A high-efficiency hybrid white organic light-emitting diode enabled by a new blue fluorophor

Article abstract of DOI:10.1039/c5tc00285k

A new efficient blue fluorophor 4-(4-diphenylaminophenyl)diphenylsulfone (SOTPA), with high triplet energy and balanced charge-transporting properties, has been designed and synthesized, and showed impressive performance both as blue emitter and as a host for phosphors. A green phosphorescent device containing SOTPA as host showed a maximum external quantum efficiency (EQE) as high as 19.2%, suggesting almost complete triplet harvesting from the blue fluorophor by the green phosphor. Single-emitting layer (EML) F-P hybrid white organic light-emitting devices (WOLEDs) based on SOTPA also gave outstanding electroluminescence performance, with a low turn-on voltage of 2.7 V and maximum EQE and power efficiency (PE) of 15.4% and 40.2 lm W^-1, respectively. Even at a practical brightness of 1000 cd m^-2 the PE still remained as high as 24.1 lm W^-1. This excellent performance represents the highest efficiency yet reported among single-EML F-P hybrid WOLEDs.

Full text of DOI:10.1039/c5tc00285k

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A high-efficiency hybrid white organic light-
emitting diode enabled by a new blue fluorophor†
Cite this:DOI: 10.1039/c5tc00285k
Zhan Chen,‡ab Xiao-Ke Liu,‡a Cai-Jun Zheng,*a Jun Ye,c Xin-Yang Li,a Fan Li,a
Xue-Mei Oua and Xiao-Hong Zhang*ad
A new efficient blue fluorophor 4-(4-diphenylaminophenyl)diphenylsulfone (SOTPA), with high triplet
energy and balanced charge-transporting properties, has been designed and synthesized, and showed
impressive performance both as blue emitter and as a host for phosphors. A green phosphorescent
device containing SOTPA as host showed a maximum external quantum efficiency (EQE) as high as
19.2%, suggesting almost complete triplet harvesting from the blue fluorophor by the green phosphor.
Single-emitting layer (EML) F–P hybrid white organic light-emitting devices (WOLEDs) based on SOTPA
also gave outstanding electroluminescence performance, with a low turn-on voltage of 2.7 V and
maximum EQE and power efficiency (PE) of 15.4% and 40.2 lm Wꢀ1, respectively. Even at a practical
brightness of 1000 cd mꢀ2 the PE still remained as high as 24.1 lm Wꢀ1. This excellent performance
represents the highest efficiency yet reported among single-EML F–P hybrid WOLEDs.
Received 29th January 2015,
Accepted 13th March 2015
DOI: 10.1039/c5tc00285k
www.rsc.org/MaterialsC
One of the most challenging issues for F–P hybrid WOLEDs
is to achieve full triplet harvesting from blue fluorophor to
1. Introduction
White organic light-emitting devices (WOLEDs) have gained green phosphors, since there is still a scarcity of blue fluorophors
considerable attention due to their potential application in next having triplet energy higher than that of green phosphors.17
generation solid-state lighting and full-color flat-panel displays.1–8 To address this issue, tremendous efforts have been made in
A number of approaches have been developed to produce designing optimized device structures and in developing high-
efficient WOLEDs using a variety of systems of material and triplet blue fluorophors. In device structure optimization, for
device structures, among which fluorescent and phosphorescent example, Schwartz et al. have reported a F–P hybrid WOLED
(F–P) hybrid WOLEDs are considered ideal candidates.9–14 By with a hole-transporting blue fluorophor, N,N0-di-1-naphthalenyl-
replacing the blue phosphor in fully phosphorescent WOLEDs N,N0-diphenyl-[1,10:40,100:400,1-quaterphenyl]-4,4-diamine (4P-NPD),
with a blue fluorescent emitter, F–P hybrid WOLEDs can achieve situated between an orange phosphor-doped layer at the hole
excellent stability and B100% internal quantum efficiency side and green phosphor-doped (2,20,200(1,3,5-benzenetriyl))tris-
through complete utilization of singlet excitons by the blue [1-phenyl-1H-benzimidazole] (TPBI) at the electron side. The
fluorophor, and triplet excitons by green and red (or orange) exciton recombination zone is situated close to the interface
phosphors.15,16
between 4P-NPD and TPBI; all the excitons created can be utilized,
since the triplet energy of 4P-NPD is higher than that of the orange
phosphor.18 Similarly, Sun and coworkers have demonstrated an
efficient architecture for F–P hybrid WOLEDs by doping 4P-NPD
into mixed hosts.19 In this device, energy leakage from 4P-NPD to
the green phosphor is decreased and a high EQE of 17% has been
a 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.
