Stable and efficient deep-blue terfluorenes functionalized with carbazole dendrons for solution-processed organic light-emitting diodes

Article abstract of DOI:10.1039/c5tc01711d

A series of solution processible deep-blue fluorescent emitters TFPC0 ～ TFPC2 have been designed and synthesized by incorporating different generation carbazole dendrons into the 9,9-positions of the terfluorene backbone. Compared with TFPC0, the dendriti

Full text of DOI:10.1039/c5tc01711d

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Stable and Efficient Deep-Blue Terfluorenes Functionalized with
Carbazole Dendrons for Solution-Processed Organic Light-Emitting
Diodes
†
,‡
†,‡
†
,†
,†
Lei Zhao, Shumeng Wang, Shiyang Shao, Junqiao Ding,* Lixiang Wang,*
†
†
Xiabin Jing, and Fosong Wang
†
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of
Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China
‡
University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
1

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Abstract:
A series of solution processible deepꢀblue fluorescent emitters TFPC0～TFPC2
have been designed and synthesized by incorporating different generation carbazole
dendrons into the 9,9ꢀpositions of the terfluorene backbone. Compared with TFPC0,
the dendritic TFPC1 and TFPC2 have the elevated glass transition temperatures as
well as better solubility in common organic solvents, and their high quality
amorphous films can be formed via spinꢀcoating. Noticeably, with the increasing
generation number, both the intermolecular aggregate and the formation of keto
defects can be effectively suppressed to avoid the appearance of the unwanted long
wavelength emission. Meanwhile, the highest occupied molecular orbital (HOMO)
level is gradually enhanced from TFPC0 to TFPC2, facilitating the hole injection. As
a result, TFPC2 with the second generation carbazole dendrons shows the best
photoluminescence and electroluminescence stability among TFPC0～TFPC2. Its
corresponding solutionꢀprocessed undoped device gives a stateꢀofꢀart external
’
quantum efficiency as high as 2.02% and Commission International De L Eclairge
(CIE) coordinates of (0.16, 0.04). These results indicate that the introduction of
oligocarbazole is a promising strategy towards solution processible deepꢀblue
fluoreneꢀcontaining oligomers simultaneously with high spectral stability and
efficiency.
2

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Introduction
Owing to their potential applications in fullꢀcolor flatꢀpanel displays and
1
ꢀ10
solidꢀstate lightings, organic lightꢀemitting diodes (OLEDs)
have attracted much
attention during the past three decades, where highly stable and luminescent materials
are required to produce the three primary colors, red, green and blue. Compared with
red and green counterparts, developing blue emitters remains a big challenge in terms
of their inferior device efficiency, color purity and lifetime. Especially, deepꢀblue
’
emitters with a Commission International De L Eclairge (CIE) coordinate of y < 0.10
11,12
are of paramount importance because the power consumption in fullꢀcolor
displays is dependent on the color of blue emission, that is, the smaller the CIE y
value, the lower the power consumption.
13ꢀ16
Up
to
date,
various
moieties
including
anthracene,
1
7ꢀ19
20
21ꢀ26
27ꢀ30
pyrene,
dimesitylborane, fluorene
and phenanthro[9,10ꢀd]imidazole
have
2
3,24
been utilized to design deepꢀblue fluorescent emitters. Among them, terfluorene
is
believed to be a promising candidate due to its high photoluminescence quantum yield
PLQY) and wide bandgap. However, these fluoreneꢀbased derivatives may suffer
(
from poor color purity, such as the macromolecule polyfluorene (PF). Early in 2002,
E. J. W. List et al observed the appearance of a lowꢀenergy emission band at 2.2ꢀ2.3
eV corresponding to the formation of fluorenone trapping sites in the PF main chain,
31
which turns the desired blue emission color into an undesired blueꢀgreen emission.
In addition, the carrier injection from the electrodes to the emitting layer (EML)
32,33
seems to be problematic due to the intrinsic wide bandgap of terfluorene.
For
example, there is a large holeꢀinjection barrier of about 0.7 eV between the
PEDOT:PSS modified ITO anode and the terfluorene composed EML, leading to high
driving voltage as well as low device efficiency.
To overcome these problems, in this paper, we report novel stable and efficient
deepꢀblue terfluorenes (TFPC1 and TFPC2) functionalized with different generation
carbazole dendrons for solutionꢀprocessed undoped OLEDs. As indicated in Figure 1,
the incorporation of oligocarbazole into the 9, 9’ꢀpositions of fluorene is expected to
34
suppress the aggregation and keto defects of the terfluorene backbone, and thereby
3

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improve the color stability. Secondly, the hole injection and transporting capability
could be enhanced due to the strong electronꢀdonating nature of oligocarbazole.
Thirdly, the bulky dendrons endow these deepꢀblue terfluorenes with high glass
transition temperature and good solubility in common organic solvents, so that high
quality amorphous films can be deposited through inexpensive wet processes, such
as inkjet printing and spin coating. Consequently, unlike the model compound
TFPC0, TFPC2 bearing the second generation carbazole dendrons shows excellent
photoluminescence (PL) and electroluminescence (EL) stability without the
appearance of the green emission usually observed in fluoreneꢀbased derivatives. A
peak external quantum efficiency (EQE) as high as 2.02% is simultaneously
obtained together with CIE coordinates of (0.16, 0.04), which is among the highest
ever reported for solutionꢀprocessible undoped deepꢀblue fluorescent emitters.
Results and discussion
Synthesis and characterization
The synthesis of TFPC1 and TFPC2 (Scheme 1) was started from
2
,7ꢀdibromofluorenone and 2ꢀbromofluorenone, which were arylated with aniline
through electrophilic addition reaction to afford 2Br2AnF and Br2AnF. They were
subsequently converted to 2Br2IF and Br2IF in 40ꢀ48% yields via a diazotization
route. By using CuCl/1,10ꢀphenanthroline as the catalyst and KOH as the base, the
selective Ullmann reactions were then carried out between these iodide products and
carbazole dendrons to give the key intermediates a1, a2, b1 and b2, respectively.
Among them, a1 and a2 were further lithiated and converted to the corresponding
trimethylene boronic esters c1 and c2. Finally, the Suzuki crossꢀcoupling was
performed to prepare the desired terfluorenes TFPC1 and TFPC2 in modest yields of
2
0ꢀ54%. For comparison, the model compound TFPC0 was also synthesized
21
according to the literature method. Their molecular structures were fully
1
13
characterized by H and C NMR spectra, MALDIꢀTOF mass spectroscopy and
elemental analysis. Moreover, with the introduction of carbazole dendrons, TFPC1
and TFPC2 are readily soluble in common organic solvents, such as chloroform,
4

