Optoelectronic, photovoltaic and thermoelectric properties of the inorganic double perovskite Rb 2 GeBr 6 for eco-friendly technologies

This research investigates the halide double perovskite Rb ₂ GeBr ₆ as a promising candidate for photovoltaic and thermoelectric applications. Its structural, mechanical, dynamic, optical, and electronic characteristics, as well as its photovoltaic performance, were examined using density functional theory (DFT). Additionally, the thermoelectric properties were evaluated using semi-classical Boltzmann transport theory combined with DFT. The optimized geometry of Rb ₂ GeBr ₆ confirmed a cubic structure with lattice constants of a = b = c = 10.192 Å. In addition, this material proved to be mechanically and dynamically stable. The material’s anisotropic nature and brittle, covalent bonds were also evident from the mechanical properties. Electronic analysis revealed its semiconducting behavior, showing a direct bandgap of 1.704 eV. Optical features demonstrated high absorption, surpassing 10 ⁴ /cm in the visible spectrum, supporting its use in photovoltaic devices. Additionally, thermoelectric evaluations indicated a promising figure of merit (ZT) approaching 0.7 at temperatures above 100 K, highlighting Rb ₂ GeBr ₆ as a strong candidate for thermoelectric applications.