Study of organic light-emitting diodes with exciplex and non-exciplex forming interfaces consisting of an ultrathin rubrene layer

摘要

Fluorescent organic light-emitting diodes (OLEDs) with exciplex and non-exciplex forming interfaces, where an ultrathin 5,6,11,12,-tetraphenylnaphtacene (rubrene) emissive layer was sandwiched, were fabricated. The performances of 4,4',4 ''-tris(N-carbazolyl)-triphenylamine (TCTA)/1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) exciplex-type device and 4,4'-di(9H-carbazol-9-yl)biphenyl (CBP)/ TPBi no-exciplex-type device were optimized in terms of the thickness of rubrene ultrathin layer. The results showed that the exciplex-type device yielded high device efficiency, attributing to the utilization of triplet excitons as the triplets of the exciplex can be up -converted into singlets via reverse intersystem crossing. The light emission process in exciplex-type device"was dominated by energy transfer, while the non-exciplex type device was dominated by charge trapping emission mechanism, which was verified by the single carrier devices. (C) 2016 Elsevier B.V. All rights reserved.