Simultaneous improvement to performance and stability of perovskite solar cells through incorporation of imidazolium-based ionic liquid

Despite the meteoric rise of perovskite solar cell (PSC) efficiency in recent years, commercialization of this technology is still limited by issues pertaining to perovskite instability. Herein, a novel ionic liquid (IL) – 1-ethyl-3-methylimidazolium chloride (EMIC) additive is shown to be beneficial in enhancing perovskite's ambient and operational stability. Not only does it improve crystallinity and smoothen surface topography, but the simultaneous increase in carrier lifetimes, reduction in defect density as well as improvement to interfacial band energy alignment have contributed extensively towards promoting higher power conversion efficiency (PCE) and moisture/thermal stability of the EMIC-based PCSs. The champion, unencapsulated EMIC-based PSC yields a PCE of 20.15% and retains 89% of its initial PCE after 1440 h of storage under ambient conditions (30% Relative humidity (RH), 25 °C) and retains 65% of its initial PCE after 600 h of thermal aging (85 °C, 10% RH).