New rhenium(I) complex with thiadiazole-annelated 1,10-phenanthroline for highly efficient phosphorescent OLEDs

Article abstract of DOI:10.1016/j.dyepig.2016.10.048

A new neutral tricarbonyl rhenium(I) complex (Re-TDAP) was designed and synthesized by annelating a thiadiazole unit on the frame of 1,10-phenanthroline ligand. The optoelectronic properties of Re-TDAP were fully investigated. Compared to the 589 nm peak emission of a prototype Re-PHEN (PHEN = 1,10-phenanthroline) in CH₂Cl₂ solution, annelating thiadiazole group caused the peak emission of Re-TDAP to red-shift to 621 nm. The phosphorescent organic light-emitting diodes using Re-TDAP as dopant were fabricated with the structure of ITO/m-MTDATA (10 nm)/NPB (20 nm)/CBP: x wt% Re-TDAP nm)/TPBi (30 nm)/Alq₃ (20 nm)/Liq (2 nm)/Al. The devices showed high performances with maximum efficiencies of 16.8 cd/A, 5.8 lm/W and 5.0%, which was better than that of a prototype Re-PHEN-doped device under the same conditions. These results suggest that rational molecular design is very beneficial to color tunability and photophysical regulation of the complex.

Full text of DOI:10.1016/j.dyepig.2016.10.048

Dyes and Pigments xxx (2016) 1e7
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
New rhenium(I) complex with thiadiazole-annelated
1,10-phenanthroline for highly efficient phosphorescent OLEDs
,
, **
Yong-Xu Hu a, Guang-Wei Zhao a, Yan Dong a, Yan-Li Lü a, Xiao Li a *, Dong-Yu Zhang b
a School of Chemical Engineering, University of Science and Technology Liaoning (USTL), Anshan, 114051, People's Republic of China
b Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new neutral tricarbonyl rhenium(I) complex (Re-TDAP) was designed and synthesized by annelating a
thiadiazole unit on the frame of 1,10-phenanthroline ligand. The optoelectronic properties of Re-TDAP
Received 9 September 2016
Received in revised form
23 October 2016
Accepted 26 October 2016
Available online xxx
were fully investigated. Compared to the 589 nm peak emission of
a prototype Re-PHEN
(PHEN ¼ 1,10-phenanthroline) in CH2Cl2 solution, annelating thiadiazole group caused the peak emis-
sion of Re-TDAP to red-shift to 621 nm. The phosphorescent organic light-emitting diodes using Re-TDAP
as dopant were fabricated with the structure of ITO/m-MTDATA (10 nm)/NPB (20 nm)/CBP: x wt% Re-
TDAP nm)/TPBi (30 nm)/Alq3 (20 nm)/Liq (2 nm)/Al. The devices showed high performances with
maximum efficiencies of 16.8 cd/A, 5.8 lm/W and 5.0%, which was better than that of a prototype Re-
PHEN-doped device under the same conditions. These results suggest that rational molecular design is
very beneficial to color tunability and photophysical regulation of the complex.
Keywords:
Rhenium complex
Thiadiazole
Phosphorescence
Electroluminescence
OLEDs
© 2016 Published by Elsevier Ltd.
