Hybrid halide perovskites have attracted significant recent attention due to 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 incomplete. While much attention has focused on dynamic disorder of the A-site molecular cations, this talk will discuss a key aspect of the inorganic framework that impacts electronic, thermal, and dielectric properties, revealed through the use of local structure techniques. The pair distribution functions of various AMX3 (A = Cs+, CH3NH3+, CH(NH2)2+; B = Sn2+, Pb2+, X = Br–,I–) 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 we show the chemical trends describing the magnitude of the effect are in agreement with existing theory. The work herein illustrates tunability on all three sites of the perovskite structure, offering new design principles in the search for defect-tolerant semiconductors.

Trends in the lone pair-induced local distortions in tin and lead halide perovskites: Are Sn and Pb in the center of the octahedron?

255th National Meeting (2018)

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