Impact of Nano‐Scale Defects on the Macroscopic Amplified Spontaneous Emission in Polycrystalline Perovskite Thin‐Films

Perovskite thin film-based laser diodes have emerged as promising candidates for on-chip laser sources. However, despite the successful demonstration of optically pumped lasing, the realization of electrically pumped perovskite laser has proved to be quite challenging. Here, we investigated the optical gain mechanism in polycrystalline perovskite thin film by mapping the spatial distributions of amplified spontaneous emission within the heterogeneous thin film and its spatial correlation with the local electronic properties. We discovered that optical gain within these polycrystalline perovskite thin films occurs primarily at defective sites, where despite the low photoluminescence efficiency demonstrated high optical gain efficiency, lower treshold and long photocarrier lifetime. Our findings highlight the importance of defects in the development of electrically pumped laser diodes.