Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes

Zhengqing Gan, Yun Tian, David W. Lynch, Ji Hun Kang, Q Han Park, Joseph Shinar

Research output: Contribution to journalArticle

1 Citation (Scopus)

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′ -biphenyl (DPVBi), and some guest-host small molecular organic light-emitting diodes (OLEDs), fabricated on indium tin oxide (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 l devices exhibit an apparent weak optical gain 0≤g≤1.86 cm -1, there is no observable threshold current or bias associated with this spectral narrowing. In addition, in the phosphorescent guest-host OLEDs, there is no decrease in the emission decay time of the narrowed edge emission relative to the broad surface emission. 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. However, it is not clear if such a misalignment can account for all the effects of the observed evolution of the edge-emission spectra with l.

Original languageEnglish
Article number094502
JournalJournal of Applied Physics
Volume106
Issue number9
DOIs
Publication statusPublished - 2009 Nov 30

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light emitting diodes
waveguides
misalignment
indium oxides
tin oxides
glass
grazing
diamines
threshold currents
line spectra
emission spectra
lenses
thresholds
probes
decay
room temperature

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes. / Gan, Zhengqing; Tian, Yun; Lynch, David W.; Kang, Ji Hun; Park, Q Han; Shinar, Joseph.

In: Journal of Applied Physics, Vol. 106, No. 9, 094502, 30.11.2009.

Research output: Contribution to journalArticle

Gan, Zhengqing ; Tian, Yun ; Lynch, David W. ; Kang, Ji Hun ; Park, Q Han ; Shinar, Joseph. / Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes. In: Journal of Applied Physics. 2009 ; Vol. 106, No. 9.
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