Prospective lead-free fluorine double perovskites Rb2B'BiF6 (B' = Ag, Cu, In): Unveiling solar cell and optoelectronic promise through ab-initio insights

Abstract

This study takes a comprehensive approach to investigate the optical and transport attributes of the fourth stable double perovskites—Rb2AgBiF6, Rb2CuBiF6 and Rb2InBiF6with a focus on their potential applications in photovoltaic, optoelectronic devices and thermoelectric systems. Calculated indirect band gap values are unveiled, measuring 2.07/1.90, 1.10/1.03 eV for Rb2AgBiF6 and Rb2CuBiF6 using PBE-GGA/LDA respectively. While for Rb2InBiF6 a direct band gap of 1.0/0.7 eV was found. We meticulously discuss optical features, encompassing dielectric constants, absorption coefficients, refractive indices, and reflectivity. Notably, prominent absorption peaks occur within the visible and ultraviolet spectrum across the three compounds, solidifying their suitability for solar cells and optoelectronic endeavors. Electron transport properties are scrutinized, encompassing electrical conductivity, thermal conductivity, Seebeck coefficient, and the figure of merit ZT. Utilizing the BoltzTraP code, these calculations span temperatures from 50 K to 1200 K. Our analysis of transport properties foresees the p-type semiconducting nature of the inorganic double perovskites Rb2B'BiF6 (B' = Ag, Cu, In), adding depth to the characterization of their transport behavior. These findings hold significance for their potential deployment in various photovoltaic, optoelectronic and thermoelectric applications, underlining their potential for advancing diverse technological landscapes.