Hindered Phase Transition Kinetics of α‐CsPbI₃ by External Tension

Recently, all‐inorganic perovskite solar cells have attracted a large amount of attention, due to the much better water resistance compared to the organic counterparts. Unfortunately, the undesired phase transition remains a significant challenge, despite the many attempts. An important step forward is made here by numerical simulation, which discovers the significance of external strain to the stability of desired α‐CsPbI₃, whose lifetime can be extended up to three times by nonhydrostatic tension, as is verified by both modeling and experimental results. In addition, such lifetime can be even enhanced further by hydrostatic tension, as indicated by the simulation. The unexpected observation provides not only an effective method to extend the lifetime of the perovskite devices, but also opens an unexpected path for the wide research community to utilize the straining engineering method that is extensively investigated in the perovskite research.