Solution-processed bipolar small molecular host materials for single-layer blue phosphorescent organic light-emitting diodes

Article abstract of DOI:10.1039/c3tc31641f

Three new solution processable small molecular host materials based on the bis-[3,5-di(9H-carbazol-9-yl)phenyl] structural moiety have been developed for blue phosphorescent (FIrpic dopant) organic light-emitting diodes. All three host materials have been characterized as having high glass transition temperatures (T_gs), 155-175 °C, indicative of good morphological stability of their amorphous thin films prepared from the solution process. Whereas N,N-bis-[3,5-di(9H-carbazol-9-yl)phenyl]methylamine (CzPAMe) has the highest solid state triplet energy gap (E_T) of 2.73 eV, tetrakis-[3,3′,5,5′-(9H-carbazol-9-yl)]triphenylphosphine oxide (CzPPO) and N,N-bis-[3,5-di(9H-carbazol-9-yl)phenyl]pyrimidin-2-amine (CzPAPm) are two host materials which are potentially bipolar for charge transport due to the electron deficient units of phenylphosphine oxide and pyrimidine, respectively. Due to the insufficient E_T (2.56 eV) of CzPAPm, CzPPO or CzPAMe devices are significantly better than CzPAPm devices with or without a 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD-7) co-host. Particularly, having no OXD-7 co-host and no vacuum thermal-deposited extra electron transporting layer, single-layer devices of CzPPO surpass CzPAMe devices and reach current efficiencies as high as 9.32 cd A^-1 (or power efficiency of 4.97 lm W^-1), one of the highest efficiencies among small molecular devices with the same fabrication process and same device configuration. The Royal Society of Chemistry.

Full text of DOI:10.1039/c3tc31641f

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ARTICLE TYPE
Solution-Processed Bipolar Small Molecular Host Materials for Single-
Layer Blue Phosphorescent Organic Light-Emitting Diodes
Yi-Ting Lee,a,b Yung-Ting Changa, Meng-Ting Leec, Po-Hsuan Chiangc, Chin-Ti Chen*a and Chao-Tsen
Chen*b
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Three new solution processable small molecular host materials based on bisꢀ[3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀ
yl)phenyl] structural moiety have been developed for blue phosphorescence (FIrpic dopant) organic lightꢀ
emitting diodes. All three host materials have been characterized for high glass transition temperatures
10 (Tgs), 155~175 oC, indicative of good morphological stability of their amorphous thin films prepared from
solution process. Whereas N,Nꢀbisꢀ[3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀyl)phenyl]methylamine (CzPAMe) has the
highest solid state triplet energy gap (ET) of 2.73 eV, tetrakisꢀ[3,3',5,5'ꢀ(9Hꢀcarbazolꢀ9ꢀyl)]
triphenylphosphine oxide (CzPPO) and N,Nꢀbisꢀ[3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀyl)phenyl]pyrimidinꢀ2ꢀamine
(CzPAPm) are two host materials potentially being bipolar for charge transport due to the electron
15 deficient unit of phenylphosphine oxide and pyrimidine, respectively. Due to the insufficient ET (2.56 eV)
of CzPAPm, CzPPO or CzPAMe devices are significantly better than CzPAPm devices with or without
1,3ꢀbis[(4ꢀtertꢀbutylphenyl)ꢀ1,3,4ꢀoxadiazolyl]phenylene (OXDꢀ7) coꢀhost. Particularly, having no OXDꢀ
7 coꢀhost and no vacuumꢀthermalꢀdeposited extra electron transporting layer, singleꢀlayer devices of
CzPPO surpassing CzPAMe devices reach current efficiency as high as 9.32 cd/A (or power efficiency
20 of 4.97 lm/W), one of the highest efficiency among small molecular devices with the same fabrication
process and same device configuration.
(holeꢀblocking) or electronꢀtransporting layer, such as 1,3,5ꢀ
tri(mꢀpyridꢀ3ꢀylꢀphenyl)benzene (TmPyPB),6 3ꢀ(4ꢀbiphenyl)ꢀ4ꢀ
40 phenylꢀ5ꢀtertꢀbutylphenylꢀ1,2,4ꢀtriazole (TAZ),7 diphenyl(4ꢀ
1. Introduction
Small molecular host materials have attracted increasing attention
in blue phosphorescence organic lightꢀemitting diodes (OLEDs).1
25 Solution process instead of dry process (vacuumꢀthermal
deposition) is better or more practical in terms of cost, speed, and
size for OLED fabrication.2 Materials wise, small molecular
materials are superior to polymeric materials because of the easy
synthesis and purification. However, it is very often that small
30 molecular host materials have insufficiently high triplet energy
gap (ET) in solid state or they are prone to aggregate or crystallize
in thin film state because of low glass transition temperature
(Tg).3 It is less common for those solution processable small
molecular host materials in the fabrication of singleꢀlayer blue
35 phosphorescence OLEDs due to the usually poor
electroluminescence (EL) efficiency.4,5 Regarding high EL
efficiency, a vacuumꢀthermalꢀdeposited triplet excitonꢀconfining
(triphenylsilyl)phenyl)phosphine
diphenylphenanthroline
oxide
(TSPO1),8
2.9ꢀdimethylꢀ4,7ꢀ
4,7ꢀ
(BPhen),6f
diphenylphenanthroline (BCP),9 or 2,2’,2”ꢀ(1,3,5ꢀphenylene)ꢀ
tris[1ꢀphenylꢀ1Hꢀbenzimidazole] (TPBI)4c,4d,4f,6c,10 is often
45 required for enhancing blue phosphorescence emission or charge
balance of the device.
Recently, the molecular design of the host material prefers the
bipolar charge transporting structure feature enabling charge
balance of the lightꢀemitting layer.1,11 Bipolar molecular hosts
50 may eliminate the necessity of such extra layer fabricated by the
vacuumꢀthermalꢀdeposition fabrication process and the device
fabrication keeps as simple as possible. On the other hand, a coꢀ
host material, usually a electronꢀtransporting molecule like 1,3ꢀ
bis[(4ꢀtertꢀbutylphenyl)ꢀ1,3,4ꢀoxadiazolyl]phenylene (OXDꢀ7),12
55 has been found effective in boosting EL efficiency of poly(9ꢀ
vinylcarbazole) (PVK) hosted singleꢀlayer blue phosphorescence
OLEDs. We and Qiu et al. are two of the first research groups
employing OXDꢀ7 coꢀhost in the solution processed small
molecular hosted blue phosphorescence OLEDs.4a,4c,5a In this
60 report, it will be demonstrated that both vacuumꢀthermalꢀ
deposited holeꢀblocking /electronꢀtransporting layer and OXDꢀ7
coꢀhost material maybe not necessary in our newly designed
bipolar small molecular hosted blue phosphorescence OLEDs.
