First-principles study of structural and optoelectronic properties of CsSnI3-yFy(y=0, 1, 2, 3) perovskites

The halide perovskites are attractive for solar cells due to their excellent power conversion efficiency and low cost. The structural properties of Sn-based halide perovskites CsSnI3-yFy(y = 0, 1, 2, 3) are investigated using first-principles calculation 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 fluorine atom for iodine atom. It is observed that when the halogen atom fluorine is substituted for iodine atom in CsSnI3, the energy gap values are changed. As the pressure is increased, the energy gap value of these materials decreases and at high pressure, a semiconductor to metallic transition is observed. The optical properties of these Sn-based compounds indicate that these materials may be the effective candidates for the solar cell applications.