Identification of lead-free Rb2AgBiX6 (X=Cl, Br, I) double halide perovskites for promising photovoltaic applications: First-principles investigations

This study examines double halide perovskites Rb2AgBiX6 (X = Cl, Br, I) using first-principles calculations, revealing their potential for various applications. The compounds demonstrate mechanical and thermodynamic stability, with lattice parameters aligning closely with previous reports. These semiconducting materials exhibit energy band gaps of 1.72, 1.27, and 0.82 eV for Cl, Br, and I variants, respectively. Their optical properties show maximum absorption between 2.50 and 3.50 eV, with refractive indices of 2.00-2.50 eV. Mechanically, they display high Young's moduli (78.3-82.6 GPa) and ductile characteristics. The photovoltaic properties, including the Shockley-Queisser limit efficiency (SLME), calculated for a thickness range of 10(-2) mu m-10(2) mu m, yield promising values of 26.04 %, 30.87 %, and 24.57 % for Rb2AgBiCl6, Rb2AgBiBr6, and Rb2AgBiI6, respectively, showcasing their favorable properties for photovoltaic applications.