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tetrahydrofuran, toluene and chlorobenzene, ensuring their capability to form high
quality films via spinꢀcoating. This is confirmed by their atomic force microscopy
(
AFM) topographic images (Figure 2), where the TFPC1 and TFPC2 films displays
pinholeꢀfree and smooth surface with a rootꢀmeanꢀsquare (RMS) roughness of only
.21ꢀ0.23 nm.
0
Thermal properties
The thermal properties of TFPC1 and TFPC2 together with TFPC0 were
measured by thermogravimetric analysis (TGA) and differential scanning calorimetry
(DSC). As presented in Figure 3, they are thermally stable with the decomposition
o
temperatures (determined by 5% weight loss) higher than 470 C. The glass transition
temperature is found to be dependent of the generation, and increases greatly from
o
o
o
1
90 C of TFPC0 to 304 C of TFPC1 and 376 C of TFPC2. Moreover, different
o
from TFPC0 which shows a melting peak at about 373 C, no melting process is
detected for TFPC1 and TFPC2. The enhanced glass transition temperature and
suppressed trend towards crystallization can be attributed to the restrained molecular
movement induced by the bulky carbazole dendrons, which is beneficial for the
formation of amorphous film morphology and thus the longꢀterm operation stability
of OLEDs.
Electrochemical properties:
To probe the electrochemical properties of TFPC0~TFPC2, cyclic voltammetry
4 4
(CV) were performed with a threeꢀelectrode cell setup with 0.1 M nꢀBu NClO as the
+
supporting electrolyte and ferrocene/ferrocenium(Fc/Fc ) as the internal standard.
During the anodic sweeping in dichloromethane (DCM), they all exhibit reversible
oxidation processes (Figure 4). The onset potentials of TFPC0, TFPC1 and TFPC2 are
observed at 0.91, 0.72 and 0.55 V, respectively. The negative shift from TFPC0 to
TFPC2 is related to the increased electronꢀrich feature with the increasing generation
number of the introduced carbazole dendrons. According to these onset potentials, the
highest occupied molecular orbital (HOMO) energy levels are estimated to be ꢀ5.71
5

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eV for TFPC0, ꢀ5.52 eV for TFPC1 and ꢀ5.35 eV for TFPC2, respectively. We note
that the HOMO level of TFPC2 is much closer to the work function of PEDOT:PSS
(ꢀ5.2 eV), facilitating the efficient hole injection from PEDOT:PSS to TFPC2. In
contrast, no reduction processes are observed for TFPC0~TFPC2 during the cathodic
scan in DCM. So their lowest unoccupied molecular orbital (LUMO) energy levels
are calculated from their HOMO levels and optical bandgaps. As listed in Table 1, the
LUMO levels are ꢀ2.52, ꢀ2.32 and ꢀ2.15 eV for TFPC0, TFPC1 and TFPC2,
respectively.
Photophysical properties
Figure 5 shows the UVꢀVis and PL spectra of TFPC0～TFPC2, and the related
data are summarized in Table 1. As can be clearly seen in Figure 5a, all the emitters
*
have a similar absorption peak at about 350 nm in toluene, corresponding to the πꢀπ
transition of the conjugated terfluorene backbone. But for TFPC1 and TFPC2, an
additional absorption band is observed in the range of 280ꢀ320 nm, which can be
*
*
safely assigned to the nꢀπ and πꢀπ transitions of the periphery oligocarbazole. Upon
photoꢀexcitation at 350 nm, TFPC0～TFPC2 possess strong deepꢀblue fluorescence in
toluene with a 0ꢀ0 emission peak at about 395 nm and a 0ꢀ1 shoulder at about 414 nm.
The emission profiles of TFPC1 and TFPC2 are almost the same as that of TFPC0,
indicating that the structural modification at the 9ꢀposition of fluorene can barely
affect the property of the lowest excited state of terfluorenes. By using
9
,10ꢀdiphenylanthracene as the standard, the solution PLQYs are determined to be
8% for TFPC0, 94% for TFPC1 and 69% for TFPC2, respectively. Relative to
8
TFPC0 and TFPC1, the lowered PLQY of TFPC2 may be tentatively ascribed to the
enhanced coupling of the excited state to vibrational modes of the second generation
35
36
carbazole dendron, as previously observed in carbazoleꢀbased iridium dendrimers.
In film state, the PL spectra of TFPC0～TFPC2 exhibit a 0ꢀ1 emission peak at
about 426 nm accompanied by a 0ꢀ0 shoulder at about 407 nm (Figure 5b). Compared
with the behavior in solution, the film emission maximum is redꢀshifted by about 30
nm, indicative of the existence of aggregation to some extent. The observation is in
6

