Deep Blue Exciplex Organic Light‐Emitting Diodes with Enhanced Efficiency; P‐type or E‐type Triplet Conversion to Singlet Excitons?
- 27 December 2012
- journal article
- Published by Wiley in Advanced Materials
- Vol. 25 (10), 1455-1459
- https://doi.org/10.1002/adma.201203615
Abstract
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 trapKeywords
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