The newly designed small molecular host materials are CzPAMe,
65 CzPPO, and CzPAPm (their chemical structures are shown in
aInstitute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, Republic
of China. E-mail: chintchen@gate.sinica.edu.tw; Fax:+886 2 27831237;
Tel:+886 2 27898542.
bDepartment of Chemistry, National Taiwan University, Taipei, Taiwan
11617. Republic of China.
cOLED Process Technology Department, OLED Platform Technology
Division, AUO Optronics Corporation, Hsinchu, Taiwan 30078, Republic
of China.
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DOI: 10.1039/C3TC31641F
Scheme 1). These new host materials have been characterized
with high Tg and high ET in solid state and are suitable for
solution process in the fabrication of blue phosphorescence
iridium (III) bis(4,6ꢀdifluorophenylpyridinato)picolate (FIrpic)
synthesized from a common precursor, bis(3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀ
yl)phenyl)amine (CzPA), which was in turn synthesized from
BrmCP and NH2mCP (Scheme 2). Conducting a methylation by
iodomethane and classical Ullmann reaction of 2ꢀiodopyrimidine
5
OLEDs. Based on many known literature examples, pyrimidineꢀ 45 on CzPA affords CzPAMe and CzPAPm, respectively (Scheme
and triphenylphosphine oxideꢀbearing CzPPO and CzPAPm,
respectively, are potential to be bipolar charge transporting host
materials. Herein, we report the synthesis and physical
characterization of these newly prepared host materials. Without
2). Whereas BrmCP was synthesized according to a procedure
reported in a patent,17 NH2mCP is a previously unknown
compound and we have developed
a threeꢀstep synthetic
procedure of it (Scheme 2). Starting from commercially available
10 vacuumꢀthermalꢀdeposited
holeꢀblocking/electronꢀtransporting 50 2,6ꢀdiiodoꢀ4ꢀnitroaniline, the deamination reaction providing 1,3ꢀ
layer and without including OXDꢀ7 coꢀhost material, solution
processed singleꢀlayer blue phosphorescence CzPPO OLEDs
were found significantly better than others, including those of
diiodoꢀ5ꢀnirtobenzene was readily achieved by a literature known
procedure.18 Ullmann reaction with carbazole transformed 1,3ꢀ
diiodoꢀ5ꢀnirtobenzene to 9,9'ꢀ(5ꢀnitroꢀ1,3ꢀphenylene)bis(9Hꢀ
carbazole) (NO2mCP), and then a reduction of nitro group by
bis[3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀyl)phenyl]diphenylsilane
(SimCP2)
15 (Scheme 1), which has been demonstrated by us and others as an 55 stannous chloride afforded NH2mCP (see experimental section
effective small molecular host materials suitable for solution
process in the fabrication of singleꢀlayer blue phosphorescence
OLEDs.5,10b,13
for synthetic details). All reactions conducted herein have
satisfactory isolated yields (60~88%) and all new compounds
were fully characterized by elemental analysis, MS, and 1H NMR
spectroscopies.
60
carbazole, K2CO3
NO2
NO2
N
CH3
N
N
CuI
N
N
I
I
N
N
NO2mCP
SnCl2
CzPAMe
NaH CH3I
H
N
Pd(OAc)2
P(tBu)3
N
N
N
N
N
Br
NH2
20
+
Cs2CO3
N
N
N
NH2mCP
CzPA
BrmCP
3. H2O2
N
N
1. n-BuLi
Cu
K2CO3
I
2. PhPCl2
N
N
O
N
N
N
P
N
N
N
N
N
N
CzPPO
CzPAPm
Scheme 1 Molecular structures of SimCP2, CzPAMe, CzPPO,
and CzPAPm. Their MM2 energy minimized structures (by
Chem 3D) are shown in below correspondingly.
Scheme 2 Synthesis of CzPAMe, CzPPO, CzPAPm, NO2mCP,
and NH2mCP.
25
65 2.2 Thermal and amorphousity characterization.
2. Results and discussion
All four host materials exhibit pretty good thermal stability with
thermal decomposition temperatures (Tds) in the range of 466ꢀ536
oC (Figure 1). In addition to the solution process, such high
thermal stability makes them potentially feasible for dry process
70 (vacuumꢀthermalꢀdeposition) in device fabrication. Similar to the
structure of SimCP2, the bulge dendronꢀlike structure (see Chem
3D structures displayed in Scheme 1) of CzPAMe, CzPPO, and
CzPAPm enables amorphous or semiꢀamorphous feature shown
in DSC thermograms (Figure 2) and solutionꢀcasting thin film Xꢀ
75 ray diffraction spectra (Figure 3).
2.1 Design and synthesis
SimCP2 is one of the very rare small molecular host
materials that are suitable for blue phosphorescence OLEDs
30 fabrication via either dry or solution process.10b More recently,
without including holeꢀblocking or electronꢀtransporting layer,
SimCP2 hosted blue phosphorescence OLEDs can exhibit
relatively high EL efficiency (13.6 cd/A or 8 lm/W).5b In this
study, we have utilized two 3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀyl)phenyl
35 (mCP) units of SimCP2 in developing a new series of small
molecular host materials CzPAMe, CzPPO, and CzPAPm.
Finishing with the oxidation reaction by hydrogen peroxide,
reaction of dichlorophenylphosphine with lithiated 9,9'ꢀ(5ꢀbromoꢀ
1,3ꢀphenylene)bis(9Hꢀcarbazole) (BrmCP) affords CzPPO
40 (Scheme 2). Both CzPAMe and CzPAPm were readily
All four host materials show discernible glass transition
temperatures (Tgs) relatively high around 144ꢀ175 oC in all
repeating scans. However, a stronger endothermic signal of
melting temperature (Tm) was detected for CzPAMe and CzPPO
o
80 at 292 and 328 C, respectively, in the first heating scan. The
thermal data (Td, Tg, Tm) are summarized in Table 1. Xꢀray
2
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Journal of Materials Chemistry C
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DOI: 10.1039/C3TC31641F
Quartz substrate
CzPPO
Quartz substrate
CzPAMe
diffraction spectra of the solutionꢀcasting thin film of the four
host materials confirm the amorphousity inferred from DSC
thermograms. Except for few protruding signals in CzPAMe and
CzPPO spectra, Xꢀray diffraction spectra of four host materials
are basically featureless broad halo, indicative of the amorphous
nature of thin films.
