A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH sub(3)NH sub(3)PbX sub(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: 01.04.2015
• Subjects: Halides; Neutron diffraction; Nuclear magnetic resonance; Perovskites; Relaxation time; Single crystals; Sustainability; X-rays
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c5ta01125f

The super(1)H and super(13)C NMR spectra in methylammonium lead halide perovskites, CH sub(3)NH sub(3)PbX sub(3 ) (X = I, Br and Cl) show that the CH sub(3)NH sub(3) super(+) 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 sub(3) and not the NH sub(3) groups indicate that only the amine end of the CH sub(3)NH sub(3) super(+) 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 sub(3)NH sub(3)PbI sub(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.