Modified Becke-Johnson (mBJ) exchange potential investigations of the optoelectronic structure of the quaternary diamond-like semiconductors Li2CdGeS4 and Li2CdSnS4

Li2CdGeS4 and Li2CdSnS4 compounds are diamond-like semiconductors (DLSs) and have been investigated to explore their electronic structure and optical properties for potential optoelectronic applications. Density functional theory within the modified Becke-Johnson (mBJ) exchange potential shows that the band structures exhibit direct band gap semiconductors at Γ with optical band gaps of 2.461 and 3.16 eV for Li2CdGeS4 and Li2CdSnS4 respectively. Along side showing that both compounds are optically active materials, our finding exhibit a nice harmony with experimental measured band gaps (3.10 eV and 3.26 eV for Li2CdGeS4 and Li2CdSnS4). Charge densities iso-surfaces and two-dimensional maps were reported to determine the effect of Sn/Ge on the bonding characteristics of both DLSs. The static dielectric constant ε1(0) and static refractive index n(0) are decreasing when Ge is replaced by Sn. Consequently, the possibility to tune the band gap for both DLSs could lead us to target particular optoelectronic applications in the next future such LED and solar cells.