1. Introduction
quantum efficiency (EQE) of ca. 30% [22]. For red phosphorescent
OLEDs, devices with (tmq)2Ir(acac) as red emitter showed
Organic light-emitting diodes (OLEDs) possess promising
application prospects in eco-friendly flat-panel displays and
energy-saving solid-state lighting owing to rapid progress in ma-
terial design and device fabrication [1e10]. Of the organic light-
emitting materials available, phosphorescent materials have
attracted extensive attention over the past several decades due to
their intrinsic advantages of achieving a maximum theoretical in-
ternal quantum efficiency of 100% [11e13]. Iridium(III) [Ir(III)]
[14e20] complexes have been mainly exploited as phosphorescent
emitters in OLEDs because of their high photoluminescence (PL)
efficiency, flexible color tunability, thermal stabilities, and strong
spin-orbit coupling effects. Up to now deep-blue-emitting fac-
Ir(pmp)3-based OLEDs have achieved very high brightness
(>7800 cd/m2) with CIE coordinates of (0.16, 0.09), closest to the
NTSC requirement among reported Ir-based OLEDs [21]. The green
phosphorescent OLEDs having simple device structure with the
heteroleptic ppy-type Ir(III) complexes as doped emitters exhibited
extremely high current efficiencies of 106 cd/A and external
extraordinary efficiencies of 25.9%, 37.3 cd/A, and 32.9 lm/W along
with CIE coordinates of (0.67, 0.33) [23].
From the view of device efficiency, only negligible contributions
have been demonstrated by other classes of complexes such as
rhenium (I) [Re(I)] complex with the general formula fac-
Re(CO)3(L)X [24e35]. For fac-Re(CO)3(L)X as shown in Fig. 1, L
represents a neutral bidentate diimine ligand, which functions as
not only saturating coordination number but also regulating the
optoelectric properties of Re(I) complex, and X is a halogen.
Compared with the Ir(Ⅲ) phosphorescent emitters, Re(I) complexes
exhibit the ubiquitous disadvantages such as low photo-
luminescence quantum yield (PLQY) (one or even two order of
magnitude smaller), single emissive colors and inferior electrolu-
minescent (EL) efficiency. However, many pronounced advantages
of Re(I) complexes including easy synthesis (mild reaction condi-
tion, simple isolation, high yield), short phosphorescent lifetime
(usually <1 ms) and unique luminescent properties always stimu-
late the development of Re(I) complexes as phosphorescent emit-
ters in OLEDs.
Therefore, in this study, we developed a new neutral tricarbonyl
Re(I) complex by annelating thiadiazole on the frame of 1,10-
phenanthroline, i.e. to obtain a [1,2,5]thiadiazolo[3,4-f] [1,10]phe-
nanthroline as ligand and then investigated the photophysical
* Corresponding author.
** Corresponding author.
E-mail addresses: lixiao@ustl.edu.cn (X. Li), dyzhang2010@sinano.ac.cn
(D.-Y. Zhang).
http://dx.doi.org/10.1016/j.dyepig.2016.10.048
0143-7208/© 2016 Published by Elsevier Ltd.
Please cite this article in press as: Hu Y-X, et al., New rhenium(I) complex with thiadiazole-annelated 1,10-phenanthroline for highly efficient
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2
Y.-X. Hu et al. / Dyes and Pigments xxx (2016) 1e7
rotatory evaporator and H2O (70 mL) was added. Concentrated HCl
was added to a final pH of 2, then the mixture was extracted into
CH2Cl2, washed with H2O, dried over Na2SO4 and filtered. The crude
product was purified by recrystallization from DMF and H2O with
light yellow needle crystal. Yield: 15%. M.P.: 220.1e221.1. MS (ESI):
m/z 239.2 [MþHþ]. IR data (KBr) cmꢂ1: 3045, 1400, 808, 740. 1H
NMR (500 MHz, CDCl3, TMS)
d
9.30 (s, 2H), 9.07 (d, J ¼ 7.8 Hz, 2H),
7.81 (s, 2H). 13C NMR (125 MHz, CDCl3, TMS)
d
152.00,151.81,147.42,
133.52, 124.30, 123.25. Anal. Calcd for C12H6N4S: C, 60.49; H, 2.54;
N, 23.51. Found C, 60.36; H, 2.33; N, 23.62.
