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Title: Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes
Authors: Brown, Alasdair Angus Macintyre
Hooper, Thomas J. N.
Veldhuis, Sjoerd Antonius
Chin, Xin Yu
Bruno, Annalisa
Vashishtha, Parth
Tey, Ju Nie
Jiang, Liudi
Damodaran, Bahulayan
Pu, Suan Hui
Subodh Gautam Mhaisalkar
Mathews, Nripan
Keywords: Engineering::Materials
Issue Date: 2019
Source: Brown, A. A. M., Hooper, T. J. N., Veldhuis, S. A., Chin, X. Y., Bruno, A., Vashishtha, P., . . . Mathews, N. (2019). Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes. Nanoscale, 11(25), 12370-12380. doi:10.1039/C9NR02566A
Journal: Nanoscale 
Abstract: We report the self-assembly of an extensive inter-ligand hydrogen-bonding network of octylphosphonates on the surface of cesium lead bromide nanocrystals (CsPbBr3 NCs). The post-synthetic addition of octylphosphonic acid to oleic acid/oleylamine-capped CsPbBr3 NCs promoted the attachment of octylphosphonate to the NC surface, while the remaining oleylammonium ligands maintained the high dispersability of the NCs in non-polar solvent. Through powerful 2D solid-state 31P–1H NMR, we demonstrated that an ethyl acetate/acetonitrile purification regime was crucial for initiating the self-assembly of extensive octylphosphonate chains. Octylphosphonate ligands were found to preferentially bind in a monodentate mode through P–O−, leaving polar P[double bond, length as m-dash]O and P–OH groups free to form inter-ligand hydrogen bonds. The octylphosphonate ligand network strongly passivated the nanocrystal surface, yielding a fully-purified CsPbBr3 NC ink with PLQY of 62%, over 3 times higher than untreated NCs. We translated this to LED devices, achieving maximum external quantum efficiency and luminance of 7.74% and 1022 cd m−2 with OPA treatment, as opposed to 3.59% and 229 cd m−2 for untreated CsPbBr3 NCs. This represents one of the highest efficiency LEDs obtained for all-inorganic CsPbBr3 NCs, accomplished through simple, effective passivation and purification processes. The robust binding of octylphosphonates to the perovskite lattice, and specifically their ability to interlink through hydrogen bonding, offers a promising passivation approach which could potentially be beneficial across a breadth of halide perovskite optoelectronic applications.
ISSN: 2040-3364
DOI: 10.1039/C9NR02566A
DOI (Related Dataset):
Rights: © 2019 The Royal Society of Chemistry. All rights reserved. This paper was published in Nanoscale and is made available with permission of The Royal Society of Chemistry.
Fulltext Permission: open
Fulltext Availability: With Fulltext
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