Interfacial Charge Transfer and Optoelectronic Properties of the SnS2/HfS2 van der Waals Heterostructure: Insights from Ground-State Properties and Nonadiabatic Excited-State Dynamics

Abstract

Abstract Based on density functional theory (DFT) and nonadiabatic molecular dynamics (NAMD) methods, the interface charge transfer dynamics and strain-controlled optoelectronic properties of SnS2/HfS2 van der Waals heterojunctions were systematically investigated. The results indicate that SnS2 and HfS2 can form a stable van der Waals stacking structure and form a type-I band alignment, where photogenerated electrons and holes are localized within the HfS2 layer. Optical property analysis shows that the absorption coefficient of the heterojunction is significantly improved in the ultraviolet band, and it also exhibits a remarkably enhanced light absorption capacity in the visible region. NAMD simulations further reveal that the system possesses a long electron–hole recombination lifetime of approximately 283.98 ns and an ultrafast interfacial hole transfer process of around 633.82 fs. Under weak electron–phonon coupling dominated by low-frequency vibrations, the nonadiabatic coupling strength of the system is markedly reduced, which effectively suppresses carrier recombination loss. This synergistic combination of ultrafast interfacial hole transfer and long-lived carrier retention is of great significance for boosting the performance of photodetectors. In addition, biaxial strain can significantly modulate the band gap, band alignment, and optical absorption characteristics of the system. Compressive strain can further induce band structure evolution and a redshift of the absorption spectrum, offering a feasible strategy for the tunable optimization of its optoelectronic properties.