Direct investigation of the reorientational dynamics of A-site cations in 2D organic-inorganic hybrid perovskite by solid-state NMR.

Lin, Cheng-Chieh; Huang, Shing-Jong; Wu, Pei-Hao; Chen, Tzu-Pei; Huang, Chih-Ying; Wang, Ying-Chiao; Chen, Po-Tuan; Radeva, Denitsa et al. · Nat Commun · 2022

basic_science · Level V

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Abstract

Limited methods are available for investigating the reorientational dynamics of A-site cations in two-dimensional organic-inorganic hybrid perovskites (2D OIHPs), which play a pivotal role in determining their physical properties. Here, we describe an approach to study the dynamics of A-site cations using solid-state NMR and stable isotope labelling. <sup>2</sup>H NMR of 2D OIHPs incorporating methyl-d<sub>3</sub>-ammonium cations (d<sub>3</sub>-MA) reveals the existence of multiple modes of reorientational motions of MA. Rotational-echo double resonance (REDOR) NMR of 2D OIHPs incorporating <sup>15</sup>N- and ¹³C-labeled methylammonium cations (<sup>13</sup>C,<sup>15</sup>N-MA) reflects the averaged dipolar coupling between the C and N nuclei undergoing different modes of motions. Our study reveals the interplay between the A-site cation dynamics and the structural rigidity of the organic spacers, so providing a molecular-level insight into the design of 2D OIHPs.