Langevin and Trap‐Assisted Recombination in Phosphorescent Organic Light Emitting Diodes

Hwan, Lee Jeong; Lee, Sunghun; Yoo, Sung Jin; Kim, Kwon‐Hyeon; Kim, Jang‐Joo

doi:10.1002/adfm.201303453

Cited by 164 publications

(124 citation statements)

References 37 publications

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“…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%

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

et al. 2014

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“…[6] 2. Recombination and quenching process of OLED using exciplex host [7,8] The JíV curves of the PhOLEDs were classified into the following three regions: 1) Ohmic current, 2) diffusion dominated current, and 3) drift dominated current regions. [7] Plausible origins of the high efficiency, low turn-on voltage and low roll-off of efficiency of the OLED are discussed based on analysis of recombination and quenching mechanism.…”

Section: Figurementioning

confidence: 99%

50‐2: Invited Paper: Highly Efficient OLEDs using Exciplex Hosts

Kim

2017

Symp Digest of Tech Papers

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An exciplex is an excited state charge transfer complex formed between a donor molecule and an acceptor molecule upon excitation of the donor or acceptor molecule. Because of the charge transfer characteristics, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the exciplex are considered to be located on the donor and acceptor molecules, respectively. Since the overlap between the HOMO and the LUMO of the exciplex is small, the energy difference between the singlet and the triplet excited states can be very small. Therefore, exciplex forming materials have been used to harvest triplet as well as the singlet energy in OLEDs. Exciplex forming systems can also be used as co-hosts of phosphorescent dyes for efficient OLEDs. An exciplex forming co-host can be considered as a quasi-host material possessing its singlet and triplet excited state energy close to the energy difference between the LUMO of the electron transporting material (acceptor) and the HOMO of the hole transporting material (donor) of the cohost materials, which can be utilized to achieve high efficiency and low driving voltage in OLEDs. In this talk, we will present highly efficient phosphorescent and TADF OLEDs using exciplex host doped with phosphorescent dyes with preferred emitting dipole orientation along horizontal direction to realize the external quantum efficiency over 30%, low driving voltage, and low efficiency roll-off by doping.

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“…Great efforts have been made to get high performance OLEDs, and ultimate high efficiencies have been achieved in the last decades [6][7][8][9][10][11][12][13][14][15][16]. However, there are still some problems that limit PHOLEDs' application.…”

Section: Introductionmentioning

confidence: 99%

Red phosphorescent organic light-emitting diodes based on a novel host material with thermally activated delayed fluorescent properties

Zhang

et al. 2016

Sci. China Chem.

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High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors' concentration and efficiency roll-off of PHOLEDs.In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (BCPICT), with thermally activated delayed fluorescent (TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%. When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m 2 . phosphorescent organic light-emitting diodes, red emission, efficiency roll-off, thermally activated delayed fluorescence Citation:Li Y, Zhang D, Zhang Y, Cai M, Duan L. Red phosphorescent organic light-emitting diodes based on a novel host material with thermally activated delayed fluorescent properties.

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Langevin and Trap‐Assisted Recombination in Phosphorescent Organic Light Emitting Diodes

Cited by 164 publications

References 37 publications

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

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

50‐2: Invited Paper: Highly Efficient OLEDs using Exciplex Hosts

Red phosphorescent organic light-emitting diodes based on a novel host material with thermally activated delayed fluorescent properties

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