New investigated lead free double perovskite materials Rb2LiBiX6 (X= Cl, F, Br, I) for optoelectronics and solar cell applications via first principle calculations

Abstract

The physical properties of cubic inorganic double perovskites Rb2LiBiX6 (X = Cl, F, Br, I) were investigated by using density functional theory (DFT) based on Wien2K code. The structural parameters obtained are calculated by using Murnaghan equation of state and Chapin's method. The results found by exploring the mechanical properties and the enthalpy of formation of the materials ensuring the stability of the materials. This research expansively investigates optical and transport properties of the fourth double perovskite Rb2LiBiCl6, Rb2LiBiF6, Rb2LiBiBr6 and Rb2LiBiI6 for optoelectronics devices and thermoelectric applications. The calculated indirect band gap values are 4.96, 3.62, 2.93 and 2.00 eV for Rb2TeF/Cl/Br/I6 respectively. Optical properties are discussed in terms of dielectric constants, absorption coefficient, refractive index and reflectivity. Utmost peaks absorption occurred in the ultraviolet region for all compounds, which confirm their useful employment for optoelectronic applications. The electron transport properties are studied by electrical conductivity, thermal conductivity, Seebeck coefficient, and figure of merit. ZT. The calculations are performed versus the temperature in the range of 100–1200 K using BoltzTraP code. The p-type semiconducting character of the inorganic double perovskites Rb2LiBiX6 (X = Cl, F, Br, I) has been forecast by transport properties analysis.