Ultrafast and Low Threshold Quasi-2D/3D Perovskite Wrap-Around Heterostructure Microlasers

Quasi-2D/3D perovskite heterostructures have shown great promise for both light-harvesting and light-emitting applications for their attractive properties, including high humidity stability, effective defect passivation, enhanced carrier/exciton transport, and efficient energy funneling from quasi-2D perovskite quantum wells to 3D bulk crystals. In previous studies, quasi-2D/3D heterostructures were typically fabricated using a two-step method. Here, for the first time, we report an innovative perovskite microcavity with a quasi-2D/3D wrap-around heterostructure prepared via a one-step method, consisting of (BA)2Csn–1PbnBr3n+1 quasi-2D films and 3D bulk. The microcavity exhibits an ultralow lasing threshold of 2.12 μJ/cm2, which is attributed to significantly enhanced carrier/exciton injection enabled by rapid energy funneling across the wrap-around heterojunction interfaces. Notably, this heterostructure can markedly reduce both the delay time and pulse width of the laser emission, thereby further expands its potential applications in ultrafast optical switches and flip-flops. The origin of these ultrafast characteristics is elucidated by a proposed carrier/exciton dynamics model, which is further validated unambiguously by rate-equation simulations. This work provides a comprehensive understanding of the fundamental carrier/exciton dynamics and the unique photophysical kinetics involved in the lasing process of perovskite wrap-around heterojunction microcavities and is expected to advance their technological potential in integrated photonics.