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agreement with the lower PLQYs (36ꢀ52%) in film than those in solution (69ꢀ94%).
Despite of this, on going from TFPC0 to TFPC2, the degree of the bathochromic shift
seems to be decreased, which implies that the intermolecular interactions become
weakened as the dendron generation grows. This is further verified by the gradual
increasing solution and film emission lifetimes from TFPC0 to TFPC2 (Table 1 and
Figure S1).
To evaluate the spectral stability of these deepꢀblue emitters, the film PL spectra
o
are recorded before and after annealing at 150 C for 24 hours in air (Figure 6). As for
TFPC0, a long wavelength emission occurs in the green region after annealing,
whereas TFPC1 and TFPC2 show nearly unchanged PL spectra. This suggests that
with the incorporation of oligocarbazole, TFPC1 and TFPC2 are more stable than
TFPC0. Consistent with oligofluorenes and polyfluorenes, the improved spectral
stability of TFPC1 and TFPC2 is most likely due to the reduced intermolecular
aggregation as discussed above, together with the elimination of keto defects because
the shielding effect from periphery dendrons can prevent oxygen from touching the
9
ꢀposition carbon atom and thereby avoid its possible oxidation.
Electroluminescence properties
To investigate the EL properties of TFPC0～TFPC2, solutionꢀprocessed undoped
devices with a singleꢀlayer configuration of ITO/PEDOT:PSS/ TFPC0 ～
TFPC2/Ca/Al were initially fabricated, and their EL spectra are portrayed in Figure 7.
As one can see, the EL spectra at a low driving voltage of 6 V for TFPC0～TFPC2
match well with their PL counterparts in solid states, giving CIE coordinates of (0.17,
0
.08), (0.18, 0.06) and (0.17, 0.04). However, we note that the EL spectra significantly
depend on the driving voltage. For instance, a very broad emission band in the range
of 480ꢀ700 nm is observed for TFPC0 at a high driving voltage of 14 V. This
unwanted emission may come from the molecular aggregation, similar to the gꢀband
37
emission in polyfluorenes under electrical excitation. Additionally, the contribution
from the keto defects could not be excluded, for the temporal EL spectra of TFPC0
(
Figure S6) show the occurrence of the green emission band peaked at around 530 nm
7

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31
under aging. While for TFPC1, a distinct long wavelength emission peaked at 592
nm appears when the driving voltage increases to 14 V, which is tentatively ascribed
3
8,39
to the electromer emission.
Different from TFPC0 and TFPC1, TFPC2 displays
nearly unchanged EL spectra with the increasing driving voltage. The observation
demonstrates that the second generation carbazole dendron can effectively suppress
the intermolecular interactions and keto defects so as to prevent the device from
morphologyꢀinduced deterioration during operation.
In spite of the excellent EL stability, it should be noted that, the singleꢀlayer
device performance of TFPC2 is very poor, revealing a maximum EQE of 0.11%, a
2
maximum luminous efficiency of 0.05 cd/A and a maximum luminance of 183 cd/m
(
Table 2 and Figure S3ꢀS5). Therefore, a doubleꢀlayer device is then prepared for
TFPC2 with a structure of ITO/PEDOT:PSS/TFPC2/TPBI/LiF/Al, where TPBI
1,3,5ꢀtris(1ꢀphenylꢀbenzimidazoleꢀ2ꢀyl)benzene) acts as the electron transporting
(
layer. As indicated in Figure 8, a stateꢀofꢀart EQE as high as 2.02% is achieved
together with a maximum luminous efficiency of 0.86 cd/A and a maximum
2
luminance of 1054 cd/m . The EQE is enhanced by about 20 times compared with the
singleꢀlayer device because the insertion of an additional TPBI layer could improve
the electron injection/transporting and lead to more balanced charge flux. Most
importantly, similar to the singleꢀlayer device, the EL spectrum of TFPC2 is
independent of the driving voltage. As a consequence, a very stable deepꢀblue
emission is realized with CIE coordinates of (0.16, 0.04), close to the National
Television System Committee (NTSC) standard blue value of (0.14, 0.08) or the
European Broadcasting Union (EBU) one of (0.15, 0.06). Given the efficiency and
color purity, to the best of our knowledge, TFPC2 is among the most promising
deepꢀblue fluorescent emitters used for solutionꢀprocessed undoped OLEDs.
Conclusion
In conclusion, we have designed and synthesized a series of solution processible
deepꢀblue fluorescent emitters TFPC0～TFPC2 by functionalizing the terfluorene
backbone with different generation carbazole dendrons. The introduction of the bulky
8

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holeꢀtransporting oilgocarbazole, it is found that, can improve the thermal stability
and solution processibility to ensure the formation of high quality amorphous films,
suppress the aggregate and keto defects to avoid the unwanted long wavelength
emission usually observed in fluorene derivatives, and elevate the HOMO level to
facilitate the hole injection. Consequently, a very stable and highly efficient deepꢀblue
emission is achieved for TFPC2 bearing the second generation carbazole dendrons,
which shows a promising EQE of 2.02% with CIE coordinates of (0.16, 0.04). We
believe that this work will pave the way to the development of high performance
oligofluoreneꢀbased deepꢀblue emitters used for solutionꢀprocessed undoped OLEDs.
Experimental section
General information
1
13
H and C NMR spectra were recorded with a Bruker Avance 300 NMR
spectrometer. Elemental analyses of carbon, hydrogen, and nitrogen were performed
on a VarioEL elemental analyzer. MALDI/TOF mass spectra were obtained on an
AXIMA CFR MS apparatus (COMPACT). Thermal gravimetric analysis (TGA) and
differential scanning calorimetry (DSC) were performed on Perkin ElmerꢀTGA 7 and
o
ꢀ1
Perkin ElmerꢀDSC 7 system under nitrogen at a heating rate of 10 C min . The
UV/visible absorption and photoluminescent spectra were measured by a
PerkinꢀElmer Lambda 35 UV/vis spectrometer and a PerkinꢀElmer LS 50B
spectrofluorometer, respectively. The PL quantum yields of the terfluorenes in toluene
solution were measured by excitation at 350 nm with 9,10ꢀdiphenylanthracene (ca. 5
−6
×
10 M solution in cyclohexane, PLQY = 0.9) as the standard. Thin films for
spectroscopic measurements were prepared by spinꢀcoating on quartz. The quantum
efficiencies of the solid films were recorded by measuring the total light output in all
directions in an integrating sphere (C9920ꢀ02, HAMAMATSU). Emission lifetimes
were obtained by double exponential fit of emission decay curves recorded on a
system equiped with a Quantyꢀray FLS920 pulsed Ti:Saph laser with THG 376 nm
output and ca. 20 ps pulse width. Cyclic voltammetry (CV) measurements were
−
1
obtained in anhydrous dichloromethane with Bu
4
NClO
4
(0.1 mol L ) as the
9

