A new orange-light-emitting materials based on (N-naphthyl)-1,8- naphthalimide for OLED applications

Article abstract of DOI:10.1080/15421400903217751

A new orange emitters consisting of 2-naphthalene-1-yl-benzo[de] isoquinoline-1,3-dione (NBID) as core, and bulky diphenylamine or naphthylphenylamine substituted as a side units were synthesized and characterized. These compounds have a non-planar molecu

Full text of DOI:10.1080/15421400903217751

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A New Orange-Light-Emitting
Materials Based on (N-
naphthyl)-1,8-naphthalimide
for OLED Applications
Sung Ouk Jung a , Wei Yuan a , Jin Uk Ju a , Shuang
Zhang a , Yun Hi Kim b , Jong Tae Je c & Soon Ki
Kwon a
a School of Materials Science & Engineering and ERI,
Gyeongsang National University , Jin-Ju, Korea
b Department of Chemistry and RINS , Gyeongsang
National University , Jin-Ju, Korea
c SFC CO., LTD. , Cheong-won, Korea
Published online: 10 Nov 2009.
To cite this article: Sung Ouk Jung , Wei Yuan , Jin Uk Ju , Shuang Zhang , Yun Hi
Kim , Jong Tae Je & Soon Ki Kwon (2009) A New Orange-Light-Emitting Materials Based
on (N-naphthyl)-1,8-naphthalimide for OLED Applications, Molecular Crystals and
Liquid Crystals, 514:1, 45/[375]-54/[384], DOI: 10.1080/15421400903217751
To link to this article: http://dx.doi.org/10.1080/15421400903217751
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Mol. Cryst. Liq. Cryst., Vol. 514, pp. 45=[375]–54=[384], 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400903217751
A New Orange-Light-Emitting Materials Based on
(N-naphthyl)-1,8-naphthalimide for OLED Applications
Sung Ouk Jung1, Wei Yuan1, Jin Uk Ju1, Shuang Zhang1,
Yun Hi Kim2, Jong Tae Je3, and Soon Ki Kwon1
1School of Materials Science & Engineering and ERI, Gyeongsang
National University, Jin-Ju, Korea
2Department of Chemistry and RINS, Gyeongsang National University,
Jin-Ju, Korea
3SFC CO., LTD., Cheong-won, Korea
A new orange emitters consisting of 2-naphthalene-1-yl-benzo[de]isoquinoline-1,
3-dione (NBID) as core, and bulky diphenylamine or naphthylphenylamine substi-
tuted as a side units were synthesized and characterized. These compounds have a
non-planar molecule conformation, donor-acceptor structure, and high thermal
stability. Using these materials as dopant, we fabricated electroluminescence
device with a structure of ITO=DNTPD=NPD=NBID-1, 2 (3 wt% in Alq3)=Alq3=
LiF=Al. The luminance-efficiency of NBID derivatives (1 and 2) were showed
6.6 cd=A and 5.9 cd=A, respectively. The orange emissions were observed with
Commission International de I’Eclairage (CIE) coordinates of (0.46, 0.52) for
NBID-1 and (0.48, 0.52) for NBID-2, respectively.
Keywords: amorphous; donor-acceptor structure; non-planar conformation; OLED;
orange-emitter
INTRODUCTION
Since Tang’s [1] and Burroughes’s [2] pioneering work, organic
light-emitting diodes (OLEDs) based on small molecules and polymers
have attracted interest because of their potential application to full color
flat panel displays [3–5]. For realization of full-color, organic materials
This research was supported by MKE & KIAT through the Workforce Development
Program in Strategy Technology, and by the Basic Science Research Program through
the NRF founded by Ministry of Education, Science, and Technology (2009-0080273).
Address correspondence to Prof. Soon Ki Kwon, School of Materials Science &
Engineering and ERI, Gyeongsang National University, Gajwa-dong, Jin-Ju 660-701,
Korea (ROK). E-mail: skwon@gnu.ac.kr
45=[375]

