Dual-Passivation Strategy for Improved Ambient Stability of Perovskite Solar Cells

Dual-passivation of MAPbI3-based perovskite using p-toluenesulfonic acid (PTSA) in the bulk and hydrophobic polystyrene (PS) at the surface significantly diminishes the trap-density and improves the device performances substantially. The sulfonic acid functional group of PTSA interacts with the defects in perovskite and passivates the trap-states, while PS repairs the surface defects and increases the moisture resistance of perovskites. Thus, improvement in perovskite crystallinity and formation of larger grain size occurs because of dual-passivation, thereby enhancing the power conversion efficiency (PCE) to 20.62% from 15.14% of the device without passivation. Notably, the large-area dual-passivated device also displays a PCE of ∼18.5%. The modified device (PTSA2PS2) showcases reduced hysteresis and a steady-state output of >20%. The PTSA2PS2-based devices exhibit higher photogenerated charges, lower charge recombination, reduced trap-density, and better charge transport than the control devices. The modified device retains 93% of the original PCE after 1000 h under ambient condition.