Ab-initio investigation of structural, optoelectronic, and transport properties of metal-alkali-based binary chalcogenides, X2Te [X = Na, K, Rb]: Rb2Te a potential candidate for UV-shielding and thermoelectric devices

We investigate the structural, optoelectronic, and thermoelectric properties of X 2 Te (X = Na, K, Rb) chalcogenides. The energy-versus-volume fitted with the Birch–Murnaghan equation of state suggests the structural stability of these materials. We find that Na 2 Te, K 2 Te, and Rb 2 Te have direct band gaps of 3.62, 2.26, and 0.60 eV, respectively. The optical properties revealed that Rb 2 Te is reflective over a wide UV–Vis energy range while the K 2 Te and Rb 2 Te demonstrate reflectivity in the UV region, making these materials to be potential candidates for UV-light shielding. Furthermore, the effectiveness of Rb 2 Te in thermoelectric energy converter technology is supported by its high Seebeck effect and high-power factor values. The Rb 2 Te exhibits the highest value of the figure of merit and electrical conductivity among the three binary chalcogenides. We infer that Rb 2 Te is the most promising among the studied binary chalcogenides for thermoelectric devices’ applications. Graphical abstract