Urea-lly have to appreciate the way urea improved this film growth!

Wenhui Wang, Utkur Mirsaidov and their colleagues at the National University of Singapore published in-situ observation of perovskite formation using their Hummingbird Scientific in-situ liquid cell TEM sample holder. The on-chip heating capability allowed the direct visualization of the crystallization process of methylammonium lead iodide perovskite films from precursor solution at 90 °C.

Adding urea to the precursor solution was found to increase grain size by enhancing perovskite solubility. This promoted dissolution of smaller grains and re-deposition onto larger crystals via Ostwald ripening. Further grain growth in pre-formed films was even induced by spin-coating urea solution onto them post-synthesis. The resolution enabled by liquid-phase TEM enabled the observation of transient intermediates that are missed by ex situ techniques. This revealed the intrinsic crystallization pathways, closely replicating growth under normal processing conditions.

This work uncovers the mechanisms which govern chemistry-structure-property relationships in candidate materials for photoelectric devices and provides key insights into tailoring crystallization dynamics. The team also demonstrates the utility of liquid cell TEM for the study of thin film growth by solution.

Reference:  Wenhui Wang, Tanmay Ghosh, Hongwei Yan, Ivan Erofeev, Kun Zhang, Kian Ping Loh, and Utkur Mirsaidov, J. Am. Chem. Soc. 144 17848−17856 (2022) DOI: 10.1021/jacs.2c06022

Full paper Copyright © 2022 American Chemical Society

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