Saturated deep-blue emitter based on a spiro[benzoanthracene-fluorene]-linked phenanthrene derivative for non-doped organic light-emitting diodes

Article abstract of DOI:10.1039/c4nj00735b

A spiro[benzoanthracene-fluorene] derivative containing a phenanthrene moiety, 2′,3-di(phenanthren-9-yl)spiro[benzo[de]anthracene-7,9′-fluorene] (DPSBAF), was prepared by a Suzuki coupling reaction. The photophysical and photochemical properties were investigated systematically. A non-doped organic light-emitting diode using DPSBAF as the emitter achieved a luminance efficiency of 2.18 cd A^-1 with Commission Internationale de l'clairage 1931 chromaticity coordinates of (0.15, 0.09). The synthesized spiro[benzoanthracene-fluorene] derivative with a high thermal stability, a glass transition temperature of 210 °C and a decomposition temperature of 410 °C, shows potential for application in non-doped saturated deep-blue organic light-emitting diodes. This journal is

Full text of DOI:10.1039/c4nj00735b

NJC
View Article Online
View Journal
PAPER
Saturated deep-blue emitter based on a
spiro[benzoanthracene–fluorene]-linked
phenanthrene derivative for non-doped
organic light-emitting diodes
Cite this:DOI: 10.1039/c4nj00735b
Houjie Liang,ab Xinxin Wang,c Xingye Zhang,a Zhiyang Liu,a Ziyi Ge,*a
Xinhua Ouyang*a and Suidong Wang*c
A spiro[benzoanthracene–fluorene] derivative containing a phenanthrene moiety, 20,3-di(phenanthren-
9-yl)spiro[benzo[de]anthracene-7,90-fluorene] (DPSBAF), was prepared by a Suzuki coupling reaction.
The photophysical and photochemical properties were investigated systematically. A non-doped organic
light-emitting diode using DPSBAF as the emitter achieved a luminance efficiency of 2.18 cd Aꢀ1 with
Received (in Montpellier, France)
6th May 2014,
Accepted 20th June 2014
´
Commission Internationale de l’Eclairage 1931 chromaticity coordinates of (0.15, 0.09). The synthesized
spiro[benzoanthracene–fluorene] derivative with a high thermal stability, a glass transition temperature
of 210 1C and a decomposition temperature of 410 1C, shows potential for application in non-doped
saturated deep-blue organic light-emitting diodes.
DOI: 10.1039/c4nj00735b
www.rsc.org/njc
coordinates were shown (0.16, 0.16).12 Recently, Ma et al.
reported 3,7-bis(9,9,90,90-tetrakis(6-(9H-carbazol-9-yl)hexyl)-9H,90H-
1. Introduction
Organic light-emitting diodes (OLEDs) have attracted sustained [2,20-bifluoren]-7yl)dibenzo[b,d]thiophene showing
a
deep-
attention for their potential applications in both full-color blue emission with CIE coordinates of (0.17, 0.09) and a LE of
displays and solid-state lighting.1–5 Although OLEDs have 0.9 cd Aꢀ1 13
Although many deep-blue fluorescent materials
.