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−1
electrolyte on a CHI660a electrochemical analyzer under a scan rate of 100 mV s . A
glass carbon electrode, a Ag/AgCl electrode and a Pt wire were used as the working
electrode, the reference electrode and the counter electrode, respectively.
Device fabrication and measurement
Patterned glass substrates coated with indium tin oxide (ITO) (20 ꢁ per square)
were cleaned with acetone, detergent, and distilled water and then were cleaned in an
ultrasonic solvent bath. After baking in a heating chamber at 120 °C for 8 h, the
2
ITOꢀglass substrates were treated with O plasma for 30 min. Subsequently,
poly(3,4ꢀethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, Batronꢀ
P4083, Bayer AG) was spinꢀcoated on top of the ITO at a speed of 5000 rpm for 60 s
and then baked at 120 °C for 45 min. Then, solutions of the emitters (10 mg/mL) in
oꢀdichlorobenzene were filtered through a filter (0.45 ꢂm) and spinꢀcoated on
PEDOT:PSS as the emissive layer (EML) at a speed of 1500 rpm for 60 s.
Successively, the substrate was annealed at 100 °C for 30 min inside a nitrogenꢀfilled
glovebox and then transferred to a vacuum thermal evaporator. On top of the EML,
2
calcium was thermally deposited through a shadow mask with an array of 70 mm
−
4
openings at a pressure of 4.0 × 10 Pa. Finally, aluminum was deposited
subsequently as the protective layer for calcium. For the bilayer device, a 50 nmꢀthick
TPBI film was evaporated on top of the EML, and then 1 nm LiF and 100 nm Al were
deposited subsequently as the cathode. The EL spectra and CIE coordinates were
measured using a PR650 spectra colorimeter. The current−voltage and
brightness−voltage curves of devices were measured using a Keithley 2400/2000
source meter and a calibrated silicon photodiode. All the measurements were carried
out at room temperature under ambient conditions.
Synthesis:
All solvents for chemical synthesis were refined according to the standard
procedures. 2,7ꢀdibromofluorenone, 2ꢀbromofluorenone, 3,6ꢀdiꢀtertꢀbutylꢀcarbazole
and 3,6ꢀbis(3,6ꢀdiꢀtertꢀbutylcarbazolꢀ9ꢀyl)ꢀcarbazole were prepared according to
1
0

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40ꢀ42
literature methods.
4
-(9-(4-aminophenyl)-2,7-dibromofluoren-9-yl)benzenamine
(2Br2AnF):
2
,7ꢀDibromofluorenone (3.38 g, 10 mmol), aniline (13.96 g, 150 mmol),
methylsulphonic acid (0.64 mL, 10 mmol) were mixed in a threeꢀnecked
o
roundꢀbottom flask and refluxed for 6 hours at 150 C under N atmosphere. After
2
cooling to room temperature, 100 mL water was added to the solution. The mixture
was filtered and the residue was washed with water. The residue was recrystallized
1
from ethanol to give the product as a gray solid in 67% yield. H NMR (300 MHz,
CDCl
3
) δ 7.55 (d, J = 7.8 Hz, 2H), 7.42 (m, 4H), 6.93 (d, J = 7.8 Hz, 4H), 6.56 (d, J =
8
2
2
.7 Hz, 4H), 3.62 (s, 4H).
,7-dibromo-9,9-bis(4-iodophenyl)fluorene (2Br2IF):
Br2AnF (2.03 g, 4.0 mmol), hydrochloric acid (1.33 mL, 16 mmol) and H O (20 mL)
2
o
were mixed in a flask and were cooled to 0 C. Sodium nitrite (0.56 g, 8.0 mmol) and
H
2
O (2 mL) were then slowly added. After stirring for 30 minute, a solution of KI
o
(
1.46 g, 8.8 mmol) in 5 mL H O was added into the mixture at 0 C. After aging for 1
2
o
hour, the mixture was heated at 80 C overnight. The mixture was filtered and the
residue was washed with water. The crude product was purified by column
chromatography on silica gel with petroleum ether as eluent to give a white solid in
1
4
7
4
0% yield. H NMR (300 MHz, CDCl
3
) δ 7.59 (m, 6H), 7.51 (dd, J = 8.2, 1.5 Hz, 2H),
.41 (d, J = 1.5 Hz, 2H), 6.87 (d, J = 8.7 Hz, 4H).
-(9-(4-aminophenyl)-2-bromofluoren-9-yl)benzenamine (Br2AnF):
Br2AnF was prepared in 72% yield according to a similar procedure to 2Br2AnF by
1
using 2ꢀbromofluorenꢀ9ꢀone instead of 2,7ꢀdibromofluorenꢀ9ꢀone. H NMR (300
MHz, CDCl
3
) δ 7.53 (d, J = 7.8 Hz, 1H), 7.492 (d, J = 8.1 Hz, 1H), 7.47 – 7.43 (m,
4
1
2
H), 7.42 – 7.36 (m, 1H), 7.33 (d, J = 1.6 Hz, 1H), 7.21 (ddd, J = 10.9, 6.0, 3.4 Hz,
H), 7.17 – 7.14 (m, 2H), 6.93 – 6.85 (m, 4H), 3.63 (s, 4H).
-bromo-9,9-bis(4-iodophenyl)-fluorene (Br2IF):
Br2IF was prepared from Br2AnF in 48% yield according to the procedure similar to
1
Br2IF. H NMR (300 MHz, CDCl
3
) δ 7.73 (d, J = 7.5 Hz, 1H), 7.62 (d, J = 8.1 Hz,
1
H), 7.59 – 7.52 (m, 4H), 7.52 – 7.46 (m, 1H), 7.43 (d, J = 1.6 Hz, 1H), 7.37 (ddd, J =
11

