Theoretical investigation of electronic and optical properties of 2D transition metal dichalcogenides MoX2 (X = S, Se, Te) from first-principles

To use the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method in density functional theory (DFT), we have calculated the electronic structure and linear optical properties of 2D Transition metal dichalcogenides (TMDs), MoX2 (X = S, Se, Te). The predicted optical gap of MoX2 monolayers are in good agreement with the available experimental and theoretical data. The real and imaginary parts of dielectric function, optical absorption coefficient, reflectivity and energy loss function are also discussed in details for two directions of applied external electric field (E parallel to x and E parallel to z). It is found that the dielectric functions are highly anisotropic in low energy range (below 9 eV) and becomes isotropic in high energy range (above 9 eV). The most promising feature of MoX2 monolayers is high value absorption coefficient with a wide absorption spectrum making them very suitable material for solar cells and optoelectronic applications. Also, the wide band gap of TMDs which is thickness dependent makes them promising candidates for optoelectronic devices. The results of our systematic study are expected to guide the experimentalists to achieve suitable properties related to band gap modifications via optical absorption measurements at the nanoscale.