the metal gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures in temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the metal gallium source in temperature zone 1 is 550° C. to 650° C.; and the operating temperature of the substrate in temperature zone 2 is 700° C. to 1050° C.;

[0072] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 in the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas to carry O2 and SiH4 into the quartz reaction tube; set the growth time to 1 to 3 hours to deposit an n-type β-Ga2O3 thin film on the substrate; Step 6.6: After the growth of the n-type β-Ga2O3 thin film is completed, close the O2 gas line and the SiH4 gas line and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0073] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6. x film;

[0074] Step 7 uses atomic layer deposition technology ALD, with Al(CH3)3 and H2O as precursors, and the deposition temperature is 100℃~350℃;

[0075] Step 8: AlO obtained in step 7 x SiN film deposition x film;

[0076] Step 8 uses plasma enhanced chemical vapor deposition (PECVD) technology with SiH4 and NH3 as source gases, a p-type silicon wafer temperature of 200°C to 500°C, and a radio frequency power of 3W to 5W;

[0077] Step 9: fabricating a back electrode on the p-type CuAlO2 layer obtained in step 5;

[0078] In step 9, a thermal evaporation method is used to deposit the Ag back electrode.

[0079] Step 10: SiN obtained in step 8 x A top electrode is prepared on the film, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0080] In step 10, the AlO at the top electrode position is removed by photolithography. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0081] The present invention discloses a TOPCon photovoltaic cell based on a p-type silicon substrate, which avoids the composite defects caused by BO and improves the passivation quality of p-TOPCon; at the same time, it improves the transmittance and light capture ability of the photovoltaic cell in the visible light range, thereby effectively improving the conversion efficiency of the photovoltaic cell.

[0082] Example 1

[0083] The present invention provides a method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate, which is specifically implemented according to the following steps:

[0084] Step 1: alkaline polishing is performed on the p-type silicon wafer. The alkaline polishing process is: alkaline polishing is performed on the sample using a KOH solution to remove surface saw damage.

[0085] Step 2: Texturing the front surface of the p-type silicon wafer after polishing in step 1 to form a surface pyramid structure. During texturing, NaOH solution is used to uniformly etch the surface of the p-type silicon wafer.

[0086] Step 3: Perform standard RCA cleaning on the p-type silicon wafer obtained in step 2 and briefly dip it in hydrofluoric acid (HF). The specific cleaning process is: use cleaning solution > hydrofluoric acid > alcohol > deionized water to clean the p-type silicon wafer step by step.

[0087] Step 4: After the cleaning in step 3, an oxide layer is grown on the back of the p-type silicon wafer. The oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, an HF / HNO3 solution is used to remove the oxide layer plated on the front side. The details are as follows:

[0088] Step 4.1, place the p-type silicon wafer in a 65% HNO3 solution for 3 minutes, the HNO3 solution temperature is 90°C;

[0089] Step 4.2: Use a radio frequency PECVD system to perform plasma-enhanced chemical vapor deposition oxidation on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the radio frequency power to 20 W, and the duration to 250 s;

[0090] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:1.5 and clean the front and edge of the p-type silicon wafer for 160 seconds.

[0091] Step 5: Growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4. When depositing p-type CuAlO2 on the oxide layer, Cu(NO3)2·5H2O and Al(NO3)3·9H2O are used as Cu and Al sources, and polyvinyl alcohol (PVA) is used as a stabilizer. A sol-gel method is used to grow a p-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0092] Step 5.1. Prepare the sol: Place Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a flask at a molar ratio of 1:1. Add polyvinyl alcohol (PVA) and deionized water to the flask to make the concentration of PVA in the solution 0.05 mol / L.

[0093] Step 5.2: Place the flask in a magnetic stirrer equipped with a condenser reflux device, heat in a water bath with stirring, control the water bath temperature to 80°C, control the heating time to 3 hours, and cool to room temperature after heating.

[0094] Step 5.3: Spin-coat the prepared sol on the oxide layer at a spin-coating speed of 2500 rpm for 30 seconds. After spin-coating, heat-treat the sample in air for 5 minutes at a temperature of 300°C.

[0095] Step 5.4: After the heat treatment, the sample is cooled to room temperature in air before the next spin coating and heat treatment. The thickness of the CuAlO2 heteroepitaxial layer is controlled by adjusting the number of repetitions of the above spin coating and heat treatment.

