Highly efficient deep-blue organic light-emitting diodes based on pyreno[4,5-d] imidazole-anthracene structural isomers

Article abstract of DOI:10.1039/c9tc02990g

High-efficiency deep-blue luminophores, especially those satisfying the National Television Standards Committee (NTSC) blue standard Commission Internationale de l'éclairage (CIE) coordinates of (0.14, 0.08), are vital for full-color displays and solid-state illumination. However, deep-blue luminescent materials with efficient photoluminescence quantum yields (φ_PLs) and high external quantum efficiencies (EQEs) over 5% remain very limited. Imidazole has shown great potential in optoelectronic fields owing to its ambipolar nature. Combining imidazole with rigid aromatic rings, such as naphthalene, phenanthrene and pyrene, could effectively enlarge the π-electronic delocalization, reduce non-radiative transitions of molecules and ensure high φ_PLs in the solid-state. Herein, two symmetrically twisted pyreno[4,5-d]imidazole-anthracene structural isomers, 9,10-bis(4-(10-phenyl-9H-pyreno[4,5-d]imidazol-9-yl)phenyl)anthracene (N-BPyIA) and 9,10-bis(4-(9-phenyl-9H-pyreno[4,5-d]imidazol-10-yl)phenyl)anthracene (C-BPyIA), have been designed and synthesized by connecting one anthracene group with two pyreno[4,5-d]imidazole groups at the N1 and the C2 position, respectively. They both show high φ_PLs in neat films (46% for N-BPyIA and 54% for C-BPyIA), good thermal stabilities (T_d > 541 °C), and appropriate energy levels for carrier injection. N-BPyIA shows better performance than C-BPyIA when applied in OLEDs. The non-doped device based on N-BPyIA shows sky blue emission with CIE coordinates of (0.22, 0.31), achieving a high EQE of 5.63% with a low efficiency roll-off. In particular, a doped device with better performance is further realized, providing an EQE of 7.67% and deep-blue emission (CIE (0.15, 0.10)), which is very close to the NTSC standard. Such high OLED efficiency may be ascribed to triplet energy harvesting by triplet-triplet annihilation. And to our best knowledge, this is one of the best outcomes of deep-blue imidazole-based fluorescent OLEDs. The results also pave the way for a new type of high-efficiency deep-blue organic luminescent materials regulated by structural isomerization.

Full text of DOI:10.1039/c9tc02990g

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Highly Efficient Deep-Blue Organic Light-Emitting Diodes Based on
Pyreno[4,5-d]imidazole-Anthracene Structural Isomers
Hui Liu,a Liangliang Kang,b Jinyu Li,a Futong Liu,a Xin He,a Shenghong Ren,a Xiangyang Tang,a Changli
Received 00th January 20xx,
Accepted 00th January 20xx
Lv,b and Ping Lu*,a
DOI: 10.1039/x0xx00000x
High-efficiency deep-blue luminophores, especially those satisfying the National Television Standards Committee (NTSC)
blue standard Commission Internationale de l’Éclairage (CIE) coordinates of (0.14, 0.08), are vital to full-color displays and
solid-state illumination. However, deep-blue luminescent materials with efficient photoluminescent quantum yields (φPLs)
and high external quantum efficiencies (EQEs) over 5% remain very limited. Imidazole has shown great potential in
optoelectronic fields owing to its ambipolar nature. Combining imidazole with rigid aromatic rings, such as naphthalene,
phenanthrene and pyrene, could effectively enlarge the π-electronic delocalization, reduce non-radiative transitions of
molecules and ensure high φPLs in solid-state. Herein, two symmetrically twisted pyreno[4,5-d]imidazole-anthracene
structural isomers, 9,10-bis(4-(10-phenyl-9H-pyreno[4,5-d]imidazol-9-yl)phenyl)anthracene (N-BPyIA) and 9,10-bis(4-(9-
phenyl-9H-pyreno[4,5-d]imidazol-10-yl)phenyl)anthracene (C-BPyIA) have been designed and synthesized by connecting
one anthracene group with two pyreno[4,5-d]imidazole groups at N1 and C2 position, respectively. They both show high
φPLs in neat films (46% for N-BPyIA and 54% for C-BPyIA), good thermal stabilities (Td > 541 °C), and appropriate energy levels
for carrier injections. N-BPyIA shows better performance than C-BPyIA when applied in OLEDs. The non-doped device based
on N-BPyIA shows sky blue emission with CIE coordinates of (0.22, 0.31), achieving a high EQE of 5.63% with a low efficiency
roll-off. In particular, doped device with better performance is further realized, providing an EQE of 7.67% and the deep-
blue emission (CIE (0.15, 0.10)), which is very close to the NTSC standard. Such high OLED efficiency maybe be ascribed to
the triplet energy harvesting by triplet–triplet annihilation. And to our best knowledge, this is one of the best outcomes of
deep-blue imidazole-based fluorescent OLEDs. The results also pave the way to a new type of high-efficiency deep-blue
organic luminescent materials regulated by structural isomerization.
www.rsc.org/
over 20%.4 However, it is hard to acquire efficient pure or deep-
blue phosphors due to the serious non-radiative process via
metal d-orbitals when lifting the radiative metal−ligand charge
Introduction
Organic light-emitting diodes (OLEDs) have been widely
researched and applied in flat-panel display applications owing
to their distinct superiorities such as flexibility, light weight, low
energy cost and so forth.1 Blue light-emitting materials is
indispensable in OLEDs because they furnish one of the three
primary colors (red, green, and blue), lower the power loss in
full-color displays, and can be applied as excitation source to
generate green, red and white lightings by energy transfer to
emissive dopants.2 Nevertheless, The device performance of
blue OLEDs falls behind the green and red ones on account of
the intrinsically wider energy gaps of blue emitters.3 During the
past decades, blue phosphorescent materials based on
transition metal complexes have already achieved satisfying
device performance with external quantum efficiency (EQE)
transfer (MLCT) band into the higher energy region.5 In
addition, blue phosphorescent materials are not circumstance-
friendly and cost-effective, which hampers their large-scale
applications. Recent developments in blue OLEDs mainly focus
on the thermally activated delayed fluorescence (TADF)
materials, which in principle could achieve 100% internal
efficiency through reversed intersystem crossing between the
lowest singlet (S1) and triplet (T1) excited states via directly
connecting donor (D)-acceptor (A) groups with a big torsion
angel.6 However, on account of strong charge transfer (CT)
effect, most of high-efficiency TADF blue materials emit the sky
blue or bluish-green lighting and only a few chromophore
systems could achieve satisfactory device performance in deep-
blue region but with severe efficiency roll-off.7 Therefore, deep-
blue emitters based on pure aromatic structures still remain an
urgent concern.
aState Key Laboratory of Supramolecular Structure and Materials,Jilin University,
Qianjin Street No. 2699, Changchun, 130012, P. R. China. E-mail: lup@jlu.edu.cn.
