Sublimable cationic Ir(iii) phosphor using chlorine as a counterion for high-performance monochromatic and white OLEDs

Article abstract of DOI:10.1039/c8cc06201c

Different from the previous design strategy, herein, a cationic Ir(iii) complex ([(ptbi)₂Ir(bisq)]Cl) with a small chlorine as the counterion was synthesized, which realized the formation of a solid film via a vacuum-deposition process. The whi

Full text of DOI:10.1039/c8cc06201c

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Sublimable cationic Ir(III) phosphor using chlorine as counterion
for high-performance monochromatic and white OLEDs
Lei Ding,a Chun-Xiu Zang,b Hui-Ting Mao,a Guo-Gang Shan,*a Li-Li Wen,a Hai-Zhu Sun,*a Wen-Fa
Xie,*b and Zhong-Min Su*ac
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
Different from the previous design strategy, herein, a cationic Ir(III) phosphor as emitting layer in multi-layered OLEDs,
Ir(III) complex ([(ptbi)2Ir(bisq)]Cl) with small chlorine as the achieving current efficiency (CE) of 19.7 cd A−1 and external
counterion was synthesized, which realized the formation of solid- quantum efficiency (EQE) of 6.5%.5a More recently, Ma et al.
film via vacuum-deposited process. The white OLED by employing demonstrated a strategy to construct sublimable cationic Ir(III)
it as orange-emitting layer achieved excellent performances with phosphors by introducing large steric hindrance counter-ions
brightness of 50122 cd m-2, CE of 25.5 cd A-1, EQE of 13.1%, into complexes (Scheme 1).5b Despite the great progress
accompanied with low CE efficiency roll-off of 4.7%. These are the achieved, the study on this issue is still in its infancy, and the
best results among evaporated cationic Ir(III)-based white OLED different molecular design concepts and/or new material
reported so far.
systems are highly desired but remain a challenge.
White organic light-emitting diodes (WOLEDs) have drawn
much attention due to the immense potential for highly
efficient flat-panel displays and solid-state lighting.6-10 In 2016,
Ma et al. successfully realized the fabrication of ionic Ir(III)-
based WOLEDs by vacuum evaporation deposition, showing
the CE of 3.4 cd A-1 and EQE of 1.8%, respectively.5d However,
these device performances are far from satisfaction, which lag
behind their neutral counterparts, particularly for maximum
brightness and efficiencies. On the other hand, although many
reported OLEDs exhibit high efficiencies, they usually undergo
Iridium(III) complexes have attracted much attention in the
field of optoelectronic and biological media because of their
high photoluminescence quantum yield (PLQY), short radiative
lifetime, good thermal and photostability, and facile colour
tunability across the whole visible spectrum.1 As superior
phosphorescent emitters in organic light-emitting diodes
(OLEDs), they achieve internal quantum efficiency of nearly
100% by harvesting both single and triplet excitons.2 In
comparison with the neutral counterparts, ionic Ir(III)
complexes possess unique characteristics such as ease of
molecular design, synthesis, and purification as well as good
solubility, making them possible to find applications in
solution-processed light emitting electrochemical cells (LECs).3
In view of the ionic nature and low vapour pressure, however,
conventional cationic Ir(III) complexes seldom realize the
a
serious efficiency roll-offs at high current densities.7
Consequently, it is necessary to fabricate OLEDs with high
efficiency and small efficiency roll-off simultaneously.
Furthermore, the ENERGY STAR rules that the color rendering
index (CRI) of qualified lamps cannot be less than 80 and the
saturated red R9 value should be greater than 0.8 These are
the important parameters for WOLEDs used for lighting
illumination but are usually less reported.
formation of film via vacuum evaporation method that has
4
been proved to have high accuracy and stability
.
