Lead-Halide Scalar Couplings in (207)Pb NMR of APbX(3) Perovskites (A = Cs, Methylammonium, Formamidinium; X = Cl, Br, I)

Understanding the structure and dynamics of newcomer optoelectronic materials - lead halide perovskites APbX(3) [A = Cs, methylammonium (CH(3)NH(3)(+), MA), formamidinium (CH(NH(2))(2)(+), FA); X = Cl, Br, I] - has been a major research thrust. In this work, new insights could be gained by using (207)Pb solid-state nuclear magnetic resonance (NMR) spectroscopy at variable temperatures between 100 and 300 K. The existence of scalar couplings (1)J(Pb-Cl) of ca. 400 Hz and (1)J(Pb-Br) of ca. 2.3 kHz could be confirmed for MAPbX(3) and CsPbX(3). Diverse and fast structure dynamics, including rotations of A-cations, harmonic and anharmonic vibrations of the lead-halide framework and ionic mobility, affect the resolution of the coupling pattern. (207)Pb NMR can therefore be used to detect the structural disorder and phase transitions. Furthermore, by comparing bulk and nanocrystalline CsPbBr(3) a greater structural disorder of the PbBr(6)-octahedra had been confirmed in a nanoscale counterpart, not readily captured by diffraction-based techniques.