The Polymer Society of Korea

Abstract

Metal halide perovskites provide exceptional optical gain and have been widely studied as lasing media. Realizing an electrically pumped perovskite laser—the key step toward practical devices—remains the field’s central objective. Here, we reduce the amplified spontaneous emission (ASE) threshold in solution-processed FAPbBr₃ thin films using methylammonium chloride (MACl) as a morphology-control additive. MACl-mediated microstructure optimization suppresses pinholes/roughness and associated scattering and non-radiative losses. Importantly, threshold reduction alone does not reveal the underlying gain-relevant photophysics at lasing-level carrier densities. We therefore perform pump–probe transient absorption measurements under high-density excitation to track carrier/exciton formation and ultrafast relaxation pathways.