Transport Dynamics of Neutral Excitons and Trions in Monolayer WS₂

Understanding the spatial motion of excitons is of both fundamental interest and central importance for optoelectrical applications. Here, we have investigated the temperature ( T ) dependence of the transport dynamics of neutral excitons and charged excitons (trions) in atomically thin two-dimensional crystals of the transition-metal dichalcogenide WS 2 . The transport dynamics of neutral excitons can be divided into three temperature ranges, where the diffusion of neutral excitons is governed by thermal activation (≤∼75 K), ionized impurity scattering (∼75 K ≤ T ≤∼200 K), and LO phonon scattering (≥∼200 K). The trions have a diffusion length that is over 20 times longer than that of neutral excitons at very low temperatures (≤∼10 K), which may be related to theoretically predicted Pauli-blocking effects during the excitation process.