Highly efficient deep-blue organic electroluminescent devices doped with hexaphenylanthracene fluorophores

Article abstract of DOI:10.1039/c1jm10424a

Fluorescent 2,3,6,7,9,10-hexaphenylanthracene-based derivatives (HPhAn) were synthesized to serve as deep-blue dopants in organic electroluminescent (EL) devices. The fluorescent emissions of HPhAn fluorophores, fine-tuned from 462 to 449 nm with varied f

Full text of DOI:10.1039/c1jm10424a

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PAPER
Highly efficient deep-blue organic electroluminescent devices doped with
hexaphenylanthracene fluorophores†
*
Sheng-Hsun Lin, Fang-Iy Wu, Hsiu-Yun Tsai, Pei-Yu Chou, Ho-Hsiu Chou, Chien-Hong Cheng
*
*
and Rai-Shung Liu
Received 27th January 2011, Accepted 23rd March 2011
DOI: 10.1039/c1jm10424a
Fluorescent 2,3,6,7,9,10-hexaphenylanthracene-based derivatives (HPhAn) were synthesized to serve as
deep-blue dopants in organic electroluminescent (EL) devices. The fluorescent emissions of HPhAn
fluorophores, fine-tuned from 462 to 449 nm with varied fluorinated phenyl rings attached to the central
carbons of the anthracene core, produced photoluminescence quantum yields of 82–88% in the solid
state. Unlike the known monostyrylamine deep-blue dopant, these blue dopants in dilute solutions
showed no pronounced spectral red shift with increasing solvent polarity; the emission color of HPhAn
dopants is thus insensitive to the polarity of the medium. The highest-occupied molecular orbital
(HOMO) and lowest-unoccupied molecular orbital (LUMO) energy levels calculated from the
oxidation potentials and optical energy gaps are 5.61–5.70 eV and 2.73–2.89 eV, respectively. These
thermally robust compounds undergo thermal decomposition at temperatures greater than 300 ꢀC. The
relationships among current density, voltage and luminance, the EL efficiency and the operational
stability of devices based on the blue HPhAn dopants were examined. These HPhAn-doped EL devices
are activated at voltages less than 3.5 V and attained an external quantum efficiency as much as 5.3% in
ꢀ
the deep-blue light region with Commission Internationale d’Eclairage (CIE) coordinates (0.14, 0.10),
near the National Television System Committee (NTSC) standard blue coordinates (0.14, 0.08).
radiative decay if efficient transfer of energy and charge occurs
from host to guest.10 Although blue host materials of many kinds
have been developed, suitable dopants that emit light in the deep-
blue region are still rare. Among the blue fluorescent dopants,
distyrylamine derivatives (DSA) are the most promising that
commonly serve in highly efficient fluorescence OLED (FlO-
LED).3e,h,7c,9a,11 For example, Lee et al. reported that a light-blue
EL device with p-bis(p-N,N-diphenyl-aminostyryl)benzene
(DSA-Ph) as dopant attains a current efficiency of 9.7 cd Aꢁ1
with CIE color coordinates (0.16, 0.32).9a To decrease the
conjugation of DSA-Ph and to shift the emission color toward
saturated blue light, an unsymmetric monostyrylamine,
diphenyl-[4-(2-[1,10;40,100]terphenyl-4-yl-vinyl)-phenyl]-amine
(BD-1), was prepared; the resulting device achieved an external
quantum efficiency (EQE) of 5.1% (5.4 cd Aꢁ1) and CIE coor-
dinates (0.14, 0.13).12 Several deep-blue dopants were subse-
quently prepared based on a similar strategy of molecular
design,13 but the emission color of monostyrylamine dopants is
sensitive to the medium and tends to shift to the red with
increasing local polarity in the vicinity of the active dopants.12b,13c
Wee et al. prepared a deep-blue dopant of another kind based on
a phenylaminopyrene structure; the resulting EL device gave an
EQE of 4.1% with CIE coordinates (0.14, 0.10).14
1. Introduction
Organic light-emitting diodes (OLED) have shown great poten-
tial as a technology of the next generation for flat-panel display
and solid-state lighting, following the pioneering achievements of
the Kodak group.1 Among the three primary-color (red, green
and blue) emitters, the hunt for blue-emitting materials and
devices is of particular importance because these are essential
components for OLED applications.2 Several efficient blue host
emitters and their non-doped electroluminescent (EL) devices
based on anthracene, styrylarylene, fluorene, triphenylene,
quinoline and pyrene derivatives have been reported,3–8 some of