1,3-Imidazole is a flat asymmetric aromatic heterocycle,
bFaculty of Chemistry, Northeast Normal University, Changchun 130024, P. R. which contains two nitrogen atoms with different bonding
China.
modes and thus intrinsic ambipolar property.8 The idea that
Dr. Hui Liu and Dr. Liangliang Kang contributed equally to this work.
Electronic Supplementary Information (ESI) available: Instrumentation, and
characterization of N-BPyIA and C-BPyIA Please see DOI: 10.1039/x0xx00000x.
combining imidazole with rigid aromatic rings, such as
naphthalene, phenanthrene and pyrene, to construct highly
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efficient blue emitters is proven to be successful in
optoelectronic fields.9 Bipolar electronic structure of 1,3-
imidazole derived from two distinct sp2 hybrid nitrogen atoms
also meets well with the requirement of balanced charge
transport in OLEDs. Rigid planar π conjugation could reduce
non-radiative transitions of molecules and ensure high φPLs in
solid-state. Phenanthro[9,10-d]imidazole (PI) has been
extensively studied to build numerous efficient blue fluorescent
emitters with notable device performances in recent years.10
Pyreno[4,5-d]imidazole (PyI), as another important type
derivative of 1,3-imidazole with a more extended acene
structure, has also attracted more and more attentions
recently.11 Benefited from the expansive π-electronic
delocalization as well as rigidity of molecular plane, PyI group
possesses high φPLs, enhanced thermal stability, and promising
carrier mobility, which endows it to be a promising unit for light-
emitting materials with pure aromatic structure. However,
pyrene itself tends to form excimers in solid state due to
extensive π conjugation, resulting in red-shifted emission and
Results and Discussion
Synthesis and Characterization
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DOI: 10.1039/C9TC02990G
The molecular structures and synthetic routes of C-BPyIA and
N-BPyIA are shown in Scheme 1. The precursors of C-PyIBr and
N-PyIBr were attained by one-pot reactions according to our
previous report.12b And then, BAnB which was obtained by the
boronation of BAnBr, were coupled with C-PyIBr and N-PyIBr,
respectively, via Suzuki reactions to obtain the end-products of
C-BPyIA and N-BPyIA with high yields. The purity and chemical
structures of C-BPyIA and N-BPyIA were detailly characterized
by NMR, elemental analysis, FTIR, and MS. The synthetic details
are offered in the Supporting Information.
Thermal Properties
Thermodynamic properties were studied by means of
thermogravimetric analysis (TGA) and differential scanning
calorimetry (DSC) under nitrogen atmosphere, and the results
are given in Fig. 1 and Table 1. C-BPyIA and N-BPyIA both
exhibited the same high decomposition temperature (Tds,
corresponding to 5% weight loss) of 541 °C owing to their similar
molecular weight, indicating that they could remain stable at
high temperature and would not decompose during device
evaporation process. C-BPyIA and N-BPyIA did not show any
glass transition temperatures (Tgs) or melting points during the
second heating cycle in DSC, revealing that they tended to form
an amorphous morphology. This was further proved by XRD
measurement which gave the similar result that no diffraction
peak appeared in the XRD patterns (Fig. S2). The good thermal
stabilities of C-BPyIA and N-BPyIA are significant to get fine
device performances. compounds could endure high
temperatures and would not go through decomposition in the
device fabrication process by vacuum thermal deposition. Such
high Tds and no Tg implied that they could keep amorphous
morphology in a wide range of temperature, which is highly
important to obtain the appreciable device performance.
reduced
solid-state
φPLs,
high-efficiency
deep-blue
luminophores containing PyI moiety remain rather rare.12
In this work, we attempt to achieve new deep-blue emitters
with pure aromatic structure by constructing PyI-based
structural
isomers.
9,10-Bis(4-(9-phenyl-9H-pyreno[4,5-
d]imidazole)-10-phenyl) anthracene (C-BPyIA) and 9,10-bis(4-
(10-phenyl-9H-pyreno[4,5-d]imidazole)-9-phenyl) anthracene
(N-BPyIA) are designed and synthesized, in which the 9,10-
diphenylanthracene (PAnP) moiety is coupled with two PyI
groups at C2 or N1 position to form two structural isomers with
symmetrically twisted skeletons. In this way, the steric
hindrance between anthracene (An), adjacent benzene as well
as PyI would render C-BPyIA and N-BPyIA with different
distorted configuration to reduce the intermolecular
interactions, suppress the red-shifted emission and acquire high
φPLs in blue spectral range. An is also a frequently-used organic
group to generate efficient blue emitter with triplet–triplet
annihilation (TTA) characteristics.13 By combining PyI with An, it
is anticipated that C-BPyIA and N-BPyIA could exhibit good
device performance if the non-emissive triplet excitons could be
effectively utilized by triplet up-conversion. C-BPyIA and N-
BPyIA both exhibit excellent thermal stabilities and blue
emission with high φPLs of 46% and 54%, and appropriate
energy levels for carrier injections, respectively. The non-doped
OLEDs using C-BPyIA and N-BPyIA as the emitting layers display
efficient sky-blue emission with an EQE of 4.78% and 5.63% and
CIE coordinates of (0.21 0.32) and (0.22, 0.31), respectively.
Notably, better device performances with deeper blue
emissions are achieved when C-BPyIA and N-BPyIA are used as
dopant emitters. As compared with C-BPyIA which gives an
EQEmax of 5.90%, the EQEmax of N-BPyIA could reach 7.67%.
