Stabilizing Black-Phase CsPbI3 Perovskite Thin Films via Bending Strain (2026)

CsPbI3 perovskites have complex short-/long-range order defining their complex polymorphism; however, they are unstable under ambient conditions, transforming rapidly to a non-perovskite phase, hindering optoelectronic applications. This calls for novel approaches to engineer strain and regulate the phase properties. Here we use flexible polymer substrates to impose bending strain (via custom sample moulds), which empirically improves the phase stability and provides a powerful platform for basic research. This proposal aims to elucidate the (micro)structural changes under different bending/strain profiles using GIWAXS and develop physical models to rationalize their phase stabilising effects.