which even provide highly efficient blue EL with excellent
ꢀ
Commission Internationale d’Eclairage (CIE) coordinates that
are near the National Television System Committee (NTSC)
standard blue coordinates (0.14, 0.08).3a,c,g,5a,6a,7b
Doping a blue emitter into a host material can significantly
improve the device performance, such as both the EL efficiency
and the device operational stability.3b,9 The emission color of the
doped emissive layer (EML) is determined by the dopant
Department of Chemistry, National Tsing Hua University, Hsinchu, 30013,
Taiwan. E-mail: rsliu@mx.nthu.edu.tw
† Electronic supplementary information (ESI) available. CCDC
reference number 818416. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1jm10424a
Many high-performance blue FlOLED have been demon-
strated using anthracene-based host emitters,3 but only little
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research has been reported on the utilization of anthracene
derivatives as blue dopants in OLED applications.15 We
prepared novel 9,10-disubstituted-2,3,6,7-tetraphenylanthracene
fluorophores and demonstrated the effective color tuning of their
emission across the entire visible region through their
9,10-functionalities.16a Here we describe the preparation and
characterization of three new deep-blue 2,3,6,7,9,10-hexa-
phenylanthracene-based derivatives (HPhAn) having varied F or
CF3 substituents on the two phenyl rings attached at the 9/10
positions of the anthracene core, and a detailed examination of
their EL properties. These HPhAn fluorophores exhibit satis-
factory thermal stability; their emission wavelengths can be fine-
tuned in the deep-blue region with fluorescent quantum yields of
82–88% in the solid state. Moreover, the HPhAn-doped devices
attain an EQE of 5.3% with excellent CIE coordinates (0.14,
0.10) that are near the NTSC standard blue coordinates. We also
report lifetime tests of the HPhAn-doped devices with varied
charge-transporting layers.
under high vacuum (10ꢁ6 Torr), these HPhAn derivatives are
thermally stable for vacuum deposition during OLED
fabrication.
2.2. Photoluminescent properties
Fig. 2 depicts the normalized absorption and photoluminescent
(PL) spectra of the HPhAn derivatives (10ꢁ5 M) in dichloro-
methane solution. The structured absorption near 400 nm is
characteristic of an electronic transition of the anthracene core;
the band near 320 nm is associated mainly with a transition of the
attached phenyl groups.3c–i Introducing small F substituents onto
the phenyl group attached at the 9/10 position of the anthracene
core made the PL spectrum of 1bb become blue-shifted by 8 nm
relative to its tert-butyl substituted analogue (4a);16a in contrast,
the PL spectrum of the CF3 substituted analogue 3bb is red-
shifted by 4 nm relative to 4a. This opposite trend of luminescent
behavior between F- and CF3-substituted analogues is attributed
to mesomeric and inductive effects of substituents of the two
kinds on these HPhAn derivatives.17 The PL spectrum of 2bb,
having two F substituents more than 1bb, is identical with that of
1bb (see Fig. 2). The monostyrylamine-based blue dopants in
solution are reported to show a spectral red shift with increasing
solvent polarity; this propensity was believed to cause the
unwanted EL red shift found in their doped devices.12b,13c Such
a red shift was, however, not observed for our HPhAn deriva-
tives. As shown in Fig. 3, for example, the PL spectra of 1bb
remain almost invariant when the solvent polarity is raised from
2.4 (toluene) to 5.8 (acetonitrile), whereas a 48 nm red shift is
observed for BD-1, a monostyrylamine dopant, under the same
conditions.12b To examine the PL properties in the solid state,
we homogeneously introduced the blue HPhAn dopants into
2. Results and discussion
2.1. Synthesis and characterization
Scheme 1 outlines the synthetic route for HPhAn derivatives
1bb-3bb. These three HPhAn derivatives were readily obtained
with one-step Suzuki coupling between 9,10-dibromo-2,3,6,7-
tetrakis(4-tert-butylphenyl)anthracene16a and the respective
phenylboronic ester16b–d in the presence of palladium catalyst
with yields ranging from 79 to 89%. The target products were
1
fully characterized with H and 13C NMR spectra, mass spectra
and elemental analysis; the chemical structure of 3bb was
confirmed with single-crystal X-ray diffraction analysis.
