Distinct phosphorescence enhancement of red-emitting iridium(III) complexes with formyl-functionalized phenylpyridine ligands

Article abstract of DOI:10.1039/c6tc00856a

A new highly efficient red-emitting Ir(iii) complex, bis [9-(4-(2-ethylhexyloxy)phenyl)-3-(4-phenylquinolin-2-yl)-9H-carbazole] [3-(pyridin-2-yl) benzaldehyde]iridium(iii) (Ir-CHO), has been synthesized and characterized to investigate the impact of the e

Full text of DOI:10.1039/c6tc00856a

View Article Online
View Journal
Journal of
Materials Chemistry C
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Cao, L. Hao, W.
Lai, H. Zhang, Z. Yu, X. Zhang, X. Liu and W. Huang, J. Mater. Chem. C, 2016, DOI: 10.1039/C6TC00856A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
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
Information for Authors.
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 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.
www.rsc.org/materialsC

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 1 of 11
View Article Online
DOI: 10.1039/C6TC00856A
W}µŒvꢀo bꢀuꢁ
wÇL/[9
!
5
]•š]vꢂš ‰Z}•‰Z}Œꢁ•ꢂꢁvꢂꢁ ꢁvZꢀvꢂꢁuꢁvš }( Œꢁꢃrꢁu]šš]vP ]Œ]ꢃ]µu~LLL•
§
ꢂ}u‰oꢁÆꢁ• Á]šZ (}ŒuÇor(µvꢂš]}vꢀo]Ìꢁꢃ ‰ZꢁvÇo‰ÇŒ]ꢃ]vꢁ o]Pꢀvꢃ•
ꢀ
U
ꢀU
ꢀU ꢄ
ꢀ
ꢀ
ꢀ
ꢀ
]ÌZꢁv /ꢀ}U • []v Iꢀ}U • íꢁvrò}vP [ꢀ]UŽ Iꢀ} ùZꢀvPU ùZ}µ òµU ó]vÁꢁv ùZꢀvPUŽ óµ []µU íꢁ]
{
IµꢀvPŽ
ꢀU ꢄ
!
vꢁÁ Z]PZoÇ ꢁ((]ꢂ]ꢁvš Œꢁꢃrꢁu]šš]vP LŒ~LLLꢀ ꢂ}u‰oꢁÆU ꢄ]• €õr~ðr~îrꢁšZÇoZꢁÆÇo}ÆÇꢀ‰ZꢁvÇoꢀrïr~ðr‰ZꢁvÇo‹µ]v}o]vrîrÇoꢀrõIr
ꢂꢀŒꢄꢀÌ}oꢁꢁ €ïr~‰ÇŒ]ꢃ]vrîrÇoꢀ ꢄꢁvÌꢀoꢃꢁZÇꢃꢁꢁ]Œ]ꢃ]µu~LLLꢀ ~LŒr/Ihꢀ Zꢀ• ꢄꢁꢁv •ÇvšZꢁ•]Ìꢁꢃ ꢀvꢃ ꢂZꢀŒꢀꢂšꢁŒ]Ìꢁꢃ š} ]vÀꢁ•š]Pꢀšꢁ šZꢁ
u‰ꢀꢂš }( šZꢁ ꢁoꢁꢂšŒ}vrÁ]šZꢃŒꢀÁ]vP (}ŒuÇo PŒ}µ‰ }v šZꢁ }‰š}ꢁoꢁꢂšŒ}v]ꢂ ‰Œ}‰ꢁŒš]ꢁ• }( šZꢁ Œꢁ•µoš]vP LŒ~LLLꢀ ꢂ}u‰oꢁÆꢁ•X C}Œ
ꢂ}u‰ꢀŒ]•}vU ꢄ]• €õr~ðr~îrꢁšZÇoZꢁÆÇo}ÆÇꢀ‰ZꢁvÇoꢀrïr~ðr‰ZꢁvÇo‹µ]v}o]vrîrÇoꢀ rõIrꢂꢀŒꢄꢀÌ}oꢁꢁ €~ïr~‰ÇŒ]ꢃ]vrîrÇoꢀ ‰ZꢁvÇoꢀ uꢁšZꢀv}oꢁ
Œ]ꢃ]µu~LLLꢀ ~LŒrhIꢀ ꢀvꢃ (ꢀꢃršŒ]•€õr~ðr~îrꢁšZÇoZꢁÆÇo}ÆÇꢀ‰ZꢁvÇoꢀrïr~ðr‰ZꢁvÇo‹µ]v}o]vrîrÇoꢀrõIrꢂꢀŒꢄꢀÌ}oꢁꢁ ]Œ]ꢃ]µu~LLLꢀ ~LŒrtv/Ìꢀ
ÁꢁŒꢁ ꢀo•} ‰Œꢁ‰ꢀŒꢁꢃX wꢁuꢀŒlꢀꢄoÇU LŒr/Ihrꢃ}‰ꢁꢃ Œꢁꢃ }ŒPꢀv]ꢂ o]PZšrꢁu]šš]vP ꢃ]}ꢃꢁ ~h[95ꢀ ꢁÆZ]ꢄ]šꢁꢃ šZꢁ Z]PZꢁ•š ‰ꢁŒ(}ŒuꢀvꢂꢁU
ꢂZ]ꢁÀ]vP ꢀ uꢀÆ]uµu oµu]vꢀvꢂꢁ ꢁ((]ꢂ]ꢁvꢂÇ ~[9ꢀ }( íðXï ꢂꢃl! ꢀvꢃ ꢁÆšꢁŒvꢀo ‹µꢀvšµu ꢁ((]ꢂ]ꢁvꢂÇ ~9v9ꢀ }( ôXð9U ÁZ]ꢂZ Áꢀ•
ꢄꢁššꢁŒ šZꢀv šZ}•ꢁ }( LŒrhIrꢃ}‰ꢁꢃ ꢀvꢃ LŒrtv/Ìrꢃ}‰ꢁꢃ Œꢁꢃ h[95•X ÇZꢁ Œꢁ•µoš ꢂꢀv ꢄꢁ ꢀššŒ]ꢄµšꢁꢃ š} šZꢁ ]všŒ}ꢃµꢂš]}v }( šZꢁ
oꢁꢂšŒ}vrÁ]šZꢃŒꢀÁ]vP (}ŒuÇoU ÁZ]ꢂZ ]u‰Œ}Àꢁꢃ šZꢁ ꢁoꢁꢂšŒ}v ꢀ((]v]šÇ ]v LŒr/Ih ꢀvꢃ o}ÁꢁŒꢁꢃ ꢁoꢁꢂšŒ}vr]viꢁꢂš]}v ꢄꢀŒŒ]ꢁŒ ]v
h[95 ꢄꢀ•ꢁꢃ }v LŒr/IhX {]u]oꢀŒoÇU ÁZ]šꢁ h[95 ~íh[95ꢀ Á]šZ LŒr/Ih ꢀ• šZꢁ Œꢁꢃ ꢁu]ššꢁŒ ꢃꢁu}v•šŒꢀšꢁꢃ ꢀv ꢁÆꢂꢁooꢁvš Z]PZ [9
]
]
ꢀ
ꢁ
wꢁꢂꢁ]Àꢁꢃ ììšZ WꢀvµꢀŒÇ îìÆÆU
!