[0096] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample is placed in an Ar gas environment for annealing at a temperature of 900°C for 4 hours.

[0097] Step 6: Grow an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer. Chemical vapor deposition equipment is used to deposit the n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer, using 99.99999% pure gallium as the gallium source, inert gas as the carrier gas, O2 as the growth source gas, and SiH4 as the doping source gas, as follows:

[0098] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0099] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0100] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0101] Step 6.4: Simultaneously heating the quartz boat containing the gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures in temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the gallium source in temperature zone 1 is 550° C.; the operating temperature of the substrate in temperature zone 2 is 700° C.;

[0102] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 within the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas carrying O2 and SiH4 to enter the quartz reaction tube; set the growth time, and deposit an n-type β-Ga2O3 thin film on the substrate;

[0103] Step 6.6: After the growth of the n-type β-Ga2O3 film is completed, close the O2 gas line and the SiH4 gas line, and keep the temperature and inert gas flow rate of temperature zone 1 and temperature zone 2 unchanged for a period of time;

[0104] Step 6.7: After the holding time is over, repeat steps 5 and 6, then turn off the gas and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0105] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6 x Thin film, AlO deposited on n-type β-Ga2O3 heteroepitaxial layer x The thin film was deposited using atomic layer deposition (ALD) technology, with Al(CH3)3 and H2O as precursors and a deposition temperature of 100°C.

[0106] Step 8: AlO obtained in step 7 x SiN film deposition x Thin film, in AlO x SiN film deposition x The thin film was deposited using plasma enhanced chemical vapor deposition (PECVD) technology, with SiH4 and NH3 as source gases, the p-type silicon wafer temperature at 200°C, and the RF power at 3W.

[0107] Step 9: Make a back electrode on the p-type CuAlO2 layer obtained in step 5. When making the back electrode on the p-type CuAlO2 layer, use thermal evaporation to deposit Ag back electrode.

[0108] Step 10: SiN obtained in step 8 x The top electrode is prepared on the film to finally form the TOPCon photovoltaic cell based on the p-type silicon substrate. x When preparing the top electrode on the film, first use photolithography to open the hole, and then remove the AlO at the top electrode position through exposure and development. x and SiNx layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0109] Example 2

[0110] The present invention provides a method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate, which is specifically implemented according to the following steps:

[0111] Step 1: alkaline polishing is performed on the p-type silicon wafer. The alkaline polishing process is: alkaline polishing is performed on the sample using a KOH solution to remove surface saw damage.

[0112] Step 2: Texturing the front surface of the p-type silicon wafer after polishing in step 1 to form a surface pyramid structure. During texturing, NaOH solution is used to uniformly etch the surface of the p-type silicon wafer.

[0113] Step 3: Perform standard RCA cleaning on the p-type silicon wafer obtained in step 2 and briefly dip it in hydrofluoric acid (HF). The specific cleaning process is: use cleaning solution > hydrofluoric acid > alcohol > deionized water to clean the p-type silicon wafer step by step.

[0114] Step 4: After the cleaning in step 3, an oxide layer is grown on the back of the p-type silicon wafer. The oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, an HF / HNO3 solution is used to remove the oxide layer plated on the front side. The details are as follows:

[0115] Step 4.1, place the p-type silicon wafer in a 65% HNO3 solution for 3 minutes, the HNO3 solution temperature is 95°C;

[0116] Step 4.2: Use a radio frequency PECVD system to perform plasma-enhanced chemical vapor deposition oxidation on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the radio frequency power to 20 W, and the duration to 250 s;

[0117] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:2 and clean the front and edge of the p-type silicon wafer for 170 seconds.

[0118] Step 5: Growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4. When depositing p-type CuAlO2 on the oxide layer, Cu(NO3)2·5H2O and Al(NO3)3·9H2O are used as Cu and Al sources, and polyvinyl alcohol (PVA) is used as a stabilizer. A sol-gel method is used to grow a p-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0119] Step 5.1. Prepare the sol: Place Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a flask at a molar ratio of 1:1. Add polyvinyl alcohol (PVA) and deionized water to the flask to make the concentration of PVA in the solution 0.05 mol / L.

[0120] Step 5.2: Place the flask in a magnetic stirrer equipped with a condenser reflux device, heat in a water bath with stirring, control the water bath temperature to 85°C, control the heating time to 3.5 hours, and cool to room temperature after heating.

