First-principles study of lead-free double perovskites Rb2SiX6 (X=Cl, Br, and I) for solar cells and renewable energy

Double perovskites are crucial to renewable energy and offer a viable substitute for lead-based solar cells in meeting the energy needs of sustainable growth and development. We have examined the mechanical, optical, thermoelectric, and electronic properties of double perovskites, Rb2SiX6 (X=Cl, Br, and I). To determine the brittleness and ductility of the material under study, the Poisson's and Pugh's ratios are calculated. The direct band gaps of (3.19,1.68, and 0.17 eV) are determined for Rb2SiX6 (X=Cl, Br, and I) respectively based on the analysis of band structure, ensuring the materials' suitability for solar cell applications in the ultraviolet, visible, and infrared spectrums. Analyzing the optical loss, refractive index, light absorption, and dielectric constants allows for the investigation of optical properties. Slack's model is used to study lattice thermal conductivity. Through the figure of merit (ZT), the thermoelectric performance is examined. For Rb2SiX6 (X=Cl, Br, and I) the ZT values at room temperature are 0.77, 0.76, and 0.44, respectively.