ꢂꢂꢁ‰šꢁꢃ ììšZ WꢀvµꢀŒÇ îìÆÆ
}
( îòXí ꢂꢃl! ꢀvꢃ 9v9 }( íìXõ9X ! ꢂ}uꢄ]vꢀš]}v }( šZꢁ šZꢁŒuꢀoU ‰Z}š}‰ZÇ•]ꢂꢀoU ꢁoꢁꢂšŒ}ꢂZꢁu]ꢂꢀo ꢀvꢃ ꢁoꢁꢂšŒ}oµu]vꢁ•ꢂꢁvš ~9[ꢀ
Œ}‰ꢁŒš]ꢁ• }( šZꢁ•ꢁ LŒ~LLLꢀ ꢂ}u‰oꢁÆꢁ• ꢂꢀv šZµ• oꢁꢀꢃ š} ꢀ ꢂ}vꢂoµ•]}v šZꢀš šZꢁ ]vꢂ}Œ‰}Œꢀš]}v }( šZꢁ ꢁoꢁꢂšŒ}vrÁ]šZꢃŒꢀÁ]vP
5hLW íìXíìïõlÆìÆÆìììììÆ
‰
(
}ŒuÇor•µꢄ•š]šµšꢁꢃ ‰ZꢁvÇo‰ÇŒ]ꢃ]vꢁ ~‰‰Çr/Ihꢀ ꢂꢀv ꢀ‰‰ꢀŒꢁvšoÇ ]u‰Œ}Àꢁ šZꢁ ‰Z}•‰Z}Œꢁ•ꢂꢁvꢂꢁ }( šZꢁ Œꢁ•µoš]vP Œꢁꢃrꢁu]šš]vP
Œ]ꢃ]µu ꢂ}u‰oꢁÆꢁ• ꢀvꢃ šZµ• šZꢁ h[95 ‰ꢁŒ(}ŒuꢀvꢂꢁX ÇZꢁ Œꢁ•µoš• •µPPꢁ•š ꢀ •]u‰oꢁ uꢁšZ}ꢃ}o}PÇ (}Œ šZꢁ Œꢀš]}vꢀo ꢃꢁ•]Pv }(
((]ꢂ]ꢁvš ‰Z}•‰Z}Œꢁ•ꢂꢁvš ꢂ}u‰oꢁÆꢁ• (}Œ o]PZšrꢁu]šš]vP ꢀ‰‰o]ꢂꢀš]}v•X
ÁÁÁXŒ•ꢂX}ŒPl
]
ꢁ
efficiency and brightness of Ir(III) complexes strongly
LvšŒ}ꢃµꢂš]}v
depend on the molecular structures of cyclometalated
ligands. Simple changes of the substitution pattern with
acceptor and donor groups can allow the variation of the
Solution-processed phosphorescent organic light-emitting
diodes (OLEDs) are attracting a lot of attention in the past
decades owing to their potential application in the field of
large-area and cost-effective manufacturing of full-color
flat panel displays and solid-state lighting sources. Over
the past decade, numerous Ir(III)-based phosphorescent
4
phosphorescence wavelength. For example, the emission
wavelength of the Ir(III) complexes can shift from green to
near-infrared by changing the number and/or the locations
of electron-donating methoxyl grafted on cyclometalated
1
2
materials have been developed. The performance of
5
phenylpyridine (ppy) ligands. Seo et al. investigated the
OLEDs can be greatly improved by using Ir(III)-based
phosphorescent emitters because both the singlet and
triplet excitons can be harvested for radiative decay and
the internal quantum efficiency can reach close to 100%.
According to previous studies, the emission wavelength,
functionalization of ppy by substituting electron-donating
methyl at 4-position on the pyridine ring and electron-
withdrawing groups such as fluoro and trifluoromethyl on
the phenyl ring to adjust the photoluminescent quantum
3
6
yield (NPL) and emission color of the Ir(III) complexes.
Similarly, the strong electron-withdrawing perfluoro
carbonyl was introduced onto ppy by Lee group, achieving
ꢀ
X
Key Laboratory for Organic Electronics & Information Displays (KLOEID) & the Ir(III) complexes with wide band gaps. Moreover, the
Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation
corresponding OLEDs exhibited high external quantum
Center for Advanced Materials (SICAM), Nanjing University of Posts
Telecommunications, 9 Wenyuan Road, Nanjing 210046, China
&
efficiency (EQE) and good Commission Internationale de
7
Email: iamwylai@njupt.edu.cn (W.-Y. Lai), iamxwzhang@njupt.edu.cn (X. Zhang)
L‘Eclairage (CIE) coordinates.
ꢂX
Key Laboratory of Flexible Electronics (KLOFE)
& Institue of Advanced
Surprisingly, as one of the well-known electron-
Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced
Materials (SICAM), Nanjing Tech University, 30 South Puzhu Road, Nanjing withdrawing groups, the formyl based Ir(III) complexes
2
11816, China.
have rarely been explored for phosphorescent OLEDs. As
previously reported, the ketone or formyl units can largely
†
These authors contributed equally.
Electronic Supplementary Information (ESI) available: NMR spectroscopy,
§
MALDI-TOF mass spectra and some other parameter results for Ir(III) quench the fluorescence due to the strong electron-trapping
complexes, and OLEDs parameter data. See DOI: 10.1039/x0xx00000x
properties and consequent intersystem crossing from the
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
WX bꢀuꢁXU îìíòU ììU írï n í
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

Journal of Materials Chemistry C
Page 2 of 11
View Article Online
DOI: 10.1039/C6TC00856A

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 3 of 11
W}µŒvꢀo bꢀuꢁ
View Article Online
DOI: 10.1039/C6TC00856A
!wÇL/[9
Photophysical properties
Ir-CHO
Ir-OH
Ir-PQCz
Figure 2 shows the UV-visible absorption and the
photoluminescence (PL) spectra of the Ir(III) complexes in
CH Cl , and the related photophysical properties are
2 2
1
00
9
8
7
6
5
4
3
0
0
0
0
0
0
0
summarized in Table 1. The higher energy absorption
peaks in the short wavelength region below 400 nm are
1
attributed to spin-allowed Œ-Œ* transitions of the
cyclometalated ligands. Common to most Ir(III)
14
complexes, the weaker absorption tails located at above
00 nm, can be assigned to the spin-forbidden, ligand-
4
3
centered Œ-Œ* transition induced by spin-orbit coupling,
0
100 200 300 400 500 600 700
o
which is combined with the singlet and triplet metal-to-
Temperature ( C)
1
3
ligand charge-transfer transitions ( MLCT and MLCT).
Under photoexcitation, all the Ir(III) complexes emitted
red light in solution state as shown in Figure 2b. The
maximum emission peaks of Ir-CHO, Ir-OH and Ir-
PQCz were located at 615, 627 and 615 nm, respectively.
Ir-CHO had similar PL peaks to Ir-PQCz, suggesting that
the incorporation of ppy-CHO did not obviously change
the emission wavelength of Ir(III) complexes based on
phenylquinoline-carbazole main ligands. However, Ir-OH
exhibited a 12 nm red-shift compared to Ir-CHO, mainly
because the oxygen lone-pair orbitals in ppy-CHO ligand
lowered the highest occupied molecular orbital (HOMO)
energy level, leading to a larger band gap. Therefore, the
modified ppy can serve as a second cyclometalated
C]PµŒꢁ íX ÇD! ꢂµŒÀꢁ• }( šZꢁ LŒ~LLLꢀ ꢂ}u‰oꢁÆꢁ• uꢁꢀ•µŒꢁꢃ ꢀš ꢀ
Zꢁꢀš]vP Œꢀšꢁ }( íì £/ u]v µvꢃꢁŒ b X
î
rí
Thermal properties
The thermal characteristics of the Ir(III) complexes were
examined by thermogravimetric analysis (TGA) and
differential scanning calorimetry (DSC) under a nitrogen
stream. As shown in Figure 1, all the Ir(III) complexes
d
were thermally stable with 5% mass loss temperatures (T )
up to 300 °C, preventing the degradation of the emitting
layer by heat generation during the device operation.