[0121] Step 5.3: Spin-coat the prepared sol on the oxide layer at a spin-coating speed of 2600 rpm and a spin time of 35 s. After spin-coating, heat-treat the sample in air at 350°C for 6 min.

[0122] Step 5.4: After the heat treatment, the sample is cooled to room temperature in air before the next spin coating and heat treatment. The thickness of the CuAlO2 heteroepitaxial layer is controlled by adjusting the number of repetitions of the above spin coating and heat treatment.

[0123] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample is placed in an Ar gas environment for annealing at a temperature of 950°C for 4.5 hours.

[0124] Step 6: Grow an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer. Chemical vapor deposition equipment is used to deposit the n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer, using 99.99999% pure gallium as the gallium source, inert gas as the carrier gas, O2 as the growth source gas, and SiH4 as the doping source gas, as follows:

[0125] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0126] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0127] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0128] Step 6.4: Simultaneously heating the quartz boat containing the metal gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures in temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the metal gallium source in temperature zone 1 is 550° C.; the operating temperature of the substrate in temperature zone 2 is 800° C.;

[0129] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 within the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas carrying O2 and SiH4 to enter the quartz reaction tube; set the growth time, and deposit an n-type β-Ga2O3 thin film on the substrate;

[0130] Step 6.6: After the growth of the n-type β-Ga2O3 film is completed, close the O2 gas line and the SiH4 gas line, and keep the temperature and inert gas flow rate of temperature zone 1 and temperature zone 2 unchanged for a period of time;

[0131] Step 6.7: After the holding time is over, repeat steps 5 and 6, then turn off the gas and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0132] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6 x Thin film, AlO deposited on n-type β-Ga2O3 heteroepitaxial layer x The thin film was deposited using atomic layer deposition (ALD) technology, with Al(CH3)3 and H2O as precursors and a deposition temperature of 150°C.

[0133] Step 8: AlO obtained in step 7 x SiN film deposition x Thin film, in AlO x SiN film deposition x The thin film was deposited using plasma enhanced chemical vapor deposition (PECVD) technology, with SiH4 and NH3 as source gases, the p-type silicon wafer temperature at 300°C, and the RF power at 3.5W.

[0134] Step 9: Make a back electrode on the p-type CuAlO2 layer obtained in step 5. When making the back electrode on the p-type CuAlO2 layer, use thermal evaporation to deposit Ag back electrode.

[0135] Step 10: SiN obtained in step 8 x The top electrode is prepared on the film to finally form the TOPCon photovoltaic cell based on the p-type silicon substrate. x When preparing the top electrode on the film, first use photolithography to open the hole, and then remove the AlO at the top electrode position through exposure and development. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0136] Example 3

[0137] The present invention provides a method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate, which is specifically implemented according to the following steps:

[0138] Step 1: alkaline polishing is performed on the p-type silicon wafer. The alkaline polishing process is: alkaline polishing is performed on the sample using a KOH solution to remove surface saw damage.

[0139] Step 2: Texturing the front surface of the p-type silicon wafer after polishing in step 1 to form a surface pyramid structure. During texturing, NaOH solution is used to uniformly etch the surface of the p-type silicon wafer.

[0140] Step 3: Perform standard RCA cleaning on the p-type silicon wafer obtained in step 2 and briefly dip it in hydrofluoric acid (HF). The specific cleaning process is: use cleaning solution > hydrofluoric acid > alcohol > deionized water to clean the p-type silicon wafer step by step.

[0141] Step 4: After the cleaning in step 3, an oxide layer is grown on the back of the p-type silicon wafer. The oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, an HF / HNO3 solution is used to remove the oxide layer plated on the front side. The details are as follows:

[0142] Step 4.1: Place the p-type silicon wafer in a 68% HNO3 solution for 4 minutes at a temperature of 100°C.

[0143] Step 4.2: Use a radio frequency PECVD system to perform plasma-enhanced chemical vapor deposition oxidation on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the radio frequency power to 15 W, and the duration to 270 s;

[0144] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:2 and clean the front and edge of the p-type silicon wafer for 180 seconds.

