Diagonal binding prevails over edge anchoring for surface passivation of perovskite solar cells: A theoretical study

Surface passivation is widely regarded as an effective approach to boost the efficiency and stability of perovskite solar cells (PSCs). The key to surface passivation lies in understanding the structure–activity relationship of the passivation molecules. Herein, based on density functional theory (DFT) calculations and ab initio molecular dynamics simulations (AIMD), we investigated the effects of molecular anchoring orientation on perovskite surface passivation. The results indicated that anchoring along the diagonal of the lattice (diagonal binding) prevails over binding along the edges (edge anchoring) for surface passivation. Diagonal anchoring demonstrates significantly stronger interaction with the perovskite lattice than edge anchoring, and it increases lattice toughness and flexibility, manifested by greater elasticity in both bond lengths and bond angles. Moreover, diagonal anchoring induces four times the interface charge transfer of edge anchoring. Diagonal anchoring is also more effective in blocking the penetration of water molecules and reducing atomic fluctuations, enhancing moisture tolerance, primarily due to its larger surface coverage area and stronger interaction with perovskite. The elucidated mechanism would inspire the rational design of passivation molecules for high-efficiency photoelectric devices.