Organic Light‐Emitting Diodes with 30% External Quantum Efficiency Based on a Horizontally Oriented Emitter

Kim, Sei-Yong; Jeong, Won-Ik; Mayr, Christian; Park, Young-Seo; Kim, Kwon‐Hyeon; Lee, Jeong‐Hwan; Moon, Chang‐Ki; Brütting, Wolfgang; Kim, Jang‐Joo

doi:10.1002/adfm.201300104

Cited by 528 publications

(389 citation statements)

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“…The orientations of the transition dipole moments of the red dyes in the mixed co-host films were determined by analysing the angle-dependent PL spectra of the films 5,12,13,15 . The birefringence of the EML was considered in the theoretical fittings.…”

Section: Materials Formentioning

confidence: 99%

“…External quantum efficiencies (EQEs) of 30% have been reported recently [1][2][3][4][5][6] ; this is considered to be the light-outcoupling efficiency limit of phosphorescent OLEDs under isotropically oriented transition dipole moments 4 . It has long been recognized that orienting the transition dipole moment of an emitter along the horizontal direction (parallel to the substrate) can enhance the outcoupling efficiency beyond that achieved under isotropic orientation, as demonstrated in polymer-based and vacuumevaporated fluorescent molecule-based OLEDs [7][8][9][10][11][12][13] .…”

mentioning

confidence: 99%

“…Therefore, it is believed that the theoretical EQE limit of phosphorescent OLEDs is 30%. Recently, however, some heteroleptic iridium complexes (HICs) have been reported to have transition dipole moments oriented preferentially along the horizontal direction 5,[14][15][16][17][18] . This implies that it may be possible to exceed the efficiency limit of 30% under isotropic orientations of the emitting dipoles.…”

mentioning

confidence: 99%

“…The measured q PL 's of the dyes were 0.71 for fac-Ir(phq) 3 , 0.83 for Ir(mphq) 2 acac, 0.82 for Ir(MDQ) 2 acac and 0.96 for Ir(mphmq) 2 tmd. The co-host system was selected to take advantage of its exciplex-forming characteristics because OLEDs containing an exciplex-forming co-host have an almost perfect electron-hole balance, low driving voltage and low efficiency rolloff 1,5,22,23 . Figure 1b shows the PL spectra of vacuum-evaporated films of NPB and B3PYMPM and a co-evaporated film of NPB and B3PYMPM with a molar ratio of 1:1.…”

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confidence: 99%

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Phosphorescent dye-based supramolecules for high-efficiency organic light-emitting diodes

et al. 2014

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Organic light-emitting diodes (OLEDs) are among the most promising organic semiconductor devices. The recently reported external quantum efficiencies (EQEs) of 29-30% for green and blue phosphorescent OLEDs are considered to be near the limit for isotropically oriented iridium complexes. The preferred orientation of transition dipole moments has not been thoroughly considered for phosphorescent OLEDs because of the lack of an apparent driving force for a molecular arrangement in all but a few cases, even though horizontally oriented transition dipoles can result in efficiencies of over 30%. Here we use quantum chemical calculations to show that the preferred orientation of the transition dipole moments of heteroleptic iridium complexes (HICs) in OLEDs originates from the preferred direction of the HIC triplet transition dipole moments and the strong supramolecular arrangement within the co-host environment. We also demonstrate an unprecedentedly high EQE of 35.6% when using HICs with phosphorescent transition dipole moments oriented in the horizontal direction.

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Section: Materials Formentioning

confidence: 99%

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Phosphorescent dye-based supramolecules for high-efficiency organic light-emitting diodes

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“…To fabricate high-efficiency OLEDs, we used heteroleptic iridium complex (Ir(ppy) 2 (acac)) as a green phosphorescent dopant that prefers horizontal dipole orientation; this can increase the optical light outcoupling of OLED devices. 41 As we increased the number of graphene layers by stacking SLGs on the substrate, the anode's electrical conductivity and work function increased gradually, but its optical transparency decreased simultaneously. Therefore, we chose the 4LG that provides the optimal number of graphene layers for flexible OLEDs by considering the trade-off between electrical properties and optical transparency.…”

Section: Resultsmentioning

confidence: 99%

Approaching ultimate flexible organic light-emitting diodes using a graphene anode

et al. 2016

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Ultimate flexible organic light-emitting diodes (OLEDs) should have an ultra-high device efficiency, a low-efficiency roll-off at a high luminance and excellent flexibility. Here, we realized flexible tandem OLEDs using a graphene anode with a very high electroluminescent efficiency of~205.9 cd A − 1 , 45.2% (~396.4 cd A − 1 , 87.3% with a hemispherical lens) and a very low efficiency roll-off at a high luminance of~6.6% at 10 000 cd m − 2 (~3.8% with a hemispherical lens) by stacking two organic electroluminescence (EL) units. For the first time, we used an easily controlled and low-temperature processable charge generation layer with lithium nitride (Li 3 N). This simultaneously provided efficient stacking of EL units and enhanced compatibility of the flexible device on a thin plastic substrate. The flexible tandem OLEDs with a graphene anode also showed great flexibility against bending up to a bending strain of 6.7%. These results represent a significant advancement towards the production of next-generation flexible displays and solid-state lighting that use a graphene anode.

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Organic Light‐Emitting Diodes

Chang

2014

Wiley Encyclopedia of Electrical and Electronics Engineering

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The organic light‐emitting diode (OLED) is considered the ultimate technology for displays because of its unique form factor and its ability to produce vibrant colors. It is being actively studied for use as the most desired broadband light source for next‐generation solid‐state lighting. Already, small active matrix OLED (AMOLED) displays have become popular in smartphones worldwide and even large‐sized (55 in.) AMOLED televisions are now commercially available. The key features of OLED include high energy efficiency, high color quality, environmental friendliness, and most distinctively, an ultrathin and flexible form factor, which provides a unique opportunity for a plethora of innovative designs such as wearable screens, semitransparent displays, and lighting panels. In this article, the fundamental concepts and current status of OLEDs will be presented.

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Organic Light‐Emitting Diodes with 30% External Quantum Efficiency Based on a Horizontally Oriented Emitter

Abstract: Organic light-emitting diodes with 30% external quantum efficiency based on a horizontally oriented emitter

Cited by 528 publications

References 31 publications

Phosphorescent dye-based supramolecules for high-efficiency organic light-emitting diodes

Phosphorescent dye-based supramolecules for high-efficiency organic light-emitting diodes

Approaching ultimate flexible organic light-emitting diodes using a graphene anode

Organic Light‐Emitting Diodes

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