E-mail: xhzhang@mail.ipc.ac.cn, zhengcaijun@mail.ipc.ac.cn;
Fax: +86-10-64879375; Tel: +86-10-82543510
b University of Chinese Academy of Sciences, Beijing 100039, P. R. China
c China-Australia Joint Research Center for Functional Molecular Materials, School
of Chemical and Material Engineering, Jiangnan University, Wuxi 214122,
P. R. China
d Functional Nano and 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
realized at a practical brightness of 1000 cd mꢀ2
.
Although high efficiency can be achieved with this design,
these multi-emitting-layer (multi-EML) F–P hybrid WOLEDs
have some disadvantages. Firstly, due to the complexity of the
devices and their manufacture, they are expensive and difficult
to reproduce. Secondly, they cannot be produced by a solution
process, which would be the preferred method for large-area
and low-cost manufacture.20,21
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c5tc00285k
On the other hand, high-triplet blue fluorophosphors do not
suffer from these difficulties since they can be applied with
‡ Z. Chen and X. K. Liu contributed equally to this work.
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single emitting-layer (single-EML) architecture, and they have by reaction between diphenylsulfide and bromine. The bromine
therefore come to be regarded as offering more appropriate solution. was rapidly recovered by H2O2 in the two-phase system of
A number of blue fluorophosphors with triplet state higher than CH2Cl2–H2O, and this significantly assisted the reaction.23 The
green phosphors have been reported, and some single-EML F–P resulting 4-bromodiphenylsulfide underwent a MnSO4-assisted
hybrid WOLEDs have been described.13–15 However, the reported oxidization by KMnO4, giving 4-bromo-diphenylsulfone.24
blue fluorophosphors either show low fluorescence efficiency or Finally, a palladium-catalyzed Suzuki cross-coupling reaction25
act incompetently as hosts for green phosphors, hindering their between 4-bromodiphenylsulfone and 4-diphenylaminophenyl-
application in high-efficiency F–P hybrid WOLEDs.
boronic acid gave SOTPA in good yield. The chemical structure
In the present contribution, we report an efficient new blue of SOTPA was fully characterized by mass spectrometry and
fluorophosphor, 4-(40-diphenylaminophenyl)diphenylsulfone 1H NMR and 13C NMR spectroscopy.
(SOTPA), with triplet energy as high as 2.48 eV. SOTPA showed
2.2 Photophysical properties
impressive performance as a blue emitter and as a host for
green phosphors. A non-doped blue fluorescent device based
on SOTPA exhibited a maximum EQE of 4.6%, and a green
phosphorescent device containing SOTPA as host showed a
maximum EQE as high as 19.2%, suggesting B100% triplet
harvesting from the blue fluorophor by the green phosphor.