According to that crystal structure (Fig. 1), the two phenyl rings
with CF3 substituents are twisted with respect to the anthracene
core by an angle 61–62ꢀ; the torsion angles between the other
four phenyl groups and the core were 40–42ꢀ. The twisted
conformation of the HPhAn derivative is expected to diminish
the intermolecular interaction.3c,e,i The thermal stability of the
HPhAn derivatives was investigated with thermogravimetric
analysis (TGA) under a nitrogen atmosphere; these tests showed
that loss of mass began at a temperature greater than 300 ꢀC
(Table 1). Their glassy temperatures are very high, exceediꢀng
a
solid solvent, 1-(2,5-dimethyl-4-(1-pyrenyl)phenyl)pyrene
(DMPPP),8d through their vacuum co-deposition on a quartz
plate at a layer thickness of 30 nm and a doping concentration of
2%. As the absorption band and emission band of the HPhAn
dopants at 350–440 nm and ca. 450 nm overlap well with the
emission band of the DMPPP host (ranging from 390 to 550 nm,
lmax ¼ 446 nm, see ESI†),8d efficient energy transfer from the
DMPPP host to HPhAn dopants is expected. As shown in
Fig. 3b, the PL spectra of the doped thin films show emission
maxima at 449–462 nm accompanied with a small vibrational
structure. The excitation spectra (not shown here) of the doped
ꢀ
194 C. As their sublimation temperatures are only 220–250 C
Scheme 1 Synthesis and chemical structures of HPhAn dopants.
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Fig. 1 ORTEP drawing of 3bb.
thin films have maxima at 353–360 nm that are near the main
absorption band of DMPPP (354 nm);8d efficient energy transfer
indeed occurs between the DMPPP host and HPhAn dopants.
The emission spectra of the doped films are red-shifted by 8–
10 nm relative to the corresponding PL spectrum in dilute
solution. As shown above, varying the polarity of the medium
results in no spectral red shift for these HPhAn dopants; we
tentatively conclude that the effect of solvation in the solid state
does not account for the observed lower-energy emission of the
thin-film sample.18 The molecular geometry of the HPhAn
dopant tends to more planar in the solid state than in the fluid
state, resulting in an effective conjugation. This hypothesis would
account for the spectral red shift of the thin film PL compared to
that in solution.8d
The electrochemical behavior of the three HPhAn derivatives
was investigated with cyclic voltammetry. The HOMO (highest
occupied molecular orbital) energy levels were calculated from
the oxidation potential using ferrocene as a standard referenced
to the energy level of ferrocene (4.8 eV below the vacuum level),19
Fig. 2 UV-vis absorption and PL spectra of HPhAn derivatives (10ꢁ5 M)
in dichloromethane solution.