300
200
100
300
200
100
5
10
20
30
40
10
20
30
40
2 Theta (degree)
2 Theta (degree)
100
80
Quartz substrate
CzPAPM
Quartz substrate
SimCP2
300
300
200
100
60
T
d
200
100
(5% weight loss)
CzPPO 536 o
C
40
20
0
CzPAMe 471 o
CzPAPm 473 o
C
C
SimCP2 466 o
C
10
20
30
40
10
20
30
40
100 200 300 400 500 600 700 800 900
Temperature (oC)
2 Theta (degree)
2 Theta (degree)
Fig. 3 Xꢀray diffraction spectra of the thin film samples
40 of CzPAMe, CzPPO, CzPAPm, and SimCP2 on quartz
Fig. 1 TGA thermograms of CzPAMe, CzPPO, CzPAPm, and
10 SimCP2.
substrate.
Tm = 328 o
C
CzPPO
Tm = 292 o
C
CzPAMe
40
30
20
10
0
CzPPO 5.84 eV
CzPAMe 5.96 eV
CzPAPm 5.88 eV
SimCP2 6.01 eV
Heating
Heating
Tg = 159 o
C
T
g = 169 o
C
Cooling
Cooling
50
100
150
200
250
300
350
50
100
150
200
250
300
350
Temperature (oC)
Temperature (oC)
CzPAPm
SimCP2
Heating
Cooling
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.4
Tg = 175 o
C
Energy (eV)
Heating
Tg = 144 o
C
Fig. 4 Low-energy photoelectron spectra (from AC-2) of
45 CzPAMe, CzPPO, CzPAPm, and SimCP2.
Cooling
Absorption spectra (Figure 6) of solid state thin film of the
host materials are used to acquire lowest photoexcitation state
energy, i.e. LUMO energy gap. Once again, bipolar host
50 materials CzPPO and CzPAPm tend to have smaller LUMO
energy gap due to the stronger dipolar interaction in solid state.
Accordingly, having determined HOMO energy level, LUMO
energy level can thus be calculated as 2.44, 2.42, 2.35, and 2.34
eV, for SimCP2, CzPAMe, CzPPO, and CzPAPm, respectively
55 (see data summarized in Table 1).
The order of these experimentally estimated LUMO energy
levels is different from what anticipated from the structural
feature of four host materials, i.e., electron deficientꢀbearing
CzPPO or CzPAPm should have lower LUMO energy levels
60 than that of CzPAMe or SimCP2. Our DFT calculation acquired
LUMO energy levels are ꢀ1.11, ꢀ1.04, ꢀ1.32, and ꢀ1.36 eV for
SimCP2, CzPAMe, CzPPO, CzPAPm, respectively. Such
theoretically estimated order of LUMO energy levels fits better to
he structural intuition based on electron deficient feature. Once
65 again, in condense phase, the stronger molecular interaction of
bipolar host, either CzPPO or CzPAPm, alters the order of
LUMO energy levels of the host materials, which are in the gas
phase with isolated molecules in terms of theoretical estimation.
50
100
150
200
250
300
350
50
100
150
200
250
300
350
Temperature (oC)
Temperature (oC)
Fig. 2 DSC thermograms of CzPAMe, CzPPO, CzPAPm, and
15 SimCP2.
2.3 Spectroscopic and energy level characterization.
Solid state HOMO energy levels of the host material were
determined by a lowꢀenergy photoelectron spectrometer (Rikenꢀ
20 Keiki ACꢀ2). The ACꢀ2 spectra are shown in Figure 4 and 6.01,
5.96, 5.84, and 5.88 eV are determined HOMO energy levels for
SimCP2, CzPAMe, CzPPO, and CzPAPm, respectively. In
spite of different central bridging unit, the HOMO energy level of
four host materials shows moderate variation. Furthermore, those
25 bipolar hosts (i.e., CzPPO, and CzPAPm) bearing electron
deficient bridging unit tend to have shallower HOMO energy
level. At first glance, this is somewhat contradictory to the
general intuition. However, based on the electron density contour
plots of the four host materials (Figure 5), there are little
30 involvement of the central bridging unit in HOMO and HOMOꢀ1.
Therefore, we suggest that it is the molecular interaction of the
host material in solid state that mainly decides the ground state
energy level. Our suggestion is consistent with that bipolar
CzPPO and CzPAPm have a stronger molecular interaction (i.e.,
35 dipolar interaction) than the nonꢀbipoar SimCP2 and CzPAMe.
This journal is © The Royal Society of Chemistry [year]
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DOI: 10.1039/C3TC31641F
Table 1. The Thermal, Photophysical Data of SimCP2, CzPAMe, CzPPO, and CzPAPm.
a
b
b
f
i
HOMOg
(eV)
LUMOh
(eV)
2.44
2.42
2.35
2.34
T1
abs d
fl e
Host
materials
SimCP2
CzPAMe
CzPPO
Td
(oC)
466
471
536
473
Tm
Tg
(oC)
144
159
169
175
ET
(nm, eV)
λon set
λmax
(nm)
382
405
408
426
(oC)
(eV)
(nm, eV)
347, 3.57
350, 3.54
355, 3.49
350, 3.54
ꢀc
292
328
ꢀc
460, 2.70
454, 2.73
458, 2.71
6.01
3.31
5.96
5.84
5.88
3.23
3.15
3.32
CzPAPm
466, 2.56
aObtained from TGA (5% weight loss). bObtained from DSC measurement. Not observed in range of less than 350 oC Measured in
thin film. eMeasured in thin film. fTriplet energy gap estimated from the highestꢀenergy vibronic subband of emission spectra recorded in
thin film at ~10 K. gObtained from ACꢀ2 lowꢀenergy photoelectron spectrometer. hDetermined as the lowest photoexcitation state
c
d
5
energy from the onꢀset absorption energy (i.e., λon setabs) in thin film absorption spectra and HOMO energy level. Triplet state energy
i
level calculated from HOMO energy level and ET.
carrier mobility (i.e., hole and electron mobility) has been
30 determined by timeꢀofꢀflight (TOF) tenique.13a
Calculated electron density contour plots of LUMO of the host
10 materials are shown in Figure 7.
With the timeꢀgated, low temperature emission spectra
acquiring (Figure 8), we are able to estimate the triplet energy
gap (ET) of the host materials, which is vital for
phosphorescenceꢀbased OLEDs. For blue phosphorescence
35 dopant Firpic, the ET of host materials has to be larger than
CzPPO
CzPAMe
CzPAMe HOMOꢀ1
CzPAMe HOMO
Eg
Eg
3.54 eV
3.49 eV
(350 nm)
(355 nm)
275 300 325
350 375 400 425 450
275
300
325
350
375
400
425
450
Wavelength (nm)
Wavelength (nm)
CzPAPm
SimCP2
CzPPO HOMOꢀ1
CzPPO HOMO
Eg
Eg
3.54 eV
(350 nm)
3.57 eV
(347 nm)
275
300
325
350 375
400
425 450
275 300 325 350 375 400 425 450
Wavelength (nm)
Wavelength (nm)
Fig. 6 UVꢀvisible absorption spectra of the thin film samples of
40 CzPAMe, CzPPO, CzPAPm, and SimCP2.
15
CzPAPm HOMOꢀ1
CzPAPm HOMO
2.59 eV, which is the triplet energy gap of FIrpic based on our
emission spectra (Figure 8). Particularly, the spectra were
recorded on neat thin film samples instead of frozen solution.