2.2.3. Synthesis of Re-TDAP
TDAP (47.6 mg, 0.2 mmol) and Re(CO)5Br (81.2 mg, 0.2 mmol)
were refluxed in toluene (20 mL) for 5 h under a nitrogen atmo-
sphere. After the mixture was cooled to RT, the solvent was
removed and the resulting yellow solid was purified by silica-gel
column chromatography with petroleum ether and acetic ether
as mobile phase. Orange-red powder. Yield: 73%. IR data (KBr)
cmꢂ1: 3080, 2024, 1915, 1877, 1410, 825, 733. 1H NMR (500 MHz,
Fig. 1. The general formula of fac-Re(CO)3(L)X. L: neutral bidentate diimine ligand; X:
halogen.
properties and application in OLEDs of the Re(I) complex (Re-TDAP)
as a dopant emitter. Re-TDAP showed very short luminescent life-
time and high thermal stability. Re-TDAP-based OLEDs exhibited
orange-red emission with the maximum efficiency of 16.8 cd/A, 5.8
lm/W, 5.4% along with low efficiency roll-off.
CD2Cl2, TMS)
d
9.47 (d, J ¼ 3.6 Hz, 2H), 9.31 (d, J ¼ 8.0 Hz, 2H),
8.06e7.99 (m, 2H). 13C NMR (125 MHz, CD2Cl2, TMS)
d
196.87,
196.83, 196.38, 154.23, 150.54, 149.11, 135.37, 127.15, 125.66. Anal.
Calcd for C15H6BrN4O3ReS: C, 30.62; H,1.02; N, 9.53. Found C, 30.53;
H, 1.01; N, 9.65. UVeVis: lmax (CH2Cl2): 265 nm. Photo-
luminescence: excitation lmax: 324 nm, emission lmax (CH2Cl2):
621 nm, stokes shift: 221 nm.
2. Experimental section
2.1. General information
2.3. Device fabrication and EL measurements
Commercially available reagents and starting materials were
used for the synthesis of the Re(I) complexes without further pu-
rification. Solvents were purified and dried by standard procedures
prior to use. NMR spectra were recorded on a Bruker AC 500
spectrometer with tetramethylsilane (TMS) as an internal refer-
ence. Mass spectroscopy (MS) was performed on an AB SCIEX API
3200 spectrometer. Fourier transform infrared (FT-IR) spectroscopy
was recorded with samples as KBr pellets using NICOLET-IS5 FTIR
spectrophotometer. Elemental analysis was performed on Vario EL
III CHNS instrument. Thermogravimetric analysis (TGA) was un-
dertaken under a N2 atmosphere at a heating rate of 10 ꢀC/min on a
Perkin-Elmer Diamond TG-DTA 6300 thermal analyzer. UVevis
absorption and PL spectra of the Re(I) complexes in CH2Cl2 solution
of 1.0 ꢁ 10ꢂ5 mol/L were completed on a PerkinElmer Lambda 900
spectrophotometer and LS 55 fluorescence spectrophotometer,
respectively. Luminescence decay data were obtained with a
355 nm light generated from the third-harmonic-generator pump,
using a pulsed Nd: YAG laser as the excitation source. Cyclic vol-
tammetry experiments were conducted using a CHI 660D electro-
chemical analyzer with a scan rate of 100 mV/s. All measurements
were carried out at room temperature (RT) unless otherwise
specified.
OLEDs were fabricated through vacuum deposition of the ma-
terials at about 1 ꢁ 10ꢂ6 Torr onto ITO-coated glass substrates with
a sheet resistance of 25
U/sq. The ITO-coated substrates were
routinely cleaned by ultrasonic treatment in solvent and then
cleaned by exposure to a UV-ozone ambient. All organic layers were
deposited in succession without breaking the vacuum. The devices
were prepared with the following structures of ITO/m-MTDATA
(10 nm)/NPB (20 nm)/CBP: x wt% Re-TDAP (30 nm)/TPBi (30 nm)/
Alq3 (20 nm)/Liq (2 nm)/Al, in which m-MTDATA {4,40,400-tris[3-
methylphenyl(phenyl)amino]triphenyl-amine}, CBP (4,40-N,N0-
dicarbazolebiphenyl), TPBi [1,3,5-tris(1-phenyl-1H-benzimidazol-
2-yl)benzene] and Alq3[tris(8-hydroxyquinoline)aluminum] were
used as hole-transporting layer, host, exciton-blocking layer and
electron-transporting
layer,
respectively,
and
Liq
(8-
Hydroxyquinolinolato-lithium)/Al as the composite cathode.