Homoleptic complex Ir-PQCz displayed excellent thermal
stability with T
heteroleptic complexes Ir-CHO and Ir-OH (382 and
03°C, respectively). In contrast to Ir-CHO and Ir-PQCz,
Ir-OH tended to exhibit a lower T , probably arising from
d
at 424 °C, which was higher than those for
15
ligand. This perception can also be verified by the
3
density functional theory (DFT) calculations and
electrochemical measurements (see below). Moreover, NPL
in solution were measured by a relative method using
d
the decomposition of unstable alcoholic hydroxyl under
high temperature. As has been reported, compared with
2
(piq) Ir(acac) as a standard (0.20). The NPL value for Ir-
[
Ir(piq)
improve the thermal stability of Ir-PQCz. According to
DSC measurements, the glass transition temperature (T§
3
], the presence of rigid carbazole units can
CHO was 82%, which was higher than those of Ir-OH
and Ir-PQCz (14% and 40%, respectively).
13
g
)
In order to understand the excited relaxation process
of Ir-PQCz was found to be 146 °C (Figure S10, ESI ),
while Ir-CHO and Ir-OH exhibited glassy morphology
with no obvious crystallization or melting processes
detectable during the repeated scan cycles, suggesting
good amorphous properties that matched well with the
of these complexes, room-temperature lifetimes (2
measured in N -degassed CH Cl and found to be in the
range of sub-microseconds (2 = 0.65, 0.60 and 0.51 ꢀs for
p
) were
2
2
2
p
Ir-CHO, Ir-OH and Ir-PQCz, respectively) (Figure S12,
§
ESI ). As far as we are concerned, the phosphorescence
results obtained from wide-angle X-ray diffraction
lifetime of the complexes has played an important role in
generating triplet-triplet annihilation during the device
§
(
WAXD) patterns (Figure S11, ESI ).
Ir-CHO
Ir-OH
Ir-PQCz
Ir-CHO
Ir-OH
Ir-PQCz
1.0
0.8
0.6
0.4
0.2
0.0
1.0
(a)
(b)
0.8
0.6
0.4
0.2
0.0
300
400
500
600
700
450 500 550 600 650 700 750 800
Wavelength (nm)
Wavelength (nm)
C]PµŒꢁ îX !ꢄ•}Œ‰š]}v ~ꢀꢀ ꢀvꢃ t[ ~ꢄꢀ •‰ꢁꢂšŒꢀ }( šZꢁ LŒ~LLLꢀ ꢂ}u‰oꢁÆꢁ• ]v /I
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
î î
/o ꢀš îõô YX
WX bꢀuꢁXU îìíòU ììU írï n ï
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 4 of 11
View Article Online
DOI: 10.1039/C6TC00856A
!wÇL/[9
W}µŒvꢀo bꢀuꢁ
Çꢀꢄoꢁ íX ÇZꢁŒuꢀoU ‰Z}š}‰ZÇ•]ꢂꢀoU ꢀvꢃ ꢁoꢁꢂšŒ}ꢂZꢁu]ꢂꢀo ꢃꢀšꢀ (}Œ LŒr/IhU LŒrhI ꢀvꢃ LŒrtv/ÌX
T
C]
d
ꢀ
abs
ꢀ
em
[c]
N
[%]
PL
[d]
2
p
HOMO/LUMO
Compound
Ir-CHO
Ir-OH
o
[a]
[b]
[e]
[f]
[
[log0(nm)]
96 (7.43), 320sh (6.53), 365
4.37), 410sh (3.22)
98 (7.20), 319sh (5.64), 379
3.61)
02 (11.58), 324sh (9.81), 376
5.94), 406sh (5.14)
[nm]
[ꢀs]
[eV]
2
2
382
303
424
615
627
615
82
14
40
0.65
0.60
-5.20/-2.72
-5.10/-2.71
-5.21/-2.44
(
(
3
Ir-PQCz
0.51
(
[
a]
o
-1
[b]
Temperature with 5% weight loss measured by TGA with a heating rate of 10 C min under N
2
.
2 2
Measured in CH Cl at 298 K
-6
-
6
[c]
with a concentration of 10 M. Maximum emission wavelength, measured in CH
2
Cl
relative to Ir(piq)
2 2
Measured in degassed CH Cl at 298 K. Examined from the onset of oxidation and reduction potentials. sh = shoulder.
2
at 298 K with a concentration of 10 M and an
2
(acac) (NPL = 0.20) with 400 nm excitation.
[
d]
[e]
excitation wavelength of 400 nm. Measured in degassed CHCl
3
[
f]
p
operation. The longer 2 of the complexes usually results in The oxidation potentials were measured to be 0.44, 0.34
16
a more significant triplet-triplet annihilation. Such short and 0.45 V for Ir-CHO, Ir-OH and Ir-PQCz, respectively
§
lifetimes of the three red-emitting complexes can improve (Figure S13, ESI ). The corresponding HOMO and LUMO
spin-state mixing and decrease the probability of device values of the Ir(III) complexes were estimated to vary in
1
3
efficiency decay. Moreover, Ir-CHO and Ir-OH have the range of -5.10 ~ -5.21 eV and -2.44 ~ -2.72 eV,
longer 2 than Ir-PQCz, indicating that the introduction of respectively (Table 1). According to the analysis,
p
formyl-functionalized ppy can increase the 2
complexes based on PQCz as main ligands.
p
of Ir(III) integration of the electron-withdrawing ppy-CHO can
slightly affect the HOMO energy level. Moreover, the
reduction of formyl group in Ir-CHO to hydroxyl group
raised the HOMO level of Ir(III) complex, indicating a
Density functional theory calculations
To understand the electronic properties of the resulting greater propensity for Ir-OH to lose an electron.
Ir(III) complexes, DFT calculations for Ir-CHO, Ir-OH
and Ir-PQCz were performed using the Becke‘s three
parameterized Lee-Yang-Parr exchange functional
Compound
HOMO
4.81 eV
4.58 eV
4.51 eV
LUMO
-1.73 eV
-1.59 eV
-1.67 eV
17
(B3LYP) and a suite of Gaussian 09 programs. The split
valance basis set 6-31G was used for C, N, O, and H atoms,
while effective core potentials of a double zeta basis set
(
LanL2DZ) were utilized for Ir atom. These calculated
Ir(III) complexes had similar structures with octahedral
geometry. According to DFT calculations (Figure 3), the
HOMOs of Ir-CHO and Ir-OH were mainly located on
the carbazole moieties of the PQCz ligands, and d orbitals
of the iridium atom and phenyl moieties of the second
modified ppy cyclometalated ligands, whereas the lowest
unoccupied molecular orbitals (LUMOs) came from the
quinoline parts of PQCz. The LUMOs of Ir-CHO and Ir-
OH showed similar distributions. However, the
distributions of their HOMOs were slightly different on the
oxygen atom grafted on ppy. Therefore, the change of
substituents grafted on ppy can greatly adjust the HOMOs
without largely affecting the LUMOs. Compared with Ir-
OH, the incorporation of electron-withdrawing formyl
substituents onto Ir-CHO lowered the HOMO energy
level. Meanwhile, the HOMO/LUMO energy levels of Ir-
CHO, Ir-OH and Ir-PQCz were calculated to be -4.81/-
Ir-CHO
-
-
-
Ir-OH
1
.73 eV, -4.58/-1.59 eV and -4.51/-1.67 eV , respectively.
