Electronic and Optical Properties of CsSnI3−yCly (y = 0, 1, 2, 3) Perovskites: a DFT Study

Halide perovskite-based solar cells are attractive due to their excellent power conversion efficiency and low cost. Sn-based halide perovskites CsSnI 3− y Cl y ( y = 0, 1, 2, 3) are investigated in this work using first-principles calculations based on density functional theory. The computed electronic structure profile reveals that these materials exhibit semiconducting behavior. The energy gap value of CsSnI 3 is tuned by substituting Cl atom for iodine atom. As the pressure is increased, the energy gap value of these materials decreases, and a semiconductor to metallic transition is observed at high pressure. The optical properties of these Sn-based compounds, including the real and imaginary parts of the dielectric function, electron energy loss function, refractive index, and reflectivity, are computed. The dynamical stability of these perovskites is analyzed based on the phonon dispersion curve.