InSb/Janus MoSSe van der Waals heterostructure: First-principles calculation study of electronic structure and optical properties

The Janus MoSSe and InSb monolayers exhibit direct bandgaps of 1.60 eV and 0.70 eV, respectively, positioning them as promising candidates for optoelectronic applications. The InSb/Janus MoSSe van der Waals heterojunction is characterized as a direct bandgap semiconductor with a bandgap of 0.56 eV, classifying it as a Type II heterojunction. Computational density of states analysis reveals that the valence band maximum is predominantly derived from the Sb 5s orbital. In contrast, the conduction band minimum is attributed to the hybridization of Mo 4d orbitals. As the interlayer spacing increases, the band gap gradually decreases and stabilizes at approximately 0.36 eV, whereas a reduction in spacing progressively narrows the band gap, ultimately inducing metallic characteristics. The work function of the Janus MoSSe monolayer is determined to be 5.57 eV, contrasting with the 4.79 eV work function of the InSb monolayer, yielding a composite work function of 5.15 eV for the heterojunction. Differential charge density analysis indicates electron transfer from the InSb monolayer to the Janus MoSSe layer, facilitating charge separation and transfer. Optical property investigations demonstrate that the InSb monolayer predominantly absorbs in the infrared and visible spectra. In contrast, the Janus MoSSe monolayer exhibits significant absorption in the visible and near-ultraviolet regions. Notably, the InSb/Janus MoSSe heterojunction synergistically integrates the optical advantages of its constituents, enabling broadspectrum photon absorption spanning the infrared, visible, near-ultraviolet, and far-ultraviolet regions. These findings provide valuable theoretical insights, paving the way for advanced applications of the InSb/Janus MoSSe van der Waals heterojunction in next-generation optoelectronic devices.