Regulation of Amplified Spontaneous Emission Dynamics in Quasi-Two-Dimensional Perovskites via the Energy-Funneling Effect

Quasi-two-dimensional perovskites with mixed-phase multiple-quantum-well distributions are promising gain media for amplified spontaneous emission (ASE), but the regulatory role of phase distribution in ASE behavior remains unclear. Here, quasi-two-dimensional (BA)2(MA)n−1PbnBr3n+1 films with different phase distributions were investigated using steady-state optical spectroscopy, femtosecond Kerr-gated time-resolved ASE measurements, and transient absorption spectroscopy. Compared with large-n-dominated films, those with a more balanced phase distribution exhibit a lower ASE threshold, smaller emission-peak shift, and weaker line width broadening. Time-resolved ASE and transient absorption analyses further indicate that small-n phases buffer photoexcited carriers and delay their transfer into large-n emissive phases, thereby moderating carrier accumulation in the emissive phase and yielding a more stable emission wavelength and narrower line width. These findings clarify how phase distribution regulates ASE through carrier buffering and redistribution, demonstrating phase engineering as an effective strategy for stable perovskite gain media.