Enhanced Optoelectronic Properties of Cs2SnI6 Perovskite Through Fluorine Doping: First-Principles Calculations

In this paper, we conducted a theoretical study of structural and optoelectronic properties of Cs2SnI6-xFx (x = 0, 1.5, and 3) using first-principles calculations. The stability was confirmed through formation energy calculations. The electronic density demonstrated the strong character ionic of bands between Sn and (F/I) and less covalent bonds between Cs and (F/I). The calculated direct band gap was tuned with increasing the fluorine content from 1.36 eV for x = 0 to 1.46 for x = 3, which is a suitable band gap for photovoltaic applications, and all the results are in excellent agreement with the experimental data. Furthermore, the partial density of states of Cs2SnI6-xFx changes significantly at the top of valence band and hence we conclude that the F doping affects the electronic band structure of Cs2SnI6. Besides, the optical properties such as the coefficient absorption, the transmittance, and reflectivity are systematically investigated. The rising of the fluorine content indicates an enhanced coefficient absorption in the visible region and a strong transmittance in the UV and Infra-red region. We have also calculated the static values of reflectivity, stablishing a comparison between different concentrations. Moreover, the optical band gap was computed to be in excellent agreement with the experimental results. The data presented in this paper highlight the favorable optoelectronic properties of Cs2SnI6 and demonstrate trends in these properties with fluorine doping, thereby facilitating the development of high-performance solar cells and other optoelectronic devices with improved efficiency.