45 Because of the relatively high ET of FIrpic, accurate and reliable
ET estimation can assure the sustainability of the host materials
for blue phosphorescence dopant and that can be only achieved
from the neat thin film sample rather than frozen solution. We
have already demonstrated that there is always a redꢀshifting in
50 phosphorescence spectra of neat thin film compared with those of
frozen solution (2ꢀmethyltetrahydrofuan is most common).3 As
shown in our spectroscopic results (Figure 8 and Table 1), ET of
the four host materials is in range of 2.56 and 2.73 eV. Except for
that of CzPAPm, they are all larger than 2.59 eV of blue
55 phosphorescence dopant FIrpic. Among four host materials,
CzPAPm has the smallest ET of 2.56 eV, which is very close to
2.59 eV of FIrpic and is most possible for impairing the EL
efficiency of the OLEDs.
SimCP2 HOMOꢀ1
Fig. 5 Calculated electron density contour plots of HOMO and
20 HOMOꢀ1 of the host materials.
SimCP2 HOMO
Bipolar feature may be inferred from that more significant
involvement of central bridging unit of CzPPO or CzPAPm than
CzPAMe in LUMO. A bit surprise to us, SimCP2 possesses
25 bipolar feature as well according to the substantial electron
density found on the central bridging unit in the calculated
LUMO contour plot (Figure 7). For SimCP2, the bipolar feature
is consistent with our previous report that relatively close charge
4
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Journal of Materials Chemistry C
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DOI: 10.1039/C3TC31641F
lm/W) is probably the best of FIrpic OLEDs that are fabricated
with solution processed small molecular host without including
OXDꢀ7 coꢀhost and no ETL after the active single layer. We
50 attribute such unique features of CzPPO devices mostly to the
bipolar feature of CzPPO host material, which is an
arylphosphine oxideꢀcontaining compound well known for the
bipolar charge transport feature.
LUMO of CzPAMe
LUMO of CzPPO
Delayed time
CzPAMe
4000
11 ms
100 ms
200 ms
3000
454 nm (2.73 eV)
2000
Delayed fluorescence
(400 nm)
1000
LUMO of CzPAPm
LUMO of SimCP2
300 350 400 450 500 550 600 650
5
Figure 7. Calculated electron density contour plots of LUMO of
the host materials.
Wavelength (nm)
55
12000
CzPPO
Delayed
10000
Delayed time
150 ns
fluorescence
(410 nm)
2.3 Solution Processed, Single-Layer, Blue Phosphorescence
OLEDs.
8000
6000
4000
2000
0
1 ꢀs
1 ms
100 ms
458 nm
(2.71 eV)
10 To test the viability of four host material for solution processed,
singleꢀlayer blue phosphorescent dopant FIrpic, we have
fabricated a series of OLEDs: ITO/PEDOT:PSS(65 nm)/host:coꢀ
host:FIrpic (95ꢀx:x:5, ~70 nm)/CsF(2 nm)/Al (100 nm), where x
is four different weight ratio 0, 15, 30, and 50% of the OXDꢀ7 coꢀ
15 host for each of four host materials. Intentionally, we did not
300 350 400 450 500 550 600 650
Wavelength (nm)
3000
CzPAPm
Delayed time
21 ms
vacuumꢀthermal deposit
a triplet excitonꢀconfining (holeꢀ
2500
2000
1500
1000
500
blocking) or electronꢀtransporting layer after the solution
processed active single layer. In addition, by varying the coꢀhost
weight ratio from nil to 50%, we are able to quest the bipolar
101 ms
191 ms
485 nm
(2.56 eV)
20 charge transport feature of the host materials.
Table 2
Delayed
fluorescence
(450 nm)
summarizes the EL characteristics data; EL spectra and current
density dependent EL efficiency (in unit of cd/A and lm/W) are
plotted in Figure 9.
0
In general, regardless of which host materials, all devices
25 show an increasing trend on the EL efficiency (either cd/A or
lm/W) in parallel with the weight ratio of OXDꢀ7 coꢀhost. Except
for SimCP2, devices reach the highest maximum current
efficiency of 9.2, 10.6, 12.2, 8.15 cd/A for SimCP2, CzPAMe,
CzPPO, and CzPAPm, respectively, with OXDꢀ7 coꢀhost ratio
30 of 50%. OXDꢀ7 coꢀhost weight ratio of 30% is the best condition
for SimCP2 devices. In terms of reducing driving voltage, OXDꢀ
7 coꢀhost is very effective for all host materials. Surveying our
device data, it is easy to see that CzPPO devices are special
because of relatively small variation of EL efficiency (both cd/A
35 and lm/W) with varied weight ratio of OXDꢀ7 coꢀhost (Figure 9).
With or without OXDꢀ7 coꢀhost, CzPPO devices outperform
others in low turnꢀon voltage (Von) and high EL efficiency,
either cd/A or lm/W (Table 2). Particularly, without OXDꢀ7 coꢀ
host, CzPPO device is the best in terms of device brightness,
40 current density, or low driving voltage (Figure 10). CzPPO is the
only host material enables devices with driving voltage less than
15 V in achieving 1000 cd/m2 brightness without OXDꢀ7 coꢀhost
in the active layer. Without OXDꢀ7 coꢀhost, current efficiency of
CzPPO device reaches 9.32 cd/A, which is far better than
45 1.34~3.43 cd/A of devices based on the other three host materials.