Table 1 Physical properties of HPhAn derivatives
Abssola/nm (3)g
PLsola/nm
441,463
441,463
453, 475
PLfilmb/nm
449 (82%)
451 (84%)
462 (88%)
E1/2 c/V
0.81
HOMO/LUMOd/eV
5.61/2.73
Band gape/eV
2.88
Tg , Td /ꢀC
251, 340
248, 358
194, 300
h
f
ox
1bb
2bb
3bb
318 (2576)
397 (209)
320 (2027)
398 (1428)
324 (1095)
401 (991)
0.83
5.63/2.77
2.86
0.9
5.70/2.89
2.81
a
In CH2Cl2 at 10ꢁ5 M. b Doped DMPPP film at a concentration of 2%; the quantum yields in parentheses were determined with an integrating sphere.
c
Oxidation potential vs. Fc/Fc+. d HOMO level was determined by E1/2ox and LUMO level was estimated by subtracting the optical band gap from the
HOMO level. e Estimated by absorption onset energy at the long wavelength end. f Measured under N2 atmosphere ata heating rate of 10 ꢀC minꢁ1
.
g
h
Extinction coefficient (102 Mꢁ1 cmꢁ1). Obtained from DSC measurements.
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Fig. 4 EL spectra of HPhAn-doped devices A–D at 6 V relative to the PL
spectrum of the 1bb-doped DMPPP film.
doping concentration increased from 2% to 4% (devices A–C),
indicating that the dopant molecules are well dispersed in EML
without aggregation. Their EL emission maxima are located at
450 nm with an accompanying shoulder near 465 nm. Both the
shape and peak position of these EL spectra are near those in the
PL spectrum of the 1bb-doped film mentioned above. As a result,
the EL emission of devices A–C originates predominantly from
the dopant fluorescence. Because the band has a full width only
58–59 nm at half maximum centered in the blue region, the 1bb-
doped devices A–C can deliver a saturated blue EL with CIE
coordinates (0.14, 0.10) (Table 2).
Fig. 3 PL spectra of (a) 1bb in varied solvents and (b) HPhAn-doped
DMPPP films at a dopant concentration of 2%.
and the LUMO (lowest unoccupied molecular orbital) levels
were estimated by subtracting the band-gap energy (calculated
from the onset at the long wavelength end) from the HOMO
level. With a F or CF3 substituent, the HOMO and LUMO levels
of the HPhAn derivatives lie lower than those of 4a by 0.25–0.34
eV and 0.11–0.27 eV, respectively (Table 1).16a
As seen in Fig. 5, curves of current density and voltage of the
1bb-doped devices are insignificantly influenced on altering the
doping concentration. This observation is explained in term of
a small energy-level offset between the host and dopant in the
EML. Trapping of charge carriers on the dopant sites generally
causes formation of a space-charge field near the interface in the
emissive layer; this field in turn impedes further injection of
charges of the same kind from the adjacent layer. Under these
conditions, an increased concentration of dopant results in an
increased voltage required to detrap the trapped charges.10 As the
differences between HOMO and LUMO energy levels of 1bb and
DMPPP are only 0.1–0.2 eV (HOMO and LUMO energy levels
of DMPPP are 5.7 and 2.5 eV, respectively),8d the holes and
2.3. Electroluminescent properties
We chose 1bb and 2bb as dopants for device fabrication because
of their appropriate emission color to achieve deep-blue elec-
troluminescence. To find the optimal doping ratio in EML, we
fabricated several devices with various doping ratios of 1bb in
a structure with ITO/TCTA (4,40,400-tris(N-carbazolyl)triphenyl
amine) (50 nm)/(2, 3, 4) % 1bb derivative: DMPPP (30 nm)/BCP
(2,9-dimethyl-4,7- diphenyl-1,10-phenanthroline) (10 nm)/TPBI
(1,3,5-tri(phenyl-2-benzimidazole)-benzene) (30 nm)/LiF (1 nm)/
Al (100 nm).8d,3f,h Details of the device performances of the blue
EL devices appear in Table 2. As shown in Fig. 4, the blue EL
spectra of 1bb-doped devices show negligible variation as the
Table 2 Performance of deep-blue EL devices doped with HPhAn derivatives
c
c
Device (x% dopant) a
Von/Vb
EQE (%)c
CE/cd Aꢁ1
PE/lm Wꢁ1
lmax/nmd
CIE (x, y)d
A (2%-1bb)
B (3%-1bb)
C(4%-1bb)
D (2%-2bb)
E (2%-1bb)
F (2%-2bb)
3.2
3.2
3.2
3.3
3.5
3.4
5.28
4.63
3.97
5.06
5.20
4.72
4.83
4.52
3.64
5.17
5.38
5.87
4.03
3.36
2.87
3.98
4.23
4.23
450
450
450
452
450
451
(0.14,0.10)
(0.14,0.10)
(0.14,0.10)
(0.14,0.11)
(0.14,0.12)
(0.14,0.14)
a
Device structures A–D and E–F are ITO/TCTA (50 nm)/HPhAn-doped DMPPP (30 nm)/BCP (10 nm)/TPBI (30 nm)/LiF (1 nm)/Al and ITO/NPNPB
(60 nm)/NPB (10 nm)/HPhAn-doped DMPPP (30 nm)/BAlq (20 nm)/LiF (1 nm)/Al, respectively. b Voltage required for 1 cd mꢁ2 (V). c Maximum value
of external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE). Measured at 6 V.
