Electronic and Optical Properties of Cubic Perovskites CsPbCl3-yIy (y=0, 1, 2, 3)

Lead-based halide perovskites are attractive substrates for solar cells because of their excellent power conversion efficiency and low cost. The ground-state properties, electronic structure, as well as optical and phonon properties of lead-based halide perovskites (CsPbCl3-y I-y (y = 0, 1, 2, 3) are investigated by first-principles calculations based on density functional theory. Their electronic structure indicates that CSPbCl3-y I-y (y = 0, 1, 2, 3) compounds exhibit semiconducting behaviour at normal pressure. The energy gap of CsPbCl3 can be tuned by substituting iodine atoms for chlorine atoms. The energy gap values are found to be 3.06, 2.681, 2.330, and 2.030 eV using HSE06 calculations for CsPbCl3, CsPbCl2I, CsPbClI2, and CsPbI3, respectively. Also, it is found that the energy gap values of these materials decrease with increase in pressure and that a semiconductor-to-metallic phase transition is observed at high pressure. The optical properties of these Pb-based compounds are analysed. The dynamical stability of these perovskites is analysed by their phonon dispersion curves.