Deposition rates and thicknesses of the layers were monitored in
situ using oscillating quartz monitors. Thermal deposition rates for
organic materials, Liq and Al were ~1, ~1 and ~10 Å/s, respectively.
EL spectra were measured by a PR 655 spectra scan spectrometer.
The current density-voltage-luminance (J-V-L) characteristics were
recorded simultaneously with the measurement of EL spectra by
combining the spectrometer with a Keithley 2400 source meter. All
measurements were carried out at RT under ambient conditions.
2.2. Synthesis of Re-TDAP
2.2.1. Synthesis of 1,10-phenanthroline-5,6-diamine
3. Results and discussion
1,10-Phenanthroline-5,6-diamine was synthesized according to
previously modified methods [36]. Yield: 50%. 1H NMR (DMSO-d6,
TMS): 8.83 (t, J ¼ 2.57 Hz, 2H), 7.79 (t, J ¼ 4.32 Hz, 2H), 6.23 (s, 4H).
3.1. Synthesis and characterization
Scheme 1 depicts the synthesis of the ligand TDAP and the
corresponding Re(I) complex. Re-TDAP was synthesized by
sequential reaction including oxidation, condensation, catalytic
reduction, cyclization and complexation. The ligand TDAP and Re-
TDAP were all characterized by 1H NMR, 13C NMR, FT-IR spectros-
copy, and satisfactory analytical results were obtained.
2.2.2. Synthesis of [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline
(TDAP) [37]
5,6-Diamine-1,10-phenanthroline (1.0 g, 4.8 mmol), CH2Cl2
(30 mL) and Et3N (1.92 g, 19.0 mmol) were combined and the so-
lution was stirred for 15 min, until the diamine went into solution.
Thionyl chloride (1.13 g, 9.5 mmol) was added slowly dropwise and
the mixture was refluxed for 4 h. The solvent was removed in a
FT-IR spectra (KBr pellets) are presented in Fig. 2. The FT-IR
spectra of TDAP and Re-TDAP showed three bands in
Please cite this article in press as: Hu Y-X, et al., New rhenium(I) complex with thiadiazole-annelated 1,10-phenanthroline for highly efficient
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Y.-X. Hu et al. / Dyes and Pigments xxx (2016) 1e7
3
Scheme 1. Synthetic routes of Re-TDAP.
3.2. Photophysical properties
For comparison, (1,10-phenanthroline)Re(CO)3Br (Re-PHEN)
was also prepared. Fig. 4 depicts the UV absorption and PL spectra
of two Re(I) complexes in dilute CH2Cl2 solution. Absorption spectra
of the Re(I) complexes were very similar to those of analogous
tricarbonyl Re(I) complexes [38], and the assignments had been
made accordingly. The major absorption bands of two Re(I) com-
plexes located at 260e270 nm could be assigned to spin-allowed
1p
/p* ligand-centered electronic transitions. The moderately
intense, poorly distinguished absorption bands extending into the
visible region from ca. 350e500 nm were tentatively assigned to an
admixture of metal-to-ligand charge transfer states, d
p (Re)/p*
(ligand) (1MLCT and 3MLCT) and halide-to-ligand (XLCT) transitions
which could been supported through the theoretical calculations
(vide infra) [39]. Re-TDAP showed red phosphorescent emission
peaked at 621 nm in CH2Cl2 under the irradiation with UV light at
365 nm at RT and red-shifted 32 nm compared with that of Re-
PHEN, which was attributed to increasing the conjugation in the
ligand by annelating rigid thiadiazole into 1,10-phenanthroline.
