Enhancing the Photoinduced Interlayer Charge Transfer and Spatial Separation in Type-II Heterostructure of WS₂ and Asymmetric Janus-MoSSe with Intrinsic Self-Build Electric Field

Two-dimensional heterostructure manipulation is promising to overcome the high recombination rates and limited redox abilities of photogenerated electron-hole pairs in a single photocatalyst. The built-in electric field (Ehetero) in the type-II heterojunction is normally unfavorable for the desired charge transfer, which is an important but easily neglected issue that needs to be solved. Here, on the basis of the density functional theory (DFT) and the nonadiabatic molecular dynamics (NAMD) calculations, we obtain a type-II band alignment in Janus-MoSSe/WS2 heterostructure, which meets the band-edge position requirement for water splitting. Importantly, the intrinsic self-build electric field (Eself) of Janus-MoSSe can effectively weaken the hindrance effect of Ehetero for charge transfer by constructing a suitable Se-S stacking configuration, improving charge separation efficiency in the Janus-MoSSe/WS2 heterostructure. Our work provides a materials-by-design paradigm and interlayer charge-transfer dynamics understanding of heterostructure engineering against asymmetric structures lacking reflection symmetry.