DFT and modified Becke Johnson (mBJ) potential investigations of the optoelectronic properties of SnGa4Q7 (Q = S, Se) compounds: Transparent materials for large energy conversion

Abstract

Electronic structure and optical properties of SnGa4Q7 (Q = S, Se) compounds were investigated using a full potential linearized augmented plane wave method based on density functional formalism. Electronic band structures show an indirect semiconducting wide band gap two different approaches (EV-GGA and mBJ). The band gap values are estimated at 2.90 (2.25 eV) and 3.11 (2.49 eV) for EV-GGA and mBJ for SnGa4S7 (SnGa4Se7), respectively. Densities of states show that Sn-5s and S/Se-3p/4p states are dominating the region around Fermi level form valence band maximum and conduction band minimum. The computed electronic charge density contours demonstrate that SnGa4Q7 (Q = S, Se) show a mixture between ionic and covalent characters. Optical parameters including the dielectric constant, absorption coefficient, reflectivity, refractive index, energy loss function, and birefringence are also reported to investigate the potential role of SnGa4Q7 (Q = S, Se) compounds for solar energy conversion application.