First‐principles investigation of Rb₂Ag(Ga/In)Br₆ for thermoelectric and photovoltaic applications

In this article, we have systematically investigated the structural, electronic, optical and thermoelectric properties of Rb 2 Ag(Ga/In)Br 6 . The resulting negative formation energy along with the absence of imaginary phonon modes confirm the thermodynamic stability of Rb 2 Ag(Ga/In)Br 6 . In addition, the derived electronic properties by using GGA‐PBE + mBJ + SOC functional show that the direct band gap values are 1.21 eV and 1.42 eV for Rb 2 AgGaBr 6 and Rb 2 AgInBr 6 , respectively. Furthermore, the dispersed direct band nature of Rb 2 Ag(Ga/In)Br 6 leads to their outshining optical properties such as higher order (10 5 cm −1 ) absorption coefficient, appreciable optical conductivity, and low reflectivity. Moreover, the higher figure of merit values of Rb 2 Ag(Ga/In)Br 6 are resulted from their ultra‐low thermal conductivity and high electrical conductivity. Thus, Rb 2 Ag(Ga/In)Br 6 are predicted to be potential photovoltaic and thermoelectric materials.