Ultrafast charge transfer in MoS 2 /WSe 2 p–n Heterojunction

Abstract

Atomically thin and sharp van der Waals heterojunction can be created by vertically stacking p-type monolayer tungsten diselenide (WSe₂) onto n-type molybdenum disulfide (MoS₂). Theory predicts that stacked MoS₂ and WSe₂ monolayer forms type II p–n junction, creating a built-in electric field across the interface which facilitates electron–hole separation and transfer. Gaining insights into the dynamics of charge transfer across van der Waals heterostructure is central to understanding light-photocurrent conversion at these ultrathin interfaces. Herein, we investigate the exciton dissociation and charge transfer in a MoS₂/WSe₂ van der Waals hetero-structure. Our results show that ultrafast electron transfer from WSe₂ to MoS₂ take place within 470 fs upon optical excitation with 99% charge transfer efficiency, leading to drastic photoluminescence quenching and decreased lifetime. Our findings suggest that van der Waals heterostructure may be useful as active components in ultrafast optoelectronic devices.