recently been employed in small display panels, their wider have been developed in the past decade, saturated deep-blue
application in the mainstream display panel market will emitters with a CIE coordinate of y o 0.10 should be further
depend on the development of blue electroluminescent (EL) investigated.10,14–17
materials.6–8 Compared with green and red OLEDs, it is difficult to
Spiro compounds have evolved as promising optoelectronic
obtain non-doped deep-blue electroluminescent materials with a materials with high glass transition temperatures (Tg) and
Commission Internationale de l’Eclairage (CIE) coordinate of y o solubility.18,19 Asymmetrical spiro[benzoanthracene–fluorene]
´
0.15 due to the intrinsic wide band gap nature of deep-blue derivatives possessing a naphthalene group are one kind of
emitters.8–10 Fisher et al. reported luminance efficiencies (LEs) of spiro compound which have recently been used in OLEDs.20
0.47 cd Aꢀ1 and 1.49 cd Aꢀ1 for a spin-coated device and an Gong et al. introduced spiro[benzoanthracene–fluorene]/carbazole
evaporated device with CIE coordinates of (0.156, 0.069) and compounds as host materials for orange phosphorescent OLEDs
(0.157, 0.079).11 Linton et al. showed external quantum efficiencies with twisted structures in 2012.20 Subsequently, Kim et al. reported
(EQEs) of 0.20% and 0.54% for oxadiazole derivatives applied as a series of novel spiro[benzoanthracene–fluorene] derivatives as
deep-blue emitters with CIE coordinates of (0.158, 0.120) and host materials and obtained sky-blue fluorescent emissions.21
(0.164, 0.114), respectively.5 3,7-Bis(9,9-bis(6-(9H-carbazol-9-yl)hexyl)- Recently, we demonstrated that spiro[benzoanthracene–fluorene]/
9H-fluoren-2-yl)dibenzo[b,d]-thiophene 5,5-dioxide (TCSoC) was benzoimidazole could be used as a non-doped deep-blue emitter
reported by Yao et al. as a blue emitter in solution-processed OLEDs, with CIE coordinates of (0.15, 0.10).22 Relatively little attention has
which achieved a LE of 1.6 cd Aꢀ1, but insufficient deep-blue CIE been paid to non-doped saturated deep-blue OLEDs with spiro-
[benzoanthracene–fluorene] derivatives as emitters. Therefore, it is
desirable to develop non-doped saturated deep-blue OLEDs based
a Ningbo Institute of Materials Technology & Engineering, Chinese Academy of
on spiro[benzoanthracene–fluorene] derivatives.
Sciences, Ningbo 315201, China. E-mail: geziyi@nimte.ac.cn,
In this work, we designed and synthesized 20,3-di(phenanthren-
ouyangxh@nimte.ac.cn
9-yl)spiro[benzo[de]anthracene-7,90-fluorene] (DPSBAF) due to
b University of Chinese Academy of Sciences, Beijing 100049, China
c Institute of Functional Nano & Soft Materials, Soochow University, Suzhou
the high thermal stability of the spiro[benzoanthracene–fluorene]
moiety and the low conjugation of the phenanthrene unit,
215123, China. E-mail: wangsd@suda.edu.cn
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem.

View Article Online
Paper
NJC
which can improve the color purity.9,20 The twisted and rigid 126.41, 125.84, 125.57, 125.43, 125.31, 125.24, 123.48, 122.86, 122.68,
structure of DPSBAF prevents close-packing and effectively inhibits 122.51, 120.33, 120.25, 120.03, 119.18, 60.04. HRMS (m/z): calcd for
fluorescence quenching in the film.23–27 The non-doped saturated (M+) C57H34 718.2661; found 718.4522. Anal. calcd for C57H34:
deep-blue OLED employing DPSBAF as the emitter achieved a C 95.23, H 4.77; found: C 95.14, H 4.80.
maximum luminance efficiency of 2.18 cd Aꢀ1 with CIE coordinates
2.3. Device fabrication and characterization
of (0.15, 0.09), which is very close to the National Television System
Committee (NTSC) blue standard.
DPSBAF was purified twice by vacuum sublimation with the
tube heating up to 340 1C. The compound was deposited for 6 h
at 5 ꢁ 10ꢀ4 Pa before the OLED fabrication. The device
configuration of ITO/MoO3 (5 nm)/NPB (40 nm)/TCTA (5 nm)/
DPSBAF (30 nm)/B3PyPB (40 nm)/LiF (1 nm)/Al (100 nm) was
fabricated by vacuum deposition. All of the organic layers and
inorganic layers were prepared in sequence at 10ꢀ6 Torr. The
electroluminescence spectra and the Commission Internationale
2. Experimental
2.1. Measurements and characterization
Nuclear magnetic resonance (NMR) spectra were recorded on a
Bruker DRX-400 spectrometer. High-resolution mass spectra
(HRMS) were recorded on a Bruker Esquire LC/Ion Trap Mass
Spectrometer and JEOL/HX-110. Elemental analyses were
obtained with a Perkin-Elmer 2400 II elemental analyzer.
