Exciton Character and High‐Performance Stimulated Emission of Hybrid Lead Bromide Perovskite Polycrystalline Film

Abstract Electronic states of hybrid perovskites enable their exceptional optoelectronic applications. Herein, through heterojunction enhanced exciton dissociation and global tracing of multiple radiative electronic states across wide temperature regions, it has been found that excitons while not free carriers dominate the bandedge photoelectric properties of hybrid lead bromide perovskite (MAPbBr 3 ). MAPbBr 3 has exhibited two types of excitons with giant binding energies and superior phase stability. A bound exciton (BE) has been clearly confirmed according to a saturated photo‐induced bleaching behavior and a correlation of the exciton to the perovskite deep trap state. By stabilizing the excitonic phase of polycrystalline MAPbBr 3 , impressively low‐threshold and high‐gain stimulated emission from the BE has been realized at room temperature. Overall, this work provides new insight into the photophysics characteristics of the hybrid perovskite and more importantly brings huge opportunities for exploiting perovskite excitonic mechanism to realize more abundant optoelectronic applications.