Intrinsic formamidinium tin iodide nanocrystals by suppressing the Sn(IV) impurities
Résumé
Lead halide perovskites successfully advance towards applications in solar cells, light-emitting devices, and high-energy radiation detectors. Recent progress in understanding their uniqueness highlights the role of optoelectronic tolerance to intrinsic defects, particularly long diffusion lengths of carriers, and highly dynamic 3d inorganic framework. This picture indicates that finding an analogous material among non-group-14 metal halides can be very challenging, if possible at all. On the other hand, Sn (II) iodide perovskites exhibit comparably good performance in photovoltaics when synthesized with a low number of trap states. The main challenge with this material originates from the easiness of the trap states generation, which are typically ascribed to the oxidation of Sn(II) to Sn(IV). In this work, we describe the synthesis of colloidal monodisperse FASnI3 NCs, wherein thorough care on the purity of precursors and redox chemistry reduces the concentration of Sn(IV) to an insignificant level, to probe the intrinsic structural and optical properties of these NCs.