Recently,
some efforts have been made to develop sublimable cationic
Ir(III) complexes suitable for OLEDs manufacture.5 In 2007,
Wong et al. reported the first example of sublimable cationic
Our previous work has focused on the design of cationic
Ir(III) complexes as sensors, and excellent emitting layer for
LECs, et al. Herein, we obtained cationic Ir(III) complex that can
be vacuum evaporated by introducing a small volume counter-
ion such as Cl- (Scheme 1). Employing it as the emitting-layer,
monochromatic orange-emitting OLED exhibits excellent
performance with a maximum CE of 17.8 cd A-1 and EQE of
10.5%. Optimized WOLED shows a maximum brightness of
50122 cd m -2, a maximum CE of 25.5 cd A-1, EQE of 13.1% and
tiny CE efficiency roll-off of 4.7%, all of which are the best
results of the reported cationic Ir(III)-based WOLED by now.
The resulting WOLED well satisfy the premise of colour
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Scheme 1. Chemical structures of reported sublimable cationic Ir(III) complexes and studied in this work.
purity stipulated by the ENERGY STAR with CRI of 80 and R9 > potential to be fabricated WOLEDs with high CRI in
0. combination with blue-emitting and green-emitting
Cl was easily synthesized with a high yield of materials.11 PL spectrum of [(ptbi
2Ir bisq) Cl measured at 77 K
bisq) Cl realized outstanding thermal stability exhibits a maximum emission peak at 580 nm (Fig. S5, ESI†).
[
(ptbi
)
2Ir
(
bisq)
]
)
(
]
68%. [(ptbi
)
2Ir
(
]
with high decomposition temperature of 337 °C, and no glass Because solvent reorganization in solution at 77 K cannot
transition peak was observed on its DSC curve (Figs. S1 and S2, stabilize the CT states,12 the energy level of the transition
ESI†). In addition, the 1H-NMR measurements before and after increases,13 leading to the blue-shifted emission of about 20
vapor deposition were carried out (Fig. S3, ESI†). The data nm compared with that at R.T.. The emission lifetimes (τp) of
suggested that [(ptbi
)2Ir
(bisq)]Cl barely decomposed during
[(ptbi)2Ir(bisq)]Cl are 0.67 and 0.86 μs in the solution and film,
the vacuum evaporation, demonstrating its good sublimability. respectively, as shown in Table S1. The shorter lifetimes
indicate that [(ptbi)2Ir(bisq)]Cl may suppress the serious
triplet-triplet annihilation (TTA) effect14 and improve the
transition efficiency from singlet to triplet state.15
Interestingly, PLQY of [(ptbi)2Ir(bisq)]Cl in solution is 17.8%,
while it increases to 32.4% in neat film, which is as twice times
as that in acetonitrile (10-5 M). From the radiative (kr) and
nonradiative (knr) rate constants data shown in Table S1, kr
increases and knr decreases after film formation, which are
responsible for the higher PLQY of [(ptbi
)
2Ir
(
bisq)]Cl in neat
film.16 It is clear that the emission of [(ptbi
)2Ir
(
bisq)]Cl in the
solution is weak, however, PLQY is enhanced in the solid state,
probably due to its inherent aggregation-induced
phosphorescent emission (AIPE) effect.17 In order to estimate
Fig.
acetonitrile solution (10
photographs of (ptbi 2Ir bisq)]Cl in acetonitrile solution and neat film.
1 Ultraviolet-visible absorption and PL spectra of [(ptbi)2Ir(bisq)]Cl in
-5
M) and neat film at 298 K. Inset: luminescence the electron density distributions and energy levels of the
[
)
(
orbitals, theoretical calculations of [(ptbi)2Ir(bisq)]Cl were
performed. The highest occupied molecular orbital (HOMO)
and lowest unoccupied molecular orbital (LUMO) levels and
Absorption and photoluminescent (PL) spectra of
(ptbi 2Ir bisq) Cl at room temperature (R.T.) are presented in
[
)
(
]
distributions of [(ptbi
)2Ir(bisq)]Cl are shown in Fig. S6 (ESI†).