Differential scanning calorimetry (DSC) curves were measured
using a Metler Toledo DSC 822 instrument with a heating rate
of 20 1C minꢀ1 under nitrogen flushing. Thermogravimetric analyses
(TGAs) were carried out using a Perkin-Elmer Pyris thermo-
´
de l’Eclairage coordination of the device were measured using a
PR655 spectra scan spectrometer. The luminance–current and
density–voltage characteristics were recorded simultaneously from
the measurement of the EL spectra by combining the spectrometer
with a Keithley 2400 programmable voltage–current source. All
measurements were carried out at room temperature under
ambient conditions.
gravimeter under nitrogen gas at a heating rate of 10 1C minꢀ1
.
UV-vis absorption spectra were recorded on a Perkin-Elmer
Lambda 950 spectrophotometer. Fluorescence (PL) measure-
ments were carried out with a FLSP 920 spectrophotometer in a
10ꢀ6 mol Lꢀ1 solution and in the solid state. The electrochemical
properties of DPSBAF were studied through cyclic voltammetry
(CV) on a CHI 660D electrochemical workstation with a Pt disk as
the working electrode, a Pt wire as the counter electrode, and
Ag/AgCl as the reference electrode, in a dichloromethane solution
containing 0.1 M of tetrabutylammonium hexafluorophosphate as
the supporting electrolyte.
3. Results and discussion
3.1. Synthesis
The synthetic route and structure of DPSBAF are shown in Scheme 1.
Compound 1 was synthesized via the Sandmeyer reaction
of 1,8-diaminonaphthalene. A Suzuki coupling reaction of
compound 1 with phenylboronic acid yielded compound 2.
Compound 2 was treated with n-BuLi and 2-bromo-9H-fluoren-
9-one at ꢀ78 1C to give an aromatic alcohol intermediate. Then
compound 20-Br–SBAF was obtained through a Friedel–Crafts
reaction with HCl and acetic acid as catalysts. A bromination
reaction was employed in the synthesis of 20,3-dBr–SBAF with a
yield of over 90%. DPSBAF was obtained by a Suzuki coupling
2.2. Synthesis of the compounds
The compounds 1,8-diiodonaphthalene (1),28 1-iodo-8-phenylna-
phthalene (2),29 20-bromospiro[benzo[de]anthracene-7,90-fluorene]
(20-Br–SBAF)20 and 20,3-dibromospiro[benzo[de]anthracene-7,90-
fluorene] (20,3-dBr–SBAF)22 were synthesized according to or
slightly modified literature procedures.
20,3-Di(phenanthren-9-yl)spiro[benzo[de]anthracene-7,90-fluorene]
(DPSBAF). 20,3-dBr–SBAF (1.0 g, 2.0 mmol), phenanthren-9-ylboronic
acid (1.0 g, 4.6 mmol), Pd(PPh3)2Cl2 (0.20 g, 0.28 mmol) and toluene
(150 mL) were stirred in a three-necked flask for 30 min. Potassium
carbonate (2 M, 20 mL) and anhydrous ethanol (30 mL) were added
to the above solution. The resulting solution was refluxed for 3 days
at 105 1C. The reaction mixture was extracted with dichloromethane.
After the organic layer was evaporated using a rotary evaporator, the
resulting powdery product was purified by column chromatography
to give a white solid. Yield 93.9%. 1H NMR (400 MHz, CDCl3) d 8.85–
8.79 (m, 2H), 8.75–8.86 (m, 2H), 8.37 (t, 1H, J = 7.28 Hz), 8.30 (d, 1H,
J = 7.99 Hz), 8.04–7.53 (m, 16H), 7.50–7.29 (m, 6H), 7.25–7.06 (m, 4H),
6.85–6.77 (m, 2H). 13C NMR (400 MHz, CDCl3) d 157.30, 157.15,
156.85, 140.94, 140.85, 139.99, 139.66, 139.16, 138.86, 138.60, 138.53,
137.48, 137.30, 133.46, 132.16, 131.91, 131.69, 131.48, 130.99, 130.66,
130.41, 130.31, 129.91, 129.78, 129.66, 128.74, 128.60, 128.33, 127.81,
127.68, 127.60, 127.44, 127.38, 127.20, 126.93, 126.78, 126.69, 126.57,
Scheme 1 The synthetic route to DPSBAF.
