A first-principles investigation into the rational design of Sn-halide perovskite materials as an alternative to Pb-based perovskites

The development of Pb-free alternatives for perovskite-based photovoltaics is extremely important due to the toxicity of Pb to the environment. Sn-based organic inorganic hybrid halide perovskites are considered to be the most suitable alternative to Pb-based ABX(3) perovskites due to their similar optoelectronic properties. The selection of A site cation in ABX(3) type perovskites is crucial for favorable structural and mechanical properties. Using first principle methods, we have designed and investigated Sn-I based hybrid halide perovskite materials with different organic cations mixed in equal proportions. Observed tolerance (TF) and octahedral factors (mu) indicate the formation of stable three-dimensional perovskite structure. Our studied materials also exhibit thermodynamic stability due to the negative value of their formation energies. Observed band gap values indicate the semiconducting nature of our studied perovskite materials. Calculated optical properties indicate that all of the compounds exhibit suitable dielectric functions and absorption coefficients in the visible range of the electromagnetic spectrum. The observed highest value of theoretical power conversion efficiency of MA-AMSnI(3) (11.24%) indicates its potential to be used in photovoltaics. Our investigation will be beneficial for researchers to develop less toxic and efficient perovskite materials for the fabrication of optoelectronic devices.