The effect of replacing halides on the physical properties of titanium-based vacancy-ordered halide double perovskites using density functional theory

In the present work, we have simulated the vacancy-ordered double perovskites Cs2TiX6 (X = Cl, Br or I) using ab initio calculations. The structural and electronic properties of the Ti-based perovskites show high stability and suitable band gap for them. The direct band gap predicted by the calculations decreases with enhancing the atomic radius of the halide and is relatively in good agreement with the reported theoretical and experimental values. Also, by calculating the absorption spectrum, several optical properties for these materials have been studied, which show the excellent optical absorption for these compounds, especially iodide perovskite. These properties make this group of halide perovskites suitable candidates for photovoltaic applications.