The effect of potassium insertion on optoelectronic properties of cadmium chalcogenides

Abstract

In the present work potassium inserted cadmium chalcogenides are investigated using density functional theory. This insertion is very important in the sense that it reduces dimensions of the compounds. The dimension reduction results in two dimension layers [Cd 3Q4]2- separated by K+ ions and blue shift in the band gaps of the binary compounds. The ternary compounds K2Cd3Q4 (Q = S, Se and Te) exist in orthorhombic crystal structure with space group Pnma (no. 62). These investigated compounds are wide and direct band gap semiconductors. The conduction band minimum is highly dispersive and mainly composed of cadmium s-orbital whereas the maximum of valence band is less dispersive and dominating by chalcogen's p-orbital. The band gap decreases in the series Q = S, Se, and Te, which is due to the increasing extension of the chalcogen p-orbital. The band energies belong to the visible energy range, therefore optical and thermoelectric properties are also calculated.