Fig. 1. The strong absorption bands ranging from 200 to 325
nm are ascribed to spin-allowed 1π–π* transitions from the
ligands, while the weaker bands from 325 nm extending to 475
nm are attributed to metal-to-ligand charge-transfer (1MLCT),
For [(ptbi)2Ir(bisq)]Cl, the HOMO (-5.81 eV) is localized on the
Ir(III) atom and main ligands, whereas the LUMO (-2.70 eV) is
distributed over the whole ancillary ligand with a small part on
the Ir(III) atom. The triplet excited state (T1) was calculated to
understand the transition characteristic. As shown in Fig. S6
3
3
3
ligand-to-ligand charge-transfer (1LLCT), MLCT, LLCT and LC
3π-π* transitions.9 As shown in Fig. 1, the PL spectra of
(ESI†) and Table S2, it is found that T1 of [(ptbi)2Ir(bisq)]Cl is
[(ptbi)2Ir(bisq)]Cl in acetonitrile solution and neat film
from HOMO-2 to LUMO transition with a contribution of
measured at R.T. show similar peak position of 608 and 610
nm, respectively. The broad and structureless PL spectra
indicate that its emissive excited state predominantly results
from MLCT and/or LLCT rather than LC π-π*characters.10 In
addition, there is no significant change in emission spectrum
for the spin-coated film and evaporated film, as shown in Fig.
S4. The broad full width at half maximum (FWHM) of both
solution and neat film are about 94 nm and 85 nm, showing its
approximately 78%. The orbital analysis indicates that the T1
3
Cl contains a mixture of LLCT and
emission of [(ptbi
)
2Ir
(
bisq)
]
3MLCT transitions, which agrees well with the photophysica
results discussed above.
l
3
3
3
3
Cyclic voltammetry (CV) measurements were also recorded
to explore its electrochemical property (Table S1). The peak
appeared at 0.37 V is attributed to the oxidation of the Ir(III)
2 | J. Name., 2012, 00, 1-3
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Table 1 EL performances for monochromatic and white OLEDs
a)
d)
Device
Vturn-on
[V]
CEb), c)
PEb), c)
EQEb), C)
[%]
Efficiency roll-offs
[%]
Lmax
CIE
CRIe)
R9e)
[cd A−1
]
[lm W−1
]
[cd m−2
]
[(x, y)]
CE
PE
EQE
monochromatic
W4
3.3
3.6
17.8/14.4
25.5/24.3
15.4/8.4
10.5/8.4
19.1
4.7
45.5
23.7
20.0
7.0
25035
50122
(0.60,0.40)
(0.49,0.45)
/
/
17.3/13.2
13.1/12.2
80
4
a) Measured at 1 cd m -2 b) Maximum efficiencies. c) Efficiencies of the devices at 1000 cd m -2 d) Maximum luminance. e) Values of the devices at 7 V
. .
metal cationic site [Ir(III)→ [(ptbi
Ir(IV)].18 Consequently, the HOMO nm)/TCTA (5 nm)/DCzPPy:
)
2Ir
(
bisq)
]
Cl (10%,
O
B
of [(ptbi)2Ir(bisq)]Cl is determined to be -5.17 eV. LUMO is - nm)/DCzPPy:Ir(ppy)3 (10%, G nm)/DCzPPy:FIrpic (10%
2.83 eV, calculating from the HOMO energy level and the nm)/TmPyPB (40 nm)/LiF(0.5 nm)/Ag:Mg (Fig. S9). Generally,
absorption spectrum. These electrochemical data provide the the excellent WOLEDs will have high efficiency, low efficiency
useful information to design and fabricate devices.
roll-off and high CRI, etc. To obtain WOLEDs with high
To investigate the potential of the cationic Ir(III) complex in performance that install above parameters together, herein,
the device performance, vacuum deposition-processed OLED device structures were systematically optimized by adjusting
was fabricated by using [(ptbi
structure of OLED is ITO/MoO3 (3 nm)/TAPC (35 nm)/TCTA (5
nm)/DCzPPy: [(ptbi 2Ir bisq)]Cl (10%, 20 nm)/TmPyPB (40
)2Ir(bisq)]Cl as the dopant. The thickness of each emitting layer.
)
(
nm)/LiF (0.5 nm)/Mg:Ag (Fig. 2a). Herein, MoO3, TAPC, TCTA,
TmPyPB, LiF and DCzPPy (2,6-bis(3-(9H-carbazol-9-yl)phenyl)-
pyridine
) were employed as hole-injecting layer, hole-
transporting layer, electron-blocking layer, electron-
transporting layer, electron-injecting layer and host material,
respectively. The corresponding EL data are depicted in Table 1
.
