Exciton efficiency beyond the spin statistical limit in organic light emitting diodes based on anthracene derivatives

We report two donor-acceptor (D-A) materials based on a cyanoanthracene acceptor paired with diphenylamine ( DPAAnCN ) and carbazole ( CzAnCN ) donor moieties. These compounds show hybrid locally excited (LE) charge-transfer (CT) excited states (HLCT), which we demonstrated through a combined photophysical and computational study. Vacuum- deposited organic light emitting diodes (OLEDs) using these HLCT emitters exhibit maximum external quantum efficiencies (EQEmax) close to 6%, with impressive exciton utilization efficiency (Φs) of >50%, far exceeding the spin statistic limit of 25%. We rule out triplet-triplet annihilation and thermally activated delayed fluorescence as triplet harvesting mechanisms along with horizontal orientation of emitters to enhance light outcoupling and, instead, propose a “hot exciton” channel involving the nearly isoenergetic T2 and S1 states.

Citation

Sharma , N , Wong , M Y , Hall , D , Spuling , E , Tenopala Carmona , F , Privitera , A , Copley , G J , Cordes , D B , Slawin , A M Z , Murawski , C , Gather , M C , Beljonne , D , Olivier , Y , Samuel , I D W & Zysman-Colman , E 2020 , ' Exciton efficiency beyond the spin statistical limit in organic light emitting diodes based on anthracene derivatives ' , Journal of Materials Chemistry C , vol. In press . https://doi.org/10.1039/C9TC06356K

Publication

Journal of Materials Chemistry C

Status

Peer reviewed

DOI

https://doi.org/10.1039/C9TC06356K

ISSN

2050-7526

Type

Journal article

Rights

Copyright © 2020 The Author(s). This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1039/C9TC06356K

Description

E.Z.-C. acknowledges the University of St Andrews and the Leverhulme Trust (RPG- 2016-047) for financial support. E.Z.-C. and I.D.W.S. thank EPSRC (EP/P010482/1) for support. We thank EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical services. The work in Mons was supported by the European Union’s Horizon 2020 research and innovation program under Grant Agreement N°. 646176 (EXTMOS project). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.- FNRS) under Grant No. 2.5020.11. C.M. and G.C acknowledge funding by the European Commission through a Marie Skłodowska Curie fellowship (No. 703387 and 799302, respectively). M.C.G. acknowledges funding from EPSRC (EP/R010595/1). A.P. acknowledges the European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska Curie Grant agreement No. 722651 (SEPOMO project). EPR measurements were performed in the Centre for Advanced ESR (CAESR), located in the Department of Chemistry of the University of Oxford, and this work was supported by the EPSRC (EP/L011972/1).

Collections

University of St Andrews Research

URI

http://hdl.handle.net/10023/21337