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1
2
2
0.9, 6.0, 3.4 Hz, 1H), 7.32 – 7.27 (m, 2H), 6.93 – 6.85 (m, 4H).
,7-dibromo-9,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]fluorene (a1):
Br2IF (2.10 g, 3.0 mmol) and 3,6ꢀdiꢀtertꢀbutylꢀcarbazole (1.70 g, 6.3 mmol,), CuCl
(0.11 g, 1.2 mmol), KOH (1.02 g, 18 mmol) , 1,10ꢀphenanthroline monohydrate (0.23
g, 1.2 mmol) and xylene (20 mL) were added into aroundꢀbottom flask and refluxed
o
for 24 hours at 150 C under N
2
atmosphere. After cooling to room temperature, the
Cl (50 mL × 2). The combined organic phase
was washed with water, dried over anhydrous Na SO , filtered and the solvent was
removed in a vacuum. The crude product was purified by column chromatography
reaction mixture was extracted with CH
2
2
2
4
2 2
over silica gel eluting with a mixture of CH Cl /hexane (1/4) to give a white solid in
1
5
4
1
2
0% yield. H NMR (300 MHz, CDCl
3
) δ 8.13 (d, J = 1.5 Hz, 4H), 7.74 – 7.66 (m,
H), 7.59 (dd, J = 8.2, 1.6 Hz, 2H), 7.52 (d, J = 8.6 Hz, 4H), 7.49 – 7.37 (m, 12H),
.46 (s, 36H).
,7-dibromo-9,9-bis{4-[3,6-bis
(3,6-di-tert-butylcarbazol-9-yl)carbazole-9-yl]phenyl}fluorene (a2):
a2 was prepared in 21% yield according to a similar procedure to a1 by using
3
,6ꢀbis(3,6ꢀdiꢀtertꢀbutylcarbazolꢀ9ꢀyl)ꢀcarbazole instead of 3,6ꢀdiꢀtertꢀbutylꢀcarbazole.
1
H NMR (300 MHz, CDCl
3
) δ 8.24 (d, J = 1.8 Hz, 4H), 8.16 (d, J = 1.6 Hz, 8H), 7.81
–
8
2
7.74 (m, 4H), 7.74 – 7.69 (m, 6H), 7.67 – 7.57 (m, 12H), 7.46 (dd, J = 8.7, 1.8 Hz,
H), 7.34 (d, J = 8.6 Hz, 8H), 1.46 (s, 72H).
-bromo-9,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]fluorene (b1):
b1 was prepared in 48% yield according to a similar procedure to a1 by using Br2IF
1
instead of 2Br2IF. H NMR (300 MHz, CDCl
3
) δ 8.12 (s, 4H), 7.82 (d, J = 7.4 Hz,
1
3
2
H), 7.76 – 7.67 (m, 2H), 7.58 (d, J = 8.3 Hz, 2H), 7.53 – 7.33 (m, 18H), 1.45 (s,
6H).
-bromo-9,9-bis{4-[3,6-bis
(3,6-di-tert-butylcarbazol-9-yl)carbazole-9-yl]phenyl}fluorene (b2): b2 was
prepared in 29% yield according to a similar procedure to a1 by using Br2IF instead
of 2Br2IF and 3,6ꢀbis(3,6ꢀdiꢀtertꢀbutylcarbazolꢀ9ꢀyl)ꢀcarbazole instead of
1
3
,6ꢀdiꢀtertꢀbutylꢀcarbazole. H NMR (300 MHz, CDCl
3
) δ 8.23 (d, J = 1.7 Hz, 4H),
1
2

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8
.15 (d, J = 1.7 Hz, 8H), 7.89 (dd, J = 6.3, 2.2 Hz, 1H), 7.80 (dd, J = 7.7, 4.9 Hz, 2H),
.75 – 7.64 (m, 12H), 7.64 – 7.56 (m, 5H), 7.54 – 7.48 (m, 2H), 7.45 (dd, J = 8.7, 1.9
7
Hz, 8H), 7.32 (d, J = 8.6 Hz, 8H), 1.46 (s, 72H).
,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]fluorine-2,7-bis(trimethylene
9
boronate) (c1):
Compound a1 (0.93 g, 0.5 mmol) was disolved in dry tetrahydrofuran (30 mL)
o
under argon and cooled to ꢀ78 C. Then nꢀbutyl lithium (0.52 mL, 1.3 mmol) was
slowly added under vigorous stirring. After stirring for 2 hours, triethyl borate (0.17
o
mL, 1.5 mmol) was added and the mixture was stirred for another 8 hours at ꢀ78 C.
Subsequently the mixture was warmed to room temperature and poured into 2 N HCl
aqueous. The mixture was extracted with ether, washed with brine and dried over
anhydrous Na SO . The extract was evaporated to dryness affording a yellow solid.
2
4
This solid was then dissolved in 30 mL toluene and 1,3ꢀpropylenediol (0.45 g, 5
o
mmol). The mixture was stirred at 110 C under argon for 8 hours. After cooling to
room temperature, the mixture was extracted with ether, washed with brine and dried
2 4
over anhydrous Na SO . The extract was evaporated to dryness to afford the crude
product as a yellow solid, which was further purified by column chromatography over
1
silica gel with CH
2
Cl
2
/hexane (1/4) as the eluent to give a white solid in 56% yield. H
NMR (300 MHz, CDCl
3
) δ 8.12 (d, J = 1.3 Hz, 4H), 7.95 (s, 2H), 7.91 – 7.83 (m, 4H),
7
1
9
.45 (ddd, J = 18.6, 14.9, 8.6 Hz, 16H), 4.17 (t, J = 5.2 Hz, 8H), 2.14 – 2.02 (m, 4H),
.45 (s, 36H).
,9-bis{4-[3,6-bis (3,6-di-tert-butylcarbazol-9-yl)carbazole-9-yl]phenyl}fluorene
-2,7-bis(trimethylene boronate) (c2):
Compound c2 was prepared from a2 in 44% yield according to the procedure similar
1
to c1. H NMR (300 MHz, CDCl ) δ 8.22 (d, J = 1.8 Hz, 4H), 8.15 (d, J = 1.7 Hz, 8H),
3
8.05 (s, 2H), 7.92 (q, J = 7.7 Hz, 4H), 7.75 – 7.63 (m, 12H), 7.60 (dd, J = 8.7, 1.8 Hz,
4H), 7.45 (dd, J = 8.7, 1.8 Hz, 8H), 7.33 (d, J = 8.6 Hz, 8H), 4.19 (t, J = 5.1 Hz, 8H),
2.14 – 2.02 (m, 4H), 1.44 (s, 72H).
TFPC1:
3 4
Compound c1 (0.52 g, 0.5 mmol), b1 (1.04 g, 1.1 mmol) and Pd(PPh ) (12 mg, 0.01
1
3