The morphology of both non-doped evaporated film and
doped evaporated film were also tested by atomic force
microscope (AFM). As shown in AFM images (Fig. S7, in ESI),
they exhibit no special aggregation behaviors with the root
mean square (RMS) values of 0.747 nm and 0.507 nm for non-
doped and doped evaporated film, respectively.
Fig. 2 (a) The general structure of OLED (b) EL spectra (c) Current-voltage-
luminance (J-V-L) (d) EQE, PE, CE curves.
From Fig. 2b, [(ptbi)2Ir(bisq)]Cl-based OLED shows orange
emission peak at 589 and 622 nm, with CIE coordinates of
(0.60, 0.40). Similar to EL spectrum, the PL spectrum of
Fig. S10 (ESI†) shows the electroluminescent properties for
[
(ptbi
and 623 nm, indicating that the complete charge and/or energy
transfer occurs from the host to the (ptbi 2Ir bisq) Cl upon
excitation (Fig. S8, ESI†) An obviously blue-shifted emission of
)2Ir(bisq)]Cl in the co-evaporated film is peaked at 590
W1-W3 and corresponding device parameters are depicted in
Table S4 (ESI†). From device W1 to W3, the thickness of FIrpic
layer is changed from 25 nm to 17 nm. After optimization, W3
shows negligible efficiency roll-off of 2.7% at 1000 cd m-2,
which indicates that thinner FIrpic layer facilitates the
electron-transport. According to schematic energy-level
[
)
(
]
.
20 nm from the PL spectrum in neat film is observed, which is
probably caused by rigidochromic effect as its dominant 3MLCT
excited-state characteristic.19 The monochromatic device
exhibits maximum luminance (Lmax) of 25035 cd m-2, a
maximum CE of 17.8 cd A-1, power efficiency (PE) of 15.4 lm W-
1, and EQE of 10.5%. Although the efficiency decrease at
brightness of 1000 cd m-2, it still remains CE of 14.4 cd A-1, PE
diagram of WOLEDs
(Fig. 3a), electrons and holes are
effectively confined within the EML and the main carrier
recombination zone is located at the interface between orange
and green emitting layers. Thereby, it is believed that WOLEDs
performances will be further enhanced via ingeniously
adjusting the orange and green emitting layers simultaneously.
More obvious enhancements in efficiency can be obtained
of 8.4 lm W-1, respectively. [(ptbi
)2Ir(bisq)]Cl exhibits excellent
EL performance in comparison with reported cationic Ir(III)-
based monochromatic OLEDs, which will be in favor of its
potential to construct WOLEDs (Table S3, ESI†).
after
optimization
of
device
architectures.
All
electroluminescent properties are summarized in Fig. 3 and
Table 1. As shown in Fig. 3, a starting voltage of 3.6 V, a
maximum brightness of 50122 cd m-2, a maximum CE of 25.5
cd A-1, a maximum PE of 17.3 lm W-1 and EQE of 13.1% are
realized in W4. At luminance of 1000 cd m-2, W4 has a
To validate this issue, we fabricated WOLEDs by using
[(ptbi)2Ir(bisq)]Cl as the complementary emitter in
combination with blue-emitting FIrpic and green-emitting
Ir(ppy)3. The device structure is ITO/MoO3 (3 nm)/TAPC (35
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here will open a new avenue to construct efficient sublimable
cationic Ir(III) complexes in future.
decrease in efficiency due to TTA effect and field-induced
quenching effect, but it still remains CE of 24.3 cd A-1, PE of
13.2 lm W-1 and EQE of 12.2%. This is the highest reported
efficiency of WOLEDs based on cationic Ir(III) complexes (Table
S5). Furthermore, because of the broad FWHM of
The authors gratefully acknowledge financial support from the
NSFC (21574018, 51433003, 21303012 and 21273030), the 973
Program (2013CB834801), and the Science and Technology
Development Planning of Jilin Province (20130522167JH).