Ir-PQCz
Electrochemical properties
To evaluate the electronic properties of these materials,
cyclic voltammogram (CV) of the drop-coated films were
measured in 0.1 M tetra-n-butylammonium hexafluoro-
4 6
phosphate (Bu NPF ) nonaqueous acetonitrile solution.
C]PµŒꢁ ïX /ꢀoꢂµoꢀšꢁꢃ Ihah• ꢀvꢃ [Üah• (}Œ šZꢁ LŒ~LLLꢀ ꢂ}u‰oꢁÆꢁ•X
ð n WX bꢀuꢁXU îìíòU ììU írï
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

Page 5 of 11
Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C6TC00856A

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 6 of 11
View Article Online
DOI: 10.1039/C6TC00856A
!wÇL/[9
W}µŒvꢀo bꢀuꢁ
Çꢀꢄoꢁ îX 9[ ꢂZꢀŒꢀꢂšꢁŒ]•š]ꢂ• }( Œꢁꢃ h[95• ꢄꢀ•ꢁꢃ }v ꢀ •}oµš]}vr‰Œ}ꢂꢁ••ꢁꢃ ꢁu]šš]vP oꢀÇꢁŒX
V
on
Luminance
(cd/m )
LE
(cd/A)
PE
(lm/W)
EQE
(%)
ꢀ
max
[b]
Device
Emitter
2
[a]
[a]
[a]
[a]
(V)
(nm)
R1
R2
R3
Ir-CHO
Ir-OH
4.2
5.4
19871
15730
19251
14.3
7.1
6.6
2.4
8.4
608 (0.60, 0.40)
624 (0.63, 0.38)
616 (0.62, 0.38)
5.8
7.3
Ir-PQCz
4.9
8.7
3.9
[
a]
[b]
2
Maximum values of the devices. Data were collected at a luminance of 1000 cd/m .
3
resulting Ir(III) complexes. The LE and EQE (Firpic and Ir(ppy) ) as emissive dopants. As shown in
characteristics of R1-R3 are present in Figure 6c and 6d, Figure 4, the WOLEDs have the configuration of
respectively. With increasing current density, the ITO/PEDOT:PSS (40 nm)/Ir-CHO or Ir-OH or Ir-PQCz
3
efficiencies of R1-R3 present very low roll-off. Among the (x wt%): Ir(ppy) (0.2 wt%): Firpic (10 wt%): mCP (60
red devices, Ir-CHO-doped device R1 exhibited the nm)/TmPyPb (60 nm)/LiF (0.8 nm)/Al (80 nm) (Ir-CHO
highest performance with a maximum LE of 14.3 cd/A, based WOLED: W1; Ir-OH based WOLED: W2; Ir-
EQE of 8.4%, PE of 6.6 lm/W and a maximum brightness PQCz based WOLED: W3). We fixed mCP (100 wt%):
2
of 19871 cd/m , achieving comparable or even superior LE Ir(ppy)
3
(0.2 wt%): FIrpic (10 wt%) as the basis for the
and brightness compared with those solution-processed red matrix, and tuned the emitting color by controlling the
2
a,13,20
phosphorescent OLEDs ever reported.
The results blending ratio of red phosphors. White emissions with
2
indicate that the introduction of the electron-withdrawing good CIE coordinates of (0.32, 0.43) (at 1000 cd/m ) for
ppy-CHO can obviously improve the OLED performance. 0.55 wt% Ir-CHO-doped device (W1), (0.32, 0.41) (at
2
This unexpected result can be attributed to the 1000 cd/m ) for 0.6 wt% Ir-OH-doped device (W2) and
2
incorporation of ppy-CHO, which lowered LUMO without (0.33, 0.39) (at 1000 cd/m ) for 0.4 wt% Ir-PQCz-doped
largely affecting HOMO that aided to reduce the electron- device (W3), were successfully obtained, respectively.
injection barrier and matched better with that of the
The key data of W1-W3 are present in Figure 7 and
electron-injection layer for Ir-CHO based device.
summarized in Table 3. Figure 7a depicts the EL spectra of
2
To further investigate the EL properties of these Ir(III) W1-W3 at 1000 cd/m . Three peaks at 472, 500 and 580-
complexes, WOLEDs were fabricated using these red 596 nm (580 nm for W1 and 596 nm for W2-W3) were
phosphors in combination with the blue and green emitters observed, which corresponded to the emission from Firpic,
a)
b)
5
4
3
2
00
00
00
00
[
R1] Ir-CHO
R2] Ir-OH
R3] Ir-PQCz
[R1] Ir-CHO
R2] Ir-OH
[R3] Ir-PQCz
1
0
0
0
0
0
.0
.8
.6
.4
.2
10k
[
[
[
1
1
1
1
k
00
0
100
0
.0
4
00
500
600
700
800
0
3
6
9
12
15
18
Voltage (V)
Wavelength (nm)
c)
d)
1
0
8
6
4
2
1
5
2
9
6
3
0
[R1] Ir-CHO
R2] Ir-OH
R3] Ir-PQCz
[R1] Ir-CHO
R2] Ir-OH
[R3] Ir-PQCz
[
[
1
[
0
50
100
150 2
200
0
50
100
1502
200
Current density (mA/cm )
Current density (mA/cm )
C]PµŒꢁ òX tꢁŒ(}Œuꢀvꢂꢁ }( šZꢁ •}oµš]}vr‰Œ}ꢂꢁ••ꢁꢃ h[95• ꢄꢀ•ꢁꢃ }v LŒr/IhU LŒrhI ꢀvꢃ LŒrtv/ÌW ~ꢀꢀ 9[ •‰ꢁꢂšŒꢀU ~ꢄꢀ Wrër[ ꢂZꢀŒꢀꢂšꢁŒ]•š]ꢂ•U ~ꢂꢀ
9rꢂµŒŒꢁvš ꢃꢁv•]šÇ ꢀvꢃ ~ꢃꢀ 9v9rꢂµŒŒꢁvš ꢃꢁv•]šÇX
[
ò n WX bꢀuꢁXU îìíòU ììU írï
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 7 of 11
View Article Online
DOI: 10.1039/C6TC00856A
Çꢀꢄoꢁ ïX 9[ ꢂZꢀŒꢀꢂšꢁŒ]•š]ꢂ• }( íh[95• ꢄꢀ•ꢁꢃ }v ꢀ •}oµš]}vr‰Œ}ꢂꢁ••ꢁꢃ ꢁu]šš]vP oꢀÇꢁŒX
W}µŒvꢀo bꢀuꢁ
!wÇL/[9
CRI
Red
[a]
V
on
Luminance
LE
PE
(lm/W)
EQE
(%)
[c]
Device
B:G:R
2
[b]
[b]
[b]
[b]
CIE
[c]
Emitter
(V)
(cd/m )
(cd/A)
W1
W2
W3
Ir-CHO
Ir-OH
10:0.2:0.55
10:0.2:0.6
10:0.2:0.4
4.8
26397
26459
26667
26.1
19.4
19.1
10.8
7.8
10.9
(0.32, 0.43)
(0.32, 0.41)
(0.33, 0.39)
69
72
73
4.9
8.8
8.9
Ir-PQCz
4.6
7.2
[
a]
[b]
[c]
2
Mass ratio. Maximum values of the devices. Data were collected at a luminance of 1000 cd/m .
