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dc.contributor.authorEvariste, Sloane
dc.contributor.authorSandroni, Martina
dc.contributor.authorRees, Thomas W.
dc.contributor.authorRoldán-Carmona, Cristina
dc.contributor.authorGil-Escrig, Lidon
dc.contributor.authorBolink, Henk J.
dc.contributor.authorBaranoff, Etienne
dc.contributor.authorZysman-Colman, Eli
dc.identifier.citationEvariste , S , Sandroni , M , Rees , T W , Roldán-Carmona , C , Gil-Escrig , L , Bolink , H J , Baranoff , E & Zysman-Colman , E 2014 , ' Fluorine-free blue-green emitters for light-emitting electrochemical cells ' , Journal of Materials Chemistry C , vol. 2 , no. 29 , pp. 5793-5804 .
dc.identifier.otherPURE: 160124947
dc.identifier.otherPURE UUID: 3e030a0b-0804-4805-a174-f78ca8298fb1
dc.identifier.otherScopus: 84903991252
dc.identifier.otherORCID: /0000-0001-7183-6022/work/56639137
dc.identifier.otherWOS: 000339396700008
dc.descriptionDate of Acceptance: 29/05/2014en
dc.description.abstractThere is presently a lack of efficient and stable blue emitters for light-emitting electrochemical cells (LEECs), which limits the development of white light emitting systems for lighting. Cyclometalated iridium complexes as blue emitters tend to show low photoluminescence efficiency due to significant ligand-centred character of the radiative transition. The most common strategy to blue-shift the emission is to use fluorine substituents on the cyclometalating ligand, such as 2,4-difluorophenylpyridine, dFppy, which has been shown to decrease the stability of the emitter in operating devices. Herein we report a series of four new charged cyclometalated iridium complexes using methoxy- and methyl-substituted 2,3′-bipyridine as the main ligands. The combination of donor groups and the use of a cyclometalated pyridine has been recently reported for neutral complexes and found electronically equivalent to dFppy. We describe the photophysical and electrochemical properties of the complexes in solution and use DFT and TDDFT calculations to gain insights into their properties. The complexes exhibit bluish-green emission with onsets around 450 nm, which correspond to the maximum emission at 77 K. Furthermore, photoluminescence quantum yields in solution are all above 40%, with the brightest in the series at 66%. Finally, LEECs were prepared using these complexes as the emissive material to evaluate the performance of this particular design. Compared to previously reported devices with fluorine-containing emitters, the emitted colours are slightly red-shifted due to methyl substituents on the coordinating pyridine of the main ligand and overall device performances, unfortunately including the stability of devices, are similar to those previously reported. Interestingly within the series of complexes there appears to be a positive effect of the methoxy-substituents on the stability of the devices. The poor stability is therefore attributed to the combination of cyclometalated pyridine and methoxy groups.
dc.relation.ispartofJournal of Materials Chemistry Cen
dc.rights© Royal Society of Chemistry 2014. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at No further copies may be made or distributed.en
dc.subjectQD Chemistryen
dc.titleFluorine-free blue-green emitters for light-emitting electrochemical cellsen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews. School of Chemistryen
dc.contributor.institutionUniversity of St Andrews. EaSTCHEMen
dc.description.statusPeer revieweden

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