Quasi-quantum dot-induced stabilization of α-CsPbI3 perovskite for high-efficiency solar cells

Abstract

All-inorganic cesium lead iodide perovskites (CsPbI₃) are promising materials for efficient solar cells. However, they suffer from the formation of an undesired yellow δ-phase under ambient conditions. Herein, we provide a novel strategy to in situ prepare quasi-quantum dot (QQD) CsPbI₃ films by using a new ligand, adamantan-1-yl methanammonium (AMDA), with ultralow contents (∼0.25 wt%) in the perovskite films. Strong interaction and charge coupling between the ligands and nanocrystals significantly increase the surface Gibbs energy of CsPbI₃ and suppresses the grain sizes to around 30 nm, which effectively protects the black α-phase from the destruction of moisture and heat. By reducing the trap density of states in the QQD CsPbI₃ films, the all-inorganic PSCs exhibit a power conversion efficiency of 13.5%. Most importantly, the QQD CsPbI₃ films can substantially maintain an α-phase and the QQD-based PSCs retain 90% of their initial efficiency after storage either under ambient conditions for 30 days or 85 °C heating for 336 h. These results indicate that in situ prepared QQD films are a potential strategy to effectively improve the long-term stability of all inorganic perovskite materials.