Efficient passivation on halide perovskite by tailoring the organic molecular functional groups: First-principles investigation

Organic molecules with various functional groups have been implemented to engineer the surface and grain boundary of perovskite, and improve the efficiency and stability of perovskite solar cells (PSCs). However, there is a lack of systematic comparison and comprehensive understanding about the intrinsic effect of various functional groups on the perovskite surface. Herein, we investigate the effect of molecular layer adsorption of eight different organic molecules on the structural and electronic properties of CH3CH2PbI3 via first-principles methods. Our results show that the pyridine is the most effective passivation molecule which not only has the most anchoring ability, but also can mostly decrease the electron-hole interaction. And the carboxyl group can form hydrogen bond with the iodine on perovskite surface and suppress the migration of iodine consequently. Moreover, deriving from molecular adsorption, the work function of perovskite surface has undergone dramatic changes, mainly due to the contributions of the interfacial charge transfer and the intrinsic dipole moment of molecules. Based on molecular engineering method, we also decouple the para-substituted functional groups from the anchor group and emphasize the importance of it. This work provides a theoretical guidance for the selection and design of organic passivation molecules.