First-principles calculations to investigate optoelectronic, thermoelectric and elastic properties of novel lead-free halide perovskites CsRbPtX6 (X = Cl, Br and I) compounds for solar cells applications

The tunability and stability of halide perovskites have made them promising for a large number of applications. In this study, the optoelectronic and thermoelectric properties of novel halide lead-free halide perovskites of the form CsRbPtX6 (X = Cl, Br and I) are investigated for the first time using the Density Functional Theory (DFT). The Quantum Espresso package was used in performing the calculation of the properties of the perovskites. An analysis of their tolerance factors and octahedral factors indicated that the CsRbPtX6 (X = Cl, Br and I) are structurally stable. Likewise, their negative formation energy values imply their chemical stability and since their elastic constants meet the Born-Huang stability criteria, their mechanical stability is also confirmed. In addition to their remarkable stability, the materials are also predicted to have outstanding optoelectronic properties such as low reflectivity and good absorption in the visible region, indicating that they are suitable for photovoltaic applications. The calculated powers conversion efficiencies are ƞ = 7.27%, ƞ = 3.23% and ƞ = 6.3% for CsRbPtCl6, CsRbPtI6 and CsRbPtBr6, respectively. The materials also demonstrate excellent thermoelectric properties including ZT values close to unity and are therefore expected to possess high thermo-power convergence efficiency.