Especially, the device based on N-BPyIA displays CIE coordinates
of (0.15, 0.10), which is very close to the NTSC blue standard
(0.14, 0.08). TTA mechanism may be assumed to be the major
reason for such high efficiency. To the best of our knowledge,
this is one of the best results of deep-blue imidazol-based
fluorescent OLEDs.
Theoretical Calculations
To understand the electronic properties and geometrical
structures of C-BPyIA and N-BPyIA, density functional theory
Scheme 1 Synthesis routes of C-BPyIA and N-BPyIA. a) Suzuki coupling
reaction: Pd(PPh3)4, K2CO3, toluene, 85 °C, 48 h under N2 protection.
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exhibited large degree orbital overlap and spatial separation,
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DOI: 10.1039/C9TC02990G
while HOMO and LUMO of N-BPyIA almost complete separation
on account of the twisted almost conformations and ineffective
electronic communications. In addition, these distributions of
HOMO and LUMO indicated that C-BPyIA and N-BPyIA
possessed some CT property. This orbital-distribution
characteristic originating from PyI orientation effect in N-BPyIA
was beneficial to the transportation of holes and electrons and
thus the enhancement of device performance.15
Fig. 1 TGA A) and DSC B) thermograms of C-BPyIA and N-BPyIA
.
Photophysical Properties
(DFT) calculations were performed with the ground state geometry
optimized at the B3LYP/6-31G(d,p) level. The optimized molecular
geometry, the lowest unoccupied molecular orbital (LUMO) and the
highest occupied molecular orbital (HOMO) density maps are shown
in Fig. 2. C-BPyIA and N-BPyIA both possessed nearly orthogonal
geometries between the An and adjacent phenyl with similar torsion
angel of 76.2° and 78.1°, respectively, which was attributed to the
steric repulsion effect of the neighbouring hydrogens at the 2,6-
position of phenyl group and 1,4,5,8-position of An.14 Whereas the
dihedral angles between the phenyl and PyI group were much
different, which were found to be 25.3° for C-BPyIA and 79.4° for N-
BPyIA, respectively. This is derived from the various linking fashion of
PyI and PAnP in these two structural isomers. It could be inferred that
stronger steric hindrance and repulsion effect between hydrogen
atoms on phenyl and pyrene ring manifested relatively bigger torsion
angle when the PAnP moiety was coupled with PyI groups at N1
position in N-BPyIA. The twisted molecular conformation can
efficiently limit the π conjugation and lead to bluer emission. C-BPyIA
and N- BPyIA had similar LUMOs distributions, mainly located on the
electron-deficient An unit. However, the HOMO distributions were
significantly different, where the HOMO were mainly delocalized
over the backbone in C-BPyIA, but for C-BPyIA, HOMO and LUMO
Fig. 3 shows the UV-vis absorption and PL spectra measured in
tetrahydrofuran (THF) dilute solution and thin films on quartz
substrates of C-BPyIA and N-BPyIA. Detailed photophysical data are
summarized in Table 1. The absorption profiles of C-BPyIA and N-
BPyIA in THF and thin films were nearly the same. Compared to the
absorption spectra of PAnP and PyI (Fig. S3-S4), the well-resolved 394
nm absorption peaks were π–π* characteristic transitions of An
moiety.16 The absorption band centred at 380 nm in THF belonged to
the π–π* transitions of PyI group. However, because the absorption
profiles of PAnP and PyI at short wavelength below 450 nm showed
a big overlap, the absorption peaks at 355 nm might belong to
overlapped peak of PAnP and PyI. Both compounds showed blue
emissions in THF and solid-state films. In THF, PL emission peak of the
C-BPyIA was located at 443 nm, whereas N-BPyIA showed a little
blue-shifted PL emission peak owing to more distorted molecular
structure. When deposited on quartz substrates, the emission peaks
were red-shifted to 463 and 461 nm for C-BPyIA and N-BPyIA,
respectively, due to the enhanced intermolecular interactions in film
state. No excimer emission was observed in film state. The solvation
effect on PL properties was investigated in several solvents with
different polarities. As displayed in Fig. S7-S8, the emission peak of
C-BPyIA shifted from 435 nm in n-hexane to 465 nm in acetone with
a 30 nm variation and the emission peak of N-BPyIA shifted from 433
nm in n-hexane to 461 nm in acetone with 29 nm variation
accompanied by the gradually broadening of emission spectra,
indicating C-BPyIA and N-BPyIA possessed some CT property. The
φPLs of N-BPyIA in dilute THF solution, neat films, and doped PMMA
films (5 wt%) were 65%,46%, and 61%, respectively. By contrast,
N
N
N
N
N
N
N
N
Fig. 3 Absorption and PL spectra of A) C-BPyIA and N-BPyIA in THF dilute
solution (Concentration: 10-5 mol L-1) and B) evaporated films.
Fig.
2 Optimized molecular geometries and LUMO and HOMO
distributions of the molecular C-BPyIA and N-BPyIA.
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Table 1 Key thermal and photophysical properties of C-BPyIA and N-BPyIA
λabs (nm)
Td/Tg
g
λPL (nm)
φPLsc
HOMO/LUMOf
(eV)
Eg
Compound
sola/filmb
sola/filmb/dfilmd/ dfilme
(eV)
Sola
Filmb
[℃]
C-BPyIA
355,383,395
355,383, 395
353,385
359, 384
443/463
440/461
74/54/70/67
65/46/61/56
-5.42/-2.64
-5.41/-2.57
2.78
2.84
541/-
541/-
N-BPyIA.
a Measured in dilute THF solution (10−5 mol L−1) at room temperature. b Thin films on quartz. c Absolute PL quantum yield evaluated using an integrating
sphere. d Doped PMMA films (5 wt%). e Doped CBP films (15 wt%). f Measured by cyclic voltammetry and calculated by comparing with ferrocene (Fc). g
Bandgap calculated from Eg = LUMO – HOMO.
