On the interplay of waveguide modes and leaky modes in corrugated OLEDs

Hauss, Julian; Bocksrocker, Tobias; Riedel, Boris; Lemmer, Uli; Gerken, Martina

doi:10.1364/oe.19.00a851

Cited by 27 publications

(29 citation statements)

References 25 publications

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“…2(c). These findings are in agreement with recent results in [24] where we discussed the complex interplay of scattering processes between waveguide modes, substrate modes and radiation modes. For certain geometries the losses due to enhanced incoupling of radiation modes into waveguide modes might overcompensate the enhanced outcoupling of waveguide modes into radiation modes.…”

Section: Measurement and Resultssupporting

confidence: 93%

White organic light emitting diodes with enhanced internal and external outcoupling for ultra-efficient light extraction and Lambertian emission

Bocksrocker¹,

Preinfalk²,

Asche-Tauscher³

et al. 2012

Opt. Express

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White organic light emitting diodes (WOLEDs) suffer from poor outcoupling efficiencies. The use of Bragg-gratings to enhance the outcoupling efficiency is very promising for light extraction in OLEDs, but such periodic structures can lead to angular or spectral dependencies in the devices. Here we present a method which combines highly efficient outcoupling by a TiO 2 -Bragg-grating leading to a 104% efficiency enhancement and an additional high quality microlens diffusor at the substrate/air interface. With the addition of this diffusor, we achieved not only a uniform white emission, but also further increased the already improved device efficiency by another 94% leading to an overall enhancement factor of about 4.

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Section: Measurement and Resultssupporting

confidence: 93%

White organic light emitting diodes with enhanced internal and external outcoupling for ultra-efficient light extraction and Lambertian emission

Bocksrocker¹,

Preinfalk²,

Asche-Tauscher³

et al. 2012

Opt. Express

Self Cite

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“…Hence, the emission from Device C cannot be understood simply as the emission of a planar microcavity with superposed Bragg scattering. The weak perturbation approach previously discussed by Hauss et al [34] and Fuchs et al [28] does not suffice to describe these experimental data, despite the fact that the previously mentioned thickness criterion h C /d opt = 0.33 < 1 holds. This thickness criterion was originally derived for weak optical microcavities of dielectric media excluding metals within the optical microcavity [33].…”

Section: Mode Analysis Of Top-emitting Oleds On Periodically Corrugatmentioning

confidence: 89%

“…Hauss et al [34] observed a reduction of emission in a corrugated bottom-emitting OLED due to a more prominent transfer of light intensity from the air cone into wave-guided modes in comparison to the reverse scattering of guided modes into the air cone. However, their approach cannot account for the absence of the fundamental cavity mode in our corrugated microcavity top-emitting OLEDs nor for the observed bending of the dispersion relations.…”

Section: Mode Analysis Of Top-emitting Oleds On Periodically Corrugatmentioning

confidence: 99%

Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates

Schwab¹,

Fuchs²,

Scholz³

et al. 2014

Opt. Express

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Abstract:Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to 17.5 % for a corrugated OLED with a grating period of 1.0 µm and a modulation depth of about 70 nm. Detailed analysis and optical modeling of the angular resolved emission spectra of the OLEDs provide evidence for Bragg scattering of waveguided and surface plasmon modes that are normally confined within the OLED stack into the air-cone. We observe constructive and destructive interference between these scattered modes and the radiative cavity mode. This interference is quantitatively described by a complex summation of Lorentz-like resonances.

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“…The broad background is due to the light which was directly emitted from the OLED with wavevectors within the light escape cone and thus not affected by the photonic microstructures. Currently the most common method to model the spatial emission pattern of a microstructured OLED is simply to analyse the photonic dispersion of a grating by the Bragg condition [14][15][16][17]. This calculates the out-coupling elevation and azimuthal angles of trapped modes, but does not provide information about the relative power distribution of the far field emission.…”

Section: Introductionmentioning

confidence: 99%

Calculation of the emission power distribution of microstructured OLEDs using the reciprocity theorem

et al. 2015

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Integrating photonic microstructures into organic light-emitting diodes (OLEDs) has been a widely used strategy to improve their light out-coupling efficiency. However, there is still a need for optical modelling methods which quantitatively characterise the spatial emission pattern of microstructured OLEDs. In this paper, we demonstrate such rigorous calculation using the reciprocity theorem. The calculation of the emission intensity at each direction in the far field can be simplified into only two simple calculations of an incident plane wave propagating from the far field into a single cell of the periodic structure. The emission from microstructured OLED devices with three different grating periods was calculated as a test of the approach, and the calculated results were in good agreement with experiment. This optical modelling method is a useful calculation tool to investigate and control the spatial emission pattern of microstructured OLEDs.

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On the interplay of waveguide modes and leaky modes in corrugated OLEDs

Cited by 27 publications

References 25 publications

White organic light emitting diodes with enhanced internal and external outcoupling for ultra-efficient light extraction and Lambertian emission

White organic light emitting diodes with enhanced internal and external outcoupling for ultra-efficient light extraction and Lambertian emission

Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates

Calculation of the emission power distribution of microstructured OLEDs using the reciprocity theorem

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