Electronic and optical properties of strontium doping in formamidinium lead iodide

Pb-containing perovskites are among the higher-performing materials for solar cells to date. The toxicity of Pb-containing materials has fueled the search for Pb-free and stable perovskites for space and commercial solar cell applications. We hypothesize that the partial substitution of Pb+2 by the homovalent cation Sr+2 will result in materials that retain the preferable optoelectronic properties of purely Pb-containing materials while reducing their toxicity. Given the almost identical bonding pattern of Pb and Sr ionic radii, interchanging the two has been achieved. Upon substitution by the non-toxic alkaline earth metal, there is increased thermal/environmental stability and an inherent reduction in overall toxicity of the host material. Here we utilize first-principles density functional theory (DFT) methodologies to investigate the effects of Sr-doping on the electronic and optical properties of FAPbI3, such as the electronic structure, bandgap, dielectric function, absorption spectra, and the reflectivity of the doped/undoped materials. These results can provide insight into the role that partial substitution of the Pb-site in perovskite materials has in the development of non-toxic Pb-free materials for solar cell applications.