Molecular design and synthetic approach to C2,C3,C4-modified carbazoles: High triplet energy bipolar host materials for efficient blue phosphorescent organic light emitting diodes

Article abstract of DOI:10.1039/c9cc03843d

Herein, we report the first examples of the design of and synthetic approach to C3/C4 and C2/C3/C4-modified carbazole based high triplet energy bipolar host materials for blue phosphorescent organic light emitting diodes and demonstrated excellent device performance with the maximum external quantum efficiency as high as 25.3% and current efficiency of 48.1 cd A^-1.

Full text of DOI:10.1039/c9cc03843d

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: K. Rajendra
kumar, K. H. Lee and J. Y. Lee, Chem. Commun., 2019, DOI: 10.1039/C9CC03843D.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Volume 52 Number
1 4 January 2016 Pages 1–216
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/C9CC03843D
COMMUNICATION
Molecular Design and Synthetic Approach of C2,C3,C4-Modified
Carbazoles: High Triplet Energy Bipolar Host Materials for Efficient
Blue Phosphorescent Organic Light Emitting Diodes
Received 00th January 20xx,
Accepted 00th January 20xx
Rajendra Kumar Konidenaa, Kyung Hyung Leea, and Jun Yeob Leea*
DOI: 10.1039/x0xx00000x
Herein, we report the first examples of design and synthetic materials for blue PHOLEDs with high triplet energy (> 3.0 eV)
approach of C3/C4 and C2/C3/C4-modifed carbazole based high appropriate HOMO and LUMO levels is still dearth in the
triplet energy bipolar host materials for blue phosphorescent literature, because it is difficult to satisfy both the criteria
organic light emitting diodes and demonstrated excellent device simultaneously.4 Till date, several molecular designs have been
performance with maximum external quantum efficiency as high as proposed for high triplet energy bipolar host materials, among
25.3% and current efficiency of 48.1 cd/A.
which the employment of high triplet energy building block that
can effectively suppress the donor-acceptor interactions is
attractive.3,4
Since their first discovery,1 phosphorescent organic light
emitting diodes (PHOLEDs) received immense attention as the
high efficiency organic light-emitting diode technology.2 Unlike
conventional fluorescent emitters, the phosphorescent
emitters have ability to convert both the singlet (25%) and
triplet (75%) excitons into photons to realize 100% theoretical
internal quantum efficiency (IQE).3 In general, the phosphors
possess long exciton lifetimes and thus need to be dispersed in
a suitable host matrix to alleviate the undesired factors such as
exciton diffusion, concentration quenching and triplet-triplet
annihilation (TTA).2,3 Consequently, the host materials have
equal importance to dopants in deciding the overall device
performances.2,3 To realize superior device performances, the
host materials are required to possess 1) a balanced charge
transporting property to precisely manage the recombination
zone within emitting layer (EML), 2) a higher triplet energy than
the dopant to ensure efficient energy transfer and prevent back
energy transfer, 3) a suitable highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital (LUMO)
energy levels matching with the adjacent layers to reduce
driving voltage of the devices and 4) a high thermal and
morphological stability for thermal evaporation and good
stability of the EML.3 In this regard, bipolar host materials
comprised of both the hole (electron donor) and electron
transporting (electron acceptor) units were ideal as the host.3
Currently, bipolar hosts for green and red PHOLEDs show
superior device performances such as high external quantum
efficiency (EQE) and long lifetime.3,4 However, bipolar host
In the past few decades, 9H-carbazole has been widely
employed as one of the most promising building blocks to
develop efficient host materials for PHOLEDs due to its
attractive features such as excellent hole transporting ability,
high thermal and morphological stability and high triplet energy
(~ 2.95 eV).3-5 In addition, its rigid molecular skeleton allows to
introduce different aromatic chromophores through a facile
chemical modifications.3-5 So far, numerous carbazole-based
functional materials have been developed based on C3/C6,
C2/C7, C1/C8 and N-functionalization.3-5 Recently, multi-
functionalization of C1, C3, C6 and C8-positions was also
reported in the literature.5 However, C2, C3 and C4-modified
carbazoles have not been reported yet, due to the requirement
of tedious synthetic protocols. As per the carbazole electron
distribution, the C4 position of carbazole is electron deficient
and effectively interrupts the conjugation between the
carbazole and substituents, leading to high triplet energy.6
Besides, cyano entity was exemplified as one of the most
promising acceptors for designing high triplet energy bipolar
host materials due to its less extended conjugated structure.3
Here, we presumed that the modification of carbazole building
block with carbazole and cyano acceptor at C4 and C3 positions
would minimize extended conjugation and guarantee the
development of high triplet energy host materials without
compromising the bipolar charge transporting character for
blue PHOLEDs.
