Lead-halide organic-inorganic perovskites consist of an organic molecule inside an inorganic host framework. These materials are of considerable interest due to their exceptional photovoltaic properties, which offer the potential of improved solar panels. The behaviour of the organic molecule is thought to be key to understanding the overall properties of the material, particularly the way in which it rotates within the framework. Although the structure and dynamics of these materials have been extensively studied, the exact nature of this rotation is not yet understood. A team of researchers from the University of Edinburgh, Imperial College London and ISIS used a combination of inelastic neutron scattering, Raman spectroscopy, and quasielastic neutron scattering to study the temperature dependent dynamics of the organic molecule in CH3NH3PbBr3. Their results confirm the strong role of hydrogen bonding and a coupling between molecular and framework dynamics.
Related publication: K. L. Brown et al. “Molecular orientational melting within a lead-halide octahedron framework: The order-disorder transition in CH3NH3PbBr3" Phys. Rev. B 96(2017), 174111, DOI: 10.1103/PhysRevB.96.174111