Investigation of the Octahedral Network Structure in Formamidinium Lead Bromide Nanocrystals by Low-Dose Scanning Transmission Electron Microscopy

• DOI: 10.1021/acs.nanolett.4c02811
• Publication Date: 2024-08-20T11:42:33Z
• Authors: Nadine J. Schrenker; Tom Braeckevelt; Annick De Backer; Nikolaos Livakas; Chu-Ping Yu; Thomas Friedrich; Maarten B. J. Roe...; Johan Hofkens; Johan Verbeeck; Liberato Manna; Veronique Van Spe...; Sandra Van Aert; Sara Bals
• Keywords: Technology and Engineering; hybrid organic-inorganic metal halide perovskites; neural network; PHASE; molecular dynamics; HALIDE PEROVSKITES; PATHWAY; MODEL; 4D-STEM; transmission electron microscopy; hybrid organic-inorganic metal halide perovskites; neural network; octahedral tilt; molecular dynamics; Chemistry; Physics and Astronomy; transmission electron microscopy; octahedral tilt; 4D-STEM; Engineering sciences. Technology

Metal halide perovskites (MHP) are highly promising semiconductors. In this study, we focus on FAPbBr3 nanocrystals, which are of great interest for green light-emitting diodes. Structural parameters significantly impact the properties of MHPs and are linked to phase instability, which hampers long-term applications. Clearly, there is a need for local and precise characterization techniques at the atomic scale, such as transmission electron microscopy. Because of the high electron beam sensitivity of MHPs, these investigations are extremely challenging. Here, we applied a low-dose method based on four-dimensional scanning transmission electron microscopy. We quantified the observed elongation of the projections of the Br atomic columns, suggesting an alternation in the position of the Br atoms perpendicular to the Pb-Br-Pb bonds. Together with molecular dynamics simulations, these results remarkably reveal local distortions in an on-average cubic structure. Additionally, this study provides an approach to prospectively investigating the fundamental degradation mechanisms of MHPs.