Overall, a single-EML F–P hybrid WOLED based on SOTPA had
excellent efficiency, with a maximum EQE of 15.4% and a
maximum PE of 40.2 lm Wꢀ1 in the forward direction, without
the use of out-coupling enhancement techniques. In addition,
even at a brightness of 1000 cd mꢀ2, the PE remained as high as
24.1 lm Wꢀ1. Such excellent efficiency is the highest found
among single-EML F–P hybrid WOLEDs.13–15,22
The photophysical properties of SOTPA were investigated using
ultraviolet-visible (UV-vis) and photoluminescence (PL) spectro-
metry. As shown in Fig. 1 and Table 1, the strong absorption
peak at 356 nm of SOTPA in ethyl acetate may be assigned to
the intramolecular charge transfer (ICT) transition from the
electron-rich diphenylamine moiety to the electron-deficient
sulfone core, while the absorption band around 299 nm could
be attributed to a diphenylamine-centered n–p* transition.
However, SOTPA showed a single PL peak at 460 nm in ethyl
acetate. This was an overlapped spectrum involving the fluores-
cence decay of both the ICT and the n–p* transitions. These
could be clearly observed in a low-polarity solution such as
cyclohexane and toluene. As shown in Fig. 1(b), SOTPA exhibited
deep blue emission in dilute cyclohexane, with a peak at 404 nm
and a shoulder at 423 nm associated with the n–p* transition
and ICT transition, respectively. As the polarity of the solvent
2. Results and discussion
2.1 Synthesis
Scheme 1 shows the synthetic route to SOTPA and its molecular increased, the PL intensity of ICT transition also increased, and
structure. The intermediate 4-bromodiphenylsulfide was prepared strong solvato-chromaticity was observed due to the large dipole
Scheme 1 Synthesis and chemical structure of SOTPA.
Fig. 1 (a) UV-vis absorption and PL spectra of SOTPA in dilute ethyl acetate solution at room temperature, and the fluorescence and phosphorescence
spectra of SOTPA in 2-methyltetrahydrofuran (2-MeTHF) at 77 K; (b) PL spectra of SOTPA in various solvents at room temperature.
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Table 1 Physical properties of SOTPA
HOMOg
(eV)
LUMOg
(eV)
Eg
a
a
b
b
d
d
e
ox
f
red
f
h
labs
lem
labs
lem
lfluo
lphos
(nm)
T1
E
E
onset
onset
c
(nm)
(nm)
(nm)
(nm)
Ff
(nm)
(eV)
(V)
(V)
(eV)
SOTPA
356
460
371
453
0.93
425
500
2.48
0.49
ꢀ2.28
ꢀ5.59
ꢀ2.82
2.77
a
b
c
In dilute ethyl acetate solution at room temperature. In solid films. In dilute cyclohexane using 9,10-diphenylanthracence (Ff = 0.90 in
d
e
f
ox
onset
cyclohexane solution) as standard. In 2-MeTHF glass matrix at 77 K. Calculated from the phosphorescence peak at 77 K.
E
: onset
oxidation potential vs. Fc/Fc+; E
: onset reduction potential vs. Fc/Fc+ (Fc denotes ferrocene). HOMO (highest occupied molecular orbital) =
red
onset
g
ox
onset
red
onset
ꢀeE
ꢀ 5.1, and LUMO (lowest unoccupied molecular orbital) = ꢀeE
ꢀ 5.1.36 h The energy bandgap, calculated as LUMO–HOMO.
Fig. 2 Calculated spatial distribution of (a) the HOMO and (b) LUMO of SOTPA.
of the ICT-excited state.26 As illustrated in Fig. 1(b), the ICT distributions in SOTPA are shown in Fig. 2. The HOMO is
characteristic of SOTPA was confirmed by the gradual batho- localized predominantly on the electron-rich diphenylamine
chromic shift in its fluorescence emission with increasing unit and the benzene p-bridge, whereas the LUMO is dominant
polarity of the solvent. In addition, the fluorescence quantum on the electron-deficient diphenylsulfone unit and the benzene
yield (Ff) of SOTPA in dilute cyclohexane solution was found to p-bridge. This observation indicates that the diphenylamine
be 0.93, using 9,10-diphenylanthracence (Ff = 0.90 in cyclohexane and diphenylsulfone moieties are, respectively, the hole- and
solution) as standard.27 This finding confirmed that SOTPA was electron-transporting contribution elements of SOTPA, resulting in
an efficient blue emitter.
