Ultrafast Charge Transfer in Lithium-Ion and Water-Intercalated MoS/WS Heterostructures.

Heterostructures of monolayer transition metal dichalcogenides such as MoS and WS are promising for applications in optoelectronics and photocatalysis. However, the strong interlayer coupling in MoS/WS heterostructures results in indirect bandgaps that significantly hinder their performance and efficiency in practical applications. Here, we use first-principles calculations to demonstrate an effective method to weaken interlayer coupling in MoS/WS heterostructures by intercalating lithium ions with water molecules. This approach results in a direct bandgap while maintaining the type-II band alignment. Interestingly, the charge transfer process in the intercalated MoS/WS heterostructures is greatly accelerated, which is attributed to the enhanced nonadiabatic coupling between different energy states and the inversion of the effective electric field within the heterostructures. Our results provide a strategy for achieving ultrafast charge transfer in MoS/WS heterostructures via intercalation and offer insight into modulation of other van der Waals materials for enhanced performance.