To the best of our knowledge, 9.32 cd/A (corresponding to 4.97
300 350 400 450 500 550 600 650
Wavelength (nm)
SimCP2
20000
15000
10000
5000
0
Delayed
fluorescence
(393 nm)
Delayed time
150 ns
1 ꢀs
1ms
460 nm
(2.70 eV)
300 350 400 450 500 550 600 650
Wavelength (nm)
70000
Delayed time
500 ns
FIrpic
60000
50000
40000
30000
20000
10000
0
1 ꢀs
1 ms
478 nm
(2.59 eV)
300 350 400 450 500 550 600 650
Wavelength (nm)
60 Fig. 8 Low temperature (~10 K) and varied timeꢀgated emission
spectra of the thin films of CzPAMe, CzPPO, CzPAPm, and
SimCP2. Spectra of FIrpic are included herein for comparison.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5

Journal of Materials Chemistry C
Page 6 of 10
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DOI: 10.1039/C3TC31641F
Table 2. Electroluminescence Characteristics of Single-layer FIrpic OLEDs Based on Four Host Materials.
c
Lmax, b Voltage at
Lmax (cd/m2,V)
d
ηC
OXDꢀ7
ratio (%)
Von, J, V
ηP
Host
CIE (x, y)e
(V, mA/cm2, V)a
(lm/W)
(cd/A)
0
7.2, 35, 11.1
5.7,47, 10.1
5.0,11.7, 7.8
5.0, 19.1, 9.0
7.2, 65.7,12.8
5.2, 22.7,8.8
5.2, 11.6,8.2
5.6, 12.7, 8.9
4.5, 12.6, 7.1
5.0, 9.1, 7.5
4.6, 9.6, 7.2
4.6, 8.6, 8.3
8.7, 54.8, 13.1
5.8, 23.8, 8.9
5.1, 16.7, 8.0
5.4, 12.8, 8.9
3293, 15.0
1582, 12.5
3775, 11.5
1479, 12.5
1344, 15.0
2441, 11.5
3207, 11.5
2839, 12.5
6498, 11.5
4382, 11.5
3803, 10.5
3149, 12.5
1814, 17.0
2344, 11.5
3247, 10.5
3162, 12.5
3.43, 3.52, 2.89
3.58, 3.58, 2.13
9.2, 5.64, 9.08
6.29, 3.28, 5.55
1.34, 0.98, 0.69
6.61, 6.02, 4.72
8.80, 7.40, 8.61
10.6, 10.02, 9.61
9.32, 6.14, 9.02
10.4, 9.02, 9.64
11.0, 9.28, 10.5
12.2, 9.47, 11.46
2.82, 2.75, 1.81
5.26, 4.72, 4.58
6.70, 4.93, 6.52
8.15, 2.61, 8.02
1.42, 1.24, 0.82
1.79, 1.6, 0.68
2.64, 2.8, 3.67
3.85, 1.62, 1.98
0.56, 0.31, 0.19
3.07, 2.77, 1.68
3.45, 3.87, 3.30
4.90, 4.81, 3.45
4.97, 3.28, 3.98
5.13, 4.93, 3.98
5.30, 4.91, 4.61
5.38, 4.87, 4.30
0.93, 0.82, 0.44
2.20, 2.13, 1.63
3.12, 2.39, 2.60
2.87, 1.21, 2.85
(0.15, 0.35)
(0.15, 0.33)
(0.14, 0.30)
(0.15, 0.33)
(0.14, 0.30)
(0.15, 0.34)
(0.15, 0.34)
(0.16, 0.39)
(0.15, 0.35)
(0.15, 0.34)
(0.15, 0.34)
(0.16, 0.39)
(0.15, 0.36)
(0.15, 0.35)
(0.15, 0.34)
(0.17, 0.40)
15
30
50
0
15
30
50
0
15
30
50
0
15
30
50
SimCP2
CzPAMe
CzPPO
CzPAPm
aTurnꢀon voltage of 10 cd/m2 (Von); current density (J) and voltage at 1000 cd/m2. bMaximum luminance. cMaximum current efficiency,
current efficiency at 100 and 1000 cd/m2, respectively.
respectively. e Measured at ~200 cd/m2.
Maximum power efficiency, power efficiency at 100 and 1000 cd/m2,
d
5
6
14
Host SimCP2 with varied OXD-7
Host SimCP2 with varied OXD-7
1.0
Host SimCP2 with varied OXD-7
0%
15%
30%
50%
0%
15%
30%
50%
5
12
0%
15%
30%
50%
0.8
10
8
4
3
2
1
0
0.6
0.4
0.2
0.0
6
4
2
0
5
10
15
20
25
400
450
500
550
600
650
700
5
10
15
20
25
Current Density (mA/cm2)
Current Density (mA/cm2)
Wavelength (nm)
6
5
4
3
2
1
0
Host CzPAMe with varied OXD-7
Host CzPAMe with varied OXD-7
14
Host CzPAMe with varied OXD-7
1.0
0.8
0.6
0.4
0.2
0.0
0%
0%
15%
30%
50%
0%
15%
30%
50%
12
10
8
15%
30%
50%
6
4
2
0
5
10
15
20
25
5
10
15
20
25
400
450
500
550
600
650
700
Current Density (mA/cm2)
Current Density (mA/cm2)
Wavelength (nm)
6
Host CzPPO with varied OXD-7
Host CzPPO with varied OXD-7
14
Host CzPPO with varied OXD-7
1.0
0.8
0.6
0.4
0.2
0.0
0%
15%
30%
50%
0%
15%
30%
50%
5
4
3
2
1
0
0%
15%
30%
50%
12
10
8
6
4
2
5
10
15
20
25
5
10
15
20
25
400
450
500
550
600
650
700
Current Density (mA/cm2)
Current Density (mA/cm2)
Wavelength (nm)
6
| Journal Name, [year], [vol], 00–00
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Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C3TC31641F
14
6
5
4
3
2
1
0
Host CzPAPm with varied OXD-7
Host CzPAPm with varied OXD-7
Host CzPAPm with varied OXD-7
1.0
0.8
0.6
0.4
0.2
0.0
12
10
8
0%
15%
30%
50%
0%
15%
30%
50%
0%
15%
30%
50%
6
4
2
0
5
10
15
20
25
5
10
15
20
25
400
450
500
550
600
650
700
Current Density (mA/cm2)
Current Density (mA/cm2)
Wavelength (nm)
Figure 9. Current density dependency of current efficiency and power efficiency of CzPAMe, CzPPO, CzPAPm, and SimCP2 hosted
devices with varied ratio of OXDꢀ7 coꢀhost. Corresponding EL spectra of each device were recorded at~200 cd/m2.
30 low turnꢀon voltage, high brightness, high current density, and
high EL efficiency. We attribute the superior CzPPO OLED
Host without OXD-7
SimCP2
CzPPO
CzPAPm
CzPAMe
performance to the bipolar charge transport feature of CzPPO
host material. Without OXDꢀ7 coꢀhost and without vacuumꢀ
thermal deposited ETL, CzPPO OLED exhibits EL efficiency as
35 high as 9.32 cd/A (~5 lm/W), which is one of the best among
FIrpic devices, using small molecular host material, fabricated by
solution process, without coꢀhost material or ETL.
100
10
1
4
6
8
10
12
14
4. Experimental
Voltage (V)
5
10000
40 4.1 General Information
1H and 13C NMR spectra were recorded on a Bruker AVꢀ400
MHz or AVꢀ500 MHz Fourier transform spectrometer at room
temperature. Elemental analyses (on a PerkinꢀElmer 2400 CHN
elemental analyzer), matrixꢀassisted laser desorption/ionization
45 timeꢀofꢀflight (MALDIꢀTOF), or fast atom bombardment (FAB)
mass spectroscopy (MS) were performed by the Elemental
Analyses and Mass Spectroscopic Laboratory, respectively, inꢀ
house service of the Institute of Chemistry, Academic Sinica.