N
N
N
N
N
N
N
4
N
N
N
N
N
N
5
3
6
7
2
a. School of Chemical Engineering
Sungkyunkwan University
N
N
N
1
8
9
N
2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi 440-746, Korea
E-mail: leej17@skku.edu
4CzCzCN
4CzCNCzCN
24CzCzCN
24CzCNCzCN
Electronic Supplementary Information (ESI) available: [Phosphorescence spectra,
DFT studies, TGA and DSC analysis, NMR spectral details of the compounds]. See
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
COMMUNICATION
Journal Name
Chart 1. Chemical structures of the host materials
substituents, the cyanocarbazole improved the tVriiepwleArtticelenOenrlginye
(ET), stabilized the LUMO energy leveDlOIa: 1n0d.10i3n9c/Cre9aCsCe0d384th3De
thermal stability of the compounds. The single carrier device
studies revealed good bipolar charge transporting property for
all compounds. Further, the potential of these materials as
hosts for blue PHOLEDs was investigated using CNIm dopant.
Notably, all the compounds showed excellent device
performances with EQE exceeding 20%. In the series,
4CzCNCzCN hosted device demonstrated superior performance
with EQE of 25.3% and current efficiency of 48.1 cd/A due to its
high ET and balanced charge transporting feature.
Inspired by the above discussions, in this communication we
developed a series of carbazole-based bipolar host materials
viz., 4CzCzCN, 4CzCNCzCN, 24CzCzCN and 24CzCNCzCN
featuring one or two carbazole/cyanocarbazole units at C2 and
C4 positions and cyano acceptor at C3 position for blue
PHOLEDs. The structure-property relationship of the
compounds
was
investigated
systematically.
The
physicochemical properties of the compounds were highly
dependent on the nature of the substituent and conjugation
connectivity. Comparing the carbazole and cyanocarbazole
Br
I
O
CN
O
F
R1
NO2
NC
X
NC
R2
CN
B
B
CN
X
F
F
CN
NC
X
O
X
F
O
X
F
PPh3, oDCB
reflux, 12h
Cz or CzCN
O
N
N
N
N
Pd(PPh3)4, K2CO3
THF:H2O, reflux, 4h
Pd(dppf)Cl2, KOAc
dioxane, 100 oC, 6h
B
CuI, 1,10-phenanthroline
K2CO3, 100 oC, 3h
Br
N
Cs2CO3, DMF
150 oC, 2h
O2N
O
H
CzCN
Cz
1, X = H
2, X = F
3, X = H
4, X = F
7, X = H
8, X = F
5, X = H
6, X = F
9, X = H
10, X= F
4CzCzCN, R1 = Cz, R2 = H; 4CzCNCzCN, R1 = CzCN, R2 = H
24CzCzCN, R1 = R2 = Cz; 24CzCNCzCN, R1 = R2 = CzCN
Scheme 1. Synthetic protocol of the compounds
Our molecular design mainly emphasis on exploring new bands appearing below ~ 320 nm is assigned to the localized π-
functionalization of carbazole at C3/C4/C2 and C3/C4 positions π* electronic transitions of the carbazole/cyanocarbazole
for developing high triplet energy bipolar host materials for blue building blocks. Whereas, the weak absorption bands above ~
PHOLEDs. We envisaged that the introduction of weak 320 nm is attributed to n-π* transitions of carbazole unit.
