Solid-state Nuclear Magnetic Resonance Spectroscopy applied to formamidinium-methylammonium mixed hybrid perovskites

Abstract

The incorporation of formamidinium into hybrid perovskites has proven beneficial in terms of stability as well as efficiency. Indeed, the highest efficiency lab-scale devices currently contain a certain percentage of the formamidinium cation. Therefore this system was chosen for an in-depth NMR study. Formamidiniummethylammonium lead iodide phases (FAxMA1-xPbI3) with different FA/MA ratios were prepared. Powders obtained via a precipitation method were compared with powders obtained by scarping off films. The powders were analyzed using X-ray diffraction and 1H-, 13C- and 207Pb solid–state NMR. The incorporation of formamidine and methylamine in the hybrid perovskite crystal lattice can be derived from differences in relaxation behavior compared to the precursor salts. The 207Pb resonance peak shifts systematically with the FA/MA ratio present in the powders.