Theoretical investigation of electronic and optical properties of doped and defective MoSe2 monolayers

In this work, we have investigated the various electronic and optical properties of undoped molybdenum diselenide (MoSe2) monolayer, such as band structure, density of states, electron density, dielectric function, refractive index, extinction coefficient, reflectivity and energy loss function using density functional theory. Additionally, substitutional doping using niobium (Nb) and manganese (Mn) atoms and introducing defects in undoped MoSe2 lattice were investigated to know the detailed effect of the same on its properties. It is found that the undoped MoSe2 monolayer demonstrates a direct energy bandgap of similar to 1.44 eV, which reduces after Mn, Nb doping and after introducing Mo, Se vacancy. The energy bandgap attains a very small value 0.2 eV after introducing Se vacancy defect in MoSe2 lattice. The extinction coefficient of MoSe2 monolayer demonstrates a significant increase from 1.79 to 2.66 a.u. after introducing the Mo vacancy in the undoped lattice. The variation of semiconductor to nearly semi-metallic character of MoSe2 by introducing defects makes it very suitable for the application in high-performance solar cells, photo-electrochemical cells, sensors and biosensor applications.