TiO2 modification with multi-acid treatment for efficient interfacial perovskite-TiO2 electron transport

•A simple and practical way to passivate the surface defects of TiO2 was reported.•Modified TiO2 is beneficial for the crystallization and growth of perovskite film.•Modified TiO2 can facilitate the electron extraction and inhibit the charge recombination at the perovskite-TiO2 interface.•A high PCE of 20.27% has been achieved, along with negligible hysteresis, improved device reproducibility and stability.