carbazole/cyanocarbazole donor and cyano acceptor at C3 and Interestingly, no absorption band appeared in the long
C4 positions of carbazole (4CzCzCN and 4CzCNCzCN) can wavelength region, indicating that the charge transfer between
interrupt the extension of π-conjugation between the donor at carbazole donor and cyano acceptor is not significant in the
C4 and central carbazole (Figure S1), which would result in high electronic transition. This could be attributed to the existence
triplet energy without sacrificing bipolar charge transporting of large twisting between the appended donors and central
property for the materials. In addition, an additional donor was carbazole (vide infra). The molar extinction coefficients of the
introduced at C2 position (24CzCzCN and 24CzCNCzCN) to di-substituted derivatives (24CzCzCN and 24CzCNCzCN)
investigate the effect of the extra donor on material properties. increased significantly in the short wavelength region compared
The employed synthetic procedures to synthesize the target to its mono-substituted analogues (4CzCzCN and 4CzCNCzCN)
materials were accomplished in Scheme 1. Borate ester by the additional carbazole or cyanocarbazole units. The optical
formation of intermediates 1 and 2 using palladium-catalyzed band gaps of the compounds determined from the absorption
reaction conditions resulted in 3 and 4, respectively. The 3 and edges were 3.65 eV for 4CzCzCN, 3.61 eV for 4CzCNCzCN, 3.54
4 intermediates were reacted with 1-bromo-2-nitrobenzene eV for 24CzCzCN and 3.57 eV for 24CzCNCzCN, indicative of
using palladium-catalyzed Suzuki-Miyaura coupling to get 5 and their wide band gap nature. Upon photo-excitation in THF
6, respectively.5 Furthermore, triphenylphosphine mediated solution, all compounds showed deep-blue emission with peak
ring closing reactions was performed on intermediates 5 and 6 wavelength varying in the range of 370~390 nm. In contrast to
in o-dichlorobenzene to yield
7 and 8, respectively. the UV-vis absorption trend, the emission profiles of the
Subsequently, N-phenylation reactions were performed on 7 compounds were highly dependent on the number of carbazole
and 8 using CuI/1,10-phenanthroline in iodobenzene to get the units. The di-substituted derivatives (24CzCzCN and
desired fluro intermediates (9 and 10) in reasonable yields. 24CzCNCzCN) showed broad and red-shifted emission
Finally, aforementioned intermediates were treated with compared to their mono-substituted analogues (4CzCzCN and
carbazole or cyanocarbazole units under cesium carbonate 4CzCNCzCN), respectively, which is attributed to extended
mediated N-arylation reaction conditions to accomplish target conjugation by the substitution at C2 position of carbazole. The
host materials (Chart 1) in excellent yields after vacuum train broadening of the long wavelength emission in the carbazole
sublimation purification. The chemical structures of the substituted compounds (4CzCzCN and 24CzCzCN) relative to the
intermediates and final compounds was confirmed by the corresponding cyanocarbazole substituted counterparts
nuclear magnetic resonance spectroscopy (1H and 13C NMR) and (4CzCNCzCN and 24CzCNCzCN) is caused by excited state
mass spectroscopy measurements.
intramolecular charge transfer (ICT) interactions. As the lowest
The optical properties of the compounds were investigated triplet excited state energy (ET) of compounds are very
using ultraviolet-visible (UV-vis) absorption and fluorescence important to understand their potential as hosts for PHOLEDs,
spectroscopy measurements. The absorption spectra of the we recorded the phosphorescence spectra of the compounds in
compounds are shown in Figure 1 and the pertinent data were frozen THF matrix at low temperature (77 K) (Figure 1b). The
tabulated in Table S1. Interestingly, all compounds manifested phosphorescence spectra of the compounds showed similar
similar absorption spectral profiles with multiple absorption trends as fluorescence. All compounds displayed vibronic
bands in the range of 250-360 nm. The high energy absorption features indicative of their phosphorescence stemming from
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
ChemComm
Please do not adjust margins
Journal Name
the local triplet excited states (3LE). The ET of the compounds
COMMUNICATION
To understand the relationship between the molecular
View Article Online
DOI: 10.1039/C9CC03843D
estimated from the highest energy vibronic peaks was found to structure and electronic properties of these materials, density
be 3.00 eV for 4CzCzCN, 3.06 eV for 4CzCNCzCN, 2.81 eV for functional theoretical (DFT) computations were performed on
24CzCzCN, and 2.85 eV for 24CzCNCzCN. As described in the their model compounds using B3LYP/6-31G* functional on
fluorescence emission of the compounds, the C2 position Gaussian 09 program (Figure S3). The HOMOs of the
substitution decreased the ET of the 24CzCzCN and compounds are mainly localized on the appended carbazole or
24CzCNCzCN. Nevertheless, all compounds showed high ET cyanocarbazole units, while the LUMO is primarily constructed
above 2.80 eV, which is sufficiently higher than 2.69 eV of the by the central cyanocarbazole building block. All the
CNIm blue phosphorescent emitter for efficient energy transfer. compounds revealed highly twisted molecular configurations
with large dihedral angles between the appended carbazole
substituents and central cyanocarbazole. The dihedral angles
lied in the range of 65 to 85o. Interestingly, the carbazoles at C4
position showed relatively large twisting (77~82o) compared to
the carbazoles at C2 position (65-68o). These findings further
confirm that the intramolecular electronic transitions between
the donor and acceptor is effectively interrupted by the
disrupted π-conjugation, which is beneficial to secure high
Fig. 1 a) Absorption and emission spectra of the compounds recorded in THF
triplet energy without sacrificing the bipolar character. The
trends in calculated HOMO, LUMO and HOMO-LUMO gap of the
materials are in good agreement with the experimentally
deduced values.
