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

Journal article

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 (EQE_max) 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.

Authors: Sharma, S; Wong, MY; Hall, D; Spuling, E; Tenopala-Carmona, F

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Royal Society of Chemistry (RSC)
• Journal: Journal of Materials Chemistry C
• Volume: 8
• Pages: 3773-3783
• Publication date: 2020-01-28
• Acceptance date: 2020-01-27
• DOI: 10.1039/c9tc06356k
• EISSN: 2050-7534
• ISSN: 2050-7526
• Language: English