Ultrafast charge transfer in MoS₂/WSe₂ p-n Heterojunction

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 lightphotocurrent 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.