d
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Fig. 7 Comparison of operational stability for devices D–F under
a constant operating current density of 22.2 mA cmꢁ2 in a nitrogen-filled
glove box.
Fig. 5 Current density–voltage–luminance characteristics for 1bb-doped
devices A–C.
electrons injected in the EML are poorly confined at the dopant
sites by the shallow trapping depths under the influence of an
external electrical field. The curves of current density and voltage
of the 1bb-doped devices appear to be independent of the dopant
concentration. The 1bb-devices were activated at only 3.2 V and
attained a brightness of 1000 cd mꢁ2 about 6.0 V (Fig. 5). The
maximum EQE of device A is 5.28% observed at 67 cd mꢁ2
(Fig. 6). We constructed a 2bb-doped device D at the same
dopant concentration of 2% for comparison; this device was
activated at 3.3 V and attained a maximum EQE of 5.06% at
5.0 V. The EL spectrum of device D shows an emission maximum
at 452 nm with CIE coordinates (0.14, 0.11). Device A appears to
be the first blue-fluorescent doped device that achieves EQE >
5% with CIEy coordinate & 0.10.13d,14
The operational lifetime of 2bb-doped device D was tested
under a constant current density of 22.2 mA cmꢁ2 (corresponding
to an initial luminance L0 ¼ 990 cd mꢁ2); the half life, T50, of
device D was about 2.9 h (Fig. 7). A device using BCP or TPBI as
charge-transporting layer is reported to display typically a poor
device stability.20a–b For improved durability, BCP/TPBI layers
Fig. 8 EL spectra of HPhAn-doped devices E–F at 6 V.
Fig. 6 Plots of external quantum efficiency vs. current density for
HPhAn-doped devices A–D.
Fig. 9 Applied voltage–luminance characteristics for HPhAn-doped
devices E–F.
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were replaced with a Balq (aluminium(III) bis(2-methyl-8-qui-
nolinate)-4-phenylphenolate) layer (thickness 20 nm) that served
as ETL,20 and the TCTA layer was replaced with layers of
used without further purification. DMPPP was prepared by the
reported method.8d HPhAn derivatives for fabricating devices
were purified by temperature-gradient vacuum sublimation. The
EL devices were fabricated by vacuum deposition of the mate-
rials at a base pressure of 10ꢁ6 Torr onto glass precoated with
a layer of indium tin oxide (ITO) with a sheet resistance of
25 U/square. Before deposition of an organic layer, the clear ITO
substrates were treated with UV/ozone for 20 min. The rate of
NPNPB
(N,N0-di-phenyl-N,N0-di-[4-(N,N-diphenylamino)
phenyl]benzidine) (thickness 60 nm) and NPB (4,40-bis[N-
(1-naphthyl)-N-phenylamino]biphenyl) (thickness 10 nm), and
a thick NPNPB layer on top of the ITO was used to decrease the
surface roughness.20,21 The modified device structure is thus ITO/
NPNPB (60 nm)/NPB (10 nm)/2%-HPhAn-doped DMPPP
(30 nm)/BAlq (20 nm)/LiF (1 nm)/Al. Doping 2bb in the modified
device structure (device F) showed a similar EL spectrum, acti-
vation voltage, peak efficiency relative to device D (see Fig. 8, 9
and Table 2), but a much improved operational stability with
T50 ¼ 49 h was observed in device F. T50 for 1bb in the modified
device structure (device E) is 109 h, comparable with highly
efficient devices based on light-blue dopants.13c
deposition rate of organic compounds was 0.5–1 A sꢁ1. The
ꢁ
cathode (Al/LiF) was deposited on evaporation of LiF at a rate
ꢁ
of 0.1 Asꢁ1 followed by evaporation of Al metal at a rate of 3–10
A sꢁ1. Measurements (Keithley 2400 source meter and Newport
ꢁ
1835-C optical meter equipped with Newport 818-ST silicon
photodiode) of current, voltage and light intensity were made
simultaneously. EL spectra were measured on a Hitachi F-4500
fluorescence spectrophotometer. The operational lifetime was
tested in a nitrogen-filled glove box under a constant current
density of 22.2 mA cmꢁ2. Half-life, T50, is defined as the time for
the luminance to decay to half of the initial luminance (L0).
