Enhancing the Hot Carrier Injection of Perovskite Solar Cells by Incorporating a Molecular Dipole Interlayer

Surface passivation engineering of perovskite films via organic functional small molecules has emerged as an effective strategy for improving the efficiency and stability of perovskite solar cells (PSCs). However, a systematic understanding of underlying mechanisms behind these improvements is still missing. In this work, two new naphthalimide-based organic small molecules (PX, X = F, I) are designed and employed to efficiently passivate the surface defects of perovskite films in PSCs. Consequently, superior photovoltaic properties for PI-treated PSCs are achieved with a power conversion efficiency of 23.06%, which is significantly higher than that of the reference device without passivators (20.45%). Theoretical calculations reveal that PX can give rise to interfacial electrical dipole. It is found that incorporating a dipole interlayer between perovskite layer and hole transport layer can enhance ultrafast charge-carrier injection and suppress the charge-carrier recombination in device, which is illustrated by transient absorption spectroscopy. These present results can provide valuable information on the understanding interfacial charge-carrier dynamics in PSCs to further improve the device performance.