Layer-Number-Dependent Exciton Recombination Behaviors of MoS₂ Determined by Fluorescence-Lifetime Imaging Microscopy

Abstract

The fluorescence-lifetime imaging microscopy (FLIM) technique is utilized to probe the photoluminescence properties of individual MoS2 flakes. This measurement allows identification of the layer number of the flakes: two fluorescence decay lifetimes (τ1 and τ2) exhibit linear relationships with the layer number. Our investigation of the fluorescence lifetime reveals exciton dynamics in monolayer and multilayers MoS2. We find the distinct difference on the decay rates between A exciton (fast) and B exciton (slow). K′/Γ emission has different decay behaviors with respect to the layer number (N) because of its variable energy in monolayer and multilayer samples. The interplay of these transition channels also plays an important impact on the overall decay. Our results demonstrate that FLIM is an effective measurement for studying the luminescence properties of transition metal dichalcogenides.