solution and b) phosphorescence spectra recorded in THF matrix at 77K.
The thermal stabilities of these materials were analysed by the
thermogravimetric analysis (TGA) and differential scanning
calorimetry (DSC) measurements (Figure S2 & Table S1). All
compounds showed excellent thermal stability with marked
thermal decomposition temperatures (Td) corresponding to 5%
weight loss over 340 oC due to the robust chemical structures of
carbazole and cyano units. The di-substituted derivatives
(24CzCzCN and 24CzCNCzCN) revealed superior thermal
stability with Td of 382 oC and 441 oC, respectively, compared to
Td of 342 oC (4CzCzCN) and 359 oC (4CzCNCzCN). In addition, the
To gain further insights into the relationship between the
molecular structure and charge transport properties of these
compounds, we fabricated single carrier devices. The electric
field dependent current-density (J) versus voltage plots of the
hole-only (HOD) and electron-only (EOD) devices are shown in
Figure S4. The 4CzCzCN and 24CzCzCN showed relatively higher
hole current densities than 4CzCNCzCN and 24CzCNCzCN,
respectively, at the same bias, indicating that the hole transport
ability of former derivatives is better than that of the latter
compounds owing to the presence of strong carbazole donor
compared to cyanocarbazole donor. Whereas, the 4CzCNCzCN
and 24CzCNCzCN revealed high electron current densities
compared to 4CzCzCN and 24CzCzCN, suggesting better
election transporting ability of former derivatives due to the
cyanocarbazole units. Nevertheless, each of the mono-carrier
devices exhibited significant currents at a given voltage range,
proving that all the compounds possess sufficiently high hole
transporting and electron transporting abilities and secured
bipolar charge transporting character.
The high triplet energy and bipolar transport properties of
compounds motivated us to explore their potential applicability
as hosts for blue PHOLEDs employing CNIm dopant. The
optimized device configuration of the blue device:
ITO/PEDOT:PSS/TAPC/mCP/host:CNIm(EML)/TSPO1/TPBi/LiF/
Al. Where, PEDOT:PSS and LiF used as hole and electron
injection layers, respectively. The TAPC and TPBi served as hole
and electron transporting layers, respectively. The mCP and the
TSPO1 used as hole and electron transporting type exciton
blocking layers for efficient recombination of charge carriers in
the EML, respectively. The films of 10wt% doped CNIm in
4CzCzCN or 4CzCNCzCN or 24CzCzCN or 24CzCNCzCN host were
adopted as the emitting layer. The chemical structures of each
layers used in the device and the energy level alignment of the
devices were shown in Figure S5.
o
o
DSC curves revealed high Tg of 118 C for 4CzCzCN, 141 C for
4CzCNCzCN, 170 oC for 24CzCzCN and 215 oC for 24CzCNCzCN.
Notably, the cyanocarbazole substitution of 4CzCNCzCN and
24CzCNCzCN boosted the thermal stability of the compounds
compared to their congeners, 4CzCzCN and 24CzCzCN,
respectively, which further attested the importance of cyano
functionality in improving the thermal stability of the
compounds.
