期刊
ORGANIC ELECTRONICS
卷 13, 期 10, 页码 1937-1947出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.orgel.2012.06.009
关键词
Host material; Singlet-triplet exchange energy; Phosphorescent; Organic light-emitting diode; Exciplex
资金
- National Natural Science Foundation of China [51073057]
- Ministry of Science and Technology [2009CB930604, 2011AA03A110]
- Ministry of Education [NCET-11-0159]
- Fundamental Research Funds for the Central Universities [2011ZZ0002]
A host material containing a triazine core and three phenylcarbazole arms, called 2,4,6-tris(3-(carbazol-9-yl)phenyl)-triazine (TCPZ), was developed for phosphorescent organic light-emitting diodes (OLEDs). Ultra-low driving voltages were achieved by utilizing TCPZ as the host due to its decreased singlet-triplet exchange energy (Delta E-ST) and low-lying lowest unoccupied molecular orbital (LUMO) energy level. Interaction between the RGB triplet emitters and TCPZ were studied in both photoluminescent and electroluminescent processes. Transient photoluminescence (PL) measurement of the co-deposited film of fac-tris(2-phenylpyridine) iridium (Ir(PPy)(3)): CPZ exhibits a shoulder at 565 nm whose lifetime is about two times longer than that of the Ir(PPy)(3) triplet excitons and can be attributed to the triplet exciplex formed between Ir(PPy)(3) and TCPZ. Such exciplex was also found for the green phosphorescent OLED, giving the most efficient phosphorescent OLED with triplet exciplex emission hitherto. Different from the PL process, a broad featureless band with a maximum at 535 nm was found for the OLED based on an EML of iridium(III) bis(4,6-(di-fluorophenyl) pyridinato-N,C-2') picolinate (FIrpic): TCPZ, which can be attributed to the emission from the singlet excited state of TCPZ formed by direct hole-electron recombination. A multi-emitting-layer white OLED was also fabricated by utilizing FIrpic and tris(1-phenylisoquinolinolato-C2,N)iridium(III) (Ir(piq)(3)) as the complementary triplet emitters and TCPZ as the host. Different from most of ever reported white OLEDs fabricated with blue/red complementary triplet emitters that exhibit color rendering index (CRI) lower than 70, a high CRI of 82 is achieved due to the combination of blue and red phosphorescence emissions from FIrpic and Ir(piq)(3), and the emerging green fluorescence emission from TCPZ. (C) 2012 Elsevier B.V. All rights reserved.
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