C-BPyIA had even better φPLs, 74%, 54%, and 70% in the above benefiting to the electron injection in devices. The energy gaps
states, which confirmed that partly degree orbital overlap of between the HOMO and LUMO energy levels of the two compounds
HOMO and LUMO expressed a more powerful radiative were calculated to be 2.78 and 2.79 eV, respectively, indicating that
transition rate and thus higher φPLs. In addition, C-BPyIA and N- two pyreno[4,5-d]imidazole groups substituted either at C2 or N1
BPyIA still remained decent φPLs in neat films, manifesting that position barely changed the emission colour, which was also in
twisted molecular conformation could suppress intermolecular accordance with the photophysical results.
interactions and keep the high φPLs in solid-state. As displayed
in Fig. S9, the PL of C-BPyIA and N-BPyIA in nondoped films
exhibited monoexponential attenuation with nanosecond time
The single-carrier devices
scale. No delayed constituent could be viewed，demonstrating
the emission merely originated from transient decay of S1 state
and excluding the possibility of TADF. According to the PL
emission in n-hexane, the S1 state energy was calculated as 2.80
eV for C-BPyIA (443 nm) and 2.82 eV (440 nm) for N-BPyIA. In
both 2-methyltetrahydrofuran solution and neat film at 77 K,
phosphorescence spectra of N-BPyIA and C-BPyIA could not be
detected due to the low population and high non-radiative
transition rate of T1 exciton. As shown in Fig. S5, the
phosphorescence spectrum of PyI in 77 K after 50 ms delayed
emission exhibited fine vibrational structure and the
corresponding energy value of T1 was thus confirmed to be 2.17
eV according to the first vibrational peak of phosphorescence at
572 nm. According to literatures, the T1 value of anthracene
derivatives is approximately 1.8 eV on account of the long π
conjugation of anthracene, which is lower than the T1 of PyI.14
Thus, T1 energies of N-BPyIA and C-BPyIA should be equal to or
lower than the T1 of An (1.8 eV) according to the Kasha's rule.
Apparently, TADF cannot take place because of such large
energy gap between S1 and T1. However, TTA process is energy-
permitting because of 2T1 > S1. Therefore, we deem that TTA is
likely to happen to benefit the enhancement of the device
efficiency.
To evaluate the hole and electron injection/transport abilities, single
carrier devices were fabricated with the structures of indium tin
oxide (ITO)/ hexaazatriphenylenehexacarbonitrile (HATCN) (6 nm)/
N,N0-bis(naphthalen-1-yl)-N,N,O-bis(phenyl)-benzidine (NPB) (10
nm)/ C-BPyIA or N-BPyIA (80 nm)/NPB (20 nm)/Al (100 nm) for hole-
only device and ITO/ (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)-
benzene (TPBi) (20 nm)/ C-BPyIA or N-BPyIA (80 nm)/TPBi (10
nm)/LiF (1 nm)/Al (100 nm) for electron-only device. For hole-only
device, NPB neighboring to the cathode Al was employed to block
electrons, which guaranteed the hole-only characteristic of the
devices. Likewise, TPBi in the electron-only device near the anode
ITO was applied to prevent hole injection. The current density-
voltage (J-V) curves are shown in Fig. S10 and C-BPyIA and N-BPyIA
all showed decent transmitting capacity of holes and electrons. In
addition, N-BPyIA possessed better transmitting capacity of holes
and electrons, which was benefited to the enhancement of device
performance.
Electrochemical Properties.
Cyclic voltammetry (CV) was employed to calculate the
HOMO/LUMO energy levels of the target materials. The onset
oxidation potentials of C-BPyIA and N-BPyIA were at 0.82 and 0.79 V,
respectively, and the HOMO energy values were calculated to be -
5.42 and -5.39 eV. The LUMO energy levels could be obtained in the
same way of -2.64 and -2.60 eV, respectively, which are higher than
the classical electron-transporting material TPBi (-2.70 eV),
Fig. 4 Cyclic voltammograms of C-BPyIA and N-BPyIA, the potentials are
calibrated against Fc/Fc+ internal standard.
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Table 2 Key Performance Parameters of the EL performances of OLEDs based on C-BPyIA and N-BPyIA
a
b
c
d
f
device
Von
Lmax
CEmax
PEmax
EQEe (%)
max/100/1000 cd m-2
4.78/4.70/4.60
5.63/5.63/4.93
5.90/4.12/3.10
7.67/6.60/5.13
EL λmax
CIEg
(x, y)
(0.21,0.32
(0.22,0.31)
(0.15,0.12)
(0.15,0.10)
(V)
3.0
3.0
3.6
3.6
(cd m-2)
43127
46509
18027
15674
(cd A-1)
10.12
12.64
6.69
(lm W-1)
8.53
10.66
5.83
(nm)
476
472
450
448
A
B
C
D
7.98
6.78
a Turn-on voltage at 1 cd m-2. b Maximum luminance. c Maximum current efficiency. d Maximum power efficiency. e Maximum external
quantum efficiency/100/1000 cd m-2. f EL emission peak of EL spectrum at 5V. g Commission International de l’Éclairage (CIE) coordinates at
5 V.
respectively. In addition, the both of the non-doped devices
showed quite small efficiency roll-offs.
Meanwhile, to further improve the device efficiency and color
purity, we also constructed the doped EL device. CBP was
selected as the host because of the good overlap between the
absorption spectrum of C-BPyIA and N-BPyIA and the emission
band of CBP (Fig. S13). The doped devices consisted of
ITO/HATCN (6 nm)/NPB (25nm)/TCTA (15 nm)/emitting layer
(C-BPyIA or N- or N-BPyIA/CBP-15 wt%, 20 nm)/TPBi (40 nm)/LiF
(0.5 nm)/Al (120 nm) (Device C or D). The performance of device
Fig. 5 Characteristics of nondoped multilayer devices A and B:A) Current density (J−V)
and luminance (L−V) plots;B) Luminance efficiency−voltage and EQE−voltage C (C-BPyIA:15%) and device D (N-BPyIA:15%) are provided in Fig.
characteristics; Inset: EL spectra of the devices).
6 and summarized in Table 2. Both the doped OLEDs showed
significantly improved blue colour purities and blue-shifted EL
emission, with the maximum peak of 450 nm for C-BPyIA and
448 nm for N-BPyIA. It is worth noting that the CIE (0.15, 0.10)
Electroluminescence Properties.
of device D based on N-BPyIA was very close to the NTSC blue
standard (0.14, 0.08). The EL spectra barely changed under
different voltages (Fig. S14), illustrating the good stability of
device. The Von increased from 3 to 3.6 V for C-BPyIA and N-
BPyIA because of the larger Eg of the host. The doped OLEDs all
showed improved device efficiencies compared with that of
nondoped devices. Device C achieved good LEmax and EQEmax
of 5.83 cd A-1 and 5.90%, respectively. Moreover, device D
possessed an even better performance with the LEmax up to 7.98
cd A-1 and the EQEmax of 7.67%.
