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

Abstract

We report on Pb,Br, N,H, C andH 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. ThereforePb 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 andN 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.

Screening Approach for the Discovery of New Hybrid Perovskites with Efficient Photoemission

“…By contrast, the two crystallographic sites are difficult to observe in the 207 Pb MAS NMR spectrum of the bromide perovskite Br‐E6 . Recently, Roiland et al carried out an extended NMR study of (CH 3 NH 3 )PbX 3 compounds with X = Cl, Br, and I . From X = Cl to X = Br, they showed that the 207 Pb signal shifts by ≈ +1000 ppm along with a fourfold increase in linewidth.…”

Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites

“…Since the first preparation of the hybrid lead halide perovskites, 12 the behavior of the molecular cations has been studied by calorimetry, 13,14 infrared spectroscopy, 13,15,16 dielectric spectroscopy, 14,[17][18][19][20] Raman spectroscopy, 21 quasi-elastic and inelastic neutron scattering, [22][23][24][25][26] nuclear magnetic resonance (NMR) spectroscopy, [27][28][29][30][31][32] isotopic substitution, 33 and ab initio methods, [34][35][36][37][38][39] and these findings have been correlated to the structure evolution from crystallographic techniques. 19,[40][41][42][43][44][45][46] Most of these efforts have focused on MAPbX 3…”

Doping and phase segregation in Mn2+- and Co2+-doped lead halide perovskites from133Cs and1H NMR relaxation enhancement

“…On the other hand, NMR is capable of providing atomic-level resolution by utilizing local nuclear probes such as 1 H, 13 C, 14 N, 133 Cs, 87 Rb, 39 K and 207 Pb. [37][38][39][40][41][42][43][44][45] In particular, 207 Pb is a good probe of the halide composition 38 but is far less sensitive to other changes in composition. 46,47 Solid-state NMR spectra are acquired by placing a powder sample inside a strong homogeneous magnetic eld (typically between around 10 and 20 T) and then recording spectra of the transitions between nuclear spin states which occur in the radiofrequency region.…”