Vertical stacking approach for tailoring electronic and optical properties of ultrathin two-dimensional vdW heterostructures of P-MAB (M=Ti, Zr, Hf; A=S, B=Se)

The vertical stacking in the form of heterostructures, is an effective way to enhance the performance of corresponding isolated monolayers. Strong interactions between Janus monolayers (MAB) and Phosphorus (P) monolayers result in significant improvements in both physical and chemical properties compared to single layer configurations. Using first-principle (hybrid) calculations, we explore electronic structure and optical properties of P–MAB (M = Ti, Zr, Hf; A = S, B=Se) van der Waals heterostructures, for potential applications in electronic and optoelectronic devices. Ab initio molecular dynamic (AIMD) simulations confirm the thermal stability, while phonon spectra confirm the dynamical stabilities of these systems. Our analysis reveals that all configurations maintain semiconducting nature with an indirect bandgap. The type-II band alignment in the P–MAB heterostructures is demonstrated through calculations of the partial density of states (PDOS). Bader charge analysis and planar-averaged charge density differences indicate an electron transfer from the P monolayers to the MAB monolayer. Furthermore, our investigation of the dielectric function ${ϵ}_2\left(\omega \right)$ shows that the lowest energy shift are primarily influenced by excitonic effects.