3
Ir(ppy) and the red dopants, respectively. The absence of introduction of the electron-withdrawing ppy-CHO
any other emission peaks indicates no exciplex formation apparently helps to improve the OLED performance.
at the interface between the charge transporting layer and
/
}vꢂoµ•]}v•
the emitting layer. The EL spectra of W1-W3 remained
almost the same while the operating voltage increased
from 6 to 13 V (Figure S15, ESI ). The J-V-L
In conclusion, a novel red-emitting Ir(III) complex Ir-
CHO with formyl-functionalized phenylpyridine ligands
was synthesized and characterized to investigate the
impact of the electron-withdrawing formyl group on the
optoelectronic properties. The resulting Ir(III) complexes
showed excellent thermal stability and can be fabricated
via solution processing. Remarkably, the introduction of
the electron-withdrawing ppy-CHO aids to enhance the
phosphorescence properties. Ir-CHO-doped red OLED
exhibited the highest performance, achieving a maximum
LE of 14.3 cd/A and EQE of 8.4%, which was superior to
those of Ir-OH and Ir-PQCz based red OLEDs.
Furthermore, WOLEDs with Ir-CHO as the red emitters
achieved an excellent high LE of 26.1 cd/A and EQE of
§
characteristics of W1-W3 are shown in Figure 7b. The
turn-on voltages of W1-W3 were very similar (4.8, 4.9 and
4
.6 V for W1-W3, respectively). W1 based on Ir-CHO
present higher current density at the same voltage
compared with those of W2 and W3, following a similar
trend as to the red OLEDs mentioned above. The
maximum LE for W1-W3 were recorded between 19.1 and
2
6.1 cd/A, and their corresponding EQE values were
between 8.8 and 10.9%. From W1-W3, LE and EQE was
slightly decreased by increasing current density (Figure 7c
and 7d). In comparison with the solution-processed white
21
phosphorescent OLEDs ever reported in the literature, the
present WOLEDs, especially for W1 based on Ir-CHO
with maximum LE of 26.1 cd/A and brightness of 26397
1
0.9%. Keeping the results in mind, we believe that this
study suggests a simple and useful strategy to design novel
Ir(III) complexes for highly efficient phosphorescent
OLEDs by exploring the potential of electron-withdrawing
2
cd/m , exhibited comparable or even superior device
performance. The result further confirm that the
a)
b)
[
[
[
W1] Ir-CHO
W2] Ir-OH
W3] Ir-PQCz
[W1] Ir-CHO
[W2] Ir-OH
[W3] Ir-PQCz
1.0
0.8
0.6
0.4
0.2
0.0
400
00
00
00
10k
1k
100
10
1
3
2
1
0
0
400
500
600
700
800
3
6
9
12
Wavelength (nm)
Voltage (V)
c)
d)
3
0
5
0
5
0
5
12
10
8
[
[
[
W1] Ir-CHO
W2] Ir-OH
W3] Ir-PQCz
[W1] Ir-CHO
[W2] Ir-OH
[W3] Ir-PQCz
2
2
1
1
6
4
2
0
0
50
100
1502
200
0
50
100
1502
200
Current density (mA/cm )
Current density (mA/cm )
C]PµŒꢁ óX tꢁŒ(}Œuꢀvꢂꢁ }( šZꢁ •}oµš]}vr‰Œ}ꢂꢁ••ꢁꢃ íh[95• ꢄꢀ•ꢁꢃ }v LŒr/IhU LŒrhI ꢀvꢃ LŒrtv/ÌW ~ꢀꢀ 9[ •‰ꢁꢂšŒꢀ ꢀš ꢀ oµu]vꢀvꢂꢁ }( íììì
î
ꢂꢃlu U ~ꢄꢀ Wrër[ ꢂZꢀŒꢀꢂšꢁŒ]•š]ꢂ•U ~ꢂꢀ [9rꢂµŒŒꢁvš ꢃꢁv•]šÇ ꢀvꢃ ~ꢃꢀ 9v9rꢂµŒŒꢁvš ꢃꢁv•]šÇX
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
WX bꢀuꢁXU îìíòU ììU írï n ó
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 8 of 11
View Article Online
DOI: 10.1039/C6TC00856A
!wÇL/[9
W}µŒvꢀo bꢀuꢁ
formyl functional groups.
nitrogen for 1 h and then quenched by careful addition of
water (4 mL). The crude mixture was extracted with
dichloromethane (3þ10 mL), dried over anhydrous
magnesium sulfate, and filtered. The filtrate was collected,
and the solvent was removed. The residue was purified by
column chromatography over silica using dichloromethane
9ƉꢁŒ]uꢁvšꢀo •ꢁꢂš]}v
Materials
All commercial reagents were used as received unless
otherwise noted. Tetrahydrofuran was distilled from
sodium and benzophenone under a nitrogen atmosphere
before use.
/
light petroleum mixtures (2:1-1:0) as eluent to give Ir-OH
1
as a red powder (140 mg, 92%). H NMR (400 MHz,
CDCl ): / 8.66 (s, 1H), 8.53 (s, 1H), 8.31-8.21 (m, 3H),
.05 (t, J = 8.3 Hz, 2H), 7.96 (d, J = 5.2 Hz, 1H), 7.79 (dd,
J = 7.8, 3.7 Hz, 3H), 7.75-7.50 (m, 13H), 7.46 (s, 1H), 7.30
3
8
Synthesis of Ir(III) complexes
Synthesis of Ir-CHO: A mixture of 3 (635 mg, 1.1 mmol),
iridium chloride hydrate (176 mg, 0.5 mmol), 2-
ethoxyethanol (6 mL) and water (2 mL) was stirred at 130
(t, J = 7.4 Hz, 3H), 7.19 (dd, J = 13.3, 6.7 Hz, 3H), 7.13-
7.07 (m, 3H), 7.06-6.90 (m, 4H), 6.85 (d, J = 9.0 Hz, 3H),
6.76-6.69 (m, 2H), 6.57 (d, J = 6.6 Hz, 1H), 6.44 (d, J =
9.7 Hz, 2H), 6.23 (d, J = 7.8 Hz, 2H), 4.43 (d, J = 5.1 Hz,
2H), 3.86 (d, J = 5.5 Hz, 2H), 3.18-2.93 (m, 2H), 1.80-1.73
o
C for 16 h under nitrogen. The reaction was allowed to
cool to room temperature and the resultant solid was
collected by filtration and purified by column
chromatography over silica with dichloromethane as eluent
to give chloro-bridged iridium dimer 4 (550 mg). The
intermediate 4 (550 mg, 0.2 mmol), 3-(pyridin-2-
yl)benzaldehyde (366 mg, 2 mmol), silver triflate (128 mg,
(
m, 1H), 1.55 (d, J = 15.1 Hz, 8H), 1.26 (s, 8H), 0.90 (ddd,
13
J = 14.0, 8.6, 5.5 Hz, 12H). C NMR (100 MHz, CDCl
3
):
/
1
1
1
1
1
6
3
1
166.66, 157.13, 149.49, 148.83, 148.38, 143.83, 140.54,
40.24, 139.53, 138.43, 135.62, 134.84, 132.43, 130.19,
29.79, 129.24, 128.98-128.24, 127.58, 126.49, 126.18,
25.91, 124.88, 124.43, 124.15, 122.54, 121.98, 119.92,
19.61, 119.12-118.64, 118.53, 118.21, 117.62, 117.10,
15.51, 114.93, 114.25, 109.63, 77.29, 77.03, 76.71, 70.83,
9.70, 66.07, 39.65-39.28, 34.24, 31.95, 31.45, 30.60-
0.11, 29.72, 29.54-29.01, 23.97-23.57, 23.11, 22.71,
4.17, 11.56-11.03, 1.09, 0.67. MALDI-TOF MS (m/z):
0
.5 mmol) and diglyme (5 mL) were deoxygenated by
placing under vacuum and back filling with nitrogen four
times and then heated at 110 C for 13 h under nitrogen
o
before cooling to ambient temperature. The mixture was
diluted with diethylether (40 mL). The organic layer was
washed with brine (100 mL), and dried over anhydrous
magnesium sulfat and filtered. The filtrate was collected
and the solvent was removed. The residue was purified by
column chromatography over silica using dichloromethane
Calcd for C94
523.92; Found: 1523.52.