The redox behaviour of these compounds were examined by
the cyclic voltammetry measurements in dichloromethane
solution using 0.1 M tetrabutylammonium perchlorate as the
supporting electrolyte and ferrocence as an internal standard
(Table S1). All compounds showed irreversible oxidation peaks
attributed to the removal of electron from the appended
carbazole donors. The 4CzCzCN and 24CzCzCN exhibited
relatively high oxidation propensity as evident from their low
oxidation potentials (EOX) of +1.40 and +1.42 V compared to
4CzCNCzCN (+1.60 V) and 24CzCNCzCN (+1.57 V), respectively.
This is due to the presence of relatively strong carbazole donor
in former compounds compared to cyanocarbazole donor in
later derivatives. The calculated HOMO energy levels of
compounds are of -6.26 eV for 4CzCzCN, -6.40 eV for
4CzCNCzCN, -6.20 eV for 24CzCzCN and -6.31 eV for
24CzCNCzCN. The LUMO energy levels of the compounds
calculated from the HOMO level and optical gap were -2.61 eV
for 4CzCzCN, -2.79 eV for 4CzCNCzCN, -2.66 eV for 24CzCzCN
and -2.81 eV for 24CzCNCzCN.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
COMMUNICATION
Journal Name
develop high triplet energy bipolar host materials for blue
View Article Online
DOI: 10.1039/C9CC03843D
PHOLEDs.
In summary, a series of bipolar host materials viz., 4CzCzCN,
4CzCNCzCN, 24CzCzCN and 24CzCNCzCN, were designed and
synthesized for blue PHOLEDs by modifying the carbazole with
carbazole/cyanocarbazole donor and cyano acceptor at C4
and/or C2 and C3 positions, respectively. They showed high
triplet energy over 2.80 eV and bipolar carrier transport
properties. The blue PHOLEDs fabricated using the hosts for
blue CNIm dopant showed excellent device performance with
EQE over 20%. In the series, the 4CzCNCzCN host demonstrated
superior performance with EQE of 25.3% and CE of 48.1 cd/A
due to its high triplet energy (~ 3.03 eV) and balanced charge
transport. We believe that these results provide fundamental
insights to design efficient high triplet energy bipolar host
materials by modifying a carbazole building block.
Fig. 2 a) Current density (J)-voltage (V)-luminance (L) and b) EQE vs luminance
plots of the devices
The current density (J)-voltage (V)-luminance (L) plots of the
devices are portrayed in Figure 2 and the related device
parameters are summarized in Table S2. Notably, the
cyanocarbazole featured compounds (4CzCNCzCN and
24CzCNCzCN) showed relatively high current densities and
luminance compared to the carbazole substituted derivatives
(4CzCzCN and 24CzCzCN). This can be explained based on the
current density of single carrier devices as discussed above.
Generally, in the CNIm doped devices, hole trapping dominates
the device performance due to the shallow HOMO level of the
CNIm dopant. Thus, the J of EOD is critical for the J of the hole
trapping devices because the electrons would be predominantly
carried by the host materials. As discussed above, the
compounds 4CzCNCzCN and 24CzCNCzCN displayed relatively
high J for EOD compared to 4CzCzCN and 24CzCzCN due to their
good electron transport properties and shallow LUMO levels,
which facilitated efficient electron injection and transport. As a
result, it is expected that the high J of 4CzCNCzCN and
24CzCNCzCN EOD improved the J of hole trapping type CNIm
based blue PHOLEDs and led to balanced charge transport in the
devices. Also, the 4CzCNCzCN and 24CzCNCzCN devices
revealed low turn-on voltage (Von) compared to the 4CzCzCN
and 24CzCzCN device due to the deep LUMO level of the former
derivatives enabling facile electron injection. All compounds
showed blue electroluminescence (EL) with peak maximum of
464 nm originating from the emission of CNIm phosphor (Figure
S6) and the CIE color coordinates lies in the range of x ~ 0.15,
0.29 ≤ y ≤ 0.30. No other emission peaks are observed from the
host materials or any other layers, indicating efficient energy
transfer from the host to the dopant. Transient PL data in
supporting information also confirms the energy transfer.
