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Table 1. Performance of EL devices of 3TPETPA and 4TPEDTPA [a].
the devices were inferred from photocurrents of the photodiode. EL spectra
were obtained on a PR650 spectrophotometer.
Synthesis of 3TPETPA: To a 100 mL, two-necked, round-bottom flask
Device
l
max
V
on
L
max
ꢁ
PEmax
ꢁ1
CEmax
EQE
2
]
ꢁ1
were added 1 (187 mg, 0.3 mmol), 2 (376 mg, 1.0 mmol), and Pd(PPh
(20 mg). The flask was evacuated under vacuum and then flushed with dry
3 4
)
[
nm]
[V]
[cd m
[lm W
]
[cd A
]
[%]
I
493, 511
499, 513
488
5.4
4.5
4.1
1662
6935
1.1
1.9
5.2
3.1
4.0
8.0
1.2
1.5
3.7
nitrogen three times. THF (50 mL) and sodium carbonate solution (2 M,
3 mL) were injected into the flask and the mixture was refluxed overnight
and then slowly cooled to room temperature. The solution was poured into
water (50 mL) and extracted with DCM. The collected organic layer was
filtered, washed with water and brine twice, and then dried over anhydrous
sodium sulfate (3 g). After solvent evaporation, the crude product was
purified by silica-gel column chromatography using chloroform/hexane
II
III
10723
[
3
a] Device configuration: ITO/X/TPBi (10 nm)/Alq (30 nm)/LiF (1 nm)/Al (100 nm);
for device I: X ¼ NPB (60 nm)/3TPETPA (20 nm); for device II: X ¼ 3TPETPA (80 nm);
for device III: X ¼ 4TPEDTPA (30 nm). Abbreviations: lmax ¼ EL peak, Von ¼ turn on
voltage, Lmax ¼ maximum luminance, PEmax ¼ maximum power efficiency, CEmax
maximum current efficiency, and EQE ¼ maximum quantum efficiency.
¼
(1:5 by volume) as eluent. A yellow solid was obtained in 63.2% yield.
1
H NMR (400 MHz, CDCl
, d):
46.66, 143.79, 142.40, 141.02, 140.58, 138.16, 131.79, 131.41, 131.35,
3
, d): 7.45 (d, 6H), 7.32 (d, 6H), 7.02ꢁ7.14
13
3
(aromatic protons of TPE moieties). C NMR (100 MHz, CDCl
1
1
27.74, 127.66, 127.62, 126.45, 125.67, 124.31. HRMS (MALDI-TOF, m/z):
þ
In summary, a new approach to efficient solid emitters by
surmounting the notorious ACQ problem is developed in this
work. Our approach is distinctly different from the conventional
ones. The traditional processes mitigate the ACQ effect but
generate new problems, whereas our new strategy solves the ACQ
problem without causing adverse effects. Almost all the old
approaches attempt to prevent luminophores from forming
aggregates. However, because the luminophores have an inherent
tendency to aggregate in the condensed phase, the old approaches
are basically working against a very natural process and have thus
ended up with only limited success and partial control. In sharp
[
M ] calcd for C96
H69N, 1236.5464; found, 1236.6827.
Synthesis of 4TPEDTPA: The experimental procedure for this luminogen
is similar to that for the synthesis of 3TPETPA described above. A yellow
1
solid was obtained in 55.9% yield. H NMR (400 MHz, CDCl
3
, d): 7.46 (d,
, d): 146.72,
143.77, 143.74, 142.40, 141.02, 140.58, 138.18, 135.00, 132.72, 131.79,
1
3
12H), 7.33 (d, 8H), 7.02ꢁ7.17 (m). C NMR (100 MHz, CDCl
3
1
1
1
31.41, 131.35, 130.99, 127.74, 127.66, 127.62, 127.39, 126.45, 126.25,
þ
25.68, 124.32. HRMS (MALDI-TOF, m/z): [M ] calcd for C140
H N
100 2
,
809.7920; found, 1810.0371.
contrast, our new approach takes advantage of the intrinsic Acknowledgements
aggregation process and thus does not suffer from temporal and
This work was partially supported by the Research Grants Council of Hong
Kong (604509, 603008, 601608, and HKUST13/CRF/08), the University
Grants Committee of Hong Kong (AoE/P-03/08), the Ministry of Science
and Technology of China (2009CB623605), and the National Science
Foundation of China (20634020 and 20974028). B.Z.T. thanks the Cao
Gaungbiao Foundation of Zhejiang University. Supporting Information is
available online from Wiley InterScience or from the authors.
spatial instabilities. The success of our approach is manifested by
the development of new luminogens with FF,f up to 100% in the
solid state. The AIE nature and hole-transport capability of the
luminogens have enabled the fabrication of EL devices with
simple structures but good performances. We are now working
on expanding the applicability of our new structural design
strategy: it is working so well that even such infamous ACQ
luminophores as pyrene and anthracene are readily transformed
to AIE luminogens with FF,f of unity in the aggregate state.
Received: November 26, 2009
Revised: December 8, 2009
Published online: March 8, 2010
Experimental
[
1] a) S. W. Thomas III, G. D. Joly, T. M. Swager, Chem. Rev. 2007, 107, 1339.
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General Information: Tris(4-iodophenyl)amine (1) was prepared follow-
ing our previously published procedures [15]. Intermediates 2 and 3 were
prepared according to the synthetic routes shown in Scheme 1 (see also the
Supporting Information). H and C NMR spectra were measured on a
Bruker ARX 400 NMR spectrometer. Thermogravimetric analyses and
differential scanning calorimetry studies were conducted on TA TGA Q5500
1
13
[2] a) C.-T. Chen, Chem. Mater. 2004, 16, 4389. b) G. Qian, Z. Zhong, M. Luo,
D. Yu, Z. Zhang, Z. Y. Wang, D. Ma, Adv. Mater. 2009, 21, 111.
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Y. Park, Adv. Mater. 1998, 10, 1112.
ꢁ
1
and DSC Q1000 under nitrogen at heating rates of 20 and 10 8C min
,
respectively. HRMS spectra were measured on a GCT premier CAB048
mass spectrometer operating in MALDI-TOF (matrix-assisted laser
desorption/ionization–time-of-flight) mode. The FF,s values in THF
solutions were estimated using 9,10-diphenylanthracene (F
cyclohexane) or quinine sulfate (F SO ) as standards,
4
while the FF,f values of the solid films were determined using an integrating
sphere.
EL devices were fabricated on an ITO-coated glass substrate with a sheet
resistance of 25 V/&. The substrate was ultrasonically cleaned with
[
3] J. B. Birks, Photophysics of Aromatic Molecules, Wiley, London 1970.
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I. D. Rees, J. Li, Y. Ma, K. Robinson, A. B. Holms, E. Hennebicq,
D. Beljonne, F. Cacialli, Adv. Funct. Mater. 2005, 15, 981. e) C. Fan,
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[
F
¼ 90% in
F
¼ 54% in 0.1 M H
2
detergent and deionized water, followed by CF
4
plasma treatment. Thermal
evaporation of organic materials was carried out at a chamber pressure of
2
ꢁ
7
7
ꢂ 10 Torr. Light-emitting area was 4 mm . I ꢁ V curves of EL devices
were measured by a HP4145B semiconductor parameter analyzer. The
forward direction photons emitted from the devices were recorded by a
calibrated UDT PIN-25D silicon photodiode. The L and EQE parameters of
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2
162
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Adv. Mater. 2010, 22, 2159–2163