Thermal decomposition temperatures (Td’s) of the host materials
50 were measured by thermogravimetric analysis (TGA) using
PerkinꢀElmer TGAꢀ7 analyzer systems.Melting temperatures
(Tm’s) and glass transition temperatures (Tg’s) of the host
materials were measured by differential scanning calorimetry
(DSC) using PerkinꢀElmer DSCꢀ6 analyzer systems. The xꢀray
55 diffraction measurement of solutionꢀcasting thin film was carried
out by using the Philips X’Pert diffractometer equipped with an
X’Celerator detector. The radiation used was a monochromatic
Cu Kα beam of wavelength λ = 0.154 nm. UVꢀvisible absorption
spectra were recorded on a HewlettꢀPackard 8453 diode array
60 spectrophotometer. Room temperature fluorescence spectra were
recorded on a Hitachi fluorescence spectrophotometer Fꢀ4500.
The ionization potentials (or HOMO energy levels) of the host
materials were determined by low energy photoꢀelectron
spectrometer (RikenꢀKeiki ACꢀ2). To measure the triplet energy
65 gap of a thin film sample, we established a system with a
temperature control of Model 350 (LakeShore Company) as low
as 10 K by Model 22C/350C Cryodyne Refrigerators (Janis
1000
100
10
Host without OXD-7
SimCP2
CzPPO
CzPAPm
CzPAMe
4
5
6
7
8
9
10 11 12 13 14 15
Voltage (V)
Fig. 10 Voltage dependency of current density (top) and
brightness (bottom) of CzPAMe, CzPPO, CzPAPm, and
SimCP2 hosted devices without OXDꢀ7 coꢀhost.
10
3. Conclusion
By utilizing amorphous glass enabling bisꢀ[3,5ꢀdi(9Hꢀcarbazolꢀ9ꢀ
yl)phenyl] structural moiety of previously known, solution
processable SimCP2, we have successfully developed three new
15 host materials, CzPAMe, CzPPO, and CzPAPm. We have
physically characterized (by DSC and XRD) the amorphous
feature of the host materials in thin film or solid state. Regarding
the energy levels, particularly the solid state triplet energy gap
was determined by timeꢀgated, low temperature emission
20 spectroscopy on thin film samples and they are 2.73, 2.71, and
2.56 eV for CzPAMe, CzPPO, and CzPAPm, respectively.
Except for CzPAPm, they are all proper host materials for blue
phosphorescence dopant FIrpic in the fabrication of OLEDs
considering triplet energy gap. With or without OXDꢀ7 coꢀhost
25 material, singleꢀlayer, CzPAMe, CzPPO, or CzPAPm hosted
FIrpic OLEDs were successfully fabricated via solution process.
In this study, SimCP2 hosted device was included for
comparison. From the acquired device data, we have
demonstrated that CzPPO outperforms other host materials with
Research Company) and
a tunable laser with excitation
wavelengths of 213, 266,355, 532, and 1064 nm (Brilliant B
70 laser, Quantel Company), which is couple to a timeꢀdelay
controller of LP920 flash photolysis spectrometer (Edinburgh
Instrument).
This journal is © The Royal Society of Chemistry [year]
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Journal of Materials Chemistry C
Page 8 of 10
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DOI: 10.1039/C3TC31641F
4.2 Computational studies.
previously.17,18 2ꢀIodopyrimidine was smoothly prepared from
reacting 2ꢀchloropyrimidine with 57% hydriodic acid.19
The molecular structures of CzPAMe, CzPPO, CzPAPm, and
SimCP2 were optimized by applying density functional theory
(DFT) with the hybrid B3LYP functional and 6ꢀ31G* basis set.
With the optimized structure, calculations on the electronic
ground states of CzPAMe, CzPPO, CzPAPm, and SimCP2
were processed using DFT with the hybrid B3LYP functional and
60
9,9'-(5-Nitro-1,3-phenylene)bis(9H-carbazole)
(NO2mCP). 1,3ꢀDiiodoꢀ5ꢀnirtobenzene (10.0 g, 26.7 mmol) was
added to a dried DMF solution (100 mL) containing carbazole
(9.8 g, 58.7 mmol), potassium carbonate (8.1 g, 58.7 mmol),
5
copper(I) iodide (11.2 g, 58.7 mmol), and 18ꢀcrownꢀ6 (1.4 g, 5.3
6ꢀ31G* basis set.14 The singlet excited states of the four host 65 mmol). The mixture was heated to 155 C for 24 hours under
o
materials were studied with timeꢀdependent density functional
nitrogen atmosphere. After cooling, the reaction mixture was
poured on ice and the resulting solid material was filtered. The
solid was dissolved in dichloromethane and dried over anhydrous
MgSO4. The solution was evaporated till dryness under reduced
10 theory (TDDFT) by using the hybrid B3LYP functional.15 All
calculations were preformed with a developmental version of Qꢀ
Chem.16
70 pressure.
The product was subjected to flash column
4.3 OLED Fabrication and EL Characterization.
chromatography (silica gel, dichloromethane/hexanes: 1/4) for
purification. Yield: 78% (9.4 g). H NMR (400 MHz, CDCl3): δ
[ppm] 8.55 (d, J = 1.6 Hz, 2H), 8.19 (t, J = 2.0 Hz, 1H), 8.15 (d, J
= 8.0 Hz, 4H), 7.54 (d, J = 8.4 Hz, 4H), 7.47 (t, J = 7.6 Hz, 4H),
1
15 The ITO substrate was purchased from Buwon with sheet
resistance around 25 ꢁ/sq and thickness of 100 nm. The hole
transport layer, Poly(3,4ꢀethylenedioxythiophene) (PEDOT)
doped with poly(styrenesulfonate) (PSS) (CH8000), was 75 7.35 (t, J = 7.6 Hz, 4H). 13C NMR (100 MHz, CDCl3): δ [ppm]
purchased from SigmaꢀAldrich. The OXDꢀ7 electron transport
20 layer and FIrpic blue phosphorescent dopant were obtained
commercially from either SigmaꢀAldrich or Lumtec. The new
small molecule hosts CzPAMe, CzPPO, and CzPAPm were
synthesized according to a procedure reported herein. The indium
tin oxide (ITO) substrates were preꢀcoated with the PEDOT:PSS
25 hole transporting layer (HTL) and baked in the air at 150 °C for
10 min. We would change ratios between each host (take one of
hosts from SimCP2, CzPAMe, CzPPO, and CzPAPm) and
150.86, 141.08, 140.37, 127.01, 124.49, 121.70, 121.122, 120.28,
110.91, 109.66. MALDIꢀMS: calcd MW, 453.15, m/e = 454.16
(M+H)+.