[(ptbi)2Ir(bisq)]Cl, the obtained CRI of WOLEDs are 80 and R9
are greater than 0.
Conflicts of interest
There are no conflicts to declare.
Notes and references
1 a) H. Na and T. S. Teets, J. Am. Chem. Soc., 2018, 140, 6353; b) R.
D. Costa, E. Orti, H. J. Bolink, F. Monti, G. Accorsi, N. Armaroli,
Angew. Chem. Int. Ed. 2012, 51, 8178.
2 a) P. T. Chou and Y. Chi, Chem. Eur. J., 2007, 13, 380; b) T. Zhang, C.
Shi, C. Zhao, Z. Wu, J. Chen, Z. Xie, D. Ma, ACS Appl. Mater.
Interfaces 2018, 10, 8148.
3 M. Lenes, G. Garcia-Belmonte, D. Tordera, A. Pertegás, J. Bisquert,
H. J. Bolink, Adv. Funct. Mater., 2011, 21, 1581.
4 a) Y. Zhang , J. Lee , S. R. Forrest , Nat. Commun. 2014, 5, 5008; b)
M. Sessolo, D. Tordera, H. J. Bolink, ACS Appl. Mater. Interfaces
2013, 5, 630.
5 a) W. Y. Wong, G. J. Zhou, X. M. Yu, H. S. Kwok and Z. Lin, Adv.
Funct. Mater., 2007, 17, 315; b) D. Ma, Y. Qiu and L. Duan, Adv.
Funct. Mater., 2016, 26, 3438; c) F. Zhang, Y. Guan, S. Wang, S. Li,
F. Zhang, Y. Feng, S. Chen, G. Cao and B. Zhai, Dyes Pigments,
2016, 130, 1; d) D. Ma, L. Duan and Y. Qiu, J. Mater. Chem. C,
2016, 4, 5051.
6 a) B. W. D'Andrade and S. R. Forrest, Adv. Mater., 2004, 16, 1585;
b) S. Wang, Q. Yang, B. Zhang, L. Zhao, D. Xia, J. Ding, Z. Xie, L.
Wang, Adv. Optical Mater., 2017, 5, 1700514.
7 a) R. Cui, W. Liu, L. Zhou, X. Zhao, Y. Jiang, Y. Zheng, H. Zhang, J.
Mater. Chem. C, 2017, 5, 2066; b) Z. Wang, X.-L. Li, Z. Ma, X. Cai,
C. Cai, S.-J. Su, Adv. Funct. Mater., 2018, 28, 1706922.
8 a) M. Du, Y. Feng, D. Zhu, T. Peng, Y. Liu, Y. Wang, M. R. Bryce, Adv.
Mater., 2016, 28, 5963; b) H. Cao, G. Shan, X. Wen, H. Sun, Z. Su,
R. Zhong, W. Xie, P. Li, D. Zhu, J. Mater. Chem. C, 2013, 1, 7371.
9 M. K. Nazeeruddin, R. Humphry-Baker, D. Berner, S. Rivier, L.
Zuppiroli, M. Graetzel, J. Am. Chem. Soc., 2003, 125, 8790.
10 a) M. G. Colombo, H. U. Guedel, Inorg. Chem. 1993, 32, 3081; b)
S. G. Nelson, C. Zhu, X. Shen, J. Am. Chem. Soc., 2004, 126, 14.
11 P. Tao, W.-L. Li, J. Zhang, S. Guo, Q. Zhao, H. Wang, B. Wei, S.-J.
Liu, X.-H. Zhou, Q. Yu, B.-S. Xu, W. Huang, Adv. Funct. Mater.,
2016, 26, 881.