46=[376]
S. O. Jung et al.
emitting the three primary colors of red, green, and blue with high
efficiency, good color purity are required [6–8]. Recently, much attention
has been paid to OLEDs based on red and orange emitting materials [9].
Although there has been great progress on the development of new red
fluorescent and phosphorescent materials [10], it remains to be the
weakest part in realizing the full potential of full color OLED due to
the low efficiency, poor color purity [11]. Therefore, many efforts have
been made to improve the properties of red and orange materials [12].
In this article, we designed efficient orange emitter having short
p-conjugation length. The triphenylamine or N,N-diphenylanphtha-
lene-2-amine are electron donating group as well as hole transporting
group, and isoquinoline is electron withdrawing group as well as elec-
tron transporting group. Therefore, the new orange emitting materials
with donor-acceptor structure are expected to have high efficiency by
controlling intermolecular dipole-dipole interaction due to its bulky
and asymmetric structure.
EXPERIMENTAL
Synthesis
(N-naphthyl)-4-bromo-1,8-naphthalimide (NBID) [13]. To a solution of
4-bromo-1,8-naphthalic anhydride (5.0 g, 18.1 mmol) in m-cresol
(70 mL) were added 1-naphthylamine (6.46 g, 45.1 mmol) and isoquino-
line (4.66 g, 36.1 mmol). The mixture was stirred for overnight at
220ꢀC. After completion of the reaction, resulting mixture was cooled,
poured into methanol, and filtered. And then, the product was dis-
solved in chloroform and purified by column chromatography on silica
gel using hexane=dichloromethane (3:1) as a eluent. Finally, the
product was recrystallized from hexane. Yield: 5.2 g, 71%.
(N-naphthyl)-4-diphenylamino-1,8-naphthalimide (NBID-1) [14],
To a 100 mL three-necked flask under nitrogen were added (a)
(1.00 g, 2.5 mmol), diphenylamine (0.70 g, 3.0 mmol), Pd(OAc)2
(0.07 g, 0.10 mmol), tri-tert-butyl phosphine (0.01 g, 0.04 mmol), and
sodium tert-butoxide (0.36 g, 3.70 mmol). Toluene (10 mL) was then
added to the flask via a syringe and the mixture was stirred for 24 h
at 120ꢀC. After completion of the reaction, resulting mixture was
cooled and poured into water. The product was extracted with ethyl
acetate. The organic layer was separated from the aqueous layer,
washed with water, and brine sodium hydroxide. Furthermore, the
product was dried over anhydrous MgSO4. After removal solvent,
the crude product was purified by column chromatography on silica
gel using hexane=dichloromethane (5:1) as a eluent. Yield : 0.9 g,

A New Orange-Light-Emitting Materials
47/[377]
73%, 1H NMR (300 MHz, CDCl3), d (ppm): 8.59ꢁ8.65 (m, 2 H),
8.30ꢁ8.33 (m, 1 H), 7.94ꢁ8.04 (m, 2 H), 7.45ꢁ7.72 (m, 7 H),
7.28ꢁ7.36 (m, 4 H), 7.11ꢁ7.16 (m, 6 H); 13C NMR (300 MHz, CDCl3),
d (ppm): 118.67, 122.02, 123.37, 123.87, 123.97, 125.55, 125.65,
126.29, 126.43, 126.76, 127.10, 128.19, 128.69, 129.41, 129.69,
130.22, 131.00, 131.73, 131.88, 132.48, 132.73, 134.57, 148.42,
151.41, 163.93, 164.51; Analalysis Calcd. for C34H22N2O2: C, 83.25;
H, 4.52; N, 5.71; O, 6.52. Found: C, 83.31; H, 4.61; O, 6.46.
(N-naphthyl)-4-naphthalene-2-yl-phenyl)amino-1,8-naphthalimide
(NBID-2) was synthesized by the same method with NBID-1. To a
100 mL three-necked flask under nitrogen were added (a) (1.00 g,
2.5 mmol), N-phenylnaphthalene-2-amine (0.70 g, 3.0 mmol), Pd(OAc)2
(0.07 g, 0.10 mmol), tri-tert-butyl phosphine (0.01 g, 0.04 mmol), and
sodium tert-butoxide (0.36 g, 3.70 mmol). Toluene (10 mL) was then
added to the flask via a syringe and the mixture was stirred for 24 h
at 120ꢀC. After completion of the reaction, resulting mixture was
cooled and poured into water. The product was extracted with ethyl
acetate. The organic layer was separated from the aqueous layer,
washed with water, and brine sodium hydroxide. Furthermore, the
product was dried over anhydrous MgSO4. After removal solvent,
the crude product was purified by column chromatography on silica
gel using hexane=dichloromethane (5:1) as a eluent. Yield: 1.0 g,
74%. 1H NMR (300 MHz, CDCl3), d (ppm): 8.64ꢁ8.65 (t, 1 H),
8.61ꢁ8.63 (t, 1 H), 8.34ꢁ8.38 (m, 1 H), 7.98ꢁ8.05 (m, 2 H), 7.82ꢁ7.85
(t, 2 H), 7.59ꢁ7.72 (m, 3 H), 7.44ꢁ7.57 (m, 8 H), 7.34ꢁ7.37 (m, 3 H),
7.17ꢁ7.20 (t, 3 H); 13C NMR (300 MHz, CDCl3), d (ppm): 118.89,
120.61, 122.05, 123.42, 123.69, 124.11, 124.18, 125.26, 125.67, 125.76,
126.32, 126.59, 126.78, 127.12, 127.16, 127.74, 128.23, 128.71, 129.43,
129.65, 129.78, 130.24, 130.46, 131.04, 131.69, 131.93, 132.49, 132.75,
134.29, 134.58, 145.97, 148.37, 151.29, 163.94, 164.51; Analalysis
Calcd. for C38H24N2O2: C, 84.42; H, 4.47; N, 5.18; O, 6.52. Found: C,
84.46; H, 4.40; O, 5.87.
Fabrication of OLED
Prepatterned indium tin oxide (ITO) substrates were cleaned by soni-
cation in a detergent solution for 2 min and then washed with a large
amount of doubly distilled water. Sonication in ethanol for 2 min was
done before blowing dry with a stream of nitrogen. The ITO substrates
were then treated with O2 plasma for 1 min before being loaded into
the vacuum chamber. The organic layers were deposited thermally
at a rate of 0.1–0.3 nm sꢂ1 under a pressure of about 10ꢂ6 torr. The
OLEDs devices were constructed with 60 nm of DNTPD as the hole