[0145] Step 5: Growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4. When depositing p-type CuAlO2 on the oxide layer, Cu(NO3)2·5H2O and Al(NO3)3·9H2O are used as Cu and Al sources, and polyvinyl alcohol (PVA) is used as a stabilizer. A sol-gel method is used to grow a p-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0146] Step 5.1. Prepare the sol: Place Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a flask at a molar ratio of 1:1. Add polyvinyl alcohol (PVA) and deionized water to the flask to make the concentration of PVA in the solution 0.1 mol / L.

[0147] Step 5.2: Place the flask in a magnetic stirrer equipped with a condenser reflux device, heat in a water bath with stirring, control the water bath temperature to 85°C, control the heating time to 4 hours, and cool to room temperature after heating.

[0148] Step 5.3: Spin-coat the prepared sol on the oxide layer at a spin-coating speed of 2800 rpm for 40 seconds. After spin-coating, heat-treat the sample in air for 8 minutes at a temperature of 400°C.

[0149] Step 5.4: After the heat treatment, the sample is cooled to room temperature in air before the next spin coating and heat treatment. The thickness of the CuAlO2 heteroepitaxial layer is controlled by adjusting the number of repetitions of the above spin coating and heat treatment.

[0150] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample is placed in an Ar gas environment for annealing at a temperature of 1000°C for 5 hours.

[0151] Step 6: Grow an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer. Chemical vapor deposition equipment is used to deposit the n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer, using 99.99999% pure gallium as the gallium source, inert gas as the carrier gas, O2 as the growth source gas, and SiH4 as the doping source gas, as follows:

[0152] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0153] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0154] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0155] Step 6.4: Simultaneously heating the quartz boat containing the metal gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures in temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the metal gallium source in temperature zone 1 is 600° C.; the operating temperature of the substrate in temperature zone 2 is 850° C.;

[0156] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 within the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas carrying O2 and SiH4 to enter the quartz reaction tube; set the growth time, and deposit an n-type β-Ga2O3 thin film on the substrate;

[0157] Step 6.6: After the growth of the n-type β-Ga2O3 film is completed, close the O2 gas line and the SiH4 gas line, and keep the temperature and inert gas flow rate of temperature zone 1 and temperature zone 2 unchanged for a period of time;

[0158] Step 6.7: After the holding time is over, repeat steps 5 and 6, then turn off the gas and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0159] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6 x Thin film, AlO deposited on n-type β-Ga2O3 heteroepitaxial layer x The thin film was deposited using atomic layer deposition (ALD) technology, with Al(CH3)3 and H2O as precursors and a deposition temperature of 200°C.

[0160] Step 8: AlO obtained in step 7 x SiN film deposition x Thin film, in AlO x SiN film deposition x The thin film was deposited using plasma enhanced chemical vapor deposition (PECVD) technology, with SiH4 and NH3 as source gases, the p-type silicon wafer temperature at 400°C, and the RF power at 4W.

[0161] Step 9: Make a back electrode on the p-type CuAlO2 layer obtained in step 5. When making the back electrode on the p-type CuAlO2 layer, use thermal evaporation to deposit Ag back electrode.

[0162] Step 10: SiN obtained in step 8 x The top electrode is prepared on the film to finally form the TOPCon photovoltaic cell based on the p-type silicon substrate. x When preparing the top electrode on the film, first use photolithography to open the hole, and then remove the AlO at the top electrode position through exposure and development. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0163] Example 4

[0164] The present invention provides a method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate, which is specifically implemented according to the following steps:

[0165] Step 1: alkaline polishing is performed on the p-type silicon wafer. The alkaline polishing process is: alkaline polishing is performed on the sample using a KOH solution to remove surface saw damage.

[0166] Step 2: Texturing the front surface of the p-type silicon wafer after polishing in step 1 to form a surface pyramid structure. During texturing, NaOH solution is used to uniformly etch the surface of the p-type silicon wafer.

[0167] Step 3: Perform standard RCA cleaning on the p-type silicon wafer obtained in step 2 and briefly dip it in hydrofluoric acid (HF). The specific cleaning process is: use cleaning solution > hydrofluoric acid > alcohol > deionized water to clean the p-type silicon wafer step by step.

[0168] Step 4: After the cleaning in step 3, an oxide layer is grown on the back of the p-type silicon wafer. The oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, an HF / HNO3 solution is used to remove the oxide layer plated on the front side. The details are as follows:

[0169] Step 4.1, place the p-type silicon wafer in a 68% HNO3 solution for 5 minutes, the HNO3 solution temperature is 105°C;

[0170] Step 4.2: Use a radio frequency PECVD system to perform plasma-enhanced chemical vapor deposition oxidation on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the radio frequency power to 10 W, and the duration to 270 s;

[0171] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:2.5 and clean the front and edge of the p-type silicon wafer for 200 seconds.