its excellent hole- and electron-transporting properties.30 In addition,
Fig. 1(a) also shows the fluorescence and phosphorescence the separated HOMO and LUMO orbital distributions provide
spectra of SOTPA in 2-MeTHF at 77 K. The structureless further evidence for the ICT character of SOTPA, which is an
fluorescence spectrum exhibited a peak at 425 nm, while the advantage in attaining a high T1. On the other hand, a suitable
phosphorescence spectrum displayed a vibrational structure overlap between the HOMO and LUMO was also observed,
characteristic of diphenylamine. This observation suggested guaranteeing high fluorescence efficiency, demonstrated by the
that the T1 of SOTPA was a type of p–p* excited state, situated high Ff.10
mainly on the electron-donating diphenylamine moiety.28,29
A cyclic voltammetry (CV) measurement was performed using
According to the highest energy phosphorescence peak at a three-electrode cell, in order to arrive at experimental values for
500 nm, the T1 of SOTPA was estimated to be 2.48 eV, which was the HOMO and LUMO of SOTPA. As shown in ESI,† Fig. S1,
higher than that of common green phosphorescent dopants such
as (acetylacetonato)bis(2-phenylpyridine) iridium(III) (Ir(ppy)2acac)
at 2.4 eV.19
The high T1 of SOTPA makes itself an adequate candidate as
a host for the green phosphors. Moreover, it is important to
note that a D–p–A–p–D structured molecule (DADBT) using
dibenzothiophene-S,S-dioxide as the acceptor and diphenylamine
as the donor showed a low T1, of 2.38 eV.15 The fact that the T1 of
SOTPA was higher than that of DADBT is attributable to the
shortened p conjugation of the molecular skeleton.
2.3 Theoretical calculations and electrochemical properties
Quantum chemical calculations were employed at the B3LYP/
6-31G(d) theoretical level to gain a better insight into the electronic
structure of SOTPA at the molecular level. The molecular orbital
Fig. 3 Current density–voltage curves of hole-only and electron-only
SOTPA devices.
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SOTPA showed irreversible oxidation and reduction curves,
attributable to the electron-rich diphenylamine moiety and the
electron-deficient diphenylsulfone moiety, respectively. As listed
in Table 1, the HOMO and LUMO energy levels of SOTPA were
estimated from the onset potentials of the redox curves as ꢀ5.59
and ꢀ2.82 eV, respectively, using ferrocene (Fc) as reference. On
the basis of the HOMO/LUMO energy levels, the energy bandgap
(Eg) of SOTPA was estimated to be 2.77 eV. Suitable HOMO and
LUMO energy levels and a narrow Eg are appropriate for hole
and electron injection, respectively, from charge-transporting
materials, benefiting from a reduction in driving voltage and
improvement in power efficiency.31
Fig. 4 Energy level diagram for materials used in the SOTPA-based
devices.
2.4 Single-carrier devices
The bipolar properties of SOTPA were further demonstrated by
investigating the mobility of hole-only and electron-only devices.
The hole-only device had the configuration ITO/MoO3/SOTPA/
MoO3/Al, and the electron-only device was ITO/Al/SOTPA/Al; in
both cases MoO3 was 12 nm and SOTPA and Al were 60 nm in
thickness. It was assumed that only single carriers could be
injected and transported through the devices, the work function
of MoO3 (or Al) being high (or low) enough to block electron (or
hole) injection.32,33 As shown in Fig. 3, SOTPA exhibited clearly
balanced hole- and electron-current densities, indicating that it
was a promising ambipolar host material with remarkable
charge-transporting mobility.
