Passivation of Perovskite Solar Cells with Natural Flavors: Roles of Hydrogen Bonding in Ion Migration and Moisture Resistance.

The passivation strategy is considered to be an essential approach for enhancing the efficiency and stability of perovskite solar cells (PSCs). Herein, based on density functional theory calculations and ab initio molecular dynamics simulations, we investigated the ion migration and moisture stability for MAPbI passivated with a Lewis base represented by natural molecules: cinnamaldehyde (CA) and anethole (AT). The results reveal that hydrogen bonding in different forms plays a significant role in both ion migration and moisture stability for surface passivation. The passivation inhibits ion migration by enhancing intrinsic hydrogen bonding through space compression effect, leading to a boosted activation barrier and a reduced rate by up to 3-10 orders of magnitude. Passivations prevent in-depth water infiltration and diminish the disturbance of the lattice by water. In addition to the familiar water-shielding behavior, the water-locking effect induced by the intermolecular hydrogen bonding chains was observed. The experimental results of durable water stability and alleviated hysteresis for passivated PSCs fully confirmed the theoretical study. The established mechanism provides valuable guidance to deal with troublesome ion migration and moisture resistance in stable and efficient PSCs.