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
NJC
Paper
Table 1 Thermal properties, photophysical properties and electrochemical
properties of blue emitters
Compound
DPSBAF
DPSF (ref. 9)
SAFBI (ref. 22)
Tg (1C)
Td (1C)
210
410
320
418
178
503
254
383
398
ꢀ5.8
ꢀ2.3
—
426
325
440
lmax Absa (nm)
lmax PLa (nm)
lmax PLb (nm)
HOMOc (eV)
LUMOd (eV)
Fig. 2 The optimized geometry and molecular orbital distribution of DPSBAF.
422, 425
ꢀ5.77
ꢀ2.48
456
ꢀ5.62
ꢀ2.51
3.3. Theoretical calculations
a
b
Measured in CH2Cl2. Measured as a solid film on quartz plates.
Highest occupied molecular orbital by cyclic voltammetry. Esti-
c
d
The ground-state geometry of DPSBAF in a vacuum was optimized
by density functional theory (DFT) with the B3LYP functional and
the basis set 6-31G(d,p) using the Gaussian 03 program. The
frontier molecular orbitals were drawn using an isovalue of
0.02 a.u. As shown in Fig. 2, the HOMO and LUMO of DPSBAF
were located at the SBAF core. The twisted geometry of DPSBAF
could efficiently prevent recrystallization in the film due to the large
torsional stresses, which can induce the formation of either an
exciplex or excimer.8 The HOMO and LUMO energy levels of
DPSBAF were calculated to be ꢀ5.35 eV and ꢀ1.39 eV, respectively.
mated based on absorption onset and HOMO.
reaction in aqueous potassium carbonate solution. Further
details are given in the Experimental section. DPSBAF was
characterized by 1H NMR spectroscopy, 13C NMR spectroscopy,
HRMS and elemental analysis. DPSBAF was found to be soluble
in many common organic solvents such as dichloromethane,
chloroform, THF and toluene.
3.4. Optical properties
3.2. Thermal properties
The UV-vis absorption and PL spectra of DPSBAF in diluted
CH2Cl2 solution and as a solid film spin-coated on quartz plates
were explored as shown in Fig. 3. The photophysical data of
the compound are summarized in Table 1. DPSBAF showed a
UV-vis absorption maximum at 320 nm, which is attributed to
the p–p* transition of the spiro[benzoanthracene–fluorene] core
in the CH2Cl2 solution.20 Compared with the absorbance in solution,
the main absorption peak in the film was blue-shifted and the long
wavelength absorption was much weaker. These differences could be
explained by the formation of H-aggregation.33–35 Furthermore,
DPSBAF exhibits a fluorescence peak at 418 nm in dilute CH2Cl2
solution. In the film state, DPSBAF shows dual emission peaking at
422 nm and 425 nm. The emission lmax in the film was slightly red-
shifted compared with the diluted solution, which can be attributed
The thermal properties of DPSBAF were measured by differential
scanning calorimetry and thermogravimetric analysis under a
nitrogen atmosphere, and the data is shown in Table 1 and
Fig. 1. The glass transition temperature of DPSBAF was found to
be 210 1C and no obvious melting transition (Tm) was observed
even when heated up to 400 1C. This result indicates that the highly
twisted structure might mitigate the intermolecular interactions of
DPSBAF in the solid state.23 From the TGA result, DPSBAF exhib-
ited a decomposition temperature (Td, corresponding to 5% weight
loss) as high as 410 1C. Such a high Td value indicates that DPSBAF
is stable and has the potential to be used as a emitter by vacuum
thermal evaporation.30–32
Fig. 1 DSC trace of DPSBAF recorded at a heating rate of 20 1C minꢀ1 and
Fig. 3 UV absorption and PL spectra of DPSBAF in CH2Cl2 and in the film
state.
TGA thermogram of DPSBAF recorded at a heating rate of 10 1C minꢀ1
.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem.

View Article Online
Paper
NJC
Table 2 Electroluminescent characteristics of OLEDs
Compound
DPSBAF
DPSF (ref. 9)
SAFBI (ref. 22)
a
Von (V)
3.7
4.5
—
lmax EL (nm)
448
2.18
1.59
2.87
—
1.97
—
3.41
436
1.96
—
2.23
LEmax (cd Aꢀ1
)
PEb (lm Wꢀ1
EQEmax (%)
CIEc (x, y)
)
(0.15, 0.09)
(0.15, 0.08)
(0.15, 0.10)
a
b
c
Turn-on voltage at 1 cd mꢀ2
.