2.5 Electroluminescence performance
Fig. 5 EL spectra of device B at different luminances.
In terms of the measurement of physical properties, SOTPA
showed a high Ff with blue emission, high T1 (2.48 eV), suitable
Fig. 6 PE–luminance–EQE plots of (a) device B, (b) device G, and (c) device R.
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HOMO/LUMO energy levels and balanced hole- and electron- electron-mobility of SOTPA. As shown in Fig. 5, the non-doped
transporting ability. These excellent physical properties make blue device exhibited stable blue EL spectra at different luminance,
SOTPA a promising candidate for blue fluorescent emitters in with peaks at 460 nm and CIE coordinates (0.14, 0.14). The
addition to hosts for green and red phosphors. To provide maximum PE of device B was 5.3 lm Wꢀ1, and its current efficiency
experimental support, the electroluminescence (EL) of SOTPA (CE) and EQE were 5.4 cd Aꢀ1 and 4.6%, respectively (Fig. 6(a) and
as a blue emitter and as a host for green and red phosphors was Table 2). Considering the 5% theoretical limit for EQE of conven-
investigated. A non-doped blue fluorescent OLED was con- tional fluorescent devices (assuming a light out-coupling efficiency
structed (device B) with a configuration of ITO/NPB (25 nm)/ of 20%),34 SOTPA is clearly an excellent blue fluorophor.
TCTA (5 nm)/SOTPA (30 nm)/TPBI (40 nm)/LiF (1 nm)/Al. In this
In order to confirm the host properties of SOTPA for green
device, ITO (indium-tin oxide) and LiF/Al formed the anode and and red phosphors, two devices (G and R) were constructed,
cathode, respectively, NPB was the hole-transporting layer (HTL), with a configuration of ITO/NPB (25 nm)/TCTA (5 nm)/SOTPA:
TCTA (4,40,400-tris(N-carbazolyl)triphenylamine) the exciton-blocking 6 wt% Ir(ppy)2acac, or 4 wt% Ir(MDQ)2acac (30 nm)/TPBI
layer, and TPBI served as the electron-transporting layer (ETL), the (40 nm)/LiF (1 nm)/Al, respectively. In these Ir(MDQ)2acac was
hole-blocking layer and exciton-blocking layer. An energy level bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) iridium.
diagram for materials used in the SOTPA-based device is illustrated The green-emitting device turned on at 2.5 V and the red-
in Fig. 4.
emitting device at 2.7 V. The PE–luminance–EQE plots for these
The non-doped blue device turns on at 2.8 V, a very low two devices are shown in Fig. 6(b) and (c), and their luminance–
voltage, which is very close to the energy bandgap of 2.77 eV. voltage–current density characteristics in ESI,† Fig. S2.
Such a low turn-on voltage may be attributed to the HOMO/
As summarized in Table 2, device G gave high performance,
LUMO energy levels, matching HTL/ETL and the high hole- and with a maximum CE of 68.6 cd Aꢀ1. Owing to the low driving
Table 2 Electroluminescence properties of the devices
a
Von
(V)
Max CEb
Max PEc
(lm Wꢀ1
Max EQEd
(%)
CE@1000 cd mꢀ2
PE@1000 cd mꢀ2
EQE@1000 cd mꢀ2
(%)
(cd Aꢀ1
)
)
(cd Aꢀ1
)
(lm Wꢀ1
)
CIE(x,y)e
Device B
Device G
Device R
Device W
2.8
2.5
2.7
2.7
5.4
68.6
33.4
38.4
5.3
78.1
35.0
40.2
4.6
19.2
16.4
15.4
4.5
66.5
28.6
26.8
2.8
64.2
25.4
24.1
3.9
18.6
14.0
10.8
(0.14, 0.14)
(0.28, 0.65)
(0.58, 0.41)
(0.45, 0.44)
a
b
c
d
e
Turn-on voltage, estimated at the brightness of 1 cd mꢀ2
.