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mmol) were dissolved in 30 mL toluene. An aqueous solution of 2 M K
2
CO
3
(1 mL,
2
.0 mmol) and one drop of Aliquat 336 was added to the solution and then the mixture
o
2 2
was heated to 100 C for 12 hours under argon. After reaction, 50 mL CH Cl was
added to the solution. The organic phase was washed with water and dried with
anhydrous Na SO . Solvents were removed under vacuum and the residue was
2
4
2 2
purified by column chromatography over silica gel with CH Cl /hexane (1/2) as the
1
eluent to give the product as a white solid in 54% yield. H NMR (300 MHz, CDCl
3
)
δ 8.06 (d, J = 8.6 Hz, 12H), 7.95 (dd, J = 7.9, 5.1 Hz, 5H), 7.89 (d, J = 6.3 Hz, 6H),
7
7
=
.76 (d, J = 7.9 Hz, 4H), 7.62 (d, J = 8.3 Hz, 7H), 7.56 (d, J = 8.6 Hz, 9H), 7.52 –
.45 (m, 14H), 7.43 (d, J = 7.6 Hz, 3H), 7.38 – 7.28 (m, 17H), 7.24 (s, 3H), 1.37 (d, J
13
3
13.3 Hz, 108H). C NMR (300 MHz, CDCl ) δ151.93, 151.67, 151.17, 144.19,
1
1
6
44.12, 142.81, 141.05, 140.89, 139.77, 139.23, 139.11, 137.23, 137.10, 129.48,
28.04, 127.23, 126.67, 124.93, 123.53, 123.36, 120.83, 120.60, 116.15, 109.23,
+
5.25, 34.66, 34.62, 31.96. MS (MALDIꢀTOF) m/z: 2613.48 [M ]. Anal. Calcd for
C H N : C, 89.54; H, 7.24; N, 3.21. Found: C, 89.60; H, 7.21; N, 3.16.
195 188
6
TFPC2:
TFPC2 was prepared from c2 and b2 in 20% yield according to the procedure similar
1
to TFPC1. H NMR (300 MHz, CDCl
3
) δ 8.13 (dd, J = 14.0, 1.5 Hz, 26H), 8.09 –
7
8
5
.99 (m, 18H), 7.93 (dd, J = 12.4, 7.5 Hz, 6H), 7.80 (d, J = 8.5 Hz, 4H), 7.73 (d, J =
.6 Hz, 8H), 7.62 (q, J = 8.5 Hz, 24H), 7.54 – 7.47 (m, 12H), 7.43 (dd, J = 8.8, 1.7 Hz,
H), 7.40 – 7.29 (m, 18H), 7.29 – 7.20 (m, 23H), 7.17 (d, J = 8.6 Hz, 8H), 1.38 (d, J =
13
1
1.0 Hz, 216H). C NMR (300 MHz, CDCl ) δ151.55, 151.35, 150.78, 145.43,
3
1
1
1
42.52, 140.99, 140.60, 140.24, 140.15, 140.03, 139.97, 139.67, 139.37, 137.83,
36.56, 136.36, 130.96, 129.92, 129.02, 128.21, 127.50, 127.25, 125.84, 125.29,
24.04, 123.47, 123.09, 123.05, 119.31, 116.16, 111.03, 109.04, 65.37, 34.54, 32.00.
+
MS (MALDIꢀTOF) m/z: 5271.16 [M ]. Anal. Calcd for C387
H
368
N18 : C, 88.18; H,
7
.04; N, 4.78. Found: C, 88.32; H, 6.96; N, 4.96.
Acknowledgements
The authors are grateful to the 973 Project (No. 2015CB655001) and Natural Science
1
4