The transient EL decay of N-BPyIA-based device was measured
to explore the origin of its high efficiency in OLED. As displayed
in Fig. 7, given a fleet electric excitation pulse, nondoped and
doped devices of N-BPyIA both showed a fleet EL response with
the lifetime (τs) of nanosecond scale originating from the
transient fluorescence of emitters and a delayed EL decay with
microsecond scale. In addition, the percentage of delayed
To verify the potential application of C-BPyIA and N-BPyIA as
blue luminophores in electroluminescence (EL) devices, we first
fabricated the nondoped multilayer devices with the
configuration of ITO/HATCN (6 nm)/NPB (25 nm)/tris(4-
(9Hcarbazol-9-yl)phenyl)amine (TCTA) (15 nm)/C-BPyIA or N-
BPyIA (20 nm)/TPBi (40 nm)/LiF (0.5 nm)/Al (120 nm) (devices A
or B), where ITO was the anode, HATCN was the hole injecting
layer, NPB was the hole transporting layer (HTL), TCTA was the
exciton blocking layer. C-BPyIA or N-BPyIA was the emitting
layer (EML), TPBi was the electron transporting layer and hole-
blocking layers owing to its deep HOMO level (-6.30 eV). LiF was
the electron injecting layer and Al was the cathode. The
characteristic curves and device data are shown in Fig. 5 and
Table 2, respectively. Non-doped devices showed blue
electroluminescence peaking at 476 nm for C-BPyIA and 472 nm
for N-BPyIA. The EL emission coincided with the corresponding
thin-film PL spectra of emitters (Fig. S12), suggesting that the EL
emission was from the EML and no excimer emission existed in
device. The EL spectra of devices A and B remained stable over
various driving voltages (Fig. S14), ensuring good colour
stability. The turn-on voltage (Von) was only 3.0 V, disclosing
effective charge injections. The maximum luminescence (Lmax
)
was over 40000 cd m-2. The C-BPyIA-based devices exhibited
moderate performance with a maximum current efficiency
(LEmax) of 10.12 cd A-1, a maximum power efficiency (PEmax) of
8.53 lm W-1, and a maximum EQEmax of 4.78%. By contrast, the
Fig. 6 Characteristics of doped multilayer devices C and D: A) Current density (J−V) and
luminance (L−V) plots; B) Luminance efficiency−voltage and EQE−voltage
characteristics; Inset: EL spectra of the devices.
N-BPyIA-based devices showed better performance with LEmax
,
PEmax and EQEmax values of 12.64 cd A-1, 10.66 lm W-1, 5.63%,
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
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Journal of Materials Chemistry C
Page 6 of 9
ARTICLE
Journal Name
strategy to obtain the deep-blue material by conveniently
View Article Online
DOI: 10.1039/C9TC02990G
adjusting the substituent positions on An skeleton.
Experimental
General information
All the reagents and solvents used for the syntheses were
purchased from Aldrich and Acros and used as received.
Synthetic procedures
9,10-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)
anthracene (BAnB)
Fig. 7 Transient EL decay of non-doped and doped devices based on N-BPyIA emitter at
In a 250 mL round flask, a mixture of 9,10-dibromoanthracene
(3.36 g, 10 mmol), bis(pinacolato)diboron (4.6 g, 18 mmol),
KOAc (5.9 g, 60 mmol), 1,4-dioxane (80 mL), and Pd(dppf)Cl2
the same current density.
attenuation gradually decreased from 5 V to 10 V (Fig. S17). At
low voltage, enough triplet excitons were converted by TTA
process and lead to a great part of delayed constituent which
could benefit to the enhancement of device performance. As
the voltage increased, the triplet excitons may be consumed by
charges or undergo other consumption processes which would
result in the decrease of delayed constituent and thus the
decline of the EQE. The variation tendency about the delayed
component along with the driving voltage was in consistent
with the driving voltage-EQE curves (Fig. S16). Considering the
large energy gap difference between S1 and T1, the delayed
component could not be caused by TADF process. In addition,
as TADF materials tend to show more distinct delayed curve and
much slower EL attenuation,10c we could infer that TADF
mechanism could not explain the delayed constituent of device.
TTA probably may be the pathway to utilize the non-emissive
triplet excitons which contributed to such a high device
efficiency.
(490
mg,
0.6
mmol;
dppf
=
1,1’-bis(-
diphenylphosphino)ferrocene) was added and stirred at 85 °C,
under N2 protection for 48 h. The reaction was then quenched
by water and the mixture was extracted with dichloromethane
for three times. After evaporating the solvent, the crude
product was purified by column chromatography to give a
yellow solid (petroleum ether/dichloromethane = 4:1 v/v) (2.6
g, yield: 62%). 1H NMR (500 MHz, DMSO-d6) δ：8.22 (dd, J = 6.7,
3.2 Hz, 4H), 7.56 (dd, J = 6.7, 3.2 Hz, 4H), 1.54 (s, 24H). MALDI-
TOF (m/z): [M+] Calcd for C26H32B2O4: 430.16; Found: 430.3.
pyrene-4,5-dione (PyO2)
NaIO4 (12.30 g, 57.3 mmol), H2O (80 mL), and RuCl3 • xH2O (0.35
g, 1.7 mmol) were added to the solution of the pyrene (2.80 g,
14.0 mmol) in dichloromethane (60 mL) and acetonitrile (60
mL). The dark brown suspension was stirred at room
temperature overnight. The resulting mixture was extracted by
chloroform, and the solvent was removed under reduced
pressure to afford
a dark orange solid. Then column
chromatography on silica gel gave red powder (petroleum
ether/dichloromethane = 1:1 v/v) (1.21 g, Yield: 36%). 1H NMR
(500 MHz, CDCl3) δ:8.53 (dd, J = 7.4, 1.1 Hz, 2H), 8.22 (dd, J =
7.9, 1.1 Hz, 2H), 7.89 (s, 2H), 7.79 (t, J = 7.7 Hz, 2H). MALDI-TOF
(m/z): [M+] Calcd for C16H8O2: 232.16; Found: 232.1.
