Molecular Engineering in Perovskite Solar Cells: A Computational Study on 2‐Mercaptopyridine Derivatives as Surface Passivators against Water

Abstract Contemporary perovskite solar cells (PSCs) have drawn substantial interest due to their high photovoltaic efficiency. However, the instability of perovskite in a humid environment restricts the service time extension and limits the large‐scale application of PSCs. Herein, a series of passivation molecules (PMs), 2‐MEP, 2‐MDEP, 2‐MTEP, and 2‐MQEP, featuring different lengths of alkyl chains have been designed based on 2‐mercaptopyridine (2‐MP) which greatly improve the stability of PSCs in the humid environment. First‐principles calculations demonstrate that the designed molecules offer stronger adsorption on the perovskite surface compared with 2‐MP. The charge density difference and Bader charge analysis show that the newly designed Lewis bases improve the charge transfer ability, leading to effective separation of carriers at PM@MAPbI 3 interfaces. Furthermore, molecular dynamics simulations verify that the steady Pb‐N/S interactions in the MAPbI 3 /PM/H 2 O system effectively prevent H 2 O from approaching the perovskite surface. This work not only provides a set of promising surface passivators (especially 2‐MDEP), but also paves a way for the design of PMs that endow PSCs stability and make PSCs highly competitive in the photovoltaic market.