Multinuclear NMR as a tool for studying local order and dynamics in CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites Article - Octobre 2016

Claire Roiland, Gaelle Trippé-Allard, Kaoula Jemli, Bruno Alonso, Jean-Claude Ameline, Regis Gautier, Thierry Bataille, Laurent Le Polles, Emmanuelle Deleporte, Jacky Even, Claudine Katan

Claire Roiland, Gaelle Trippé-Allard, Kaoula Jemli, Bruno Alonso, Jean-Claude Ameline, Regis Gautier, Thierry Bataille, Laurent Le Polles, Emmanuelle Deleporte, Jacky Even, Claudine Katan, « Multinuclear NMR as a tool for studying local order and dynamics in CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites  », Physical Chemistry Chemical Physics, numéro spécial Physical chemistry of hybrid perovskite solar cells, octobre 2016, pp. 27133-27142. ISSN 1463-9076

Abstract

We report on Pb, Br, N, H, C and H NMR experiments for studying the local order and dynamics in hybrid perovskite lattices. Pb NMR experiments conducted at room temperature on a series of MAPbX compounds (MA = CHNH ; X = Cl, Br and I) showed that the isotropic Pb NMR shift is strongly dependent on the nature of the halogen ions. Therefore Pb NMR appears to be a very promising tool for the characterisation of local order in mixed halogen hybrid perovskites. Pb NMR on MAPbBrI served as a proof of concept. Proton, C and N NMR experiments confirmed the results previously reported in the literature. Low temperature deuterium NMR measurements, down to 25 K, were carried out to investigate the structural phase transitions of MAPbBr. Spectral lineshapes allow following the successive phase transitions of MAPbBr. Finally, quadrupolar NMR lineshapes recorded in the orthorhombic phase were compared with simulated spectra, using DFT calculated electric field gradients (EFG). Computed data do not take into account any temperature effect. Thus, the discrepancy between the calculated and experimental EFG evidences the fact that MA cations are still subject to significant dynamics, even at 25 K.

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