Conclusions
In summary, two blue light-emitting symmetrically structural
isomers, C-BPyIA and N-BPyIA, by coupling two PyI groups with
one 9,10-diphenylanthracene moiety at C2 and N1 positions,
respectively, have been successfully synthesized and well
characterized. The design strategy has induced highly twisted
torsion angels between PyI and An, especially in N-BPyIA, which
entitles N-BPyIA with a bluer emission as compared with C-
BPyIA. Both C-BPyIA and N-BPyIA exhibit excellent thermal
stabilities, high φPLs and suitable HOMO and LUMO energy
levels for applications in OLEDs. Their non-doped devices show
blue electroluminescence, high EQE and small efficiency roll-
offs. When doped with CBP host, much improved device
efficiencies and better blue colour purities are all achieved. In
particular, utilizing N-BPyIA as emitter, the doped device
exhibits a LEmax up to 7.98 cd A-1 and a maximum EQE of 7.67%
with CIE coordinates of (0.15, 0.10), which is close to the NTSC
blue standard (0.14, 0.08) and comparable to state-of-the-art
deep-blue emitters. These encouraging results would
contribute to the development of highly efficient deep-blue PyI-
based luminophores. The work also provides a novel design
10-(4-bromophenyl)-9-phenyl-9H-pyreno[4,5-d]imidazole (C-
PyIBr)
A mixture of aniline (2.3 mL, 25.0 mmol), pyrene-4,5-dione (1.2
g, 5.0 mmol), 4-bromobenzaldehyde (1.2 g, 6.0 mmol),
ammonium acetate (1.5 g, 20.0 mmol), and acetic acid (15 mL)
was refluxed under nitrogen in oil bath. After 2 h, the mixture
was cooled and filtered. The solid product was washed with an
acetic acid/water mixture (1:1, 50 mL). And then, it was
separated
by
chromatography
(petroleum
ether/dichloromethane = 1:1 v/v) to afford a white solid. (1.93
g, yield: 84%). 1H NMR (500 MHz, DMSO-d6) δ:8.95 (d, J =7.0 Hz,
1 H), 8.33 (d, J =7.4 Hz, 1 H), 8.27-8.17 (m, 4 H), 7.86-7.72 (m, 6
H), 7.63-7.58 (m, 4 H), 7.32 (d, J =7.9 Hz, 1 H). MALDI-TOF (m/z):
[M+] Calcd for C29H17BrN2: 473.37; Found: 472.7.
9-(4-bromophenyl)-10-phenyl-9H-pyreno[4,5-d]imidazole (N-
PyIBr)
A mixture of 4-bromoaniline (2.3 mL, 25.0 mmol), pyrene-4,5-dione
(1.2 g, 5.0 mmol), benzaldehyde (1.2 g, 6.0 mmol), ammonium
6 | J. Name., 2012, 00, 1-3
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Page 7 of 9
Journal of Materials Chemistry C
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Journal Name
ARTICLE
Acknowledgements
acetate (1.5 g, 20.0 mmol), and acetic acid (15 mL) was refluxed
under nitrogen in oil bath. After 2 h, the mixture was cooled and
filtered. The solid product was washed with an acetic acid/water
mixture (1:1, 50 mL). And then, it was separated by chromatography
(petroleum ether/dichloromethane = 1:1 v/v) to afford a white solid.
View Article Online
DOI: 10.1039/C9TC02990G
We appreciate the National Key R&D Program of China (Grant
No. 2016YFB0401001), National Natural Science Foundation of
China (91833304, 21774047) and the Jilin Provincial Science
and Technology Department (20180201084GX).
1
(1.86 g, yield: 81%). H NMR (500 MHz, CDCl3) δ:9.14 (d, J = 6.9 Hz,
1H), 8.23 (d, J = 6.9 Hz, 1H), 8.20-8.12 (m, 2H), 8.08 (dd, J = 12.3, 8.2
Hz, 2H), 7.84-7.76 (m, 2H), 7.73 (t, J = 7.8 Hz, 1H), 7.65 (dd, J = 7.4,
2.1 Hz, 2H), 7.53-7.44 (m, 3H), 7.42-7.35 (m, 3H). MALDI-TOF (m/z):
[M+] Calcd for C29H17BrN2: 473.37; Found: 471.8.
9,10-(4-(9-phenyl-9H-pyreno[4,5-d]imidazole)-10-phenyl)
anthracene (C-BPyIA)
Notes and references
1
a) B. W.D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585-
1595; b) H. Sasabe, J. Kido, Eur. J. Org. Chem., 2013, 2013,
7653-7663; c) S. Reineke, Nat. Photonics, 2014, 8, 269-270; d)
G. B. Nair, S. J. Dhoble, Lumin., 2015, 30, 1167-1175.
a) S. Krotkus, D. Kasemann, S. Lenk, K. Leo, S. Reineke, Light:
Sci. Appl., 2016, 5, e16121; b) Y. Sun, N. C. Giebink, H. Kanno,
B. Ma, M. E. Thompson, S. R. Forrest, Nature, 2006, 440, 908-
912; c) D. Zhang, L. Duan, Y. Li, D. Zhang, Y. Qiu, J. Mater.
Chem. C, 2014, 2, 8191-8197; d) D. Zhang, L. Duan, Y. Zhang,
M. Cai, D. Zhang, Y. Qiu, Light: Sci. Appl., 2015, 4, No.e232; e)
B. Q. Liu, L. Wang, D. Y. Gao, J. H. Zou, H. L. Ning, J. B. Peng, Y.
Cao, Light: Sci. Appl., 2016, 5, No. e16137; f) Y. Li, W. Wang, Z.
Zhuang, Z. Wang, G. Lin, P. Shen, S. Chen, Z. Zhao, B. Z. Tang,
J. Mater. Chem. C, 2018, 6, 5900-5907; g) J. Jiang, X. Li, M.
Hanif, J. Zhou, D. Hu, S. Su, Z. Xie, Y. Gao, B. Yang, Y. Ma, J.
