Dimethylammonium: An A-Site Cation for Modifying CsPbI3

All-inorganic perovskite materials are attractive alternatives to organic-inorganic perovskites because of their potential for higher thermal stability. Although CsPbI3 is compositionally stable under elevated temperatures, the cubic perovskite alpha-phase is thermodynamically stable only at >330 degrees C and the low-temperature perovskite gamma-phase is metastable and highly susceptible to non-perovskite delta-phase conversion in moisture. Many methods have been reported which show that the incorporation of acid (aqueous HI) or "HPbI3"-recently shown to be dimethylammonium lead iodide (DMAPbI(3)) -lowers the annealing temperature required to produce the black, perovskite phase of CsPbI3. Herein, the optical and crystallographic data presented show that dimethylammonium (DMA) can successfully incorporate as an A-site cation to replace Cs in the CsPbI3 perovskite material. This describes the stabilization and lower phase transition temperature reported in the literature when HI or HPbI3 is used as precursors for CsPbI3. The Cs-DMA alloy only forms a pure-phase material up to approximate to 25% DMA; at higher concentrations, the CsPbI3 and DMAPbI(3) begin to phase segregate. These alloyed materials are more stable to moisture than neat CsPbI3, but do not represent a fully inorganic perovskite material.