Exciton efficiency beyond the spin statistical limit in organic light emitting diodes based on anthracene derivatives. Issue 11 (17th February 2020)

• Record Type: Journal Article
• Authors: Sharma, Nidhi; Wong, Michael Yin; Hall, David; Spuling, Eduard; Tenopala-Carmona, Francisco; Privitera, Alberto; Copley, Graeme; Cordes, David B.; Slawin, Alexandra M. Z.; Murawski, Caroline; Gather, Malte C.; Beljonne, David; Olivier, Yoann; Samuel, Ifor D. W.; Zysman-Colman, Eli
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 11(2020)
• Page Start: 3773
• Page End: 3783
• Publication Date: 2020-02-17
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc06356k
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : We report two donor–acceptor (D–A) materials based on a cyanoanthracene acceptor paired with diphenylamine (DPAAnCN ) and carbazole (CzAnCN ) donor moieties. Abstract : 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 ( Φ s ) 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.