Trapped carrier hopping and unusual bottleneck in coalescence dynamics of MoS2 few layers

Abstract

Unravelling the qualitative descriptions of ultrafast energy relaxation dynamics in transition metal dichalcogenides (TMDCs) is very important for the fundamental understanding of the nature of photoexcited carriers. Herein, we discuss the temporal evolution of B-exciton dynamics of colloidal MoS2 few layers by using femtosecond transient pump-probe absorption spectroscopy. We observe trapped carrier hopping and bimolecular recombination, which is portrayed as phonon-assisted coalescence through indirect bandgap at lower carrier-density and an unconventional bottleneck in decay kinetics above a critical density (⁓ 40×1013 cm-2). Also, we propose a new model describing the mechanistic origin of dynamical characterization of exciton relaxation with unprecedented carrier-density-dependent phenomena. This model is feasible to explain the physics behind the obscured nature of quenching of photoluminescence quantum yield of TMDCs and will provide powerful insight for fabricating defect-free optoelectronic devices in the near future.