The invention discloses a gradient annealing-based TOPCon
solar cell and a preparation method thereof, and relates to the technical field of
cell production, and the method comprises the steps: carrying out a three-stage gradient annealing process on a
silicon-based substrate on which a tunneling
oxide layer is formed, and comprises the steps: heating the
silicon-based substrate to 400-450 DEG C in a mixed
atmosphere of H2 and N2, and filling dangling bonds in the tunneling
oxide layer; heating the
silicon-based substrate to 600-650 DEG C by adopting a pulse heating mode, and switching the
atmosphere into a mixed
atmosphere of O2 and N2 to form a SiOxNy transition region; and cooling the silicon-based substrate to 300-350 DEG C, putting the silicon-based substrate into
plasma equipment, treating the silicon-based substrate in a mixed atmosphere of H2 and Ar for 3 minutes, and exciting
hydrogen free radicals to permeate into the interface to repair the interface defects. According to the method, low-temperature
hydrogen annealing is set, H atoms are promoted to diffuse to a SiO2 / Si interface in a low-temperature area, dangling bonds are repaired, Si-O bond rearrangement is induced in a medium-temperature area, a compact tunneling layer is formed, then
hydrogen free radicals are excited to permeate to the interface and interface defects are repaired through the
plasma treatment step, the minority
carrier lifetime is prolonged, and the
photoelectric conversion rate is improved.