DOI: 10.1002/ijch.201400055
A New Multifunctional TriazineCarbazole Compound
with High Triplet Energy for High-Performance Blue
Fluorescence, Green and Red Phosphorescent Host, and
Hybrid White Organic Light-Emitting Diodes
Xiao-Ke Liu,
[a, b]
Cai-Jun Zheng,*
[a]
Jing Xiao,
[d]
Ming-Fai Lo,
[c]
Zhan Chen,
[a, b]
Chun-Sing Lee,*
[c]
Chuan-
Lin Liu,
[a]
Xue-Mei Ou,
[a]
Fan Li,
[a]
and Xiao-Hong Zhang*
[a, e]
1 Introduction
Fluorescence and phosphorescence hybrid white organic
light-emitting diodes (WOLEDs) have attracted consider-
able attention in recent years due to their unique advan-
tages of combining the excellent stability of blue fluoro-
phores and complete exciton utilization.
[1]
Thus, hybrid
WOLEDs are considered as the ideal candidates for the
next generation of solid-state lighting sources and full-
color, flat-panel displays with long lifetimes and high effi-
ciencies.
[1a]
Generally, hybrid WOLEDs can be realized
by adopting multiple emitting layer (EML)
[1a–d,2]
or single
EML
[1e–g,3]
device structures with different color emitting
materials. For multi-EML hybrid WOLEDs, the film
thicknesses need to be precisely controlled to effectively
separate the singlet and triplet excitons. Moreover, the
complicated multi-EML structure is impracticable to
obtain by a solution process, which is the most ideal pro-
cess for large-area, low-cost manufacturing.
[4]
Corre-
spondingly, single-EML hybrid WOLEDs undergo simple
manipulation of the EML and can also achieve high elec-
troluminescent (EL) performance.
[1f,g]
Therefore, the
single-EML architecture is the more appropriate strategy
for hybrid WOLEDs.
In single-EML hybrid WOLEDs, the blue fluorophore
has to double as the blue fluorescent emitter to utilize
the singlet excitons and the host for green and red phos-
phorescent dopants for triplet excitons, and therefore, has
become the key point of these devices. Since triplet exci-
tons are expected to be harvested by the green phosphor
Abstract: A blue fluorescent compound, 9-[4-(4,6-diphenoxy-
1,3,5-triazin-2-yl)phenyl]-9H-carbazole (POTC), the triplet
energy level of which reaches 2.76 eV, has been designed
and synthesized. POTC is an excellent blue emitter as well
as host for green and red phosphors, and therefore, match-
es the requirements of the host for single-emitting-layer
fluorescence and phosphorescence hybrid white organic
light-emitting diodes (OLEDs). The blue, green, red, and
white devices based on POTC show maximum external
quantum efficiencies (EQEs) of 2.4, 22.4, 13.0, and 8.1%,
respectively. Even at a high brightness of 1000 cdm
2
, these
values maintain EQEs of 2.3, 22.1, 11.1, and 7.0%, respec-
tively, indicating less than 15% roll-offs from the maxima.
Keywords: electrochemistry · heterocycles · fluorescence · luminescence · organic light-emitting diodes
[a] X.-K. Liu, C.-J. Zheng, Z. Chen, C.-L. Liu, X.-M. Ou, F. Li,
X.-H. Zhang
Nano-organic Photoelectronic Laboratory and Key Laboratory of
Photochemical Conversion and Optoelectronic Materials
Technical Institute of Physics and Chemistry
Chinese Academy of Sciences
Beijing 100190 (P. R. China)
Tel : + 86-10-82543510
Fax: + 86-10-64879375
e-mail: xhzhang@mail.ipc.ac.cn
zhengcaijun@mail.ipc.ac.cn
[b] X.-K. Liu, Z. Chen
University of Chinese Academy of Sciences
Beijing 100190 (P. R. China)
[c] M.-F. Lo, C.-S. Lee
Center of Super-Diamond and Advanced Films (COSDAF)
& Department of Physics and Materials Sciences
City University of Hong Kong
Hong Kong (S.A.R. China)
e-mail: apcslee@cityu.edu.hk
[d] J. Xiao
College of Physics and Electronic Engineering
Taishan University
Shandong 271021 (P. R. China)
[e] X.-H. Zhang
Functional Nano & Soft Materials Laboratory (FUNSOM)
Jiangsu Key Laboratory for Carbon-Based Functional Materials
& Devices and Collaborative Innovation Center of Suzhou
Nano Science and Technology, Soochow University
Suzhou, Jiangsu 215123 (P. R. China)
Isr. J. Chem. 2014, 54, 952 – 957 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 952