Furthermore, the photoluminescent quantum yields (PLQYs) of Re-
TDAP and Re-PHEN were 4% and 13% respectively, which were
measured at RT in degassed CH2Cl2 by a relative method using
Fig. 2. FT-IR spectra of TDAP and Re-TDAP in KBr pellets.
1870e2023 cmꢂ1 region, which could be attributed to the
stretching vibrations of the three carbonyl groups at different po-
sitions around the Re metal. Those evidences indicated that the
Re(I) complex accorded with the proposed structure.
As shown in Fig. 3, the thermal decomposition temperature of
Re-TDAP (Td, corresponding to 5% weight loss in the thermogravi-
metric analysis) was 326 ꢀC, indicating its satisfactory thermal
stability.
Ir(ppy)2(acac) (
F
¼ 0.34) as reference.
The lifetime of a phosphorescent complex is a crucial factor that
determines the rate of triplet-triplet annihilation (TTA) in OLEDs. A
long lifetime of a phosphorescent dopant usually causes a serious
Fig. 4. UV absorption and PL spectra of Re-TDAP and Re-PHEN in dilute CH2Cl2
solution.
Fig. 3. TGA trace of Re-TDAP in N2 atmosphere at a heating rate of 10 ꢀC/min.
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Y.-X. Hu et al. / Dyes and Pigments xxx (2016) 1e7
Table 1
The photophysical and thermal properties of the Re(I) complex.
laabs (nm)
laem (nm)
4b
tp
(m
s)
Td (ꢀC)
HOMOd (eV)
LUMOe (eV)
Efg (eV)
c
Re-complex
Re-TDAP
Re-PHEN
261,287,420
272, 378
621
589
0.04
0.13
0.07 (1.75)
0.22 (1.69)
326
e
ꢂ5.54
ꢂ5.52
ꢂ3.05
ꢂ2.95
2.49
2.57
a
Measured in CH2Cl2 solution with 1 ꢁ 10ꢂ5 mol/L.
b
c
d
e
f
Photoluminescence quantum yields in deaerated CH2Cl2.
Excited-state lifetimes measured in CH2Cl2 solution. Parenthesis is the radiation lifetime calculated with tt
Estimated from the CV.
¼
tp/4.
Estimated from the HOMO and energy gaps.
Calculated from the onsets of absorption spectra.
(shown in Table 1), respectively. Accordingly, the radiative life-
times (tt) of the triplet excited state calculated from tt p/4 are
1.75 and 1.69 s of Re-TDAP and Re-PHEN, which was indicative of a
¼
t
m
phosphorescent origin of the excited states in each case.
3.3. Electrochemical properties
The redox properties and the highest occupied molecular orbital
(HOMO)/the lowest unoccupied molecular orbital (LUMO) energy
of the dopants are related to the charge-transporting ability and the
OLEDs structure. The electrochemical behaviors of Re-TDAP and Re-
PHEN were investigated by CV, which was shown in Fig. 5. The
Ⅰ
anodic waves were associated with a Re -based oxidation process
Ⅰ
Ⅱ
(Re /Re ), and the cathodic waves were associated with a ligand (L)-
based reduction process ([ReIBr(CO)3(L)]/[ReIBr(CO)3(L$-)]-) [42,43].
Re-TDAP and Re-PHEN showed irreversible anodic waves with
onset oxidation potentials of 1.14 and 1.12 V, respectively. The
HOMO energy levels were calculated to be ꢂ5.54 and ꢂ5.52 eV for
Re-TDAP and Re-PHEN by comparison with ferrocene [EHOMO ¼ e
(Eoxonsetþ4.4)]. The corresponding LUMO levels calculated from the
HOMO values and the band gaps from the absorption spectra were
found to be approximately ꢂ3.05 and ꢂ2.95 eV for Re-TDAP and Re-
PHEN. We noted that the introduction of thiadiazole group lowered
the LUMO level of Re-TDAP and made HOMO level of Re-TDAP
Fig. 5. Cyclic voltammograms of Re-TDAP and Re-PHEN measured in CH2Cl2 (vs. SCE)
at a scan rate of 100 mV/s.
