Effect of manganese on electronic and optical properties of Ba2ZnS3: A DFT study

Abstract

The structural, electronic, and optical properties of pristine Ba2ZnS3 and Mn4+ doped Ba2ZnS3 at Ba-site have been carried out by employing the first-principles calculations based on density functional theory (DFT). For the calculation of exchange and correlation interactions, the modified Becke Johnson (TB-mBJ) potential and generalized gradient approximation with the Hubbard parameter (GGA ​+ ​U) were used for pristine and Mn4+ doped Ba2ZnS3 respectively. The defective states due to Mn4+ doping are introduced below the conduction band which produces n-type conductivity in both spin-up and spin-down states. The direct band gaps are observed for Ba2ZnS3 and Ba2ZnS3:Mn4+ (spin up and spin down) with bandgap values 3.157 ​eV, 1.582 ​eV, and 2.176 ​eV respectively. For spin-up states, the intermediate states are induced due to the majority contribution of s-orbital of Mn atom, while minority contribution of p-orbital of Mn atom. For spin-down states, the defective states are produced as a result of the prominent contribution of d-orbital of Mn atom and minor contribution of s-orbital of Mn atom. The optical properties such as the real and imaginary parts of the dielectric function, reflectivity, electron energy loss spectrum, extinction coefficient, refractive index, absorption coefficient, and optical conductivity as a function of photon energy are calculated. Our results revealed that Mn4+ doped Barium zinc sulfide emerged as a highly efficient luminescent phosphor material, and is more suitable for optical devices due to its direct bandgap nature and small bandgap value (1.582eV).