A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH 3 NH 3 PbX 3 (X = I, Br and Cl)

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 3; no. 17; pp. 9298 - 9307
• Main Authors: Baikie, Tom, Barrow, Nathan S., Fang, Yanan, Keenan, Philip J., Slater, Peter R., Piltz, Ross O., Gutmann, Matthias, Mhaisalkar, Subodh G., White, Tim J.
• Format: Journal Article
• Language: English
• Published: 2015
• ISSN: 2050-7488; 2050-7496
• 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.