Diffuse Neutron and X-Ray Scattering from Inorganic Halide Perovskites

Halide perovskites have enjoyed significant attention over the past several years due to their intriguing optoelectronic properties, both in hybrid organic-inorganic and pure inorganic forms. In both cases, the long carrier lifetimes underpinning these properties appear to be strongly coupled to local structure. Diffuse neutron and x-ray scattering measurements on the inorganic halide perovskites CsPbBr3, CsSnBr3, CsPbCl3, and Cs2AgBiBr6 show clear similarities in diffuse scattering, all showing a network of rods indicative of two-dimensional correlations. Neutron scattering measurements from CORELLI show that this scattering is quasi-static, consistent with an overdamped two-dimensional phonon. This static scattering can be further modelled via correlated tilts in the halide octahedron, with the octahedral tilt systems that define the low temperature structure persisting at higher temperatures in a short-range form. The commonality of this feature suggests that short-range order is a defining part of the physics in these systems.