Small Molecules with Controllable Molecular Weights Passivate Surface Defects in Air‐Stable p‐i‐n Perovskite Solar Cells

Abstract

AbstractThe passivation of surface defects at the interfaces and grain boundaries of perovskites has great potential to improve the optoelectronic properties of related devices. In this study, the small molecules LG0.5, LG1.5, and LG2.5—having precise and controllable molecular weights (various generations synthesized through click reactions) and featuring urethane, urea, and malonamide functionalities—are synthesized, and their ability to passivate the defects of perovskites are evaluated. X‐ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and time‐resolved photoluminescence spectroscopy are used to observe the interactions between the perovskites and these molecules. The embedding of LG0.5 promotes the growth of large‐grain perovskite crystals, leading to increases in the intensities of the UV–vis absorption and photoluminescence spectral signals of the perovskite as well as longer carrier lifetimes. A power conversion efficiency of almost 20% for a p‐i‐n perovskite solar cell having the layer structure indium tin oxide/NiOx/CH3NH3PbI3 (with LG0.5)/[6,6]‐phenyl C61 butyric acid methyl ester/bathocuproine/Ag is observed. This device (without encapsulation) exhibits excellent air‐stability, retaining 89.8% of its initial performance after storage in an ambient environment (25 °C, 40% humidity) for over 120 d.