In silico investigation of Rb2SiX6 (X=Cl, Br, and I) perovskite for photovoltaic applications

Abstract

In this work, lead-free double perovskite Rb₂SiX₆ (X = Cl, Br, and I) is thoroughly examined and analyzed employing the density functional theory (DFT) approach. The computed values of the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gap for such compounds are in the range of (2.11–3.96) eV. The highest value of the energy gap is observed for Rb₂SiCl₆ with values of 3.96 and 3.41 eV, and the lowest values are observed for Rb₂SiI₆ with values of 2.11 and 2.46 eV using B3LYP and M06 methods, respectively. The chemical reactivity descriptors, including molecular hardness and softness, are also studied. The highest value of optical electronegativity is observed for Rb₂SiCl₆ with values of 1.06 and 0.91 using B3LYP and M06 methods, respectively. The optical properties are also computed employing different techniques. Rb₂SiI₆ has the highest value of refractive index and dielectric constant. From the molecular electrostatic potential (MEP), the studied compounds are electrically neutral and have a symmetric charge distribution. Due to the high values of dielectric constant and refractive index, the double perovskite Rb₂SiX₆ has the potential for optoelectronic and solar cell applications.