[0172] Step 5: Growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4. When depositing p-type CuAlO2 on the oxide layer, Cu(NO3)2·5H2O and Al(NO3)3·9H2O are used as Cu and Al sources, and polyvinyl alcohol (PVA) is used as a stabilizer. A sol-gel method is used to grow a p-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0173] Step 5.1. Prepare the sol: Place Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a flask at a molar ratio of 1:1. Add polyvinyl alcohol (PVA) and deionized water to the flask to make the concentration of PVA in the solution 0.15 mol / L.

[0174] Step 5.2: Place the flask in a magnetic stirrer equipped with a condenser reflux device, heat in a water bath with stirring, control the water bath temperature to 90°C, control the heating time to 4.5 hours, and cool to room temperature after heating.

[0175] Step 5.3: Spin-coat the prepared sol on the oxide layer at a spin-coating speed of 2900 rpm and a spin time of 42 s. After spin-coating, heat-treat the sample in air at 350°C for 9 min.

[0176] Step 5.4: After the heat treatment, the sample is cooled to room temperature in air before the next spin coating and heat treatment. The thickness of the CuAlO2 heteroepitaxial layer is controlled by adjusting the number of repetitions of the above spin coating and heat treatment.

[0177] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample is placed in an Ar gas environment for annealing at a temperature of 1050°C for 5.5 hours.

[0178] Step 6: Grow an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer. Chemical vapor deposition equipment is used to deposit the n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer, using 99.99999% pure gallium as the gallium source, inert gas as the carrier gas, O2 as the growth source gas, and SiH4 as the doping source gas, as follows:

[0179] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0180] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0181] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0182] Step 6.4: Simultaneously heating the quartz boat containing the gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures of temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the gallium source in temperature zone 1 is 650° C.; the operating temperature of the substrate in temperature zone 2 is 950° C.;

[0183] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 within the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas carrying O2 and SiH4 to enter the quartz reaction tube; set the growth time, and deposit an n-type β-Ga2O3 thin film on the substrate;

[0184] Step 6.6: After the growth of the n-type β-Ga2O3 film is completed, close the O2 gas line and the SiH4 gas line, and keep the temperature and inert gas flow rate of temperature zone 1 and temperature zone 2 unchanged for a period of time;

[0185] Step 6.7: After the holding time is over, repeat steps 5 and 6, then turn off the gas and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0186] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6 x Thin film, AlO deposited on n-type β-Ga2O3 heteroepitaxial layer x Atomic layer deposition (ALD) technology was used for thin films, with Al(CH3)3 and H2O as precursors and a deposition temperature of 250°C.

[0187] Step 8: AlO obtained in step 7 x SiN film deposition x Thin film, in AlO x SiN film deposition x The thin film was deposited using plasma enhanced chemical vapor deposition (PECVD) technology, with SiH4 and NH3 as source gases, the p-type silicon wafer temperature at 450°C, and the RF power at 4.5W.

[0188] Step 9: Make a back electrode on the p-type CuAlO2 layer obtained in step 5. When making the back electrode on the p-type CuAlO2 layer, use thermal evaporation to deposit Ag back electrode.

[0189] Step 10: SiN obtained in step 8 x The top electrode is prepared on the film to finally form the TOPCon photovoltaic cell based on the p-type silicon substrate. x When preparing the top electrode on the film, first use photolithography to open the hole, and then remove the AlO at the top electrode position through exposure and development. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

[0190] Example 5

[0191] The present invention provides a method for preparing a TOPCon photovoltaic cell based on CuAlO2 / SiO2 passivation, which is specifically implemented according to the following steps:

[0192] Step 1: alkaline polishing is performed on the p-type silicon wafer. The alkaline polishing process is: alkaline polishing is performed on the sample using a KOH solution to remove surface saw damage.

[0193] Step 2: Texturing the front surface of the p-type silicon wafer after polishing in step 1 to form a surface pyramid structure. During texturing, NaOH solution is used to uniformly etch the surface of the p-type silicon wafer.