TTA effect [40,41]. The phosphorescent lifetimes
(tp) were
measured in deaerated CH2Cl2 (1 ꢁ 10ꢂ5 M) with excitation at
370 nm at RT and were 0.04 ms of Re-TDAP, 0.22 ms of Re-PHEN
Fig. 6. Spatial distributions of the HOMO/LUMO levels for Re-TDAP and Re-PHEN.
Please cite this article in press as: Hu Y-X, et al., New rhenium(I) complex with thiadiazole-annelated 1,10-phenanthroline for highly efficient
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5
should have more influence on the electronic structure of the
LUMOs, which was in line with the electrochemical characteriza-
tion results.
3.5. Electrophosphorescent properties
In order to evaluate the potential of Re-TDAP as a phosphores-
cent emitter, Re-TDAP had been used for fabrication of OLEDs with
the conventional structure of ITO/m-MTDATA (10 nm)/NPB
(20 nm)/CBP: x wt% Re-complex (30 nm)/TPBi (30 nm)/Alq3
(20 nm)/Liq (2 nm)/Al. The device configuration and energy band
diagram were shown in Fig. 7, in which m-MTDATA and Liq served
as hole- and electron-injecting materials; NPB was used as the
hole-transporting material; Alq3 and TPBi were used as electron-
transporting material and hole-blocking material, respectively;
and CBP was employed as host material. Re-PHEN-doped device
was also fabricated for comparison. All the EL data were collected in
Table 2.
The J-V-L characteristics, current efficiency/power efficiency
versus luminance, and EL spectra of the Re-TDAP-doped devices
were all shown in Fig. 8. All devices displayed EL spectra peaking at
590 nm with the CIE color coordinates of (0.55, 0.45), and the
emission spectra were almost invariant of the voltage and also did
not show any concentration dependence. In addition, the EL spectra
were very similar to the PL spectrum of Re-TDAP in CH2Cl2 solution,
and this indicated that the EL emission of those devices originated
from the triplet excited states of the phosphor. It should be pointed
out that the emission of the host peaked at ca. 420 nm is also
discernible in the EL spectra of those devices. This may be ascribed
to the unfavorable energy level alignment in the devices and the
relatively low energy transfer efficiency between the host material
and Re-TDAP.
Fig. 7. Energy-level diagrams of HOMO and LUMO (relative to vacuum level) for
devices.
nearly invariant compared with those of Re-PHEN, which had been
verified in the following theoretical calculations.
3.4. Theoretical calculations on Re(I) complexes
The ground state geometries and electronic structures of Re-
TDAP and Re-PHEN were calculated according to density func-
tional theory (DFT) calculations using the GAUSSIAN-03 software
package (Gaussian, Inc.) at the B3LYP/LANL2DZ level since the
frontier molecular orbitals, especially the HOMO and LUMO, were
crucial for the photophysical properties and also important in
designing the structure of OLEDs.
As indicated in Fig. 6, the calculated results revealed that the
ground state geometries of the two complexes displayed a distorted
octahedral configuration of ligands around the metal Re center. The
As shown in Fig. 8, the 9 wt% Re-TDAP-doped OLED exhibited a
maximum current efficiency of 16.8 cd/A, a maximum power effi-
ciency of 5.8 lm/W and a EQE of 5.0%. It is noteworthy that in those
devices, satisfactory current efficiency could be achieved at high
brightness. For 9 wt% doped device, its current efficiency maintains
to be as high as 9.0 cd/A at 1000 cd/m2 and 5.0 cd/A at 2000 cd/m2.