80
3,5-Di(9H-carbazol-9-yl)aniline (NH2mCP). NO2mCP
(10.0 g, 22.1 mmol) was added to ethanol (200 mL) containing
tin(II) chloride dihydrate (19.9 g, 88.4 mmol). The mixture was
heated to reflux for 12 hours. After cooling, the reaction mixture
was poured on ice and alkalized with sodium hydroxide solution
OXDꢀ7 to optimize hole and electron transport. The ratios of 85 until basic conditions were reached. The basic solution was
OXDꢀ7 were x=0, 15, 30, and 50% and the hosts were (95ꢀx)%,
30 respectively. Blends of host (SimCP2, CzPAMe, CzPPO, or
CzPAPm), OXDꢀ7, and FIrpic in chlorobenzene were spinꢀ
coated on ITO/PEDOT:PSS. The active layer was then annealed
extracted with dichloromethane and dried over anhydrous
MgSO4. The solution was evaporated till dryness under reduced
pressure.
The product was subjected to flash column
chromatography (silica gel, dichloromethane/hexanes: 2/3) for
1
at 90 °C for 30 min. After spinꢀcoating active singleꢀlayer, an 90 purification. Yield: 75% (7.0 g). H NMR (400 MHz, CDCl3): δ
ultrathin CsF (2 nm) interfacial layer and then aluminum cathode
35 (100 nm) were vacuumꢀ thermal deposited.
[ppm] 8.12 (d, J = 7.7 Hz, 4H), 7.56 (d, J = 8.2 Hz, 4H), 7.42 (t, J
= 7.8 Hz, 4H), 7.27 (t, J = 7.5 Hz, 4H), 7.16 (s, 1H), 6.96 (d, J =
1.2 Hz, 2H), 4.10 (s, 2H). 13C NMR (100 MHz, CDCl3): δ [ppm]
149.28, 140.82, 140.27, 126.24, 123.71, 120.56, 120.31, 115.35,
A
surface profiler (Dektak 150 Veeco) was used for
calibrating the thickness of HTL and active layer. After the
deposition of cathode, the devices were hermetically sealed with 95 112.29, 110.22. MALDIꢀHRMS: calcd MW, 424.1814, m/e =
glass and UVꢀcured resins in a glove box (O2 and H2O
40 concentration below 0.1 ppm). The device active area was 0.04
cm2 was defined by selfꢀmade shadow mask applied in the
cathode deposition. Current density and voltage characteristics
424.1818 (M+H)+.
Bis(3,5-di(9H-carbazol-9-yl)phenyl)amine
Under dry nitrogen atmosphere, a mixture of BrmCP (3.5 g, 7.2
(CzPA).
were measured by a dc current/voltage source meter (Keithley 100 mmol), NH2mCP (3.0 g, 7.1 mmol), cesium carbonate (2.5 g, 7.8
2400), and the device brightness (or electroluminance, cd/m2), EL
45 spectra, corresponding 1931 CIEx,y chromaticity was monitored
and recorded with a spectrophotometer (PR650; Photo Research).
mmol), palladium acetate (0.04 g, 0.18 mmol), P(tꢀBu)3 (0.17 mL,
0.71 mmol), and dry xylenes (40 mL) was heated at 120 oC for 20
hours. The reaction was quenched by an excess amount of
saturated sodium chloride solution. The solution was extracted
105 with dichloromethane. The organic solution was dried over
anhydrous MgSO4. After the removal of drying agent, the
solution was evaporated till dryness. The product was subjected
to purification by flash column chromatography (silica gel,
dichloromethane/hexanes: 2/3). Yield: 73% (4.3 g). 1H NMR
4.4 Synthesis.
All chemicals were purchased from Aldrich, Alfa Aesar, Acros,
50 and TCI Chemical Co., and they were used without further
purifications. Solvents such as dichloromethane (CH2Cl2),
chlorobenzene, terrahydrofuran (THF), N,Nꢀdimethylformamide
(DMF) and toluene and were distilled after drying with 110 (400 MHz, CDCl3): δ [ppm] 8.16ꢀ8.12 (m, 8H), 7.56ꢀ7.52 (m,
appropriate drying agents. The dried solvents were stored over
55 4Å molecular sieves before usage. 9,9'ꢀ(5ꢀBromoꢀ1,3ꢀ
phenylene)bis(9Hꢀcarbazole) (BrmCP) and 1,3ꢀDiiodoꢀ5ꢀ
nirtobenzene were synthesized by procedures reported
12H), 7.44 (s, 2H), 7.29ꢀ7.23 (m, 16H), 6.35 (s, 1H). 13C NMR
(100 MHz, CDCl3): δ [ppm] 145.04, 140.78, 140.61, 126.38,
123.84, (2×)120.60, 118.59, 115.17, 109.97. MALDIꢀHRMS:
calcd MW, 830.3283, m/e = 830.3279 (M+H)+.
115
8
| Journal Name, [year], [vol], 00–00
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Journal of Materials Chemistry C
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DOI: 10.1039/C3TC31641F
Bis(3,5-di(9H-carbazol-9-yl)phenyl)(phenyl)phosphine
insoluble metal and inorganic salt. The dichloromethane solution
oxide (CzPPO). To a dry THF solution (40 mL) containing 60 was dried over anhydrous MgSO4. The solution was evaporated
BrmCP (2.o g, 4.1 mmol) was added nꢀBuLi (1.8 mL, 4.5 mmol,
2.5 M in hexane) slowly at 78 C. The mixture was stirred for 1
hour under nitrogen atmosphere. After the slow addition of
till dryness under reduced pressure and subjected to flash column
chromatography (silica gel, dichloromethane/hexanes: 1/4) for
purification. Yield: 65% (1.4 g). H NMR (300 MHz, CDCl3): δ
o
1
5
dichloro(phenyl)phosphine (0.36 g, 2.0 mmol), the reaction
[ppm] 8.59 (d, 2H), 8.06 (d, 8H), 7.72 (s, 4H), 7.68 (s, 2H), 7.57
o
solution was kept at 78 C for 1 hour. The reaction mixture was 65 (d, 8H), 7.30ꢀ7.20 (m, 16H), 6.93 (t, 1H). 13C NMR (100 MHz,
then warmed up to room temperature and stirred overnight. 2N
HCl solution was added to the reaction solution. The solution was
10 extracted with ethyl acetate, dried over MgSO4. The solution was
evaporated till dryness under reduced pressure. The solid was
CDCl3)：δ [ppm] 162.04, 158.42, 146.73, 140.49, 140.12, 126.45,
123.93, 123.87, 121.71, 120.72, 120.65, 115.25, 110.12. MALDIꢀ
TOF MS: calcd MW, 907.34, m/e = 908.4 (M+H)+. Anal. Found
(calcd) for C64H41N7：C 84.49 (84.65), H 4.52 (4.55), N 10.88
dissolved in dichloromethane (20 mL) and to the solution was 70 (10.80).
