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Adv Mater. 2013 Mar 13;25(10):1455-9. doi: 10.1002/adma.201203615. Epub 2012 Dec 27.

Deep blue exciplex organic light-emitting diodes with enhanced efficiency; P-type or E-type triplet conversion to singlet excitons?

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Physics Department, University of Durham, Durham, UK.


Simple trilayer, deep blue, fluorescent exciplex organic light-emitting diodes (OLEDs) are reported. These OLEDs emit from an exciplex state formed between the highest occupied molecular orbital (HOMO) of N,N'-bis(1-naphthyl)N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and lowest unoccupied molecular orbital (LUMO) of 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi) and the NPB singlet manifold, yielding 2.7% external quantum efficiency at 450 nm. It is shown that the majority of the delayed emission in electroluminescence arises from P-type triplet fusion at NPB sites not E-type reverse intersystem crossing because of the presence of the NPB triplet state acting as a deep trap.


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