LAUSR

Van der Waals heterojunctions of 2D layered semiconductors and nonlayered technological important II–V semiconductors provide unprecedented opportunities to engineer exciton and carrier dynamics in 2D optoelectronic devices. However, fabrication of such artificial heterojunctions with type-II band alignment structure and realization of interlayer excitons is challenging. Here, CdS–MoS2 type-II heterojunctions vertically stacked with few layered MoS2 and ultrathin CdS film are reported. Steady-state spectroscopy and time-resolved photoluminescence spectroscopy are used to study exciton and carrier dynamics in these heterojunctions. The surface states of the ultrathin CdS film caused by dangling bonds mediate interlayer exciton emission located at 753 nm in a CdS–bilayer MoS2 heterojunction via charge transition between the MoS2 indirect band and the CdS valence band. As a contrast, the surface states of CdS impede the recombination of interlayer excitons in a CdS-monolayer MoS2 heterojunction. These results are helpful for development of high-performance ultrathin optoelectronic and energy devices including light emission diodes, solar cells, and photodetectors.