Anion-cation replacement effect in lead free tin based variant perovskites

Search of new lead free perovskite for solar cell and other optoelectronic applications is an active area of research. Herein, we report investigation of the detailed structural, electronic and optical properties of the tin based perovskite, X2SnY6 (X = K, Rb, Cs; Y= Cl, Br, I), using density functional theory (DFT). A highly accurate scheme of the DFT, full potential linearized augmented plane wave method, was employed for present calculations. Structural parameters obtained through volume optimization process were found in fair agreement with available experimental results. The electronic band structure indicates direct band nature making them ideal for various optoelectronic applications. The prominent contribution to the density of states comes from Sn-s and X-p orbitals. The optical properties suggest that Cs2SnI6 and Rb2SnI6 possess maximum optical absorption. Moreover, some of the compounds with I anions have band gap in the order of 1 eV, indicating their ability for efficient optoelectronic devices.