[0194] Step 3: Perform standard RCA cleaning on the p-type silicon wafer obtained in step 2 and briefly dip it in hydrofluoric acid (HF). The specific cleaning process is: use cleaning solution > hydrofluoric acid > alcohol > deionized water to clean the p-type silicon wafer step by step.

[0195] Step 4: After the cleaning in step 3, an oxide layer is grown on the back of the p-type silicon wafer. The oxide layer is grown using a step-by-step oxidation method. That is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method. Finally, an HF / HNO3 solution is used to remove the oxide layer plated on the front side. The details are as follows:

[0196] Step 4.1, place the p-type silicon wafer in a 70% HNO3 solution for 5 minutes, the HNO3 solution temperature is 110°C;

[0197] Step 4.2: Use a radio frequency PECVD system to perform plasma enhanced chemical vapor deposition oxidation on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the radio frequency power to 5 W, and the duration to 300 s;

[0198] Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:2.5 and clean the front and edge of the p-type silicon wafer for 220 seconds.

[0199] Step 5: Growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4. When depositing p-type CuAlO2 on the oxide layer, Cu(NO3)2·5H2O and Al(NO3)3·9H2O are used as Cu and Al sources, and polyvinyl alcohol (PVA) is used as a stabilizer. A sol-gel method is used to grow a p-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer, as follows:

[0200] Step 5.1. Prepare the sol: Place Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a flask at a molar ratio of 1:1. Add polyvinyl alcohol (PVA) and deionized water to the flask to make the concentration of PVA in the solution 0.15 mol / L.

[0201] Step 5.2: Place the flask in a magnetic stirrer equipped with a condenser reflux device, heat in a water bath with stirring, control the water bath temperature to 90°C, control the heating time to 5 hours, and cool to room temperature after heating.

[0202] Step 5.3: Spin-coat the prepared sol on the oxide layer at a spin-coating speed of 3000 rpm for 45 s. After spin-coating, heat-treat the sample in air for 10 min at a temperature of 400°C.

[0203] Step 5.4: After the heat treatment, the sample is cooled to room temperature in air before the next spin coating and heat treatment. The thickness of the CuAlO2 heteroepitaxial layer is controlled by adjusting the number of repetitions of the above spin coating and heat treatment.

[0204] Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample is placed in an Ar gas environment for annealing at a temperature of 1100°C for 6 hours.

[0205] Step 6: Grow an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer. Chemical vapor deposition equipment is used to deposit the n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer, using 99.99999% pure gallium as the gallium source, inert gas as the carrier gas, O2 as the growth source gas, and SiH4 as the doping source gas, as follows:

[0206] Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace;

[0207] Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa.

[0208] Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber;

[0209] Step 6.4: Simultaneously heating the quartz boat containing the gallium metal source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures of temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the gallium metal source in temperature zone 1 is 650° C.; the operating temperature of the substrate in temperature zone 2 is 1050° C.;

[0210] Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 within the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas carrying O2 and SiH4 to enter the quartz reaction tube; set the growth time, and deposit an n-type β-Ga2O3 thin film on the substrate;

[0211] Step 6.6: After the growth of the n-type β-Ga2O3 film is completed, close the O2 gas line and the SiH4 gas line, and keep the temperature and inert gas flow rate of temperature zone 1 and temperature zone 2 unchanged for a period of time;

[0212] Step 6.7: After the holding time is over, repeat steps 5 and 6, then turn off the gas and cool down to complete the preparation of the n-type β-Ga2O3 thin film.

[0213] Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6 x Thin film, AlO deposited on n-type β-Ga2O3 heteroepitaxial layer x The thin film was deposited using atomic layer deposition (ALD) technology, with Al(CH3)3 and H2O as precursors and a deposition temperature of 350°C.

[0214] Step 8: AlO obtained in step 7 x SiN film deposition x Thin film, in AlO x SiN film deposition x The thin film was deposited using plasma enhanced chemical vapor deposition (PECVD) technology, with SiH4 and NH3 as source gases, the p-type silicon wafer temperature at 500°C, and the RF power at 5W.

[0215] Step 9: Make a back electrode on the p-type CuAlO2 layer obtained in step 5. When making the back electrode on the p-type CuAlO2 layer, use thermal evaporation to deposit Ag back electrode.