3. Conclusion
We synthesized deep-blue fluorescent HPhAn derivatives with
a simple method. The doped EL device with 1bb as dopant
achieved an EQE of 5.3% (4.8 cd Aꢁ1) in the deep-blue visible
region with excellent CIE chromaticity coordinates (0.14, 0.10)
that are near the NTSC standard blue coordinates. Our results
demonstrate that these new HPhAn derivatives are promising
deep-blue dopants for OLED applications.
Preparation of blue-emitting HPhAn derivatives
1bb, 2bb and 3bb were prepared by Suzuki coupling between the
dibromo starting material and the arylboronic ester in yields of
79–89%. The fluorinated phenylboronic esters resulted from the
reaction of aryl halides with pinacol diborane in the presence of
a palladium catalyst.16e
4. Experimental
2,3,6,7-Tetrakis(4-tert-butylphenyl)-9,10-bis(3,5-difluorophenyl)
anthracene (1bb)
Characterization
All reagents were used as received from commercial sources,
unless otherwise stated. All experiments were performed under
a N2 atmosphere in oven-dried glassware using standard syringe,
cannula and septa apparatus. 1H and 13C NMR were recorded in
CDCl3 solution unless otherwise stated. Coupling parameters (J
values) are given in hertz (Hz) and chemical shifts are expressed in
parts per million (ppm). UV-vis (Hitachi U-3300 spectropho-
tometer) and PL (Hitachi F-4500 fluorescence spectrophotom-
eter) spectra were recorded for dilute solutions (10ꢁ5 M). The
fluorescent quantum yields in the solid state were determined with
an integrating sphere connected to a spectrophotometer. The
thermal stability of the prepared HPhAn derivatives was investi-
gated with thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC) under a nitrogen atmosphere at
a heating rate of 10 ꢀC minꢁ1. The HOMO energy level of a tested
2,3,6,7-Tetrakis(4-tert-butylphenyl)-9,10-bis(3,5-difluorophenyl)
anthracene (1bb) is taken as an example. 2-(3,5-Difluorophenyl)-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(0.4g,
2.1mmol),
9,10-dibromo-2,3,6,7-tetrakis(4-tert-butylphenyl)anthracene
(0.6 g, 0.64 mmol), Pd(Ph3P)4 (0.04 g, 0.35 mmol) and Cs2CO3
(0.064 g, 0.46 mmol) were dissolved in a mixed solvent of toluene
(50 mL), ethanol (25 mL) and water (40 mL); the resulting
mixture was heated to 80 ꢀC for 8 h. The solution was cooled to
room temperature, extracted with dichloromethane, dried over
MgSO4 and concentrated under reduced pressure. The residues
were eluted through a silica column to afford the desired product.
Further sublimation at 315 ꢀC (5 ꢂ 10ꢁ3 Pa) gave extra pure
compound 1bb (0.52 g, 80.1%).