Values collected at 1 mA cmꢀ2
.
Values
collected at 20 mA cmꢀ2
.
to the twisted structure of DPSBAF preventing close molecular
packing in the solid film.23
Fig. 5 Current density–voltage–luminance characteristics of the DPSBAF
3.5. Electrochemical properties
device.
Cyclic voltammetry analysis was carried out to study the HOMO
energy level of DPSBAF, and the result is shown in Table 2
and Fig. 4. The HOMO value was calculated from HOMO =
ꢀ([Eonset ox
]
+ 4.4).36 The onset oxidation potential of DPSBAF
was 1.37 V during the anodic scan in CH2Cl2 and the HOMO
value of DPSBAF was ꢀ5.77 eV. The energy band gap of
DPSBAF, which was estimated by analysing the absorption edge
of the UV-vis curve, was 3.29 eV. The LUMO level of DPSBAF,
calculated from HOMO + Eogpt, was ꢀ2.48 eV.
3.6. Electroluminescent properties
The non-doped OLED device was fabricated with a structure of
ITO/MoO3 (5 nm)/NPB (40 nm)/TCTA (5 nm)/DPSBAF (30 nm)/
B3PyPB (40 nm)/LiF (1 nm)/Al (100 nm). Indium tin oxide (ITO)
and Al were utilized as the anode and cathode, MoO3 was used
as a hole injecting layer, N,N0-bis(naphthalene-1-yl)-N,N0-bis(phenyl)-
benzidine (NPB) was used as a hole transporting layer, 4,40,400-
tri(N-carbazolyl)benzene (TCTA) was used as an electron blocking
layer, 3,300,5,500-tetra(pyridin-3-yl)-1,10:30,100-terphenyl (B3PyPB)37,38
was used as an electron transporting and hole blocking layer, and
LiF was used as an electron injecting layer.
Fig. 6 Luminescent efficiency curve and power efficiency curve versus
current density for the DPSBAF device.
The current density–voltage–luminance characteristics of the
device are shown in Fig. 5. As shown in Fig. 6, the maximum
luminance efficiency for DPSBAF was found to be 2.18 cd Aꢀ1, and
the power efficiency (PE) was found to be 1.59 lm Wꢀ1 at 1 mA cmꢀ2
.
The maximum external quantum efficiency of the DPSBAF non-
doped OLED was 2.87% (see Fig. 7). The maximum emission lmax of
DPSBAF was located at 448 nm, and the FWHM value was 84 nm.
Compared with PL, it is common that there is a 23 nm red-shift for
the emission peak in the EL spectrum.39,40 The red-shift can be
ascribed to face-to-face p–p stacking in the vacuum-deposited film,
unlike the randomly arranged molecules in the spin-coated film.23,41
When the current density was 20 mA cmꢀ2, the CIE coordinates (x, y)
of the DPSBAF device were found to be (0.15, 0.09), which is close to
the blue standard (0.14, 0.08) of the NTSC. The EL properties of the
DPSBAF device are summarized in Table 2.
4. Conclusions
In summary, a spiro[benzoanthracene–fluorene] derivative,
namely DPSBAF, with a Tg of 210 1C was designed and synthe-
sized for use as a deep-blue emitter in a non-doped OLED. The
Fig. 4 Cyclic voltammogram of DPSBAF in CH2Cl2.
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
NJC
Paper
9 X. Xing, L. X. Xiao, L. L. Zheng, S. Y. Hu, Z. J. Chen, B. Qu
and Q. H. Gong, J. Mater. Chem., 2012, 22, 15136.
10 W. Wan, H. L. Du, J. Wang, Y. P. Le, H. Z. Jiang, H. Chen,
S. Z. Zhu and J. Hao, Dyes Pigm., 2013, 96, 642.
11 A. L. Fisher, K. E. Linton, K. T. Kamtekar, C. Pearson,
M. R. Bryce and M. C. Petty, Chem. Mater., 2011, 23,
1640.
12 L. Yao, S. F. Xue, Q. Wang, W. Y. Dong, W. Yang, H. B. Wu,
M. Zhang, B. Yang and Y. G. Ma, Chem. – Eur. J., 2012,
18, 2707.
