Ab-initio investigation of the structural, electronic and optical properties of lead-free halide Cs2TiI6 double perovskites

We investigate the structural, electronic and optical properties of lead-free halide Cs2TiI6 halide perovskites using ab-initio calculations. It is shown that the Ti-based halide perovskites possess several interesting properties, including high stability, suitable bandgap, and excellent optical absorption. It is demonstrated that the Cs2TiI6 compound presents a bandgap energy value of 0.998 eV. The absorption coefficient is in the order of 105 cm−1, these properties make Cs2TiI6 halide perovskites a good candidate for photovoltaic applications. In addition, the effect of pressure on the electronic properties were studied, in which we demonstrate that the bandgap energy depend significantly on the applied pressure.