Synthesis of Ir-PQCz: A mixture of 4 (275 mg, 0.1
5 3
H84IrN O , Exact Mass: 1523.62, Mol. Wt.:
1
/light petroleum mixtures (1:3-1:2) as eluent to give Ir-
mmol), silver triflate (128 mg, 0.5 mmol), 3 (574 mg, 1
mmol) and diglyme (0.5 mL) was deoxygenated by placing
under vacuum and back filling with nitrogen four times
1
CHO as a red powder (171 mg, 28%). H NMR (400 MHz,
DMSO): / 9.73 (s, 1H), 9.07 (d, J = 3.6 Hz, 2H), 8.58 (d, J
=
13.2 Hz, 2H), 8.34 (d, J = 8.0 Hz, 1H), 8.28-8.16 (m,
o
and then heated at 170 C for 20 h under nitrogen. The
3H), 8.00 (t, J = 7.3 Hz, 2H), 7.84 (dd, J = 12.0, 4.7 Hz,
1H), 7.73-7.54 (m, 13H), 7.34-7.11 (m, 9H), 7.05-6.90 (m,
6H), 6.84 (d, J = 9.0 Hz, 2H), 6.75 (dd, J = 11.9, 4.7 Hz,
1H), 6.66-6.60 (m, 2H), 6.37-6.28 (m, 3H), 3.78 (d, J = 5.7
reaction was allowed to cool to ambient temperature and
the mixture was purified by column chromatography over
silica using light petroleum/ethyl acetate (12:1) as eluent.
Further recrystallization using a dichloromethane /light
Hz, 2H), 3.15 (td, J = 9.1, 5.1 Hz, 1H), 3.02 (td, J = 9.4,
petroleum mixture afforded Ir-PQCz as a red powder (202
5
1
1
1
1
1
1
1
1
7
3
1
.1 Hz, 1H), 1.65 (dd, J = 11.9, 6.0 Hz, 1H), 1.43-1.20 (m,
7H), 0.91-0.80 (m, 12H). C NMR (100 MHz, CDCl ): /
3
1
mg, 53%). H NMR (400 MHz, CDCl
3
): / 8.44 (s, 3H),
1
3
8
3
.31 (d, J = 8.8 Hz, 3H), 8.15 (s, 3H), 8.00 (d, J = 7.6 Hz,
H), 7.71 (d, J = 7.7 Hz, 3H), 7.66-7.51 (m, 15H), 7.22 (dd,
92.05, 174.68, 166.51, 164.73, 160.39, 158.32, 157.85,
57.22, 149.43-149.15, 148.80, 148.42, 145.27, 143.75,
42.82, 140.57, 140.30, 139.36, 138.26, 137.68, 136.16,
35.36, 132.04, 129.74, 128.80, 128.29, 127.89, 127.16,
26.49, 126.14, 125.24, 125.06-124.53, 124.41, 122.88,
22.43, 120.06, 119.77, 119.32, 119.22-118.66, 118.66-
18.20, 117.97, 117.24, 115.43, 115.03, 114.27, 109.80,
7.33, 77.07, 76.75, 70.69, 69.70, 39.61-39.30, 30.66-
0.37, 30.25, 29.89-28.82, 23.98-23.62, 23.13, 22.75,
4.20, 11.61-10.92, 1.08. MALDI-TOF MS (m/z): Calcd
J = 14.5, 7.3 Hz, 6H), 7.12 (t, J = 7.3 Hz, 6H), 6.95 (d, J =
.8 Hz, 6H), 6.78 (t, J = 7.5 Hz, 3H), 6.70 (s, 3H), 6.40 (d,
J = 8.5 Hz, 6H), 3.25 (qd, J = 14.5, 7.9 Hz, 6H), 1.56 (s,
8
5
1
1
1
1
1
2
H), 1.30 (dd, J = 14.8, 9.7 Hz, 22H), 0.90 (ddd, J = 18.7,
1.0, 5.5 Hz, 19H). C NMR (100 MHz, CDCl ): / 166.33,
3
13
58.90, 157.28, 149.23, 148.46, 143.08, 140.26, 138.92,
38.53, 130.00, 129.79, 129.02, 128.51, 126.72, 125.95,
24.89, 124.12, 119.67, 118.62, 117.75, 114.77, 114.45,
09.73, 77.29, 77.03, 76.71, 70.16, 39.37, 30.43, 29.72,
9.22, 23.71, 23.11, 14.17, 11.24, 1.04. MALDI-TOF MS
5 3
for C94H82IrN O , Exact Mass: 1521.60, Mol. Wt.: 1521.91;
Found: 1521.96.
Synthesis of Ir-OH: Lithium aluminum hydride (1 M
in tetrahydrofuran, 0.13 mL) was added to a solution of Ir-
CHO (152 mg, 0.1 mmol) in tetrahydrofuran (3 mL). The
reaction mixture was stirred at ambient temperature under
6 3
(m/z): Calcd for C123H111IrN O , Exact Mass: 1912.83,
Mol. Wt.: 1913.45; Found: 1913.54.
Measurements
ô n WX bꢀuꢁXU îìíòU ììU írï
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 9 of 11
W}µŒvꢀo bꢀuꢁ
View Article Online
DOI: 10.1039/C6TC00856A
!wÇL/[9
NMR spectra were recorded on a Bruker Ultra Shield Plus were performed in ambient atmosphere without
1
13
4
00 MHz NMR ( H: 400 MHz, C: 100 MHz). MALDI- encapsulation.
TOF mass spectra measurements were carried out with a
Shimadzu AXIMA-CFR mass spectrometer. UV-visible
absorption spectra were recorded on a Shimadzu UV-3600.
UV-VIS-NIR spectrophotometer. PL spectra were
measured using a RF-5301PC spectrofluorophotometer.
Electrochemical behaviors were investigated by CV with a
standard three-electrode electrochemical cell in 0.1 M
!
ꢂlv}ÁoꢁꢃPꢁuꢁvš•
We acknowledge financial support of the National Key
Basic Research Program of China (973 Program,
2
014CB648300), the National Natural Science Foundation
of China (21422402, 20904024, 51173081, 61136003), the
Natural Science Foundation of Jiangsu Province
Bu
4
NPF
6
nonaqueous acetonitrile solution at room
(
BK20140060, BK20130037, BM2012010), Program for
Jiangsu Specially-Appointed Professors (RK030STP
5001), Program for New Century Excellent Talents in
temperature under nitrogen with a scanning rate of 50
mV/s. A platinum working electrode, a glassy carbon
electrode and an Ag/AgNO reference electrode were used.
