Light‐Ferroic Interaction in Hybrid Organic–Inorganic Perovskites

Abstract Given the remarkable performance of hybrid organic–inorganic perovskites (HOIPs) in solar cells, light emitters, and photodetectors, the quest to advance the fundamental understanding of the photophysical properties in this class of materials remains highly relevant. Recently, the discovery of ferroic twin domains in HOIPs has renewed the debate of the ferroic effects on optoelectric processes. This work explores the interaction between light and ferroic twin domains in CH₃NH₃PbI₃. Due to strain and chemical inhomogeneities, photogenerated electrons and holes show a preferential motion in the ferroelastic twin domains. Density functional theory (DFT) shows that electrons and holes result in lattice expansion in CH₃NH₃PbI₃ differently. Hence, light generates strain in the ferroelastic domains due to preferential photocarrier motion, leading to a screening of strain variation. X‐ray diffraction studies verify the DFT simulations and reveal that the photoinduced strain is light intensity dependent, and the photoexcitation is a prerequisite of inducing strain by light. This work extends the fundamental understanding of light‐ferroic interaction and offers guidance for developing functional devices.