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Foundation of China (Nos 21174144, 51322308 and 91333205) for financial support
of this research.
References
1
2
3
4
C. W. Tang and S. A. Vanslyke, Appl Phys Lett, 1987, 51, 913ꢀ915.
M. A. Baldo, M. E. Thompson and S. R. Forrest, Nature, 2000, 403, 750ꢀ753.
B. W. D'Andrade and S. R. Forrest, Adv Mater, 2004, 16, 1585ꢀ1595.
C. C. Wu, Y. T. Lin, K. T. Wong, R. T. Chen and Y. Y. Chien, Adv Mater, 2004,
16, 61ꢀ65.
5
6
S. J. Su, E. Gonmori, H. Sasabe and J. Kido, Adv Mater, 2008, 20, 4189ꢀ4194
Z. Q. Jiang, Z. Y. Liu, C. L. Yang, C. Zhong, J. G. Qin, G. Yu and Y. Q. Liu, Adv
Funct Mater, 2009, 19, 3987ꢀ3995.
7
8
K. T. Kamtekar, A. P. Monkman and M. R. Bryce, Adv Mater, 2010, 22,
572ꢀ582.
M. R. Zhu, Q. A. Wang, Y. Gu, X. S. Cao, C. Zhong, D. G. Ma, J. G. Qin and C.
L. Yang, J Mater Chem, 2011, 21, 6409ꢀ6415.
9
1
G. X. Jiang, C. L. Bian, J. Q. Ding and L. X. Wang, Chinese J Polym Sci, 2013,
31, 787ꢀ797.
0 D. B. Xia, B. Wang, B. Chen, S. M. Wang, B. H. Zhang, J. Q. Ding, L. X. Wang,
X. B. Jing and F. S. Wang, Angew Chem Int Edit, 2014, 53, 1048ꢀ1052.
1
1 B. Chen, J. Q. Ding, L. X. Wang, X. B. Jing and F. S. Wang, Chem Commun,
2012, 48, 8970ꢀ8972.
1
2 M. Q. Yu, S. M. Wang, S. Y. Shao, J. Q. Ding, L. X. Wang, X. B. Jing and F. S.
Wang, J Mater Chem C, 2015, 3, 861ꢀ869.
1
3 C. Adachi, T. Tsutsui and S. Saito, Appl Phys Lett, 1990, 56, 799ꢀ801.
4 R. Kim, S. Lee, K. H. Kim, Y. J. Lee, S. K. Kwon, J. J. Kim and Y. H. Kim, Chem
Commun, 2013, 49, 4664ꢀ4666.
1
1
1
1
1
1
2
5 H. Park, J. Lee, I. Kang, H. Y. Chu, J. I. Lee, S. K. Kwon and Y. H. Kim, J Mater
Chem, 2012, 22, 2695ꢀ2700.
6 Z. Q. Wang, C. Xu, W. Z. Wang, L. M. Duan, Z. Li, B. T. Zhao and B. M. Ji,
New J Chem, 2012, 36, 662ꢀ667.
7 G. Mallesham, C. Swetha, S. Niveditha, M. E. Mohanty, N. J. Babu, A. Kumar, K.
Bhanuprakash and V. J. Rao, J Mater Chem C, 2015, 3, 1208ꢀ1224.
8 F. Liu, W. Y. Lai, C. Tang, H. B. Wu, Q. Q. Chen, B. Peng, W. Wei, W. Huang
and Y. Cao, Macromol Rapid Comm, 2008, 29, 659ꢀ664.
9 J. You, G. Y. Li, R. J. Wang, Q. P. Nie, Z. G. Wang and J. Y. Li, Phys Chem
Chem Phys, 2011, 13, 17825ꢀ17830.
0 S. L. Lin, L. H. Chan, R. H. Lee, M. Y. Yen, W. J. Kuo, C. T. Chen and R. J.
1
5

Journal of Materials Chemistry C
Page 16 of 29
View Article Online
DOI: 10.1039/C5TC01711D
Jeng, Adv Mater, 2008, 20, 3947ꢀ3952.
2
1 K. T. Wong, Y. Y. Chien, R. T. Chen, C. F. Wang, Y. T. Lin, H. H. Chiang, P. Y.
Hsieh, C. C. Wu, C. H. Chou, Y. O. Su, G. H. Lee and S. M. Peng, J Am Chem
Soc, 2002, 124, 11576ꢀ11577.
2
2
2
2 S. Tang, M. Liu, P. Lu, H. Xia, M. Li, Z. Q. Xie, T. Z. Shen, C. Gu, H. P. Wang,
B. Yang and Y. G. Ma, Adv Funct Mater, 2007, 17, 2869ꢀ2877.
3 C. G. Zhen, Y. F. Dai, W. J. Zeng, Z. Ma, Z. K. Chen and J. Kieffer, Adv Funct
Mater, 2011, 21, 699ꢀ707.
4 C. G. Zhen, Z. K. Chen, Q. D. Liu, Y. F. Dai, R. Y. C. Shin, S. Y. Chang and J.
Kieffer, Adv Mater, 2009, 21, 2425ꢀ2429.
2
2
5 X. C. Wang, L. Zhao, S. Y. Shao, J. Q. Ding, L. X. Wang, X. B. Jing and F. S.
Wang, Polymer Chemistry, 2014, 5, 6444ꢀ6451.
6 X. C. Wang, L. Zhao, S. Y. Shao, J. Q. Ding, L. X. Wang, X. B. Jing and F. S.
Wang, Macromolecules, 2014, 47, 2907ꢀ2914.
2
2
2
7 C. J. Kuo, T. Y. Li, C. C. Lien, C. H. Liu, F. I. Wu and M. J. Huang, J Mater
Chem, 2009, 19, 1865ꢀ1871.
8 W. J. Li, D. D. Liu, F. Z. Shen, D. G. Ma, Z. M. Wang, T. Feng, Y. X. Xu, B.
Yang and Y. G. Ma, Adv Funct Mater, 2012, 22, 2797ꢀ2803.
9 Y. Zhang, S. L. Lai, Q. X. Tong, M. F. Lo, T. W. Ng, M. Y. Chan, Z. C. Wen, J.
He, K. S. Jeff, X. L. Tang, W. M. Liu, C. C. Ko, P. F. Wang and C. S. Lee, Chem
Mater, 2012, 24, 61ꢀ70.
3
3
3
0 S. T. Zhang, W. J. Li, L. Yao, Y. Y. Pan, F. Z. Shen, R. Xiao, B. Yang and Y. G.
Ma, Chem Commun, 2013, 49, 11302ꢀ11304.
1 E. J. W. List, R. Guentner, P. S. de Freitas and U. Scherf, Adv Mater, 2002, 14,
374ꢀ378.
2 C. Ego, A. C. Grimsdale, F. Uckert, G. Yu, G. Srdanov and K. Mullen, Adv
Mater, 2002, 14, 809ꢀ811.
3
3 Z. Q. Gao, Z. H. Li, P. F. Xia, M. S. Wong, K. W. Cheah and C. H. Chen, Adv
Funct Mater, 2007, 17, 3194ꢀ3199.
3
4 S. Setayesh, A. C. Grimsdale, T. Weil, V. Enkelmann, K. Mullen, F. Meghdadi, E.
J. W. List and G. Leising, J Am Chem Soc, 2001, 123, 946ꢀ953.
3
5 D. Phillips, J. Photochem. Photobiol. A, 1997, 105, 307ꢀ315.
3
6 K. A. Knights, S. G. Stevenson, C. P. Shipley, S. –C. Lo, S. Olsen, R. E. Harding,
S. Gambino, P. L. Burn, I. D. W. Samuel, J. Mater. Chem., 2008, 18, 2121ꢀ2130.
7 R. Grisorio, G. Allegretta, P. Mastrorilli and G. P. Suranna, Macromolecules,
3
3
3
4
2
011, 44, 7977ꢀ7986.
8 J. Kalinowski, G. Giro, M. Cocchi, V. Fattori and P. Di Marco, Appl Phys Lett,
000, 76, 2352ꢀ2354.
9 J. Y. Hu, Y. J. Pu, Y. Yamashita, F. Satoh, S. Kawata, H. Katagiri, H. Sasabe and
J. Kido, J Mater Chem C, 2013, 1, 3871ꢀ3878.
2
0 J. Q. Ding, J. H. Lu, Y. X. Cheng, Z. Y. Xie, L. X. Wang, X. B. Jing and F. S.
1
6

