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A Small Cationic Organo-Copper Cluster as Thermally Robust Highly Photo- and Electroluminescent Material.

Marian OlaruElena RychagovaSergey Yu KetkovYevhen ShynkarenkoSergii YakuninMaksym V KovalenkoArtem YablonskiyBoris AndreevFlorian KleemissJens BeckmannMatthias Vogt
Published in: Journal of the American Chemical Society (2019)
Organic light-emitting diodes (OLEDs) are revolutionizing display applications. In this aspect, luminescent complexes of precious metals such as iridium, platinum, or ruthenium still playing a significant role. Emissive compounds of earth-abundant copper with equivalent performance are desired for practical, large-scale applications such as solid-state lighting and displays. Copper(I)-based emitters are well-known to suffer from weak spin-orbit coupling and a high reorganization energy upon photoexcitation. Here we report a cationic organo-copper cluster [Cu4(PCP)3]+ (PCP = 2,6-(PPh2)2C6H3) that features suppressed nonradiative decays, giving rise to a robust narrow-band green luminophore with a photoluminescent (PL) efficiency up to 93%. PL decay kinetics corroborated by DFT calculations reveal a complex emission mechanism involving contributions of both thermally activated delayed fluorescence and phosphorescence. This robust compound was solution-processed into a thin film in prototype OLEDs with external quantum efficiency up to 11% and a narrow emission bandwidth (65 nm fwhm).
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