Spectrally narrowed edge emission from leaky waveguide modes in OLEDs - art. no. 66550K

TitleSpectrally narrowed edge emission from leaky waveguide modes in OLEDs - art. no. 66550K
Publication TypeBook Chapter
Year of Publication2007
AuthorsGan ZQ, Tian Y, Lynch DW, Kang JH, Park QH, Shinar J
EditorKafafi ZH, So F
Book TitleOrganic Light Emitting Materials and Devices Xi
CityBellingham
PublisherSpie-Int Soc Optical Engineering
Volume6655
PagesK6550-K6550
Series TitleProceedings of the Society of Photo-Optical Instrumentation Engineers (Spie)
ISBN Number0277-786X978-0-8194-6803
Accession NumberISI:000253181700014
KeywordsAMPLIFIED SPONTANEOUS EMISSION, CATHODE, DIODES, EXCITATION, GAIN, INJECTION, LASERS, LIGHT-EMITTING DEVICES, POLYMER, solid-state, thin-films
Abstract

A dramatic spectral line narrowing of the. edge-emission, at room temperature, from tris(quinolinolate) Al (Alq(3)), N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPD), 4,4'-bis(2,2'-diphenyl- vinyl)-1,1'-biphenyl (DPVBi), and some guest-host small molecular OLEDs, fabricated on ITO-coated glass, is described. In all but the DPVBi OLEDs, the narrowed emission band emerges above a threshold thickness of the emitting layer, and narrows down to a full width at half maximum of only 5 - 10 nm. The results demonstrate that this narrowed emission is due to irregular waveguide modes that leak from the ITO to the glass substrate at a grazing angle. While measurements of variable stripe length ( devices exhibit an apparent weak optical, gain, there is no observable threshold current or bias associated with this spectral narrowing. It is suspected that the apparent weak optical gain is due to misalignment of the axis of the waveguided mode and the axis of the collection lens of the probe, but it is not clear if such a misalignment can account for the for the observed evolution of the edge emission spectra with l.