Application
of two-dimensional (2D) organic-inorganic hybrid halide perovskites for
optoelectronic devices requires detailed understanding of the local
structural features including the Pb-I bonding in the 2D layers and the capping
ligand-perovskite interaction. In this study, we show that <sup>1</sup>H and <sup>207</sup>Pb
solid-state Nuclear Magnetic Resonance (NMR) spectroscopy can serve as a
non-invasive and complementary technique to quantify the composition and to
probe the local structural features of 2D Ruddlesden-Popper phase BA<sub>2</sub>MA<i><sub>n</sub></i><sub>-1</sub>Pb<i><sub>n</sub></i>I<sub>3<i>n</i>+1</sub> (<i>n</i>=1-4) with butylammonium (BA) spacers. <sup>207</sup>Pb
echo and <sup>1</sup>H-detected <sup>207</sup>Pb→<sup>1</sup>H heteronuclear
correlation (HETCOR) experiments enables layer-by-layer structural detection of
2D halide perovskites. We show that the observed correlation between <sup>207</sup>Pb
NMR shifts and mean Pb-I bond lengths around each Pb site allows us to probe
the local bonding environment of Pb via its <sup>207</sup>Pb NMR shift. We
envisage that this technique will be vital for better understanding the
materials properties as determined by the local atomistic environments in
multi-dimensional halide perovskites.