Elucidation of Chemical Species and Reactivity at Methylammonium Lead Iodide and Cesium Tin Bromide Perovskite Surfaces via Orthogonal Reaction Chemistry

Abstract

We quantified the chemical species present at and reactivity of the (100) face of tetrahedral single-crystal methylammonium lead iodide, MAPbI3(100), and polycrystalline cesium tin bromide, CsSnBr3. For these ABX3 perovskites, experiments utilized the orthogonal reactivity of the A+-site cation, the B2+-site cation, and the X–-site halide anion. Ambient pressure exposure to BF3 solutions probed the reactivity of interfacial halides. Reactions with p-trifluoromethylanilinium chloride probed the exchange reactivity of the A+-site cation. A complex-forming ligand, 4,4′-bis(trifluoromethyl)-2,2′-bipyridine, probed for interfacial B2+-site cations. Fluorine features in X-ray photoelectron spectroscopy (XPS) quantified reaction outcomes for each solution-phase species. XPS revealed adsorption of BF3, indicating surface-available halide anions on both MAPbI3(100) and on CsSnBr3. Temperature-programmed desorption quantified a ∼200 kJ mol–1 desorption activation energy from MAPbI3(100) and a ∼215 kJ mol–1 desorpti...