Coordination Modulated Passivation for Stable Organic-Inorganic Perovskite Solar Cells

•To minimize surface defects and prevent ion migration, a passivation material with a greater binding energy is required.•Greater binding with the perovskite layer is achieved after post-passivation using octylammonium sulfonate salt, which lowers the hysteresis index to 0.01.•The passivation increases power conversion efficiency from 21.06% for the control to 24.37% for the devices treated with OAC.•The passivated perovskite films maintain more than 85% of their original PCE under 60% RH over 1600 h.