A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH3NH3PbX3 (X = I, Br and Cl)Electronic supplementary information (ESI) available. See DOI: 10.1039/c5ta01125f

The 1 H and 13 C NMR spectra in methylammonium lead halide perovskites, CH 3 NH 3 PbX 3 (X = I, Br and Cl) show that the CH 3 NH 3 + units undergo dynamic reorientation, as the organic component tumbles in the perovskite cage. In addition, the differences in the anomalously long relaxation times of the protons associated with the CH 3 and not the NH 3 groups indicate that only the amine end of the CH 3 NH 3 + group is interacting with the inorganic network. Using this information, we have refined some single crystal X-ray and neutron diffraction data to probe their unusual structures in more detail. Furthermore, impedance spectroscopy has been used to monitor the high-temperature phase transition of CH 3 NH 3 PbI 3 , which confirms a significant increase in conductivity, when it is in its high temperature and higher symmetry structural regime. The optical band-gaps of each halide perovskite were determined using UV-visible spectroscopy and are consistent with previous reports. This article describes a variable temperature solid-state NMR and single crystal X-ray/neutron diffraction study of the hybrid perovskites (CH 3 NH 3 )PbX 3 (X = I, Br and Cl).