Electrical Control of Exciton Diffusion via Tuning Exciton States

Stacking of monolayer 2D transition metal dichalcogenides (TMDs) into van der Waals heterostructures can enable the formation of interlayer excitons (IXs) with long lifetimes and permanent out-of-plane electric dipoles, allowing them to propagate over long distances. While early studies on TMD heterobilayrs show efficient electrical control of excitonic transport of IXs by creating different energy potentials, the electrically controllable exciton states and associated spatial migration remain elusive. Here, an electrical control of exciton diffusion through the change of exciton states between charged IXs (CIXs) and charged intralayer excitons is reported. The repulsive dipolar interaction of IXs accounts for the growing exciton cloud size and increasing diffusion length in the power-dependent PL study. More importantly, the electrically tunable spatial exciton distribution is demonstrated by switching the exciton states, which shows a 1.5-fold change in diffusion length and an order of magnitude increase in lifetime from charged intralayer excitons to CIXs. The electrical control of exciton states and the relevant diffusion dynamics provide another knob to study the interplay between propagation and many-body interactions for the development of excitonic devices. Van der Waals heterostructures assembled from a variety of 2D materials hold great promise to study the complex exciton states, especially IXs formed in type-II heterostructures possess long lifetimes which allow them to propagate over long distances. The electrically tunable exciton diffusion by switching the exciton states from CIXs to charged intralayer excitons in the WS2/(iso-BA)2PbI4 heterostructure is demonstrated here. image