Cs2TlRhX6 (X = Cl, Br, I): promising halide double perovskites for efficient energy harvesting in photovoltaic and thermoelectric applications

Abstract

The majority of halide double perovskites, particularly chlorides and bromides, possess large band gaps. However, we have identified a composition of halide double perovskites with a narrow band gap, making them ideal for energy harvesting purposes. First-principle methods are employed to compute the structural, electronic, mechanical, optical, and thermoelectric properties of Cs2TlRhX6 (X= Cl, Br, I). The stability of the cubic perovskite compounds is confirmed through the formation energy, the Goldschmidt tolerance factor, and the elastic constant. The optical bandgaps of all the compositions are determined through the TBmBJ potential. The ductile nature of the present compounds is verified by the values of Pugh’s ratio and Cauchy’s pressure. The optical properties are investigated to check the availability of the materials for harvesting solar energy. Temperature-dependent parameters including electrical conductivity, see-beck coefficient, power factor, and figure of merit also have been computed for thermoelectric applications. All the explored characteristics of the double perovskites under study have been discussed briefly on the basis of interesting and informative Physics behind the observed results.