All compounds showed excellent device performances with
maximum EQE/current efficiency (CE)/power efficiency (PE) of
24.5%/48.0 cd/A/31.8 lm/W for 4CzCzCN, 25.3%/48.1
cd/A/39.3 lm/W for 4CzCNCzCN, 22.2%/43.7 cd/A/31.7 lm/W
for 24CzCzCN and 21.4%/40.8 cd/A/34.4 lm/W for 24CzCNCzCN
because of high triplet energy above 2.80 eV and good bipolar
charge transporting property. Indeed, the mono-substituted
derivatives demonstrated superior device performance than
the di-substituted analogues due to their high triplet energy.
Overall, the 4CzCNCzCN hosted device characterized best
performance in the series with superior EQE, CE and PE due to
high ET (~ 3.06 eV) for efficient forward energy transfer and
balanced charge carrier transport in the EML. The device data
at 5% doping concentration showed the same trend. These
results indicates that the modification of carbazole core at C4
and C3 positions with donor and acceptor units is promising to
This work was funded by the Basic Science Research Program
(Grant No. 2016M3A7B4909243 and 2018R1D1A1B07048498)
through the National Research Foundation (NRF) of Korea
funded by the Ministry of Science, ICT, and Future Planning.
Conflicts of interest
There are no conflicts to declare
References
1
M. A. Baldo, D. F. O’Brien, Y. You, A. Shoustikov, S. Sibley, M.
E. Thompson and S. R. Forrest, Nature, 1998, 395, 151;
a) Y. Chi and P. T. Chou, Chem. Soc. Rev. 2010, 39, 638; b) D.
Ma, T. Tsuboi, Y. Qiu and L. Duan, Adv. Mater. 2017, 29,
1603253; c) A. K. Pal, S. Krotkus, M. Fontani, C. F. R.
Mackenzie, D. B. Cordes, A. M. Z. Slawin, I. D. W. Samuel and
E. Z. Colman, Adv. Mater. 2018, 30, 1804231; d) Z. Q. Zhu, C.
D. Park, K. Klimes and J. Li, Adv. Optical Mater. 2019, 7,
1801518; e) H. Shin, J. H. Lee, C. K. Moon, J. S. Huh, B. Sim and
J. J. Kim, Adv. Mater. 2016, 28, 4920; f) K. Udagawa, H. Sasabe,
F. Igarashi and J. Kido, Adv. Optical Mater. 2016, 4, 86; g) M.
C. Tang, M. Y. Leung, S. L. Lai, M. Ng, M. Y. Chan and V. W. W.
Yam, J. Am. Chem. Soc. 2018, 140, 13115;
2
3
4
a) Y. Tao, C. Yang and J. Qin, Chem. Soc. Rev. 2011, 40, 2943;
b) A. Chaskar, H. F. Chen and K. T. Wong, Adv. Mater. 2011,
23, 3876; c) Q. Bai, H. Liu, L. Yao, T. Shan, J. Li, Y. Gao, Z. Zhang,
Y. Liu, P. Liu, B. Yang and Y. Ma, ACS Appl. Mater. Interfaces.
2016, 8, 24793; d) W. Song, L. Shi, L. Gao, P. Hu, H. Mu, Z. Xia,
J. Huang and J. Su, ACS Appl. Mater. Interfaces. 2018, 10,
5714.
a) S. Y. Chang, G. T. Lin, Y. C. Cheng, J. J. Huang, C. L. Chang, C.
F. Lin, J. H. Lee, T. L. Chiu and M. K. Leung, ACS Appl. Mater.
Interfaces. 2018, 10, 42723; b) W. C. Chen, Y. Yuan, Z. L. Zhu,
S. F. Ni, Z. Q. Jiang, L. S. Liao, F. L. Wong and C. S. Lee, Chem.
Commun. 2018, 54, 4541; c) L. S. Cui, J. U. Kim, H. Nomura, H.
Nakanotani and C. Adachi, Angew. Chem. 2016, 55, 6864
a) H. Huang, Q. Fu, B. Pan, S. Zhuang, L. Wang, J. Chen, D. Ma
and C. Yang, Org. Lett. 2012, 14, 4786; b) R. K. Konidena, K. R.
J. Thomas, A. Pathak, D. K. Dubey, S. Sahoo and J. H. Jou, ACS
Appl. Mater. Interfaces. 2018, 10, 24013;
5
6
a) S. Ameen, S. B. Lee, Y. G. Lee, S. C. Yoon, J. Lee and C. Lee,
ACS Appl. Mater. Interfaces, 2018, 10, 8893
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins