Solid State NMR of Tin-based Perovskites

Metal halide perovskites (MHPs) have attracted significant attention in the last decades, due to their exceptional optoelectronic properties, particularly in the fields of photovoltaic panels and light-emitting devices. While most progress has been made with lead (Pb)-based perovskites due to their excellent solar cell performance, it is widely known that lead is toxic and environmentally harmful. As a result, tin (Sn(II)) based perovskites, have emerged as a promising alternative. However the poor stability of tin and its tendency to oxidize have hindered the development of these materials. The slow pace of progress in this field is also due to a scarcity of methods capable of probing the microstructure and supramolecular environment of perovskites, which is essential for improving their stability and performance. This work seeks to characterize two tin based perovskites, FASnI3 (3D) and PEA2SnI4 (2D), by solid-state NMR and single-crystal X-ray diffraction (SCXRD), with the purpose of granting a comprehensive understanding of their structure and dynamics. In fact, solid state NMR can provide an in-depth analysis of the local environments of individual atoms, as well as their orientation and mobility, while XRD offers a broader view of their 3D crystalline structure. The focus is primarily on PEA2SnI4, as it was observed that the use of two distinct precursors, SnO and SnI2, generated significant differences in both ss-NMR spectra and XRD data, suggesting that the choice of precursor affects the material’s structure and order. This study highlights the potential of solid-state NMR in advancing research on tin-based perovskites and it opens the door for future exploration of how structural disorder impacts their performance.