3
1
University (NCET-13-0872), Specialized Research Fund
for the Doctoral Program of Higher Education
The CV curves were calibrated using ferrocene/
+
ferrocenium (Fc/Fc ) redox couple (4.8 eV below the
(20133223110008, and 20113223110005), the Synergetic
vacuum level) as the internal standard. The formal
potential of Fc/Fc+ was measured as 0.04 V against
Innovation Center for Organic Electronics and Information
Displays, the Priority Academic Program Development of
Jiangsu Higher Education Institutions (PAPD), the NUPT
+
Ag/Ag . Thus, HOMO and LUMO energy levels could be
calculated according to: EHOMO = -e(Eox + 4.76 V), ELUMO
"1311 Project", the Six Talent Plan (2012XCL035), the
=
-e(Ered + 4.76 V); where Eox and Ered is the onset
3
33 Project (BRA2015374) and the Qing Lan Project of
oxidation and reduction potential, respectively. The
Jiangsu Province.
thermal analyses were undertaken with Shimadzu DTG-
o
b}šꢁ• ꢀvꢃ Œꢁ(ꢁŒꢁvꢂꢁ•
6
min
0A and DSC-60A equipment at a heating rate of 10 C
-1
under nitrogen. Measurements of surface
1
(a) S.-C. Lo, R. E. Harding, C. P. Shipley, S. G.
Stevenson, P. L. Burn and I. D. W. Samuel, J. Am.
Chem. Soc., 2009, 131, 16681; (b) Y. Zhu, C. Gu, S.
Tang, T. Fei, X. Gu, H. Wang, Z. Wang, F. Wang, D.
Lu and Y. Ma, J. Mater. Chem., 2009, 19, 3941; (c) Q.
Wang, I. W. H. Oswald, X. Yang, G. Zhou, H. Jia, Q.
Qiao, Y. Chen, J. Hoshikawa-Halbert and B. E. Gnade,
Adv. Mater., 2014, 26, 8107; (d) G. Li, J. Ecton, B.
Obrien and J. Li, Org. Electron., 2014, 15, 1862; (e) P.-
K. Chow, G. Cheng, G. S. M. Tong, W.-P. To, W.-L.
Kwong, K.-H. Low, C.-C. Kwok, C. Ma and C.-M. Che,
Angew. Chem. Int. Ed.,2015, 54, 2084; (f) W.-Y. Lai, M.
N. Balfour, J. W. Levell, A. K. Bonsal, P. L. Burn, S. -C.
Lo and I. D. W. Samuel, Macromolecules, 2012, 45,
morphology were conducted by Bruker icon Dimension
with Scan Asyst AFM. WXRD were measured by Bruker
D8 ADVACE.
Fabrication of OLEDs
The red and white OLEDs were fabricated with a structure
of ITO/PEDOT:PSS (40nm)/EML (40 nm)/TmPyPb (60
nm)/LiF (0.8 nm)/Al (80 nm). The ITO substrates were
pre-cleaned with routine procedures and treated by UV-
ozone for 4 min. A layer of PEDOT:PSS was deposited on
the ITO substrate via spin coating to form a hole-injection
layer/hole transport layer (HIL/HTL). The PEDOT:PSS-
coated substrates were dried at 120°C in a vacuum oven
for 15 min. In the next fabrication step the HIL/HTL
coated substrates were transferred into a nitrogen filled
glove box and the EML was spin-coated on the top. Small
molecules, namely the host materials CBP and TCTA (7:3
in weight) were dissolved in chlorobenzene (CB) to obtain
the solution (15 mg/mL) and 6 wt% of the phosphorescent
emissive dopant Ir-CHO, Ir-OH and Ir-PQCz were
separately added. As for the white EML, the ratio of mCP
2
963; (g) W.-Y. Lai, J. W. Levell, M. N. Balfour, P. L.
Burn, S.-C. Lo and I. D. W. Samuel, Polym. Chem.,
012, 3, 734; (h) J.-X. Cai, T.-L. Ye, X.-F. Fan, C.-M.
2
Han, H. Xu, L.-L. Wang, D.-G. Ma, Y. Lin, P.-F. Yan, J.
Mater. Chem., 2011, 21, 15405; (i) H. Xu, D.-H. Yu, L.-
L. Liu, P.-F. Yan, L.-W. Jia, G.-M. Li, Z.-Y. Yue, J.
Phys. Chem. B, 2010, 114, 141.
(a) X. Liu, S. Wang, B. Yao, B. Zhang, C.-L. Ho, W.-Y.
Wong, Y. Cheng and Z. Xie, Org. Electron., 2015, 21, 1;
2
3
to FIrpic, Ir(ppy) was fixed at 100:10:0.2 (w/w/w), and
the emission spectra were solely tuned by changing the
concentration of the three red dopants. Then, the EML was
spin-coated and annealed at 80°C for 20 min. A device
structure of TmPyPb (60 nm)/LiF (0.8 nm)/Al (80 nm) was
thermally deposited in sequence in a vacuum chamber at a
(
b) H. Wu, G. Zhou, J. Zou, C.-L. Ho, W.-Y. Wong, W.
Yang, J. Peng and Y. Cao, Adv. Mater., 2009, 21, 4181;
c) J. W. Levell, W.-Y. Lai, R. J. Borthwick, P. L. Burn,
S.-C. Lo and I. D. W. Samuel, New J. Chem., 2012, 36,
07; (d) J. W. Levell, S. Zhang, W.-Y. Lai, S.-C. Lo, P.
(
4
-4
base pressure of less than 5þ10 Pa. The J-V-L
characteristics were measured by a keithley source
measure unit (Keithley 2602) and a calibrated luminance
meter. The EL spectra of the devices were measured by a
spectra-scan PR655 spectrophotometer. All measurements
L. Burn and I. D. W. Samuel, Opt. Express, 2012, 20,
A213; (e) W.-Y. Lai, J. W. Levell, A. C. Jackson, S.-C.
Lo, P. V. Bernhardt, I. D. W. Samuel and P. L. Burn,
Macromolecules, 2010, 43, 6986; (f) W.-Y. Lai, J. W.
Levell, P. L. Burn, S.-C. Lo and I. D. W. Samuel, J.
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
WX bꢀuꢁXU îìíòU ììU írï n õ
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•
Journal of Materials Chemistry C
Page 10 of 11
View Article Online
DOI: 10.1039/C6TC00856A
!wÇL/[9
W}µŒvꢀo bꢀuꢁ
Mater. Chem., 2009, 19, 4952; (g) H. Xu, R. F. Chen, Q. 12 A. B. Tamayo, B. D. Alleyne, P. I. Djurovich, S.
Sun, W.-Y. Lai, Q. Q. Su, W. Huang, X. G. Liu, Chem.
Soc. Rev., 2014, 43, 3259; (h) F. Q. Han, X. L. Zhang, J.
Lamansky, I. Tsyba, N. N. Ho, R. Bau and M. E.
Thompson, J. Am. Chem. Soc., 2003, 125, 7377.
Zhang, Y. Wei, X. W. Zhang, W. Huang, H. Xu, Chem. 13 C.-L. Ho, W.-Y. Wong, Z.-Q. Gao, C.-H. Chen, K.-W.
