Ultrafast Interlayer Charge Transfer between Bilayer PtSe₂ and Monolayer WS₂

Interlayer charge transfer (CT) between PtSe₂ and WS₂ is studied experimentally. Layer-selective pump-probe and photoluminescence quenching measurements reveal ultrafast interlayer CT in the heterostructure formed by bilayer PtSe₂ and monolayer WS₂, confirming its type-II band alignment. The CT facilitates the formation of the interlayer excitons with a lifetime of several hundred ps to 1 ns, a diffusion coefficient of 0.9 cm² s^-1, and a diffusion length reaching 200 nm. These results demonstrate the integration of PtSe₂ with other materials in van der Waals heterostructures with novel charge-transfer properties and help develop fundamental understanding on the performance of various optoelectronic devices based on heterostructures involving PtSe₂.