Current efficiency. Power efficiency. External quantum efficiency. Estimated at
1000 cd mꢀ2
.
Fig. 7 (a) Current density–luminance–voltage characteristics, (b) EL spectra, and (c) PE–luminance–EQE plots for device W.
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voltages a maximum PE as high as 78.1 lm Wꢀ1 was achieved. blue emission with high Ff, a high T1 of 2.48 eV, suitable
In particular device G showed a maximum EQE of 19.2%, HOMO/LUMO energy levels and a balanced hole- and electron-
approaching the theoretical limit of 20%.34,35 This result indicated transporting ability. These excellent physical properties make
that almost 100% of excitons, including singlets and triplets from SOTPA a promising candidate, both as a blue fluorescence
the blue-emitting host, were harvested by the green phosphor. emitter and as a host for green and red phosphors. A non-
Device R exhibited a maximum PE of 35.0 lm Wꢀ1, a maximum CE doped blue-emitting fluorescent device based on SOTPA exhibited a
of 33.4 cd Aꢀ1 and a maximum EQE of 16.4%. Both the blue- maximum EQE of 4.6%, and a green phosphorescent device
emitting fluorescent device and the green- and red-emitting containing SOTPA as the host showed a maximum EQE as high
phosphorescent devices exhibited remarkably high efficiency, as 19.2%, suggesting B100% triplet harvesting from the blue
confirming that SOTPA can be simultaneously used as a blue fluorophor by the green phosphor. By using SOTPA simultaneously
emitter and as a host for green and red phosphors.
as blue emitter and as host for green and red phosphors, the single-
Finally, simultaneously using SOTPA as the blue emitter and EML F–P hybrid WOLED showed outstanding electroluminescence
a host for green and red phosphors, a single-EML F–P hybrid performance, with a low turn-on voltage of 2.7 V and a maximum
WOLED was constructed with a configuration ITO/NPB (25 nm)/ EQE and PE of 15.4% and 40.2 lm Wꢀ1, respectively. Even at a
TCTA (5 nm)/SOTPA: Ir(ppy)2acac: Ir(MDQ)2acac (30 nm)/TPBI practical brightness of 1000 cd mꢀ2, the PE still remained as high
(40 nm)/LiF (1 nm)/Al (device W). In the EML, the concentrations as 24.1 lm Wꢀ1. Such excellent performance represents the highest
of both Ir(ppy)2acac and Ir(MDQ)2acac were optimized at 0.3 wt%. efficiencies so far found among single-EML F–P hybrid WOLEDs.
Such low dopant concentrations in the EML increased the average
distance between the host and the dopant molecules, and most of
the blue fluorophor molecules were thus maintained at a distance
of more than 3 nm (the diffusion length of singlet excitons) from
Acknowledgements
the phosphorescent dopant molecules. Almost all singlet excitons
The study was supported by the National Natural Science Foun-
therefore remained on the SOTPA host and could be utilized for
dation of China (Grant No. 51373190, 51033007, and 51103169),
blue fluorescence, while the triplet excitons were transferred to
the Beijing Nova Program (Grant No. Z14110001814067) and
the dopant molecules for green and red phosphorescence (the
the Instrument Developing Project of the Chinese Academy of
diffusion length of triplet excitons is approximately 100 nm),
Sciences (Grant No. YE201133).
