Lee et al.
Enhanced Lifetime of OLEDs Using an Anthracene Derivative with High Glass Transition Temperature
introducing a hole conducting buffer layer possessing high
Tg is very helpful for the enhanced device stability in
OLEDs. In this work, we report highly stable OLEDs by
using a novel anthracene-based hole conducting organic
transport layer, LiF, and Al electrodes were deposited
−
6
under the vacuum of about 2 ×10 Torr. The active area
was defined by the overlap of ITO and Al cathode as
2
2×2 mm . The current–voltage–luminance properties and
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compound, 9,10-bis(3,3 -(N ,N -diphenyl-(N-naphthalene-
electroluminescence (EL) spectra were measured by using
a Keithley 2400 source-measure unit and Konica-Minolta
CS-2000 spectroradiometer. For the lifetime measurement,
the devices were covered with a thin glass cap and UV-
epoxy resin.
2
-yl)benzene-1,4-diamine)phenyl)anthracene
(TANPA),
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having high T of 154 C. We fabricated OLEDs using this
g
material as the hole injection/transport layers (HIL/HTL)
in combination with a commercial hole transporting mate-
rial (NPB), characterized the performances, and analyzed
the operational lifetime.
2.4. Synthesis
2.4.1. (4-Nitro-phenyl)-Diphenyl-Amine (1)
2. EXPERIMENTAL DETAILS
NaH (0.13 g, 5.3 mmol), diphenylamine (0.43 g, 2.5 mmol)
and 10 ml of DMSO were added to a two-neck
glass reactor with under nitrogen atmosphere. Then
2
.1. Materials
Sodium hydride, diphenylamine, 1-fluoro-4-nitrobenzene,
Palladium on activated charcoal, hydrazine monohydrate,
1-fluoro-4-nitrobenzene (0.52 g, 3.7 mmol) was added to
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the mixture under stirring. The mixture was stirred at
[1,1 -bis(diphenylphosphino)ferrocene]dichloropalladium (II)
,
,
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1
40 C for 24 h. It was poured into a large amount of dis-
1
,1 -Bis(diphenylphosphino)ferrocene, 2-bromo-naphthalene
tilled water after cooling to room temperature and extracted
with chloroform several times. The combined organic layer
was dried by a rotary evaporator. Thus obtained solid was
recrystallized from ethyl acetate and n-hexane to afford
sodium-tert-butoxide, potassium carbonate, Cu powder,
dibenzo 18-crown-6, o-dichlorobenzene, n-butyllithium
-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 9,10-
dibromoanthracene, tetrakis(triphenylphosphine)palladium(0)
Aldrich), 1-bromo-3-iodobenzene (Acros organics), and
,
2
1
(63%).
(
other solvent were from commercial sources and used
without purification.
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2
.4.2. N ,N -Diphenylbenzene-1,4-Diamine (2)
Delivered by Publishing Technology to: Chinese University of Hong Kong
IP: 80.222.139.222 On: Wed, 25 Nov 2015 08:45:44
The mixture of 1 (0.58 g, 2 mmol), 10 mg of Pd/C
palladium on activated charcoal), hydrazine monohydrate
(0.4 g, 8.0 mmol) and 15 ml of ethanol was stirred at
90 C for 5 h under nitrogen atmosphere. The Pd/C was
separated by filtration. After stripping off ethanol under
vacuum, it was recrystallized from ethanol and water to
afford 2 (58%).
2
.2. Measurements
Copyright: American Scientific Publishers
(
1
13
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The H and C NMR spectra were recorded at 25 C
on a Bruker DPX-300 spectrometer. Mass spectra were
recorded on a Shimadzu LCMS-IT-TOF. Differential scan-
ning calorimetry (DSC) was performed on a TA Instru-
ments DSC 2020 instrument with a heating rate of
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1
0 C/min and a cooling rate of 20 C/min. Thermogravi-
metric analysis (TGA) were conducted on a TA Instruments
TGA 2050 unit under a heating rate of 10 C/min and a
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2
.4.3. N ,N -Diphenyl-(N-naphthalene-2-yl)Benzene-1,4-
ꢁ
Diamine (3)
N flow rate of 90 ml/min. UV-Vis. spectra were measured
2
with an HP 8453 spectrophotometer. The highest-occupied-
molecular-orbital (HOMO) energy levels were measured
with a Riken Keiki AC-2 photoelectron spectrometer.
In an inert atmosphere dry box, 33.5 mg (0.046 mmol)
(DPPF)PdCl and 76.0 mg (0.137 mmol) of DPPF
were added to a solution of 188.9 mg (0.917 mmol)
-bromo-naphthalene and 110 mg (1.14 mmol) sodium-
2
2
tert-butoxide in 8 mL of anhydrous THF. To the resulting
solution was added 296.5 mg (1.14 mmol) of compound 2.
The reaction vessel was sealed, removed from the dry box,
2
.3. Device Fabrication and Characterization
Organic light-emitting diodes were fabricated according
to the following procedure: Indium-tin-oxide (ITO) sub-
strates were cleaned in ultrasonic bath with organic sol-
vents (isopropyl alcohol, acetone, and methanol) and
deionized water. On the substrates, TANPA and/or NPB
as hole injection/transport layers, 4,4 ,4 -tri(9-carbazoyl)
triphenylamine (TCTA) as an exciton blocking layer,
4
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and heated at 100 C for 3 h. The reaction was cooled to
room temperature, and the volatile materials were removed
by rotary evaporation. The product 3 was isolated by sub-
limation from the resulting residue (75%).
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2
.4.4. (N-3-bromophenyl)-N ,N -Diphenyl-(N-
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,4 -N,N -dicarbazole-biphenyl (CBP) doped with tris
naphthalene-2-yl)Benzene-1,4-Diamine (4)
[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy) ) as an
3
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emission layer (EML), 2,2 ,2 -(1,3,5-benzinetriyl)-tris
1-phenyl-1-H-benzimidazole) (TPBI) as an electron
Compound 3 (9.23 g, 23.9 mmol), 1-bromo-3-iodobenzene
(8.12 g, 28.7 mmol), potassium carbonate (13.2 g,
(
J. Nanosci. Nanotechnol. 13, 4216–4222, 2013
4217