Commun., 2016, DOI: 10.1039/C6CC01414C; (i) L.
Ying, C.-L. Ho, H. B. Wu, Y. Cao, W.-Y. Wong, Adv.
Mater., 2014, 26, 2459.
Cheah, B. Yao, Z. Xie, Q. Wang, D. Ma, L. Wang, X.-
M. Yu, H.-S. Kwok and Z. Lin, Adv. Funct. Mater.,
2008, 18, 319.
3
(a) R. N. Bera, N. Cumpstey, P. L. Burn and I. D. W. 14 (a) C. Yang, X. Zhang, H. You, L. Zhu, L. Chen, L.
Samuel, Adv. Funct. Mater., 2007, 17, 1149; (b) M. A.
Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley,
M. E. Thompson and S. R. Forrest, Nature, 1998, 395,
Zhu, Y. Tao, D. Ma, Z. Shuai and J. Qin, Adv. Funct.
Mater., 2007, 17, 651; (b) S. Lamansky, P. Djurovich,
D. Murphy, F. Abdel-Razzaq, H.-E. Lee, C. Adachi, P.
E. Burrows, S. R. Forrest and M. E. Thompson, J. Am.
Chem. Soc., 2001, 123, 4304.
1
51; (c) M. A. Baldo, D. F. O'Brien, M. E. Thompson
and S. R. Forrest, Phys. Rev. B, 1999, 60, 14422; (d) C.
Adachi, M. A. Baldo, M. E. Thompson and S. R. Forrest, 15 H. U. Kim, J.-H. Jang, W. Song, B. J. Jung, J. Y. Lee
J. Appl. Phys., 2001, 90, 5048; (e) M. Ikai, S. Tokito, Y. and D.-H.Hwang, J. Mater. Chem. C, 2015, 3, 12107.
Sakamoto, T. Suzuki and Y. Taga, Appl. Phys. Lett., 16 (a) M. A. Baldo, C. Adachi and S. R. Forrest, Phys. Rev.
2
001, 79, 156; (f) S. C. Lo, N. A. H. Male, J. P. J.
B, 2000, 62, 10967; (b) E. B. Namdas, A. Ruseckas, I.
D. W. Samuel, S. C. Lo and P. L. Burn, Appl. Phys.
Lett., 2005, 86.
Markham, S. W. Magennis, P. L. Burn, O. V. Salata and
I. D. W. Samuel, Adv. Mater., 2002, 14, 975.
4
5
(a) H. J. Bolink, E. Coronado, S. G. Santamaria, M. 17 M.J. Frisch et al., Gaussian 09, Revision B.01;
Sessolo, N. Evans, C. Klein, E. Baranoff, K. Gaussian Inc.:Wallingford, CT, 2010.
Kalyanasundaram, M. Graetzel and M. K. Nazeeruddin, 18 X. Zhang, X. Guo, Y. Chen, J. Wang, Z. Lei, W.-Y Lai,
Chem. Commun., 2007, 3276; (b) P. Coppo, E. A. Q. Fan and W. Huang, J. Lumin., 2015, 161, 300.
Plummer and L. De Cola, Chem. Commun., 2004, 1774; 19 I. Avilov, P. Minoofar, J. Cornil and L. De Cola, J. Am.
c) T. Sajoto, P. I. Djurovich, A. Tamayo, M. Chem. Soc., 2007, 129, 8247.
Yousufuddin, R. Bau, M. E. Thompson, R. J. Holmes 20 (a) S.-J. Lee, J.-S. Park, M. Song, I. A. Shin, Y.-I. Kim,
(
and S. R. Forrest, Inorg. Chem., 2005, 44, 7992.
K. Hasan, A. K. Bansal, I. D. W. Samuel, C. Roldan-
Carmona, H. J. Bolink and E. Zysman-Colman, Sci.
Rep., 2015, 5;
H.-J. Seo, K.-M. Yoo, M. Song, J. S. Park, S.-H. Jin, Y. I.
Kim and J.-J. Kim, Org. Electron., 2010, 11, 564;
S. Lee, S.-O. Kim, H. Shin, H.-J. Yun, K. Yang, S.-K.
Kwon, J.-J. Kim and Y.-H. Kim, J. Am. Chem. Soc.,
J. W. Lee, J.-W. Kang, Y.-S. Gal, S. Kang, J. Y. Lee,
S.-H. Jung, H.-S. Kim, M.-Y. Chae and S.-H. Jin, Adv.
Funct. Mater., 2009, 19, 2205; (b) J. Ding, J. Lu, Y.
Cheng, Z. Xie, L. Wang, X. Jing and F. Wang, Adv.
Funct. Mater., 2008, 18, 2754.
6
7
21 (a) R. Wang, D. Liu, R. Zhang, L. Deng and J. Li, J.
Mater. Chem. , 2012, 22, 1411; (b) Y. Li, W. Zhang, L.
Zhang, X. Wen, Y. Yin, S. Liu, W. Xie, H. Zhao and S.
Tao, Org. Electron., 2013, 14, 3201; (c) C.-C. Fan, M.-
H. Huang, W.-C. Lin, H.-W. Lin, Y. Chi, H.-F. Meng,
T.-C. Chao and M.-R. Tseng, Org. Electron., 2014, 15,
517.
2
013, 135, 14321.
8
(a) D. W. Boldridge, B. L. Justus and G. W. Scott, J.
Chem. Phys., 1984, 80, 3179; (b) S. Hirayama and T.
Kobayashi, Chem. Phys. Lett., 1977, 52, 55; (c) S.
Hirayama, J. Chem. Soc., Faraday Trans.1, 1982, 78,
2
411; (d) C. V. Kumar, S. K. Chattopadhyay and P. K.
Das, Photochem. Photobiol., 1983, 38, 141; (e) S. K.
Lower and M. A. El-Sayed, Chem. Rev., 1966, 66, 199;
(f) M. Baba, J. Phys. Chem. A, 2011, 115, 9514; (g) W.
G. Herkstroeter, A. A. Lamola and G. S. Hammond, J.
Am. Chem. Soc., 1964, 86, 4537.
9
(a) A. Beeby, S. Bettington, I. D. W. Samuel and Z.
Wang, J. Mater. Chem., 2003, 13, 80; (b) S. Mukherjee,
P. Thilagar, Chem. Commun., 2015, 51, 10988.
1
0 (a) A. K. Agrawal and S. A. Jenekhe, Chem. Mater.,
992, 4, 95; (b) S. J. Lee, J. S. Park, K.-J. Yoon, Y.-I.
1
Kim, S.-H. Jin, S. K. Kang, Y.-S. Gal, S. Kang, J. Y.
Lee, J.-W. Kang, S.-H. Lee, H.-D. Park and J.-J. Kim,
Adv. Funct. Mater., 2008, 18, 3922.
1
1 J. P. Gunning, J. W. Levell, M. F. Wyatt, P. L. Burn, J.
Robertson and I. D. W. Samuel, Polym. Chem., 2010, 1,
7
30.
íì n WX bꢀuꢁXU îìíòU ììU írï
ÇZ]• i}µŒvꢀo ]• ž ÇZꢁ w}Çꢀo {}ꢂ]ꢁšÇ }( /Zꢁu]•šŒÇ îìÆÆ
toꢁꢀ•ꢁ ꢃ} v}š ꢀꢃiµ•š uꢀŒP]v•

Page 11 of 11
Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C6TC00856A