Mater. Chem. C, 2017, 5, 11053-11058; h) Y. Li, Z. Xu, X. Zhu,
B. Chen, Z. Wang, B. Xiao, J. W. Y. Lam, Z. Zhao, D. Ma, B. Z.
Tang, ACS Appl. Mater. Interfaces, 2019, 11, 17592-17601; i)
B. Chen, B. Liu, J. Zeng, H. Nie, Y. Xiong, J. Zou, H. Ning, Z. Wang,
Z. Zhao, B. Z. Tang, Adv. Funct. Mater., 2018, 28, 1803369.
a) H. Sasabe, J. Kido, Chem. Mater., 2011, 23, 621-630; b) C.
Li, Z. Li, X. Yan, Y. Zhang, Z. Zhang, Y. Wang, J. Mater. Chem. C,
2017, 5, 1973-1980; c) C. He, H. Guo, Q. Peng, S. Dong, F. Li, J.
Mater. Chem. C, 2015, 3, 9942-9947; d) S.-K. Kim, B. Yang, Y.
Ma, J.-H. Lee, J.-W. Park, J. Mater. Chem., 2008, 18, 3376; e)
R. Kim, S. Lee, K. H. Kim, Y. J. Lee, S. K. Kwon, J. J. Kim, Y. H.
Kim, Chem. Commun., 2013, 49, 4664-4666; f) W. Liu, S. Ying,
Q. Zhang, S. Ye, R. Guo, D. Ma, L. Wang, Dyes Pigm., 2018, 158,
204-212.
2
In a 100 mL round flask, a mixture of C-PyIBr (2.13 g, 4.5 mmol), BAnB
(0.79 g, 1.8 mmol), K2CO3 (4.43 g, 32 mmol), distilled water (16 mL),
toluene (24 mL), and [Pd(PPh3)4] (0.62 g, 0.54 mmol) was added and
refluxed at 90 °C under N2 atmosphere for 48 h. The reaction was
then quenched by water and the mixture was extracted with
dichloromethane for three times. The organic phase was collected
and dried with anhydrous Na2SO4 for 30 min. After evaporation of
the solvent, the residue was purified via column chromatography
using THF as eluent to afford light yellow solid. (0.88 g, yield: 51%).
1H NMR (500 MHz, CD2Cl2) δ:8.33 (s, 2H), 8.29 – 8.10 (m, 9H), 8.09 –
7.91 (m, 8H), 7.90 – 7.69 (m, 13H), 7.68 – 7.46 (m, 8H), 7.43 (m, 2H).
13C NMR (126 MHz, CDCl3) δ:133.66, 132.94, 132.58, 131.94, 130.65,
130.02, 129.33, 128.72, 128.33, 127.64, 127.01, 126.29, 125.81,
124.25, 123.60, 122.64, 121.58. FTIR (KBr, ν, cm-1): 3040, 1921, 1791,
1597, 1496, 1452, 1387, 1297, 1221, 1185, 1149, 1102, 1070, 1019,
976, 944, 893, 828, 766, 720, 698, 665, 615, 550, 485, 420. MALDI-
TOF (m/z): [M+] Calcd for C72H42N4: 963.16; Found: 965.4. Anal. Calcd
for C72H42N4: C 89.79, H 4.40, N 5.82; Found: C 89.86, H 4.45, N 5.79.
9,10-(4-(10-phenyl-9H-pyreno[4,5-d]imidazole)-9-phenyl)
anthracene (N-BPyIA)
In a 100 mL round flask, a mixture of N-PyIBr (2.13 g, 4.5 mmol), BAnB
(0.79 g, 1.8 mmol), K2CO3 (4.43 g, 32 mmol), distilled water (16 mL),
toluene (24 mL), and [Pd(PPh3)4] (0.62 g, 0.54 mmol) was added and
refluxed at 90 °C under N2 atmosphere for 48 hours. The reaction was
then quenched by water and the mixture was extracted with
dichloromethane for three times. The organic phase was collected
and dried with anhydrous Na2SO4 for half an hour. After evaporation
of the solvent, the residue was purified via column chromatography
using THF as eluent to afford light yellow solid. (0.97 g, yield: 56%).
1H NMR (500 MHz, CD2Cl2) δ:8.33 (s, 2H), 8.27 – 8.23 (m, 4H), 8.22 –
8.10 (m, 5H), 8.07 – 7.91 (m, 9H), 7.90 – 7.68 (m, 12H), 7.68 – 7.45
(m, 9H), 7.45 – 7.38 (m, 1H). 13C NMR (126 MHz, CDCl3) δ:133.66,
132.67, 132.05, 130.93, 130.31, 129.90, 128.80, 128.36, 127.73,
127.24, 126.33, 125.63, 124.97, 124.16, 123.23, 122.74, 122.08,
121.03, 120.06, 118.38. FTIR (KBr, ν, cm-1): 3040, 1921, 1798, 1596,
1513, 1485, 1459, 1441, 1394, 1304, 1275, 1185, 1145, 1102, 1070,
1022, 976, 939, 896, 828, 770, 744, 715, 694, 669, 607, 557, 485, 416.
MALDI-TOF (m/z): [M+] Calcd for C72H42N4: 963.16; Found: 965.2.
Anal. Calcd for C72H42N4: C 89.79, H 4.40, N 5.82; Found: C 89.88, H
4.43, N 5.78.
3
4
a) H. Shin, J. H. Lee, C. K. Moon, J. S. Huh, B. Sim, J. J. Kim, Adv.
Mater., 2016, 28, 4920-4925; b) H. Liu, G. Cheng, D. Hu, F.
Shen, Y. Lv, G. Sun, B. Yang, P. Lu, Y. Ma, Adv. Funct. Mater.,
2012, 22, 2830-2836.
5
6
a) H. Xu, R. Chen, Q. Sun, W. Lai, Q. Su, W. Huang, X. Liu, Chem.
Soc. Rev., 2014, 43, 3259-3302; b) P.-T. Chou, Y. Chi, M.-W.
Chung, C.-C. Lin, Coord. Chem. Rev., 2011, 255, 2653-2665.
a) H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi,
Nature, 2012, 492, 234-238; b) S. Hirata, Y. Sakai, K. Masui, H.
