Ultrafast and Highly Mobile Photocarriers in Monolayer WSe₂ Doped by α-RuCl₃

We report an experimental investigation of photocarrier dynamics in a heterostructure formed by a WSe₂ monolayer stacked on a multilayer α-RuCl₃ flake. The samples were fabricated using mechanical exfoliation and dry transfer techniques. Photoluminescence measurements showed that the excitonic photoluminescence of WSe₂ is quenched by more than 3 orders of magnitude upon contact with α-RuCl₃. Transient absorption measurements revealed an ultrashort photocarrier lifetime of 0.5 ps in the heterostructure. Spatially resolved transient absorption microscopy measurements were employed to probe the transport properties of these photocarriers, resulting in a room-temperature diffusion coefficient of 370 cm² s^-1, which is higher than the exciton diffusion coefficients of most previously studied 2D semiconductors. These results suggest that α-RuCl₃-doped WSe₂ could be utilized in high-speed optoelectronic devices.