Ryu et al.
The Effect of the Molecular Structure on the Optoelectronic Properties of a Fluorophore for Use in OLEDs
2.2. Measurement
1H-NMR and 13C-NMR spectra were recorded on a Varian
Unity INOVA 500 spectrometer operating at 499.761 MHz
and 125.701 MHz, respectively. Elemental analysis was
performed on a CE instrument EA1112 analyzer. The melt-
ing point was measured to be 366.2 ꢁC by differential
scanning calorimetry (DSC) using a Seiko Exstar 7000
(DSC7020) with a scan rate of 10 ꢁC/min at the tem-
ꢁ
perature range of 40∼400 C. UV-visible absorption and
PL spectra were measured by HP model 8453 and Perkin
Elmer LS55, respectively.
Electroluminescence spectra and brightness-current–
voltage characteristics of the device were measured using
keithley 2400, CHROMA METER CS-1000A. All the
measurement was carried out at room temperature.
Scheme 1. Synthetic procedure of BDAT-P.
2.3. Fabrication of OLED
atmosphere with stirring for 3 hr. The reaction mixture
was cooled, filtered and washed with ethyl acetate and
n-hexane. Removal of the solvents and drying under high
vacuum afforded 785 mg (2.28 mmole) of the product (II)
as a green solid and further purification was not required.
The device with the structure of ITO (100 nm)/NPB
(50 nm)/BDAT-P (40 nm)/BCP (10 nm)/Alq3 (20 nm)/Liq
(2 nm)/Al (100 nm) was fabricated by the high-vacuum
thermal deposition (8 × 10−7 Torr) of organic materials
onto the surface of indium tin oxide (ITO)-coated glass
substrate. The deposition rates were 1.0∼1.1 Å/sec for
organic materials, 0.1 Å/sec for lithium quinolate (Liq)
and 10 Å/sec for aluminum (Al) cathode. The EL emis-
sion spectra were recorded on Perkin Elmer LS-55 and
device performance was measured using Keithley 236 and
CHROMA METER CS-100A instruments.
1
Yield: 75%; H-NMR (500 MHz, CDCl3) ꢂ (ppm) 10.069
(s, 1 H), 8.189 (s, 1 H), 7.804 (d, 1 H), 7.475 (d, 1 H),
7.290 (d, 2 H), 7.588 (d, 2 H), 6.810 (d, 4 H), 3.013
(s, 12 H); 13C-NMR (125 MHz, CDCl3ꢁ ꢂ (ppm) 193.40,
Delivered by Ingenta to: Purdue University Libraries
150.16, 143.83, 139.50, 133.71, 131.04, 131.01, 128.99,
IP: 191.101.55.235 On: Thu, 19 May 2016 20:09:55
128.18, 127.56, 127.39, 125.10, 124.64, 112.67, 112.06,
Copyright: American Scientific Publishers
40.46, 40.39.
(2Z)-3-[4,4ꢀꢀ-bis(dimethylamino)-1,1ꢀ:4ꢀ,1ꢀꢀ-terphenyl-2ꢀ-
yl]-2-phenylacrylonitrile (BDAT-P) (III) was prepared
from the Knoevenagel reaction of 4,4ꢀꢀ-bis(dimethylam-
ino)-1,1ꢀ:4ꢀ,1ꢀꢀ-terphenyl-2ꢀ-carbaldehyde (II) with benzyl
cyanide. The mixture of 4,4ꢀꢀ-bis(dimethylamino)-1,1ꢀ:4ꢀ,
1ꢀꢀ-terphenyl-2ꢀ-carbaldehyde (400 mg, 1.16 mmol), benzyl
cyanide (0.536 ml, 4.64 mmol) and sodium ethoxide (pre-
pared by the reaction of 64 mg of Na with 10 ml of absolute
EtOH) in 150 ml of EtOH was stirred at room temperature
for 4 days. The yellow solid formed in reaction mixture was
filtered and washed with EtOH, MeOH and chloroform.
Removal of the solvents and drying under vacuum afforded
343 mg (0.73 mmole) of the product (III) as a yellow solid.
Mp 243.3 C (DSC); Yield: 66.6%; H-NMR (500 MHz,
CDCl3) ꢂ (ppm) 8.338 (d, 1 H, aromatic), 7.668 (dd, 1 H,
aromatic), 7.640 (d, 2 H, aromatic), 7.624 (s, 1 H, vinyl),
7.615 (d, 2 H, aromatic), 7.471 (d, 1 H, aromatic), 7.396
(t, 2 H, aromatic), 7.344 (t, 1 H, aromatic), 7.275 (d,
2 H, aromatic), 6.842 (d, 2 H, aromatic), 6.776 (d, 2 H,
aromatic), 3.002 (s, 12 H, methyl); 13C-NMR (125 MHz,
CDCl3) ꢂ (ppm) 150.07, 149.86, 143.37, 140.46, 139.50,
134.48, 131.81, 130.79, 130.21, 128.94, 128.76, 128.19,
127.86, 127.79, 127.33, 126.39, 125.94, 118.41, 112.84,
112.03, 111.75, 40.53, 40.40; Anal. calcd. for C31H29N3:
C: 83.92, H: 6.59, N: 9.47. Found: C: 83.77, H: 6.55,
N: 9.25.
3. RESULTS AND DISCUSSION
Optoelectronic properties such as the PL and EL emis-
sion colors, the charge-transporting property and the lumi-
nescent performance of a fluorescent compound used
in OLED application depend on the molecular structure
such as conjugation length, molecular planarity and rigid-
ity of the molecule. One type of red emissive material
that may be most commonly used in OLEDs is elec-
tron donor–acceptor molecules with strong intramolecular
charge transfer (ICT).8
In our previous work, we have reported study on
some optoelectronic properties of ABCV-P which have
electron donor–acceptor groups within the molecule.9
Presently, we have synthesized BDAT-P having the
ꢁ
1
Fig. 1. The molecular structures of BDAT-P and ABCV-P.
J. Nanosci. Nanotechnol. 12, 4142–4146, 2012
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