[0216] Step 10: SiN obtained in step 8 x The top electrode is prepared on the film to finally form the TOPCon photovoltaic cell based on the p-type silicon substrate. x When preparing the top electrode on the film, first use photolithography to open the hole, and then remove the AlO at the top electrode position through exposure and development. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

Claims

1. TOPCon photovoltaic cells based on p-type silicon substrates, characterized in that: The invention comprises a p-type silicon wafer (8), wherein a tunneling layer (1), a p-type CuAlO2 layer (2), and a back electrode (3) are sequentially provided on the back of the p-type silicon wafer (8) from near to far; an n-type β-Ga2O3 layer (4), a passivation layer (5), and an anti-reflection layer (6) are sequentially provided on the front of the p-type silicon wafer from near to far; a pair of top electrodes (7) are provided on the n-type β-Ga2O3 layer (4), and the two top electrodes (7) sequentially penetrate the passivation layer (5) and the anti-reflection layer (6) and extend out of the anti-reflection layer ( 6) Externally, the p-type silicon wafer (8) has a thickness of 100 μm to 200 μm and a resistivity of 0.1 Ω·cm to 5 Ω·cm. The tunneling layer (1) is made of one of SiO2, Al2O3 or SiC, and has a thickness of 1 nm to 3 nm. The p-type CuAlO2 layer (2) has a thickness of 100 nm to 200 nm. The n-type β-Ga2O3 layer (4) is made of a β-Ga2O3 (-201) crystal plane, a β-Ga2O3 (001) crystal plane or a β-Ga2O3 (010) crystal plane material doped with one of Sn, Si or Al, and has a doping concentration of 10 18 ~10 20 cm ~3 , with a thickness of 50nm~200nm; the material of the passivation layer (5) is Al2O3, with a thickness of 5nm~20nm; the material of the anti-reflection layer (6) is one of Si3N4 or Si2N2O, with a thickness of 60nm~150nm.

2. A method for preparing a TOPCon photovoltaic cell based on a p-type silicon substrate, characterized in that: Please follow the steps below to implement: Step 1, performing alkaline polishing on the p-type silicon wafer (8); Step 2, texturing the front surface of the p-type silicon wafer (8) polished in step 1 to form a surface pyramid structure; Step 3: Cleaning the p-type silicon wafer obtained in step 2 and briefly immersing it in hydrofluoric acid (HF); Step 4, growing an oxide layer on the back side of the p-type silicon wafer (8) cleaned in step 3; Step 5: growing a p-type CuAlO2 epitaxial layer on the oxide layer obtained in step 4; Step 6, growing an n-type β-Ga2O3 heteroepitaxial layer on the front side of the p-type silicon wafer (8); Step 7: Deposit AlO on the n-type β-Ga2O3 heteroepitaxial layer obtained in step 6. x film; Step 8: AlO obtained in step 7 x SiN film deposition x film; Step 9: fabricating a back electrode on the p-type CuAlO2 layer obtained in step 5; Step 10: SiN obtained in step 8 x preparing a top electrode on the film, and finally forming the TOPCon photovoltaic cell based on the p-type silicon substrate; In step 1, a KOH solution with a concentration of 3% to 5% is used to perform alkaline polishing on the p-type silicon wafer to remove surface damage, and in step 2, a NaOH solution with a concentration of 3% to 5% is used to uniformly corrode the surface of the p-type silicon wafer during texturing; The cleaning process in step 3 is as follows: cleaning the p-type silicon wafer step by step using cleaning solution 1, cleaning solution 2, hydrofluoric acid, alcohol, and deionized water in sequence, wherein cleaning solution 1 is composed of NH3H2O:H2O2:deionized water in a ratio of 1:1:5; cleaning solution 2 is composed of HCl:H2O2:deionized water in a ratio of 1:1:5; the concentration of hydrofluoric acid is 3% to 6%; the concentration of alcohol is 99.9%; In step 4, the oxide layer is grown using a step-by-step oxidation method, that is, the back of the p-type silicon wafer is first oxidized using a thermal nitric acid oxidation method, and then the back of the p-type silicon wafer is oxidized again using a PECVD-N2O method, and then the oxide layer plated on the front side is removed using an HF / HNO3 solution, as follows: Step 4.1: Place the p-type silicon wafer in a 65% to 70% HNO3 solution for 3 to 5 minutes at a temperature of 90°C to 110°C. Step 4.2: Plasma-enhanced chemical vapor deposition (PECVD) oxidation is performed on the back side of the p-type silicon wafer, using 99.999% pure N2O as the gas source, controlling the RF power to 5W-20W, and the duration to 250s-300s. Step 4.3: Prepare an HNO3:HF solution with a volume ratio of 335:1.5 to 335:2.5 to clean the front and edge of the p-type silicon wafer for 160s to 220s. In step 5, Cu(NO3)2·5H2O is used as a Cu source, Al(NO3)3·9H2O is used as an Al source, and polyvinyl alcohol (PVA) is used as a stabilizer. A sol-gel method is used to grow a P-type crystalline CuAlO2 heteroepitaxial layer on the oxide layer. The details are as follows: Step 5.