48/[378]
S. O. Jung et al.
injection layer, 20 nm of NPD as the hole transporting layer, 20 nm of
NBID-1, 2 (3 wt% in Alq3) as the emission layer, 40 nm of Alq3 as the
electron transporting emission layer, 0.5 nm of Al as the cathode.
Furthermore, the EL was measured under ambient conditions.
Measurements
The 1H NMR and 13C NMR spectra were recorded with a Bruker
AM-200 spectrometer. The FT-IR spectra were measured on a Bomen
Michelson series FT-IR spectrometer. The melting points were deter-
mined with an Electrothermal Mode 1307 digital analyzer. The ther-
mal analysis were performed on a TA TGA 2100 thermogravimetric
analyzer in a nitrogen atmosphere at a rate of 20ꢀC=min. Differential
scanning calorimeter (DSC) was conducted under nitrogen on a TA
instrument 2100 DSC. The sample was heated with 20ꢀC=min from
30ꢀC to 300ꢀC. UV-vis absorption spectra and photoluminescence
spectra were measured by Perkin Elmer LAMBDA-900 UV=VIS=IR
spectrophotometer and LS-50B luminescence spectrophotometer,
respectively. The photoluminescence spectra were reacted on a
Perkin-Elmer LS-50 fluorometer utilizing a lock-in amplifer system
with a chopping frequency of 150 Hz. Cyclic voltammetry (CV) was
˚
performed on an EG and G Parc model 273 A potentiostat=galvanostat
nostat system with a three-electrode cell in a solution of Bu4NBF4
(0.1 M) in acetonitrile at a scan rate of 100 Mv=S. The polymer films
were coated on a square Pt electrode (0.50 cm2) by dipping the elec-
trode into the corresponding solvents and then drying in air. A Pt wire
was used as the counter electrode, and an Ag=AgNO3 (0.1 M) electrode
was used as the reference electrode.
Results and Discussion
As shown in Scheme 1, NBID derivatives can be easily synthesized in
relatively good yield and it has a non-planar conformation and push-
pull structures. Monomer (a) was readily performed in the presence
of 4-bromo-1,8-naphthalic anhydride, 1-naphthylamine, isoquinoline,
and m-cresol. Finally, NBDI derivatives (1 and 2) were prepared by
N-arylation. The NBDI derivatives were examined by spectroscopy
1
analysis. The structure of NBID derivatives identified by H NMR,
13C NMR, FT-IR, mass spectrometry, and elemental analysis. The
thermal properties of these materials were obtained via a thermal
gravimetric analysis (TGA) and differential scanning calorimetry
(DSC) (Fig. 1). The glass-transition temperature (Tg) were observed

