Nuclear Quadrupole Resonance of multinary FA1-xCsxPbI3-yBry perovskites
Marcel Aebli a b, Nikolaus Porenta a, Nina Aregger a, Maksym Kovalenko a b
a Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, CH-8093, Switzerland
b Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Überlandstrasse 129, CH-8600, Switzerland
Proceedings of Atomic-level characterization of hybrid perovskites (HPATOM)
Online, Spain, 2021 January 26th - 28th
Organizers: Dominik Kubicki and Amita Ummadisingu
Oral, Marcel Aebli, presentation 017
Publication date: 14th January 2021

Formamidinium (FA)-based hybrid lead iodide perovskites (FAPbX3, X = I or Br/I) have recently led to significant improvements in the performance of perovskite photovoltaics. One of the remaining major hurdles is the instability of α-FAPbI3, which undergoes a phase transition from the desired three-dimensional cubic perovskite phase to a non-perovskite one-dimensional hexagonal lattice. Partial substitution of FA with Cs and, concomitantly, iodide with bromide is known to stabilize the material's cubic perovskite structure, as shown by X-ray diffraction. Nuclear quadrupole resonance (NQR) has been reported to resolve structural changes with accuracies commensurate with synchrotron X-ray diffraction and scattering.[1] We report the 127I NQR spectra of FA1−xCsxPbI3−yBry (x = 0 - 0.1, y = 0 - 3) showing not only the averaged but also the local iodide structures. Upon ion replacement, massive line broadening and new species can be observed, and these new species could be assigned to various coordination environments. These findings showcase the great potential of halide NQR for characterizing perovskite-based materials.

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