Novel Cs2AuIMIIIF6 (M = As, Sb) double halide perovskites: sunlight and industrial waste heat management device applications.

The upcoming lead-free double halide perovskites are sustainable alternatives to lead perovskites in renewable energy technologies. This study conducted a comprehensive investigation into the structural, electronic, optical, and thermoelectric properties of novel Cs2AuIMIIIF6 (M = As, Sb) double halide perovskites using a density functional theory-based approach. The tolerance factors and negative formation energies, as well as analysis of phonon dispersion, confirm structural and dynamic stability. There are favorable values of elastic coefficients and Pugh's and Poisson's ratios, which prove that there is mechanical stability, and ductility is also proven. The compounds show indirect band gaps of 1.144 eV (Cs2AuAsF6) and 1.746 eV (Cs2AuSbF6), which fall within the range of absorption of visible light. Optical analysis reveals high absorption coefficients, thereby making this material suitable for photovoltaic applications. Thermoelectric properties show moderate ZT values of approximately 0.64 and 0.61 at 500 K, which signify their application for waste heat recovery. Thus, the currently presented work proves the potential of Cs2AuIMIIIF6 (M = As, Sb) perovskites as effective materials from an environmental perspective for energy harvesting devices.