Enhanced Grain-boundary Emission Lifetime and Additive Induced Crystal Orientation in One-Step Spin-Coated Mixed Cationic (FA/MA) Lead Perovskite Thin Films Stabilized by Zinc Iodide Doping

Mixed cationic lead perovskites containing formamidinium and methylammonium can be stabilized by incorporating ZnI₂ as an “internal desiccant”. Next to prolonged stability under ambient conditions we show with XRD that the use of an additive, 3-chloropropyl ammonium chloride, influences crystal formation by orienting the crystals. These ~500 nm crystals show individual photoluminescent behavior in thin films and have a longer photoluminescence lifetime at the grain boundaries as compared to the center of the crystal or relative to un-doped materials without the additive made under identical conditions. Charges recombine slower at the edges of the crystals as observed with confocal laser scanning microscopy