Page 17 of 29
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Wang, Adv Funct Mater, 2008, 18, 2754ꢀ2762.
4
1 P. Moonsin, N. Prachumrak, R. Rattanawan, T. Keawin, S. Jungsuttiwong, T.
Sudyoadsuk and V. Promarak, Chem Commun, 2012, 48, 3382ꢀ3384.
2 X. D. Wang, S. M. Wang, Z. H. Ma, J. Q. Ding, L. X. Wang, X. B. Jing and F. S.
Wang, Adv Funct Mater, 2014, 24, 3413ꢀ3421.
4
1
7

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Figure 1. Molecular structures of TFPC0~TFPC2
Scheme 1. Sythesis of TFPC1 and TFPC2.
o
Reagents and conditions: (i) aniline, CH
3
SO
3
H, 130 C; (ii) HCl, NaNO
2
, KI; (iii)
o
KOH, CuCl, 1,10ꢀphenanthroline ,3,6ꢀdiꢀtertꢀbutylꢀcarbazole, xylene, 140 C; (iv)
KOH, CuCl, 1,10ꢀphenanthroline, 3,6ꢀbis(3,6ꢀdiꢀtertꢀbutylcarbazolꢀ9ꢀyl)ꢀcarbazole,
o
+
xylene, 140 C ; (v) nꢀC
4
H
9 3 3 4 2 3
Li, B(OCH) , THF, then H ; (vi) Pd(PPh ) , 2 M K CO ,
o
Aliquat 336, toulene, 100 C.
1
8

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Figure 2. AFM images of the TFPC1 (a) and TFPC2 (b) films prepared through
spinꢀcoating from chlorobenzene solutions at a concentration of 10 mg/mL Surface
roughness amplitude: (a) 0.23 nm; (b) 0.21 nm.
1
9

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Figure 3. TGA (a) and DSC (b) traces of TFPC0~TFPC2 measured at a heating rate
o
ꢀ1
2
of 10 C min under N .
2
0

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Figure 4. Cyclic voltammograms of TFPC0~TFPC2 measured in CH
2
Cl
2
under a
ꢀ1
scan rate of 100 mV s .
2
1

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ꢀ6
Figure 5. Absorption and PL spectra in toluene (10 M) (a) as well as PL spectra in
film state (b) for TFPC0~TFPC2.
2
2

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Figure 6. PL spectra of TFPC0 (a), TFPC1 (b) and TFPC2 (c) before and after
o
annealling in air at 150 C for 24 hours.
2
3

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Figure 7. EL spectra of TFPC0 (a), TFPC1 (b) and TFPC2 (c) under different driving
voltages for the singleꢀlayer devices.
2
4

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Figure 8. The current densityꢀvoltageꢀbrightness characteristics (a), external quantum
efficiency and luminous efficiency as a function of current density (b) as well as EL
spectra at different driving voltages (c) for the doubleꢀlayer device of TFPC2.
2
5

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Table 1. Thermal, electrochemical and photophysical properties of TFPC0~TFPC2.
a
a
b
c
d
a
c
T
d
T
g
/T
m
λabs
nm]
352
λem
τ
ФPL
λem
τ
ФPL
HOMO LUMO
Compound
o
o
[
C]
[ C]
[ns]
[ns]
[eV]
[eV]
[
[nm]
[%]
88
[nm]
[%]
39
TFPC0
TFPC1
TFPC2
471 190/374
395/417
0.78
0.86
1.60
413/426
407/426
0.33
0.46
0.50
ꢀ5.71
ꢀ5.52
ꢀ5.35
ꢀ2.52
ꢀ2.32
ꢀ2.15
503 304/n.d. 348/298 394/414
521 376/n.d. 349/298 395/417
94
52
69
406/426
36
a
ꢀ6
b
Measured in toluene at a concentration of 10 M. Measured in toluene using
c
d
9
,10ꢀdiphenylanthracene as a standard. Measured in film. Measured in film using
an integrating sphere.
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6

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Table 2. EL performance of the devices.
c
d
e
f
g
h
V
on
L
max
η
c, max
η
p, max
η
ext, max
CIE
Device
ꢀ2
ꢀ1
ꢀ1
[
V]
[cd m ]
[cd A ]
[lm W ]
[%]
(x, y)
a
a
a
b
TFPC0
TFPC1
TFPC2
TFPC2
5.6
4.5
5.3
4.5
178
394
0.07
0.16
0.05
0.86
0.03
0.09
0.02
0.56
0.08
0.24
0.11
2.02
(0.17, 0.08)
(0.18, 0.06)
(0.17, 0.04)
(0.16, 0.04)
c
183
1054
a
b
e
ITO/PEDOT:PSS/EML/Ca/Al.
Voltage. Maximum luminance. Maximum current efficiency. Maximum power
efficiency. Maximum external quantum efficiency. Commission Internationale de
Eclairage coordinates at a driving voltage of 6 V.
ITO/PEDOT:PSS/EML/TPBI/LiF/Al.
Turnꢀon
d
f
g
h
’
1
2
7

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2
8

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Table of Contents
Deep-blue terfluorenes simultaneously with highly spectral stability and device efficiency
have been successfully developed by functionalizing the backbone with carbazole dendrons,
showing a peak external quantum efficiency as high as 2.02% and CIE coordinates of (0.16,
0.04) for solution-processed undoped OLEDs.