Tanaka, S. Y. Lee, H. Nomura, N. Nakamura, M. Yasumatsu, H.
Nakanotani, Q. Zhang, K. Shizu, H. Miyazaki, C. Adachi, Nat.
Mater., 2015, 14, 330-336; c) Q. Zhang, J. Li, K. Shizu, S. Huang,
S. Hirata, H. Miyazaki, C. Adachi, J. Am. Chem. Soc., 2012, 134,
14706-14709; d) X. He, T. Shan, X. Tang, Y. Gao, J. Li, B. Yang
and P. Lu, J. Mater. Chem. C, 2016, 4, 10205-10208.
7
8
a) M. Y. Wong, E. Zysman-Colman, Adv. Mater., 2017, 29, No.
1605444; b) Y. Im, M. Kim, Y. J. Cho, J.-A. Seo, K. S. Yook, J. Y.
Lee, Chem. Mater., 2017, 29, 1946-1963; c) Z. Huang, S. Xiang,
Q. Zhang, X. Lv, S. Ye, R. Guo, L. Wang, J. Mater. Chem. C, 2018,
6, 2379-2386.
a) Y. Zhang, S.-L. Lai, Q.-X. Tong, M.-Y. Chan, T.-W. Ng, Z.-C.
Wen, G.-Q. Zhang, S.-T. Lee, H.-L. Kwong, C.-S. Lee, J. Mater.
Chem. 2011, 21, 8206-8214; b) Z. Wang, P. Lu, S. Chen, Z. Gao,
F. Shen, W. Zhang, Y. Xu, H. S. Kwok, Y. Ma, J. Mater. Chem.,
2011, 21, 5451-5456; c) Y. Yuan, J.-X. Chen, F. Lu, Q.-X. Tong,
Q.-D. Yang, H.-W. Mo, T.-W. Ng, F.-L. Wong, Z.-Q. Guo, J. Ye,
Z. Chen, X.-H. Zhang, C.-S. Lee, Chem. Mater., 2013, 25, 4957-
4965.
Conflicts of interest
There are no conflicts to declare.
This journal is © The Royal Society of Chemistry 20xx
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9
W.-C. Chen, Z.-L. Zhu, C.-S. Lee, Adv. Opt. Mater., 2018, 6,
1800258.
View Article Online
DOI: 10.1039/C9TC02990G
10 a) Z. Gao, G. Cheng, F. Shen, S. Zhang, Y. Zhang, P. Lu, Y. Ma,
Laser Photonics Rev., 2014, 8, L6-L10; b) X. Tang, Q. Bai, Q.
Peng, Y. Gao, J. Li, Y. Liu, L. Yao, P. Lu, B. Yang, Y. Ma, Chem.
Mater., 2015, 27, 7050-7057; c) X. Tang, Q. Bai, T. Shan, J. Li,
Y. Gao, F. Liu, H. Liu, Q. Peng, B. Yang, F. Li, P. Lu, Adv. Funct.
Mater., 2018, 28, 1705813; d) J. Tagare, S. Vaidyanathan, J.
Mater. Chem. C, 2018, 6, 10138-10173; e) S. Chen, J. Lian, W.
Wang, Y. Jiang, X. Wang, S. Chen, P. Zeng, Z. Peng, J. Mater.
Chem. C, 2018, 6, 9363-9373; f) Y. Xu, X. Liang, X. Zhou, P.
Yuan, J. Zhou, C. Wang, B. Li, D. Hu, X. Qiao, X. Jiang, L. Liu, S.
J. Su, D. Ma, Y. Ma, Adv. Mater., 2019, 31, e1807388.
11 a) D. Kumar, K. R. Thomas, C. C. Lin, J. H. Jou, Chem.- Asian. J,
2013, 8, 2111-2124; b) J. S. Valera, J. Calbo, R. Gomez, E. Orti,
L. Sanchez, Chem. Commun., 2015, 51, 10142-101425; c) T.
Jadhav, B. Dhokale, S. M. Mobin, R. Misra, J. Mater. Chem. C
,
2015, 3, 9981-9988.
12 a) T. Shan, Y. Liu, X. Tang, Q. Bai, Y. Gao, Z. Gao, J. Li, J. Deng,
B. Yang, P. Lu, Y. Ma, ACS Appl. Mater. Interfaces, 2016, 8,
28771-28779; b) Y. Liu, Q. Bai, J. Li, S. Zhang, C. Zhang, F. Lu,
B. Yang, P. Lu, RSC Advances, 2016, 6, 17239-17245.
13 a) C.-J. Chiang, A. Kimyonok, M. K. Etherington, G. C. Griffiths,
V. Jankus, F. Turksoy, A. P. Monkman, Adv. Funct. Mater.,
2013, 23, 739-746; b) J.-Y. Hu, Y.-J. Pu, F. Satoh, S. Kawata, H.
Katagiri, H. Sasabe, J. Kido, Adv. Funct. Mater., 2014, 24, 2064-
2071; c) W. Liu, S. Ying, R. Guo, X. Qiao, P. Leng, Q. Zhang, Y.
Wang, D. Ma, L. Wang, J. Mater. Chem. C, 2019, 7, 1014-1021;
d) L. Peng, J.-W. Yao, M. Wang, L.-Y. Wang, X.-L. Huang, X.-F.
Wei, D.-G. Ma, Y. Cao, X.-H. Zhu, Sci. Bull., 2019, 64, 774-781.
14 L. Yao, Y. Pan, X. Tang, Q. Bai, F. Shen, F. Li, P. Lu, B. Yang, Y.
Ma, J. Phys. Chem. C, 2015, 119, 17800-17808.
15 C. Li, S. Wang, W. Chen, J. Wei, G. Yang, K. Ye, Y. Liu, Y. Wang,
Chem. Commun., 2015, 51, 10632-10635.
16 R. N. Jones, Chem. Rev., 1947, 41, 353-371.
8 | J. Name., 2012, 00, 1-3
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Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C9TC02990G
By integrating PyI with anthracene, two high-efficiency blue emitters C-BPyIA and N-BPyIA
are obtained. Especially, N-BPyIA exhibits decent device performance with EQEmax of 7.67 %
in deep blue region.
TOC figure
1