13 L. Yao, S. H. Sun, S. F. Xue, S. T. Zhang, X. Y. Wu,
H. H. Zhang, Y. Y. Pan, C. Gu, F. H. Li and Y. G. Ma,
J. Phys. Chem. C, 2013, 117, 14189.
14 Y.-C. Chang, S.-C. Yeh, Y.-H. Chen, C.-T. Chen, R.-H. Lee
and R.-J. Jeng, Dyes Pigm., 2013, 99, 577.
15 B. A. Kamino, Y.-L. Chang, Z.-H. Lu and T. P. Bender, Org.
Electron., 2012, 13, 1479.
16 Y. Zhang, S.-L. Lai, Q.-X. Tong, M.-F. Lo, T.-W. Ng,
M.-Y. Chan, Z.-C. Wen, J. He, K.-S. Jeff, X.-L. Tang,
W.-M. Liu, C.-C. Ko, P.-F. Wang and C.-S. Lee, Chem. Mater.,
2012, 24, 61.
17 X. Xing, L. P. Zhang, R. Liu, S. Y. Li, B. Qu, Z. J. Chen,
W. Sun, L. X. Xiao and Q. H. Gong, ACS Appl. Mater.
Interfaces, 2012, 4, 2877.
18 T. P. I. Saragi, T. Spehr, A. Siebert, T. Fuhrmann-Lieker and
J. Salbeck, Chem. Rev., 2007, 107, 1057.
Fig. 7 The external quantum efficiency and EL spectra of the DPSBAF
OLED.
device based on DPSBAF exhibited a maximum LE of 2.18 cd
Aꢀ1 with a maximum EQE of 2.87%. A saturated deep-blue
emission with CIE coordinates of (0.15, 0.09) was achieved by
using DPSBAF as the emitter. DPSBAF showed a high thermal
stability and potential for application in non-doped saturated
deep-blue OLEDs.
19 D. Thirion, M. Romain, J. Rault-Berthelot and C. Poriel,
J. Mater. Chem., 2012, 22, 7149.
20 J.-Y. Kim, C.-W. Lee, J. G. Jang and M.-S. Gong, Dyes Pigm.,
2012, 94, 304.
21 M.-J. Kim, C.-W. Lee and M.-S. Gong, Dyes Pigm., 2014,
105, 202.
22 H. J. Liang, X. X. Wang, X. Y. Zhang, Z. Y. Ge, X. H. Ouyang
and S. D. Wang, Dyes Pigm., 2014, 108, 57.
Acknowledgements
This work was given financial support from the National
Natural Science Foundation of China (51273209, 21102156),
Ningbo International Cooperation Foundation (2012B10022,
2012D10009, 2013D10013) and External Cooperation Program
of the Chinese Academy of Sciences (No. GJHZ1219).
23 H. Park, J. Lee, I. Kang, H. Y. Chu, J.-I. Lee, S.-K. Kwon and
Y.-H. Kim, J. Mater. Chem., 2012, 22, 2695.
24 Y.-H. Chen, S.-L. Lin, Y.-C. Chang, Y.-C. Chen, J.-T. Lin, R.-H.
Lee, W.-J. Kuo and R.-J. Jeng, Org. Electron., 2012, 13, 43.
25 C.-J. Zheng, W.-M. Zhao, Z.-Q. Wang, D. Huang, J. Ye,
X.-M. Ou, X.-H. Zhang, C.-S. Lee and S.-T. Lee, J. Mater.
Chem., 2010, 20, 1560.
Notes and references
1 W. J. Li, D. D. Liu, F. Z. Shen, D. G. Ma, Z. M. Wang, T. Feng,
Y. X. Xu, B. Yang and Y. G. Ma, Adv. Funct. Mater., 2012,
22, 2797.
26 Q. Wang, I. W. H. Oswald, M. R. Perez, H. P. Jia, B. E. Gnade
and M. A. Omary, Adv. Funct. Mater., 2013, 23, 5420.
27 Q. Wang, I. W. H. Oswald, M. R. Perez, H. P. Jia,
A. A. Shahub, Q. Q. Qiao, B. E. Gnade and M. A. Omary,
Adv. Funct. Mater., DOI: 10.1002/adfm.201400597.
