Passivation improvement of nitric acid oxide by ozone post-treatment for tunnel oxide passivated contacts silicon solar cells

We demonstrate the passivation improvement of tunnel oxide formed by nitric acid oxidation and followed by ozone post-treatment. A tunnel oxide passivated contacts (TOPCon) structure was fabricated through polysilicon crystallization using POCl3 diffusion on a wet-chemical oxide that was grown by nitric acid solution and underwent ozone post-treatment. To improve the quality of nitric acid oxide used as a tunnel oxide of TOPCon, ozone post-treatment was performed at 400 °C. Ozone post-treatment of wet-chemical oxide improved the passivation performance owing to the reduction of sub-oxide in silicon oxide. Excellent passivation was achieved for the n-type passivated contacts with implied open-circuit voltage of 740 mV after crystallization of amorphous silicon using POCl3 diffusion at 875 °C.