Metal Halide Perovskite and Perovskite-like Materials through the Lens of Ultra-wideline Cl-35/37 NMR Spectroscopy

With their exceptional optoelectronic features, metal halide perovskites (MHPs) are pushing the next wave of energy-related materials investigations have focused on readily accessible nuclei. In contrast, the halogen environments have been avoided due to their challenging quadrupolar nature. Here, we report a rapid 35/37Cl NMR strategy for MHPs, halide double perovskites (HDPs), and perovskite-inspired (PI) materials embracing ultra-wideline acquisition approaches at moderate and ultrahigh magnetic fields. The observed quadrupolar NMR parameters (CQ and eta), supported by GIPAW-DFT computations, provide an analytical fingerprint revealing distinct features for chemically unique Cl environments sensitive to ion mixing, dimensionality, cell volume, and Cl coordinating polyhedra. Moreover, we report resolution between two nearly identical and two distinct Cl environments of 3D and 2D Cs-based lead halide perovskites, respectively. These results reveal a strategy for a routine and robust spectroscopic approach to analyze local Cl chemical environments in metal halide perovskites that can be extended broadly to other halogencontaining semiconductors.