Ultrafast charge transfer in MoS sub(2)/WSe sub(2) p-n Heterojunction

Atomically thin and sharp van der Waals heterojunction can be created by vertically stacking p-type monolayer tungsten diselenide (WSe sub(2)) onto n-type molybdenum disulfide (MoS sub(2)). Theory predicts that stacked MoS sub(2) and WSe sub(2) 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 MoS sub(2)/WSe sub(2) van der Waals hetero-structure. Our results show that ultrafast electron transfer from WSe sub(2) to MoS sub(2) 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.