1H NMR (400 MHz, CDCl3): d 7.64 (s, 4H), 7.19–7.17 (m, 8H),
7.08–7.06 (m, 4H), 7.00–6.98 (m, 10H), 1.26 (s, 36H); 13C NMR
(100 MHz, CDCl3/CS2): d 163.0 (dd, J ¼ 249, 13 Hz), 149.3,
142.0, 139.3, 137.9, 134.5, 129.3, 128.9, 127.3, 124.6, 114.1 (d, J ¼
25 Hz), 103.2 (t, J ¼ 25 Hz), 34.1, 31.2; MALDITOF-MS calcd
for C66H62F4: 930.479, found m/z ¼ 931.051. Anal. calcd for
C66H62F4: C 85.13; H 6.71. found: C 85.44; H 6.74%.
compound was calculated from the oxidation potential (E1/2
)
obtained from a cyclic voltammetry (CV) measurement in
dichloromethane with Pt wire as counter electrode and a Pt elec-
trode as working electrode. The potentials were measured against
an Ag/Ag+ (Ag/0.01 M AgNO3) reference electrode. The final
results were calibrated with the ferrocene/ferrocenium (Fc/Fc+)
couple under the assumption that the energy level of ferrocene/
ferrocenium is 4.8 eV below vacuum. The HOMO energy levels
were determined from the equation 4.8 eV + E1/2 (vs. Fc/Fc+).
2,3,6,7-Tetrakis(4-tert-butylphenyl)-9,10-bis(3,4,5-
trifluorophenyl)anthracene (2bb)
The desired product was sublimed at 310 ꢀC (5 ꢂ 10ꢁ3 Pa) to
afford compound 2bb in 78.5% yield. 1H NMR (600 MHz,
CDCl3): d 7.61 (s, 4H), 7.22 (d, J ¼ 8.4 Hz, 8H), 7.18–7.16 (m,
4H), 7.02 (d, J ¼ 8.4 Hz, 8H), 1.30 (s, 36H); 13C NMR (150 MHz,
CDCl3/CS2): d 151.4 (ddd, J ¼ 251, 9.8, 3.5 Hz), 149.7, 139.6,
OLED fabrication and measurement
TCTA, TPBI, NPNPB, NPB and BAlq (Nichem Fine Tech-
nology Ltd) and BCP (Luminescence Technology Corp) were
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139.5 (dt, J ¼ 252, 15 Hz), 137.9, 134.6–134.5 (m), 133.9, 129.5,
127.1, 124.9, 115.5–115.3(m), 34.3, 31.2; MALDITOF-MS calcd
for C66H60F6: 966.460, found m/z ¼ 966.316. Anal. calcd for
C66H62F6: C 81.96; H 6.25. found: C 81.69; H 6.28%.
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9,10-Bis(3,5-bis(trifluoromethyl)phenyl)-2,3,6,7-tetrakis(4-tert-
butylphenyl)anthracene (3bb)
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The desired product was sublimed at 265 ꢀC (5 ꢂ 10ꢁ3 Pa) to
afford compound 3bb in 89.1% yield. 1H NMR (600 MHz,
CDCl3) d 8.14 (s, 4H), 8.10 (s, 2H), 7.65 (s, 4H), 7.22 (d, J ¼ 8.4
Hz, 8H), 7.03–7.02 (m, 8H), 1.29 (s, 36H); 13C NMR (150 MHz,
CDCl3): d 150.1, 140.8, 140.2, 137.8, 134.1, 132.2 (q, J ¼ 33),
131.9, 129.4, 127.0, 124.8, 123.4 (q, J ¼ 272 Hz),122.0, 34.5, 31.3;
MALDITOF-MS calcd for C66H62F4: 1132.482, found m/z ¼
1130.348. Anal. calcd for C66H62F4: C 74.19; H 5.69. found: C
74.26; H 5.23%.
Acknowledgements
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Ministry of Economy (98-EC-17-A-08-S1-042) and National
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8128 | J. Mater. Chem., 2011, 21, 8122–8128
This journal is ª The Royal Society of Chemistry 2011