First-principles study of the electronic structure and optical properties of MoSSe/GaGeSe3 heterostructures

Abstract

Two-dimensional van der Waals heterojunctions hold great promise in photocatalysis and optoelectronics; however, utilizing the synergistic modulation of interfacial polarization and built-in electric fields to achieve efficient charge separation and broadband spectral response remains a challenge. In this work, we systematically investigate the structural stability, electronic properties, interfacial charge transfer, and optical response of a novel Janus MoSSe/GaGeSe 3 heterojunction using density functional theory (DFT). The results indicate that all six stacking configurations possess negative binding energies, and ab initio molecular dynamics (AIMD) simulations further confirm the thermal stability of the representative heterostructures over a timescale of 5000 fs. Due to the interfacial polarization induced by the intrinsic vertical dipole moment of Janus MoSSe, the band alignments and carrier transport properties of the heterojunctions exhibit significant differences. Notably, the SeMoS/GaGeSe 3 structure forms a typical type-II band alignment. Driven by the built-in electric field, the photogenerated carriers follow an S-scheme transfer pathway, achieving efficient spatial separation of electrons and holes while maintaining strong redox capabilities. Bader charge and work function analyses reveal significant charge redistribution and a directionally tunable built-in electric field at the interface, which effectively promotes the spatial separation of photogenerated electron–hole pairs. Furthermore, optical studies demonstrate that this heterojunction exhibits enhanced dielectric response and broad-spectrum absorption capabilities. This study elucidates the underlying mechanism by which Janus structures induce interfacial polarization to modulate optoelectronic properties, providing a theoretical basis for the design of high-performance photocatalysts and optoelectronic devices.