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

Bocksrocker, Tobias; Preinfalk, Jan B.; Asche-Tauscher, Julian; Pargner, Andreas; Eschenbaum, Carsten; Maier-Flaig, Florian; Lemme, Uli

doi:10.1364/oe.20.00a932

Cited by 35 publications

(27 citation statements)

References 25 publications

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“…The waveguided light confined in the active organic and ITO layers comprises 40–60% of the total emission. To further extract the waveguided light confined within high‐refractive‐index organic and ITO anode regions (waveguide modes), various strategies to engineer substrates have been proposed . The method based on a high‐refractive‐index substrate has been demonstrated to be highly effective, and can remarkably increase the amount of waveguided light coupled from the ITO/organic layers into the substrate .…”

Section: Flexible Photonic Devicesmentioning

confidence: 99%

“…Instead of using high‐refractive‐index substrates, the extraction of the waveguided light can be realized by implementing internal extraction structures, such as optical gratings or photonic crystals between the substrate and the transparent electrode . Most recently, Qu et al demonstrated a method for extracting the waveguided light of OLEDs by inserting a planar, non‐diffractive, dielectric grid layer between the transparent ITO electrode and the substrate .…”

Section: Flexible Photonic Devicesmentioning

confidence: 99%

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Toward Scalable Flexible Nanomanufacturing for Photonic Structures and Devices

et al. 2016

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Continuous and scalable nanopatterning over flexible substrates is highly desirable for both commercial and scientific interests, but is difficult to realize with traditional photolithographic processes. The recent advancements in nanofabrication methodologies enable light management with photonic structures on flexible materials, providing an increasingly popular strategy to control the light harvesting in the optoelectronic devices of photovoltaics, and in organic and inorganic light-emitting diodes. Here, the current status of nanopatterning technologies for the fabrication of optoelectronic devices is summarized. Scalable nanopatterning technologies for nanomanufacturing on flexible materials are emphasized. Critical challenges in various patterning techniques when considering the resolution, scalability, processing throughput, and the use of masks and resists are addressed. The integration of flexible nanopatterned substrates with light manipulation in organic optoelectronic devices is also discussed; this enables the control of light flux and spectra. Finally, potential development directions are highlighted.

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Section: Flexible Photonic Devicesmentioning

confidence: 99%

Section: Flexible Photonic Devicesmentioning

confidence: 99%

Toward Scalable Flexible Nanomanufacturing for Photonic Structures and Devices

et al. 2016

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“…Previous studies have shown that η OC of conventional OLEDs is limited at about 20% because total reflection at internal interfaces that light incidents from high refractive index medium to low refractive index medium 11‐13 . The η OC of OLEDs with various light‐out‐coupling (LOC) layers has been already reported 14‐25 . But there is still room for improvement because the η OC of OLEDs is only 30–50%.…”

Section: Introductionmentioning

confidence: 99%

“…[11][12][13] The η OC of OLEDs with various light-out-coupling (LOC) layers has been already reported. [14][15][16][17][18][19][20][21][22][23][24][25] But there is still room for improvement because the η OC of OLEDs is only 30-50%. Simulation methods for the design of a white OLED (WOLED) structure with a LOC layer are indispensable to improve η OC .…”

Section: Introductionmentioning

confidence: 99%

Characterization of light extraction efficiency for WOLEDS with light‐out‐coupling layer

et al. 2015

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“…To extract the waveguided light, internal outcoupling structures can be categorized into two groups. One is to modulate the photon states to extract light via optical gratings or photonic crystals 10,11 . This method leads to emission properties that depend on both viewing angle and wavelength, making it incompatible with display and lighting applications.…”

mentioning

confidence: 99%

Enhanced light extraction from organic light-emitting devices using a sub-anode grid

Slootsky

Forrest

2015

Nature Photon

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We demonstrate the highly effective extraction of waveguided light from the active region of organic light-emitting devices using a non-diffractive dielectric grid layer placed between the transparent anode and the substrate. The subanode grid couples out all waveguide mode power into the substrate without changing the device electrical properties, resulting in an increase in both the external quantum efficiency and luminous efficacy for green phosphorescent organic light-emitting devices from 15 ± 1% and 36 ± 2 lm W -1 to 18 ± 1% and 43 ± 2 lm W -1 . These characteristics are further increased to 40 ± 2% and 95 ± 4 lm W -1 when all glass modes are also extracted. The use of a thick electron transport layer further reduces surface plasmon modes, resulting in an increase in the substrate and air modes by 50 ± 8% compared with devices lacking the grids. The sub-anode grid has minimal impact on organic light-emitting device emission wavelength and viewing angle, and is likely to prove beneficial for a broad range of display and lighting applications. E lectrophosphorescent organic light-emitting devices (PHOLEDs) can yield 100% internal quantum efficiency (η IQE ) 1,2 . This provides an external quantum efficiency (η EQE ) of ∼20% without outcoupling enhancement. The remaining emitted photons are trapped in the substrate due to total internal reflection at the glass-air interface 3 , are guided within the organic material layers and the transparent anode because of their high refractive indices compared to glass 4 , and are dissipated at the organic-cathode interface by exciting surface plasmon modes 5,6 .Numerous methods have been explored to solve the problem of inefficient optical extraction. To overcome total internal reflection at the glass substrate-air interface, microlens arrays 7,8 and microsphere scattering layers 9 have been used. These solutions are effective for coupling out the majority of substrate mode photons, but have no effect on optical power confined within the high-index organic and anode regions (waveguide modes) or at the metalorganic interface (surface plasmon modes). To extract the waveguided light, internal outcoupling structures can be categorized into two groups. One is to modulate the photon states to extract light via optical gratings or photonic crystals 10,11 . This method leads to emission properties that depend on both viewing angle and wavelength, making it incompatible with display and lighting applications. A second is to scatter the waveguided optical power using refractive index contrast or corrugated structures within the waveguide region itself. For example, high-index substrates 12,13 and outcoupling structures embedded in the organic layers have proven effective. High-index glass, however, is expensive, and raises concerns about toxicity and environmental impact 14 . Other implementations such as low-index grids 15,16 or surface corrugations 17 introduce unwanted modifications into the device active region which is already affecting the optimized optoelectronic performance...

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

Cited by 35 publications

References 25 publications

Toward Scalable Flexible Nanomanufacturing for Photonic Structures and Devices

Toward Scalable Flexible Nanomanufacturing for Photonic Structures and Devices

Characterization of light extraction efficiency for WOLEDS with light‐out‐coupling layer

Enhanced light extraction from organic light-emitting devices using a sub-anode grid

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