Multinuclear solid-state NMR investigation of structurally diverse low-dimensional hybrid metal halide perovskites

Abstract

Owing to their synthetic versatility and optoelectronic tunability, low-dimensional hybrid metal halide perovskites (MHPs) provide a key avenue for the design of future optoelectronic materials. Nuclear magnetic resonance (NMR) spectroscopy has emerged as a powerful tool for structural characterisation and molecular dynamics elucidation in MHPs, which are known to control the materials' optoelectronic properties. In this work, we utilise solid state NMR to study structurally diverse hybrid MHPs containing 2D, 1D and 0D inorganic motifs that are templated by a series of xylylenediammonium cations and compare their characteristics with those of archetype 3D perovskites. The highly resolved scalar coupling pattern (J¹(²⁰⁷Pb–^79/81Br) = 1.98 kHz) in the ²⁰⁷Pb NMR spectrum of 0D meta-xylylenediammonium lead bromide ((mXDA)₂PbBr₆), reveals that ²⁰⁷Pb NMR of methylammonium lead bromide (MAPbBr₃) and formadinium lead bromide (FAPbBr₃) is sensitive to local Br positional disorder, associated with the fast reorientation of the MA/FA cations. Variable temperature ¹H spin–lattice relaxation quantifies the correlation time of the reorientation of the MA/FA cations at picosecond timescales, in contrast to the slower motion of the bulky cations in the low-dimensional perovskites. Additionally, the study of meta-xylylenediammonium tin halides ((mXDA)₂SnX₆) provides the first direct detection of tin-halide scalar coupling patterns (J¹(¹¹⁹Sn–^79/81Br) = 1.51 kHz; J¹(¹¹⁹Sn–^35/37Cl) = 260 Hz).