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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
Author(s)
Jang, Seok HoonHan, S.H.Lee, J.Y.Lee, Youngu
DGIST Authors
Jang, Seok HoonHan, S.H.Lee, J.Y.Lee, Youngu
Issued Date
2018-05
Type
Article
Article Type
Article
Author Keywords
Hole blockingTriplet energyGlass transition temperatureOLEDPhosphorescence
Keywords
LIGHT-EMITTING-DIODESELECTRON-TRANSPORT MATERIALSSTRUCTURE-PROPERTY RELATIONSHIPHIGH-EFFICIENCYOPERATING VOLTAGEROLL-OFFGREENSTABILITYRED
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 BV
Related Researcher
  • 이윤구 Lee, Youngu 에너지공학과
  • Research Interests OTF Solar cell; OLED; Printed Electronics; 유기박막형 태양전지
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Department of Energy Science and Engineering Organic & Printed Electronics Laboratory(OPEL) 1. Journal Articles

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