Small Twist Angles Accelerate Electron and Hole Transfer in MoSe₂/WSe₂ Heterostructures

Van der Waals (vdW) heterostructures host interlayer excitons that act as robust carriers of valley information and sensitive probes of strongly correlated electronic phases. The formation and properties of these interlayer excitons critically depend on efficient charge transfer across the heterointerface. Among the various factors influencing these processes, the twist angle emerges as a key degree of freedom, allowing precise modulation of the stacking configuration and electronic band structure of the heterostructure. In this study, we perform ultrafast pump-probe measurements on MoSe₂/WSe₂ heterostructures with various twist angles. Counterintuitively, the results show that both electron and hole transfer rates are strongly influenced by twist angles, peaking at 0 and 60° twist angles, respectively. Theoretical calculations indicate that this behavior stems from reduced valley energy offsets and enhanced interlayer hybridization at small twist angles, which collectively promotes more efficient electron and hole transfer. Our findings demonstrate the influence of twist-angle engineering on interfacial carrier dynamics and its impact on the optoelectronic properties of vdW heterostructures.