A New Orange-Light-Emitting Materials
49/[379]
&
.
SCHEME 1
at 128ꢀC for NBID-1 and at 148ꢀC for NBID-2, respectively. In addi-
tion, the 5% weight loss of NBID derivatives were at 368ꢀC for
NBID-1, 407ꢀC for NBID-2, respectively. The high thermal stability
indicate that NBID derivatives can form homogeneous and amor-
phous film through thermal evaporation [15]. UV-vis absorption
maximum (kmax,UV), PL maximum (kmax,PL), and CV values of NBID
derivatives (1, 2) were summarized Table 1. As shown in Figure 2(a, b),
Photophysical properties of the NBID derivatives were examined by
TABLE 1 Photophysical (in Solution) and Electrochemical (CV) Data of NBID
Derivatives (1, 2)
Dichloro-
methane
Hexane
Toluene
THF
HOMO=LUMOc
DEd
[eV]
a
b
a
b
a
b
a
b
kabs kem kabs kem kabs kem kabs
kem
[eV]
NBID-1 442 496 451 551 450 591 462 611
NBID-2 448 511 456 566 456 610 467 632
5.48
5.46
3.06
3.04
2.42
2.42
aAbsorption maximum wavelength (nm).
bFluorescence maximum wavelength (nm).
cThe HOMO energy levels were estimated from the onset oxidation potentials, and the
LUMO levels were obtained by subtracting the respective optical band-gaps from the
HOMO levels.
dOptical band-gap, calculated from the absorption edge.

50/[380]
S. O. Jung et al.
FIGURE 1 TGA and DSC thermograms of NBID derivatives.
UV-vis and fluorescence spectroscopy in solvents of different polarity
(hexane, toluene, tetrahydrofuran (THF), and dichloromethane).
Red-shift is observed in the solution emission spectrum increases as
the solvent polarity, indicating that these molecules possess intra-
molecular charge transfer from the donor to acceptor unit [16–18].
Electrochemical properties of NBID derivatives were examined by
cyclic voltammetry (CV). The LUMO of NBID derivatives were esti-
mated at ꢂ3.06 eV (NBID-1) and ꢂ3.04 eV (NBID-2), respectively.
The HOMO were calculated by the LUMO value and the optical

A New Orange-Light-Emitting Materials
51/[381]
FIGURE 2 UV-vis absorption and photoluminescence (PL) spectra of NBID
derivatives in different solvents. (a): NBID-1 and (b): NBID-2.
band-gap from the edge of the absorption spectrum. CV measurement
of NBID derivatives in 0.1 M solution of tetraammonium perchlo-
rate (Bu4NClO4)=acetonitrile solution was carried out. A platinum
plate was used as the working electrode, a platinum wire as the
counter electrode, and Ag=Agþ as the reference electrode [20]. The
current-density-voltage (J-V), luminance-current-density (L-J),

52/[382]
S. O. Jung et al.
FIGURE 3 EL characteristics of the device: ITO=DNTPD (60 nm)=NPD
(20 nm)=Alq3% dopant (20 nm)=Alq3 (40 nm)=LiF=Al. (a) EL spectra of NBID
derivatives. (b) Voltage-current density. (c) Current density-brightness.
(d) Current density-luminous efficiency. (e) Current density-power efficiency.

A New Orange-Light-Emitting Materials
53/[383]
efficiency-current-density (g-J), and power-efficiency-current-density
(gp-J) characteristic of the device was Figure 3(a–e), respectively.
The EL maximum was observed at 574 nm for NBID-1 and at
588 nm for NBID-2, respectively. The Commission International de
I’Eclairage (CIE) coordinates of the EL device were found to be
(0.46, 0.52) for NBID-1 and (0.48, 0.52) for NBID-2 at 10 mA=cm2,
respectively. Furthermore, luminance-efficiency were obtained
6.6 cd=A at the voltage of 5.9 V for NBID-1 and 5.9 cd=A at the voltage
of 6.3 V for NBID-2, respectively.
CONCLUSIONS
We have synthesized and characterized NBID derivatives as an
orange emitting material, where arylamine serves as an electron
donor and isoquinoline plays the role of an electron acceptor. NBID
derivatives were simply synthesized by N-arylation with high yield.
NBID derivatives emitted orange light with a peak 574 nm (NBID-1),
588 nm (NBID-2).The CIE coordinates of (0.46, 0.52) for NBID-1 and
(0.48, 0.52) for NBID-2 at 10 mA=cm2, respectively.
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