Layer-by-Layer Structural Identification of 2D Ruddlesden–Popper Hybrid Lead Iodide Perovskites by Solid-State NMR Spectroscopy

Application of two-dimensional (2D) organic-inorganic hybrid halide perovskites in optoelectronic devices requires a detailed understanding of the local structural features including the Pb-I bonding in the 2D layers and the organic-inorganic interaction between the organic spacer molecules and the perovskite layer. In this study, we show that H-1 and Pb-207 solid-state nuclear magnetic resonance (NMR) spectroscopy can serve as a noninvasive and complementary technique to probe the local structural features of the 2D Ruddlesden-Popper phase BA(2)MA(n-1)Pb(n)I(3n+1) (n = 1 - 4) with butylammonium (BA) spacers. Pb-207 echo and Pb-207 -> H-1 heteronuclear correlation experiments enable layer-by-layer structural detection of 2D halide perovskites. We show that the observed correlation between Pb-207 NMR shifts and mean Pb-I bond lengths around each Pb site allows us to probe the local bonding environment of Pb. We envisage that this technique will be vital for a better understanding of the properties of materials as determined by the local atomistic environments in multidimensional halide perovskites.