Polarity and Interfacial Charge Transfer at Janus SnSSe/MoSi ₂ N ₄ Heterojunctions: A Nonadiabatic Molecular Dynamics Study

The development of efficient photocatalysts is crucial for addressing the energy crisis and environmental pollution. However, the charge transfer mechanisms in polar materials along with the influence of external electric fields are still unclear. Herein, this research explores the dipole moments and carrier dynamics in Janus SnSSe/MoSi₂N₄ heterojunctions by first-principles calculations and nonadiabatic molecular dynamics simulations. Our results show that the S/N configuration has a dipole moment of 0.03 eÅ, and the Se/N configuration exhibits a much larger dipole moment of 0.18 eÅ. Both configurations follow an S-scheme charge-transfer mechanism, with interfacial electron-hole recombination times as short as 11 ps (S/N) and 25.13 ps (Se/N), which are substantially faster than the intralayer electron and hole transfer times. The application of an external electric field influences the electronic properties and polarity of the heterojunction. Moreover, a positive electric field further strengthens the S-scheme charge-transfer character. The S/N contact configuration demonstrates superior photocatalytic performance compared to the Se/N configuration and individual monolayers, exhibiting promising reaction activity. This letter provides deep insights and theoretical guidance for designing novel S-scheme heterojunctions with tunable photocatalytic properties.