Ultrafast Charge Transfer in Lithium-Ion and Water-Intercalated MoS₂/WS₂ Heterostructures

Heterostructures of monolayer transition metal dichalcogenides such as MoS₂ and WS₂ are promising for applications in optoelectronics and photocatalysis. However, the strong interlayer coupling in MoS₂/WS₂ 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 MoS₂/WS₂ 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 MoS₂/WS₂ 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 MoS₂/WS₂ heterostructures via intercalation and offer insight into modulation of other van der Waals materials for enhanced performance.