For comparison, Re-PHEN-doped device with the optimized con-
centration of 9 wt% was also fabricated under the same condition.
As shown in Fig. 9, the device showed the maximum efficiency of
15.1 cd/A, 6.1 lm/W and 4.3% together with the peak emission of
560 nm. Overall, 9 wt% Re-TDAP-doped device shows better EL
efficiency than Re-PHEN-doped device probably due to very short
lifetime of Re-TDAP.
HOMOs of Re-TDAP and Re-PHEN were mainly located on the
p
orbitals of the carbonyl group, the bromine, and the d orbitals of Re
cation which was in antibonding coordination with the axial
bromine group and bonding with the three carbonyl groups. While
the LUMOs of Re-TDAP and Re-PHEN were primarily distributed on
Nevertheless, although the performances of these Re(I)-doped
devices are still inferior to those of the Ir(Ⅲ)-based OLEDs, much
improved EL performances could be expected after further opti-
mization has been carried out on the host species, device structure,
doping concentration as well as layer thickness.
the p
* orbitals of the entire N^N ligand, with very slim contributions
from Re atom. As indicating in Fig. 6, the thiadiazole annelated 1,10-
phenanthroline was mainly involved in LUMOs, and therefore
Table 2
EL performances of Re-doped devices.
Dopant
Ratio(%)
lmax (nm)a
Lmax (cd/m)b
LE(cd/A)c
PE (lm/W)d
EQE (%)e
Re-TDAP
5
7
9
12
9
590
590
590
590
560
4002
3926
3982
4420
4055
12.6
14.6
16.8
10.3
15.1
4.3
4.6
5.8
3.6
6.1
4.6
5.4
5.0
4.0
4.3
Re-PHEN
a
Maximum wavelength measured at 10 V.
Maximum luminance.
Maximum current efficiency.
Maximum power efficiency.
Maximum external quantum efficiency.
b
c
d
e
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6
Y.-X. Hu et al. / Dyes and Pigments xxx (2016) 1e7
Fig. 8. (a) JꢂVꢂL characteristics of Re-TDAP-doped device; (b) current efficiency versus luminance of Re-TDAP-doped device; (c) power efficiency versus luminance of Re-TDAP-
doped device; (d) EL spectra of Re-TDAP-doped device at 10 V.
Fig. 9. (a) current efficiency and power efficiency versus luminance of 9 wt% Re-PHEN-doped device; (b) EL spectra of 9 wt% Re-PHEN-doped device at 10 V.
4. Conclusions
Liaoning Provincial Natural Science Foundation (Grant No.
2015020651), Talents training project of USTL (Grant No. 2014RC01)
and Innovation team construction project of USTL (Grant No.
2015TD02).
In summary, we have designed and synthesized a new rhenium
complex Re-TDAP by annelating thiadiazole on the frame of 1,10-
phenanthroline to develop a highly efficient orange-red phos-
phor. The influence of the thiadiazole group on the optoelectronic
properties of the corresponding rhenium complex was systemati-
cally investigated. Re-TDAP showed a very short lifetime, good
thermal stability and its emission color has been tuned to orange-
red area peaked at 590e620 nm. OLEDs based on Re-TDAP
exhibited high performance with maximum efficiencies of
16.8 cd/A, 5.8 lm/W and 5.0%, which was better than that of pro-
totype Re-PHEN-doped device.
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Acknowledgements
Authors gratefully acknowledge the supports from the National
Natural Science Foundation of China (Grant No. 61204021),
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phosphorescent OLEDs, Dyes and Pigments (2016), http://dx.doi.org/10.1016/j.dyepig.2016.10.048

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Please cite this article in press as: Hu Y-X, et al., New rhenium(I) complex with thiadiazole-annelated 1,10-phenanthroline for highly efficient
phosphorescent OLEDs, Dyes and Pigments (2016), http://dx.doi.org/10.1016/j.dyepig.2016.10.048