resulting in white emission.9,15
Fig. 7(a) shows the luminance–voltage–current density charac-
teristics of device W, revealing an extremely low turn-on voltage of
2.7 V and a low driving voltage of 3.5 V at a practical brightness of
References
1000 cd mꢀ2. As shown in Fig. 7(b) and ESI,† Table S1, warm white
light emission covering the range 400–750 nm was achieved in
device W. The CIE coordinates showed a moderate blue shift from
(0.46, 0.46) to (0.39, 0.39), with an increase in luminance from
100 to 10 000 cd mꢀ2, which may be the result of triplet–triplet
annihilation at high current density. On the one hand the occur-
rence of triplet–triplet annihilation (TTA) decreased the triplet
exciton concentration, and on the other, singlet excitons could be
generated during the TTA process. The singlet/triplet ratio therefore
increased with increasing luminance, resulting in the increasing EL
intensity of the blue fluorescent spectrum. The EL efficiencies
(forward-viewing) of device W are illustrated in Fig. 7(c) and listed
in Table 2. By full triplet harvesting from SOTPA to Ir(ppy)2acac and
Ir(MDQ)2acac, the maximum EQE, CE and PE of device W reached
15.4%, 38.4 cd Aꢀ1 and 40.2 lm Wꢀ1, respectively. Furthermore,
even at a brightness of 1000 cd mꢀ2, the PE still remained as high
as 24.1 lm Wꢀ1, which is the highest value among the single-EML
F–P hybrid WOLEDs previously reported.13–15,22
1 M. C. Gather, A. Kohnen and K. Meerholz, Adv. Mater., 2011,
23, 233.
2 K. S. Yook and J. Y. Lee, Adv. Mater., 2012, 24, 3169.
3 K. T. Kamtekar, A. P. Monkman and M. R. Bryce, Adv.
Mater., 2010, 22, 572.
4 G. M. Farinola and R. Ragni, Chem. Soc. Rev., 2011, 40, 3467.
5 S. L. Lai, W. Y. Tong, S. C. F. Kui, M. Y. Chan, C. C. Kwok
and C. M. Che, Adv. Funct. Mater., 2013, 23, 5168.
6 J. Zou, H. Wu, C.-S. Lam, C. Wang, J. Zhu, C. Zhong, S. Hu,
C.-L. Ho, G.-J. Zhou, H. Wu, W. C. H. Choy, J. Peng, Y. Cao
and W.-Y. Wong, Adv. Mater., 2011, 23, 2976.
7 H. Sasabe, J. Takamatsu, T. Motoyama, S. Watanabe,
G. Wagenblast, N. Langer, O. Molt, E. Fuchs, C. Lennartz
and J. Kido, Adv. Mater., 2010, 22, 5003.
8 C. M. Han, G. H. Xie, H. Xu, Z. S. Zhang, L. H. Xie, Y. Zhao,
S. Y. Liu and W. Huang, Adv. Mater., 2011, 23, 2491.
9 Y. R. Sun, N. C. Giebink, H. Kanno, B. W. Ma,
M. E. Thompson and S. R. Forrest, Nature, 2006, 440, 908.
10 G. Schwartz, S. Reineke, T. C. Rosenow, K. Walzer and
K. Leo, Adv. Funct. Mater., 2009, 19, 1319.
3. Conclusions
11 D. Qin and Y. Tao, Appl. Phys. Lett., 2005, 86, 113507.
An efficient new ambipolar blue fluorophor, SOTPA, has been 12 J. Wan, C. J. Zheng, M. K. Fung, X. K. Liu, C. S. Lee and
designed and synthesized, incorporating diphenylamine as an X. H. Zhang, J. Mater. Chem., 2012, 22, 4502.
electron donor and diphenylsulfone as electron acceptor. 13 C.-J. Zheng, J. Wang, J. Ye, M.-F. Lo, X.-K. Liu, M.-K. Fung,
SOTPA shows excellent physical properties, including strong
X.-H. Zhang and C.-S. Lee, Adv. Mater., 2013, 25, 2205.
J. Mater. Chem. C
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View Article Online
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Paper
14 X.-K. Liu, C.-J. Zheng, M.-F. Lo, J. Xiao, Z. Chen, C.-L. Liu, 25 N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95, 2457.
C.-S. Lee, M.-K. Fung and X.-H. Zhang, Chem. Mater., 2013, 26 W. Li, D. Liu, F. Shen, D. Ma, Z. Wang, T. Feng, Y. Xu,
25, 4454.