added 30% aqueous H2O2 (6 mL). The mixed solution was stirred
for 6 hours at room temperature. The solution was then extracted
15 with dichloromethane, dried over MgSO4. The solution was
evaporated till dryness under reduced pressure. The product was
subjected to flash column chromatography (silica gel,
References
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1
dichloromethane) for purification. Yield: 60% (1.1 g). H NMR
(400 MHz, CDCl3): δ [ppm] 8.20 (d, J = 1.6 Hz, 2H), 8.17 (d, J =
20 1.6 Hz 2H), 8.15ꢀ8.10 (m, 8H), 8.08 (s, 2H), 8.07ꢀ8.01 (m, 2H),
7.69ꢀ7.64 (m, 3H), 7.47ꢀ7.42 (m, 8H), 7.31ꢀ7.26 (m, 16H). 13C
NMR (75 MHz, CDCl3): δ [ppm] 140.55 (d, J = 16.1 Hz, 4C),
3. M.ꢀF. Wu, S.ꢀJ Yeh,. C.ꢀT. Chen, H. Murayama, T. Tsuboi,
140.29, 136.60 (d, JPC = 101.6 Hz, 2C), 133.33, 132.22 (d, JPC
=
80
W.ꢀS. Li, I. Chao, S.ꢀW. Liu and J.ꢀK. Wang, Adv. Funct.
Mater. 2007, 17, 1887.
9.9 Hz, 2C), 131.02 (d, JPC = 106.0, 1C), 129.48 (d, JPC = 12.5
25 Hz, 2C), 128.55, 128.48 (d, JPC = 10.3 Hz, 4C), 126.62, 124.08,
121.10, 120.76, 109.59. MALDIꢀTOF MS: calcd MW, 938.3, m/e
= 939.3 (M+H)+. Anal. Found (calcd) for C66H43N4OP：C 84.34
(84.42), H 4.69 (4.62), N 5.85 (5.97).
4. (a) L. Hou, L. Duan, J. Qiao, W. Li, D. Zhang and Y. Qiu,
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Y. Sun, Dyes Pigments 2013, 97, 286.
85
30
3,5-Di(9H-carbazol-9-yl)-N-(3,5-di(9H-carbazol-9-
yl)phenyl)-N-methylaniline (CzPAMe). CzPA (4.5 g, 5.4
mmol) was fully dissolved in dried N,Nꢀdimethyl formamide (60
ml) under nitrogen atmosphere. Sodium hydride (0.24 g, 5.9
mmol, 60% dispersion in mineral oil) was slowly added, and the
90
35 obtained mixture was stirred for 30 minutes at room temperature.
Then, iodomethane (1.0 g, 7.0 mmol) was added and the reaction
solution was heated at 60 oC for 2 hours. The solution was poured
into ice water to terminate the reaction and any NaH left over.
After filtration, the isolated product was subjected to purification
95
40 by
flash
column
chromatography
(silica
gel,
5. (a) S.ꢀW. Liu, C.ꢀH. Yuan, S.ꢀJ. Yeh, M.ꢀF. Wu, C.ꢀT.
Chen and C.ꢀC. Lee, J. Soc. Inform. Displ. 2011, 19, 346.
(b) S.ꢀW. Liu, Y.ꢀT. Chang, C.ꢀC. Lee, C.ꢀH. Yuan, L.ꢀA.
Liu, Y.ꢀS. Chen, C.ꢀF. Lin, C.ꢀI. Wu and C.ꢀT. Chen, Jpn.
J. Appl. Phys. 2013, 52, 012101.
dichloromethane/hexanes: 1/5). Yield: 88% (4.0 g). 1H NMR
(400 MHz, CDCl3): δ [ppm] 8.09 (d, 8H), 7.50 (sd, 4H), 7.47ꢀ
7.45 (m, 8H), 7.41 (t, 2H), 7.25ꢀ7.20 (m, 16H), 3.58 (s, 3H). 13C
NMR (100 MHz, CDCl3): δ [ppm] 150.90, (2×)140.66, 126.44,
45 123.87, 120.63, 120.61, 118.93, 117.88, 110.00, 41.04. MALDIꢀ
TOF MS: calcd MW, 843.34, m/e = 844.3 (M+H)+. Anal. Found
(calcd) for C61H41N5: C, 86.75 (86.81); H, 4.93 (4.90); N, 8.38
(8.30).
100
105
110
6. (a) S. Gong, Q. Fu, Q. Wang, C. Yang, C. Zhong, J. Qin
and D. Ma, Adv. Mater. 2011, 23, 4956. (b) N.ꢀJ. Lee, D.ꢀ
H. Lee, D.ꢀW. Kim, J.ꢀH. Lee, S. H. Cho, W. S. Jeon, J.
H. Kwon and M. C. Suh, Dyes Pigments, 2012, 95, 221.
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Kwon, Org. Electron. 2012, 13, 586 (d) S. Gong, Q. Fu,
W. Zeng, C. Zhong, C. Yang, D. Ma and J. Qin, Chem.
Mater. 2012, 24, 3120. (e) Q. Fu, J. Chen, C. Shi and D.
Ma, ACS Appl. Mater. Interf. 2012, 4, 6579. (f) S. Gong,
C. Zhong, Q. Fu, D. Ma, J. Qin and C. Yang, J. Phys.
Chem. C 2013, 117, 549. (g) X.ꢀH. Zhao, Z.ꢀS. Zhang, Y.
Qian, M.ꢀD. Yi, L.ꢀH. Xie, C.ꢀP. Hu, G.ꢀH. Xie, H. Xu,
C.ꢀM. Han, Y. Zhao and W. Huang, J. Mater. Chem. C
50
N,N-Bis(3,5-di(9H-carbazol-9-yl)phenyl)pyrimidin-2-
amine (CzPAPm). CzPA (2.0 g, 2.4 mmol) was added to a
dichlorobenzene solution (20 mL) containing 2ꢀiodopyrimidine
(0.65 g, 3.1 mmol), potassium carbonate (0.4 g, 2.9 mmol),
copper powder (0.2 g, 3.1 mmol) and 18ꢀcrownꢀ6 (0.13 g, 0.5
55 mmol). The mixture was heated to 180 oC for 24 hours under
nitrogen atmosphere. After cooling to room temperature, the
reaction solution was filtered. The resulting solid mixture was reꢀ
dissolved in dichloromethane and the filtration removed the
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