Micro/Nano‐Structures Mediated Tunable Amplified Spontaneous Emission in Reduced‐Dimensional Tin‐Perovskites at Room Temperature

Large organic cations in reduced‐dimensional perovskites (RDPs) can form quantum wells and block moisture and oxygen, improving the efficiency and stability of perovskite emitters. However, the strong Auger recombination in RDPs, especially 2D perovskite, raises the lasing threshold and presents a significant challenge for the realization of amplified spontaneous emission (ASE) at room temperature. In this study, PEA 2 SnI 4 perovskite nanosheets with varying sizes, stacking structures, and morphologies were successfully designed. A systematic investigation of their excited‐state processes was conducted, establishing an optimization strategy centered on size/structure‐dependent Auger recombination and regional‐induced excitons recombination. This approach led to the achievement of low‐threshold room‐temperature ASE. Furthermore, by specific nano‐structure design, abnormal <n> value dependent Auger recombination strength was observed in PEA 2 FA n‐1 Sn n I 3n+1 series with the lowering of threshold. It clarifies the decade‐long controversy that the four‐level structure, but not Auger recombination, plays a key role on the decrease of lasing threshold as n value increases in some cases. It enables the broadband tunable ASE from the visible to the near‐infrared region. This work addresses the long‐standing problem of achieving low‐threshold, room‐temperature ASE in RDPs. It will not only promote the development of RDP lasers, but also LEDs.