B. Yang and Y. Ma, Adv. Funct. Mater., 2012, 22, 2797.
15 J. Ye, C.-J. Zheng, X.-M. Ou, X.-H. Zhang, M.-K. Fung and 27 D. F. Eaton, Pure Appl. Chem., 1988, 60, 1107.
C.-S. Lee, Adv. Mater., 2012, 24, 3410.
16 G. Schwartz, S. Reineke, T. C. Rosenow, K. Walzer and
K. Leo, Adv. Funct. Mater., 2009, 19, 1319.
17 X.-K. Liu, C.-J. Zheng, M.-F. Lo, J. Xiao, C.-S. Lee, M.-K. Fung
and X.-H. Zhang, Chem. Commun., 2014, 50, 2027.
28 Q. S. Zhang, J. Li, K. Shizu, S. P. Huang, S. Hirata, H. Miyazaki
and C. Adachi, J. Am. Chem. Soc., 2012, 134, 14706.
29 X.-K. Liu, C.-J. Zheng, J. Xiao, M.-F. Lo, Z. Chen, C.-S. Lee,
C.-L. Liu, X.-M. Ou, F. Li and X.-H. Zhang, Isr. J. Chem., 2014,
54, 952.
18 G. Schwartz, M. Pfeiffer, S. Reineke, K. Walzer and K. Leo, 30 C. J. Zheng, J. Ye, M. F. Lo, M. K. Fung, X. M. Ou,
Adv. Mater., 2007, 19, 3672. X. H. Zhang and C. S. Lee, Chem. Mater., 2012, 24, 643.
19 N. Sun, Q. Wang, Y. Zhao, Y. Chen, D. Yang, F. Zhao, J. Chen 31 Z. Q. Gao, M. Luo, X. H. Sun, H. L. Tam, M. S. Wong,
and D. Ma, Adv. Mater., 2014, 26, 1617.
20 B. H. Zhang, G. P. Tan, C. S. Lam, B. Yao, C. L. Ho, L. H. Liu,
B. X. Mi, P. F. Xia, K. W. Cheah and C. H. Chen, Adv. Mater.,
2009, 21, 688.
Z. Y. Xie, W. Y. Wong, J. Q. Ding and L. X. Wang, Adv. Mater., 32 P. C. Kao, J. H. Lin, J. Y. Wang, C. H. Yang and S. H. Chen,
2012, 24, 1873. J. Appl. Phys., 2011, 109, 094505.
21 S. Xue, L. Yao, F. Shen, C. Gu, H. Wu and Y. Ma, Adv. Funct. 33 W. Jiang, L. Duan, J. Qiao, G. F. Dong, L. D. Wang and
Mater., 2012, 22, 1092. Y. Qiu, Org. Lett., 2011, 13, 3146.
22 W. Y. Hung, L. C. Chi, W. J. Chen, Y. M. Chen, S. H. Chou 34 C. G. Zhen, Y. F. Dai, W. J. Zeng, Z. Ma, Z. K. Chen and
and K. T. Wong, J. Mater. Chem., 2010, 20, 10113. J. Kieffer, Adv. Funct. Mater., 2011, 21, 699.
23 A. Bravo, B. Dordi, F. Fontana and F. Minisci, J. Org. Chem., 35 C. Adachi, M. A. Baldo, M. E. Thompson and S. R. Forrest,
2001, 66, 3232. J. Appl. Phys., 2001, 90, 5048.
24 A. Shaabani, A. Rahmati, M. Sharifi, J. M. Rad, B. Aghaaliakbari, 36 C. M. Cardona, W. Li, A. E. Kaifer, D. Stockdale and
E. Farhangi and D. G. Lee, Monatsh. Chem., 2007, 138, 649.
G. C. Bazan, Adv. Mater., 2011, 23, 2367.
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