Fig. 3 (a) Energy level diagram of WOLED (b) EL spectra of W4 (c) Current-
voltage-luminance (J-V-L) (d) EQE, PE, CE curves. Insert of Fig.3b is EL image of
W4
To further check the feasibility of such system, we replaced
1-phenyl-2-p-tolyl-1H-benzo[d]imidazole (ptbi) with 2-(4-tert-
butylphenyl)-1-phenyl-1H-benzo[d]imidazole (tbpbi), and
synthesized other structurally similar cationic Ir(III) complex,
[(tbpbi)2Ir(bisq)]Cl (Fig. S11, ESI†). The thermal stability of
[(tbpbi)2Ir(bisq)]Cl and the relevant test results are
summarized in the supporting information (Figs. S12 and S13,
ESI†). All results indicate that [(tbpbi)2Ir(bisq)]Cl can also be
vacuum evaporated. We tried to gain insight into the solid-
packing by culturing their single-crystal structures but failed. It
is hypothesized that the chlorine counterion may form the
special interactions with emissive cation part, which can
improve its volatility to some context. To verify our hypothesis,
[(tbpbi)2Ir(bisq)]PF6 with hexafluorophosphate as counterion
12 D. Ma, T. Tsuboi, Y. Qiu, L. Duan, Adv. Mater., 2017, 29, 1603253
13 A. B. Tamayo, S. Garon, T. Sajoto, P. I. Djurovich, I. M. Tsyba, R.
Bau, M. E. Thompson, Inorg. Chem., 2005, 44, 8723.
1
was synthesized and its H-NMR data before and after vapor
deposition have been measured. Similar to reported cationic
Ir(III)
complex,
the
results
demonstrate
that
14 a) Y.-M. Jing, F.-Z. Wang, Y.-X. Zheng, J.-L. Zuo, J. Mater. Chem. C,
2017, 5, 3714; b) B. Jiang, C. Zhao, X. Ning, C. Zhong, D. Ma and
C. Yang, Adv. Optical Mater., 2018, 1800108.
15 a) Y. C. Zhu, L. Zhou, H. Y. Li, Q. L. Xu, M. Y. Teng, Y. X. Zheng, J. L.
Zuo, H. J. Zhang, X. Z. You, Adv. Mater., 2011, 23, 4041; b) C. L.
Ho, Q. Wang, C. S. Lam, W. Y. Wong, D. Ma, L. Wang, Z. Q. Gao,
C. H. Chen, K. W. Cheah and Z. Lin, Chem. Asian J, 2009, 4, 89.
16 J.-L. Liao, P. Rajakannu, P. Gnanasekaran, S.-R. Tsai, C.-H. Lin, S.-
H. Liu, C.-H. Chang, G.-H. Lee, P.-T. Chou, Z.-N. Chen and Y. Chi,
Adv. Optical Mater., 2018, 6, 1800083.
17 a) Q. Zhao, L. Li, F. Li, M. Yu, Z. Liu, T. Yi and C. Huang, Chem.
Commun., 2008, 685; b) Y. You, H. S. Huh, K. S. Kim, S. W. Lee, D.
Kim and S. Y. Park, Chem. Commun., 2008, 3998.
18 A. B. Tamayo, B. D. Alleyne, P. I. Djurovich, S. Lamansky, I. Tsyba,
N. N. Ho, R. Bau and M. E. Thompson, J. Am. Chem. Soc., 2003,
125, 7377.
[(tbpbi)2Ir(bisq)]PF6 suffers from unsatisfactory volatility (Fig.
S14, ESI†). Therefore, we speculate that the small chlorine
counterion might play very important role in enhancing the
volatility for studied cationic Ir(III) complexes. The more clear
reason is undergoing in our lab.
In summary, we synthesized one novel sublimable orange
emitting cationic Ir(III) complex [(ptbi)2Ir(bisq)]Cl using
chlorine as counterion. An orange-emitting OLED with CE of
17.8 cd A-1 and a high EQE of 10.5% was successfully fabricated
by vacuum evaporation deposition. Employing it as orange-
emitting layer, obtained WOLEDs achieve
a maximum
brightness of 50122 cd m -2, and a maximum CE of 25.5 cd A-1,
EQE of 13.1 % with tiny efficiency roll-off of 4.7%. As far as we
know, this is the highest reported efficiency of WOLEDs based
on sublimable cationic Ir(III) complexes. The results reported
19 H. Cao, H. Sun, Y. Yin, X. Wen, G. Shan, Z. Su, R. Zhong, W. Xie, P.
Li and D. Zhu, J. Mater. Chem. C, 2014, 2, 2150.
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