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Pyrimidine based hole-blocking materials with high triplet energy and glass transition temperature for blue phosphorescent OLEDs

Title
Pyrimidine based hole-blocking materials with high triplet energy and glass transition temperature for blue phosphorescent OLEDs
Authors
Jang, Seok HoonHan, S.H.Lee, J.Y.Lee, Youn Gu
DGIST Authors
Lee, Youn Gu
Issue Date
2018-05
Citation
Synthetic Metals, 239, 43-50
Type
Article
Article Type
Article
Keywords
Aromatic compoundsElectron transport propertiesElectronsGlassHydrogen bondsLight emissionMolecular orbitalsOptical propertiesOrganic light emitting diodes (OLED)PhosphorescenceTemperatureBlue phosphorescent OLEDBlue phosphorescent oledsExternal quantum efficiencyHighest occupied molecular orbital energy levelsHole-blockingIntermolecular hydrogen bondsOLEDTriplet energyGlass transition
ISSN
0379-6779
Abstract
We designed and synthesized new hole-blocking materials (HBMs), mPyrPPB and pPPyrPB, consisting of pyrimidine and phenylene segments for high-performance blue phosphorescent OLEDs. The thermal, electrochemical, and optical properties of mPyrPPB and pPPyrPB were systemically investigated. It was found that the Tg values of mPyrPPB and pPPyrPB were 118 and 137 °C, respectively. Especially, the triplet energy and highest occupied molecular orbital (HOMO) energy level of mPyrPPB were 2.77 eV and −6.86 eV, respectively, indicating that it had sufficiently high triplet energy and deep HOMO energy level for the hole-blocking layer (HBL) in blue phosphorescent OLED devices. It was found that all the meta conjugation of mPyrPPB molecular structure effectively prevented π-electron delocalization and thus increased the triplet energy and electron transport property. In addition, mPyrPPB exhibited higher electron-transporting property than pPPyrPB because mPyrPPB possessed effective intermolecular hydrogen bonds. When mPyrPPB was utilized as a HBM for a blue phosphorescent OLED device, external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) values effectively increased to 16.4%, 36.7 cd/A, and 13.4 lm/W, respectively. Compared to the reference device without HBM, EQE, CE, and PE increased by 38%, 35%, and 54% respectively, mainly due to the confinement of triplet excitons and holes and improved electron-transporting ability. © 2018 Elsevier B.V.
URI
http://hdl.handle.net/20.500.11750/6148
DOI
10.1016/j.synthmet.2018.03.002
Publisher
Elsevier Ltd
Related Researcher
  • Author Lee, Youn Gu Organic & Printed Electronics Laboratory(OPEL)
  • Research Interests OTF Solar cell; OLED; Printed Electronics; 유기박막형 태양전지; OLED; Printed Electronics
Files:
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Collection:
Department of Energy Science and EngineeringOrganic & Printed Electronics Laboratory(OPEL)1. Journal Articles


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