1. Prepare the sol: Cu(NO3)2·5H2O and Al(NO3)3·9H2O in a molar ratio of 1:

1. Then, add polyvinyl alcohol (PVA) and deionized water to the mixed solution of Cu(NO3)2·5H2O and Al(NO3)3·9H2O to adjust the concentration of PVA in the solution to 0.05 mol / L–0.15 mol / L. Step 5.2: Stir the solution obtained in step 5.1 at 80°C to 90°C for 3 to 5 hours, and then cool to room temperature; Step 5.3: Spin-coat the solution prepared in step 5.2 on the oxide layer at a spin-coating speed of 2500-3000 rpm for 30-45 s. Heat-treat the sample obtained in an air environment for 5-10 min at a heat treatment temperature of 300°C-400°C. Step 5.4: After the sample obtained in step 5.3 is cooled to room temperature in air, repeat step 5.3 to control the thickness of the CuAlO2 heteroepitaxial layer; Step 5.5: After the CuAlO2 heteroepitaxial layer is grown, the sample obtained in step 5.4 is placed in an Ar gas environment for annealing at a temperature of 900°C to 1100°C for 4 to 6 hours. In step 6, metallic gallium with a purity of 99.99999% is used as the gallium source, inert gas is used as the carrier gas, O2 is used as the growth source gas, and SiH4 is used as the doping source gas, as follows: Step 6.1, placing a metal gallium source into a quartz boat, and placing the quartz boat into temperature zone 1 of a dual-temperature zone quartz tube furnace; Place the p-type silicon wafer obtained in step 6.2 and step 5 on a substrate holder as a substrate, and place the substrate holder with the substrate into temperature zone 2 of a quartz tube furnace; evacuate the reaction chamber to a pressure of 1 Pa. Step 6.3, introducing an inert gas as a carrier gas into the quartz reaction chamber; Step 6.4: Simultaneously heating the quartz boat containing the gallium source in temperature zone 1 and the substrate in temperature zone 2 in the tube furnace; setting the heating time so that the operating temperatures in temperature zone 1 and temperature zone 2 reach the corresponding set temperatures simultaneously. The operating temperature of the gallium source in temperature zone 1 is 550° C. to 650° C.; and the operating temperature of the substrate in temperature zone 2 is 700° C. to 1050° C.; Step 6.5: When the operating temperature of the reaction boat in temperature zone 1 and the operating temperature of the substrate in temperature zone 2 within the quartz tube reach the set temperature, open the O2 gas line and the SiH4 gas line to allow the inert gas carrying the O2 and SiH4 to enter the quartz reaction tube; set the growth time to 1 to 3 hours, and deposit an n-type β-Ga2O3 thin film on the substrate; Step 6.6: After the growth of the n-type β-Ga2O3 thin film is completed, close the O2 gas line and the SiH4 gas line and cool the temperature to complete the preparation of the n-type β-Ga2O3 thin film; Step 7 uses atomic layer deposition technology ALD, with Al(CH3)3 and H2O as precursors, and a deposition temperature of 100°C to 350°C; Step 8 uses plasma enhanced chemical vapor deposition technology PECVD, with SiH4 and NH3 as gas sources, a p-type silicon wafer temperature of 200°C to 500°C, and a radio frequency power of 3W to 5W; Step 9 uses thermal evaporation to deposit the Ag back electrode; In step 10, the AlO at the top electrode position is firstly removed by photolithography and then exposure and development. x and SiN x layer, and then an electron beam evaporation coating machine is used to evaporate the Ti / Pd / Ag stacked layer top electrode, and finally the TOPCon photovoltaic cell based on the p-type silicon substrate is formed.

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