2 L. Yao, S. T. Zhang, R. Wang, W. J. Li, F. Z. Shen, B. Yang
and Y. G. Ma, Angew. Chem., Int. Ed., 2014, 126, 2151.
3 L. Li, J. J. Liang, S.-Y. Chou, X. D. Zhu, X. F. Niu, Z. B. Yu and
Q. B. Pei, Sci. Rep., 2014, 4, 1.
4 Y. Yuan, D. Li, X. Q. Zhang, X. J. Zhao, Y. Liu, J. Y. Zhang and
Y. Wang, New J. Chem., 2011, 35, 1534.
¨
28 M. Weimar, G. Du¨rner, J. W. Bats and M. W. Gobel, J. Org.
Chem., 2010, 75, 2718.
5 K. E. Linton, A. L. Fisher, C. Pearson, M. A. Fox, L.-O.
Pålsson, M. R. Bryce and M. C. Petty, J. Mater. Chem.,
2012, 22, 11816.
6 H. Fukagawa, T. Shimizu, N. Ohbe, S. Tokito, K. Tokumaru
and H. Fujikake, Org. Electron., 2012, 13, 1197.
7 X. H. Ouyang, X. Y. Zhang and Z. Y. Ge, Dyes Pigm., 2014,
103, 39.
29 M. Lejeune, P. Grosshans, T. Berclaz, H. Sidorenkova,
C. Besnard, P. Pattison and M. Geoffroy, New J. Chem.,
2011, 35, 2510.
30 X. Q. Zhang, Z. G. Chi, B. J. Xu, H. Y. Li, Z. Y. Yang, X. F. Li,
S. W. Liu, Y. Zhang and J. R. Xu, Dyes Pigm., 2011, 89, 56.
31 J. H. Huang, J.-H. Su, X. Li, M.-K. Lam, K.-M. Fung,
H.-H. Fan, K.-W. Cheah, C. H. Chen and H. Tian, J. Mater.
Chem., 2011, 21, 2957.
8 I. Cho, S. H. Kim, J. H. Kim, S. Parka and S. Y. Park, J. Mater.
Chem., 2012, 22, 123.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem.

View Article Online
Paper
NJC
32 S. Tang, W. J. Li, F. Z. Shen, D. D. Liu, B. Yang and Y. G. Ma, 37 H. Sasabe, E. Gonmori, T. Chiba, Y.-J. Li, D. Tanaka, S.-J. Su,
J. Mater. Chem., 2012, 22, 4401.
33 H. Wang, H. S. Lim, S. Kim, J. Lim, C. Lee and D. W. Kim,
Synth. Met., 2009, 159, 2564.
T. Takeda, Y.-J. Pu, K. Nakayama and J. Kido, Chem. Mater.,
2008, 20, 5951.
38 J.-Y. Hu, Y.-J. Pu, Y. Yamashita, F. Satoh, S. Kawata, H. Katagiri,
H. Sasabe and J. Kido, J. Mater. Chem. C, 2013, 1, 3871.
34 S. Kim, T. K. An, J. Chen, I. Kang, S. H. Kang, D. S. Chung,
C. E. Park, Y.-H. Kim and S.-K. Kwon, Adv. Funct. Mater., 39 Z.-Q. Liang, Z.-Z. Chu, D.-C. Zou, X.-M. Wang and X.-T. Tao,
2011, 21, 1616. Org. Electron., 2012, 13, 2898.
35 T. K. An, S.-H. Hahn, S. Nam, H. Cha, Y. Rho, D. S. Chung, 40 X. J. Feng, S. F. Chen, Y. Ni, M. S. Wong, M. M. K. Lam,
M. Ree, M. S. Kang, S.-K. Kwon, Y.-H. Kim and C. E. Park,
Dyes Pigm., 2013, 96, 756.
36 H. Q. Zhang, X. J. Wan, X. S. Xue, Y. Q. Li, A. Yu and
Y. S. Chen, Eur. J. Org. Chem., 2010, 1681.
K. W. Cheah and G. Q. Lai, Org. Electron., 2014, 15, 57.
41 X. Xing, L. W. Zhong, L. P. Zhang, Z. J. Chen, B. Qu,
E. Q. Chen, L. X. Xiao and Q. H. Gong, J. Phys. Chem. C,
2013, 117, 25405.
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014