Hybrid halide perovskites have taken the community by storm with their excellent photovoltaic performance, ease of preparation, and abundant constituent elements. However, a full description of the chemical and structural drivers of their remarkable functionality remains elusive. While much attention has focused on dynamic disorder of the A-site molecular cations, I will discuss a key aspect of the inorganic framework that impacts electronic, thermal, and dielectric properties. The pair distribution functions of various AMX3 (A = Cs+, CH3NH3+, CH(NH2)2+; B = Sn2+, Pb2+) halide perovskites at and above 300 K reveal temperature-activated, dynamic displacements of the divalent group IV cations from their nominal sites, a phenomenon previously referred to as emphanisis in rock-salt group IV chalcogenides.[1-3] This anharmonicity arises as a consequence of lone pair stereochemistry, and the chemical trends describing the magnitude of the effect are in agreement with existing theory.

Trends in the lone pair-induced local off-centering of tin and lead atoms in halide perovskites

253rd National Meeting (2017)

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