Local Structure and Distortions in Crystalline, Glass and Melt States of 2D Hybrid Perovskites

The pursuit of structure-property relationships in metal halide perovskites (MHPs) has yielded an unprecedented combination of advantageous characteristics for wide-ranging optoelectronic and quantum applications. Among the typically examined crystalline MHPs, distortions within the inorganic framework critically define transport- and spin-related material properties (e.g., band gap, spin splitting, ferroelectric or non-linear optical character). These distortions are often governed by relatively weak supramolecular (non-covalent) interactions, notably including hydrogen (H) bonding. However, H atom positions are difficult to accurately distinguish employing standard X-ray diffraction, especially in the presence of heavy Pb and I atoms.¹ Recent extensions to MHP glassy and melt states,² which lack long-range order, pose additional challenges for connecting properties with local structure and require approaches beyond single crystal X-ray diffraction.³ The current presentation will introduce techniques for characterizing crystalline (long-range ordering) and amorphous (local ordering) states of MHPs—e.g., including, for example, combining X-ray diffraction with neutron diffraction, pair distribution function (PDF) analysis, density functional theory (DFT), solid-state NMR, and infrared spectroscopies. Such a multimodal approach to structural analysis provides unique insights into structure-property relationships in the continuously evolving MHP family.

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2. A. Singh, M. K. Jana, D. B. Mitzi, Adv. Mater. 33, 2005868 (2021).
3. A. Singh, D. Dayton, D. M. Ladd, G. Reuveni, P. Paluch, L. Montagne, J. Mars, O. Yaffe, M. Toney, G. N. M. Reddy, D. B. Mitzi, J. Am. Chem. Soc. 146, 25656 (2024).