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


Image of FIG. 1.
FIG. 1.

Edge-emission detection system.

Image of FIG. 2.
FIG. 2.

The angle-dependent VSL measurement setup.

Image of FIG. 3.
FIG. 3.

(a) Edge and (b) surface emission from glass/[ ITO]/[5 nm CuPc]/[45 nm NPD]/[ nm Alq3]/[1 nm CsF]/Al OLEDs, where , 85, 105, 125, and 145 nm.

Image of FIG. 4.
FIG. 4.

Edge-emission spectrum of a glass/[ ITO]/[5 nm CuPc]/[45 nm NPD]/[120 nm DPVBi]/[7 nm Alq3]/[1 nm CsF]/Al OLED.

Image of FIG. 5.
FIG. 5.

Edge-emission EL spectra of ITO/[5 nm CuPc]/[40 nm NPD]/[ nm 1:1 NPD:spiro-DPVBi]/[40 nm spiro-DPVBi]/[8 nm Alq3]/[1 nm CsF]/Al OLEDs, , 30, 50, 70, and 90 nm.

Image of FIG. 6.
FIG. 6.

The edge-emission intensity vs polarization angle in polar coordinates: the solid line is the experimental data, the dashed line is the theoretical data fitting by Eq. (1).

Image of FIG. 7.
FIG. 7.

A drop of various liquids is placed between a photoexcited spot of the emitting film and the edge. If the edge emission is due to waveguide modes in the organic and ITO layers (top figure), then the change in the index of the cladding layer will strongly distort the edge-emission spectrum, since reflections on the upper boundary control the phase condition for mode selection. If the edge emission is due to the leaky modes in the glass substrate (bottom figure), the change in the cladding layer index will have no effect on the mode, because all energy flux has leaked into the substrate.

Image of FIG. 8.
FIG. 8.

PL Edge-emission spectra of (a) glass/ITO/[ nm DPVBi] and (b) glass/ITO/[ nm DPVBi]/Al, with , 76, 91, 106, and 121 nm, photoexcited at 363 nm (see the small peak at that wavelength) by an .

Image of FIG. 9.
FIG. 9.

Glass/[ ITO]/[5 nm CuPc]/[40 nm NPD]/[60 nm DPVBi]/[6 nm Alq3]/[1 nm CsF]/[100 nm Ag (solid line) or Al (dotted line)]/Al. Note that the FWHM of the device with a Ag cathode is half that of the device with an Al cathode.

Image of FIG. 10.
FIG. 10.

The simulated asymmetric slab waveguide modes.

Image of FIG. 11.
FIG. 11.

Dotted line: the surface emission spectra, which is assumed to be the spectrum of the light emitted in the organic film. Dashed line: the observed SNEE. Solid line: the simulated leaky waveguide mode spectrum.

Image of FIG. 12.
FIG. 12.

The normalized (left) and un-normalized (right) edge-emission spectra from DPVBi OLEDs with stripe length from . The arrows indicate increasing stripe length.

Image of FIG. 13.
FIG. 13.

The intensity of the peak of the TE mode vs the OLED stripe length. The black squares are the experiment data, and the curve is the fit of Eq. (5) to the data.

Image of FIG. 14.
FIG. 14.

(a) Edge-emission spectra vs stripe length . (b) The peak TE mode edge-emission intensity vs . (c) The FWHM of the TE mode edge-emission spectrum vs .

Image of FIG. 15.
FIG. 15.

The peak edge-emission intensity vs the stripe length at different voltages, the lines are the best fits of the function .

Image of FIG. 16.
FIG. 16.

The FWHM of the TE mode edge-emission spectrum vs the stripe length .

Image of FIG. 17.
FIG. 17.

ITO layer (black area) is patterned into a staircase-type in steps. Rectangular Al cathodes (gray area) are deposited. The overlapped area defines OLED devices.

Image of FIG. 18.
FIG. 18.

Edge-emission spectra of an OLED with the device structure: glass/ITO/[5 nm CuPc]/[45 nm NPD]/[61 nm DPVBi]/[9 nm Alq3]/[1 nm CsF]/Al, the excitation stripe length l is varied from 100 to .

Image of FIG. 19.
FIG. 19.

The intensity vs stripe length at detection angles of 0°, −5°, and −10°.

Image of FIG. 20.
FIG. 20.

The FWHM of the edge-emission spectrum at detection angles from −25° to 60°.

Image of FIG. 21.
FIG. 21.

FDTD-predicted intensity of edge emission for various sample lengths.

Image of FIG. 22.
FIG. 22.

Intensity profiles of modes excited at (a) top: , (b) center: , and (c) bottom: .

Image of FIG. 23.
FIG. 23.

(a) Surface and (b) edge-emission spectra of Ir(ppy)3 OLEDs with various emitting layer thicknesses. (c) The magnification of the edge-emission spectra.

Image of FIG. 24.
FIG. 24.

(a) Surface and (b) edge-emission decay time of Ir(ppy)3 OLEDs with different emitting layer thicknesses at different bias.

Image of FIG. 25.
FIG. 25.

(a) Surface and (b) edge-emission spectra of FIrpic OLEDs with different thicknesses. (c) The lifetime of the edge (dot) and surface (square) emission.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes