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 X2Te (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 Na2Te, K2Te, and Rb2Te have direct band gaps of 3.62, 2.26, and 0.60 eV, respectively. The optical properties revealed that Rb2Te is reflective over a wide UV–Vis energy range while the K2Te and Rb2Te demonstrate reflectivity in the UV region, making these materials to be potential candidates for UV-light shielding. Furthermore, the effectiveness of Rb2Te in thermoelectric energy converter technology is supported by its high Seebeck effect and high-power factor values. The Rb2Te exhibits the highest value of the figure of merit and electrical conductivity among the three binary chalcogenides. We infer that Rb2Te is the most promising among the studied binary chalcogenides for thermoelectric devices’ applications.